Good MG chemicals flux ? - Page 1
Forum section: electronics / repair

author: MathWizard
author_rank: Super Contributor
timestamp: January 05, 2022, 02:41:46 am
content: I'm pretty new to buying solder/flux and getting good soldering techniques, I stopped using the cheap waxy types on ebay LOL , but then maybe they are better at some stuff.I have the RA MG chemicals flux, and I guess it works fine as a stronger RA type, but it spits a lot of stuff around, and also can leave a real nasty layer of conductive resin/solder sludge. IDK if it's more the flux or solder, but both are MG chem anyways.For instance, I was soldering NJM2060V which are SOP-16And the gunk would get under the chip, even as I got pretty good and soldering/de-soldering them.And even on proto-boards, I would clean it off with a bare q-tip, and it would look fine under 30x mag, but still be leaking to screw up low-ish impedance section. Once I scrubbed it under hot-water with dish-soap, it was fine.So what's a good flux for IC work, and for proto-boards where I might pack stuff too close sometimes. I see the gel type in syringes, how many $1000/Liter is that

author: abdulbadii
author_rank: Frequent Contributor
timestamp: January 05, 2022, 03:06:08 am
content: IMHO nothing with its type but with solder material composition suitable to the soldered one to succeed solderingAll good flux is good if correspondingly soldered to which materialIMHO IC soldering need low/med solder melting point so avoid its impairment, worked by quality tweezer soldering iron clearly better than usual one

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 05, 2022, 10:14:09 am
content: Note that, failing an ultrasonic cleaner, you're pretty much stuck with goop under the chip (at least, that's been my experience -- I don't have one, either). At least the goop can be under the chip, and not glomming up the pads, causing corrosion and leakage -- at least, until enough condensation occurs to dissolve and spread that residue out again, I guess.Alas, I don't have recommendations, at least as yet; I've been coasting for years on a small tub of goo, which has served me very well. If it gives you any idea of how many years -- it's RadioShack brand.It's finally starting to run low, and I did pick up a syringe of Chipquik SMD291, we'll see how that goes -- but I haven't actually needed to use it just yet so I don't have anything to report. Hm, I hope it even stays fresh for the years that it'll take to go through it...(I also have a not-quite-as-old but still rather old syringe of solder paste, which seems to keep well in the fridge. It gets dry near the nozzle, but the bulk seems to be reasonable still. Not very tacky, also I'm terrible at using stencils in the few times that I do, but even with all that, it's still doing its job.)Tim

author: tooki
author_rank: Super Contributor
timestamp: January 05, 2022, 10:44:59 am
content: Quote from: MathWizard on January 05, 2022, 02:41:46 amMG Chemicals is a good brand, though they don’t have a huge selection of fluxes. Are you using a liquid or paste flux?What kind of solder are you using? Many rosin fluxes don’t like the higher temperatures of lead free solder, causing them to burn, which makes them harder to clean.Ultimately, it comes down to cleaning technique. Paste fluxes, due to their much higher solids content, often require more thorough cleaning. What technique are you using?For many soldering tasks, extra flux isn’t needed. Generally speaking, I try to use the weakest flux possible for a task, e.g. liquid when I only need a little bit, paste for longer soldering operations like rework.Quote from: abdulbadii on January 05, 2022, 03:06:08 amICs certainly do not require special low temp solders. And tweezers, for ICs?!?

author: tooki
author_rank: Super Contributor
timestamp: January 05, 2022, 11:52:58 am
content: Quote from: T3sl4co1l on January 05, 2022, 10:14:09 amOne can accomplish a lot with solvent and compressed air, though!Even just soaking it and giving the PCB a good strong swing in the air can dislodge a ton of trapped gunk.Quote from: T3sl4co1l on January 05, 2022, 10:14:09 amFWIW, in my own corrosion testing, the tube of Radio Shack rosin flux gel was by far the most corrosive flux I tried. It’s absolutely fine once fully heated, but any parts of it that don’t get fully heated absolutely must be cleaned off.Quote from: T3sl4co1l on January 05, 2022, 10:14:09 amThat’s a good flux, but if incompletely heated, is still corrosive. FWIW, I recommend the SMD291NL variant, whose fumes smell like toasted hazelnuts instead of being acrid. Same cleaning requirements. (Basically, every no-clean paste I tried required cleaning if not fully heated. Liquid no-clean fluxes varied much more, with corrosion correlating primarily to how long it took to dry: thin layers that dry quickly cause little or no corrosion, drops that take a while to dry cause corrosion.In my experience, fluxes last way, way, way beyond their expiration dates.Quote from: T3sl4co1l on January 05, 2022, 10:14:09 amYou could thin it with a tiny amount of thinner (IPA, etc). But I do mean tiny, since it takes very little to turn it to liquid. Ask me how I know…

author: xavier60
author_rank: Super Contributor
timestamp: January 05, 2022, 08:51:26 pm
content: I have been using Caig brand flux for a year now and can't fault it. I have checked the leakage with a high voltage insulation tester and was able to detect leakage only while being heated which is expected.The residue is hard rosin which is good for hand SMD work as tweezers only get a bit sticky.It doesn't bubble under components during reflow soldering.https://caig.com/product/caig-rosin-flux-rsf-r80-2/https://www.jaycar.com.au/solder-flux-paste-56g-tub/p/NS3070?pos=2&queryId=1e75f2a99339a6fadb4c9038874eb8bc

author: Vtile
author_rank: Super Contributor
timestamp: January 09, 2022, 12:37:17 am
content: Heh, you can make your own rosin flux, by boiling pine pitch in water, drying in oven at low temperature 50C-100C and then crushing it and finally adding IPA, until the mixture is usable. Easier and more controlled way is however buy the flux somewhere.Also scottsbrite (that green abrasive kitchen sponge) is handy for dry cleaning copper surfaces before soldering (old veroboards etc.), much better than any flux (acids are different case).

author: tooki
author_rank: Super Contributor
timestamp: January 09, 2022, 10:09:03 am
content: I’ve made rosin in IPA, and while it works for very clean components and boards, it’s simply not active enough to use as an everyday flux. There’s a reason standard fluxes (including the flux core in solder wire) use activated flux, not just unactivated rosin.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 09, 2022, 11:43:12 am
content: I've used virgin rosin to tin boards as well. It's cheap and abundant, but not very effective. So I can afford to (and need to) use a lot of it there. I use proper stuff for on-board joint use.Quote from: tooki on January 09, 2022, 10:09:03 amSpeaking of IPA solutions -- I've always found those to be unhelpful? The solvent boils off, spattering rosin everywhere, and moves away from the source of heat, making it impossible to target. Finally, the prepared solutions that I've seen, just aren't very active anyway? Maybe they actually start with virgin rosin... which, it seems pine-ier than usual; that would explain the poor activity too...(And by "prepared", I mean stuff that came from a jar/jug with Kester branding on it. Not, like, ragging on your idea -- it's a good enough idea, certainly others have had the same thought as you can see -- it just ends up not so nice in practice.)I think if you can afford to wait for it to dry up, maybe using a heat gun to accelerate that (i.e., without the targeted heat of an iron), and don't mind that it migrates everywhere, an IPA solution is fine. It's just not very often that I'm doing something like that, and so the goo/gel types are much nicer to use. Or just straight up block rosin, heat the area then dab some around, it stays in place fairly well.Tim

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: January 09, 2022, 02:18:27 pm
content: Quote from: T3sl4co1l on January 09, 2022, 11:43:12 amIf the original poster is referring to MG Chemicals #835 RA liquid rosin flux I have a bottle and it claims:835 is a rosin-based liquid flux with moderate activity. This rosin flux is composed of pure Water White (WW) grade gum rosin in a unique solvent system, combined with highly effective activators. Post-soldering residues from this RA liquid flux are non-conductive, non-corrosive, hydroscopic, non-tacky, and fungus resistant.msds contents:Section 3: Hazardous Ingredientsrosin, polymerized 45–51%butan-2-ol 25–28%ethanol 23-26%I can report it does work OK but I find it messy as hell and it leaves a sticky residue all over. Like Tim says this type migrates even if you only apply a .001 Louis Rossmann's amount.I wish I had paste right now.

author: Vtile
author_rank: Super Contributor
timestamp: January 09, 2022, 10:09:06 pm
content: Quote from: T3sl4co1l on January 09, 2022, 11:43:12 amThe rosin flux and fluxes in general do have two main functions (I'm sure you are much more in tune with the actual chemistry of it) first and most important is the ability to flow the solder by I assume reacting with the impurities (ie. Oxidation) in the molten metal, it kind of liquify the solder, by moving the oxidation from the surface to somewhere and forming a pretective layer on top. In this function the pure rosin works flawlessly (at least with lead-tin solders) even with tiny amounts (10% of solder volume or less). Second property is the cleaning the mating surface from oxidation, for this pure rosin is poor, and for this there is activators added to flux, those are different kind of acids, plain and simple.For many other metal work than electronics soldering, this cleaning process is separate step where first acid bath is used for surface cleaning (with or without washing) and then soldering is done with a rather passive flux. Also interesting thing is that ie. in forge welding the flux is silica sand (old voodoo) or borax powder (modern tech), which liquify and let the iron oxide to flow out from the seam.It is good call to mention the liquid rosin, I did make a bunch of it from self harvested rosin (hardened pitch), without boiling, just melted to IPA and filtered, work as expected (my reason was and is to just "why not") by now the needle nose bottle have a nice thick rosin coating around and I have noticed myself to using that goo more than solution as the solution is impossible to control. Next step therefore is to evaporate most of the IPA and place part ofit to jar with a poke stick and good lid.

author: mazurov
author_rank: Frequent Contributor
timestamp: January 10, 2022, 12:56:34 am
content: If you are OK with the flux performance and just want a less messy dispenser both MG and Kester have their fluxes loaded into felt pen applicators. MG cat.no. 835-P RA, Kester #186 RMA. Both dispense very little flux - my 10ml Kester pen has 2013 date code and still have about 5ml left. They both work very well for SMT IC rework, esp. QFN packages.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 10, 2022, 01:43:09 am
content: Quote from: Vtile on January 09, 2022, 10:09:06 pmYeah, it's probably kinda two things.When you have a liquid surface, if you have a surfactant that can disturb whatever crusties are on the surface, then they can just be kinda washed away and clean metal exposed. I think this is mostly how aluminum metal fluxes work (as in melting of bulk metal) -- in that case mostly a mixture of salts, which disperses the aluminum oxides, but has no chemical or physical reaction otherwise (well, if fluorides are included, some oxide will dissolve), allowing the metal to coalesce into a clean and solid melt. Whereas doing it dry, you can only skim off very sticky shiny goop, taking lots of good metal with it. (This is probably a terrible example as far as familiarity goes,but if you're interested, aluminum melting videos are easy to find online. You can probably get the gist of it, as far as seeing how sticky the dross is -- especially when melting high-surface scrap like soda cans.)The other side of it is actively dissolving oxides, including from solid surfaces. This is where more active (usually acid) substances come along.And yeah, virgin rosin doesn't have too much activity; it is an organic acid, but it's quite a heavy one, and as prone to cross-linking or decomposition at soldering temperatures as it is actually dissolving metal oxides, and at that mainly the less tenacious ones like copper and lead oxide, not so much iron or zinc, say.So, addition of lighter acids, or halogens or stuff that breaks down into more active species (one thing that was used, perchlorohexane IIRC -- yikes -- yeah, I think I'll stick with "low halogen" blends if it means avoiding chemicals like that!), a good way to improve it.QuoteIn this case, the slag/flux acts in part as an acid -- silica and boria are indeed acids at high temperature, they form salts with alkali and other, and displace mineral acids like HCl and H2SO4. It also acts as a solvent, simply dissolving the oxide, whether it's forming a salt as such, or just a mixture. As a glassy substance, it has to be cooled rather slowly to crystallize anything recognizably salty, so, it's not that big of a dealwhatit is, it's just a soup of whatever ions, y'know?And so you have stuff like borax being quite effective for anything from silver soldering to steel forge welding, and slag more or less comparable to soda-lime glass being useful as a cover and cleaner/flux for melting bronze and steel.Interesting note about iron oxide: Fe(II) is strongly basic, being comparable to Mg, Ca, Zn, etc., though not as active as Na, K, Li... Fe(III) is more neutral, along with Al, Ti(IV), etc. Slag in contact with metal, at temperature, is probably going to be the reduced form. So adding an acid like silica will do a good job to make a free flowing glass melt, maybe with some other fluxes to get it going (so, lime and silica are an essential component of steelmaking). And particularly for forge welding, something that's almost watery in consistency helps get it out of the way under the brief impact of a hammer.Tim

author: mazurov
author_rank: Frequent Contributor
timestamp: January 10, 2022, 02:17:55 am
content: Quote from: T3sl4co1l on January 10, 2022, 01:43:09 amBack in the days when computers were large the popular concoction in my place of work was rosin/ethanol mix with diethylamine and triethanolamine added (0.5%-ish v/v of each). The former is a corrosion inhibitor and the latter is an activator. Worked very well, better than RMA on old pins.

author: David Hess
author_rank: Super Contributor
timestamp: January 10, 2022, 06:20:33 pm
content: Quote from: chickenHeadKnob on January 09, 2022, 02:18:27 pmMy benchmark rosin flux is Kester 1544:Rosin, 40-55%sec-butanol, 10-25%ethanol, 10-25%Isopropanol, 1-3%I have never had problems with it spattering, charring, or being difficult to remove.