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Heat transfer in a PCB

Posted 27.09.2011, 07:36 GMT-4 Heat Transfer & Phase Change, Geometry, Mesh Version 4.2 4 Replies

Pauli Auramaa
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Hi,
I'm preparing my thesis with Comsol-software. Target is to make thermal simulation of a LED luminare. I have never before used Comsol, so first I have to learn how it works. I have done some tutoriasl and read material available at the Comsol-site. Now I am at that point that the first model is prepared. It is a simple FR4-PCB (circuit board) and 36 LED chips on it. I have made the model with Comsol geometry tools (see attached file). Now I'd like to generate mesh for simulation, but it does not succeed. Or actually Comsol-software continues the calculation for ever and uses gigabytes memory. What's wrong? I use physics controlled and normal size settings. Is there any simple instructions available how to make the meshing in Comsol Multiphysics?

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4 Replies Last Post 21.10.2011, 09:20 GMT-4
Tero Hietanen
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Posted: 1 decade ago 27.09.2011, 15:52 GMT-4
Hi

Model contain very thin layer below PCB. Mesher is trying to do tetrahedral mesh to this very thin layer and that is making problems. Try to define layer other means (highly conductive layer or thin resistive layer) or make mesh to layer manually. Without layer meshing is working fine (check simplified model).

Best regards

Tero
Hi Model contain very thin layer below PCB. Mesher is trying to do tetrahedral mesh to this very thin layer and that is making problems. Try to define layer other means (highly conductive layer or thin resistive layer) or make mesh to layer manually. Without layer meshing is working fine (check simplified model). Best regards Tero

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Pauli Auramaa
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Posted: 1 decade ago 29.09.2011, 05:00 GMT-4
Tero, thanks for solution of the thin layer problem. Another question is, how thermal vias through PCB should be modeled? Manufacturer of led chips recommend a solder pad layout with vias, which achieves a thermal resistance of 7K/W.
Tero, thanks for solution of the thin layer problem. Another question is, how thermal vias through PCB should be modeled? Manufacturer of led chips recommend a solder pad layout with vias, which achieves a thermal resistance of 7K/W.
Tero Hietanen
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Posted: 1 decade ago 02.10.2011, 10:19 GMT-4
In Comsol there is no possibility to define thermal resistance. You have to transfer thermal resistance to thermal conductivity, k=s/(R*A) (s=thickness of solder, R=thermal resistance, A=area of solder).

Best regards

Tero
In Comsol there is no possibility to define thermal resistance. You have to transfer thermal resistance to thermal conductivity, k=s/(R*A) (s=thickness of solder, R=thermal resistance, A=area of solder). Best regards Tero
Pauli Auramaa
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Posted: 1 decade ago 21.10.2011, 09:20 GMT-4
Late thanks for good advice,Tero.
Late thanks for good advice,Tero.

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