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Membrane switch layers
Posted by Nancy Figueroa | july 2021
If you have used a microwave oven, washing machine or any devices with a keyboard you have been using a membrane switch and maybe you don't know, as final users we only interact with the devices but never we are involved in technical things, but... have you ask how its possible communication between us and the devices? How does it make a keyboard? What kind of materials contains it? Well, in this article we are going to talk about some features and briefly explain a basic example of a membrane switch.
What is a membrane switch?
A membrane switch commonly known as a flexible keyboard or membrane keypad is an interface between a machine and the user, the machine receives instructions from the user through the membrane switch.
A membrane switch has some thin flexible layers and can be tactile or non tactile, the first one has a metal dome to give the feeling of pressing a button, on the other hand, non tactile has no domes but often include led indicators.
Applications
Membrane switches are used in many devices and machines from different industries some of them are:
Home appliances(washing machines, microwaves oven, fridges, etc)
Medical equipment(instruments, beds, Monitoring system, etc.)
Food processing equipment (fryers, ovens, etc.)
Industrial machinery
Membrane switch components
A membrane switch can contain different materials like polyester, polycarbonate, conductive inks, metal domes, adhesives, resistances and leds; these materials are distributed on thin layers, commonly 4 to 6 layers.
Below we are going to explain an example of a membrane switch with a basic keyboard design.
Graphic Overlay
This layer contains the design, in this example is a keyboard, that is the interface that the final user interacts with.
Graphics can be printed by screen printing or digital printing.
Adhesive
This layer is used to join the graphic overlay layer and the dome retainer layer.
Dome retainer
This layer is used to keep fixed the position of the domes from the previous layer.
Spacer and metal domes
This layer contains the metal domes, are components that when pressed complete the circuit, and the spacer provides space for the dome under graphic overlay.
Circuit
This layer contains the circuit with the conductive paths, this can be printed by screen printing using a conductive ink.
Mounting Adhesive
This layer is used to facilitate the assembly of membrane switches with the final device or machine.
Additional components
Some components can be added are indicators leds, backlighting, or electroluminescence, it depends on the environment of the application, but if you like to read more about this please click here.