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Aussie Pinball Forums => Technical Matters => Handy hints and tips => Topic started by: JRK1971 on February 23, 2012, 11:37:18 PM

Title: Circuit board paint to seal copper tracks after repairs???
Post by: JRK1971 on February 23, 2012, 11:37:18 PM

Hi guys,
After completing some repairs lately that involved sanding back the green screening paint on the copper tracks of some PCB's, I was wondering if anybody seals the copper afterwards to stop corrosion afterwards. If so, im wondering what you use? !@#

Given that the aim is to get the electronics gonig reliably, it seems a little silly to remove the protective paint for a repair and not seal it again - kinda sounds like sanding a car back to repair a dent and leaving it in bare metal after you straighten the panel. *.*

You can see the repair I just did and the bare copper under the resistors and below – Can’t help but wonder if I should have painted the surface under the resistors before installing them to stop copper corrosion.

Your thoughts/ advice?

Title: Re: Circuit board paint to seal copper tracks after repairs???
Post by: goodolddays on February 23, 2012, 11:48:59 PM

Clear nail polish will do the job

Title: Re: Circuit board paint to seal copper tracks after repairs???
Post by: JRK1971 on February 23, 2012, 11:52:53 PM

Cool, thanks, I should have thought of that @.@

I just found this on eBay...

http://www.ebay.com.au/itm/Green-UV-Solder-Mask-PCB-Repairing-Paint-Anti-Corrosion-/220951883133?pt=AU_B_I_Electrical_Test_Equipment&hash=item3371c22d7d

Seems like a cheap solution as well and saves me getting in trouble with the missus #@#

Title: Re: Circuit board paint to seal copper tracks after repairs???
Post by: Homepin on February 24, 2012, 09:33:42 AM

The paint on eBay will require UV to cure it (sunlight would work OK).

It WILL NOT "air dry" inside so you would need to put your painted board in the sun for a few hours.

Title: Re: Circuit board paint to seal copper tracks after repairs???
Post by: faza on February 24, 2012, 09:45:54 AM

If you will be needing it again you can buy the laquer from Jaycar in a spay can.
http://www.jaycar.com.au/productResults.asp?keywords=spray&keyform=KEYWORD&SUBMIT.x=0&SUBMIT.y=0

Title: Re: Circuit board paint to seal copper tracks after repairs???
Post by: JRK1971 on February 24, 2012, 11:55:21 AM

Thanks guys, always best to ask the experts ^^^ ^^^ ^^^

I'll go the Jaycar way, should give a nice neat solution that you can solder through (according to the specs)...

Goes to show you need to know what to look for, I couldn't find it on Jaycar last night @.@

Title: Re: Circuit board paint to seal copper tracks after repairs???
Post by: Homepin on February 24, 2012, 12:37:23 PM

The Jaycar circuit board lacquer (in the link above) is exactly the one we use here at Homepin to finish our aftermarket replacement PCBs

Title: Re: Circuit board paint to seal copper tracks after repairs???
Post by: johnwartjr on July 28, 2012, 05:39:25 AM

Ive always just tinned the traces with solder, but the spray lacquer looks like a neat alternative. I'll have to check that out!

Title: Re: Circuit board paint to seal copper tracks after repairs???
Post by: beaky on July 28, 2012, 06:06:24 PM

Well done on your repair.  ^^^

there is still alot of corrosion that still needs to be removed from the tracks.

the areas that have lost the green screening and are grey, plus the areas with the bubbled green screening have still got corrosion and will eventually be eaten away if it is not removed.

I have highlighted the areas that still need attention for long term reliability. hope you find these pointers helpful and i hope my comments haven't offended you  ^^^

when i do my acid repairs I spray the board with clear lacquer that can be soldered through before installing the components so the copper under the components and i.c sockets are not left exposed.
I then clear lacquer again once all the components have been fitted
 

Title: Re: Circuit board paint to seal copper tracks after repairs???
Post by: JRK1971 on July 30, 2012, 03:27:05 PM

Thanks beaky, Appreciate the advice, any advice to keep the beast alive is greatly appreciated. $#$ I'll go back and do some rework. You mention spray laquer that you can solver through, are you talking the same stuff from Jaycar that we mentioned earlier. Ie this stuff http://www.jaycar.com.au/productView.asp?ID=NA1002&keywords=spray&form=KEYWORD

Regards John.

Title: Re: Circuit board paint to seal copper tracks after repairs???
Post by: beaky on July 31, 2012, 11:50:37 AM

yes, this stuff will do the job. you only need a thin coat if you are going to spray before fitting the components you can put on the thicker coat after you have done your repairs.
make sure you mask off any connection areas on the board with masking tape, you don't want any lacquer on the pcb tracks / traces where the connectors slide on (A1-J1 A1J6 etc.) I know most or the contacts or on the bottom of the board but you can still get minimal amounts of over spray on there.

make sure the board is clean from any dust or oily residues or else your clear lacquer will not stick and look horrible. use PCB cleaner for this
and last make sure if you are going to spray any I.C. sockets that do not have the I.C. installed that they are masked up also.

 ^^^ 

Title: Re: Circuit board paint to seal copper tracks after repairs???
Post by: Homepin on July 31, 2012, 12:09:22 PM

I like to warm the boards a little before spraying as well.

Clean off any flux or residue then wave a hot air gun over the board to drive off any remaining solvents and warm the surface a bit.

This helps the spray to dry a lot faster and I find it dries with a much higher gloss.