WHAT ARE MEMBRANE SWITCH KEYBOARDS?
Is there a more iconic piece of hardware associated with computers than the keyboard? Born from the lowly typewriter, most keyboards today still have the QWERTY key layout, designed to slow a typist down so the keys would not jam together. Whether you type 60 WPM or punch it one finger style, your keyboard must do its job day in and day out without fail. Did you know a membrane switch is hidden within the keyboard you are using right at this moment?
Membrane switches are ideal for use in a keyboard application for many reasons, including the low cost of manufacturing so many switches in such a tight proximity, low material cost, the high reliability rate, and the need for sealing out the occasional liquid bombardment of soda or coffee. The membrane switch resides directly under the plastic key caps which are there mostly for tactile feel. The plastic cap acts as a plunger and pushes down on the membrane creating a momentary contact of the membrane layer.
The membrane itself is made of layers of polyester with printed conductive traces that is die cut and folded three times. The middles layer of the tri-fold has the spacer holes and this is what makes it a membrane switch. The three layers are bonded together with ultrasonic welds, eliminating the need for costly adhesives. The membrane layer typically connects to the wire harness by means of a Z axis connector and a small circuit board all held together by the plastic housing which makes up your keyboard.
MEMBRANE KEYBOARD SWITCH ASSEMBLY
A membrane keyboard switch assembly can also be incorporated into molded rubber rather than the hard plastic keycaps. This useful combination works well when making custom keyboards of all different shapes, sizes and colors. Rubber keyboards can be used in extreme environments in which normal keyboards would fail. Typical high volume keyboards for computers are designed around low cost and are generally not sealed. Membrane keyboards applications used in hostile environments include medical devices, CNC mills, and irrigation controllers.