Lead break mode and alloy growth of microsoldered layer at fine pitch leadframe microjoining -a study on microjoining of leadframe for LSI package (No.2)-

摘要

In high temperature aging test (150℃ in Air),the peel strength is weakened by intermetalic compound growth of copper and tin. This report focused on the analysis of soldered layer to understand the reasons of reduced peel strength after thermalexposure. Even if 42 alloy (Fe-42 massNi), under-plated copper layer (electric copper plating) causes the Cu-Sn intermetalic growth and break from 71 layer (C6Sn5) - And in case of the copper lead, Cu-Sn intermetalic layer is very thick. Because of that, copper lead bulk thickness is reduced and causing the lead bulk break before intermetalic break. These break modes are changing through the again time, from solder bulk, lead bulk and finally to intermetalic compound layer breaking.