Effects of electrical current on microstructure and interface properties of Sn-Ag-Cu/Ag photovoltaic ribbons

Abstract

This study presents an electrical current testing that is based on the Sn-xAg-0.5Cu (x = 1, 3 mass%) photovoltaic (PV) ribbon, and investigates the growth mechanism of the intermetallic compounds (IMCs). The microstructure of both alloy solders contains the eutectic region (β-Sn+Cu6Sn 5+Ag3Sn) and the base phases (β-Sn). The eutectic phases in the Sn-3Ag-0.5Cu (SAC305) alloy presented a continuous distribution, and its amount was higher. After soldering, the Cu6Sn5 and Ag3Sn IMCs were found at the interfaces, and their morphologies were dominated by Ag contents in the Sn-Ag-Cu (SAC) solder. The whole interfacial characteristics of IMCs were affected after biasing for 40 h. The growth behavior of these IMCs was controlled by the bias-induced thermal diffusion mechanism and the evolution of IMC morphology was dominated by the growth dynamics. The IMCs, formed at the interfaces (SAC/Cu, SAC/Ag), dominated the series resistance of the PV ribbon. © 2013 The Japan Institute of Metals and Materials.