Linkage-spring model in analyzing wirebonding loops

Several wirebonding loops were proposed to prevent the necking in wire. Most of experimental statistical methods were applied in the analysis of wirebonding and it was time consuming and without the precise analysis. Further, the finite element analysis is the most powerful tool for stress analysis; however, it is too complex for analyzing a large deformation. Hence, this paper proposes a novel method using springs to simulate the condition of forces acting on a section of the bonding wire. The bonding wire profile can be formed by combining several sets of linkage with springs, wherein the coefficients of elasticity and plasticity of the springs are determined by the bending angle of two linkages which simulates the elastic-plastic deformation of the bonding wires. The operational model ran be simplified by using the multiple degrees of freedom of the linkages/springs to analyze the profile and forces of the bond wire. Experiments have been conducted to validate the model. Good agreement is obtained between analytical prediction and experimental data. Finally, three basic preforms for wirebonding are introduced, and it ran be seen that the loop sagging at the second bond is improved and the loop height can be controlled by proper design. Necking and fracture during the bonding process can be avoided by the present method and the optimum wire bonding profiles can also be achieved