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Orthotropic PCB material for heat conductivity


I'm new to this forum and to simulating using NX
Currently, I am simulating a simplified PCB with 6 components (heat loads) and I want to find the temperature change above ambient that occurs in another component representing a thermistor. This is placed on an extended arm of the PCB. The simulation is working so far.

However, I'm using an isotropic PCB material definition (using an effective thermal conductivity based on some papers and estimations), but PCB's are not isotropic because of the layered structure of insulators and copper. I would want to define an orthotropic material (with in- and through-plane thermal conductivity). I am recreating, for a large part, a simulation from an old report where both conductivity components are given, but without explanation on how they are applied in the model. So now, I keep getting an error that no material orientation is defined.

I found settings for this in the FEM file, under Mesh Associated Data, but I can't figure out the right settings to define the orientation. If I check the material orientation (right-click on mesh in the FEM tree > Check > Material orientation) it does show orientation arrows in each element.

Someone who maybe has some tips on how to get this working? Thanks in advance!


Re: Orthotropic PCB material for heat conductivity

[ Edited ]


I'm also new to this forum...

For definition direction of a 2-d-element use "2D Element Normal by Seed" in the dialog of "Model Check".


Re: Orthotropic PCB material for heat conductivity

The shell normal controls the orientation of the Z-axis of the element coordinate system, which determines the "top" and "bottom" faces of the element.


The plane of the element contains the XY plane of the element coordinate system. The material coordinate system (which gives an orthotropic material its orientation) is specified by defining the orientation of the X-axis within this plane. This is given by an angle with respect to the first element edge, or by specifying a coordinate system ID to project the X axis of onto the element.


In NX, this is defined as Mesh Associated Data (MAD) or Element Associated Data (EAD). Most typically done with MAD by right clicking on the mesh in the navigator and selecting "Edit Mesh Associated Data". Methods are provided to specify orientation by MCID, Angle, Tangent Curve or Vector.