On Fri, 9 Oct 2015, John Wilson wrote:
On Fri, Oct 09, 2015 at 09:48:18PM -0500, Jay Jaeger wrote:
Do U17,U15,U10,U6 perhaps have some solder bridges, or is that just
some flux hanging around?
It's flux, but thanks for the heads-up! I went over everything with
liquid-flux-soaked solder-wick and a stereo microscope ... there were a
ton of solder bridges before. Scrubbing the board in alcohol and then
water gets 99% of the flux off, but turns the remainder white. Now I've
scraped most of it out with a razor blade.
Also, I think I have ninjas. Cooking this board let out an unusually
large cloud of vile rosin smoke, and until I aired the house out, there
were weird thumps and bumps coming from every corner but there was
nothing there when I turned to look.
Was your solder paste too old perhaps? I generally use a liquid RMA type
flux from Kester or Alpha since I mainly do hand assembly/rework, however
I have had issues in the past removing residues from certain "no-clean"
fluxes.
My own cleaning technique is usually an initial scrub with a plastic
bristle brush continually re-wetted with clean isopropyl from a dispenser
pump bottle. After getting all the flux deposits loose, and not letting
the board dry in between, I rinse with either isopropyl or water from a
wash bottle over a glass tray. If any residue remains, a second cleaning
almost always seems to get rid of it.
One important thing I have noticed though is not to let flux sit on the
board for too long. As the solvent carriers in it evaporate, it hardens up
more and more which makes it all the more difficult to clean. After a few
days to a week, it takes a lot more work to get the flux residue off.
