Reaction characteristics of the In-15Pb-5Ag (wt.%) solder with a Au/Ni/Cu pad during reflow soldering and aging treatment were examined. Interfacial reaction during reflow resulted in either an AuIn2 or Ni28In72 layer, depending on reflow time. The AuIn2 layer became thinner and disappeared from the interface, and only the Ni28In72 layer grew with the progress of aging treatment at 130°C. Based on those observations, the dissolution rate of the Au top layer was estimated, and the behavior of the AuIn2 layer during reflow and aging treatment was discussed. In addition, peak shear load and fracture energy of the solder bump were measured as a function of reflow time and aging treatment. The results were compared with those measured with the Sn-37Pb solder bump.