Shear creep and fracture behavior of micro-scale BGA structured Cu/Sn–3.0Ag–0.5Cu/Cu joints under electro-thermo-mechanical coupled loads

Shear creep performance and fracture of BGA structured Cu/Sn-3.0Ag-0.5Cu(SAC305)/Cu joints under coupled electrical load, thermal load and mechanical shear load were studied. The current stressing imposed on the mechanical shear stress does not change the basic feature of creep strain curves of the joints. The shear creep strain rate of solder joints is increased by electric current stressing. In addition, compared with the joints without electric current stressing, creep activation energy and stress exponent at a current density of 6 × 10³ A/cm² increase from 69.2 kJ/mol to 90.8 kJ/mol and 5.3 to 11.4, respectively, which indicates that lattice diffusion may become the dominant creep mechanism. Moreover, the imposed current on the joint causes a shift of fracture location from the solder matrix to the region near the interface between the solder and intermetallic compound (IMC), and correspondingly the fracture mode turns to the mixed ductile-brittle fracture.