Development of highly reliable flip-chip bonding technology using non-conductive adhesives (NCAs) for 20 μm pitch application

A 20 μm pitch flip-chip bonding with Sn/Cu bumps and nonconductive adhesives (NCAs) was developed to satisfy the requirement for high density electronic packaging. The Sn/Cu bumps of a 20 μm pitch are peripheral distributed in a line. The bonding process was performed at 150°C for 10 s using three commercial NCAs. All the joints were successfully fabricated with NCAs, and have similar contact resistance values, regardless of NCA type. To evaluate the reliability, a thermal cycling (T/C) test (-55°C/125°C, 1000 cycles) and a temperature and humidity (T&H) test (70°C/95% RH, 1000 h) were performed. The effect of NCA type on reliability was investigated. NCA, which has lower moisture absorption and a lower coefficient of thermal expansion, had the best performance in a reliability test. Our results showed that bonding using Sn/Cu bumps and NCA can be applied in ultra-fine pitch (less than 20 μm) flip-chip bonding if the proper NCA is selected.