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Old paste solder?

Discussion in 'Electronic Repair' started by mc, Feb 23, 2007.

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  1. mc

    mc Guest

    Greetings,

    I've never done hot-air soldering but am helping set up a lab. I understand
    we need solder paste and its shelf life is short. But I just found some
    solder paste that has been out of refrigeration more than 7 years, and it
    still looks like paste. What quality has it lost? Stickiness?

    Thanks!
     
  2. How important are reliability and traceability (ISO 9000) in your lab?
     
  3. mc

    mc Guest

    So can you tell me what happens to solder paste when it gets old?
     
  4. No, that would be your problem.
     
  5. mc

    mc Guest

    I've never done hot-air soldering but am helping set up a lab. I
    Precisely -- I asked the question because I wanted to know the answer.

    Can anyone tell me what happens, physically, to solder paste that gets old,
    and why it's no longer considered suitable for use? I know the
    specifications say not to use it.

    More generally, if I didn't know whether some solder paste was fresh, what
    changes should I look for?
     
  6. Jim Yanik

    Jim Yanik Guest

    IIRC,old solder paste tends to form little balls instead of reflowing
    properly. Then you have them getting into the worst places and shorting
    things.
     
  7. Jim Yanik

    Jim Yanik Guest

    perhaps the flux degrades,absorbs O2(oxidizes),loses it's fluxing ability??
    It may not be readily apparent from a visual inspection.
     
  8. mc

    mc Guest

    Thanks! Just the information I was looking for.
     
  9. I'd like to know this myself, as I'm in the final stages of getting
    set up to do SMD work and I just spent $250 for supplies (solder paste,
    flux, wetting solution, tools, etc.)

    Simply being told "How important is reliability and traceability?"
    doesn't cut it with me, any more than pointing to the expiration date on
    a tube of solder paste and saying "Never use this after this date!"

    I want to know what, exactly, changes, and how it affects
    reliability (I don't give a flying poof-ball about traceability as long
    as the solder holds). I also want to know how these alleged changes will
    affect the stuff in terms of making simple repairs with (mostly) PLCC's
    and QFP's.

    I'm not doing mil-spec production here... just trying to do decent
    repairs.

    Keep the peace(es).
     
  10. They'd like to sell you new stuff before you use up the old stuff. Try it
    and see what happens.

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  11. N Cook

    N Cook Guest

    Can you try accelerated aging tests.
    I remember there was a daily cycle of over-night freezing and (day ) low
    oven heating that closely resembled aging for paint, so 1 week accelerated,
    simulated about 1 year of normal conditions
     
  12. Arfa Daily

    Arfa Daily Guest

    Why not just contact the solder paste manufacturer's technical department
    and ask them ? Most makers of service materials are happy to answer
    questions on their products. FWIW, I seem to recall the same as Jim, but it
    seems pretty clear that none of us on here *really* know, so we could be
    giving you a completely bum steer. If you do find out from the
    manufacturers, post back, and tell us all, as it would seem that there is at
    least one more in this thread who *needs* to know, and probably a few of us
    who would *like* to know.

    Arfa
     
  13. Supertech

    Supertech Guest

    Well done you! There is so much bullshit around these
    days...ROHS..Health and Safety...WEE..
    compliance this etc., the list goes on and on. The rules and
    regulations have gone mad in Europe, they are killing our industries.
    Stuff em all I say! Does it do the job? Yes? USE IT. If not DONT.
     
  14. Meanwhile the Chinese do whatever they like and stick a sticker on that says
    they did what YOU wanted.

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  15. Well, then you go elsewhere to determine that (the manufacturer of the paste
    seems so dreadfully obvious). Or, you just try the stuff and see what
    results you obtain and see how many failures occur that haunt you later.

    Geez ... this is a repair group. "What, exactly, changes, reliability" ...
    you are expecting too much.
     
  16. mc

    mc Guest

    I want to know what, exactly, changes, and how it affects
    Pardon me for asking a question in a newsgroup, then!

    I got a remarkable cascade of "you shouldn't expect us to know" and only one
    helpful answer.

    I assumed the people in a repair newsgroup would have experience using paste
    solder and might be able to tell me about their experiences with it. Or if
    they didn't, they wouldn't reply.
     
  17. Arfa Daily

    Arfa Daily Guest

    Now now, there's no need to get arsey. I think that you got a number of
    reasonable replies amongst them all, not the least of which being, from
    several of us, "ask the manufacturer". It's hardly rocket science is it ?
    Those of us who use the stuff in our everyday work don't let it get out of
    date, so we don't have any direct experience of what goes wrong with it. The
    guesses about the flux going bad or maybe the carrier, seem reasonable, but
    they are just that - guesses. Probably, nothing much happens. If you keep a
    packet of cornflakes past their 'sell by' or 'best by' date, without opening
    them, they will probably be ok a year later. If you have opened them, they
    won't be. Probably the same with the solder paste, but if you are going to
    be using it professionally, do you want to risk it ? Could cause you all
    sorts of problems down the line, so I say again, ask the manufacturer, then
    you will know for sure, and you can tell the rest of us. If you don't feel
    confident enough to talk to them by 'phone, I'm sure that they will have an
    e-mail that will reach their technical people ...

    Arfa
     
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