Principle and Process Flow of Thin-Film Switches

Release date:

2023-05-05

Have you ever heard of membrane switches in our daily lives? In fact, they are essentially the buttons used for switching functions. With today's advanced technology, switches have been redesigned into a new form, which is why they're called membrane switches. But do you know what principles underlie their operation? And do you understand what components make up a membrane switch? Next, let's explore together with the editors from Decoration Home—what exactly are the principles behind membrane switches?

A薄膜 switch is a multi-layered (planar, non-locking) type of key switch composed of an insulating material layer with a certain degree of elasticity, yet integrated with functional elements such as circuits, keys, indicator components, and instrument panels. Additionally, the operation of the薄膜 switch is achieved solely through the vertical deflection of the elastic membrane, which can withstand millions of cycles of movement—albeit with minimal amplitude during each cycle.

The membrane switch is an integrated operating system that combines button functions, indicator components, and a dashboard into a single unit. It consists of four key components: the panel, the upper circuit layer, the isolation layer, and the lower circuit layer. When the membrane switch is pressed, the contact point in the upper circuit deforms downward and makes contact with the electrode plate in the lower circuit. Once the finger is released, the contact point springs back, breaking the circuit and triggering a signal. Membrane switches feature a robust structure, elegant design, and excellent sealing performance, offering advantages such as moisture resistance and long service life. They are widely used in various fields, including electronic communications, electronic measuring instruments, industrial control systems, medical devices, the automotive industry, smart toys, and household appliances.

1. At the panel level, the panel layer typically consists of colorless and transparent sheets such as PET or PC, with a thickness of less than 0.25 mm, onto which exquisite patterns and text are screen-printed. Since this layer serves the purpose of providing identification and button functionality, it must possess characteristics such as high transparency, excellent ink adhesion, superior elasticity, and exceptional toughness.

2. The primary functions of the face adhesive and layer adhesive are to firmly bond the panel layer with the circuit layer, achieving a sealed connection. Typically, the thickness of this layer should be maintained between 0.05 and 0.15 mm, while also requiring high viscosity and excellent resistance to aging. Specialized double-sided adhesives designed specifically for film switch applications are commonly used in production. Additionally, certain film switches demand waterproof and high-temperature-resistant properties; therefore, the face adhesive must also be selected based on specific performance requirements.

3. The upper and lower layers of the control circuit use high-performance polyester film (PET) as the substrate for the switching circuit patterns, with a special process applied to shield conductive silver paste and conductive carbon paste, ensuring their electrical conductivity. Typically, the thickness ranges from 0.05 to 0.175 mm, with 0.125 mm PET being the most common choice.

4. The sandwich layer is positioned between the upper and lower circuit layers, serving to seal and connect. Typically, PET double-sided adhesive with a thickness of 0.05–0.2 mm is used. When selecting materials for this layer, it is essential to carefully consider the overall product thickness, insulation properties, tactile feedback during circuit button encapsulation, and sealing performance.

5. The type of adhesive used in the back adhesive layer is closely related to the material of the membrane switch being applied. Commonly used adhesives include standard double-sided tape, 3M adhesive, and waterproof adhesive, among others.

Introduction to the Main Working Principle of Capacitive Membrane Switch Products

One minute to learn about the advantages of membrane switches.