Does KiCad have a way to handle footprints for things like USB-C connectors that attach to the edge of a PCB? I’m using a Hirose USB-C male connector that solders onto the edge of a .8mm thick PCB. when I preview the 3D model, it looks like this:
KiCad assumes all 3D models sit on top of a PCB, while this part is supposed to be on the edge and cantilever out from it. The preview is completely wrong for this part, and makes it very hard to properly align the 3D model with the footprint.
If I add a rectangle to the Edge Cuts layer, I get something that more closely approximates what is supposed to happen.
Now I can see the way the connector will sit on the edge of the board, but there are still two problems:
1 - The footprint preview still expands the sample board it creates for the preview to be a bounding box that includes the 3D model, the copper pads, and the rectangle on the Edge Cuts layer. What I really want is for the rectangle on the Edge Cuts layer to chop of the part of the preview sample board that it intersects with. Although if I’m totally honest, it seems odd to me that adding a rectangle to the Edge Cuts layer removes board from the preview sample shape rather than adding to it, but in this case it helps so I’m not complaining (yet).
2 - If I use this footprint in a board, the board will add the rectangle on the edge cuts layer of the footprint to the board outline on the PCB Edge Cuts layer which results in a larger board. Here’s what the generated Gerber file looks like for the Edge Cuts layer on my PCB: You can see two distinct outlines which is not what you’d expect based on the 3D Preview of the footprint:
So, is this is a wish list request to be made on GitLab, or is there some built in method to handle a case like this? Ideally there would be some way add a a custom PCB outline for previews only. If the user didn’t add one, then KiCad does its usual thing of creating a sample PCB outline. If the user does add one, then KiCad uses that custom outline for the preview board shape.
immediately after posting I stumbled on this related GitLab issue:
As a test, I changed the position of the rectangle on the footprint to be the shape I wanted for the preview and got this this 3D preview result:
This is pretty much exactly what I want, except if I use this footprint in a PCB I get the 3D preview telling me the board outline is malformed, which is true since there are essentially two board outlines on it. This is what the Gerber of the Edge Cuts layer looks like now:
I get the 3D preview telling me the board outline is malformed, which is true since there are essentially two board outlines on it.
Thanks for video link. I need to spend some time watching it. It looks like an interesting, if somewhat low level, manual way to handle this.
In the meantime, I’ve gone with a simpler approach. I’m using the version of the footprint that shows the small chunk of board edge so I can verify the footprint looks good. In my project, I just edit the footprint in the project (not the library) and remove the rectangle that defines the board shape for the 3D preview in the footprint editor. This gives me a single board outline on the Edge Cuts layer and everything works perfectly. The drag is that it involves manual work, and if I update the library footprint for any reason and need to update it in my project, I then have to edit the project footprint copy again.
Not worried. It sits on the edge of a PCB of 0.8mm thickness. Regardless of the datasheet calling it a “paddle card”, it’s still a PCB. This connector would normally be used inside an overmolded cable or adapter like this:
Whatever connector you use, you should look at Spec sheet as it will specify the Interface Geometry (example here for Hirose USB-C).
Regarding Updating a Library footprint of particular interest, to avoid the Update Problem, simply Save a Copy of it to your desired folder where you should keep Footprints/etc (not the Kicad library). And set Paths appropriately…
