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repairing traces on PCB

Discussion in 'Electronic Repair' started by Orange, Aug 23, 2004.

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  1. Orange

    Orange Guest

    Liquid silver is too expensive, is there any other way of repairing
    traces on PCB?
    Actually, I need to repair graphite traces on keyboard connector.
    Using spray GRAPHITE 33 totally messed everything.
     
  2. Ross Herbert

    Ross Herbert Guest

    |Liquid silver is too expensive, is there any other way of repairing
    |traces on PCB?
    |Actually, I need to repair graphite traces on keyboard connector.
    |Using spray GRAPHITE 33 totally messed everything.

    I haven't had any luck repairing flexible pcb traces. I tried silver
    loaded epoxy but like you I found it is not easy when traces are close
    together. If the keyboard is for a PC then it only costs ( $5 or
    free) to replace the keyboard. That always works effectively.
     
  3. Orange

    Orange Guest

    I see.. thanks Ross.
    This part isnt so flexible; its the tip of connector that goes into
    PCB connector. It was worn out from frequent replacing. It seems that
    I've completely destroyed it with that graphite spray (different type
    of graphite?)
    Its an Amiga 500.
    I know the whole of it costs 5 to 10 $ , but its my first Amiga..
     
  4. Brett

    Brett Guest

    Tried very small jumper wires?
     
  5. CJT

    CJT Guest

    Conductive paint isn't _that_ expensive ... Presumably you don't need
    much.

    Even an auto supply store should have something suitable -- they need
    it to repair the traces in rear window defoggers.
     
  6. Orange

    Orange Guest

    nope, they are not suitable.
    Guess I'll have to buy that "back car window heater repair liquid".
    Why don't they make liquid copper instead of silver?
     
  7. L.

    L. Guest

    There are some pens designed for PC Board Trace repair..... sold by
    Electronics Supply Houses. Are they any good? I don't know.. Never used one,
    but they're only like $6 or so..... If memory serves me correctly, there are
    two types for thickness. One is a thin and one wider. There are also pens
    available at about the same cost for "covering" traces, much like the
    protective green coating you usually see over the traces.

    L.
     
  8. CJT

    CJT Guest

    The pens are ok, but I found them prone to clogging/drying out.
    I prefer something I can brush on.
     
  9. Ray L. Volts

    Ray L. Volts Guest


    GC Chemicals offers a product called "Nickel Print". It's on the pricey
    side nowadays. I've seen it lately at $20 for a 2 oz. bottle. It's
    somewhat flexible, though not really intended for flex traces. It comes
    with a brush which is far too wide for most uses, but you should be able to
    use small art brushes for fine traces. It's fairly thick and you may want
    to use masking tape (really narrow drafting tape works) between closely
    spaced traces.

    I've found that even the finest point conductive ink pens lay down a line
    that's too wide for closely-spaced traces. They also crack if flexed much.
    For hard (non-flex) PCB traces, I normally just scrape off the bad section,
    scrape the solder resist off both ends of the remaining trace and solder a
    jumper bridge.

    A cheaper (free, in fact) alternative to using paints on flex boards is
    simply to make a new end, IF the cable is long enough to allow for this;
    some aren't. There will most likely be a second, non-trace layer of the
    cable which you'll have to peel back to expose the underlying traces for the
    next step. Do this before you do any cutting, as you'll need the original
    end for gripping. The glue is usually pretty sticky, so don't just rip it
    off in haste -- you can and will pull off traces if you aren't careful.
    Next, cut off an equal amount of this non-trace layer as was absent on the
    original cable end. Now that you have twice the length of non-trace layer
    gone, you can cut off the original, damaged end with scissors. Cut off only
    the bad portion of the plated end and no higher. Make certain the cut is a
    STRAIGHT 90 degrees. Next, very gently clean the tacky glue off the new end
    to expose the metal traces. You can use masking tape for this, but again,
    be careful so as not to pull off trace material. I haven't tried using
    solvents to remove the glue, but if you use one that isn't too strong, it
    might leave the traces intact. You should now have a new end that looks
    like the original with the exception of fully-plated traces. I've done this
    successfully with numerous flex boards.
    However, as a caveat, some are absolutely uncooperative and the traces will
    lift with the greatest of ease.

    If you're successful with the above method, you can go the extra mile and
    replate the traces with a tin plate wash (I use it for protecting home-brew
    hard PCB etchings). Also, the original end may have had a stiff plastic
    piece to keep the traces from bending/creasing. Unless you add one to your
    new end, it will be susceptible to damage from rough handling, so be gentle
    when inserting it into the board connector, and don't remove/replace it
    repeatedly.

    Good luck...
     
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