Gold-to-aluminum bonding for TAB applications

In an effort to reduce the bonding temperature for a TAB (tape automated bonding) application, a laser-processed gold-plated balltape was used for thermocompression bonding to aluminum. The effects of hardness, thickness, and morphology of the gold layer on thermocompression bonding were investigated. Thermocompression bonding of hard gold plated balltape was shown to be inferior to that of soft gold balltape. Thick plating of soft gold on balltape did not provide any advantage over the balltape with the standard thickness and morphology in terms of bonding to aluminum. An improved gold layer surface morphology was developed by controlling the plating rate. The new bumped tape structure was bonded at temperatures from 500°C down to as low as 350°C. The new balltape could be bonded using a shorter bonding time than the standard balltape at the equivalent temperature