Ah, new information.
Thanks Rudy, Brian and Doug.
For our boards with the slip ring dust it looks like a quick 1 minute wash will remove the dust without attacking the conformal coating. Having said that I will do some testing to confirm this.
Phil
________________________________
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Tuesday, May 27, 2008 8:51 AM
To: TechNet E-Mail Forum; Phil Nutting
Subject: Re: [TN] Conformal coating washing off
Phil,
Most of the pure acrylic coatings are not that good in terms of chemical resistance. We do not allow our conformally coated assemblies (Humiseal 1B31) to go through saponified aqueous cleaning for just the reason you are seeing, the adhesion gets affected and the coating comes off.
Doug Pauls
Phil Nutting <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
05/27/2008 07:46 AM
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Re: [TN] Conformal coating washing off
Brian,
I guess I should add that we have been using this conformal coating for about six years with "great success". It has only been in this test of a new washing system that we are seeing the coating peel off. The DI wash in my original post was the wash step after soldering with an OA flux. Maybe the detergent in the wash system is really good for cleaning conformal coating off the boards... if that was what I really wanted.
Phil
-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Saturday, May 24, 2008 2:04 AM
To: TechNet E-Mail Forum; Phil Nutting
Subject: Re: [TN] Conformal coating washing off
Some types of solder mask contain nasties that may prevent a decent
adhesion of a CC or they may not have been properly polymerised, leaving
insoluble monomers or other components on the surface. I suggest you
start looking in this direction.
Brian
Phil Nutting wrote:
> We are using Chemtronics Konform AR on some circuit boards. The boards are batch washed in DI water and pre-baked prior to coating and then cured in a 60° or 77° C oven.
>
> In a recent test of a new washing system where we are removing slip ring dust (brass and carbon) on these boards and dielectric oil from other boards and aluminum castings, I noticed the conformal coating peeling off in sheets after both the wash and DI rinse cycles. Both wash and rinse are between 140 and 150° F.
>
> Is this stuff peeling off because of the water temperature, poor pre-coating prep or possibly something else?
>
> Thanks in advance,
>
> Phil
>
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