Abstract
In recent years, light emitting diode (LED), which has applied in outdoor illumination, automotive front lighting, and backlighting for large LCD display. It has become the key for the next generation illumination application. Wire bonding is one of the main processes used for connecting the signal of LED chip, it’s a multi-physic process including impact stage, ultrasonic vibration stage, and lift off stage. The failures of LED such as pad peeling, cracking, and delamination limit the development of LED and some are influenced by the wire bonding process. In a word, predicting and analyzing the failure of LED chip during wire bonding process is an important issue for decades, and this research will dedicate to constructing an effective simulation methodology on impact stage during wire bonding process. In wire bonding system, the material property of free air ball (FAB) is much softer than that of the capillary, which compresses the FAB to land on pad. Thus, a large deformation phenomenon comes out on FAB during wire bonding process. Due to the large deformation problem, it’s easy to have element distortion issue on FAB while executing simulation work of wire bonding process. To avoid the divergent problem of finite element (FE) analysis, many researches reduce the compression distance of capillary on their contact simulation. Consequently, it is not easy to meet a good agreement with the real wire bonding process since the contact procedure of simulation is not completed. To solve the divergence problem, this research will construct FE models to discuss the element distortion issue using commercial software ANSYS®/LS-DYNA 3D with implicit and explicit method. Especially, an arbitrary lagrangian-eulerian (ALE) algorithm and the remesh concept will be proposed while utilizing the explicit method to solve the element distortion problem. By utilizing the explicit method with 2nd level accuracy ALE algorithm, an effective simulation methodology is successfully achieved. Observing the ball height after impact stage, there’s only 0.5% discrepancy between this model and the real wire bonding sample, the geometry of bonded wire is also similar to the real one. It is concluded that the FE model established in this research not only conquer the element distortion problem, but proposed an effective methodology for simulating wire bonding process in the future as well.