Solder FLUX types

[Yaro]

Hi all,

I want to ask something about solder flux. I've a very old solder flux were I can't read it's name on the label so it's old(and not well keeped or maybe it's not original package), but I remember it had in compositions something with cyanide. It's aspect is something very dark and brown and consistency like a gel. I've always used this solder flux and now is going to finish. It worked very well, when placed on a wire and goes in contact with solder iron it fizzes and create some smoke but it attract very well tin. Recently I've ordered two new solder flux to replace this:




(it's similar but mine have a lighter color)

I've done some tests, but it's a far away to work well like the one I was using. I want to ask if someone have more experience with solder flux to tell me better what I was using or to advice me a better solder flux to use.

Thank you!

[exe]

May be these videos will be helpful:
http://dangerousprototypes.com/2012/02/02/workshop-video-battle-of-the-solder-flux/
http://dangerousprototypes.com/2012/05/03/workshop-video-flux-off-part-2-more-flux-reviews/

I don't know any other reliable sources of flux benchmarks For sure people will be promoting what they use . Also, there are also fake fluxes on ebay...

I went for fl-22, it works fine for non-acid flux, but VERY expensive in online stores where I could buy it. So, I would consider replacement if there is something similar. Not because I cannot afford buying one syringe a year, but because paying some thousands of dollars per liter (although I need only 5ml) looks overpriced...

[ROBOT]

I strictly use Kester 2331-ZX pens. Works wonders. But so far no issues drag soldering 0.4mm pitch QFN-EP.

[sleemanj]

Both of those fluxes will be fine, they are probably close to the same mixture, the tub paste one will be a bit firmer consistency than the syringe gel one.  I've used plenty of both.

Electronics flux is basically Rosin (boiled resin from pine trees), a solvent, and additives to give it the necessary consistency, usually things like stearic acid, glycerine, petroleum jelly.

Your old flux might have been a high content of rosin giving it a dark colour, or it might even have been something more like plumbers flux, which is very aggressive acid flux and should not be used with electronics.

Note: the syringe flux you posted is often sold or labelled as "Amtech", which is a well known American brand of fluxes, but (and the spelling errors on the labels should be a give-away), this flux from China is not Amtech flux.  Not that it doesn't work just fine, but it's not made by Amtech, for whatever that is worth.   Amtech and Kester both are counterfeited in China, that is, there is flux sold under those brand names that is not actually Amtech or Kester.

[nanofrog]

I'm not sure how much you know, so bear with me if this is familiar....

There's 3 basic types of flux suitable for electronics use (chemical composition).
1. Rosin based.
2. No-clean formulations; some are made from modified rosin, others from synthetic resins.
3. Water soluble.

Rosin comes in 3 basic types, R (Rosin), RMA (Rosin, Mildly Activated), and RA (Rosin, Activated) from least active to most active. No-clean is also good for hobbyist electronics use as well, but be aware it is harder to clean. Either of these can be left on the boards or cleaned off if desired for cosmetic reasons or there is a specific requirement for doing so, such as high impedance.

I wouldn't recommend water soluble flux for hobbyist use however, as it must be cleaned off in a timely manner or it will corrode your joints. Best to just avoid this stuff entirely. And whatever you do, stay away from acid flux or plumbers flux (i.e. zinc chloride or ammonia chloride) as it's not suited for electronics use at all.

Just stick to quality brands, such as:

• Multicore (Henkel)
• Stannol
• Kester
• AIM (American Iron & Metals)
• MG Chemicals
• Indium
• Alpha (older labels may be marked Alpha Metals; Alpha is owned by Cookson)

Not sure which of the above you'd be able to find in your market, as I've no idea where you're located ATM.

That said, MG Chemicals 835 (liquid RA), is available in small bottles that are reasonably priced which is very useful for hobbyists (125ml and 1L sizes), and is easily found in North America, the UK and EU. Not sure about other markets.  Kester flux is excellent stuff IME (186, 186-18, and 1544 are all liquid & rosin based). Unfortunately, Kester only offers their fluxes in disposable pens or large containers (1gal & larger, up to 55gal drum). It's readily available in the US, and although can be had in the UK/EU, it's expensive as it's usually shipped from the US from what I've seen (Farnell).

For paste, Kester RF741 is a modified rosin no-clean that's very nice to use (comes in a syringe). Amtech is supposed to be good as well (also a syringe), but the real stuff is hard to find as their distribution is nearly non-existent (highly counterfeited too).

FWIW, I usually use liquid in a refillable brush pen as it's less expensive and gives me better control than the disposable pens.


BTW, if you go into your user profile and set your country, it's flag will display beneath your userID for each post. That way you don't have to answer this all the time, and you get answers faster as well. 

[GreyWoolfe]

+1 for MG Chemicals 835 in the smaller bottles.