Help identifying PCB substance growth

Discussion in 'General Electronics Chat' started by VoodooMojo, Oct 20, 2011.

  1. VoodooMojo

    Thread Starter Active Member

    Nov 28, 2009
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    I have dealt with Whiskers before but this is a new one on me.
    Has anyone here dealt with something like this and know what the possible causes are?
    It is a crystal type substance.
    The PCB has been assembled for only a month so this is rapid growth.
    There is also a blue, mold type substance, growing on the PCB beneath the affected components.

    The components (4 total) are BTS621L1 Two Channel High-Side Power Switch

    The cut pin at the center is the Vbb Power Supply In. It is shorted to the tab, that is why it has been removed. +13 volts.
    The post to the left is the Diagnostic Feedback. The pin on the right is Input to Channel 1.

    The stuff is causing faults in the system from the feedback circuit which in turn is responsible for system shutdown.
    It is not in a caustic environment.
    [​IMG]

    [​IMG]
     
  2. #12

    Expert

    Nov 30, 2010
    16,260
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    That's dreadful! Looks like you need a "conformal coating". I use Krylon crystal clear acrylic spray, 3 coats. Of course, REAL conformal coating would be better.

    Possible cause? I would have to say you have a corrosive atmosphere in spite of the fact that you don't think so.
     
  3. VoodooMojo

    Thread Starter Active Member

    Nov 28, 2009
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    It does have a bit of coating on it.
    I contacted the manufacturer (Sauer Danfoss) about the thickness. They cite heat disapation as the reason for not applying a thicker coating.

    This photo shows the location of the components on the circuit board.
    None of the others are showing the same reaction.
    [​IMG]
     
  4. #12

    Expert

    Nov 30, 2010
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    Knowing where it comes from and how old it is suggests that mailing it to the mfg might be a reasonable way to get answers.
     
  5. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    What is the environment? (high humidity,etc..?)
    Was no-clean or OA flux used in the fabrication?
    What cleaning process was used?
     
  6. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Between the leads the white stuff looks to me like uncleaned flux. These boards do not appear to have been properly cleaned before coating.

    I agree, the green stuff on the leads looks like some sort of mold. I've never seen that.
     
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    It looks very much like acid salts. I've seen very similar stuff on equipment near an acid pickling line. Is it near a lead acid battery?
     
  8. VoodooMojo

    Thread Starter Active Member

    Nov 28, 2009
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    The truth is revealed.

    The tech that gave it to me held back that the board was in a control system at a Phosphate plant.
    That explains the crystalline growth and the white flakes, but the mold-type stuff has me puzzled.

    His reason for neglecting to tell me this was to keep me from dismissing all other research because of that fact. Smart fellow!
    He pointed out that the installation was less than a month old and the board was in a tamper-proof, sealed from environment, compartment. A sister installation a few feet away has no contamination whatsoever.

    I kept a sample of the mold and sent the board on to Sauer Danfoss. They appear to be curious, if not concerned.
     
  9. #12

    Expert

    Nov 30, 2010
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    I'd say the environmentally sealed compartment isn't.
     
    VoodooMojo likes this.
  10. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Look, you have the board there, but that second picture looks like the white contamination is UNDER the conformal coating.

    Does this phosphate material at the plant have the ability to tunnel under the coating or is this an illusion in the picture?
     
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