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  After 20 years, your life may be like this:The electronic skin on your pulse can monitor your heart rate and blood sugar at any time to realize intelligent pulse detection;The electronic skin on your throat can "voice" for the deaf and mute by feeling the pressure changes produced by the movement of the throat muscles;Your whole body may become a network center, and the sensors in your body will connect with the outside world...All this seems very far away, but these technologies are quietly gestating, and are very likely to become disruptors of new technologies.Flexible Electronics: The Future of TECHNow is the era of smart phones, but the current smart electronic products are still rigid electronic devices. In the future, mankind is about to enter a new era, the era of flexible electronics. Flexible electronic devices that are as soft as human skin will be the next development trend of the electronics industry, and may even subvert human life. Catalog I What is Flexible electronics?II Applications of flexible electronics2.1 Flexible electronic display2.2 Thin film solar panels2.3 RFID2.4 Electronic skinIII ConclusionFAQ  I What is Flexible electronics? The concept of flexible electronics started in the 1980s, when people tried to replace inorganic semiconductors such as silicon with organic semiconductors, so that organic electronic devices have flexible characteristics.Flexible electronic technology is a brand-new electronic technology revolution. It is an emerging electronic technology that makes organic and inorganic materials electronic devices on flexible, malleable plastic or thin metal substrates. It has a wide range of fields in information, energy, medical treatment, and national defense.  Applications of flexible electronics In addition to integrating electronic circuits, functional materials, micro-nano manufacturing and other fields of technology, flexible electronic technology also spans industries such as semiconductors, packaging, testing, materials, chemicals, printed circuits, and display panels. Not only that, it can also help the transformation and upgrading of traditional industries, such as plastics, printing, chemicals, and metal materials.By improving its performance and industrial added value, flexible electronics will frequently appear in human life, bringing revolutionary changes to the industrial structure and future life. As technology upgrades, flexible electronics materials research and development and rich application products have emerged.II Applications of flexible electronicsWith the development of flexible electronic technology, various electronic products have emerged. Just as microelectronics technology provides a technology platform for large-scale integrated circuits and computer chip technologies, flexible electronic technology provides a brand-new technological platform for the research and development of new products. 2.1 Flexible electronic displayThe flexible electronic display is a brand-new product developed on the flexible electronic technology platform. Unlike traditional flat-panel displays, such displays can be repeatedly bent and folded, thus bringing great convenience to our lives.For example, all visual materials, including books, newspapers, magazines, and video files, can be presented on this display and can be viewed anytime, anywhere. Although current popular MP4 players and personal digital assistants (PDAs) can meet such use needs, the display screen cannot be bent and folded, and can only be read and viewed in a small screen area. And video, visual effects are greatly constrained. In contrast, flexible electronic displays have unparalleled advantages. They are like newspapers. When they are needed, they are unfolded. When they are used, they are curled or even folded. This guarantees the convenience of portability while giving full consideration to the visual effects.Flexible electronic displaySamples of flexible electronic displays have been successfully developed and it is believed that it will be a long way from entering the market. It is worth mentioning that flexible electronic displays use more lightweight organic materials instead of inorganic materials, so their weight is lighter than traditional displays, and this feature helps to improve their portability. In addition, the use of high molecular organic materials offers possibilities for reducing costs. In addition, the flexible electronic display has the characteristics of a thin thickness, and its thickness can be much smaller than that of the popular liquid crystal display. Therefore, another name of the flexible electronic display is a paper-like electronic display.2.2 Thin film solar panelsThin film solar panel is another specific application of flexible electronics technology. In today's world, energy has become a topic of global concern. China not only faces energy shortages but also faces environmental pollution. As a clean energy source, solar energy can effectively alleviate the contradiction of energy shortage under the premise of zero environmental pollution.As the most common way to use solar energy, solar panels can cover a large area at the lowest cost to effectively use solar energy. At present, thin film amorphous Sili-Con solar panels have been successfully developed and marketed. Thin film solar panel Thin-film solar panels based on flexible electronic technology can meet high-power generation needs, such as the use of thin-film solar panels in solar power plants in sunny desert areas.In addition, it can also make full use of its flexible and lightweight features to integrate it into clothing. Putting on such clothes to walk or exercise in the sun, the power of small appliances (such as MP3 players and laptops) that are carried around can be supplied by the thin-film solar panels on the clothes, thus achieving the purpose of saving and environmental protection.2.3 RFIDRadio frequency identification (RFID) technology can be used to complete information input and processing, fast and convenient operation, and rapid development without manual contact, and is widely used in production, logistics, transportation, medical, food, security and other fields. RFID systems usually consist of transponders and readers.The electronic tag is one of many forms of transponder, and can be understood as a transponder with a thin film structure, which has the characteristics of convenient use, small size, thin and light, and can be embedded in the product. More and more electronic tags will be used in future RFID systems.Flexible Electronics in RFIDIn this response to Covid-19, flexible electronic technology has played a huge role in body temperature measurement.Group body temperature measurement has problems such as huge number of monitoring people, cumbersome temperature measurement work, and difficulty in continuous temperature recording. Wearable temperature measuring stickers made by introducing flexible electronic technology can record and analyze the body temperature data of the target population. In this way, potential threats can be discovered and eliminated through long-term monitoring, thereby helping management departments to achieve personnel management monitoring.2.4 Electronic skinAnother important application of flexible electronics is electronic skin. Electronic skin, also called skin-like electrons, is basically characterized in that various electronic components are integrated on a flexible substrate to form a skin-like circuit board, which has high flexibility and elasticity like skin and can be used in many other applications. electrical equipment.It can be said that the potential of flexible electronic skin is great. With the popularization of technologies such as smart medical care, virtual reality, and artificial intelligence, the demand for wearable devices has surged, and flexible electronic skin is a perfect combination of wearable devices. Think about an electronic component installed on the body and used as a skin, isn't it sci-fi?Electronic skinIII Conclusion Folding computers, folding mobile phones, and wearable digital products are in the ascendant. With the development of science and technology, flexible electronic devices have received more and more attention from the society. Such devices can still work under bending, folding, twisting, compression or stretching conditions. In the future, flexible electronic equipment will have a very broad development space in the fields of energy, medical, information and communication.Pieces of work brought by flexible electronics are interpreting the integration of innovation and tradition in the era of the Internet of Everything, and the era of science and technology connecting everything is approaching.You can boldly imagine that in 20 years, your life might be like this:In the morning, the flexible electronic skin watch on your body wakes you up and reports the quality of your sleep. Put on your glasses, and the day’s schedule has been displayed for you on the transparent screen. After washing, the robot has prepared breakfast for you and your family; After going out, the smart watch on your wrist shows that the air quality is excellent; the smart assistant called "Flying" for you and has parked outside the house, waiting for you to start your day's itinerary... FAQ 1. Why are electronics flexible?The key advantages of flexible electronics, compared with current silicon technologies, are low-cost manufacturing (e.g. ink-jet printing and roll-to-roll imprinting) and inexpensive flexible substrates (e.g. plastics). ... In principle, flexible electronics is ideal for integration. 2. Where are flexible electronics used?Consumer electronics devices make use of flexible circuits in cameras, personal entertainment devices, calculators, or exercise monitors. Flexible circuits are found in industrial and medical devices where many interconnections are required in a compact package. 3. How could Flexible Electronics benefit the consumer?Among the benefits of flexible electronics (compared to traditional, rigid alternatives) are size, weight, portability, and energy efficiency. Above all, they make previously impossible designs and technologies (such as wearable devices) possible. 4. When was flexible electronics invented?1960s. Flexible electronics have a long history. The first flexible device was made in the 1960s by thinning crystalline silicon solar cells for use in extraterrestrial satellites. Today, smart credit cards carry bendable microchips which are made using stretchable Silicon. 5. What are flexible electronics made of?Flexible Electronics: generally refers to a class of electronic devices built on conformable or stretchable substrates, usually plastic, but also metal foil, paper and flex glass. 6. What are the two major approaches of making flexible electronics?(1) Transfer and bonding of completed circuits to a flexible substrate(2) Fabrication of the circuits directly on the flexible substrate  7. What makes flexible electronic display attractive?One property of flexible electronics which deserves to be highlighted is their robustness. This makes a great difference for applications such as wearables, notebooks and other consumer electronics which traditionally feature glass-based displays or sensors. 8. How flexible electronics are made?Compared with conventional microelectronics, flexible electronics does not require extrinsic packages such as ceramics. Instead, flexible circuits and packages can be manufactured and integrated together using only plastics. ... These layers can then be stacked together to complete the flexible electronic systems. 9. Why are flexible electronics important?Among the benefits of flexible electronics (compared to traditional, rigid alternatives) are size, weight, portability, and energy efficiency. Above all, they make previously impossible designs and technologies (such as wearable devices) possible. 10. Why do we need flexible materials?Not only does flexible packaging use less material than its rigid counterparts, leading to a lower overall packaging cost, it also creates less waste. Fres-co states that flexible packaging formats create 50 percent less waste than rigid ones, while also reducing greenhouse gas emissions and BTU consumption. 

What is a LED?Video related to LEDLED Colours and materialsHow do LEDs work?Types of LedsCalculating LEDs resistor valueHow to Test LED LightsThe warning of LEDs useLEDs FAQWhat is a LED?LED = Light Emitting Diode. An LED must be prevented against transferring too much current because its electrical behavior differs significantly from that of a light. Typically, this is done by connecting a resistor in series with the LED. Never attach an LED directly to a power source or battery.LEDs must be wired in the proper direction; the diagram may be labeled with the letters an or + for the anode and k or - for the cathode (yes, it really is k, not c, for cathode). In the case of spherical LEDs, the cathode is the short lead and there may be a slight flat on the body. Although the cathode is the larger electrode within the LED if you can see it, this is not a recognized method of identification.LEDs Video related to LEDVideo Description: This video is mainly talk about how to design LED circuits, how to calculate resistor size, how to protect LED, how long will a battery power a circuit, how to calculate resistor power rating, how to connect LED and much more. LED Colours and materialsThe semiconductor material, not the coloring of the "package," determines the color of an LED (the plastic body). All colors of LEDs are available in uncolored, diffused (milky), or clear (commonly referred to as "water clear") packaging. The colored packaging is also offered in diffused (the typical type) and clear forms. White and blue LEDs could cost more than the other colors.ColorWavelength (nm)Voltage Drop (V)Semiconductor MaterialInfrared> 760< 1.9Gallium ArsenideInfrared> 760< 1.9Aluminium Gallium ArsenideRed610 - 7601.6 -2.0Aluminium Gallium ArsenideRed610 - 7601.6 -2.0Gallium Arsenide PhosphideRed610 - 7601.6 -2.0Aluminium Gallium Indium PhosphideRed610 - 7601.6 -2.0Gallium PhosphideOrange590 - 6102.0 -2.1Gallium Arsenide PhosphideOrange590 - 6102.0 -2.1Aluminium Gallium Indium PhosphideOrange590 - 6102.0 -2.1Gallium PhosphideYellow570 - 5902.1 -2.2Gallium Arsenide PhosphideYellow570 - 5902.1 -2.2Aluminium Gallium Indium PhosphideYellow570 - 5902.1 -2.2Gallium PhosphideGreen500 - 5701.9 -4.0Gallium Indium PhosphideGreen500 - 5701.9 -4.0Aluminium Gallium Indium PhosphideGreen500 - 5701.9 -4.0Aluminium Gallium PhosphideGreen500 - 5701.9 -4.0Indium Gallium NitrideBlue450 - 5002.5 -3.7Zinc SelenideBlue450 - 5002.5 -3.7Indium Gallium NitrideBlue450 - 5002.5 -3.7Silicon CarbideBlue450 - 5002.5 -3.7SiliconViolet400 - 4502.8 -4.0Indium gallium NitridePurplemultiple types2.4 -3.7Dual Blue/Red LEDsPurplemultiple types2.4 -3.7Blue with Red PhosphorPurplemultiple types2.4 -3.7White with Purple Plasticultraviolet< 4003.1 -4.4Diamondultraviolet< 4003.1 -4.4Boron Nitrideultraviolet< 4003.1 -4.4Aluminium Nitrideultraviolet< 4003.1 -4.4Aluminium Gallium Nitrideultraviolet< 4003.1 -4.4Aluminium gallium Indium NitridePinkmultiple types3.3Blue with phosphorPinkmultiple types3.3Yellow with Red, Orange or Pink phosporPinkmultiple types3.3White with Pink pigmentWhiteBroad spectrum3.5Blue/UV diode with Yellow Phosphor How do LEDs work?A P-type semiconductor (which has a higher hole concentration) and an N-type semiconductor are combined to create LEDs, which are semiconductor light sources (larger electron concentration). The P-N junction's electrons and holes will join once more when a strong enough forward voltage is applied, releasing energy in the form of light.LEDs (Light Emitting Diodes) transform electrical energy directly into light as opposed to conventional light sources, which first convert electrical energy into heat before turning it into light. This results in efficient light creation with minimal electricity waste.LEDs Emit Light Types of LedsDual In-Line Package (DIP) LEDs:The first LED chips were DIP ones, which are what most people think of when considering LED lights. Despite being more established than its more recent counterparts, DIP LED chips are still in use and are more frequently seen integrated into electronics because of their small size. However, they are not very strong and can only provide a small amount of brightness.DIP LEDs Surface Mounted Diode (SMD) LEDs:These are likely the most popular sort of LED chip available; they are installed and soldered onto the circuit board. They are more adaptable when it comes to encasing them within smaller electronics or across other forms of lighting, such as strip lighting, because they are brighter than their DIP counterparts and are also smaller. Three diodes can fit on a single SMD chip, allowing you to produce a variety of colors and provide customers more options. The LED market has undergone this significant progress. SMD 3528 and SMD 5050, both of which measure 5mm in width, are the two most used SMD chip sizes.SMD LEDs Chip on Board (COB) LEDs:The most recent advancement in LED technology is represented by these chips. Out of the three, COB LED chips are the brightest since they can frequently fit nine or more diodes onto a single chip. In what ways does this affect LED lighting? First off, it increases lighting efficiency by improving brightness-to-energy output. They can therefore be utilized with a variety of various lighting types. However, it's important to keep in mind that a COB LED chip's circuitry prevents it from emitting a wide variety of colors.COB LEDs Calculating LEDs resistor valueTo limit the current flowing through an LED, a resistor must be connected in series with the LED; otherwise, the LED will burn out fairly immediately. R, the resistor's value, is determined by:R = (VS - VL) / IR = resistor value in ohms (ohm).VS = supply voltage.VL = LED voltage (2V, or 4V for blue and white LEDs).I = LED current in amps (A) The LED current needs to be lower than what your LED is capable of handling. Since the The maximum current for typical 5mm diameter LEDs is frequently 20mA; however, many circuits can work with 10mA or 15mA. Divide the mA current by 1000 to convert it to amps (A) for the calculation.If the projected value is unavailable, pick the nearest larger standard resistor value so that the current will be a little less than what you chose. If you choose a higher resistor value to reduce the current, the LED will be less bright (for example, to extend the battery life).The color of the LED affects the voltage VL of the LED. The voltage of red LEDs is the lowest; yellow and green have a somewhat higher value. The highest voltages are used in blue and white LEDs. You can use 2V for red, yellow, and green LEDs and 4V for blue and white LEDs for the majority of applications where the precise value is not crucial. According to Ohm's law, the resistor's resistance, R = V/I, is determined by:V = voltage across the resistor (= VS - VL in this case) I = the current through the resistorSo R = (VS - VL) / IResistor Value How to Test LED LightsStep One: Use a MultimeterGet a digital multimeter with a diode reading capability. Simple multimeters only measure voltages, amps, and ohms. A multimeter with a diode setting is required to test LED lighting. Mid-range to high-range multimeters, which are more likely to offer this capability than affordable versions, can be found online or at your neighborhood hardware store.Multimeter Step Two: Connect the black and red test leadsTo the outlets on the front of the multimeter, attach the red and black test leads. The positive charge is in the red lead. The input marked "COM" should be connected in with the black lead, which is the negative.Multimeter Connect Step Three: Select the diode setting on the multimeter's dialTo move your multimeter's front dial from the "off" position, turn it clockwise. Up till you reach the diode setting, keep twisting it. The diode setting may be represented by the diode circuit symbol if it is not labeled explicitly. The cathode and the anode of a diode are both visually represented by the diode symbol. In this digital multimeter dial picture, we need to set the multimeter’s dial on 14 to test diode.Multimeter dial Step Four: The red probe should be connected to the anode and the black probe to the cathodeThe cathode end of the LED, which is typically the shorter prong, should be touched with the black probe. The red probe should then be pressed against the anode, which is the longer prong. Ensure that the black probe is connected before the red probe because doing so can result in inaccurate readings. During this test, be sure the cathode and anode are not in contact with one another since this could prevent electricity from flowing through the LED light and affect your results. Throughout the test, the red and black probes must not come into contact. After making the connections, the LED ought should turn on.Diode test Step Five: Verify the reading on the digital multimeter displayA healthy LED light should show a voltage of about 1600 mV when the probes are in contact with the cathode and anode. If during the test there is no reading displayed on your screen, repeat the procedure to ensure that the connections were completed correctly. This can indicate that the LED light isn't functioning if the test was done correctly. The transformer needs to be changed if your supply does not provide any output voltage. LED lights need to be replaced if there is voltage present at the output. The warning of LEDs useIn general, it is not a good idea to connect multiple LEDs in parallel with just one resistor shared between them. Only the lowest voltage LED will light if the other LEDs require slightly different voltages, and the higher current running through it could damage the other LEDs. One resistor can be used to successfully link identical LEDs in parallel, but since resistors are so inexpensive and the current utilized is the same as connecting the LEDs separately, this rarely provides any significant benefit.LEDs in parallelInstead, we should do as follows: Connecting LEDs in seriesConnecting LEDs in series LEDs FAQWhat can the LEDs be applied to?LEDs (Light Emitting Diodes) are mostly used to illuminate items and even spaces. Due to its small size, low energy consumption, long lifespan, and versatility in terms of use in many applications, it is applied everywhere. LED usage and applications include TV backlighting. How many types that LEDs own?Fundamentally, LED lighting uses three major forms of LED technology: DIP, SMD, and COB. What is LED and how it works?When an electric current passes through a semiconductor device called a light-emitting diode (LED), the LED emits light. When current flows through an LED, the electrons and holes recombine and produce light. How long do LED lights last?The longer lifespan of LED lighting fixtures is one of its main benefits. The most durable LED light fixtures have been evaluated to survive as long as 100,000 hours, whereas incandescent light bulbs were designed to last roughly 1,000 hours. On average, LED light bulbs last at least 20 years before needing to be replaced. Which is not a benefit of LED?On a capital cost basis, LEDs are now more expensive (price per lumen) than the majority of conventional lighting solutions.

What is the soldering?What is the PCB soldering?Video about the pcb solderingPCB Soldering MaterialTypes of SolderingTypes of PCB SolderingWhat is the Wave SolderingWave Soldering ProgressThe advantages and disadvantages of wave solderingWhat is the Reflow Soldering?Reflow Soldering ProgressThe advantages and disadvantages of Reflow SolderingWhat is the Selective Soldering?Selective Soldering ProgressThe advantages and disadvantages of Selective SolderingWave Soldering VS Reflow SolderingSelective Soldering VS Wave SolderingReflow Soldering VS Selective SolderingThe conclusion of Wave Soldering VS Reflow Soldering VS Selective SolderingPCB Soldering FAQ What is the soldering?Soldering is the process of putting metal parts together with melted solder, a metal having a lower melting point than other metals. It is a process that is essential to the electronics industry and the main way to connect electrical components. Soldering is utilized in the construction of printed circuit boards (PCBs), as well as in the manufacture of jewelry, pipes, and plumbing. When soldering, a soldering iron or gun is used with solder at a temperature of less than 840 degrees Fahrenheit. Solder typically appears as a thin wire or tube. A flux-like acidic mixture is present inside the tube to stop oxidation.Despite the fact that there are many various kinds of solder, it is often an alloy of lead or tin, brass, or silver that is made to have a low melting point. This metal is melted by the soldering iron and then used to adhere components together rather like glue. The solder metal will re-harden into a single, substantial form that joins the two pieces as it cools. There are currently various lead-free solder options available in an effort to reduce lead usage due to environmental and safety concerns. These substitutes frequently consist of brass, copper, tin, or silver. Lead-free solder can be less effective than conventional solder and has a greater melting point.SolderingWhat is the PCB soldering?Soldering electrical circuit boards is also referred to as PCB soldering. One of the most fundamental skills for everyone who wants to deal with electronics and electrical circuits is this kind of soldering. The most fundamental definition of the soldering process is that it is a technique of attaching two little components together on the surface of the PCB, which is an abbreviation for Printed Circuit Board. There are many various ways you can finish the soldering process. To join two or more separate electrical components on your circuit board, in other words, soldering is a technique.The soldering action itself is pretty straightforward at its heart. A soldering iron, some solder, and the materials you are joining together are all you need to execute the simplest soldering task. A soldering iron is a tool that melts solder and is used to connect two pieces together. It resembles a pen and gets quite hot.Despite the fact that there are many various kinds of solder, it is often an alloy of lead or tin, brass, or silver that is made to have a low melting point. This metal is melted by the soldering iron and then used to adhere components together rather like glue. As the solder metal cools, it will re-harden into one large shape that connects the two parts.Pcb Soldering Video about the pcb solderingVideo Description: How to solder a through hole connection on a printed circuit board (PCB). PCB Soldering MaterialChoosing the correct sort of solder can seem like a daunting chore for a rookie designer or assembler because there are so many different varieties on the market. By enabling the molten, soft alloy solder to produce a eutectic that fuses as it cools, solders are used to create electrical connections between metal contacts. A soldered PCB's mechanical strength after solidification, the needed melting temperature, and any fumes released during soldering will all depend on the combination of metals used to build it. By looking at the core material, metallic components, and soldering flux kinds, we can distinguish between various PCB soldering materials. Lead-based filler metals, such as lead patch, were originally used in patching, however because to regulations, lead-based filler metals are gradually being replaced with lead-free fastens. These may consist of the following metals:BrassCopperAntimonyTinIndiumSilver or bismuth Types of SolderingLead-free solderLead-based solderFlux-core soldersSilver alloy solder Types of PCB SolderingWave SolderingReflow SolderingSelective Soldering What is the Wave SolderingElectronic components are attached to a printed circuit board (PCB) using the large-scale soldering technique known as wave soldering. The name comes from the method of attaching metal components to the PCB by applying waves of hot solder. The components are inserted into or placed on the PCB, which is then passed over a pumped wave or cascade of solder. The technique employs a tank to contain an amount of molten solder. A reliable mechanical and electrical connection is made when the solder wets the exposed metallic portions of the board (those not covered by solder mask, a protective layer that stops the solder from bridging across connections). The process is much faster and can create a higher quality product than manual soldering of components.Surface mount and through-hole printed circuit assemblies both use wave soldering. In the latter instance, before being subjected to the molten solder wave, the components are first attached to the printed circuit board surface by the placement apparatus.Wave Soldering Wave Soldering ProgressIt is essential that an electronics printed circuit board be produced and designed correctly in order to process it properly using a wave soldering equipment. It contains two steps to wave soldering progress.Step One Solder resist layer: The first is now considered best practice for board design. The PCB design incorporates a solder resist or solder mask layer, which provides a layer of "varnish"-like material to the board and prevents solder from adhering to it. Only the necessary parts for soldering are left exposed. The color of this solder resist is most frequently green.Step Two Pad spacing: The second major precaution is to make sure there is enough space between the solder pads that need to be soldered. There is a chance that the solder may bridge the two pads if they are too close together, leading to a short circuit. The spacing requirements for wave soldering depend on the orientation of the board in relation to the solder flow because the solder wave is created by solder flowing out of the reservoir tank as the board passes over it. Pads that are separated from one another perpendicular to the solder flow should have a wider separation than those that are separated perpendicular to it. This is due to the fact that solder bridges are considerably more likely to form in the direction that solder flows. The advantages and disadvantages of wave solderingThe advantages of wave solderingNo glue is needed to secure components during reflow soldering.Board areas where no soldering is required do not have to be masked off.Soldering machines that conduct selective soldering are generally cheaper to operate.Parameters for each are variable and can be more finely controlled.Allows wave soldering to be applied to boards with SMDs and vias.Suited for PTH assemblyIs more time-saving than hand solderingMore affordableLess prone to PCB warpageProvides strong solder joint quality The disadvantages of wave solderingHigh solder consumptionHigh flux consumptionHigh power consumptionHigh nitrogen consumptionAn increase in post-wave solder reworkMasking of sensitive areas on PCB assembliesCleaning of wave solder aperture pallets or masksCleaning of soldered assemblies What is the Reflow Soldering?Although reflow soldering differs slightly from wave soldering, it is still the most used method for joining surface mount components to a circuit board. For soldering through-hole components, wave soldering is more frequently utilized. Reflow soldering can be used for this purpose, however it is rarely done because wave soldering is more affordable.Reflow soldering is the process of attaching components to contact pads by creating a solder paste from powdered solder and flux. The solder is then melted and the junction is connected by heating the entire assembly in a reflow oven or under an infrared lamp. If necessary, you might use a hot air pencil to solder each individual link.Reflow Soldering Reflow Soldering ProgressThere are numerous separate steps that make up the reflow process itself. These are necessary to make sure that the board is heated to the appropriate degree for reflow soldering without causing any excessive amounts of thermal shock. The greatest quality solder junctions are produced when the temperature of the reflow tunnel or chamber is properly profiled. These are the four steps that are typically employed:Preheat: The boards must gradually warm up to the necessary temperature. The board or the components could be harmed by the thermal stress if the rate is too high. Thermal soak: The board then enters what is frequently referred to as a thermal soak area after being brought up to temperature. For two reasons, the card in this case is kept at a certain temperature. One is to make sure that any spaces that aren't heated enough due to shadowing effects are brought up to the necessary temperature. The other is to eliminate the solvents or volatiles from the solder paste and to activate the flux. Reflow: The soldering process's reflow area is where the maximum temperature is reached. The solder is made to melt and form the necessary solder joints here. The real reflow procedure involves the flux lowering the surface tension at the metal-to-metal contact to achieve metallurgical bonding, which enables the melting of the individual solder powder spheres. Cooling: After reflow, the boards need to be cooled, but it needs to be done without stressing the components. Excess intermetallic development and thermal shock to the components are prevented by proper cooling. The cooling zone typically has temperatures between 30 and 100°C (86 and 212°F). The temperature in this zone causes a relatively quick cooling rate, which is selected to give the solder a fine grain structure for the structurally soundest union possible. The advantages and disadvantages of Reflow SolderingThe advantages of Reflow SolderingTrusted by many manufacturersBest suited for SMT assemblyEffective for numerous SMT package types in a single processEasy to monitor and controlIt is a less wasteful method when dealing with specific parts of a PCB The disadvantages of Reflow SolderingFor those seeking to enhance certain aspects of the convection reflow soldering process, the use of nitrogen can be the key. But the use of nitrogen may be expensive.The temperature thresholds of the PCB assembly and the unique requirements of the solder paste must be taken into account while creating the reflow soldering profile. Accurate profiling must be obtained in order to be effective. What is the Selective Soldering?For THT and mixed technology soldering applications, selective soldering, commonly referred to as mini-wave soldering, provides economical, consistent outcomes. Individually programmable and monitored soldering spots are used to regulate flux quantities and soldering time. Additionally, it is the only technique that can be repeated to solder THT components onto a two-sided PCB assembly.Selective Soldering Selective Soldering ProgressStep 1: Fluxing or the application of liquid flux.Step 2: Preheating of the PCB assembly.Step 3: Soldering with a site-specific solder nozzle. The advantages and disadvantages of Selective SolderingThe advantages of Selective SolderingSecure and fast process optimizationReliable solder joint creation without overheating componentsGuaranteed process repeatabilityThe elimination of expensive wave solder palletsThe ability to solder around tall parts with tight spacingThe ability to solder dense concentrations of THT pins The disadvantages of Selective SolderingSince each circuit board must have a customized program, the technique is time-consuming and not well suited for mass production.As there are several parameters, processing problems may occur. Wave Soldering VS Reflow SolderingHow do you decide which soldering technique to employ when? Pad shapes, how much time you have, component orientations, the type of printed circuit board, and other variables could all play a role. Wave soldering is more difficult in several aspects. Careful observation is required for factors like board temperature and the length of time the board is in the solder wave. Board flaws are far more likely to occur when the proper wave soldering environment is not created.When you use reflow soldering to create your printed circuit boards, you won't have to worry nearly as much about protecting the environment. Even yet, wave soldering is frequently more expedient and less expensive than reflow soldering. It is frequently the only feasible method of soldering a board. Reflow soldering is frequently employed for smaller-scale manufacturing projects that don't call for a technique that can be used for quick, low-cost mass production.Remember that in some circumstances you might be able to employ both reflow soldering and wave soldering. It is possible to wave solder components after reflow soldering them on one side. Additionally, you can always manually solder or hand solder PCB components, but if you have access to one of the mechanical techniques of soldering, this will rarely be a suitable strategy. Reflow soldering is still significantly superior, and manual soldering is simply a substitute for it. Selective Soldering VS Wave SolderingWhen it comes to Printed Circuit Boards with through-hole and bigger surface mount components, wave soldering is the best technique. On the other hand, selective soldering is advantageous for a densely populated board since it enables the consideration of a lot of factors. However, because it necessitates the development of a special program for every circuit board, it is inappropriate for mass production. Reflow Soldering VS Selective SolderingWhen producing a circuit board, through-hole components require the use of a selective soldering machine. Reflow is only suitable for SMT components because it only solders the board's top surface. However, all sides of through-hole components need to be soldered.Fewer businesses are using selective soldering for component assembly due to the high production capacity and ease of reflow oven soldering. There are simply too many benefits to ignore. Reflow ovens have replaced hand soldering as the predominant method of PCB assembly in the industry, whereas selective soldering was formerly far more common. In a given amount of time, a reflow oven can produce many more units.The assembly process is also made simpler. A solder ball (often a mixture of solder and flux) is deposited at the location of the joint after the components have been positioned on the board. The solder starts to flow plastically and form the solder junction when the board is conveyed through the oven. The board exits the oven and can either be used in the product of which it is a part or it can be transported to the person who will use it before the end user. Component assembly takes longer using selective soldering machines. They usually cost more money. Furthermore, assembling a lot of PCB designs doesn't need for intricate soldering. Reflow is frequently used by component manufacturers rather as selective soldering for this very reason. The conclusion of Wave Soldering VS Reflow Soldering VS Selective SolderingWave soldering is more challenging in various respects and close inspection is required for elements like board temperature and the amount of time the board remains in the solder wave, while Environmental preservation won't be a major concern when you employ reflow soldering to make your printed circuit boards. What’s more, wave soldering is frequently more expedient and less expensive than reflow soldering. So if you want to take the cost and environment into account, the wave soldering must be the best choice.Wave soldering is the optimum method for Printed Circuit Boards with through-hole and larger surface mount components. However, because selective soldering allows for the evaluation of numerous variables, it is favorable for a board that is densely packed. But selective soldering is not suitable for mass production, though, as it calls for the creation of a unique software for each circuit board.Due to the great production capacity and simplicity of reflow oven soldering, fewer companies are adopting selective soldering for component assembly. When employing selective soldering machines, component assembly takes longer. They typically have higher prices. Furthermore, complex soldering is not necessary for the assembly of many PCB designs. For this exact reason, component manufacturers commonly use reflow instead of selective soldering. PCB Soldering FAQWhat is the PCB soldering?Your circuit board is the PCB. As you use your soldering equipment to connect various components and terminals to one another and to the board, all of the soldering you conduct will occur on the surface of this board. What are the 4 types of soldering?Lead-free solder, lead-based solder, and flux-core solder are the three primary varieties of solder. The silver alloy solder is a different variety. These kinds are created using alloy composition. Other solder kinds exist as well, depending on the form, core type, and application. What is the difference between reflow soldering and wave soldering?There are two soldering methods that are completely distinct from one another: wave soldering and reflow soldering. In wave soldering, the components are joined together with the aid of a melted solder wave crest. Components are soldered using reflow, which is created by hot air, in reflow soldering. What is the difference between selective soldering and wave soldering?In contrast to wave soldering, which strikes all solder joints simultaneously, selective soldering progressively solders individual components using a local wave on an x-y gantry. However, additional benefits have made selective soldering the method of choice in many circumstances. What are the advantages of wave soldering?Components are held in place during reflow soldering without the use of adhesive. No need to mask off board sections that don't need to be soldered. Selective soldering equipment are typically less expensive to run. Each has adjustable parameters that can be more precisely regulated.

IntroductionA printed circuit board (PCB) mechanically supports and electrically connects electrical or electronic components using conductive tracks, pads and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. A PCB allows signals and power to be routed between physical devices.What are PCBs? How Do PCBs Work?CatalogIntroductionⅠ PCB Basics1.1 PCB MaterialsⅡ PCB Product CharacteristicsⅢ Common Sense of PCB ProcessⅠ PCB Basics1.1 PCB Materialsa. Copper Clad Laminate（referred to as CCL, or sheet material）Tg: Glass Transition Temperature, which is the temperature at which glassy substances are transformed between glassy and highly elastic (usually softened). In the PCB industry, this glassy substance is generally referred to as resin or dielectric layer composed of resin and glass fiber cloth. Tg is an important technical index reflecting the heat resistance of printed circuit board substrates. Generally, the higher the Tg value of printed circuit boards, the better the heat resistance. The Tg of general FR-4 copper-clad epoxy glass laminates for SMT printed circuit boards is 130 ～ 140℃, which can meet the requirements when using Sn-Pn solder. For lead-free solders with higher melting points, the Tg of the substrate can not withstand the high temperature of welding if the Tg ≤ 150 ° C. In special cases (high temperature use), the Tg can be greater than 170 ° C. However, excessive Tg will cause the hardness of the substrate to increase and the material to become brittle. Therefore, we cannot simply pursue high Tg. We should comprehensively consider the performance of the board and choose a suitable printed board substrate with a higher Tg, which is one of the requirements for lead-free welding.CTI: Comparative Tracking lndex (or comparative leakage index, tracking index). The highest voltage value that the surface of the material can withstand 50 drops of electrolyte (0.1% ammonium chloride aqueous solution) without the formation of leakage traces. The unit is V.CTE: Coefficient of thermal expansion. Generally, the sheet material performance of a PCB is measured by the linear expansion coefficient, which is defined as the ratio of the increase in length to the original length under a unit temperature change, such as Z-CTE. The lower the CTE value, the better the dimensional stability and vice versa.TD: Thermal decomposition temperature refers to the temperature at which the base material resin loses weight by 5%. It is a sign of delamination and performance degradation caused by the heat of the base material of printed circuit boards.CAF: Conductive Anodic Filament of printed boards is the phenomenon of electrochemical insulation damage on insulating substrates. It refers to the state where dendritic metals are precipitated between wires under the action of an electric field after a voltage is applied to parallel circuits on printed circuit boards. Or conductive anodic filament(CAF) occurs along the glass fiber surface of the substrate, thereby reducing the insulation between the wires.T288: It is a technical index that reflects the welding resistance of the printed circuit board substrate. It refers to the maximum time that the printed circuit board substrate can withstand the high temperature of welding at 288°C without blistering and delamination. The longer this time, the better it is for welding. For traditional Sn-Pb alloys with low welding temperature (220 ～ 230℃), when the thermal decomposition time of printed circuit board substrate is 260 ℃, T260≥30s can meet the requirements of SMT printed circuit board. For lead-free welding, the temperature is generally 250 ~ 260℃, the thermal decomposition temperature of the substrate of the printed circuit board will increase, and only T288≥300s at 288 ℃ can ensure that the substrate does not decompose and the performance is not damaged during welding.DK: dielectric constant.DF: Dissipation factor refers to the ratio of the energy that has been lost in the insulation sheet material of the signal line to the energy that still exists in the line.OZ: oz is the abbreviation of the symbol ounce, which is British measurement unit and also unit of weight. 1 OZ means the thickness of copper with a weight of 1 OZ evenly spread over an area of 1 square foot (FT2). It is the average thickness of copper foil expressed by the weight per unit area. It is expressed by a formula, that is, 1OZ = 28.35g / FT2. b. Copper FoilED Copper Foil: Electrodeposited copper, copper foil commonly used in PCB, cheap.RA Copper Foil: Rolled annealed copper, copper foil commonly used in FPC.Drum Side: smooth side of electrodeposited copper foilMatt Side: rough side of electrodeposited copper foilCopper: Elemental symbol Cu, atomic weight 63.5, density 8.89 g / cm3, and the electrochemical equivalent of Cu2 + is 1.186 g / Ah. c. Prepreg: referred to as PPEpoxy Resin: an organic polymer compound containing two or more epoxy groups in the resin molecule, which is a resin component used in prepregs that are currently commonly used.DICY: Dicyandiamide, a common hardenerR.C: resin contentR.F: resin flowG.T: gel timeV.C: volatile contentHarden: Under certain conditions (high temperature, high pressure or light), the epoxy resin and the hardener undergo cross-linking polymerization to form a polymer with a three-dimensional mesh structure. d. InkViscosity: Viscosity refers to the relative movement between adjacent fluid layers when fluid is flowing, and frictional resistance will be generated between the two fluid layers. Unit: Pascal. Seconds (pa.s).Hardness: The hardness of the ink after pre-baking is 2B, the hardness of the ink after exposure is 2H, and the hardness of the ink after finishing is 6H. Thixotropic: a property that the ink is gelatinous when it is left to stand, but its viscosity changes when it is touched. It is a physical property of a liquid, that is, its viscosity decreases under agitation, and it will return to its original viscosity soon after standing. By stirring, the thixotropic effect lasts for a long time and it is enough to reconstitute its internal structure. To achieve high-quality screen printing, the thixotropic of the ink is very important. In particular, during the squeegee process, the ink is agitated to make it liquid. This action speeds up the speed of ink passing through the mesh, and promotes the original ink with separate wires to be evenly integrated. Once the squeegee stops moving, the ink returns to a stationary state, and its viscosity quickly returns to the original required data. e. Dry Film· Structure of dry film Figure 1. Structure of Dry Film· Dry film consists of three parts and ingredients:   — Supporting film(Polyester)   — Photo-resist dry film   — Covering film(Polyethylene)· Main ingredients① Binder(film-forming resin) ②Monomer ③Photo-initiator ④Plasticiser ⑤Adhesion promoter ⑥Thermal polymerization inhibitor ⑦Dye ⑧Solvent· The types of dry film are divided into three types according to the different methods of developing and removing the dry film: solvent-based dry film, water-soluble dry film, and peel-off dry film; according to the purpose of dry film, it is divided into: dry resist film, masking dry film and solder mask dry film.· Photosensitivity: It refers to the amount of light energy required for the photoresist to react to form a polymer with a certain resistance under the irradiation of ultraviolet light. In the case of constant light source intensity and light distance, the sensing speed is expressed as the length of exposure time. Short exposure time means that the sensing speed is fast.· Resolution: refers to the number of lines (or intervals) that can be formed by the dry film resist within a distance of 1mm. The resolution can also be expressed by the absolute size of the lines (or intervals). f. Net YarnNet density:— T number mesh number: refers to the number of meshes within 1 cm. g. Drill bit· geometry structure name of drill bitFigure 2. Geometry Structure Name of Drill Bit· Point AngleThe point angle is composed of two narrow and long first point angle surfaces and two triangular hook-shaped second point angle surfaces. These four sides meet at the point angle, forming two short edges called chisel edges at the center of the joint. This is the place that the sheet material first touches. This chisel edge is first positioned under pressure and rotation to drill into the stack. A protruding square strip on each of the two outer sides of the first point angle surface is called a margin. This margin tends to spiral upward along with the drill body part, which is the contact part between the drill pin and the hole wall. The right angle at the intersection of the margin and the edge lip is very important to the quality of the hole wall. The point angle has a long edge between the first and second point angle surfaces. The point where the two long edges and the two chisel edges meet in the middle is the point angle. The angle formed by the two long edges is called the point angle. When the drilling paper is made of phenolic resin substrate, the drill point angle is about 90° ~ 110° due to less resistance. When drilling paper is FR4 glass fiber board, the point angle should be slightly blunt at 115° ~ 135°. The most common one is 130°. The angle between the first point angle surface and the horizontal plane of the long edge is about 15°, which is called primary face angle. The second point angle is about 30°, and the angle formed by the chisel edge and the edge lip is called a cheisel edge angle. · Types of drill bitFigure 3. Types of Drill Bit Ⅱ PCB Product Characteristics1) Impedance· The sum of resistance and reactance (capacitance, inductive reactance) on a vector. Common impedance types are characteristic impedance and differential impedance.2) Warpage· Maximum bow (Figure a) and twist (Figure b) of printed circuit boards using surface mount components should be less than or equal to 0.75%3) RoHSRoHS, the abbreviation of restriction of hazardous substances, is the restriction of the use of certain hazardous substances in electrical and electronic equipment. RoHS lists a total of six harmful substances, including: lead(Pb), cadmium(Cd), mercury(Hg), hexavalent chromium( Cr6+), polybrominated diphenyl ether(PBDE), polybrominated biphenyl(PBB).4) BacklightIt is an enlarged visual inspection method to check the integrity of the copper wall of the through hole. The method is to carefully thin the substrate outside the hole wall from a certain direction, and then use the principle of resin translucency to shoot light from the back. If the quality of the chemical copper hole wall is intact and there is no any holes or pinholes, the copper layer must be able to block light and be dark in the microscope. Once there are holes in the copper wall, light spots must appear and be observed , and can be enlarged as photographic evidence. The ground sample is about 4-6mm wide.Figure 5. Backlight Standard Diageam5) Anode Phosphor Copper Ball· Purity requirementsElementContent(%)ElementContent(%)Cu≥99.91Ni≤0.002P0.040-0.06Sb≤0.002Pb≤0.002As≤0.002Fe≤0.0025S≤0.002Sn≤0.002O≤0.002 · Features— A black (or brown-black) film forms on the surface of phosphor copper after power is applied.— Black (or brown-black) film is Cu3P, also called phosphor copper anode film.· Role of phosphor copper anode film— The anode film itself can catalyze and accelerate the (Cu+-E → Cu2+) reaction, thereby reducing the accumulation of CU+.— After the anode film is formed, it can inhibit the continuous generation of Cu+.— The electrical conductivity of the anode film is 1.5X104-1 cm-1, which has metal conductivity.— Phosphor copper is less anodized than pure copper (1A / DM2 P0.04-0.065%, phosphor copper is less anodized than oxygen-free copper, 50MV-80MV) and will not cause anode passivation.— Anode film will greatly reduce the phenomenon of tiny grains falling off the anode.— Anode film prevents the copper anode from dissolving too quickly.6) Method for Estimating Surface Area of Electroplated Copper Anode· Method for estimating surface area of round titanium basket copper anode: pDLF/2p = 3.14 D = diameter of titanium basket L = length of titanium basket F = factor· Method for estimating surface area of square titanium basket copper anode: 1.33LWFL = length of titanium basket W = width of titanium basket F = factor· F is related to the diameter of the copper ball:Diameter = 12 mm    F = 2.2Diameter = 15 mm    F = 2.0 Diameter = 25 mm    F = 1.7Diameter = 28 mm    F = 1.6 Diameter = 38 mm    F = 1.27) ICD IssuesInternal Connection Defects Ⅲ Common Sense of PCB Processa. Etching FactorThe index used to consider the amount of etching lateral erosion, because the amount of lateral erosion will be different for different copper thickness, so the etching factor is different from the total copper thickness.Calculation method:b. Lateral ErosionThe etching of the side wall of the wire under the resist pattern is called lateral erosion, and the degree of lateral erosion is expressed by the width of the side etching:· lateral erosion is related to the type, composition and etching process and equipment of the etching solution. c. Pool EffectDuring the etching process, the circuit board passes through the etching machine horizontally. Due to the gravity acting on it, the fresh medicine is blocked by the old one and cannot effectively react with the copper surface. d. Different Stages of ResinsA-stage resin: Some thermosetting resins are liquid in the early stages of manufacture or liquid when heated, and can still dissolve in some liquids at this time.B-stage resin: Some thermosetting resins can soften when heated in the middle stage of the reaction, but they cannot be completely dissolved or melted. At this time, they can swell or partially dissolve when contacted with some solvents.C-stage resin: The later stage of the reaction of some thermosetting resins, when it is practically insoluble or infusible. e. Font Color of SubstrateRed font: flame retardant grade, other fonts: non flame retardant grade. f. OthersMSDS: Material Safety Data Sheet provides a variety of information on safety, health and environmental protection for chemical substances and products, and can provide information on basic knowledge, protective measures and emergency actions of chemicals. In some countries, MSDS is also called SDS, and SDS terminology is used in ISO 11014.SGS: Societe Generale de Surveillance S.A. Founded in 1887, it is currently the world's largest and oldest non-governmental third party engaged in product quality control and technical certification of multinational companies. Headquartered in Geneva, it has 251 branches around the world, 256 professional laboratories and 27,000 professional and technical personnel, and carries out product quality inspection, monitoring and assurance activities in 142 countries.UL: UNDER WRITERS LABORATORIES INCIPC: The Institute for International and Packaging Electronic CircuitsISO: International Standards OrganizationMIL: Military StandardJPC: Japan Printed Circuit AssociationCOV: Coefficient of variationFR4: Abbreviation for Flame Retardant Type 4. It is the name of a flame-resistant printed circuit board material composed of a composite material of glass fiber and epoxy resin. It is the most widely used printed circuit board. g. pH ValueAlso known as the hydrogen ion concentration index and pH value, it is a scale of the hydrogen ion activity in a solution, which is a measure of the acidity and alkalinity of a solution in the usual sense. The concept was proposed by Danish biochemist Søren Peter Lauritz Sørensen in 1909. P stands for German Potenz, which means strength or concentration, and H stands for hydrogen ion (H +). Sometimes pH is also written in Latin as pondus hydrogenii.Under normal conditions (25°C, about 298K), when pH <7, the solution is acidic, when pH> 7, the solution is alkaline, and when pH = 7, the solution is neutral. h. Hull Cell TestHull designed Hull cell in 1939. The Hull cell test only requires a small amount of plating solution. After a short time test, the plating effect of the plating solution can be obtained in a wide range of current density. Because this test is sensitive to the composition and operating conditions of the plating solution, it is commonly used to determine the concentration and pH value of each component of the plating solution, and to determine the current density range for obtaining a good coating. The Hull cell has become an indispensable tool for electroplating research and electroplating process control.Hull cells are usually made of insulating materials such as plexiglass or rigid polyvinyl chloride. The bottom surface is trapezoidal, and the cathode and anode are placed on two sides that are not parallel. There are five types of capacity: 250ml, 267ml, 320ml, 534ml, and 1000ml. Generally, 250ml plating solution is often added to a 267ml test cell, which is convenient for converting the additives into how many grams per liter.Figure 8. Dimensions of Hull Celli. Current Density A / dm2A/dm2 — how many amperes per square decimeter area, 1A / dm2 — This is the current density of electroplating, which means that the current passes through the plating area of the workpiece per square decimeter is 1A and dm means decimeter. Generally, we use a 267ml Hull cell, place the test piece at the cathode and immerse it in the test solution. The area of the test piece is approximately 1dm2. j. TP: THROUGH POWERCalculation method:k. Replacement ReactionA replacement reaction is a chemical reaction in which a simple substance reacts with a compound to form another simple substance and a compound. Any replacement reaction is a metathesis reaction, including a reaction of metal and metal salt, the reaction of metal and acid, etc.; the replacement reaction must be a redox reaction, and the redox reaction is not necessarily a replacement reaction; the replacement reaction occurs according to the active list of metals. l. EDS：Energy Dispersive X-ray SpectroscopyThe surface of the sample being tested is irradiated with a condensed electron beam. Due to the interaction between the electron beam and the sample, various electrons or X-rays, photons, and other information are generated. Then, this information is collected and processed in different ways to display various characteristics of the sample (morphology, microstructure, composition, crystal plane, etc.) m. SEM：Scanning Electron MicroscopeAn electron beam with a diameter of 20 mm to 30 mm emitted from the cathode of the electron gun is accelerated by the voltage between the cathode and the anode, and is directed toward the lens barrel, and is condensed by the condenser lens and the objective lens, and is reduced into an electron probe with a diameter of about several nanometers. Under the action of the scanning coil on the upper part of the objective lens, the electron probe scans the surface of the sample in a raster pattern and excites a variety of electronic signals. These electronic signals are detected by corresponding detectors, amplified, converted into voltage signals, and finally sent to the grid of the picture tube and modulate the brightness of the picture tube. The electron beam in the picture tube is also raster scanned on the phosphor screen, and this scanning movement is strictly synchronized with the scanning movement of the electron beam on the sample surface, so that a scanning electron image corresponding to the contrast and the intensity of the received signal is obtained. The image reflects the topographical features of the sample surface. n. BONDINGBonding is a wiring method in the chip production process. It is generally used to connect the chip's internal circuit with gold or aluminum wires to the package pins or gold-plated copper foil on the circuit board before packaging. Ultrasonic waves from an ultrasonic generator (generally 40-140KHz), which generates high-frequency vibration through the transducer, are transmitted to the splitter through the horn. When the splitter is in contact with the lead wire and the welded part, under the action of pressure and vibration, the surfaces of the metal to be welded rub against each other, the oxide film is destroyed, and plastic deformation occurs, causing the two pure metal surfaces to closely contact each other to achieve the combination of atomic distance, and finally form a strong mechanical connection. After bonding (ie, after the circuit is connected to the pins), the chip is packaged with black glue. o. The Giovanni EffectIt means that due to the potential difference between two metals, an electric current is generated through the medium, and then an electrochemical reaction occurs, and the anode with a high potential is oxidized. p. Vacuum Degree; Degree of VacuumThe degree of thinness of the gas under vacuum is usually expressed by "high vacuum" and "low vacuum", high vacuum indicates "good" vacuum, and low vacuum indicates "poor" vacuum. If the pressure in the device under test is lower than atmospheric pressure, a vacuum gauge is required for pressure measurement. The value read from the vacuum gauge is called the degree of vacuum. The degree of vacuum is a value indicating that the actual value of the system pressure is lower than the atmospheric pressure, that is: the degree of vacuum = atmospheric pressure-absolute pressureThere are usually two ways to identify the degree of vacuum:   — First, it is marked with "absolute pressure" and "absolute vacuum degree" (that is, how much pressure is higher than "theoretical vacuum"); in actual cases, the absolute pressure value of the vacuum pump is between 0 and 101.325KPa. The absolute pressure value needs to be measured with an absolute pressure meter. The initial value of the gauge (absolute vacuum gauge) for measuring the vacuum degree at 20°C and the place where the altitude = 0 is 101.325KPa (ie, a standard atmospheric pressure).   — The second is to use "relative pressure" and "relative vacuum degree" (that is, how much pressure is lower than "atmospheric pressure") to identify. "Relative vacuum degree" refers to the difference between the pressure of the measured object and the atmospheric pressure at the measurement site and is measured with an ordinary vacuum gauge. In the absence of vacuum (that is, at atmospheric pressure), the initial value of the gauge is 0. When measuring vacuum, its value is between 0 and -101.325KPa (usually expressed as a negative number).Commonly used vacuum units are Pa, Kpa, Mpa, atmospheric pressure, kilogram (Kgf / cm2), mmHg, mbar, bar, PSI, etc. The approximate conversion relationship is as follows:   — 1MPa = 1000KPa   — 1KPa = 1000Pa   — 1 atmospheric pressure = 100KPa = 0.1MPa   — 1 atmospheric pressure = 1 kg (Kgf / cm2) = 760mmHg   — 1 atmospheric pressure = 14.5 PSI   — 1KPa = 10mbar   — 1bar = 1000mbar Frequently Asked Questions about PCB Basic1. What is PCB and types of PCB?A printed circuit board (PCB) is a thin board made from fiberglass, composite epoxy, or other laminate materials. PCBs are found in various electrical and electronic components such as beepers, radios, radars, computer systems, etc. Different types of PCBs are used based on the applications. 2. What is the basis of PCB?PCB is the acronym of Printed Circuit Board, a mechanical base that contains tracks and footprints reflecting the schematic of the design. Modern PCBs are typically made of a non-conductive substrate that is overlayed by copper layers. 3. What are the basic steps of PCB design?Here's the full list of PCB layout and design steps:Create the Schematic.Create a Blank PCB Layout.Schematic Capture: Linking to Your PCB.Designing Your PCB Stackup.Defining Design Rules and DFM Requirements.Place Components.Insert Drill Holes.Route Traces. 4. What are the common types of PCB?Common Types of Printed Circuit BoardsSingle Layer PCB. Single layer printed circuit boards are among some of the simplest to design and manufacture. ...Double Layer PCB.Multi-Layer PCB.High Density Interconnect (HDI) PCB.High Frequency PCB. 5. Which material is used in PCB?copper circuitryPrinted circuit boards (PCBs) are usually a flat laminated composite made from non-conductive substrate materials with layers of copper circuitry buried internally or on the external surfaces. They can be as simple as one or two layers of copper, or in high density applications they can have fifty layers or more.

Warm hints: The word in this article is about 3000 words and  reading time is about 10 minutes.   The transformer is a static electrical device, mainly composed of an iron core (or magnetic core) and coil. The coils have two or more windings, of which the ones connected to the power are called primary coils, and the rest are called secondary coils. Transformers are widely used in electrical equipment such as household appliances, electronic equipment, switching power supply, and so on. Circuit symbols commonly used T as the beginning of the number, for example, T01, T201.    This article covers the construction, functions, classification, and design of transformers and materials used for building magnetic cores in transformers.     Catalogs   I. The Composition of Transformer II. The Construction and Functions of Transformer III. High-frequency Transformer Design Program 3.1 Program structure 3.2 Matters needing attention when doing the core material   selection 3.3 Ferrite magnetic material requirements IV. Power Transformer Classification V. Principle and method of Transformer Design FAQ   I. The Composition of Transformer 1）The primary side 2）The secondary side 3）Magnetizing inductance 4）Leakage inductance 5）Open-circuit or short-circuit measurement of the primary side leads to the  Magnetic inductance and the leakage inductance turns ratio respectively:  K=Np/Ns=V1/V2   II. The Construction and Functions of Transformer 1) Electrical isolation 2) Energy storage 3) Voltage change for same power input.   III. High-frequency Transformer Design Program   3.1 Program structure (1) Core material (2) Core structure (3) Core parameters (4) Transformer Winding Parameter (5) package assembly (6) Temperature rise check   (1) Core material Soft magnetic ferrite is widely used in switching power supply because of its own characteristics. It has the advantages of high resistivity, low AC eddy current losses, low price, and easy to be machined into magnetic cores of various shapes. The disadvantages are low working magnetic flux density, low permeability, large magnetostriction, and high sensitivity to temperature changes. Which kind of soft magnetic ferrite material can satisfy the design requirement of a high-frequency transformer more fully, only when it is carefully considered and the transformer design can reach the high-cost performance.   (2) Magnetic core structure The factors considered in the selection of magnetic core structure are as follows: reducing magnetic leakage and leakage inductance, increasing the area of coil heat dissipation, which is beneficial for shielding and makes it easier to wind coils, more convenient to wire for assembly and so on.   The magnetic leakage and leakage inductance are directly related to the magnetic core structure . If the magnetic core does not need air gap, then a enclosed ring-like or square type magnetic core may be used as far as possible.   (3) Magnetic core parameters In the design of core parameters, special attention should be paid to the operating flux density only limited by the magnetization curve, but also by the losses, and also related to the working mode of power transmission. When the flux changes in one direction, there is ΔB=Bs-Br, which is not only limited by the saturation flux density but also mainly by the losses (Losses cause temperature rise, which in turn affects magnetic flux density). The operating flux density Bm=0.6～0.7ΔB.   An air gap can decrease Br and therefore increase the flux density ΔB. The exciting current can be increased after using an air gap opening, but the core volume can be decreased either. For the two-way operation of magnetic flux, the flux density ΔB is twice the maximum operating flux density Bm, that is ΔB=2Bm. In bidirectional operating mode, we should pay attention to the problem of transformer DC magnetic bias due to the inequality of volt-second areas of positive and negative excitation variation, which is caused by different reasons. A small air gap will be needed in the core, or a DC capacitor can also be added to the circuit design.   Magnetic properties of ferromagnetic materials Magnetic hysteresis loops of the core   (4) Coil parameters Coil parameters include: turns, conductor section (diameter), wire form, winding arrangement and insulation. The conductor section (diameter) depends on the current density of winding, using taking 2.5～4A/mm2. When doing some choosing of section conductor diameter don’t forget to take the skin effect into consideration and do regulations necessary after some temperature rise tests of the transformer.   General winding arrangements: the primary winding is close to the core and the secondary windings & feedback windings are gradually arranged outward. The following two winding arrangements are recommended:   1) If the voltage of the original windings is high (for example, 220V) and meanwhile that of the secondary windings is low, a more appropriate arrangement is the secondary winding being close to the core, and then goes the feedback winding, the original winding is arranged on the outermost ends, which is advantageous to the insulation arrangement of the original winding to the core;   2) If we want to increase the coupling between the primary and secondary windings, we can make half of the original windings be close to the core, then goes the feedback winding and secondary winding, and the other half of the original winding being the outermost ends, which is an arrangement advantageous to reduce the leakage inductance.   (5) Assembly structure The assembly structure of high-frequency power transformers are divided into horizontal and vertical types. If you'd like to select the planar core, sheet magnetic core and thin-film magnetic core, then a horizontal-type assembly would do you good.   (6) Temperature rise tests The temperature rise tests can be carried out by calculation and sample test. The temperature rise is lower than the allowable temperature rise above 15 degrees, the current density and the cross-section of the wire are appropriately increased. Appropriately increase the current density and decrease the cross-section of the wire, and do the exact opposite if temperature rise exceeds the allowable value, such as increasing the diameter or enlarging the core if necessary, to increase the area of coil heat dissipation.       3.2 Matters needing attention when doing the core material selection (1) Soft ferrite, due to its low price, good adaptability, and high performance at high frequency, has been widely used in switching power supply.   (2) Soft ferrite is commonly divided into two series: Mn-Zn ferrite and Ni-Zn ferrite. The Mn-Zn ferrite is composed of Fe2O3，MnCO3，ZnO and so on, which is widely used in all kinds of filters, inductors, transformers, and so on below 1MHz. The Ni-Zn ferrite is composed of Fe2O3，NiO，ZnO and so on, which is widely used in all kinds of adjustable inductor windings, anti-jamming magnetic beads, antenna matching devices, and so on above 1MHz.    (3) Mn-Zn ferrite is the most widely used core in switching power supply, and the selection of its material depends on its use. The core for the input filter part of the power supply is mostly high-conductivity magnetic core, and its material number mostly is R4K～R10K, that is, the ferrite core of relative permeability is about 4000~10000, but the main transformer and output filter are magnetic materials with high saturation flux density, where Bs is about 0.5T (5000GS).     3.3 Ferrite magnetic material requirements   Ferrite magnetic materials for switching power supply shall meet the following requirements:   (1) High saturation flux density Bs and low residual flux density Br   The residual flux density Bs has a certain influence on the transformer and winding results. Theoretically speaking, the number of turns of transformer windings can be reduced and the copper loss can be reduced because of the high Bs. In practical applications, there are different types of circuits of high-frequency converters in switching power supply.    For transformers, their operations can be divided into two categories:   1) Bipolar: The circuit topologies include half-bridge, full-bridge, push-pull, etc. In the primary winding of the transformer, the excitation current is equal and opposite in direction during the positive and negative half-cycles. Therefore, the magnetic flux changes in the magnetic core of the transformer are symmetrically moved up and down. The maximum variation range of B is  ΔB=2Bm, and the DC component of the magnetic core is basically canceling out.   2) Unipolar: The circuit topologies include single-ended forward, single-ended flyback, etc. The transformer primary winding adds a unidirectional square wave pulse voltage in one cycle (this is the case for single-ended flyback). The magnetic flux density varies from the maximum Bm to the residual flux density Br in the unidirectional-excitation transformer core. If we decrease the Br and increase the saturation flux density Bs, then the △B will be increased, and the turns and copper loss will also be reduced.   (2) Transformers or inductors are divided into three categories according to their topology:   1) An DC-filter inductor's magnetic core only works in one quadrant, the topologies of this operating state including Boost, Buck, buck/boost inductors, single end flyback converter transformer, forward and all push-pull converters and output filter inductors.   2) The core of the transformer in the forward converter also works in one quadrant, but the transformer needs to magnetic reset.   3) The core of the transformer with push-pull topology is in bidirectional alternating magnetization. These kinds of converters include push-pull, half-bridge and full-bridge converters, AC filter inductors, and so on.   (3) Low power loss at high frequency   The power loss of ferrite not only affects the power output efficiency but also leads to the heating of the magnetic core and waveform distortion.   The heating problem of the transformer is very common in practical applications, which is mainly caused by copper loss and core loss of the transformer. If the selected Bm is too low and the turns of winding are too many, it will cause the winding to heat up and transfer the heat to the core at the same time, and vice versa.   When selecting the ferrite material, we must make the power loss change with temperature characterized by a negative temperature coefficient. This is because if the core loss is the main heating, making the transformer temperature rise up, which then will lead to a further increase of core losses, thus it will form a vicious circle and eventually make the power tube, transformer, and other components burn down. Therefore, in the researches of power ferrite at home and abroad, we must solve the problem of negative temperature coefficient of magnetic material power loss itself, which is also a remarkable feature of magnetic materials having met the requirements for power supply applications, such as PC40 from Japanese company TDK and R2KB from China manufacturers and so on.   (4) A relatively moderate permeability   (5) How we choose the appropriate relative permeability?    Well, this depends on the switching frequency of your actual circuit, mostly 2000, meanwhile its applicable frequency must be below 300kHz, and sometimes can be a little higher, but the maximum will not be higher than 500 kHz.   (6) A relatively high Curie temperature   Curie temperature is the temperature at which a magnetic material loses its magnetic properties, generally above 200 ℃. However, the actual operating temperature of the transformer should not be higher than 80℃, at which the saturation flux density Bs will drop to 70% of that at the normal temperature when the temperature is above 100℃. That is, the saturation flux density of the core will drop more seriously when the operating temperature is too high. Furthermore, when the temperature is higher than 100℃, the power loss has been experiencing a positive temperature coefficient, which will lead to a vicious circle. For R2KB2 materials, the temperature corresponding to the allowable power consumption has reached 110℃ and the Curie temperature is up to 240℃, which meets the requirements of high-temperature use.     IV. Power Transformer Classification Power transformers are divided into three categories according to their topology: (1) Flyback transformers; (2) Forward transformers; (3) Push-pull transformers (full-bridge/half-bridge converters)   The appropriate topologies for various core structures are shown in the following table:   Core structureTypes of converter circuitFlybackForwardPush-pullE cores++0Planar E Cores-+0EFD Cores-++ETD Cores0++ER Cores0++U Cores+00RM Cores0+0EP Cores-+0P Cores-+0Ring Cores-++    "+"=fit; "0"=normal; "-"=unfit Summary of High frequency transformer core.XLS V. Principle and Method of Transformer Design   (1) There are two main ways to design transformer: Area Product (AP) Method AP: The product of core effective cross section Ae and Area of window Aw PT-The calculation power of the transformer Ae-Core effective cross section Aw- Area of window Ko-Core window utilization coefficient, typically 0.4 Kf-Waveform coefficient, usually square wave being 4 and sine wave being 4.44 Bw-The operating magnetic intensity of core FS-Switching frequency Kj-Current density coefficient, usually 395A/cm2 X-Core structure coefficient     (2) According to the area product (AP) method, the general steps of designing transformer are as follows: 1. Select the core material to calculate the apparent power of the transformer; 2. Determine the core cross section AP and select the core size according to AP value; 3. Calculation of the primary side inductance and the number of turns; 4. Calculation of the length of air gap; 5. Calculating the line diameter according to the current density and the secondary side RMS current. 6. Determine whether the copper loss and iron loss meet the requirements (eg allowable loss and temperature rise)   Selecting the flyback topology, the basic parameters of the power supply are as follows: Input voltage: 175-264 VAC Output voltage: 21V Output current: 3A Output power P0=63W Frequency set at 60Khz Duty cycle set at 0.45 initially   1) Select the core material to determine the apparent power PT of the transformer   and select the PC40 material here considering the cost factor and check the PC40 data to get Bs=0.39T, Br=0.06T. In order to prevent the core from becoming saturated instantly, a certain margin is reserved. Let Bm= ΔBmax*0.6=0.198T, and pick up the 0.2T. For flyback topology, the transformer apparent power PT is:   2) Calculating AP values with Excel tables   Where, J is the current density, usually 395A/cm2, and Ku is the effective use coefficient of copper window, usually 0.2～0.4, now we set Ku as 0.4.    Based on the figure above, we select the core EE3528 due to its being greater than the calculated AP value, with the following parameters: Ae: 84.8mm2 AP：1.3398cm4 Wa：158mm2 AL：2600nH/H2 In order to adapt to the abrupt load current, the power supply is designed in critical mode and the critical current is: I0B=0.8×I0=2.4A     3) Calculation of the primary side inductance and the number of turns (A) Minimum input voltage Vimin=ViACmin*1.2=210V (B) Turns ratio n=[Vimin/(V0+Vf)]*[Dmax/(1-Dmax)] n=[210V/(21V+1V)*[0.45/(1-0.45)] n=7.8 (C) Peak secondary current ^IsB=2*IoB/(1-Dmax) ^IsB=2*2.4A/(1-0.45) ^IsB=8.72A (D) Secondary inductance Ls=(V0+Vf)*(1-Dmax)*[1/(Fs*1000)]/^IsB*1000000 Ls=(21V+1V)*(1-0.45)*[1/(60Khz*1000)]/8.72A*1000000 Ls=23.58Uh (E) Primary inductance Lp=n*n*Ls Lp=7.8*7.8*23.58uH Lp=1434uH   Primary and secondary peak currents (F) Calculation of peak secondary current in continuous mode ^Isp=Io/(1-Dmax)+(^IsB/2) ^Isp=3A/(1-0.45)+(8.72A/2) ^Isp=9.81A (G) Calculation of peak primary current in continuous mode ^Ipp=^Isp/n ^Ipp=9.8A/7.8 ^Ipp=1.257A (H) Calculating the turns of the primary and secondary auxiliary windings a) Number of turns in the primary side Np=Lp*^Ipp/(^B*Ae) Np=1434uH*1.257A/(0.2*84.8) Np=106.28T After rounding: Np=106T b) Number of turns in the secondary side Ns=Np/n Ns=106T/7.8 Ns=13.58T After rounding: Ns=14T c) Number of feedback turns Nv=(Vcc+Vf)/[(V0+Vf)/Ns] Nv=(14.5V+1V)/[(21V+1V)/14T] Nv=9.87T After rounding: Nv=10T   To avoid core saturation, an appropriate air gap is added to the magnetic loop, the calculation go as follows: The number of turns may need to be corrected by the air-gap flux edge effect.   4) There are two ways to calculate the wire diameters of the primary, secondary and auxiliary windings: Effective current of original side diameter: Iprms=Po/^n/Vimin Iprms=63W/0.8/210V Iprms=0.375A (A) Calculating the area of bare wire (B) Calculating the wire diameter (current density J to take 4A/mm2) Using two 0.18mm-diameter wires wound around or AWG #28 a single strand The secondary diameter: Use four wires with a diameter of 0.25mm (AWG #31) and wind around. Calculation of Skin Depth: The diameter of multi-strand parallel winding must be less than or equal to dwH, in single wire winding, however, if the diameter exceeds the dWH value,  the multi-strand wire winding should be taken into account.   5) Calculation of copper loss Pcu and iron loss Pfe (total transformer loss Ploss) (A) Calculating the loss of primary and secondary windings.  Where, MLT is the average turn length of magnetic core (B) Calculating the allowable total loss Ploss and allowable iron loss at efficiency η (C) According to the loss curve of iron core, the actual loss (iron loss per unit weight and actual iron loss) is obtained by: The Ploss is the loss of the whole circuit, including diode/MOSFET losses and other losses, the actual losses Pfe must be much smaller than the calculated one, so here is only for reference. (D) Calculating the loss per unit area by Φ=Ploss/As If the temperature rise caused by Φ is less than 25 degrees, then the design is wonderful.   6) Calculating the BW The working flux density BW should be below Bs-Br within the design specifications, that is Bw<Bs-Br, to avoid saturation of the core.   FAQ   1. What is the use of transformer? Transformers are employed for widely varying purposes; e.g., to reduce the voltage of conventional power circuits to operate low-voltage devices, such as doorbells and toy electric trains, and to raise the voltage from electric generators so that electric power can be transmitted over long distances.   2. What are the 3 types of transformers? There are three primary types of voltage transformers (VT): electromagnetic, capacitor, and optical.   3. What is the basic principle of transformer? A transformer consists of two electrically isolated coils and operates on Faraday's principal of “mutual induction”, in which an EMF is induced in the transformers secondary coil by the magnetic flux generated by the voltages and currents flowing in the primary coil winding.   4. Does a transformer convert AC to DC? A transformer is built to transfer the energy from one circuit into another circuit by way of magnetic coupling. ... An alternating current creates a magnetic flux in the core on its way through the first winding, inducing the voltage in the others. It can convert high and low voltages, it cannot convert AC to DC.   5. What are the main parts of transformer? There are three basic parts of a transformer: a. an iron core which serves as a magnetic conductor, b. a primary winding or coil of wire and. c. a secondary winding or coil of wire.   6. What are the classification of transformer? Depending upon the type of construction used, the transformers are classified into two categories viz.: (i) Core type, and (ii) Shell type. Depending upon the type of service, in the field of power system, they are classified as: (i) Power transformers, and (ii) Distribution transformers.   7. Can a transformer work on DC? As mentioned before, transformers do not allow DC input to flow through. This is known as DC isolation. This is because a change in current cannot be generated by DC; meaning that there is no changing magnetic field to induce a voltage across the secondary component.   8. How do you convert a transformer? This conversion is made by winding two separate conductors around a common iron core. Applying an alternating voltage to the primary conductor produces current which sets up a magnetic field around itself. This is known as mutual inductance.   9. What are two components of no load current in transformer? The no-load current of a transformer consists of two components: The Magnetization Current iM is the current required to produce the flux in the transformer core. The Core-loss Current ih+e is the current required to make up for hysteresis and eddy current losses.   10. Which type of transformer core is most efficient? SHELL CORE. The most popular and efficient transformer core is the SHELL CORE, as illustrated in figure (4). As shown, each layer of the core consists of E- and I-shaped sections of metal. These sections are butted together to form the laminations.   You May Also Like: Analysis of Calculation Theory for Transformer Temperature Rise Some suggestions about protecting transformers Learn Some Basic Knowledge about Capacitor Voltage Transformer      

Warm hints: The word in this article is about 2800 words and  reading time is about 15 minutes.     Lithium-ion batteries can be said to be the most mature and widely used new energy sources in the world at present, such as portable electronic products like mobile phones and computers, electric vehicles, electric tools, and energy storage projects. Especially the current Chinese government and other countries are investing to support the development of new energy vehicles and power battery industries. Looking ahead, the lithium industry has a long way to go, such as the development of high energy density systems. The problems of further reduction of cost, the resources recovery, and the utilization are in front of us.   This article will mainly explain what is a lithium battery, then introduce the current situation and future development of lithium-ion battery materials.       Catalog I. What is A Lithium Battery? II. How Does the Lithium Battery Work? III. Distinction Between Lithium-ion Battery & Polymer Lithium Battery IV. Types and Characteristics of Material Used in Lithium Batteries V. Application of Lithium Battery VI. Future Development of Lithium Battery FAQ I. What is A Lithium Battery?   "Lithium battery" is a kind of battery that takes lithium metal or lithium alloy as negative electrode material and using a non-aqueous electrolyte solution. In 1912, lithium-metal batteries were first proposed and studied by Gilbert N. Lewis. In the 1970s, M.S. Whittingham proposed and began to study lithium-ion batteries.   Because of the active chemical characteristics of lithium metal, the environmental requirements of the processing, preservation, and use of lithium metal are very high. Therefore, lithium batteries have not been applied for a long time. With the development of science and technology, lithium batteries have become the mainstream now.   Lithium batteries can be roughly divided into two categories: lithium metal batteries and lithium-ion batteries. Lithium-ion batteries do not contain metallic lithium and are rechargeable. The fifth generation of rechargeable lithium metal batteries was born in 1996. Its safety, specific capacity, self-discharge rate, and the ratio of performance to price are superior to those of lithium-ion batteries, which are now produced by a few companies in only a few countries due to their own high-tech constraints.   Li-ion batteries are secondary battery system in which two different kinds of lithium intercalated compounds that can be inserted and removed as positive and negative electrodes respectively. When charged, lithium-ions are removed from the lattice of cathode materials. After the electrolyte is inserted into the lattice of the anode material, the negative electrode is rich in lithium, and the positive electrode is poor in lithium.   When discharged, the lithium-ion is removed from the lattice of the anode material, and then inserted into the lattice of the positive electrode material after the electrolyte, so that the positive electrode material is extremely rich in lithium while the negative electrode is poor in lithium. In this way, the difference between the potential of the cathode material and the lithium-ion when inserted and removed from the lithium metal is the working voltage of the battery.   Li-ion battery is a new generation of green high-energy battery with excellent performance and has become one of the key points in the development of high-tech.   Li-ion battery has the following characteristics: high voltage, high capacity, low consumption, no memory effect, no pollution, small volume, small internal resistance, less self-discharge, and more cycle times.   Because of the above characteristics, the lithium-ion battery has been applied to many civil and military fields, such as mobile phones, notebooks computers, cameras, digital cameras, and so on.   II. How Does the Lithium Battery Work?   The charging and discharging process of lithium battery is realized by the removal and embedding of lithium-ion in the positive and negative electrode of the battery. The reaction equation of the lithium-ion battery with iron phosphate liquid as an example is as follows:   Charging: Discharging:   The electrode reaction of Li/PEO-LiClO4/Pan polymer lithium-ion battery is as follows:   Positive electrode reaction: Negative electrode reaction： The working schematic diagram of lithium battery: Schematic-of-the-lithium-ion-battery-working-principle   1. The positive electrode structure:  LiMn2O4( lithium manganate ) + Conductive agent (acetylene black) + adhesive(PVDF) + Collector negative ( aluminium foil )electrode   2. The negative electrode structure:  Graphite+ Conductive agent (acetylene black) + adhesive(PVDF) + Collector negative ( copper foil )electrode   3. Charging process: The battery is charged by the power supply, and the electron e on the positive electrode runs from the external circuit to the negative electrode. Positive lithium-ion Li+ "jumps" from the positive electrode to the electrolyte, "climb" through the winding hole in the diaphragm, then "swim" to the negative electrode and combine with the electron.    The reaction on the positive electrode is: LiMn2O4 ==Li1-xMn2O4+Xli++Xe (electron).  The reaction on the negative electrode is:  6C+XLi+Xe==LixC6   4. Discharging process When the battery discharges, the electron e on the negative electrode runs from the external circuit to the positive electrode. Positive lithium-ion Li+ "jumps" from the negative electrode to the electrolyte, "climb" through the winding hole in the diaphragm, then "swim" to the positive electrode and combine with the electron.    The reaction on the positive electrode is: Li1-xMn2O4+xli++xe (electron) ==LiMn2O4 The reaction on the negative electrode is: LixC6 == 6C+xLi+xe III. Distinction Between Lithium-ion Battery & Polymer Lithium Battery   As the following table: Electrolyte for Polymer Lithium Battery PolymerElectrolytePure solid polymer electrolyteGel polymer electrolytePAn, PPY, PA, PPPPEO, PPOPAN,PMMA,PVdF   As the following diagram: Different electrolytes are the main differences between lithium-ion batteries and polymer lithium batteries. Diagram IV. Types and Characteristics of Material Used in Lithium Batteries (This is a tutorial on the Lithium Battery Explorer provides an overview of Li-ion battery technology and the properties that are relevant to battery researchers.)   1.Lithium manganate (LMO) LMO, as a kind of lithium battery material with a long history, has high safety, especially strong resistance to overcharge, which is a prominent advantage.   Because of the good structural stability of lithium manganate, the amount of cathode material does not have to exceed the negative electrode in the design of the electric core.   In this way, the number of active lithium ions in the whole system is small, and after the negative electrode is filled, there will not be too many lithium ions in the positive electrode. Even if overcharge occurs, there will not be a large number of lithium ions deposited in the negative electrode to form crystallization. Therefore, the overcharge resistance of lithium manganate is the best in common materials.   In addition, its material price is low, and the production process requirements are relatively low. It is a relatively early widely used cathode material.   But it also has obvious defects. The elevated temperature property of spinel lithium manganese oxide is poor. The existence of oxygen defect makes the core prone to capacity decay at the high voltage stage, at the same time, the cycle use at high temperature would cause a similar capacity decay. The reason is that the trivalent manganese ion which causes the disproportionation effect. The main way to prevent high-temperature attenuation is to reduce the trivalent manganese.   Lithium manganese, limited by its high-temperature performance, is generally not used in high-power or high-temperature environments, such as high-speed passenger vehicles, plug-in cars, and so on. But for electric buses, local logistics vehicles, and so on, lithium manganese is completely competent.     2. Lithium iron phosphate (LFP) The advantages of lithium iron phosphate are mainly reflected in its safety and cycle life. The main determinants are the olivine structure of lithium iron phosphate, which, on the one hand, leads to the lower ion diffusion capacity of lithium iron phosphate. On the other hand, it also has good high-temperature stability and good cycle performance.   The disadvantages of lithium iron phosphate are also obvious, such as low energy density, poor consistency, and poor low-temperature performance.     a) The low energy density is determined by the chemical properties of the material itself. A lithium iron phosphate macro-molecule can accommodate only one lithium-ion.   b)The consistency, especially poor batch stability, is related to not only the level of production management but also its own chemical properties. Lithium iron phosphate is one of the more difficult materials for the preparation of cathode materials for lithium-ion batteries.   The difficulty of consistency and uniformity in this chemical reaction raises another problem at the same time: The impurity of iron and iron in the lithium iron phosphate material always exists, which brings hidden trouble to the battery.   Lithium iron phosphate battery, because of its high safety, although The energy density part affects its range of use., but it is still the main power lithium battery variety of electric vehicle in our country at present, especially buses involving the safety of a large number of people, the national police enforce the use of lithium iron phosphate batteries.     3.Ternary lithium The ternary lithium cathode material synthesizes the advantages of LiCoO2、LiNiO2 and LiMnO2 and forms a synergistic effect within the same core. It combines three requirements of stability and activity of material structure and lower cost, which is one of the three main cathode materials with the highest energy density. The low-temperature performance is also obviously better than the lithium iron phosphate battery.    The higher the content of Ni in the three elements, the higher the energy density of the core and the lower the safety of the core will be. In practical application, the proportion relation of three kinds of materials in the electric core has been changing with the passage of time. The pursuit of energy density is higher and higher, so the proportion of Ni is higher and higher.   The most mentioned disadvantage of ternary material is safety. During the process of thermal runaway, the side reaction product contains a lot of gas, which greatly improves the risk of accident and the ability to spread.   Secondly, the cycle life of ternary materials is also a bottleneck, which has not reached the level of lithium iron phosphate. Last but not least, due to the special microstructure of ternary materials, it is not suitable for high-pressure compaction operation, thus the popular way to increase the energy density is not applicable to it.   The market share of ternary materials is gradually expanding, mainly driven by the pursuit of vehicle range. To catch up with or even surpass that of fuel vehicles, electric vehicles must have as much power as possible in a limited space.   This makes energy density particularly important. The improvement of the safety performance of the battery itself and the improvement of system monitoring and handling accident capability will also promote the expansion of the lithium ternary battery market.   V. Application of Lithium Battery   1. Lithium Iron Phosphate is the most suitable cathode material for Power Battery   After introducing the Types and characteristics of Lithium batteries above, now we will discuss about the most suitable cathode material for power supply.    Since 1996, when the Japanese NTT first exposed lithium iron phosphate cathode materials of olivine structure, John.B.Goodenough professor at Texas University also reported the characteristics of reversible intercalation and removal of lithium from LiFePO4 in 1997.   Since then, lithium iron phosphate has gradually become one of the low-cost, multi-element, and environmentally friendly cathode materials. Compared with traditional cathode materials, spinel LiMn2O4 of spinel structure and layered LiCoO2, the LiMPO4 of olivine structure is extremely stable.   The bond with oxygen is very strong, it will not explode because of the short circuit, the capacity is up to 170 mAh / g, the raw material is more extensive and the price is lower. Because of the similar structure of LiFePO4 and FePO4, the crystal structure of LiFePO4 has almost no rearrangement after the release/embedding of lithium-ion.   Therefore, LiFePO4 has better cycling performance, lithium-ion can enter and exit freely and can charge and discharge more than 1,000 times. It is also reported that lithium iron phosphate can be modified more than 10,000 times.   According to the following picture: Performance comparison of Lithium batteries with different cathode Materials.   Performance comparison Lithium iron phosphate is the most ideal cathode material at present. In comparison, the biggest problem of LiCoO is that it is easy to explode at a low temperature of 150C, and its cost is high (cobalt price is about 500,000 yuan/ton, and the price of LiCoO containing 60% cobalt will be over 400,000 yuan/ton). Also, it has a short cycle life.   The safety of lithium manganese oxide is much better than that of lithium cobaltate, but the cycle life in a high-temperature environment is even worse than that in a high-temperature environment(500 times).   With the advantages of high discharge power, low cost (about 18.3 million yuan/ton), rapid charging and long cycle life of more than 1000 times, the high stability of high temperature and high heat environment, and the good safety performance, lithium iron phosphate is the most ideal lithium cathode material for power vehicles.   At present, though the lithium iron phosphate battery is developing rapidly in China, there are several problems, including patent hidden trouble, low conductivity, and low capacitance, poor low-temperature performance, and low yield. VI. Future Development of Lithium Battery   Polymer Lithium Battery: one of the Future Development directions In addition to pure solid or gel polymer electrolytes, the principle and charge-discharge process of polymer lithium-ion batteries are consistent with those of liquid lithium-ion batteries.   Polymer lithium battery features include plastic flexible, more stable, safer, and less flammable, longer cycle life, higher energy density, high volume utilization(10-20% higher than lithium-ion batteries), no need to use traditional diaphragm materials, and easier for large scale production.   Polymer electrolyte is a kind of functional polymer material with ionic conductivity in solid-state which is formed by complexation of strong polar polymer and metal salt through acid-base reaction. Pure solid-state electrolyte dissolves lithium salts such as LiPF6, LiClO4, and LiBF4 in polymer bulk such as PEO and PPO as solid solvents. Gel electrolytes are electrolytes in a gel state by mixing more liquid solvents with polymer bulk.   Because there is no liquid flowing in the electrolyte, there is no leakage of the battery, so the problems such as burning and explosives are avoided. In order to reduce the thickness of the battery, a polymer lithium battery is usually packaged with aluminum plastic film with a thickness of only 0.1 mm, so it has a higher specific capacity than the ordinary lithium-ion battery.   FAQ   1. What is the difference between a lithium battery and a lithium ion battery? Lithium batteries feature primary cell construction. This means that they are single-use—or non-rechargeable. Ion batteries, on the other hand, feature secondary cell construction. This means that they can be recharged and used over and over again.   2. What are the disadvantages of lithium ion batteries? Despite its overall advantages, lithium-ion has its drawbacks. It is fragile and requires a protection circuit to maintain safe operation. Built into each pack, the protection circuit limits the peak voltage of each cell during charge and prevents the cell voltage from dropping too low on discharge.   3. Why is lithium ion the best battery? Li-ion batteries are able to be recharged hundreds of times and are more stable. They tend to have a higher energy density, voltage capacity and lower self-discharge rate than other rechargeable batteries. This makes for better power efficiency as a single cell has longer charge retention than other battery types.   4. What is the life of lithium ion battery? about two to three years. The typical estimated life of a Lithium-Ion battery is about two to three years or 300 to 500 charge cycles, whichever occurs first. One charge cycle is a period of use from fully charged, to fully discharged, and fully recharged again.   5. Is it good to fully discharge a lithium ion battery? Lithium-ion batteries should not be frequently fully discharged and recharged ("deep-cycled"). You may need to discharge it fully occasionally to recalibrate the capacitiy measuring electronics in the accumulator. Every 30 cycles or so should be enough.   6. How do I know if my lithium ion battery is bad? If the battery is dead or at the end of life, then it won't take charge anymore. If the battery is dead or at the end of life, the battery will swell a bit. The battery starts to heat up very quickly is also one of the indication that your battery is at the end of life.   7. Is there an alternative to lithium-ion batteries? Zinc-ion: A competitive alternative to lithium-ion for stationary energy storage. Lithium-ion batteries are the leading battery technology for both electric vehicles (EVs) and the renewable energy industry.   8. Do lithium ion batteries go bad if not used? Lithium Ion batteries "go bad" when they are stored in discharged state. It is all about battery voltage. If voltage is too low - undesireable chemical reactions will happen and battery will degrade. If battery is not empty and not used for long time - it will be fine.   9. What temperature is bad for lithium batteries? At temperatures above +60°C the Li-ion battery loses capacity constantly and thus performance capability.   10. At what voltage is a lithium ion battery dead? 3.4V. The voltage starts at 4.2 maximum and quickly drops down to about 3.7V for the majority of the battery life. Once you hit 3.4V the battery is dead and at 3.0V the cutoff circuitry disconnects the battery (more on that later. You may also run across 4.1V/3.6V batteries.     You May Also Like: How to Learn Analog Circuit Design Topological Materials are a Promising Material For Boosting Thermoelectric Generation Efficiency Use Polymer Films Material to Make Solar Cell Learn Some Basic Knowledge about Capacitor Voltage Transformer The First Full-Size IBC Bifacial Solar Module in the World