Hi Phil,

We don't use RTV but we do encapsulate a printed circuit assembly in a box.
It's a mixed technology assembly with SMT and through hole. This assembly
is a relay board that goes into vehicle HVAC systems, (ie: farm equipment,
construction equipment, trucking) that we pot with a 2-part polyurethane
compound from Epic Resins called their S7144. Here's a photo of a failed
one that I cut the top of the case of a failed relay just to look and see
what I could see. I'll see if this google image works:
https://photos.app.goo.gl/oQvHwCbEm9TBFYvn9

Steve

On Wed, Feb 10, 2021 at 1:14 PM Nutting, Phil <[log in to unmask]>
wrote:

> Technetters,
>
> We build several power supplies that use RTV in place of dielectric oil
> for our high voltage multipliers.  The RTV allows us to get the same output
> level in a smaller package than a similar design using the dielectric oil
> as the insulator.  The proper process is to medial blast (lightly) the
> circuit boards, prime them and then encapsulate the boards in the RTV.
> Both the media blasting and priming can be very subjective processes.  And
> both have process issues in our manufacturing group. Simply eliminating the
> media blasting and priming is not a solution as the RTV will not bond to
> the boards and ultimately creating the potential for arcing to ground.
>
> Ideally potting a small box makes a disposable assembly, so the bonding
> quality and thermal size change of the RTV is not an issue.  We use between
> 20 and 100 pounds of RTV per potted assembly.  Disposal or repair of failed
> units is expensive.
>
> I am looking for folks that use RTV for encapsulation and what they use
> for a process to ensure good bonding between the RTV and circuit boards.
>
> Phil Nutting | Senior Development Engineer | Lab: +1-978-224-4334 |
> Mobile: +1-978-828-8664
> 35 Congress Street | Salem, MA 01970 | U.S.A. | www.excelitas.com<
> http://www.excelitas.com/>
>
> [cid:[log in to unmask]]
>


-- 
Steve Gregory
Kimco Design and Manufacturing
Process Engineer
(208) 322-0500 Ext. -3133
Cell Phone: (918) 706-2779

-- 



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