How do *you* seal PCB trace rework? - Page 1
Forum section: electronics / general

author: Traceless
author_rank: Frequent Contributor
timestamp: January 02, 2023, 12:08:09 pm
content: Hey everyone,I need something to reseal rework of corroded traces - before I go and buy something random I'm curious what everyone uses (UV-curable solder mask, clear coat, sth else?) And if you can recommend any particularly good products or name some to stay away from.

author: screwbreaker
author_rank: Regular Contributor
timestamp: January 02, 2023, 12:20:13 pm
content: This:https://www.chemtronicseu.com/circuitworks-epoxy-overcoat-adhesive-syringeOr conformal coating.But depends on the case, sometimes you can just put some solder on top of the tracks.

author: Ian.M
author_rank: Super Contributor
timestamp: January 02, 2023, 12:24:11 pm
content: What's the environment? Protecting a a reworked computer or home entertainment board is considerably different to protecting boards from sea-going small boat cockpit instruments. I would generally prefer a solder-through coating for the latter if its my own equipment as once the seals have failed once, its fairly certain you will be back in there!

author: Traceless
author_rank: Frequent Contributor
timestamp: January 02, 2023, 12:39:09 pm
content: @screwbreaker: Thank you for the link.Quote from: Ian.M on January 02, 2023, 12:24:11 pmIt should mostly be suitable for consumer grade electronics (mainboard, graphics cards, notebooks, game consoles and eventually household appliances). For the future I also plan to do some restoration work on old test equipment. Environmentally the worst case I can think of would be a washing machine located in the basment (humidity + temperature changes). And good point somthing that is removable in case a subsequent repair is required would be nice.

author: TERRA Operative
author_rank: Super Contributor
timestamp: January 02, 2023, 01:07:00 pm
content: Sometimes (most times) I just use clear or green nail polish. It's basically enamel paint.

author: Traceless
author_rank: Frequent Contributor
timestamp: January 02, 2023, 01:10:07 pm
content: One more thing I should mention: For some reason the selection of suitable products seems to be pretty limited in Germany. Most electronics stores offer stuff likeKontakt Plastic 70orTeslanol 26028which comes in either in spray cans or 5l canisters. Reichelt for instance seems to offer only one suitable product:CW 3300 C Acrylic insulating varnish in stick dispenser,conraddoesn't seem to offer anything suitable so I may have to get stuff from ebay.

author: SilverSolder
author_rank: Super Contributor
timestamp: January 02, 2023, 01:10:15 pm
content: As long as the exposed tracks are completely tinned and the area is cleaned, I don't bother with any further coating for indoor / dry use.

author: Traceless
author_rank: Frequent Contributor
timestamp: January 02, 2023, 01:12:16 pm
content: @TERRA Operative: I've seen people use fingernail clear coat. I'm not super sure how temperature resistant that stuff is, how well it seals PCBs or if it has any corrosive properties - it is not made for electronics afterall.

author: Ian.M
author_rank: Super Contributor
timestamp: January 02, 2023, 01:20:43 pm
content: A safer bet would be clear automotive scratch repair lacquer. Its usually acrylic (so can be stripped if you have to), with a convenient applicator brush in the cap of the bottle.

author: Traceless
author_rank: Frequent Contributor
timestamp: January 02, 2023, 02:02:35 pm
content: Quote from: Ian.M on January 02, 2023, 01:20:43 pmAcrylic clear coat for cars, is much easier to get. When you talk about stipping i guess you mean using paint stripper (e.g. nitro-cellulose combination thinner)? That stuff can be quite agressive won't that potentially damage the PCB/components? Alternatively you could probably solder through acrylic lacquer but I'm not sure what that will do to the soldering iron tips tbh?Does anyone have thoughs/comments aboutthis UV solder mask?

author: Ian.M
author_rank: Super Contributor
timestamp: January 02, 2023, 02:25:12 pm
content: No. I wouldn't even try to strip it from a whole board, especially not with paint stripper. Spot application of acetone on a Q-tip should soften thin coatings of 'one-pot' Acrylic lacquer enough to let you scrape most of it off the joints you need to rework, and FR4 is reasonably acetone resistant. *Don't* get it on plastic cased components e.g. its instant death for polystyrene capacitors, but so's solvent based Acrylic lacquer.The problems with soldering through it aren't just severe tip corrosion (the usual consequences of burning non-waxy plastics on the tip), but also noxious fumes and the probability it will leave a partially conductive charred ring round the joint.

author: Traceless
author_rank: Frequent Contributor
timestamp: January 02, 2023, 02:57:08 pm
content: @Ian.M. Thanks for the clarification. The Q-tip application sounds reasonably safe - usually I use a pipet to apply contact cleaner or IPA to small areas of the board and then clean with a Q-tip.

author: TERRA Operative
author_rank: Super Contributor
timestamp: January 02, 2023, 04:06:40 pm
content: Quote from: Traceless on January 02, 2023, 01:12:16 pmCan't be too corrosive, it's standard-ish enamel used on your skin.Although sometimes I just tin the traces and leave it at that.

author: Traceless
author_rank: Frequent Contributor
timestamp: January 02, 2023, 09:23:08 pm
content: @TERRA Operative: Nice thanks for sending the sample pictures. The trace repair on the 2nd picture looks really clean. The stuff on the right side on top and between the ICs is clear flux residue or also clear coating?Quote from: TERRA Operative on January 02, 2023, 04:06:40 pmWell the pH-value human skin is usually around ~4.7-5.7 (which already is a bit on the acidic side) so substances with a similar pH value would be no problem for our bodies but might not be exactly ideal for electronics. That being said I have no knowledge about the chemical properties of nail coating - so it may just be pH neutral or its pH value even vary between brand/product. Which product/brand of clear coat do you use? Did you ever check back on any of the boards you did use the clear coat on after a longer time period?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 02, 2023, 09:47:32 pm
content: I don't think nail polish and most other lacquers have anything that attacks metal. They just might not be a very good seal (bubbles, pinholes), or very resistant to environment (permeable to moisture, etc.? easily abraded? easily flaked off?).Standard professional fix is, well, same as the original: you can get UV-cure green soldermask resin, and a UV LED pen to cure it. Available at the usual places, not excruciatingly expensive or anything.Even if it's not particularly good stuff (permeable, soft, removable with solvents), that can still be good enough. The value of conformal coating and potting is largely just occupying space, keeping liquid water (and contaminants, especially salts, and especially chlorides and other ligands that accelerate oxidation) away from the metal surface, or trapped in small enough cells/bubbles/pores that it can't do much. So, don't feel too bad about using something like that, but it does of course depend on the environment and use.Tim

author: SilverSolder
author_rank: Super Contributor
timestamp: January 03, 2023, 11:41:40 pm
content: There are some automotive clearcoat repair pens/markers that you could "paint over" the damaged area with. The stuff cures/hardens with UV light... so there may not be any solvents involved. I have purchased some to play with, they are only like $1.50 each on eBay.

author: coppercone2
author_rank: Super Contributor
timestamp: January 04, 2023, 03:52:35 am
content: I got the UV mask you are supposed to squeegee. It worked but holy shit what a mess it made. I say the difficulty of use is 8/10. You are supposed to put a transparancy on it and irradiate it but god damn that does not work like you would think, appearance wise. I did a distribution board and it ended up looking like shoddy sheet rock repair (VNA).I would recommend you put some Q-Dope on it after abrasion and cleaning.

author: Jeroen3
author_rank: Super Contributor
timestamp: January 04, 2023, 07:30:12 am
content: This stuff:https://electrolube.com/product/apl-acrylic-protective-lacquer/Comes in little bottle with brush:https://octopart.com/apl15ml-electrolube-84706434Ideal for rework coating or fixing kynar wires.

author: Traceless
author_rank: Frequent Contributor
timestamp: January 06, 2023, 10:28:31 pm
content: Okay thanks for all the replies - I guess the winner is acrylic lacquer (pen or bottle with brush) for use on cars.

author: mastershake
author_rank: Frequent Contributor
timestamp: January 15, 2023, 06:14:31 am
content: imo it all depends on how and where it will be used