We report on using a Scanning White Light Interferometer (SWLI) for quality control of aluminum lead single-point Tape Automated Bonding (spTAB). A spTAB process was used to connect 14 μm thick, 42 μm wide aluminum leads on a 12 μm thick polyimide layer to a micro chip. Three different bonding process parameters were varied in order to maximize the pull force: bond force, ultrasonic power, and ultrasonic time.
A custom built SWLI was used to measure the topography of the bonds in order to find features that correlate with the tensile bond force. This force was obtained in a destructive way by a pull test.
By keeping the bond height within 3±1.5 μm, bonds with acceptable tensile forces in excess of 54 mN were obtained. This was verified by a separate validation measurement where the pull force of bonds complying with the height requirement was recorded.