Alternative Gnuk token board design

[Mike Tsao]

Evangelos:

I did a project a few years ago that has a similar form factor to yours:
https://github.com/sowbug/weblight

A notable difference is that the Weblight board can be inserted in either
top or bottom orientation in the Type A slot, a little like Type C but
through the magic of diodes rather than symmetric design of the female
connector. This was more important for my project because it had a visual
component to it, but I'm sure users would appreciate the flexibility. Plus
you're already solder-masking both sides of the PCB, so it's no additional
manufacturing cost except for the diodes.

As you can see in the board order I did
<https://github.com/sowbug/weblight/blob/master/hardware/mfg/production/1.0/pcbcart-pcb-order-160930.pdf>,
I chose ENIG finish with 2.0mm thickness. We ended up ordering another
1,000 in addition to that order, and we've never had a complaint about
proper fit in USB ports.

I also took the ProtoProg
<http://protofusion.org/wordpress/2013/05/open-hardware-pogo-pin-programmer/>
concept
for the pogo programming, ordering the PCBs from OSH Park
<https://oshpark.com/shared_projects/fqvxyzoH> (I'm in the US, so that was
a perfect option for me). That tool is AVR-based, so it's not applicable to
your project except to the extent you might want to copy that design and
alter it for STM32 programming.

Mike

On Thu, Mar 21, 2019 at 7:37 AM Rigas, Evangelos <e.rigas at cranfield.ac.uk>
wrote:

> On Thu, 2019-03-21 at 13:43 +0100, Peter Lebbing wrote:
> > And a nice touch to include a design for the pogo pins.
>
> Thanks Peter.
> I plan to design a PCB (some sort of a jig) for programming. That way
> it will be easier to make, instead of relying on expensive 3D printers.
>
> As for the gold platting of the connector, you are right. That is why I
> ordered the PCB with ENIG (Immersion Gold).
> Is not the same quality as hard gold, but an order of magnitude
> cheaper.
>
> In addition, ENIG offers better planarity on the exposed pads which
> helps with SMD soldering; compared to the default hot air solder
> leveling (HASL) process.
>
> Cheers,
>
> Evangelos
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