why do you need heat blocks in the process of wire bonding an ic? what's the purpose of hte heat blocks?
There are several processes use to connect IC's during packagingTwo are ultrasonic bonding of aluminum wires, and thermosonic welding of gold wiresUltrasonic bonding is used for aluminum wireThe wire is pressed against an aluminum pad on the IC and moved rapidly back and forthThis breaks the Aluminum oxide off both the wire and the padOnce you have clean metal, stop vibrating the wire, and they weld nicelyFor gold wires, thermosonic welding is usedJust rubbing the wire against the pad will not reliably remove the aluminum oxide from the padThe gold wire, of course, does not significantly oxidizeHeating the IC with a heater block warms it sufficiently to weaken the bond between the aluminum pad and its oxide, so the oxide can break offThen, the ultrasonics weld the gold wire to the pad in a somewhat equivalent manner to the aluminum U/S bond mentioned above.
