Hello All,
Has anyone tried using KiCad to do Interposer designs for Chiplets? I’ve been playing with wire bonding lead-frames to die using a script to take DEF and create a footprint and symbol for the die and the packing wizard for the lead-frame. I would expect an interposer wouldn’t be a stretch since it is technically the PCB and the chiplets are the IC. I would say the only limitation I’ve run into is the scaling since chiplet bump pitches are in um vs mm, and the packing wizard should have an option to generate a generic symbol for the footprint it just made.
I do not know what are interposers and chiplets and maybe others on the forum do not either. Maybe include a few links in your next post?
Never done one, but if the job is done with ‘standard’ PCB and DevTools, probably KiCad can do it (or be modified to)
the minimum grid spacing currently doable is 0.001mm:
KiCad’s native resolution is in nano meters, so there is plenty of resolution.
I tried to set a small grid in the preferences, but KiCad complains and the smallest it will accept is 1um just as Claudio.Lorini mentioned.
You will also bump into other limitations / bugs at this scale level. For example: PCB Editor / Inspect / Measure Tool is struggling with this resolution.
I’m not a KiCad developer, but I guess that support for fine pitch stuff will improve over time, but at the moment the KiCad development team is still quite small, and there are many feature requests, and features that appeal to a small set of the users have a lower priority.
You can create a test project to find out how good it works for you and get an overview of the most pressing issues. If you’re really serious about this, then contacting https://www.kipro-pcb.com/ is an option. They do commercial support for KiCad (so it’s not free) and they also do priority development and bug fixes for customers.
I’m in the investigation side of this. So far, wire bonding QFN packages KiCad is a go. Just need to dig in more and I will update as I learn more.
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Never done it myself, but did see some youtube video’s about wire bonding. All the magic needed to make wire bonding work, is build into the wire bonding machine. In the video I remember, first chiplets were glued on the PCB roughly inside the wirebonding location. Then a camera in the wirebonding machine takes a picture and analyzes both the PCB pad coordinates and the exact orientation of the chiplet, and then makes all the wire bonds automatically. (Something like 50 wires in 3 seconds) I don’t see any problem for designing footprints in KiCad that can be used with wire bonding techniques, but there are probably specific requirements for the materials of the PCB itself, but that’s part of the ordering process.
Seems like what you need is a “scaler” utility. Setup your design rules and footprints at a larger resolution and create your design, then scale down the Gerbers (or whatever your output format is) to the needed resolution.
That could work. Some people used to scale things in eagle to get around the board size limits of that program. However, KiCad already uses nanometer resolution internally, and has plenty of resolution. I would much rather see bug fix requests to make direct use of that resolution.