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Old 22nd Nov 2017, 4:26 pm   #1
GW4FRX
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Default Cleaning PCB track side?

The Radford amplifier I'm currently restoring uses a printed-circuit motherboard to support the audio and PSU boards via edge connectors. I don't know whether it's the effect of fifty years in a domestic (possibly smoking) environment but the tracks look very 'oxidised' and dull.

It doesn't matter in the slightest -- the electrons don't know any better after all -- but it would be nice to clean the tracks up a little before applying a protective lacquer coating. Can anyone suggest the best way to do it? Or could the track side be re-tinned if one was careful not to immerse any actual components?

I've defluxed the board with propanol and toothbrush in the time-honoured way but even vigorous rubbing with cotton buds and so on hasn't done anything for the appearance of the tracks.

Any advice gratefully received...
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Old 22nd Nov 2017, 5:06 pm   #2
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Default Re: Cleaning PCB track side?

Are the tracks bare copper, tinned or lacquered? If bare or tinned, have you thought about one of those fibre pen things? I've got one and it's brilliant at scrubbing away the grime of ages. Time-consuming for a big board though!
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Old 22nd Nov 2017, 5:13 pm   #3
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Default Re: Cleaning PCB track side?

Popping the whole board into a hot cycle in the dishwasher is a good start.

The difficulty after that is that reagents that deoxidise copper can sometimes make a bit of a mush with the lead content in the solder.
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Old 22nd Nov 2017, 5:26 pm   #4
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Default Re: Cleaning PCB track side?

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Are the tracks bare copper, tinned or lacquered? If bare or tinned, have you thought about one of those fibre pen things? I've got one and it's brilliant at scrubbing away the grime of ages. Time-consuming for a big board though!
They're tinned and no, I've not come across those. Sounds as though a visit to Maplins or RS is indicated. The dishwasher idea is appealing but unfortunately the edge connectors aren't readily removable from the board, so maybe not this time. I was wondering about Brasso or Silvo or thereabouts (or even Silver Dip) but haven't summoned up the courage to try yet.
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Old 22nd Nov 2017, 5:27 pm   #5
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Default Re: Cleaning PCB track side?

I also use a fibreglass pencil.
Probably one of the most useful small tools.

Also, sometimes a bit of brasso on a soft cloth works.
I usually start with a cotton bud dipped in acetone to degrease, carefully testing first as acetone eats plastics.

I also use an ultrasonic cleaner with solvent/soap solution for cleaning complete boards.
But, with this you have to dry it out very thoroughly before corrosion sets in.

If all else fails 600 to 1000 grit wet and dry paper soaked in contact cleaner.

Mark
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Old 22nd Nov 2017, 5:53 pm   #6
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Default Re: Cleaning PCB track side?

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I was wondering about Brasso or Silvo or thereabouts (or even Silver Dip) but haven't summoned up the courage to try yet.
Ahah, that's the situation I was describing where the lead (or less likely, the tin) produces an ugly black residue after interacting with the reagents in Brasoo or Silvo.

The result is uglier than the starting situation!
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Old 22nd Nov 2017, 6:05 pm   #7
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Default Re: Cleaning PCB track side?

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Ahah, that's the situation I was describing where the lead (or less likely, the tin) produces an ugly black residue after interacting with the reagents in Brasoo or Silvo. The result is uglier than the starting situation!
I'll give those a big miss then Had a go with Silver Dip on the end of a cotton bud but that doesn't seem to achieve anything interesting.

Sounds as though the magic fibre pencil is the way to go.
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Old 22nd Nov 2017, 6:15 pm   #8
David G4EBT
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Default Re: Cleaning PCB track side?

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Quote:
Originally Posted by Andrew2 View Post
Are the tracks bare copper, tinned or lacquered? If bare or tinned, have you thought about one of those fibre pen things? I've got one and it's brilliant at scrubbing away the grime of ages. Time-consuming for a big board though!
They're tinned and no, I've not come across those. Sounds as though a visit to Maplins or RS is indicated.
Here you go, 4.85 inc VAT, and you can also buy a pack of ten refills for the pen for 6.16 inc VAT.

http://cpc.farnell.com/unbranded/101...26%20Chemicals

Watch out for the tiny fibreglass 'splinters' that as shed in use. They're vicious little blighters and unlike wooden splinters, are all but invisible so may torment you for days!

As the fibres war down, the 'pencil' is just like a propelling pencil - you just wind more out as needed.

Have fun!
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Old 22nd Nov 2017, 6:47 pm   #9
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Default Re: Cleaning PCB track side?

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Here you go, 4.85 inc VAT, and you can also buy a pack of ten refills for the pen for 6.16 inc VAT...<...SNIP...>...Watch out for the tiny fibreglass 'splinters' that as shed in use. They're vicious little blighters and unlike wooden splinters, are all but invisible so may torment you for days! As the fibres war down, the 'pencil' is just like a propelling pencil - you just wind more out as needed. Have fun!
Wonderful -- many thanks, duly ordered along with some more Servisol and propanol...
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Old 22nd Nov 2017, 7:41 pm   #10
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Default Re: Cleaning PCB track side?

Yes, like David says, parts of those microfine strands can hurt if they get into your skin. Like unseen splinters. I was once told that some large organisations banned their use due to h&s implications. You certainly would not want a strand of that in your eye!
As a trial, just try it on a dull 2p coin. You will see the effect quickly.
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Old 22nd Nov 2017, 7:51 pm   #11
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Default Re: Cleaning PCB track side?

An ink india rubber eraser works well and no fibreglass splinters.
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Old 22nd Nov 2017, 7:52 pm   #12
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Default Re: Cleaning PCB track side?

I'd second the Acetone suggestion - if you have access to any nail polish remover, that's Acetone to all intents & purposes.

Just try a little on a cotton bud, but be wary anywhere near plastics.
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Old 22nd Nov 2017, 10:26 pm   #13
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Default Re: Cleaning PCB track side?

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An ink india rubber eraser works well and no fibreglass splinters.
Another + for the old eraser. We used to use these on PCB contacts on TRS type 62 card connectors.
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Old 23rd Nov 2017, 3:40 am   #14
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Default Re: Cleaning PCB track side?

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An ink india rubber eraser works well and no fibreglass splinters.
Tried to buy some of those a few months back - none to be found anywhere.

All they have nowadays are those horrible plasticky things that corrodes everything you leave them lying on.
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Old 23rd Nov 2017, 7:28 am   #15
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Default Re: Cleaning PCB track side?

Another vote for glass fibre pen's. Came to them late and wouldn't be without one.

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Old 23rd Nov 2017, 9:34 am   #16
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Default Re: Cleaning PCB track side?

I've never had a fibre glass pen. But as we are talking abrasion, what's wrong with some really fine steel wool (the stuff polishers use to remove stains from polished surfaces)?

In the context of tarnished metals, where the surface has oxidised, organic solvents like IPA and acetone are quite useless. To lift an oxide, it's going to take something like...citric acid , or physical abrasion.

As for putting old circuit boards in hot dishwashers - no comment!

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Old 23rd Nov 2017, 9:54 am   #17
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Default Re: Cleaning PCB track side?

I have some fibreglass pens, but hardly ever use them. Mention of the dull coin reminded me that Vim (is that still available??) was good for cleaning coins and similar objects.
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Old 23rd Nov 2017, 1:21 pm   #18
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Default Re: Cleaning PCB track side?

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I've never had a fibre glass pen. But as we are talking abrasion, what's wrong with some really fine steel wool (the stuff polishers use to remove stains from polished surfaces)?
Conductive swarf?
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Old 23rd Nov 2017, 2:13 pm   #19
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Default Re: Cleaning PCB track side?

I can verify the need for caution when using a fibreglass pencil, I had a nasty experience with one over the weekend!
I was trying to remove some corrosion from a battery terminal, and suddenly remembered the "pencil". I was sat on the floor in the lounge, holding the offending component in one hand and cleaning it with the pencil. It worked a treat, and after a few minutes the contact was as good as new.As I stood up I noticed that my trousers were covered in a fine dust, and without thinking, I attempted to brush it off with my hand, it felt like I had grabbed a cactus plant!
I spent the next couple of hours with a torch, tweezers, and magnifying glass, extracting the splinters from my hand, to make matters worse I had to throw away a good pair of trousers, as I didn't fancy putting them in the wash.
Next time I need to use it, it will be outdoors and I'll be wearing gloves and safety glasses, I really wouldn't want a piece in my eye's, still lesson learned.
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Old 23rd Nov 2017, 2:22 pm   #20
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Tried to buy some of those a few months back - none to be found anywhere.
Would this be the type of thing you're looking for?

https://www.ebay.co.uk/itm/FABER-CAS...Po263y-Vab-TJw
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