I need your ideas on how to test flux!

RE: I need your ideas on how to test flux!

indeterminatus — Wed, 27 Jul 2022 21:30:59 GMT

I would be interested in a fourth comparison: solder with flux core.

If it makes any difference at all, what about health hazards? Are all fumes somewhat equally bad?

Is one type of flux more "forgiving" towards beginner errors than another? (Say, accidentally applied too much flux)

What would happen (over time) if flux residue is not properly cleaned? No idea how to simulate/show that, though, unfortunately.

RE: I need your ideas on how to test flux!

Workshopshed — Wed, 13 Jul 2022 16:01:01 GMT

Can you get hold of some really old boards? I find brass connectors are often hard to solder.

Tips for oxidisation recommend salt and vinegar and of course air.

RE: I need your ideas on how to test flux!

coffeeBuzzBuzz — Fri, 01 Jul 2022 15:47:44 GMT

Not everyone has the luxury of soldering on a well-lit, clean bench. How do the offerings compare e.g. on an incline?

RE: I need your ideas on how to test flux!

DAB — Thu, 26 May 2022 18:15:58 GMT

You could look at the different types of metals that each type of flux can clean.

You could also look at the temperatures at which the flux actually need to attain before it supports the soldering.

Something like the rule of thumb for plumbing flux, where you wait until the flux bubbles before you apply the solder.

RE: I need your ideas on how to test flux!

michaelkellett — Thu, 26 May 2022 08:56:03 GMT

I don't think there is much point in testing flux on deliberately chosen bad parts - the solution to that problem is not to use bad parts !

On the other hand testing on a nice new gold plated pcb maybe gives the flux little chance to show its goodness.

So I suggest hand soldering 0603 surface mount caps and resistors and TQFP packages (by "drag" soldering) on new but cheap solder levelled or immersion silver coated boards.

I use very runny (like water) flux applied with a paint brush. (Warburtons Future 315). It's sold as no clean but I almost always clean using Safewash (water soluble soap) in an ultrasonic cleaner and rinse with tap and then 2 flushes of de-ionised water.

For re-work I might just use IPA as Shabaz suggests.

I've had Doug's problem with residues being OK until they absorb moisture.

RE: I need your ideas on how to test flux!

robogary — Thu, 26 May 2022 00:45:06 GMT

I grade flux by how much billowy smoke it creates :-)

RE: I need your ideas on how to test flux!

dougw — Wed, 25 May 2022 19:40:48 GMT

I don't know exactly how to test this but we recently had a case where no-clean flux became slightly conductive, causing big issues. presumably it was from moisture absorption. It was very unexpected but repeatable.

It probably isn't a fair test, but you could try soldering to aluminum - flux is definitely important for this application

RE: I need your ideas on how to test flux!

shabaz — Wed, 25 May 2022 19:22:27 GMT

Hi!

Regarding "Maybe an additional test needs to be soldering new components/PCBs for comparison?" it could be worth showing how to prepare old components, i.e. clean the leads (sandpaper would be the 'keeping it real' method ; ) or those fiberglass pens etc). However, also there could be an explanation why old stock is not always a good idea (e.g. connectors can oxidise/corrode on the mating surfaces, so no matter how much flux is used, the connector can still be unusable), this might also apply to IC sockets.

Regarding cleaning flux, for home use at least, I get great results with just isopropyl alcohol, a brush (this brush is excellent, unlike others it is very stiff) and then mop up the flux and IPA with Bemcot M1 or M3 wipes. Visibly the result is spotless, perhaps not the same as production-grade chemicals of course. MG Chemicals 70/30 wipes are also excellent, but they are more expensive. A bottle of 99% IPA and some packs of Bemcot wipes is cheaper.

RE: I need your ideas on how to test flux!

wolfgangfriedrich — Wed, 25 May 2022 18:05:31 GMT

There has to be a smell test. It will be highly subjective, but I, for one, love the smell of hot rosin flux.

If you think it is a health risk, don't try this at home. [emoticon:c4563cd7d5574777a71c318021cbbcc8]

RE: I need your ideas on how to test flux!

rsjawale24 — Wed, 25 May 2022 17:57:20 GMT

https://www.youtube.com/watch?v=iKDAmY9Rdag

Watch this video. This guy has many videos on soldering. He is like the guru of soldering.

RE: I need your ideas on how to test flux!

Jan Cumps — Wed, 25 May 2022 17:08:26 GMT

> Are there any other areas we should explore?

application:

a pot like you show,
paste in a syringe
fluid with a brush
fluid with a pen