Asymmetric QFN?

Hi! This is my first post, by way of introduction I’ve been using Eagle for 20 years and since they’re basically obsoleting it I wanted to try something more stable and so far Kicad looks very nice and is making sense for the most part. I am using Kicad 5.99 because I figure if I’m going to use this long term I may as well start by learning on the version I’ll be using for a while.

One thing I am missing is that I have parts which are basically QFN but have different pitches and pad sizes for the top/bottom and left/right sides. The below screenshot shows an infrared photodiode, but I encounter this all the time.

I was hoping to find that the package generator could handle this because I’d love to have a 3D model generated for the part automatically, but the QFN footprint wizard seems to only allow symmetric packages with equal numbers of pads per side, the same size pads everywhere, and the spacings all the same.

Does anyone have any advice for a newbie? I made the footprint manually for the LED part and I think I made the footprint fine, even has a courtyard, but there is just no 3D model and I don’t know of a good way to get one other than making it by hand in SolidWorks and exporting as a STP which seems extremely roundabout.

Thanks for any suggestions!

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A footprint wizard that senses your brain waves and turns it into a perfect (for you) footprint has not been invented yet.
It could also be a bit dangerous…

I usually start with something that is “close”. I either make a copy of an existing footprint from one of the default libraries, or fiddle a bit with one of the footprint wizards. Once you found something close, it’s loaded in the footprint editor, and I do whatever is needed to make it fit my needs.

A simple piece of pen & paper can help with making some notes or scribbling some numbers down, for example if the datasheet specifies corners of pads, while KiCad wants coordinates for the center of pads.

KiCad’s mechanical CAD capabilities are quite limited, but it’s enough for all simple footprints.

There are other alternatives.

  • There is the “StepUp” workbench for FreeCAD. It has much more powerful drawing capabilities, but it also has a quite steep learning curve.
  • Websites such as snapeda have databases which can generate footprints for different EDA progams. Some people like them, I find the quality of those footprint dubious.
  • KiCad is an Open Source program and friendly to hacking and addons made by others. There are some 60+ side projects around KiCad, and some of them are for generating footprints. A few years ago I saw a (beginning) project that lived in a web browser and could generate footprints from some parametric data. It looked promising, but I do not have much use for it and forgot it’s name.

Well the footprint wizards of kicad are quite limited. This is why the official library team has their own scripts. The QFN script is found here

However i think the qfn script does not yet support missing pads. But the gullwing one does so it should be rather easy to port this over to the qfn one (it is not documented in the readme but i remember that i added it quite some time ago.)

And of note: neighter the kicad internal wizards nor the footprint generators make a 3d model! But there are scripts available to make models over on


Thanks Rene!

Very helpful, I thought it was like the Eagle package generator that does accept a height argument to make primitive 3D models, I’ll check out the scripts for generating them. That said, with the Eagle one I would often generate a full part (ex: BGA) and then delete the pads that don’t actually exist. None can cover all use cases for sure.

I’ll look at using the scripts next time, I didn’t realize they weren’t all part of the UI so it’s super helpful to have that link.

I just made the below LED part by hand, but since the 3D model generation is in a separate program it’s nice that I could go back after the fact and generate a model and just use that STP file for this part (I imagine?). Seems good enough in any case, thank you for the information Rene!

Thank you for explaining how you would do it, very interesting approach.

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