A microslip model of the bonding process in ultrasonic wire bonders Part I: Transient response

Abstract

Ultrasonic wire bonders with precision capillary tips are widely used for bonding electrical wires to IC chips and circuits. The industry is driving wire-bonding technology towards increased yields, decreased pitch, and ever decreasing cost. However, many technical and material issues will be involved in achieving these goals, such as bond quality monitoring, new failure modes, reliability problems in new plastic mold compounds, and increasing wire sweep problems, in particular lack of the quantitative understanding and validated mathematical model of the bonding process. In this paper, a microslip model is proposed for the bonding process based on the bonding pattern observed, i.e. the wire is bonded at the periphery while the centre is left unbonded. A bilinear hysteresis restoring force is assumed in the microslip model because of its simplicity. The transient displacement response is calculated, and its pattern shows very good agreement with the experiment.

Initial bond formation in thermosonic gold ball bonding on aluminium metallization pads

“…Many efforts have been made to establish bonding mechanisms to explain the complex thermosonic/ultrasonic bonding process (Hulst, 1978;Hu et al, 2006). A fretting mechanism proposed by Hulst (1978) assumed that interfacial sliding cleaned and heated the contact surface, resulting in robust bonds.…”

A brief review of selected aspects of the materials science of ball bonding

“…3a illustrates [7]. During ball deformation the maximum plastic stresses generally occur under the inner chamfer region of the capillary, resulting in maximum interfacial plastic stresses around the ball periphery [8][9][10]. The contact mechanics of the ball and wire is important and Qi et al [11] show that at low ultrasonic power the centre of balls may be un-bonded with welding only at the ball periphery where the highest plastic stresses occur.…”

In-Situ Observation of Adhesion Behavior During Ultrasonic Al Ribbon Bonding

“…Because the bonding interface is typically invisible, it is not simple to directly observe the bonding interface during the bonding process. Therefore, in general, off-line observations of the bonded interface have been implemented [1,2,11,12,14,15,17,19,22,28]; in lieu of this, numerical analyses of bonding processes have been performed [4,13,18,[34][35][36][37][38][39]. A few studies Annealed pure aluminum ribbon made by Tanaka Denshi Kogyo, Japan was used in the present study.…”