Oxidation and reduction kinetics of eutectic SnPb, InSn, and AuSn: a knowledge base for fluxless solder bonding applications

Jochen Friedrich Kuhmann, A. Preuss, B. Adolphi, K. Maly, T. Wirth, W. Oesterle, W. Pittroff, G. Weyer, M. Fanciulli

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    Abstract

    For microelectronics and especially for upcoming new packaging technologies in micromechanics and photonics fluxless, reliable and economic soldering technologies are needed. In this article, we consequently focus on the oxidation and reduction kinetics of three commonly used eutectic solder alloys: (1) SnPb; (2) InSn; (3) AuSn. The studies of the oxidation kinetics show that the growth of the native oxide, which covers the solder surfaces from the start of all soldering operations is self-limiting. The rate of oxidation on the molten, metallic solder surfaces is significantly reduced with decreasing O2 partial-pressure. Using in situ Auger electron spectroscopy (AES) it could be shown for the first time, that H2 can reduce Sn-oxide as well as In-oxide at moderate heating duration and temperatures. In the second part of this study, the results, obtained by the investigation of oxidation and reduction kinetics, are applied to flip-chip (FC) bonding experiments in vacuum with and without the injection of H2. Wetting in vacuum is excellent but the self-alignment during flip-chip soldering is restricted. The desired, perfectly self-aligned FC-bonds have been only achieved, using evaporated and reflowed AuSn(80/20) and SnPb(60/40) after the introduction of H2
    Original languageEnglish
    JournalIEEE Transactions on Components, Packaging, and Manufacturing Technology, Part C
    Volume21
    Issue number2
    ISSN1083-4400
    DOIs
    Publication statusPublished - 1998

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    Copyright: 1998 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE

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