Effect of surface contamination on solid-state bondability of Sn-Ag-Cu bumps in ambient air

Abstract

Two solid-state bonding methods, thermocompression bonding (TCB) and surface activated bonding (SAB), were used for studying the effect of surface contamination on the bonding of Sn-Ag-Cu bumps in ambient air. The surface contamination was analyzed by X-ray photoelectron spectroscopy. Correlated to the surface contamination, the influence of Ar-plasma pretreatment time as well as the air exposure time on the shear strength was investigated in SAB process. The bonding of Sn-Ag-Cu bumps was achieved at 25-200 C benefiting from dispersing the surface contamination. With an Ar-plasma activation process prior to the assembly under a low-vacuum background, the carbon contaminants on the bump surfaces in SAB process was removed, and the required bonding pressure or temperature to achieve a high shear strength and bond yield is lower than that in TCB process. © 2008 The Japan Institute of Metals.