General Classification of Membrane Switches: (Primarily categorised by structure)
1: Flat Non-tactile Type Characteristics: Long service life, but lacks tactile feedback
2: Film-based Convex Tactile Type Characteristics: Offers good tactile feedback, but relatively shorter service life;
3: Raised Frame Non-tactile Type Characteristics: Aesthetically pleasing appearance with strong three-dimensional effect, but lacks tactile feedback;
4: Raised-frame tactile type Features: Aesthetically pleasing appearance with pronounced three-dimensional effect and tactile feedback;
5: Panel embossed tactile type:
a: Prone to two-stage response if poorly designed, but electrical functionality remains intact even with panel damage
b: No two-stage response, fewer structural layers for cost-effectiveness; electrical functionality ceases if panel is damaged
6: Metal spring leaf type
a: The most fundamental and commonly used structure. The spring leaf serves both tactile and upper circuit functions;
b: Complex structure used where numerous, densely spaced spring leaves require no jumper wires. Spring leaves are positioned on the upper circuit, with both upper and lower conductive surfaces facing upwards; the upper circuit requires punching. In this structure, when conductive, the four legs of the spring leaf and the central point are not coplanar, resulting in a ‘two-stage’ effect. Additionally, the spring contact frequently remains in an excessively concave state. Over time, this may cause the spring contact to lose its resilience and fail to rebound. This configuration is not recommended.
Type C: The spring contact is positioned on the upper circuit, serving solely as a tactile element. Its upper circuit conductive surface faces downwards, while the lower circuit conductive surface faces upwards, creating a ‘two-stage’ configuration. This is not recommended.
d) Type: The spring contact is positioned on the lower circuit trace, with traces routed on both upper and lower traces. The spring contact provides tactile feedback while also connecting the upper and lower traces. This is suitable for scenarios requiring numerous, densely packed spring contacts without jumpers, offering a simpler structure than Type (b). During design, ensure trace routing avoids the four legs of the spring contact to prevent short circuits.
7: Light-Emitting Type (Requires bottom adhesive moulding)
a: LED circuit on same layer as lower circuit: Simple structure, but if taller LEDs are selected, they may lift the panel. In this case, either emboss the LED window on the panel or increase the thickness of the top adhesive layer to exceed the LED height;
b: LED circuitry on a different layer from the lower circuitry: Complex structure, though the LED window need not be raised. However, the area above the LED must be hollowed out to prevent light from being blocked by the LED aperture. Note: When routing the lower circuitry, avoid routing traces around the LED aperture.
8: Folded Type Characteristics: This type often avoids jumpers and permits conductive surfaces to face downward without potting holes. The drawback lies in the susceptibility of circuits to breakage at the fold.
9: Inner-Outer Frame Waterproof Type Characteristics: The outer frame forms a sealed enclosure without wiring, protecting the inner frame and preventing moisture ingress through cable exit grooves into the housing.
