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riscy00 December 22, 2010 08:23

QFN & thermal capacitance
 
Hi

Has anyone have thermal capacitance and resistance model for the QFN and TSSOP package (QFN, 4x4, 7x7 and 9x9 with exposed pad) and similar size for TSSOP with exposed pad.

I actually have thermal resistance, derived from IC website but they do not have thermal capacitance, I need this to estimate heat flow from IC (ie 3W) into PCB.

Thanks

RobinB December 22, 2010 10:16

Some package vendors will publish transient impedence curves from which you could derive the thermal capacitance but mainly only for power packages.

The only advice I can give would be to get a geometrically detailed 3D numerical model, solve it in a transient CFD model (in an operating environment close to the intended one) then get C (J/s) from the resulting T vs t curve.

I work for Mentor Graphics and so would of course advise use of our tools to achieve this.

Robin.


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