How does a membrane switch work?

The operator panels of many devices have membrane switch, which is widely used in electronic communication, electronic measurement, industrial control, medical equipment, automotive industry, smart toys, household appliances and other fields.

1.Introduction

With the multi-layered structure, membrane keypad made of flexible insulating material, which function are switching, indication and control. The function of membrane switch is realized by the vertical movement of the elastic membrane. Although the elastic film is deformed million times, the suitable material and the slight deformation(only 0.1-0.3mm) make it possible to have a long life. Membrane Switch have the characteristics of beautiful appearance, long service life, simple structure, easy installation and good user experience, which make it widely used in various industries, from household appliances to high-tech products, slowly replacing some of the touch switch and occupying a huge share in the market.

2.Structure

The membrane switch is mainly composed of 6 layers, which are the graphic overlay, graphic adhesive, upper circuit layer, adhesive separator(with metal dome), lower circuit layer and adhesive bottom layer.

1. 1. Graphic Overlay: Like the coat of membrane switch, it arranges the position of the function key and decorates the keyboard with different colors, patterns and shapes. The graphic overlay play an important role of identification and switch. Therefore, the materials of membrane switch must be highly transparent, high ink adhesive, highly elastic, anti-folding.
2. 
   
3. 2. Upper Circuit Layer and Lower Circuit Layer: Covering conductive material on the film, the upper and lower circuits are the electrical components, which is the key of the switch function. Their performance directly affects the quality of the switch. The upper circuit and the lower circuit play the connection role when the switch is closed. The thickness of circuit layer is generally within 0.05--0.175MM, and the most common is 0.125MM PET.
4. 
   
5. 3. Graphic adhesive, Adhesive Separator and Adhesive Bottom Layer: The materials of these three layers are adhesive. But they have own names and thickness according to the different they are in.

3.Principle of work

When the membrane switch in the normal state, the upper circuit layer and lower circuit layer are separate by the adhesive separator. Once the switch is pressed, the contact of upper circuit deforms and recombine with the lower to make the whole circuit conductive, which will sign to external instruments to achieve their corresponding functions.