During wave soldering and reflow soldering, the soldering area of a pushbutton switch often experiences instantaneous temperatures of 250–300°C. Since the switch contains sensitive components such as contacts, springs, plastic frames, and clips, improper structural design can lead to contact performance degradation, spring annealing, plastic deformation, or clip loosening, ultimately affecting tactile feedback and reducing lifespan. To address these issues, anti-reflow structures (Anti-reflow Design) are a key consideration in pushbutton switch design. The following sections explain common effective strategies, combining design principles with practical examples.

1. Heat Insulation Barrier: Slowing Down Heat Transfer to Stabilize Temperature Gradient

Using high-temperature resistant materials (such as PBT or LCP) as an insulation layer at the bottom of the switch serves as the first line of defense against heat. By designing air gaps, expanded terminals, or localized thickening above the terminals, the thermal resistance is significantly increased, delaying heat conduction to the contacts and springs.

For example, in a typical metal pushbutton switch, soldering temperatures may reach 260°C. By installing an LCP insulation base and creating a narrow air cavity around the terminals, measurements often show that the temperature at the contact area can be reduced by 60–80°C. The upper springs and movable contacts remain unaffected by rapid temperature rise and retain their elasticity.

The principle behind this design is to increase thermal resistance and extend the heat transfer path, keeping sensitive components in a lower temperature zone and maintaining stable performance.

2. Layered Structure Layout: Keeping Sensitive Components Away from High-Temperature Zones

Contacts and springs are extremely sensitive to heat. Therefore, pushbutton switches often adopt a dual-chamber structure: the lower chamber houses the terminals and solder pins, while the upper chamber contains contacts, movable parts, and springs, separated by an insulating partition.

For example, in a typical self-reset pushbutton switch, the dual-chamber layout allows the lower chamber to absorb most of the heat. Even when the solder pins reach 260°C, the temperature transmitted to the upper chamber is significantly reduced, usually remaining in the 130–150°C range. After soldering, key parameters such as travel, spring force, and tactile feedback remain stable without noticeable drift.

This design leverages the principle that heat dissipates with distance, using spatial separation to reduce thermal impact on sensitive components.

3. Independent Terminal Support: Preventing Travel Shift from Thermal Expansion

Metal terminals expand when exposed to high temperatures. If terminals directly support the contact frame or spring seat, this expansion can affect travel and tactile feedback. Many pushbutton switches use independent terminal support, isolating the terminals from the functional mechanism to minimize thermal expansion effects.

For example, in tactile switches, terminals are embedded in the base and supported by separate plastic posts for the contact frame. Even if the terminals expand slightly during soldering, the upper structure remains stable. Measurements show that travel changes after soldering are minimal, maintaining consistent tactile feedback.

This approach effectively decouples mechanical and thermal effects, preventing heat-induced displacement from affecting the upper mechanism.

4. Reinforced Plastic Structure: Preventing Deformation of Clips and Posts

Plastic components are highly susceptible to heat, especially clips, support posts, and positioning pillars. Softening of plastic under high temperature can cause loose clips or tilted contacts, affecting both tactile feedback and electrical performance. Design strategies include:

Using high-temperature resistant plastics (PBT, LCP, PA66GF)

Thickening key structures

Adding reinforcement ribs

Adjusting the relative position of solder joints and plastic surfaces

For example, in waterproof pushbutton switches, the base often includes cross-shaped or grid-shaped reinforcement ribs around the terminals. During soldering, this structure prevents warping or localized sinking of the base, keeps clips secure, and maintains contact positions, ensuring stable travel and feedback.

5. Conclusion

Pushbutton switches face high-temperature challenges during soldering. Key anti-reflow design strategies include:

Blocking heat transfer (insulation barriers)

Increasing thermal dissipation distance (layered structure)

Isolating thermal expansion (independent terminal support)

Enhancing temperature resistance and mechanical strength (plastic reinforcement)

These measures help reduce the impact of high temperatures on contacts, springs, and plastic components, maintaining consistent travel, tactile feedback, and performance, thereby ensuring reliability and lifespan after soldering.

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