Some years ago I've also bought Kingbo RMA218 from China, it needs cleaning but worked also good. I've bought it again recently but unfortunatelly some ingredients (or manufacturer) must have changed and now it works very poorly (I even stopped using it).
Which flux has actually the best price vs quality ratio?
SMD291 is the worst tacky flux I tried ever. Wetting not that good, when heated bubbles as hell, leaves ton of awful sticky residues, somewhat conductive. Worse than most of Chinese counterfeits.
Is that SMD921 active enough to solder so-called NOS components? I've got a bunch of old components with oxidized legs. Especially silver plated ones can be difficult to solder.
Are you sure--? That sounds like a counterfeit product to me.
it does contain volatiles which sizzle off quickly under the soldering iron
Are you sure--? That sounds like a counterfeit product to me.Counterfeit from Digikey?
I gave illustrations of successful use, which you are free to contradict, but, I guess if you're letting it stand, my description should be considered priority? But then why raise paranoia over something you aren't confident about..?
I gave illustrations of successful use, which you are free to contradict, but, I guess if you're letting it stand, my description should be considered priority? But then why raise paranoia over something you aren't confident about..?I don't know how badly it was oxidized but it's a poorly tinned lug.
I've been using this stuff. Works really well so far.
https://www.digikey.com/en/products/detail/sra-soldering-products/TF5000/10709784
The way you speak, seems to suggest the product is utterly useless, and this proves it's not.
Oh, you mentioned easy to clean.
They make flux remover. Again, GC is one brand.
https://gcelectronics.com/~gcelectronics/switches-2/flux-remover
I have used it. It works. It isn't cheap.
I've been using this stuff. Works really well so far.
https://www.digikey.com/en/products/detail/sra-soldering-products/TF5000/10709784It solders OK, although not the best. However it's slightly conductive. So I would not recommend it for using with soldering iron due to incomplete activation. Unless you can do very sophisticated cleaning, like with ultrasonic bath as Just brushing with IPA won't remove it from under MLCC and chip resistors.
I've been using this stuff. Works really well so far.
https://www.digikey.com/en/products/detail/sra-soldering-products/TF5000/10709784It solders OK, although not the best. However it's slightly conductive. So I would not recommend it for using with soldering iron due to incomplete activation. Unless you can do very sophisticated cleaning, like with ultrasonic bath as Just brushing with IPA won't remove it from under MLCC and chip resistors.
They don't give conductivity in the data:
https://www.sra-shops.com/pub/media/docs/srasolder/sds/sds-tf5000.pdf
https://www.sra-shops.com/pub/media/docs/srasolder/datasheet/tds-tf5000.pdf
Is this something that caused you a specific problem? Was it a circuit that was especially sensitive to leakage or something? After hot air rework, I've left components submerged in blobs of this stuff on mostly digital boards and I haven't seen anything I would call an issue due to stray conductivity.
For me personally no, but I also do not use unverified flux on sensitive electronics either. But if you start soldering some sensitive analog electronics, you may experience problems. I check all new fluxes I use for resistance, and most of them are slightly conductive, including Amtech and Kester fluxes I tested. It's anecdotal evidence but IME white colored, creamy tacky fluxes are not conductive even in inactivated state. But translucent fluxes generally are slightly conductive. By that I mean you may have resistance in Megohms between traces. Of course leakage will depend a lot on actual trance configuration, not just flux type, its amount and proper activation during soldering.
For me personally no, but I also do not use unverified flux on sensitive electronics either. But if you start soldering some sensitive analog electronics, you may experience problems. I check all new fluxes I use for resistance, and most of them are slightly conductive, including Amtech and Kester fluxes I tested. It's anecdotal evidence but IME white colored, creamy tacky fluxes are not conductive even in inactivated state. But translucent fluxes generally are slightly conductive. By that I mean you may have resistance in Megohms between traces. Of course leakage will depend a lot on actual trance configuration, not just flux type, its amount and proper activation during soldering.I've had an actual problem with a flux in this regard. It was a water-soluble flux for which a multimeter showed resistance about IIRC ~10-30 MOhm, maybe even less, with leads ~1mm apart (I still have it, I can re-measure it later if I want).
I used it in a circuit that included the well-known Chinese LM399-based voltage reference module, which allows to select one of 6 output voltages using jumpers, and my "wrapper" circuit had several small relays to short the respective sets of jumpers on a repeated pressing of a button.
The flux got under the relays and became trapped there, and, because of stray conductivity, the voltage readings from the module were actually off. It was impossible to wash the flux away from there, so I had to remove the relays, wash the board, and replace the relays (with new ones because I failed to desolder them without damage -- ouch), using a non-conductive flux.
Of course I didn't measure the flux beforehand. It was marketed as "no-clean", so I assumed it would be fine. One of local brands, so no use mentioning its name here.
Lesson learned, now I never use fluxes that show any sign of conductivity on anything that can even remotely be affected by it.
But I was not careful and some of the dissolved flux washed into the relays, which were not sealed, and on the contacts. It acted like an insulator and the low level signals were attenuated. I had to wash those relays with generous amounts of the flux cleaner about a half dozen times or more before I got it all out.
You do need to be careful when washing flux off your boards.
But as soon as liquid or paste flux is used for rework, cleaning becomes mandatory.
I just visited the Amtech website and found this line in the product description of the STIRRI-V3-TF : This product is designed for a professional consumers.
A professional consumer ?
Who here feels addressed ?
The residue left is clear, non-corrosive and non-conductive so there is no need to remove it, but it can be easily cleaned with isopropanol, solvent, or semi-aqueous systems.
It bears repeating that no-clean fluxes are only guaranteed to be safe for their stated purposes once heated fully to reflow temperature. When hand-soldering using only the flux in flux-core solder wire, the flux is guaranteed to reach that temperature. But when hand-soldering with external flux (paste, gel, liquid), it may not get heated at all, or may get only partly heated. Unheated or partially-heated flux may be left in an active state and be corrosive. In those cases, flux residues must be removed.
The same applies to many rosin fluxes, which may be corrosive if still wet or pasty. (In tests I’ve done, some liquid fluxes caused no corrosion at all when applied in a thin layer that could dry within a short amount of time, but droplets big enough to take a day to dry caused corrosion.)
My approach is this: when hand-soldering using no external flux, or when using solder paste on a board then reflowed in an oven, I consider cleaning as completely optional. But as soon as liquid or paste flux is used for rework, cleaning becomes mandatory.
I have ordered one more from ali: the "Relife Green". It hasn't arrived yet. There are hopes that it may turn out good, will see. It is also somewhat of a brand name, so lower risk of getting a different stuff under the same name.
Tinning a copper-clad board for example
just did a test right now, put some copper tape on a piece of paper then loaded up the iron with some solder and waited for some time for it to burn off the flux then tried to put the solder to the copper tape but it wouldnt stick. put a drop of the home made flux on the tape then applied the soldering iron and it just flowed onto the tape no issues. so it does work. copper tape has been out of the bag for a while so it wasnt shiny copper more of a duller appearance. shockingly the tape is still stuck down firmly to the paper, a little lifting on the edges where the flux soaked into the paper but this gives me a good idea in using this tape to fix pcb traces and stuff. will have to try it out at some point.
pic attached.
Tinning a copper-clad board for exampleHave you tried "liquid tin"?
Have not. Frankly I don't do it often enough that I would think it worth keeping chemicals around; I don't happen to have much of a place to store or dispose of chemicals here. But that might be an option in those circumstances.
I have been using the MG Chemicals 8341 series and it works quite well.
So it has finally arrived. Looks like your regular gel/paste flux, nothing unusual in this regard. Has zero conductivity at up to 2.5 kV, as measured by BM869s in nanosiemens mode and Aneng MH13 megohmmeter, which is already a good sign. Haven't yet tried to solder anything with it. Applied a blob of it to a strip of bare copper and left on a shelf in the bathroom to test for corrosive properties: if there is anything, it'll show itself in a few days at most.
I tried MG Chemicals 8341, and it's probably the best tacky flux I tried yet. The major upside, its residues instantly dissolve in IPA. So can be cleaned like a charm instead of trying to clean something like barely solvable OM-338. Also it's non conductive, has a long work time, no nasty fumes and actually is quite inexpensive. The only downside is its viscosity, so needs either thick nozzle it comes with, or conical, as it will be very hard to squeeze it though a thin needle.
I tried MG Chemicals 8341, and it's probably the best tacky flux I tried yet. The major upside, its residues instantly dissolve in IPA. So can be cleaned like a charm instead of trying to clean something like barely solvable OM-338. Also it's non conductive, has a long work time, no nasty fumes and actually is quite inexpensive. The only downside is its viscosity, so needs either thick nozzle it comes with, or conical, as it will be very hard to squeeze it though a thin needle.It comes in a proper syringe with a plunger, too: opinions may differ, but I think that plungerless syringes that require a dispenser suck. Surprisingly, it's available locally where I live. $15-$20 sounds a bit steep, but I'm now tempted to try it after the positive reviews here, the easy cleaning with IPA being an important point of attraction -- this is not something that you find often, at least in non-conductive fluxes.
A colleague who is a very experienced electronics technician said my flux was better than a top shelf $60
Technician grade isopropyl alcohol
I never realised that as a kid I was infringing on an IBM parent
QuoteTechnician grade isopropyl alcohol
What the feck is that ?
it works surprisingly well for me although i have it in max concentration so maybe that makes the difference?
An extract from the patent is here (I didn't worry about the surfactant): https://patents.google.com/patent/US3730782A/en
A colleague who is a very experienced electronics technician said my flux was better than a top shelf $60
A very experienced electronics technician never heard of flux made from rosin dissolved in alcohol?
I never realised that as a kid I was infringing on an IBM parentQuoteTechnician grade isopropyl alcohol
What the feck is that ?
That's almost a life-changing experience when you do need to tin boards (and wires, too!). Like going straight from an old style iron to T12.
Proper disposal is a valid point, though. It, however, can be used and reused multiple times, as there's a lot of tin in it, and it takes a lot of surface plating to deplete it.
I think I have found my new favorite.
Also, there were mentions that the 8341 (unlike 8342!) is not conductive. How was it tested? Did someone here test it with a megohmmeter or a DMM in nanosiemens mode? Please share the results.
Tested several chinese craps, but this one worked pretty nice, doesn't burn the tip, instantly evaporate or emit nasty fumes, it's easy to clean with IPA, pretty similar to original Amtech.
I recall buying it from a different store and being absolute ***, then bought this one, actually by mistake (I was decided to never buy Kingbo again), performed great, ordered again few months later and the quality was the same.
https://www.aliexpress.com/item/1005001424090098.html
So, the MG Chemicals 8341 is conductive, at least, before heating. I have tested it with a megohmmeter with the probes simply shoved into the flux with the tips as close to each other as practically possible without shorting. Result: ~6.5-7 GOhm.
BM869s in nanosiemens range registers ~0.06-0.07 nS.
Definitely unsuitable for high impedance/high sensitivity stuff, at least when hand soldering. I have no data on the conductivity after heating.
This instantly disqualifies it from the potential holy grail category.
Well, to be fair its datasheet mentions the need to clean after use, so not necessarily surprising.
https://mgchemicals.com/downloads/tds/tds-8341.pdf
Overall I found it cleans much easier than the other types I have used, so that is a big plus. Also, for anything high impedance or high voltage I would not rely on leaving residue on the PCB anyways, but YMMV.
So even with cleaning, for the circuits where the fluxes' conductivity, even if very low, may matter, I would still prefer a flux whose conductivity is below the sensitivity of a megohmmeter. At least for hand soldering -- it is said that when the "no-clean" fluxes are heated in a reflow oven to a certain temperature, they lose conductivity. I cannot verify this.
Also, regarding the longer term corrosion and other effects, over the two years that I have been using this flux I have not yet experienced any problems - however I don't live in humid environments which could contribute to this.
Neither it is very humid here (at least when it's cold), but I have a bathroom for this, and in that bathroom sits a piece of a copper-clad board with some flux smeared on it .
If there is anything, it will show itself in a few days.
There are lots of fluxes, including cheap offerings from aliexpress, that do not cause even the slightest hint of corrosion when they are left on a copper surface in a humid room for at least several months.
Well, to be fair its datasheet mentions the need to clean after use, so not necessarily surprising.
https://mgchemicals.com/downloads/tds/tds-8341.pdf
Overall I found it cleans much easier than the other types I have used, so that is a big plus. Also, for anything high impedance or high voltage I would not rely on leaving residue on the PCB anyways, but YMMV.
Neither it is very humid here (at least when it's cold), but I have a bathroom for this, and in that bathroom sits a piece of a copper-clad board with some flux smeared on it .
If there is anything, it will show itself in a few days.So after 9 days of MG Chemicals 8341 sitting on a bare copper surface in the bathroom there is a well visible green coloration appearing under the layer of flux.
Now, while the slight conductivity may be fine, the corrosive activity is totally unacceptable.
This stuff, when you compare it to alternatives, isn't worth the money asked, especially in the 10 ml package. I call it unsuitable for anything involving SMD or other components that do not leave a gap above the board that allows to wash the flux residue out completely. At least for hand soldering.
There are lots of fluxes, including cheap offerings from aliexpress, that do not cause even the slightest hint of corrosion when they are left on a copper surface in a humid room for at least several months. In fact, most of the fluxes I tried didn't cause any corrosion, and the only corrosive one (except for the actual acids) was some liquid very active flux specifically purposed for oxidated copper and such.
Easy washing and less stinky fumes aren't worth it for me.
This is why I always remind people that no-clean fluxes must be cleaned when used for hand soldering, because you can’t guarantee it’s been heated enough to neutralize it.
Time to repeat the experiment. Here goes.
Time to repeat the experiment. Here goes.16 days later. Hi-res photos are attached.
...
...But you left off my favorite flux, TF5000, so I'm going to have to ask you to do that over... hah!
...But you left off my favorite flux, TF5000, so I'm going to have to ask you to do that over... hah!
Epic experiment! Thanks for doing that.
If you post csv file, or contents here it's trivial to paste that back into any spreadsheet.
About the flux attacking bare copper... how big of an issue is that really? I'm only ever using flux over board area that is either soldered or has soldermask.
More is coming: I ordered two more Relife fluxes, they'll be here in a week or two.
Geuine rosin, Kester 44
We use only 63/37 Eutectic solder with those flux cores.
Avoid commie china junk solder or wire
Of course, both 44 paste and 1544 would fail shapirus’s requirement to be non-conductive before heating. I don’t think he understands that flux specs refer to the conductivity of the post-soldering residues.
...but I might try something, just for a quick test: for example, set the hot air gun to what, say, 280 °C, heat the PCB with the flux on top from below (to avoid direct blowing on the flux so that more of it stays in place) for, say, 30 seconds, then let it cool and measure what remains. Just to see if the "it must be heated to stop conducting" claims are substantiated, and to what extent, if they are.
I realize I'm late to the party here but....
Indium TACFlux 020B-RC is pretty much the only flux I use for hand soldering/rework anymore, for the reasons everyone mentions in this thread.
Of course, both 44 paste and 1544 would fail shapirus’s requirement to be non-conductive before heating. I don’t think he understands that flux specs refer to the conductivity of the post-soldering residues.Not that I don't understand, but I don't care. I test the fluxes I get my hands on for my specific requirements, which is hand soldering of both THT and SMD parts. And I believe this specific use case is of interest to many electronics hobbyists that can read this, too. Another way of looking at it is worst case scenario testing.
Of course, both 44 paste and 1544 would fail shapirus’s requirement to be non-conductive before heating. I don’t think he understands that flux specs refer to the conductivity of the post-soldering residues.Not that I don't understand, but I don't care. I test the fluxes I get my hands on for my specific requirements, which is hand soldering of both THT and SMD parts. And I believe this specific use case is of interest to many electronics hobbyists that can read this, too. Another way of looking at it is worst case scenario testing.
Besides, the two fluxes from my last post are specifically advertised for BGA rework and general repair, which does not guarantee full heating, either (I believe even when using a hot air gun). And hey, they are 500-1000 times (!) more conductive than the other fluxes I tested.
It would also be interesting to test conductivity after full heating, but that would require having a reflow oven, which I don't have, and the motivation to do it, which I also don't have, since I don't do that kind of soldering.
...but I might try something, just for a quick test: for example, set the hot air gun to what, say, 280 °C, heat the PCB with the flux on top from below (to avoid direct blowing on the flux so that more of it stays in place) for, say, 30 seconds, then let it cool and measure what remains. Just to see if the "it must be heated to stop conducting" claims are substantiated, and to what extent, if they are.
My main concern was you trying to get a refund for flux because of it not meeting the claimed conductivity specs, even though you hadn’t reflowed it. That’s not fair unless they specifically said it was nonconductive in a non-reflowed state.
It’s only whatever flux has flowed far away that is of concern.
You should reconsider. Reflow in an oven is exceedingly efficient. (And practically mandatory for many modern packages.) A simple $50 toaster oven is enough for basic use.
You make it sound as though that’s some crackpot theory… No, it’s how no-clean fluxes are designed to work.
However, I would be leery of your proposed methodology, because it’s quite possible that it wouldn’t heat it evenly enough to draw any conclusions.
Remember: there are TWO temperature thresholds to reach. The first (lower) one activates the flux, the second (higher) one neutralizes it again. If you heat to a temperature that reaches the activation temperature, but not the neutralization temperature, it may be left in a more conductive, more corrosive condition than the unheated state! So the only fair test of this “claim” is to actually get it hot enough to melt solder, since that’s what it was designed for.
It’s only whatever flux has flowed far away that is of concern.That's the point. Unless you heat entire board, you can't guarantee that the still conducting residues do not get trapped in some high impedance circuitry where it can cause trouble. I agree that it's not very likely, especially with almost exclusively digital circuits like laptop or smartphone boards, but it may be an issue with sensitive analog devices.
As I said there: that’s why I always tell people to always clean no-clean flux (except from flux-core solder) when using it for rework.
As I said there: that’s why I always tell people to always clean no-clean flux (except from flux-core solder) when using it for rework.Correct. But cleaning also does not guarantee that all of the residue will be removed. I'm not sure just how much of an issue will the trapped flux be, but even when washing entire boards in ultrasonic bath, some flux easily remains under SMT parts and generally in hard to reach spots.
Well, by “cleaning” I mean “actually cause to be clean”, not just “perform a cleaning procedure regardless of outcome.”
I do recognize that this can be hard to do with some components. I’m very glad I have compressed air at work, since that’s super useful for getting stuff out from under SMD parts.
As I said above, which you didn’t respond to then, either:Well, by “cleaning” I mean “actually cause to be clean”, not just “perform a cleaning procedure regardless of outcome.”
I do recognize that this can be hard to do with some components. I’m very glad I have compressed air at work, since that’s super useful for getting stuff out from under SMD parts.The emphasis is “cause to be clean”. That is, perform cleaning until it is actually clean. Not just “do” a cleaning once, regardless of outcome, and consider it good.
A friend said a -- drat, now I forget which brand exactly, but probably any will do? -- window cleaner is effective on flux residues.
Seems like it would be slow, to me, but maybe a solvent-rich variety, or boosted with a little alcohol or ethyl acetate, would cover that.
16 days later. Hi-res photos are attached.
(I like the MG4381 except for one feature that has me looking for an alternative: it's lumpy. I can squeeze a few dabs from a syringe and then it's blocked and useless.)
Got some of the Relife 422 stuff with which I did a board last week.
The MG8341 is easy to clean because it dissolves quickly in IPA.
I will put a couple of drops (or cotton bud load) of IPA on the area to clean, then get some paper kitchen towel and dab it up using tweezers to move it around. The MG8341-loaded IPA is quickly sucked up and nothing seems to be left behind.
I think that process successfully gets unused flux from under components too.
So, what I would be interested in seeing is a repeat of your bare copper test but this time with the flux cleaned off. Not cleaned off as in bath washed in an ultrasonic cleaner, but using an appropriate cleaner in the way a repair might be done (because that's the worst case). Dribble or spray the cleaner, wipe with rag/towel/whatever then let's see which corrodes. I think the MG4381 might pass the test after doing that, and some others might not (if they just get spread around rather than actually cleaned off).
(I like the MG4381 except for one feature that has me looking for an alternative: it's lumpy. I can squeeze a few dabs from a syringe and then it's blocked and useless.)
(I like the MG4381 except for one feature that has me looking for an alternative: it's lumpy. I can squeeze a few dabs from a syringe and then it's blocked and useless.)How old is yours? I have definitely noticed lumpiness in my syringe of it, which is near its end, but I don’t remember it being lumpy when it was new (which was probably 2015 or so).
BTW, the sticker on the jar says "made in China". Doesn't look counterfeit though, everything looks as it should. Was yours made in Canada?
(I like the MG4381 except for one feature that has me looking for an alternative: it's lumpy. I can squeeze a few dabs from a syringe and then it's blocked and useless.)How old is yours? I have definitely noticed lumpiness in my syringe of it, which is near its end, but I don’t remember it being lumpy when it was new (which was probably 2015 or so).
Got some of the Relife 422 stuff with which I did a board last week.Which of them, exactly? They have several 422 fluxes that have different suffixes in their model names and they differ in properties.
I think that process successfully gets unused flux from under components too.Unfortunately it doesn't. Not for me, at least -- even when I wash entire board by fully immersing it in alcohol, even in an ultrasonic bath. As I mentioned before, that's easy to check: heat the board after washing and drying (even if blowing with compressed air), and it starts to smoke. Some of the flux remains trapped at least under SMT resistors and caps, and I believe generally under the parts that have very small gaps between their bodies and the board. Not an issue (with this flux) for THT stuff.
A test better suited to real world application would be to solder some SMT parts (fully covering the footprints with the flux first) onto a board without solder mask, with traces passing under components, ideally with components placed individually and in side by side groups, then wipe the excess flux using the spray-and-soak method and leave it to rest for a few weeks or months. Then, to see the result, use a hot air gun to desolder the components. I would expect, but I'm not certain, that there won't be any (or at least significant) corrosion under the components either. That would be an interesting one.
I however lack the enthusiasm to do it at this time.
(I like the MG4381 except for one feature that has me looking for an alternative: it's lumpy. I can squeeze a few dabs from a syringe and then it's blocked and useless.)Yes, other than the lumpiness, it's a pleasure to work with, that's for sure. I have even ordered some conical Luer lock compatible dispenser tips to solve the needle blocking issue, but haven't had a chance to try them yet.
Yes, other than the lumpiness, it's a pleasure to work with, that's for sure. I have even ordered some conical Luer lock compatible dispenser tips to solve the needle blocking issue, but haven't had a chance to try them yet.