VARIATION AND CONTROL OF BONDING FORCE

摘要

A lead wire bonding machine is described for ball bonding the end of a lead wire held in a bonding tool to a die pad of an integrated circuit chip and for wedge bonding a segment of the lead wire spaced from the ball bond to a lead frame finger during successive ball bond wedge bond cycles. The bonding machine includes a variable linear drive such as a solenoid or small linear motor coupled to the bonding head for applying the first bond force to the bonding tool during ball bonding and the second bond force to the bonding tool during wedge bonding. A control circuit coupled to the solenoid or other variable linear drive delivers a first current having a desired profile or amplitude wave envelope for applying the first bond force with a first force profile during ball bonding to die pads and by delivering a second current having a desired profile or amplitude wave form for applying the second bond force with a second force profile during wedge bonding to lead frame fingers. A wave form generator generates the wave form envelopes for achieving the desired force profile so that the bond force may be varied according to the force profile during bonding at a particular site. Thus, the bond force may be varied and modulated according to the welding requirements at different die pads or lead frame fingers and according to the composition of the constituent metals of the lead wire and bonding substrate.