Tactile switches

July 7, 2005
Tactile switches are so named because they give the user tactile feedback in the form of a detent or snap action when the switch has actuated.

are so named because they give the user tactile feedback in the form of a detent or snap action when the switch has actuated. Versions of these devices that mount on circuit boards serve as the switching element for keyboards or buttons mounted in consumer handheld devices, computer peripherals, and numerous other applications.

are momentary contact devices that operate when depressed with a force of between 100 and 300 gm. They are also generally single-pole single-throw elements and are designed for high-density mounting. The actuation element is an elastomeric actuator top that impinges on a metal contact. Applied force exceeding a threshold pushes the contact onto stationary contacts to complete the circuit.

Contacts are gold or silver depending on design requirements. Silver contacts typically are rated at 3 VA at dc. Gold contacts are generally specified for low-current needs and generally are rated at 28 Vac/dc max. Gold contacts experience little or no oxidation or sulfurization.

As with many circuit-board components, tactile switches come in surface-mount and through-hole styles. Through-hole models have crimped terminals with a spring action to ensure secure mounting during automated soldering. Surface-mount styles have gull-wing terminals for mechanical stability during soldering. The devices are typically sealed to lock out flux, solvents, and other contaminants.

New versions of tactile switches have recently become available that comply with RoHS hazardous-substance directives that ban lead, cadmium, certain plastic additives, and other materials. These new components are designed for lead-free soldering processes through use of high-temperature plastics and flame-retardant additives that the RoHS directive permits.

NKK Switches (www.nkkswitches.com) provided information for this article.

About the Author

Leland Teschler

Lee Teschler served as Editor-in-Chief of Machine Design until 2014. He holds a B.S. Engineering from the University of Michigan; a B.S. Electrical Engineering from the University of Michigan; and an MBA from Cleveland State University. Prior to joining Penton, Lee worked as a Communications design engineer for the U.S. Government.

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