The undercut issue of the Cu/Ni/Sn2.5Ag microbump has been solved by reducing the Cu seed layer thickness and dry etching, but the bump height uniformity was degraded. Therefore, microjoints with different standoff heights were acquired by both thermo-compressive bonding and reflow soldering. The numerical analyses indicated that the microjoints with a lower standoff sustained a higher fatigue stress under temperature cycling and the growth of Ni3Sn4 layer was more rapid because of a shorter diffusion route, which hastened the formation of micropores in the interconnection zone and was the root-cause of early failure. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.023203esl] All rights reserved.