QFN & thermal capacitance

riscy00 · December 22, 2010, 08:23

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.

December 22, 2010, 08:23	QFN & thermal capacitance	#1
riscy00 New Member riscy Join Date: Dec 2010 Posts: 2 Rep Power: 0	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

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December 22, 2010, 10:16		#2
RobinB New Member Robin Bornoff Join Date: Mar 2009 Posts: 23 Rep Power: 17	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.