Layered PCB Boards
Producing layered PCB Boards using KiCad and Fusion 360, without the use of decals.
Initial Release. Some expansion on steps required.
Step 1: Introduction
This tutorial will go through the process of creating a feature rich PCB board in step file format. This is a more complex creation method that creates a multilayered board that retains the board design.
This process does not use the decal placement feature that vastly simplifies the process but does not hold for all situations. This will be covered in another tutorial.
We will only used available tools without plugins. The final step file has been provided, as one of my models, for review.
The PCB created in Kicad is a two layer simple design for use in this tutorial.
Windows 10 Software Versions used
Kicad: (5.1.4)-1, release build
Fusion 360: 2.0.11186 Subscription
The Picture below uses the decal placement process. To be covered in Separate Tutorial.
The Picture below uses a version of the actual board created in this tutorial.
This tutorial will only deal with the front side of the PCB Board but the Back is created in the exact same method.
Step 2: KiCad Export
Open up your PCB in KiCad Pcbnew. The Board should be finalized and properly setup for production.
Use Alt 3 to open the 3D Viewer to review the Board and confirm all 3D components required are in place.
Once Board is setup as required export the Model to a STEP file.
Create the Step file paying close attention to any errors. In certain cases these errors will prevent the file from being created and will need to be rectified.
Next the dxf cad files will need to be created much similar to how Gerber files are created using the Plot function.
Select the plot format as DXF.
Pay attention to the DXF export units. This should match your Fusion 360 setup. Also make sure you have drill marks set to "Actual Size" so that the drill holes will be available in the copper layers.
If all has gone correct we should have all the files required to assemble the board in Fusin 360.
Step 3: Fusion 360 Import
The Fusion 360 Import is relatively simple but can run into a few issues depending on how complex the exported dxf files are.
One common issue is that the files import without fully forming boundaries. This is hard to solve as it is not apparent at which location line breaks occur. In most cases the import should work fine. If not then a DXF import plugin tool can be installed. This tool better handles certain files. We will not use any plugins in this example but the plugin will be mentioned at the end of the Tutorial.
Create a new design and confirm that the document settings are set to match the export selected on KiCad.
Select the Insert DXF File from the Insert Menu Item.
Select the plane you would like the sketch created on. In most cases the board step file will be created on the top down view.
The first DXF file to select should be the edge cut layer as this will probably be the simplest and can also be used to confirm import dimensions are correct.
Once Imported the new sketch file will be created. Do not worry about the sketch file offset from the origin and do not attempt to move or re-center the sketch as all other files will appear in this position. I believe this is due to KiCad's Pcbnew origin point that is not movable in reference to the page setup.
Once the layer is imported use the measurement tool to make sure the board is the correct size. If not it is usually a mismatch between KiCad export and Fusion Page setting differences. These should match to prevent requirements to scale.
Continue the same process of DXF import till all required Front Layers are loaded as sketches.
- Edge Cuts
- Front Copper
- Front Mask
- Front Silk
The Import to Fusion should now be complete.
Step 4: PCB Creation
In this step the PCB will be created, the actual layer depth is dependent on how the design will be used. Some depths can be manipulated for visual effect or kept close to real so overall depth is consistent with final board if the is to be incorporated into another assembly such as a case.
For this tutorial we will be aiming for a board that has 1.6mm width. Both front and back layers need to be considered when calculating layer depth.
Initially the Cut layer should be extruded to a depth of 1.5mm. This has been set negative so all sketches remain on the top side of the main board.
At each stage a new component should be created to contain the individual bodies for each layer. This aids greatly when assigning physical and appearance settings.
Layer Depths that will be used are
- PCB Board 1.5mm
- Front Copper 0.035mm
- Front Solder Mask 0.01mm
- Front Silk 0.005mm
When theses are added with other layers the full 1.6mm board depth is obtained.
As we are placing layers on top of layers when producing the front layers a 2 Sided Extrude should be used. Values for the two side extrude would look like below.
- PCB Board -1.5mm (Note this value is negative)
- Front Copper 0 to 0.035mm (Not really 2 sided required)
- Front Solder Mask 0.035mm to 0.045mm
- Front Silk 0.035mm to 0.050mm
The actual depths can be manipulated so that the layers meet. The Front Silk Layer may be set to fill down to the board depending on preference. This fills any gaps. The same can be done with the Solder Mask.
Using the Front Copper Sketch the drill holes can be used to cut the board holes as required.
In order to set each individual hole or via to copper it is easier to do the whole board body as copper and then reset the main board faces to the desired color.
Remember to move the bodies from each layer (When the layer is created) to a new component so they are easily identified and visibility of layers is much easier set.
With a Normal PCB the board color is over the copper and main PCB layer. As such setting these layers to a similar required color will produce this effect. The mask can then be set to silver or a close approximation to solder.
Final Board should be a realistic rendition of the real device.
Step 5: Final Assembly
Once the PCB is created the step file created in the 1st step can be opened in Fusion as a separate design.
The exported PCB Board can be seen as plain and featureless.
Once imported the full feature PCB board should be inserted into the design and positioned to replace the default unit.
Once Inserted then the whole assembly can be rendered to produce results as required.
If the design is exported to a Step File and then reopened from the step file the base colors and design remain.