关键词: 微组装, 倒装焊, 助焊剂, 真空汽相清洗, 底部填充

Abstract: Flip chip packaging is one of the key technologies to realize miniaturization, lightweight and multi-function of electronic products, because it has higher assembly density and signal transmission rate than traditional wire bonding. The chip active surface that has pin array and prefabricated solder bumps is interconnected by flip chip bonding technology. It is much more difficult to clean for the flip chip with small size and micro pitch, so cleaning technology is an important factor affecting the flip chip bonding process. In this paper, the distinction of cleaning effects between different methods and parameters and the influence of residual flux on the underfill effect are studied in order to optimize the cleaning technology of flip chip. The results show that the flux in the fine gap between flip chip and substrate can be fully cleaned by the vacuum vapor cleaning process of pre-cleaning (≥3 min) – regular cleaning (≥3 min) – steam rinsing (≥3 min) – vacuum drying (≥4 min). There is no residual flux and cleaning solution, thus ensuring the rapid flow and completely curing of underfill material, and the void rate of underfill can be less than 5 %.

Key words: micro-assembly, flipchip, flux, vacuumvaporcleaning, underfill