SMK spring over dome

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SMK spring over dome
Manufacturer SMK
Switch type Clicky
Sense method Conductive dome
Keycap mount SMK two-prong ,
Switch mount Plate mount

SMK spring over dome is a name given to a keyswitch produced by SMK. The construction is described as "slider-over-spring-over-conductive rubber dome-over-PCB".[1] It appears to be similar in concept to Alps integrated dome, except the contacts are on the PCB, rather than being contained within the switch module. A miniaturised version exists for use with small keys.


The PCB contains a pair of conductive traces for each key. Over this, switch modules are mounted on a plate. The modules contain a rubber dome with a conductive pad on the underside which bridges the traces when pressed. A spring sits over the dome, which in turn has a square slider on top.

The slider is notably large, covering most of the area of the switch. The switch bears a passing visual resemblance to Logitech Romer-G switches, and to a lesser extent, Alps SKCP series.

Like other spring-over-dome switches, such as Fujitsu Peerless, the switch is linear until a distinct tactile/actuation event near the bottom, with only a slight click noise. Unlike the Peerless, however, it is very smooth and wider keys are fully stabilised. The normally muted click is louder in a disassembled keyboard.[2]


Two-prong mount

The keycap mount consists of a pair of holes: north and south on the slider, for two prongs on the inside of the keycap.

Related switches

There is also a miniaturised switch for use with smaller-sized keys. This appears to be similar in design to the full-sized version, but uses a different mount, with a cruciform shape.

Another switch which appears to be related to this and may be an additional variant has also been observed.[3] This features a grey-coloured slider with a different pattern. The keycap mount is the same as the normal full-size version.


  • Various Canon typewriters, including the S-51[1], Typestar 5[4] and Typestar 6[5] (Keys with lock lights have a round window in the top left of the cap.)
  • DataDesk PC 8700 JR/XT[6]
  • Sony KI-9700P keyboard contains a potential variant