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Ukkie: My smallest project so far

Meet the Ukkie: Yet another small dev board. But seriously, I created this design primarily to get some hands on experience with reflowing BGA chips. This combined with a case of "where the f*ck did I leave my USB to serial converter?" led to a quick and dirty in-port USB dev platform.

Pushing OSH Park to the limit

The Ukkie (version 2.0) is based on the Freescale Kinetis K22 Arm Cortex M4F. I also threw in a couple of LEDs and a Maxim MAX4372F to do some current monitoring, which will come in handy evaluating parts and modules for my projects.

Quite small
Quite small

As you can see the device is quite small, the 8x8 BGA-121 package barely fitting a USB connector. The whole design is close to single layer routing, because of the bottom USB contacts. For this to work I had to make the BGA pads pretty close to the minimum size and take the clearance & trace width to 0.15mm, a touch under the min. 0.006" specified by OSH Park. Nontheless the traces looked fine.

Components used

Pinout

Ukkie2 pinout
Ukkie2 pinout

The top and bottom rows are 2mm pitch pads for some edge soldered headers, allowing me to cram in a bit more functionality than with the regular 2.54mm pin spacing.

What's next?

I'll do a follow-up about the soldering process and actual functioning of the device, as I'm waiting on the Maxim samples to arrive.