Veroboards start conducting between tracks, behaving nasty - Page 1
Forum section: electronics / beginners

author: mvno_subscriber
author_rank: Regular Contributor
timestamp: February 01, 2022, 05:21:18 am
content: Hi,every time I solder veroboards I get strange issues. Some of the cheap ones start conducting between tracks, especially if I rework them (once I had 10Kohm between two unused tracks, one track apart!). I always thought it was perhaps because the structure of the boards was made of hardpaper, and maybe its dielectric properties broke down by the heat or something, so this time I got hold of a nice fiberglass-type with tinned tracks.However, although it doesn't conduct between tracks, it started behaving strangely. I had a bunch of transistors there arranged in darlington fashion (one driving eight others), not anything particularly fancy. Worked on the breadboard, no issues. This time, it starts doing weird things, transistors turn on and off do all kinds of magic.I measured diligently between all tracks and made sure all was as it should be. My DMM goes up to 50Mohm and showed OL where it should. Everything checks out. Still, the same issue.Tried soldering point to point (i.e. no veroboard), and everything was super duper.So I'm wondering, is the board at fault? Or could there be some micro contamination I'm not seeing? Would it make sense to wash the board after soldering, and if so how? I haven't used any flux besides what's in my solder.

author: Gyro
author_rank: Super Contributor
timestamp: February 01, 2022, 09:37:27 am
content: I suppose it might be possible for very cheap phenolic stripboard to carbonise under very high temperatures, but that would be way above normal soldering temperatures and tip contact duration, so seems unlikely.If you are seeing the same behaviour with fibreglass boards, then I would have to suspect the type of flux that you are using. No-clean flux can show some leakage, but only under really high impedance situations. Are you sure that you aren't using plumbers solder / flux? Some of the residues can be very conductive - and corrosive.Sorry, but that's the only explanation that comes to mind.

author: mvno_subscriber
author_rank: Regular Contributor
timestamp: February 01, 2022, 09:49:22 am
content: I use normal lead free solder for electronics. Soldering iron set to 350C. I typically don't need any extra flux, and try to minimize component heat exposure.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 01, 2022, 10:09:36 am
content: I switched to solderable breadboards several years ago and have never seen the problems you describe. Is your veroboard the one hole per pad type or is it configured with tracts and plated through holes? Maybe a picture of both sides and schematic would help?Is it possible that leakage on solderless breadboard is responsible for good behaviour and that the higher impedance of the soldered connections leaves something floating or susceptible to static?

author: tooki
author_rank: Super Contributor
timestamp: February 01, 2022, 10:14:39 am
content: Quote from: mvno_subscriber on February 01, 2022, 09:49:22 amBut what type of flux core is in your solder? “Lead free” tells us the alloy, not the flux type.

author: mvno_subscriber
author_rank: Regular Contributor
timestamp: February 01, 2022, 10:22:41 am
content: Quote from: jpanhalt on February 01, 2022, 10:09:36 amIt's the type with conductive rows underneath, that you can solder to. Like picture here:https://en.wikipedia.org/wiki/VeroboardQuote from: tooki on February 01, 2022, 10:14:39 amDon't know. It's a Sn 99.3 Cu 0.7 blend, marked "The best quality solder" -- i.e., probably the cheapest you can get in all aspectsHowever... embarassing as it may be -- I think I've fixed it. I ran the knife long and good between each column. Then, the DMM started at a couple of Megohms and slowly crept up to infinity (10-20 seconds, not between tracks but between + and - on the board -- it shouldn't draw any power until activated by an input pin).Not sure if there were flux residue or whatnot. At least, I won't trust my eyes next time. And why the meter/circuit had to "acclimatize" I wonder. But life is full of wonders. At least the hours I put in there didn't end up wasted, after all.And perhaps I should consider using a solder with different flux. It might be that roll o' tin who has been my secret enemy all the way- it's the same roll I've used on everything, ever. Do you have any recommendations for good solder wire for allround use? I'm a bit hesitant to use leaded solder.

author: Gyro
author_rank: Super Contributor
timestamp: February 01, 2022, 10:33:01 am
content: Yes, that definitely sounds like dodgy flux then.Get yourself a nice roll of 63/37 leaded from a reputable source. Not only will it give you nicer joints in a hobby setting, but the flux will be rosin based, which is far kinder to you than the aggressive types used in lead free. There is no risk in using Leaded as long as you wash your hands before eating.

author: RoGeorge
author_rank: Super Contributor
timestamp: February 01, 2022, 10:47:16 am
content: Maybe the flux inside the solder is not good, or maybe it's not a no-clean flux.https://foreverest.cn/news-list/how-to-choose-the-right-soldering-flux(random search link)I think non activated flux can be conductive, too, so if the temp is too low or the soldering too fast for flux activation to happen then any flux residues must be cleaned away.Try washing any flux residues after soldering, then measure again the resistance between traces. I suspect it's the flux, not the board. Also, the board should be clean of grease/dust before soldering.

author: tooki
author_rank: Super Contributor
timestamp: February 01, 2022, 11:04:25 am
content: Quote from: mvno_subscriber on February 01, 2022, 10:22:41 amI definitely recommend buying quality solder -- I maintain that because the amount of solder used in a project is so small, even "expensive" solder doesn't actually cost much on a per-project basis. At home, a 450-500g roll of solder lasts me something like 5 years (a bit hard to tell exactly since I have multiple sizes), so who cares whether it cost $10 or $60?There are tons of threads about choosing solder, but in the end, any name brand (Kester, Stannol, Loctite/Multicore, Felder, AIM, Alpha, Indium, Almit, Tamura, MG Chemicals, Chip Quik, etc) is going to be good -- the choice of flux core will make a bigger difference.Given the choice, Kester is my absolute favorite so far, but surprisingly, the fairly inexpensive Felder from Germany is my second. Their lead-free solders are available from reichelt.com at very reasonable prices.As for veroboard: I've had cheap Chinese phenolic (what you called "hard paper", a term I know from German, but unused in English) boards where the etching is so bad that there are actually thin bridges between tracks. Some were easily visible, but some were barely visible to the naked eye. Dragging the knife through may have severed such a short.There's an easy way to test whether the flux is an issue: do a test without cleaning, then thoroughly clean the flux off using solvents and measure again.Quote from: RoGeorge on February 01, 2022, 10:47:16 amThe fluxes in a flux core definitely reaches the temperatures needed both to activate it and to neutralize it again. The warnings about insufficiently heated no-clean flux refer to separate flux (liquid or paste).

author: mvno_subscriber
author_rank: Regular Contributor
timestamp: February 01, 2022, 01:05:52 pm
content: Thanks for a very thorough reply! I do, sadly, like to have a bit to eat when I solder, so I've only used leaded solder when I have to.Currently, I have these two other rolls of solder:The leaded one I've been avoiding (and I do intermittently have some snacks while I work, it's very easy to forget washing my hands) -- and the Chipquik one I abandoned using quite quickly, as the flux has a nasty smell to it. But would the Chipquik one be ok, in your book? Or should I just buy a big roll of something else?Links to for example Mouser, RS or Elfa Distrelec would be very handy!

author: Bud
author_rank: Super Contributor
timestamp: February 01, 2022, 02:50:51 pm
content: I strongly believe your water washable solder is a problem here. You should wash it away from boards after soldering. Do not take its "no clean" for face value.

author: jonpaul
author_rank: Super Contributor
timestamp: February 01, 2022, 09:48:08 pm
content: Bonjour, been building designs protos and breadboards for SMPS, electronic lighting and digital audio since 1970.1/ We used GENUINE US made Vector (not Vero) boards of G-10 fiberglass for decades and never had such issues!The paperboard Chinese clones may show their poor quality first in HV, high Z or high freq circuits.As the board is worth a fraction of your time expended to build and debug, we recommend only high quality fiberglass G-1- based.We used 0.1" pad per hole.2/ The only solder acceptable was Kester 44 resin 5 core Eutectic, 63/37. We saved perhaps 25# of it in 1 # and 5# spools.The RoHS solders have higher melt points and longer plastics region so bad for protos.The Chipquik alloys are used by some to remove parts but we never used it.The Ersin was never as good.No info re Chinese clone solder we have never used it.Again the cost of solder is essentially zero compared to your time!Hope this is useful,Jon

author: SmallCog
author_rank: Frequent Contributor
timestamp: February 02, 2022, 02:07:07 am
content: I was taught to always run a blade down the gaps when using Vero/Strip boards even if your soldering looks goodPerhaps this is why?The guy that told me wasn't one you asked "why" to but it's a habit I've continued with.