Modeling And Simulation Of Wire Bonding Looping Process Based On Variable-length Link-spring Model

Abstract:Thermosonic wire bonding is the most widely used technology to achieve chip interconnect in microelectronic packaging. Wire looping process is the key technology to deform the wire in wire bonding. The final loop profile is one of the key factor affecting the reliability of interconnecting and the size of chip packaging. The development of electronics packaging is aimed at increasing packaging density, Miniaturization and improving performance, and there is a need to improve wire looping technology and optimize loop profile. In this paper, a variable-length link-spring (VLLS) model was proposed. The whole looping process was simulated. The factors influencing the final loop profile were studied. The moments and the curvature of wire were analyzed. This paper included the following:1) A real-time shooting experiment platform of wire bonding looping process was built. The experiments of wire bonding looping process with different capillary trace parameters were carried on. The high speed video camera was used to record the dynamic wire bonding looping process. The loop profiles were obtained by using digital image processing technology.2) The variable-length link-spring (VLLS) model was proposed. And the solutions of the model were obtained by Newton’s method for nonlinear equations. The simulations of the dynamic wire bonding looping process were realized. And the accuracy of the simulation results was verified by experiment.3) The wire bonding looping process of standard loop and complex loop was simulated by the variable-length link-spring (VLLS) model. The influences of link length, HAZ length, the temperature distribution of HAZ, the length and the height of reverse motion on the standard loop profiles were studied. The results show that the most proper link length is10μm. The HAZ length affects the position of kink on the wire. The temperature of HAZ affects the deformation of kink. The length and the height of reverse motion affect the height of the final loop profile. The height of reverse motion affects the position of kinks on the wire.4) The instantaneous distributions of the bending moment and the curvature of wire in the wire bonding looping process were calculated and analyzed with theoutput of the model. The relationship between the deformation of wire and the load histories of bending moment and the curvature was analyzed. The results show that the wire profile is the result of the residual curvature and the instantaneous bending moment. The residual curvature is related to the bending moment loading history. The residual bending moment of the final wire profile is small. The bending moment was mainly changed in loopup stage. While in the loop down stage, the bending moment changed a little.