# CircuitWorks and SolidWorks PCB do vias dissipate heat to ground plane

Question asked by Jake Ridden on May 8, 2011
Latest reply on May 10, 2011 by Alec Chalmers
Hi. I was looking at the tutorial for Flow Simulation's 'First Steps - Conjugate Heat Transfer.' This is a great tutorial.
In this tutorial you analyze cooling over a pcb using a fan. The pcb contains several ICs (chips) that generate a few Watts of
power. One of the ICs has a heat sink on top of it, which will display some of the heat dissipation once you run the flow
simulation.
In this tutorial we only define the pcb as FR4. The tutorial doesn't take into account the heat dissipation through the ground
plane (copper) of the pcb. Obviously this is just a tutorial so I don't expect this analysis and that's why I'm asking about
this concern..to see if anyone else simulated this issue.
I thought more about this and took a pcb I had and converted it to CircuitWorks and then to SolidWorks. This turned out great
actually..the  pcb looks just like the one I built. The problem I had with the  CircuitWorks/SolidWorks assembly (pcb) I converted
and created was that my design was 2 layers and when  CircuitWorks converts the pcb file it only converts the pcb to ONE material
block (a rectangular prism).
I think it should have converted to 3 rectangular material blocks (or 3 rectangular prisms). This would make sense because I'll
need to define each layer of copper and each layer of FR4 that is between the copper. 3 material blocks is from: 2 layers of
copper + 1 layer of FR4 (the material between the copper).
I want to know if anyone has tried to model heat transfer of an IC on a pcb (like the tutorial..the heat sink on top of the IC
isn't necessary), but in addition has made the IC connect to the pcb copper (bottom layer) through the vias from the circuit
board. CircuitWorks is good for this because when you create the assembly for SolidWorks the vias are already imported.
Is the following approach correct when trying to show how much heat is dissipated through the pcb using vias from the IC to the
ground?   ..I attached my circuitBoard assembly file for view.
I took the circuit works file and offset all components on the bottom side of the pcb. This let me add in a copper ground plane
(shown in brown). I also offset the main IC (shown in checkered board color and defined as a heat source @ 5W). This allowed me
to put a copper pad below the IC to resemble a ground pad (also shown in brown). I'm hoping that this will make a connection to
the plated through hole vias, which will connect to the copper ground on the bottom layer.
In flow simulation I defined all material as default 'Tutorial Component Package' and then I defined 3 other solid materials: 1
for the FR4, and 1 for each copper (the copper IC pad and the copper ground plane).
What I'm hoping is that the IC will radiate heat through the package then heats the copper pad below, this will heat the PTH
(plated vias) then this will heat the copper ground plane below.
My problem is that my vias are PTH ( which I think is plated through hole ) , but I need to define the pcb material as FR4
..will this change the plated via material? I don't even know what the plated material is? Do you ? I'm just not sure if my
setup / approach is correct..will this even work ?  I'm also curious as to the mesh settings I'd need to set because the  vias are
very tiny.
After simulation I looked at the cut plot..it seems like the FR4 pcb as a whole is heating up and the heat isn't being
dissipated through the vias. Can someone comment on this?
Long post, but I wanted to be thorough.