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What is this stuff on this pc board?

Discussion in 'Electronic Repair' started by David Farber, Aug 16, 2007.

  1. David Farber

    David Farber Guest

  2. UCLAN

    UCLAN Guest

    Rosin core solder leaves flux if not cleaned. So, yes.
     
  3. Arfa Daily

    Arfa Daily Guest

    I'm not sure what that is, but it doesn't look like any flux residue that
    I've ever seen. The little brownish 'blobs' on the tops of Q200's legs do,
    as does the lttle patch at the upper edge of its centre leg. If it is flux
    residue, I'm sure that you would agree, as a repairer yourself, that it is
    very unusual for it to be white like that, which is why you are asking for
    the opinions of others on here, I would guess ? Perhaps solder guru Smitty
    could offer an opinion from the production point of view.

    Arfa
     
  4. Meat Plow

    Meat Plow Guest

    Looks like dried coffee creamer :)
     
  5. I've seen it before; It's flux residue that has become damp, then dried out
    again.
    Is there also a touch of rust on the end of the transistor's legs (the
    brownish blobs)?
    And possibly a bit of corrosion on the edges of the tracks, or just poor
    resist?
    Yet I can't see any corrosion on the 0R22-resistor, but the solder is a bit
    grainy, so it's probably either lead-free or has been damp.
    I bet the white deposits will turn back to ordinary flux deposit if heated.
    Martin.
     
  6. Ross Herbert

    Ross Herbert Guest

    The "brownish blobs" are not flux or anything else. They are simply
    the ends of the cropped component leads. The device was soldered with
    long leads and then the leads were cropped.

    The white residue could be water soluble flux which has not been
    removed after soldering the component.
    http://www.kester.com/en-us/documentation/White Residue (26Jan05).pdf
     
  7. Ryan Weihl

    Ryan Weihl Guest

    looks like flux residue. But the boaed has not been washed and dried
    properly after soldering process.
    rw

    --
     
  8. Smitty Two

    Smitty Two Guest

    Guru? Surely you exaggerate. But that dry, flaky, powdery white stuff
    looks exactly like rosin flux residue that's been incompletely cleaned
    using a saponifier and hot water. That methodology largely replaced
    solvents some time back, as one alternative to water-soluble fluxes.
     
  9. Bob  AZ

    Bob AZ Guest

    David

    Conformal coating. Probably used for moisture protection among other
    things. Like a varnish. Also some coatings were epoxy types.

    Bob AZ
     
  10. Eeyore

    Eeyore Guest

    Plenty of solder processes these days do not require washing and cleaning. Most
    consumer goods in fact.

    Graham
     
  11. Eeyore

    Eeyore Guest

    It is NOT conformal coating. Besides you'll probably only ever see that on
    high-end industrial or military gear.

    Graham
     
  12. Ross Herbert

    Ross Herbert Guest

    On Fri, 17 Aug 2007 03:20:40 GMT, Ross Herbert

    SNIP
    It seems that the brackets around the date in the link act as a
    terminator to the hyperlink underlining so you will have to copy and
    paste the full url to get the document.
     
  13. Eeyore

    Eeyore Guest

    It works for me.

    Graham
     
  14. JW

    JW Guest

    Or just about anything marine related.
     
  15. Ross Herbert

    Ross Herbert Guest

    Thanks Graham. When I paste the url link using Agent the underlining
    stops before the opening bracket so I thought I'd better give a
    warning.
     
  16. Al

    Al Guest

    It is flux residue. All of the VOCs have been removed and the solids are
    left. Not to worry. Not pretty, but, ehhh...

    Al
     
  17. Meat Plow

    Meat Plow Guest

    When I double click the link it is incomplete.
     
  18. It is not of manufacturing origin.

    It looks like a (field? post-inspection?) repair -- the replacement of
    "Q200". After soldering, the leads of Q200 have been snipped off with a
    pair of flush wire cutters -- leaving a clean exposure of the copper of
    the leads.

    So, the residue is probably dictated by the brand and the quality of the
    solder used in the repair.

    Jonesy
     

  19. That is flux residue left after a run through a PC board washer, and
    oven dry cycle. I saw it all the time in manufacturing. The ladies that
    worked the cleaning room hand cleaned that with IPA and flux brushes, or
    with a spray defluxer when they couldn't reach it with a brush.

    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     

  20. That isn't conformal coating. It is a poor cleaning after the board
    was made. The thinnest flux was washed away, the thickest is still
    there. The powder is where the flux was a little too thick to
    completely wash away in the automated cleaning process, and there was no
    attempt to finish the job.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
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