Does flux expire ?? Flux discussion.

[eccerr0r]

Coliformia is the state made of colifony of course <BOOO! HISS!>

[Dannyx]

Remember that can of polish flux ? The one I said I had no idea what it was called because the sticker was on the bottom ? Gave it a whirl today and it was....meh. I had to reflow some connections on a QFP and a USB mini-B connector. It went...mediocre at best: solder blobs everywhere and the flux seemed to dry rather quickly. The tip I used was the bevel one (slanted) and it seem to go worse than the T-IS (curved) one, so I ended up using that one instead and I kept adding flux and wicking around until I managed to get somewhat acceptable results, but it wasn't fast and not exactly professional....a pro tech would not be impressed with the time it took me to reflow those....

The tips and temperature also seem to play a role. I ended up dialing down the temp from 420C to around 390C (on the display at least) on my Gordak because the tip was starting to get gray and looked burnt and charred, so solder wasn't sticking to it and was instead blobbing on my pins instead . Lowering the temperature allowed it to stay shiny a bit longer and I got somewhat more acceptable results, but STILL had to wick around more than I would like....or perhaps that's not a bad thing.

[stj]

i wouldnt go over 350 with flux of any type.
it is pretty crap though, i only use mine for tinning old wires

[Dannyx]

Originally Posted by stj

i wouldnt go over 350 with flux of any type.
it is pretty crap though, i only use mine for tinning old wires

The temperature on the display is probably considerably off compared to the actual temperature at the tip, so I prefer to keep it a bit higher, knowing the tip is going to be colder anyway. Besides, I mostly go by feel rather than numbers and I sometimes found that not enough heat can lead to poor/frustrating results just as well as TOO MUCH heat....

[momaka]

Originally Posted by diif

Sure is. Mine is about 3 years old and has the same Lot# as half of those sold today. It's like a copy of a copy of a copy. A bit pot luck how good it is, some stays thick longer than others.

Yup.

Apparently, Kingbo is just another generic Chinese RMA flux, so the quality will vary. But from what I've seen myself and heard from others so far, it's anywhere from acceptably working to very decent. So it's not junk / terrible, typically.

My jar is about 7 years old now. It used to be light tan when it was new. Now it's piss-yellow (the kind of yellow urine you get after not drinking enough water and eating salty shit all day.) It still works, though. Just seems to smoke a lot more and definitely smells worse. Also doesn't seem to stay active for as long at high temperatures / gunks up faster. But like I said, it still works okay, more or less.

So I wouldn't say flux expires - especially rosin fluxes. But in the case of my Kingbo, it did drop down a bit of its stability at high temperature, it seems. And in the case of rosin fluxes... well, those could dry up due to the alcohol evaporating from them - but that's usually fixable by adding more alcohol.

[Dannyx]

Originally Posted by momaka

Now it's piss-yellow (the kind of yellow urine you get after not drinking enough water and eating salty shit all day.)

ROFL ! I think I just spat my drink all over the laptop - liquid damage !

Ok, so it wasn't the flux that was bad after all, it was just me who sucked on those QFNs back there

I too noticed the kingbo flux I pictured below smokes a LOT - Mr G. let me use some once when I quickly needed to desolder something at his table and I dipped the wick in it to make it more absorbent and it smoked so much that I couldn't see what I was doing and choked on the smoke. Then again, he keeps his iron turned all the way up, so it was probably REALLY hot...

[zhang]

Could it be hot air settings?
if the "air" is too high, when the fluxes melted it will go everywhere but the "place you want to melt"

[Dannyx]

True, though I did turn it way down because of this reason. Not to mention, it also tends to blow away the part you're working on as well, plus other smaller ones around it, quickly turning a 5 minute repair job into a 1 hour nightmare....

[diif]

The air speed is too high if you're blowing away other parts.

[clearchris]

Can confirm momaka's experience with kingbo. It has darkened, especially where I dip the tip in. When new, it was a light cream color. Still seems to work just fine. It does smoke a lot, I hold my breath when soldering anyway, helps to keep the hands steady. I used to seal it after using and it stayed the same color, but it has spent the past three years open on my bench.

The only way the residue will come off is with brake cleaner in my experience. Must be careful about that stuff, the cleaner must be completely gone before soldering.

[momaka]

Originally Posted by clearchris

Can confirm momaka's experience with kingbo. It has darkened, especially where I dip the tip in. When new, it was a light cream color. Still seems to work just fine. It does smoke a lot, I hold my breath when soldering anyway, helps to keep the hands steady. I used to seal it after using and it stayed the same color, but it has spent the past three years open on my bench.

Well, I keep mine closed and have never dipped my iron's tip in it, but it still went dark. I'm thinking it has more to do reaction to UV light. Although I keep my flux away from direct sunlight for the most part, I do have a ton of natural light (big North-facing bay window) on my workbench area, which is where the flux is.

And yes, I try to hold my breath too when using large amounts of Kingbo. Though, I usually apply very very little - about the size of a tiny beach sand grain (or two) per joint, which turns out to be just enough. Any less, and I get cold-looking joints. Any more, and I have to do more clean up. Speaking of which...

Originally Posted by clearchris

The only way the residue will come off is with brake cleaner in my experience.

I use 99.9% IPA, and the Kingbo flux comes off fine. Only time I've had problems removing it is if I burned it onto the board to a crisp. But in that case, I just chip it off.

Originally Posted by Dannyx

I too noticed the kingbo flux I pictured below smokes a LOT - Mr G. let me use some once when I quickly needed to desolder something at his table and I dipped the wick in it to make it more absorbent and it smoked so much that I couldn't see what I was doing and choked on the smoke.

Oh man, I've seen a rookie tech do that before, and it was so funny! The smoke made him think the board must have caught fire or something, so he dropped the iron and the wick and jumped back. Made me laugh seeing it. Almost had a hard time convincing him this was actually normal... at least for the amount of flux he was using (which was too much!) If you have to flux wick, do it with a brush and apply little. Or use a tootpick and spread a rice grain -sized or smaller piece of flux.

[eccerr0r]

I would guess the animal fat based fluxes could expire when they go rancid (but even then...). Now how about fully hydrogenated shortening instead...?