Experimental and Numerical Simulation Study of Pre-deformed Heavy Copper Wire Wedge Bonds

Abstract

To implement a self-optimization technique for ultrasonic wire bonding machines, a model of the pre-deformation phase is essential. The local material characteristics change abruptly because of the cold work during deformation. Investigations confirm a significant influence on the material properties of the contact members during touchdown. In a first step this paper validates the importance of modeling the pre-deformation experimentally. In a second step, the paper presents a numerical study of the elasto-plastic deformation based on the finite element method. This model includes measured overshoots in the touchdown forces in order to achieve accurate model responses. A validation of the model with the resulting nominal contact area, surface pressure and penetration depth reveals the high model quality.

Multi-dimensional Ultrasonic Copper Bonding – New Challenges for Tool Design

“…The pressure distribution between pin and substrate has a high impact on the welding result. Parts of the contact are sliding and parts are sticking, due to non-homogeneous pressure distribution which was also described in [4] and [5] for copper wire bonding. Fig.…”

“…In the first step the frictional energy to bond a copper connector pin is estimated from heavy copper wire bonding assuming one-dimensional excitation. A relative velocity of v r = 1,6 m/s and a normal load of F N = 30 N are measured during 500 µm copper wire bonding [4]. It is assumed that the expansion of bonded area between two contacting surfaces during ultrasonic bonding is proportional to the frictional power…”