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 www.ElectronicsProtectionMagazine.com http://www.ElectronicsProtectionMagazine.com

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

Electronics Protection - March/April 2013