Lead frame wire bonding by preheating

摘要

In a method for welding a lead wire or bonding wire from a microcircuit chip mounted on a lead frame to a lead frame finger, the lead frame finger is preheated prior to any substantial electrical or thermal coupling between the lead frame finger and chip. Intense but controlled energy is applied to the lead frame finger at levels which might otherwise damage the IC chip. In one embodiment the lead frame finger is preheated to a temperature below the melting point of the metal comprising the lead frame. Enhanced bonding is thereafter effected by thermocompression bonding etc. In another embodiment the preheating step comprises melting a portion of the surface of the lead frame finger, forming a molten pool or puddle in the surface. Bonding of the lead wire is effected by immersing a section of the wire in the molten pool or puddle. In order to preheat the lead frame finger a controlled pulse train is delivered for arc discharge at the bonding location. Bonding apparatus and circuitry for preforming the method are described.