Effect of Ni addition to the Cu substrate on the interfacial reaction and IMC growth with Sn3.0Ag0.5Cu solder

The formation and growth of intermetallic compound (IMC) layer at the interface between Sn3.0Ag0.5Cu (SAC305) solder and Cu-xNi (x = 0, 0.5, 1.5, 5, 10 wt%) substrate during reflowing and aging were investigated. The soldering was conducted at 270 degrees C using reflowing method, following by aging treatment at 150 degrees C for up to 360 h. The experimental results indicated that the total thickness of IMC increased with increasing aging time. The scallop-like Cu6Sn5 and planar-like Cu3Sn IMC layer were observed between SAC305 solder and purely Cu substrate. As the content of Ni element in Cu substrate was 0.5% or 1.5%, the scallop-like Cu6Sn5 and planar-like Cu3Sn IMC layer were still found between solder and Cu-Ni substrate and the total thickness of IMC layer decreased with the increasing Ni content. Besides, when the Ni content was up to 5%, the long prismatic (Cu, Ni)(6)Sn-5 phase was the only product between solder and substrate and the total thickness of IMC layer increased significantly. Interestingly, the total thickness of IMC decreased slightly as the Ni addition was up to 10%. In the end, the grains of interfacial IMC layer became coarser with aging time increasing while the addition of Ni in Cu substrate could refine IMC grains.