A membrane switch is an electrical switch for turning on and off a circuit. It differs from a mechanical switch, which is usually made of copper and plastic parts: a membrane switch is a circuit printed on a PET or ITO. The ink used for silk screening printing is usually copper / silver / graphite filled and therefore conductive.

The ASTM defines a membrane switch as a momentary switch device in which at least one contact is on, or made of, a flexible substrate.

Structure of a PET

A membrane switch usually consist of 2 - 4 layers of PET:

1. The first layer PET with circuit printed
2. Second layer acting as a spacer can be another PET film.
3. Third layer as a circuit closer.
4. The front panel, a PVC or Polycarbonate layer with button pattern and picture printed

Usage

Use in any electrical appliances in which the rebouncing feeling is not important. Classic applications includes microwave oven panel, air conditioner control panel, TV remote control etc. Tactile feedback of keys can be provided by embossing the top PET layer or embedding metal snap domes.