While both the internal dampening layers of a keyboard (such as bottom foam or plate foam) and the gasket mounts utilize soft materials—like PORON or silicone—they serve fundamentally different mechanical functions. Gasket mounts act as the “springs” of a suspension system, physically isolating the internal assembly (the “plate-PCB sandwich”) from the outer case and providing room for rebound. Dampening layers, by contrast, function as the “shock absorbers” of the system, absorbing sound waves within the cavity and eliminating high-frequency vibrations. The former dictates the “travel distance and firmness” of the internal assembly’s downward movement, while the latter determines the “clarity or depth” (muffled quality) of the typing sound. These two components inherently conflict in terms of their direction of deformation under pressure, the points at which they bear force, and their overall impact on the keyboard’s tactile feel.
I. Differences in Force Application and Deformation Direction
Gasket mounts (structural components) are positioned between the edges of the plate/PCB and the outer case. They are subjected to **longitudinal (Z-axis) shear and compression**. When a key is pressed, the entire internal assembly shifts downward, compressing the gaskets between the top and bottom case; this creates a soft, springy bottom-out sensation. The degree of deformation in these gaskets directly defines the keyboard’s signature “gasket feel.”
Dampening layers (acoustic components) are located beneath the internal assembly (bottom foam) or between the plate and the PCB (plate foam). They are subjected to **uniform surface compression**. These layers do not participate in the suspension or support of the internal assembly; rather, they fill the voids within the case to absorb sound wave energy. While they do undergo compression during key presses, they are not structurally constrained—they are simply compressed passively.
II. Fundamental Mechanical Roles
Gasket mounts determine the “firmness” of the typing experience. The material properties of the gaskets—such as their hardness and rebound rate—along with their thickness, dictate the extent to which the internal assembly “floats.” Using high-hardness silicone strips results in minimal downward travel, yielding a firmer feel with direct, immediate feedback. Conversely, using low-hardness PORON or foam allows for greater downward travel, resulting in a softer, springier feel. In essence, the gasket mount serves to provide a predictable, elastic boundary for support. The dampening layer determines the “sound.” Its primary function is to disrupt the reflection paths of sound waves within the cavity, effectively eliminating the “hollow” or “boomy” resonance often produced by plastic enclosures. If the dampening layer is too thin—or the cavity too large—the sound becomes diffuse and hollow. Conversely, a high-density dampening layer absorbs more high-frequency noise, resulting in a more focused, “muffled” (or “thocky”) sound profile. In essence, the dampening layer acts as an acoustic damper.
III. Physical “Tension and Conflict”
In practical keyboard design, a physical conflict often arises between the gasket mounts and the dampening layer.
Over-stuffing and Compressing the Gaskets: If the bottom dampening layer (such as bottom foam or a silicone pad) is too thick or over-stuffed, it pushes the internal assembly (the “plate-PCB” unit) upward. This compresses the gaskets, leaving them no room to deform downward. The keyboard’s suspension structure is effectively nullified, causing the typing feel to shift from “soft and springy” to “hard as a rock.” This is a common pitfall in mass-produced keyboards, where manufacturers sacrifice typing feel in pursuit of a specific “mahjong-like” (deep, resonant) sound.
Deformation Coupling: When a user strikes a key with force, the internal assembly sinks, compressing the bottom dampening layer. If the rebound rate of the dampening layer does not align with that of the gaskets—for instance, if the gaskets are very soft while the bottom foam is quite rigid—the internal assembly may tilt unevenly when keys near the edges are pressed, leading to inconsistent typing feedback.
IV. Mechanical Implications of Material Selection
These two components impose vastly different requirements on material properties:
Gasket mounts prioritize compression set (resistance to permanent deformation) and rebound speed. Like a spring, they must be able to return to their original shape quickly after being pressed; otherwise, the edges of the keyboard assembly may collapse.
Dampening layers prioritize sound absorption coefficients and density. They do not require rapid rebound—in fact, some designs intentionally utilize “soft, pliable” materials to ensure they fill every available gap. For instance, while PORON is also used for gaskets, when employed as a bottom dampening layer, a softer, thinner version with a higher closed-cell content is typically chosen to serve the sole purpose of sound absorption.
