Editing Keyboard technology (section)

=== Capacitive ===
[[File:Topre switch.png|right|thumb|Topre electrostatic capacitive switch]]
In a capacitive mechanism, pressing a key changes the capacitance of a pattern of capacitor pads. The pattern consists of two D-shaped capacitor pads for each switch, printed on a [[printed circuit board]] (PCB) and covered by a thin, insulating film of [[soldermask]] which acts as a [[dielectric]].

For the most common, foam and foil implementation of this technology, the movable part ends with a flat foam element about the size of an [[Tablet (pharmacy)|aspirin tablet]], finished with aluminum foil. Opposite the switch is a PCB with the capacitor pads. When the key is pressed, the foil tightly clings to the surface of the PCB, forming a [[series circuits|daisy chain]] of two capacitors between [[contact pad]]s and itself separated with a thin soldermask, and thus "shorting" the [[contact pad]]s with an easily detectable drop of [[capacitive reactance]] between them. Usually, this permits a pulse or pulse train to be sensed.

An advantage of the capacitive technology is that the switch is not dependent on the flow of current through metal contacts to actuate. There is no [[debouncing]] necessary.

The sensor tells enough about the distance of the keypress to allow the user to adjust the actuation point (key sensitivity). This adjustment can be done with the help of the bundled software and individually for each key, if so implemented.<ref>Topre keyboard documentation, describing various features [http://www.realforce.co.jp/en/products/R2SA-US4-IV/index.html] {{Webarchive|url=https://web.archive.org/web/20190723000131/http://www.realforce.co.jp/en/products/R2SA-US4-IV/index.html|date=23 July 2019}} and they software manual [http://www.realforce.co.jp/en/support/download/REALFORCE_Software_Manual_EN.pdf pdf] {{Webarchive|url=https://web.archive.org/web/20210917195133/https://www.realforce.co.jp/en/support/download/REALFORCE_Software_Manual_EN.pdf|date=17 September 2021}}</ref> A keyboard which utilizes these abilities include the Real Force RGB.

[[IBM]]'s [[Model F keyboard]] is a design consisting of a buckling spring over a capacitive PCB, similar to the later Model M keyboard, but instead used membrane sensing in place of a PCB.

The [[Topre|Topre Corporation]] design for switches uses a conical spring below a rubber dome. The dome provides resistance, while the spring does the capacitive action.<ref>{{Cite magazine |last1=Wong |first1=Anson |last2=Li |first2=Tom |date=6 April 2019 |title=The complete guide to mechanical keyboard switches for gaming |url=https://www.pcgamer.com/best-mechanical-switches-for-gaming/ |magazine=[[PC Gamer]] |access-date=9 January 2020 |archive-date=4 March 2020 |archive-url=https://web.archive.org/web/20200304195543/https://www.pcgamer.com/best-mechanical-switches-for-gaming/ |url-status=live }}</ref>{{clear}}