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What has been your experience with low-temperature solder?

baldengineer

Recently I found Chip Quik Sn Bi Ag Solder PasteChip Quik Sn Bi Ag Solder Paste. It is a low-temp alloy with Bismuth (and Silver.) When using hot air to solder parts, or during re-work, it makes the process go so much faster. It melts around 140C. It also does not appear to need refrigeration and has a long shelf-life. With all of those positives, I'm wondering what the downsides to using it are compared to more "traditional" solder alloys.

 

So whether positive or negative, what has been your experience when using "low temp" solder?

  • in reply to mp2100

    The bismuth Wikipedia  link reminded me, don’t forget this use.image https://pepto-bismol.com/en-us

  • Sometimes the most innocuous question leads to some really useful insights. 

  • in reply to Andrew J

    No kidding!

     

    I love the responses from the community on questions like these.

  • in reply to baldengineer

    For prototypes I would normally use tin/lead for convenience and good results in a prototype process and then we would use standard lead free for production

     

     

    I've been looking at using Tin/Bismuth solder for a new production process.

    We need lead free and low melting point (because we have a special component that can't take more than 220C).

     

     

      raises some interesting points:

     

    The lead issue - not a problem - the whole point is to have a lead free process, all components are bought lead free.

    Care should be taken with whatever other coatings are used on compent pads.

    Could be a problem with mixed assemblies (like BGA where the solder balls and the solder paste get mixed together).

     

    Temperature range - unless a max joint temperature of 85C is OK - then forget it. We are OK since ours is an ultra low power product with a limited temperature range.

     

    Adding silver, massively improves joint strength and stability.

     

    I'll be trying some: Sn42/Bi57.6/Ag0.4 when it arrives.

     

    Using low mp solder to "wash" other solder off a board for repair is fine if the alternative is a dead board.

    The reliability of the repair will depend on the skill of the operator and other things that may be hard to estimate.

     

    MK