Wettability of Cu Plate by a Sn-Bi Solder.

Abstract

For the development of lead-free solder, wettability of 41.2Sn-58.8Bi and 61.6Sn-38.4Pb solders was compared by use of meniscometer. It has been reported by several researchers that the wettability of Sn-Bi solder is poor as compared with Sn-Pb solder. In order to obtain fundamental data, no flux was used in this work because wettability of solder is significantly affected by the kind of flux and the available fluxes have been developed for Sn-Pb solder. Oxygen-free copper plate and copper alloy plate containing 0.3 mass % Cr, 0.1 mass % Zr and 0.02 mass % Si of 0.5mm in thickness and 10mm wide were immersed into the molten solders at the temperature range from 483 K to 543 K. It was found that wettability of both Sn-Bi and Sn-Pb solders to these plates was poor without use of flux. Then a parameter (surface tension) by cosine (contact angle) was used for the comparison of wettability of these solders. No significant difference in the parameter between these solders was observed. Consequently, it is thought that the Sn-Bi solder will be promising provided that flux suitable for this solder is developed.