Hi all! New user of KiCAD here and new to board making in general. Using KiCAD 5.1.4 on Ubuntu.
I’m trying to learn more about electronics by making a small project for friends and as training. I think I went a little too adventurous but oh well, that’s what I do…
I would like to install WS2812-2020 LEDs but mounted in reverse, as the package of this particular LED seems to allow. After looking for solutions online, I decided to adapt the footprint I found by rearranging the 4 pads and creating a hole in the middle with a NPTH pad (picture below).
This way, the LED can be installed in the hole, showing up on the other side of the board, while I can solder and make all connection on the other side.
As I understand it, in KiCAD the NPTH is created as a pad, and that brings me a few problems:
the routing tool does not want to connect to the real pads of the footprint (because it comes too close to the NPTH pad)
the GND plane does not connect to these pads either
The DRC check complains about pads too close to the NPTH pad (plus errors related to the previous points)
I would be really grateful if you could help me on either of these two options I consider:
find a solution about the NPTH pad so that it’s no longer considered as a real pad (or equivalent)
advise me on whether I can ignore the DRC warnings if I visually check that connections are, indeed, good.
I thank you in advance and I’ll be happy to give more details or pictures if needed.
To allow for connections you probably have to change some clearance parameter. I can’t be more precision (am not KiCad skilled yet - would need to search and check). You should also check if your fab has nothing against cooper pads touching the hole.
Few years ago I agreed with my PCB fab that for not rounded holes I can:
draw its contour at Edge.Cuts, or
make a separate layer with tracks defining milling, or
do both of this.
But the most important for them was to have no doubts of what I need.
If you draw it at Edge.Cuts KiCad can have objections as against your pad.
If you draw milling at separate layer KiCad will not notice it, but it is probably not typical solution.
I changed the clearance parameter for the groundplane (still within fab capabilities) and it fixed the problem for that.
As for pad/NPTH clearances, I guess this is not possible due to the characteristics of the pads in KiCAD (clearances cannot be zero). The workaround is ignoring DRC check warnings for this I guess.
I’ll wait a few days for a more precise answer and I’ll send this to production… and see what happens next.
Feel free to advise more on this and tell me your opinion whether or not it is a bug/feature request that I can file.
Another thing to watch is the size of your slot. Many manufacturers have a minimum radius/diameter for slots because they only stock milling bits down to a certain size. Drill-bits aren’t designed for side milling so they will refuse to use (and potentially break several) drill bits to mill a slot sideways.
Before sending out to fab, you may want to get a dimensioned picture of your intent (A screen-shot with dimensions hand annotated using a paint package should be sufficient) and ask your fab house if they are able to make it and how to best communicate your design request in the Gerber and Excelon files.
As default, I was planning to send my design to jlcpcb. They say in their capabilities page that slots have to be incorporated in the board outline layer, so I’m going to find out how to do it in KiCAD. https://jlcpcb.com/capabilities/Capabilities
Thanks for the information about milling and drill bits, I didn’t think about the fact that holes and slots required different tools.
They accept and make oval (stadium) pad slots perfectly well in the default KiCad way, i.e. in the drill file with default settings. Large slots or differently shaped slots are a different thing.
