Subject: | |
From: | |
Reply To: | |
Date: | Mon, 28 Oct 2013 09:17:46 -0500 |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
Phil,
I will go along with what Lee said. CTE is one major consideration for
thick coatings. Another would be residual stresses from shrinkage when
the coating dries and cures. High residual stress can mean cracking and
flaking of the coating in the end use environment if thermal cycling is
expected. Another is coating adhesion is you try to apply a thick
coating all in one pass. As most coatings skin over and cure/dry from the
outside in, the last surface to cure is the the one at the
coating/substrate interface. In a very thick coating, that may not
properly cure for a LONG time, and if you go into HASS or some other kind
of cyclical thermal stress, you can get coating delamination.
Doug Pauls
From: Phil Bavaro <[log in to unmask]>
To: <[log in to unmask]>
Date: 10/25/2013 02:48 PM
Subject: [TN] Exceeding Maximum thickness of urethane conformal
coating
Sent by: TechNet <[log in to unmask]>
I was reviewing a process specification regarding Type UR conformal
coating and it contained a sentence which struck a nerve.
This particular specification stated that the thickness shall be
.003"+/-.002" and .010" maximum if two coatings are applied.
I always thought there was a good reason why the coating should not exceed
.005" such as CTE mismatch which might cause cracking of the coating or
perhaps worse, component damage in thermal cycling. But I haven't found
any papers to that effect yet.
Naturally, any comments/experiences from this forum will be appreciated,
especially if I am completely off based.
Phillip Bavaro
Senior Manufacturing Engineer, Manufacturing Engineering
L-3 Telemetry-West
9020 Balboa Ave. | San Diego, CA 92123
858-694-7874 | 858-740-8260 mobile
[log in to unmask]<mailto:[log in to unmask]> |
L-3com.com/TW
________________________________
This message and any attachments are solely for the use of the addressee
and may contain L-3 proprietary information that may also be defined as
USG export controlled technical data. If you are not the intended
recipient, any disclosure, use or distribution of its content is
prohibited. Please notify the sender by reply e-mail and immediately
delete this message and any attachments.
______________________________________________________________________
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]
______________________________________________________________________
|
|
|