In this study, we used daisy chain structure (40 bumps per chain) for electromigration testing. The thickness of each layer of the microbumps is Cu:5μm /Ni:2μm/Eutectic SnAg Solder:15μm /Ni:2μm/ Cu:5μm; the diameter of the solder joint is 30μm.Microbumps were stressed with a current density of 6 x 104 A/cm2. As the simulation result showed, current distributed homogeneously in the solder, which means current crowding effect is not the key of the failure mechanism in this structure. We observed that IMCs grew fast in earlier stage (20%), however, as the stressing time increased, not only IMCs but also continuous voids are formed, which means the structure is under the risk of early failure. In addition, most of the continuous voids are found at the cathode with serious UBM dissolution. The location of voids formation indicated that the electromigration is still an important reliability issue in Ni/SnAg/Ni microbumps.