Clear nail polish for pcb copper coating?

[crawler486]

So do you think it will help?
Or will it just cause problems later.

[gez]

Might chip with time (and might clash with the colour of the box), but who knows?  Not a bad idea though, I wonder if some other type of varnish wouldn't be more appropriate (floor?).

[Skreddy]

I'm thinking about using a light coat of nitrocellulose lacquer on my copper after soldering.  I have some more generic clear coat too, but I know nitro is real easy to work with and touchups and repairs probably wouldn't be difficult at all.  Hopefully nitrocellulose lacquer won't oxidize the copper over time.  I had a Rangemaster clone on perfboard self destruct over a period of about a year because I has used liquid flux, which invariably gets everywhere because of splattering when heated.  The liquid flux and possibly even its fumes gradually chewed up not only the copper traces but also killed the Fulltone 3PDT switch and made a white powerdered mess of the enclosure interior.  BAD STUFF.  

Sidenote: after seeing vintage Ibanez pedal enclosures rot from the inside, I now clearcoat the interiors of my pedals.  I think also from now on, in addition to clearcoating the copper and enclosure insides, I'm gonna give all my stomp switches a little squirt of Caig Deoxit before I install them.  --And the contacts of all switching jacks, too.

[Fret Wire]

Sidenote: after seeing vintage Ibanez pedal enclosures rot from the inside, I now clearcoat the interiors of my pedals.  I think also from now on, in addition to clearcoating the copper and enclosure insides, I'm gonna give all my stomp switches a little squirt of Caig Deoxit before I install them.  --And the contacts of all switching jacks, too.

If you're going to coat the inside of a pedal, what better to use than conductive shielding paint. Corrosion protection, plus shielding properties. Krylon makes a magnetic aerosol paint that Walmart sells. It's a conductive, poor man's version of shielding paint.

http://www.krylon.com/main/product_template.cfm?levelid=5&sub_levelid=8&productid=1765&content=product_details

BTW, nitro may not be so good for boards, as it hardens and cracks with age.

[Eric H]

So do you think it will help?
Or will it just cause problems later.

It's lacquer --nitro, or acrylic; and should work fine.

-Eric

[Paul Perry (Frostwave)]

How much nitro is in that lacquer? I wonder if it would ignite if you tried to do rework on a trace.. I remember setting a celluloid fountainpen on fire as a child!

[Skreddy]

How much nitro is in that lacquer? I wonder if it would ignite if you tried to do rework on a trace.. I remember setting a celluloid fountainpen on fire as a child!

I think as thin as it is with a single light coat, it's not gonna be flammable (or likely to crack when it ages).  That's one of the things I like about it; it goes on so thin.  Being an ultra thin coating over a solid substrate, it won't have enough of it's own fuel to overcome the choking effect of being stuck to a solid surface that has no oxygen.  I'll run a test, though.  I don't even think a soldering iron is hot enough to ignite a Fender celluloid pick.  I think it will decompose under a soldering iron (making touchups a breeze) but won't catch on fire.

[Hal]

how tragic is it to leave the copper bare... ?

[Paul Perry (Frostwave)]

how tragic is it to leave the copper bare... ?

Well, it's going to LOOK very bad in a few years, but I have seen stuff 30 years old working fine, FWIW. It is the old problem of dissimilar metals (in this case copper and the lead/tin alloy) encouraging corrosion, in this case mostly greyish tarnish on the solder.

[Jim Jones]

I used clear nail polish on the foil side of my Anderton Phase Shifter board years ago.  I haven't had any problems, of course I haven't touched any solder joints since I did it.

Jim

[zeppenwolf]

Second the motion of conductive paint for coating insides of boxes: notice you could therefore sorta build boxes out of wood or anything else...  My guitar cavity is coated with a nickel-based paint; very low R.

For coating the trace, may I suggest  POLYURETHANE which is widely available, even water-based, even in spray forms.  It will never age, it will always remain flexible and never crack, and if you ever decide to adjust your circuit, (like scratch off part of the coating, cut the trace, etc), I think you will find it much more workable-friendly than a shellac/lacquer.

I don't guarantee that urethane is not conductive, but I would be extremely surprised if it were..?

Eden

[Skreddy]

how tragic is it to leave the copper bare... ?

Well, like I said, I had a perfboard project go 'poof' over a period of about a year because the copper traces gave out under the corrosion of the liquid soldering flux I had used.  That may have been an extreme test (as it turns out), but it was a completely unanticipated failure and proves to me that copper is very sensitive and reactive to environmental contaminants which you can never be sure of.  Better safe than sorry.

I used nail polish on the backside of my very first PCB, a fuzzface clone, several years ago, and it's still doing great MANY mods later.

[Peter Snowberg]

If you're worried about the copper oxidizing, just run over all the traces with a soldering iron and coat the board with a thin coating of solder. When you get boards made by a board house they call this the "tin over copper" process. Well.... at least the end result is the same.

I've had bad results leaving bare copper on boards, but R.G. has one that's just about as old as I am and it's still working. It all depends on your local humidity.

If you want to use a polymer coating, I like zeppenwolf's suggestion of a polyurethane over nitrocellulose.

Take care,
-Peter

[RedHouse]

The solder method is expensive (to me) since good solder is like $16/lb.

Better to use "Tinnit" which is relatively cheap and coats the copper much like the process Peter mentioned.
(plus it makes your board look very professional)

Parts Express has it:
http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=340-188

Note that fingernail polish is normally an Enamel based coating, and be aware that some have nail conditioners that contain moisturizing oils which might not help.
(RTV Silicone can help oxidise when applied over bare copper too)

Years ago I used to do some prototyping work and learned a few tips when making one-off manual assembled boards. If you do use solder as Peter mentioned, doing a "re-flow" will help it look professional.

To do solder re-flow at home, after you apoply solder to the traces (and clean the flux off) heat up a small pan with 1/4" of cooking oil to medium-high heat, place your board in a preheated 200° oven for a few minutes to keep thermal shock to a minimum (could warp or discolor the board) then place the board trace side down into the oil for a moment or two, the oil will melt the solder temporarily ad "re-flow" it into an even coating. Remove, cool and clean the oil residue off the board.

Always clean solder flux off of your boards, flux is hydroscopic meaning it pulls moisture from the air and holds onto it, helping turn your nice copper traces to green.

(I use paint thinner because I have a big can in the garage, and it's cheaper than flux remover)