3D multilayer PCB capabilities?

[javiermail89]

I'm trying to desing a 6-layers PCB and, in order to export it as a .step file, I see that you have to transfer it to a 3D PCB first. However, only my top and bottom layers seem to be on the 3D menu when I select that option.

Looking online, I ran into the question linked below, where it is said that Autodesk Fusion had no multilayer PCB capability as of 2020.

 Is this still the case? If so, is there any other way I can export my PCB as  a .step model, for it to be used in CAD?

Thank you for your time.

Javier

[https://forums.autodesk.com/t5/fusion-electronics/view-3d-pcb-only-shows-top-and-bottom-layers-no-in...)

[jorge_garcia]

Hello @javiermail89 ,

I hope you're doing well. The 3D PCB can't currently show internal layers, it can only show the surface layers. For the purposes of mechanical design, you don't need the internal layers you can still get all of the component contours and board dimensions. 

Could you elaborate a little more on what you are trying to achieve and how the internal layers would help you.

Let me know if there's anything else I can do for you.

Best Regards,

[javiermail89]

Hello @jorge_garcia,

Thank you for your reply. What I'm trying to do is take my PCB design in Autodesk Fusion and do a thermal analysis of it, for which I need the PCB as a CAD .step 3D model. Do you know any way to do this?

Kind regards,

Javier

[jorge_garcia · Accepted solution]

Hello @javiermail89 ,

If your design is already in Fusion then you don't need to do anything else. Generate the 3D PCB and then in the simulation environment you can run an e-cooling study. Since the six layers can not be taken into account fully, the result will be approximate but it will give you are ballpark idea of the thermal behavior of the board.

Let me know if there's anything else I can do for you.

Best Regards,

[javiermail89]

Hello, @jorge_garcia ,

Thanks for your reply, I'll try to do the thermal analysis of the board with 2 layers to get a rough idea. Do you know any resources where I can learn to do that?

Edit: I tried to do a thermal analysis and was unable to do so, because the program told me that some bodies haven't got any thermal restrictions, even though I gave them one. How can I fix it and make sure the simulation can begin?

Kind regards,

Javier

[jorge_garcia]

Hello @javiermail89 ,

I hope you're doing well. See this page for the instructions to setup the simulation.
https://help.autodesk.com/view/fusion360/ENU/?guid=SIM-ECOOLING-OVERVIEW-TASK

If you continue to run into issues please let me know. A big part of getting this to work is making sure to setup some thermal loads in the design, specifying the wattage it is dissipating and what it's critical temperature is.

Best Regards,

[javiermail89]

Hello, @jorge_garcia 

You linked me an electronics cooling analysis tutorial, but I was trying to do a thermal analysis.

What I want to do is to check if my pcb heats up more than permitted when the tracks are "carrying" X amount of watts. Which kind of analysis is closer to what I want, thermal or electronics cooling? 

Kind reagrds,

Javier

[jorge_garcia]

Hello @javiermail89 ,

I hope you're doing well. For what you are interested in, perhaps a thermal analysis might be more fitting since the e-cooling study won't analyze the traces for current carrying capacity. I don't know how that would be done in Fusion though, since its outside of the actual electronics purview and part of the general purpose thermal simulation.

With that said, you can check that without running a simulation. I highly recommend the Saturn PCB Toolkit. Just google it

That piece of freeware will calculate, the temperature rise and maximum current for specific trace parameters. This will give you the confirmation you need. Give it a try and let me know.

If there's anything else I can do for you.

Best Regards,

[javiermail89]

Hi @jorge_garcia 

thanks for your reply. I'm still trying to do a thermal simulation, to check the temperature of the pcb tracks, but I keep getting an error. 

After simplyfying the geometry a bit, I try to define a thermal load (internal heat of 250W) on the copper elements.

After this I run automatic contacts, which seems to work, and do the pre-simulation check. The check gives me an error that says: "Error, the model contains 87 groups without themral restrictions in the load case "Load case 1"". It seems to select the copper bodies, so I don't understand what this means or how to solve it. Can you help me or know who can?

Screencap of error screen:

Kind regards,

Javier

[jorge_garcia]

Hello @javiermail89 ,

I hope you're doing well. I'm going to reach out to the simulation team to see if they can provide some guidance. With that said, if the traces themselves are dissipating 250W, I don't think that board will survive very long. How many amps are running through those traces?

I still stand by the recommendation of the PCB Toolkit.

You can enter the conductor parameters in the top section and it will calculate everything else. 

Let me know if there's anything else I can do for you.

Best Regards,

[henderh]

Hi @javiermail89,

I suspect the 87 groups of bodies do not have a contact to the others, due to a gap between the bodies which is greater than the default contact detection tolerance of 0.1mm. If this is the case, use the Measure inspection tool to determine the gap distance, and use that value as the new contact detection tolerance distance before regenerating the Automatic Contacts. It should pick up those 87 groups and allow the solve to be sent.

If this is not the case, please attach the dataset (or a portion of it that can reproduce the behavior) and we'll be happy to take a closer look.

• File > Export... > Autodesk Fusion Archive Files (*.f3d)

Hope this helps.

[javiermail89]

Hi, @jorge_garcia, thanks for your reply. 250 W is the "worst case senario" we are using to make sure, also the tracks are quite thick and wide, so we're hoping it withstands it. 

I will check both the PCB toolkit as well as run a simulation, and constrast their results. ç

Regards,

Javier

[javiermail89]

Hi, @henderh ,

I can do the simulation now, thanks 🙂

On a side note, the 3D editor seems to group all the copper elements (tracks and connections) into two bodies, one with the top and another with the bottom elements. Is there a way to separate them, in case I want to remove the connections that would be connected to the inner layer tracks?

Regards,

Javier

[jorge_garcia]

Hello @javiermail89 ,

I hope you're doing well. At this point in time unfortunately it's not possible to separate those in the 3D PCB and still preserve a connection back to the 2D PCB.

Let me know if there's anything else I can do for you.

Best Regards,

[javiermail89]

Hello @jorge_garcia ,

Yes, I'd like to know if there's any way for me in Fusion to do a thermal analysis with each track of each layer (top and bottom) as its own sepparate body (in order to give it its own thermal load)? I don't need to preserve the connection to the 2D PCB. All my top tracks count as one body i nthe 3D model, same with the bottom ones and I'd like to fix this.

Regards,

Javier

[jorge_garcia]

Hello @javiermail89 ,

I don't know of any way to do this. The thermal analysis is already being pushed because it's not really setup to handle thin objects. If you separate the top and bottom the result will be less accurate because it's further removed from the reality of the PCB.

@henderh I you have any ideas, I'm all ears very much out of my simulation depth here.

Let me know if there's anything else I can do for you.

Best Regards,

[javiermail89]

Hi @jorge_garcia 

I'm not trying to separate the top and bottom. I think I'm not explaining myself very clearly. I will try to be more precise:

What I'm trying to do is give each PCB track its own thermal load, because, although the current running through each of the tracks should be the same, the power that they dissipate is not the same (longer ones will have more impedance, for instance). When I click on a track to give it a thermal load, it selects all of the top copper elements (all top tracks and pins) instead of the specific track I want to select. Apparently, my board only has these bodies (not counting electronic components):

- Dielectric substrate

- Top solder mask

- Bottom solder mask

- Top copper (tracks and hole connections)

- Bottom copper (tracks and hole connections)

I want to somehow make the top copper and bottom copper, which are currently just one body each, into many bodies that can be thermally loaded separately, if it is the case that it can be done (I'm not experienced in thermal modelling, so I'm of course open to suggestions).

Regards,

Javier

[henderh]

Hi @javiermail89 and @jorge_garcia,

---

I want to somehow make the top copper and bottom copper, which are currently just one body each, into many bodies that can be thermally loaded separately, if it is the case that it can be done (I'm not experienced in thermal modelling, so I'm of course open to suggestions).

---

I believe it's a known issue that traces are imported in this manner. Internally, in our Autodesk Shape Manager geometry kernel, we call this multiple lumps in a single body (which AFAIK, we generally don't allow the user to create). However, Fusion will import multi-lumped bodies from other CAD systems if they are produced this way in a neutral file format. Since Fusion Sim works on a body level as the 'lowest common denominator' we unfortunately cannot delineate the lumps as individual entities automatically.

If I can contrive a workaround that isn't too painful, I'll definitely share it here.

Best regards,

[javiermail89]

Hello, @henderh

multiple lumps in a single body (which AFAIK, we generally don't allow the user to create). However, Fusion will import multi-lumped bodies from other CAD systems if they are produced this way in a neutral file format.

---

I'm not sure if I understand you correctly, but I designed my PCB in Autodesk Fusion (starting from a circuit schematic folowing the tutorial) from the start; I didn't import it from any other CAD system. Is fusion supposed to lump the traces together even then, or did I do something along the way that made it lump them together?

Kind regards and thank you both for your time.

[henderh]

Hi @javiermail89, I stand corrected for assuming you imported the geometry. I'm not super familiar with the electronics workspace.

Perhaps it is for performance / capacity reasons the traces datamodel is created this way, I see it in the 3D PCB Electronics sample for 'One Dimensional Pong'. I don't see an option in the 2D PCB to change this for the Push to 3D PCB design creation.

Hi @jorge_garcia are you aware of any hidden option to control this?

Best regards,