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repairing broken traces on a PCB

Discussion in 'Electronic Design' started by samIam, Feb 24, 2006.

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  1. samIam

    samIam Guest

    I have broken traces on a PCB I recently etched. Just a handful ...

    I am wondering how some of you repair them. Trying to tap into your body
    of experience with this.

    I tried soldering wirewrap from one trace to another ... but thats not
    very effective ... I might try pin to pin this weekend.

    ALso I have seen (on some pcbs from commercial equiptment) special
    round shaped adhesive tape that placed on the strip repair wire to hold
    it to the board.

    Anyone know what these are called and where I can get some?
  2. You bare tinned wire. 1N4148 diode leads are about 0.5mm diameter and
    work well down to fairly fine pitch. Lay across the break, solder on
    both sides.

    Best regards,
    Spehro Pefhany
  3. ^^^
    can use

    Best regards,
    Spehro Pefhany
  4. samIam

    samIam Guest

    Thats the problem ... its shifting around (the wire). I can get it fixed
    but the time its soldered its sloppy and the sligthly nudge breaks it
  5. Jim Thompson

    Jim Thompson Guest

    I use "solder-sucker" braid to bridge breaks like that.

    ...Jim Thompson
  6. Noway2

    Noway2 Guest

    There are also kits available for PCB repair that contain adhesive
    backed materials that get applied to the board with a special tip in a
    soldering iron. I have one by Pace and they call it a thermobond kit.
  7. Tim Wescott

    Tim Wescott Guest

    Make sure the traces are tinned so you don't waste time and motion on
    that when your wire is down. Hold the wire down on one end and solder
    the other end. Now solder the unsoldered end. If you're just spanning
    a crack then heating one end of the wire will melt the other end's
    solder -- if that happens then hold the wire down with something small
    (I use an X-Acto knife) through the whole process.


    Tim Wescott
    Wescott Design Services

    Posting from Google? See
  8. That's particularly good if the PCB itself is phenolic & cracked.

    Best regards,
    Spehro Pefhany
  9. How wide are your traces? The solder surface tension should pull the
    wire towards the center of the trace.

    Bend the wire into an "L first (to give you a handle to position the
    wire with fingers or needle-nosed pliers), solder one side down
    securely, trim the other side so it's flat with the board, and solder
    the other side down. You should end up with a smooth solder and secure
    joint on either side. If you have solder resist, make sure to remove
    it *thoroughly* from enough area to get a secure joint.

    Best regards,
    Spehro Pefhany
  10. Ken Taylor

    Ken Taylor Guest

    Rather than scratching about traces trying to make them solder-able, we
    always go from pad to pad with wirewrap wire, complete with insulation. Good
    quality cutters, fine iron tip, steady hand, followed up by some adhesive to
    keep the wire in place (following over the trace that was damaged) and then
    covered with a spray-on conformal coating.


  11. colin

    colin Guest

    I use the finest self fluxing enameled coper wire I can find wich is 0.2mm,
    if its a small gap then tin enough of the end of the wire to brifge the gap,
    clean of the solder resist of the track, flux and tin, then solder the wire
    acros the gap, then gently press a sharp scalpal on the bit to cut off end
    tear the wire against the scalpal, DONT press down with the scalpal or your
    cut even more tracks. if the tracks are too fine to handle, trace back to
    the nearest via or pad, glue down with super glue if needed. as the wire is
    quite fine it shldnt be a problem one end coming unsoldered while soldering
    the other end.

    I use this for prototyping to modify track paths etc and connecting new
    tracks guaged out from the copper. you can get quite a good density and the
    insulation doesnt melt if you touch it with a soldering iron unless u hold
    it there for a while.

    Colin =^.^=
  12. More interesting is to hear about experiences in finding hairline
    cracks in tracks.
  13. I rather enjoy paying for 100% electrical inspection. Let the machines
    find the problems.

    Best regards,
    Spehro Pefhany
  14. Well, I have a board here worth $100 perhaps, that certainly passed
    all tests, but fails now. When I bend it, it works. I should add, that
    after bending it ~15 times it stayed in failure mode. I found one
    decoupling cap standing in the air, some flux rubbish (?) between a few
    legs of a TQFP, but nothing that causes the failure. Ditched it

    I wonder what the dropout percentage is for tested boards, and if
    it is worth paying for. Difficult to anwer of course, I simply have
    excellent experience with untested boards, even with 7mil tracks/distance.
    Seems that more goes wrong with the assembly of parts, imo
  15. Probably wise. I've found such problems, out of sheer stubborness, but
    it's hardly cost-effective in itself, but necessary sometimes if you
    want to make sure it isn't something more ominous than a single
    Around 1% for moderate quantity 2-sided boards, IME, but hair shorts
    are more likely, and it's not that sensitive to design rules (10 mils
    and 8 mils are about the same).
    We got a batch from a Taiwan manufacturer one time that was more than
    20% bad. That was a long time ago.

    Best regards,
    Spehro Pefhany
  16. samIam

    samIam Guest


    This is the most informative post here thus far. Thank you again.
    I need to change my methods ... its the reason behind my failure
    repairing this board so I can complete my testing

    thanks again
  17. John Fields

    John Fields Guest

    Yes, and I think a lot of it can be attributed to the "need" for
    lead free solder that the european community has, so far,
    successfully foisted on the rest of the world.

    IMO, you can thank higher solder melt temperatures, brittle solder
    joints, and poorly understood metallurgy for the reason you had to
    throw away $100.
  18. I don't like it a bit, all that Rohs stuff. Pressing down the TQFP's
    didn't bring any luck here, neither did pressing down other discrete
    parts, so I figured this board suffered from a hairline crack in one
    of the tracks.

    Thanks, Frank.
    (remove 'q' and '.invalid' when replying by email)
  19. Jim Yanik

    Jim Yanik Guest

    Wick thin superglue in the PCB crack.
  20. I was always a bit more "belt and braces" as Tony W. would say. Splint
    the board on both sides with sheared-to-size strips of epoxy-glass
    laminate and smother with good epoxy (not the 5-minute junk).

    Best regards,
    Spehro Pefhany
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