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Anatomy of a Mechanical Keyboard

Oct 4, 201835903 VIEWS

Hi! I'm Isabela Moreira and I'm a software developer at Microsoft and a mechanical keyboard enthusiast.
You can find me on Twitter @isabelacmor talking about keyboards, tech, and design.

About me
I signed up for a computer science class my junior year of high school. Towards the end of the class, my teacher told me I should sign up for the high school programming team competition. I thought "there's no way I'm qualified for that..." (at the time, I had no idea what imposter syndrome was). But I signed up anyway. The day of the competition, I was actually shocked to see how few girls there were. I never really knew about the gender disparity in the field until that moment. We placed somewhere around top 5 and I was invited to come back the following year, which I did.
When I started college, I debated back and forth about whether I should go to the collegiate programming team tryouts. Even though I had experience with competitive programming, I still didn't feel like I belonged. But I went anyway. I actually made the junior varsity team and went on to compete and place in various ICPC competitions.
All throughout college, I had applied for internships at big tech companies. I'd gotten several offers for each summer, but I had never gotten an offer from Microsoft. The second year I interviewed with them, I actually had gotten a call back almost immediately saying I "didn't have the technical skills we require of software developer interns. Maybe program management would be more up your alley?" I politely declined, but it really hit my confidence. Maybe I didn't know the first thing about the tech world after all? When it was finally time to apply for full time positions, I wasn't sure if I was going to get in. But I applied anyway.
I've been a software engineer at Microsoft for two years now and my journey into mechanical keyboards started about a year ago.

How I got into mechanical keyboards
I was hosting a party and had invited my friend Cassidy Williams. We got around to talking about some new keyboard she had recently bought and I finally told her - "Give it to me straight... what's the big deal about mechanical keyboards?" Little did I know, she carries around a presentation on her phone explaining just that. I was sold, but I definitely didn't want to spend more than $100 on a keyboard (little did I know...). I settled on a Vortex Pok3r and it's still one of my go-to boards. But since that day, I've learned so much more about mechanical keyboards but I also had a lot of questions along the way. There's so many details I wish I would have known about before venturing into this hobby, but I couldn't find a lot of good beginner-level resources that didn't overwhelm me.
Despite how little knowledge I had when I first started the hobby, I decided to join Cassidy at the Seattle Mechanical Keyboard meetups, hosted by cKeys. I found the community to be so nice and inclusive, which is something that I hadn't really experienced before as a woman in tech.
When Branden Byers from cKeys approached me before the Summer 2018 SMK meetup and asked me to give a beginner-level talk on mechanical keyboards, I was a bit overwhelmed. This would have been only my third meetup and the meetup itself had been growing so quickly, it was actually being hosted at a newer, much larger venue. But I thought, if I don't give this talk, who will? While I still get waves of imposter syndrome, I've learned that it's important to be confident enough in who you are to take risks.
A beginner-level talk was something I had so deeply wanted when I was first starting in mechanical keyboards and "you have to be the change you want to see in the world" or something like that. So I agreed to talk and set to work on the talk. Of course, I still had imposter syndrome and couldn't imagine that I had enough experience to be talking about how mechanical keyboards work. But I think that my being so fresh to this hobby played out to my advantage. My audience for the talk was me about a year ago and I think that perspective really helped me stay focused on a talk that would be super easy to understand.
So let's dive in!

Anatomy of a Mechanical Keyboard Rubber domes
Before we even talk about mechanical keyboards, it's important to get a quick overview of how a "normal" keyboard works so we can look at the differences.

Normal keyboards are usually called "membrane" keyboards because they have a rubbery layer that sits between the key you press down on and the circuit / brains of the keyboard. This layer has a rubber dome with a metal contact on it that sits underneath each key. When a key is pressed down, the rubber dome squishes down and the metal contact touches the circuit, sending a signal to the computer about which key was pressed.
How is this different from mechanical keyboards? What's even the big deal about mechanical keyboards? Well, for starters, mechanical keyboards are a work of art! They come in all shapes and sizes and are highly durable and customizable. They feel great to type on and use a special mechanism to send the key press signal to the computer.

Mechanical switches
Instead of rubber, switches in mechanical keyboards are made of actual mechanical, moving parts. These switches are soldered directly onto the circuit board, instead of hovering over the circuit board like the metal contact in the rubber dome.
There's a variety of different brands and kinds of mechanical switches, which we'll get to later, but all mechanical switches have the same basic components - a leaf spring, a slider, and a spring. All three sit inside the switch housing. Outside the switch housing is the switch's stem, which is what connects the switch to the keycap.

The leaf spring is a little piece of metal shaped like an upside-down U. It sits on the edge of the housing with one side of the U shape sticking a bit out of the bottom of the housing. There's another straight bit of metal that sticks out of the housing that isn't connected to the leaf spring. These two pieces are what actually get soldered onto the circuit and are separated by the leg on the side of the slider.
In order for the circuit to close, this leg needs to move out of the way so the two pieces of metal can touch. This happens when the slider moves down far enough within the switch housing. When this happens, the leg on the slider no longer separates the leg on the leaf spring with the straight metal bit and the signal gets sent to the computer. When the slider is released, the spring sitting under the slider pushes the slider back up and so the slider's leg opens the circuit back up.

Since you need to compress the spring enough to move the slider down and close the metal gap, you can customize the feel of the keyboard even more by changing what kind of spring your switches use. Springs that are more difficult to compress create a category of switches called heavy switches, because you need a lot of force to press down on them. Similarly, there's a category of switches called light switches because they need less force. You can tell how heavy or light a switch is by looking for its actuation force on whatever website you're buying switches from. This will tell you how many grams of force are needed to complete the circuit.

Types of mechanical switches
Now that we've covered how mechanical switches work, there's several different types of switches that feel different. It's a really personal decision which switches you get and it can be handy to get a switch tester (basically a numpad-sized thing that holds a bunch of different switches) or go to your local keyboard meetup ;).

Switches usually fall into three separate categories, depending on how you want them to feel and sound.

Tactile - you can feel a bump when you press down, but it's completely quiet.
Tactile and clicky - the stereotypical click clack sound. You can feel and hear a bump when you press down.
Linear - no bump or sound. It's completely smooth all the way up and down.

You can tell what kind of switch you have just by looking at the internals too. If the slider's leg has no bumps, it's a linear switch. If it has a bump, it's definitely a tactile switch, but that doesn't necessarily mean it's clicky. In order for it to be clicky, it needs to have a floating middle part. This floating part will actually hit the bottom of the switch housing when the switch is pressed and that's what make the clicking sound. In each of the categories above, you can get switches with different actuation forces. For example, if you wanted a tactile switch that's on the heavier side, you could get MX Clears. If you wanted something lighter, you could get MX Browns instead.

There's also a few different manufacturers for mechanical switches. The most common is probably MX switches, which have a cross-shaped stem. There's also Alps switches with boxy looking stems and Topre switches with rounded stems.

PCB

Once you've decided what switches you want, you have to have a circuit! Mechanical keyboards usually use PCBs (printed circuit boards), although some people choose to hand wire their own circuit boards. The PCB is the actual circuit board where the switches are soldered on. The highlighted area is the area where a switch would be solder on. The PCB pictured is from a Planck, so you can see that it has room for 46 switches since its a 4 x 12 grid.

PCBs come in all sizes and layouts, so it's important to decide which works best for you. Typically, boards come in full size, tenkey-less (TKL), or 60% as pictured. However, there's boards in all sizes from 0-100%, so you don't have to feel like you're limited to just those three options. Mechanical keyboards also come in different layouts - most commonly staggered (the standard layout you're probably used to), ortholinear (made up of straight rows and columns like we saw with the Planck PCB), and ergo (which are usually split into a left hand keyboard and a right hand keyboard).

If you're interested in LEDs, you'll want to check that the PCB comes with LEDs pre-soldered on or if it at least supported you soldering on your own. You also need to make sure that the PCB you're using supports the switches you want on it. This usually isn't a huge issue, especially if you're buying a kit or an assembled board, but something to look out for if you're building something completely custom. The last important thing to think about when you're considering what PCB your board has is what firmware that PCB supports. If you plan on programming your keyboard with custom macros and layouts, it's important to make sure that you get a PCB that runs on highly customizable firmware. The most popular ones include:

QMK: https://github.com/qmk/qmk_firmware/
TMK: https://github.com/tmk/tmk_keyboard/
Kiibohd: https://github.com/kiibohd/controller
EasyAVR: https://github.com/dhowland/EasyAVR

Other boards, like those made by Vortex, while still good boards, don't run on customizable firmware and the only way to program them is through various key combinations on the board itself, which can get annoying, or have various limitations on which keys can be programmed.

Plate

After you pick the PCB, you generally need a plate to sit over it. The plate protects the PCB and acts as a guide when soldering the switches on so they are all placed evenly. The only thing to make sure of is that the plate is compatible with the PCB, meaning that all the cutouts for the switches on the plate align with the holes in the PCB where each switch will get soldered. Once you start assembling your board, it should look something like this picture. The white part on the bottom is the PCB and you can see that the plate nicely outlines where each switch goes on the PCB. From there you pop all the switches through the plate (I usually start with the corners to stabilize it) and then you turn the whole thing over and solder the little pins from the switches onto the PCB.
Case

Once all that's done, you can put the assembled board in a case. The only thing to make sure of here is that the case snugly fits the assembled PCB (since that's the whole point of the case). Cases come in tons of different materials and it's totally up to you what you go with. Aluminum is a popular choice because it's heavy, durable, and can be anodized tons of different colors. Wood, acrylic, and plastic are also used. You can even build your own case with a 3D printer, laser cutter, or LEGOs.

Keycaps
Keycaps are mostly cosmetic but they can actually change the way you type and the kind of feeling you get from your board. Just like switches, there's a whole bunch of different types of keycaps. They're usually differentiated by their profile and material.

The most well-known profiles are SA, DSA, and DCS, although there's tons of others as you can see from the chart and new profile coming out all the time. My favorites are DSAs and SAs, depending on which board I'm using. To me, SAs feel really sturdy and I think go well with clicky switches and DSA feel lighter and more minimalistic.
Keycaps are usually made from ABS or PBT plastic, although most artisans are made of clay or resin. PBT is usually considered better than ABS because they don't wear as easily, don't show shine from oily fingers, and don't yellow. Another thing that makes a big difference in the quality of keycaps is how the legends on the caps are done. They can either be printed on or they can be doubleshot. You can see the blue and green keycaps in the pictures are doubleshot because they have an extra layer of plastic that makes up the actual legend - that's the black and white striped-looking layer. The rest of the keycap plastic is then filled in around the legend plastic. This makes the legends much more durable because you know they can never wear off. But if you have printed legends like the white cap, it's just a matter of time before they wear off.

Before buying a bunch of cool keycaps though, you have to take into account what layout your keyboard is. Different layouts have different sized keys, as you can see by comparing the WASD board on top with the HHKB on the bottom. Keycaps are measured based on the size of the alpha keys since they're square. Those are considered 1 unit in size. Non-character keys, called modifiers, are described as being some multiple of that. For example, "enter" is usually a 2.25u key, meaning is 2 and 1/4 size of the alphas.
You also have to make sure that the keycaps you get match the stems of your switches. Alps switches, MX switches, and Topre switches all have different stems and can't share keycaps. Usually, most of the popular keycap sets are sold with MX stems.

End game
Once everything's assembled (or purchased assembled and in your hands), you'll end up with a beautiful 100% customized board and you'll actually know how it works inside and out! It'll be everything you've ever wanted.... until the next board you get.

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Yulian

Jul 14, 2019

(Not sure if my last post went through). Great article, really helps get an idea of how to make something custom. I have been holding off on mechanical keyboards since majority of them don't have flat/chiclet/low-profile keys, and thats what I prefer, flat laptop style keys. Luckily its starting to gain some traction. I kickstarted the Hexgears X-1 and its been great. Coolermaster I think now makes a low profile mechanical in all 3 main sizes (full, tkl, and 60%). As more parts and stuff comes out for it, I plan to make a custom mechanical keyboard finally.

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philippeback

Jul 14, 2019

Cool. Albeit not as extreme, I have quite a couple of mechanical keyboards. The key factor in picking one or the other is how much it would inconvenience coworkers when on site. In my own office, yeah, very clicky stuff rules.

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alourie

Oct 31, 2018

great writeup @isabela. Are there many mech keyboard people working at the office with you? :-)

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ZenAtWork

Keyboard Club Member

Oct 22, 2018

Outstanding work! I've been looking for a good diagram of switch types for a long time! Imposter? No more!

jeremyvdw

Oct 21, 2018

Great writeup, congrats!

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devyhia

Oct 13, 2018

Great article! I learned something up there.

Kevnwin

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Vendor Services

Oct 11, 2018

That was a great read, thanks! I've been into mechs for a while but I only knew the basics and bought premade boards.
Since joining MD, now, I'm learning more about different keycaps, artisan caps and trying different layouts. It's all downhill from here!