Discrete LEDs are surface mounted LEDs that are typically either lit individually or together to illuminate a small area. They are ideal for lighting small icons and indicators. They are popular in many user interface designs due to their low cost and thin construction.
However, there are situations when discrete LEDs are not suitable for an application or design. The biggest issue is that they can create hotspots (bright areas) over or near the LED. As a result, they aren’t ideal when lighting larger areas because the backlighting is often inconsistent with some areas brighter than others.
There are a couple of ways to avoid hotspots in your design. The first way is through the use of an elastomeric or silicone rubber faceplate overlay (versus polyester/polycarbonate). Elastomer is a great conductor of light and therefore allow for excellent light dispersion across a large area using discrete LEDs.
If you prefer to use a polyester or polycarbonate overlay, CSI could also utilize side firing LEDs and light guide film to backlight a larger area. Other options are fiber optic technologies, or EL panels.