Subject: Re: Thermal effects of potting compound?
Date: Wed, 16 Oct 2002 13:49:27 -0700
Organization: SCN Research of Tigard, Oregon, USA.
NNTP-Posting-Date: Wed, 16 Oct 2002 20:50:57 +0000 (UTC)
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Try a thermally conductive potting material. For deep sections, choose a
two part or heat cure material. Some of the higher conductivity materials
that may work,
DOW CORNING® 1-4173 THERMALLY CONDUCTIVE ADHESIVE DOW CORNING® 1-4174
THERMALLY CONDUCTIVE ADHESIVE DOW CORNING® SE 4450 THERMALLY CONDUCTIVE
ADHESIVE DOW CORNING® SE 4486
Keep in mind, that with silicones, the boards need to be very clean. With
any system (polyurethane, acrylic, epoxy, varnish, silicone) , it is
important not to have trapped air, which can turn into a moisture cell.
Don't use an acetic acid cure silicone material. Choose a material, heat
cure or two part, that is designed for deep cure sections.
Many automakers have switched to a very soft silicone material, called a
gel, it is used in the electronic modules in the engine compartment, and
with the very small fine pitch parts, the materials of yester-year were
causing stress on the very small parts used these days, resulting in
failures during repeated heating cooling cycles.
"Ge0" wrote in message
> I have a circuit with surface mount power electronics on it (DPAK MOSFET,
> How will:
> A.) turning the circuit upside down affect its thermal performance? Heat
> will rise into FR-4 instead of air.
> B.) Encapsulating the whole thing in a 5mm layer (eah side) of potting
> compound affect its thermal performance?
> Is there a certain de-rating I need to do in each instance?
> Are there various grades of potting compound that will actually help
> heat rather than be an insulator?
> Thanks a lot