THERMOCOMPRESSION BONDING EFFECTS ON BUMP-PAD ADHESION

In the wafer bumping process, metal bumps are deposited on aluminum pa ds and are later used to bond the silicon die to the I/O connections, The bump strength is important for the mechanical integrity and overal l reliability of the interconnect. In this paper the effects of the fo llowing thermocompression bonding parameters on the bump-pad adhesion of TAB (tape automated bonding) bonds are experimentally determined an d analytically explained: thermode temperature, base temperature, bond ing pressure, and bonding duration. Experiments were performed on a 32 8-lead TAB device (gold bump on 4-mil pitch) and were based upon a 4-p arameter, 3-level, Taguchi orthogonal array, The experimental results are compared with results obtained from finite element analyses, A con sistent increase in the bump strength was observed after thermocompres sion bonding, Applied thermode pressure and bonding duration were foun d to be the most significant parameters that affect bump-pad adhesion.