材料期刊网

Effects of thermal aging on the interfacial microstructure and reliability of the SnAgCu/FeNi-Cu joint are investigated. It is found that aging effects depends strongly on the temperature. Aging at low temperature, e.g., at 125 degrees C, a submicron meter thick FeSn(2) IMC layer formed at the SnAgCu/FeNi-Cu interface during reflowing grows at a rate twenty times slower than the growth rate of the IMC at the SnAgCu/Cu interface. At high temperature, e.g., at 180 degrees C, the Cu element is found to diffuse through FeNi layer to produce the (Cu, Ni)(6)Sn(5) IMC and this IMC layer grows even faster than the IMC at the SnAgCu/Cu interface. Solder ball shear test results show that the SnAgCu/FeNi-Cu joint has a comparable strength to the SnAgCu/Cu joint after reflowing, and the strength drop after aging at 125 degrees C is less than that of the SnAgCu/Cu joint. However, after aging at 180 degrees C, the strength of the SnAgCu/FeNi-Cu joint is degraded to a low value, along with a shift in failure mode from the solder fracture to the brittle intermetallics fracture.