Electronic components are preferred and should conform to the product selection manual or the list of preferred products (PPL) issued by foreign authorities. Planners should formulate precise and clear technical standards for purchasing electronic components. In order to ensure reliability requirements, standards should be clearly selected (including secondary selection) and measures and methods for quality consistency checking. A list of qualified meta-equipment acquisitions should be drawn up in accordance with the type rules.
It is necessary to clarify the factors affecting the reliability and quality of electronic components in the acquisition list, such as quality level, environmental conditions, power loss, technical standards, packaging methods, special requirements (antistatic characteristics, chip protection technology), manufacturers, etc. The acquisition criteria shall be approved in accordance with the rules before they can be implemented. After the application of meta-equipment in products is clear, the reliability of meta-equipment should be predicted, and the requirement of reliability of meta-equipment for circuit should be considered.
Selection criteria for electronic components:
1. Selection of standard components from manufacturers with stable quality, high reliability, promising development and good reputation proved by practice can not select selected or inferior components.
2. The technical functions, quality grades and operating conditions of electronic components should satisfy the requirements of circuit planning.
3. In the case of satisfactory functional parameters, components with low power consumption, low thermal resistance, low loss, high power gain and high efficiency should be selected.
4. Optimum selection of domestic electronic components. It is preferred to select components that meet the national standards determined by certification; components that can be safely supplied by testing; other components that have successful application experience and meet the requirements.
5. Import of electronic components. Components in PPL (Optimum Product List) and QPL (Qualified Product List) of foreign authoritative organizations; High reliable components selected strictly in the production process; and high quality components that meet the requirements through domestic application.
6. Selection should follow the criteria of standardization and generalization.
The importance of electronic component selection:
The standard, type and parameter of each component equipment are clearly marked on the circuit diagram, which is the basis for the selection of electronic component equipment. For the products that have been finalized, the equipment marked on the schematic diagram is put into production through planning, R&D and trial production. The parameters are determined by means of "qualitative analysis, quantitative budget and experimental adjustment". Normally, is the selected meta-equipment allowed to be replaced? However, for the developers, amateurs and repairmen of electronic products, due to the influence of many factors, such as objective conditions, under the conditions of meeting the technical requirements and standards, due to the small consumption, they can also choose flexible meta-equipment.
In some specific cases, even if there are schematic diagrams, but because of the incomplete labeling parameters of some components, such as electrolytic capacitors with standard capacitance and withstand voltage, it should be reconsidered in power supply circuit; the site conditions of product use are not in conformity with technical data, and some components can be adjusted for customary practice; single components can not be bought locally. It can be replaced by electronic components that meet the requirements. When a single electronic component is found to be unreasonable in the repair process, it is necessary to replace it with suitable electronic components.
Electronic components are basic circuit units that perform predetermined functions without dismantling and differentiation, such as resistors, semiconductor discrete devices, semiconductor integrated circuits, magnetic components of microwave components `relays', switches, electrical connectors, filters, sensors, fiber optics, etc. Practice has proved that 44%~67% of the total failure of electronic equipment is caused by improper selection, while 33%~46% of the loss of power is caused by the quality of electronic equipment itself. Therefore, the selection of meta-equipment plays an important role in the circuit planning, so it is necessary for planners to attach great importance to it.