Re: TO3 & HEATSINK

From: exxos (exxos_at_home.co.uk)
Date: 07/28/04 

Date: Wed, 28 Jul 2004 15:53:12 +0100

"Norm Dresner" <ndrez@att.net> wrote in message
news:svONc.144428$OB3.71995@bgtnsc05-news.ops.worldnet.att.net...
>
> "Norm Dresner" <ndrez@att.net> wrote in message
> news:_vCNc.337854$Gx4.89883@bgtnsc04-news.ops.worldnet.att.net...
> > "exxos" <exxos@home.co.uk> wrote in message
> > news:4106d62f$0$6451$cc9e4d1f@news-text.dial.pipex.com...
> > > Hi all,
> > >
> > > Instead of mounting the TO3 transistor ont he flat part (bottom) onto
> the
> > > heatsink, do you lot recon I could drill a large hole in a heatsink
and
> > > mount the can side into it, and put heatpaste around the can and screw
> it
> > > down from the top ? does anyone have any thoughts if this would work
as
> > good
> > > or worse than the bottom just being bolted to the heatsink ?
> > >
> > > The transistor I have in mind is a 2N5038, a little higher wattage
than
> > the
> > > 3055, I plan to have around 50watts constant disipation, it should be
> ok,
> > > right ??
> > >
> > > Thanks
> > > chris
> >
> > The actual die is mounted to the base of the package. Your scheme
> increases
> > the thermal resistance from the junction to the case.
> >
> > Norm
> >
>
> After rereading your post, I see an even worse situation than poor thermal
> conduction (which can be alleviated with an appropriate H/S and that's the
> fact that the transistor case isn't at ground potential. With traditional
> mounting, you can get nice mica (or other material) insulators to isolate
> the transistor's electric potential from the H/S but not (as far as I
know)
> with your scheme.
>
> Exactly what are you trying to accomplish?
>
> Norm
>

Its not a good idea then, I was just trying to see if I could avoid routing
the connection wires though the finn side of the heatsink. The device I
have found is the 2N5038, its for a audio amplifier, its about the best gain
and wattage I can find, The only other transistor is the TIP3055 which is no
problem to mount, but lower gain and wattage, perhaps someone where knows
of a good gain transistor ? 5amps 80V 100W or there about with a good gain,
more there better I guess.

Chris

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