# Sinc Split Mechanical Keyboard Build Log


**tl;dr**: I built a split mechanical keyboard. It looks like this:

![](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/split.jpg)

## Intro

At the beginning of the COVID-19 lockdown, I noticed that I was feeling wrist
strain while working at home. I've been using a vertical mouse for several
years, but up until recently I was using a conventional keyboard.[^1] I'd seen
anecdotes that split keyboard designs can be more ergonomic, and I'd experienced
that myself when I used Microsoft's
[Sculpt Keyboard](https://en.wikipedia.org/wiki/Microsoft_ergonomic_keyboards#Sculpt_ergonomic_keyboard)
during an internship. I eventually bought a
[Kinesis Freestyle Pro](https://kinesis-ergo.com/shop/freestyle-pro/), and in
the process of researching that keyboard I became more interested in split
mechanical keyboards.

![Kinesis Freestyle Pro](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/freestyle_pro.jpg)

I've been using my Kinesis keyboard for the past few months, and have found the
split layout to be very comfortable. It allows me to have my wrists and arms in
a more neutral position, which reduces strain during long sessions of use.
Importantly, the split layout doesn't affect my typing speed -- it's essentially
just a normal QWERTY keyboard split along the middle. Other split layouts (like
the [Ergodox](https://ergodox-ez.com/)) require a longer re-learning period.

Though I really like my Kinesis keyboard, it's not a particularly aesthetically
pleasing object. During my research, I stumbled upon a
[community sourced list of split keyboards](https://docs.google.com/spreadsheets/d/19-rTWbp8SCKdZFByPZu3RT8NSF8vVddDe8WL6R6b1qQ/edit#gid=0)
by a user of [/r/mechanicalkeyboards](https://reddit.com/r/mechanicalkeyboards).
This inspired me to want to build my own split keyboard.

It was around this time that I found [Keebio](https://keeb.io/)'s online store,
which sells PCB and case kits for split keyboards. Many of the split keyboard
PCB sellers I'd seen online focused on minimalist layouts (<=60% layouts), which
I didn't want. Keebio had 2 models that interested me: the _Quefrency_
(pronounced "key-frency") and the newly-released _Sinc_, both of which were full
sized:

![Quefrency](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/quefrency.jpg)

![Sinc](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/sinc.jpg)

The Sinc board had a full set of function and macro keys, so I went with that
model. Keebio's boards tend to go out of stock quickly, so I was lucky to get
one from the first production run of PCBs...

## PCB

![](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/pcb.jpg)

The Sinc PCB I ordered came with a microcontroller and surface-mount diodes
already soldered to the board, which made assembly quite easy. From what I saw
online, it's fairly common to get a "naked" PCB, and you have to bring your own
microcontroller (usually something like an Arduino or ESP32) and solder on a
diode for each key switch.

I was pretty impressed with Keebio's PCBs -- the Sinc even came with underglow
LEDs and a reset button on each half of the board.

### Deciding on a Layout

The Sinc PCB design supports a number of layout variants. I used the excellent
open source [keyboard-layout-editor.com](http://www.keyboard-layout-editor.com/)
to plan my layout. Though, there weren't a ton of decisions to make; the biggest
areas for customization were the arrangement of meta keys on the right side of
the board and the layout of the keys surrounding each space bar.

![Layouts supported by the Sinc](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/layouts.jpg)

I opted for a layout that included a set of arrow keys and a larger right space
bar:

![](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/final_layout.png)

## Keycaps

One of my motivating reasons for building a custom keyboard was to make
something that "looked cool", so I spent a fair amount of time researching
keycap designs and styles. Since my keyboard had a split layout, many
traditional keycap sets wouldn't be compatible. Notably, I needed a set that had
support for the shorter split space bars, and the shorter right shift key.

After a bunch of comparisons, I settled on PimpMyKeyboard's
[DSA "Granite"](https://pimpmykeyboard.com/dsa-granite-keyset-sublimated/) set.
The DSA keycap profile is uniform and flat, and aside from ergonomics I think
that they just look nice.

![DSA Profile](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/dsa.jpg)

Of course, one's choice of key cap is almost entirely based on aesthetics, so
this was one of the more fun parts of the process. In particular, I liked the
choice of font and the size of the key labels; I think it lends the board a good
mixture between "retro" and modern design.

![](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/macro_closeup.jpg)

I opted for symbolic modifier keys (i.e. the shift _symbol_ (⇧) instead of the
written out "Shift" word). I'm pretty happy with how they look, and I like that
I was able to repurpose some of the more obscure modifiers (i.e. scroll lock,
insert, etc.) as macro keys, because their meaning is ambiguous enough to be
repurposed.

![](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/right_side_closeup.jpg)

The tricky part of choosing keycaps was making sure that I got full coverage of
all the keys I needed. The layout I chose had non-standard space bars and some
other funky keys (non-standard right shift and modifiers). Fortunately, PMK made
it easy to customize my keycap set. Ultimately, I ended up needing:

-   A full alphanumeric set.
-   A set of symbolic modifier keys.
-   Additional keys:
    -   1.75u Right Shift, 1.5u Ctrl, 1.5u Alt, 5 additional 1u keys to fill out
        the macro pad.

## Assembly

### Hotswapable Key Switches

One goal that I had when building my Sinc was to support hotswappable key
switches. One of the benefits of mechanical keyboards over traditional "rubber
dome" keyboards is that you can customize the feel of the key switches. Some
people prefer tactile or clicky switches, and others (like myself) prefer a
smoother keypress. Currently, I've really been enjoying using linear (Cherry
Red) switches, but I could imagine wanting to try out different switches in the
future.

Making a keyboard "hot swapable" was easier than I anticipated: You solder a
small socket into each through-hole in the PCB, and then the key switches are
effectively just pressure-fitted into those sockets.

![PCB Socket](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/pcb_socket.jpg)

I found a source of PCB sockets
[online](https://www.mouser.com/ProductDetail/mill-max/0305-2-15-80-47-80-10-0/?qs=QtQX4uD3c2Uys0ai6Tr8NQ%3D%3D&countrycode=US&currencycode=USD),
and ordered enough to have two for each key. These sockets were surprisingly
expensive, given they're just tiny pieces of metal. But, they're a lot cheaper
than a whole new keyboard -- which is otherwise what you'd be looking at if you
wanted to try out a new switch type.

![Socket (unsoldered)](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/socket_unsoldered.jpg)

Normally, you'd solder the key switches directly to the PCB, skipping the socket
step. Surprisingly, soldering the sockets instead of the switches themselves
actually made assembly _easier_. I messed up on the placement of a couple of the
keys[^2], and instead of having to desolder the switch, I could just solder in
additional sockets (consequently, it helps to buy some extras!).

![Socket (soldered)](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/socket_soldered.jpg)

### Key Switches

As for the actual key switches I used, I bought a set of Gateron Red switches
from
[KEBO](https://kebo.store/products/gateron-5-pin-switches?variant=14608737337386).
I use Cherry Red switches on my Kinesis, and like the linear switch type.
However, I'd heard good things about Gateron's version of the Red switch (and
they're slightly cheaper).

![](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/gateron_red.jpg)

Now that I've typed on the Gateron Reds for a bit, I can't say that I notice a
huge difference between them and the Cherry Reds. They do feel a bit "looser"
and that they require a bit less force to actuate, but I can't really say that
they feel any "smoother", contrary to claims I'd seen online.

### Case

When I ordered the Sinc PCB from Keebio, I also ordered a set of plates to use
as a case. The design of the plate is really straight forward: two pieces of
metal with cutouts for the keys that are fastened together by several screws and
standoffs around the perimeter. However, I was initially a bit disappointed
about how it all fit together. The PCBs' USB-C and TRRS sockets give the board a
bit of height, so they didn't sit flat on the bottom plate. It took a fair
amount of tinkering to get the case to close correctly, and even then I felt
like I'd done something wrong.

Making matters worse, the build documentation was fairly lacking (the portion
about assembling the plate kit was copy/pasted from an older design), but since
the Sinc is a new product for Keebio, I'll give them the benefit of the doubt.

After enough messing with the tightness of each screw, I did get a final result
that felt sturdy enough. I also put some rubber feed on the bottom of the plates
to prevent the keyboard from slipping on my desk.

## Finished Product

I really like the way that the keyboard came out! Aesthetically, I think it
looks pretty cool, and ergonomically it's nearly as comfortable as my Kinesis.

![](https://benjamincongdon.me/blog/2020/07/30/Sinc-Split-Mechanical-Keyboard-Build-Log/angled.jpg)

I showed my completed keyboard to some coworkers, and one of the first questions
I got was "what does the Space Invader key do?". My answer was... "nothing yet".
I still haven't decided how to map each of the macro keys, but the Sinc supports
the open-source [VIA Firmware](https://caniusevia.com/) (as well as
[QMK](https://qmk.fm/)), which makes it really easy to setup macros. My current
favorite macro key is one that automatically locks my machine. Dedicated media
keys are also handy...

Building a custom mechanical keyboard was certainly more expensive (not to
mention time-consuming) than purchasing a pre-made one, but that's
understandable given the economics of short-run manufacturing.

Overall, this was a fun project. It's rewarding to have built something that
I'll continue to use daily, and I enjoy seeing the finished keyboard on my desk
-- it's almost like a functional piece of art.

[^1]:
    I used to use an old full-size Apple keyboard. I don't recall what the
    "official" name was, but it was the _old_ style scissor switches, predating
    the "magic keyboard" era.

[^2]:
    Since the Sinc supports multiple layouts, some of the key switch locations
    are ambiguous. I guessed wrong a couple times, and only discovered my
    mistake once I'd put the whole thing together and was in the processes of
    attaching the key caps. Fortunately, since I was using the sockets, I didn't
    have to desolder any switches.