抄録
In this study, the crack initiation and propagation behaviors in Si/Cu joints with Sn-6.4Sb-3.9Ag （mass%）, Sn-6.4Sb-3.9Ag-0.25Ni-0.003Ge （mass%） and Sn-3.0Ag-0.5Cu （mass%） lead free solder were investigated using an electrolytic Cu plated substrate. The Si chip which surface is coated with Ti/Ni/Au thin layers was prepared. （Cu,Ni）6Sn5 layers formed at both Si/solder and Cu/solder interfaces in the joints with Sn-6.4Sb-3.9Ag based solder. In contrast, Cu6Sn5 layers formed at both the interfaces in the joints with Sn-3.0Ag-0.5Cu, although very thin discontinuous Cu6Sn5 layer formed at the Si/solder interface. It was found that a crack growth occurs at the （Cu,Ni）6Sn5/β-Sn interface in the Sn-6.4Sb-3.9Ag based solder joints by the pseudo power cycle test. The electron backscattered diffraction analysis result shows that fine recrystallized grains generate in the cracked area in Sn-6.4Sb-3.9Ag based solder joints, and crack propagation occurs in the high-angle grain boundaries of their recrystallized grains. In the joint with Sn-6.4Sb-3.9Ag-0.25Ni-0.003Ge, many fine IMCs such as SbSn, Ag3Sn and （Cu,Ni）6Sn5 were formed. Their IMCs can suppress the recrystallization of β-Sn and the crack propagation. Thus, heat cycle resistance of the joint with Sn-6.4Sb-3.9Ag-0.25Ni-0.003Ge was improved. In contrast, the heat cycle resistance of the joint with Sn-3.0Ag-0.5Cu was inferior to that with Sn-6.4Sb-3.9Ag based solder, due to rapid interfacial cracking between the Ti layer and solder.
