A membrane switch failing to rebound after being pressed is also known as a dead key phenomenon, which is fatal for the switch; it directly causes the entire product to malfunction. Why does this dead key phenomenon occur? Let us briefly analyse the causes below:
1. Standard dome switches measure 0.06mm thick, with a lifespan of 500,000 to 1.5 million cycles (depending on load requirements). When the lifespan reaches or exceeds twice the design life, the switch is prone to failing to rebound and becoming dead keyed.
2. Conventional dome switch designs specify a rebound force of ≥40gf. When employing specialised designs with values below 40gf, failure to rebound and dead keying may occur as the switch approaches its lifespan limit.
3. The dome is constructed from stainless steel, typically designed within the thickness range of [0.06–0.1mm]. Standard load capacity is set at 100–300gf. Prolonged exposure to loads exceeding twice the design capacity may cause non-rebound.
4. Removing the release liner before PCB mounting, or bending during production, subjects the dome to external forces causing deformation. This may result in non-rebound dead keys (damaging the dome, creating creases, or altering its concave structure).
5. If the dome switch lacks venting channels in its design, trapped air within the travel range prevents full actuation, causing a dead key phenomenon.
6. When no pre-compression travel is incorporated in the design, silicone or plastic guide pins exert prolonged pressure on the dome. This causes the dome to become heavy, shortening its service life and resulting in dead keys or loss of actuation functionality.
