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Properties and Uses of Low-Temperature Solder Alloys – (Part 3)

  • Indium Alloy
  • Indium
  • Bismuth

  • If you missed the first part of this series, you can find it here.

    Expansion during cooling is a low-temperature alloy property that can be very useful. Remember your material science courses: most metals expand during heating - not cooling! This chart shows the expansion of various bismuth alloys. Indium, lead, tin, cadmium, and/or antimony can be used to tune the natural properties of bismuth in order to achieve the desired melting point, expansion, or conductivity of the resulting alloy. Much like freezing ice in a closed container, solidifying these alloys in an enclosure can be used to add pressure to the vessel, or act as an anchor against the inner walls of the container.

    Some other bismuth alloys do not expand during cooling, but rather shrink at a much lower rate than other solders. This can be used in bonding applications when CTE (coefficient of thermal expansion) must be precisely controlled. Some alloys are nearly isostatic, resulting in a negligible amount of expansion over a wide range of temperatures. These alloys can be used as solders as well as for many other non-soldering purposes.

    Next we will discuss other unique properties of low-temperature alloys.