A method to determine the sweep resistance of wire bonds for microelectronic packaging

Many kinds of gold wire and bond profiles have been used in wire bonding technology. To date, no solid experimental results have been available to guide the bond designer in the choice of a better looping system. A method is proposed for evaluating the sweep resistance of wire bonds during the transfer molding process. The wire sweep method was developed to obtain load–transverse displacement curves of wire bonds. The sweep stiffness of a wire bond is defined as the index of sweep resistance to drag during the transfer molding process, and can be evaluated on the basis of the load–transverse displacement curves. A wire bond with high sweep stiffness possesses a low wire sweep and sag for integrated circuit packaging. In this study, three types of wire bonds, Q-loop, S-loop and M-loop bonds, were examined to determine the sweep stiffness. The results showed that the Q-loop bond has the highest sweep stiffness for fixed bond spans and bond heights. For longer connections or crossing another chip in multi-chip module/three-dimensional packages, the M-loop bonds were affected significantly by their kinking numbers within a bond. The experimental results indicated that the M-loop bond has 13–75% better sweep resistance than the S-loop bond, depending on the bond span and bond height used.