Looking for a good flux - Page 1
Forum section: electronics / beginners

author: nbritton
author_rank: Frequent Contributor
timestamp: October 14, 2015, 03:28:49 am
content: I'm assembling an order on all-spec.com, and one thing I need is a good flux pen. I'm not sure what to get, they recommend Kester 186, but from what I understand that is an RMA flux. Don't I need RA? For a hobbyist does it make sense to buy an empty pen and a bottle of flux?Kester 186 Flux PenBonkote BON-102-1 Empty Flux PenChemtronics Empty Flux PensAll-spec.com Flux & ThinnersThe other things I'm getting are a 1 LB roll of Kester 44 .020" diameter, Chemtronics #1 through #6 solder wick, ESD-Safe Nylon Brush, and 3C-SA Fine Tipped Tweezers. What else do I need to get me going?

author: miguelvp
author_rank: Super Contributor
timestamp: October 14, 2015, 04:36:34 am
content: I use the Kester 186 Flux Pen and I like it, but I don't have enough experience to say is better than the others you mentioned but it's better for me than the Deoxit Rosin Flux in a syringe.One thing to take into account and the real reason I'm replying is that they will split your shipment since the flux pen is flammable so that has to be shipped ground.

author: nanofrog
author_rank: Super Contributor
timestamp: October 14, 2015, 04:46:57 am
content: 186 is RMA, but it's activity borders on RA. FWIW, RA makes better sense for a hobbyist as it allows you to keep a single bottle of flux that will handle both new and old work (reduced consumables cost without sacrificing quality).As per disposable pens vs. refillable device w/ liquid flux, the refillable route is a lot less expensive. Personally, I'm partial to the Bonkote pens and Kester flux (186 & 1544).Unfortunately, Kester doesn't sell hobbyist friendly sized bottles (1gal is the smallest), so you either have to find a vendor that breaks it down into smaller bottles (potential risk of getting a counterfeit*), or opt for MG Chemicals 835 (125ml size). It's an RA flux of excellent quality (youmightneed to thin it just a bit to get it to flow easily through a Bonkote pen, as another member recently reported an issue with this).*I found an eBay seller that seems to sell genuine Kester in small bottles (has the right smell to it, and performance is on par as well if memory serves correctly at any rate; seller =Dickie's Garage Sale).CML Supplyalso breaks some Kester products down into smaller sizes suited for hobbyists, such as RF741 no-clean paste flux, and EP256 solder paste (they only offer liquid flux in their own Tekline labeled pens). They also have aneBay store.

author: JoeN
author_rank: Frequent Contributor
timestamp: October 14, 2015, 05:41:45 am
content: I use MG Chemicals 835-P Rosin Flux Pen. Found them at Fry's and buy them usually on Amazon now, throw them on orders with other stuff to get over the $35 limit. They work well for me. All-Spec sells them too.

author: Cliff Matthews
author_rank: Unknown
timestamp: October 14, 2015, 11:48:30 am
content: https://www.eevblog.com/forum/beginners/ra-vs-no-clean-flux/

author: LukeW
author_rank: Frequent Contributor
timestamp: October 14, 2015, 02:02:56 pm
content: Any recommendations for a good RA/RMA flux from a distributor in Australia?

author: nbritton
author_rank: Frequent Contributor
timestamp: October 14, 2015, 08:12:43 pm
content: Quote from: nanofrog on October 14, 2015, 04:46:57 amI found all my old electronics components in my storage unit, I forgot I had thousands and thousands of old chips and jelly bean parts that I pulled from dead boards. They are all oxidized so I think it would be smart to get a RA flux.Quote from: nanofrog on October 14, 2015, 04:46:57 amIf I buy a bottle of MG Chemicals 835 flux how long will it last and when does it expire, and if I kept it in the refrigerator would it last longer? Do I use isopropyl to thin it out?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 14, 2015, 08:33:27 pm
content: The flux pens I've tried (something or other in an alcohol base) were all rather mediocre to my taste. The solvent carrier evaporates and spatters when the iron is brought in, and pushes all the goo away from the exact freaking place you need it. And the goo isn't very effective to begin with; a low reactive/volatile fraction (maybe this is just RMA vs. RA) means it doesn't clean very well, which is the very purpose I wanted it for in the first place.I've had quite good experience with RadioShack goo, actually. It's in a high-boiling solvent (think I've heard of petroleum jelly for this purpose, but it actually claims an ethylene glycol base), and is reasonably reactive (it doesn't say what type of activation, unfortunately). It doesn't spread badly, and evaporates more slowly. I can solder under a blob of the stuff if I want, though that's a rather intense and wasteful use.I don't have the catalog number offhand, but I think it's the same stuff that's still on the shelves, if you happen to still have an RS nearby.Tim

author: John Coloccia
author_rank: Super Contributor
timestamp: October 14, 2015, 08:39:27 pm
content: 186 is what I use. Please be aware that while heated flux turns into something like amber and can be left on the board, unheated flux must be cleaned off. Essentially, if you ADD flux above and beyond what's in the solder, be prepared to properly clean the board. This comes straight from one of the experts over at Kester that I had the pleasure of chatting with. As a workaround, he suggested simply applying a small amount of flux to the component lead (either a light dipping or brushing, something like that) if you just needed a touch more, and that should be OK without additional cleaning.That said, I HATE the flux pens, but there's a fix. Get a flux dispenser (I like the little glass bottles with the brush in it) and buy a flux pen. When it shows up, grab some pliers and twist off the tip end of the pen. The cap that the tip sits in is just pressed on. It will come right off and you can pour the flux into your dispenser. Ta da!

author: nanofrog
author_rank: Super Contributor
timestamp: October 14, 2015, 11:23:25 pm
content: Quote from: nbritton on October 14, 2015, 08:12:43 pmI would think so.Depending on just how badly they're oxidized, you they might also require some mechanical abrasion prior to soldering. An ink eraser or fiberglass scratch brush are great for this, and both are inexpensive should you need to do this.Quote from: nbritton on October 14, 2015, 08:12:43 pmHow long it will last depends on both how frequently you use it, and how much you use per joint (i.e. PTH, passive SMD, drag solder an IC, ...). You'll go through it faster doing mostly drag soldering vs. SMD passives for example. Generally speaking however, that bottle of MG Chemicals should last you quite a while (may even be years).It doesn't have an expiration date, but you do want to store it in a cool dry place (refrigerator is unnecessary). Even if it did have a date, you'd still be able to use it, just like a roll of solder wire.You can thin it with alcohol (isopropyl, ethanol, or methanol), or acetone, and all of which should be easily found in local stores (Kleen Strip brand Denatured Alcohol = ethanol + methanol mix). The same brand also sells acetone, as well as xylene, which mixed with ~80% alcohol, makes a great DIY flux cleaner (more aggressive than plain alcohol, but not as aggressive as acetone, which tends to solve plastics). No need to order expensive containers of 99+% IPA at $30+ per gallon either, as 1gal of Kleen Strip Denatured Alcohol was ~$16 last I checked at HomeDespotDepot. Works better than IPA as well (ethanol, methanol, and IPA = most to least aggressive for alcohols IIRC).Quote from: T3sl4co1l on October 14, 2015, 08:33:27 pmWhat exactly were you using?Quote from: John Coloccia on October 14, 2015, 08:39:27 pmInteresting. Did he give the exact reason for this?I ask, as the information I've come across has indicated that rosin and no-clean flux are only active while heated, so neither fresh flux or residues are corrosive (from product info/datasheets IIRC). Only things I can think of, are the solvents are flammable and possibly conductive (ethanol and methanol are, as they're polar molecules; isopropyl alcohol and acetone are not). And both of these issues are temporary.Quote from: John Coloccia on October 14, 2015, 08:39:27 pmStill expensive, but if you don't want to break down a gallon of Kester yourself, and don't trust eBay sellers that claim to do so, then it's the one way you can be sure to get the real thing in small quantities.BTW, I'd be willing to go in on 186 (186-18 would be even better, as lower solids = easier to clean), or 1544 .

author: John Coloccia
author_rank: Super Contributor
timestamp: October 15, 2015, 12:42:34 am
content: Quote from: nanofrog on October 14, 2015, 11:23:25 pmIt's true that when you heat the rosin core, it activates and becomes acidic. Here's the thing: when they test these fluxes for corrosion, they test the properly activated and cooled flux. That sorta' hard amber shell you get actually helps to seal the joint, particularly the flux, and if air/moisture can't get to it, corrosion can't happen. When you add additional flux by hand, there's just no way you'll ever properly heat all of that up with the possible exception if you add just a tiny amount to the lead before insertion.None of their corrosion specs apply to uncleaned liquid flux, unactivated flux residues, burnt to a crisp flux, dissolved and sloshed around flux from poor cleaning, etc. It ONLY applies to a properly soldered joint left undisturbed. This is why the general consensus is that if you can't clean the board properly, and just a 2 second rub with IPA will not clean it properly, it's much better to just leave the joint alone. Once you start spreading around all of the stuff inside the joint, you really should properly remove it at that point. I think we all know this as the common wisdom, but this at least partly accounts for WHY it's so.When you think about it, it all kind of makes sense, but who spends time thinking about this stuff? My products are lifetime warranted so *I* worried about it just a little and called Kester to have a nice chat about fluxes and lead free alloys, but it's a pretty boring subject and it's hard to get good information anywhere except right from the source.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 16, 2015, 12:02:39 am
content: Afraid I don't remember which pen it was (Kester, MG, ?)...Hard deposits are relatively okay, because physics. Rosin is a mixture of organic acids, which like acetic acid and others, ionizes in water. The acids present in this case are relatively large, fatty kinds (that can be made into soap, just like the more familiar straight-chain fats we eat), which gives them a higher melting point. The flux, straight out of the dispenser (for whichever mixture you have), is rather mobile because of lower boiling components (solvents, carriers, lighter (and more reactive) fatty acids), which evaporate (hence the wiff of delicious (or not) odors while soldering with it!), leaving a hard, crusty deposit.Now, if it's solid, it's *solid*. Nothing's moving, not molecules, not ions, not electrons. So, it's a good insulator. Compare solid ice to liquid water, or, well, solid most anything nonmetallic. (Even table salt starts an insulator, then becomes a quite excellent conductor when it melts around red hot.)This is, of course, complicated by trace liquids. Not everything evaporates, at finite temperature and time. Some solvent will be left. Especially on humid days, water will be hanging around, and condensing on the surface (at the molecular level, at least), and diffusing into the deposit. Leakage will certainly rise. How much, depends on how hydrophobic the deposit is, and so on. (It's pretty waxy or crusty, so usually not a big deal. But hey, on some scale or another, say, teraohms or greater...)Tim

author: zapta
author_rank: Super Contributor
timestamp: October 16, 2015, 03:14:22 am
content: Quote from: nanofrog on October 14, 2015, 04:46:57 amHow does the 186 compare to the MG 835 in wetting effectiveness, thickness (how well does it flow) and stickiness (the 835 I got is more sticky that super glue ;-)).

author: nanofrog
author_rank: Super Contributor
timestamp: October 16, 2015, 04:21:44 am
content: Quote from: zapta on October 16, 2015, 03:14:22 am186 performs better IME, and do prefer it to 835 (don't get me wrong, the 835 isn't junk by a long shot, it's just not *quite* as good overall, particularly regarding the stickiness/harder to clean aspect). The primary reason I tend to recommend 835 is it's easy to get small amounts in a cost effective manner than 186.186 spreads better (thinner; not quite water, but not far off either), wets fast (~ instantly on light oxidation), and if you get it hot enough to activate and drive out the solvents, it dries to a hard, translucent amber shell. Otherwise it will be sticky, such as what spreads out with drag soldering that's not heated sufficiently (not as sticky as 835 though; cleaning highly advised).FWIW, Kester's 1544 would be a more appropriate comparison to 835 as it's RA; ultra fast wetting, thicker than 186 (~ light pancake syrup), and will definitely be stickier than 186 if it's not thoroughly heated, as there's a higher % of rosin IIRC.Also, realize it takes just a tad longer for liquid flux to drive out the solvents than with solder wire due to the higher solvent content, so this may be part of the cause with the stickiness issue you're running into.Get a disposable pen, and give it a go and see how you like it or 1544 vs. the 835.

author: zapta
author_rank: Super Contributor
timestamp: October 16, 2015, 05:55:32 am
content: Quote from: nanofrog on October 16, 2015, 04:21:44 amThanks, I will give it a try. This guy on ebay sells in small quantitieshttp://r.ebay.com/NvqhmkAs for the 835, just a minor touch with my finger or hand and they become sticky. Works well otherwise.BTW, I had bad experience with the Bon Pen, evan with kester 951 which is watery. I am a hobbyist and use the flux occasionally, sometimes not touching it for a week or two, and it difficult to re-prime it after long intervals. May work better for pros that use it daily. I got instead a R&R Lotion FD-1 with #26 needle and it works much better. To open the needle I place a hot iron for a second or two and it then flows easily, even with non diluted 835.

author: nanofrog
author_rank: Super Contributor
timestamp: October 16, 2015, 09:13:43 am
content: Quote from: zapta on October 16, 2015, 05:55:32 amI've bought a bottle of 186 from this seller, and I think it's genuine.Quote from: zapta on October 16, 2015, 05:55:32 amThe solvent will evaporate out if they just sit, so thinning it out would be necessary (incl. the brush by giving it a short soak), and occasional thorough cleaning of the brush head. I like the control & ease of use enough that it would be worth the hassle IMHO.FWIW, Kleen Strip Denatured Alcohol will do both inexpensively (~$16 per gallon @ Home Depot, so cheaper & easier to find than IPA in gallon containers).Given it's sitting for a week or so at a time, a nail polish brush bottle may even be a better alternative to the needle bottle (solvent can evaporate through plastic). For example, I can smell acetone on the outside of the bottle of 186 I purchased from the eBay seller linked above (no spillage to generate the odor).

author: John Coloccia
author_rank: Super Contributor
timestamp: October 16, 2015, 02:59:41 pm
content: Pretty much all of the issues with longer term storage are why I simply take the pens apart and put them in my own dispenser (glass bottle with a brush). Buying a gallon, even if you share it, is just way more hassle than it's worth, and just one or two pens worth of flux is enough to last a very very long time unless you're painting your boards with it. I also have a local supply for 186 pens so I don't even pay shipping.

author: veedub565
author_rank: Frequent Contributor
timestamp: October 16, 2015, 08:06:32 pm
content: Can't say I'm a fan of flux pens, never found them to be very good. not sure if you can get this where you are but I prefer No-Clean NR205 flux, in a small bottle with a needle dispenser.

author: GreyWoolfe
author_rank: Unknown
timestamp: October 16, 2015, 10:27:11 pm
content: Quote from nanofrog-No need to order expensive containers of 99+% IPA at $30+ per gallon either, as 1gal of Kleen Strip Denatured Alcohol was ~$16 last I checked at Home Despot Depot. Works better than IPA as well (ethanol, methanol, and IPA = most to least aggressive for alcohols IIRC).If you REALLY want 99% alcohol, here it is for $23 USD plus shipping.https://www.healthykin.com/p-4898-99-isopropyl-alcohol.aspx?gclid=Cj0KEQjwwIKxBRDKhOz7ytT30vkBEiQAT1NaPdrTrpsqFGcT3qzciwln6SSFuC1Nmh10DIOQ3micbYIaAhto8P8HAQ

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 17, 2015, 05:30:27 am
content: Am I the only person who still likes rosin paste flux for anything but SMD? You can dip your leads in it, to smear it on a wire, or hole with a fine wire (I use a breadboard lead like a toothpick to apply the stuff.My dad always used paste, and I kinda grew up with it. Seems to work a treat, with the solder flowing wherever I apply it.

author: veedub565
author_rank: Frequent Contributor
timestamp: October 17, 2015, 04:17:38 pm
content: I've used rosin paste flux, that's also pretty good, can't remember which brand it was.

author: GreyWoolfe
author_rank: Unknown
timestamp: October 17, 2015, 09:59:26 pm
content: I use the MG Chemicals liquid RA flux with either a cheap 2 oz bottle with needle or a syringe for playing with smt practice soldering kits. I can easily control the amount of flux I dispense with either.