Filling the epoxy etc with quartz powder also make the temperature expansion=
 more like that of a PCB, and enhances the thermal conductivity.  I have=
 used an epoxy with 70% filling.

=C5ke, look in Elfa.

There are also silicone types, some filled to enhance termal conductivity.
Silicones have the great advantage that they are flexible so thermal=
 expansion and cycling does not meake mechanical stress and wear on solder=
 joints, components in general etc.

The best ever I have used also for total water safe applicaiton is a tacky=
 silica gel from Wacker, it is very flexible, transparent and somewhat=
 self-healing: you can push a test neeedle down to the PCB for testing, then=
 withdraw it and it is water tight again.  I have the PCB completely=
 suspended in this mass and tha tmake it shock proof.  Even the casing may=
 break and the PCB is protected from water!  Just remember to have air in=
 the casing for thermal expansion.

/Morgan

William Chops Westfield 11:55 2004-06-18:
>On Friday, Jun 18, 2004, at 00:55 US/Pacific, Ake Hedman wrote:
>
>>>I have looked around for electronic filling
>>>material and obviously found the epoxy type. But it's so damn
>>>expensive. Is there some lower cost material one can use?
>note that general purpose epoxy or polyurethane resins are considerably
>cheaper in moderate quantities, and can be "filled" with a large
>percentage of "really cheap" stuff like sawdust or sand...
>
>BillW
>
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Morgan Olsson, Kivik, Sweden

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