Gold bonding reliability in high density FPGA devices

The formation of intermetallic mass along the edge of the ball has been observed inherent to the gold bonded Aluminum pads. In a well-bonded sample, it occurs only near the edge of the ball resulting to still strong, reliable bonds after the parts have been exposed at a long duration to elevated temperature. Hence, the presence of intermetallic mass along the periphery of the ball is not an indication of unreliable bond.