Effect of Minute Bends and/or Kinks of Wire Bond Profile on Sag Deflection for 3-D and Multichip Module Semiconductor Packaging

Wire sag and wire sweep developed during encapsulation process are counted for the lower yield rate of chip packaging in semiconductor industry. For conventional packaging, only one single layer of wire bond was constructed along the perimeter of chip system. The issue of wire sag is not a concern until 3-D and multi-chip modules packaging prevails due to the desperate demands of smaller and faster advanced microelectronics devices. Very few researches have been documented on this subject of sag deflection. An empirical equation based upon major profile parameters of a wire bond has been developed by author to predict sag deflection of ellipse shape wire bond. However, the effect of minute bends and/or kinks of wire bond profile on sag deflection has not been included. In this paper, we investigate three frequently used wire bond loops, Q loop, S loop, and M (modified) loop, to look into these minor characteristics of wire bond profile as compared to bond span and bond height. Based on current results, we find that these minute features may dominate the response of sag deflection of a wire bond.