Effects of thermo-compression bonding parameters on joint formation of micro-bumps in non-conductive film (NCF)

Effects of thermo-compression bonding parameter on Cu-pillar/Sn-Ag interconnection reliability of NCF-assembled Chip-on-board (COB) package were investigated. Parallelplate modeling of gap size during the thermo-compression bonding process was performed. By using the viscosity/time graph and the modeling, prediction of gap size was performed in both bare chip to chip and real chip to board. The actually NCF bonding of COB module was performed with different heating rate of 5°C/min, 10°C/min, and 20°C/min. The gap height decreased as the heating rate increased and the results well corresponded with the modeling. All the bonded samples showed stable daisy and contact resistance at as bonded state, however 5°C/min sample showed severe T/C failures due to high gap height and unstable wetting of solder on pad.