Cleaning up after using MG835 Flux

[jewelie]

So, I've had my first go using a proper/decent flux: MG-835.

Afterwards, there's a bit of residue on the board.  I've tried cleaning it off with 99% Isopropyl Alcohol and with a lot of work it mostly cleans it up, but not entirely.

Should I really be attempting to clean this flux off or should I leave it be? 

It's a little sticky and ugly after, although it makes a big difference when soldering SMD stuff as components seem to want to jump into place a bit etc.  Although again, my tweezers can get a bit sticky (the IPA does stop that though.)

[GreyWoolfe]

I use IPA and an old toothbrush.  It all comes off.

[Paul Moir]

I use a cheap "acid" brush with the bristles trimmed way down so you can scrub any burnt flux.  Also I'll do a "wash" reusing the solvent over and over, then a "rinse" with clean solvent to get rid of the last bit of stickyness. 
Incidentally I use ethanol which is denatured with methanol.  It doesn't work any better than IPA, I just have more of it on hand.  Also I more often use the MG paste flux that comes in a syringe because it seems to be easier to clean up.  Though maybe it's just that I use less due to the applicator.
Final edit:  EU denatured ethanol is apparently not suitable for cleaning PCBs.

[timelessbeing]

or

[helius]

[perchloroethylene] or [alcohol based flux remover]

The former is in my opinion too toxic for regular use at the soldering bench. It can be used outside, with a respirator, for degreasing engine parts.
Perc is also not compatible with many types of plastic used in electronics and pretty useless for removing ionic residues (the white chloride salts that the OP is having trouble with).
The latter is fine, pretty similar to straight isopropyl but a little more expensive and maybe works a little better.

Hot water and soap, then agitate in 91% IPA. It's what they do in China.

Aqueous cleaning of rosin residues uses saponifiers to turn the rosin into soap. 91% isopropyl is a really useful cleaner but I think that method can create water spots if you don't get it just right.

[jewelie]

I use IPA and an old toothbrush.  It all comes off.

How do you get it off the wretched tooth brush though?

I got some acid brushes, chopped right down. It ended up sticky after cleaning one tiny board. Perhaps tooth brushes might work better for the clean up?

[timelessbeing]

for degreasing engine parts.

It's for electronics. Not engine parts. It's completely safe if you're careful, not particularly volatile, and extremely good at cleaning the flux that the OP mentioned. I've never had problems with the plastics used on PCBs, but you have to be careful about overspray because it will dissolve styrenes.

[jewelie]

or

That means buying yet more things, which I'm trying to avoid.  Very tight budget and no space!

[helius]

How do you get it off the wretched tooth brush though?

I got some acid brushes, chopped right down. It ended up sticky after cleaning one tiny board. Perhaps tooth brushes might work better for the clean up?

When you clean soil off a workpiece, it doesn't disappear; it gets transferred onto something else that you throw away. That's what paper towels are for. You can lay the paper towel across the board, spray it wet, and scrub to transfer the soil into the towel (it turns yellow). You can also hold the board vertical and spray solvent downwards so it runs off, after scrubbing.
With typical paper towels, some lint may get stuck on the component leads, but it isn't much of a problem. There are lintless towels available.

[jewelie]

How do you get it off the wretched tooth brush though?

I got some acid brushes, chopped right down. It ended up sticky after cleaning one tiny board. Perhaps tooth brushes might work better for the clean up?

When you clean soil off a workpiece, it doesn't disappear; it gets transferred onto something else that you throw away. That's what paper towels are for. You can lay the paper towel across the board, spray it wet, and scrub to transfer the soil into the towel (it turns yellow). You can also hold the board vertical and spray solvent downwards so it runs off, after scrubbing.
With typical paper towels, some lint may get stuck on the component leads, but it isn't much of a problem. There are lintless towels available.

Ah ha! Success!  99% IPA and decent 3-ply toilet roll.  I'd forgotten that, of course, IPA doesn't immediately break down toilet roll and I've always got some in (Crohns disease!)  Really didn't grab much lint and good enough for my basic hobby level soldering.

I do love a simple low tech solution like that.