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The 3.5×6.0mm Normally Closed (NC) SMD Tactile Switch is a specialized component designed for safety, security, and power-interruption circuits. Unlike standard “Normally Open” (NO) switches that complete a circuit when pressed, this switch breaks the connection upon actuation.
In its resting state, the circuit is closed (conductive). When the plunger is depressed, the internal metal dome lifts or shifts to disconnect the terminals, making it an essential “logic-flip” component for compact electronics.
| Feature | Details |
|---|---|
| Dimensions | 3.5mm x 6.0mm (Rectangular Base) |
| Circuit Type | SPST-NC (Normally Closed) |
| Mounting Type | Surface Mount (SMD / SMT) |
| Actuation Force | 160gf to 250gf (Standard “click” feel) |
| Contact Rating | 50mA @ 12V DC |
| Travel Distance | ~0.25mm |
| Operating Life | 50,000 to 100,000 cycles |
| Reflow Temp | Designed for 260°C peak (Lead-free compatible) |
How the “Normally Closed” Logic Works
In a standard switch, you press to “Turn On.” In this NC version, the behavior is inverted:
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Resting State: Current flows freely through the switch (Logic HIGH).
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Pressed State: The circuit is interrupted, and current stops (Logic LOW).
Unique Advantages of the 3.5x6mm NC SMD
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Fail-Safe Design: NC switches are frequently used in “tamper-evident” circuits. If a wire is cut or the switch is damaged, the circuit stays open, triggering an immediate alert.
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Edge-Mount Friendly: The 3.5mm slim profile allows it to be placed right at the edge of a PCB, perfect for “lid-closed” sensors or side-accessible reset buttons.
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Battery Preservation: It can be used as a “Kill Switch” that physically cuts power to a sub-system only when the button is held, preventing accidental battery drain during storage or transit.
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SMD Efficiency: Being a surface-mount component, it is compatible with automated SMT production lines, reducing manufacturing time for high-volume products.
Common Applications
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Security & Alarms: Used as a “Tamper Switch” on the back of enclosures. If someone opens the device, the button is released, closing the circuit and triggering the alarm.
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Smart Covers: Detecting when a tablet cover or laptop lid is opened/closed.
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Emergency Stops: Small-scale “E-Stops” for handheld robotics where a press must immediately halt a motor.
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Logic Inversion: Simplifies circuit design when you need a “High” signal by default without adding an extra transistor or NOT-gate to your PCB.
Design Note: Identifying NC vs. NO
Visually, an NC switch often looks identical to its NO counterpart.
