Plate Materials and Sizes
What the plate does, how each material changes the sound and the flex, and what thickness, flex cuts and half plates actually alter.
The plate is a sheet of material with a hole for every switch, sitting between the switches and the circuit board. It is the least visible part of a keyboard and one of the two or three that most changes how the board feels, which is an unfortunate combination: you choose it from a dropdown, months before you can type on it.
What the plate is for
Two jobs, one obvious and one not.
The obvious one is alignment. Switches clip into the plate’s cutouts, which holds every switch square and at the same height. Without one, each switch is held only by its solder joints or its hot-swap socket, and switches sit at slightly different angles.
The less obvious one is taking the force out of your typing. When you bottom out a key, that force has to go somewhere. With a plate, most of it is spread into the plate and then into the case. Without one, it goes straight into the circuit board, which flexes. That is why plateless builds are described as bouncy: the board really is bending under your fingers.
Neither job is the reason people argue about plates. They argue because the plate is a large flat sheet rigidly attached to the case, and a large flat sheet is a very effective way to turn a keypress into a sound.
Materials
The plate’s material sets two things at once, and they move together: how stiff the typing surface is, and what pitch the bottom-out has.
The rule is density. A dense, stiff plate barely flexes and rings at a higher pitch. A less dense plate flexes more, absorbs more, and sounds lower and duller.
| Material | Stiffness | Pitch | In practice |
|---|---|---|---|
| Brass | Very stiff | High | Heavy, bright and loud. The most distinctive and the most divisive. Adds real weight to the board. |
| Stainless steel | Very stiff | High | Similar to brass and cheaper, slightly less resonant. |
| Aluminum | Medium | Medium high | The default. A little flex, a clear bottom-out, nothing extreme. |
| Copper | Very stiff | High | Brass-like, heavier again, and it will patina. |
| FR4 | Soft | Low | Fiberglass composite, the same material as circuit boards. Flexes noticeably, muted sound. |
| Carbon fiber | Soft | Low | Similar to FR4, lighter, more expensive, does not ring at all. |
| Polycarbonate | Soft | Low | The softest common choice. Deep and muted, with obvious flex. |
| POM | Soft | Low | Slippery and dense-feeling but acoustically dead. Uncommon and well liked. |
| Acrylic | Soft | Low | Cheap and brittle, which is why acrylic plates are made thick. |
If you do not know what you want, aluminum is the sensible default, and it is the default for a reason rather than by accident. If you know you want a soft, deep board, polycarbonate or FR4. If you want the board to be sharp and audible and you have heard one, brass.
One thing to understand is that the plate does not act alone. A brass plate in a gasket-mounted case with foam under the board will sound nothing like a brass plate in a rigid tray-mount case. The mounting style decides how much of the plate’s character reaches you at all, and a soft mount can largely cancel a stiff plate.
Thickness
Almost every plate is 1.5 mm, and POM and acrylic tend to be 1.6 mm. That is not a coincidence: MX switches are designed to clip into a plate of roughly that thickness, and the clips on the side of the switch housing are what holds them.
Two exceptions matter.
Thicker plates, around 5 mm, appear in acrylic because a thin acrylic sheet snaps, and in premium builds for acoustic reasons. At that thickness the switch no longer clips to the plate; instead the plate surrounds the lower part of the switch housing. That changes the sound a lot, because the sheet can no longer flex or ring as a membrane, so the reverberation thin plates produce mostly disappears and the bottom-out becomes uniform and dry.
Thinner plates exist but are rare, since the clips stop engaging properly and switches can work loose.
If you are choosing between two plate options and one is thicker, expect it to sound tighter and less lively, not just louder or quieter.
Flex cuts
A flex cut is a slot machined into the plate somewhere other than a switch hole, usually in long runs between the rows.
Removing material makes the sheet bend more easily, which is the whole point: the typing surface gives slightly instead of stopping dead. People who like flex cuts describe the result as softer and more consistent across the board, because a solid plate is much stiffer near its mounting points than in the middle, and cuts even that out.
The side effects are worth knowing. A cut plate is a lighter, looser membrane, so it tends to produce more reverberation rather than less, and a board with aggressive flex cuts and no foam can sound hollow. Flex cuts also only do what the rest of the build allows: cuts in a plate bolted rigidly to a case at twelve points will not flex much regardless.
A related idea is the acoustic cut, a slot placed around the long keys such as enter, shift and the spacebar. Those keys sit on stabilizers and bottom out differently from the alphas, and isolating them slightly evens out the difference.
Half plates
A half plate keeps the cutouts for the modifiers and the top rows and removes the section under the letters entirely, so the alphas are held only by the circuit board.
The effect is not subtle. The letters, which are the keys you actually hit, now sit on a flexing PCB with no plate reinforcement, so they feel softer and noticeably quieter, because there is no plate for them to send a sound into. The modifiers around the edge stay firm. Some people love the contrast and some find the inconsistency between the alphas and the modifiers distracting.
Half plates are most common in top-mount and sandwich-mount cases, where the plate has to exist to hold the board together but you may not want its stiffness everywhere.
Layouts
A plate’s cutouts are cut for a specific layout, and they must match both your circuit board and your keycaps. The common ones are ANSI, ISO, WKL (winkeyless), Tsangan and HHKB, and they differ mainly in the bottom row: how many modifiers, how wide, and whether there are Windows keys at all.
Some plates are universal, with extra cutouts covering several bottom-row options at once. Those cost a little stiffness, because more holes means less material, and they save you from discovering that your plate, board and keycaps agree on only two of the three.
Check all three together before ordering. A plate that does not match the PCB is the one mistake here you cannot fix with a file.
What to actually pick
If this is your first build, take aluminum at 1.5 mm in whatever layout your PCB uses, and spend your attention on the switches instead. The plate is a real variable but it is a second-order one, and you need a reference board before the differences mean anything.
If you have a board already and want it to change:
- Deeper and quieter: polycarbonate, FR4 or carbon fiber, or a half plate.
- Sharper and louder: brass or steel, and a thicker plate if one is offered.
- Softer typing feel without changing the sound much: flex cuts, or a softer mounting style, which will do more than the plate will.
Most kits sell plates separately for around 25 to 60 dollars, which makes this one of the cheaper things to change your mind about later, and one of the few you can swap without desoldering anything if your board is hot-swap.