Time to get flux again

[throbscottle]

I got some very cheap no-brand no-clean liquid flux a few years ago so I could re-flow the PS3 (worked well, btw) and ever since I've been using the stuff for all kinds of soldering since it makes quite a big improvement. Well the bottle is getting quite low now, so I'd like to get some more, but a bit more suitable for general soldering, since this one is really watery in consistency - I'd like a more viscous version that doesn't pour away quite so easily! So, any suggestions, anyone? Has to be no-clean, and has to be cheap, I am on a non-existent budget!

 

[gary350]

I have always used plumber copper pipe flux. It is cheap and it works but I am not sure it is the best choice.

When I was on college we were told to use ???? I dont recall the name but it looks like a white bar of soap.

If you go to an industrial welding supply store they will give you a bottle of stuff that works great for solder flux. I dont remember the name of this stuff either. I use to have some it may be the same stuff they use for silver solder.

 

[Nigel Goodwin]

I have always used plumber copper pipe flux. It is cheap and it works but I am not sure it is the best choice.

It's certainly NOT a 'good' choice at all, never mind the 'best' - you shouldn't use it for electronics, or anything other than plumbing.

It's corrosive, electronics flux is formulated not to be.

 

[crutschow]

I have always used plumber copper pipe flux. It is cheap and it works but I am not sure it is the best choice.
...........................

As Nigel noted, that's a "no-choice" for electronic circuits.
It may appear to work fine initially for fluxing a solder joint but a few years down the road the circuit will likely be seriously corroded, perhaps to the point of failure, especially on something small like PCB joints and traces.

 

[flat5]

https://www.banggood.com/buy/Flux.html

You might like this one.
No-Clean, good packaging, good quantity for the price.
https://www.banggood.com/100g-Kingb...der-Paste-for-BGA-PCB-Repairing-p-930905.html

or

https://www.banggood.com/100g-AMTEC...-Clean-Solder-Flux-Solder-Paste-p-930871.html

 

[throbscottle]

Wow, that /is/ cheap! I'll have another look when I've got some work again. Thanks

 

[Blueteeth]

Ehh I've tried a few fluxes here and there, for soldering DFN SMT, and I find it rather hit and miss.

On the one hand, ebay has tons of stuff, usually in large easy-to-apply bottles, labelled 'no clean flux'. Whilst this can work, it often floods, and instantly cools the iron, leaving lots of steam, and by the time its hot enough to melt the solder, the flux has gone. If applied with a cloth, or a cotton bud - does the job just fine. (I still clean off the residue though, as it generally wipes clean with isopropyl alcohol). Almost always for ROHS, lead-free solder temps. The stuff used for leaded solder is much more forgiving - I can swipe the pins of a TQFP in one pass leaving no solder bridges - all whilst its flooded.

On the other hand... there is expensive brand names from RS, Farnell, (and rapid in the UK) available in pastes, and pens, both of which are excellent and leave beautiful shiny joints even with cheap lead-free solder. They are however expensive.

Also, as most solder wires these days come with flux cores, usually resin, sometimes no-clean, these can leave residues themselves, another reason to clean. I've only used water soluble fluxes once, never again. Sure you can clean it with water, but if any residue remains under a SMT cap in an oscillator, or something, it can cause all sorts of troubles. Even some no-clean fluxes have caused this problem for me

I settled on buying one of those pen applicators. Expensive, but I really use very small amounts.... plus I can refill the pen with cheapo flux if needs be. Cheap in the long run, does the job. Like the OP I'm also looking for effective flux for lead-free soldering (mostly SMT parts) that isn't ridiculously priced

BT

Edit: just noticed in that link the 'Kester 186' - thats the stuff I've used time and time again. The nib gets fluffy and old, but it works like a charm.

 

[throbscottle]

Thanks for the useful info, BT. I think I got one of those Kester pens when bought my first lot of flux. Didn't realise it was refillable.
So do you reckon it's better to use liquid flux, applied properly, than one of the pastes then?

 

[throbscottle]

flat5, there is a very great responsibility upon your shoulders... you have made me start looking at all the /things/ on Banggood now!

 

[flat5]

Ha! Welcome to the club
I've spent 1717.16 Euros, so far, almost all on electronic parts and equipment and tools.
Since June, 2014. Everything has eventually been delivered.
Every question has been answered. Every problem resolved.
Anytime I tell them something is defective they ask for a movie
I have sent pictures and they credit my Paypal account. No problem.

 

[throbscottle]

Oh my goodness, I wish I had that much money! Anyway thanks for the useful info, good to know they are good to deal with.
My next contract should be fairly juicy so might have some pennies to spend

 

[Nigel Goodwin]

Oh my goodness, I wish I had that much money! Anyway thanks for the useful info, good to know they are good to deal with.
My next contract should be fairly juicy so might have some pennies to spend

I've just had yet another parcel from them today

Only one out standing now, the one with the Arduino starter kit.

Only 'problem' is how long it takes to come, but the prices are good, it's free postage, and coming a hell of a long way - so you can't really moan too much

 

[Blueteeth]

Thanks for the useful info, BT. I think I got one of those Kester pens when bought my first lot of flux. Didn't realise it was refillable.
So do you reckon it's better to use liquid flux, applied properly, than one of the pastes then?

Well, the one I had wasn't refillable, but I made it so by drilling a small hole, and using a syringe to refill, then sealing it with epoxy

As for liquid vs paste. I would say paste is easier, as it stays where it is! A lot of folks hate the pens because the way you get the flux out is to press down on the nib. This is meant to just 'wet the nib' - just like an ink pen - and often it just leaks and lets it piss all over the board. Ideally, it shouldn't flood at all, press it down just enough so the nib is wet, then use that to 'paint on' a very small amount onto pins/pads. I'm still surprised at just how little one needs.

The paste, or the thicker stuff on the other hand is much easier to control. In a syringe, you can apply absolutely tiny 'dots' of it which still provides enough flux to clean the pads and leave a beautiful shiny fillet, it also means that such syringe last a stupidly long time.

Sorry for the small rant! In summary, the pens are handy, the flux works just fine, just use it as a pen, rather than a 'dispenser' If the nib is dry, shake it, but never press it down on a PCB or it leaks like toddler on tizer.

BT

ps. I am also now hemorrhaging money on banggood. Thanks a lot for introducing it to me >.<