Wire Bondability Evaluation of Concave Bond Pad

Wire bonding is an important process of semiconductor assembly by providing electrical connection between integrated circuit and the external leads of semiconductor package. Wire bonding on none-flat surface is uncommon and less exploration as compare to flat surface bond pad. In certain circumstances, wire bonding is required to conduct on none-flat surface. Bond pad with concave surface is initially designed for solder bumping. Nevertheless, assembly flexibility to conduct wire bonding on concave bond pad is required in certain product application. In view of this, bondability study of concave bond pad was conducted by applying conventional thermasonic wire bonding. It was discovered that concave bond pad displayed a unique behavior in term of ball bond deformation. Ball bond diameter increment rate of concave bond pad is lower than flat bond pad. Difference in term of ball bond deformation eventually lead to distinctive ball shear respond and process parameter window on concave bond pad. Wire pull test and ball bond cross section analysis also included in this study to complete the evaluation. Despite of differences between flat and concave bond pad, standard methodology of wire bond process characterization on concave bond pad is still applicable.