Abstract:

The contamination on contact surfaces was found to be one of the main reasons to cause electric contact failure by analyzing lots of gold plated contacts in failed mobile phones. The contaminants are with complex morphology, and mainly concentrated on the contacts on printed circuit boards. The element compositions of contaminants include C, O, Si, Al, S, Cl, Na, Ni etc. They come from the dusts in environment and wear debris by fretting. Image process technology was adopted to compute the coverage areas percentage of contaminants; it concluded that the contamination degree on contacts was classified into 5 levels. As the contamination levels increased, the average thickness of the contaminants raised and the wear zones also expanded. 60% of the contact resistance tested on contaminated zones was higher than the design limitation. The maximum contact resistance attained to 4?Ω. The unreliable electric contact made the reliability of mobile phones degraded.

Key words: gold plated contacts, contamination, wear, contact resistance, mobile phones