Interactions between liquid Sn-Bi based solders and contact metals for high temperature applications
Year: 2005
Type: conference-paper
Abstract: Liquid solder interconnects are promising as an alternative\napproach to conventional high melting point solder\ninterconnects for applications where the operating\ntemperature is likely to exceed 125°C. In order to ensure that\na liquid solder interconnect remains in contact with the\nterminations on the component and the substrate, and that\nelectrical contact between them remains unbroken, there must\nbe some growth of an intermetallic compound (IMC) at the\ninterfaces between the solder and the contact metallizations.\nHowever, given that IMC growth is generally much faster\nwhen the solder is liquid, the growing IMC must act as a\nstrong diffusion barrier to suppress further IMC growth. This\npaper presents preliminary studies of liquid-phase Sn-Bi\nbased solders that result in stable interfaces between the\nsolders and three common contact metallizations, consisting\nof electroless Ni(P)/Au, of Cu and of Ti-W. Small quantities\n(1 or 2 %) of an additional element, including Cr, Si, Zn, Ag,\nAu, Al and Cu, have been alloyed with the eutectic Sn-Bi\ncomposition to find an effective inhibitor additive that can\nachieve a strong IMC diffusion barrier. IMCs and their\ngrowth rates, as well as the consumption rates of the three\ncontact metallizations in contact with the molten solders, were\ninvestigated. Storage temperatures of 200°C and 240°C were\nused, with storage times ranging between two hours and one\nmonth. Results to date show that suitable additives can\nsignificantly reduce IMC growth rates for both the Ni(P)-Au\nand Cu contact metallizations, while no appreciable IMC\ngrowth is observed for Ti-W in contact with both the original\nand the various alloyed Sn-Bi based solders. Based on the\ncurrent results, criteria to further assist the design of feasible\nmolten liquid solder – contact metallization systems have\nbeen deduced.
Authors: J.F. Li, S.H. Mannan, M.P. Clode, H.M. Lobato, C. Liu, D.C. Whalley, F.T. Lawrence, G. Jackson, H. Steen
Institution: King's College London
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2160640593