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All of my veroboard-copper-tracks gradually slowly becoming blackish, scratch-like marks, or sometimes brown-black patches.

Here's one from extreme (sorry for bad soldering, it is 7- 8 months old, when I was beginner).

are these copper tarnish

Fig: Black patches, marked with arrow. Are they sort of copper tarnishing?

However all these blackened tracks are yet fully conductive. But would they create problem later-on?

I can prevent it by using a thin layer of solder, but is that okay? (since no-one around me do it on a veroboard).

Is there any other available alternatives in market? (like readymade PCBs use a green paint).

Another older board

This board around same time, 5 or 6 months old.

unused board

A qute-recent un-used board from stock at home, approx. 3 or 4 months old. It was not like this when I bought from shop.

much new Much new board. 1 or 2 month old. (btw it is a repetition of circuit of first one). Only a few little places showing any visible reaction.

a stranded wire

Other than veroboards, here is a piece of stranded copper-wire, maybe approx an years old. It was kept in open air. the inner-portion (which has been split-out today), is normally shiny, but the terminal portions is blackish-brown, almost lustreless, and as brittle as as half-burnt hair.

Whereas those wires were kept inside a tight aluminium-box, are almost like new-one, and exposed-portions are just more deep-coloured and slightly less-shiny.

Once I also once saw, some pieces of stranded wires were kept inside a shaving-box (whose strands were used as fuse), accumulated green waxy rusts in places to places!!! (they were disposed, so could not be photographed)

Always Confused
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    Use a spray lacquer. – Andy aka Sep 13 '16 at 07:51
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    @Andyaka: I just want to know where he lives so I can avoid the place. – jonk Sep 13 '16 at 07:53
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    Just get a new one, those things are made for prototypes,not to last forever. Whatever you apply on it, it may be hiding damages that are later hard to find – PlasmaHH Sep 13 '16 at 07:53
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    This same question is also valid for boards etched at home. – pipe Sep 13 '16 at 08:03
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    *I can prevent it by using a thin layer of solder, but is that okay?* Yes that is perfectly OK, many PCBs that are wave soldered have this, mainly to allow for more current to flow (compared to only the copper). – Bimpelrekkie Sep 13 '16 at 08:06
  • @jonk You need not to worry, all professional circuits are made of PCB, comes with a green-colored coating. Stay assure I'm not going to sell these rough works. – Always Confused Sep 13 '16 at 08:07
  • @FakeMoustache Thanks this is the good answer I was looking for. – Always Confused Sep 13 '16 at 08:08
  • @PlasmaHH, jonk I'm thinking way of prevention, not repair. Thanks for statement "it may hide damage" – Always Confused Sep 13 '16 at 08:14
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    I just don't want to be around a chemical atmosphere that is causing that. I've got lots of veroboard here -- some decades old -- and none of it looks like that. Well, not unless half the parts suddenly exploded because I randomly crossed both hot sides of the 240VAC split phase on the board. Are you keeping these under your sink, next to the sodium hypochlorite crystals container. – jonk Sep 13 '16 at 08:17
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    I'm from Kolkata, West bengal, India. yes air-pollution is common here, As well it is a very hot place, and rainy-season is going on. I think that is more important factor I think. – Always Confused Sep 13 '16 at 08:22
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    No. Here is no corrosive chemical container in my home, but due to rainy-season each and every corner of my home feels slightly humid on finger's touch, including tables and almirah. As well in city there is air pollution and dusts, too. Here in our ceiling-fan every day some dust is gathered, whereas when I go to village, there is much less rate of dust-covering, even in certain places in several years no dust accumulates on ceiling fans. – Always Confused Sep 13 '16 at 08:29
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    I'm truly sorry to hear that. I just looked it up and there's a wiki page on the atmospheric and drinking water pollution there. So that looks very serious to me. Add heat and humidity to all that and I can see it happening to the boards. I wish I had a solution not just for your boards, but for you. But just oxygenation and moisture will eat copper, I suppose, and I think it does turn black. – jonk Sep 13 '16 at 08:30
  • Here is an Wikipedia page about that protective-layer on PCB. https://en.wikipedia.org/wiki/Conformal_coating – Always Confused Sep 13 '16 at 09:21
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    I've got a few bits of vero several decades old and they don't look like that, it seems clear to me there is something chemical or even galvanic going on. Presumably it's from trace chemicals carried in the moisture (humidity) in the air. It probably isn't much problem for human respiration which within limits is self cleaning and self healing, but clearly it's bad news for copper. I wonder if something is catalysing the conversion of copper to copper (II) oxide. – Ian Bland Sep 13 '16 at 09:22
  • @IanBland +1'd for "galvanic". However there are no corrosive chemicals in my home, except Harpic (bathroom cleaner) and Zeoline (a chlorophore, water purifier) which comes in tight bottoles. – Always Confused Sep 13 '16 at 09:30
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    @Always Confused, I meant there may be trace pollutants in the air generally. It doesn't take much concentration of chemicals to produce an effect over time. Here in Britain in the great industrial era, factory pollution stained and corroded everything. – Ian Bland Sep 13 '16 at 09:46
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    @AlwaysConfused what sort of flux do you use when soldering? Because to me that board looks like you used a sort of acid based plumbers flux which has continued to eat away at the copper on the board. I have never seen veroboard or strip board look so bad. – Steve G Sep 13 '16 at 10:24
  • @SteveG Resin. Sold in elecrtronic parts shop. – Always Confused Sep 13 '16 at 10:28
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    @SteveG It has not "eat up" yet. If I scrap this thin layer with a knife it is glossy, shiny red copper underneath. Also copper-coins (used one upon a time) get tarnished into blue-green (that is very well-known). However none of the tarnishes on my veroboards are blue-green, rather it is blackish. – Always Confused Sep 13 '16 at 10:32
  • I use resin which is hard, transparent, reddish-brown, and have aroma. – Always Confused Sep 13 '16 at 10:36
  • @SteveG the portions you're seeing covered with some excess resin, is perfectly ok. The untouched portions are actually affected. Some unused small pieces of veroboards are also affected. The more old they are, more affected they are. – Always Confused Sep 13 '16 at 10:40
  • @SteveG should I use soldering-paste instead resin? honestly I used resin (hard, red-brown, transparent, aroma) bought from electronic parts shop and nothing else. – Always Confused Sep 13 '16 at 15:06
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    @AlwaysConfused I don't know why you are using such resin. All solder for electronic work has resin cores in the solder, there is no need for extra resin. – Steve G Sep 13 '16 at 15:13
  • Thanks I did not knew this. However I was using the low-price solder (out of 2 available types). Without resin or paste the solder often behaves very tight, and does not take proper place on hole, and even sometimes doesn't shine, or even some batches doesn't melt properly. Nowadays I'm using the costlier one, and it melts fast and helps me work much more neat and clean way. – Always Confused Sep 13 '16 at 15:30
  • @SteveG if solder needs no extra resin or paste, then why people buy them? just to clean the iron? plz could inform? – Always Confused Sep 13 '16 at 15:32
  • As a student, also consider a [solderless breadboard](https://en.wikipedia.org/wiki/Breadboard) for temporary experiments. Note flip it over or put in a box if storing for awhile - dust settling on them tends to contaminate the pins, which are quite challenging to clean. – rdtsc Dec 30 '20 at 18:53

3 Answers3

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Another option is to "electro-less" (immersion) tin-plate the boards when new. Mix the powder into (distilled) water, dip board, wait a few minutes, remove. Puts a layer of tin onto the copper, which will resist corrosion for awhile. Same can be said for electro-less nickel-immersion-gold (ENIG), although this is more expensive.

But it seems to me that something else is at work here. That is an extreme amount of corrosion, and if it hasn't caused electrical problems already, it looks likely to start soon. A tin plate is really only a band-aid solution, as after the tin is consumed, the copper will start corroding. ENIG would be better, but still not impervious. So this may buy you some more usable time from the board, but not solve the problem completely.

As for the corrosion itself, some common chemicals which could be contributing to this are halogen salts. Fluorine, chlorine, bromine, iodine... if any of these are present near the PCB's (even in trace quantities) they will readily destroy them.

But since it looks like most of the corrosion is near solder joints, I strongly suggest you obtain several different fluxes purpose-made for electronics work. Yes, solid rosin can be used as "flux" but there are many newer formulas today (completely different chemicals) which are much better in every way. First and foremost, acid-core solder on PCB's will destroy them. Same with zinc chloride flux. (I don't even like these for soldering copper pipes, they will corrode!)

Try these types of flux (you may need to find a local distributor or import these): Farnell, Mouser, Digikey, etc.

  • "Liquid" is just that, some are very good.
  • "Paste" is fairly thick and goopy, so holds small SMT parts in place.
  • "RA" stands for "Rosin-Activated", meaning it cleans well but is slightly more acidic. Good for "dirty" boards and parts.
  • "RMA" is "Rosin-Mildly-Activated", meaning it cleans ok, and is less acidic. Good for fairly new and clean boards.
  • "R" stands for "Rosin", meaning it is traditional rosin flux, no additives. It is least acidic, but also cleans less. Good for new parts and boards.
  • "No-clean" claims that it does not need cleaning.* May be a synthetic compound, not rosin at all. (ChipQuik smells like sizzling beer!)
  • "Water Soluble" tends to be rather strong and acidic, but can be cleaned with water.
  • "ROHS lead-free" can withstand the higher temperatures of lead-free soldering.
  • Flux Pen - many have tried these and do not like them. Try at your own risk.

Now of these, some fluxes must be removed after soldering. "Water Soluble flux" remains acidic after cooling, so must be removed. WS is also not recommened for fine-pitched parts, as it is difficult to remove all of the product, even if detergent is added to the rinse water. An ultrasonic bath may help.

RMA and RA fluxes may become slightly conductive as they absorb moisture. This is mostly an issue for high-impedance circuits. For low-impedance (simpler) circuits in mild environmental conditions it matters little, but R(M)A should be cleaned for best reliability. Always check the flux manufacturer's datasheets. R(M)A generally won't attack metals like water-soluble flux can.

Here is a video about testing several fluxes. Common Brands to look for:

  • Kester
  • MG Chemicals
  • ChipQuik
  • EdSyn
  • Chemtronics

Note that "no-clean" fluxes are somewhat a misnomer - all fluxes dissolve the oxidization and impurities on the metals, which can remain in the flux and cause problems with conductivity later. Always clean the board (remove all traces of flux) after soldering for best results.

The final step for PCB protection in an environment such as this would be conformal coating. This is essentially encapsulating the PCB in a plastic coating which should block all humidity and corrosive compounds from reaching it. For a one-off design though, a simple dip of the PCB into urethane "clear" would probably work just fine. If any corrosive compounds are present before coating, the coating will not stop this process and the PCB will still corrode.

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rdtsc
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  • What I use is solid resin. (I don't know is it same as rosin). Also in our class, paste and resin any one is used, I'm using resin at home. Did you mean it can cause that? Should I use paste instead resin? – Always Confused Sep 13 '16 at 14:30
  • Trace amount of salt can com from hands (my hands sweat a bit), or may come from dust from air or cardboard boxes (previous clothing-packet from my home). – Always Confused Sep 13 '16 at 14:34
  • You are correct about the fact "salt", because those-boards' copper-side get fingerprints or finger's touch, become black within few days. While those boards hold strictly only at margin, doesn't turn black so fast. – Always Confused Sep 13 '16 at 14:53
  • Veroboards probably come with a very thin layer of resin or lacquer or such, because when my fingers are sweaty, the new boards feel like slight sticky (not like copper-wires), and catch a deep fingerprint. And the moment when the solder is just applied, i.e board is warm, it caught more prominant fingerprints. – Always Confused Sep 13 '16 at 15:03
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    BTW, solutions for immersion tin plating are not supposed to go down your sink after use. Especially in India where only God knows where the drinking water comes from. – Dmitry Grigoryev Sep 13 '16 at 15:07
  • honestly I used resin (hard, red-brown, transparent, aroma) bought from electronic parts shop and nothing else. – Always Confused Sep 13 '16 at 15:09
  • No . the pictures I gave none were tin-plated... or even not looking like magnet-wire. They exactly look like fresh bright pinkish bare copper. – Always Confused Sep 13 '16 at 15:10
  • where drinking water comes from? in cities, there are pumping and purification stations. In villages people use tube-well mostly. – Always Confused Sep 13 '16 at 16:57
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Applying a layer of solder to your board is going to give you basically the same result as HASL finish. It has much better shelf life than bare copper, but it won't last forever either. With time, two things will happen:

  • tin will oxidize, though slower than copper
  • copper and tin will diffuse into each other, creating bronze

Both processes will result in worse solderability and worse electrical properties of the traces.

Here are a few pointers to prevent the damage in the future:

  • keep your PCBs in a dry place (I keep mines in a plastic food container toghether with some silica gel)
  • buy PCBs with a better finish if you can. HASL is much more durable than bare copper and not too expensive.
Dmitry Grigoryev
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  • PCBs with green layer never caused any such problems. Veroboards actually give more flexibility to think-out new circuits , and as a student I found it more helpful. Nothing else. – Always Confused Sep 13 '16 at 14:40
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Your photos are useful. Your last photo shows the corrosion spots around the perimeter of the board. The center of the board is relatively free of corrosion. This tells me that some of your corrosion is due to chemical transfer from your fingers to the board.
However, photo #3 is most disturbing - looks like little hand contact. This one suggests an environmental source of corrosion.
Your suggestion to "solder-plate" bare copper is Ok, and allows you to re-work solder connections at a later time. Protecting surfaces with a "paint" makes re-work much harder and more dangerous - heating "paint" with a soldering iron could release dangerous fumes.
Your photos suggest to me that your flux is indeed a rosin type, and I see little corrosion due to active flux. However, be aware that some of these fluxes are "heat-activated" - they clean actively while hot and liquid, then are supposed to de-activate at room temperature when they go crystaline. This appears to be the case in your photos.

glen_geek
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  • Yes your analysis is very helpful. look at bottom right portion (but not at terminus, but towards middle) of fresh bord ( # 3), there is one blackish fingerprint mark. – Always Confused Sep 13 '16 at 17:40
  • Maybe trace of sweat from my finger-tips added some salt as user @rtdsc told, that facilitated the corosion process. – Always Confused Sep 13 '16 at 17:44
  • may be the same happens for old copper coins used once upon a time. – Always Confused Sep 13 '16 at 19:04
  • Transfer of 'chemicals' from fingers... don't know would there be any specific 'chemicals'... because I do not work with chemicals... I last did work with biology laboratory reagents (not in home) at least 6 months before I start join electronics repair course. I think, since my palms sweat a little, that could add up trace amount of NaCl. – Always Confused Sep 14 '16 at 04:59
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    @AlwaysConfused - My own copper boards appear as your last photo after a month, and I'd guess that many others have similar experience. Biology and its chemical reactions to Cu are not for this forum. Your photo #3 is exceptional. Since its source is different from others, it may have come to you not properly factory-cleaned of etchant. – glen_geek Sep 14 '16 at 05:16
  • My photo # 3 and some other board contained a slight-amount of black muddy wax-like material on some-of its holes (specifically at holes). Several-times I found boards where the hole is totally clogged with greasy or waxy matter, I had to clean the holes with a pin or needle or such to pass the leads. – Always Confused Sep 14 '16 at 05:25
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    @AlwaysConfused - am proposing that you have an air-borne contaminant, carried by water vapour (humidity). If copper-etching chemicals are stored nearby (even if sealed) or if they share air-flow, this could be the source. Your environment of heat and humidity is a very difficult one that makes a small contaminating source very active. – glen_geek Sep 14 '16 at 07:22
  • May be. I don't know. In a crowded place it is very possible these chemicals are being used nearby ... however at-present this-locality is not an industrial area. If you include ammonia and ammonium compounds as 'copper-etching chemicals', then yes sometimes urines from dirty places and other rotten matter create ammoniacal smell. Smells of hydrogen sulphide (H2S) is quite common here, and like any other big cities, various unknown smells come from far-distance sources, though not always. – Always Confused Sep 14 '16 at 07:36