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Unread 11-25-2005, 11:06 AM   #310
Cooling Savant
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Join Date: Sep 2002
Location: Cincinnati, OH
Posts: 229

Originally Posted by Incoherent
Lee, I like this arrangement for many reasons but there is one problem with the vertical hole for the temperature sensor that I think is insurmountable.

Basically it means that there is a large uncertainty in the vertical location of the point that is measured which makes it impossible to use the data for any kind of modelling.
Thanks Incoherent,

Yes, I agree with what you are saying. I did a quick calc and for a 14mm^2 cross-area with 100W load thru copper, I get ~1.3 deg C per mm... not so good.

"Today" I am leaning towards a one-piece heat die and heatspreader with two or three temp sensors located in the sides of the die to generate a heat flux curve and that use an extrapolated temp value for calculating the WB dT and C/W. I also like the idea of a rectangular die (maybe 14 x 16mm?) since that seems to be the direction more of the newer CPU's are going in. (I know, much controversey there... )

Bill: Yes, I have considered integrating a load cell underneath the die and creating the upwards force by regulating the air pressure to a small cylinder instead of a spring. Considered "clamping" the WB under test and then pushing the die/heat spreader up with a known force. This is great for analytical testing but removes the variability of specific mounting hardware that the end user will have to deal with. As you said though, complexity often leads to no action...
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