Thermocompression bonding effects on bump-pad adhesion

In the wafer bumping process, metal bumps are deposited on aluminum pads and are later used to bond the silicon die to the I/O connections. The bump strength is important for the mechanical integrity and overall reliability of the interconnect. In this paper the effects of the following thermocompression bonding parameters on the bump-pad adhesion of TAB (tape automated bonding) bonds are experimentally determined and analytically explained: thermode temperature, base temperature, bonding pressure, and bonding duration. Experiments were performed on a 328-lead TAB device (gold bump on 4-mil pitch) and were based upon a 4-parameter, 3-level, Taguchi orthogonal array. The experimental results are compared with results obtained from finite element analyses. A consistent increase in the bump strength was observed after thermocompression bonding. Applied thermode pressure and bonding duration were found to be the most significant parameters that affect bump-pad adhesion