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Alps KFL Series



KFL is a compact, PCB-mount keyboard switch series from Alps. The earliest known mention of it is from magazines in 1982, as (in one instance) “KFL Series” and “Model KFL” simultaneously; this material is partially accessible on Google Books. Advertisements placed in magazines in 1983, including Electronic Engineers Master 83–84, are however fully accessible. Here, it is advertised as “Series KFL Low Profile Keyboards”, which covers both the switches and completed keyboards (prior to Alps putting keyboards into separate series). The utility models filed by Alps are contemporary with this, suggesting that the switches entered production around 1983.

The legs protrude out from the sides of the switch, entering the shell high up. This strange design characteristic may be intended to prevent fouling of the switch contacts by the ingress of solder, flux or cleaning fluids during the wave soldering process, without the need to apply terminal sealant (as was used with KCC, KCM and KCL series in some cases).


The specifications given in the Alps Low-Profile Keyboard Switches sample pack are indicated to apply to both the standard momentary (SKFLAC and SKFLFB) and alternate action (SKFLJB) types, but this is unlikely to be true as it is definitely not true in the case of SKCL; thus, the force specifications below likely apply only to SKFLAC. The “operating force” is given as 60 gf, while the official force curve shows 60 gf to be the total travel force. If the operating point is taken to be half travel at 2 mm, this would correspond to roughly 50 gf, and the preload appears to be around 40 gf. There is no indication of a date with these specifications.

Operating force ca. 50 gf
Total travel force 60 gf
Preload ca. 40 gf
Total travel 4.0 mm
Lifetime 10 million cycles
Contact resistance 1 Ω maximum


The older part numbers come from Roland service literature, and cover just the standard momentary switches (non-illuminated, and illuminated with a red LED). The newer part numbers are taken from the Alps Low-Profile Keyboard Switches sample pack.

Type KFL model SKFL model Colour
Momentary, standard weight KFL10903 SKFLAC Pale grey
Momentary, standard weight, red LED KFL11904 SKFLFB
Momentary, heavy weight Pale cyan
Alternate action SKFLJB Pale yellow
Compact Pale grey
Dummy Dark green

Patents and utility models

The following patents (“A”) and utility models (“U1”) were located by a search for “スイッチ” (switch) and “キーボード” (keyboard) from Alps Electric (アルプス電気) on J-PlatPat (the Japanese Patent Platform). J-PlatPat does not provide inbound links to documents.

Document Filed Granted Description
S57-095717, U1 1982 Contact assembly, a little bit like that of KFL
S58-174821, U1 1982-05-18 1983-11-22 KFL alternate action
S58-188928, U1 1983 KFL momentary, possibly unused variation
S58-193428, U1 1982-06-15 1983-12-22 KFL momentary, actual implementation
S59-161227, U1 1984 KFL keycap mount
S59-161226, U1 1984 KFL keycap mount, production version
S59-162729, U1 1984 KFL keycap mount
S59-162727, U1 1984 KFL keycap mount
S60-107528, U1 1985 KFL compact
S60-131925, U1 1985 KFL LED and KFL compact
S63-141219, A 1988 KFL switch contact manufacturing process



See also