Indium Blog

80Au20Sn Solder Applications: When to choose Preform or Paste

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  • On a daily basis, Indium’s tech support receives calls and emails about soldering with the 80Au20Sn alloy. We sell both 80Au20Sn solder paste and preforms because both have particular attributes that make them ideal for certain bonding applications. Sometimes certain applications are strictly driven by your furnace capabilities, like open air, inert or forming gas capability, or vacuum.

    Reflowing In open air: you will need to chemically remove the oxidation from the bonding surface. 80Au20Sn solder paste or flux-coated preforms work well in these applications.

    Inert or forming gas furnace: typically people use solder preforms in a fluxless process. On some occasions they use inert gas in a solder paste application to help prevent oxidation occurrence if the flux prematurely burns up before reflow at these high temperatures. But, people never use solder paste in forming gas reflow because of potential flare-ups or explosions, depending on hydrogen percentages.

    Vacuum furnace application: this is a flux-less process and most have the capability to purge forming gas in the furnace during certain portions of the reflow profile. A popular application is hermetic package lid attachment using combo lids with 80Au20Sn frame solder preforms.

    Below are other attributes that make solder pastes and preforms ideal for certain applications:


    • Easier to automate the process in stencil printing/dispensing
    • Can be reflowed in open air applications (hot plates)
    • Bond complex shaped bonding surfaces
    • Ideal for bonding small components, paste secures them until reflow.


    • Longer shelf life (1yr+)
    • Be reflowed in fluxless process with nitrogen or forming gas
    • No post-cleaning process
    • Easier repeatability of solder volume
    • Ideal for large component bonding in flux-less applications (fewer voids)

    With both solder paste and preforms you still get the all the great attributes of 80Au20Sn that make it one of the most reliable solders in the industry.

    If you would like to learn more about our 80Au20Sn solder paste and preforms, and get some literature or help on an application, please send me an email me at or