[SI-LIST] Re: Potting/encapsulation/conformal coating and SI
- From: Ray Anderson <reanderson@xxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 05 Oct 2004 07:50:24 -0700
One other thing to deal with if you intend on using conformal coating or
potting on your PCB assembly is to make absolutely sure your PCB is
absolutely DRY and free of contaminants prior to applying the coating
lest you want bad things to happen to the circuitry some time in the
future. A pre-coating bake is usually recommended to ensure a dry board
prior to coating.
As others have mentioned, some coatings can be lossy at RF frequencies.
An option to consider is called selective coating. This allows only
selected portions of the circuitry to be coated while allowing other
areas to be left uncoated.
-Ray
VVLP wrote:
>I've been involved in the trials and tribulations of potting small
>transmitters operating at 900MHz. We used a silicon based potting
>compound which was not that lossy and had a reasonably controllable Er
>which (from memory)was about 2. This had a significant impact on microstrip
>that obviously had to be designed with the layer of potting rather
>than air above it. It is quite soft and has little mechanical impact on
>components.
>The major problems for us were in the board / potting interface where
>sometimes the material wouldn't cure properly - but that's a different
>story.
>
>Regards
>Dave
>
>
.
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
