Keyboard Mounting Styles
How the plate is held in the case, what each mount does to flex and sound, and why the label alone does not predict how a board feels.
The plate and circuit board have to be attached to the case somehow. How they are attached is the mounting style, and it does more to how a keyboard feels than the case material, the plate material or the switches.
It is also the hardest thing to judge before buying, because the only honest description is what happens to the force when you press a key, and every review reaches for adjectives instead.
What is actually being decided
One question: how rigidly is the typing surface connected to the object sitting on your desk?
Press a key and the force goes into the plate. If the plate is bolted hard to a solid aluminium case, it goes nowhere, the surface does not move, and you feel a hard stop. If the plate is suspended on rubber, it flexes a fraction of a millimetre and the impact is softened.
Everything else follows. A rigid mount is sharper, louder and higher pitched, with the sound of the case in it. A soft mount is quieter, deeper, and more cushioned, with less of the case audible.
Neither is better. They are different, and preference here is genuinely split.
The mounts, rigid to soft
Integrated plate
The plate and the top case are one piece of metal. There is no join, so there is nothing to flex.
The stiffest possible arrangement, and it feels like typing on a solid block. Divisive: some people find it precise, others find it harsh over a long day. It also means you cannot change the plate material, because it is the case.
Tray mount
The PCB screws down onto posts standing up from the bottom case. The oldest and most common design, and what most inexpensive boards use.
The characteristic here is unevenness, and it is the thing worth knowing: the board is stiff directly over each post and softer between them, so the typing feel is not consistent across the keyboard. The posts are usually where your hands are not. People describe tray mount boards as having a dead spot, and that is what they mean.
Sandwich mount
Screws pass through the bottom case, the plate and the top case, clamping the plate in the middle.
Stiff and, unlike tray mount, evenly stiff, because the plate is held around its whole perimeter. The plate edge is often visible around the outside of the board, which is a look people either want or do not.
Top mount
The plate screws to the top case, and the top case screws to the bottom.
The most common arrangement on custom boards, and a reasonable default. The plate is held at its edges and unsupported in the middle, so there is some give in the centre and very little near the sides. Stiffer than gasket, much more even than tray.
Bottom mount
The same idea inverted: the plate screws to the bottom case. Similar in feel to top mount, slightly different in sound because the top case is no longer part of the structural path. Less common.
Gasket mount
The plate is not screwed to anything. Strips or pads of rubber, silicone or poron sit between the plate and the case, above and below, and the plate is held by compression.
The softest common mount, and currently the most fashionable. The whole typing surface can move slightly, evenly, with no hard connection to the case, which makes it quieter and deeper than anything above it. The trade is that a heavily gasketed board can feel spongy, and that some people miss the definition of a hard stop.
O-ring and leaf spring
Two variations on the same idea. O-ring mount suspends the plate on a rubber cord running around its edge. Leaf spring uses springy metal tabs on the plate, resting in the case. Both sit near gasket mount in feel, both are less common, and both are usually chosen deliberately by someone who knows what they are after.
Plateless, or PCB mount
No plate at all. Switches are held only by the circuit board.
Very flexible, because a PCB is thin and bends, and the softest and most muted option here. It needs five-pin switches to hold everything square, and it is not for everyone: a board that visibly flexes under typing is either delightful or alarming depending on the person.
The thing most descriptions leave out
The mount is one of four variables, and the label alone tells you very little.
A gasket-mounted board with a brass plate and foam under the PCB will be firmer and duller than a top-mounted board with a polycarbonate plate and no foam. The mount sets a range; the plate material, the foam and the case weight decide where in that range you land.
Which is why “gasket mount” on a product page is not the answer to how a board feels, and why the same mount from two designers can feel nothing alike. If you are choosing between boards, the mount narrows it down and a sound test decides it.
What to pick
First custom board: top mount or gasket mount. Both are forgiving, both are common enough that plenty of people can tell you what they sound like, and neither is an extreme.
You want it soft, quiet and deep: gasket mount, a softer plate, foam.
You want it sharp, defined and audible: top or sandwich mount, a stiff plate, no foam.
You are buying cheaply: tray mount, and know that the unevenness is the design rather than a fault in your particular board.
You already have a board and want it changed: the plate and the foam are far cheaper to swap than the case, and will move the sound more than you expect. Change those before concluding the mount is wrong.