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From: John Popelish
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X-Mailer: Mozilla 4.7 [en] (Win98; U)
Subject: Re: Question about linear derating factor for MOSFETs
References: <firstname.lastname@example.org> <3DCF50E9.CF58D143@rica.net> <3DCF5916.50B32FE1@rica.net> <email@example.com>
Date: Mon, 11 Nov 2002 14:51:17 GMT
NNTP-Posting-Date: Mon, 11 Nov 2002 09:51:17 EST
John Muchow wrote:
> OK, so am I buying a few pounds of freon or mercury?
> John Muchow ;-)
> >>> ** But the phase change has to be happening at no more than 25 to 50
> >>>degrees on the device surface for that to work - right ? The liquid would
> >>>have to be constantly replaced as it evaporates too so the whole device
> >>>surface was wetted.
I would try something that was volatile (so it would boil at ambient
under only a slight vacuum) and a good electrical insulator (rules out
mercury). Trichloroethylene (or trichloroethane) might be good, but
I am not sure how stable the epoxy in the device package will last if
submerged in it indefinitely. Pure alcohol might also work. It is a
material compatibility problem. If the liquid has a high heat of
vaporization, that is a bonus. As heat from the device evaporates the
liquid, the pressure rises incrementally, forcing vapor to condense
on all surfaces exposed to the vapor that are the slightest bit cooler
than the surface of the device, and heat energy is deposited there.
Amazing amounts of heat can be carried away from very small surfaces
with little temperature rise (if the vapor container has enough area
and external heat removal means). On the order of kilowatts per
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