Thermocompression joining of copper to copper for TAB

A copper-to-copper joining process was developed which could consistently give bond pulls in excess of 50 grams. The key to the process was found to be the cleaning process and the control of the punch geometry. This process was put into production at several million parts a month. The key to the success of the process was found to be control of the inside edge of the punch. The inner edge had to be chamfered in a controlled manner. During the bonding process, the punch tends to wear out. Hence, the punches were changed every 100000 bonds.<
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