Thermosonic Flip Process Heat - Stress Modeling And Multi-parameter Simulation

Rich experience on craft recognition and craft parameters choices has been accumulated through long term practice in the industry, and also various of bonding equipment has been developed. However, nobody can clarify the principle of bonding and many phenomena associated with the core mechanism of bonding have been kept on the quantitive description which is far from satisfying the requirement of high density packing. By comprehensive action of physics, chemical and mechanics, real-time measure on the tiny bump becomes extremely difficult and the method of FEA makes it easy to tackle this problem.In this paper, aiming at the thermosonic flip chip bonding process, the finite element model is formed, where data from experiment are used as initial conditions. From the FEA, the multi-parameters are got and the main innovations are as the followings:1,In the process of ultrasonic bonding, the softened material only affects the stress on its value and has little effect on its distribution. Different friction conditions have influents on the stress in both values and distributions and the bigger is the friction coefficient, the larger is the stress concentration in the flip chip interface.2,The simultaneous temperature in the bonding area will also affect bonding quality for different bonding parameters have different influence on it. The temperature in bonding process has much to do with the bonding press stress and the ultrasonic amplitude and the slope of the temperature increase when the bonding press stress and ultrasonic amplitude increase. When the bonding process continue for 9 millisecond with amplitude of 0.7μm and a press stress of 30g, temperature in the bonding interface rise 74.5 degree.3,Combine the distribution and evolution figure of the plastic strain from the simulation and the results from the experiment, the bonding position is analyzed.4,With the cooperation of ultrasonic and press stress, stress concentration happen in the bonding interface and the stress is amplified. The normal stress is 2 times larger than original one and the shear stress is 0.7 time larger than the original one. The powerful stress is big enough to cause plastic strain and plastic flow on the interface which can provide good conditions for bonding.All these results above will have import referential value for the study on the bonding mechanism and improvement of the bonding quality.