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# coupling 2d to 3d mesh

Creator
I want to couple a 15micro thick layer to a 1 mm thick block. The layer is silver and the block is a ceramic. I didn't create a mmc as i want to use 2d mesh for the silver layer. So i created a 2d mesh on the top surface of the silver and gave it the physical thickness of 15micro. The block is meshed with 3d tet meshes. I made a thermsl coupling between top surface silver and top surface block and calculated the thermal resistance of the layer as thickness/cond x area and plugged this vale in the thermal coupling. I made a tc as the meshes are not connected to each other. What is the meaning of the physical thickness in the 2d mesh. Normally i would not need to enter the thicknesd as i plugged in the thermsl resistance of that layer. Am i not accounting 2 times the thermal resistance?
3 REPLIES

# Re: coupling 2d to 3d mesh

Siemens Experimenter

Hi Gvdp,

2d meshes do not have a thru-plane thermal resistance. The implicit assumption is that they conduct heat only in-plane.

The thickness is used to compute capacitance for that mesh, when running transient solutions.

I hope this clarifies things.

# Re: coupling 2d to 3d mesh

Creator
Hi Nicolas,
Thanks for the clear answer!
Br
Gunther

# Re: coupling 2d to 3d mesh

Creator
Hi Nicolas,
I want to model a silver pad on a pcb but the pad is smaller in area than the pcb and is only 15micro thick.Above the silver pad I have connected a 3d swept mesh representing the solder of a die. I modeled the silver layer with a 2d mesh which is not connected to the 3d mesh of the pcb.I assigned a TC between the pad and the pcb and gave it a thermal resistance value for the through plane conductance.The mesh size of both primary as secondary region is appox the same.With the one to one coupling resolution,I got a very big temperature gradient over the silver pad while with the fine coupling the gradient is much lower. The solder has only a small contact area with the pad. I would expect that the silver spreads out the heat in plane very good. Which coupling method is preferred? Is this the right model set up?
GVDP