At a certain point, if you're going for "smallest", it's a bit of a cheat not to include Z-height, especially if you're relying on a vertical micro-USB connecto

At a certain point, if you're going for "smallest", it's a bit of a cheat not to include Z-height, especially if you're relying on a vertical micro-USB connector in your design. 45x18=810 vs 33x10=330, great. But If you're adding another 5mm z-height for a connector, the volume is now kind of significant. Just think of the stack-up at this point: Motherboard + female socket (1.6mm + 5mm?) + daughterboard (1.6mm) + pins (5mm?) + vertical USB (5mm?). You're looking at something that's +/-18mm tall. Given that this whole design is basically just a way of attaching a 1mm tall IC to a design, that starts to feel a bit extreme if you care about size. If you really care about a tiny board, and don't need the DIP compatibility (or removability), I feel like a castellated design that can be soldered down is more useful. Designs like the Piksey Atto (20x13 = 260, but also something like 5mm tall) For me, the killer feature of not having the microcontroller soldered down is that you can flash something on a dev PC, and then insert it into the device. But in that case, I like something like the tinyduino, which eschews .1 headers and uses a B2B connector. More of a pain to deal with, but you get the benefit of tiny size + low z-height + removable: https://tinycircuits.com/products/tinyduino-processor-board https://tinycircuits.com/products/tinyduino-processor-board Regardless, more options are always better. But it's also useful to really think about what your requirements really are.