1. Beijing University of Posts and Telecommunications Beijing 100876 China 2. CALCE Electronic Products and Systems Center University of Maryland College Park 20742 USA
Abstract：This paper discusses failure issues of immersion silver (ImAg) finished printed circuit boards (PCBs) under high-sulfur environments with a focus on creep corrosion. It is found that the coverage extent of ImAg finish on pads is dependent on the relative location of the pad edges and the solder mask, which causes the different formation extent, the creep distance and the compositions of the corrosion products with dendrite shape. The simulation approach is studied by adapting clays containing sulfur as the source to drive creep corrosion on ImAg finished PCBs. Weibull distribution with two parameters is used to analyze the length of creep corrosion products, and the creep corrosion resistance of ImAg finished PCBs is quantitatively evaluated by the mean length. The effects of the corrosion time, the times of heating the clays and increasing relative humidity on the simulation tests are studied. Both the evaluation method for the creep corrosion resistance of ImAg finished PCBs by sulfur contained clays and the simulation method for the harsh industrial environments are proposed.
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2011, Vol. 26 
