High-temperature wire sweep characteristics of semiconductor package for variable loop-height wirebonding technology

This paper studies the elevated-temperature sweep characteristics of wire bond during the transfer molding process for semiconductor packages. The material properties of gold wire are obtained experimentally at various temperatures. A set of sweep experiments is also performed to acquire the sweep stiffness of wire bond for several bond spans and bond heights. The linearity of the load–transverse displacement curves from sweep experiments indicates that the ranges of the allowance bond pitch in most semiconductor packages may be within linear elasticity limits. The elastic numerical analysis may be applied to predict the sweep behavior of the wire bond. In order to predict the elevated temperature behavior of wire bond sweep, a methodology is proposed in this study. With the aids of geometry factor defined in Eq. (6) and the three drag force models, Lamb’s, Sherman’s and Takaisi’s, the predictions of the elevated-temperature sweep deflections of wire bond can be tested. The results show that the increase of the sweep deflections is more related to bond span than bond height.