The wire sweep analysis based on the evaluation of the bending and twisting moments for semiconductor packaging

The sweep deflection of wire bond caused by compound flow during the transfer molding process can seriously result in wire crossover and shorting. To predict the sweep deflection of wire bond, a sweep deflection model based on the contributions of the bending moment and the twisting moment applied on the wire bond is proposed in this study. By analyzing the numerical and experimental results of sweep deflection, the model predicts that most sweep deflection of wire bond is caused by the twisting moment instead of the bending moment in semiconductor packaging applications. The sweep deflection percentages from the twisting moment and the bending moment depend closely on the ratio of bond height and bond span. The lower the ratio of bond height and bond span, the larger the twisting moment induced sweep deflection. A set of sweep experiments is also performed to compare with the predictions of the model. The results show that a good agreement among the proposed model predictions, the FEA numerical predictions and the wire sweep experiments.