Any special precautions to take when cleaning PCBs with isopropyl alcohol? - Page 1
Forum section: electronics / general

author: JoeN
author_rank: Frequent Contributor
timestamp: October 02, 2016, 03:23:06 am
content: My usual construction process these days is to use Kester ".44" 63/37 and sometimes extra Kester RA flux and then clean the board with 99.95% IPA with an anti-static "tooth" style brush and then jet it off with canned air. It usually takes three passes to get everything perfect. But my soldering looks better with lots of flux. Is it safe to scrub all common components with IPA or are there precautions I should take? I wonder about pots. The ones I have seem pretty well sealed (example:http://www.bourns.com/docs/Product-Datasheets/3361.pdf"Withstands harsh environments and immersion cleaning processes") Is that safe? How about SMA board-edge connectors? Any concerns? Thanks.

author: John Coloccia
author_rank: Super Contributor
timestamp: October 03, 2016, 11:11:28 am
content: It's safe but IPA is not the right cleaner for the job. Which Kester flux are you using? 186? One thing I do is if I need extra flux, I put just a drop on the lead of the part. Then I don't have to clean. I have capacitors here that for whatever reason always prove challenging to solder, so I give each one a very, very light coating of 186. It's exactly right to get a perfect joint every time. I had a nice, long chit chat with a chemist over at Kester, and this was one of the tricks he suggested.Anyhow, you're likely just making things worse by disturbing the flux and then smearing it all around. When I have to clean, I use Chemtronics Flux Off for Rosin, and then I follow it up with a cheaper alcohol spray from TechniTool. That actually gets the boards clean. IPA is lousy for cleaning off flux.Anyhow, the only thing I generally worry about is pots and switches, but it looks like your particular pot is designed for it so it's fine.

author: German_EE
author_rank: Super Contributor
timestamp: October 03, 2016, 12:05:18 pm
content: IPA is no problem for PCB cleaning and I don't know of any component that will be affected by it apart from paper dielectric capacitors. What is will do is remove anything written with a biro pen or a felt tip marker so make sure that any essential markings are not washed away.Acetone is a problem though, don't use it or various things might start to melt including connectors and polystyrene capacitors

author: John Coloccia
author_rank: Super Contributor
timestamp: October 03, 2016, 12:42:00 pm
content: Quote from: German_EE on October 03, 2016, 12:05:18 pmAgain, I spoke with one of the chief head mucky-muck scientific type guys there, and he told me flat out that IPA doesn't work and likely just leaves a thin, invisible layer that's worse than the just leaving it alone.And the datasheet has also been updated recently.Quotehttp://www.kester.com/DesktopModules/Bring2mind/DMX/Download.aspx?Command=Core_Download&EntryId=1072&language=en-US&PortalId=0&TabId=96If you NEED to get it off, then IPA is not the correct solvent. If you don't need to get it off, then it's best to let it be.

author: Jeff_Birt
author_rank: Regular Contributor
timestamp: October 03, 2016, 12:47:35 pm
content: IPA may affect some clear plastics and it will dry out many soft rubber parts (like rubber feet), other than that it is pretty benign. I have always found that on some fluxes, like rosin, it does a great job. In fact if you look at the MSDS for most flux removers I bet you'll find the main ingredient is IPA. Fluxes that are designed to be water cleaned are best cleaned with distilled water. 'No Clean' fluxes may still need to be cleaned as they can cause problems under some RF components (as a former employer of mine found out after failing a UL testing session as the board failed under certain hi humidity conditions.)

author: John Coloccia
author_rank: Super Contributor
timestamp: October 03, 2016, 12:57:04 pm
content: Quote from: Jeff_Birt on October 03, 2016, 12:47:35 pmYou need to actually look at the MSDS. Most rosin flux removers are not alcohol based, though they may contain some alcohol, either Ethanol or Methanol. The alcohol based ones do have some IPA in them, but they contain a lot more Ethanol or Methanol. I've looked at all of these simply because my work requires that I have a lot of different chemicals/solvents in my shop, and I simply have to know what I'm dealing with. This is just one of those cases where the conventional wisdom that everyone "known" just happens to be wrong. We all get away with it because Kester 44's and 186 flux is pretty well behaved even when we botch it up.

author: helius
author_rank: Super Contributor
timestamp: October 03, 2016, 01:00:43 pm
content: Flux Off appears to be an isohexane and ethanol mixture. That is pretty benign, but it may not be as compatible with some plastics as IPA. The faster drying time, compared with IPA, could be worse when working with burnt flux residue.My experience with 99.9% anhydrous IPA is that it doesn't leave residues. Do avoid the 70% grocery store rubbing alcohol.

author: Jeff_Birt
author_rank: Regular Contributor
timestamp: October 03, 2016, 01:28:02 pm
content: Quote from: John Coloccia on October 03, 2016, 12:57:04 pmJohn, very good catch. I was having a bit of brain fog this morning so I went and looked at the 1qt can of alcohol I buy which is 'denatured alcohol', i.e. ethanol rendered undrinkable :http://www.jasco-help.com/uploads/general/Jasco_Denatured_Alcohol_GJDA300_QJDA304_MSDS.pdf. Looking at the MSDS it seems it is much more inline with commercial flux cleaners than IPA is. Looking up what IPS 'is' reveals it is indeed not the same as denatured alcohol. So, I stand corrected. I have been using denatured alcohol all of these years, not IPA.

author: John Coloccia
author_rank: Super Contributor
timestamp: October 03, 2016, 01:46:14 pm
content: Quote from: Jeff_Birt on October 03, 2016, 01:28:02 pmHere's something interesting. The Kester 44 datasheet has recently been updated. It used to say something to the effect of "Flux residues normally do not need to be removed. There has not been a single verified case of flux residues causing problems." I don't remember the exact wording.That's now been removed and has been replaced with the simple admonishment that IPA is not sufficient to remove the residues. I wonder what changed. I also thought that 44 used an "RMA" flux, but it seems to be an "RA" now? Am I remembering that incorrectly? I can't imagine that they would have changed 44's flux after so many decades. Maybe I'm remembering it wrong.

author: M4trix
author_rank: Frequent Contributor
timestamp: October 03, 2016, 01:52:00 pm
content: Someone tried this ?http://www.tme.eu/gb/details/pcb-cleaner-a-1l/cleaning-maintaining-products/ag-termopasty/zmywacz-pcb-alkoholowy/Contains:1. propanol 40-60%2. hexane 8-14%3. Pentane 5-12%4. Acetone 15-25%

author: wraper
author_rank: Unknown
timestamp: October 03, 2016, 01:53:05 pm
content: Quote from: Jeff_Birt on October 03, 2016, 01:28:02 pmYou never know which additives denaturated alcohol contains. Usually it is some nasty shit which will form a film on the board once it dries. Useless for final rinsing as minimum.

author: wraper
author_rank: Unknown
timestamp: October 03, 2016, 01:58:08 pm
content: Quote from: M4trix on October 03, 2016, 01:52:00 pmRemoves rosin after hand soldering well. If it is heavily burnt, a little bit of mechanical help may be needed. Not good for removing flux residues after the reflow, there will be some left. Evaporates pretty fast, so you will need some good ventilation if don't want to get high.

author: M4trix
author_rank: Frequent Contributor
timestamp: October 03, 2016, 02:00:36 pm
content: Thanks for the info.

author: Jeff_Birt
author_rank: Regular Contributor
timestamp: October 03, 2016, 02:03:59 pm
content: QuoteIt depends on the flux used. I use rosin paste most of the time and the denatured alcohol does a good job. When reworking some boards that used a different flux you can get a white film which is a PITA. For surface mount soldering I like a liquid no-clean or water clean flux. There is not going to be 'one' flux cleaner that will work in every case.

author: wraper
author_rank: Unknown
timestamp: October 03, 2016, 02:23:42 pm
content: Quote from: Jeff_Birt on October 03, 2016, 02:03:59 pmI did't write about flux. Denaturated alcohol leaves residues by itself on completely clean board. If don't believe me, then swipe a finger over the dry "clean board" which was cleaned with denaturated alcohol, and then touch/taste the finger with your tongue. Clean board shouldn't have any taste, right?

author: CraigHB
author_rank: Regular Contributor
timestamp: October 03, 2016, 04:33:20 pm
content: I've been using technical grade isopropyl alcohol with Kester 285 RMA flux in the solder and a Kester 186 RMA flux pen. Iso alcohol seems to work well and doesn't smear flux all over the board as far as I can tell. But I don't know for sure, could be doing that and I just can't see it. I don't like the idea of denatured alcohol because I don't know what they're putting in there to make it undrinkable. Could be a problem. Maybe I should go to a proper flux cleaner. How does the price compare to buying technical grade iso alcohol? That stuff goes fast and cost is actually a bigger consideration.

author: rrinker
author_rank: Super Contributor
timestamp: October 03, 2016, 06:50:05 pm
content: Something that is constantly stressed in my other hobby as well - rubbing alcohol is NOT the same as isopropyl. Rubbing alcohol has oils and other additives, which WILL leave a film on anything. Isopropyl does not have this. 70% isopropyl is 30% water - also not good unless the application includes diluting it, but you are still better off with the full strength stuff and adding your own distilled water to dilute it. Used full strength, IPA should not leave residue.

author: JoeN
author_rank: Frequent Contributor
timestamp: October 05, 2016, 02:24:13 am
content: Quote from: John Coloccia on October 03, 2016, 11:11:28 amFor me at least, it isn't making it worse, it starts out as a sticky mess, and ends up as a perfectly clean board, even under the microscope. I guess it isn't working for you but it does work for me, at least with what I am using. Of course, it takes three passes and what a normal person would call a decent bit of brushing to get to this level of perfection. That is sort of why I am wondering if it is safe or not.The flux is 186 plus also MG Chemicals 835 flux pen. My vendors on these two products:http://www.ebay.com/itm/KESTER-186-ROSIN-NO-CLEAN-FLUX-FOR-XBOX-360-REFLOW-/131124985951https://www.amazon.com/MG-Chemicals-835-P-Rosin-Flux/dp/B0080X79HG/Vendor on IPA:https://www.amazon.com/MG-Chemicals-Isopropyl-Alcohol-Cleaner/dp/B005DNQX3CQuote from: John Coloccia on October 03, 2016, 12:42:00 pmNow that is interesting. If it is an invisible layer then it may affect precision circuits and is something I need to think about. For me, what I am doing is getting my board to not be sticky and look like a mess. IPA does that well at least. It does get it down to either clean or "an invisible layer". I guess I can accept that. Now keep in mind I am scrubbing it a bit so that may be providing a better solution that just a soak or whatever might happen in a mass production environment.Thanks for speaking to your head honcho. That was really nice of you. I am digesting all of this. It wasn't replied to for a day and now I came back and I have a bunch of info all at once.If I am good on using IPA, which I really like to do because it is not extremely smelly or aggressive, what is good for a final clean for precision circuits?I read in Troubleshooting Analog Circuits by Pease that he though a run through the dishwasher was a good idea.

author: sainter
author_rank: Regular Contributor
timestamp: October 05, 2016, 04:55:13 am
content: As far as I understand, you have to chemically deactivate the flux with flux remover, or you can wash it away with IPA, but smearing with IPA just distributes the residue all over the place (there is a military say, cleanliness is not removal of dirt, but a even distribution of dirt). The solution given by most people I seen is using Kimtech wipes or something similar to gather the residue you release from PCB.

author: JoeN
author_rank: Frequent Contributor
timestamp: October 05, 2016, 05:02:41 am
content: Quote from: sainter on October 05, 2016, 04:55:13 amI actually do use those wipes as much as possible, but they can be hard to get around small parts. The strategy I use is to use the wipe on maybe the first pass and then what I am doing is using lots of IPA to get all the crap into solution and blowing it off the board with the compressed air. Yes, if you dissolve the flux into the IPA and let it dry on the board, that does not work, it just evenly spreads out the flux. You have to dissolve the flux with the IPA and then remove it from the board. I do that.Keep in mind, my process is not a production process that has to be done by a machine. I am putting significant elbow grease in getting these boards clean with IPA, I admit that. If people are saying that IPA is considered a mild cleaner, that makes me happy. I'd rather do the work than use something stronger and save on labor but screw up my boards.