Abstract
According to the results of Part A of this paper [Microelectron. Reliab., this issue], the vertical tension loading transferred from the capillary is clarified as the direct driving force for bond pad metal peeling. Furthermore, the crack on the bonding pad is identified as the direct cause of the pad peeling. However, the major driving force for the crack that is correlated to the four main loadings described in the part A of this paper is not clarified. In order to find the driving force for the crack, whole ball bonding process of ultrasonic wire bonding is simulated by finite element method. The results of this study indicate that the horizontal vibration of the capillary controlled by ultrasonic power of the bonding machine has the most serious effect on the crack on the bonding pad as well as its propagation into the oxide layers in SDRAM chip. Thus it can be the major driving force for the crack.
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