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When we play "Capacitive Touch Keyboards", what are we actually playing?

8 minute read

In the past couple of years, many enthusiasts who got bored with mechanical keyboards have ventured into the world of capacitive touch keyboards. Apart from the pioneer in capacitive switches, Deskeys, who has been tinkering for several years and has basically cooled off to go fishing, domestic brands like Niz have also been customizing capacitive keyboards for a few years now. The capacitive keyboard solutions from Tab have also become increasingly mature, and figures like A-ko and Rainman have been providing capacitive switch internals for various customizations. Overseas, KLC's capacitive keyboard components are also on par. Writing this post at this moment may resonate with more people, so let's fill in this gap.

capacitive touch keyboards

Just as mechanical keyboards have dwindled down to Cherry as the last survivor, the capacitive touch keyboard landscape has largely boiled down to Topre Corporation. The renowned RealForce capacitive keyboard is a product of Topre. Others, such as PFU's HHKB, which pioneered a generation of classic layouts, and domestic mass-production giants like Leopold, are using Topre's original solution to create capacitive keyboards. In fact, apart from Topre, Alps also dabbled in capacitive keyboards in the past, and they even developed their own independent capacitive switches with built-in rubber domes.

Our main focus here, however, is returning to the Topre solution. Before the era of Des, Niz, and Tab keyboards, most capacitive keyboard enthusiasts had to rely on disassembling and scavenging old keyboards to get ahead. Although there have been sporadic products like keycaps from KBDFans, sliders from JTK, domes from BKE, and cases from Clueboard, the overall feedback quality wasn't quite perfect, and the manufacturers themselves couldn't establish a comprehensive ecosystem. A capacitive touch keyboard consists of more than just the keyboard shell, PCB, and keycaps; each key is composed of a slider, housing, rubber dome, and conical spring. So, when we were playing with them, apart from the conical springs, there wasn't much else we could experiment with.


Capacitive Touch Keyboards


Before everyone started thinking outside the box and integrating capacitive switch internals into custom keyboards, the common practice was to cut out a chunk of aluminum and simply fit the mass-produced switch internals inside. Moreover, retrofitting mass-produced keyboards was not always straightforward; for example, many enthusiasts favored the HHKB, but its plate and housing were integrated, making replacements a cumbersome process. A PC case shell used to cost several thousand dollars, enough to get a high-quality and fully functional mechanical keyboard. The cost-effectiveness was extremely low.


Because traditional capacitive keycaps have a different profile, often referred to as "volcano" or "hi-pro," compared to regular mechanical keycaps, early enthusiasts were mostly limited to playing around with keycap customization. For instance, RealForce had previously released some fancy keycap sets. Fortunately, Topre had offered various OEM solutions in the past, so there was still a rich variety of keycaps to experiment with. For example, big companies like Sony customized many keyboards for media use, and their keycaps were quite intricate and stylish.

For enthusiasts who preferred original equipment, a significant number opted to collect high-profile keycaps. These spherical keycaps were a product of Topre's earlier days, featuring a process involving sublimation printing. However, their durability was not on par with Topre's regular-profile keycaps. Nevertheless, due to their rarity and aesthetic appeal, there are still many enthusiasts who appreciate and collect high-profile keycaps.

In fact, there has always been a substantial community of capacitive keyboard enthusiasts abroad, so you can find many artisan keycaps designed for capacitive switches. However, compared to the extensive customization options available for MX systems, Topre's in-house capabilities in this regard have been somewhat limited. This leads to the issue of sliders, which we'll discuss later.


The term "sliders" refers to the plastic components in capacitive key switches that connect the keycap to the switch and are responsible for transmitting the force between the keycap and the rubber dome. They are called sliders because they push or slide down into the rubber dome to actuate the key. The original design of these sliders is what led to the term "volcano."

Now, going back to the keycap issue mentioned earlier, Cooler Master, a Taiwanese PC accessory manufacturer, came up with a clever solution. In 2013, Cooler Master entered the keyboard market and, in 2014, introduced the NOVATOUCH TKL, a capacitive touch keyboard that, for the most part, was considered unremarkable. However, its standout feature was that, as a keyboard using the Topre switch design, it replaced the original volcano-shaped sliders with custom-made cross-axis sliders, now known as "Zilents."

These sliders not only addressed the problem of limited keycap compatibility in the Topre system but also provided an exceptional typing experience. When enthusiasts transplanted these sliders into their original keyboards, they found that the thicker sliders, when combined with the stock housings, resulted in an astonishing level of stability. The keystrokes felt incredibly steady, with minimal lateral movement due to the reduced clearance between the slider and housing. This unique characteristic was not replicated by subsequent cross-axis slider designs from other manufacturers like JTK, leading to a period where enthusiasts preferred Zilents and their prices soared.

From left to right in the image are the original Topre sliders, Zilents sliders, Des sliders, Niz sliders, and Tab sliders. Subsequently, Des, Niz, and Tab all made cross-axis sliders a standard feature in their capacitive switch systems, making it easier for custom enthusiasts to swap keycaps. However, only Des sliders are fully compatible with the original Topre components. Niz and Tab made certain modifications to the Topre design, so their sliders must be used with their respective components.

This extends to the structure of larger keys as well. The original Topre design employed a somewhat unique mechanism for large keys. However, if you pair Zilents with the original housing, the stability is sufficient to eliminate the need for a stabilizer on large keys other than the spacebar. Niz and Tab, for the sake of convenience, opted for steel plate stabilizers, which are more practical.


The housings are a relatively straightforward component, but each manufacturer has its own approach. Since they are all proprietary, they tend to prioritize compatibility with their own sliders. For example, Zilents' housing for larger keys has two additional holes to accommodate keycaps compared to the original Topre housing, but the 1u size is generally similar. The original Topre housings also include a very rare and peculiar variant, which is purple and has smaller holes than the standard housings. I learned a valuable lesson this time: I initially intended to pair the purple housing with Zilents sliders, only to discover that they wouldn't fit.

From left to right in the image are the original Topre housing, the original purple Topre housing, Niz housing, and Tab housing. You can see that the second purple housing lacks any markings or indications, confirming that it is indeed a different mold and quite unconventional.


The rubber dome, known as the "dome sheet," is the part of the Topre system that has the most significant impact on the typing feel. The pressure distribution design used in the original RealForce keyboards is also quite interesting. The keypress sensation in Topre capacitive keyboards primarily revolves around the deformation of the rubber dome, which can make it feel softer and less clicky compared to mechanical switches. Some people may find it a bit mushy in comparison. Many capacitive keyboards also include a silencing ring, further emphasizing the quietness aspect. As a result, some individuals might consider capacitive keyboards as "burnout keyboards." This notion doesn't necessarily mean that capacitive keyboards are superior to mechanical ones; it's more about the fact that after experiencing capacitive keyboards, the elements that mechanical keyboard enthusiasts often chase, such as tactile feel and typing sound, become non-existent, leading to a decrease in interest.

The rubber dome that has garnered the most attention in the capacitive keyboard community is undoubtedly the one custom-made for Sony editing machines, known as the "Sony BKE OG" dome sheet. These domes provide a unique, large tactile bump sensation. Typically, these rubber domes can only be sourced from Sony editing machines. One of the most common models in China is the PVE500, which comes in two versions: one with capacitive switches and the other with Alps switches. Many film and television production companies purchase these machines, and when they go out of business or clear their fixed assets, these domes become available. The domes with a circular light hole in the upper right corner of certain keycaps are for capacitive switches, while those with a square light hole in the upper left corner are for Alps switches, as seen in the image below.

Among these four different colors of rubber domes, there are subtle differences in pressure and feel. The most recommended one is the brown rubber dome because it provides a typing experience that is not as forceful as the other colors, making it less fatiguing during prolonged use. The rarest one is the black dome, which is only found on a few large keys and is quite heavy in terms of actuation force.

Furthermore, it's important to note that these rubber domes need to be modified by trimming the central portion to create a hollow area before they can be used.

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