Au-coated Ag alloy bonding wires with enhanced oxidation resistance for electronic packaging applications

Abstract

Purpose The purpose of this paper is to develop high-performance Au-coated Ag alloy wires (ACAA wires) and demonstrate the effect of Au coating layers on the bonding performance and oxidation resistance for stable and reliable electronic packaging applications. Design/methodology/approach ACAA wire with a diameter of approximately 25 µm and Au layer thickness of approximately 100 nm were prepared by the continuous casting, plating and wire drawing method. The bonding performance of the ACAA wires were studied through bonding on 3,535 chips. The oxidation resistance of ACAA wires and Ag alloy wires (AA wires) were comparatively studied by means of chemical oxidation tests, accelerated life tests and electrochemical tests systematically. Findings ACAA wires could form axi-symmetrical spherical free air balls with controllable diameter of 1.5∼2.5 times of the wire diameter after electric flame-off process. The ball shear strength of ACAA wire was higher than that of AA wires. Most importantly, because of the surface Au coating layer, the oxidation resistance of ACAA wires was much enhanced. Research limitations/implications ACAA wires with different lengths of heat affected zone were not developed in this study, which limited their application with different loop height requirements. Practical implications With higher bonding strength and oxidation resistance, ACAA wires would be a better choice than previous reported AA wire in chip packaging which require high stability and reliability. Originality/value This paper provides a kind of novel ACAA wire, which possess the merits of high bonding strength and reliability, and show great potential in electronic packaging applications.

A Review of Silver Wire Bonding Techniques

“…In addition to the coating process being constantly updated and iterated, the alloying manufacturing process of silver-based bonding wire is also constantly optimized. The patent [55] discloses a preparation method for palladium alloy reinforced composite bond wire. Unlike conventional methods for preparing palladium-silver alloy wire, this method utilizes liquid-phase chemical synthesis and powder metallurgy techniques to avoid the problem of increased electrical resistance caused by the formation of Ag alloys with elements such as Ag and Pd.…”