When it comes to keycap types there are quite a lot of things that distinguish them. Profile, material and top form are just a few of them. In this article I will go over the more standard keycap types and show you where the differences are and how you can categorize more novel keycap types.
Keycap size is measured in units – a standard alpha-numeric key has a width and height of one unit. Other keys are multiples of this, for example the TAB key is 1.5 units, CAPSLOCK 1.75 units and SHIFT is 2 units wide. The width of the specific keycaps can vary depending on your exact type of keyboard and layout. Sometimes you can use two of one unit keycaps instead of a single one unit keycap, this depends on your PCB.
The ISO Enter Key for example is two units high, same as the Enter key on the numpad.
There are three basic touch area styles:
This is pretty self explanatory – the top (touch area) of the keycap is completely flat – most notebook keyboards have this top form.
The spherical style was the norm for a long time but since it is more complicated to print the legends on those types of caps the cylindrical touch area gained more popularity.
The term profile refers to how the keycaps looks when viewing them from the side, there are two different types:
- non sculptured
To understand the keycap profiles it is also important to understand how the rows on a keyboard are numbered:
As you can see, the function key row is sometimes numbered 1 or 5 – it depends on the profile. Some Profiles have different sizes for the function keys and some use the same keys that are also used in the first row. The “Z” row and the row with the space bar are often both row four. If all keycaps have the same height they are considered row 3. If not stated otherwise, the numbering basically indicates the height of the key for this row.
Sculptured keycaps have a curved profile when viewing them from the side. The profiles are also distinguished by height: low, medium and high. Sometimes you can find row numbers on the bottom of the sculptured keycaps.
The DSC profile is a medium high profile with cylindrical tops.
The SA profile is a high profile with spherical tops.
The DSS profile is a medium high profile with spherical tops.
Non sculptured keycaps are flat among all rows – the keycaps all have the same height.
The LP profile is, a low profile with a cylindrical top. This profile is specific to ML switches. This style also has a smaller brother – the LP 13 – everything is the same, the keycaps are just smaller in width and length. The tilt is always the same – 1° to the back. So when your keyboard itself has an angle of 1°, the keys are all perfectly flat in relation to the surface.
The KT profile is a high profile with a cylindrical top. The keys on all rows have exactly the same shape, only the space-bar is slightly rounded. The tilt is always the same – 8° to the back. So when your keyboard itself has an angle of 8°, the keys are all perfectly flat in relation to the surface.
The DSA profile is a medium high profile with cylindrical tops and no angle. The keys on all rows have exaclty the same shape, except for the space bar – which is again, slightly rounded.
The G20 profile is a medium high profile with flat tops and a 3° angle. The keys on all rows have exaclty the same shape, except for the space bar – which is again, slightly rounded.
When discussing keycaps it is important to also discuss mount styles – not all keycaps fit on every switch. There are two ways of mounting:
The mount protrudes from the keycap, meaning it is taller than the keycap.
The mount is shorter than the keycap.
Additionally to this information there is also often a length specified, indicating how much the mount protrudes or recesses from the keycap.
There is a couple of different materials with varying costs that are used in keycap manufacturing:
- ABS –Acrylnitril-Butadien-Styrol-Copolymere: very smooth and shiny, relatively soft especially in comparison to PBT
- PBT – Polybutylenterephthalat: often has a bit of a texture to it, more durable than ABS. Many people like PBT because of how it feels thanks to the texture
- PC – Polycarbonate: often used for the transparent part of a double shot keycap
Most (if not all) mass produced keycaps are manufactured by injection molding. There are two different ways: single and double shot.
Double shot means that the keycap is composed from two different materials with different colors – one shot for the keycap base and one shot for the legend. This is the most durable variant for the legends – they will never come off. Usually first the part with the legend and the mount is shot, which is then inserted into the next form where the cover is shot:
The limitation is, that those keys can only have two colors – one per shot.
When single shot manufacturing is used there are different ways the legend can be applied:
Dye Sublimation printing
Dye sublimation printing is transferring a design from a foil onto the key using heat. This is very similar to how the T-Shirt transfer foils work. The template is applied to the keys, heat is added and the design is transferred to the keys. The big upside of this is, that you can use as many colors as you want. The downside is that the keys will fade over time.
Pad printing is a very common method to get prints on oddly shaped items. This method is also used to print on pens for example. A stencil is filled with ink, a silicone pad comes down, picks up the ink and is then stamped on the keycap. This process also allows multiple colors to be applied layer by layer.
Here the keycap is painted after the injection process. After that a laser is used to etch away the color and thus produce the legend. Since you are touching the paint every time you press the keycap the paint is not so durable. WIth this method also only two colors are possible. The color of the base material and the color used to paint it. This method is the cheapest of them all – so if you see a cheap keycap set, chances are, that it is laser etched.
But this process also has a big upside – if you use keycaps that have a shine through legend, it will be much more vibrant and bright using this method than for example a double-shot keycap with transparent base material.
Laser dye sublimation
Here a pigment – the dye – is applied to the top of the keycap. A laser is then used to melt the dye onto the keycap.
Artisan keycaps are often cast using a silicone form and resin, but there are different other ways for those (mostly one off) keycaps.