Bump height confinement governed solder alloy hardening in Cu/SnAg/Ni and Cu/SnAgCu/Ni joint assemblies

Abstract Near eutectic SnAg and SnAgCu solders with various solder bump heights were adopted to characterize the microstructure in solder alloys. The eutectic structure was refined and the secondary dendrite arm spacing of β-Sn decreased monotonously with the shrinkage of solder joints. Linear relationship between the secondary dendrite arm spacing and natural logarithm of the solder bump height was demonstrated in this study. The hardness and the creep deformation resistance increased with respect to the increase of solder dimension and microstructural variation due to the frequent interaction between dislocation and the precipitations in solder alloys.