Introduction

Metal push button switches, despite their robust design, are still subject to various failure modes in practical applications. These failures not only reduce product reliability but also lead to maintenance costs and safety issues in customer sites. This article analyzes common failure modes of metal push button switches—such as contact arcing, button jamming, LED failure, and seal degradation—and reviews real customer cases to provide targeted design optimization suggestions.

1. Common Failure Modes and Root Cause Analysis

1.1 Contact Arcing and Wear

Phenomenon: After long-term use, switch contact resistance increases, even resulting in failure to conduct.

Cause:

• High inrush current without arc suppression.

• Inadequate contact material (e.g., pure copper without plating).

• High operating voltage or inductive load.

Optimization:

• Use silver-nickel or gold-plated contacts for high current reliability.

• Add arc suppression components (RC snubber or MOV).

• Reinforce spring force to ensure contact pressure.

1.2 Button Jamming

Phenomenon: The button becomes stuck in the pressed position and does not rebound.

Cause:

• Debris ingress due to poor sealing.

• Deformation of spring plate.

• Excessive wear on plastic guide sleeve.

Optimization:

• Use dustproof and waterproof structures (e.g., IP67 design).

• Reinforce spring plate material and shape (e.g., double-curvature dome).

• Use self-lubricating plastic or metal guide sleeves.

1.3 LED or Light Ring Failure

Phenomenon: LED does not light up or flickers after a period of use.

Cause:

• LED solder joint fracture due to vibration.

• Electrostatic breakdown or surge.

• Moisture ingress leading to corrosion.

Optimization:

• Use flexible PCB and reinforcement glue for LED solder joints.

• Add TVS protection to the LED circuit.

• Improve potting and waterproof design of light ring.

1.4 Seal Failure (IP Degradation)

Phenomenon: Moisture ingress, fogging inside switch, corrosion.

Cause:

• Poor sealing design (e.g., thin O-ring, low contact pressure).

• Material aging (e.g., silicone rubber hardening).

• Incorrect installation causing compression loss.

Optimization:

• Use high-performance fluorosilicone O-rings.

• Design mechanical structures that maintain sealing pressure under thermal expansion.

• Add secondary sealing like glue filling or ultrasonic welding.

2. Case Studies from Customer Sites

Case A: Food Processing Machine Button Fails after 3 Months

Problem: Button became sticky and unreliable; LED flickered.

Analysis: High humidity and oil vapor caused internal corrosion and solder failure.

Solution: Upgraded to IP68 switch with epoxy-sealed LED and food-grade silicone sealing ring. After redesign, no failure in 6-month follow-up.

Case B: Elevator Call Panel Button Lost Tactile Feedback

Problem: Users reported button was soft and unresponsive.

Analysis: Long-term mechanical fatigue led to spring plate deformation.

Solution: Changed to double-spring structure (coil + dome), added fatigue life test in production. Mechanical cycles improved from 300,000 to 1.2 million.

Case C: Industrial Panel with Intermittent Contact

Problem: Switch signal occasionally failed.

Analysis: Contact surface oxidation due to prolonged storage and lack of current load.

Solution: Switched to gold-plated contacts, added low-current self-cleaning pulse during power-on to ensure reliability.

3. Proactive Design Recommendations

• Reliability testing: Include high/low temperature cycling, salt spray, vibration test.

• Redundancy: In critical environments, use redundant contacts or signal confirmation circuits.

• Installation training: Guide customers to use correct torque and mounting methods to avoid sealing damage.

Conclusion

By thoroughly understanding the failure modes of metal push button switches and drawing lessons from field failures, we can implement targeted design optimizations to improve product reliability. This not only enhances user satisfaction but also reduces after-sales maintenance costs, building long-term trust with B2B clients.