Two disadvantages of mechanical touch keyboard are that the mechanical spring is easy to damage, and the electrical contacts will be oxidized after a long time of use, leading to key failure. So after 90's, mechanical touch keyboard gradually withdrew from the stage of history.
At first, they were replaced by electromagnetic-mechanical keyboards. Electromagnetic mechanical keyboard is still a mechanical keyboard, but unlike mechanical touch keyboard, it does not rely on mechanical force to connect the two electrical contacts. Instead, the electrical contacts are enclosed in a tiny potentiometer, and a magnet is placed under the key, through which the current is connected.
Compared with mechanical keyboard with contacts, strong electromagnetic mechanical keyboard life a lot, but still failed to solve the mechanical keyboard mechanical movement part of the inherent problems, which are easily damaged, so the electromagnetic mechanical keyboard how long can not survive in the market, was soon appeared in the late 80 s the non-contact replaced the keyboard.
Therefore, the non-contact keyboard is relative to the previous various "contact keyboard". Different from the "contact keyboard", they do not rely on the mechanical connection of conductive contacts to obtain the key signal, but rely on the change of the electric parameters of the key itself to obtain the key signal. Since no mechanical contact is required, its service life is much better.
The main contactless keyboards are resistive and capacitive keyboards. Among them, capacitive keyboard is more widely used because of its simpler process and lower cost. Compared with the mechanical keyboard, its two characteristics are that the spring made of elastic rubber replaces the mechanical metal spring, and at the same time, the electrical connection of the mechanical keyboard is changed to the change of the electric capacity caused by the change of the distance between the bottom of the key and the bottom of the keyboard to obtain the key signal.
