Topology optimization on targeting frequency and mode of ultrasonic bonding tool for microchip packaging

Ultrasonic flip chip bonding is one of the widely used methods in semiconductor chip or microsystem packaging and ultrasonic (US) bonding tool is important part for the bonding machine. To perform the proper operation of US bonding, the adequate vibration frequency and mode of US tool is required and the vibration design of the tool is very important. Until recent days, however, the most of practical aspect of the tool design follows the trial-and-error approach. In this study, we introduce the method of topology optimization for US bonding tools. The solid isotropic material with penalization (SIMP) method is used to formulate topology optimization and optimal criteria (OC) method is introduced for the update scheme. The objective resonance frequency and longitudinal mode is tracked using Modal Assurance Criterion (MAC). We compare between 2D and 3D finite element models, and realize two types of US tools which are based on 3D optimization results. To ensure the validity of topology optimization applied to the high frequency and tough devices such as US bonding tools, the vibration displacements at anti-nodal points of the optimized US tools are measured by laser vibrometer.