Cleaning PCB after soldering - Page 1
Forum section: electronics / beginners

author: sairfan1
author_rank: Frequent Contributor
timestamp: October 06, 2022, 09:12:45 pm
content: In videos, I saw cleaning PCB with some liquid after soldering, I wanted to know what commonly available liquid can we use to clean PCBs

author: planet12
author_rank: Regular Contributor
timestamp: October 06, 2022, 09:50:19 pm
content: Probably the easiest to get and most commonly used is isopropyl alcohol aka isopropanol. It's pretty cheap, dries very quickly and doesn't leave a residue.I've used methylated spirits before, but it's not the best, as it has dye and bitterants in it that will get left behind - so I wouldn't use it on a high voltage or very sensitive board where the residues might cause problems.

author: Benta
author_rank: Super Contributor
timestamp: October 06, 2022, 09:57:56 pm
content: Isopropyl alcohol (IPA, 99%) and a small paint brush is the thing. All components I've encountered have no issue with it. Used it for years myself.

author: jmelson
author_rank: Super Contributor
timestamp: October 07, 2022, 02:04:48 am
content: If you really want to clean your boards, use water soluble flux. But, then you MUST wash the boards. But you will be amazed how quickly they clean up! But, for general-purpose electronics, you can use no-clean flux and just not bother with cleaning.Jon

author: tooki
author_rank: Super Contributor
timestamp: October 07, 2022, 05:27:10 am
content: As always, I suggest using commercially available flux cleaner instead of isopropyl (IPA). Many fluxes are not 100% soluble in IPA, leaving white residue behind. And even with fluxes that are fully soluble, the solvent blends of flux removers dissolve the flux noticeably faster, saving time.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 07, 2022, 05:44:27 am
content: For whole boards, I use ZEP heavy duty floor stripper diluted 1:3 with DI or distilled water and an ultrasonic cleaner ( 2 minutes) + rinse. For spot cleaning, I use absolute ethanol plus a little acetone if there are no susceptible plastic components on the board. If there are, then just ethanol.

author: BlackICE
author_rank: Regular Contributor
timestamp: October 09, 2022, 01:34:46 am
content: By volume, 90% solution of 99% IPA with 10% heptane.

author: EPAIII
author_rank: Super Contributor
timestamp: October 09, 2022, 05:21:06 am
content: Yes, any electronics store or supply or E-bay or Amazon will have flux cleaner. Don't confuse it with contact cleaner. The flux removers are better than IPA, even the 99% IPA. You will use a lot less of them.A good brand:https://www.amazon.com/Chemtronics-ES1696-FLUX-REMOVER-CLEAN/dp/B000E9TMC4/ref=sr_1_26?crid=OF2EKV8KP990&keywords=flux+remover+for+electronics&qid=1665292346&qu=eyJxc2MiOiIwLjAwIiwicXNhIjoiMC4wMCIsInFzcCI6IjAuMDAifQ%3D%3D&sprefix=flux+remover+for+electronics%2Caps%2C388&sr=8-26Another that I have used:https://www.ebay.com/itm/401848286028?hash=item5d90063b4c:g:9PYAAOSwRuFjH6EA&amdata=enc%3AAQAHAAAA4FWQqGtyTV9aIfbfXO6E%2BTmi%2FnrP17fIPvSYkKpbT3IiHo%2BfcOOFn98HSyShNPMcXUrI1uuugUkssEBXNzi5Qh2E%2FGvM1OLeBck1iAWcfYbAWv0uYk%2BgoJRfv18c0tk9b9Z%2FSHSClxWO1J2mpXVs%2BMMCbMI7GzSlpXHLfR9C4sqNac%2BBApUs7O1A3soF5GnHStQknkI1IEDETuV833AXQfcrFNTI4IwumZGkn0GA6sImHj2viRgneNL0C%2FqX5FR%2FXLXLe1SCagIejrpWa%2BxmRHXcw3OxTDfJ97aiHEXSIi5K%7Ctkp%3ABk9SR86F8bL3YAQuote from: tooki on October 07, 2022, 05:27:10 am

author: TC
author_rank: Contributor
timestamp: October 09, 2022, 10:31:52 pm
content: As others have said... the quick/easy way is to use isopropyl alcohol, a brush, and lint free cloth to clean off excess. But this will leave some residue.If you want to get it cleaner then flux remover is the way to go. I don't use spray. I use a flux remover concentrate mixed with distilled water. I keep a small pre-mixed amount in a dispenser. My quick method is to use a brush and flux cleaner and then follow it with isopropyl and a lint free cloth. That works much better.But when I really want it clean I use a cheap jewelry ultrasonic cleaner, flux remover mixed in warm distilled water (degassed), and follow that with a water bath, then a isopropyl bath. That yields excellent results.Nothing new in any of these suggestions. These are commonly used methods.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 09, 2022, 10:52:35 pm
content: Quote from: TC on October 09, 2022, 10:31:52 pmYou don't name the flux cleaner you use. If it is one of Kester's water-based cleaners, then the MSDS/SDS will show it is essentially the same as ZEP floor stripper, which is much cheaper and more readily available at home improvement stores. That's why I switched to ZEP. Actually, there is nothing special about the brand. Any product for stripping acrylic floor wax is probably very similar.Frankly, I was amazed at how clean an Oshpark reflowed board with TGFP parts came out. It was Kester's solder paste with rosin-based flux.

author: Benta
author_rank: Super Contributor
timestamp: October 09, 2022, 11:03:16 pm
content: Looking through the safety sheets of the "flux cleaners" available in the EU. Main ingredient:Propan-2olWhich is (TaaDaaaah!):Isopropyl alcohol.Go buy your over-priced snake oil where ever you want. It's your money. I'll save mine and use what always worked: pure IPA.

author: KaneTW
author_rank: Frequent Contributor
timestamp: October 09, 2022, 11:26:13 pm
content: Water with suitable ultrasonic detergent in an ultrasonic cleaner. Rinse with DI water, then IPA to displace the water and dry the board.Careful with ultrasonic cleaning if you have a low frequency crystal.https://www.iqdfrequencyproducts.com/media/pg/1589/1524142577/ultrasonic-cleaning-of-pcb-s-with-quartz-based-products.pdf

author: jpanhalt
author_rank: Super Contributor
timestamp: October 09, 2022, 11:41:03 pm
content: Quote from: Benta on October 09, 2022, 11:03:16 pmTrue for the non-aqueous cleaners, but not for any cleaner that is water based. Kester has made a point that many fluxes require a "saponifier" to get rid of the bothersome "white precipitate" that one sees. Saponification does not happen pure IPA. (Methanolysis might be considered a type of saponification, but that reaction, as I remember, is pretty specific to methanol.) The neat thing I saw and should have realized beforehand is that solder resist is quite hydrophobic. So, when using a water-based remover, the boards come out virtually dry. As I said earlier, for spot cleaning, I still use an anhydrous alcohol, typically ethanol.

author: tooki
author_rank: Super Contributor
timestamp: October 10, 2022, 01:19:58 pm
content: Quote from: Benta on October 09, 2022, 11:03:16 pmIt’s not snake oil. The other ingredients make a difference. Most have a hydrocarbon, and some heavy-duty ones also acetone. Some use citrus terpenes, too.IPA alone does NOT clean all fluxes well. It’s fine for some, but it leaves white residue with many fluxes.Additionally, even for fluxes that are fully soluble in IPA, they dissolvefasterin flux cleaner, and need less of it.

author: tooki
author_rank: Super Contributor
timestamp: October 10, 2022, 01:25:07 pm
content: Quote from: aixun-2022 on October 10, 2022, 09:27:24 amAssuming this isn’t just spam: Most rosin fluxes do NOT need to be removed in most applications. They can be removed with solvent cleaners (doesn’t need to be fluorocarbon, and usually isn’t!) or with water and saponifying agent.

author: Benta
author_rank: Super Contributor
timestamp: October 10, 2022, 07:08:13 pm
content: Quote from: tooki on October 10, 2022, 01:19:58 pmSure, sure. Like I said, it's your money, spend it as you like. Citrus terpenes is a great argument, and if you throw in folic acid it'll be a killer flux remover.

author: tooki
author_rank: Super Contributor
timestamp: October 10, 2022, 08:35:48 pm
content: Quote from: Benta on October 10, 2022, 07:08:13 pmStop being a smartass. Citrus terpenes aren’t there as fragrance, they’re there because they’re an effective solvent.

author: coppice
author_rank: Super Contributor
timestamp: October 10, 2022, 08:40:02 pm
content: Quote from: Benta on October 09, 2022, 11:03:16 pmThe main ingredient in humans is water. Are you the same as a puddle?

author: rdl
author_rank: Super Contributor
timestamp: October 11, 2022, 07:54:05 am
content: Years ago I tried to find information on the solubility of "rosin". Never did find much. I still wonder what it is actually soluble in and what gives the lowest viscosity.

author: Psi
author_rank: Super Contributor
timestamp: October 11, 2022, 08:09:09 am
content: isopropyl alcohol is fine but you have to brush it in and all around the pcb, then rinse withfreshclean isopropyl alcohol.The rinse is important otherwise the flux dissolved in the IPA will leave streaks on the PCB as it evaporates.If you have two containers, a scrub and a rinse tub, then it works pretty well.When the rinse bath starts leaving streaks you swap that for the scrub bath and get new IPA for rinse.But you still go through lots of IPA and you shouldn't pour used IPA down the drain.Compressed air is nice to dry off the PCB instantly, but you are aerosolizing flammable liquid, so you do need to be careful.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 11, 2022, 09:48:16 am
content: Quote from: rdl on October 11, 2022, 07:54:05 amKnowing the solubility of rosin won't help much. It's the pyrolytic products from rosin and anything else in the flux that you need to know how to dissolve. From Wikipedia: "It is soluble in alcohol, ether, benzene and chloroform." To which you can add a long list of other organic solvents.

author: rdl
author_rank: Super Contributor
timestamp: October 11, 2022, 12:26:09 pm
content: That's a good point, but I'd be willing to bet all that gunk is held together mostly by rosin. A just because a given organic solventwilldissolve something doesn't mean it's thebestsolvent for that purpose. For medium to high molecular weight polymers in general, the best solvents usually result in the lowest viscosity solutions. I don't know how well that applies to "rosin" though.

author: tooki
author_rank: Super Contributor
timestamp: October 11, 2022, 04:48:55 pm
content: The white residue in question is not from insufficient rinsing. (I.E. it’s not just flux being redeposited.) It’s compounds that won’t dissolve. From a Kester article on the subject (attached):“Chlorinated or fluorinated solvent, alcohols and saponifier/water cleaning seem to have little effect for removing this residue.” And that’s just for one of the several types of residues created.

author: jpanhalt
author_rank: Super Contributor
timestamp: October 11, 2022, 06:29:47 pm
content: Reading just a little further in the report,QuoteNote additional cautions about using alkaline anything. I wish Kester defined what it meant by a "saponifier" in water that was not alkaline.My guess is that technical personnel wrote what was actually used (e.g., ethanolamine and related). Legal got involved and warned they couldn't be that specific, so marketing came up with "saponifier." (tongue in cheek)

author: KaneTW
author_rank: Frequent Contributor
timestamp: October 11, 2022, 09:36:13 pm
content: As long as you don't add hydroxide to the cleaning bath, you'll be fine.

author: Vovk_Z
author_rank: Super Contributor
timestamp: October 12, 2022, 09:22:28 am
content: Quote from: jpanhalt on October 09, 2022, 11:41:03 pmThat's why good cleaning liquid ('a flux cleaner') contains not only pure IPA, but some (10-35 %) amount of some benzine/gas, e.g. nefras (pure gasoline) etc (don't know the right English/Americal equivalent).Yes, it stinks much (better for me), but it does its job without 'a white residual'.

author: tooki
author_rank: Super Contributor
timestamp: October 12, 2022, 04:52:58 pm
content: Quote from: Vovk_Z on October 12, 2022, 09:22:28 amThat’s what I’ve been saying all along. But some people insist that it’s “snake oil”…