OPTIMUM BONDING SHAPE CONTROL OF MICRO-SOLDER JOINT OF IC AND LSI

A solder bonding method called stretching soldering technology has been developed to realize high density packaging for electronic circuits. As micro-solder bonding of IC-LSI undergoes thermal stress caused by the thermal expansion difference between the chip and the substrate during use, a lower thermal stress bonding method is required. The waist bonding shape has a low stress structure under constant solder volume, according to FEM simulation. The waist shape could be controlled by the balance of upper and lower directional forces causing surface tension of molten solder. The molten solder shape and control balance equation follows Laplace-Young theory.