Microelectronic Wire Bonding with Insulated Au Wire: Effects of Process Parameters on Insulation Removal and Crescent Bonding

The characteristics of the crescent bond process with insulated Au wire are investigated. Au wire with a sub-micron thick insulation coating is bonded on standard Ag plated leadframe diepads at 493 K. The wire loops are oriented perpendicular to the ultrasonic horn. The pull force obtained with a basic bonding process of insulated Au wire and bare Au wire are optimized by iteration and compared. Subsequently, the process is modified for the application with insulated wire. To increase the pull force an insulation layer removing stage (cleaning stage) is inserted before the bonding stage. The cleaning stage consists of a scratching motion (shift) toward to the ball bond in combination with ultrasound. The pull force obtained in this way with the insulated wire is 90.1±7.9 mN which is 2.4±2.0 mN larger than that obtained with bare Au wire.