Copper Ball Wedge Bonding to Copper Thick Film

This paper describes the first of a two part study of copper ball wedge thermosonic wire bonding and concentrates on the second wedge bond to copper thick film. Results of varying the bonding machine parameters of force, amplitude of vibration, weld time, substrate temperature and bonding direction on bond strength are discussed and optimum conditions to give maximum yield suggested. Methods of providing adequate gas shielding of the wire and substrate and the effect of wire ductility are also presented. Particular attention has been given to improving the accuracy and speed of testing of the loop pull test by correcting for variations in wire loop geometry. A method will be described for measuring loop height automatically during each test and the incorporation of a computer to obtain corrected values of force.