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Membrane Keypads

Membrane keypad touch switches offer product designers and engineers a customised and flexible user interface for electronically controlled products which are compact, reliable, cost effective and assembly friendly. Permark have a solution to suit your next product design. Permark are specialists in Membrane Keypads Switches.

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Membrane Features

Permark’s membrane keypads can feature the following:

  • Stainless Steel Tactile Inserts – for a positive “click” when buttons are pressed.
  • Dome embossed buttons with no inserts – for a tactile feel when buttons are pressed
  • Embossing of logo’s and buttons – either “rim” or “Pillow” embossing for buttons.
  • LCD Windows – can be a high gloss window on an otherwise “matt” finished overlay.
  • Embedded LED’s available in white, red, green, orange, blue.
  • Transparent tinted LED windows – any colour.
  • “Dead front” Windows – invisible until they are back lit. (like seatbelt signs in most cars)
  • ZIF or Female Clinch Connectors for tail termination. ( tail pitch of 2.4′ or 1mm).

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Award winning membrane keypad, showing embossed buttons, and a small black transparently tinted display window. Bright, vivid colours and perfect print registration were achieved by reverse screen printing onto a clear hard coated polyester film.

Lighting Options

Electroluminescent Lighting (EL)

EL lighting may be incorporated into membrane switches by a printing process, which allows the designer great flexibility in customizing the design to suit a specific application. Phosphorescent material is printed between two conductive electrodes. When AC current is applied to the electrodes, the current causes the phosphor to emit light. EL technology has a definite life cycle, and in a typical application the half life will be about 3000 hours.

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EL panels are driven by an AC source (usually 120AV at 400Hz). An inverter derives AC from DC supply of 5-24VDC. Higher frequency give a higher light output, however, increased light intensity reduces lifetime. Integration of a light sensor or timer within the circuit to switch the panel on and off can extend the effective life of the panel. Electroluminescent Lighting Panels are sensitive to moisture, humidity, and UV light, so these things need to be factored into the design of the panels.

Lumitex Woven Fibre Backlighting

Lumitex is a patented woven fibre optic sheet found in applications such as LCD backlighting, Membrane switches, and machine vision applications.

A computer controlled loom produces a sheet of precisely laid optical fibres. The fibres are then laminated into layers to form the backlighting panel. The finished panel is thin, and emits no heat, is EMI free and provides superior brightness, longer life, and excellent design flexibility compared with other backlighting technology. Power requirements from as low as 10-20mA at 2 VDC and no inverter. The light source is LED, or gas filled bulb or halogen and is simple to change.

Above: Fibre optics bundled into a round ferrule where a light source is then attached.

Membrane Keypad Construction

Membrane keypad construction will typically be either “single layer” or “double layer” construction., depending on the features required. For single layer keypads, one contact layer is usually printed on the reverse side of the graphic overlay panel. For double layer construction, the top circuit is printed on a separate layer. In determining which construction should be used, consideration for the number of buttons in the unit, whether a humidic seal is required, are tactile inserts and/or embedded LED’s required, and what environment will the keypad be subjected to, are taken into account. Permark’s technical and sales staff can advise on solutions to suit your specific design.

Layers of polyester (PET) film are laminated to a spacer with adhesive. Conductive silver ink circuits are printed onto the printed circuit layers. Finished membrane thickness is usually 1-2mm. The material for the graphic overlay is selected to withstand the environment it will be subjected to – for example to resist harsh environments such as high moisture, high UV and chemicals. The switches can be built into the keypads by insertion of stainless steel tactile discs or embossing of the overlays. Permark can supply either Female Clinch or ZIF connectors.

Applications for Membrane Keypads

Membrane switches are a cost effective alternative to conventional mechanical switches and as such are used extensively in plant and equipment that is electronically controlled and requires a user interface such as:

  • Eftpos Terminals and cash register keyboards.
  • Electric Fence Controllers
  • Petrol Station Pump Keypads
  • Hand held instruments
  • Weighting & Measuring Equipment
  • Industrial machines
  • Alarm control panels

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Quality Testing of Membranes

Quality testing is conducted both in-line and prior to despatch for all products manufactured by Permark. In addition to standard tests for things such as ink adhesion, resistance testing of printed circuits and density tests for inks, specific testing of Membrane Keypads is also carried out, including:

  • Button Actuation force (when specified)
  • Switch Actuation life (mechanical finger)
  • Loop Resistance (all work)
  • Continuity / High Resistance test (every switch)

Permark is an ISO 9001:2009 certified manufacturer.

Membrane Keypad Quote Request.

The beginning of design stage of a product development is the best time to contact Permark. Issues such as recess depth of plastic housings that the membrane may fit into and the tail slot position and dimensions can be determined.

Information that is helpful in providing an accurate quote will include the following:

Company Contact Details

  • Quantity Required?
  • Dimensions of membrane?
  • Tail Length?

Operating Voltage

  • Operating Voltage (V)?
  • Operating Current (mA)?
  • Max Loop Resistance (ohms)?
  • EMI Shielding required?
  • ESD Shielding required?

Contact Configuration

  • Matrix?
  • Common bus?
  • Combination?

Tactile Switching

  • Stainless Steel Inserts?
  • Inserts & Emboss?
  • Emboss Only?

Termination

  • None?
  • Clampon Female?
  • ZIF?

Usage

Estimate of daily key actuation

  • Low (0-15 actuations per day)
  • Med (30 + actuations per day)
  • High (100 + actuations per day

Environment

  • Outdoors?
  • Humidic Sealing?
  • Chemical or toxic exposure?

Overlay

  • Number of colours?
  • Material Finish (Gloss or Matt)?
  • LED Display or Windows?
  • Transparent Tints or Dead fronts?

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