Study on failure mechanism and process control of medium current on relay

In consideration of derating design, the current load actually switched by miniature relays might be under the condition of medium current. While medium current is the most likely load condition that leads to failure of relays, the medium current performance of relays affects the reliability of the system operation directly. Aiming at this problem, electron microscopy scanning and atmosphere analysis were used to analyze the causes of failure of relays when switching medium current, and the conclusion is that the pollution of internal organic atmosphere and materials leads to this problem. Under the condition of medium current, internal organic atmosphere and materials pollution will accumulate carbon at the surface area of contacts, causing the increase of relay contact resistance, resulting in unreliable contact. To control the content of organic atmosphere effectively, design of appropriate process steps and parameters was carried out by DOE experiment method, and control method of reasonable degree of vacuum, temperature and time was finally obtained. The study also proposed the solution of contact material pollution. The results showed that optimum vacuum baking degassing treatment temperature and duration can be found by DOE experiment, according which relay internal atmosphere pollution can be inhibited effectively. Material pollution can be reduced by technical process control, which can ultimately improve the relay current moderate performance and product quality.