Study of Grain Size and Orientation of 30 mu m Solder Microbumps Bonded by Thermal Compression

Abstract

Grain size and orientation of microbump play very important roles on thermal-cycling test and electromigration failure. In this study, Cu/Sn-2.5Ag/Cu and Ni/Sn-2.5Ag/Ni microbumps assembled by thermal-compression bonding are investigated grain size and orientation by electron-backscattering diffraction inverse pole figure. Cu/Sn-2.5Ag/Cu microbumps appear much more single crystal-like structures than Ni/Sn-2.5Ag/Ni. By the distribution of grain size, a large quantity of the small Sn grains appears in Ni/Sn-2.5Ag/Ni microbump due to the very low solubility of Ni in Sn. Finally, Cu/Sn-2.5Ag/Cu microbumps possess more grain areas with the lower angles between c-axis and normal dirction.