PUR belongs to a group that are hard to achieve chemical bonds, so then
remains mechanical and electrostatic binding. I think acid is not a good
way, because you may cause corrosion damage. As far as I can remember we
used sand blast with aluminum oxide and when that was not suitable, we used
600 emery cloth. Suitable degreaser is 40 Centigrade Acetone.  There is a
miracle primer too, but I've forgotten the name. If you get it, remember
that it's extremely dangerous to inhale, therefore you need a box with
evacuation. We had to skip the primer finally. Our environment guy banned
the product. I can get more information, but i guess the real chem Merlins
will come in before that.

Inge

On 14 February 2013 15:29, Glidden, Kevin <[log in to unmask]>wrote:

> Hi everyone,
> We have a PCB that is using a gloss soldermask, and we are having extreme
> difficulty getting urethane conformal coating to adhere.   We use this same
> soldermask on many PCBs, but only this one particular PCB gives us issues.
>  It has occurred for some time, across multiple lots of PCBs. We do
> pre-clean all PCBs with IPA and DI water just prior to coating.  This is
> just a light surface clean just to remove any fingerprints or whatever
> contaminants might be introduced between post solder cleaning, through
> e-test, and then masking.  I think much of the issue for this particular
> PCB is due to geometry.  The PCB is small and has large masked areas- a few
> dots and all around the perimeter.  When the masking is removed, all the
> coating flakes off.  Ultimately, converting this PCB to matte finish is my
> goal, but I have many PCBs in stock to use up.  HDBK-830 states no primer
> is known to be needed for urethanes.  Is anyone out there using primers for
> urethanes, and would you care to recommend one?  What about alternate
> methods to roughen the gloss surface?  I am thinking perhaps if the PCB
> supplier could somehow dull the finish with an acid etch, or possibly light
> grit-blast internally?
> Just looking for ideas.
> Thanks,
> Kevin Glidden
> Mfg Engineer
> Astronics Luminescent Systems Inc.
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________