Bonding of Ag-alloy wire in LED packages

Abstract

The LED lighting market has grown rapidly in recent years. Silver (Ag) and silver-rich alloy wire are drawing more and more attention in the LED industry because of its better thermal and electrical conductivity, much lower price as well as higher reflectance rate. Being considered as a potential alternative to Au wire in LED packages, the bonding capability of Ag-alloy wire on a LED device was evaluated in this study. The performance of Ag-alloy FAB with and without a cover gas was first studied. Using the bonding results of Au wire as the benchmark, investigation of the bonding capability and reliability of the Ag-alloy wire with and without cover gas was also carried out. Generally, Ag-alloy wire delivers better performance when bonding with a cover gas. During bonding of Ag-alloy wire without a cover gas, degradation of FAB repeatability, ball uniformity and bonding strength were observed. However, for low-end LED devices, bonding of Ag-alloy wire without a cover gas is a possible compromise for more cost savings.