Mechanical properties of intermetallic compounds in solder joints

Abstract

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, Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> and Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn, 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 Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> and Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn 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.