Solid rosin flux - how is it used?

[DTJ]

I've been looking for some liquid rosin flux at a nice price here in Oz.

I found this solid rosin flux at the link below. How is it used? Dissolved in IPA?


http://kinsten.co/soldering/rosin/


Does anyone have any practical experience with it?


Thanks.

[Deathwish]

I mix mine at a ratio of 25% to IPA

[tszaboo]

You can use it in a wave solder machine, or a solder pot. Not really for a hobbyist. Just get one in a syringe.

[LukeW]

Grind it to a powder and dissolve (eg. IPA as the solvent).

OR - use it molten. You can stick a soldering iron in it to melt it, or use a hot-air pencil to melt it a little, just enough to allow a drop to drip off the block of rosin onto the work area.

[Ian.M]

https://www.eevblog.com/forum/beginners/anyone-tried-pure-rosin-flux/10/

Its useful to have some around, and I've made up a few jars of liquid flux from it over the years whenever the boss was bitching about the cost of good rework flux, and even showed him how to make a flux pen out of a thoroughly washed out and dried  hiliter pen with the adsorbent foam saturated with the liquid, but it certainly isn't a cost-effective way of getting liquid flux in a 1st world country, as I proved to my boss when I had him add up my hourly rate and overheads for the time spent making up the liquid flux.   From then on, I was authorised to order the good stuff . . .

[continuo]

I use it all the time, works surprisingly well   

~15g crushed pale violin rosin, dissolved in ~50ml 2-propanol (IPA). You may want to toss in a powdered aspirin tablet for that eXtra flux-oomph 

[DTJ]

Thanks for all the replies and ideas guys. I might just buy some and try it out.

I use rework flux in syringes for SMD work but I want something for dipping wires into prior to tinning in a solder pot.

[tszaboo]

I use it all the time, works surprisingly well   

~15g crushed pale violin rosin, dissolved in ~50ml 2-propanol (IPA). You may want to toss in a powdered aspirin tablet for that eXtra flux-oomph 

This is not the first time I hear about aspirin. What exactly does it do (other than probably poison you while soldering)?

[SeanB]

Organic acid, added to provide extra corrosion removal when heated. You could use pretty much any of the family of weak organic acids, though some are a lot more toxic than others. Vitamin C will do as well, but it is going to release some nasty vapours, like the asprin as well, when heated. Asprin because it is easy to get as a very pure powder and in a high purity, plus it is cheap. Nice thing is it is easy to clean afterwards with plain water or alcohol.

[Ian.M]

Hmm. 

Commercial Asiprin is Sodium acetylsalicylate (+ various pharmaceutically inactive fillers and binders).   Sodium acetylsalicylate has high solubility in water but very low solubilty in isopropanol (to the point that isopropanol can be used to precipitate it).

Acetylsalicylic acid has high solubility in isopropanol and very low solubility in cold water (and can be precipitated from a solution in isopropanol by adding ice cold water).

I therefore suspect that if one follows the usual practice of decanting the clear liquid flux off the insoluable residue after settling, the actual acetylsalicylic acid activater concentration in the flux will be low and uncertain. 

Aspirin tends to decompose in the presence of moisture from the air to Sodium salts of acetic acid and salicylic acid + free acids which will increase the proportion of isopropanol soluable organic acids if you use date expired aspirin, but if you want a consistent result, you would need to acidify a strong aqueous solution of Sodium acetylsalicylate with hydrochloric acid to precipitate acetylsalicylic acid and dissolve a known weight of the room temperature dried precipitate in isopropanol to make your activator. 

It may be easier to use an alternative organic acid or ester as an activator that is more readily soluable in isopropanol.

[gibbled]

Browsing around I ran across this list of activators.  Not sure how to accquire them in small quantities though.

http://www.esprixtech.com/products-applicationindustry/aluminum-brazingflux-activators/solder-flux-activators

[Ian.M]

I ran into this page: http://www.harshsolders.com/flux-and-chemicals.html#Flux%20and%20Chemicals
Citric acid is readily available.

[ivaylo]

I use it all the time, works surprisingly well   

~15g crushed pale violin rosin, dissolved in ~50ml 2-propanol (IPA). You may want to toss in a powdered aspirin tablet for that eXtra flux-oomph 

This is not the first time I hear about aspirin. What exactly does it do (other than probably poison you while soldering)?

Aspirin is great for soldering heavily oxodized metals, it's an acid so do the math (ahem..., the chemistry I mean). It's the nastiest to breath though. Another used for centuries and very strong flux is http://en.m.wikipedia.org/wiki/Ammonium_chloride#Applications .

[nanofrog]

Browsing around I ran across this list of activators.  Not sure how to accquire them in small quantities though.

http://www.esprixtech.com/products-applicationindustry/aluminum-brazingflux-activators/solder-flux-activators

Check out Sigma-Aldrich (they usually carry stuff like this, and in small quantities).

FWIW, I looked into them for industrial grade DMA-HCL as an activator (here). And although DIY'ing it comes to an initial sticker price similar to buying it, you may avoid the shipping and hazardous materials fees tacked on 1gal & larger containers (not sure if Canadian law is different on this).

Formula:

• 1 gal Denatured alcohol - from a local building supply store  (Kleen Strip brand ~= 50/50 ethanol & methanol, with up to 1 - 4% of MIBK as a denaturing agent, which is also a solvent)
• 1lb Rosin (eBay)
• 50 - 75g of DMA-HCL (min & max by weight respectively)

Based on what I'm getting for pricing here in the US, it's possible to DIY an RA liquid flux very similar to Kester 1544 or MG Chemicals Rosin 835 for ~$50 - $65 per gallon (depending on how much activator you add). 

A gallon is a lot of flux for a hobbyist though IMHO, and buying in smaller quantities to DIY ^ just doesn't work out. So sticking to small containers of MG Chemicals Rosin 835 makes better financial sense (or an eBay seller you trust that breaks up bottles of Kester for example).

[smjcuk]

I ran into this page: http://www.harshsolders.com/flux-and-chemicals.html#Flux%20and%20Chemicals
Citric acid is readily available.

I used coke zero on various occasions as a flux. It doesn't have sugar in it so doesn't leave a nasty residue like normal coke. Also drinkable!

[Ian.M]

Apparently DMA is a precursor for a nerve agent and a rocket fuel, so even if you can get DMA-HCL as a private individual, you are likely to end up on anti-terror watch lists. 
I would suggest concentrating on finding activators that have a legitimate domestic use.

[SeanB]

I ran into this page: http://www.harshsolders.com/flux-and-chemicals.html#Flux%20and%20Chemicals
Citric acid is readily available.

I used coke zero on various occasions as a flux. It doesn't have sugar in it so doesn't leave a nasty residue like normal coke. Also drinkable!

I use regular coke as a degreaser for clothes, it works well on those stubborn grease stains. Can also be used as an engine degreaser in a pinch.