06/16/2019 at 22:38 •
I have received the PCBs now and soldered the first board!
It was harder than it sounds, because I screwed up the QFN footprint!
I used KiCad's QFN footprint wizard and followed the dimensions specified in the datasheet without thinking twice. The problem is that those dimensions are meant for stencil use and I decided to skip the stencil on this one since "QFNs are easy to solder". Sure, they are, when there is more than 0.1mm solder mask opening!!
In the end, I managed to solder the chip with solder paste and a reflow oven, it needed some cleanup after the reflow, but I have now verified that the chip enumerates on I2C, I need to write more code to verify the actual functionality. Unfortunately, I'm not sure if all the pins are connected, so it's hard to say if this board can be trusted. I will make a second revision with a more proper footprint.