Investigation of Strip Warpage Behavior in Wire Bonding Process

Abstract

This study successfully established a strip warpage simulation model that is applied to the wire bonding process, and explored the effects of structural designs, material types, and processes such as molding, post and mold cure (PMC), pretreatment, and ball mounts on the strip warpage. The error between the experimental values and the simulation values is less than 13.7%. In addition, the Taguchi method is used to determine that the key factors affecting the strip warpage are the die thickness and the mold compound thickness, and that the secondary key factor is the molding temperature. This study concluded that in order to reduce strip warpage, the die thickness must be increased, while the compound thickness and the molding temperature must be decreased. To solve this problem, the structural design criteria proposed in this study use a smaller distance ratio of the neutral axis of the strip (zn) to the dice centroid (zdie). With this modification, it can reduce warpage and overall thickness of the strip. These observations indicate that the proposed model can be used to understand the effects of structural design, material types, and process parameter changes on the strip warpage. Strip design criteria are also provided in order to reduce the strip warpage, and thus, meet the requirement of thin and compact production lines, accelerate product development cycles, improve product quality, and reduce development costs.