Introduction

In industrial and commercial applications, metal push button switches are widely valued for their robust appearance and high reliability. Among various performance metrics, mechanical lifespan is one of the core indicators, particularly in applications that require frequent operation. This article delves into how different mechanical structures—spring plates, levers, and bimetallic strips—affect the lifespan of metal push button switches. It further explores how to achieve a service life of over 1 million presses through advanced structural design and material selection.

1. Evaluation of Structural Designs on Mechanical Lifespan

1.1 Spring Plate Structure

Spring plates are the most commonly used mechanisms in metal push button switches. The lifespan is primarily determined by the material fatigue resistance and structure optimization. High-performance stainless steel (such as SUS301 or SUS304) is often selected for its excellent elasticity and fatigue resistance.

• Advantages: Simple structure, low cost, easy to mass produce.

• Drawbacks: Susceptible to fatigue under high-frequency operation if not well-treated (e.g., insufficient heat treatment or residual stress relief).

1.2 Lever Mechanism

Lever mechanisms are typically used in high-end or precision devices. They use a pivot structure to transfer motion to the contacts.

• Advantages: Effective at reducing operating force and distributing mechanical stress.

• Drawbacks: Slightly more complex design and higher cost; requires precise alignment and tolerance control.

1.3 Bimetallic Strip Design

Though more common in thermal switches, bimetallic strips are sometimes used in specialized buttons to combine temperature sensing and switching functions.

• Advantages: Thermal sensitivity and mechanical actuation combined.

• Drawbacks: Not designed for high-frequency mechanical actuation; lower lifespan under repetitive mechanical cycling.

2. Design Strategies for >1 Million Cycle Lifespan

2.1 Optimized Contact Geometry

Contact area and shape should be designed to minimize contact bounce and arcing. Dome-shaped contacts, convex-convex designs, and double-contact structures can help distribute wear and reduce concentrated stress.

2.2 Reinforced Return Springs

To ensure consistent tactile response and recovery, high-end switches often use precision coil springs made from piano wire or phosphor bronze, with strict fatigue testing to ensure resilience over 1 million actuations.

2.3 Material Selection for High Wear Resistance

• Moving components: Use wear-resistant alloys (e.g., stainless steel + PTFE coating) to reduce friction.

• Housing and actuator cap: Use anodized aluminum or reinforced plastic to maintain structural integrity over repeated use.

2.4 Advanced Surface Treatments

• Hardening treatment: Improve fatigue strength of spring plates and levers (e.g., shot peening, nitriding).

• Contact plating: Use gold-plated or silver-nickel contacts to minimize wear and oxidation.

Example:

A switch used in an elevator panel was redesigned from a flat spring to a dome spring + reinforced coil spring structure, using SUS301 and Au-plated contacts. After modification, its mechanical lifespan increased from 500,000 to 2 million cycles under 2 Hz press frequency.

3. Testing and Validation

• Mechanical cycle test: Performed at 2–5 Hz for at least 1 million cycles, monitoring contact bounce and force curve.

• High-frequency fatigue testing: To simulate rapid-use scenarios such as gaming keyboards or vending machines.

• Environmental simulation: Validate design under humidity, dust, temperature cycling, and vibration.

Conclusion

To improve the mechanical lifespan of metal push button switches, manufacturers must consider structure, material, and surface treatment holistically. With optimized design and rigorous testing, it's entirely feasible to achieve a lifespan beyond 1 million actuations, making the switches more reliable and competitive for high-demand applications.