Membrane Touch Switches
The conventional membrane switch is made from two flexible substrates. However the term "membrane switch" is used, not because both substrates are flexible, but because the top substrate must be made from a thin and pliable material. This top substrate is referred to as the "membrane layer" or "overlay film".
When pressed with an actuator or finger the two poles of the switch make direct contact. Upon release, the poles immediately separate as the flexing membrane returns to its original open state. In meeting these conditions of "normally open, push to close, and immediate opening", the switch is considered to have "momentary action".
Tactiles or non tactiles: In general terms there are two types of membrane switches, tactile and non tactile. These can be constructed as a keyboard with or without a graphic overlay. Polyester is the most popular film used in the construction of membrane switches due to its durability and high temperature properties. Autostat is a range of heat stabilised polyester films which offer high stability specification and are designed to be screen printed with conductive, graphite and dielectric inks. Autostat is an ideal film choice for printing the membrane switch layers, for further details please see the Autostat product information section.
Hard coated polyester: MacDermid Autotype also offers a range of hard coated, 'Autoflex' and textured 'Autotex' polyester films . These films have been designed specifically for the graphics overlay film on membrane switches. Both product ranges are screen printable on the second surface, are solvent, chemical and scratch resistant on the first surface, and can be embossed giving over 5 million actuations during their life time. For further information on Autotex and Autoflex EB please see the relevant product information sections.