The mask-2.0.0 by madbadmax is a 4x6 split keyboard with Cherry MX-ULP switches.
KBD.news Published December 22, 2022
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Fellow redditor madbadmax released his first split keyboard utilizing the rather rare Cherry MX ULP keyswitches announced in early 2021.
I bought the switches from Reichelt and contacted Cherry about some resources for footprint and keycap design – which they provided me (I am not sure though, if I am allowed to share those) – madbadmax.
The keyboard is about 6.7mm thick. The overall height of the surface mounted CHERRY MX6C-K3NB "Ultra Low Profile RGB" switches is 3.5mm:
clicky
65 cN operating force
0.8 mm pre-travel
1.8 mm total travel
Soldering
For soldering, the author suggests using a stencil, solder paste and oven.
I wouldn't try it any other way, since the switch contacts themselves are beneath the switch so that hand-soldering is not really feasible. But it might also work with paste and a hot air gun – since I had soldering errors on 2 switches I heated those with about 310°C from the bottom for a while and it worked like a charm!
Sound and feel
I still have to test it a bit more. The keycaps are quite slippery and maybe I'll have to do another run on those (maybe with something curved). But for such low profile switches those feel quite good.