Flux Removal? Ultrasonic Bath? - Page 1
Forum section: electronics / projects

author: NivagSwerdna
author_rank: Super Contributor
timestamp: February 10, 2021, 02:16:59 pm
content: I've been creating hand soldered boards recently and during assembly I tend to use a Topnik TK83 (or similar depending on what is to hand). This claims to be No Clean but it definitely creates a pool of residue. (I am of the Louis Rossman school of flux application... i.e. don't be too mean). I have also noticed that the thicker solder I use for connectors must be multicore with some flux as it also creates residue.Anyway... I try and clean up to some extent using IPA and absorbent paper tissue and this makes a half hearted job but the end result is that I end up with a thin film of residue across the board.Typically my boards are 10cm x 10cm max (to fit with the cheap PCB services) and have a height from top to bottom of say 5cm (they have DIP sockets on top and pins on the bottom)I don't have fancy MEMs components, just a mixture of 74 series, transistors, R, C, LED, tactile switches etc. It's all SMD.I was wondering if I should think about some ultrasonic cleaning? Would this be friendly to the silk screen?

author: PKTKS
author_rank: Super Contributor
timestamp: February 10, 2021, 02:39:32 pm
content: Quote from: NivagSwerdna on February 10, 2021, 02:16:59 pmYes definitely.The problem with whatever flux you may use...is that all flux tend to be hygroscopic and in due timethe moisture will be trapped in the flux residues... and corrosion starts.The second problem is that Ultasonic baths tend to consume *ALOT*of IPA.. alternatives agents (BRANSON) may be used.. still expensive.Rinsing the board still requires an expensive oven to dry.The mid term in budget compromise is one of these "small"ultrasonic devices which can do the job fine at very low extra cost.NoClean still attracts moisture.. while ROSIN based tend to dryand form an isolation coat over the board.. ugly but safer..Hard to choosePaul

author: jmelson
author_rank: Super Contributor
timestamp: February 10, 2021, 05:04:48 pm
content: Quote from: NivagSwerdna on February 10, 2021, 02:16:59 pmGet solder with WATER Soluble flux! It is amazing stuff! You MUST clean the board, as the residue is somewhat corrosive.But, just wash the board in running water, or run an old toothbrush over it very quickly, and the board comes out TOTALLY sparkling clean.I do some gear with high voltage and/or very high impedance circuits, and the WS flux has made things so much easier.Jon

author: nctnico
author_rank: Super Contributor
timestamp: February 10, 2021, 05:19:47 pm
content: Just use flux-off from Chemtronics (article number: ES896BE ) Works like a charm.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: February 10, 2021, 05:43:41 pm
content: An interesting rabbit hole...I found a cheapo second hand 50kHz ultrasonic... and then discover that 37kHz seems to be the place to be... also.. sweep...I have used some "Maplin PCB & Flux Cleaner" I bought in their closing sale but to be honest it seems to just help moving it around the board... it's hard to actually wipe it off using a paper towel given the relief created by the parts.

author: nctnico
author_rank: Super Contributor
timestamp: February 10, 2021, 07:37:31 pm
content: Then I guess you never used real flux removerThe Flux-off from Chemtronics (note the order number) does the business! Put on some plastic gloves, hold the PCB over a bin to collect the liquid and start washing top to bottom. The trick is to wash the board; let the Flux remover carry the flux from the board into the bin.

author: tooki
author_rank: Super Contributor
timestamp: February 11, 2021, 07:18:58 pm
content: Quote from: PKTKS on February 10, 2021, 02:39:32 pmNo, ALL flux is not hygroscopic. Most rosin fluxes are not. You even say this later on...Quote from: jmelson on February 10, 2021, 05:04:48 pmTake this advice with a HUGE warning: 1. While it’s easy to remove, it must be removedperfectlyevery time, no exceptions, as any residue is highly corrosive. You must be fastidious every single time. 2. Under no circumstances is it to be used anywhere that flux can wick into a place the aforementioned flawless cleaning cannot be 100% guaranteed. This means you cannot use it on stranded wire, since itwillwick into the strands and under the insulation (and even on insulated solid wire it’s risky).So while it’s good for many PCB applications, it cannot be used as your only flux type, and the degree of perfection required in its cleaning is, frankly, not feasible for most hobby use, so I consider it borderline reckless to recommend it to hobbyists.Quote from: NivagSwerdna on February 10, 2021, 05:43:41 pmWell... yeah, it’s asolvent, not a magic neutralizer. You still have to mop it up. Typically, stiff brushes are used to push the towel in between components so you can absorb it all. And you’ll have to repeat it a few times if you want to truly get rid of all residue. And/or rinse with generous amounts of solvent instead, to wash away the dissolved residue as ntcnico describes.The typical process is to use the brush and solvent to scrub the flux to get it dissolved, then use the brush and lint-free cloth to pull up the flux-laden solvent.Another option to consider is Electrolube Safewash. It’s a water-based flux remover (i.e. saponifier) that works great. And since it’s not flammable, you can use it in any ultrasonic bath. (Flammable solvents must only be used in specially designed ultrasonic cleaners.) You can also get it in a spray can: you scrub with a brush as above, but then instead of mopping up with cloths or rinsing in more solvent, you just rinse with water (ending with a DI/distilled water final rinse). I recently discovered a can of it at work and was quite surprised at how well it dissolved both rosin and no-clean flux residue.

author: David Hess
author_rank: Super Contributor
timestamp: February 11, 2021, 07:22:30 pm
content: Quote from: NivagSwerdna on February 10, 2021, 02:16:59 pmYou could do that, or place the board in a bath for a few minutes, scrub it with a toothbrush, and then rinse it off into the bath with clean solvent.An ultrasonic cleaner is more likely to remove component marks than the silk screen.

author: Miti
author_rank: Super Contributor
timestamp: February 12, 2021, 11:28:19 am
content: Quote from: tooki on February 11, 2021, 07:18:58 pmI don't know if this fear of WS flux comes from personal experience or is theoretical but, in my opinion, is mostly unjustified. While I agree that I wouldn't use it to solder wires for the reasons explained above, for PCB assemblies, it is amazing and I use it for years. It does need to be cleaned perfectly but that is easily achieved. Just hold the board by the corner and rinse it under hot water from the tap, turned to maximum pressure, and rotate in all angles that the parts are installed. The water need to hit the low profile parts from the side to remove the flux from underneath. I also use a long hair soft artist brush, but that is optional.Blow the board with compressed air from a shop vac output.Wash and dry one more time.I do this for years and never had any issues.

author: KT88
author_rank: Frequent Contributor
timestamp: February 12, 2021, 01:23:19 pm
content: I used ethanol vapor back in the days - it worked fantastic. It requires only a small puddle at the bottom of a canister that can be closed pretty well. The PCBs are stored upright in the canister and shouldn't touch the ethanol puddle.Let it sit over night and the vapors will have done the job.CheersAndreasP.s. Don't smoke or have any other source for ignition nearby!!!!!

author: wraper
author_rank: Unknown
timestamp: February 12, 2021, 01:30:45 pm
content: Quote from: NivagSwerdna on February 10, 2021, 02:16:59 pmUnless you use expensive sealed switches, you are not allowed to wash them with anything.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: February 12, 2021, 01:40:43 pm
content: Quote from: wraper on February 12, 2021, 01:30:45 pmThat's interesting.

author: wraper
author_rank: Unknown
timestamp: February 12, 2021, 02:08:16 pm
content: If you wash this, they may work. But how well and for how long is questionable.https://www.symmetron.ru/suppliers/omron/files/pdf/omron/Tactile-Switches.pdfQuoteQuote

author: CJay
author_rank: Super Contributor
timestamp: February 12, 2021, 03:02:18 pm
content: I second, third or fourth the Chemtronics recommendation, it's awesome stuff, not cheap but it works really well.

author: jmelson
author_rank: Super Contributor
timestamp: February 12, 2021, 06:59:58 pm
content: Quote from: tooki on February 11, 2021, 07:18:58 pmWell, I think this is a bit excessive. I actually, by mistake made some boards with WS wire solder and did NOT clean them after. Yes, there was some corrosion, the solder eventually looked "frosty" but it did NOT eat the parts or traces off the board. It sure could have caused issues on high impedance circuits, though.My experience with the WS flux is that fairly simple washing removes or deactivates the flux so it is no longer corrosive. I do worry just a bit about how well it can get the flux out from under SMT components. I'm going to be doing some boards with 1500 V on them for photomultiplier voltage dividers, so I will find out if there might be issues. If we have to do the ultrasonic bath, we do have the gear at work.Jon

author: ogden
author_rank: Super Contributor
timestamp: February 12, 2021, 07:25:06 pm
content: No need for ultrasonic. Use flux removers instead:https://www.chemtronics.com/flux-removershttp://www.kontaktchemie.com/koc/KOCproductdetail.csp?division=&product=KONTAKT%20PCC&ilang=all&plang=allTogether with ANY generic "canned air" bottle to blow-off remains of dirt and cleaning fluid, drying. Like this:https://www.amazon.com/Dust-Off-Disposable-Compressed-Duster-Cans/dp/B00FZYT278

author: tooki
author_rank: Super Contributor
timestamp: February 13, 2021, 02:49:32 pm
content: Quote from: Miti on February 12, 2021, 11:28:19 amRespect ≠ fear.You understand what “thorough” means. You’d be surprised how many people don’t. That’s why I am extremely reluctant to recommend it to hobbyists.

author: tooki
author_rank: Super Contributor
timestamp: February 13, 2021, 02:50:57 pm
content: Quote from: KT88 on February 12, 2021, 01:23:19 pmAlas, since some of the ingredients in no-clean fluxes aren’t soluble in alcohol, this approach is no longer feasible.

author: nctnico
author_rank: Super Contributor
timestamp: February 13, 2021, 10:25:00 pm
content: Quote from: ogden on February 12, 2021, 07:25:06 pmI recommend against using compressed air in combination with liquid chemicals. Chances are you blow all the nasty stuff right into your face. Don't ask how I knowBTW: Flux removers come in many variants. Oddly enough the 'no clean plus' from Chemtronics works best for Rosin & leadfree fluxes in my experience.

author: wraper
author_rank: Unknown
timestamp: February 13, 2021, 11:00:01 pm
content: Quote from: nctnico on February 13, 2021, 10:25:00 pmDon't blow in your face maybe? FWIW compressed air is very effective. It will blow away flux cleaner together with dissolved flux. Without compressed air, you need more rounds of cleaning to get comparable result.

author: nctnico
author_rank: Super Contributor
timestamp: February 13, 2021, 11:41:44 pm
content: Quote from: wraper on February 13, 2021, 11:00:01 pmThe problem is that larger parts on the PCB may (will, when Murphy seems fit) direct the air stream back at you.

author: wraper
author_rank: Unknown
timestamp: February 14, 2021, 12:21:50 am
content: Quote from: nctnico on February 13, 2021, 11:41:44 pmWear a face mask and protective googles. I usually was blowing at my waist level, so it was quite hard to anything get in my face.

author: srb1954
author_rank: Super Contributor
timestamp: February 14, 2021, 01:25:48 am
content: Quote from: KT88 on February 12, 2021, 01:23:19 pmBetter still is Freon vapor. Very fast and effective.Many, many years ago the factory where I worked had a Freon vapor flux cleaner. This had two deep side-by-side tanks; the main tank was full of cold Freon liquid and the other had a small heater at the base to boil off any Freon. First the PCB was dipped in the cold Freon tank which softened and dissolved most of the flux. The dipping of the PCB would spill some of the cold Freon into the adjacent heated tank where it would start to boil away. After dipping in the Freon liquid the PCB was held above this boiling Freon whereby the Freon vapor would condense onto the PCB and carry away any residual flux residue. Using this system resulted in spotlessly clean PCBs in less than a minute without the need for any scrubbing. The PCBs were clean and dry immediately after removal from the vapor tank.So the Freon didn't escape into the atmosphere there was a refrigerant coil around the top of the tanks so any of the rising Freon vapor was re-condensed and flowed back into the main tank. This effectively continuously distilled the Freon to ensure that the Freon on the main tank was always pure. The removed flux accumulated in the bottom of the heated tank and had to occasionally be cleaned out.Unfortunately due to the pesky ozone layer problem we are not allowed use nice methods like this any more and now have to put up with inferior chemicals and techniques.

author: helius
author_rank: Super Contributor
timestamp: February 14, 2021, 02:38:27 am
content: Any kind of volatile solvent is a big problem in ultrasonic cleaners. The instructions typically forbid them completely.The cleaners used in ultrasonics are non-volatile, water-based solutions of detergents and sequestering agents. They can effectively remove both rosin-based and water-soluble flux residues. That is because the residue doesn't actually need todissolve: simply being knocked off the board by cavitation, and suspended for a period of time, is sufficient.

author: floobydust
author_rank: Super Contributor
timestamp: February 14, 2021, 03:42:22 am
content: Ultrasonic cleaning is hard on IC bonding wires and also etches all parts on the board. It is abrasive scrubbing action, after all. After a soak, use a short timer.For manually cleaning boards, soak the board for a few minutes first, then a toothbush or hog hair brush works fine.One company I worked for put production boards in a dishwasher to clean off flux.

author: ogden
author_rank: Super Contributor
timestamp: February 14, 2021, 08:44:48 am
content: Quote from: floobydust on February 14, 2021, 03:42:22 amWith some preconditions: 1) water-soluble flux 2) no BGAs no flip-chips or alike 3) deionized water for rinse or even washing, optionally 2nd rinse using alcohol

author: David Hess
author_rank: Super Contributor
timestamp: February 15, 2021, 12:39:31 pm
content: Quote from: ogden on February 14, 2021, 08:44:48 amI have seen boards put into a dishwasher with deionized water before assembly to lower leakage and remove contaminates which interfere with soldering.

author: Gibson486
author_rank: Frequent Contributor
timestamp: February 15, 2021, 05:02:41 pm
content: Be careful what you put in that ultrasonic bath. Research it before you do it. I have seen it suggested many times...but do not put IPA in there. That is actually a hazard.

author: radeohedca
author_rank: Contributor
timestamp: February 15, 2021, 05:31:31 pm
content: Believe it or not, we use a dishwasher at work to clean boards... it was bought specifically for this purpose. It works very well for the flux used in newer ROHS lead free solders. They come out sparkling clean and the dry cycle ensures there's no residual water.

author: tooki
author_rank: Super Contributor
timestamp: February 15, 2021, 10:40:00 pm
content: What flux type? Lead-free solders are available with all the major types of fluxes, including rosin, no-clean, and water-soluble.

author: wraper
author_rank: Unknown
timestamp: February 15, 2021, 10:46:10 pm
content: Quote from: tooki on February 15, 2021, 10:40:00 pmNo-clean is not a type of flux in such context. No-clean can be rosin based, synthetic or even water soluble. All it means it is marketed by manufacturer as flux that can be left on PCB.

author: tooki
author_rank: Super Contributor
timestamp: February 16, 2021, 12:30:09 am
content: Quote from: wraper on February 15, 2021, 10:46:10 pmOnly if you dissect the term literally, which is not wise — That's what smart alecks do when they want to show how smart they are, but in fact are just being turds.In the solder industry, solders are practically always broadly divided into rosin, no-clean, and water-soluble. Moreover, I said "all the major types of fluxes,includingrosin, no-clean, and water-soluble", meaning it was not an exhaustive list, leaving room for things like water-soluble no-clean.Now, I actually kinda hate the term "no-clean" since it can indeed mean damned near any formulation, it not being a strictly defined term. Nonetheless, the overwhelming majority of solders and fluxes fall into those three categories, whose basic meaning is this:Rosin: a flux with a high rosin content, where rosin is the dominant active ingredientWater-soluble: water-soluble organic acids, with the expectation of cleaningNo-clean: low amounts of harmless residuesAnd your entire argument/lecture added exactly what to the discussion anyway? My question to radeohedca remains: what type of flux is it?

author: wraper
author_rank: Unknown
timestamp: February 16, 2021, 12:39:52 am
content: Quote from: tooki on February 16, 2021, 12:30:09 amWhat solder industry you are talking about? And how you distinguish rosin from no-clean? Rosin flux on the other hand might need cleaning for active types. Not all fluxes which must be washed are water-soluble too. Your way of describing flux types is a complete ambiguous mess.

author: tooki
author_rank: Super Contributor
timestamp: February 16, 2021, 12:50:59 am
content: Quote from: wraper on February 16, 2021, 12:39:52 am"Solder industry" is English for "the industry that manufactures soldering consumables (solders and fluxes)".Quote from: wraper on February 16, 2021, 12:39:52 amRead my previous reply.Quote from: wraper on February 16, 2021, 12:39:52 amCorrect.Quote from: wraper on February 16, 2021, 12:39:52 amI didn't say that only water-soluble fluxes must be washed.Quote from: wraper on February 16, 2021, 12:39:52 amIt's not "my" way. It's the way the industrybroadlycategorizes them.Look at the product names of practically all fluxes/solders: almost all contain EITHER "rosin", "no-clean", OR "water soluble". That tells you what broad category it's in. Then the specs will tell you the precise flux classification.

author: wraper
author_rank: Unknown
timestamp: February 16, 2021, 12:54:11 am
content: Quote from: tooki on February 16, 2021, 12:50:59 amAnd they certainly don't describe fluxes this way.QuoteHuh? It's meaningless. You separate rosin and no-clean as different types. They are not, they describe different properties and overlap a lot.QuoteDidn't notice this in datasheets at all.

author: wraper
author_rank: Unknown
timestamp: February 16, 2021, 01:02:51 am
content: Say this onehttps://www.kester.com/DesktopModules/Bring2mind/DMX/Download.aspx?EntryId=3558&PortalId=0&DownloadMethod=attachmentIt's rosin mildly activated (ROM0) no-clean flux. Almost everything that is non-corrosive and non-conductive is called no-clean these days.Or thishttps://www.kester.com/DesktopModules/Bring2mind/DMX/Download.aspx?EntryId=31875&PortalId=0&DownloadMethod=attachmentNon diluted rosin flux with low activation, still called no-clean. It's not even mentioned that it's rosin, you need to look into ROL0 classification to see what it actually is.

author: helius
author_rank: Super Contributor
timestamp: February 16, 2021, 01:16:55 am
content: The flux and solder companies, like most industries, have multiple audiences they need to communicate with and advertise to. The engineers are going to want to see the IPC STD category and test results as this lets them know that the product is suitable for their reliability requirements. The managers who sign the purchase orders, on the other hand, want to know that what they're doing is in line with industry trends they read about in the trade press. "No-Clean" is a very easy concept to understand: you don't need a post-cleaning line. The details of the formulation would be lost on them anyway.

author: tooki
author_rank: Super Contributor
timestamp: February 16, 2021, 01:20:06 am
content: Quote from: wraper on February 16, 2021, 12:54:11 amBullshit. They absolutely do:Kester:https://www.kester.com/products/category/tacky-solder-fluxType: No-Clean/Rosin/Water-SolubleAIM:https://aimsolder.com/liquid-flux-and-paste-fluxFlux Type: No Clean/Rosin/Water SolubleMG Chemicals:https://www.mgchemicals.com/category/soldering-supplies/soldering-flux/"The flux comes in both liquid and paste formats, and in Rosin Activated (RA), No Clean (NC) and Water Soluble (WS) flux chemistries."Chip-Quik:https://www.chipquik.com/store/index.php?cPath=300No-Clean/RMA/no-clean water-washable/water-solubleElsold:https://www.tamura-elsold.de/datenblaetter/tacky_flux_en/TEG_TDS_EN_ELSOLD%20Tacky%20Flux.pdfFlux Type: No clean/water solubleNoteverymanufacturer applies the broad categories (or only uses them in body text), but they're widely understood throughout the industry.As I already stated: the datasheets will always tell you the precise classification (and often more, since the formal classifications themselves don't tell you everything, either).Quote from: wraper on February 16, 2021, 12:54:11 amOf course there's overlap. But those terms explain thedominant characteristic, which I explained.Quote from: wraper on February 16, 2021, 12:54:11 amThen you haven't read enough datasheets, or didn't pay attention.

author: tooki
author_rank: Super Contributor
timestamp: February 16, 2021, 01:22:06 am
content: Quote from: wraper on February 16, 2021, 01:02:51 amThat's all correct, and none of that is in any way contradictory to anything I've said so far.No-clean isn't a formal flux classification, as you've correctly identified and repeated over and over under the impression nobody else understands that. That's why you shouldn't be surprised that you find "traditional" classifications on no-clean fluxes: the classification tells younothingabout the amount of residue, which is, next to the inert nature of the residue, the biggest part of what makes a flux "no-clean".

author: wraper
author_rank: Unknown
timestamp: February 16, 2021, 01:34:59 am
content: Quote from: tooki on February 16, 2021, 01:20:06 amThose are just quick filters. And selecting "Rosin" in most cases will show rare rosin fluxes which are not called no-clean.EDIT: and under "Rosin" name usually hides some really old flux formulation.QuoteWhat dominant characteristic there is for rosin vs no-clean rosin? What bugs me is that you separated rosin from no-cleanas different typeswith no proper explanation. And so many people for years misunderstand this Rosin vs no-clean thing.

author: tooki
author_rank: Super Contributor
timestamp: February 16, 2021, 02:28:52 am
content: Quote from: wraper on February 16, 2021, 01:34:59 amYes, now you're starting to understand!Nobody ever said they were formal, strictly defined classifications/standards.Quote from: wraper on February 16, 2021, 01:34:59 amThat's literally the point: they're not "hiding" it, "rosin" as a category is used to refer totraditional-style formulations, specifically to contrast with the newer formulations, which are almost entirely water-soluble or no-clean.Quote from: wraper on February 16, 2021, 01:34:59 amI take issue with you repeatedly blamingmefor this terminology, when I am simply going by the industry-standard nomenclature. I am not calling them "rosin" vs "no-clean" because of not understanding the chemistry, I call them that becausethat's what the manufacturers (and the electronics industry at large) call them.And I did give you a "proper explanation":Quote from: tooki on February 16, 2021, 12:30:09 amQuote from: wraper on February 16, 2021, 01:34:59 amYes, so the confusion wasnotcaused bymychoice of words in this thread. I think it's more your personal frustration with the emergence of fluxes labeled as "no-clean" despite the fact that a) no-clean fluxes still need to be cleaned in some situations, and b) before "no-clean" fluxes came out, it was widely understood that rosin flux residues didn't need to be removed in most situations.But good luck trying to convince the entire electronics industry to abandon the term "no-clean" in favor of the more accurate "non-corrosive, low-residue" just because the imprecision of the wording irritates you…Wait till you find out that ROM is actually random-access, too, and that tomatoes and watermelons are actually berries!

author: ogden
author_rank: Super Contributor
timestamp: February 16, 2021, 05:59:00 am
content: It shall be noted that rework/hand-solder flux and solder-paste flux formulations differ. Engineers are usually fine with "no-clean" and "water-soluble" classification. Those who are responsible for process then read datasheets and IPC standards. Obviously it is good idea to use water soluble flux when washing is part of the process for some (absolute necessity) reason.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: February 16, 2021, 09:30:33 am
content: This thread has developed in an interesting way. To be clear on my original requirement though... this is absolutely not a rework context... it is a small manufacturing context, and currently hand soldered. (In fact there are many components that are not easily reflowable)

author: ogden
author_rank: Super Contributor
timestamp: February 16, 2021, 06:45:39 pm
content: For small amount of hand-soldered connections local cleaning is always better choice. Just bulk-buy cleaning solution and swabs, use flux that is easy to (hand)clean, test your process. When think about full washing also consider - if your components are not OK in reflow, then maybe they do not like (immersion in) water as well? Saying rework solder I mean hand soldering as well. Edited previous post accordingly.

author: helius
author_rank: Super Contributor
timestamp: February 16, 2021, 09:50:01 pm
content: Hand soldering for assembly and hand rework are similar in many ways, and some operators may use the same tools and materials for both. But as long as the components are fresh and shiny, you can often use less active fluxes for assembly, and lower temperatures, than you would for rework.Metcal advertises its MFR workstations with different handpieces for assembly (tips fitting over a coil unit) or rework (cartridges). Since assembly is less demanding, but has a higher work cycle (more joints /hr?) the tip version has lower cost of ownership.

author: ogden
author_rank: Super Contributor
timestamp: February 16, 2021, 10:45:06 pm
content: Quote from: helius on February 16, 2021, 09:50:01 pmRight. Cartridges for rework is logical choice because rework most likely requires often change of the tips. Assembly must be optimized as much as possible meaning change of the tip shall be expected only when it is worn-out/unusable. Thus different types of irons.