The reliability problem of components is the problem of basic failure rate, which is a kind of random failure. The difference from quality problems is that the failure rate of components depends on the level of working stress. Under a certain stress level of KE DIP switch, the failure rate of components will be greatly reduced. In order to eliminate the components that do not meet the requirements for use, including unqualified electrical parameters, unqualified sealing performance, unqualified appearance, poor stability, and early failure, a screening test should be carried out.

This is a non-destructive test. Through screening, the failure rate of components can be reduced by one to two orders of magnitude. Of course, the cost of screening tests (time and expense) is high, but comprehensive maintenance, logistics support, and joint testing of the entire frame are still cost-effective, and the development cycle will not be extended. General requirements for screening test of main components of power equipment:

　　①The resistance is 100% tested under technical conditions at room temperature, and unqualified products are eliminated.

　　②Ordinary capacitors are 100% tested under technical conditions at room temperature, and unqualified products are eliminated.

　　③The connectors shall be sampled and tested for various parameters according to the technical conditions.

　　④Semiconductor devices are screened according to the following procedures:

　　Visual inspection→Preliminary test→High temperature storage→High and low temperature impact→Electric power aging→High temperature test→Low temperature test→Normal temperature test

　　 After screening, the rejection rate Q should be calculated

　　Q=(n / N)×100%

　　 In the formula: N——the total number of tested samples;

　　N——the number of samples rejected;

　　 If Q exceeds the upper limit specified by the standard, all components of this batch are not allowed to be put on the machine, and shall be handled in accordance with relevant regulations.

　　 When it meets the requirements of the standard, KE will mark the paint spots of the selected components, and then put them into the special warehouse for installation.