Mechanical properties characterization of CuSn intermetallics for advanced flip-chip bonding

摘要

In this paper, we investigate the mechanical properties of CuSn intermetallics formed in the Cu/Sn system in three different ways. First, we characterize CuSn intermetallic films by nano-indentation. Here the CuSn intermetallics are formed by interdiffusion of Cu/Sn bi-layer films. Second, we do Cu/Sn flip-chip bonding to form CuSn intermetallic joints and then characterize the intermetallics on small bumps also by nano-indentation. Third, unlike the afore-mentioned two approaches, we fabricate a free-standing CuSn intermetallic beam for micro-tensile test, from which we can extract the Young's modulus, yield strength, and fracture strength. Combining all these experiments, we find the Young's modulus of CuSn intermetallic is between 75 to 150 GPa, the yield strength is ～810 MPa, and the fracture strength is ～980 MPa.