How to Build a Custom Mechanical Keyboard: Part II

Custom Mechanical Keyboard Guide Cover Image

You can’t build a custom mechanical keyboard without knowing what goes inside one. That’s exactly what the last installment of this guide covers. If you haven’t read it, now would be a good time to do just that. Unless, of course, you plan on YOLOing your way through the keyboard component procurement process and make a right mess of things. Either way, it’s time to get your hands dirty putting together a mechanical keyboard.

Buying components needed to build a custom mechanical keyboard isn’t a straightforward affair. You can’t just head over to the nearest Micro Center or log into Amazon.com. This is a niche hobby. Custom mechanical keyboards are rare beasts that aren’t exactly mass produced. One way to procure a DIY mechanical keyboard kit is via some Chinese mechanical keyboard brands.

Chinese Custom Keyboard Brands

Few Chinese mechanical keyboard brands such as KBDFans and KPRepublic now produce mechanical keyboard kits made from high-quality machined aluminum and brass at surprisingly low (relatively speaking, of course) prices. Unlike Western boutique custom keyboard makers who run limited (and sometimes unpredictable) group buys, you can pick up a mechanical keyboard kit from either of these websites precisely when you need one.

I’m not aware of any other custom mechanical keyboard sellers apart from these two that follow the familiar retail model instead of the usual group buy route. Out of the two aforementioned options, I have personally spent about $2000 on keyboard parts with KBDFans without any hiccups. The brand is widely well-regarded in the custom mechanical keyboard community. You can also look at similar options on AliExpress, but the actual keyboard kits will invariably originate from one of these two sources.

Both websites provide plenty of options between 40, 60, 65, 80, and 96 percent keyboards and let you further choose between numerous plate and case materials as well as stabilizer types. Use the information gleaned through the last installment of this guide to pick a custom mechanical keyboard kit of your choice. You can also choose to buy individual components separately, but that ends up costing a bit more, and you have to be especially mindful about compatibility. Once you have that figured out, all that remains is the painful wait for the mailman.

Tools Required

  • Metal tweezers, or a small length of hook-up wire or paperclip
  • Basic screwdriver set
  • Anti-static wrist strap (optional, if you like to be dangerous)
  • Soldering iron (optional for hot-swap PCBs)
  • Desoldering pump (optional for hot-swap PCBs)
  • 67/33 rosin core solder (optional for hot-swap PCBs)
  • Solder flux (optional for hot-swap PCBs)

Caution: Some steps in this guide involve handling bare PCB, which is susceptible to damage by electrostatic discharge from the human body. Working bare feet is the best way to minimize the buildup of electrostatic charge. However, this isn’t effective when working on carpet, wooden, or other non-conductive flooring. Using an anti-static wrist rap is the safest way to eliminate the risk of electrostatic discharge.

1. Testing the PCB

You ideally want to kick things off by testing the PCB. That involves determining whether all terminals interfacing with the switches are operational. Connect the PCB to the computer. We use a pair of tweezers to short the plated through-holes (solder points) associated with each key to register an input. A simple hook-up wire or non-insulated paperclips can be used in a pinch if you don’t have tweezers handy.

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Online tools, such as KeyboardTester.com and dedicated software such as Switch Hitter, work great as nifty visual aids for this task, making it much easier to keep track of the keys that have passed testing. Validating each key involves shorting the terminals (through holes) on the PCB with a conductive wire, paperclip, or a pair of tweezers as shown in the image.

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Regular PCBs that require soldering employ multiple solder points (plated through-holes) for certain keys to accommodate alternate keyboard layouts. In short, don’t panic if multiple adjacent terminals trigger the same key. The process is more or less the same for PCBs sporting hot-swap sockets. The only difference is that the switch terminals are accessible only from the bottom side of the PCB. That’s the side on which the hot-swap sockets are soldered onto the PCB.

If all the keys on the PCB register inputs – congratulations, you can proceed to the next step. Otherwise, contact the seller for a replacement if fate has dealt you a faulty PCB.

2. How Stabilisers Work

Virtually all custom mechanical keyboards ship with Cherry style stabilizers. Without stabilizers, long keys such as the Spacebar, Shift, Enter, and Backspace will prove difficult to operate. The Spacebar, for example, will only be supported by a single spring-loaded switch at the centre in the absence of a stabilizer. That could work provided you only ever tap it exactly at the centre. But tap the key on either end, and it will pivot about the switch like a seesaw. Stabilizer basically allows the long keys to work reliably even when actuated from the extremities.

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Stabilizers come in two major flavors: plate mount and PCB mount. Choosing between either of these is subject to the compatibility of both the PCB and plate with each type of stabilizer. You don’t have to worry about compatibility if you have purchased a DIY kit. However, those of you who plan to purchase individual components, be sure to double-check for compatibility.

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PCB mount stabilizers are generally considered superior compared to their plate mount counterparts since they run a lower risk of popping out of place. The PCB mount variety itself is available in regular and screw-in options, with the latter being objectively better at staying securely anchored to the PCB and eliminating wobble.

All three types of stabilizers are comprised of a post, housing, and steel wire. The post is the smallest part with a cross shaped protrusion at the end that interfaces with the corresponding slot on the keycap. This slides up and down inside the housing, with the steel wire slotting orthogonally into a socket on the post. The other end of the wire slots into the second pair of stabilizer post and housing. The pairs of posts and housings connected by a wire collectively form the stabilizer assembly.

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3. Assembling Stabilisers

The stabilizers usually come pre-assembled. Even if yours don’t, assembly is pretty straightforward and identical for all Cherry-style stabilizer variants.

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1. The stabilizer post goes in through the opening at the bottom of the housing with the cross-shaped end entering first. The housing accommodates the stabilizer wire through the vertical slot highlighted in the image.

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2. The post has a single large rectangular socket on one vertical face, whereas the other face has two square sockets stacked on top of each other. When inserting the post into the housing, ensure that the two square sockets on the post correspond with the vertical slot on the housing.

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3. One end of the stabilizer wire can now be inserted into the square socket at the bottom of the post. It must enter through the vertical slot on the housing.

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4. Snap the wire into the channel at the edge of the housing. This should allow the wire to pivot about the channel and move the post up and down as it rotates inside the channel.

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5. Repeat the same step for the assembly at the other end of the wire. Your finished stabilizer should resemble the corresponding variant in the image.

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6. Depending on your keyboard form factor and layout you have chosen, you will need one long (6.25 unit) stabilizer for the space bar and various shorter ones (2 unit) for the rest of the stabilized keys. Prepare the right amount of stabilizers that are warranted by your keyboard layout.

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4. Installing PCB Mount Stabilisers

These instructions are applicable to both regular and screw-in PCB mount stabilizers. Let’s begin by learning how to install screw-in PCB mount stabilizers. Before we can proceed, we must determine the top and bottom faces of the PCB. The top of the PCB is bare and devoid of any SMD mount components such as the microcontroller, diodes, reset button, and DIP switches. This is the side where you can mount the stabilizers.

1. Observe the bottom of the stabilizer housing. You can spot the retention tab jutting out of the bottom along the end nearest to the stabilizer wire. This is indicated by a green dot in the image below. The screw post has been marked by a red dot at the opposite end of the housing.

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2. Let’s move onto the PCB. The above image shows corresponding holes on the PCB marked by the appropriated color. The larger hole (green) accommodates the retention tab, whereas the smaller one (red) accepts the screw post.

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3. Insert both retention tabs of the stabilizer housings into the corresponding large holes on the PCB.

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4. Ease the screw posts into the smaller holes on the PCB. Apply enough pressure so that both stabilizer housings sit flush on the PCB.

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5. Turn the PCB around and screw it securely in place as the name suggests. I recommend using a plastic washer to avoid any chance of the metal screw causing a short circuit on the PCB.

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6. Installing regular PCB mount stabilizers sans screws isn’t much different. The screw post in this stabilizer variant is replaced by a snap-in post. Instead of using screws to anchor the stabilizer, the posts simply snap into the corresponding holes on the PCB.

7. Plate mount stabilizers install directly onto the plate in a similar manner. The short side housing the stabilizer wire is inserted into the corresponding short edge of the socket that is the furthest away from the notches cut out for the locking mechanism along the long sides. With this side hooked onto the plate, you can simply press down on the other end of the stabilizer to snap it into place.

8. Repeat this process for all stabilized keys.

5. Fixing the Plate onto the PCB

It might sound hard to believe, but the toughest part of this guide is already behind us. Like we did with the PCB, the first step involves figuring out the correct orientation of the plate.

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1. Place the plate on the workbench. It may look like a confusing array of sockets, but pointing it in the right direction is easier than it appears. We will tackle the plate for a 40-percent keyboard here. Other keyboard form factors are easier to identify, so you should be alright even if your keyboard isn’t 40 percent.

This is a simple matter of determining the orientation based on the positioning of the stabilized long keys. Because we know where these long keys are located on this 40-percent keyboard (refer to the above image), we can use these to help us orient the plate correctly.

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Look for the edge with the widest hole in the plate. That is where the Spacebar goes. Because we know that the Spacebar is located at the bottom of the keyboard, you can orient the plate such that the cut-out for the space bar is at the bottom. This 40 percent plate has slots for two Spacebars.

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2. We are still not out of the woods yet. We can now focus on the lone socket meant for the Shift key. In this orientation of the plate, the slot for the Shift key (marked in green) is on the right side, which is incorrect. So we flip the plate horizontally. That’s how you orient the plate correctly. The PCB will interface with the bottom of the plate, whereas the switches will slot in from the top.

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3. Since the plate attaches to the PCB by the means of switches, we must first attach a few switches to serve as anchoring guides along the corners of the plate. Attach no more than four to six switches along the plate periphery. Make sure that you only populate the 1u (one unit) plate sockets. The sockets for the Esc, Ctrl, and Right Arrow keys are examples of 1u sockets, whereas the Shift and Spacebar sockets are 2u and 6.25u sockets, respectively. Use the image for reference, but don’t attach the anchoring switches until you have read and understood the next step.

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4. Pay attention to the accompanying images to determine the correct orientation of the switches. The two conductive legs on the switches correspond to the plated through-holes on the PCB. Depending on the PCB design, these may be oriented along the top edge or the bottom edge of the PCB. In some hot-swap PCBs, only a few switches such as Esc will be inverted to accommodate the USB port. Make a note of every switch, or you will end up crushing the pins while inserting switches upside down into the PCB.

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5. Before we mate the PCB with the plate, double-check to verify that the switch pins are straight and not bent at weird angles. This will cause them to miss the corresponding plated through-holes and flatten out on the PCB.

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6. Carefully align the pins on the anchoring switches attached to the plate with the corresponding through-holes on the PCB. The pair of plastic PCB mounting pins on the switches allow the PCB to be anchored into the plate even before the switches are soldered to the PCB. These plastic pins (refer to the above image) friction-lock into the corresponding holes on the PCB and are designed to provide switch alignment and mechanical stability against wobble.

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7. Fill in all remaining switches one by one. The long keys such as Spacebar, Shift, Capslock, and Backspace may have more than one set of plated through-holes to accommodate various layouts. Slotting the switches in correct through-holes completely depends on your specific layout. Be sure to make a note of this little detail.

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Don’t sweat any mistakes at this stage because we will identify and fix any of those that crop up in the next section. But please, for the love of all that is holy, turn the PCB over and check all plated through-holes to verify if the pins are poking out. If some pins are missing, that’s either because switches aren’t supposed to be there or the pins have been bent.

Checking for bent pins now will save you the heartache of discovering them after the board has been soldered. Desoldering an entire keyboard is not a fun endeavor.

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6. Dry-Testing the Stabilizers/Layout and Troubleshooting Common Problems

In a perfect world, the next step would have been soldering the switches onto the PCB. But the world isn’t perfect, and first-time keyboard builders are prone to making mistakes. Let’s take a look at the common errors encountered at this stage.

1. Place the PCB and plate assembly with the switches pointing upwards and facing away from the tabletop. Bring out your keycaps and attach them only to the keys that are stabilized. These snap right on along three mounting points: one is located on the switch and two on the stabilizers. Press firmly on the keycap along these three points until it has snapped on securely. Repeat for all stabilized keys.

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2. Test each one of these keys by actuating them repeatedly until you are sure they work as intended. If there’s any seesawing or otherwise an impediment to the actuation of the switches, remove the keycap of the affected key and place it on a flat surface such as a mirror or a sheet of plate glass. It should lie perfectly flat, with no signs of bowing or any distortion. If any of those structural issues exist, replacing the faulty keycap should ideally solve the problem.

3. If the keycap is fine, the fault may lie with the stabilizer. Remove the plate off the PCB and take off the erring stabilizer. Check if the stabilizer wire has popped out of either channel along the edges of the housings. Popping it back in should make the switch work perfectly.

4. If the wire hasn’t popped off, there’s a chance that you may have inserted the stabilizer posts incorrectly into the housings. This can be verified by holding both stabilizer housings in one hand and using your thumb and index fingers to rotate the stabilizer wire. Both stabilizer posts should move up and down freely inside the housing. If that doesn’t happen, disassemble the entire stabilizer assembly and repeat all steps in section 4 to reassemble and fix the stabilizer onto the PCB.

5. If none of these steps seem to help, it’s fair to assume that your stabilizer has a manufacturing defect. Replacing it altogether is the only solution in that case.

6. Install all remaining keycaps. If all keycaps are in place without any unsightly gaps or clearance issues, pat yourself on the back for getting things right the first time. The rest of you will notice that all clearance issues can be tracked right back to the long keys with optional switch mounting points explained in step 5.6. Now you can choose the correct switch mounting point option and make necessary adjustments to fix the clearance issues.

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7. Soldering Switches to the PCB

Skip this section if you have a hot-swap PCB, because soldering is only applicable to regular PCBs. You can either choose to leave the keycaps on while soldering or remove them. The latter is a good idea if your workspace is dirty or otherwise liable to scratch or stain the keycaps.

Refer to the Keyboard Switch Replacement Guide and follow steps 7 through 16 to learn how to solder and desolder switches. You will primarily use the soldering techniques mentioned in that guide to solder all switches to the PCB. However, the desoldering instructions therein will prove useful in the rare case that you make any mistakes that call for a switch or two to be replaced.

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8. Putting It All in the Case

With the switches soldered and final testing done, installing the PCB/plate assembly into the case is the final step. Unlike regular consumer mechanical keyboards, the case assembly process is ridiculously easy for custom mechanical keyboards.

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That’s primarily because mainstream keyboard manufacturers are largely preoccupied with making products as cheaply as possible, while actively and deliberately making them hard to disassemble. Don’t expect large corporate entities to respect consumers’ rights to self-repair when it is directly at odds with their bottom line.

Having said that, these steps are applicable to all keyboard-case types and plate-mounting styles covered in the previous installment of this guide.

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1. Insert the PCB/plate assembly into the case starting from the top edge of the PCB that houses the USB port. This is important because the port protrudes out of the PCB and must be eased into the corresponding opening in the case before you can align the PCB/plate assembly into it. Top mount cases will require the plate to be screwed onto the top frame before moving onto the next step.

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2. For tray-mount cases, secure the assembly onto the case with screws and call it a day. Bottom-mount cases will call for the plate to be screwed onto the bottom half of the case, followed by the top frame being screwed into place. Top-mount cases similarly need you to screw in the top frame (containing the PCB/plate assembly) onto the bottom half of the case. Gasket mount cases simply require the PCB/plate assembly sandwiched between the top and bottom halves of the case with a screw securing all three sections.

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That is all there is to building your own custom mechanical keyboard. Slap on some keycaps and hook it up to your computer for a superior typing experience. You can customise your keyboard further by changing the layout through the firmware, but that is best reserved for a separate guide. The custom mechanical keyboard rabbit hole goes much deeper than you can imagine at the moment. But for now, you can revel in the satisfaction of building something rare and beautiful with your own hands.

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Nachiket Mhatre Nachiket Mhatre

Growing up, Nachiket had a penchant for disassembling household electronics and appliances; most of which couldn’t be reassembled successfully. His parents didn’t approve. These days, he leverages his lifelong pursuit of dissecting gadgets to write about technology. His parents still don’t approve.

5 comments

  1. Another way to procure a DIY mechanical keyboard kit that I couldn’t include in the article for the sake of brevity is to join a group buy hosted on forums such as geekhack and deskthority. This isn’t an option for the faint hearted and those averse to risk and months of waiting. But it is the only way to acquire one-off exotic custom mechanical keyboard kits.

    As the name suggests, a group buy involves anywhere between 50 to a few hundred people paying the entire value of the keyboard kit upfront to the organiser, who then usually outsources production to a factory in China. This is followed by waiting six months to sometimes even several years until everyone receives their kit, or the Chinese liaison vanishes with the money. Whichever happens first. This is an option best reserved for mechanical keyboard enthusiasts seeking the most exotic of custom keyboards.

    Fortunately, the article includes a few sane retail options for the rest.

  2. I’ve just built my first mechanical keyboard kit, and found your article while trying to figure out how to put the stabilisers together – many thanks, it was very helpful!

    1. I’m glad the article was of help. Which keyboard kit was it, if you don’t mind me asking? Coincidentally, I’ll be building a BM43a this weekend.

      1. It’s this one: https://www.aliexpress.com/item/33006060286.html?spm=a2g0s.9042311.0.0.40694c4d0QkXn4 – it came with the electronics pre-soldered, which was a great relief when I saw the size of the SMDs! It made a good first project for someone whose soldering skills are a bit rusty.

        Enjoy your build!

        1. SMD soldering is fairly easy once you have some sort of magnification. Everything just nicely falls into place once you apply some hot air. That’s a nice kit given the price!

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