Mechanical Properties of Ni$_{3}$ Sn$_{4}$ and Cu$_{3}$Sn Determined by Inverse Method

Intermetallic compound (IMC) formation is crucial to electronic packaging reliability because of its brittleness. Mechanical properties including Young's modulus and thermal expansion coefficient (CTE) of two kinds of IMC, Cu$_{3}$Sn and Ni $_{3}$Sn$_{4}$ , were determined and discussed in this paper. In order to test in the real solder joint condition, a multilayer structure of IMC/deposited metal film/silicon substrate was used. In addition to metal films, metal foils were also used to be another growing base for IMC to form a composite structure as IMC/foil. Through measuring the deformation and slope change of these multilayer structures at different temperatures by moirÉ technique, the Young's modulus and CTE of the IMC layer can be determined simultaneously using a numerically constructed convolutional relationship and an inverse method. Although IMC on both kinds of bases (metal films and foils) experience similar growing condition, results show that their mechanical properties are quite different. Both Young's moduli and CTE of Ni $_{3}$Sn$_{4}$ and Cu$_{3}$Sn on deposited metal films are larger than those on metal foils, and their SEM images also show different microstructures.