Keyboard Rabbit Hole Guide - Hardware Edition

Introduction

A while ago, I was swayed by Amazon’s recommendations and picked up a Nuphy Air60, subsequently spending practically the entire weekend browsing mechanical keyboards. Even though keyboards are everyday peripherals, delving deeper revealed that this hobby is a deep rabbit hole, with plenty of enthusiasts treating keyboards as genuine collector’s items.

How Keyboards Work

A mechanical keyboard can generally be broken down into several parts: the case, keycaps, switches, PCB, and layout. However, the most core component is the PCB, which determines whether the entire keyboard works properly and provides input functionality.

In essence, a keyboard is just a matrix of numerous switches. When a key is pressed, the microcontroller detects which key was activated and transmits the corresponding signal to the computer. I will dive into the details of this in tomorrow’s firmware post.

Actuation Methods

Earlier, I mentioned that a keyboard is just numerous switches—that’s only half true. Keyboards can be categorized mainly by how their electrical circuits close (actuation method):

Membrane Keyboards

Between the circuit board and the keycaps, there is a three-layer membrane. The middle layer acts as an insulator, while the top and bottom layers correspond to key positions. The top membrane layer is conductive; when a key is pressed down, it makes contact with the bottom layer, completing the circuit. Most cheap, common keyboards are membrane keyboards.

(Image credit: Wikipedia)

Mechanical Keyboards

Mechanical keyboards actuate primarily through the mechanical structure of switch mechanisms, where each switch is independent. When a key is pressed, the switch stem pushes metal contact leaves together to complete the circuit. Depending on the design, different keystroke sensations can be achieved.

Switches

The most common types are Brown, Red, Blue, and Black switches. However, looking deeper reveals far more varieties than just these four. Broadly speaking, they fall into two main categories: linear switches and tactile switches.

Case

Keyboard cases can be divided mainly into plastic and metal. While there isn’t much difference functionally, the case significantly affects typing feel and aesthetics.

Most mass-produced keyboards on the market use plastic, though some brands like Keychron also offer aluminum cases. Plastic keyboards are lighter, but their finish and tactile feel pale in comparison to metal, which is why most custom keyboard enthusiasts prefer metal cases.

Keycaps

Keycaps can be distinguished by material, profile (shape), and printing/coloring methods.

Materials

The most common keycap materials are ABS and PBT.

ABS keycaps generally have lower production costs and lower hardness; over prolonged use, they tend to develop a shiny, greasy sheen. PBT has higher production costs, tends to be more brittle compared to ABS, and features a slightly textured, matte surface.

However, even if a keycap set is labeled PBT, it isn’t necessarily made of 100% PBT.

For example, GMK, renowned for their ABS keycaps, produces almost exclusively in ABS. Yet, their quality is exceptionally high, making them a top choice for keyboard enthusiasts.

Coloring Techniques

The main techniques include laser engraving, pad printing, dye-sublimation (dye-sub), and double-shot injection molding. Each method has its pros and cons, but higher-end keycaps typically use dye-sublimation or double-shot molding because pad printing and laser engraving are prone to fading or wearing off over time.

Dye-sublimation is a printing process where ink is heated to dye the keycap, penetrating directly into the plastic’s microscopic pores. Consequently, legends practically never wear off, appearing as if they are embedded into the keycap itself.

Because dye-sub requires heating the ink, it is usually applied to heat-resistant PBT keycaps. Double-shot molding, on the other hand, is more commonly used on ABS keycaps.

Double-shot molding involves molding the legend with one resin first, then molding the rest of the keycap with another color around it. Since the legend is physically part of the keycap, it never fades and allows for vibrant, sharp color combinations. While every legend requires its own tooling/mold, high-volume production can help bring costs down.

Profile

Keycaps can be categorized by profile (shape), mainly: Cherry, MDA, OEM, and XDA. The most common profile is Cherry profile.

To newcomers, they might all look similar at first glance, but each profile has its own characteristics, with varying heights and sculpts row by row.

PCB

The circuitry aspects of the PCB will be discussed in tomorrow’s firmware post. However, in the pursuit of typing feel, custom keyboard enthusiasts have developed exacting standards even for the PCB. The most common considerations are PCB thickness and whether it has flex cuts (slots).

Cutouts on PCBs usually serve several purposes in electronics; commonly, they separate high and low voltage sides around a transformer to prevent short circuits.

On keyboard PCBs, flex cuts are introduced to add elasticity and softness. Cutting slots into the PCB makes the typing feel noticeably softer.

Furthermore, modern mechanical keyboard PCBs frequently feature hot-swappable functionality. Instead of soldering switches directly onto the board, hot-swap sockets are pre-soldered, allowing you to easily swap switches simply by pulling them out.

Mounting Styles

The most common mounting styles currently are tray mount and the wildly popular gasket mount. Tray mount is a classic mounting style where the PCB is screwed directly into the case—standard for most mass-produced mechanical keyboards.

Another style is Gasket mount. Instead of being screwed down from below, the plate holding the PCB is sandwiched between the top and bottom cases. Gaskets (cushion strips) line the edges of the plate, providing a softer, more cushioned and flexible typing experience.

Layout

Based on key count, layouts are mainly classified into 30%, 40%, 60%, 65%, 70%, 80%, and 100%. Based on key arrangement, they are divided into ANSI, ISO, and JIS. JIS is the Japanese layout, while users in Taiwan mostly use ANSI.

Some PCBs are designed with high versatility, supporting both ANSI and JIS, as well as split spacebars, split backspace, and more. For instance, I’ve gotten used to split backspace, placing Backspace directly above Enter.

Epilogue

The custom keyboard hobby really is a deep rabbit hole; many enthusiasts amass countless boards on their quest for the “endgame” keyboard. Because of this high turnover, if you’re patient enough, you can often pick up barely-used boards on the second-hand market for great prices.

The custom keyboard market is also quite saturated. Anyone can produce a PCB nowadays, so custom keyboards today often compete on industrial design, craftsmanship, finishes/colors, and extensive customization options. If you’ve looked into the hobby, you’ll also notice a massive number of custom boards coming out of China.

Due to the bespoke nature of “custom” keyboards, mass production is difficult. Most rely on group buys (GB), and waiting for factory production schedules often means waiting three to four months.

Still, if you’re interested in keyboards, it’s worth searching for a custom board that fits your needs. Personally, I feel the quality and aesthetics are truly unmatched by mass-produced boards. At least it’s much cheaper than buying cars.