Author Topic: Restoring dried solder flux paste  (Read 3569 times)

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Offline SilverSolder

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Restoring dried solder flux paste
« on: May 01, 2020, 12:21:51 pm »

Cheapskate project last night, that worked so well I thought it might appeal to other cheapskates out there!   :-DD

I have a pot of rosin flux paste that had dried out to the point of becoming a little difficult to use.  I don't use it often, but when I do, I want it to work...

Rosin flux paste is thinned at the flux factory with chemicals that are a little difficult or expensive to buy in small quantities, e.g. diethylene glycol dibutyl ether and other esoteric compounds.

In the past, I have tried to make flux paste thinner with isopropyl alcohol and other thinners, but the ones I tried were never really satisfying and in any case always ended up evaporating relatively quickly, leaving the flux just as hard as before.

Then it struck me:  why not use a liquid rosin flux as a solvent for the partially dried paste?  The idea being that the thin flux already has an appropriate type of rosin solvent in it...

So, while my wife was not looking, I went to work in the kitchen...  I added a small amount of the liquid flux to the pot (one or two ml),  then heated the mixture in the microwave oven for about 15 seconds, enough to melt everything - stirred thoroughly.  Let sit overnight to solidify.

The result is awesome -  soft, supple, beautiful flux!   A miracle cure - absolutely worth the effort.  8)

[attachimg=1]

 
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Offline shakalnokturn

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Re: Restoring dried solder flux paste
« Reply #1 on: May 01, 2020, 02:53:23 pm »
Beware heating things in the microwave, the right stuff in the wrong conditions is a recipe for having the door blown open.

 What would be in the liquid rosin paste to keep it liquid?

I break small chips off the solid rosin, dissolve it in acetone and keep that in a small syringe for use. The most common use being running the needle over the four sides of TQFP's.
 

Offline SilverSolder

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Re: Restoring dried solder flux paste
« Reply #2 on: May 01, 2020, 04:10:50 pm »
Beware heating things in the microwave, the right stuff in the wrong conditions is a recipe for having the door blown open.

The flux paste melts like wax, at a fairly low temperature.  It did not start to smell or anything.  Obviously we are talking seconds in the microwave - it would definitely not be a good idea to heat this up too much.

Quote
What would be in the liquid rosin paste to keep it liquid?

2-Butanol and Ethanol, about 25% of the total product of each.  The "secret ingredient" is the 2-Butanol which will not evaporate as fast as alcohols.

Quote
I break small chips off the solid rosin, dissolve it in acetone and keep that in a small syringe for use. The most common use being running the needle over the four sides of TQFP's.

That's basically how I use the liquid product in the picture.  It is really good, and now I have another use for it, every couple of years hopefully!
 

Online David Hess

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Re: Restoring dried solder flux paste
« Reply #3 on: May 01, 2020, 05:45:12 pm »
I have also restored paste flux using a microwave oven for heating.  For a solvent, I have had good results with acetone and toluene.  50/50 toluene and isopropyl alcohol is a common rosin flux thinner and cleaner.
 
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Online rubidium

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Re: Restoring dried solder flux paste
« Reply #4 on: May 01, 2020, 09:50:28 pm »
Completely agree with the 50/50 2-butanol (AKA sec-butanol) / ethanol mixture. It's more than likely this was the original solvent mixture in the paste.
 
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Offline jackthomson43

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Re: Restoring dried solder flux paste
« Reply #5 on: May 02, 2020, 07:17:54 am »
« Last Edit: March 07, 2021, 12:46:06 am by jackthomson43 »
 

Offline SilverSolder

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Re: Restoring dried solder flux paste
« Reply #6 on: May 02, 2020, 12:12:33 pm »
Completely agree with the 50/50 2-butanol (AKA sec-butanol) / ethanol mixture. It's more than likely this was the original solvent mixture in the paste.

I believe the original paste used diethylene glycol dibutyl ether as its solvent, but the sec-butanol in the thin flux works very well as an "additional solvent" even in very small quantities.

 

Offline SilverSolder

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Re: Restoring dried solder flux paste
« Reply #7 on: May 02, 2020, 12:13:31 pm »
50/50 always does the job .....  :-DD

Yes, especially for a gin & tonic!
 

Offline ryan780

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Re: Restoring dried solder flux paste
« Reply #8 on: January 30, 2021, 07:54:27 pm »
As a fellow cheapskate, I just wanted to say thank you.  I don't know why it never occurred to me to use liquid flux to rejuvenated this tub of paste.  My paste wasn't quite as far gone as yours it sounds like so all I had to do was squeeze in the liquid flux and then stir with a stir stick.  Done!  I found this via a simple Google search and this was the first link that popped up.  I so rarely find searching for anything provides real answers anymore.  Instead the first 5 results are usually just links to buy things.  But when I found this on the first try I just had to register so I could say THANK YOU!  You've saved me having to spend money on a new tub of flux and you've made my Saturday.   :clap:
 

Online T3sl4co1l

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Re: Restoring dried solder flux paste
« Reply #9 on: January 30, 2021, 10:14:21 pm »
Ethyl acetate (can be found in nail polish remover? not sure about pure sources though) also comes to mind, having a higher boiling point.

Turpentine is the OG solvent: it's the volatile fraction in natural pine resin (colophony) which gives it its rich piney smell.  It has a high enough boiling point that the sap stays just a little gooey and runs over the wound, but still volatile enough that, soon enough a crust forms, then eventually the deposit hardens.  100% organic! :D

Note, colloquial "turpentine" is more often mineral spirits (petroleum distillate, plain old kerosene).  Probably not a great idea.  Though I suppose any combination is about as flammable?  Guess it's worth a try.  Probably something with a slightly higher boiling point would be nice, so it doesn't bubble and fume so much when the soldering iron hits.

Tim
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Bringing a project to life?  Send me a message!
 

Offline SilverSolder

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Re: Restoring dried solder flux paste
« Reply #10 on: January 31, 2021, 01:04:05 am »
As a fellow cheapskate, I just wanted to say thank you.  I don't know why it never occurred to me to use liquid flux to rejuvenated this tub of paste.  My paste wasn't quite as far gone as yours it sounds like so all I had to do was squeeze in the liquid flux and then stir with a stir stick.  Done!  I found this via a simple Google search and this was the first link that popped up.  I so rarely find searching for anything provides real answers anymore.  Instead the first 5 results are usually just links to buy things.  But when I found this on the first try I just had to register so I could say THANK YOU!  You've saved me having to spend money on a new tub of flux and you've made my Saturday.   :clap:

Welcome to the EEVblog, where we don't just use our solder flux - we take it apart!   :-DD

I actually used the "restored" flux (discussed in the original post) just a couple of days ago, and it still works like new - this is a durable fix!

 

Offline uli12us

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Re: Restoring dried solder flux paste
« Reply #11 on: February 04, 2021, 11:46:07 pm »
The tacky flux in syringes contain petroleum jelly as well. Unfortunately the fraction of it is a secret. I think a third of the weight can not be bad. So you have 1 part rosin, 1part IPA or other alcohol and 1 part petroleum jelly.
 

Offline Alex Eisenhut

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Re: Restoring dried solder flux paste
« Reply #12 on: February 05, 2021, 10:26:35 am »
That's not cheap. Cheap is getting the rosin from a tree... Just need to pick some bark out of it and you're good. I actually cleaned some tips with it. My Dad has several leaky pine trees in his yard...
*Except AC/DC adapters on eBay. Avoid them all!
 
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Online T3sl4co1l

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Re: Restoring dried solder flux paste
« Reply #13 on: February 05, 2021, 10:39:05 am »
Heh, way ahead of you, I actually picked some like a month ago on a walk...  Dissolved in acetone, filtered (ooh it's so sticky, be careful!), let to dry in a warm place.  Such a lovely amber-brown brew... not very tasty, even if you're into those really resinous-piney IPAs. :-DD

The turpentine fraction dries out very slowly indeed, and diffuses slowly, hence it skins over... right now I've got the container sitting above the stove pilot light, it's pretty toasty, but not enough to full melt.  It crusts over, leaving a liquid center.  Tempted to just put it in the oven and get it nice and cooked.  If I do, it'll smell like a saw mill in here... :-DD

As it is, yeah, it definitely works, but it's not as good as a proper blend.  The turpentine fraction evaporates rapidly on soldering heat, bubbling and melting everywhere, releasing nostril-burning fumes of turpentine and assorted light rosin compounds.

In a pinch?  Definitely recommended over nothing at all. :)

Tim
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Offline Ian.M

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Re: Restoring dried solder flux paste
« Reply #14 on: February 05, 2021, 11:01:33 am »
Let someone else boil out the turpentine!  In many less developed countries you can find good quality pale lump rosin at a street market spice stall.  In developed countries, you can usually get it affordably online - avoid 'violin rosin' as it may have additives undesirable in flux.  If the country isn't 'dry' you can probably also get 95% pure ethanol, though you may have to settle for denatured alcohol.   Provided you let the mixed flux settle out and decant it to remove undissolved solids, detritus that was embedded in the rosin, and any aqueous layer, the resulting liquid flux is comparable to commercial ROL0 (unactivated rosin 'R') flux.
 

Offline Alex Eisenhut

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Re: Restoring dried solder flux paste
« Reply #15 on: February 05, 2021, 04:48:54 pm »
And if you get enough of it it's time to boil some potatoes in it.

*Except AC/DC adapters on eBay. Avoid them all!
 

Offline SilverSolder

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Re: Restoring dried solder flux paste
« Reply #16 on: February 05, 2021, 05:21:21 pm »

I didn't have very good results thinning flux paste with either isopropyl alcohol or "regular" alcohol -  the product became grainy and opaque, and the alcohol evaporates out of the mix relatively quickly, leaving you back where you started (paste too thick) in short order.

The liquid fluxes made by the 'Big Flux' companies contain different/additional chemicals that provides desirable properties in addition to thinning the flux, such as longevity and (hopefully) safety!   And it works so well for thinning paste:  a few ml to do a whole tin.
 

Online David Hess

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Re: Restoring dried solder flux paste
« Reply #17 on: February 12, 2021, 09:11:23 pm »
I didn't have very good results thinning flux paste with either isopropyl alcohol or "regular" alcohol -  the product became grainy and opaque, and the alcohol evaporates out of the mix relatively quickly, leaving you back where you started (paste too thick) in short order.

The liquid fluxes made by the 'Big Flux' companies contain different/additional chemicals that provides desirable properties in addition to thinning the flux, such as longevity and (hopefully) safety!   And it works so well for thinning paste:  a few ml to do a whole tin.

Ethylene glycol comes to mind as an additive but I do not remember if that is what they use.  The flux thinner I have commonly seen for liquid fluxes is 50/50 isopropyl alcohol and toluene.

Since Kester no longer provides flux or other chemicals in smaller packages, I would not mind learning how to process raw rosin into RA and RMA flux.
 

Offline SilverSolder

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Re: Restoring dried solder flux paste
« Reply #18 on: February 12, 2021, 09:26:51 pm »
I didn't have very good results thinning flux paste with either isopropyl alcohol or "regular" alcohol -  the product became grainy and opaque, and the alcohol evaporates out of the mix relatively quickly, leaving you back where you started (paste too thick) in short order.

The liquid fluxes made by the 'Big Flux' companies contain different/additional chemicals that provides desirable properties in addition to thinning the flux, such as longevity and (hopefully) safety!   And it works so well for thinning paste:  a few ml to do a whole tin.

Ethylene glycol comes to mind as an additive but I do not remember if that is what they use.  The flux thinner I have commonly seen for liquid fluxes is 50/50 isopropyl alcohol and toluene.

Since Kester no longer provides flux or other chemicals in smaller packages, I would not mind learning how to process raw rosin into RA and RMA flux.

The MG Chemicals product uses 2-Butanol and Ethanol, it seems to me the 2-Butanol is the "secret sauce" to getting a professional result.  I wonder if you could just dissolve raw rosin in the MG Chemicals' liquid flux, to thicken it up?
 

Offline jpanhalt

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Re: Restoring dried solder flux paste
« Reply #19 on: February 12, 2021, 09:44:45 pm »
I have used a lot of butanol in my days and can't stand its smell.

There are many alternative solvents with little or no smell:
1) Glycol ethers (https://en.wikipedia.org/wiki/Glycol_ethers)
2) Low molecular weight Cellosolves (e.g., ethyl or methyl cellosolve)
3) Diacetone alcohol, which is odorless to most people.

Of those three, diacetone alcohol is probably the weakest solvent, but it may still work.  It is used in "whiteboard" markers because it's a decent solvent and doesn't have a strong "chemical" smell that some people object to.
 
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Offline tooki

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Re: Restoring dried solder flux paste
« Reply #20 on: February 15, 2021, 03:40:47 pm »
The tacky flux in syringes contain petroleum jelly as well. Unfortunately the fraction of it is a secret. I think a third of the weight can not be bad. So you have 1 part rosin, 1part IPA or other alcohol and 1 part petroleum jelly.
There's more to it. (Though I don't know what it is.) I tried some experiments with making flux paste from rosin, and nothing I did ever resulted in it actually mixing with the petroleum jelly. With alcohol, it just formed a separate liquid layer. Without alcohol, the rosin could be melted, but always separated back out, so just rosin particles suspended in grease. Awful to solder with.

Various commercial fluxes I've looked at use processed rosin (polymerized or various other processes I've forgotten). So I don't think they're actually just mixing in raw rosin.
 

Offline jpanhalt

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Re: Restoring dried solder flux paste
« Reply #21 on: February 15, 2021, 04:49:00 pm »
Kester (MSDS, SDS) shows that its rosin is 40% to 55% rosin ( CAS:8050-09-07) with an empirical formula of C19H29COOH and isopropy alcohol 55% to 70% (IPA).  The rosin is soluble in "alcohol," benzene, and ether.  "Alcohol" probably refers to ethanol (absolute).

If one searches on that CAS number you may get two different structural formulas (see here: https://www.sigmaaldrich.com/catalog/search?term=8050-09-7&interface=CAS%20No.&N=0&mode=partialmax&lang=en&region=US&focus=product). Of the two, only abietic acid has the empirical formula of C19H29COOH.  Moreover, it is commonly said that rosin flux is mostly abietic acid.

Wikipedia lists the solubility of abietic acid as very soluble in ethanol, acetone, diethyl ether, and petroleum ether.  The latter is a distillation product from petroleum and is mostly aliphatic hydrocarbons, but can contain other hydrocarbons as impurities.

Whether it is soluble in petroleum jelly is not clear.  Rate of dissolution is temperature dependent.  If heated above abietic acid's melting point, it may well dissolve or form a cloudy mixture. I know you can dissolve it in paraffin wax that way. (I used it as a vacuum sealer in high school.)

I suspect any relatively short chain alcohol or any of the substitutes* mentioned earlier will dissolve it.  Kester does list the principle component of its flux thinners as isopropyl alcohol, e.g,. 85% to 100%.

Since abietic acid is insoluble in water, I'd expect its solubility in "alcohol" to be highly dependent on whether the alcohol was absolute or had water in it.  For example, absolute ethanol is an excellent solvent for fats, but 95% ethanol is not.  Same goes for IPA.

*Even with a 10% to 30% water, cellosolves will dissolve rosin flux.
« Last Edit: February 15, 2021, 04:51:15 pm by jpanhalt »
 

Offline SilverSolder

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Re: Restoring dried solder flux paste
« Reply #22 on: February 15, 2021, 05:30:09 pm »

[...] For example, absolute ethanol is an excellent solvent for fats, but 95% ethanol is not.  Same goes for IPA. [...]


That is very interesting, wonder why that is?  Do the water molecules somehow block the alcohol molecules by being more attracted to them than fat, or something like that?
 

Offline tooki

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Re: Restoring dried solder flux paste
« Reply #23 on: February 15, 2021, 08:01:07 pm »
Kester (MSDS, SDS) shows that its rosin is 40% to 55% rosin ( CAS:8050-09-07) with an empirical formula of C19H29COOH and isopropy alcohol 55% to 70% (IPA).  The rosin is soluble in "alcohol," benzene, and ether.  "Alcohol" probably refers to ethanol (absolute).

If one searches on that CAS number you may get two different structural formulas (see here: https://www.sigmaaldrich.com/catalog/search?term=8050-09-7&interface=CAS%20No.&N=0&mode=partialmax&lang=en&region=US&focus=product). Of the two, only abietic acid has the empirical formula of C19H29COOH.  Moreover, it is commonly said that rosin flux is mostly abietic acid.

Wikipedia lists the solubility of abietic acid as very soluble in ethanol, acetone, diethyl ether, and petroleum ether.  The latter is a distillation product from petroleum and is mostly aliphatic hydrocarbons, but can contain other hydrocarbons as impurities.

Whether it is soluble in petroleum jelly is not clear.  Rate of dissolution is temperature dependent.  If heated above abietic acid's melting point, it may well dissolve or form a cloudy mixture. I know you can dissolve it in paraffin wax that way. (I used it as a vacuum sealer in high school.)

I suspect any relatively short chain alcohol or any of the substitutes* mentioned earlier will dissolve it.  Kester does list the principle component of its flux thinners as isopropyl alcohol, e.g,. 85% to 100%.

Since abietic acid is insoluble in water, I'd expect its solubility in "alcohol" to be highly dependent on whether the alcohol was absolute or had water in it.  For example, absolute ethanol is an excellent solvent for fats, but 95% ethanol is not.  Same goes for IPA.

*Even with a 10% to 30% water, cellosolves will dissolve rosin flux.
We all know it dissolves in most solvents.

It definitely does not readily dissolve in petroleum jelly. Again, I've tried. Both with and without the help of alcohol (>99% IPA, specifically). I melted it to the point the rosin was fully liquid (and the petroleum jelly, too, of course, since its melting point is far lower). Oddly, the wiki article on abietic acid lists two wildly different melting points: "as low as 85 °C" in the body text, "172–175 °C" in the infobox, each with a citation. I'm pretty sure I exceeded 85 °C, but no way did I reach 172 °C.

When melted, they'd appear to mix, but as it cooled, it separated into two distinct phases. :(

 It might be interesting to try dissolving it with a hydrocarbon solvent and petroleum jelly, since I would expect each of those to be miscible with each other.
 

Offline jpanhalt

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Re: Restoring dried solder flux paste
« Reply #24 on: February 15, 2021, 08:59:25 pm »
Even pure substances can crystalize or form glasses from "solutions" of themselves.  We "all know that."  For example, you can purify hexadecane (cetane, a major component of diesel fuel) simply by crystallization from liquid hexadecane.  I would not necessarily assume petroleum jelly and rosin are miscible at all temperatures.  If the rosin precipitates, increase the amount of petroleum jelly, or reverse the ratios (i.e., more rosin, less petroleum jelly).  Maybe that is the reason the composition is a secret.
 

Offline tooki

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Re: Restoring dried solder flux paste
« Reply #25 on: February 15, 2021, 09:16:01 pm »
I tried various ratios, stirring while cooling vs. leaving it still, nothing made any difference. Nothing at all like the old Kester 44 rosin flux paste I have a tin of, which is clearly a true dissolved mixture, since it can be remelted without any kind of separation, so it's not a suspension or emulsion. From the (many, many) flux MSDSs I looked at, and a few other sources, it's pretty clear that for liquid fluxes, unprocessed rosin can be dissolved in solvent, but that for petroleum jelly based paste fluxes, the rosin is processed first.
 

Offline SilverSolder

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Re: Restoring dried solder flux paste
« Reply #26 on: February 15, 2021, 09:57:14 pm »

Are all paste fluxes based on petroleum jelly, or only some of them?
 

Offline jpanhalt

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Re: Restoring dried solder flux paste
« Reply #27 on: February 15, 2021, 10:00:22 pm »
@tooki

I just bought a pound of gum rosin.  That's about 8X the amount of paste flux I have used in 50 years.  Should last me awhile. :)

My hypothesis is that your mixture is all wrong.  I suspect something like 1% to 5% petroleum jelly is what is needed, maybe even less.

Should arrive later this week, but an unusually strong Winter storm is brewing, and shipping may be delayed (i'm in a very remote area).  Will test and report.

John
 

Offline tooki

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Re: Restoring dried solder flux paste
« Reply #28 on: February 15, 2021, 10:28:55 pm »

Are all paste fluxes based on petroleum jelly, or only some of them?
No, not all are. Newer flux formulations tend to use other things.

@tooki

I just bought a pound of gum rosin.  That's about 8X the amount of paste flux I have used in 50 years.  Should last me awhile. :)
I should think so! :D

My hypothesis is that your mixture is all wrong.  I suspect something like 1% to 5% petroleum jelly is what is needed, maybe even less.
Not a chance. A 99% rosin concoction, provided you found a way to make a stable mixture, would be a solid, not a paste.

Kester SP-44 was 25-50% rosin according to the MSDS. (The MSDS doesn't list petroleum jelly, but other sources say that's what its base was.)

MG Chemicals 8342 rosin flux paste's MSDS says it's just 5% rosin, 10% paraffin oils (which could overlap with petroleum jelly, that being such a loosely defined term), a few % acids, with the balance unspecified.

SRA #135 rosin flux paste's MSDS says it's 30-50% rosin, 20-40% petroleum jelly, and the balance "non-hazardous stabilizers, and water". (That paste has the most similar appearance to the Kester SP-44 of all the still-available rosin paste fluxes I've seen.)

Should arrive later this week, but an unusually strong Winter storm is brewing, and shipping may be delayed (i'm in a very remote area).  Will test and report.
Please do!!! If you do find a way to make a functional rosin flux paste, I think many people would be curious.

(I've seen a few youtube videos claiming to do so, but I am quite certain they're fake, in that they claim to add a small amount of IPA to solid gum rosin to make a paste, but then when they demo the paste, it's a very pale yellow paste, not the dark amber the rosin would be.)
« Last Edit: February 15, 2021, 10:33:22 pm by tooki »
 

Offline jpanhalt

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Re: Restoring dried solder flux paste
« Reply #29 on: February 15, 2021, 10:43:12 pm »
One experiment is worth 1000 expert opinions or TDS's.  Why do you think ChipQuik's TDS's are so vague?  (PS: ChipQuik's use of bismuth in its low-melting solder is a matter of marketing.)

Will report back as weather and the USPS allows.
 

Offline tooki

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Re: Restoring dried solder flux paste
« Reply #30 on: February 16, 2021, 12:02:32 am »
One experiment is worth 1000 expert opinions or TDS's.
Yet my multiple experiments apparently didn't count?

Why are you being so combative, trying to find something to criticize about every utterance I make?

Why do you think ChipQuik's TDS's are so vague?  (PS: ChipQuik's use of bismuth in its low-melting solder is a matter of marketing.)
Ummm… what? Who said anything about ChipQuik? Even so, how is bismuth "marketing" when it makes up the bulk of the alloy?!?


MSDS's (I didn't say TDS's!) are designed to be vague so as to preserve a manufacturer's exact recipe. All the same, they do offer some insight into what goes into products. Nobody is saying they're complete (since nonhazardous ingredients aren't generally listed), nor detailed enough to be used as a recipe guide.
« Last Edit: February 16, 2021, 12:09:51 am by tooki »
 

Offline helius

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Re: Restoring dried solder flux paste
« Reply #31 on: February 16, 2021, 12:24:18 am »
I'm interested in what you find. I have a nearly-full pint tub of Kester SP-44, but it has evaporated into a hard, rock like solid with needle shaped crystals. Is the consensus here that a 50%-50% mixture of (absolute ethanol or isopropyl) and sec-butanol is what's needed to restore it to a paste?
 
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Offline tooki

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Re: Restoring dried solder flux paste
« Reply #32 on: February 16, 2021, 12:34:42 am »
I'm interested in what you find. I have a nearly-full pint tub of Kester SP-44, but it has evaporated into a hard, rock like solid with needle shaped crystals. Is the consensus here that a 50%-50% mixture of (absolute ethanol or isopropyl) and sec-butanol is what's needed to restore it to a paste?
The crystals are normal. My ca. 1990 tin of SP-44 is still a stiff paste. I don't recall it ever being truly soft.
 
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Offline helius

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Re: Restoring dried solder flux paste
« Reply #33 on: February 16, 2021, 01:07:53 am »
Hmm, thanks. The only thing I tried so far was mixing some with a small amount of glycerin and IPA. I wasn't able to mix it smoothly so these don't seem to be compatible with it.
 

Offline SilverSolder

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Re: Restoring dried solder flux paste
« Reply #34 on: February 16, 2021, 01:12:23 am »
I am super happy with the recipe in the original post - I actually used the flux "repaired" that way today, and it still looks, feels, and works like new.

If you have any liquid flux to hand, it is easy enough to try a small experiment to see if it is compatible with your paste...   this method is strong on the principle "use what you have", in my case at least! :D

This is what it looks like after 9 months - crystals beginning to form on the top, but it is still buttery smooth.

« Last Edit: February 16, 2021, 01:22:04 am by SilverSolder »
 

Offline jpanhalt

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Re: Restoring dried solder flux paste
« Reply #35 on: February 16, 2021, 01:12:32 am »
I am in the same shape as both you guys are with a tub of #44.  It is at least 25 years old.  I just use it and avoid the crystals.  As I recall, I once put it in the microwave or more likely used a heat gun for a short time to remelt the surface -- long enough ago I don't remember .  It still works.  I would not add additional solvents to it unless as a last resort.

Maybe by the weekend, if we are not snowed in, I will have something to report.
 

Online T3sl4co1l

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Re: Restoring dried solder flux paste
« Reply #36 on: February 16, 2021, 01:31:23 am »
FYI, I tried melting some rosin into (very old) paste flux of that sort of composition (sublimates acicular crystals); it seems it sunk to the bottom, and remains brittle and gummy.  I didn't try much mixing, just stirring.  Hard to see if it mixed much, everything is pretty brown and opaque...

Perhaps the commercial product is an emulsion, but it doesn't seem to be a solution anyway, if the rosin isn't chemically altered.

I wonder which alterations would do.  Oxidation of unsaturated bonds?  Cleavage of esters?  And what is "activation" anyway?  (I was poking around a little earlier, and found one 1960s patent using light alkyl polybromides -- yikes!)

Tim
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Offline helius

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Re: Restoring dried solder flux paste
« Reply #37 on: February 16, 2021, 01:49:14 am »
I think hydrogenation of abietic acid esters is more common than oxidation. Those fluxes would then be categorized as "REsin".

As you found, activators are frequently halides, but not always. Some recent formulas are "halide and halogen free" so their activators are in another class, such as citrates, imides or (pyro)phosphates. They are there to react with oxides and slightly etch the metal surface so solder can wet it better.

The alkyl bromides might be scary from a toxicity standpoint, but the main concern is to avoid corrosion or metal migration in the assembled product. Having the halide ion bound up in an organic molecule makes it less likely to migrate and react with copper.
« Last Edit: February 16, 2021, 01:50:51 am by helius »
 

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Re: Restoring dried solder flux paste
« Reply #38 on: February 16, 2021, 07:14:01 am »
Indeed. :) In the same patent, they detailed the tests used to qualify formulations -- some MIL and ASTM standards I think they were, where a copper sheet is thoroughly cleaned and buffed (with steel wool), floated on a lead bath (not tinned, at least not thoroughly!) and left to oxidize in air for an hour at 400C, or a minute at 500.  They say the coating is fractional microns of cuprous oxide, giving it a delightful flat brown appearance.  Seemingly even more impressive is using the solder on it, getting significant wetting (measured by how far a blob of solder and rosin, I seem to have missed how much of each -- spreads out).  I know the fluxes I have here, and my patience level, well enough to get out the sandpaper or steel wool if I saw a surface like that. ;D

They also describe a corrosion test, which is vacuum deposited copper on glass: very thin, so when the rosin is cooked on it (how hot and for how long, was garbled, I was just reading the OCR..), if the copper oxidizes much due to air or rosin, it will disappear pretty much instantly; and the affected area is measured optically.

Hmm, hydrogenation should make the "resin" more lipophilic than alcohol-philic (heh, I don't think there's really such a thing as that, it would just be plain hydrophilicity, wouldn't it), that may be why it doesn't mix with petroleum jelly.

Citrates would be like partial esters, I suppose?  Alkylated to get them in solution, but not fully so there's free acids to be active (and the oxygen-studded citrate will be more active than the chunky abietic acid is); and pyrophosphates would be the same idea?  And imides like the uh, whatever the OSP stuff is, probably?  Yeah, I can see that.  Some of those might be pretty easily accessible to the home chemist; hydrogenation a bit less so.  (I imagine Pd:C or such should do the job, and H2 gas is easy enough to generate on demand -- it's one of the easier organic reactions to perform -- but it's a reaction (and subsequent workup, augh, filtering catalyst from sticky sticky resin solution? :P ) nonetheless, not just mixing raw materials together.)

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Offline SilverSolder

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Re: Restoring dried solder flux paste
« Reply #39 on: February 16, 2021, 02:20:28 pm »

Who knew flux was so complicated!  :D

Presumably the recipes for some old school fluxes are more realistic to execute at home?
 

Offline tooki

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Re: Restoring dried solder flux paste
« Reply #40 on: February 16, 2021, 08:20:35 pm »

Who knew flux was so complicated!  :D

Presumably the recipes for some old school fluxes are more realistic to execute at home?
Not necessarily. If you can get the ingredients, many modern fluxes are very easy to mix, though it hardly makes sense given how cheaply flux can be purchased.
 

Offline jpanhalt

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Re: Restoring dried solder flux paste
« Reply #41 on: February 26, 2021, 05:48:30 pm »
Sorry for the delayed response.  I had to order some "stuff" (rosin, beeswax, petroleum jelly (Walmart), and stearic acid).  I spent a little time searching for formulations on the web and much less time experimenting.

My control/comparison standard is Kester SP-44 flux (I still have half a tin) and Kester 63/37 solder with SP-44 flux.  The MSPS/SDS for SP-44 shows:
Rosin: 30%
Petroleum jelly (PJ): 40%
Stearic acid: 10%

Another SDS for the same thing is similar but shows a few percentage of benzoic acid and ethanediol + "nonhazardous additions" (presumably petroleum jelly).

My first experiment was to test a simple mixture of rosin and petroleum jelly in the ratio of 8g PJ and 6g rosin (43%).  On heating they dissolved each other to give a clear, light amber color.  On cooling there was no separation of phases.  Although, it was cloudy.  A small amount (0.5g) was removed to test as a solder flux.

 

With arrival of my stearic acid, I added 1g to the mixture, heated and let cool.  The product looked the same as the one without stearic acid and was maybe just a little more stiff (no picture).  Final composition:

Rosin: 39.9%
Petroleum jelly:53.2%
Stearic acid: 6.9%

I wanted to oxidize the surface of some PCB without adding halides or sulfates.  I simply used a flame to get a little disolaration.  I then tested the strips using 63/37 leaded solder without flux core.

Here are the results:


#1: No flux, solder simply balled up and didn't stick.
#2: Rosin+PJ only -- almost as bad as #1, ball fell off and was lost.  Some solder stuck to board.
#3: Rosin/PJ/Stearic acid -- Good adhesion
#4: Control (Kester 63/37 w/SP-44 flux
« Last Edit: February 26, 2021, 05:54:51 pm by jpanhalt »
 
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Offline SilverSolder

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Re: Restoring dried solder flux paste
« Reply #42 on: February 26, 2021, 06:17:32 pm »

Interesting experiment!  - does there always has to be some kind of acid in a solder flux, even if it is a mild one, to cut through the oxide layer?
 

Offline jpanhalt

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Re: Restoring dried solder flux paste
« Reply #43 on: February 26, 2021, 06:41:12 pm »
The principle component of rosin is a tertiary carboxylic acid (abietic acid).  So, I'd say, "yes." 

Stearic acid is not that much different, but is softer than rosin.  It has fewer carbons (18 vs. 20) and is a primary carboxylic acid.  I suspect there could be a lot of changes in the formula without affecting performance. 

SP-44 flux has a distinct odor that reminds me of iso-amyl alcohol.  I suspect there are other GRASS (generally regarded as safe) components that aren't on the label. 
 

Online T3sl4co1l

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Re: Restoring dried solder flux paste
« Reply #44 on: February 26, 2021, 06:50:47 pm »
Possibly it could be a complexing salt, or amine, but this would work more on the copper than the solder (tin and lead form fewer complexes, AFAIK), and probably slower anyway.

This is why, for example, copper (as salts, or slowly with exposure to air) can dissolve in ammonia solution, forming the deep blue tetraamminecopper(II) hydroxide.

There is stannate, and plumbate maybe not so much I think; that is, the metals are amphoteric, meaning they can be dissolved in acid or base.  Lead I think requires high oxidation state (not going to happen in contact with bare metal), tin may be happy enough, not sure.  No idea if these are stable and soluble in organic substances, at soldering temperatures.

Whereas the carboxylic acid complexes, of all the above metals, are pretty simple (in any oxidation state, besides metal of course), and reasonably stable.

Tim
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Offline helius

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Re: Restoring dried solder flux paste
« Reply #45 on: February 26, 2021, 09:35:05 pm »
SP-44 is the paste form of Kester 44 flux (the liquid form is 1544). It is IPC class ROM1 (rosin, medium activation, detectable halides). The name "44" comes from its halide portion, 0.44% by weight. This is an important part of the formula that is missing in the homebrew test. Note that this would be an organic bromide, not an inorganic type.

Where can a person get alkyl bromides? One source is oddly in degreaser cans. 1-bromopropane (NPB) is a solvent used in some flux removers (which I do not recommend for that purpose as it has been associated with peripheral neuropathy). If someone else wants to experiment with it, I will pay close attention.
 
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Offline jpanhalt

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Re: Restoring dried solder flux paste
« Reply #46 on: February 26, 2021, 09:50:02 pm »
My purpose was not to replicate SP-44 (which apparently is no longer available) but to show that rosin and petroleum jelly do mix and remain a stable jell.  I would never consider making, rather than buying a flux.
 

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Re: Restoring dried solder flux paste
« Reply #47 on: February 26, 2021, 11:41:02 pm »
Where can a person get alkyl bromides?

Just call up Max Gergel, obviously. :P  (Passed author of _Excuse Me Sir, Would You Like To Buy a Kilo of Isopropyl Bromide?_, a not-too-bad telling of the swashbuckling time that was chemical manufacturing during the uh, 40s to 60s I think it was.  Given the title, I don't think we'd have any trouble in this regard...)

Tim
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Bringing a project to life?  Send me a message!
 
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Offline tooki

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Re: Restoring dried solder flux paste
« Reply #48 on: February 26, 2021, 11:49:51 pm »
My purpose was not to replicate SP-44 (which apparently is no longer available) but to show that rosin and petroleum jelly do mix and remain a stable jell.  I would never consider making, rather than buying a flux.
I wonder what the deal is with my rosin, since it didn’t end up looking anything like that, and just congealed in a layer under the PJ.
 

Offline helius

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Re: Restoring dried solder flux paste
« Reply #49 on: February 27, 2021, 03:09:37 am »
Just call up Max Gergel, obviously. :P  (Passed author of Excuse Me Sir, Would You Like To Buy a Kilo of Isopropyl Bromide?
Thanks for that, I hadn't thought of that book in nearly a week :) It's full of crazy anecdotes, the best perhaps being when the salesman demonstrates the gentleness of a tile cleaner by gargling with it. Unbeknownst to him, the chemist who mixed the cleaner substituted trisodium phosphate for sodium pyrophosphate, completely changing the pH of the product.

I was so interested in this story that I tracked down the detergent ingredient he mentions, DuPont MP-189. The only information I was able to find is that it is a type of hydrocarbon sodium sulfonate, which is entirely unsurprising given the narrative description.
 

Offline ubuntuwi

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Re: Restoring dried solder flux paste
« Reply #50 on: June 22, 2021, 09:13:22 am »
The tacky flux in syringes contain petroleum jelly as well. Unfortunately the fraction of it is a secret. I think a third of the weight can not be bad. So you have 1 part rosin, 1part IPA or other alcohol and 1 part petroleum jelly.

I think it's a recipe like:
55% petroleum jelly
40% rosin
5% alcohol
because Vaseline is a rosin thinner ... 
(Hi I'm new to the forum, I would like to participate)
 

Offline SilverSolder

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Re: Restoring dried solder flux paste
« Reply #51 on: June 24, 2021, 01:43:32 am »
The tacky flux in syringes contain petroleum jelly as well. Unfortunately the fraction of it is a secret. I think a third of the weight can not be bad. So you have 1 part rosin, 1part IPA or other alcohol and 1 part petroleum jelly.

I think it's a recipe like:
55% petroleum jelly
40% rosin
5% alcohol
because Vaseline is a rosin thinner ... 
(Hi I'm new to the forum, I would like to participate)






Welcome to the flux party, @Ubuntuwi

Have you tried making the recipe you suggested?

 

Offline ubuntuwi

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Re: Restoring dried solder flux paste
« Reply #52 on: June 27, 2021, 11:48:52 am »
SilverSolder
yes, I tried to make the recipe that I suggested!: in a few days I will publish some tricks, which I learned immediately, in the meantime I tell you: you have to mix the rosin powder with vaseline, (cold), then using a stove electric, put everything in an earthenware pot, bring the temperature to 130 ° celsius, (everything melts) mix with a piece of wood; always turn ... when you see that the rosin wants to separate from the petroleum jelly ... spray the alcohol, isopropilic. (at this point the temperature should be around 80 ° celsius, and hot alcohol is soluble with rosin, but also with petroleum jelly, all this giving an inseparable mixture). continue to mix until cool.
 
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