hi

Basically FR4 should run up to 130degC, and your semiconductor can most
likely handle this temperature (but need to assess the reliability based on
the manufacturers rating and your derating req's). I would consider thermal
transients that can cause

The biggest problem I have had is the conduction across the PCB to other
components that can't handle these temperatures, a bipolar electrolytic cap
was my biggest concern. Also need to consider that at these temperatures
semiconductors have very different parameters, which will complicate your
design.

cheers

> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On
> Behalf Of Jon Elson
> Sent: Thursday, 18 July 2002 8:07 AM
> To: Protel EDA Forum
> Subject: Re: [PEDA] 90 degree C?
>
>
> Michael Biggs wrote:
>
> > Hi all,
> >         Anyone run very hot traces @ like 90 degree C on
> there PWBs and or
> > use surface mount heat sink around the component( like a D-PAK)?
> > Thanks for any response.
> > I know this is a Protel questions group but everyone seem
> knowledgeable in
> > design layout.
>
> I would assume that over a fairly short time the epoxy
> holding the copper to
> the laminate would deteriorate, and the foil would lift off
> the board due to
> the thermal mismatch.  Some cycles of this might cause the
> foil to crack.
>
> I'm pretty sure a recognized safety testing lab would not approve any
> device designed that way, if they discovered that is what you
> were doing.
>
> Using a foil area to draw heat away from a heat source is
> pretty common
> practice.  I imagine some people let their junctions run at
> 90 C, but I
> suspect the heat sink surface runs cooler than that.
>
> Jon
>
>
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