Thermal Via conductivity in Flotherm

jitender · June 26, 2009, 03:17

I am Using Flotherm for simulation of power supplies. I want to use thermal via in PCB to cool D2PAK and other diodes. Please let me know how we calcilate thermal conductivity to key in in Flotherm. Do we use Orthotropic conductivity or normal conductivity. What value generally we key in. I know it will depend on Pitch also. Please anyone clarify the method of calculation.

RobinB · June 26, 2009, 07:08

Are you using the FloEDA window to define the vias?

jitender · June 28, 2009, 21:21

No, I am still using Flotherm 7.1. So to create thermal via, i just use cuboid and apply all the concerned property.

RobinB · June 29, 2009, 01:57

I'd strongly advise you upgrade to 8.1 and use the new FloEDA window that has advanced PCB import and creation capabilities, including the specification of an area of vias (in terms of number+pitch or %coverage). Kx=Ky and Kz are automatically calculated.

If you want to do it manually then it's a question of considering thermal resistances in parallel to calculate an area Kz (FR4 // Cu // PlatingMaterial), Kx and Ky are going to be near FR4 value. If I explain it in any more detail maybe you wouldn't upgrade

June 26, 2009, 03:17	Thermal Via conductivity in Flotherm	#1
jitender New Member Jitender kumar Join Date: May 2009 Location: Bangkok Posts: 3 Rep Power: 16	I am Using Flotherm for simulation of power supplies. I want to use thermal via in PCB to cool D2PAK and other diodes. Please let me know how we calcilate thermal conductivity to key in in Flotherm. Do we use Orthotropic conductivity or normal conductivity. What value generally we key in. I know it will depend on Pitch also. Please anyone clarify the method of calculation.

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June 26, 2009, 07:08		#2
RobinB New Member Robin Bornoff Join Date: Mar 2009 Posts: 23 Rep Power: 17	Are you using the FloEDA window to define the vias?

June 28, 2009, 21:21		#3
jitender New Member Jitender kumar Join Date: May 2009 Location: Bangkok Posts: 3 Rep Power: 16	No, I am still using Flotherm 7.1. So to create thermal via, i just use cuboid and apply all the concerned property.

June 29, 2009, 01:57		#4
RobinB New Member Robin Bornoff Join Date: Mar 2009 Posts: 23 Rep Power: 17	I'd strongly advise you upgrade to 8.1 and use the new FloEDA window that has advanced PCB import and creation capabilities, including the specification of an area of vias (in terms of number+pitch or %coverage). Kx=Ky and Kz are automatically calculated. If you want to do it manually then it's a question of considering thermal resistances in parallel to calculate an area Kz (FR4 // Cu // PlatingMaterial), Kx and Ky are going to be near FR4 value. If I explain it in any more detail maybe you wouldn't upgrade