Improving Thermosonic Gold Ball Bond Reliability

A comprehensive study using normal probability paper to project gold wire bond reliability has been performed. Reliability projections have been made using ceramic capillaries, tungsten carbide capillaries, gold wire, gold/palladium alloy wire, three different device metallizations, nine different wire lot numbers, and seven ultrasonic power settings. The reliability projections from all of the tests were then compared to the ball shear force from each test to correlate shear force with reliability. The results indicate that several orders of magnitude increase in reliability can be achieved from using optimum wire bond parameters. The ball shear force value has also been shown to be very useful in predicting reliability and thus eliminating time consuming wire pull tests.