Anyone,

We are in process of performing a rework on a double sided surface mount
PCB assembly containing 603-1206 chips and SOIC packages.  The PCB also has
DCA /COB (direct chip attach, chip on board) with a layer of polyurethane
conformal coating on both sides. My plan is to remove, the conformal
coating, remove the unneeded components, hand place solder paste, send PCB
through chip placement, reflow solder paste, clean residues and then
re-coat.

We do not have experience with DCA/COB so I need some questions answered.

1.  What is best way to remove conformal coating in selected areas?

2.  Will a reflow of DCA/COB encapsulant be a problem? If so what?

3.  Will reflow temperatures change the properties of conformal coating?

4.  What is the best way to clean, remove flux residues form PCB with out
causing problems on contacts, conformal, and DCA?

5.  Will an aqueous washes create a problem with DCA and Conformal?

I would appreciate any help that you can give me or any contacts of
manufactures that may provide me with more information.
My time frame is kind of short so please respond as soon as possible.

Thanks alot!

Tom Braswell
Engineering
Fawn Industries, Electronics Div.

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