Tact Switch
A tact switch is a momentary, normally-open four-pin pushbutton. Pressing the cap snaps a stainless-steel dome down onto the contact pad and shorts two pin pairs; releasing it lets the dome pop back up and the circuit reopens.
Inside the molded body sits a click dome — a 5–6 mm convex disc of phosphor-bronze or stainless. When the actuator pushes its center past the buckling threshold (typically 160–260 gf), the dome snaps inverted, contacts the printed pad below, and bridges the two NO terminals. The buckling is what gives the unmistakable tactile click.
In plain terms
A miniature cymbal-shaped metal dome you snap flat with a fingertip; it pops back the moment you let go.
Why designers use it
- Reset, mode, and program buttons on every microcontroller dev board.
- Power and menu buttons inside consumer devices where size matters.
- User input on PCBs that already have a flat surface to mount on.
Best for
- Reset/boot buttons
- Menu navigation
- PCB-mounted UI
Key specifications
- Actuation force: 160 – 260 gf
- Travel: 0.25 – 0.5 mm
- Lifetime: 100k – 1M cycles
- Contact rating: 50 mA at 12 VDC
- Standard footprint: 6.0 × 6.0 mm
When not to use it
- When the user-facing button needs travel and weight — tact switches feel cheap; use a snap-action or mechanical key.
- When the switch is exposed to dust, water, or vibration — IP-rated sealed buttons are a different category.
- Where >50 mA needs to flow through the contacts — tact switches are signal-only.
Common mistakes
- Skipping debounce in firmware — a single press registers as 3–5 events.
- Pressing the cap from the side instead of straight down and snapping the dome out of alignment.
- Soldering a 6 × 6 mm tact rotated 90° — the four pins swap which pair is the closed contact.
Where you will find it
- Every Arduino, ESP32 dev kit, and Raspberry Pi Pico ships with a 6×6 mm tact switch as its RESET button — the tactile click is the universal hardware-engineer signal that a fresh boot is happening.
- Inside a consumer remote control, six tact switches sit beneath a silicone keymat: the silicone deforms to push each tact's plunger when you press a key, and the click feedback is what the user actually feels.
- A laptop's lid-closed sensor is sometimes a tact switch hidden under a magnet-aligned plunger — closing the lid mechanically depresses the actuator and the BIOS triggers sleep.
A short history
The tactile dome switch evolved from the metal-dome keyboards developed by IBM in the 1960s and 1970s. The compact PCB-mountable 6×6 mm tact switch as we know it today was popularised in the late 1970s by Japanese makers — most notably Alps Alpine — and standardized further by Omron and Panasonic. The trademark crisp click comes from the snap-action buckling of a stainless-steel dome, a mechanism patented variously through the 1970s. By the 1990s, surface-mount tact switches at standard 6×6 mm and 4.5×4.5 mm footprints had become a default catalog part across distributors.
Good to know
- The audible 'click' you hear and the tactile 'click' you feel come from the same buckling event — the dome inverts past its center of curvature.
- A new tact switch's bounce typically lasts 5–20 ms; firmware must debounce or it will register one press as several.
- Storing tact switches in humid air for years can let sulfur tarnish the contact pad, raising contact resistance until the first few presses scrub it off.