Reliability studies of Sn-9Zn/Cu and Sn-9Zn-0.06Nd/Cu joints with aging treatment

In this article, the microstructures and the properties of Sn-9Zn/Cu and Sn-9Zn-0.06Nd/Cu soldered joints with aging at a constant temperature 150 degrees C for different hours were studied. It was found that the microstructure of Sn-9Zn-0.06Nd solder aged for 240 h remarkably changed and formed a combination net of Sn grains due to diffusion and aggregation of rare earth element Nd. Moreover, the interfacial reaction of solder/Cu was systematically investigated. Cu5Zn8 intermetallic compound (IMC) can be found at the soldered joints interface, and its thickness increased with the increased aging time. Moreover, the thickness of intermetallic compound layer (IML) can be repressed with the addition of 0.06% Nd compared to that of Sn-9Zn. For the tensile property, the pull strength of soldered joints gradually decreased as the aging time prolonged and even decreased by 55.1% and 44.9% respectively after aging for 720 h. Furthermore, the fracture of Sn-9Zn-0.06Nd soldered joints indicated ductile fracture before aging treatment, while after aging for 720 h it presented both ductile and brittle fracture. (C) 2011 Elsevier Ltd. All rights reserved.