Robust low-temperature soldering of Cu plates via a novel Ni@Cu10Ni alloy mesh reinforced SAC305 composite solder

Purpose With the rapid evolution of semiconductor technology, the demand for high bonding reliability in electronic devices has become increasingly stringent. This study aims to overcome the limited mechanical strength of conventional Sn-based solders. Design/methodology/approach This study introduced a Cu-10Ni (Wt. %) alloy layer coated on a pure Ni mesh, forming a Ni@Cu10Ni composite reinforcement. This hybrid mesh was incorporated into a SAC305 alloy to fabricate a composite solder, which was subsequently applied in low-temperature soldering of Cu substrates. The influence of mesh composition and soldering time on the microstructure and mechanical performance of the joints was systematically examined. Findings It was found that the reaction kinetics between the Ni@Cu10Ni mesh and the SAC305 matrix were markedly accelerated compared to those of pure Ni mesh-reinforced solders. After 1 min of soldering, the joint microstructure comprised predominantly (Cu,Ni)6Sn5 intermetallic compounds (IMCs), residual Ni skeletons and trace amounts of unreacted ß-Sn; prolonging the soldering time to 5 min resulted in IMC grain refinement; further extension of the soldering time induced IMC coarsening. Correspondingly, the shear strength initially increases and then decreases, reaching a maximum of 79.0 MPa at 5 min, representing a 50.5% improvement compared to joints using pure Ni mesh/SAC305 composite solder. Originality/value This research offers a promising strategy for producing high-strength solder joints under low-pressure, short-duration soldering conditions.