The Impact of Gold Plating Process for Bonding Pads on Interconnection Quality

Abstract

Ball-wedge bonding wires are widely used in microwave circuits and chip packaging. Plating process is an important factor that affects the interconnection quality of ball-wedge bonding wires. In this article, the impact of Gold (Au) plating processes for bonding pads on interconnection quality was studied using model analysis and experimental testing. For this purpose, printed circuit boards (PCBs) were manufactured using both electroless Nickel immersion Gold (ENIG) process and electroplating soft Gold process. The thickness and roughness of Gold plating layer of circuit boards were measured. For circuit boards with different Gold plating processes, based on the material and size parameters of ball-wedge bonding wires and pads, a finite element analysis (FEA) model of connection area was developed. the deformations and von-Mises stresses at the interfaces between bonding points and Gold-plated layers under tensile force were calculated and analyzed. The maximum tensile breaking force and qualified rate of ball-wedge bonding wires were analyzed from the perspectives of both thickness and roughness of Gold plating layer. In addition, the bonding wire failure modes were also observed and analyzed. The results of this investigation provide the theoretical support for selection of Gold plating processes in Gold wire bonding.