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Co Nguyen, GMN
By Co Nguyen | May 11, 2015
LED backlighted membrane switch

Last week we began a five-part blog series on backlighting.  Now that you have read the blog on getting started, we’ll jump into the first backlighting technology; discrete LEDs. 

Discrete LEDs are SMD (surface mounted) LEDs that are lit individually or together to illuminate a small area.  They are ideal for lighting small icons and indicators (e.g. a small circle that lights up next to some text to indicate on or off).  They are popular because of their low cost, thin construction and no impact on the tactile feel of buttons. 

However, there are situations when discrete LEDs are not a good choice.  The biggest issue is that they can create hot spots (bright areas) over or near the LED.  As a result, they aren’t a good fit when lighting large areas because the backlighting is often inconsistent with some areas brighter than others. 

One way to overcome hotspots, is through the use of an elastomer/rubber keypad for larger areas with discrete LEDs. For this reason, it is common to see discrete LEDs being used with elastomer keypads. Elastomer keypads allow for good even light across a large area using discrete LEDs. The draw back to them is it needs to be designed for from the beginning, adds cost, has a different feel than a polyester overlay and adds thickness to a part.

If you need to backlight a larger area and elastomer is not possible, you may want to consider light guide film or fiber optic weave technologies, which will be covered in our next two articles. 

Read our other blogs in this series: 

Co Nguyen, GMN
By Co Nguyen | May 5, 2015
Backlit touchscreen

This month we are kicking off a five-part blog series on backlighting.  The series will begin with an overview of how to approach a backlighting project and then each subsequent blog will review one of the four most popular options in backlighting: discrete LEDs, light guide film, fiber optic weave and electroluminescence.  

GMN frequently works with customers to integrate backlighting solutions into products including membrane switches, displays, and even branding pieces such as nameplates. We’ve developed applications for industries as diverse as appliance, medical, automotive, and more.

To establish the best backlighting solution without hotspots (uneven brightness, usually due to the location of LEDs) or light bleed (light coming through where it shouldn’t), the first step is to create a list of necessary requirements and assess the proposed design.  Start by asking these questions:

  • In what type of light will the device be used? Will the backlighting need to be visible in bright sunlight, the ambient light of offices, dark hospital rooms, etc.?
  • What needs to be backlit?  Is it a full screen, keypad, specific buttons, status or discrete indicators, a combination?
  • What colors will be used and where? 
  • What are the power requirements? 
  • What are the space constraints?
  • If there is a keypad or buttons, what type of tactile feedback is required? 

Based on the responses to these questions, you should be able to evaluate which backlighting solution, or combination of backlighting solutions could work with your device. 

Learn more about backlighting from one of our other blogs: