SMTA International Conference Proceedings


EFFECT OF FLUX AND COOLING RATE ON MICROSTRUCTURE OF FLIP CHIP SAC BUMP

Authors: Dr. Wusheng Yin and Dr. Ning-Cheng Lee et al.
Company: Indium Corporation of America
Date Published: 9/25/2005   Conference: SMTA International


Abstract: Solder joints with a smaller grain size have been known to be desirable for improved fatigue life. The flip chip solder joint is studied by examining the microstructure of solder bumps at reflow. The microstructure of flip chip SAC solder bumps can be affected by flux chemistry and cooling rate, with higher cooling rate results in a slightly finer microstructure in both grain and dendrite size.

However, the effect of flux chemistry exhibits a greater effect than the cooling rate. Therefore, selecting a flux may not only affect solder wetting, but also may affect the microstructure of solder joints. Intermetallics appear to remain constant, therefore are a non-factor in this study.

Key words: Solder, flux, cooling rate, flip chip, microstructure, bump, lead-free, SnAgCu



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