Influence of capillary trace on the wire bond loop profile

With the rapid development of IC manufacturing industry, wire bonding, as a traditional interconnection method, continues to develop towards high density, high speed and high reliability. The loop profile significantly influences the reliability of wire bonding, and it is necessary to study the wire bond looping process. The loop profile of the bonding wire is determined by the tension and material property of bonding wire as well as the trace and structure of capillary, in which the capillary trace has a major impact on the wire bond loop profile. At present, in the production practice of semiconductor industry, the settings of capillary motion parameters are mainly based on engineering experience. The influence of capillary trace on the loop profile is still unclear, which induces the loop profile is difficult to control. In this study, the influence of capillary trace on the looping process was investigated by finite element method on the software ANSYS LS-DYNA. The simulation results show that the lower the loop height is, the closer the horizontal position of highest point is to the first bonding point, the larger is the von Mise stress of the first bonding point. Loop height can be increased by rising kink height, reducing flat length, and the span of the highest point. The curvature of loop can be increased by increasing the height of the capillary motion and conversion, while overlarge conversion angle deteriorates the reliability of the loop. When the horizontal position of the highest point of the loop is located between the first bonding point and the center of the loop, the loop profile has ideal tensile strength and stability. Therefore, using a suitable capillary trace to generate a well-structured loop is beneficial to improve the reliability of electronic packaging.