Solder/solder joint for low temperature reflow by multi plating method

Abstract

The electrolytic multi plating method (EMPM) of Bi and Sn was studied as the approach that supplied Sn-Bi solder. Ni/Bi/Sn and Cu/Bi/Sn coupon were prepared to compare the influence of the different under layer for Bi dispersion. And then, these coupons were jointed under 170 or 190 oC with the coupon which plated electrolytic Sn-Ag. When it’s jointed under 190 oC, uniform Bi dispersion in the solder was confirmed for the coupon by multi plating method from SEM observation and EDS analysis, which was similar to one by solder paste method[1]-[2]. Also, after the heat soak test under 100 oC for 500 hours, Bi aggregation and some cracks were observed in the solder near the Ni deposit for the coupon of Ni/Bi/Sn. On the other hand, Bi was dispersed to the center of the solder for the coupon of Cu/Bi/Sn and no cracks were observed.