Rosin based flux vs other types - Page 1
Forum section: electronics / beginners

author: VSV_electron
author_rank: Regular Contributor
timestamp: November 11, 2022, 06:08:03 pm
content: Hello, getting back into the hobby.Last time I seriously touched my iron, it was 32 years ago when I soldered-assembled and setup a clone of the ZX Spectrum Z80 MPU based computer.To make it short: I used rosin core solder then BUT! - I was taught at that time (remember, it was over 30 years ago) not to rely solely on the rosin core solder but use spirit (alcohol) soluble rosin at every solder point in addition to the rosin activated flux and I did exactly that.I fact I tried to solder with the rosin core solder only and it didn't work just as good as it worked with the rosin solution added.Now, when I'm returning to the hobby I find the majority use some sort of paste flux that comes from China in syringes or plastic jars. Amtech, Kingbo, you name it, are being the most popular ones but despitethe fact they are fakepeople buy them in tonnes and enjoy soldering with them.However, there is a warning on those plastic jars: Don't use at home, it's toxic, harmful, so on. Remember, those warnings are copied over to the Chinese made fake stuff but since it exists on the original ones as well it must be twice as bad!Nevertheless people quote those warnings and continue to use it... Weird...NOW - a big question: What's wrong with the Rosin? If I go my old way and solder with the rosin solution in spirit - is there anything wrong with that?Last question: To make a paste like flux is it possible to mix the ethanol alcohol, rosin and Vaseline (petroleum jelly)? Will it work as a paste flux?

author: mariush
author_rank: Super Contributor
timestamp: November 11, 2022, 06:57:57 pm
content: Modern solder wires have some amount of flux in them .. typically 1 to 3% flux depending on diameter of wire and other factors.It's not always enough, it depends on the parts you want to solder, how old and oxidized they are... and it's possible to have the solder iron tip too hot and actually burn the flux before it gets a chance to activate and do its job.The flux inside the solder is supposed to become liquid as it heats up from the solder iron tip, drop on the leads or pads your want to solder and attack the surfaces and corrode the oxides and shit so that when you bring the actual solder, the solder metal has a chance to chemically combine with the metals on the pads or leads and make a strong connection.Rosin flux is relatively mild and active only when it's heated up, and helps make better solder joints and in general it's not needed to removed from the circuit board as it's not conductive ... but it can be cleaned usually with isopropyl alcohol or acetone or flux removers if you don't want reside on the circuit board.Gels and pastes are good for when you need some flux and don't want it flowing it around ... for example let's say in SMD, when you want to clean the pads for a soic or a qfn part, you may apply a bit of flux over the pads so that you can then bring some solder into a cup solder tip (used often for drag soldering), tin the pads, then clean the pads with solder wick (to remove the old solder plus freshly applied solder), apply flux again and now tin the pads again with just the fresh solder.You can do the work with liquid flux as well, it's just going all over the place more easily.I actually mentioned to another person this morning that you can make your own flux by buying colophony (pure rosin) and mix it with isopropyl alcohol and optionally with acids that make the flux more active.For example a liquid flux I often use - Topnik TK83 by AG Termopasty is made according to the MSDS with <25% rosin, <75% isopropyl alcohol and <5% each of benzoic acid and adipic acid.They sell on TME.eu 500g bags of colophony preactivated with 2.5% adipic acid for less than 5 EUR plus shipping :https://www.tme.eu/gb/details/kalafonia-500/fluxes/ag-termopasty/art-agt-094/So you can just add isopropyl alcohol and optionally benzoic acid ... it's available at Amazon, food grade stuff, like $10 for 12 ounces/340g bag that will last for tens of liters of liquid flux:https://www.amazon.com/Glycerin-Supplier-Benzoic-Acid-12oz/dp/B07W6JQ7X9/For gels... I recommend checking out MSDS for various gel fluxes to see what they use to make them gel like ... but some are quite complex.. for examplebga flux gel :https://www.tme.eu/gb/details/topnik-gel-bga/fluxes/alpha/om-338/the msds (in Polish but scroll down to page 3 )https://www.tme.eu/Document/70b5eada471e90192ee6e8780aa61c84/TOPNIK-GEL-BGA.pdfex 10-25% rosin reacted with acrylic acid, <10% 2-decyltetradecanoic acid, <10% Carboxylic acids, <10% 2-hexyldecanoate, <10% 2-ethylimidazole , <5% succinic acid and <5% castor oilYou can buy most of these chemicals but minimum quantities are kind of big, considering the percentages you need

author: jpanhalt
author_rank: Super Contributor
timestamp: November 11, 2022, 07:31:23 pm
content: Quote from: VSV_electron on November 11, 2022, 06:08:03 pmYes, you can make an emulsion/solution of rosin and petroleum jelly. If you want something harder, rosin and beeswax also mix well. Of course, the mixing needs to be done with heat for both.

author: TimFox
author_rank: Super Contributor
timestamp: November 11, 2022, 08:49:34 pm
content: Especially with older leaded parts and connectors, a bit of mechanical cleaning before soldering makes the job much easier.

author: Vovk_Z
author_rank: Super Contributor
timestamp: November 11, 2022, 09:36:34 pm
content: As a DIYer I always use rosin ethanol solution. It is called "F1 flux" here. It is much easier to solder with it because of ethanol and rosin comparing with pure dry rosin. And mechanical cleaning first for old parts of cause (and then F1 flux again). There are F2 and F3 fluxes too - they are more and more active respectively, but with not too old parts you need only simple F1 (rosin ethanol solution without any additional activators).Of cause, if you are not DIYer but have to manufacture devices then things change, and other fluxe types arrive.

author: tooki
author_rank: Super Contributor
timestamp: November 12, 2022, 06:13:22 pm
content: Quote from: VSV_electron on November 11, 2022, 06:08:03 pmAdding flux often helps, particularly if the parts are tarnished at all.Quote from: VSV_electron on November 11, 2022, 06:08:03 pmWell, you don’tknowthat most people use the Chinese fluxes. I doubt any professionals do, they buy the good stuff, and you should too.Quote from: VSV_electron on November 11, 2022, 06:08:03 pmYou can buy liquid rosin flux, or liquid flux of other types.Rosin fluxes tend to not stand up as well to the higher temperatures of lead-free soldering, which is one reason why rosin fluxes aren’t used as much as they used to be. As a consequence of their reduced use, far fewer rosin fluxes are made now, so they’re becoming harder (not impossible, before anyone jumps down my throat…) to find, especially here in Europe.Most fluxes nowadays are “no-clean”, which encompasses a huge range of flux formulations whose only shared characteristic is that their residues don’t need to be cleaned. (Note that this is only true if fully heated to soldering temperatures, which is not guaranteed with pastes or liquids used in hand soldering, where excess flux runs around your board.) Many no-clean fluxes contain rosin (or synthetic rosin), many do not. And yes, if you’re thinking to yourself “huh? I thought most rosin fluxes could be left on the board, too.” you’d be absolutely correct. In fact, many rosin flux formulations fall into the same formal flux classifications as some no-clean fluxes.Quote from: VSV_electron on November 11, 2022, 06:08:03 pmSome people claim that works, but I bought pure rosin to try and make paste, and I absolutely could not get it to emulsify. I tried rosin and Vaseline, heated, both with and without solvent, and tried several solvents, and in various proportions, but the end result once cooled was always just a layer of rosin with a layer of Vaseline on top. Totally useless and in no way worth the effort given that you can buy superb name-brand flux pastes for just a few dollars.I like the ChipQuik SMD291NL flux gel. It’s lovely: no acrid smell like so many modern fluxes, it smells like toasted hazelnuts. A 10ml tube of it — which will last you years — is £10.50 on Digi-Key:https://www.digikey.co.uk/en/products/detail/chip-quik-inc/SMD291NL-10M/14636550They ship free on orders above £33, so just add some to your next order.

author: Infraviolet
author_rank: Super Contributor
timestamp: November 12, 2022, 06:19:25 pm
content: The only time I've ever needed to manually add a flux of any kind to a joint, beyond the flux core already present in the solder reel was when DESOLDERING stubborn components. For all soldering I've found the flux-core within solder to be enough on its own.Rosin fluxes come in further options too, normal, activated, or super activated. The more active ones are harsher, for soldering together very dirty corroded contacts, they also really ought to be thoroughly IPA'd or flux-removed off stuff after soldering lest they slowly disvvolve in to copper over time. The normal or less activated ones are good for most soldering situations with clean parts, and don't need rinsing off though it can be good practice anyway.P.S. additional flux doesn't have to come in paste form, you can get flux-pens too, like felt-tip markers but with liquid flux inside, not ink.

author: jpanhalt
author_rank: Super Contributor
timestamp: November 12, 2022, 06:31:11 pm
content: Quote from: tooki on November 12, 2022, 06:13:22 pmMaybe it's like making a roux? Here I describe my experience with petroleum jelly + rosin etc. that I posted:https://www.eevblog.com/forum/repair/restoring-dried-solder-flux-paste/msg3484434/#msg3484434Nevertheless, I don't disagree with the ultimate conclusion to buy rather than make.

author: tooki
author_rank: Super Contributor
timestamp: November 12, 2022, 06:52:31 pm
content: Quote from: jpanhalt on November 12, 2022, 06:31:11 pmAs someone very familiar with making roux, what exact part of the roux-making process do you suggest translating to the rosin-flux-making process?In my attempts, the Vaseline would melt first, then the rosin. But the rosin never dissolved in the Vaseline. I tried constant stirring while cooling it off, and that did produce asomewhatmixed product I’m one or two attempts, but mostly the rosin just coalesced as it cooled in the Vaseline (which of course stayed melted at temperatures where the rosin already solidified).I also tried dissolving the rosin in solvent and then mixing it with Vaseline, but it never became a stable mixture.I still have an ancient tin of the Kester SP-44 you mention in the linked post, and so I’m very familiar with how it’s a completely stable mixture: if you melt it, all the ingredients are dissolved.Given your wildly different result, I can only surmise that at least one of the ingredients I used is fundamentally different than yours. I used Vaseline brand Vaseline, and pharmaceutical grade rosin from the localapothecarynatural pharmacy. For solvents I had 99% IPA, and commercial flux remover (solvent blend).

author: TimFox
author_rank: Super Contributor
timestamp: November 12, 2022, 06:53:31 pm
content: Quote from: Infraviolet on November 12, 2022, 06:19:25 pmWhen using rosin-core leaded solder in TH assemblies, the only times that I needed extra flux was when I had not cleaned the older crudded surfaces before soldering.

author: jpanhalt
author_rank: Super Contributor
timestamp: November 12, 2022, 07:24:09 pm
content: Quote from: tooki on November 12, 2022, 06:52:31 pmWell mixed and not too hot or too cold.QuoteMy petroleum jelly was Walmart Equate brand (I'm cheap). The rosin was "pure gum pine" from Amazon (https://www.amazon.com/gp/product/B00JFF6XP2/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1) Next time you are in the vicinity of Cleveland, Ohio, drop by and I will show you.

author: John B
author_rank: Frequent Contributor
timestamp: November 12, 2022, 08:44:31 pm
content: The 2 types of paste I keep are MG Chemicals 8341 and 8342.8341 is a no-clean type which is what I normally use for concealed pads, ie the thermal pads on the bottom of some SO packages which you can't solder with an iron.8342 is what I would use for the same purposes...but I found out the hard way that it becomes conductive, so you have to completely clean it off the PCB.

author: mcovington
author_rank: Regular Contributor
timestamp: November 12, 2022, 09:21:28 pm
content: There have been 3 main changes in soldering practice since the 1990s.(1) Lead-free solder is used a lot. I like Kester K100LD.(2) Partly because of that, and partly because it just makes life easier, we very often add flux from a syringe when we're going to solder something. Also when desoldering with braid. It really helps!(3) Tack-soldering is now recognized as legitimate. If two things are already well coated with the same kind of solder, they can be joined by re-melting the solder and adding just a little more. This heats the objects much less than soldering from scratch.