Before entering the world of building custom mechanical keyboards, it is important to note the differences between them and what is commonly available on the market.  Keyboards all use what is called a switch in order to make the board function.  In essence, the switch completes a circuit, therefore sending an electrical signal to register a keystroke.  Each key on a keyboard has its own distinct switch soldered to a part of the printed circuit board – or PCB.  The PCB maps the location of each switch and sends a corresponding signal to the computer when that specific switch is actuated.

Not all switches are the same, however.  Cheaper keyboards such as office keyboards or Bluetooth keyboards will use a different type of switch than a mechanical one.  The two most common types of switches are what’s called rubber dome switches or membrane switches, and both types function very similarly.  Essentially, these switches utilize two rubber surfaces with inward facing metal contact points that, when a key is depressed, complete a circuit – (or ‘actuate’ the switch).  These switches are common as they are the most cost effective method for manufacturing switches.  Consequently, many sacrifices are observable in terms of quality.  For starters, membrane and rubber dome switches have a much shorter lifespan than their mechanical counterparts, only lasting about 5 million keystrokes per switch.  This sounds like a relatively large amount, but in actuality this is only an operating life of about 2-3 years for the average typist.  Additionally, due to the rubber materials used in production, these types of switches often have a mushy, dampened feel, and provide little to no tactile feedback when typing.  They also make modifying the acoustics of a keyboard very difficult and therefore produce a keyboard that sounds just as mushy as it feels.  The last major drawback is that these switches have little to no travel distance, meaning that it is very easy to accidentally actuate switches by missing a key, or pressing in between two keys.  No one is perfect, so having a keyboard that increases typing errors is clearly less than desirable.

Enter mechanical switches.  Mechanical switches are manufactured out of durable plastics such as ABS, PBT, POM, or nylon, and have four main components: a bottom housing, top housing, spring, and a stem.  Instead of utilizing two metal contacts positioned opposite each other, mechanical switches use what is called a ‘leaf’, which is a U-shaped piece of conductive foil located on the wall of the bottom housing.  It actuates the switch when the ends of the “U” are compressed together.  The part that actually performs this action within the mechanical switch is the stem, which has outward facing legs that compress the leaf as it slides downward along rails on the other walls of the bottom housing.  The stem is able to return to the top of the switch due to the spring that is located between it and the bottom housing.  The top housing is the least instrumental part in the actual mechanics of the switch, only serving to sandwich everything together.

The benefit to using this type of switch is that the switch can be actuated before the stem reaches the very bottom, and the spring is fully compressed – (this is called “bottoming out”).  This is different than rubber dome or membrane, which must be fully depressed for the metal contacts to meet, and the result is a more fluid and less stiff typing feel.  These switches are also extremely versatile and customizable, and modifying the shape of the leaf, the type of plastic, the force of the spring, etc. can have great impact on the properties of the keyboard.  One such property is tactility, which deserves a little more of an explanation.  Tactility is when there is a bump at some point in the key’s travel that takes more force to overcome than depressing the key during any other part of its travel.  Many typists enjoy tactile switches because each individual keystroke provides a tactile response when typing.  Additional aspects such as sound, smoothness, and weight can all be modified as well to meet the individual needs of a typist, which is why enthusiasts much prefer mechanical boards over anything else.