Removing Conformal Coating

[jerryk]

I have a marine spec inverter that I'm working on and all circuit boards are covered in conformal coating.  I would like to remove all the coating on most of the boards.  IPA softens the coating but is slow to work with.  I have used acetone on the back sides of a couple of boards using a tooth brush to work the coating off.  So far this is most effective but I would prefer to avoid such a harsh method for the smd side of the boards.  Can I soak a circuit board over night or longer in IPA  or IPA/Acetone mix without damage to the board are components?

Any suggestions on completely stripping these boards would be appreciated.

Jerry

[GopherT]

Acetone will soften and eventually dissolve the adhesive that bonds the copper traces to the FR4 board. You can try ipa over night but I would not get acetone into the story until you are sure ipa is not doing the trick.

Do you know what type of coating it is?

Conformal coating thickness requirements are in accordance with IPC J-STD-001 for the following coating types:

Type AR   Acrylic Resin   0.00118 to 0.00512 in
Type ER   Epoxy Resin   0.00118 to 0.00512 in
Type UR   Urethane Resin   0.00118 to 0.00512 in
Type SR   Silicone Resin   0.00197 to 0.00827 in
Type XY   Parylene Resin   0.000394 to 0.00197 in

[KaneTW]

I've used a special conformal coating stripper to remove urethane coating. Tried burning it off with a soldering iron in a fume hood at first, but that didn't go anywhere. Solvent got it out with no effort.

[jerryk]

No idea on the coating type.  It softens with IPA is the only real evidence that I can grasp.  Heat with hot air rework station and I can peel it with limited success.  The problem with IPA and a brush is it gets quite gummy and seems to hold that gummy state for awhile.  Acetone is effective using a stiff brush but still is a lot of work on the back sides of headers or any thing that's busy with tht components.  There is a lot of places for this stuff to hide so a prolonged soak seemed like a good idea but don't want the board to delaminate or the like.  Other concerns are inductors and transformers and the way they are wrapped.  I can't seem to strip that wire when I try but don't want to violate the windings in any way.

Jerry

[T3sl4co1l]

If it's acrylic then I think you need THF.  I've done a bit of this recently, actually; the pen we got is basically 100% THF -- same stuff used for PVC cement, by the way.

Tim