Mechanical properties of intermetallic compounds in solder joints

Intermetallic compounds (IMCs) that grow on the interface between the solder alloy and its bonding pads play a crucial role in the reliability of solder joints. It has been identified that the cracking around the IMC layer is the primary failure mode in lead-free solder joints. Therefore the mechanical behavior of the IMC has attracted great attentions. In this paper, mechanical properties of two kinds of intermetallics, Cu6Sn5 and Cu3Sn, which are two major species of IMCs in lead-free solder with Cu pad metallization, are collected and discussed. The measurements on Young's modulus and hardness of Cu6Sn5 and Cu3Sn show a great diversity among different researchers' work. Although the strength of IMC exhibits diversity, some common trends emerge. Tensile and shear strength if the IMC decrease with the increasing of the thickness of interfacial intermetallic layer.

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