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 The heat sink has a thermal conductor that carries heat away from the device into fins that provide a large surface area for the heat to dissipate throughout the rest of the components, thus cooling both the heat sink and processor. Both a heat sink and a radiator require airflow and, therefore, both have fans built-in. At present, the main failure form of electronic equipment is thermal failure. According to statistics, 55% of failure of electronic equipment is caused by temperature exceeding the rated value. With the increase of temperature, the failure rate of electronic equipment increases exponentially. Therefore, the thermal design of power devices is most important in the structural design of electronic equipment, which directly determines the success of the products. Good thermal design is the basis for the stable and reliable operation of the equipment. Electronics Thermal Heatsink Design Tutorial CatalogI. Main Parameters of Thermal PropertiesII. Thermal Design of Power DeviceIII. Heat Dissipation CalculationIV. Calculation ExampleV. Selection of RadiatorVI. ConclusionFAQ I. Main Parameters of Thermal Properties The thermal stress of the power device can come from the inside of the device or from the outside of the device. If the heat dissipation capacity of the device is limited, the consumption of power will lead to the rise of temperature and junction temperature in the active region of the chip inside the device, reducing the reliability of the device lower and making the device unable to work safely. The main parameters to characterize the thermal capacity of power devices are junction temperature and thermal resistance. The active region of the device can be the PN junction region of the junction device (such as a transistor), the channel region of the field-effect device, the diffused resistor, or the thin film resistance of the integrated circuit, and so on.  When the junction temperature Tj is higher than the ambient temperature Ta, the heat through the temperature difference to form a diffusive heat flow, which is emitted from the chip through the tube shell, and the heat emitted increases with the increase of the temperature difference (Tj-Ta).  In order to ensure that the device can work properly for a long time, an allowable maximum junction temperature Tj max has been made. Tj max is determined by chip materials, packaging materials, and reliability of devices. The heat dissipation ability of power devices is usually characterized by thermal resistance, called Rt. The larger the thermal resistance is, the worse the heat dissipation ability is. Thermal resistance is also divided into internal thermal resistance and external thermal resistance.  Internal thermal resistance is the inherent thermal resistance of the device itself, which is related to the thermal conductivity, thickness, and cross-sectional area of the tube core, shell material, and processing technology, while external thermal resistance is related to the form of tube package. Generally speaking, the larger the shell area, the smaller the external thermal resistance. The external thermal resistance of the metal shell is obviously lower than that of the plastic. When the power consumption reaches a certain level, the junction temperature of the device goes up and the reliability of the system decreases. In order to improve the reliability, the thermal design of the power device should be carried out.  II. Thermal Design of Power Device The thermal design of the power device is mainly to prevent thermal failure caused by overheating or alternating temperature. It can be divided into the thermal design of the internal chip, thermal design of the package, thermal design of the tube, and thermal design in practical use. For general power devices, only the thermal design of the device's interior, package, and the tube should be considered. But when the power consumption is high, the appropriate radiator should be installed, through which the heat can be effectively dissipated to ensure the device works normally and reliably within the safe junction temperature.   III. Heat Dissipation CalculationThe most commonly used heat dissipation method is to install the power device on the radiator, using the radiator to disperse the heat into the surrounding, if necessary, to add the fan to strengthen the heat dissipation with a certain wind speed.  Flow cold water cooling plate is also used in some large power devices, which has a better heat dissipation effect. Heat dissipation calculation is to determine the appropriate heat dissipation measures and radiators through calculation under certain working conditions. There is a certain thermal resistance in the heat transfer process. The thermal resistance from the core of the device to the bottom is Rjc, between the bottom and the radiator is Rcs, a radiator that spreads heat into the surrounding is Rsa, the total resistance is Rja=Rjc+Rcs+Rsa.  If the maximum power loss of the device is Pd, and the permitted junction temperature of the device is Tj, ambient temperature is Ta, the reasonable total thermal resistance Rja can be obtained by the following formula.Rja ≤(Tj-Ta)/Pd The thermal resistance of the maximum allowable Rsa is: Rsa ≤(Tj-Ta)/Pd-(Rjc+Rcs) For design consideration, Tj is generally set to 125℃, Ta=40℃ ~ 60℃ generally used in the case of bad ambient temperature. The size of Rjc depends on the size of the core and the package structure, which can be found from the parameter list. Rcs size depends on the installation technology and device packaging. If the device adopts heat conducting grease or heat transfer pad, installing with the radiator, the typical value of Rcs is 0. 1 ℃/W / ~ 0. 2 ℃/W; If the bottom surface of the device is not insulated and additional mica insulation is required, the Rcs can reach 1 ℃/W. Pd is the maximum power loss calculated according to the working conditions of different devices. In this way, Rsa can be calculated to select an appropriate radiator. IV. Calculation ExampleA power operational amplifier PA02 as low-frequency power amplifier, the device is 8-pin and TO-3 metal shell package. The operating conditions are as follows: the operating voltage Vs is 18 V, the load impedance RL is 4Ω, the ambient temperature is 40 ℃, and the natural cooling is adopted. According to the data of PA02: the typical value of static current Iq is 27mA, the maximum value is 40mA, and the typical value of Rjc (from tube core to shell) is 2.4 ℃/W, and the maximum value is 2.6 ℃/W. The power consumption of the device is Pd=Pdq+ Pdout(Pdq is the internal power consumption and Pdout is the output power consumption). The calculation is as follows: Pdq=Iq(Vs+|-Vs|)  Pdout=Vs2/(4RL)  Iq=37mA                                                                                 Pd=Iq(Vs+|-Vs|)＋Vs2/(4 RL)                                                                                     =0.037×(18+18)＋182/(4×4)                                                                                     =21.6 W Radiator thermal resistance: Rsa ≤(Tj-Ta)/Pd-(Rjc+Rcs) Tj=125℃, Ta=40℃, Rjc=2.6℃/W, Rcs=0.2℃/W(PA02 installed directly on radiator with heat conductive grease in the middle) Substitute the above data into the formula to get Rsa≤ (125-40)/21.6-(2.6+0.2)≤ 1.135℃/W The thermal resistance HSO4 in natural convection is 0. 95 ℃/W, which can meet the requirement of heat dissipation. V. Selection of RadiatorRadiators are generally standard parts, but also provide customization. The surface of the radiator is treated by electrophoretic coating or black oxygen polarization, which aims to improve heat dissipation and insulation performance.  In natural cooling can be increased by 10%~15%, in ventilation cooling can be increased by 3%, and electrophoretic coating can withstand pressure 500V~800V. The heat resistance of different types of radiators in different heat dissipation conditions is given by the radiator manufacturers. The radiator is used to control the temperature of the power device, especially the junction temperature (Tj), making is lower than the safe junction temperature of the power device, so as to improve the reliability of the power device.  Conventional radiators tend to be standardized, serialized, universal, and new products develop towards low thermal resistance, multifunction, small volume, lightweight, and suitable for automatic production and installation.  The internal thermal resistance of various power devices is different and the difference of contact surface and installation torque will lead to the thermal-resistance difference between the contracts.  The main factor of selecting a radiator is the heat resistance Rtf. Under different environmental conditions, the heat dissipation of power devices is also different. Therefore, environmental factors, the matching between radiator and power device, and the volume and quality of the whole electronic equipment should be taken into account in selecting the appropriate radiator. First of all, according to the performance parameters and environmental parameters of the power device in normal operation, calculate whether the junction temperature of the power device is within the safe condition, determine whether it is necessary to install the radiator, and calculate the corresponding thermal resistance of the radiator if it needs to be installed.  The junction temperature of the power device is recalculated to determine whether the junction temperature of the power device is within the range of safe junction temperature, so as to judge whether the selected radiator meets the requirements. For the radiator that meets the requirements, the optimum design should be carried out according to the actual engineering requirements.   VI. ConclusionThrough the analysis and calculation of the heating principle of the power device, it can guide the design of the heat dissipation mode and the selection of the radiator, ensure the power device work in the safe temperature range, reduce the quality problem, and improve the reliability of the electronic products.  The reliability of electronic equipment is also related to the components, structure, assembly, process, processing quality, and so on. In practical engineering applications, feedback data should be obtained through various tests to perfect the design and further improve the reliability of electronic equipment. FAQ 1. What is a heat sink and how does it work?A heat sink (also commonly spelled heatsink) is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant, where it is dissipated away from the device, thereby allowing regulation of the device's temperature. 2. What is a heat sink used for?A heat sink is a component that increases the heat flow away from a hot device. It accomplishes this task by increasing the device's working surface area and the amount of low-temperature fluid that moves across its enlarged surface area. 3. Does a heat sink need a fan?Most heatsinks have denser fins, which requires a fan to be mounted directly on the cooler. If your heatsink has heat pipes (copper tubes running through the fins), then it's most likely designed to be used with a fan. It's simple to test whether or not a heatsink can safely be run without a fan on it. 4. What material dissipates heat the best?Thermal conductivity is the measure of a metal's ability to conduct heat. What this means is that that the metal acts to cool temperatures, through a process of dissipation. The metals with the highest thermal conductivity are copper and aluminium. The lowest are steel and bronze. 5. How many types of heat sinks are there?The Two Major Heat Sink Categories. All heat sinks can be broken down into two major categories… active and passive. 6. What is the difference between active and passive heat sinks?An active heat sink has a fan attached to it, to actively pull heat away from the heat sink and chip that lies underneath it. A passive heat sink is just a heat sink, a piece of flat metal with fins on top that directs heat away from the chip set it is installed on. 7. Which is better heat sink or fan?Generally though, with good airflow provided by the fan heatsinks can often be a lot smaller. The only benefit to a heatsink-only arrangement is less noise. ... Out of preference you want the heatsink fins to be standing upwards so that hot air can immediately rise off of it and cool air be pulled in. 8. What is the difference between a heatsink and a CPU fan?The heatsink draws the heat away from the CPU, and the fan ensures a steady stream of air for the heatsink to pass the heat to. However, there is more to selecting a heatsink and fan than just looking for a good price or one that looks cool. 9. What is the difference between a heat sink and a heat pipe?Vapor chambers are most often used to spread heat to a local heat sink, whereas heat pipes are generally better for moving heat to a remote sink. ... If you need a heat sink that's minimally 10 times, but usually closer to 20 times, the area of the heat source, consider vapor chambers. 10. How is a heat sink attached to an electrical component?A heat sink is a mechanical component that is attached to an electrical component for the sake of transferring heat from the electrical component into the surrounding environment. This environment is most commonly air, but it can also be other fluids, such as water or coolant. 

ROM and RAM belong to the semiconductor memory. ROM is the abbreviation of read only memory, and RAM is the abbreviation of random access memory. ROM can keep data when the system powers off, and RAM is in the opposite, a typical RAM is the computer memory. But sometimes we are not clear: what is the difference between Flash Memory and ROM and RAM? How much do you really know about memory, or RAM, ROM, and flash memory specifically? Here we will tell them in different aspects, this article will act as a guide to basic memories.   Catalog     I What are types of RAM?  1.1 Static RAM (SRAM)  1.2 Dynamic RAM (DRAM) II What are types of ROM? III What is Flash Memory?  3.1 Performance Comparison  3.2 Interface Difference  3.3 Capacity and Cost  3.4 Reliability and Durability  3.5 Simple Operation  3.6 Software Support IV Conclusion FAQ     I What are types of RAM? RAM Upgrade Guide - What You Need to Know 1.1 Static RAM (SRAM) SRAM is very fast and the fastest storage device to read and write currently, but it is also very expensive, so it is only used in demanding places, such as the first and second level buffer of CPU. 1.2 Dynamic RAM (DRAM) DRAM keeps data for a short time and its operation is slower than the SRAM, but it's still faster than the ROM. In addition, it's much cheaper than SRAM. The computer memory is DRAM. DRAM is divided into many kinds, the most common ones are FPRAM / FastPage, EDORAM, SDRAM, DDR, RAM, RDRAM, SGRAM, WRAM and so on. DDR RAM, one of which is introduced here. DDR RAM (Double-Date-Rate RAM), also known as DDR SDRAM, the improved RAM and SDRAM, are essentially the same, except that they can read and write data twice in one clock, doubling the speed of data transmission. This is the most used memory in a computer today, and it has a cost advantage, which in fact defeats another Intel memory~ Rambus DRAM. Many high-end graphics cards are also equipped with high-speed DDR RAM to increase bandwidth, which can greatly improve the pixel rendering capability of 3D accelerator cards.     II What are types of ROM? PROM (programmable ROM), is programmed once that can not be modified, this is an early product, now it is gone. EPROM (erasable and programmable ROM), is a kind of universal memory which erases the original program by ultraviolet radiation. EEPROM, is electronically erased, very expensive, long writing time. For example, mobile phone software is generally placed in the EEPROM, when we call, some of the last numbers that are dialed are temporarily in the SRAM, but not immediately written in the call log (the call record is stored in the EEPROM).   Memory is used to storage data and programs that are currently in use (that is in execution), and the memory of the computer we normally used refers to dynamic memory (that is DRAM). The so-called "dynamic" in dynamic memory refers to when we write data to the DRAM, after a period of time, the data will be lost, so we need an extra circuit to refresh the memory. It works like this: whether a DRAM's memory cell stores 0 or 1 depends on whether the capacitor has a charge. 1 represents a charge, 0 represents no charge. But over time, the capacitance of 1 will discharge, and the capacitance of 0 will absorb the charge, which is why the data is lost. Taking refresh operation regularly checks the capacitor, if the charge is greater than 1/2 of the full charge, it is considered to represent 1, charging the capacitor fully; If the quantity of electricity is less than 1/2, it is considered to represent 0, and the capacitor is discharged to maintain the continuity of the data. ROM III What is Flash Memory? Flash memory combines the advantages of ROM and RAM. It not only has the electrically erasable and programmable capability (EEPROM), but also can read data quickly without power loss (the advantage of NVRAM). This memory is used in USB  and MP3. For the past 20 years, embedded systems have been using ROM (EPROM) as their storage device. However, in recent years, FLASH has completely replaced the position of ROM (EPROM) in embedded systems to store Bootloader and operating systems, or Program code or directly as the hard disk (U disk). At present, there are two kinds of NOR Flash and NAND Flash. NOR Flash reading is the same as the common SDRAM reading. Users can run the code loaded in NOR FLASH directly, which reduces the capacity of the SRAM and saves cost. NAND Flash doesn’t have memory random read technique, which reads in the form of a block at a time, usually 512 bytes at a time, thus it is cheaper. Users cannot run program code on NAND directly, so many developers using NAND have to use a small NOR Flash to startup and run code. NOR Flash, is generally used in small capacity because of its fast reading speed, and it is used to store important information such as operating system. The most common NAND FLASH used for large capacity, combines with embedded system DOC (Disk On Chip) and common "flash disk", which can be erased online. At present, the FLASH on the market mainly comes from Intel, AMD, Fujitsu and Toshiba, and the main manufacturers of NAND Flash are Samsung and Toshiba. NOR and NAND are the two main non-volatile flash memory technologies in the market. Memory IC Intel first developed NOR flash technology in 1988, which completely changed the situation in which EPROM and EEPROM dominated the world. Then, in 1989, Toshiba published its NAND flash architecture, emphasizing lower cost per bit, higher performance, and easy upgrades via interfaces like disks. But after more than a decade, a considerable number of hardware engineers still can not distinguish between NOR and NAND flash memory. Flash memory is often used interchangeably with phase NOR memory. Many in the industry are also confused about the advantages of NAND flash over NOR, because in most cases flash memory is only used to store a small amount of code, and NOR flash memory may be more appropriate, while NAND is an ideal solution for data needed high storage density. NOR is the main non-volatile flash memory technology in the market. NOR is generally used to store a small amount of code, especially in code storage media. NOR is characterized by simple application, no special interface circuit, high transmission efficiency, it belongs to the in-chip execution(XIP, eXecute In Place), so that applications can run directly in (NOR) flash memory. No longer need to read the code into the system RAM. Low write and erase speed can be very cost-effective but affect its performance for small capacity when it is 1~4MB. NOR flash comes with an SRAM interface and has enough address pins to access, it is convenient to storage and use each byte. NOR flash accounts for the majority of the 1~16MB flash market. NAND structure can provide extremely high cell density and high storage density, and fast write and erase speed. The difficulty of applying NAND lies in the management of flash and the need of special system interface. 3.1 Performance Comparison Flash memory is non-volatile memory and can be erased and reprogrammed on memory cell block. The write operation of any flash device can only be done in an empty or erased cell, so in most cases, the erasure must be performed before the writing. In general, the NAND devices perform the erasure operation easily. But NOR requires that all bits in the target block be written as 1 before erasing. Since the NOR device is erased as a block of 64~128KB, the time to perform a write / erase operation is 5s. In contrast, the erasure NAND device is performed as a block of 8~32KB, and the same operation only needs 4 ms at most. The performance gap between NOR and NADN is further widened by the difference of block size in the execution of erasure. It is shown that for a given set of write operations (especially when updating small files), more erasure operations must be performed in NOR based cells. Therefore, when choosing a storage solution, the designer must weigh the following factors: The read speed of NOR is a little faster than NAND, but the writing speed is on the opposite. The 4ms erasure speed of NAND is much faster than that of NOR. Most writing operation need running erasure. The NAND erasure unit is smaller and the corresponding erasure circuit is less. Flash memory 3.2 Interface Difference NOR flash has a SRAM interface, and enough address pins to address, and easy storage and program to every byte inside. NAND devices use complex I/O ports to serially access data, which may vary from product to product or from manufacturer to manufacturer. Eight pins are used to transmit and control address and data information. NAND read and write operations use 512-byte blocks, which is similar to the hard disk management. Naturally, NAND based memory can replace hard drives or other block devices. 3.3 Capacity and Cost The cell size of NAND flash is almost half that of NOR devices. Because of the simpler manufacturing process, the NAND structure can provide higher capacity within a given die size, thus lowering the price accordingly. NOR flash accounts for most of the 1~16MB flash market, while NAND flash is only used in 8~128MB products, which means that NOR is mainly used in code storage, and NAND is suitable for data storage, mainly used in CompactFlash, Secure Digital, PC Cards and MMC memory cards. 3.4 Reliability and Durability One of the key issues needed to consider is reliability when using flahs media. For systems that need to extend MTBF, Flash is a very suitable storage solution. So the reliability of NOR and NAND can be compared between bit switching, lifetime (durability) and bad block processing. - Service Life The maximum number of erasures per block in NAND flash memory is one million times, while that of NOR is 100,000 times. In addition, NAND memory has the advantage of 10: 1 erasure speed, 8 times smaller than that of the NOR device, and each NAND memory block has fewer deletions at a given time. - Bit Switching All flash devices are plagued by bit switching. In some cases (rarely, NAND occurs more often than NOR), a bit reverses or its reversion is reported. One changing bit may not be obvious, but if it happens on a critical file, this minor failure could cause the system to shut down. If existing wrong report, it may be solved by reading it a few more times. Of course, if the bit really changes, the error detection / error correction (EDC/ECC) algorithm must be used. The problem of bit inversion is more common in NAND flash memory, therefore, it is  recommended that using NAND flash memory and EDC/ECC algorithm at the same time. But this problem is not fatal when storing multimedia information in NAND. Of course, if you use a local storage device to store an operating system, configuration file, or other sensitive information, you must use the EDC/ECC system to ensure reliability. - Bad Block Processing The bad blocks in NAND devices are randomly distributed. There have been previous efforts to eliminate bad blocks, but they found that the yield is too low and the cost is too high. The NAND device needs to initialize the medium to detect the bad block and mark it. In the fabricated devices, the failure rate will be high if this treatment cannot be carried out by a reliable method. 3.5 Simple Operation NOR-based flash memory can be used very directly, can be connected as other memory, and can run code directly on it. NAND is much more complex because of the need for an I / O interface. Access methods for various NAND devices vary from manufacturer to manufacturer. When using NAND devices, you must write to the driver before doing anything else. Writing information to NAND devices requires that designers don’t write to bad blocks, which means virtual mapping is necessary all the time on NAND devices. 3.6 Software Support When discussing software support, a distinction should be made between basic read / write / erasing operations and higher-level software for disk emulation and algorithms of flash management, also including the performance optimization. Running code on a NOR device doesn't require any software support. But using a NAND device, you usually need a driver, that is MTD(Memory Technology Driver). Both NAND and NOR devices need MTD when writing and erasing operations. NOR devices requires less MTD, because many vendors offer more advanced software for NOR devices, including M-System 's TrueFFS driver, which is used by manufacturers such as Wind River System, Microsoft, QNX Software System, Symbian and Intel. It also used to simulate DiskOnChip products and manage the NAND flash memory, including error correction, bad block handling, and loss balancing. The main manufacturers of NOR FLASH is INTEL and MICRO, used to be the mainstream of FLASH products, but its market share now squeezed by NAND FLASH. Its advantage is that it can run programs directly from FLASH, but the process is complex, thus it is expensive. NAND FLASH's main suppliers are SAMSUNG and Toshiba, and it widely used in USB drives, memory cards, and MP3 players. With different processes, it has larger storage capacity and is cheaper than the NOR FLASH. But also has the drawback, is unable to address runs the program directly, only used to store the data. In addition, NAND FLASH is very prone to bad blocks, so it is necessary to detect it by the related algorithm.  NAND FLASH is used to store data and programs in laptops, but it must be started with NOR FLASH. In addition to SAMSUNG processors, other mainstream processors for laptops do not support NAND FLASH startup directly. Therefore, you must start the machine with a small piece of NOR FLASH, and run OS and other software through the NAND FLASH load into SDRAM. IV Conclusion The DRAM uses the charge on the gate capacitor of the MOS transistor to store the information. Once the power is down, all the information will be lost. Because the grid will leak, it needs refresh operation to replenish the charge on these gate capacitors regularly. And every time the data is read out, it requires running the same work. This is called dynamic refresh, so it is called dynamic RAM. Because it uses only one MOS to store information, it can be highly integrated and can do a lot of work. SRAM uses registers to store information, so once the power is down, the data will be lost. But when the power supply, its data will always exist without the need for dynamic refresh, thus it is called static RAM. The above is mainly used in the system with large capacity, do not need to recover data through refresh operation. Flash ROM uses the capacitor on the floating gate to store the charge to store the information, because the floating gate does not leak, so the information can still be saved after the power is off. Also because of its simple mechanism, it can be integrated highly, and the capacity can be very large. Flash rom needs to be erased by electricity before writing, but in different approach of erasure, EEPROM can be erased in bytes, and flash rom can only be done in sector. However, it can be written in byte units, mainly used for bios, U disk and Mp3 devices that require large capacity and data storage when power is down.   FAQ   1.What is ROM and its function? Read-only memory (ROM) is a type of storage medium that permanently stores data on personal computers (PCs) and other electronic devices. It contains the programming needed to start a PC, which is essential for boot-up; it performs major input/output tasks and holds programs or software instructions.   2. What are the four types of ROM? MROM (Masked ROM) ... PROM (Programmable Read Only Memory) ... EPROM (Erasable and Programmable Read Only Memory) ... EEPROM (Electrically Erasable and Programmable Read Only Memory) ...   3. What is a RAM in a computer? RAM stands for random-access memory, but what does that mean? Your computer RAM is essentially short term memory where data is stored as the processor needs it. This isn't to be confused with long-term data that's stored on your hard drive, which stays there even when your computer is turned off.   4. What is flash memory used for? Flash memory is a long-life and non-volatile storage chip that is widely used in embedded systems. It can keep stored data and information even when the power is off. It can be electrically erased and reprogrammed. Flash memory was developed from EEPROM (electronically erasable programmable read-only memory).   5. Is Flash memory a RAM or ROM? RAM is Read Only Memory. Unlike RAM, ROM is the persistent storage. ... Flash Memory is one category of ROM i.e Electrically Erasable Read Only Memory (EEPROM).   6. What is flash memory and its types? Flash memory is a type of erasable read-only memory (EEPROM) that clears and rewrites data in chunks for fast, energy-efficient access and rewriting. Flash memory, or flash storage, is non-volatile, which means it remains viable even without an active power source.   7. What is RAM and ROM? RAM, which stands for random access memory, and ROM, which stands for read-only memory, are both present in your computer. RAM is volatile memory that temporarily stores the files you are working on. ROM is non-volatile memory that permanently stores instructions for your computer.   8. Which is better RAM or ROM? RAM is random access memory and cannot hold the data without the power, whereas ROM is a read-only memory and can hold the data even without the power. ... With RAM, writing data is a much faster and lightening process, whereas ROM, writing data speed is much slower as compared to RAM.   9. What are the disadvantages of ROM? The disadvantages of Erasable Programmable ROM (EPROM) are: The static power consumption is high as the transistors used have higher resistance. It is not possible for a particular byte to be erased, instead the entire content is erased. UV based EPROM takes time to erase the content.   10.What are the disadvantages of RAM? If CPU wants to read data only from the RAM, then the data access from the cache and the registers is slow in comparison to ROM. RAM is volatile, which means it is difficult to store data for a lengthy period of time. Unplanned circumstances like a power outage can result in data loss.   11. What is the work of ROM? Read only memory (ROM) provides permanent storage for instructions needed during bootstrapping, or the process of turning on the computer. It does so by storing the BIOS and other firmware for the computer hardware. This firmware is very hardware-specific and rarely needs updating.   12. Why is more RAM better? Generally, the faster the RAM, the faster the processing speed. With faster RAM, you increase the speed at which memory transfers information to other components. Meaning, your fast processor now has an equally fast way of talking to the other components, making your computer much more efficient.   13. Is RAM is a volatile memory? Volatile memory is computer memory that requires power to maintain the stored information. Most modern semiconductor volatile memory is either Static RAM (see SRAM) or dynamic RAM (see DRAM).   14. Why is ROM so important? ROM provides the necessary instructions for communication between various hardware components. As mentioned before, it is essential for the storage and operation of the BIOS, but it can also be used for basic data management, to hold software for basic processes of utilities and to read and write to peripheral devices.   15. What is stored in ROM? ROM is memory that cannot be changed by a program or user. ROM retains its memory even after the computer is turned off. For example, ROM stores the instructions for the computer to start up when it is turned on again.  

The larger the resistance of the drive, the longer the turn-on time of MOSFET, and the longer the voltage and current overlap time in the switching time, the greater the switching loss. Therefore, the smaller the resistance, the better the drive resistance should be, provided that the drive resistance can provide enough damping to prevent the drive-current oscillation. When designing switch power supply or motor drive circuit with MOSFET, the factors such as on resistance, maximum voltage and maximum current of MOSFET should be considered. In general, the MOSFET tube can be divided into the enhanced and depleted, P-channel or N-channel is a total of 4 types, but the enhanced NMOS tube and PMOS tube are mainly used, in these two commonly mentioned enhanced type, the more commonly used is NMOS, The reason is its small on-resistance and easy to manufacture. However, it is not enough to consider these, because the current will have different losses in various devices, so we must ensure that sufficient current to drive the MOSFET.  Figure 1. MOS schematic diagram In this paper, we will discuss the calculation of the MOS gate drive resistor. The range of the MOSFET drive resistance is between 5~100ohms, so how to further optimize the selection of the resistance value in this range?  Equivalent Drive Circuit Figure 2. Equivalent drive circuit L is the PCB line inductor, according to the professional experience its straight line value is 1nH/ mm, considering other line factors, take L=Length +10 (nH), where Length unit is mm. Rg is the gate drive resistance, and the driving signal is a square wave with a peak value of 12 V. Cgs is the gate and source capacitance of MOSFET, with different tubes and driving voltage its value will be different, here is 1nF. VL+VRg+VCgs=12V Taking drive circuit: Getting differential equation of driving voltage of Cgs: Obtaining Transformation function by method of Laplace transform: This is a third-order system, which is an overdamped vibration when its poles are three different real roots, there are two same solid roots is critical damped vibrations, and there are imaginary roots is underdemped vibrations, which will generate waves of oscillation up and down at the gate of MOFET. This is something we do not want to see, so the choice of gate resistance Rg should make it work in the critical damping and over damping states, but the parameter error is actually working in the overdamped state. Based on the above, therefore, the minimum range of Rg values can be obtained according to the length of the line. Making the length of running line of 20mm and 70mm respectively: L20= 30nH , L70= 80nH, then Rg20=8.94Ω, Rg70=17.89Ω, Here are the voltage and current waveforms   Figure 3. Driving current ripple curve According to the diagram when the Rg is small, the driving voltage surge will be higher, more and more oscillation will exist when the L becomes large, and the performance of MOSFET and other devices will be affected obviously. However, when the resistance value is too large, the driving waveform will rise slowly, while it will have a negative effect when the MOSFET has a large current passing through. In addition, we should note that when L is small, the peak value of driving current is larger, and the output capacity of general IC is limited. When the actual driving current reaches the maximum value of IC output, the output of IC is equivalent to a constant current source. When Cgs is charged linearly, the rising of driving voltage waveform will slow down. The current curve may be shown on the follow (the inductance does not work because the current is constant), this may have an impact on the reliability of the IC, and a small step or burr may occur in the rise of the voltage waveform. Figure 4. Current curve The PWM OUT output of the general IC is shown in the left figure. The internal integration includes the current-limiting resistor Rsource and Rsink, usually Rsource > Rsink, but the actual values are related to the peak driving output ability of the IC. It can be approximately considered that R=Vcc/Ipeak. The drive output capacity of IC is about 0.5A, and meanwhile Rsource is about 20Ω. From the previous voltage and current curves, we can see that the IC driver can drive MOSFET,  but the drive line is usually not a straight line, the inductance may be greater, and in order to prevent external interference, it is necessary to use the Rg drive resistor to suppress. This resistance should be as close as possible to the gate of the MOSFET when considering the effect of the line distribution capacitance. Figure 6. PWM OUT The effect of Rg and L on rising time: (Cgs=1nF, VCgs=0.9*Vdrive) TR(nS)19492302045229Rg(ohm)10221001022100L(nH)303030808080 It can be seen that L has little effect on TR, but Rg has great influence on TR. TR can be estimated approximately by 2*Rg*Cgs. Usually, the rise time is less than 20 percent of the conduction time, and the loss of the MOSFET switch when it is switched on will not cause a heat problem. So when the minimum conduction time of MOSFET is determined, the maximum value of Rg is determined . Generally, the smaller the Rg is, the better, but if considering the EMI, its value should be taken as large as possible. The selection of resistor in MOSFET on-state is discussed above. In order to ensure the fast discharge of gate charge in MOSFET off-state, the resistance should be as small as possible, which is the reason of Rsink<Rsource. To ensure rapid discharge, a diode can be connected in parallel on the Rg. When the discharge resistance is too small, it will also cause resonance due to the inductance of the line (so in some applications there will be a small resistance on the diode.). But the reverse current of the diode is not conductive, at the same time, the Rg is involved in the reverse resonant circuit. Therefore, the peak of reverse resonance can be suppressed. This Diodes usually use a high frequency and small signal tube 1N4148. In practice, we should also consider the influence of the gate and drain of MOSFET and a capacitor Cgd. When MOSFET is on, Rg has to charge Cgd, which will change the voltage rise slope. When off, VCC will charge Cgs through Cgd. In this case, the charge on Cgs must be removed quickly, otherwise, it will lead to abnormal conduction of MOSFET. Figure 7. MOSFET schematic diagram FAQ   1. Why do MOSFETs need resistor? MOSFET gates are exceptionally high impedance. Just like a GPIO pin set to be an input, a pull-down or pull-up resistor helps keep the transistor on or off during power-on. ... When used with a switch or cable that could be disconnected, it is obvious to use a pull-down or pull-up resistor.   2. Do MOSFETs need pull down resistors? You either need a resistor to pull it down to ground or you need the input signal to drive it low. ... You only have to drain the inherent capacitance on the MOSFET gate when you're pulling it low so even at a high resistance to ground the RC time constant is usually relatively short.   3. Does Mosfet have resistance? The MOSFET behaves like a resistor when switched ON (i.e. when Vgs is large enough; check the data sheet). Look in the data sheet for the value of this resistor. It's called Rds(on). It may be a very small resistance, much less than an Ohm.   4. What is the purpose of gate resistor? A gate resistor is used is to slow down the turn-on and turn-off of the MOSFET. (This is more relevant to power circuits that switch a fair amount of current.)   5. What is Mosfet used for? The MOSFET (Metal Oxide Semiconductor Field Effect Transistor) transistor is a semiconductor device which is widely used for switching and amplifying electronic signals in the electronic devices. The MOSFET is a three terminal device such as source, gate, and drain.   6. What is Mosfet and how it works? In general, the MOSFET works as a switch, the MOSFET controls the voltage and current flow between the source and drain. The working of the MOSFET depends on the MOS capacitor, which is the semiconductor surface below the oxide layers between the source and drain terminal.   7. How Mosfet can be used as a resistor? When you slowly increase the gate voltage the MOSFET slowly starts conducting by entering the linear region where it starts developing voltage across it which we call as VDS . In this region, the MOSFET acts as a resistance of finite value.   8. Can Mosfet switch AC? Yes, but you need to connect two back to back to deal with the body diode. Connect the source terminals and gate terminals and connect a floating voltage supply between sources and gates. This circuit is typically called a solid state relay.   9. How much current can a Mosfet handle? Modern MOSFETs can have on resistances of less than 10 milliohms. A little math shows that this device can handle 10 amps with one watt converted into waste heat (power = current2 x resistance). Since many MOSFETs come in TO-220 packages, no heatsink is needed in this instance.   10. How many types of Mosfet are there? four types. There are two classes of MOSFETs. There is depletion mode and there is enhancement mode. Each class is available as n- or a p-channel, giving a total of four types of MOSFETs. Depletion mode comes in an N or a P and an enhancement mode comes in an N or a P.

Many engineers who have not used the switching power supply may have some worry about it, such as the PCB layout, the parameter and type selection of components, and so on. In fact, as long as you understand the basic principle, the use of switching power supply design is very convenient. In today's article, we will introduce you to some basic knowledge of switch-mode power supply, along with some experience sharing when using the switch-mode power supply. SMPS Tutorial: Switch Mode Power Supplies and Power Conversion  Catalog I. What is the Switch Mode Power SupplyII. How to Debug the Switching Power Supply Circuit?III. What Needs to Be Grounded?3.1 Definition of Grounding3.2 Grounding Mode3.3 How is the Signal of the Single Board Grounded?3.4 How Do the Single Board Interface Devices   Grounding?3.5 How to Grounding the Shield Layer?IV. Introduction of Signal Backflow and TranspartitionV. Should Analog Separate from the Digital , and How?FAQ I. What is the Switch Mode Power Supply  A switch-mode power supply usually consists of a controller and an output part. Some controllers integrate MOSFET into the chip, which makes it easier to use and simplify the PCB design, but the flexibility of components is weakened. The switching controller is actually a closed-loop feedback control system, so there is a sampling circuit of output-voltage feedback and a feedback-loop control circuit. Therefore, this part of the design is to ensure an accurate sampling circuit and to control the feedback depth, because if the feedback loop response is too slow, it will have a great impact on the transient response-ability. The output parts include output capacitance, output inductor, MOSFET, and so on. The selection of these devices is basically to balance the performance need and cost. For example, the high switching frequency can use small inductance (which means small package and low cost), but a high switching frequency will increase interference and the switching loss of MOSFET, result in reducing efficiency and increasing cost. Lower switching frequency has the opposite effect. The selection of Rds_on parameters of MOSFET and the ESR for output capacitance is also very important. ESR is small can reduce output ripple, but the cost of the capacitor will increase. And It is important to note that switching power controllers can not be well driven with too much MOSFET. In general, suppliers of switching power supply controllers will provide specific formulas and usage options for engineers. Figure. 1 Switch Mode Power Supply Circuit   II. How to Debug the Switching Power Supply Circuit? （1）The output of the power supply circuit is installed to the board through the low resistance and high power resistor, so that the power circuit can be debugged first before welding resistance, avoiding the influence of the latter circuit.  （2）The switching controller is a closed-loop system. If the output deterioration beyond the range that the closed-loop can control, the switching power supply will work improperly. This situation requires careful examination of feedback and sampling circuits. Especially, if the output capacitance with a large ESR, lots of ripple of power supply will be produced, which will also affect the operation of switching power supply.  III. What Needs to Be Grounded? At the very start, the introduction of grounding technology is a protective measure to prevent lightning strikes on electric power or electronic equipment. The purpose is to introduce lightning current through the lightning rod to the earth to protect buildings. And meanwhile, grounding is also an effective way to protect personal safety.  When the phase line touches the shell of the equipment causing by some reason (such as poor insulation of the wire, line aging, etc.), there will be a dangerous voltage in the shell of the equipment. Having grounding, the resulting fault current will flow to the earth, thus it plays a protective role.  For example, in communication systems, the interconnection of signals between a large number of devices requires each device to have a point as a reference, and with the complication of electronic equipment, the signal frequency is becoming higher and higher, therefore, grounding design as special attention paid to the electromagnetic compatibility problems such as mutual interference between signals.  In addition, improper grounding will seriously affect the reliability and stability of system operation. Recently, the concept of "grounding" has also been introduced into high-speed signal backflow technology.  3.1  Definition of GroundingIn the modern concept of grounding, for line engineers, the term usually means "reference point for line voltage"; for system designers, it is often a cabinet or frame; for electrical engineers, it is a green and safe ground line or a wire connected to the earth. A more general definition is that "grounding is the low impedance channel which the current returns its source." Noting that the points are "low impedance" and "channel".  3.2  Grounding ModeThere are many ways of grounding: single-point grounding, multi-point grounding, and mixed type of grounding. Single-point grounding is divided into a series of single-point grounding and parallel single-point grounding. In general, single-point grounding is used in simple circuits, and low frequency (f10MHz) circuits use multipoint grounding or multilayer (complete a ground plane layer).  3.3   How is the Signal of the Single Board Grounded?For the general device, the near ground is the best. After adopting the multilayer design with a complete ground plane, the grounding of the general signal is very easy. The basic principle is to ensure the continuity of the line, reduce the number of holes, approach the ground plane or the power plane, etc. 3.4  How Do the Single Board Interface Devices  Grounding?Some veneers will have external input-output interfaces, such as serial port connectors, RJ45 connectors, etc. If their grounding is not well designed, it will also affect normal operation, such as error codes, packet loss, etc. And it will become an external source of electromagnetic interference sending the noise out. In general, a single interface grounding will be made, and the signal is connected by a thin wire connection, string 0 ohms, or small resistance. Thin lines can be used to block signal ground noise. At the same time, the interface and the interface power filter should also be considered seriously.  3.5  How to Grounding the Shield Layer? The shielding layer of cables is connected to the interface grounding instead of the signal grounding, because there are various noises on the signal grounding. If the shield layer is connected to the signal ground, the noise voltage will drive the common-mode current to interfere outward along the shield layer. Therefore, the poorly designed cable is generally the maximum noise output source of electromagnetic interference. Of course, the interface ground should keep clean. IV. Introduction of Signal Backflow and TranspartitionFor an electronic signal, it needs to find a way with the lowest impedance to return current to the ground, so how to deal with the signal backflow becomes very important. First, according to the formula, we can know that the radiation intensity is proportional to the area of the loop. Specifically, the longer the path the return is, the bigger the ring is formed, and the greater the external radiation interference is, thus the power-circuit flow back and signal loop area should as small as possible when design PCB. Second, for a high-speed signal, providing a good signal backflow can guarantee its signal quality. Because the characteristic impedance of the transmission line on the PCB is generally calculated by reference to the ground (or power layer), if there is a continuous ground plane near the high-speed line, the impedance of this line can be kept continuous, and if there is no ground reference near the section line, the impedance will change and the signal will be affected as well. Therefore, the high-speed lines should be distributed to the layer near the ground plane, or they should be walked in parallel next to each other, to shield interference and provide backflow nearly.  Third, do not divide wires when having power supply in wiring way, this is because the signal backflow path across different power layers will be longer, and be vulnerable to interference. For low-speed signals, it is not strictly required that, because the resulting interference signal can not be concerned about. But for high-speed signals should be checked carefully, do not cross as far as possible, you can adjust the power part of the wire. (this is for multiple power supplies on multilayer boards).  V. Should Analog Separate from the Digital , and How? Whether analog signal or digital signal should return to the ground. Because the digital signal changes quickly and the noise caused by the digital signal will be very large, if analog and digital mixing, the noise will affect the analog signal.  In general, the grounding of analog and digital processing must be separated, then connected by a thin line, or a single point. The general idea is to try to block the noise from the digital ground to the analog ground. But it is not a very strict requirement that analog and digital ground must be separated, if the analog section near the digital ground is still very clean, they can be combined. FAQ 1. What are the 3 types of power supply?There are three subsets of regulated power supplies: linear, switched, and battery-based. Of the three basic regulated power supply designs, linear is the least complicated system, but switched and battery power have their advantages. 2. What is meant by switch mode power supply?A switch mode power supply is a power converter that utilises switching devices such as MOSFETs that continuously turn on and off at high frequency; and energy storage devices such as the capacitors and inductors to supply power during the non-conduction state of the switching device. 3.What are the advantages and disadvantages of switch mode power supply?Advantages & disadvantages of switch mode power supply (SMPS)a. The switch mode power supply has a smaller in size.b. The SMPS has light weight.c. It has a better power efficiency typically 60 to 70 percent.d. It has a strong anti interference.e. SMPS has wide output range.f. Low heat generation in SMPS. 4. What is a DC switching power supply?A Switching DC power supply (also known as switch mode power supply) regulates the output voltage through a process called pulse width modulation (PWM). The PWM process generates some high frequency noise, but enables the switching power supplies to be built with very high power efficiency and small form factor. 5. What is the difference between a switching power supply and a linear power supply?Linear power supplies deliver DC by passing the primary AC voltage through a transformer and then filtering it to remove the AC component. Switching power supplies feature higher efficiencies, lighter weight, longer hold up times, and the ability to handle wider input voltage ranges. 6. Do I need a switching power supply?The switching power supply implies higher efficiency due to the high switching frequency, enabling it to use a smaller, less-costly high-frequency transformer as well as lighter, less-costly filter components. Switching power supplies contain more overall components, therefore are usually more expensive. 7. Is a switching power supply regulated?A switch mode power supply regulates an output voltage with pulse width modulation (PWM). This process creates high-frequency noise but it provides a high-efficiency rating in a small form factor. ... The low DC voltage is finally converted into a steady DC output with another set of diodes, capacitors, and inductors. 8. How do I know if my power supply is regulated?You can generally stick one probe into the middle of the connector, and hold the other against the outside. With a few exceptions, the middle is positive, so use the red lead there, and use the black lead on the outside shell. Regulated supplies, without any load, should measure very close to the target voltage of 12v. 9. Can I use a switching power supply to drive a DC motor?A simple unregulated analog power supply may be easier and be able to supply the large starting under load current more that the switching one. DC motors are not too fussy about the supply, and will usually run quite well on unfiltered DC. 10. Are switch mode power supplies any good?Switch mode power supplies, SMPS provide improved efficiency & space saving over traditional linear supplies, but care has to be taken to ensure noise on the output is low. Switch mode power supplies are widely used because of the advantages they offer in terms of size, weight, cost, efficiency and overall performance. You May Also LikeSwitching Power Supply Guide: Protection CircuitSwitching Power Supply Tutorial: 4V～16VSwitched Mode Power Supply Tutorial: Principles & Functions of SMPS Circuits

With the development of science and technology, electronic products are changing with each passing day. Also, electronic assembly technology is facing challenges. Following the development of electronic technology, people work harder to make innovations in electronic assembly technology.  And in this context, a flexible circuit board invented used which made of the thin-and-flexible polymer film. It can complete the application of surface mounting technology and bend without affecting the normal circuit operation.  Clear Flexible Printed Circuit Catalog I. Brief IntroductionII. Five Main Materials for Flexible Circuit Board2.1 Insulating Firm2.2 Bonding Sheet2.3 Copper Foil2.4 Overburden2.5 Reinforcement PlateFAQ I. Brief Introduction Today's flexible electrons are all made of SMT technology, so they are thin and exquisite with insulation thickness of fewer than 25 μm. It can be bent arbitrarily and rolled into a cylinder. And it makes full use of three-dimensional volume. It breaks the stereotype of the traditional area of use and creates the ability to make full use of the shape of the volume, which can significantly enhance the effective density of use in the length of the conductor currently routinely used per unit area, forming a high-density assembly. In recent years, flexible circuit technology has been applied in various fields, such as radio communication, computer, and automobile electronic equipment. Unlike in the past, flexible circuits have been used as substitutes for rigid cables, and they have been used as substitutes for rigid circuits and printed circuit boards (PCB) in applications where thin or three-dimensional circuits are required. In order to meet the requirements of rigid and flexible applications, it is combined flexible circuit technology in the rigid circuit board, making flexible circuit board used widely. The functions of the flexible circuit board can be divided into four categories, including the lead line, printed circuit, connector, and IntegraTIon of FuncTIon, which covers the computer, Computer peripheral auxiliary system, civil electrical appliances and cars, and other areas. For different applications, the material of the flexible circuit board should select carefully. And the followings are some rules of the five main materials of the flexible circuit board.  II. Five Main Materials for Flexible Circuit Board 2.1 Insulating FirmThe insulating film is flexible and can be used as the insulation carrier of the circuit board to form the basic layer of the circuit. When selecting the flexible dielectric film, the heat resistance, overlay, thickness, mechanical properties and electrical properties of the material should be tested.  Insulation film is usually available on the market, the most common is polyimide and polyester materials. Of all the flexible circuit manufacturers in the United States, nearly 80% use polyimide film as the material for flexible circuits, and about 20% use polyester film. Because polyimide material is nonflammable, stable geometry, high anti-tear, and able to withstand high temperature during welding. 2.2 Bonding Sheet It is made up of two insulating films coated with adhesive, the ability is gluing the film to the foil, and the film to the film in the flexible circuit, In order to provide mechanical support and eliminate stress during insertion of components and connectors. It also can provide protection and electrical insulation. Different types of adhesive sheets can be used for different film substrates, such as polyester bonding sheets and polyimide bonding sheets are different, for example, the polyimide substrate has epoxy resin and acrylic acid. 2.3 Copper FoilCopper foil is a conductor layer that is coated on the insulating substrate and then selectively etched to form a conductive line. The vast majority of this copper foil is rolled copper foil or electrolytic copper foil. The ductility and bending resistance of the rolled copper foil is better than that of the electrolytic copper foil.  The elongation of the rolled copper foil is 20%~45% and the electrolytic copper foil is 4%~40%. The commonly used thickness of copper foil is 35um (1oz), also they have 18um (O.5oz), 70um (2oz), or even 105um (30z). According to different applications, we have to choose different forms of copper foil.  If only to replace wires and connectors, and to reduce manufacturing time and cost, the best choice is electrolytic copper foil. The electrolytic copper foil will increase the weight of copper to level the load capacity of the current, thus obtaining the suitable width of the copper sheet. 2.4 OverburdenThe brand, Novaclad, created by Sheldahl, applies the vacuum metal spraying technology which is a patent. It is a technology that applying a thin layer of pure copper to the surface of a polyimide film, then electroplating into a specific thickness to form the substrate of Novaclad. The base material is used in Novaflex, a flexible circuit without adhesive. After all the circuits have been made, a layer of Novaflex insulation is applied. The Novaflex is designed to work under harsh conditions, and Novaflex without adhesive provides better flexibility, chemical resistance, high-temperature properties, and maximum heat dissipation properties. 2.5 Reinforcement PlateThe reinforced plate to the local position of the flexible plate plays the role of super supporting and strengthening the flexible film substrate, which is convenient for the connection, fixation, or other functions of the PCB. According to different needs, the reinforcement board materials commonly use polyester, polyimide sheet, epoxy fiberglass cloth plate, phenolic-aldehyde paper board, steel plate, aluminum plate, etc.  FAQ 1.What is a flexible circuit board?A flexible printed circuit board features a combination of several printed circuits as well as components that are positioned on a flexible substrate. These circuit boards are also known as flex circuit boards, flex PCBs, flex circuits, or flexible printed circuits. 2. What is flex circuit used for?Flex circuits are often used as connectors in various applications where flexibility, space savings, or production constraints limit the serviceability of rigid circuit boards or hand wiring. A common application of flex circuits is in computer keyboards; most keyboards use flex circuits for the switch matrix. 3. What are flexible circuit boards made of?Flexible circuits are thin, light-weight electrical circuits that conform to small spaces and contoured shapes. They consist of conductive strips of metal, usually copper, encapsulated with an insulating dielectric material made of polyimide or a solder mask. 4. Where are flexible PCBS used?a. Automobiles.b. Consumer electronics including smartphones, SLR cameras and camcorders,c. Medical systems and devices such as heart monitors, pacemakers and the bionic knee.d. Motion systems.e. GPS systems.f. Aerospace and avionics systems. 5. When was the first flex printed circuit made?From early applications during World War II to the present, growth and proliferation for flex circuits and flexible printed circuit boards continues exponentially. A flexible circuit in its purest form is a vast array of conductors bonded to a thin dielectric film. 6. What are the advantages and disadvantages of flexible circuit boards?The advantages of the flexible circuit board are mainly high assembly density, which can save the connection of redundant cables, in addition, it has good bendability, high flexibility, small size, simple structure, and convenient installation.Disadvantages of flexible circuit boards: 1. High initial cost 2. Difficult to change and repair 3. Size limited 4. Improper operation and easy damage, etc. 7. What do flexible circuit boards and rigid circuit boards mean?a.  Flexible circuit boards are used more in digital products. The difference between it and the rigid circuit board is that the substrate of the circuit board is different. As the name implies, the board can be bent and softer.b. "Multilayer board" and "double-sided board" mainly refer to the number of sides of wiring on the circuit board. Above 2 layers are multi-layer boards.From the perspective of the process flow, the multilayer board needs to be processed by the inner layer map, and the outer layer can be processed after being pressed. The processing flow of the outer layer is basically the same as the processing flow of the double-sided board. 8. What is the temperature resistance of fpc flexible circuit boards?FPC flexible circuit board can withstand high temperature of 280 degrees, about 1 hour. However, the recommended temperature for normal use is not less than -20 and not higher than 80. 9. With flexible circuit boards, why pcb hard printed circuit boards are still not eliminated?For PCBs that need to use plug-in components, only rigid boards can be used, which is what you call rigid boards; for many PCBs with stress requirements, only rigid boards can be used. The cost of flexible boards is currently much higher than rigid boards, more than doubled. And the straight-through rate of rigid boards is higher than that of flexible boards 10.Classification of flexible circuit boards?According to the combination of base material and copper foil, flexible circuit boards can be divided into two types: flexible boards with glue and flexible boards without glue. Among them, the price of the glueless flexible board is much higher than that of the glued flexible board, but its flexibility, the bonding force of the copper foil and the substrate, and the flatness of the pad are also better than the glued flexible board. You May Also LikeSwitching Power Supply Tutorial: 4V～16VWhat is A MCU’s internal Structure: Single Chip Micro-ComputerPCB Wring Tutorial: A/D converterMonitoring Technology in Communication Power Supply: Application GuideDIY CommunityDIY Flxible Printed CircuitsMake Flexible Circuit Boards Using A 3D Printer

The solid-state capacitor is called a solid-state aluminum electrolytic capacitor. The biggest difference between it and ordinary capacitors (i.e. liquid aluminum electrolytic capacitors) lies in the use of different dielectric materials. The dielectric materials of liquid aluminum capacitors are electrolyte, while the dielectric materials of solid capacitors are electroconductive polymer materials.   Electronic Basics #14: Capacitors Catalog I. Solid State Capacitor Introduction II. Solid State Capacitor Advantages III. Solid State Capacitor Types IV. Advantages and Disadvantages of Solid Capacitors FAQ   I. Solid State Capacitor Introduction   In view of the many problems of liquid electrolytic capacitance, the solid aluminum electrolytic capacitor has emerged as the times require. Since the 1990s, solid conducting polymer material has been used as cathode instead of electrolyte for aluminum electrolytic capacitor, which has achieved great development. The conductivity of conductive polymer materials is usually 2 ~ 3 orders of magnitude higher than that of electrolytes.    The application of aluminum electrolytic capacitors can greatly reduce the ESR and improve the features of temperature frequency, what’s more, because of the good processability of polymer materials, it is easy to be packaged. All greatly promote the development of aluminum electrolytic capacitance.   On the market, there are two types of aluminum electrolytic capacitors: organic semiconductor aluminum electrolytic capacitors (OS-CON) and polymer conductor aluminum electrolytic capacitors (PC-AC) (PC-CON).    The structure of an organic semiconductor aluminum electrolytic capacitor is similar to that of a liquid aluminum electrolytic capacitor; both are packaged in straight-pin and vertical configurations.   The difference is the cathode material of solid aluminum polymer electrolytic capacitor using the organic semiconductor extract, which can effectively solve the tough problems of electrolyte evaporation, leakage, flammability, and so on. Also, a solid aluminum polymer patch capacitor is a unique structure formed by combining the characteristics of aluminum electrolytic capacitance and tantalum capacitance.   Like liquid aluminum electrolytic capacitors, solid aluminum polymers are mostly in the form of patches. The film of polymer electrode with high conductivity is deposited on alumina as cathode, carbon, and silver as an extraction electrode, which is similar to the structure of solid tantalum electrolytic capacitance.     II. Solid State Capacitor Advantages   （1）With high stability, the solid aluminum electrolytic capacitor can work stably in a high-temperature environment, and improve the performance of the motherboard directly. At the same time, it is suitable for power filters because of its stable impedance in a wide temperature range, provides a stable and abundant power supply effectively, especially in overclocking.    Solid-state capacitors can work at high temperatures and maintain various electrical properties. The capacitance changes less than 15% in the whole temperature range, which is obviously superior to the liquid electrolytic capacitance. Meanwhile, the capacitance of solid-state electrolytic capacitor is independent of its working voltage, so it can work stably in the environment of voltage fluctuation.   （2）The solid-state aluminum electrolytic capacitor has an extremely long service life (over 50 years). It longer than the liquid aluminum electrolytic capacitance. And it will not be broken down, nor need to worry about liquid electrolyte drying and leakage affecting the stability of the motherboard. Solid-state electrolytes do not expand or even burn as liquid electrolytes do at high temperatures. Even if the temperature of the capacitor exceeds its limit, it just melts, which does not cause the capacitor metal shell to burst, so it is very safe.    The working temperature has a direct effect on the life of electrolytic capacitance. Advantages of its electrolyte make a longer service life than liquid electrolytic capacitor under different temperature conditions.   （3）Low ESR(Equivalent Series Resistance) and high mA rms are important indexes of capacitance. The lower the ESR, the faster the charge and discharge speed of capacitance. It directly affects the decoupling performance of the microprocessor power supply circuit, which is more obvious in high-frequency circuits. Therefore, it can be viewed the biggest difference between solid-state electrolytic capacitance and liquid capacitance.   Solid aluminum electrolytic capacitance with the lower ESR and energy dissipation under high power operation conditions can fully absorb the high amplitude voltage between the power lines in the circuit and prevent its interference to the system. When the CPU changes from a low power state to a full load state, the transient (generally less than 5 milliseconds) power required for this CPU switch comes from the CPU power supply circuit, at this moment, the high peak current can be output instantly by the high-speed charge-discharge characteristic of the solid-state capacitor, which can guarantee sufficient power supply and ensure the CPU to work stably.     III. Solid State Capacitor Types     According to the medium, capacitors can be divided into inorganic dielectric capacitors, organic dielectric capacitors, and electrolytic capacitors three categories.   1. Inorganic dielectric capacitors: including familiar ceramic capacitors and mica capacitors, we will often see ceramic capacitors on the CPU. Ceramic capacitors have excellent comprehensive properties and can be used in GHz-class UHF devices, such as CPU/GPU, thus its price is also very expensive.   2.Organic dielectric capacitors: such as thin-film capacitors, which are often used in loudspeakers with their precision, high temperature, and high-pressure resistance.   3. Electrolytic capacitors: known as aluminum capacitors. The traditional method of classifying electrolytic capacitors is based on anode materials, such as aluminum, tantalum, or niobium. However, this method of judging capacitance performance based on the anode is out of date. At present, the key to determine the performance of electrolytic capacitance lies not in the anode, but in the electrolytic, cathode. According to the classification of cathode materials, electrolytic capacitors can be divided into electrolyte, manganese dioxide, TCNQ organic semiconductors, solid polymer conductors, and so on.      IV. Breif Analysis of Advantages and Disadvantages of Solid Capacitors   The dielectric of liquid electrolytic capacitors is liquid electrolyte: liquid particles are very active at high temperatures and have a low boiling point relative to the internal pressure of the capacitor, making it easily explosible. The solid-state capacitance is made of polymer dielectric: at high temperatures, the particle growth and behavior of solid particles are lower than that of liquid electrolytes, and its boiling point will reach 350 degrees Celsius, making it almost impossible to burst.    The ESR of solid-state capacitance in high-frequency operation is shown to be very weak, and the conductivity is very fine. It has the properties of lowering impedance and producing less heat, which is the most obvious between 100KHz and 10MHz.   Traditional electrolytic capacitance is easily influenced by the operating environment's temperature and humidity, and it is less stable at high and low temperatures. The ESR of the solid capacitance can be as low as 0.0040.005 ohms between minus 55 and 105 degrees Celsius, but the electrolytic capacitance varies with temperature.   In terms of capacitance values, liquid capacitance would be lower than the indicated capacitance value below 20 degrees Celsius, and the lower the temperature, the lower the capacitance value. At minus 20 degrees Celsius, capacitance decreases by around 13%, and at minus 55 degrees Celsius, capacitance decreases by 37%. Since solid capacitance decreases by less than 5% at minus 55 degrees, solid state capacitors are guaranteed not to be harmed by lower temperatures. The low-frequency response of solid-state capacitance is not as good as electrolytic capacitance.     In other words, a motherboard with all-solid-state capacitance is not the most reasonable. Whether solid or electrolytic capacitors, their main function is to filter clutter, so long as the capacity and quality of capacitance can reach certain requirements, it can also ensure a stable operation. Solid-state capacitors at 105C have the same lifetime as electrolytic capacitors for 2000 hours.    When the temperature drops, their lives increase, but the solid-state capacitors increase even more. In general, the operational temperature of the capacitor is 70 degrees or less. In addition, the service life of solid-state capacitance can last 23 years, almost six times than the electrolytic capacitance. Compared with electrolytic capacitors, the capacity of electrolytic capacitors is much larger than that of solid capacitors at the same volume and voltage.     At present, solid capacitors are mostly used in the CPU power supply of computer motherboard, but the capacity redundancy is very little, it is necessary to improve the switching frequency of the part of the CPU power supply. Both solid and electrolytic capacitors will have the problem of capacity attenuation in the process of use. However, although the capacity of the circuit board with solid-state capacitance fluctuates slightly, the power supply will appear ripples, which will cause the CPU to work improperly.     Therefore, the lifetime of the solid-state capacitor is very high theoretically, but not in practice. Maintenance when using solid-state capacitor computer board: the power supply part of the CPU is often connected with multiple capacitors, so the solid-state capacitance will not have deformation, explosive slurry, leakage, etc. There is no way to determine which one is out of order basically. Therefore, in maintenance, one of them is often removed (no matter good or bad), and a large-capacity capacitor can be replaced (often with electrolytic capacitance). This method can usually solve the problem quickly.      In theory, the lifetime of the solid-state capacitor is very long, but there will still be a lot of faults in the process of practical use. At present, it seems that most motherboards with overclocking as the selling point put forward by many manufacturers will use solid-state capacitors. But it is not the capacitance that determines the performance of the CPU. The design of the circuit, the development of BIOS, the quality of the CPU itself, and the heat dissipation measures may determine the success or failure of the CPU.   FAQ   1. What is a solid state capacitor? The full name of a solid capacitor is a conductive polymer aluminum electrolytic capacitor, also called a polymer aluminum capacitor. It is currently the highest level of capacitor products. The dielectric material of the solid capacitor is a functional conductive polymer, which can greatly improve the product.   2. Are Solid Capacitors better? Solid capacitors have a higher tolerance not only for higher temperatures, but they also perform better with higher frequencies and higher current than electrolytic capacitors. ... Because there is less impedance at higher frequencies, solid capacitors are more stable and generate less heat than electrolytic capacitors.   3. How do you read a solid state capacitor? If you have a capacitor that has nothing other than a three-digit number printed on it, the third digit represents the number of zeros to add to the end of the first two digits. The resulting number is the capacitance in pF. For example, 101 represents 100 pF: the digits 10 followed by one additional zero.   4. What do you need to know about solid state capacitors? Solid-state capacitors have already gone down the altar. Many common electronic and digital products use these products in large quantities. The solid-state capacitors are similar to the common aluminum electrolytic capacitors, some are replaceable, and there is a solid capacitor, sheet, for Replace the common tantalum capacitor.   5. Which is the best electrolytic capacitor for motherboard? Solid aluminum electrolytic capacitors can directly improve the performance of the motherboard. At the same time, it is suitable for power supply filtering due to its stable impedance over a wide temperature range. It can effectively provide a stable and abundant power supply, which is especially important in overclocking.   6. How do you read a solid state capacitor? If you have a capacitor that has nothing other than a three-digit number printed on it, the third digit represents the number of zeros to add to the end of the first two digits. The resulting number is the capacitance in pF. For example, 101 represents 100 pF: the digits 10 followed by one additional zero.   7. What is the average lifespan of a capacitor? Design lifetime at rated temperature. Manufacturers of electrolytic capacitors specify the design lifetime at the maximum rated ambient temperature, usually 105°C. This design lifetime can vary from as little as 1,000 hours to 10,000 hours or more.   8. What metals are capacitors made of? There are three different anode metals in use for electrolytic capacitors: Aluminum electrolytic capacitors use a high-purity etched aluminium foil with aluminium oxide as dielectric. Tantalum electrolytic capacitors use a sintered pellet (“slug”) of high-purity tantalum powder with tantalum pentoxide as dielectric.   9. When should you use a capacitor? Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. In analog filter networks, they smooth the output of power supplies.   10. How do I choose the right size capacitor? You mainly need to look at 2 values: the voltage and the capacity -both are written on most capacitors-. For example, if you are going to charge a capacitor with 24V, you need to make sure your capacitor will support that voltage; so you'll need a capacitor for at least 25V (plus error margin).       You May Also Like Operational Amplifier(OP Amp) Tutorial Instructions of Common problems in the Application of Inverter About Operational Amplifier LM358: 24 Classical Circuits DIY Community:  DIY Capacitor Flux Capacitor - Back TO The Future