Hi,
In the calculation utilities, I would also like the one that determines the thermal resistance of the PCB.
Let me explain. I would like to know the thermal resistance of my pcb based on the surface that destiny as mass, top side, bottom and internal layer, and above all how many through holes I put around my smd soldered device.
So I can say that my pcb is the heatsink and therefore I can do the thermal calculations.
I have searched the internet but have not found a simple calculation example that does this to me.
Someone asked himself this problem, and how he solved it (not by shooting random holes hoping).
best regards
Thermal modelling is hard to get right and very expensive to buy as a CAD addon.
I find that the predictions are often way off due to the difficulty of describing the surrounding airflow environment
It is correct to say that
But, I use Calculix FEA in FreeCAD. Both are Free and Calculix is a very powerful tool.
Unfortunately, like all FEA, getting it installed, setup and using it requires āKnowingā enough about it to succeed. That means homework and testing (not to mention modeling the parts/pcb).
I use it for mechanical FEA but, thermal FEA is also a part of the toolbox and there are some good examples to check out. This example is for a HeatSink and is not specific to PCB and your particular need but, it does show (for about half the video) how to model a part using Calculix and not FreeCAD. If you can make models in FreeCAD, you can skip the first half. Checkout other model and FEAā¦
To help wet your appetite (or discourage you), below show a simple Hook model in FreeCAD and the Calculix analysis (shown is the ParaView addon for displaying FEAā¦)
A quick follow-up. I was curious so I found this post of thermal analysis on PCB using FreeCAD and Calculix.
Also, you can use the StepUp plugin to load the PCB/parts from Kicad, then, use it for FEAā¦
I did a quick thermal & displacement analysis using the Calculix Solver (there are several different solvers available in FreeCAD for Calculix - CCX, Z88, Elmer, cxCuitā¦etc). The process is about the same for all of them. I prefer CCX solver.
Summary of what I did:
ā¢ In Kicad, I added a Footprint of 28pin DIP-Chip to a blank PCB. Did not bother to make traces/etc.
ā¢ In FreeCAD with Stepup w.b., I loaded the PCB/Chip
ā¢ In Part w.b., I Boolean Unioned the PCB and Chip (to enable Meshing of single part).
ā¢ Created the necessary items for FEM analyisis (material, uniform Temperature loading on top surfaceā¦ etc).
ā¢ Ran the sloverā¦ 300 seconds later, the resultsā¦
Itās a Thermal analysis for funā¦ Plot shows the Deformations. Could have selected the Temperature for plottingā¦ to screenshot but, I forgotā¦ You can see the bending and pin deformationsā¦ Naturally, proper loading/etc would be required for a more realistic analysis. Perhaps, think of a Stepper Motor Driver Chipā¦ Would need to use additional tools to assess heat from High Current loadingā¦ But, you get the point.
Hi BlackCofee,
This would be far less ambitious for me.
It would be enough for me to be able to calculate the thermal resistance of the PCB (copper area, multilayer) + metal holes.
At this point I can do the calculation if the component manages to dissipate the heat.
better than nothing.
best regards
That screenshot looks backward, just as if the IC is hotter on the ends than in the center.
Iām no king with FEM, but I also seem to have seen this before with some mechanical stress analysis. The displacement is not a good indicator for the amount of stress.
Take for example some bar, that sticks out of a wall, and loaded on the āfreeā end. The highest stress in the bar is near the wall, while the āfree endā has the biggest displacement.
[Edit:]
Oops, my bad.
Did not look too close at the screenshot and missed some important parts.
Sometimes itās like cheese between my ears.
Cheese with holes, big holes.
True that a Bar fixed at one end and free at other will see stress at shear load area. But, the plot is not a Stress plot, itās a displacement plot.
The Chip shown in the post shows Displacement, not Temperatures (the Radio-button for Displacement is checked, not Tempās or Stress).
None of the Stress buttons are checked. A real analysis would contain Fixed constraints at each Pin/PCB because Solder would hold pins from moving (thus also causing stress and limiting displacement).
I have 40 years of Thermal analysis experience on Missile and Space rocket guidance systems. I was the āKingā and earned a technology award from the President of U.S. That was a lifetime agoā¦
The point of the post was to show the minimal effort needed to use Calculix for āsomeā kind of analysis.
Thus, thatās why is said:
[ADDED] It seemed sensible to conclude with the followingā¦
Finishing my 2-cents of input, a User can define Equations for a Thermal analysis (as if doing Hand-Calcās) and go through the bother of implementing into FreeCAD.
Then, after learning how to get the Traces into FreeCAD (via Stepup), user can select them and the Equation and do the necessary stepsā¦ I havenāt done this in FreeCAD but it appears simple enoughā¦
This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.