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Rela Pantaleon, Phyllis Ann Gantuangco, Marites Mandia, Intel Philippines Manufacturing, Inc.
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Solderplate composition and morphology may be readily controlled in a high speed strip-to-strip solder plating system. The purpose of this paper is to determine the effect of low metal and low acid conditions of the strip-to-strip solderplate process on the solderability performance of PLCC's. Low metal and low acid conditions during solderplating produce loosely packed, coarse-grained, and tin-rich deposits. The compositional shift to higher Sn content results in an increase in the melting point and an increase in the brittleness of the deposit. The increase in transformation temperature results in a non-replacement of the electrodeposit by the molten eutectic solder during solderability testing. The increase in brittleness results in cracking of the deposit during ensuing lead forming process. These cracks, in turn, expose base metal surfaces which undergo oxidation. This oxidation of the exposed copper base metal, as well as exposure of the tin-copper intermetallics and shift in alloy deposit compositions, result in a surface that is non-wettable to the molten solder during solderability testing, causing solderability failures.
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