de-flux pcb or not?

I'd suggest ringing around various cleaning supplies and chemical shops: I think it's used in aluminium cleaner formulations. I used to buy it from a small fibreglass supplies shop for $12 for 2L if you brought your own container.

What are peoples ideas on cleaning flux from boards after hand soldering? In particular 511 crystal & 362 rosin lead/tin solders from multicore. Places I've worked have had different attitudes. Any arguments for/against? I've heard a lot of "it looks like sh@t" but in most cases it doesn't matter does it?

"K Ludger"

Ordinary ( non acid) solder flux is non corrosive and non conductive WHILE the surface remains hard and shiny.

However, if the surface becomes damaged, scratched or broken - then it will absorb moisture from the air and become very conductive, very corrosive and so very harmful to circuit operation.

So the " Clint Eastwood Criterion " has to be applied.

The one about punks and luck ......

BTW

I have seen valuable equipment written off simply because the makers had NOT de-fluxed the PCB before installing all the op-amp ICs in sockets.

...... Phil

We had a batch of boards manufactured with "fluxless solder". Or, it doesn't need flux cleaning after the wave solder stage.

At least 90% of our boards would not function till we cleaned them, properly.

Ended up sending what's left of the batch back so they can fix their stuffup.

That was the first time we've seen this type of fluxless solder being used, (and last time we wanted to know about it) and now demand the boards are cleaned regardless of their process.

Was there anything sensitive about the board John - high gain integrators, very low currents???

Agreed

Because? - corrosive flux? humid usage environment?

Clean the boards, especially if you have high impedance areas. Ensure that your cleaning materials are clean as well. Do no allow fluxes to remain on component bodies like smd caps (0603, 0805, 1206), etc. If you have flux and dc across a cap, and a humid atmosphere, over time you will get deposition across the surface of the cap, leading to lower impedance across the component and possibly affecting circuit operation.

"K Ludger"

Then the IC pins punctured the normally impervious coating on the flux.

Then, the flux absorbed lotsa water out of the air.

Then the whole device ( a dual 1/3 oct. graphic equaliser made by Phonic of Taiwan ) became ridded with DC leakage current flowing from DC supply pins to adjacent input pins.

Result = massive " popcorn noise" in the output .

Useless and uneconomic to repair.

Fuckwits.

..... Phil

Oddly enough, we only really noticed the problem with the digital boards, we never got to testing the analogue section because of that.

And this isn't seriously high speed either, 8051 based CPUs that were clocked lower than what the CPUs were rated to save power (can't remember exactly how fast though, this was a while back). I do remember they didn't go past about

The CPU PLCC through-hole sockets were especially troublesome, where cleaning of the socket pins was required, and in some cases, removal of the socket, clean underneath and re-solder back in again.

Not happy Jan.

I've had similar experience with PLCC sockets, they can be a bitch to track down initially.

What do you/others use for cleaning?

I generally clean with IPA, sometimes metho and sometimes spot rinsing with distilled water. The IPA wash I usually repeat a few times to get rid of the flux salts from between SOIC pads etc. I tried some "citrus" based wash years ago but found it quicke and easier to just use IPA.

IPA alone. As you do, sometimes twice over, first to loosen/dissolve, second to flush that mixture off. And it evaporates faster too, where I can shake it off, let evaporate for a few minutes and I'm ready for testing again.

Works well.

I never liked metho, it didn't really do a good enough job because it was watered down, and the additives leaves streaks when you're using it for general cleaning. And I didn't want to keep too many different chemicals where I didn't have to.

I use metho and a 1" soft bristled paint brush. That's because I'm too tight to waste IPA if I don't need to.

John

Know of anywhere cheaper for the IPA than Altronics at $20 for 2L? cheers