A study on Cu-Sn soldering and shear behavior of solder joints with micro interconnection

This study focuses on the Cu-Sn-Cu sandwich structure soldering, 0.06 MPa constant pressure. Different soldering temperatures and soldering times were selected based on the Cu-Sn binary phase diagram. After soldering according to different phase composition the solder joints can be divided into three types of residual Sn/Cu₃Sn-Cu₆Sn₅-Cu₃Sn/Cu-Cu₃Sn-Cu. The relationship among shear strength of solder joints and three different phases compositions were researched by shear experiment of 1 mm/min loading rate and fracture morphology analysis. The results show that the shear strength of solder joints increases with the depletion of Sn and Cu6Sn5 in sequence. The shear strength of residual Sn solder joints, Cu₃Sn-Cu₆Sn₅-Cu₃Sn solder joints and Cu-Cu₃Sn-Cu solder joints are 23.26, 33.59, 51.83 MPa, respectively. Based on the fracture morphology analysis, residual Sn solder joint fracture can distinguish the morphology of Sn/Cu₆Sn₅/Cu₃Sn, indicating that the crack path through the Cu₆Sn₅ and Cu₃Sn phases. In Cu₃Sn-Cu₆Sn₅-Cu₃Sn solder joint fracture, Cu₆Sn₅/Cu₃Sn morphology was distinguished, crack path through the Cu₃Sn phase. When only Cu₃Sn phase was at solder joints, was Cu₃Sn only Cu₃Sn can be seen in fracture morphology of the soldering joints.