Device for bonding with a compliant medium

TLDR: In this paper, a compliant medium is used to hold the workpieces during the bonding of two workpieces by ultrasonic or thermocompression techniques, and the compliant medium eliminates the problem of size differences, as well as wear, mis-alignment and the like, and a good bond is achieved in each instance.

Abstract: The bonding of two workpieces by ultrasonic or thermocompression techniques requires the use of a rigid bonding tip or ram to transmit the bonding energy, whether it be vibratory, mechanical and/or thermal. In time, such a rigid medium is subject to wear, to mis-alignment and to pickup of material from the workpieces, the latter causing the upper workpiece to stick to the tip. Further, such a rigid medium cannot be used reliably to make a number of bonds simultaneously, because minor size differences in the workpieces can prevent a good couple for energy transmission from being established to every workpiece. It has been discovered that a compliant or deformable medium can be employed to hold the workpieces during bonding. By deforming around the workpieces, the compliant medium eliminates the problem of size differences, as well as wear, mis-alignment and the like, and a good bond is achieved in each instance. In one aspect, the bonding energy is transmitted through the compliant medium to make the bond. In a second aspect, the bonding energy is transmitted through the support for the workpieces. The quality of individual bonds is improved because, for a given set of bonding conditions, there is less deformation of the workpieces than with conventional techniques. The invention is particularly applicable to the bonding of beam-lead transistors and integrated circuits to substrates, to bonding a plurality of leads to integrated circuit and thin film devices, and to bonding brittle single crystal chips to substrates.