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Solder alloy question

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  • Solder alloy question

    I'm soldering up a contraption consisting of pieces of nickel plated aluminum and tin plated aluminum, plus copper tubes. (flame torch + flux) There will be refridgerant flowing inside. The project was handed to me with a big spool of Sn96 Ag4 solder, which I think is a somewhat standard solder to use for HVAC systems. The problem is that this is a thick and unweildy 1/8" solder that is kind of gloopy. I would prefer to use a much smaller diameter wire for more finesse. However, the closest things I could find locally was Sn96.5 Ag 3.5 and various Sn Ag Cu alloys (SAC). Would either of these work equally well? The main criteria is that it wets well and thus seals little gaps, and second, that it be relatively strong.

    I failed to find on the internet the answers to these questions:
    What are the pluses and minuses of adding a touch of copper?
    What are the + and - of going with the 96.5/3.5 eutectic?
    Last edited by beanbag; 06-12-2012, 05:35 AM.

  • #2
    Rather than chase up another suitable solder, why not roll out the wire you have? If you know someone with a jewlery maker's set of rolls, it would be a simple matter to roll the 1/8" down to 3/32" or 1/16".
    Machinery Handbook lists a VERY detailed bunch of alloys with a brief description of their application. It just does not tell you where to get them!
    Duffy, Gatineau, Quebec


    • #3
      We use both types of solder in electronic assembly. You need to also check the specs of the flux you are using. If not heated to a specific temperature, it won't be able to clean the metal properly. If heated too hot, it will burn/vaporize without being able to clean the metal.

      In addition, the flux needs to be completely washed off because any residue will continue to be active over time.

      If the resulting product is subject to mechanical or thermal stress, the lead-free solder may develop cracks. It is not very forgiving like leaded solder.

      You are probably aware of all this, already. But I thought I would mention it.

      Good luck, Paul