Wetting, solder dissolution

Thin ( 2 /mi) layers of nickel and tin are electroplated over the silver termination, the former to act as a barrier preventing dissolution of the silver during the subsequent wave-soldering operation when the chips are surface-mounted onto a substrate. The tin layer ensures good wetting of the termina tion by the solder. In the case of the BME capacitor (see below) the termination is copper fired on under reducing conditions and covered with an electroplated layer of nickel. 

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