Temperature and pressure dependence in thermocompression gold stud bonding

Low temperature metal bonding plays a very important role in the interconnection for 3D packaging technologies in VLSI integrated circuits. The effects of temperature ranging from 100-300 degrees C and pressure ranging from 200-600 g/bump on the direct gold-gold bond quality were measured using shear and tensile pulling techniques, respectively. A critical bonding temperature was observed below which no bonding will occur. Above this temperature, the shear strength improves with bonding temperature because of the increase in the true bonded area. This critical temperature can be interpreted to be the onset of the break-up of organic barrier films. Beyond this critical temperature, the tensile strength of the Au-Au bond exhibits a maximum with bonding pressure. This can be associated with the pressure dependence of the interfacial stress distribution and its effect on unbonded radius, r. (c) 2005 Elsevier B.V All rights reserved.