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 Post subject: Working with pcb trace
PostPosted: Nov Mon 05, 2018 8:41 pm 
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My question is how do you deal with trace on the pcb's? I have one where a cap leaked and hace corroded some traces. How do you remkve the corrosion etc. Chemicals?
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 Post subject: Re: Working with pcb trace
PostPosted: Nov Mon 05, 2018 9:09 pm 
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I don't know of a suitable chemical method....I just use a wire brush and maybe a scraper of some sort. You may need to recreate some traces. Depending on the situation, you might just use hookup wire--or maybe copper or brass foil.

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 Post subject: Re: Working with pcb trace
PostPosted: Nov Mon 05, 2018 10:06 pm 
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I dont want to damage the trace. I bought a kenwood 690 this weekend and it has some corrosion . Heres a picture. These traces look mighty delicate.


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 Post subject: Re: Working with pcb trace
PostPosted: Nov Mon 05, 2018 11:38 pm 
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I would use small gauge copper wire leads, soldered to the two connecting landings of each damaged trace. That way the trace itself is not touched.

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 Post subject: Re: Working with pcb trace
PostPosted: Nov Tue 06, 2018 12:19 am 
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+1
I might go so far as to remove the corroded area. Almost as good is to be sure it is neutralized.....although, if any loose material is removed and it is sealed, it will probably be fine.
To neutralize, apply a small amount of dilute muriatic acid, and then immediately neutralize with baking soda.

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 Post subject: Re: Working with pcb trace
PostPosted: Nov Tue 06, 2018 1:37 am 
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Ok, that sounds like a good way to go about it. Ill give that a shot and see what happens.
Thanks all.

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 Post subject: Re: Working with pcb trace
PostPosted: Nov Wed 07, 2018 8:59 am 
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I have cleaned the area with denatured alcohol, removed the damaged trace(s), and replaced them with silver plated wire wrap wire. I have repaired over 20 traces in just one board this way, and no callbacks on it.

The electrolyte from the "fish caps" was a major problem in TV sets, especially Mitsubishi.
One chassis always took 50 (!) caps to repair. Stunk to high heaven too, when you desoldered the caps.

I used denatured alcohol to clean the boards and traces for 30+ years, and never had a problem. I just applied it with a swab and scrubbed really well. Once in a great while I needed a tiny brush to scrub the board. A bit of conformal coating over the wiring or Krylon Clear worked well to seal the area also.

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 Post subject: Re: Working with pcb trace
PostPosted: Nov Wed 07, 2018 4:51 pm 
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To polish the cannonball a bit, what is the advantage of the wire-wrap wire over regular hookup wire? The defining attribute of wire-wrap is the mechanical strength that allows it to grip the post. This is not any benefit (or harm) in PCB patching.

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 Post subject: Re: Working with pcb trace
PostPosted: Nov Wed 07, 2018 6:49 pm 
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Wirewrap wire is thin and I found it quite easy to repair the almost hair thin traces on PCB's with.
Regular hookup wire was actually thicker than many of the traces I had to repair were wide, and I could repair traces very close to each other that were damaged. (Besides the fact I had over 1/4 mile of teflon coated, silver plated wire leftover that originally came from Boeing Surplus in Seattle.)

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 Post subject: Re: Working with pcb trace
PostPosted: Nov Wed 07, 2018 11:10 pm 
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These traces are intimidating. What if you clean the electrolytic corrosion off the traces to bare copper and you still have continuity on the traces. If you reseal them can reasonable expect them to last ?

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 Post subject: Re: Working with pcb trace
PostPosted: Nov Thu 08, 2018 12:14 am 
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Maybe.....better to at least neutralize, but even better to remove anything with corrosion on it.

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 Post subject: Re: Working with pcb trace
PostPosted: Nov Thu 08, 2018 12:31 am 
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I have a couple of dental tools I have ground to use to gently scrape the conformal coating from the trace by drawing the edge along it, as opposed to scraping like a paint scraper. The exposed area can then be buffed a little with a typing or ink eraser. Then the exposed trace can be fluxed and tinned and eroded areas can be bridged with similar gauge wire. In many cases the electrolyte from leaky capacitors can be cleaned off using distilled water on a swab or pad in a pair of hemostats.

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 Post subject: Re: Working with pcb trace
PostPosted: Nov Thu 08, 2018 7:14 pm 
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I use a fiberglass Scratch Brush to clean off broken or damaged traces and clean with alchohol. I scratch it down to the copper and solder on single strand "bell wire" or CAT5 wire.

I recently bought a small tube of conductive glue. I haven't tried it yet.


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 Post subject: Re: Working with pcb trace
PostPosted: Nov Thu 08, 2018 7:20 pm 
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Quote:

I recently bought a small tube of conductive glue. I haven't tried it yet.
for PCB work, don't.......

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 Post subject: Re: Working with pcb trace
PostPosted: Dec Sat 01, 2018 12:28 am 
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I would use a solution of salt and vinegar with q-tips to clean it back to bare copper as a starting point.

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 Post subject: Re: Working with pcb trace
PostPosted: Dec Sat 01, 2018 2:55 am 
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Thanks, ill use that solution on the next board i come across with corrosion.

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 Post subject: Re: Working with pcb trace
PostPosted: Dec Mon 03, 2018 1:27 am 
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Salt and vinegar? Then you neutralize that I assume? I use scraping, alcohol, and Q tips or a metal "acid brush" trimmed with scissors to have bristles a quarter inch or less so they are stiffer.

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 Post subject: Re: Working with pcb trace
PostPosted: Mar Sun 24, 2019 11:54 pm 
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I agree with several suggestions,vinegar and salt, then neutralize with baking soda. Fiber glass pencil brush. Also a pencil eraser would work.
using wire wrap wire is an excellent Idea also. If need be you could flatten the wire also. Clean with Isopropyl alcohol and a cut down acid brush to get stiffer bristled.

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 Post subject: Re: Working with pcb trace
PostPosted: Apr Sat 13, 2019 1:13 pm 
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My patented technique is scraping the heavy crud with a dental pick or Xacto knife, then using a fine metal brush. Can't remember where I got them, but they are still available as "soldering aids". A good solvent for MOST crud is spray on flux remover btw .... it generally dissolves most goop you're likely to find.

Depending on what caused the corrosion in the first place, if you use the fine metal brush and take the trace down to bare copper, and the surrounding PCB area is totally clean, chemical treatment may not be necessary or advisable. Damaged PCB areas can absorb stuff easily, and that includes cleaners.

For really heavy damage, I, as most have noted, simply cut out the damaged traces (Xacto knife again) and replace with wire. Thin buss bar wire is great cuz it's already tinned. Or you can just strip back some solid copper hookup wire, 24ga seems to be a nice gauge for most repairs. Wire wrap wire is perfect for finer traces. Only once did I try to "restore" the look of the board, by hammering out some copper wire so it was flat and paper thin and patching it into the area I had removed. Not gonna do that again. Life's too short.

In extreme cases where the underlying PCB has been damaged, say a HV burn or whatever, I drill out the damaged section of the board and leave just a hole, although one could fill it with epoxy if you cannot live with a hole in a pcb in a cabinet that no one will ever see again ;-). BTW ... don't try this trick on multilayer boards, and hope that there's nothing on the OTHER side of the board either for just two sided ones.

When you're done, for this board try some green nail polish to cover your sins. :). Make sure it's not conductive first lol.

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