Flux paste and conductivity

[bodger]

So about a week ago I got around to soldering my first SMD IC on a SOP8 to DIP8 PCB, I used MG Chemicals Rosin Flux Paste #8342. The soldering itself was fine, in fact I was impressed at my 1st attempt. Unfortunately, the paste was conductive, even though I'd cleaned the board with IPA after soldering; I guess some of it remained under the IC (hence it didn't behave as expected). 
So my question is how common is it for flux paste to become conductive after it's heated? Also, it would be great if someone can recommend a flux paste or liquid that is non-conductive, preferably something that's easy to obtain in the UK.

[thm_w]

If you like paste you can use 8341: https://www.mgchemicals.com/products/solder-and-accessories/fluxes/no-clean-flux-paste-8341
But any no-clean flux will be fine, it depends on your preference. Some prefer the thin watery type or thicker pastes. 8341 is a lighter paste.

8342 link: https://www.mgchemicals.com/products/solder-and-accessories/fluxes/8342-ra-rosin-flux-paste

Interesting that they say "Post soldering residues removal is much easier due to the organic acid base of the flux. Residue can easily be removed with Cat. #824 Isopropyl Alcohol or  Cat. #4140 Flux Remover".  Maybe they expect you do soak the board or something.

[wraper]

So my question is how common is it for flux paste to become conductive after it's heated?

No, usually flux is somewhat conductive before heating. After heating most of them become non conductive. The issue with that is that hand soldering in not a proper heating which will sufficiently heat all of the flux like reflow. Not to say 8342 is quite aggressive flux, must be cleaned and is water soluble on top of all.

[wraper]

nteresting that they say "Post soldering residues removal is much easier due to the organic acid base of the flux. Residue can easily be removed with Cat. #824 Isopropyl Alcohol or  Cat. #4140 Flux Remover".  Maybe they expect you do soak the board or something.

According to dataheet only warm DI water is needed: http://www.mouser.com/ds/2/265/tds-8342-1099484.pdf

[bodger]

Thanks for the replies, decided to go for some liquid no clean flux for soldering SMD parts in future and purchased some Topnik RF800 which comes with a little brush applicator.

[electronics man]

If you like paste you can use 8341: https://www.mgchemicals.com/products/solder-and-accessories/fluxes/no-clean-flux-paste-8341

I have this flux it leaves a horrible sticky residue which is extremely hard to clean off the bored.

[thm_w]

If you like paste you can use 8341: https://www.mgchemicals.com/products/solder-and-accessories/fluxes/no-clean-flux-paste-8341

I have this flux it leaves a horrible sticky residue which is extremely hard to clean off the bored.

Weird, haven't noticed that being a problem, temperature is higher maybe? Using isopropyl alcohol to clean it off, could try a flux cleaner solvent.

[bodger]

Weird, haven't noticed that being a problem, temperature is higher maybe? Using isopropyl alcohol to clean it off, could try a flux cleaner solvent.

I've been cleaning the stuff with IPA 99.9% with a ESD safe brush, but it can still leave the board a little sticky. I really like this flux paste for through-hole components, I'm using it sparingly now on the board to avoid the sticky residue.

[wraper]

Weird, haven't noticed that being a problem, temperature is higher maybe? Using isopropyl alcohol to clean it off, could try a flux cleaner solvent.

I've been cleaning the stuff with IPA 99.9% with a ESD safe brush, but it can still leave the board a little sticky. I really like this flux paste for through-hole components, I'm using it sparingly now on the board to avoid the sticky residue.

It's impossible to clean the board by just diluting flux with IPA. You can spread it over the board as much as you wish but it's still remains there, it cannot miraculously dissappear. You may not notice that you are spreading the flux instead of cleaning it if you use flux with low amount of solids like liquid flux but with tacky (gel) flux it becomes much more noticeable. If you use brush, you need something to actually remove the flux, say kimwipes. Starting from 1:00

[tooki]

If you like paste you can use 8341: https://www.mgchemicals.com/products/solder-and-accessories/fluxes/no-clean-flux-paste-8341

I have this flux it leaves a horrible sticky residue which is extremely hard to clean off the bored.

I use it too and this hasn’t been an issue.