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Solvent to clean solder site

Discussion in 'Troubleshooting and Repair' started by Zapper, Apr 7, 2016.

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  1. Zapper

    Zapper

    7
    0
    Sep 28, 2015
    Hello,

    I was replacing capacitors on my DVR board and was confronted with one terminal where the solder wont stick. It was desoldered with the correct tool but some how I can only assume the site was contaminated with the boards lacquer.

    I was thinking about using a solvent with a Q-tip. Is that the correct way to proceed? If so, what solvent is best? I have some acetone, methylene dichloride, and toluene.

    Thanks.
     
  2. 73's de Edd

    73's de Edd

    2,773
    1,159
    Aug 21, 2015
    Sir Zapper . . . . .

    If you had cap leakage of its internal electrolyte get onto a soldered joint, it could have permeated right into the actual solder joint or any solder residue.

    I remember some earlier Nichicon capacitors that would do that . . and leech their dimethylformamide carrier vehicle with its organic salts onto the board.

    It would produce an effect as non solder worthy, as trying to solder to aluminum. Sometimes, permanent black stains were left on the G4 board.

    It just required an agressive cleaning AND scraping of the solder surface and keeping trying to get new solder to be accepted and tin to the surface.
    Solder wick with pressure applyed on its top with a well tinned solder tip . . . . while moving the wick side to side . . . . produced most of the solution.
    A final scraping of minute areas with a #11 EXACTO blade cleaned up the last of any problem areas.

    Of the three solvents suggested . . . . all are better than any of the alcohol family . . . the toluene is definitely the weakest of the three.
    Of the acetone and methylene dichloride options . . .the latter has the edge . . . . . if you had any MEK . . . it would be the best . . . . as it can take the
    balls off a pool table !

    That chemical cleaning , along with the chosen manner of getting the PCB foil retinned afresh and accepting solder again should permit the solder repair.


    73's de Edd
     
    Last edited: Apr 8, 2016
    chopnhack likes this.
  3. Bluejets

    Bluejets

    3,690
    760
    Oct 5, 2014
    Maybe your iron is too small.
     
  4. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    Please post a clear photo.
    Sometimes what is actually left is just a burn circle were there used to be a pad:(
     
    chopnhack likes this.
  5. TJrhythm

    TJrhythm

    5
    1
    Feb 13, 2016
    Chemicals only cause problems for me. But a leaky cap could make tinning difficult.
     
  6. tester272001

    tester272001

    6
    0
    Sep 27, 2012
    I use alcohol 90% strength. Wipe up real well with q-tip and paper towels. Use a small wire solder "brush" to clean up the traces. Then tin after putting some flux on the traces...
     
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