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Old solder paste: the answer

Discussion in 'Electronic Repair' started by mc, Feb 24, 2007.

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  1. mc

    mc Guest

    At this web site

    http://www.kester.com/en-us/documentation/10 SMT Tips (The Inside Line).pdf

    Kester gives a test for whether solder paste is fresh enough. The test is
    to melt a drop of it onto an unsolderable surface and see whether it forms
    one ball or several. If it sheds a number of smaller balls (rather than
    forming just one), the flux has deteriorated. The failure mode is flux
    deterioration.

    The funny thing is, I have some solder paste that is 10 years old and seems
    to pass this test. I'm going to repeat the test more rigorously.

    Presumably, paste that is too old for surface mount work could still come in
    handy in larger-scale work. It's still solder, after all.
     
  2. mc

    mc Guest

    .... And it wasn't reproducible. Apparently, a lot of flux had gone to one
    end of the tube.
     
  3. Arfa Daily

    Arfa Daily Guest

    There ya go then ! So now we all know, and thanks for the update.

    Arfa
     
  4. Indeed. And I'll bet the problem can be suitably addressed by using
    supplemental flux on the pads before applying the solder paste.

    Thanks for digging into this. Good to know.
     
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