Gold-to-aluminum bonding for TAB applications

In thermocompression bonding used in tape automated bonding (TAB) technology, the gold-to-aluminum interface is one of the most difficult bonds that can be formed, because a thin aluminum oxide layer inhibits bonding at low temperatures. The usual bonding temperature is, therefore, expected to be higher than 500 degrees C. This results in extensive growth of intermetallics. In an effort to reduce the bonding temperature of a TAB 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 have been investigated. As a result, an improved gold layer surface morphology has been developed by controlling the plating rate. The new bumped tape structure was bonded at temperatures from 500 degrees C down to as low as 350 degrees C.<
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