Investigation of Interconnection Properties of Solderable Polymer Composites Reinforced with Cu Nanoparticles

The present study developed a novel solderable polymer composite (SPC) system incorporating a low-melting-point solder (LMS) filler, in which copper nanoparticles (Cu-NPs) were introduced as nano-reinforcements to improve mechanical performance. To investigate the effect of Cu-NPs content on the mechanical interconnection behavior of SPC joints, four SPCs formulations containing different Cu-NPs concentrations (0, 0.2, 0.5, and 0.8 vol%) were synthesized. The mechanical interconnection properties of the resulting SPC joints were evaluated using ball shear and microhardness tests. The results indicated that excessive Cu-NP addition deteriorated the solderability of the SPC joints. However, below a critical concentration, the SPCs produced uniform and proper spherical solder ball joints due to appropriate flow, coalescence, and wetting behavior of the molten LMS fillers. Under these conditions, the mechanical interconnection properties improved with increasing Cu-NP content. This enhancement was attributed to the reinforcing effect of the incorporated Cu-NPs as well as to microstructural grain refinement within the joint region.