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CatalogⅠThe Definition of Fuse Box1.1 What is the fuse box1.2  History and problem of Fuse Boxes1.3 The working principle of fuse boxⅡ The fuse box in a carⅢ How to Replace Fuse Box?Ⅳ The difference of fuse box in UK and North America4.1 United Kingdom4.2 North AmericanⅤFuse Box vs Circuit Breaker5.1 What is the Circuit Breaker5.2 The Difference and ApplicationⅥ Frequently Questions About Fuse Box ⅠThe Definition of Fuse Box1.1 What is the fuse boxFuse boxes are metal boxes that hold fuses, which are safety devices that shut off power when the fuse's design is exceeded. Fuses function by passing an electric current through a metal strip. If the electrical current exceeds the metal strip's limitations, the strip melts and the power is out of work.Figure1: What does the fuse box look like?  1.2  History and the problem of Fuse Boxes Before the 1960s, fuse boxes were commonly installed in homes. The majority of them have now been replaced with electrical panels.Fuse boxes are likely unmaintained and have numerous electrical wiring issues, such as cloth wiring or knob & tube, due to their age.Furthermore, because fuses had to be replaced every time one blows, many electricians upgraded/recommended that homeowners install electrical panels. Finally, fuses quickly earned a bad reputation among insurance companies due to homeowners replacing fuses with sticks of copper or larger-than-necessary fuses in order to stop blowing fuses. If the overloaded current continues to flow rather than being shut off, replacing fuses with oversized fuses or pieces of copper can quickly become hot and start a fire. 1.3 The working principle of fuse boxFuse boxes can protect electrical circuits from damage and short circuits caused by exposure to the elements. Fuses are applied to control and protect electrical currents flowing through wires to electrical components.The fuse is connected to a central fuse box, which houses the wiring for the entire home's electricity. Under normal conditions, the fuse allows electricity to freely pass between circuits across the filament. Ⅱ The fuse box in a car Fuse boxes in automobiles consist of engineering plastics such as PVC and PBT. Each material has varying degrees of resistance to high temperatures. Automotive fuse boxes required high-temperature materials because some automotive fuse boxes have to be installed in the engine compartment due to the high temperature during operation. In order to choose the correct fuse box, we should consider the current size of the car fuse used, the size requirements of the fuse, and the raw materials. The majority of vehicles have two fuse boxes. One is in the engine compartment to safeguard engine components such as the cooling system, anti-lock brake pump, and engine control unit. The other is usually located inside or beneath the dashboard on the driver's side of the cab to protect the internal electrical equipment. Avoiding the influence of external factors, the fuse box is equipped with various fuses and relays in a convenient location. Unless the vehicle has significant physical damage or electrical problems, it is usually unnecessary to replace the fuse box.  This vedio shows that how to replace fuse box in a vehicle Ⅲ How to Replace Fuse Box?Materials Needed• Owner's manual• Socket set and wrench• Screwdriver set• Pen and tape for labeling wires (optional but recommended)  Step 1: Unplug the battery cable. Disconnect the negative terminal from the battery. As a result, no electricity will flow through the system during the installation process.Set the negative cable aside in a location where it will not come into contact with any metallic objects. Figure2: battery cable  Step 2: Find and open the fuse box. Locate the fuse panel by opening the hood. It will have a cover over the fuses that you must remove to gain access to the panel.Nota bene: On most makes and models, the fuse function diagram is located on the inside of the panel's lid. It may come in handy at some point. Figure3:Locate the fuse box  Step 3: Turn off the fuse box's power supply. Locate and disconnect the power supply to the fuses once the lid has been removed and set aside.It's possible that the power supply is routed through the bottom. In that case, skip stepping 4 to remove the fuse box housing to gain access to the wires, then return to step 3 before continuing.It is most likely a single or set of red wires connected to a terminal via a bolt, similar to the battery. Remove the connections and set them aside.Note: You may want to tape and label them for ease of reinstallation.  Figure4:power supply  Step 4: Unplug the panel's housing. Remove any bolts that are holding the fuse box in place.They will be located around the perimeter and perhaps different lengths, so pay attention to where each bolt is located as you remove it.Keep bolts in a secure location while working. What is more, keep the bolts together with a magnetic tray, plastic bag, or container until you need them again.  Figure5: the panel's housing   Step 5: Unplug the wiring harnesses and label them. After removing the housing, you'll notice that there are more wires connected to the fuse box and routed to the various systems and sensors they protect. Begin removing them one by one.As you disassemble the panel, it is highly recommended that you label them properly using the fuse diagram. It reduces confusion and protects you from replacing parts that will be damaged by crossed wires.  Figure6: fuse diagram   Step 6: Confirm replacement and fuse transfer. The replacement of fuse box should be rated and designed specifically for your vehicle.  Figure7: the panel's housing  Examine both parts to ensure that your replacement is a perfect match. After you've confirmed this, installing with labeled wires should be a breeze.Use the fuses from the old box if you don't have new fuses and relays for the panel. Make sure that you place them in the exact location for which they are rated. Look to the cover of your panel for guidance on this.   Figure8: check the faulty  Note: Before you decide to reuse your fuses, make sure they are in good working order. Look for a broken filament inside the fuse's viewing window. If it is discolored or broken, the fuse is faulty, and you will need to replace it. Step 7: Reconnect all of the system's wires. After you've installed the fuses, you can begin reconnecting the various wires to all of the systems that the fuses protect.Begin with any in the most difficult-to-reach positions and finish with the easiest ones.If you labeled the wires as you disconnected them, compare the label to the diagram and reconnect the wires. Crossing these wires can result in permanent damage to the systems to which they are connected.Different systems and fuses are rated for varying amperages. After reconnecting the wires, double-check that they are securely connected.  Ⅳ The difference of fuse box in UK and North America4.1 United KingdomOlder electrical consumer units (also known as fuse boxes) in the United Kingdom are installed with either semi-enclosed (rewirable) fuses (BS 3036) or cartridge fuses (BS 1361). (Consumers usually received short lengths of 5 A-, 15 A-, and 30 A-rated wire wound on a piece of cardboard.) Modern consumer units typically use miniature circuit breakers (MCBs) rather than fuses, though cartridge fuses still worked in some applications where MCBs are prone to nuisance tripping. 4.2 North AmericanFuse boxes were used in buildings wired before 1960 in North America. These Edison base fuses, like Edison-base incandescent lamps, would screw into a fuse socket. 5 amperes, 10 amperes, 15 amperes, 20 amperes, 25 amperes, and 30 amperes were Later fuse boxes included rejection features in the fuse-holder socket, commonly known as Rejection Base (Type S fuses), which have smaller diameters that vary depending on the rating of the fuse, to prevent the installation of fuses with an excessive current rating. This means that only the preset (Type S) fuse rating can be used to replace fuses.This is a tri-national North American standard (UL 4248-11, CAN/CSA-C22.2 NO. 4248.11-07 (R2012), and NMX-J-009/4248/11-ANCE). By screwing in a tamper-proof adapter, existing Edison fuse boards can be easily converted to only accept Rejection Base (Type S) fuses. This adapter screws into the existing Edison fuse holder and has a smaller diameter threaded hole to accept the Type S rated fuse. ⅤFuse Box vs Circuit Breaker5.1 What is the Circuit BreakerA circuit breaker is another genre of safety device that has an internal switch mechanism that tripped automatically in the case of an electrical surge. An electromagnet or a bimetallic strip connected to a simple switch is applied to the basic residential circuit breaker.When the switch is ON, an electrical current can flow from a bottom terminal to an upper terminal. Unsafe levels of electrical current in an electromagnet generate a magnetic force strong enough to turn a metal lever in the switch to OFF, breaking the current. Bimetallic strips consist of two strips of two different metals; excessive current causes the thinner of the two strips to bend, causing the switch to be thrown to the off position and the connection to be broken.Circuit breakers, unlike fuses, can be reused. To re-establish the flow of electricity to the home, simply turn the circuit breakers back to the ON position. This simple switch action makes it simple to manually turn off electricity to individual circuits when working on the wiring in a specific part of the home. 5.2 The Difference and ApplicationFuses are generally more inexpensive and  Many hardware stores can purchase them. However, circuit breakers have other applications as well, protecting against more than just overheating, such as against electric shock as well.Check out the main differences and applications in the table below, based on practical factors like operation time and functionality.CharacteristicsFuse Box  Circuit BreakerFunctionDetection&interruptionInterruption OnlyOperation PrincipleBased on a conducting material’s healing propertyBased on an electromechanical principle – a switching mechanismOperation Mode•  Completely automatic• Needs manual replacement after the operation     • Needs comprehensive equipment (relays) for automatic operation• Resets quickly after the operationResponse Time~ 0.002 seconds0.1-0.2 secondsBreaking CapacitySmallLargeRepresentationProtection Protects against overload Protects against overload & short-circuits  ApplicationLow current electronic equipmentLarge current power equipment  Ⅵ Frequently Questions About Fuse Box 1. Is a fuse box necessary?Fuses leave more room for DIY errors.Putting a larger size fuse in the box than what it is equipped for can lead to electrical fires. Since circuit breakers do not need to be replaced, they do not have the same danger. 2. What is the fuse box called?consumer unitA fuse box, also sometimes known as a consumer unit, should be easy to find and is where the electricity in your home is controlled and distributed. 3. How long does a fuse box last?It is a potential lifesaver as it can detect small leakage currents in the range of 5–30 mA and can disconnect in less than 300ms which may prevent electrocution and injury. If your fuse box is greater than 25 years old it may not have an RCD. 4. Which is better fuse box or circuit breaker?In terms of circuit breaker vs fuse box, a circuit breaker is more advanced and can be used over and over again. While they don't respond as quickly as fuses, circuit breakers do not have to be replaced. The exception, of course, is replacing older or outdated circuit breakers. 5. Are fuse boxes still legal?Fuses have not been installed in homes for many decades. Electrical codes change every three years to continually improve the safety of electrical systems that are installed. As a result, no fuse panel currently in use in any home in the United States would comply with minimum code standards in effect today. 

IntroductionThe manufacture of each semiconductor components products requires hundreds of processes. After sorting, the entire manufacturing process is divided into eight steps: Wafer Processing, Oxidation, Photography, Etching, Film Deposition, Interconnection, Test, and Package.Figure 1. Semiconductor Parts Manufacturing ProcessCatalogIntroductionⅠ Wafer ProcessingⅡ OxidationⅢ PhotomaskⅣ EtchingⅤ Film DepositionⅥ InterconnectionⅦ TestⅧ PackageⅠ Wafer ProcessingFewer people know, all semiconductor processes start with a grain of sand. Because the silicon contained in sand is the raw material needed to produce wafers. A wafer is a round slice formed by cutting a single crystal column made of silicon (Si) or gallium arsenide (GaAs). To extract high-purity silicon materials, silica sand is required, a special material with a silicon dioxide content of up to 95%, which is also the main raw material for making wafers. Wafer processing is the process of making and obtaining wafers.Semiconductor Production Process Explained① Ingot CastingFirst, the sand needs to be heated to separate the carbon monoxide and silicon, and the process is repeated until the ultra-high purity electronic grade silicon (EG-Si) is obtained. High-purity silicon melts into a liquid, and then solidifies into a single-crystal solid form called an "ingot", which is the first step in semiconductor manufacturing. The manufacturing precision of silicon ingots (silicon pillars) is very high, reaching the nano level.② Ingot CuttingAfter the previous step is completed, you need to cut off both ends of the ingot with a diamond saw, and then cut it into slices of a certain thickness. The diameter of the ingot slice determines the size of the wafer. Larger and thinner wafers can be divided into more units, which helps reduce production costs. After cutting the silicon ingot, it is necessary to add a "flat area" or "indent" mark on the slice, so that it is convenient to set the processing direction based on it as a standard in the subsequent steps.③ Wafer Surface PolishingThe thin slice obtained through the above-mentioned cutting process is called a "die", that is, an unprocessed "raw wafer". The die surface is uneven, and it is impossible to directly print circuit patterns on it. Therefore, it is necessary to first remove surface defects through grinding and chemical etching processes, then form a smooth surface through polishing and then cleaning residual contaminants. Ⅱ OxidationThe role of the oxidation process is to form a protective film on the surface of the wafer. It can protect the wafer from chemical impurities, prevent leakage current from entering the circuit, diffusion during ion implantation, and the wafer from slipping off during etching.Figure 2. OxidationThe first step of the oxidation process is to remove impurities and pollutants, such as organic matter, metals and evaporation residual moisture with four steps. After the cleaning is completed, the wafer can be placed in a high temperature environment of 800 to 1200 degrees Celsius, and a layer of silicon dioxide is formed by the flow of oxygen or vapor on the wafer surface. Oxygen diffuses through the oxide layer and reacts with silicon to form oxide layers of different thicknesses, which can be measured after the oxidation is complete.✔️Dry Oxidation and Wet Oxidation MethodAccording to the different oxidants in the oxidation reaction, the thermal oxidation process can be divided into dry oxidation and wet oxidation. The former uses pure oxygen to produce a silicon dioxide layer, which is slow but the oxide layer is thin and dense. The latter requires both oxygen and high solubility. The characteristic of water vapor is that the growth rate is fast, but the protective layer is relatively thick and the density is low.Figure 3. Dry Oxidation and Wet Oxidation MethodIn addition to the oxidizer, there are other variables that affect the thickness of the silicon dioxide layer. First of all, the wafer structure, surface defects and internal doping concentration will affect the rate of formation of the oxide layer. In addition, the higher the pressure and temperature generated by the oxidation equipment, the faster the oxide layer will be formed. In the oxidation process, it is also necessary to use dummy wafers according to the location of the wafers in the unit to protect the wafers and reduce the difference in oxidation degree. Ⅲ PhotomaskPhotomask is the use of light to "print" circuit patterns onto a wafer. We can understand it as semiconductor parts drawing on the surface of the wafer. The higher the fineness of the circuit pattern, the higher the integration of the product chip, which can only be achieved through advanced photomask technology. Specifically, it can be divided into three steps: photoresist coating, exposure and development.① Coated PhotoresistThe first step in drawing a circuit on a wafer is to coat photoresist on the oxide layer. Photoresist changes the chemical properties of the wafer to become "photographic paper". The thinner the photoresist layer on the surface of the wafer, the more uniform the coating, and the finer the patterns that can be printed. In addition, this step can use the "spin coating" method.Figure 4. Coating PhotoresistAccording to the difference of UV light reactivity, photoresist can be divided into two types: positive glue and negative glue. The former will decompose and disappear after being exposed to light, leaving a pattern of unreceived areas, while the latter will polymerize after being exposed to light to let the pattern of the light-receiving part appear.② ExposeAfter covering the photoresist film on the wafer, the circuit can be printed by controlling the light irradiation. This process is called "exposure." We can selectively pass light through the exposure equipment. When the light passes through the mask containing the circuit pattern, the circuit can be printed on the wafer coated with a photoresist film underneath.Figure 5. ExposureDuring the exposure process, the finer the printed pattern, the more components can be accommodated in the final chip, which helps to improve production efficiency and reduce the cost of individual components. ③ DevelopmentThe step after exposure is to spray developer on the wafer, in order to remove the photoresist in the area not covered by the pattern, so that the printed circuit pattern can be revealed. After the development is completed, it needs to be checked by various measuring equipment and optical microscopes to ensure the quality of the drawing of the circuit diagram. Ⅳ EtchingAfter the photolithography of the circuit diagram is completed on the wafer, an etching process is used to remove any excess oxide film and only the semiconductor circuit diagram is left. To do this, liquid, gas or plasma is used to remove the unselected parts.There are two main etching methods, depending on the material used: wet etching that uses a specific chemical solution for chemical reaction to remove the oxide film, and dry etching that uses gas or plasma.1) Wet EtchingFigure 6. Wet Etching MethodWet etching that uses chemical solutions to remove oxide films has the advantages of low cost, fast etching speed, and high productivity. However, wet etching has the characteristics of isotropy, that is, its speed is the same in any direction. This will cause the mask (or sensitive film) and the etched oxide film to not be completely aligned, making it difficult to process very fine circuit diagrams.2) Dry EtchingDry etching can be divided into three different types:The first is chemical etching, which uses etching gas (mainly hydrogen fluoride). Like wet etching, this method is also isotropic, which means that it is not suitable for fine etching.The second method is physical sputtering, that is, ions in the plasma are used to strike and remove the excess oxide layer. As an anisotropic etching method, it has different etching speeds in the horizontal and vertical directions, so its fineness must exceed that of chemical etching. However, the disadvantage of this method is that the etching speed is slow, because it completely relies on the physical reaction caused by ion collision.Figure 7. Physical SputteringThe third method is reactive ion etching (RIE). It combines the first two methods, that is, while using plasma for ionized physical etching, and chemical etching is performed with free radicals generated after plasma activation. In addition to the etching speed exceeding the first two methods, RIE can use the characteristics of ion anisotropy to achieve high-definition pattern etching.Figure 8. Reactive Ion Etching (RIE)Now dry etching has been widely used to improve the yield of fine semiconductor circuits. Maintaining the uniformity of full-wafer etching and increasing the etching speed are crucial. Today's most advanced dry etching equipment is supporting the production of the most advanced logic and memory chips with higher performance. Ⅴ Film DepositionIn order to create the micro devices inside the chip, we need to continuously deposit layers of thin films and remove the excess parts by etching, and add some materials to separate the different devices. Each transistor or memory cell is constructed step by step through the above process. The "thin film" we are talking about here refers to a "membrane" whose thickness is less than 1 micron (μm, one millionth of a meter) and cannot be manufactured by ordinary mechanical processing methods. Here the process of putting a thin film containing the desired molecular or atomic unit on the wafer is "deposition."Figure 9. DepositionTo form a multi-layer semiconductor structure, we need to fabricate a device stack first, that is, alternately stacking multiple thin metal (conductive) films and dielectric (insulating) films on the surface of the wafer, and then repeat the etching process to remove excess parts and form a three-dimensional structure. Technologies that can be used in the deposition process include chemical vapor deposition (CVD), atomic layer deposition (ALD) and physical vapor deposition (PVD). The methods using these technologies can be divided into dry and wet deposition.① Chemical Vapor DepositionFigure 10. Chemical Vapor DepositionIn chemical vapor deposition, the precursor gas chemically reacts in the reaction chamber and generates a thin film attached to the surface of the wafer and by-products that are drawn out of the chamber.Plasma-enhanced chemical vapor deposition requires the use of plasma to generate reactive gas. This method reduces the reaction temperature and is very suitable for temperature-sensitive structures. In addition, the use of plasma can also reduce the number of depositions, which can often lead to higher quality films.② Atomic Layer DepositionFigure 11. Atomic Layer DepositionAtomic layer deposition forms a thin film by depositing only a few atomic layers at a time. The key to this method is to loop the independent steps in a certain order and maintain good control. Coating the precursor on the wafer surface is the first step, after which different gases are introduced to react with the precursor to form the required substances on the wafer surface.③ Physical Vapor DepositionFigure 12. Physical Vapor DepositionPhysical vapor deposition refers to the formation of thin films by physical means. Sputtering is a physical vapor deposition method. Its principle is that atoms of the target material are sputtered out by the bombardment of argon plasma and deposited on the wafer surface to form a thin film.In some cases, the deposited film can be treated and improved by techniques such as ultraviolet heat treatment. Ⅵ InterconnectionThe conductivity of semiconductors is between conductors and non-conductors (ie insulators). This characteristic allows us to fully control the current. Through wafer-based lithography, etching and deposition processes, transistors and other components can be constructed, but they also need to be connected to achieve power and signal transmission and reception.Metal is used for circuit interconnection because of its conductivity, which is need to meet the following conditions:✔️Low Resistance: Since the metal circuit needs to pass current, the metal in it should have low resistance.✔️Thermochemical stability: The properties of the metal material must remain unchanged during the metal interconnection process.✔️High Reliability: With the development of integrated circuit technology, even a small amount of metal interconnect materials must have sufficient durability.✔️Manufacturing Cost: Even if the previous three conditions have been met, high cost is not suitable for the mass production.The interconnection process mainly uses two substances, aluminum (Al) and copper (Co).Figure 13. Al and Co Interconnection Process✔️Aluminum Interconnect ProcessThis process starts with aluminum deposition, photoresist application, and exposure and development, removing any excess aluminum and photoresist before entering the oxidation process through etching tech. After the foregoing steps are completed, repeat them until the interconnection is completed.With its excellent electrical conductivity, aluminum is also easy to lithography, etch, and deposit. In addition, it has a lower cost and a better adhesion to the oxide film. The disadvantage is that it is easy to corrode and has a low melting point. In addition, in order to prevent the reaction of aluminum and silicon from causing connection problems, it is also necessary to add a metal deposit to separate the aluminum from the wafer, which is called a "barrier metal."Aluminum circuits are formed by deposition. After the wafer enters the vacuum state, the thin film formed by aluminum particles will adhere to the wafer. This process is called "Vapour Deposition" and includes chemical vapor deposition and physical vapor deposition.✔️Copper Interconnection ProcessWith the improvement of semiconductor process precision and the shrinking of device size, the connection speed and electrical characteristics of aluminum circuits are gradually unable to meet the requirements. For this reason, we need to find new conductors that satisfy the requirements of both size and cost. With its lower resistance, so it can achieve faster connection speed. What’s more, copper is more reliable because it is more resistant to electromigration than aluminum, which is the movement of metal ions that occurs when current flows through the metal.However, copper does not easily form compounds, so it is difficult to vaporize and remove it from the wafer surface. To solve this problem, we no longer etch copper, but the dielectric materials, so that metal circuit patterns composed of trenches and via holes can be formed, and then copper is filled into the aforementioned to help interconnection, which is called "inlaid process".Figure 14. Copper Interconnection BarriersAs the copper atoms continue to diffuse into the dielectric, the insulation of the latter will decrease and produce a barrier layer that prevents the copper atoms from continuing to diffuse. Then a very thin copper seed layer will be formed on the barrier layer. After this step, electroplating can be carried out, that is, the high-aspect-ratio graphics are filled with copper. After filling, the excess copper can be removed by a metal chemical mechanical polishing (CMP) method. After completion, an oxide film can be deposited, and the excess film can be removed by photolithography and etching processes. The full entire process needs to be repeated continuously until the copper interconnection is completed.It can be seen from the above comparison that the difference between the copper interconnection and the aluminum interconnection is that the excess copper is removed by metal CMP instead of etching. Ⅶ TestThe main goal of the test is to check whether the quality of the semiconductor chip meets a certain standard, thereby eliminating defective products and improving the reliability of the chip. In addition, products that are tested and defective will not enter the packaging step, which helps to save cost and time. Electronic die sorting (EDS) is a testing method for wafers.EDS is a process for inspecting the electrical characteristics of each chip in the wafer state and thereby improving the semiconductor yield. EDS can be divided into five steps, as follows:Electrical Die Sorting (EDS)1）EPMTest whether the electrical parameters of transistors, capacitors, diodes and other devices meet the standards.2）Aging TestTest method of applying a certain temperature and AC/DC voltage to the wafer.3）TestPerform temperature, speed and motion tests on the wafer through the probe card.4）RepairReplace the components in the defective wafer and test again.5）InkUse special ink to mark defective chips.1) EPMEPM is the first step in semiconductor chip testing. This step will test every device (including transistors, capacitors, and diodes) that the semiconductor integrated circuit needs to use to ensure that its electrical parameters meet the standards. The measured electrical characteristic data will be used to improve the efficiency of the semiconductor manufacturing process and product performance (not to detect defective products).2) Wafer Aging TestThe semiconductor defect rate comes from two aspects, namely, the rate of manufacturing defects (higher in the early stage) and the rate of defects occurring throughout the life cycle afterwards. Wafer aging test refers to testing the wafer under a certain temperature and AC/DC voltage to find out which products may have defects in the early stage, that is, to improve the reliability of the final product by discovering potential defects.3) Parameters TestTemp TestHigh TemperaturVerify that the chip can work at a temperature that exceeds the maximum temperature by 10% or higher.Low TemperaturVerify that the chip can work at a temperature that lower the minimum temperature by 10% or more.Room TemperaturCheck whether the chip can work at room temperature (25°C).The high and low temperature test requirements for storage semiconductors are 85-90℃ and -5-40℃ respectively.Speed TestCoreCheck whether the core functions are valid.SpeedTest movement speed.Motion TestDCApply direct current to check whether the current and voltage are normal.ACApply alternating current to test movement characteristics.FunctionCheck whether all functions are normal.4) RepairRepairing is the most important test step, because some defective chips can be repaired, and you only need to replace the defective components.5) InkThe chips that failed the electrical test have been sorted out in the previous steps, but they still need to be marked to distinguish them. In the past, we needed to mark defective chips with special inks to ensure that they can be identified with the naked eye. Today, the system automatically sorts them based on the test data values. Ⅷ PackageSquare chips (also called single wafers) of equal size are formed on the wafers processed by the previous several processes. The next thing to do is to obtain individual chips by cutting. The chip that has just been cut is very fragile and cannot exchange electrical signals, so it needs to be processed separately. This process is packaging, including forming a protective shell on the outside of the semiconductor chip and allowing them to exchange electrical signals with the outside. The entire packaging process is divided into five steps, namely wafer sawing, single wafer attachment, interconnection, molding, and packaging testing.1) Wafer SawingTo cut countless densely arranged chips from the wafer, we must first grind the back of the wafer until its thickness can meet the needs of the packaging process. After grinding, we can cut along the scribing line on the wafer until the semiconductor chip is separated.There are three types of wafer sawing techniques: blade cutting, laser cutting and plasma cutting. Blade cutting refers to cutting wafers with diamond blades, which is prone to generate frictional heat and debris and thus damage the wafers. Laser cutting has higher precision and can easily handle wafers with thin thickness or small scribing line pitch. Plasma cutting uses the principle of plasma etching, so even if the scribing line pitch is very small, this technology can also be applied.2) Single Wafer AttachmentAfter all the chips are separated from the wafer, we need to attach the individual chips (single chip) to the substrate (lead frame). The role of the substrate is to protect the semiconductor chips and allow them to exchange electrical signals with external circuits. A liquid or solid tape adhesive can be used to attach the chip.3) BondFigure 15. BondingAfter attaching the chip to the substrate, we also need to connect the contact points of the two to achieve electrical signal exchange. There are two connection methods that can be used in this step: wire bonding using thin metal wires and flip chip bonding using spherical gold or tin blocks. Wire bonding is a traditional method, and flip-chip bonding can speed up semiconductor product manufacturing.4) MoldingFigure 16. MoldingAfter completing the connection of the semiconductor chip, it is necessary to use a molding process to add a package to the outside of the chip to protect the semiconductor integrated circuit from external conditions such as temperature and humidity. After the packaging mold is made as required, we put the semiconductor chip and the epoxy molding compound (EMC) into the mold and seal it. The sealed chip is in its final product.5) Package TestThe chip that has the final form must pass the final defect test. All that enters the final test is the finished semiconductor chip. They will be put into the test equipment, set different conditions such as voltage, temperature and humidity, etc. for electrical, functional and speed tests. The results of these tests can be used to find defects, improve product quality and production efficiency. Frequently Asked Questions about Semiconductor Manufacturing Steps1. What is a semiconductor and how is it made?Semiconductors are made from materials that have free electrons in their structure that can move easily between atoms, which aids the flow of electricity. ... Silicon has four electrons in its outer orbital, which allows the covalent bonds to form a lattice and thus form a crystal. 2. How many steps are in a manufacturing semiconductor?In semiconductor device fabrication, the various processing steps fall into four general categories: deposition, removal, patterning, and modification of electrical properties. 3. How is semiconductor manufactured?In the manufacturing process of IC, electronic circuits with components such as transistors are formed on the surface of a silicon crystal wafer. A thin film layer that will form the wiring, transistors and other components is deposited on the wafer (deposition). The thin film is coated with photoresist. 4. What type of operation is semiconductor processing?In semiconductor device fabrication, the various processing steps fall into four general categories: Deposition, Removal, Patterning, and Modification of electrical properties. Deposition is any process that grows, coats, or otherwise transfers a material onto the wafer. 5. What chemicals are used in semiconductor manufacturing?Semiconductors chemstry is mainly organized around the chemical treatment by solvents and acido-basic attacks of semiconductors. Chemistry of solvents : the main chemicals used during this stage are trichloroethylene, acetone, isopropanol and also other alcohols such as denatured ethanol.

IntroductionPrinted Circuit Board(PCB) is a board of most modern electronic devices that has lines and pads that connect various points together. Even if it is a small board, its manufacturing process is very cumbersome and exquisite. Here will introduce the PCB manufacturing process steps by steps with pictures and video.How is PCB made?The following are the detailed PCB producing processes:IntroductionStep 1. PCB CAD FileStep 2. Plate ProductionStep 3. PCB Inner LayersStep 4. Board Punching and CheckingStep 5. LaminationStep 6. DrillStep 7. Copper Chemical Precipitation on the HolesStep 8. PCB Outer LayersStep 9. Computer Control and Copper ElectroplatingStep 1. PCB CAD FileThe first step in PCB production is to organize and check the PCB layout. The PCB manufacturers get the CAD files from the PCB design company, and they will convert them into a unified format-Extended Gerber RS-274X or Gerber X2, because each CAD software has its own unique file format. Then the electronic engineers will check whether the PCB layout conforms to the manufacturing process, and whether there are any defects and other issues.Figure 1. PCB CAD FileWhen making a PCB at home, the PCB layout can be printed on paper with a laser printer, and then transferred to the copper clad laminate. During the printing process, because the printer is prone to lack of ink and breakpoints, it is necessary to manually fill up the ink with an oil-based pen. Figure 2. PCB Laser PrintingHowever, the factory generally uses photocopying to print the PCB layout on the film. If it is a multi-layer PCB, the layout film photocopied on each layer will be arranged in order.Figure 3. PCB Film Arranged in OrderThen the film will be punched with alignment holes. Alignment holes are very important, which is essential to align the materials of each layer of the PCB.Step 2. Plate ProductionClean the copper plate. If there is dust, it may cause the final circuit to be short-circuited or broken.Figure 4. Clean the Copper PlateThe figure below is an example of an 8-layer PCB, which is actually made up of 3 copper clad laminates plus 2 copper films, and then glued them together with prepregs. The production sequence is to start with the middle board (4th- and 5th-layer of circuits), continuously stack together, and then fix. The production of 4-layer PCB is similar, including one core board and two copper films.Figure 5. 8-layer PCB Plate DisplayStep 3. PCB Inner LayersFirst, make the two-layer circuit of the middle core board. After the copper clad laminate is cleaned, it will be covered with a photosensitive film on the surface. This film will solidify when exposed to light, forming a protective film on the copper foil.Figure 6. PCB CoreInsert the two-layer PCB layout film and the double-layer copper clad laminate into the upper PCB layout film to ensure that the upper and lower PCB layout films are stacked accurately.Figure 7. PCB Layout Film PlacingThe machine irradiates the photosensitive film on the copper foil with a UV lamp. The transparent film is cured under the light, and there is still no cured photosensitive film. The copper foil covered under the cured film is the required PCB layout, which is equivalent to the function of the laser printer ink of the manual PCB. In addition, the copper foil covered by the black film will be corroded away, and the cured transparent film will be preserved.Figure 8. Cured Photosensitive FilmClean the uncured photosensitive film with lye, and the required copper foil circuit will be covered by the cured film.Figure 9. Clean Uncured Photosensitive FilmThen use a strong base, such as NaOH, to etch away the unnecessary copper foil.Figure 10. Copper Foil EtchingTear off the cured photosensitive film to expose the copper foil of the required PCB layout.Figure 11. Tear Off the Cured Photosensitive FilmStep 4. Board Punching and CheckingThe core board has been successfully produced. Then punch alignment holes on it to facilitate with other materials.Figure 12. Punch Alignment Holes on PCBOnce the core board is pressed together with other layers, it cannot be modified. So PCB checking is very important. The machine will automatically compare with the PCB layout drawing to find out the error.Figure 13. PCB Layout Drawing ComparisonThe first two layers of PCB boards have been made.Step 5. LaminationA new raw material is introduced here called Prepreg, which is the adhesive among the core boards(PCB layers>4), as well as the core board and the outer copper foil, and it also plays a role in insulation.Figure 14. PCB Prepreg and CopperThe lower copper foil and the two layers of prepreg have been fixed in advance through the alignment hole and the lower iron plate, and then the finished core board is also placed in the alignment hole, and finally the two layers of prepreg, a layer of copper foil and a layer of pressure-bearing aluminum plate covers the core plate.Figure 15. Fixed PCB Prepreg and CopperIn order to improve work efficiency, this factory will stack three different PCB boards together before fixing them. The upper iron plate is magnetically attracted to facilitate alignment with the lower iron plate. After the two layers of iron plates are successfully aligned by inserting the alignment pins, the machine compresses the space between the iron plates as much as possible, and then fixes them with nails.Figure 16. Fixed PCB LayersThe PCB boards clamped by the iron plates are placed on the holder, and then sent to the vacuum heat press for laminating. The high temperature can melt the epoxy resin in the prepreg and fix the core boards and copper foils together under pressure.Figure 17. PCB Layers LaminationAfter the lamination, remove the upper iron plate that presses the PCB. Then remove the pressure-bearing aluminum plate. The aluminum plate also plays the role of isolating different PCBs and ensuring the smoothness of the outer copper foil of the PCB. Finally the PCB taken out at this time will be covered by a layer of smooth copper foil.Figure 18. Remove the Upper Iron Plate and Aluminum PlateStep 6. DrillSo how to connect 4 layers of copper foils that are not in contact with each other in the PCB? First, make the through-hole through the PCB, and then metalize the hole wall to conduct electricity.Figure 19. PCB DrillPut a layer of aluminum plate on the punching machine, and then put the PCB on it. Since drilling is a relatively slow process, in order to improve efficiency, according to the number of layers of the PCB, 1 to 3 identical boards are stacked for drilling together. Finally, cover the uppermost PCB with a layer of aluminum plate. The upper and lower of aluminum plates are used to prevent the copper foil on the PCB from tearing when drilling.Figure 20. PCB DrillNext, you only need to select the correct drilling program on the computer, and the rest is done automatically by the drilling machine. The drill bit is driven by air pressure, and the maximum rotation speed can reach 150,000 revolutions per minute. Because such a high rotation speed is sufficient to ensure the smoothness of the hole wall.Figure 21. Drill ProgramThe replacement of the drill bit is also automatically completed by the machine according to the program. The smallest drill bit can reach a diameter of 100 microns, while the diameter of a human hair is 150 microns.Figure 22. Drill ReplaceIn the previous process, the molten epoxy was squeezed out of the PCB, so it needed to be cut off. Here the profiling milling machine cuts its periphery according to the correct XY coordinates of the PCB.Figure 23. Cuts PCB PeripheryStep 7. Copper Chemical Precipitation on the HolesSince almost all PCB designs use perforations to connect different layers of lines, a good connection requires a 25-micron copper film on the hole wall. The thickness of the copper film needs to be realized by electroplating, but the hole wall is composed of non-conductive epoxy resin and glass fiber board. So the first step is to deposit a layer of conductive material on the hole wall, and form a 1 micron copper film on the entire PCB surface by chemical deposition. The entire process such as chemical treatment and cleaning is controlled by the machine.Step 8. PCB Outer LayersNext, the PCB outer layer is transferred to the copper foil. The process is similar to the transfer principle of the previous PCB inner core board. The PCB layout is transferred to the copper foil by photocopying film and photosensitive film. The only difference is positive films will be used as boards.The transfer of the internal PCB layout described above uses the subtractive method, and the negative film is used as the board. The PCB is covered by the cured photosensitive film as a circuit, and the uncured film is cleaned. After the exposed copper foil is etched, the PCB layout circuit is protected by the cured film. The transfer of the outer PCB layout adopts the normal method, and the positive film is used as the board. The non-circuit area is covered by the cured photosensitive film on the PCB. After cleaning the uncured film, electroplating is performed. Where there is a film, it cannot be electroplated, and where there is no film, copper is plated first and then tin is plated. After the film is removed, alkaline etching is performed, and finally the tin is removed. So the circuit pattern remains on the board because it is protected by tin.Put the cleaned PCB on both sides of the copper foil into the laminating machine, and the photosensitive mold will be pressed onto the copper foil.Figure 24. LaminatorFix the printed PCB layout film of the upper and lower layers through the holes, and put the PCB board in the middle. Then, the photosensitive film under the light-transmitting film is cured by the irradiation of the UV lamp, which is the circuit that needs to be reserved.Figure 25. PCB Expose to the UV LightAfter cleaning off the unnecessary and uncured photosensitive film, inspect the PCB board.Figure 26. PCB CheckingClamp the PCB with clips, and electroplate the copper. As mentioned earlier, in order to ensure that the holes have sufficient conductivity, the copper film plated on the hole walls must have a thickness of 25 microns, so the entire system will be automatically controlled by the computer to ensure its accuracy.Figure 27. PCB Copper PlatingStep 9. Computer Control and Copper ElectroplatingAfter the copper film is electroplated, the computer gives instructions to electroplate a thin layer of tin. Then, check to ensure that the thickness of the plated copper and tin is correct.Figure 28. Electroplated Copper and Tin InspectionNext, a complete automated assembly line completes the etching process. Then, clean the cured photosensitive film on the PCB.Figure 29. Clean Cured Photosensitive FilmThen use a strong alkali to clean the unnecessary copper foil covered by it.Figure 30. Clean the Unnecessary Copper FoilFinally, use the tin stripping solution to strip the tin plating on the PCB layout copper foil. After cleaning, the 4-layer PCB layout is complete. Frequently Asked Questions about PCB Manufacturing Process1. Which are the techniques of PCB manufacturing?There are several PCB manufacturing methods that a PCB can be submitted to before reaching the final product. These methods include preparing the board's surface, placing components, soldering, cleaning, and inspection and testing. 2. What is PCB design process?Step 1 – The DesignStep 2 – Printing the DesignStep 3 – Creating the SubstrateStep 4 – Printing the Inner LayersStep 5 – Ultraviolet LightStep 6 – Removing Unwanted CopperStep 7 – Inspection.Step 8 – Laminating the Layers 3. Which software is best for PCB design?Top 8 Best PCB Design Software of 2021PROTEL (Altium Designer)PADS (PowerPCB)ORCADAllegroEagle (Easily Applicable Graphical Layout Editor)KicadEasyEdaFritzing 4. What is a PCB layer?A PCB is defined as a number of copper layers in a well defined sequence. Copper layers of a PCB are usually just named layers or also called SIGNAL layer. However, to define the complete PCB, other layers are required. They are usually named by their functionality and position. 5. What are the components of a PCB?Some common PCB components include:Battery: provides the voltage to the circuit.Resistors: control the electric current as it passes through them. They’re colour coded to determine their value.LEDs: light emitting diode. Lights up when current flows through it, and will only allow current to flow in one direction.Transistor: amplifies charge.Capacitators: these are components which can harbour electrical charge.Inductor: stores charge and stops and change in current.Diode: allows current to pass in one direction only, blocking the other.Switches: can either allow current or block depending if they are closed or open.

 IntroductionPower systems are more complex than we see. In reality, we cannot see components of electricity, but we can inject how it works (or does not work). A current transformer is one of many elements that come together like a puzzle to form electrical power. A CT is made up of a laminated steel core, a secondary winding around the core, and insulating material surrounding the windings in its most basic form.Current transformers can be used in a variety of metering applications and use, including Wattmeters, power factor meters, watt-hour meters, protective relays, and as trip coils in magnetic circuit breakers, or MCBs.  CatalogIntroductionⅠ What is a Current TransformerⅡ Classification and Types of Current TransformerⅢ The function of Current TransformerⅣ Application of  Current TransformerⅤ Current Transformer Ratio and Polarity    5.1 Current Transformer Ratio  5.2 Current Transformer Polarity    5.3 Electrical Drawing Conventions for CT PolarityⅥ  How to Test CT PolarityⅦ  How to Choose The Right Current Transformer7.1 Genres of System7.2 Requirement of PrecisionⅧ Frequently Asked Questions about Current  Transformer  Ⅰ What is a Current Transformer A current transformer is a device that generates an alternating current in its secondary that is proportional to the alternating current in its primary. When a current or voltage is too high to measure directly, this method is applied. The induced secondary current is then appropriate for measuring instruments or processing in electronic equipment that requires isolation between the primary and secondary circuits.Because high-voltage currents are reduced, a standard ammeter can be used to safely monitor the actual electrical current flowing in an AC transmission line.Figure1: current transformers An electrical CT differs from a voltage or power transformer in that its primary winding has only one or a few turns. It also differs from a voltage transformer in that the prime current is not controlled by the secondary load current but rather by an external load. The CT ratio is the number of secondary turns multiplied by the number of primary turns. This ratio is calculated based on the primary conductor passing through the transformer window once. Ⅱ Classification and Types of Current Transformer There are two categories in the current transformer. The first, a measuring current transformer, is applied to conjunct with measuring devices for current magnitude, energy, and power. The other, a protective current transformer, is used in conjunction with protective equipment such as trip coils, relays, and the like.Current transformers are classified into three basic types: wound, toroidal, and bar.  1. Wound Current Transformer–The primary winding of the transformer is physically connected in series with the conductor carrying the measured current flowing in the circuit. The magnitude of the secondary current is determined by the transformer's turns ratio.  2. Toroidal Current Transformer -There is no primary winding in these. Instead, the line carrying the network's current is threaded through a window or hole in the toroidal transformer. Some current transformers have a "split core," allowing them to be opened, installed, and closed without disconnecting the circuit to which they are connected.  3. Bar-type Current Transformer-The primary winding of this type of current transformer is the actual cable or bus-bar of the main circuit, which is equivalent to a single turn. They are fully insulated from the system's high operating voltage and are typically bolted to the current-carrying device. Bar-type Current Transformer.Figure2: the typical current transformer  Ⅲ The function of Current Transformer One of the functions of the current transformer is to be used for measurement, and it is often used for billing or measuring the current of the equipment in operation. When measuring large alternating currents, to facilitate meter measurement and reduce the risk of direct measurement of high-voltage electricity, it is often necessary to use current transformers to convert them into a more uniform current. Thus, current transformers are considered as the role of current conversion and electrical isolation.Another function is protection : It is frequently used in tandem with a relay device. When a short circuit or overload occurs in the line, the current transformer sends a signal to the relay device to cut off the fault circuit, thereby protecting the power supply system's safety. The current transformer used for protection is not the same as the current transformer used for measurement. It can only operate effectively when the current is tens of times greater than the normal current, and it requires reliable insulation as well as a sufficiently great accurate limit. The coefficient has adequate thermal and dynamic stability.  Ⅳ Application of  Current Transformer Current transformers are widely used for measuring current and monitoring power grid operation. Revenue-grade CTs, along with voltage leads, power the electrical utility's watt-hour meter on many larger commercial and industrial supplies.To isolate high-voltage current transformers from the ground, they are mounted on porcelain or polymer insulators. Some CT configurations wrap around the bushing of a high-voltage transformer or circuit breaker, allowing the conductor to be automatically centered inside the CT window.Current transformers can be installed on a power transformer's low or high-voltage leads. A section of a bus bar can sometimes be removed to replace a current transformer.High-voltage current transformers are mounted on porcelain or polymer insulators to isolate them from the ground. Some CT configurations wrap around the bushing of a high-voltage transformer or circuit breaker, allowing the conductor to be centered inside the CT window automatically.  Ⅴ Current Transformer Ratio and Polarity5.1 Current Transformer RatioAt full load, the CT ratio is the ratio of primary current input to secondary current output. A CT with a ratio of 300:5 is rated for 300 primary amps at full load and will generate 5 amps of secondary current when 300 amps pass through the primary.If the primary current changes, so will the secondary current output. For example, if 150 amps flow through a primary rated at 300 amps, the secondary current is 2.5 amps. Figure3: A current transformer's ratio is equivalent to a potential transformer's voltage ratio.  At full load, the CT ratio is the ratio of primary current input to secondary current output. A CT with a ratio of 300:5 is rated for 300 primary amps at full load and will generate 5 amps of secondary current when 300 amps pass through the primary.If the primary current changes, so will the secondary current output. For example, if 150 amps flow through a primary rated at 300 amps, the secondary current is 2.5 amps.   5.2 Current Transformer PolarityThe polarity of a current transformer is determined by the direction in which the coils are wound around the CT's core (clockwise or counterclockwise), as well as the manner in which the secondary leads are brought out of the transformer case.To ensure an appropriate installation, all current transformers are subtractive polarity and will have the following designations: H1 - Primary current, oriented in the direction of the lineH2 - Primary current in the load-facing directionX1 denotes secondary current (multi ratio CTs have additional secondary terminals) Figure4:  Split-Core CT with a 200A rating. Take note of the polarity marking in the center of the core, which indicates the direction of the source. (Split-Core CT with a 200A rating.) Take note of the polarity marking in the center of the core, which indicates the source's direction. (Photo courtesy of Continental Control Systems, LLC.)The H1 primary lead and the X1 secondary lead are on the same side of a subtractive polarity transformer. When the polarity of a CT is indicated by an arrow, it should be installed with the arrow pointing in the direction of the current flow.When installing and connecting current transformers to power metering and protective relays, it is critical to maintain proper polarity.   5.3 Electrical Drawing Conventions for CT PolarityFor current transformers, polarity markings on electrical drawings and diagrams can be made in a variety of ways. Dots, squares, and slashes are the three most common schematic conventions. On electrical drawings, polarity markings represent H1, which should be facing the source.Figure5: Electrical Drawing Conventions for CT Polarity   Ⅵ  How to Test CT PolarityMaterials need:an analog voltmeter9-volt batteryThe factory has occasionally misapplied markings on current transformers. The following test procedure can verify the polarity of a CT in the field with a 9V battery: Step1: Cut the Power SupplyBefore testing, turn off all power and connect an analog voltmeter to the secondary terminal of the CT to be tested. The meter's positive terminal is connected to CT terminal X1, while the negative terminal is connected to X2.  Step2: Connect the 9-volt BatteryConnect the positive end of the 9-volt battery to the H1 side (sometimes marked with a dot) and the negative end to the H2 side with a piece of wire run through the high side of the CT window. It is critical to avoid continuous contact, which will result in a short circuit of the battery.  Step3: Check the PolarityIf the polarity is correct, the momentary contact causes a tiny positive deflection in the analog meter. If the deflection is negative, the current transformer's polarity is reversed. The terminals X1 and X2 have to be switched before the test.Figure6:The factory has occasionally misapplied markings on current transformers. A 9-volt battery can be used to test the polarity of a CT in the field.   Ⅶ  How to Choose The Right Current TransformerWhen selecting a current transformer for any application, there are numerous factors to consider. As this can be confusing, and there is a lot of inaccurate information out there, it can lead to installing the wrong current transformer and having to replace equipment.To avoid this, the first step should be to contact the current transformer manufacturer if you have any questions or concerns about compatibility. Midwest Current Transformer's team is available to answer your questions and ensure that you are using the correct product. Speaking with our team before ordering current transformers ensures that you have the right equipment for the job, avoiding any last-minute decisions and potential confusion. 7.1 Genres of SystemWhen using any genre of the meter or power system, it is critical to use a current transformer that is specifically designed for that system. It is especially important with meters because they are not all uniformly designed. Another way to put it is that the system's metering or protection is matched with the type of current transformer.It is also critical to understand the primary range of the current transformer and ensure that it is compatible with the application. This type of compatibility is provided by the various configurations of the primary and secondary windings.  7.2 Requirement of PrecisionThe degree of accuracy is critical for current transformers used for measurement. Not all current transformers provide high accuracy, and the more specific the requirement, the more important the quality of data measurement provided by the CT.This accuracy rating is classified according to class, with the current having an effect on the accuracy provided by the current transformer. The ability of the current transformer to perform to the required levels is always a factor in making the right choice for protective transformers..The degree of accuracy is critical for current transformers used for measurement. Not all current transformers provide high accuracy, and the more specific the requirement, the more important the quality of data measurement provided by the CT.This accuracy rating is classified according to class, with the current having an effect on the accuracy provided by the current transformer. The ability of the current transformer to perform to the required levels is always a factor in making the right choice for protective transformers. Ⅷ Frequently Asked Questions about Current Transformer 1.What is the use of current transformer?A Current Transformer (CT) is used to measure the current of another circuit. CTs are used worldwide to monitor high-voltage lines across national power grids. A CT is designed to produce an alternating current in its secondary winding that is proportional to the current that it is measuring in its primary. 2.What is the use of CT and PT?CT is used to measure current while PT is used to measure voltage. CT is connected in series while PT is connected in parallel. CT ratio range is from 1 to 5A while the PT range is from 110V. We connect the output parameter from CT to the ampere meter while we connect the PT output to the voltmeter. 3.What do you mean by a current transformer?A current transformer is a device used to produce an alternating current in its secondary, which is proportional to the AC current in its primary. This is primarily used when a current or voltage is too high to measure directly. ... This ratio is based on the primary conductor passing once through the transformer window. 4.How is CT ratio calculated?When analog ammeters are installed, we can easily determine the CT ratio by observing the meter full scale value and then divide that value by 5. Figure 3. Ammeter with a full scale of 150 amps. The meter in Figure 3 has a full scale of 150 amps. 5 Why CT is connected in series?A CT may be considered as a series transformer. The primary current in a C.T is independent of the secondary circuit conditions (burden/load). The primary winding of the CT is connected in series with the line carrying the current to be measured. Hence it carries of the full line current.   

IntroductionThe potentiometer is a three-terminal resistive element whose resistances can be adjusted according to a certain change rule. According to it, it is used in a large variety of electrical and electronic circuits, such as voltage dividers, variable resistor, and current controllers. The potentiometer is usually composed of a resistor body and a movable brush. When the brush moves along the resistor body, the resistance value or voltage will be changed at the output end. Due to its special structure and function, it is necessary to pay attention to its damage and take regular maintenance during operation.Potentiometers - Basic IntroductionCatalogIntroductionⅠ Potentiometer Using TipsⅡ How to Clean Potentiometer?Ⅲ How to Test Potentiometer?3.1 General Methods3.2 Variable Potentiometer TestⅤ Replacing Potentiometer with 4 StepsⅠ Potentiometer Using Tips1) The resistor body of the potentiometer is mostly made of polycarbonate synthetic resin. Avoid contact with the following items: ammonia, other amines, aqueous alkali solutions, aromatic hydrocarbons, ketones, lipid hydrocarbons, and strong chemicals (excessive acid-base value), etc. Because chemical reaction with those will affect their performance.2) The terminal of the potentiometer should avoid using water-soluble flux when soldering, which will cause metal oxidation and mold material. In addition, avoid using inferior flux, and poor soldering may cause difficulty in soldering, resulting in poor contact or open circuit.3) If the soldering temperature is too high or the soldering time is too long, it may cause damage to the potentiometer terminals. The pin terminal should be soldered at 235℃±5℃ within 3 seconds, and the soldering space should be more than 1.5mm away from the potentiometer body. Do not use solder to hit through the circuit board when soldering, and wire terminal soldering should be soldered at 350℃±10℃ within 3 seconds. Except that, the terminal should avoid heavy pressure, otherwise it is easy to cause poor contact.4) During soldering, the height of the rosin (flux) entering the printing machine board should be adjusted properly, and the flux should be prevented from entering the potentiometer, otherwise it will cause poor contact between the brush and the resistor, resulting in INT, noise and other undesirable phenomena.Potentiometer Structure5) The potentiometer is best used in the voltage adjustment, and the connection method should choose "①" pin grounding. The current adjustment structure should be avoided, because the contact resistance between the resistor and the contact piece will stop the passage of large currents.6) Avoid condensation or water droplets on the surface of the potentiometer, and avoid using it in a humid place to prevent insulation deterioration or short circuit.7) When installing the rotary potentiometer, the strength should not be too tight to avoid damage to the screw teeth or poor rotation. When install the sliding type potentiometer, avoid using too long screws, otherwise it may affects the movement of the sliding handle, and even directly damages the potentiometer body.8) In the process of putting the potentiometer on the knob, the pushing force used should not be too large (not exceeding the parameter index of the pushing and pulling force of the shaft in the specification note), otherwise it may cause damage to the potentiometer.9) The operating force (rotation or sliding) of the potentiometer will become faster as the temperature rises, and slower as the temperature drops. If the potentiometer is used in a low temperature environment, it needs a kind of special low temperature resistant grease.10) The shaft or sliding handle of the potentiometer should be as short as possible when designing it. The shorter the shaft or sliding handle, the better and stable the hand feel. On the contrary, the longer the shaking, the greater the shaking, and the feel is easy to change.11) The power of the carbon film of the potentiometer can withstand the ambient temperature of 70°C, and its function may be lost when the temperature is higher than it.12) The resistor body of the sealed potentiometer is mostly made of polycarbonate synthetic resin. Avoid mixing with ammonia, aromatic hydrocarbons, lipid hydrocarbons, ketones, and strong chemicals (excessive pH), other amines, alkaline aqueous solution, etc, because they will affect its performance.Potentiometer TypesⅡ How to Clean Potentiometer?The potentiometer is to wrap the carbon sheet with POM, PC, ABS and other plastic materials. After assembly, the carbon sheet will not be exposed to the outside, it is not easy to oxidize, and dust is not easy to enter, which protects the potentiometer body.Cleaning Steps of Potentiometer1) Use a screwdriver to carefully open the sealing cover fixing card of the sealing potentiometer, and remove the protective cover.2) Remove the fixed spring card of the rotating shaft and pull out the rotating shaft.3) If some sealed potentiometers cannot take out the shaft, you can directly wipe the carbon film and the metal contacts on the shaft with a cotton ball dipped in pure alcohol.4) Adjust the position and angle of the metal contacts, changing the contact position with the carbon film and increasing the pressure.5) Apply some lubricating oil or special grease on the carbon film to delay the service life.6) Reinstall and fix the metal cover to complete the entire cleaning process. Ⅲ How to Test Potentiometer?3.1 General Methods1) Before detecting the potentiometer by the method of appearance and manual adjustment, firstly observe its appearance. Rotate the knob to check whether the rotation is smooth, whether the switch is flexible, whether the "click" sound is crisp when the switch is turned on and off, and listen to the sound of friction between the internal contact points of the potentiometer and the resistor body, if there is a loud noises indicate that the quality is not good. Normally, the handle should be slightly damped when turning.2) Using the multimeter to measure the potentiometer, you should first select the appropriate ohm gear of the multimeter according to the nominal resistance of the measured potentiometer and then do the measurement. When measuring, touch the red and black test leads of the multimeter to the pins of the fixed pins on both sides, and the multimeter reading should be the nominal resistance of the potentiometer. If the multimeter reading is much different from the nominal resistance value, it indicates that the potentiometer has been damaged.When the nominal resistance of the potentiometer is normal, then measure its changing resistance and whether the movable contact is in good contact with the resistor (fixed contact). At this time, one test lead of a multimeter is connected to the moving contact pin (usually the middle pin), and the other test lead is connected to a certain contact pin (pins on both sides).After connecting the test leads, the multimeter should display zero or the nominal resistance value, and then rotate the multimeter's shaft from one extreme position to the other extreme position, and the resistance value should continuously change from zero (or nominal resistance) to the nominal resistance value (or zero). During the rotation or sliding of the shaft of the potentiometer, if the pointer of the multimeter moves steadily or the displayed indication changes uniformly, it means that the measured potentiometer is in good condition. If the resistance reading of the multimeter fluctuates when the shaft is rotated, it means the movable contact has a fault with poor contact.3.2 Variable Potentiometer Test1) Measure the total resistance at both ends to see if it matches the nominal value.2) Measuring the resistance between a fixed end and the sliding end: rotary the potentiometer to see if the resistance change is continuous. Then measuring the resistances between the other fixed end and the sliding end, if the measured intermediate resistance value changes discontinuously, it indicates that there is a poor contact in the sliding process.PotentiometersⅣ Replacing Potentiometer with 4 StepsThere are many types of potentiometers, and most models cannot be used interchangeably, otherwise the control effect will not be very good. When replacing it, the nominal resistance value should be the same as the damaged variable resistance value or the close to. At the same time, its packages must be considered, otherwise the installation will be difficult. Therefore, we must distinguish between linear potentiometers, exponential potentiometers and logarithmic potentiometers before use. In addition, please note that the precision resistor can only be replaced with a same one when it is damaged, and cannot be replaced with an ordinary variable resistor, otherwise its adjustment accuracy will also be affected.The potentiometer has multiple pins. In order to prevent the wrong pins from being connected during replacement, the following specific operation steps and methods can be used:Step 1: Remove the set screw of the original potentiometer, but do not take off the leads on the potentiometer.Step 2: Install the new potentiometer and fix it.Step 3: Solder a lead on the original potentiometer pin slice, solder it on the corresponding pin slice of the new potentiometer, and the welding method is the same as the old one.Step 4: In the same way, solder each pin wire. Pay attention, welding the next one and then the other one can avoid the wrong position of the leads being welded to each other. Frequently Asked Questions about Potentiometer Uses and Its Replacement1. What is the use of potentiometer?The measuring instrument called a potentiometer is essentially a voltage divider used for measuring electric potential (voltage); the component is an implementation of the same principle, hence its name. Potentiometers are commonly used to control electrical devices such as volume controls on audio equipment. 2. What causes a potentiometer to fail?An electrical short or open will cause the indication to fail at one extreme or the other. If an increase or decrease in the potentiometer resistance occurs, erratic indicated valve position occurs. 3. What does a potentiometer measure?A potentiometer is an instrument which is used for measurement of potential difference across a known resistance or between two terminals of a circuit or network of known characteristics. A potentiometer is also used for comparing the emf of two cells. 4. How do you troubleshoot a potentiometer?Set your ohmmeter to a setting higher than the total resistance of the potentiometer. For example, if your potentiometer is rated at 1,000 ohms, set your ohmmeter to 10,000 ohms. Look at your potentiometer. There should be three tabs sticking out of it. 5. Does a potentiometer need to be grounded?This configuration also acts as a voltage divider and can be used in a number of ways to control a signal. Like any resistor, potentiometers per se do not need to be connected to the ground plane of the circuit, but in the majority of configurations/uses, they will be.

What is Hard Drive?Hard disk, hard disk drive (HDD), hard disk, or fixed disk is the most important storage device of computer. It is composed of one or more aluminum or glass discs. These discs are covered with ferromagnetic material. Your documents, pictures, music, videos, programs, application preferences, and operating system represent digital content all can be stored on a hard drive. Most hard drives are permanently sealed and fixed in the hard drive. Early hard disk storage media was replaceable, but today's hard disk is a fixed storage medium, which is sealed in a case. With the development, removable hard disks have also appeared, and they are becoming more and more popular with different types. In addition, most of the hard disks installed on microcomputers are called Winchester hard drive.Hard DriveTopics Covered in this GuideWhat is Hard Drive?Hard Drive Tech ParametersHard Drive ClassificationsHard Disk StructureHow Does Hard Disk Work?Hard Drive MaintenanceUsing TipsHard Drive FaultsTypes of Hard Disk InterfacesCan a Computer Run without a Hard Drive?Should I Buy SSD or HDD?What the Defferences between HDD and SSD?What is the Lifespan of a Hard Drive?How Much Do Hard Drives Cost?What are the Best Hard Drives?Hard Drive Tech Parameters1) HD CapacityCapacity is the most important parameter of the hard disk. The capacity of the hard disk is measured in megabytes (MB) or gigabytes (GB). However, the hard disk manufacturer usually takes 1G=1000MB in the nominal hard disk capacity, so the capacity we see in the BIOS or when formatting the hard disk will be smaller than the manufacturer’s nominal value.The hard disk capacity index also includes the single-disk capacity. It refers to the capacity of a single disk of a hard disk. The larger the single disk capacity, the lower the unit cost and the shorter the average access time. For users, the capacity of the hard disk is like the computer memory, and it will never be too much.2) Rotational SpeedRotational speed, or spindle speed is the rotation speed of the motor spindle in the hard disk, which is the maximum number of revolutions that the hard disk platter can complete in one minute. It is one of the important parameters indicating the grade of the hard disk. It is one of the key factors that determine the internal transmission rate of the hard disk, and directly affects the speed of the hard disk to a large extent. The faster the rotation speed of the hard disk, the faster the hard disk can find files. The hard disk speed is expressed in revolutions per minute, and the unit is expressed as RPM(revolutions per minute). The larger the RPM value, the faster the internal transfer rate, the shorter the access time, and the better the overall performance of the hard drive.The spindle motor of the HDD makes the platters to rotate at a high speed, generating buoyancy to make the head float above the platters. Bring the sector of the data to be accessed below the head, the faster the speed, the shorter the waiting time. Therefore, the rotational speed largely determines the read speed of the hard disk.The rotation speed of ordinary hard disks for household use is generally 5400rpm and 7200rpm. High-speed hard disks are the first choice for desktop users. For notebook users, it is mainly 4200rpm and 5400rpm. Although some companies have released 7200rpm notebook hard disks, they are still rare in the market. Users have the highest requirements on server for hard disk performance. The speed of SCSI hard disks used in servers is basically 10000rpm, and even 15000rpm. The performance is much higher than that of household products.A higher speed can shorten the average seek time and actual read and write time of the hard disk. However, as the speed of the hard disk continues to increase, it also brings negative effects such as temperature rise, heavy motor spindle wear, and great operating noise. The speed of notebook hard disks is lower than that of desktop hard disks, which is affected to a certain extent by this factor. The internal space of the notebook is small, and the size of the notebook hard disk (2.5 inches) is also designed to be smaller than that of the desktop hard disk (3.5 inches). The temperature rise caused by the increase in speed puts higher requirements on the heat dissipation performance of the notebook itself. In addition, the noise becomes larger, it is necessary to take noise reduction measures, so more technique requirements on the notebook hard disk productions. At the same time, the increase in speed, while the others remain unchanged, means that the power consumption of the motor will increase, the more electricity is consumed per unit time, and the working time of the battery is shortened, so that the portability of the notebook will be affected. Therefore, notebook hard drives generally use a relatively low-speed 4200rpm hard drive.3) Access TimeThe average access time refers to the time required for the head to reach the target track position from the starting position and find the data sector to be read and written on the target track.The average access time reflects the read and write speed of the hard disk, which includes the seek time and waiting time of the hard disk, that is, average access time = average seek time + average waiting time.The average seek time of the hard disk refers to the time required for the head of the hard disk to move to the specified track on the disk surface. This time is of course as small as possible. The average seek time is usually between 8ms and 12ms, while a SCSI HDD should be less than or equal to 8ms.The waiting time of the hard disk, also known as the Latency, refers to the time that the magnetic head is already in the track to be accessed and waiting for the sector to be accessed to rotate below the head. The average waiting time is half of the time required for the disc to rotate one round, and should generally be less than 4ms.4) Data Transfer RateData transfer rate refers to the speed at which the hard disk reads and writes data, in megabytes per second (MB/s). It includes internal data transfer rate and external data transfer rate.The internal transfer rate is also known as the sustained transfer rate, which reflects the performance of the hard disk buffer when it is not in use. The internal transfer rate mainly depends on the rotation speed of the hard disk.The external transfer rate is also called the burst data transfer rate or the interface transfer rate. It is nominally the data transfer rate between the system bus and the hard disk buffer. The type of hard disk interface is related to the size of the hard disk cache.The maximum external transfer rate of the Fast ATA interface HD is 16.6MB/s, while the Ultra ATA interface hard disk reaches 33.3MB/s.The hard disk using SATA (Serial ATA) port is also called serial hard disk. Serial ATA adopts a serial connection method. The serial ATA bus uses an embedded clock signal and has a stronger error correction capability. Compared with the past, its biggest difference is that it can check the transmission instructions (not just data). Errors are found to be automatically corrected, which greatly improves the reliability of data transmission. The serial interface also has the advantages of simple structure and support for hot swapping.5) Cache MemoryCache memory is a memory chip on the hard disk controller with extremely fast access speed. It is a buffer between the internal storage of the hard disk and the external interface. Since the internal data transfer speed of the hard disk is different from the transfer speed of the external interface, the cache plays a role as a buffer among them. The size and speed of the cache is an important factor directly related to the transmission speed of the hard disk, which can greatly improve the overall performance of the hard disk. When the hard disk accesses fragmented data, data needs to be continuously exchanged between the hard disk and the memory. With a large cache, the fragmented data can be temporarily stored in the cache, reducing the load on the external system and improving the data transmission speed. Hard Drive Classifications1) Mechanical Hard Disk (HDD)HDDMechanical hard disk (HDD) is a traditional hard disk, one of the main storage media for computers. It is composed of one or more magnetic discs made of aluminum or glass, magnetic heads, rotating shafts, control motors, head controllers, data converters, interfaces and caches. When working, the head is suspended on a high-speed rotating disc to read and write data. Mechanical hard disk is a computer storage device that integrates precision machinery, microelectronic circuits, and electromagnetic conversion.2) Solid State Drive (SSD)SSDA solid state drive (SSD) is an array storage composed of multiple flash memory chips plus a main control and cache, and belongs to a hard drive made of an array of solid electronic storage chips. Compared with a mechanical hard disk, the read speed is faster and the seek time is shorter, which can speed up the operating system startup speed and the software startup speed.3) Solid State Hybrid Drive (SSHD)SSHDSolid state hybrid drive is a combination of mechanical hard disk and solid-state hard disk. It uses small-capacity flash memory particles to store commonly used files. Disk is the most important storage medium. Flash memory only serves as a buffer to reduce seek time and improve efficiency. Hard Disk StructureThe hard disk is one of the most important storage for computers. Most of the software needed for the computer to function properly is stored on the hard drive. Because the storage capacity of hard disk is large, it is different from computer memory and optical disk. Hard disks are storage devices based on hard rotating disks used on computers. It stores and retrieves digital data on a flat magnetic surface.Take a Look Inside a Hard Drive1) Magnetoresistive Heads (MR heads)The magnetoresistive head is the most expensive part of the hard disk, and it is also the most important and critical part of the HD technology. The traditional magnetic head is an electromagnetic induction magnetic head that combines reading and writing. However, the reading and writing of hard disks are two completely different operations to limit the hard disk design. The MR head uses a separate head structure: the write head still uses the traditional magnetic induction head (MR head cannot write), and the read head uses a new type of MR head. In this way, during the design, the different characteristics of the two can be optimized separately to obtain the best read/write performance. In addition, the MR head gets the signal amplitude through changes in resistance rather than changes in current, so it is very sensitive to signal changes, and the accuracy of reading data is correspondingly improved. Further more, because the read signal amplitude has nothing to do with the track width, the HD track can be made very narrow, thereby increasing the density of the disc. In addition, GMR heads (Giant Magnetoresistive heads) made of materials with a multi-layer structure and better magnetoresistive effect have gradually become popular.2) Magnetic TrackWhen the disk rotates, if the head is held in one position, each head will draw a circular track on the surface of the disk, called tracks. They are invisible to the naked eye at all, because they are only some magnetized areas on the disk surface that are magnetized in a special way, and the information on the disk is stored along such tracks. Adjacent tracks are not close to each other. This is because when the magnetization units are too close, the magnetism will affect each other, and at the same time it will also cause difficulties for the magnetic head to read and write. For example, a 1.44MB 3.5-inch floppy disk has 80 tracks on one side, and the track density on the hard disk is much greater than this value, usually there are thousands of tracks on one side.The surface of the disk is coated with a magnetic medium used for recording, which are magnetic particles under the microscope. The polarity of tiny magnetic particles can be quickly changed by the magnetic head, and can be maintained stably after the change. The system distinguishes 0 or 1 in the binary system through changes in magnetic flux and magnetoresistance. It is precisely because all operations are performed under microscopic conditions, so if the hard disk is operated at high speed while being shocked by external forces, it may cause irreversible data loss due to the head slaps on the surface of the disk. In addition, the uniaxial anisotropy and volume of the magnetic particles will obviously affect the thermal stability of the magnetic particles, and the thermal stability determines the stability of the magnetic particle, that is, the correctness and stability of the stored data. However, it cannot be increased blindly, because it is limited by the write field that the magnetic head can provide and the signal-to-noise ratio of the medium.3) FanEach track on the disk is equally divided into several arc segments, which are the sectors of the disk. Each sector can store 512 bytes of info. The hard disk drive reads and writes data to the disk  from the sectors. 4) CylinderA hard disk is usually composed of a set of overlapping disks. Each disk surface is divided into an equal number of tracks, and numbered from the "0" on the outer edge. The tracks with the same number form a cylinder. The number of cylinders on a disk is equal to the number of tracks on a disk. Since each disk surface has its own head, the number of disk surfaces is equal to the total number of heads. The so-called CHS of the hard disk, namely Cylinder, Head, Sector. So when the number of CHS of the hard disk is known, the capacity of the hard disk can be determined. The capacity of the hard disk is the number of cylinders and the number of sectors. How Does Hard Disk Work?How Do Hard Drives Work?When the hard disk is working, never turn off the power forcibly, which will cause physical damage to the hard disk and data loss. In addition, with high-speed components in the hard disk, if the high-speed disk is shut down forcibly and suddenly, which is more likely to cause damage to the hard disk. So don't turn on the computer immediately after shutting down. This requires time buffering.When the hard disk is working, try to avoid its vibration, because the distance between the magnetic head and the magnetic disk is very close. If it is subjected to severe vibration, the magnetic head will hit the magnetic disk to damage it, which will make the entire hard drive unusable.In the process of using the hard disk, many users compress files to reduce the use of disk space. This will cause the compressed volume file to continue to grow. The data access speed also slowed down, and the number of reads and writes increased, which would affect the heat generation and stability of the hard disk, even reduce service life.  Hard Drive MaintenanceFirst of all, the impact of dust on the hard disk is not small. If dust is attracted to the circuit board, it will cause unstable operation of the hard disk or damage to internal parts. The functional working status of the hard disk has a great relationship with the temperature. Too high or too low temperature will cause the clock frequency of the crystal oscillator to change, which will cause the circuit components to malfunction. In addition, if the temperature is too low, it will cause the air moisture condenses on the component, causing a short circuit.Second, we need to clear your hard drive regularly. This will increase the speed of your hard drive. If there are too many junk files on the hard disk, the speed will slow down and the tracks may be damaged. However, clean up frequently will also reduce the service life of the hard drive.Finally, it is anti-virus. Viruses are the biggest threat to the files stored on the hard drive. Therefore, once we found that the virus should be cleared up in time and try not to format the hard disk. Using Tips1) Don't shut down suddenly while working.When the hard disk starts to work, it is generally in high-speed rotation, if we suddenly turn off the power in the middle, it may cause violent friction between the head and the platter to damage the hard disk. Therefore, it is necessary to avoid this. When shutting down, you must pay attention to whether the hard disk indicator on the panel is still flashing, only the indicator stops flashing and then hard disk read and write ends, you can turn off the computer.2) Prevent dust from entering.Dust can cause great damage to the hard disk. This is because in a severely dusty environment, the hard disk can easily attract dust particles in the air, causing them to accumulate on the internal circuit components of the hard disk for a long time, which will affect the heat of the electronic components, causing the temperature of the circuit components to rise, and resulting in leakage or burnout of the components.In addition, dust may also absorb moisture, corrode the electronic circuits inside the hard disk, and cause some invisible problems. Therefore, although the volume of dust is small, the harm to the hard disk cannot be underestimated. Therefore, it is necessary to maintain environmental sanitation and reduce the humidity and dust content in the air. In addition, users cannot remove the hard disk cover by themselves, otherwise the dust in the air will enter the hard disk and scratch the platters or heads during read and write operations.3) Temperature ControlAs we all known, temperature affects the service life of the hard disk. A certain amount of heat is generated when the hard disk is working, so there is a heat dissipation problem during use. 20～25℃ is better. Temperature can also cause failure of hard disk circuit components, and magnetic media can also cause recording errors due to thermal expansion.On one hand, when the humidity is too high, the surface of the electronic components may absorb a layer of water, oxidizing and corroding the electronic circuits, resulting in poor contact or even short circuits, and it will also cause the magnetic force of the magnetic medium to change, causing data reading and writing errors. On the other hand, it is easy to accumulate a large amount of static charge generated by the rotation of the machine in low temperature, which will burn out the CMOS circuit, attract dust and damage the head and scratch the disk. In addition, try not to make the hard disk close to strong magnetic fields, such as loud speakers, motors, radios, mobile phones, etc., so as to prevent the data recorded on the hard disk from being damaged due to magnetization.Hard Disk Drive StructureHard Drive Faults1) HD Cooling FanConsidering the heat dissipation effect, many people install hard drive cooling fans for their computer hard drives. However, some low-end fans have obvious vibrations and can transmit vibration to the hard drive. In the long term, it will definitely affect the life of the hard drive.2) Optical DriveThe reading speed of mainstream optical drives has reached more than 50 times speed. When the optical disc rotates at a high speed, the vibration of the optical drive itself will drive the resonance of the chassis, which affects the work of the hard disk. And this kind of high-speed rotation generates a lot of heat, because the optical drive is so close to the hard drive, the heat released from the optical drive will surely increase the temperature of the hard drive.3) Static ElectricityIn the process of repairing the computer, many people hold the hard disk with their hands, but in dry weather, tens of thousands of volts of static electricity may accumulate on the hands of people, which may break down the chips on the circuit board, causing the hard disk to malfunction.4) FormattingIf the computer hard disk has bad sectors, many users will take formatting measures. In fact, low format damages the hard disk greatly. It may cause the proliferation of bad sectors on the disk, and even cause the loss of hard disk parameters, making the hard disk unable to use.5) Power SupplyA low-quality computer will cause the hard drive to be disturbed by voltage fluctuations, especially when the hard drive is reading and writing. If there is a problem with the power supply, a hard drive can be scrapped in an instant.6) Magnetic FieldBecause the hard disk is a device that relies on magnetic media to record data, if it is interfered by the magnetic field of the external environment, it is likely to cause the loss of disk data, so you should try to stay away from the magnetic field environment. Types of Hard Disk InterfacesThere are five categories of hard disk interfaces: IDE, SATA, SCSI, SAS, FC1) IDE (Integrated Drive Electronics)IDE refers to the hard disk drive that integrates the controller and the disk body, and is a hard disk transmission interface. There is another name called ATA (advanced technology attachment).2) SATA (Serial ATA)SATA hard disk is called serial hard disk based on its serial data transmission method. In the process of data transmission, the data line and the signal line are used independently, and the transmission clock frequency remains independent. Therefore, compared with the previous PATA, the transmission rate of SATA can reach 30 times that of parallel. It can be said that SATA technology is not an improvement of PATA technology in a simple sense, but a new bus architecture.3) SCSI (Small Computer System Interface)SCSI invention is mainly because the hard disk speed of the original IDE interface is too slow. In fact, SCSI is not designed specifically for hard drives, in fact it is a bus-type interface, working independently of the system bus.4) SAS (Serial Attached SCSI)SAS is serial attached SCSI, which is a new generation of SCSI technology. Like the popular SATA hard disks, it uses serial technology to achieve higher transmission speeds, and improves internal space by shortening the cable. It is a brand new interface developed after the parallel SCSI interface, which is designed to improve the performance, availability, and expandability of the storage system, and provide compatibility with SATA hard drives.SAS interface tech can be backward compatible with SATA. Specifically, the compatibility of the two is mainly reflected in the compatibility of the physical layer and the protocol layer.5) FC (Fibre Channel)Just like the SCIS interface, FC is not an interface technology designed and developed for hard disks at first. It is specially designed for network systems. However, as storage systems require high speed, they are gradually applied to hard disk systems. FC hard disk was developed to improve the speed and flexibility of multi-disk storage system. Its appearance greatly improves the communication speed of multi-disk system, and it uses optical cable connections between systems in a point-to-point (or switching) configuration. There are something to note: the hard disk itself does not have an FC interface, where the cabinet has, which is interconnected with an optical fiber switch. Note: Get more info from Types of Hard Disk Drive Interface.Can a Computer Run without a Hard Drive?A computer can still function without a hard drive. This can be done through a network, USB, CD, or DVD. Computers can be booted over a network, through a USB drive, or even off of a CD or DVD. When you attempt to run a computer without a hard drive, you will often be asked for a boot device. Should I Buy SSD or HDD?1) According to data read and write speedA computer with the same configuration can reach a read and write speed of about 500M/S with a solid state drive, but about 150MB/S with a mechanical hard drive. The difference is nearly three times the speed, which makes the difference in computer response speed even greater.2) According to data security and shock resistanceSince the mechanical hard disk reads and writes data through the magnetic head to read the disk, it is easy to cause data damage due to the collision of the disk and the magnetic head during high-speed rotation, especially it is in the handling process that the disc may be damaged, so everyone needs to be extremely careful when touching it.3) According to weight and volumeCompared with mechanical hard disks, solid state drives are smaller and lighter in appearance, and has stronger performance and faster transfer speed than mechanical hard drives.4) According to noise and heat dissipationSince the solid state drive is made of flash memory particles, it is not equipped with mechanical parts and flash memory chips, and there is no disk and head mechanical motors, fans, etc., so that it can ensure absolute silence. The heat is also very small, and the heat dissipation is also very fast.5) According to power consumptionSSDs commonly use less power and result in longer battery life because data access is much faster and the device is idle more often. With their spinning disks, HDDs require more power when they start up than SSDs. For example, the general full-speed power consumption of a 3.5-inch mechanical hard disk is about 12W, and a 2.5-inch hard disk is only about 5W. The full-speed power consumption of the solid-state drive is about 10W, its working power is generally 2-3W, less than 1W in standby mode.Although solid state drives are definitely faster than mechanical hard drives from above mentioned, but it doesn’t mean that solid state drives are necessarily better than mechanical hard drives, because in terms of price and capacity, mechanical hard drives are "T" is the unit, and most of the solid-state drives are still in G. Although there are also "T", the price is beyond everyone's expectations. One more thing to note is that it is more difficult to restore data if the solid state drive is damaged, while the mechanical hard drive can restore data through repair. Therefore, in terms of data security, mechanical hard drives have more advantages in storing important data. In short, consider comprehensively according to the actual situations. What the Defferences between HDD and SSD?A hard disk drive (HDD) is a traditional storage device that uses mechanical platters and a moving read/write head to access data. A solid state drive (SSD) is a newer, faster type of device that stores data on instantly-accessible memory chips.Generally, SSDs are more durable than HDDs in extreme and harsh environments because they don't have moving parts such as actuator arms. SSDs can withstand accidental drops and other shocks, vibration, extreme temperatures, and magnetic fields better than HDDs.SSDs commonly use less power and result in longer battery life because data access is much faster and the device is idle more often. With their spinning disks, HDDs require more power when they start up than SSDs. However, when not in use, magnetic drives are more reliable for long-term storage than flash memory ones. Thus, HDDs are more capable of long time storage than SSDs when powered off.While normal HDDs can last about 10 years max in reality, and an SSD lifespan has a built-in time of death. To keep it simple: an electric effect results in the fact that data can only be written on a storage cell inside the chips between approximately 3,000 and 100,000 times during its lifetime.As for price, SSDs are more expensive than hard drives in terms of dollar per gigabyte. A 1TB internal 2.5-inch hard drive costs between $40 and $60, but as of this writing, the very cheapest SSDs of the same capacity and form factor start at around $100.With their ruggedness and low energy consumption, SSDs are becoming more popular with portable PCs. With all the advantages that SSD has over HDD, price, availability and capacity are probably the primary factors constraining the acceptance of this new technology. Note: Get more info from SSD vs HDD: Is an SSD Really Necessary?What is the Lifespan of a Hard Drive?Though the average might be three to five years, hard drives can theoretically last much longer (or shorter, for that matter). If a hard drive works 24 hours continuously, it will be damaged in less than 3 years. After normal use, there should be no problem for 5 or 10 years. During use, the garbage must be cleaned regularly and kept HD cool, so as not to get stuck.As with most things, if you take care of your hard drive, it will better last to its potential. How Much Do Hard Drives Cost?A 1TB internal 2.5-inch hard drive costs between $40 and $60, but as of this writing, the very cheapest SSDs of the same capacity and form factor start at around $100. That translates into 4 to 6 cents per gigabyte for the hard drive versus 10 cents per gigabyte for the SSD.According to market trend, the number of hard drives sold each year has declined recently due to the migration of consumer PCs to SSDs, and also demand for higher-capacity HDDs by exascale datacenters. When demand for HDDs spikes, retailers sell out quickly, and prices increase as dealers come into play. What are the Best Hard Drives?Best Hard Drives at a Glance1️⃣Seagate BarraCuda2️⃣Toshiba X3003️⃣WD VelociRaptor4️⃣WD Blue Desktop5️⃣Seagate Firecuda Desktop6️⃣Seagate IronWolf NAS7️⃣Seagate FireCuda Mobile8️⃣WD My Book9️⃣G-Technology G-Drive