Friction coefficient investigation on IC dam-bar trimming process by inverse method with experimental trimmed geometric profiles

In the trimming process of integrated circuit (IC), the friction between punch and workpiece has been studied extensively. The value of the friction coefficient was usually assumed as a fixed value for the simplification of the investigations in most literature. It was seldom discussed that the values of the friction coefficient would actually increase as the trimming strokes increased. The aim of this study is to propose an inverse calculation method for the variation of the friction coefficients during the IC dam-bar trimming process. This inverse calculation is based on the geometric profiles, the profiles of the trimmed section of the IC dam-bar materials in the experimental measurement. The numerically optimized Levenberg–Marquardt method, coupled with objective functions and converge criterions along with the elastic–plastic finite element approach, is used for the inverse calculation to obtain friction coefficients during the IC dam-bar trimming process. According to the profiles of material in trimming experiment, the proposed inverse calculation was used for the number of strokes at 2000, 4000, 6000, 10,000, 12,000, and 14,000, the values of the friction coefficient were obtained as 0.1545, 0.155, 0.1613, 0.1766, 0.1875, and 0.1890, respectively. Consequently, a relationship equation between the friction coefficients and the trimming strokes can be conducted by means of the regression. The inverse calculation proposed herein can be used and obtain the values of friction coefficient with only a few experimental data and these values are more close to the actual situation during the trimming process. The results obtained in the present study could upgrade the trimming processes in the IC packaging industry.