Tape Carrier with Buried Via-Holes of Copper Plating for BGA Package of Good Ball Solderability.

概要

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The deterioration of ball solderability is indicated with the narrower pitch of solder balls of BGA package. Accordingly, the tape carrier that the via-holes for the ball soldering were buried with copper plating was developed for the prevention. In order to deposit of the copper plating in minute blind via-holes of the polyimide tape, suitable copper sulfate plating bath at the thickness over 40μm was found. And, the analysis and control technique of additives as dispersing agent and brightener, etc. was also established. Uniformity of the current distribution in the plating tank was necessary for the small deviation of the copper plating thickness. In order to solve the problem, based on the computer simulation, the optimum current shielding board was installed in the tank, and the equalizing of the thickness was achieved. On the bases of these results, it was established the mass-production technology of uniformly and high-speed copper plating in minute via-holes which were formed on tape carrier of long length. And the continuous copper plating machine for tape carrier was constructed. For further miniaturization of the LSI package, the developed technology has been widely applied to the tape substrate.
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