Electronic components in the selection should at least follow the following guidelines:
1. Components of the technical conditions, technical performance, quality, etc. should meet the requirements of equipment;
2. The use of proven quality and stability, high reliability, promising standard components, does not allow the selection of out of varieties and disabled components;
3. Should be the maximum compression of the variety of components and specifications of the manufacturer;
4. No design of the components can not be stereotypes in the reliability of military products with high formal use;
5. Preferred to have a good technical services, supply timely and reasonable price of the components of the manufacturer. The key components of the user to the quality of the production side that;
6. Equal price-performance ratio, should be preferred to domestic components.
Electronic components in the application should focus on the following issues, and take effective measures to ensure the reliability of electronic components:
1. Derated use. Experience has shown that an important cause of component failure is due to its operation above the allowable stress level. Therefore, in order to improve component reliability and extend its service life, it is necessary to consciously reduce the working stress (electrical, thermal, mechanical stress) applied to the component so that the actual use stress is lower than its specified rated stress. This is the basic meaning of derating.
2. Thermal design. Electronic components of the thermal failure is due to high temperature components caused by material deterioration. As the density of electronic components used in modern electronic equipment is getting higher and higher, thermal coupling between components is caused by conduction, radiation and convection. Thermal stress has become one of the important factors affecting the reliability of components. Therefore, the layout of components, installation and other processes, we must take full account of the heat factor, to take effective thermal design and environmental protection design.
3. Anti-radiation problem. Components used in spacecraft are usually damaged by various rays from the sun and the Milky Way, and the entire electronic system is rendered useless, so the designer must consider the effects of radiation. At home and abroad have been gradually developed a number of radiation-enhanced semiconductor devices, such components should be used when needed.
4. Anti-static damage. Semiconductor devices in the manufacturing, storage, transportation and assembly process, due to equipment, materials and the relative movement of the operator, may be due to friction and produce thousands of volts of electrostatic voltage, when the device contact with these charged body, Through the device "leads legs" discharge, causing device failure. Not only are MOS devices susceptible to electrostatic discharge damage, the problem can also have serious consequences in bipolar devices and hybrid integrated circuits.
5. Damage during operation. The process of easy to semiconductor devices and integrated circuits to bring mechanical damage, should be in the structural design and assembly and installation of attention. Such as lead forming and cutting, the installation of printed circuit boards, welding, cleaning, installation of heat sinks, device layout, printed circuit board coating processes, should strictly implement Denso process requirements.
6. Storage and storage. Improper storage and storage are the main reasons for the reliability of the components to be reduced or failed, so they must be taken seriously and corresponding measures should be taken. Such as the Treasury of the temperature and humidity should be controlled within the specified range should not lead to the presence of harmful gases; storage device containers should not be used with static electricity and does not cause chemical reactions of the material made of the device; regularly check the test requirements of the components and so on.
The selection of semiconductor integrated circuits shall be carried out according to the following procedures and requirements:
1. Determine the type and model of the selected semiconductor integrated circuit according to the requirements of the electrical properties and the volume and price of the applied parts;
2. Determine the specifications (or technical conditions) and quality levels to be performed for the selected semiconductor integrated circuit, based on the reliability requirements for the application site;
3. According to the other parts of the application requirements, to determine the selected semiconductor integrated circuit package, lead coating, radiation intensity assurance level and single particle sensitivity, etc.;
4. For high-power semiconductor integrated circuits, select the heat resistance is small enough;
5. selecting a semiconductor integrated circuit having sufficient transient resistance against overload;
6. selecting a semiconductor integrated circuit that results in a lock-in minimum injection current and a minimum overvoltage sufficiently large;
7. As far as possible to choose a higher level of electrostatic sensitivity of semiconductor integrated circuits. If the candidate semiconductor integrated circuit is not marked with the level of electrostatic susceptibility, an antistatic capability evaluation test should be conducted to determine the average level of the antistatic ability of the product.
In order to ensure the application reliability of the semiconductor integrated circuit, the following measures must be taken.
Derating Design of electronic equipment, the micro-circuit stress should be under the rated stress on the basis of GJB / Z35 "derating guidelines for electronic components" derating.
2. Tolerance design. In the design of electronic equipment, we should know the range of electrical parameters (including manufacturing tolerances, temperature drift, time drift, radiation drift, etc.) of the used microcircuits, and use this as an effective means to carry out tolerance design. Should use computer-aided design (CAD) means to carry on the tolerance design as far as possible.
3. Thermal design. Temperature is an important factor affecting the failure rate of microcircuits. In the micro-circuit failure rate model, the impact of temperature on the failure rate is represented by the temperature stress coefficient πT. ΠT is a function of temperature, and its form varies with the type of microcircuit. On the micro-circuit, the temperature can be increased about 10o ~ 20o πT doubled. The ultimate goal is to prevent overheating micro-chip chip junction temperature control in the allowable range of high-reliability equipment, the requirements to control the following 100 ℃. The chip junction temperature of the microcircuit is determined by its own power dissipation, thermal resistance and thermal environment. Therefore, the chip junction temperature control in the allowable range of measures including control of their power consumption, thermal resistance and thermal environment.
4. Anti-static. For electrostatic sensitive circuits, anti-static measures can refer to the relevant works and the military standard. For electrostatic-sensitive CMOS integrated circuits, in addition to strict compliance with the use of anti-static measures, it should be noted:
(1) not to use the input terminal should be connected to the power supply or grounding, shall not be vacant;
(2) as a circuit board input interface circuit, in addition to its input voltage transient suppression diode, but also should be connected to the resistor, the resistance is generally taken 0.2 ~ 1MΩ;
(3) When the circuit and the resistor, capacitor oscillator, the capacitor storage charge generated voltage can make the relevant input voltage is higher than the power supply voltage. In order to prevent this phenomenon from locking, the current-limiting resistor should be connected in series at the input terminal (its resistance is usually 2 ~ 3 times of the timing resistor).
(4) as a circuit board input interface transmission gate, each input should be series resistors (the value of the general take 50 ~ 100Ω) to prevent locking;
(5) as a circuit board input interface logic gate, each input should be series resistor (the value of the general take 100 ~ 200Ω) to prevent locking;