The influence of selenium deposited on silver plating on adhesive strength of die-attachment

Selenium on the top surface of silver plating on the leadframe causes bleeding out (BO) of the epoxy and a decrease in the adhesive strength of the die-attachment of ICs. This phenomenon was investigated. It seemed that this BO was due to the separation and effusion of organic constituent from the epoxy resin. In the BO region, an amine component of the hardener was not detected, suggesting that the hardening of epoxy resin did not proceed sufficiently at the interface between the leadframe and the epoxy resin. The separation and effusion of epoxy resin seemed to be caused by the larger surface energy of selenium as compared to silver. It is presumed that the selenium was from the selenites added as brightener or accelerator for silver plating. The adhesive strength is improved by reduction of the selenite added in the silver plating solution to one-tenth of the initial value.<>