Factors Influencing Contact Life and Failure Mode in Compact PCB Power Relays

Compact PCB power relays were tested in repetitious on/off operations to define their reliability through a quantitative analysis of failure cycles and an investigation of relay property changes and contact erosion forms. Operation voltage was 14 V and relay temperature was 120 °C. Ten relays were used in each of two types of load test. First failure cycles were found to be high enough for practical use, 2.2 million in the lamp load (11 A) test and 7.5 million in the test using an integrated load (10 A) comprised of engine control components. Failure mode of all relays in the lamp load test revealed contact welding, while those in the integrated load test revealed significant contact resistance due to excess erosion. Wide differences between them in contact life cycle distribution and failure mode were found to be clearly distinguishable from load current characteristics.