Mechanical keyboard is a term whose meaning is poorly-defined. Different people and organisations use the term for different purposes.
Numerous manufacturers describe their switches as "mechanical"; generally, the reason for this is not explained. However, several manufacturers use "mechanical" as way to differentiate different sense methods. ITW and RAFI use the term "mechanical" to differentiate contactless sensing (magnetic valve and Hall effect respectively) from metal contact sensing. General Instrument appear to use "mechanical" to differentiate physically actuated, exposed metal contacts from their typical (magnetically-operated, sealed) reed switches.
Traditionally, the term 'mechanical keyboard' referred to the typewriter-based keyboards that were common on computer consoles in the 1950s and 1960s, where the process of determining which key had been pressed was almost entirely electromechanical. In the 1970s, these were replaced with 'electronic' keyboards, which were keyboards that used digital circuitry to determine which keys had been pressed. However, as rubber dome keyboards become ubiquitous in the 1990s, companies began to market their metal contact–based keyboards as having 'mechanical' switches.
Arguably the best-known "mechanical" keyboard in the world is the IBM Enhanced Keyboard, colloquially known as the "IBM Model M". Model M keyboards are membrane keyboards and would not fit well into the definition of "mechanical" denoting metal contacts. "Mechanical" can also get applied to Topre switches, which do not use metal contacts.
As such, "mechanical" gets used to categorize keyboards with high quality switches, regardless of the technology.
The term is sometimes defined as a keyboard that uses a switching mechanism which makes use of some sort of metal spring (thus including the IBM Model M), or a switch that actuates at some point before the end of the switch's travel. These definitions are somewhat meaningless, given the huge variation in quality across different switch designs that have these properties. Consequently, some people prefer to use terms such as "high quality keyboards", or to refer to the keyboards by their specific switch type.
Products described as "mechanical" or "mechanical contact" include:
- Alps SKCL/SKCM series
- Alps SKBL/SKBM series ("High-reliability mechanical contact." on the Forward Electronics website in 2004)
- General Instrument Series S950
- ITW magnetic valve second generation is defined in the patent as supporting either analogue magnetic sensing, or "mechanical" contacts
- Monterey K110 keyboard and KP110 keypad, per the 1992 Monterey catalogue
- Omron B3G series, as 「メカキースイッチ」 ("Mechanical key switch"), per Omron literature
- RAFI RS 74 M, RS 76 M ("M" for mechanical, compared to RAFI RS 74 C and RS 76 C contactless switches, "C")
- Tokai MM9 series
- Deskthority — We need a better adjective than "mechanical".