What Is a Tact Switch?
A tact switch is an electronic component whose contacts close momentarily when a button is pressed.
It typically consists of a small, thin plastic button with soldered contacts on a PCB. Tact switches are also known as momentary contact switches.
Tact switches have a compact, slim design, making them suitable for integration into small devices. This feature helps save space in device design.
They are available at a relatively low cost, making them an economical choice for mass-produced electronics and appliances.
Uses of Tact Switches
Tact switches find applications in various fields and functions.
1. Office Automation Equipment
One common application is in office automation equipment, such as computer keyboards and mice, where they serve as buttons and operating switches. Tact switches are also used for volume control in portable electronic devices like smartphones and portable audio players.
2. Home Appliances
Tact switches are widely used in household appliances, including TV remote controls and audio equipment. They function as buttons for controlling actions like channel switching and play/stop.
3. Medical and Measuring Equipment
These switches may also find use in medical and measuring equipment for interface functions, such as operation buttons and parameter adjustments. They are employed in devices like sphygmomanometers and thermometers.
Principle of Tact Switches
Tact switches consist of several key components, including a button cap, contact points, pins, and a plastic case.
1. Button Cap
Located at the top of the tact switch, the button cap is the part that users press. It is often made of plastic and is designed for ease of operation. The button cap may also feature markings or symbols corresponding to its function or purpose.
2. Contact Points
These are the electrical circuit components that temporarily connect when the button is pressed. They are usually made of a metal spring or catalytic metal. To reduce electrical resistance, contacts are often made from materials like silver alloys or gold. Silver alloys are commonly used due to their low electrical resistance, while gold, despite being more oxidation-resistant, is pricier and used for lighter loads. These contacts are designed for durability and can withstand 100,000 to 10 million uses.
3. Pins
Tact switches have soldered pins used for mounting on circuit boards. These pins are soldered to dedicated pads on the board and carry electrical signals.
4. Plastic Case
In addition to pins, the components mentioned above are typically housed within a plastic case. This case provides mechanical protection for the components and securely attaches them to the circuit board.
Types of Tact Switches
Tact switches are broadly categorized into two types: through-hole and surface-mount.
1. Through-Hole Type
Through-hole tact switches are soldered directly into holes drilled into the circuit board, offering robust physical connections. This design ensures highly reliable operation, even in the presence of shocks and vibrations. They can handle relatively high currents and voltages, making them suitable for high-capacity electrical circuits and applications.
2. Surface-Mount Type
Surface-mount tact switches are soldered directly onto the surface of the circuit board. They enable compact designs, occupy minimal board space, and are suitable for small devices and integrated circuits. Direct contact with short traces and pads on the board ensures high signal quality, minimizing signal loss and noise effects. These switches are also conducive to efficient soldering with automatic machines, resulting in high production speeds and cost-effective mass production.