Au (gold) is often used in the electronics industry as a protective finish to preserve the solderability of underlying finishes and/or substrate materials. However, the presence of Au in the molten solder increases the risk of embrittlement by: 1) Au saturation above the solubility limit of the liquid, resulting in formation of Au-Sn intermetallic compound (IMC) particles and 2) solid-state diffusion of Au, during long-term aging, toward the interface and formation of a layer of Au-Sn IMC. These effects are being studied by liquid-state aging and solid-state aging studies, respectively. Ring-and-plug test samples were constructued with Pb-Sn and Sn-Ag-Cu solders with 0, 2, 4, and 8 wt. % Au. Liquid-state aging was performed at 240 to 320°C for up to 60 seconds and solid-state aging was performed at 25 to 170°C for up to 400 days. The results of mechanical push tests (joint shear strength) are reported here. Interesting differences were found between the behavior of Au contaminated Pb-Sn compared to Pb-free solder joints. Also, preliminary results of microstructural characterization of the aged solder joints will be discussed and correlated with mechanical properties.

*Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the US Dept. of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000