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White residue on IC connections???

Discussion in 'General Electronics Discussion' started by groovejet, Mar 9, 2011.

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  1. groovejet

    groovejet

    53
    1
    Feb 27, 2011
    Im fault finding on a copier pcb and have come accross a few IC connections with a white residue on?

    Am i correct in thinking its Oxidizeation(spell???) if so........

    .....is this due to the pins not being used ???................Or somethng more sinister:eek:

    Thankyou
    Paul
     
    Last edited: Mar 9, 2011
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,473
    2,819
    Jan 21, 2010
    There are a number of reasons:

    1) it could be corrosion from exposure to salty air
    2) it could be corrosion from whatever was used to clean the boards after soldering
    3) It could be corrosion from something being spilt on the board.
    4) it could be corrosion from current passing across 2 dissimilar metals in a humid environment
    5) it may not be corrosion

    A (sharp) photo would probably help a great deal.
     
  3. groovejet

    groovejet

    53
    1
    Feb 27, 2011
    09032011360[2].jpg

    Hope this helps, although id already removed the residue, but if you look at pin 4 its duller than the restof the pins.
    All other pins are bright soldered but pin 4 is dull like a dry joint???

    Thanks for the v.fast responce on the problem

    Paul
     
  4. groovejet

    groovejet

    53
    1
    Feb 27, 2011
    09032011369[1].jpg

    Pin 4 had a white solid residue starting from leg of IC, closest to the chip to half way down the leg?
    There also was one IC with 2 pins with residue on
    Here another pic, sorry but im using a Nokia 5530, so not the best!
     
    Last edited: Mar 9, 2011
  5. davenn

    davenn Moderator

    13,765
    1,920
    Sep 5, 2009
    doesnt look anything serious, mainly flux residue,
    clean it off with a bit of spray can circuit board cleaner and an old toothbrush
    2 items that should be in every tech's toolkit ;)

    Dave
     
  6. shrtrnd

    shrtrnd

    3,794
    503
    Jan 15, 2010
    Yeah, I'm with davenn.
    That white residue is leftover from the board assembly process at the factory.
    One thing I'm starting to notice also, is some new spacer pads (to get the component up off the board during assembly), that the manufacturer (who I can't remember right now), CLAIMS 'dissolves and washes away', when the board is completed and washed in the manufacturing process. Maybe some of these 'dissolvable' pads aren't dissolving so good. Or maybe the manufacturer is not cleaning his board washing tanks good enough to handle the board residues (as in, 'washing' the board with contaminated water).
    I guess it doesn't matter who's copier it is, ...the boards are probably all made in China now.
     
  7. groovejet

    groovejet

    53
    1
    Feb 27, 2011
    thanx very much 4 ur help:D
     
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