Electronics Protection - March/April 2013 - (Page 16)
Feature
Tips for Selecting and Designing a Membrane Switch
Brian Tovtin, Product Manager
APEM Components
Membrane switches are known for standing up to tough environmental conditions. Flexible and durable, the membrane switch
can be customized with embossing, backlighting, sealing and
electrostatic discharge (ESD) shielding. Membrane switches can be
made with either tactile or non-tactile feedback and they can be
integrated with LEDs and other components. To get the switch that
works for your application, follow these simple guidelines.
What is a Membrane Switch and Why Use It?
A membrane switch is a multilayered momentary switch consisting of a graphic overlay, top circuit
and bottom circuit. Pressing a key
activates the electrical connection.
Membrane switches are durable
and have a low profile, which allows for space-saving designs and
adaptability to each project.
Figure 1 is a graphic of a typical
membrane switch construction.
Over the past decade, the
membrane switch has grown in
popularity as designers are seeking
a more modernized look, avoiding the older, bulky switches, and
looking for ways to fit switches
Figure 1. Membrane switch
into smaller footprints in toconstruction
day’s equipment. The membrane
switch’s sleek, flat design with
modern LED lights is appealing with a less industrial look.
Which Overlay Material is Best for My Application?
The two most common materials used in making the graphic
overlay for membrane switches are polycarbonate and polyester.
All overlays begin as clear material, with the graphics printed on
the reverse side. A variety of finishes can be placed to visually
enhance the final membrane switch, including embossing, texturing or finish, varied colors, or backlighting. Table 1 is a guide for
selecting the right material for an application.
Table 1. Guide for Selecting the Right Material
16
A Word About Environmental Regulations that Apply
To Membrane Switches
Most industries now require RoHS compliancy. The RoHS
(Restriction of Hazardous Substances) Directive, most well known
as the lead-free requirement, also restricts the use of lead (Pb),
mercury (Hg), Cadmium (Cd), Hexavalent chromium (Cr 6+), and
polybrominated diphenyls (PBB and PBDE).
Ask the Right Questions – Follow These Steps to Get
The Right Design
Membranes switches are usually customized to fit each project
and there is a virtually unlimited range of styles, colors and switch
sizes. Don’t be afraid to ask a professional, use experts who will
advise you on your design. They can help you save money, create the most efficient membrane switch, and advise on graphic
aesthetics. To find the right switch for your application, use your
imagination, and ask yourself these questions. After establishing answers to the questions, create a drawing and schematic for
your membrane switch. This will give you a good starting point for
requesting an accurate quote.
Overlay or Membrane? – Decide if you need an overlay (just
the graphic) or a membrane switch (includes circuitry).
What size does the switch need to be? Determine the dimensions of the membrane switch and the total thickness that you
can have. Remember, if you don’t adhere to the space you have
available in your product, the membrane could be too high or
too low. To save space, the circuit can be designed in a matrix
layout (mapping of the traces using leads that run in both the “X”
(rows) and “Y” (columns) directions, resulting in fewer leads with a
greater number of connections.
Is a Back Plate or Bezel Involved? – Is there a back plate
or bezel to which the membrane will be applied? If so, ask the
manufacturer to quote this. It makes your sub-assembly more
complete and easier to install into your finished product.
Where will the switch be used? Consider the environment in
which the membrane will be used so you can design your membrane switch for maximum reliability. For example, if it will be
used outdoors, you will want a graphic material with UV protection. If it will be used in an environment where electrostatic
discharge (ESD) is present, consider incorporating a shield into
the design.
Are There Any Industry-Specific Considerations that Apply
To Your Design? – Some applications are simply harder on switches than others. A control panel for farm equipment may need
to be designed to IP67 standards to prevent water ingress along
with UV protected material to prevent fading. Industrial equipment used for manufacturing in a clean room may need a shield
to prevent ESD from shorting out. Medical equipment may need
to be protected with special antimicrobial material. For example,
APEM supplies Autotex AM, a new hard-coated polyester film with
Microban protection incorporated into the textured hardcoat during the manufacturing process.
What is the Mating Connector? – You can cut cost by using a
standard 2.54 mm pitch female connector.
Are There Specific Ergonomic Concerns – Consider embossing, which allows the user to locate keys easily. There are multiple
types of embossing, including pillow, rim, logo, LED and combina-
March/April 2013
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Table of Contents for the Digital Edition of Electronics Protection - March/April 2013
Electronics Protection - March/April 2013
Newer Technology Releases Next-Generation Power2U AC/USB In Wall Charging Solution
Specifiers of Enclosures for Components in Outdoor Applications: Be Aware of Material Selection Issues
How to Protect Electronic Circuits from Power Surges
Testing for Ingress Protection of Portable Electronic Devices
Increasing the Lifespan and Reliability of Electrical Components
From the Inside: The Configurable Plastic Enclosures Revolution
Tips for Selecting and Designing a Membrane Switch
HP Intelligent Series Rack Models Available for Networking and Demanding Server Requirements
Polyonics Antistatic Tapes Solve ESD Problems Before They Damage Static Sensitive Devices
OptoTherm Introduces IR LabMate Infrared Camera Solution
Falcon Electric Offers NEMA 3R/4 Enclosures with SSG UPSs
PEM SpotFast Fasteners Enables Flush Joining of Two Sheets
Industry News
Calendar of Events
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