Modified Hypereutectic Sn-Cu Pb-Free Solder For Power Semiconductor Die Attach
Authors: Keith Sweatman, Motonori Miyaoka, Takatoshi Nishimura, Xuan Quy Tran, Stuart McDonald, and Kazuhiro Nogita Company: Nihon Superior Co., Ltd and University of Queensland Date Published: 10/13/2013
Abstract: While the search continues for replacements for the highmelting- point high-Pb solders on which the electronics industry has depended for joints that maintain their integrity at high operating temperatures an investigation has been made into the feasibility of using a hypereutectic Sn-7Cu in this application. While its solidus temperature remains at 227°C the microstructure, which has been substantially modified by stabilization and grain refining of the relatively large volume fraction of primary Cu6Sn5 by microalloying additions of Ni and Al, makes it possible for this alloy to maintain its integrity and adequate strength even after long term exposure to temperatures up to 200°C and the alloy has already demonstrated reliable performance in power semiconductors used for motor control in domestic appliances. In this paper the results of a study of elevated temperature mechanical testing of lap joints and thermal cycling of joints to a silicon die will be reported.