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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

    I should mention that the photograph of the circuit board came out of a high
    end Proceed amplifier. These amps costs big bucks and fail frequently. The
    company offered no support to the independent guy. The authorized service
    place in my area wanted $150 an hour plus parts to repair it. No surprise
    that Proceed is out of business now.

    The other amp I saw this residue in was an a/v receiver, a Marantz SR-8500.

    Thanks for your replies.
     
  2. Eeyore

    Eeyore Guest

    That looks possible.

    Note the difference in solder finish on those 3 pads compared to the 2 others.

    Graham
     
  3. Ross Herbert

    Ross Herbert Guest

    Are you using Agent?

    I referred the problem to Agent support and received this reply;

    Hello, Ross.

    Your problem has been noted to development.

    The URL recognition is a RegEx in the agent.ini file, it's the key
    "Pattern6". Unfortunately, I don't know RegEx well enough to suggest
    a modification myself.
     
  4. Ross Herbert

    Ross Herbert Guest

    To anyone who knows anything about electronics soldering and or pcb
    populating it is very obvious that this IS what happened.
     
  5. Ross Herbert

    Ross Herbert Guest

    Not in this case it isn't. This is the result of failing to clean the
    flux away at all after a manual part placement and soldering
    procedure. Such instances may occur when an OEM does not trust that
    reflow or wave soldering will be ultra reliable where heavy component
    leads are involved. The reflow time has to be adequate to ensure
    proper wetting of the heavy leads but where other very small componets
    may be damaged by heat this is not recommended. The reflow time is
    always set to ensure the most sensitive components will not be damaged
    by heat and this may require that heavy leaded components are fitted
    manually afterwards.

    The result of inadequate cleaning after finished board manufacture is
    usually a much lighter white ring or anulus of residue, nothing as
    thick or heavy as in the picture.

    This is more like what you are talking about
    http://www.residues.com/pdf/white_residue1.pdf
     
  6. Smitty Two

    Smitty Two Guest

    Ross, why do you bring up reflowing? Wave soldering, sure, but this
    ain't no SMT board. And, a small transistor like that hardly qualifies
    as "heavy" leads. However, on another look, I agree that it was added by
    hand - but only because it's on the far side of the board.

    Still, flux that is "not cleaned away at all" bears little resemblance
    to the picture.

    Again, I agree with those who say it's incompletely cleaned flux residue
    from an automated cleaning system.
     

  7. Ross, we manufactured both surface mount and through hole boards,
    plus some items like connectors were hand soldered on our surface mount
    PC boards. We had a VERY high standard of cleaning, because most of our
    equipment was sold to the aerospace industry. I've seen probably every
    possible defect in a new PC board, including a batch we received with a
    missing internal power plane. I have seen this exact type of residue on
    boards that just came out of the dryer, after being washed.


    --
    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
     
  8. Ross Herbert

    Ross Herbert Guest

     
  9. Ross Herbert

    Ross Herbert Guest

    You are right with regard to reflow - my mistake for mentioning it.
    However, with regard to the component and reasons why it would have
    been manually fitted, I was just giveing an example. It wasn't meant
    to be the ONLY reason why the component might have been added manually
    yo this particular board although I admit it would have been wise to
    stick to this point.
    In my experience it is. It is obvious that there has been some
    "scratching around" in the residue which has removed some of it
    (perhaps by the OP). In its natural state it would have been far more
    regular and quite thick as it appears to me. I would wager that after
    this component was manually soldered the operator didn't even so much
    as wave cleaning fluid over it let alone attack it with a brush. After
    adding a single component I doubt too many manufacturers would put the
    whole board through a clean and dry cycle since it takes a lot longer
    than doing it by hand immediately after soldering.
    Incompletely cleaned flux in my experience has always been more in
    keeping with this effect
    http://www.residues.com/pdf/white_residue1.pdf but a water soluble
    flux applied by hand and which has not been cleaned at all is more
    akin to the OP's situation.
     
  10. Eeyore

    Eeyore Guest

    I have seen 'cold joint' issues with TO-220 devices.

    Graham
     

  11. Sure, from crappy board houses.

    --
    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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