Thermal cycle failure behavior of SAC305/SnPb micro-hybrid solder joints: An experimental and finite element simulation approach

The electronic packaging industry encounters significant challenges due to the miniaturization of devices and the demand for enhanced performance. One promising approach to addressing these challenges is the implementation of hybrid solder joints, which have the potential to lower soldering temperatures and alleviate warpage issues. To investigate these effects, thermal cycling tests were performed on SAC305/SnPb micro-hybrid solder joints. COMSOL were employed for verification purposes. The simulation results revealed that the intermetallic compound (IMC) layer at the solder joint interface thickens as thermal cycling progresses, with cracks emerging at the solder ball-copper interface after 1200 cycles. Initially, the shear strength of the joints increased from 36.4 MPa to 42.0 MPa after 900 cycles; however, it subsequently decreased to 39.3 MPa after 1200 cycles. Fracture analysis indicated a transition from ductile to mixed-mode fracture behavior with continued cycling. Simulations reveal that the peak stress is localized at the interface between the solder and the copper pad, with stress increasing from 32.3 MPa at the high-temperature initiation to 73.1 MPa at the low-temperature termination. The stress distributions are consistent with experimental results. This localized stress concentration is crucial, as it has a substantial impact on the joint's overall reliability and operational lifespan.