Assessment of Microalloyed Sn-Zn as a Solder for Electronics AssemblyAuthors: Keith Howell, Keith Sweatman, Takashi Nozu, Tetsuro Nishimura
Company: Nihon Superior Co., Ltd.
Date Published: 5/4/2011 Conference: ICSR (Soldering and Reliability)
If solders based upon the tin-zinc eutectic are to find wider application the problem of corrosion will have to be addressed and in this paper the authors report on a detailed assessment of the effect of a microalloying addition of manganese on the mechanical integrity of tin-zinc alloy joints on copper, nickel, and silver substrates after exposure to elevated temperature (150°C) and humid heat (85°C/85%RH) for up to 1000 hours. The nature and extent of corrosion on the surface and the solder/substrate interface was examined using SEM/EDX and found to vary considerably with the substrate. Other properties of the tinzinc solder relevant to its performance in thermal cycling, coefficient of thermal expansion, elastic modulus and flow stress were also measured. Evidence of some inhibition of corrosion and mechanical properties conducive to reliability under conditions of thermal cycling appear to justify further study of microalloyed eutectic and near-eutectic tin-zinc alloys as potential lead-free solders for use in electrical and electronic assembly.
Key words: Lead-free, Sn-Zn, Corrosion
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