Once upon a time keyboards were made with mechanical switches. Each key had an individual switch below it that would register a keypress when pushed past a certain threshold. The most famous of these was the buckling spring mechanism used in IBM’s Model 15, a design still beloved by many who keep these aging keyboards alive.
Most mass market keyboards are now made with rubber membranes rather than individual switches. This cheap-to-produce design basically consists of a rubber sheet with domes pointing upwards. Each of these domes corresponds with a key, and the inside is lined with a conductive material.
When you press down on a key this dome gives way and touches a conductive material underneath the rubber sheet. This then registers the keypress electronically and sends it to the keyboard controller, which relays it to the PC.
Laptops use a similar design, but in order to ensure that the keyboard can sit in a small space the domes are smaller. To counteract this most laptop keyboards use a ‘scissor switch’ design, where plastic arms hold the keycaps in place over the domes. This ensures that the keys stay centred over the domes and that keypresses register correctly. The side effect of this low profile design is that the amount of key travel is even lower than that on a dome keyboard.
These rubber dome designs work consistently well but are commonly accused of feeling ‘mushy’. This is a side effect of relatively short key travel and rubber membranes diminishing in springy-ness with age. This complaint is largely brought by gamers, but anyone who spends a decent amount of time typing will know all too well how unsatisfying rubber dome keyboards can be over prolonged periods.
A rubber membrane keyboard uses a series of domes over a grid to register key presses.
Despite the sheer prevalence of membrane based keyboards, the old style mechanical design hasn’t gone anywhere. Products from small companies like Das Keyboard and Cherry have been keeping the design alive, and over the past year more mainstream manufacturers like Razer, Coolermaster and Thermaltake have jumped into the mechanical keyboard market.
Modern mechanical keyboards don’t use the buckling spring mechanism of days gone by, rather they all use switches from German manufacturer Cherry. So important is the role of Cherry’s switches that keyboards are marketed around the type of switch used, which directly correlates to what it feels like to push a key.
To understand modern mechanical keyboards, one first needs to understand these switches and how they are differentiated. Switches are specifically drawn from the Cherry MX range of products, and models are commonly referred to by the colour of the stem.
Each of these models has a slightly different design, which in turn affects the feel of the switch and the noise that it makes. This is down to the way in which these switches register keypresses as well as other factors like the type of spring used in the switch. The anatomy of these switches is surprisingly well documented online for those who want to go further, but at a base level the ‘feel’ of a mechanical switch is down to a few key features.
Most Cherry MX switches use a similar internal design. The Key sits on top of a stem, the colour of which is commonly used to differentiate between models. This stem has a spring at its base and a plastic tab on one side. This tab holds two metal contacts apart when the key is in its normal position. However when you depress the key, the tab moves downward and allows the metal contacts to join, which registers as a keypress.
The complexity of a mechanical keyboard is pretty astonishing, with hundreds of individual parts going into each one.
Unlike a rubber dome keyboard, where the point at which the keypress is registered is at the base of the key’s travel, the Cherry switches allow the keypress to register before the key bottoms out. The point at which this happens is known as the actuation point.
The actuation point is important when looking at one of the major means of differentiating between mechanical switches. G