The early keyboards were almost all mechanical keyboards, to be precise a mechanical contact keyboard, which used electrical contact contacts as a sign, using mechanical metal springs as the spring mechanism. The keyboard feels hard, the button stroke is long, the button resistance changes quickly and crisply, and the feel is very close to the typewriter keyboard, so it was very popular at that time, and until today, quite a few people still miss the feel of this keyboard.
However, the two biggest disadvantages of mechanical contact keyboards are that the mechanical springs are easily damaged and the electrical contacts are oxidized after prolonged use, causing the keys to malfunction. So after the 1990s, the mechanical contact keyboard gradually withdrew from the historical stage.
In the beginning, it was replaced by an electromagnetic mechanical keyboard. The electromagnetic mechanical keyboard is still a mechanical keyboard, but unlike mechanical contact keyboards, it does not rely on mechanical force to connect two electrical contacts, but instead closes the electrical contacts in a miniature potentiometer. A magnet is placed in the lower part of the button to turn on the current by magnetic force.
Compared with the mechanical contact type keyboard, the electromagnetic mechanical keyboard has a much longer service life, but it still fails to solve the problem that the mechanical movement part of the mechanical keyboard is easily damaged, so the electromagnetic mechanical keyboard fails to survive in the market. How long it took to be replaced by a non-contact keyboard that appeared in the late 1980s.
Therefore, the non-contact keyboard is opposite to the previous “contact keyboards”. Unlike the “contact keyboards”, they do not rely on the mechanical connection of the conductive contacts to obtain the button signals. It is based on the change of the electrical parameters of the button itself to obtain the button signal. Since the mechanical contact of the contacts is not required, its service life is much stronger.
The main non-contact keyboards are resistive and capacitive. Among them, the capacitive keyboard is more widely used because of its simpler process and lower cost. Compared with the mechanical keyboard, its two biggest features are the replacement of the mechanical metal spring with a spring made of elastic rubber, and the electrical connection from the mechanical keyboard to the change of the distance between the two capacitive plates through the bottom of the button and the bottom of the keyboard. The resulting capacitance changes to get the signal of the button.