Ｎｉ‐金属Ｓｎ複合めっき皮膜の作製とそのはんだ付け性

Abstract

The relationship between solderability and the structure of Ni-metallic Sn composites electroplated from Watts Ni baths, with and without brightener, were studied by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Solderability was evaluated by measurement of the spread of Sn-Pb alloy particles placed on composites kept at 240C for 5 seconds. The Sn content of composites plated with brightener was increased to 18wt% with only 1g/L of Sn particles in the bath, but the Sn content of composites plated without brightener was increased to 22wt% with 2g/L of Sn in the bath. Composites plated with brightener showed poor solderability irrespective of the Sn content, but the solderability of composites plated without brightener was excellent and increased linearly with increases in their Sn content. The differences in solderability were found to be the result of differences in the coverage of Ni on composite surfaces. Irrespective of the presence or absence of brightener, the surfaces of the codeposited Sn particles were covered with a thin film of Sn oxide. In the presence of brightener, a large part of the surface of the Sn particles was covered with deposited Ni, while in the absence of brightener, coverage of the Sn with Ni was negligible, leading to good solderability.