Keyboard is the first and most primal type of input between human and a computer. The first keyboard (or telewriter as we called in olden days) was introduced as far as 1714. The telewriter was completely mechanical parts. Four centuries later, the modern keyboards haven’t changed much in appearance compare to their predecessor. However, inside each keyboard is an amazing feat of technologies. For the first part of our series “Everything you need to know about keyboards”, we’ll talk about one of the most fundamental & exciting part of a keyboard: Switches.
Keyboard switches are first & foremorest build blocks of each keyboard: switches register a click from human, transform that physical register into electrical signal and send that signal to machine. There are several type of switches, from membrane to scissor, to the most advanced switches such as optical switches & laser projection (theoretically, laser projection keyboard does not use switches). Each type of switches serve different purposes. One type of switch may be excellent for programming keyboard, but may not survive in the harsh condition of angry clicking on your TV remote.
A typical mechanical switch is made from 4 components: Stem, Spring, Housing, Metal Leaves (aka Contact Point). The switch housing is usually seperated into 2 parts: upper housing & the base housing. The keycap of a switch sits on the stem. All moving parts of a mechanical switch is placed nicely into the switch housing.
When a key is pressed, the stem is pressed down until the 2 metal leaves make contact. The distance in which the stem travel from its original position until 2 metal leaves make contact is called actuation point. The stem can travel further pass the actuation point until it reaches the bottom of the housing, this is called bottom out distance. When the user releases the key, the stem travels back up by the decompression force from the spring. When the stem travels to a distance that the 2 metal leaves stop making contact, this point is called reset point (or pre-travel distance). The minimal force to press down the key is call actuation force.
- Actuation point (measures in milimeter): is the point where the switch registers your keypress.
- Reset point or Pre-travel distance (measures in milimeter): is the point where the switch stops registering your keypress.
- Actuation force (measures in gram): is the force required to push down the stem.
- Bottom out distance or overtravel distance (measures in milimeter): is the maximum distance a stem can travel.
- Durability (measures in milion keystrokes): is the number keystrokes that the switch can sustain in a controlled environment (aka the lab).
People often talk about the keyfeel, such as clicky or linear. Keyfeel is produced by several components inside each switch, and to understand about this topic, we’re gonna need a dedicated article (which will come soon). Keyfeel of a mechanical switch can be usually categorized into colors by combination of keyfeels:
- Tactile switch: a tactile switch will provides a change of force during a keypress, a decrease in actuation force. This tactility (or drop in force) will provide an user a point where the switch is actuated. Most notable tactile switches are Blue & Brown.
- Linear switch: a linear switch is the opposite of tactile switch. A tactile switch will produces a constant force from spring, so that to actuate a keystoke, an user will have to constantly provide more force as the stem travels down. Most notable linear switch is Red.
- Clicky switch: a clicky switch will generate a type of “clicky” sound by the use of different components inside the housing. This clicky sound will, by design, notify the user that the stroke is registered. Most notable clicky switch is Blue.
- Non-clicky switch: a non-clicky switch is, by all means, the opposite of clicky switch, that it will not generate a clicky sound. The most notable non-clicky switches are Red & Brown.
Compare to other type of switches, mechanical switches can provide a wide range of keyfeels, faster time between keystrokes, more accurate keystroke and much higher durability. On the other hand, most mechanical keyboards are much more expensive than other type of keyboards.
Mechanical switches and mechanical keyboards had formed a large & wide communities, ranging from newbies to experts in the topics. Most of long time participants of mechanical keyboard communities have their visions fixed into the perfect setup of their keyboards, or so call the endgame.
There 2 types of membrane switches: flat-panel membrane keyboard & full-travel membrane keyboard.
Memorable mention: Flat-panel membrane keyboard
It’ll be rather hard to find flat-panel membrane keyboard in the market, and I dare to say you won’t be able to find one computer keyboard built with flat-panel membrane keyboard. Flat-panel membrane keyboard exists in mostly home appliances, such as your TV remote, the buttons panel on your washing machine, etc.
A flat panel membrane keyboard devices consists of 3 layers:
- Top layer is the button layer. Top layer are often made from silicon, with shaping into buttons on the top, and conductive materials (such as conductive ink) on the bottom.
- Spacer layer is spacer layer. The spacer layer usually contains gas / air to seperate the top & bottom layer. The spacer layer is intended to force the top layer to return to its original form (or the form when the button is not exerting any force).
- Bottom layer is the circuit board. The bottom layer is where a keypress is registered to generate electrical signal.
When a button is pressed with enough force, the top layer will touch with the bottom layer. The conductive material on the button (of the top layer) will make contact with the conductive materials on the circuit board, and when that happen, a electrical signal will be registered.
Full-travel membrane keyboard
Full-travel membrane keyboard or usually known as membrane keyboard.
While the full-travel membrane keyboard share some similarities with the flat-panel membrane keyboard, but they’re essentially different in term of construction. A full-travel membrane keyboard consists of 3 layers:
- Top layer is the button layer. Buttons are made from plastic, usually ABS. Each individual button is seperated, and is placed on the middle layer.
- Middle layer is made from silicon. With the top of the middle layer is shaped into dome or with a form of spring. The bottom of the middle layer is printed with conductive material (again, conductive ink).
- Bottom layer is the circuit board.
When the button on the top layer is pressed, the button will push agains the middle layer, and then, the conductive material on the bottom of the middle layer will make contact with the circuit board and generate an electrical signal.
Membrane keyboard is usually cheap and lasts much shorter than its counter-part mechanical keyboard. Price aside, membrane keyboard has an distinct advantage agains the mechanical keyboard: silence. The middle layer will act as a cushion to dampen all the noise, but also because of the cushion on middle layer, a membrane keyboard will provide less tactile feeling to its user.
Both price & the silent nature of a membrane keyboard make membrane keyboard the perfect choise for wide-spread office usage. But the advantages of membrane keyboard are fading.
A dome-switch keyboard is somewhere between flat-panel membrane and mechanical keyboard. A silicone layer is put on on top of the circuit board. On the silicone layer, each keycap is set on top of a dome, hence the name dome-switch keyboard. Each dome is formed by using metal or polyurethane. The metal dome switches are formed on pieces of stainless steel that, when compressed, give a crisp, positive tactile feedback. Such metal domes are common & easy to find, and usually are rated at least 5 million strokes.
On the other hand, polydomes (domes built with polyurethane) provide a much more linear & soft, in somewhat mushy feedback, compare to the metal domes. Polydomes are usually cheaper than metal domes, and are rated at much lower number of strokes, usually 1 million to 2 million strokes.
You’re not likely to find dome-switch computer keyboards on the market. Dome-switch keyboards are usually found in technology gadgets, such as home appliances or car dashboard.
Scissor-switch keyboard derives from dome-switch keyboard. Scissor-switch keyboard is based on the same principles by using a dome to connect 2 circuit boards. The keycaps are held to the keyboard by two plastic pieces that interlock in a “scissor”-like fashion. Under the keycaps are the domes with the same principles as dome-switch keyboard.
Scissor-switch keyboards typically have shorter travel, usually 1-2mm, and much more expensive and harder to repair compare to other type of keyboards. The shorter travel makes scissor-switch keyboard the perfect choice for portable & slim laptops.
In this article, we talked about 5 most common type of keyboards by switches. There are several type of keyboards out there, such as: Capacitive keyboard, Buckling-spring keyboard, Hall-effect keyboard, etc. The problem is you’re not likely to find those kind of keyboards on the market, except the 5 types that we introduced above.
Mechanical keyboards are on the rise in every possible niches, from programming to office worker. Long gone the day a mechanical keyboard could cost you a fortune. Nowadays, you can find a mechanical keyboard for as low as $30. In all of our comparisons, mechanical keyboards have all the reasons to purchase.