General discrete components are mainly considered from the functional withstand voltage value, current withstand value and power consumption in the circuit, while integrated circuits are mainly considered from the aspects of interface resources, working voltage and compatibility.
1. The selected devices follow the normalization principle of the company and select as few types of materials as possible without affecting the function and reliability.
2. Materials with "preference level" of "a" in the material code library are preferred.
3. Devices with a growth and maturity life cycle are preferred.
4. Select the born and falling devices to go through the special approval process.
5. Carefully select devices whose life cycle is in decline, and it is forbidden to select devices that are out of production.
6. The power devices are preferably packaged with RJA with small thermal resistance and greater TJ junction temperature.
7. It is forbidden to select devices with package size less than 0402 (included).
8. The anti ESD capacity shall be at least 100V, and anti-static measures shall be designed.
9. MSL (humidity sensitivity level) of selected components shall not be greater than level 5 (inclusive).
10. The model of sealed vacuum packaging is preferred. If MSL (humidity sensitivity level) is greater than level 2 (included), sealed vacuum packaging must be used.
11. The models of coil packaging and pallet packaging are preferred. If it is a device with humidity sensitivity grade of grade II or above, it is required to be packaged with disc-shaped plastic braided tape, which must be able to withstand the high temperature of 125 .
12. For key devices, at least two brands of models can replace each other, and scheme level replacement should be considered for some.
13. The materials used shall meet the requirements of anti-static, flame retardant, anti rust, anti-oxidation and safety regulations.
General rules for chip selection
1. Sn63pb37 alloy is preferred for lead BGA Solder Balls, and SnPb alloy with high lead (lead content 85%) can also be selected. SnAgCu alloy is selected for lead-free BGA Solder ball.
2. For SMD and integrated circuit devices with leads, the metal materials of lead wires shall be copper, copper alloy, valvable alloy and 42 alloy. The surface alloy shall be coated evenly and the thickness shall meet the relevant standards (4 7.6) m) , the coating shall not contain metallic bismuth. Tin lead pin coating: SnPb; Lead free pin coating: preferably: matte Sn, SnAgCu, Ni / Au, Ni / Pd / Au; Sn coating: for pure Sn coating, the thickness of Sn coating is 7.6 M (electroplating process), or 2.5 M (melting process after plating), or 5.1 M (tin dipping process), or 0.5 M (electroless plating process); Barrier layer Ni: thickness 3 m SnCu coating: thickness of SnCu coating 3 m Ni / Pd coating: Pd coating thickness 0.075 m. The thickness of Ni coating is 3 M or more; Ni / Pd / Au coating: Ni thickness 3 m. PD thickness 0.075 m. Au thickness is 0.025 0.10 m
3. Carefully select Taiwan's CPU and power chip.
4. It is forbidden to select QFN encapsulated components. If only QFN encapsulated components can be selected, they must be reviewed. Any chip in QFN package can only be used after being approved by the leader at the general manager level.
5. For IC, chip packaging devices with pin spacing of at least 0.5mm are preferred.
6. The devices in chip packaging are preferred, and dip packaging devices are carefully selected.
7. Try not to use BGA packaged components, only when they have to be used. If BGA is selected, the BGA ball spacing must be greater than or equal to 0.8mm, preferably greater than or equal to 1.0mm. And try to use the model of BGA ball device with lead, and use the lead welding process.
8. It is forbidden to select CPUs that do not support online programming.
9. Try not to use Samsung chips.
Resistance selection rules
1. 10 series, 12 series, 15 series, 20 series, 30 series, 39 series, 51 series, 68 series and 82 series are preferred.
2. The chip resistors are preferably packaged in 0603 and 0805, and the packages below 0402 are prohibited.
3. The pin resistance is preferably 0.25W, 0.5W, 1W, 2W, 3W, 5W, 7W, 10W and 15W.
4. For the temperature drift of resistance, the temperature drift of gear J shall not exceed 500ppm / , that of gear f shall not exceed 100ppm / , and that of gear B shall not exceed 10ppm / .
5. It is forbidden to select metal film resistance of 1W or above, and metal film resistance of 750k or above.
6. The axis type of power resistance above 7W is prohibited.
7. Carefully select potentiometers. If it is unavoidable, select multi turn potentiometers, and use Bourns brand. The electronic potentiometer operates according to the chip selection specification.
8. The resistance brands are Yageo, MK and BEDIS.
Capacitor selection rules
selection rules of aluminum electrolytic capacitors
1. In general application, select standard type with service life of 1000hr 3000hr (for price consideration, select long-life type carefully), and select aluminum electrolytic capacitor with service life of 2000hr as far as possible.
2. For the withstand voltage of aluminum electrolytic capacitor, 10V for 3.3V system, 10V for 5V system, 25V for 12V system and 50V for 24V system; 100V is selected for systems above 48V.
3. The working temperature of aluminum electrolytic capacitor must be 105 .
4. For the capacitance value of aluminum electrolytic capacitor, series 10, 22 and 47 are preferred; Capacitance models such as 224, 105 and 475 (replaced by sheet multilayer ceramic capacitor or tantalum electrolytic capacitor) are prohibited under 25V.
5. For high voltage aluminum electrolytic capacitors, 400V shall be reserved. It is forbidden to select non-polar aluminum electrolytic capacitors.
6. The brand "SAMWHA" (Sanhe) is selected for ordinary aluminum electrolytic capacitors, and NCC (Black King Kong) or other Japanese famous brand aluminum electrolytic capacitors are selected for high-end aluminum electrolytic capacitors.
7. It is forbidden to select aluminum electrolytic capacitors with patches.
tantalum electrolytic capacitor selection rules
1. Tantalum electrolytic capacitors with withstand voltage above 35V are prohibited.
2. Pin type tantalum electrolytic capacitor is prohibited.
3. For the withstand voltage of tantalum electrolytic capacitor, 10V for 3.3V system, 16V for 5V system and 35V for 12V system, 10V, 16V and 35V are preferred, and 4V, 6.3V and 50V are disabled (replaced by aluminum electrolytic capacitor).
4. For the capacitance of tantalum electrolytic capacitor: preferably series 10, 22 and 47. Tantalum electrolytic capacitors with capacitance below 105 are prohibited (replaced by ceramic capacitors).
5. Brand of tantalum electrolytic capacitor: KEMET, AVX.
selection rules of flake multilayer ceramic capacitors
1. Careful selection of high Q ceramic capacitors; Only on RF circuits.
2. Chip multilayer ceramic capacitor packaging: 0603, 0805 preferred, 1206, 1210 carefully selected, and 1808 above prohibited.
3. Withstand voltage of sheet multilayer ceramic capacitor: preferably 25V, 50V and 100V; The withstand voltage of capacity above 106 (inclusive) shall not be greater than 25V.
4. Sheet multilayer ceramic capacitor capacity: preferably 10, 22, 33, 47 and 68 series.
5. The materials of sheet multilayer ceramic capacitors are preferably NPO, X7R and X5R, and others are prohibited.
6. Brands of chip multilayer ceramic capacitors: Taiyo, Murata, KEMET, temex (high Q ceramic capacitor).
1. It is forbidden to select such capacitors for new products (instead of sheet multilayer ceramic capacitors).
Relay selection rules
1. Brand selection: Panasonic, Omron, finder.
2. Do not use relay sockets.
Diode selection rules
1. Do not use glass encapsulated diodes.
2. The LED is preferably a pin model with a diameter of 5mm. The SMD LED is preferably a model with a welded frame, and the ESD / MSL level follows the above standards.
3. Rectifier diode: the model with the highest back voltage is preferred for the same current level. For example, 1N4007 is selected for 1a and in5408 is selected for 3a.
4. Schottky diode: the highest level of reserved back voltage of the same current level, such as 1N5819 reserved, 1N5817 forbidden, SS14 reserved and SS12 forbidden; M7,30bq060, s5g reserved.
5. Light emitting diodes preferably have edges and short legs; In order to maintain the consistency of the company's products, the models of red hair and green hair are preferred, and the models of white hair and white hair are carefully selected; If there are no special requirements, try not to use long feet and boundless.
6. The preferred brand of LED is "Yiguang".
7. The brand of transient suppression diode is ProTek and Semtech.
Selection rules of triode
1. 90129013 is selected for the triode of 901x series.
Connector selection rules
1. It is forbidden to select IC socket. If the use of IC socket cannot be avoided, the IC socket with round hole must be used.
2. The pin seat shall be in three-sided contact, and it is forbidden to use two-sided contact. Except for special requirements such as PC104.
3. The complete set of connectors shall be of the same brand, that is, the plugs and sockets shall be of the same brand.
Switch selection rules
1. No selection dial switch.
2. The power switch is preferably a boat switch.
Inductor selection rules
1. The brands of SMD inductors are "Sanli" and "Sumida".
CPU selection rules
1. If the selected CPU is different from the same series and models used by our company, it needs to be approved by the general manager of production. If the selected CPU is a new series of CPU that our company has never used, it must be decided by the company level leaders at a meeting.
2. Retain Atmega48, Atmega168, Atmega32 and ATmega128. The new products are prohibited from using attiny2313 and atmega88.
3. ATmega128 in QFN package is forbidden to select new products in the future.
4. ARM7 can only select the following types: lpc2138fbd64, lpc2292fbd144, str710fz2t6 and str711fr2t6.
5. In the future, new products will use ColdFire series to replace 68000 series.
Flash selection rules
1. Span and SST are preferred for parallel flash brands, and Samsung is prohibited.
2. Serial flash brand is preferred ATMEL. It is forbidden to reuse at45db081b-ri for new products.
SRAM selection rules
Brand preference: ISSI, cypress, micron, IDT, disable Samsung.
EEPROM selection rules
1. Parallel EEPROM is prohibited.
2. Serial EEPROM brands are preferred ATMEL and microchip.
3. 24lc65-i / SM is prohibited for new products.
Crystal and crystal oscillator selection rules
General technical requirements for crystal materials: at cut (fundamental frequency), 20pF load capacitance, temperature range - 20 70 (industrial temperature grade), manufacturing frequency deviation of 30ppm, temperature drift of 50ppm / , lead-free products.
Hosonic and Epson are preferred for crystal and crystal oscillator brands.
Power selection rules
1. For products with high reliability requirements, lambda and COSEL are preferred for power supply; For products with low reliability requirements, Lido Huafu, Xingyuan Fengtai and Mingwei can be selected.
2. When selecting lambda power supply, it is convenient for normalization. It is required that everyone uniformly select the model with JST connector.
3. Standard power supply shall be selected as far as possible for new products, and customized power supply is not recommended.
1. The isolated DC / DC power supply is preferably the product of TI company. When TI products cannot meet the requirements, C & D is preferred.
Connector selection rules
1. European connector brands are HARTING, Erni and EPT. The plugs and sockets used in the same set of products are required to use the same brand, and different brands are prohibited to be used together.
1. If it is not necessary to use external communication signals, RJ11 and rj12 connectors are prohibited.
2. For RJ45, it is preferred that the connecting shrapnel is round needle, with shielding shell and shrapnel in the shielding shell. The thickness of the gold plating layer of RJ45 connecting shrapnel shall not be less than 3uin.
3. It is forbidden to select RJ45 socket with lamp and transformer.
4. The brand of RJ series connector is pulse (FRE).
white terminal selection rules
1. Try not to use white terminals.
2. The brands of white terminals are preferably JST, AMP and Molex.
1. The brand of PCB board mounting screw wiring connector is Phoenix.
2. The brand of PCB board mounting screw wiring connector is preferably 2-position and 3-position wiring terminals. Connectors with other digits can be spliced with 2-position and 3-position wiring terminals.
3. 5.08mm spacing is preferred, and 5.00mm spacing is prohibited.
selection rules of other rectangular connectors
1. The preferred brands of other rectangular connectors are as follows: amp, MOLEX, SAMTEC, Hirose, wcon and nstech.
2. The thickness of gold plating layer of connector pin shall not be less than 3uin.
3. Universal connectors are preferred, and customized connectors are prohibited.
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