Backlighting technologies: discrete LEDs (part 2 of 5)

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: