No clean flux is a lie

[bobbydazzler]

About 2 months after it was soldered up.

[boB]

You sure that you "deactivated" it by heating it up everywhere ?

I'm not sure exactly what part of the board you are thinking about ?

What I have seen when active flux (clean or no-clean) is that when it has not been heated up everywhere, it can conduct.

Some flux like rosin  can leave a residue but doesn't necessarily have to be cleaned up.

There was this stuff called "Flux Off"  (I think ?) that worked pretty well but if active flux gets underneath a part, it can even corrode and conduct.

I know that actual washing flux can be a real pain in the arse to set up and do correctly.

Curious what your PCB is doing.

[coppice]

When they claim that you don't have to clean off the flux, its rather like claiming you don't have to clean your home. While true, there may be negative consequences.

Even if the no clean flux doesn't result in long term corrosion, you can find many high impedance designs where it fails due to surface leakage. This may be leakage through the flux itself, or by the flux promoting moisture buildup on the surface of the board. A clean board needs to be in close to 100% humidity for much moisture to settle on the surface, but a dirty or fluxy board can become moist at quite low humidity levels.

As usual in engineering, one size does not fit all.

[ataradov]

I see no damage. If you are talking about the mess sticking to the board, then this is not what is understood under "no clean",. It does not mean it will evaporate somehow. It means it will not corrode the board in 2 months.

And yes, no clean only applies to the fully activated flux, which is highly unlikely while hand soldering. So clean any type of flux.

[Doctorandus_P]

"No Clean" means that the stuff is impossible to get off your PCB.

If you want a clean PCB, then use flux that easily dissolves in water or IPA.