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Cherry MX

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Overview

Cherry’s MX series is one of very few keyboard switch lines to have remained in production for decades, having been in continual production since their introduction in late 1983. Little else is still around from that age; RAFI’s switches from the 1970s are notable example. MX switches were produced in each of Cherry’s three switch factories: Auerbach in Germany, Waukegan in the United States, and at Hirose’s factory in Japan. US switch production ended in the late 80s, and Hirose discontinued MX in 2014, with MX switches now manufactured solely in Germany.

With such a long lifetime, the MX product range has incorporated a great deal of different features. As patented, the characteristics were:

When advertised in the United States in September 1983 (and again in April 1984), the options were:

The advertisement can be seen under Documentation below. The advertisement also lists “clean IC logic signals”, which MX designer Günter Murmann confirms is incorrect (and is quite simply impossible with a mechanical switch), and a lifetime of 50 million cycles, which he explains was a requirement of the typewriter industry. (Whether the switches were capable of that longevity then, is not clear, as the original rating was 20 million, later increased to 50 million.) Angled stems have yet to be seen, but Günter noted that the MX tooling was flexible, with the keystem being an insert in the plunger mould, to allow for a variety of keycap mounts to be readily accommodated.

Additional options in the product range available either from the start or from early in its lifetime were:

In recent years, the product range has gained a few new options targeted towards the modern market, especially gamers:

See the MX variants page for more details. See also the MX part number schema.

Additional customisations discovered include the following:

Cherry MX also has the dubious honour of being by far and above the most widely copied design on the market, with more Chinese copies now circulating than it is possible to keep track of. The same general design is even used on non-mechanical types, such as some modern photoelectric switches. Some of the clone types have introduced further innovations to the product design, including “box” stems to improve dust resistance, fully-enclosed contacts, click bars to improve the tactile feel and click sound (MX switches tend to develop a rattly click, that this resolves), better tactile force curves, and support for using all four base holes simultaneously for internal RGB LEDs (where Cherry opted to use SMD LEDs, as Matias did). All these improvements have been added to a 1983 design that has stood the test of time. Notably, MX switches are remarkably free of binding: they can be pressed off-angle and never get stuck, something that many rival designs including those from Alps and SMK never achieved reliably with their equivalent products.

History

Günter Murmann—the inventor of the MX switch—explains that the objective for creating Cherry MX was to meet DIN compliance. While they did already have a DIN-compliant switch available, Serie M8, it only provided 2.5 mm of travel, and MX provided a compact design that could nonetheless offer the full 4 mm travel. Hirose Cherry did extend M8 up to the full 4 mm of travel with MJ series, but they also adopted MX.

The original MX design was of a linear switch. German typewriter manufacturer Olympia made a request for a click feedback switch, which led to the click mechanism in Cherry MX. However, they did not adopt MX switches. Because this click feedback was not desirable to Cherry’s intended market for MX, Cherry instead touted the hysteresis created by the click mechanism as a feature, with the click sound suppressed with grease. The resulting model was marketed as a tactile design, not a clicky design. This was followed a few years later by a pure tactile design, with no click sound and no hysteresis (“MX Clear”).

To meet reliability requirements, the movable contact leaf was designed to be bifurcated, with each side having its own contact prism, for a total of two pairs of prisms per pole. This design can be seen in the patent, although the patent illustrations shown the contact leaf tines to be tied and fitted with a single central prism. However, the use of redundant contacts proved to be unnecessary.

The defined characteristics of MX from its patent (filed in 1982) are tactile feedback, hysteresis, and double-pole operation; the dual contact arrangement is mentioned in Cherry advertisements, but only partially depicted in the patent without any explanation.

It seems that MX was introduced over a year after the patent was filed. The following occurrences have been discovered to date (not counting more recent switch models):

Date Occurrence Reference
1982-08-06 Date of patent application by Cherry Mikroschalter for MX White German patent 3229465
1982-11-05 Date of early (if not the original) MX part number schema (Nummern-System Tastenmodul) covering MX Black, Linear Grey, Lock, White and Click Grey (last revised 1983-09-07) Cherry drawing TS 00006
1983-01-25 Date of single-unit 8 mm keycap drawing (last revised 1987-10-21) Cherry drawing 1P■11-NNNG3
1983-07-12 Filing date of US patent for MX White by Cherry Electrical Products in the US US patent 4467160
1983-10 Introduction of Cherry MX in Japan; according to the former Hirose Electric website, “Started sales of MX series, the Low Profile Key Switch.” hirose-st.co.jp (Wayback Machine)
1983-11-07 Date that Cherry MX was introduced, according to a suspicious image from an unspecified brochure Deskthority topic
1985-07-28 Handwritten date on a German datasheet listing MX Black, Linear Grey, White and Click Grey, but curiously not MX Lock Cherry MX datasheet
1987-04-24 Application date for MX Clear patent from Cherry Mikroschalter German patent 3713775
1988-03-31 Date of a revised MX part number schema which added MX Clear, Tactile Grey, Blue and Green (last revised 1988-08-10) Cherry drawing TS 00006-2
2009 Hirose Cherry MX no longer advertised for sale Correspondence with Hirose
2014 Hirose Cherry MX discontinued Correspondence with Hirose

Details of individual switches can be found under MX variants. See timeline page for entries covering all series.

Production lines

Cherry had at least three separate production lines for MX. There is uncertainty about whether the first one was in Germany or Japan. What we do know, from Günter Murmann, is that the US production line for MX was opened following a highly successful introduction of MX. Some tooling was sent to the US factory, although the US design seemed to be a combination of both German and Japanese parts. The US-made types can be found in the rarely encountered KXN3 (enclosed) and BXN3 (unenclosed) lines of US-made MX keyboards, such as KXN3-8451.

The movable switch contacts take two shapes, termed “A” and “M” for convenience: see under contacts for details. German MX switches are “M” style. Hirose-made MX switches are “A” style, as are US-made MX switches.

German-made switches used gold-plated wire contacts. These are the same as contact style 4 from M8 and M9 switches. This was a cost reduction over the solid prisms used in older switches, and M8 and M9 were both updated to offer this contact type. MX later switched back to solid prisms; according to Cherry, this was in either 2006 or 2007, a point in time that seems somewhat unlikely, as that would make the “MX-M8 adapter” switches far more recent than expected. Hirose used their own trapezoidal solid prism design in their M8 and MX switches.

US-made switches have the “A”-style movable contacts associated with Japanese-made switches, combined with the gold-plated wire contacts of the German-made switches. The movable contact metal has a mottled appearance, suggesting some kind of heat treatment. American MX production would have ended a few years later when Cherry’s US manufacturing closed down in the late 80s.

Each factory had its own marking scheme. German-made MX switches were colour coded, hence the colloquial names of “MX Black”, “MX Blue” etc. Hirose used coloured plungers as with Germany, but their pigments were very diluted, and their colour scheme remains unknown. US practice is also not entirely clear, as so few examples are known. Originally, the US factory marked space bar switches with red paint, just as they did M5 switches, with seemingly all switches having black plungers (which may explain the all-black MX Lock type). However, an unidentified KB-5000 keyboard made in the US with American MX switches has been found with a grey space bar switch; sadly the manufacture date is not known. It may be that the US factory did adopt the German colour scheme at some point. The “linear clear” switches found by cherry-jade and sold on Taobao appear to be US-made too.

The table below summarises the production lines:

Factory Movable contact Crosspoint contacts
Cherry Electrical Products (US) “A” style Gold-plated wire
Cherry Mikroschalter (Germany) “M” style Gold-plated originally; now solid alloy prism
Hirose Cherry Precision (Japan) “A” style Hirose

There is presently no evidence to suggest that Cherry made keyboard switches in the UK. Whether some of the rare types such as those with Alps mount came from Hirose or from another production line, remains unknown, as the origin of those types remains unconfirmed. Allegedly, Deskthority co-founder sixty observed one type in official Cherry packaging, but the photograph is since lost.

Design

The idea that the return spring descends into the central post, as seen in Lethal Squirrel’s animations, is a myth. The return spring is exactly the same width as the central post; the post only provides additional movement capacity for the slider.

Keycap mount

Cherry MX introduced the 8 mm mount. This is a keycap mount almost identical in cross-section dimensions to the 6 mm mount from M8 and M9, but the keystem is significantly taller:

The following illustration uses dimensions taken from official Cherry drawings. The keystem height is given in the Cherry MX brochure (see Cherry catalogues). The keycap dimensions are taken from the Cherry MX developer page (Cherry previously supplied the official single-unit keycap drawing from 1983, but this new diagram on their website is clearer with regards the mount than the 1983 drawing). The stem dimensions are given in a drawing of the plunger posted within the Keychatter article Unpacking The Kailh Box Switch Debacle.

Now that the dimensions are known, it is possible to see that there is an 0.07 mm overlap on two of the four sides of the keystem where the keycap shaft is pushed outwards by the keystem. This is responsible for the grip. This is illustrated in the diagram below.

Switch contacts

There are two designs of movable contact, which UncleFan termed “A” and “M” based on the overall shape:

“M” style is the standard movable contact shape, and is found in most if not all German-made MX switches.

It always seemed that the “A” design was the original design, replaced soon afterwards by the “M” design. However, all Hirose-made switches examined to date (including all photos so far showing the insides of Hirose MX Orange) seem to be “A” style, including the NOS MX1A-0NNN parts stocked by Yamaha in Germany.

“A” style is currently associated with Hirose and tentatively with Cherry US. It is possible that Cherry Germany originally used this style. This is the style copied by Yali/Aristotle with Taiwan white and black shaft, and is found in the Teton Cherry MX clone.

Neither style is a match for the original patent, which depicts a distinctly different shape of movable contact.

Crosspoints

As noted earlier, the gold crosspoints differ in design depending on production line and age. The following diagram summarises the three types of contact crosspoints. The exact cross section of Hirose contacts varies from nearly trapezoidal to nearly semi-cylindrical, and possibly the movable contact prism is more trapezoid (they are not the same construction).

Cherry provided the following photos of MX wire and prism contacts in 2017 and 2016 respectively:

Cherry MX wire contacts
Cherry MX wire contacts
Cherry MX prism contacts
Cherry MX prism contacts

The images above are copyright cherrymx.de, used here with permission.

Shell

Cherry MX as patented was a non-illuminated design capable of double pole arrangement. The design that entered production changed to single-pole only, with a front-centre LED recess taking the place of the second pair of switch contacts. Two holes in the base of the switch accommodate the LED terminals. A second pair of holes in the bottom—placed either side of those for the LED—allowed the switch to contain a jumper (wire bridge) or a diode. Factory-fitted diodes, LEDs and jumpers were standard options. Only one of these options can be fitted to a single switch.

The shell came in two subtly different versions, depending on whether an LED was fitted in the factory. The MX1A-11GW page illustrates the differences between the two designs.

The rise in popularity of mechanical keyboards amongst gamers led to a need to support RGB LEDs, which have four terminals instead of two. Initially the clone market addressed this demand by retooling the shell to hold a larger LED, using all four holes at the front for the LED terminals. Cherry adopted a totally different approach, with a new shell that leaves space for an SMD LED. Above the LED is a lens formed as part of the transparent upper shell, which helps to spread the LED light out within the keycap to improve legend illumination.

Documentation

See also