How does membrane switch work

A membrane switch is a multi-layer, flexible electronic component that integrates keys, panels, and circuits. Its primary function is to transform users' mechanical operations into electrical signals for device control. When a user presses the surface of the switch, the upper conductive contacts make contact with the lower circuit, establishing an electrical connection that triggers pre-programmed instructions (e.g., starting the device, adjusting parameters, etc.). Upon release, the contacts rebound and disconnect, completing a full cycle of the switch operation.

Membrane keyboard benefits

1. Compact and lightweight: The weight of a typical membrane switch ranges from a few grams to several dozen grams, making it very convenient to carry and disassemble.

2. Aesthetics: With the modern perfect screen printing technology and the perfect design, we can produce any patterns you need.

3. Sealing: By applying unique technologies, the membrane switch can be made to have functions such as water resistance, oil resistance, anti-pollution, and anti-static interference.

4. Excellent electrical conductivity: The circuitry of the switch can be printed with carbon paste, silver paste, copper-platinum paste, etc. The conductive layer can be folded freely; moreover, the resistance can be controlled to any value you desire, and with the use of a unique technology, the film switch made can even withstand tens of thousands of volts of high voltage without damaging its functionality.

5. Low cost: Some membrane switches can even be sold at a price of only a few cents. Compared with an electronic component product with such a wide range of functions, its price advantage is beyond the reach of other similar products.

6. Long service life: Due to the excellent insulation, heat resistance, anti-bending and high elasticity of the materials used in the membrane switches, as well as the fact that the patterns are printed on the reverse side, the silk-screen patterns will not be damaged. Therefore, the service life of membrane switches can generally reach more than three years.

Membrane keyboard internals

• membrane switch panel：

The panel layer is generally made of colorless and light-transmitting sheets such as PET and PC with a thickness less than 0.25MM, with exquisite patterns and texts printed on them. Because the main function of the panel layer is to serve as a logo and button, the selected material must have the characteristics of high transparency, high ink adhesion, high elasticity, and anti-folding properties.

• Spacer top adhesive：The main function of the rubber pad layer is to connect the panel layer and the circuit layer tightly to achieve the effect of sealing and connection. This layer is generally required to be between 0.02-0.05MM thick and has high adhesion and anti-aging properties. In production, special double-sided adhesive tape for membrane switches is generally selected. Some membrane switches require waterproof and high temperature resistance, so the rubber pad layer must also use materials of different properties according to needs.

• Dome retainer

The dome holder is located underneath the adhesive layer on top of the spacer. This layer is used to hold the metal dome or pads for shorting that are used to turn on the keyboard. This layer is usually made of thin and flexible PET.

• Spacer Adhesive

The spacer layer is located underneath the dome holder. This layer has vents to facilitate air circulation when the tactile keyboard is activated. This layer acts as a divider between the top and bottom circuits. This keeps the circuits disconnected until the keyboard button is pressed. The spacer is made of polyester with an adhesive layer on the front and back.

• 
  Circuit layer:

This layer uses high-performance polyester film (PET) as the carrier of the switch circuit pattern and uses a special process to screen print silver paste, carbon paste or gold paste on it to make it conductive. Its thickness is generally within 0.05-0.175MM. The most common is 0.125MM PET. In some cases, PCB or FPC (flexible printed circuit) is also used.

• Back adhesive layer

The use of back adhesive is closely related to the material to which the membrane switch is attached. Commonly used adhesives include ordinary double-sided adhesive, 3M adhesive, waterproof adhesive, etc. The material of the membrane switch and panel, in addition to being flat and printable, must also be flexible and highly elastic.

Membrane switch material

The material selection of membrane switches directly affects their durability, touch and application scenarios, and is mainly divided into the

following three categories:

1. Polycarbonate (PC)

Characteristics: temperature resistance range -30°C to +130°C, strong impact resistance (yield point force is about 60N/mm²),

can press a variety of textures (such as sand surface, glossy surface), high transparency, suitable for equipment with LCD display windows.

Application: industrial control panel, medical equipment buttons (requires high-frequency operation and high reliability scenarios).

2. Polyester (PET)

Characteristics: high temperature resistance (-30°C to +160°C), excellent resistance to chemical corrosion and mechanical wear,

the surface can be treated as a glossy or fine sand surface, and the conductive layer can use nano silver wire technology to improve sensitivity.

Application: car center console (high temperature resistance), precision instruments (need to resist oil and solvent environment).

Special type: Kotutai PH scratch-resistant PET film, suitable for equipment with high scratch resistance requirements.

3. Polyvinyl chloride (PVC)

Features: low cost, good ductility (suitable for cold pressing of three-dimensional patterns), but poor temperature resistance (≤60°C),

easy to age and become brittle.

Applications: low-end consumer electronics (such as remote controls), short-term signage panels.

To learn more about the types of membrane keyboards, read our article WHAT IS A MEMBRANE SWITCH?

Please note that membrane keyboards require customization at every step. At Higoal, we are available 24/7 to answer all your questions about membrane keyboards. We pay attention to every detail when producing your keyboard device to ensure that you get the perfect product you want.