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A clean ultra-low profile ortho split design by @ak1_foo – with Kailh X-switches and only 7.3mm overall height.
Published February 18, 2022
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I made my own thin split keyboard, Synx42, which is completely wireless! – @ak1_foo.

The design goal was to create a portable keyboard (without USB and TRRS cables) which can be used with an iPad. Thus, something easier to handle compared to the author's Helix setup. The result is a compact wireless split ortho.

  • 42 keys
  • ortholinear
  • Kailh X switch (pg1425)
  • Actual thickness: 7.3mm
  • 17mm 17mm spacing
  • Operates with one CR1632 coin battery "without terminals such as USB".

Unfortunately, just like most Japanese models, the design is not open-source and the available info on it is scarce. @ak1-foo was kind enough to publish a little write-up on the details here (in Japanese).

We don't see Kailh X-switch based designs very often, most likely because of the hefty price-tag (above $2 per switch), the lack of switch choice and the single (?) available keycap. However, it looks like ak1_ dyed spray painted the caps black and the result is a quite clean design with a jaw-dropping height of only 7.3mm:

In order to keep the height as low as possible, all switch pins protruding from the back of the PCB were cut off. "This doesn't hurt".

Also, the caseless design utilizes a sheet of faux leather on the back of the board, stuck with double-sided tape. That means there is no bottom plate, nor stand-offs or rubber feet.


When designing the PCB, ak1_ used SatT99's Caravelle-BLE PCB as a reference.

The controller is Akizuki Denshi's Bluetooth BL652-SA-01 (about $10).

The PCB is 0.8mm thick. Depending on the PCB color, 0.8mm, 1.0mm, 1.2mm and 1.6mm may be offered for the same price at JLCPCB and the recommended PCB thickness for the x-switch is 0.8mm anyway. If you try to make it thinner than this, the price may skyrocket due to the special process fee.

Furthermore, the compact 17 x 17 spacing is a result of the x-switch-caps' dimensions (16.5 x 16.5mm) and the footprint of the switches (14.8 x 14mm).

All in all, despite being a great DIY project, the author is not really content with the result:

I don't like the feel of the keyswitch so I don't think I'll use it regularly … I prefer Everglide Aqua King switches – ak1_.
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Published on Fri 18th Feb 2022. Featured in KBD #66 (source).


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