Everything is always a sticky mess when I try to solder - Page 1
Forum section: electronics / beginners

author: Cyber Akuma
author_rank: Regular Contributor
timestamp: April 19, 2025, 08:08:06 pm
content: This does not feel normal, and I am pretty certain it has to be the flux I am using, MG Chemicals 8341. It's a flux paste that comes in a syringe and claims to be "no clean".Well, it's definitely not no-clean as it leaves a brown residue everywhere, but even worse, it's the stickiest and hardest to clean substance I have ever dealt with! During my last soldering session I had gotten flux brushes and pretty much every few points I soldered I wiped the PCB down with alcohol using the brush. The brown residue had been cleaned off but it was still sticky. I cleaned it. I cleaned it again. I wiped it down with paper towels, sprayed it directly with the alcohol, the more simple components I even practically baptized the damn things in alcohol... and then an hour later when I went to touch one of the parts I had soldered... it was still sticky, AND it made my hands sticky again if I touched them.Even cleaning it off my hands was near impossible, had to wash with soap and alcohol a dozen times before it finally came off... and just touching one of those also thoroughly cleaned parts for one second makes my fingers sticky all over again.This does not seem normal, I have soldered long in the past before when I had much less of an understanding of how to do it right and cheap equipment and the results were never... sticky. Am I doing something wrong? Is this flux expired? Is this particular flux just like this? I don't see how unless you are going to directly put whatever you soldered immediately into a casing to never be opened again considering the residue it leaves... and that's WITH very very very through cleaning of this "no clean" flux.If the 8341 flux really is just like this, what about the MG Chemicals 836LFNC? That one is a liquid, does that one leave a sticky mess too? Or is there a good one people can recommend that does not? Or have any tips on how to avoid the 8341 causing a sticky mess if I am somehow doing something wrong? (Are you actually not supposed to wash it off or something? It's sticky whether I leave it on or try to clean it off, but it feels like it becomes even stickier when it comes into contact with alcohol or water).Feels like everything I have soldered is useless now too since it's basically a toxic hazard to touch.

author: coppercone2
author_rank: Super Contributor
timestamp: April 19, 2025, 08:16:01 pm
content: wet agitate with stiff brush and spray rinseYou will find for a professional flux remover then specify how many miligrams of flux is soluble in 1ml of substance. And its cold comming out of the can so it might be less soluble.Those fast evaporating expensive flux removers do what you want, with alcohol you need to agitate it with a brush, its not super soluble in alcohol. You probobly need to follow up with a flux remover for the type of flux you are using. Alcohol is good for initial cleaning but it won't mop it up for youAnhydrous alcohol has no water, so if your flux is water soluble... it won't be doing much.Maybe your using a alcohol that has a high water content? For rosin you want anhydrousAlso, are you roasting your flux? Temperarture might be too high. If you run it hot you get some real black residue thats impossible to take off without deep scrubbing.

author: Grandchuck
author_rank: Super Contributor
timestamp: April 19, 2025, 08:18:41 pm
content: Does not sound normal. Buy some new flux.

author: coppercone2
author_rank: Super Contributor
timestamp: April 19, 2025, 08:21:34 pm
content: Specify solder type and tip temperature.

author: coppercone2
author_rank: Super Contributor
timestamp: April 19, 2025, 08:22:59 pm
content: And do a test, get a piece of blank pcb, solder to it, then do tests. Alot of people stop being thorough when there is parts in the way. Can you clean a flat solder joint?

author: prosper
author_rank: Regular Contributor
timestamp: April 20, 2025, 03:44:22 pm
content: the flux datasheet might offer some guidance. There are definitely some fluxes that don't cleanup very well with alcohols and solvents. 'no clean' fluxes are usually hardest *to* clean. Some specify a saponifier, which is essentially a strong, alkaline. Powdered laundry detergent might work. Its gonna be conductive, so you'll need a thorough second washing in water (distilled would be best), and then drying (compressed air works good).

author: prosper
author_rank: Regular Contributor
timestamp: April 20, 2025, 03:54:18 pm
content: I'd also add that one of those cheap jewelry ultrasonic cleaners does miracles. And for really glazed on flux, brake cleaner is good (chlorine-free ones sometimes have MEK or acetone in them, which may damage some plastics).

author: xvr
author_rank: Frequent Contributor
timestamp: April 20, 2025, 04:26:29 pm
content: I could personally recomend Kontakt PCC (https://www.kontaktchemie.com/koc/KOCproductdetail.csp?division=&product=KONTAKT%20PCC&ilang=all&plang=all)Very effective cleaner, removes everything

author: Kasper
author_rank: Frequent Contributor
timestamp: April 20, 2025, 11:48:22 pm
content: This is what I usually do:Avoid flux when soldering discretes and T/H.Use sparingly on fine pitch ICs.Use when tinning wires, half the time.Use short brush. Cut bristles shorter if needed.Dip brush in 99% isopropyl alcohol.Scrub area with flux.Lay down kimwipe on flux/alcohol.Scrub brush over kimwipe.Move kimwipe so dry part is over alcohol.Repeat last 2 steps.Alcohol loosens flux, kimwipe removes it. Without kimwipe, alcohol just spreads the flux around and evaporates, quickly, leaving the flux behind.

author: sleemanj
author_rank: Super Contributor
timestamp: April 21, 2025, 12:16:55 am
content: Sounds like rubbish flux to me, unless maybe you are soldering at some crazy temperature, or using a solder with some flux core that is reacting with it.I just use cheap chinese "Amtech" RMA-223 knock off you can get all over Aliexpress, have been for years, completely fake of course in terms of brand, but it works just fine, it's not no-clean but no-clean is very rarely actually no-clean I understand.

author: Bud
author_rank: Super Contributor
timestamp: April 21, 2025, 01:55:32 am
content: The 8341 is a tacky flux and it is for surface mount soldering. The datasheet says it leaves clear non-tacky residues, totally opposite to what you said. If you use it for thru hole components I am guessing it is a wrong one for that.

author: shabaz
author_rank: Frequent Contributor
timestamp: April 21, 2025, 03:31:21 am
content: Quote from: Kasper on April 20, 2025, 11:48:22 pmExactly that..I have 8341 flux (purchased from a distributor so it's definitely genuine MG 8341). If IPA is used (I do that for non-critical SMD prototyping although I do have a can of flux cleaner too) then simply it needs a very firm/stiff brush to scrub (brush first dipped in IPA as you say), and needs to be wiped off with a lightly IPA-soaked paper wipe followed by dry wipe. Visually the result is then spotless.Screenshot shows the brush I use, it's firm as mentioned (unlike many of the cheaper brushes from Amazon).

author: Cyber Akuma
author_rank: Regular Contributor
timestamp: April 21, 2025, 11:04:52 pm
content: The alcohol I was using was 91%, does 99% make that big a difference? And would that even do anything or would it still not work for removing MG Chemicals' fluxes, either the paste or liquid no-clean ones?Is Chip Quick's flux any good? They state that theirs can be cleaned off with just isopropyl alcohol, and there is one that they claim even just washed off with water (Though I am skeptical if that flux would be any good at that point).Would liquid flux even work for through-hole soldering? Or would it just spill through the hole and make a mess on the other side of the board?Quote from: coppercone2 on April 19, 2025, 08:21:34 pmKester 63/37 SN/PB and I was mostly soldering at 350, but a few points I did at 375Quote from: coppercone2 on April 19, 2025, 08:22:59 pmWhat kind of tests exactly?Quote from: prosper on April 20, 2025, 03:44:22 pmI see, these flux removers seem to cost even more than the flux, and come in a smaller container. That's a little worrying considering how much alcohol I used up during soldering, feels like I will go through these quick.Quote from: prosper on April 20, 2025, 03:54:18 pmAre those safe to just put electronics into?Quote from: xvr on April 20, 2025, 04:26:29 pmCan't seem to find it to buy, appears that it's not allowed to be sold in the US? Amazon says they will not ship it here.Quote from: Kasper on April 20, 2025, 11:48:22 pmSo I shouldwen't use flux at all on though-hole components? Not sure what you mean by discretes, like IC chips?And wouldn't those kimwipes tear up on all of the points sticking out and leave lint everywhere? That's why I was using a brush.Quote from: Bud on April 21, 2025, 01:55:32 amYeah, it was definitely not clear, it was leaving an amber-colored residue. It was sticky even before cleaning it, but it almost feels like liquid coming in contact with it makes it even more sticky? I tried checking some of the parts I soldered from last time, and some of them that I had not thoroughly cleaned were still sticky a week later, others that I had cleaned well seemed to not be very sticky, but if I tried cleaning them they became sticky again.Is this stuff not even coming off at all? I feel like I can't even use any of these components without having to thoroughly wash everything they touch every time now, is this stickiness left over still hazardous?Didn't even realize I would need a different flux for through-hole and surface mount, is there any decent flux that just works for any situation?Quote from: shabaz on April 21, 2025, 03:31:21 amI see, I was using some cheap flux brushes for now, I was planning to get those Weller brushes later, but those didn't seem very different either. $22 for a disposable brush seems like a bit much, is that the only option? As for wiping it off with paper wipes, wouldn't all of the solder points, especially from the pins of the through-hole components, just tear it up?

author: shabaz
author_rank: Frequent Contributor
timestamp: April 22, 2025, 12:49:55 am
content: I've even often used 70/30 IPA if that's what's lying around, at least it seems just as usable with 8341 flux.A very firm toothbrush might work, but I've never tried it. The $22 brush will last ages (I purchased it more than 10 years ago, still going strong). I think it's worth it, but agree it feels annoyingly expensive for what it is.Paper does snag, but it hasn't bothered me much; occasionally there might be a few very fine (finer than hair) paper fibers on the board. I'm not doing production work. I do have MG Chemicals IPA wipes too, they are tougher but more expensive. At a pinch I've sometimes used silkscreen IPA wipes if they are nearby (they are cheap, but are physically large so it feels wasteful, hence I'd rather use paper wipes if the board is just for my consumption; worth experimenting with whatever you have, in case you find it meets your needs).The attached photo shows an example board where I used 8341 flux and IPA. I'm sure there are places where there are still remnants of flux or paper fibers, easier to spot in a high-res photo, not so easy to spot when working with bare eyes.In summary I've never found 8341 to be a problem, I do have a couple of other brands of flux, but not used them as much as 8341, others may have better opinions from their experience.Ordinarily, for through-hole work, I don't use any flux; the solder I use contains enough flux for untarnished components and PCBs. If the leads are tarnished, they can be cleaned (some people use fiber brushes, but lightly scraping/sanding is an option too, since presumably old tarnished components are for non-critical use). Sometimes I will brush on a fine layer of liquid flux onto a PCB before soldering parts to it (for instance, some prototyping stripboards/perfboards benefit from that, when they are slightly oxidized).

author: Kasper
author_rank: Frequent Contributor
timestamp: April 22, 2025, 03:46:51 am
content: Chip quik works fine for me.I use these brushes, after cutting bristles short at about 30°.https://www.digikey.ca/en/products/detail/mg-chemicals/855-5/949490Don't slide the kimwipe on the PCB and it won't tear. They are designed to not leave lint etc.Lay it down, brush over it.Move the brush, not the kimwipe.Lift and move kimwipe.Repeat.I was taught this when I soldered airplane radios in a strict production environment.Brush and iso doesn't remove the flux, just loosens it briefly, until the iso evaporates and the flux doesn't.Discretes are resistors, capacitors, etc.I don't have a rule on when I use flux. I usually try to avoid it and then use a bit if I'm struggling.

author: Kasper
author_rank: Frequent Contributor
timestamp: April 22, 2025, 03:49:21 am
content: I also tend to use fairly large diameter solder. Rumour has it you get more flux out of the larger stuff. I'm not sure the math agrees but it seems to work better for me.

author: Bud
author_rank: Super Contributor
timestamp: April 22, 2025, 03:59:58 am
content: TLDR; The point is this flux may change its properties once heated in the reflow oven, all of it. Then it becomes non-sticky and clear. If you use it for thru hole, you are not heating all of it, hence is the messiness you described. This is what i think is happening.

author: wraper
author_rank: Unknown
timestamp: April 22, 2025, 04:11:58 am
content: Sticky mess is what to be absolutely expected when using tacky flux for hand soldering. It's not even really meant for soldering with soldering iron. Don't want to wash it off? Use regular rosin flux core solder without adding any additional flux, or add some liquid flux. Additional flux normally is not needed unless drag soldering anyway. If you cannot do a decent solder joint without adding a ton of tacky flux, it's just not learning a proper soldering skill and compensating it with a pool of long working time flux.

author: Smokey
author_rank: Super Contributor
timestamp: April 22, 2025, 05:58:32 am
content: If you actually want to get the majority of the flux residue off, one way is to scrub with alcohol and a toothbrush then rinse with more alcohol than you think you need. Repeat until you don't get the white sticky residue all over the board. Yes this uses a lot of alcohol.No clean just means that it won't attack the boards after soldering, not that it won't leave a residue. Also note that if you didn't get it hot enough to activate all the flux (which you probably didn't unless you reflowed the whole board) then it still might attack the board.

author: xvr
author_rank: Frequent Contributor
timestamp: April 22, 2025, 11:38:06 am
content: QuoteI bought it through Farnell. It was considered a dangerous goods, so others did not undertake to supply it.

author: wraper
author_rank: Unknown
timestamp: April 22, 2025, 11:47:55 am
content: BTW, when cleaning, you should remove as much diluted flux as possible before adding any new solvent. You can use something like Kimwipes or good paper towels which do not disintegrate as a much cheaper option (don't use toilet paper), put it over the board ASAP after brushing to avoid solvent evaporation, and brush over it so it fits into crevices and wicks the liquid. It's preferable to use either another dry brush or squeeze wet one with a wipe before brushing to not compromise wipe's liquid absorption capability. The less liquid will remain on the PCB, the less further cleaning it will need. Certainly remove liquid from the brush between cleaning passes to not reintroduce dissolved flux onto the board.

author: tooki
author_rank: Super Contributor
timestamp: April 22, 2025, 06:51:24 pm
content: Quote from: Cyber Akuma on April 19, 2025, 08:08:06 pmI have used a lot of that flux. What you go on to describe is perfectly normal for a tacky no-clean flux.First off, the elephant in the room: theterriblename "no-clean". It emerged for historical reasons to mean "flux with small amounts of harmless residues", but what the name doesn't say is what "no-clean" really means in the context oftackyflux: "flux that leaves small amounts of harmless, visually unobjectionable residueswhen used in reflow soldering, applied as a component of solder paste". (Yes, tacky fluxes are really designed to be the flux part of solder paste. Every other use is secondary at best.)This means that in their intended application, the amounts used areabsolutely minuscule, unlike the pools of flux used in rework, and in reflowing, the flux doesn't get heated as hot as in hand soldering, where it comes into direct contact with the tip (300-400°C), which is significantly hotter than it gets when reflow soldered (~240°C).Note also that many no-clean fluxes remain corrosive if not thoroughly heated.Tacky flux that melts and flows away from the iron has not reached this temperature! So you must remove it when hand-soldering.Quote from: Cyber Akuma on April 19, 2025, 08:08:06 pmNo-clean fluxes are notorious for being much harder to clean than traditional rosin fluxes. Cleanability isn't really a design criterion, since the point is to not clean it.Quote from: Cyber Akuma on April 19, 2025, 08:08:06 pmMop up excess flux with a tissue before you apply any solvent.Quote from: Cyber Akuma on April 19, 2025, 08:08:06 pmProbably using too much flux, and definitely not cleaning correctly.Forget alcohol. I know that most people online recommend straight IPA for flux cleaning. But that is, to put it bluntly, bad advice for the vast majority of fluxes. Most fluxes today are not fully cleaned with just IPA. You need to use a solvent blend that contains alcohol and something else, like a hydrocarbon (e.g. hexane) or acetone.I do a lot of flux cleaning with an eyeballed 50/50 blend of ethanol and acetone, but since acetone is aggressive to a lot of plastics and dissolves a lot of component markings, I don't use it for everything. For the rest, I use commercial flux cleaner. I use Electrolube LFFR, but in USA you'll find other brands to be easier to get, like Techclean. Any solvent-based commercial flux cleaner should do fine.Remove as much flux as possible without solvent by mopping it up with tissue. Then apply solvent and use a brush to work it in, dissolving the flux. Keep it wet with solvent. Then mop that up. Repeat if necessary. Optionally, give a final rinse with solvent.If you have access to an ultrasonic cleaner, this facilitates cleaning (especially underneath components) dramatically.I also suspect your iron may be a bit too hot.Quote from: Cyber Akuma on April 19, 2025, 08:08:06 pmIt's not expired (does your syringe not have an expiration date on it? Not that it matters, I have a syringe from 2015 and it's still fine), and it's typical for tacky no-clean flux.Quote from: Cyber Akuma on April 19, 2025, 08:08:06 pmIf there is residue of any kind, then by definition your cleaning is incomplete. If it's sticky, then it's poor cleaning, never mind "very very very thorough". You may have spent time cleaning it, but you were not actually thorough.Quote from: Cyber Akuma on April 19, 2025, 08:08:06 pmIt is resin-free so will not leave stickiness. However, because the solids content is very low, it's not going to be a high-activity flux. One pass with the iron and it's gone. This type of flux is useful for slightly improving flow when doing initial soldering, but not very good for rework or for drag soldering.

author: tooki
author_rank: Super Contributor
timestamp: April 22, 2025, 07:31:30 pm
content: Quote from: Cyber Akuma on April 21, 2025, 11:04:52 pmChip Quik fluxes are great. Well, some are. (I do not recommend SMD191, as it can only be heated once and then it's done.) I use their SMD291NL (the NL is important!!) as my everyday flux, since it works reasonably well and has a very pleasant odor akin to roasted hazelnuts, not the "burning acids" smell of most no-clean fluxes, and because it is transparent even when cold, letting you see what's going on better when working under a microscope.Chip Quik does indeed say their fluxes can be cleaned in IPA, but you'll find that using a commercial flux cleaner is much more efficient. The solvent blend simply works better and faster, so you need less of it to get the job done.I've been experimenting with the Chip Quik water-washable no-clean flux and solder wire, and my initial results are very encouraging. As long as you don't burn it with excessive heat, it washes off very quickly in hot water. But do not underestimate the "hot" part: it really only comes clean in 50-60°C water -- i.e. water that is too hot to touch. It's absolutely brilliant in a heated ultrasonic cleaner. What I've been doing is to use straight hot tap water to rinse off any leftover tacky flux, then dunk the board in the 60°C ultrasonic bath for a couple of minutes. Sometimes, if I've overheated a joint, or if it mixed with another flux (like regular rosin), there will be bits that don't come off in water. They will come clean with solvent, though.I have also been using a really weird flux from SRA, model FLS441, which is a flux and cleaner (of sorts). It is not only water-soluble, it actually makes rosin flux water-soluble, too! It does not claim to be no-clean, so I would not leave any residues. Like the Chip Quik, it cleans up best at 50-60°C. (I have not been impressed at all, however, by SRA's "water-washable no-clean" solder wire. It just doesn't want to come off in water.)In any case, when using water washing, I highly recommend using compressed air to blow off the wash water, then giving another tap water rinse, blow that off, then give a final rinse in distilled (deionized) water, then blow that off. (I'm fortunate at work to have deionized water on tap, so I use that for all steps, but it's really only necessary for the final rinse.)(Compressed air is also handy when working with solvents, to blow flux-laden solvent out from underneath components.)Quote from: Cyber Akuma on April 21, 2025, 11:04:52 pmYes, it would work. Yes, it will wick through the holes and make a mess of the other side -- but so will your tacky flux once it melts!Quote from: Cyber Akuma on April 21, 2025, 11:04:52 pmWhich solder precisely? Kester has a bunch of fluxes, and the diameter and flux percentage matter. (Though at least Kester is a really good choice. Kester 44 63/37 with size 66 (3.3%) flux core, 0.6mm and 0.8mm are my daily drivers.)350 is on the high side for leaded solder, 375 quite high. Assuming your tip temperature is accurate, then if you feel the need to go with a high temperature, chances are your tip is too small for the joint, dirty, and/or the station underpowered. I keep my station at 330°C as my everyday leaded soldering temperature.Quote from: Cyber Akuma on April 21, 2025, 11:04:52 pmBecause it's less aggressive, you go through a lot more alcohol than you would flux cleaner. But with experience, you'll tweak your soldering methodology to use less flux to begin with, and develop better cleaning strategies, both resulting in using a lot less solvent.Quote from: prosper on April 20, 2025, 03:44:22 pmWith a few exceptions, yes.You don't want to ultrasonic bathe components that you can't rinse out, like trimmer potentiometers, most environmental sensors (humidity, etc), and switches. The other component that can be sensitive is quartz crystals. Some are killed by the vibration.The best ultrasonic cleaners for electronics are ones with a frequency sweep, which helps prevent localized damage. With that said, the one I use at work doesn't have that, but since cleaning is done so quickly (just a couple of minutes), it isn't a big deal.Quote from: Cyber Akuma on April 21, 2025, 11:04:52 pmNo, there aren't, not exactly. Through-hole soldering typically does not use much, if any, additional flux. What's inside the solder wire is usually enough. The traditional added flux for through-hole soldering is liquid rosin flux. I think MG still makes one.Tacky fluxes specifically are indeed made for surface-mount use, but it doesn't mean they don't work for THT. The key thing is that they're intended to be used in tiny amounts. I use a tiny (#22, I think) needle on my syringe of SMD291NL, which lets me dispense tiny amounts.One downside to the MG 8341 is that it has a tendency to slightly crystallize with age, and those little crystals can then clog up thinner dispensing needles. Not a problem when it's fresh, but becomes an issue after a few years.Quote from: Cyber Akuma on April 21, 2025, 11:04:52 pmI just use cheap acid brushes with natural bristles, snipped short. You can get whole bags of them for next to nothing. Also wood-handle cotton swabs, kimwipes, and cleanroom wipes. I also have some very fine-bristled small paintbrushes for getting between the legs of fine-pitch SMD ICs.

author: wraper
author_rank: Unknown
timestamp: April 22, 2025, 07:47:31 pm
content: Quote from: tooki on April 22, 2025, 07:31:30 pmDidn't try SMD291NLbut I can assure that SMD291 (bought from Digikey) is among the worst I have ever tried. Way worse than Chinesium Amtech counterfeits.

author: tooki
author_rank: Super Contributor
timestamp: April 23, 2025, 06:38:01 pm
content: Quote from: wraper on April 22, 2025, 07:47:31 pmIn what regards?I have tried SMD291 and it performs OK, but I like SMD291NL better because it's completely transparent (amber, but not cloudy) and pleasant to work with. It's not the most active flux, but it does the job for most things. (It's not the best for highly tarnished surfaces, but works well for when you just need a bit of extra flux.)

author: iMo
author_rank: Super Contributor
timestamp: April 23, 2025, 06:59:22 pm
content: "Alcohol" - that could be almostanything, the water (and other ingredients like methanol, benzene, pyridine, castor oil, gasoline, isopropyl alcohol, and acetone) inside may create a sticky mess with the flux. Also it attacks plastic surfaces. Use only 99.5% or 99.9% IPA, buy a gallon or more..

author: wraper
author_rank: Unknown
timestamp: April 23, 2025, 11:24:20 pm
content: Quote from: tooki on April 23, 2025, 06:38:01 pmBecause it's shit in all regards. Short working time, boils with a lot of bubbles during reflow, nasty darkened sticky hard to clean residues, that's when using it for hot air soldering. For soldering with iron, conductive when non-activated, so-so solderability, short working time. And it like escapes from soldering iron, likely due to boiling.

author: Buriedcode
author_rank: Super Contributor
timestamp: April 26, 2025, 05:52:02 pm
content: Quote from: shabaz on April 22, 2025, 12:49:55 amWhat was the adhesive you used to hold the wires in place on that board? I often knock up quick temporary protos like that, but end up using superglue to hold the wires in place, and it looks ugly.

author: shapirus
author_rank: Super Contributor
timestamp: April 26, 2025, 06:27:34 pm
content: Interesting. My experience has been quite the opposite: MG Chemicals 8341 has been the easiest, or one of the easiest tacky fluxes to clean. It's very easily diluted with isopropanol, which makes it easy to remove compared to most other tacky fluxes that I have tried.I would hesitate to recommend it for hand soldering though: it is pretty active in terms of causing corrosion on bare copper, at least before heating. Since full heating cannot be guaranteed when hand soldering, it should be thoroughly cleaned, which ideally means washing entire boards by submerging them in IPA, ideally in an ultrasonic bath (if the components allow), brushing, and replacing the dirty IPA at least once (then brushing again).It works quite well as a flux, though, so if it is possible to wash the board, or if the entire board is heated in a reflow oven, making washing technically unnecessary, then why not.

author: shabaz
author_rank: Frequent Contributor
timestamp: April 26, 2025, 08:18:57 pm
content: Quote from: Buriedcode on April 26, 2025, 05:52:02 pmSorry, I missed seeing this earlier. It's Araldite Rapid, but more recently I've been using Araldite Instant (90-seconds to reasonably solidified). I also use superglue occasionally (e.g. with the finer wires).I've attempted UV curing hand-nail-adhesive to tack down wires, in the past, but I'm uncomfortable with the UV torch. The 90-second Araldite feels way more convenient.Another really useful product for securing thicker cables (or all manner of other uses) is Polydoh. It comes in white (which has slightly better properties) but I used the black version in the attached photo, useful to have both if there are cosmetic purposes (e.g. black strain relief).Polydoh granules are normally softened in hot water, but it's easier to use a hot air tool, and then just mash them together by hand and press into place. When solidified it feels like firm nylon.In the attached photo, Polydoh is being used on the left side of the board and on the right side.I drilled a couple of holes near the DC socket on the left side, and near the cable on the right side, and then pushed the Polydoh partially into the holes, to secure it (it's not adhesive). If Polydoh cools too rapidly, it's easy to re-heat with the hot air tool. Polydoh is really low-cost, quite handy for making up cable assemblies for prototyping purposes too (e.g. if I solder wires to a pin header, then I'll put some Polydoh on the soldered connections and press it into a convenient shape to act as a plug body for insertion into pin sockets on a PCB.(Edit: added photos)

author: Buriedcode
author_rank: Super Contributor
timestamp: April 26, 2025, 09:22:46 pm
content: It's info like this (the above post) that make forums so great. I've used epoxy putty before, but never actual playdough - kind of makes sense for solving certain problems when doing crude/rapid prototyping.I've been meaning to try the UV curing stuff myself - for a while they were all over ebay. But I don't particularly trust adhesives form places like ebay where there is zero info on it, so I've been trying to find a half decent source that's cheap but isn't full-on dental grade. The appeal is controlling exactly when it cures, and for stuff like holding wires down to a board, it shouldn't be a problem getting the light to where it needs to go.I'll have to run some tests and psot on here the results. In the meantime, I'll pick up some araldite rapid. Cheers!

author: Cyber Akuma
author_rank: Regular Contributor
timestamp: May 23, 2025, 05:30:17 pm
content: Sorry that it took me such a while to reply, I was a bit blind sighted by all the replies.Quote from: shabaz on April 22, 2025, 12:49:55 amYeah, visually you can't see any flux when I clean it, but it remains sticky from the stuff to the touch.Quote from: Kasper on April 22, 2025, 03:46:51 amThanks, I'll check those out, seem to be sold at several places. Any opinion on the MG Chemicals or Weller brushes?https://www.amazon.com/MG-Chemicals-Technical-Cleaning-Bristles/dp/B004SPGFT8https://www.amazon.com/Weller-Flux-Brush-Pack-WLACCFB-02/dp/B08FPYK2ZP/Or would a cheap toothbrush work better?Quote from: Kasper on April 22, 2025, 03:49:21 amAll I had on hand was thin solder, I'll have to see about getting different sizes too then.Quote from: wraper on April 22, 2025, 04:11:58 amWould that still work even if there is some corrosion on the component leads? I don't mean they are rusted but look like they might have a small film on them sometimes. I have been practicing on those cheap DIY soldering kits that I got long ago from Aliexpress.QuoteFor some of these I did have to drag-solder a USB 3.0 connector.Quote from: tooki on April 22, 2025, 07:31:30 pmI guess I'll try Chip Quick then, do they also have an equivalent to MG Chemicals 836LFNC liquid flux? Don't really care about the color too much since I can still see the component through the flux, and don't care about the smell at all since I use an exhaust fan and it's not like I should be smelling it anyway.I am just worried if even the flux remover won't do a good job or I will need a lot of it like I needed a lot of alcohol, that stuff isn't cheap and it comes in a tiny bottle while I can seeing that I can get gallons of IPA 99% alcohol for around the price of some of these flux removers that come in 1 oz bottles or 14 oz spray cans.QuoteNot sure if that would work out for me then, I don't have an ultrasonic cleaner or an easy way to get water that consistently hot to clean the board.I have also been using a really weird flux from SRA, model FLS441, which is a flux and cleaner (of sorts). It is not only water-soluble, it actually makes rosin flux water-soluble, too! It does not claim to be no-clean, so I would not leave any residues. Like the Chip Quik, it cleans up best at 50-60°C. (I have not been impressed at all, however, by SRA's "water-washable no-clean" solder wire. It just doesn't want to come off in water.)Quotehttps://www.amazon.com/dp/B09DQ6ZK42Quote350 I think was the iron's default, don't recall (Pinecil, though I have a Hakko FX-888 I want to switch to if I ever get the room to set it up) and I was using a chisel tip. The 375 was for when I was soldering in the large support? grounding? pins of a DB9 connector.QuoteI see, I had watched hours of soldering tutorial videos and pretty much every one kept saying to make sure to use a lot of flux.

author: tooki
author_rank: Super Contributor
timestamp: May 23, 2025, 06:09:39 pm
content: Quote from: Cyber Akuma on May 23, 2025, 05:30:17 pmThey probably do. But that style of flux I find to be rather unsatisfying for hand soldering, especially rework, because you get to heat it once and it’s spent. I’d sooner buy a liquid RMA rosin flux. Messy but easy to clean with solvent.Quote from: Cyber Akuma on May 23, 2025, 05:30:17 pmThere is only one series of soldering videos that I consider a “must-watch”, and that’s Pace’s basic soldering series:Basic soldering:EnglishSpanishFrenchChineseSwedishTheir other series go into more detail on more exotic stuff:Rework and repair:EnglishSpanishFrenchChinesePortugueseAdventures in repair (advanced multilayer board repair):EnglishP.S. you mean “blindsided”.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 25, 2025, 10:30:52 am
content: Quote from: Cyber Akuma on April 19, 2025, 08:08:06 pmI'm also struggling a bit wit flux. I do think you mis-interpret the "no clean" part. In my experience it mostly means that it can't be cleaned off the PCB.

author: Cyber Akuma
author_rank: Regular Contributor
timestamp: May 25, 2025, 11:19:32 am
content: Quote from: tooki on May 23, 2025, 06:09:39 pmI don't understand the "heat it once" issue, isn't it best to solder that part once than re-soldering it multiple times? Not to mention if you needed to melt the solder a little more, wouldn't the flux at that point have already done it's job and cleaned the parts you are soldering?QuoteOh, the pace videos were the first ones I saw, and more than once, even some of the more exotic stuff that I know I will never get around to doing like repairing traces in the middle of a a multi-layer board.Quote from: Doctorandus_P on May 25, 2025, 10:30:52 amYeah, it's become clear that no-clean meant something completely different than I was expecting. I knew that no-clean meant you didn't NEED to clean it, but I assumed it meant that either it completely evaporates when you heat it (it did not) or that it would be easy to clean (which was definitely not the case).

author: Ian.M
author_rank: Super Contributor
timestamp: May 25, 2025, 11:43:28 am
content: Quote from: tooki on May 23, 2025, 06:09:39 pm+1Unfortunately PACE's 'Adventures in Repair' is wrapped in a corny SciFi Indiana Jones style adventure narrative, so watch 7:40 - 23:50 in part 1, 2:40 - 15:30 in part 2, and 5:00 - 20:35 in part 3 to skip the corn!There's also another PACE series - SMD soldering and desoldering:English, posted by former PACE executive, Marc W. Siegel.

author: wraper
author_rank: Unknown
timestamp: May 25, 2025, 02:26:34 pm
content: Many modern fluxes form hard residues intended to be left on PCB, which usually is fine if you apply the flux in thin layer for reflow soldering. Many if not most of them are hard to dissolve with IPA or ethanol once hardened. Therefore you need something stronger like solvent based flux cleaner spray or water based flux remover like Electrolube SWAS which saponifies the flux instead of simple dissolving.

author: shapirus
author_rank: Super Contributor
timestamp: May 25, 2025, 03:55:23 pm
content: Fluxes are typically hard to clean in the "spray IPA then try to wipe off with a tissue" manner.For more or less complete cleaning they need to be actually submerged in IPA (yes, complete boards) and left to soak for a bit (like say 15-20 min). Then the residue is not dissolved, but turns into a gel-like substance that is very easy to remove using a brush. Then the board needs to be rinsed in clean IPA, job done. Ultrasonic helps.Obviously this method isn't usually very applicable for repair job. In this case, there's not much left to do than search for a flux that's eaiser to clean than others.

author: tooki
author_rank: Super Contributor
timestamp: May 26, 2025, 07:20:08 am
content: Quote from: Cyber Akuma on May 25, 2025, 11:19:32 amFlux isn’t only for cleaning the parts: its other major job is to prevent the molten solder itself from oxidizing. When solder oxidizes, it tends to make shorts, icicles, etc. This becomes especially problematic on fine-pitch SMD chips and the like. If you need to clear a short, you basically end up needing to cover it in flux so that you clean all the solder on your tip and the solder that is forming the short.Quote from: Cyber Akuma on May 25, 2025, 11:19:32 amIn another thread, someone recently posted this fantastic white paper from Metcal:https://www.newark.com/pdfs/techarticles/oki-metcal/extendingTipLife.pdfIt has the perfect definition of no-clean (emphasis mine):Quote

author: wraper
author_rank: Unknown
timestamp: May 26, 2025, 10:49:53 am
content: Quote from: tooki on May 26, 2025, 07:20:08 amIt's absolutely incorrect and bears no connection with reality whatsoever. No-Clean flux can easily be 100% solids, like what's inside usual flux core solder. Also low solids flux certainly does not mean no-clean, it can easily be a water soluble flux which must always be washed.

author: tooki
author_rank: Super Contributor
timestamp: May 26, 2025, 08:26:09 pm
content: Quote from: wraper on May 26, 2025, 10:49:53 amI see where you’re coming from, but I think you’re wrong. Remember the context of the statement: “no-clean is a process”. (And primarily, a process intended to simplify mass production, and due to when the trend emerged, especially for SMD.) So the materials are ones designed to support that process. Yes, the flux core of solder wire is 100% flux, but in no-clean solder the size of the flux core is usually substantially smaller, leaving less flux solids on the finished joint. So the flux solids content of the entire solder wire is, indeed, lower. (Traditional rosin flux core solder is around 3% flux; no-clean is 1-2%.) With liquid flux, the difference is massive: 25-35% solids in traditional rosin flux, under 3% in no-clean. Solder paste, when used commercially, is extremely carefully dosed, so the amount of flux residue is minimal.Quote from: wraper on May 26, 2025, 10:49:53 amThey didn’t say that they’re synonyms. Remember: ”all cats are animals” does not imply “all animals are cats”.

author: Cyber Akuma
author_rank: Regular Contributor
timestamp: June 02, 2025, 07:58:43 pm
content: Quote from: Ian.M on May 25, 2025, 11:43:28 amWhat's wrong with a little corn? 🍿Quote from: wraper on May 25, 2025, 02:26:34 pmSo basically, I'm using the wrong flux and this is intended for reflow soldering, not hand soldering? I got it from Microcenter which isn't really a place intended to sell tools for reflow soldering over hand soldering.

author: tooki
author_rank: Super Contributor
timestamp: June 04, 2025, 07:46:23 am
content: The thing is, other than the flux core in solder wire, I don’t think there’s any modern flux specifically designed for hand soldering. Liquid fluxes are designed around wave soldering, and tacky fluxes are designed for reflow.So whatever we use, it’s basically an industrial flux repackaged into small containers. Even if the datasheets list hand rework as a use case, that doesn’t mean it wasoptimizedfor that.

author: Ian.M
author_rank: Super Contributor
timestamp: June 04, 2025, 12:34:04 pm
content: OTOH, back in the day, there were very few electronics grade fluxes for hand soldering and one generally didn't want to use them because either application or cleanup was such a PITA. Repackaged industrial flux is nothing new, and is vastly preferable to century old recipes like powdered rosin in tallow!Any halide free rosin R or RMA (ROL0 or ROM0) flux is suitable for hand soldering, provided you are willing to clean afterwards as required. Your choice whether to use liquid, paste or tacky gel formulations and how to apply it.

author: Cyber Akuma
author_rank: Regular Contributor
timestamp: June 06, 2025, 07:56:53 pm
content: Quote from: tooki on June 04, 2025, 07:46:23 amWhat, so we should not use flux at all when hand soldering? That's the opposite of pretty much every soldering video I ever saw, pace or others.Quote from: Ian.M on June 04, 2025, 12:34:04 pmI'm a bit confused, is that designation written on the flux itself?

author: Ian.M
author_rank: Super Contributor
timestamp: June 06, 2025, 08:15:54 pm
content: Quote from: Cyber Akuma on June 06, 2025, 07:56:53 pmIt *should* be, or at least in its datasheet! See:https://evertiq.com/news/16783, which explains the designations I used.

author: tooki
author_rank: Super Contributor
timestamp: June 06, 2025, 09:32:52 pm
content: Quote from: Cyber Akuma on June 06, 2025, 07:56:53 pmI didn’t say that. All I mean is that when they design a flux, hand soldering is not what they optimize it for. That doesn’t mean it won’t work, it just means that it might have properties we consider undesirable or annoying, because we are using it for something other than what it was designed for.For example, most new flux formulations are either water-soluble or no-clean. That means that they’re either designed to require washing (for the water-soluble kind), or that they’re designed for careful application (i.e. only juuuust the right amount, meaning the minimum needed) for reflow soldering (in an oven, where the flux all gets heated thoroughly) for the no-clean kind. So they aren’t designing no-clean to have residues that are safe if not heated (because in an oven it all gets heated), nor design it to be easy to clean either before or after reflow (because it’s not being designed to be cleaned at all). This doesn’t mean that there won’t be any no-clean formulations that have neutral residues if unheated, nor that there won’t be any formulations that are easy to clean after reflow. But those aren’t design goals.So when we come along and flood our boards with no-clean flux, we are using it in a way it wasn’t designed for. So it might be corrosive if not fully heated (and when hand soldering, some of the flux will melt and flow away before being heated fully), so we have to clean any residues. But because it wasn’t designed for easy-to-clean residues, the residues might be rather stubborn.

author: tooki
author_rank: Super Contributor
timestamp: June 06, 2025, 10:01:30 pm
content: Quote from: Cyber Akuma on June 06, 2025, 07:56:53 pmI’d put it this way: if a manufacturer doesn’t specify a flux’s type (in at least one of the several systems in use), then it’s not a flux I would consider buying.The old US MIL-F-14256 military system is R, RMA, RA, WS (rosin; rosin, mildly activated; rosin, activated; and water-soluble, respectively).The most common system is IPC-J-STD-004B, which uses a 4-character code, like XXYZ where:X is the fundamental flux type: RO (rosin), RE (synthetic resin), OR (organic acid), or IN (inorganic acid). Of these, only RO and RE are of interest for general purpose electronics soldering. OR are the washing-mandatory water-soluble types (which cannot be used for everything), and IN are non-electronics fluxes (plumbing, stained glass, etc).Y is the level of activation, L (low), M (medium), or H (high). Electronics fluxes are generally L or M, and M usually (but not always) requires washing.Z is the halides content: 0 (halide-free) or 1 (contains halides).For example, Kester 44 solder wire is specified as ROM1, meaning rosin, medium activity, with halides, and also specified as having type RA performance. (However, the datasheet states explicitly that it does not require cleaning for most applications.)Here’s whathttps://www.chemtronics.com/essential-guide-to-flux-for-soldering-electronics?srsltid=AfmBOory_4LyNxdDYH0IXPwjmEls6INosDsBgMXGYKh68hWQ4wnhEk0Asays:“Fluxes are rated as RO (rosin), OR (organic), IN (inorganic) and RE (resin/synthetic resin). The activity of the flux solution is rated as L (low activity or <0.5% halide), M (medium activity or 0 to 2% halide) and H (high activity or 0 to >2 % halide). Fluxes are classified for halide ( Cl- or Br-) content as 0 (no halides) or 1 (some halides). The Under this classification scheme an ROL0 flux would be a rosin flux with low activity and zero halides An RMA flux could be classified under this scheme as an ROM1, if it contained 0.5 to 2.0% halide content.”Next is the ISO 9454-1 system, which is a 3-digit period-separated code. For example, the Kester 44 would be 1.1.2 (rosin with halide activator).Finally, there’s the old German DIN 8511 flux system, which uses “F-SW-” followed by a number. The Kester 44 would be F-SW-26 (rosin with halide activator).IPC-J-STD-004B is by far the most commonly seen, followed by MIL-F-14256 and then by ISO 9454-1.All of these are described athttps://en.wikipedia.org/wiki/Flux_(metallurgy)by the way.

author: Cyber Akuma
author_rank: Regular Contributor
timestamp: June 22, 2025, 07:27:55 pm
content: Quote from: Ian.M on June 06, 2025, 08:15:54 pmI gotta say, it's starting to sound like impossible to find a flux that will work for me if I even have to start diving into the datasheet of each one just to do some basic through-hole soldering.Quote from: tooki on June 06, 2025, 09:32:52 pmI see, though a bit annoying in that it's starting to sound like almost all flux is not made for hand soldering anymore. Rather weird when every soldering video I saw both old and new drilled in that you should use a lot of flux when they were hand-soldering.I feel lost in that post you made about all the designations of not just the flux but the wires too and how to know which one to use for what. Nothing like this was covered in the hours of videos or even just written articles I read on trying to learn how to solder. I have no idea what I should even be looking for now or what to do.

author: tooki
author_rank: Super Contributor
timestamp: June 23, 2025, 09:27:10 am
content: Quote from: Cyber Akuma on June 22, 2025, 07:27:55 pmIt depends on how picky you are.The MG Chemicals flux you have already is a fine flux (as long as it’s fresh and hasn’t crystallized, as discussed earlier in the thread). Just use less of it and learn to clean it properly. And (like all fluxes!) avoid burning it — burnt flux is FAR harder to remove than flux residues that weren’t burnt. (It’s similar to how easy it is to clean unburnt sugar from a pot, compared to the nightmare of cleaning off burnt, carbonized sugar.)Get yourself an assortment of conical dispensing tips to put on the flux syringe. Blue size 22 are my usual ones, but sometimes finer is better. With my current favorite SMD291NL flux, I can use very fine tips to lay down extremely small amounts of flux. (Needle tips can be used, but require a lot more force to dispense, so I don’t like them for most fluxes and solder pastes.)Quote from: Cyber Akuma on June 22, 2025, 07:27:55 pmHow is that surprising?!? It’s been probably more than 60 years since most electronics were hand-soldered. Machine assembly has been the name of the game for literally decades. So it makes complete sense that the lion’s share of electronics soldering materials are designed forthat. It doesn’t mean hand-soldering will ever disappearlookentirely, but let’s face it, the vast majority of solder joints are not made by hand.Quote from: Cyber Akuma on June 22, 2025, 07:27:55 pmI have watched many soldering videos, new and old, and I certainly did not come away with that impression. Older soldering tutorials (that don’t deal with SMD) almost never recommended adding external flux at all, instead relying on the flux core of the solder wire.Good SMD tutorials show a small amount of flux being added. Sometimes they use a flux pen, and apply so little flux you can barely see it.I suspect you’re seeing two things:1. A few SMD rework channels show people who apply flux extraordinarily generously. It doesn’t mean it’s necessary or helpful.2. SMD rework videos are under a microscope, which magnifies everything, including the flux. It can make a small amount of fluxlooklike an ocean, when in fact it wasn’t.Quote from: Cyber Akuma on June 22, 2025, 07:27:55 pmThe flux designations are the same for external fluxes and for flux cores in solder wires.The number of alloys you need to concern yourself with fit easily on one hand (63/37, 60/40, SAC305, Sn100 w/Ni and Ge, of which only the first and last are what I recommend; see below).Quote from: Cyber Akuma on June 22, 2025, 07:27:55 pmIn what regard? Flux core? Alloy? Diameter?Flux core: my absolute favorite so far is Kester 44Alloy: if you are OK with using lead, use 63/37. Kester 44 63/37 with size 66 core (= 3.3% flux) is my favorite. If you need lead-free, get one of the newer alloys that contain trace amounts of germanium and nickel. Despite not being the lowest melting point lead-free alloys, they flow the best. I like Felder Ultra Clear Sn100Ni+, but I doubt it’s easy to get in USA. But Kester and many others have equivalent alloys.Size: one size does not fit all. I and many others like 0.5-0.8mm diameter as “everyday” solder (I now use 0.6mm at work, but am still using up my roll of 0.8mm at home), but you will want a bit of fine stuff (0.3mm or so) for some SMD work, and thicker solder (1-1.5mm) is better for large joints. You can twist together multiple strands of a thinner solder to make a fatter one, if (like me) you only rarely need thicker stuff. The upshot is that the “correct” size for a given joint is one that gives you a good balance between fine control of the amount of solder (thin wire = more control over amount) and speed (thicker wire = faster feeding of solder), such that you can complete the joint in the recommended 3 seconds or so. Too thick and you drown the joint in solder. Too thin and you take way too long to make the joint.I am pretty sure the Pace videos do mention this.I think you need to stop overthinking all of this, and instead practice, practice, practice. Get yourself a bunch of kits, solder practice boards, etc. and have at it. You will see how different sizes of solder wire, tips, and joints, and different temperatures, affect the joints. Keep your soldering iron tip wetted with solder so it doesn’t oxidize, clean the tip right before soldering a joint, and never when returning it to the stand (in fact, add protective solder if needed). Don’t run the iron hotter than necessary. And practice. (Did I mention that?)