Common Faults and Maintenance Guide for Membrane Switches (Part 2)

Release date:

Www.zdxtt.com

2021-06-15

Thin-film switch Common Faults and Maintenance

3. The button fails to return to its original position and completely loses its elasticity.

The tactile membrane switch comes in two forms: with a reed contact (reed switch) and with an upper-circuit bubble. When the button loses its elasticity, it means that either the reed contact or the bubble inside the button has deformed, resulting in a loss of responsiveness. In particular, membrane switches equipped with reed contacts are highly susceptible to deformation under heavy pressure during packaging, transportation, and storage, which can weaken the tactile feedback and eventually lead to a complete loss of elasticity.

Another scenario involves secondary assembly during the production process, leading to deformation of the spring clips. Similarly, if users fail to properly adhere the film switch with spring clips during the initial installation and instead tear it off and reapply it later, the spring clips will also become deformed. Therefore, film switches equipped with spring clips must be assembled in one seamless step, both during production and installation.

The upper circuit features a blistered membrane switch (in some cases, the surface panel itself is blistered). To prevent deformation caused by excessive pressure at any stage, care should be taken to avoid applying heavy loads. Additionally, avoid using the device under high-temperature conditions, as thermal expansion and contraction can lead to softening of the keycaps, ultimately resulting in a complete loss of elasticity. Furthermore, uneven bulging of the upper circuit can significantly impact the consistency of keypress force. To address this issue, ventilation holes have been strategically incorporated into the adhesive layer and interlayer air channels, ensuring more uniform keypress force while also preventing the keys from failing to rebound properly.

The tactile feel of a membrane switch varies depending on the panel material and its thickness. In terms of construction—specifically, how the dome-shaped contact layer is fixed within the same panel—the buttons generally exhibit good elasticity and a strong rebound. However, it's important not to aim for a brittle feel, as excessive brittleness can lead to deformation. Instead, the switch should maintain a slightly heavier tactile response. Overseas membrane switches (e.g., those from Germany) may require more effort to press, yet customers often appreciate this characteristic for its premium quality.

4. Light-emitting diode fails to light up due to leakage current.

LEDs are soldered onto the circuit of a membrane switch to form a unified assembly, which is now widely used. In the design of membrane switches equipped with LEDs, an electrostatic shielding layer should be incorporated. Green, blue, and white LEDs are particularly susceptible to electrostatic discharge, leading to potential malfunctions. Therefore, it is crucial to protect these LED-equipped membrane switches from static electricity throughout the entire manufacturing process—especially during winter months. Prior to shipment, each LED must undergo a leakage current test to ensure proper functionality. It's important to note that LEDs paired with resistors tend to fail quickly under such conditions.

On the other hand, thin-film switches equipped with light-emitting diodes are prone to burnout if the current exceeds a certain threshold. Therefore, it is essential to incorporate resistors into the design to limit the current flow effectively.

Introduction to Common Faults and Maintenance of Membrane Switches (Part 1)

Introduction to Film Switch Types