Hi Steve,
We use Uresolve Plus Gel from Dynaloy for spot urethane c/c removal (we
use Conap CE-1155). It's a gel so it doesn't run all over the board
and works fairly quickly depending on your coating thickness.
We sometimes set-up an "assembly line" and spot strip many
boards at a time: apply the gel, wait, wipe off, rinse, clean,
inspect.
You have to be careful with microblasting. The operator can easily
blast through the coating and into the PWB butter coat or solder mask if
they are not careful. It can be tedious work if you have a large
area to do and lots of assemblies.
I think the soldering iron burn through method is OK for small components
and small jobs. However there's always a concern with thermally
overstressing the PWB with burn-though c/c removal of through-hole
components. If you are working with surface mount parts you also
need to get all the c/c off the pads so you can solder the new part in
place, which can be a challenge.
We've even evaluated a laser removal method but that was not successful
due to the normal variations you see in coating thickness across a
board. The laser wasn't "smart" enough to sense the
coating thickness and adjust it's power accordingly.
-- Gregg