Many friends who do electronic processing will face the problem of purchasing electronic components. If it is only the R&D team or the purchasing personnel who do not understand the processing, it will be a headache when choosing electronic components. Today, I will give you a popular science on how to choose and purchase electronic components.
1. The importance of electronic components selection
The size, model and basic parameters of each electronic component are indicated on the circuit diagram, which is the basis for selecting electronic components. For the products that have been formed, the electronic components on the circuit schematic are put into production and processing after design, research and development. Each basic parameter is confirmed according to the method of "qualitative analysis, quantitative estimation and experimental adjustment". Usually, whether the electronic components used are allowed to be removed or replaced. But for the research and development of electronic equipment, amateur enthusiasts, maintenance staff, because of the influence of objective reasons and many other factors, in accordance with the conditions of technical standards, because of the use of less, can also be flexible use of electronic components.
In some special cases, even with the circuit schematic diagram, but in view of the basic parameters of some electronic components are not complete, such as electrolytic capacitor only labeled capacity without breakdown voltage, in the power circuit to reconsider; if the field conditions of commodity application do not conform to the technical data, some electronic components can be changed to integrate into the reality. If an electronic component is difficult to buy locally, a standard electronic component can be used instead; when an electronic component is detected to be unreasonable in the maintenance process, the appropriate electronic component must be replaced.
Electronic components are the basic circuit units that perform the function of reservation and can not be removed, such as resistors, semiconductor discrete components, semiconductor integrated circuit chips, microwave electronic components, automotive relays' magnetic electronic components, control switches, electrical connectors, filters, temperature sensors, fiber optical components, etc. It has been proved that in electronic products, 44%~67% of the total electronic component failure is caused by improper selection, while the failure rate caused by the quality of electronic components accounts for 33%~46%. Therefore, the selection of electronic components occupies a key position in circuit design, and the design staff must attach great importance to it.
2. The selection standard of electronic components
1). Select standard electronic components from manufacturers with stable quality, high credibility, promising development prospects and good reputation that have been proved by practice, and do not use obsolete or shoddy electronic components.
2). The technical characteristics of electronic components, quality level, using conditions should meet the needs of the design circuit.
3). In the case of meeting the performance indicators, the selection of low power consumption, low thermal resistance, low loss, high power gain, high efficiency electronic components.
4). Selection of domestic electronic components. Preferably select electronic components that have been certified to meet international standards; electronic components that meet the requirements and can be delivered stably after application honing; other electronic components with successful application experience and compliance with regulations.
5). Imported electronic components. Electronic components in PPL (List of Selected Commodities) and QPL (List of Qualified Commodities) issued by overseas authorities; highly reliable electronic components that have been carefully screened during processing; electronic components of high quality that have been evaluated by domestic applications and meet the requirements.
6). Selection should be in accordance with the principle of standardization and generalization.
3. The selection of electronic components
Electronic components are preferred and should be applied to the Preferred Goods Practical Manual or the Preferred Goods List (PPL) issued by overseas authorities. The design staff shall develop accurate and clear technical specifications for the procurement of electronic components, which shall establish strategies and methods for screening (including re-screening) and quality consistency testing to ensure credibility requirements. At the same time, a qualified electronic component purchase order shall be prepared according to the model and specification requirements.
The factors that affect the reliability and quality of electronic components must be specified in the purchase order, such as quality level, environmental conditions, failure rate, technical specifications, packaging type, precautions (anti-static characteristics, integrated IC protection processing technology, etc.), production supplier, etc. The procurement specification shall be reviewed in accordance with the regulations before implementation. After the use of electronic components in the product is defined, the reliability should be estimated and taken into account whether the circuit meets the reliability criteria for electronic components.
