Study on the Fabrication of Flip Chip Lead-free Solder Bump by Electroplating

摘要

The fabrication of Sn-Pb and Sn-Ag solder bump (150 mu m diameter, 250 mu m pitch) by electroplating was studied for flip chip package. As a preliminary experiment, the effect of current density and plating time on Sn-Pb and Sn-Ag deposit was investigated. The eutectic compositions of Sn-Pb and Sn-Ag were controlled and the Sn-37 wt. percent Pb and Sn-3.5 wt. percent Ag solder bumps were fabricated in optimal condition of 6A/dm~2, 4hr and 6A/dm~2, 1.5hr, respectively. The shape of bumps was observed by SEM and ball shear test after reflow was performed to measure adhesion strength between solder bump and UBM(Under Bump Metallurgy). The shear strength of Sn-Ag bump fabricated by electroplating was higher than that of Sn-Pb.