Mechanical properties of intermetallic compounds at the Sn–3.0Ag–0.5Cu/Cu joint interface using nanoindentation

Abstract

Intermetallic compounds (IMCs) at the Sn–3.0Ag–0.5Cu/Cu joint interface were prepared through reflow soldering and isothermal aging in a QHL360 SMT fully automatic reflow soldering system and a high-temperature test chamber, respectively. The mechanical properties of IMCs were then studied and characterized by nanoindentation. The mechanical responses of both Cu6Sn5 and Cu3Sn (IMCs) show large dependence on the strain rate during loading. In addition, multiple pop-in events are observed in Cu6Sn5 but not evident in Cu3Sn. During loading, the contact stiffness of IMCs increases almost linearly with the indentation depth under each strain rate. In total, the hardness and elastic modulus of Cu3Sn are larger than those of Cu6Sn5, and the hardness of both Cu6Sn5 and Cu3Sn increase with increasing strain rate. During the holding stage, creep deformations of IMCs increase as loading strain rate increases. Indentation creep displacement–time curves for Cu6Sn5 and Cu3Sn can be well described by the generalized Kelvin model. The lower creep rate sensitivity exponent of Cu3Sn implies its relatively higher creep resistance.