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Custom Membrane Switches

We can integrate rubber keypads, metal sub-panels and housings for the most challenging panel assembly applications in the most demanding environments including medical, electronic, military/DoD, and industrial markets. 

Everything You Need To Know About
Membrane Switch Design and Manufacturing

What is a Membrane Switch?

A membrane switch is a momentary closure device used with a normally open circuit. They are called membrane switches because they are made up of flexible graphic and internal layers (or membranes) over a circuit printed on PET or etched on polyimide.

The layered nature of membrane switches allows a great deal of freedom for engineers to design and implement a very precise customer experience. Because of this flexibility, these man/machine interfaces are used across a wide range of industries, including medical, consumer electronics, military/DoD, and aerospace.

There are many parameters to consider in membrane switch design including the graphics, overlays, adhesives, and use cases.

What Are The Parts Of A Membrane Switch?

There are many parameters to consider in the development of membrane switches, including the design, overlays, adhesives, and use cases. They can vary a great deal from simple to very complex. The components of a membrane switch will vary with complexity, but all contain some combination of the following:

  • Graphic Overlays – The overlay is the top layer of a membrane switch and is the interface between the user and the machine.
  • Adhesive – There are numerous differences in adhesives. Selecting the proper adhesive for a membrane switch application requires consideration of environmental, surface, appearance and other performance requirements.
  • Embossing – There are three basic styles of embossing; pillow, rim and dome. Depending on shape and size, logos and multi-level shapes can be embossed.
  • Circuits – Circuits can be printed conductive silver ink, etched copper flex or printed circuit boards.
  • Surface Mount Devices – Membrane switches can be designed with embedded LEDs if required.
  • Shielding – Proper shielding is necessary to meet ESD, EMI or RFI requirements.
  • Tactile and Non-Tactile – Switches can be designed as tactile or non-tactile to achieve the desired product requirements.

Important Membrane Switch Considerations

Non-Tactile Switch with Silver Circuity

This three-layer switch, comprised of graphic overlay, a circuit spacer, and a screen-printed silver ink circuit, is the simplest type of membrane switch. Because they tend to be the least expensive option, they are often implemented as a cost-cutting measure in the overall design.

What Is Tactile Feedback?

Tactile feedback refers to a mechanism in membrane switches that utilizes touch for operation or activation. By using different materials and sizes for these domes, you can vary the actuation force required to activate the switch.

What are Copper Flex Membrane Switches?

Unlike screen-printed silver, copper flex circuits are manufactured by laminating copper to an underlying substrate, and then etching that substrate in a way that leaves specific conductive traces.

LED Backlighting Options for Membrane Switch

Designing the right backlighting technology into a membrane switch assembly can help deliver a superior user experience. A wide variety of backlighting options are available, allowing engineers to precisely manage light quality, color, intensity, and coverage, so it is important that your selected switch manufacturer understands the advantages and disadvantages of these different techniques.

Why Use Silicon Rubber Keypads?

More complex user interfaces require higher-density, more miniatured components. In these situations, printed circuit boards (PCBs) and printed circuit board assemblies (PCBAs) are often brought into play.

Visual Considerations in Membrane Switch Design

Choose a vendor that has a computerized color formulation system to achieve consistent results from printing to printing. Good suppliers can color match to the Pantone Matching System, Federal Standard Guide, a color swatch, or to your bezel. Calibrated light booths and/or digital densitometers are then used to inspect and measure results to ensure conformance.

Durability in Harsh Environments

More complex user interfaces require higher-density, more miniaturized components. In these situations, printed circuit boards (PCBs) and printed circuit board assemblies (PCBAs) are often brought into play.

How To Install A Membrane Switch

Very carefully cut and remove 1/8” of adhesive liner on the bottom side of the membrane switch.

Turn the membrane switch over and pass the flex cable through the tail exit slot of the unit the switch will be mounted to. With precision, position the membrane on the back support recess and adhere the membrane switch to the surface of the unit with the exposed adhesive.

Position the membrane with an angle around 30 degrees, peel off the rest of the adhesive liner keeping the set up the same as before.

Gently laminate the membrane switch starting from the side with the removed adhesive liner, using a soft roller, apply slight pressure as rolled across the top surface of the membrane switch.

Lower the angle of the membrane switch gradually and roll out the air.

The lamination is completed. You can bend the circuit slightly without damaging the switches but use extreme caution so that the metal domes/buttons are not inverted then becoming non-functional.

How to Install a Membrane Switch

JN White Membrane Switch Testing Process

Common Membrane Switch Installation Errors

Glossary

Abrasion Resistance

Ability to resist surface wear.

Accelerated Aging

A test methodology that simulates long term environmental effects.

Actuation Force

Force required to collapse a metal or polyester dome.

Adhesion

The molecular force of attraction between unlike materials. The strength of attraction is determined  by the surface energy of the material. The higher the surface energy the greater the molecular attraction, the lower the surface energy the weaker the attractive force.

Ampere (Amp)

A standard unit of current. Defined as the amount of current that flows when one volt of EMF is applied across one ohm of resistance. An ampere of current is produced by one coulomb of charge passing a point in one second.

AQL

Acceptable quality level.

ASTM

American Society for Testing and Materials.

AutoTex

Trademark for Autotype Industrial Films polyester graphic overlay film.

Bond Strength

Amount of adhesion between two surfaces.

Breakdown Voltage

The voltage at which the insulation between two conductors is destroyed.

CAD/CAM

Computer aided design/Computer-aided manufacturing.

Capacitance

The property of conductors and dielectrics which allows the storage of an electrical charge when voltage is applied. ASTM F1663-95

Carbon/Graphite Inks

Specially prepared suspensions of carbon black; these systems are employed for lower cost when the conductivity of a metal base system is not required. Often printed over silver circuitry to reduce the potential for silver migration, also employed for printed resistors.

Certificate of Compliance (C of C)

A certificate generated by a quality control department confirming that the product being shipped meets the manufacturing document.

Conductivity

The ability of a material to allow electrons to flow measured by the current per unit of voltage applied.

Contact Bounce

Intermittent contact opening and closure that may occur after switch operation. See ASTM F161-95

CSA

Canadian Standards Association.

Current, Alternating (AC)

An electric current that periodically reverses direction of electron flow. The rate at which a full cycle occurs in a given unit of time (usually a second) is called the frequency of the current.

Current, Direct (DC)

Electrical current whose electrons flow in one direction only. It may be constant or pulsating as long as it’s movement is in the same direction.

Dead Front

Cosmetic feature of a graphic overlay allowing for a display feature to be visible only when backlit.

Die Cutting

Process for blanking or cutting sheet or roll materials to predetermined shapes for membrane switch components, graphic overlays and labels.

Dielectric

An insulating (nonconducting) medium.

Digital Printing

Refers to methods of printing from a digital-based image directly to a variety of media. It usually refers to professional printing where small-run jobs from  desktop publishing and other digital sources are printed using large-format and/or high-volume laser or inkjet printers (Wikipedia)

Dome Retainer

An adhesive layer designed to hold metal domes in place

EL Lamps

A thin (.010”-.025”) illuminating device employed to light large areas, commonly used in LCD, control panel, and membrane switch backlighting (Electroluminescent)

Embedded LED

The practice of encapsulating a surface mount LED into a membrane switch construction.

Emboss

Demo content

Emboss, Rail

 

Emboss, Pillow

 

EMI/RFI/ESD Shield

 

Fiber Optic Backlighting

 

Flat Flex Connector [FFC]

 

Font

 

Gloss Level

 

HB-94HB

 

HSE

 

Insert Legend (Insert Graphics)

 

Internally Vented

 

ISO (The International Organization for Standardization)

 

ITO (Indium Tin Oxide)

 

Key Height

 

Key Travel

 

LED

 

LEXAN

 

LSE

 

Membrane Switch

 

Metal Dome

 

Moisture Resistance

 

MP

 

Munsell

 

MYLAR

 

Nema

 

Non-tacktile

Membrane switch constructed without snap action.

OHM

The electrical unit of resistance. The value of resistance through which a potential difference of one volt will maintain a current of one ampere.

Overlay

Decorative front layer of a membrane switch or control panel.

Over-Travel

The additional travel of a rubber keypad or metal dome after making contact with the circuit.

Pantone Matching System (PMS)

Color matching system originally developed for the offset printing industry, commonly used in the membrane switch industry for its broad acceptance, range of colors and ease of use. Over 1000 colors are cataloged.

PCB

Printed circuit board.

Pinout

The schematic describing the circuit output requirements for a membrane switch or other electronic device.

Polycarbonate

Graphic overlay film widely used for control panels

Polyester Dome

A spherically formed element in polyester circuit material to provide tactile response in membrane switches. Usually the domes are formed in arrays or sets to match the key configuration of the keypad. Polydomes.

Polyester

Bi-axialy oriented polyethylene terephthalate film. (PET)

Pressure-Sensitive

Adhesive materials which bond with the application of pressure alone and do not require activation by heat or solvents.

Resistance

In DC circuits, the opposition a material offers to current flow, measured in Ohms. RFI Radio Frequency Interference.

Screen Printing

Printing process using a mesh stretched over a frame allowing ink to selectively pass through by using a stencil. The process most commonly used for producing graphic overlays and membrane switch circuits.

Second Surface Printed

Inks are applied to the non-exposed side of the film to allow for the film to protect the inks from scratching or damage.

Selective Texturing

The creation of surface effects on matte or gloss films normally applied using the screen printing process.

Silicone Rubber

Rubber made from silicone elastomers and noted for its retention of flexibility, resilience and tensile strength over a wide temperature range.

Silver Inks

Specially prepared suspensions of finely milled silver particles in a variety of resin systems are used widely to produce conductive patterns on flexible substrates.

Spacer

An adhesive layer of a membrane switch used to separate circuit layers and to provide key openings allowing for conductors to contact each other when depressed.

Spectrodensitometer

A densitometer that makes use of spectral data, providing densitometric readings at discrete spectral intervals (Federal Agencies Digital Guidelines Initiative)

Static Shield

Printed conductor pattern or separate aluminum or copper film employed in membrane switch designs to reduce the effects of static discharges.

Steel Rule Die

Consists of a .750-.875 thick die-board (plywood construction) with .937” high knives inserted into laser cut groves.

Tactile Switch

A switch or switch assembly providing a positive snap-action response. The response can be achieved through the use of stainless steel domes embedded in the membrane switch, or polyester domes formed in either the circuit or graphic overlay layers.

Thixotrophy

The property of a coating or ink, which has a low viscosity when agitated, but thickens when agitation ceases.

Visible Light Transmission (%)

The ratio of the amount of total visible solar energy (370-780 nanometers) that is allowed to pass through a filter, to the amount of total solar energy falling on that filter.

Watt

A unit of electrical power. One Watt is equivalent to the power represented by one ampere of current with a pressure of one volt in a DC circuit.

Why JN White™?

At JN White™, we have developed deep expertise and experience as a membrane switch supplier – an expertise that our customers have come to rely on when they are trying to design and implement specific user interface objectives. Integrating features like those noted on this page, we design and develop for the most challenging panel assembly applications in the most demanding environments, including medical, electronic, military/DoD, and industrial markets.

Because there are so many parameters to consider in the design of membrane switches (including the graphics, overlays, adhesives, and use cases), we often work with customer engineering teams early in the development process to ensure feasibility and optimal outcomes.

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membrane switch challenge?

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