Effect of pore structure on void formation in lotus type porous Cu/solder joints

Void formation in solder joints is a critical reliability challenge in high-power electronics, as it degrades thermal dissipation and mechanical integrity. This study investigates a novel structural approach to mitigate this issue. The influence of a uni-directional porous structure in lotus-type porous Cu (Louts Cu) on void formation in solder joints was investigated. All pores in lotus Cu were infiltrated with SAC305 (Sn–3.0Ag–0.5Cu) solder paste. Then reflow soldering was performed under three different atmospheric conditions: air, nitrogen, and vacuum. The microstructure and void fraction were characterized. The shear strength was evaluated. The shear strength of Louts Cu joint was slightly higher than that of non-porous Cu joint. The characterization of void fraction in joints exhibited that lotus Cu joint is lower than that of non-porous Cu joint. • Uni-directional porous Cu substrate significantly reduces void formation in SAC305 solder. • Aligned pores provide effective escape channels for flux-generated gases during reflow. • Reduced void content leads to a ∼7.6% improvement in solder joint shear strength. • Average void ratio is reduced from ∼30% (non-porous Cu) to ∼10% (lotus Cu).