Low cost homebrew liquid flux recipe - Page 1
Forum section: electronics / projects

author: VK3DRB
author_rank: Super Contributor
timestamp: January 31, 2014, 02:40:35 pm
content: A few years ago I decided to make my own flux. Why? Because it was fun and I wanted to see how good it was. I took the recipe for the flux from an expired IBM patent dated around 1972.THE RESULTSA colleague who is a very experienced electronics technician said my flux was better than a top shelf $60 flux pen after he compared the two on a fine pitch quad flat pack IC. It certainly seemed to reduce the chance of bridging. I made a batch about 4 years ago. Still have not run out and it still works OK.Pros:Low costBetter than many expensive liquid fluxes, even for soldering quad flat pack IC'sExcellent oxide removal and wetting of a solder joint. Helps make a great solder joint.An amount in a small bottle lasts a long time.Works with lead free or lead based solders.Non corrosive according to the patent (I still wash it off using isopropyl alcohol and a toothbrush).Cons:Sticky like jam when it dries.You might be accused of wasting your time.THE RECIPEIngredients: Technician grade isopropyl alcohol (readily available), Glycerin (from the local supermarket), Colophony resin (it has to be crystallised and you can find it in some hardware and music stores or on eBay.)Crush the resin with a hammer. By weight, mix 60-70% isopropyl alcohol, 30% to 40% resin and 2-3% glycerin in a jar. Mix until the resin is dissolved. Put the lid on an leave it for couple of days and restir. Put it in small plastic eye dropper bottle. Put the bottle in a safe place.An extract from the patent is here. (I didn't worry about the surfactant.)

author: DmitryL
author_rank: Regular Contributor
timestamp: January 31, 2014, 03:46:02 pm
content: AFAIK Glycerin is hygroscopic and slightly acidic. It also absorbs moisture from the air.Thus, you might have problems with leakage currents after using your flux.I think your recipe will require cleaning both in some IPA-like solvent and deionised water; Just colophony+IPA flux doesn't need to be cleaned.

author: c4757p
author_rank: Super Contributor
timestamp: January 31, 2014, 03:51:30 pm
content: Not even a time waste IMO. When my flux pen is empty, I just pop the top off, toss in some rosin crumbs and top it off with alcohol. I've been using the same pen for a couple years now and it hasn't had the original (MG Chemicals) flux in it since shortly after it was brand new. I can't even tell the difference. Rosin by the pound is cheap on eBay - a pound of the stuff costs about the same as one dinky little flux pen.

author: t0m
author_rank: Regular Contributor
timestamp: January 31, 2014, 04:47:26 pm
content: My recipe was: pine gum + 99% IPA, filtered. (Blog post:http://bit.ly/1n2Yoy7)It's very sticky and not particularly active, but does smell nice.Next time I might boil the pine gum to drive off a few volatiles. That's basically how colophony is made.

author: Dave
author_rank: Super Contributor
timestamp: January 31, 2014, 05:16:52 pm
content: A while ago I bought rosin flakes at a local agricultural store (they are used for removing pig hair when slaughter time comes). I dissolved them in 96% pure IPA and poured the solution into one ofthese bottles. I call it my "magic solder juice".It's really nice when you need to clean the boards after soldering. Just put them in an ultrasonic bath with IPA and everything comes off, you then rinse the board with clean IPA and you are done.

author: JoeyP
author_rank: Frequent Contributor
timestamp: January 31, 2014, 06:58:57 pm
content: For extra credit, does anyone have any idea what's in water soluble flux?

author: t0m
author_rank: Regular Contributor
timestamp: January 31, 2014, 09:38:16 pm
content: I believe Kester #951 is IPA with a tiny bit of rosin, 2331-zx is IPA and inorganic acids.

author: VK3DRB
author_rank: Super Contributor
timestamp: January 31, 2014, 10:38:25 pm
content: Quote from: Dave on January 31, 2014, 05:16:52 pmSmall world indeed! I bought exactly the same bottle from the same company in Hong Kong. I also use a tiny eye dropper bottle from the local pharmacist.That company also sells top quality stainless steel tweezers for next to nothing. Shipping was free and the service was excellent.See these tweezers here.- Dave

author: con-f-use
author_rank: Unknown
timestamp: January 31, 2014, 11:07:16 pm
content: Glycerine is highly carcinogenic, when inhaled.

author: quint
author_rank: Contributor
timestamp: January 31, 2014, 11:18:20 pm
content: Quote from: con-f-use on January 31, 2014, 11:07:16 pmDo you have a reference for that information? Everything I can find with a quick search indicates that glycerine is low toxicity.

author: VK3DRB
author_rank: Super Contributor
timestamp: January 31, 2014, 11:25:41 pm
content: Quote from: con-f-use on January 31, 2014, 11:07:16 pmI doubt it. It is used in cooking. However, inhaling nitro-glycerine can make you bloated.

author: Dave
author_rank: Super Contributor
timestamp: January 31, 2014, 11:29:43 pm
content: Quote from: VK3DRB on January 31, 2014, 10:38:25 pmI have 5 or 6 of those. They are indeed very good.

author: con-f-use
author_rank: Unknown
timestamp: January 31, 2014, 11:31:12 pm
content: I think I read it in a publication of the German Cancer Research Center (Deutsche Krebsforschungszentrum). It was about how eCigarettes are not a good alternative to regular cigarettes. Bloated indeed but joking aside, nitro-glycerine is used as medication for some heart diseases. There are inhalers for it that use a stabilizing agent.

author: JoeyP
author_rank: Frequent Contributor
timestamp: January 31, 2014, 11:44:40 pm
content: Quote from: t0m on January 31, 2014, 09:38:16 pmI was thinking about the flux in solder pastes like Kester HM 531. I've wondered for a while what the liquid component was (hoping it's IPA). When doing long SMT assembly runs we sometimes end up in a situation where the solder paste on the stencil drys out. It would still be perfectly useable, except it begins to clog apertures and loose tack, so we end up throwing it away. Have always wished we could spritz some solvent on it to "freshen it up". Kester of course won't tell us what solvent they use. Maybe I'll experiment with adding some IPA next time we have a non-critical run.

author: echen1024
author_rank: Super Contributor
timestamp: February 01, 2014, 04:22:26 am
content: Quote from: c4757p on January 31, 2014, 03:51:30 pmDo you just use violin rosin?

author: BravoV
author_rank: Super Contributor
timestamp: February 01, 2014, 04:50:59 am
content: Quote from: DmitryL on January 31, 2014, 03:46:02 pmDon't think you need to worry too much on hygroscopic part, cause the 60-70% isopropyl alcohol is already content 30-40% water in it.Quote from: echen1024 on February 01, 2014, 04:22:26 amViolin rosin works well, also it is the easy source for "cleaned & filtered" rosin.

author: Fsck
author_rank: Super Contributor
timestamp: February 01, 2014, 05:11:39 am
content: Quote from: t0m on January 31, 2014, 09:38:16 pmkester's datasheet-thing says their 951 is non-rosin no-clean. it is however organic still.

author: Fsck
author_rank: Super Contributor
timestamp: February 01, 2014, 06:52:37 am
content: Quote from: c4757p on January 31, 2014, 03:51:30 pmcurious where you've found the price of 1lb rosin to = 1 pen. currently, kester 951 pens from my favorite canadian supplier of them have their normal price for it get to 5$ + shipping.The cheapest I can seem to find rosin is like 9$/lb if I want to buy a kilo or 7.7$/lb if I want to buy 5kg. (obviously the pens should/may/etc have cheaper shipping)

author: PioB
author_rank: Regular Contributor
timestamp: February 01, 2014, 12:11:52 pm
content: Quote from: JoeyP on January 31, 2014, 11:44:40 pmHi JoeyP,if you look up the MSDS of HM531 on the Kester download sitehttp://www.kester.com/downloads/they give the contents as follows:CAS: 7440-31-5 tin 50-100%CAS: 7439-92-1 lead 25-50%CAS: 61790-85-0 Ethoxylated N-(tallow alkyl)trimethylene diamines <= 2.5%CAS: 98-55-5 p-menth-1-en-8-ol <= 2.5%CAS: 4767-03-7 propanoic acid, 3-hydroxy-2-(hydroxymethyl)-2-methyl- <= 2.5%CAS: 68439-49-6 Alcohols, C16-18, Ethoxylated <= 2.5%CAS: 9004-98-2 Polyethylene glycol monooleyl ether <= 2.5%CAS: 61791-17-1 modified rosin <= 2.5%a search on the CAS numbers finds that the Ethoxylated N-(tallow alkyl)trimethylene diamines are liquid,http://www.sigmaaldrich.com/catalog/product/sigma/p4182?lang=en&region=US, so is Terpineol (p-menth-1-en-8-ol)http://www.sigmaaldrich.com/catalog/product/aldrich/432628?lang=en&region=USHowever: "Description: Mixture of substances listed below with nonhazardous additions." might mean that they use other things as solvents (water? isopropanol(would that be "nonhazardous" or merit mention..?)According to the MSDS the 951 Flux penhttp://www.kester.com/download/951.pdfconsists of"Description: Mixture of the substances listed below with nonhazardous additions.ethanol 50-65%isopropanol 20-25%n-butyl acetate 5-10%methanol 2.5-5.0%adipic acid 1.0-2.5%"So I am not sure if the Etoxylated N-(tallow alkyl)trimethylene diamines and Terpineol are the only liquid components in there.

author: DmitryL
author_rank: Regular Contributor
timestamp: February 01, 2014, 12:27:01 pm
content: Quote from: BravoV on February 01, 2014, 04:50:59 amThe problem is that the water itself evaporates. Glycerin stays on your PCB surface, it doesn't evaporate.That's te reason you need to wash it out. The clean water should be OK for this, but removing glycerin from under smd components might be tricky or impossible.I heard stories when people had to disassemble their boards and clean them to remove bad flux that was too conductive.BTW, I'm not a chemist, but I heard that despite glycerin itself is harmless (it is used in cooking and cough sirups), on heating up it can produce acrolein, which is a nasty stuff. I also heard that glycerin can very easily penetrate through skin and get into blood (which is ok, but it can take with it some unpleasant chemicals that can be dissolved in it...

author: nanofrog
author_rank: Super Contributor
timestamp: February 01, 2014, 02:22:39 pm
content: Quote from: echen1024 on February 01, 2014, 04:22:26 amYou can get colophony off eBay (example). Maybe not the least expensive source, but cheaper than what I see musical instrument rosin go for IIRC (by weight), and it's convenient.

author: t0m
author_rank: Regular Contributor
timestamp: February 01, 2014, 02:48:26 pm
content: Quote from: Fsck on February 01, 2014, 05:11:39 amYes you are right. I don't know what the organic substance is - I suppose it could be abiatic acid which is the active component of rosin.No idea what's in solder paste I'm afraid. I would have though IPA is too volatile on its own.

author: PioB
author_rank: Regular Contributor
timestamp: February 01, 2014, 02:51:53 pm
content: Quote from: t0m on February 01, 2014, 02:48:26 pmQuoting from my post above:"According to the MSDS the 951 Flux penhttp://www.kester.com/download/951.pdfconsists of"Description: Mixture of the substances listed below with nonhazardous additions.ethanol 50-65%isopropanol 20-25%n-butyl acetate 5-10%methanol 2.5-5.0%adipic acid 1.0-2.5%""So the organic substance is indeed adipic acid.

author: t0m
author_rank: Regular Contributor
timestamp: February 01, 2014, 06:31:11 pm
content: That's interesting, succinic acid is chemically rather similar and available from home brew shops as a wine additive.

author: Zero999
author_rank: Super Contributor
timestamp: February 01, 2014, 07:26:11 pm
content: Quote from: con-f-use on January 31, 2014, 11:31:12 pmGlycerine has been used for years in foods, cosmetics and pharmaceuticals so I doubt it's responsible.It's possible cheap e-cigarettes are contaminated with carcinogens but I doubt it's glycerine which is the culprit.

author: quint
author_rank: Contributor
timestamp: February 01, 2014, 11:19:38 pm
content: Quote from: DmitryL on February 01, 2014, 12:27:01 pmThis might be the issue. Glycerin does seem to get converted to acrolein during combustion and (according to Wikipedia) there is a correlation between acrolein in tobacco cigarette smoke and lung cancer. In the US, OSHA has set the occupational limit for acrolien exposure to be .1 ppm. However, given the small amount of flux used and the even smaller amount of glycerin in the flux, it doesn't seem likely that using glycerin in homebrew flux would be a problem. But I haven't done the math to see what the maximum possible level would be in a normal soldering scenario.

author: VK3DRB
author_rank: Super Contributor
timestamp: February 02, 2014, 12:44:10 am
content: Personally, I use tin/lead solder and am prepared to take the risk to get a great solder joint.Here is an interesting report from some greenies regarding toxic chemicals used in electronics...http://www.greenpeace.org/international/PageFiles/24478/toxic-tech-chemicals-in-elec.pdfI

author: jwm
author_rank: Regular Contributor
timestamp: February 03, 2014, 03:26:08 am
content: Quote from: quint on February 01, 2014, 11:19:38 pmThat is during combustion, i.e. actual burning of the glycerin. During soldering it boils off at 290C which is a very different thing and doesn't change it chemically.John