Membrane Switches

About Membrane Switches and Membrane Switch Manufacturers Including: Graphic Overlays, Membrane Keyboards, Membrane Keypads, Metal Domes & Tactile Switches.

Membrane switches are thin and flexible electronic switches that have a similar function to electric switches. They are typically low-voltage and are continually replacing the older push-button types of switches. A membrane switch works by permitting the momentary opening and closing of a circuit. Activation of the circuit is accomplished by touching the preferred keypad button on the device that uses membrane switches. This causes the switch contacts to connect and permit continuity and current flow. The connection or circuit is broken as soon as the finger is released, making it a momentary switch.
 
Membrane switch manufacturers produce two main types of membrane switches: tactile and non-tactile switches. Tactile switches basically include all switches that have a metal dome or a polydome to achieve the “snap” action that is created by pressing. Non-tactile switches are all those that do not have these domes underneath the top layers. Membrane switches have many layers. The top layer, the graphic overlay, is the decorative layer that shows the visual functions of the membrane switch. After that is the membrane layer, which carries one of the poles of the switch or a conductive shorting pad. Next is the tactile layer which has the domes in tactile switches, the static layer that has one or more poles of the switch and then the rigid backer which is attached to the instrument housing. Despite these layers, membrane switches are very thin.
 
Membrane switches are used in many different applications in industrial and commercial fields. Everyday items like ATM keypads, cell phones, computer keyboards, organizers, gasoline pump keypads and microwave ovens use these switches. In industrial settings, membrane switches are integrated into numerous devices, like control panels, numerical keypads and graphical keypads. Examples of the wide variety of industries that use membrane switches include medical, toys, gaming, aviation, boating, banking, test equipment, appliances, computers and printers and public information panels.
 
The membrane switches produced by membrane switch manufacturers have many advantages over other switches. They are thin and compact, have a low cost, are versatile and durable, user friendly and are moisture and dirt resistant. Additionally, they come in many visually-pleasing styles and colors suitable for any need. However, one of the most common problems associated with membrane switches is inadequate sealing, which causes malfunction when contaminants like moisture, chemicals and extreme temperatures interfere. Because of this, it is important to have good water- and air-tight seals on membrane switches to ensure accurate performance. Some membrane switch manufacturers produce membrane switches with such good seals that they are even able to operate underwater, which increases the number of available applications for them.

Membrane Switches and Membrane Switch Manufacturers Images Provided by Douglas Corporation

Types of Membrane Switches including: Membrane Switch Manufacturers, Membrane Keyboards and Membrane Keypads.

• Graphic overlays are decorative covers that are placed over control panels.
  
• Membrane keyboards are flat surfaces with printed symbols and outlines rather than traditional moving keys.
  
• Membrane keypads are flat surfaces, rather than moving keys, that are activated with the press of a finger.
  
• Metal dome switches supply the snap and complete the electrical circuit. The domes are from pressed stainless steel or aluminum and come in various shapes, sizes and thicknesses.
  
• Non-tactile switches are membrane switches made without a snap action.
  
• Polyester dome switches are produced by embossing domes into one of the polyester layers in the construction, which results in a very durable tactile element with a little more movement than metal domes. This diminishes the quantity of layers in the assembly.
  
• Tactile switches are assembled to supply a positive snap-action reaction to pressure. They can be attained through polyester domes made in either the graphic or circuit overlay layer or stainless steel domes embedded in the membrane switch.

Membrane Switches Terms

Abrasion Resistance – The degree to which a membrane switch is able to withstand surface wear.
 
Actuation – This is the action of working a switch apparatus.
 
Actuation Force – The pressure necessary for collapsing the walls of the dome on a polyester, rubber or metal keypad.
 
Adhesion – The molecular attraction of one material to another. The strength of the bond is determined by the surface energy in each material.
 
Backing/Rear Adhesive – An adhesive applied to the back of a membrane switch for mounting purposes.
 
Breakdown Voltage – The minimum voltage at which the insulation between two conductors is destroyed.
 
Carbon Graphite Inks – The type of ink that consists of prepared suspensions of carbon black and is frequently printed over silver circuitry to diminish the potential of migration of silver. These are used for lessening costs when the conductivity of a metal base system is not necessary.
 
Conductivity – A material’s ability to allow electrons to flow.
 
Cross-Over – A conductor intersection insulated by dielectric material.
 
Dead Front – A cosmetic feature of a graphic overlay in which a button is only visible when backlit.
 
Dielectric – An insulating or non-conducting medium.
 
Dielectric Inks – Used for printing protective patterns on conductive printing to isolate selected regions from electrical contact with other conductors. This is used for cross-overs and tail insulation on membrane switches.
 
Dome Retainer – An adhesive layer made to hold metal domes in the keyswitch.
 
El Lamp – A slender device that illuminates large areas, typically used in LCD membrane switch backlighting and control panels.
 
Embedded LED – Procedure of integrating a surface mount LED into a membrane switch assembly.
 
Emboss – A way to supply a raised characteristic to accentuate key surfaces through mechanical and thermoforming of graphical features. This also permits an embedding of a surface mount of an LED inside the switch.
 
Gloss Level – The extent of shininess of a substrate, commonly identified in percentages.
 
Graphic Keypad –Control keypads that use graphics for button functions for navigation on machines or process operations. Typical graphics include arrows or symbols indicative of a machine process or operation.
 
Internally Vented – Switch openings connected to one another to seal the switch from moisture and other contaminants.
 
Key Height – A measure of the distance from the highest point of a key to the base of the keypad.
 
Light Emitting Diode (LED) – Embedded in membrane switch layers to illuminate the button.
 
Moisture Resistance – A material’s ability to resist the absorption of water from the air or during complete submersion.
 
Overlay – The decorative front layer of a membrane switch or control panel.
 
Over-Travel – The travel that is done by the rubber keyboard or metal dome after making contact with the circuit.
 
Pillow Emboss – Creating a raised surface in the graphic overlay over the membrane keypad area of membrane switches.
 
Pinout – The schematic that describes the circuit output requirements for membrane switches.
 
Pressure-Sensitive – Adhesive materials that bond after pressure without needing heat or solvents.
 
Rail Emboss – Produces a raised ridge circling the key area.
 
Screen Printing – Printing procedure that uses a stretch of mesh over a frame, permitting the use of a stencil to discriminately allow ink through. This is typically used for creating graphic overlays and membrane circuits.
 
Silver Inks – Finely-milled particles of silver suspended in various resin systems that produce conductive patterns on rigid and flexible substrates. This is a typical conductor material for membrane switches.
 
Spacer – A membrane switch adhesive layer that separates circuit layers to supply keyswitch openings, permitting the contact of conductors when depressed.