Hacking a PCB: How to Remove Coating

Hacking a Park-Zone POS to make it work accurately, I find the PCB has a relatively thick clear coating.

What's the best way to remove the coating without damaging components?

Thanks! ...Jim Thompson

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"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

I've used lacquer thinner with success on the red conformal coating. The only thing is that it will attack some plastics and wipe the numbers off of glass diodes.

Cheers

Try acetone. IIRC it doesn't touch most electronics components, but it does dissolve conformal coat.

'course, if that clear coating doesn't come off with it, it's no help.

Coating is clear. Looks like it was just poured over areas with semiconductors. ...Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

It may be Humiseal

Try Acetone or Lacquer thinner in a corner and see if it softens it up. Hopefully it's not the UV cure.

Cheers

This was poured on _after_ soldering, which was done by hand, in China, natch.

So such a clear coat is safe to clear with an iron?

(You're right, I'm only tacking in a few extra connections, and cutting a few traces.) ...Jim Thompson

It decomposes at soldering temperatures, allowing local probing and repair with a soldering iron. It's clear, so you shouldn't have to remove it entirely, to do what you're trying to do.

RL

I can cut it with an X-acto knife, with a slight "rubbery" feel, so it's hard to scrape right down to a trace. ...Jim Thompson

Haven't been to the hardware store yet, but tried some Xylene I had on hand... just puddles up and does nothing. I _can_ dent it _slightly_ with my fingernail.

I can get Acetone or MEK or Lacquer thinner at the hardware store. Any ideas which to try? ...Jim Thompson

I'd try the laquer thinner first as it is a witches brew of chemicals.

message

NO SOLVENTS!

Fix ONLY the area where the repair is needed to be performed.

You ask for severe headaches if you use solvents.

You're not supposed to be inhaling that much of the solvents!

Inhalation Acute Exposure Effects: Vapor harmful. May cause dizziness; headache..

Best regards, Spehro Pefhany

He's not tying to repair it.

Those are not the headaches to which I refer, toot boy.

You'll have to burn through with a hot tinned iron tip and tin the intended contact with pre-fluxed solder. The tinning slakes off local residue.

Once you start burning, the opacity of the film will degrade locally, so make as many observations and notes as is possible prior to the slash and burn.

RL

Another possibility you could try is an (appropriate) abrasive tool. If all you need is to open up some solder blobs so you can unsolder parts, you might be able to use a Dremel tool and a "grinding wheel" made of that nylon-like material used in kitchen scrubbing pads. The trick, of course, would be to find a suitable abrasive that would remove the conformal coating but only polish the solder and copper.

Come to think of it, you could just try a couple of different scrubbing pads to see if they do what you want. ... Oh. One old ex-VHS PC board I found lying around, two different plastic scrubbing pads, several minutes of effort: no observable difference.

Can anyone suggest any improvements along these lines? An electric pencil eraser, perhaps?

Frank McKenney