Importance of Bonding Atmosphere for Mechanical Reliability of Reactively Bonded Solder Joints

Abstract

Selfpropagating exothermic reaction bonding (SERB) technique with Al/Ni multilayer film is fascinating in the viewpoint of lots of outstanding features, such as atmosphereindependent exothermic reaction and its selfpropagation. The reactively bonded solder joints with high bonded strength are required for practical use in semiconductor devices. We have investigated the fracture strength of rectangularsolid specimens with reactively bonded solder joint (Sn–3.5Ag solder/reacted NiAl/Sn–3.5Ag solder) sandwiched by single crystal silicon (SCS). In this paper, the influence of bonding atmosphere on the fracture behavior is discussed by means of fourpoint bending testing and fracture surface observation. The fracture strength increases with increasing pressure load during bonding. The strength of the vacuumbonded specimens is found to be higher than that of the airbonded specimens. The fracture surface observation results suggest that Al oxide and intermetallic compounds (IMCs) formed at the reacted NiAl layer and the SnAg solder layer, respectively, would have affected the strength of the Al/Ni SERB joints.