Inspection of the contaminants at failed connector contacts

Inspection on 95 failed connector contacts of 23 mobile phones shows that the contaminants at the contact areas are formed by various sizes of particles. They are adhered together. It seems that smaller ones accumulate the larger ones. The composition of contaminants is very complex, which include dust particles containing mainly silicates (quartz, mica, feldspar) and calcium compounds (gypsum, calcite and lime), wear debris of surface materials, corrosion products (sulfates, chlorides and oxides of copper and nickel) and high concentration of organics. Organic materials seem to act as adhesives at different temperatures. Contaminants causing failure usually located at or near the wear tracks. The most important function of micromotion is to move the separated contaminants and accumulate them together at the contact; they also produce wear debris, and destroy the surface metal layer as well. High contact resistance happened in several small regions at the contaminant that provide high enough thickness. Failure could be happened within very short time period (3-4 months) depends on the high resistance region is formed. Conventional ways of corrosion gas test, sand or artificial dust test, shock and vibration test can hardly simulate the failure of contact occurred in China.