Formation mechanism of pillar-shaped intermetallic compounds dispersed lead-free solder joint

Abstract

Large area joining between a substrate and a heat sink is desirable for high performance power modules. An intermetallic compounds (IMCs) pillar dispersed solder joint has been developed as a highly durable joint to achieve large area joining. The aim of this study is to clarify the generation and growth mechanism of the IMC pillar during soldering process. The structural characteristic of the IMC pillar was also examined by cross-sectional observation. The area ratio of the IMC pillars in the cross section of the joint increased with increasing the joining temperature. The shape of the IMC pillar became finer when the cooling rate was fast. In addition, the IMC pillar grew along the cooling direction.