What’s the difference between… keyboards?

Q

My old keyboard is unreliable. I went online for a browse about keyboards but was soon confused. I saw models described as ‘mechanical’ (surely all keyboards are mechanical?), ‘scissor switched’ and ‘membrane’. I suppose they all do the job of typing but I wonder if you could explain the differences, pros and cons of these varieties? Imran Ali

A

The main two keyboard technologies are membrane and mechanical. Most others tend to be variations of these.

Membrane keyboards are the simplest. The basic design comprises two plastic sheets sandwiched between a third ‘spacer’ layer.

The front of the rear-most layer contains a screen-printed conductive grid circuit, with a break in the circuit under each key position. The back of the top layer has conductive strips under each key corresponding to these breaks, so the circuit is completed when the key above that part of the membrane is pushed down.

The ‘one-piece’ design of membrane rane ne keyboards makes them cheap to manufacture. However, while specific designs vary, typing on a membrane keyboard can feel ‘spongy’: the typing action itself is obviously mechanical, but the final actuation simply squeezes together the top and bottom layers of the membrane.

That’s not a problem for ‘mechanical’ anic ical’ keyboards, which have a dedicated d sprung micro-switch under each and nd every key (pictured). When you push h down a key on a mechanical keyboard, you’ll hear the micro-switch click to register the press. You’ll also feel a little resistance from the switch’s returning spring. Some people prefer this audible and ‘tactile’ feedback. Faulty switches can typically be replaced, too — a repair that is not possible on membrane keyboards.

You also mentioned scissor-switched keyboards. This describes the returning mechanism under the key. Many membrane keyboards employ domeshaped rubber plungers to actually depress the membrane and return the key. It’s this arrangement that leads to the aforementioned ‘spongy’ feel.

To counter this, some membrane keyboards employ a scissor-shaped returning mechanism that reduces the required key ‘travel’, and prevents the keytop wobbling – even if you accidentally hit it at the corner.