Embedded LED PCBs: What are They and What do They do?

A Definition of Embedded LED PCB’s

Light emitting diodes (LEDs) are semiconductor diodes. LEDs belong to the group of electroluminescent luminaries, and they generate light by recombining charge-carrier pairs in a semiconductor with an appropriate energy band gap. LEDs are utilized in both industrial and consumer markets because of their low operating voltage and power, compact sizes, and extended lifetime and stability. One of their most appealing characteristics is their ability to generate light without generating much heat, which makes them safe for daily operation. Their characteristics are the main reason that LEDs are embedded in printed circuit boards (PCBs). The LEDs are dependable and efficient enough for PCB applications.

Embedded LED PCBs often feature single or bi-color LEDs in blue or white. They serve as indicator lights, especially in non-tactile membrane switches. Embedded LED PCBs frequently are used under polyester graphic and under rubber keypads as well.

Embedded LED PCBs and User Interfaces

Printed circuit boards often are used for the lower circuit in a membrane switch, especially because they provide structural
display windows with LED indicators. These often easily integrate into the PCB membrane switch design, but there are a few choices when it comes to deciding which type of LED to use.

• Single point and block LEDs – Single point and block LEDs are the most versatile. They function well with nearly any type of material surface finishes. Keep in mind that for greater light diffusion, it is better to use a matte or textured surface. It’s also important to remember that while LEDs cannot come through a tactile switch’s active area, they can be graphically manipulated to appear as though they are part of the switch.
• Integral, or surface mounted, single point LEDs – Integral, or surface mounted, single point LEDs may be mounted on the bottom layer lower circuit. A wider range of colors is available for these types of LEDs, including bi-color. It is fairly simple to allow for termination from the same connector tail as the switches themselves if you emboss the graphic layer to accommodate the LEDs. Keep in mind that you do not need to emboss the graphic of you provide the LED termination on a separate tail. 

Benefits of Embedded LED PCBs 
As electronics get smaller and thinner, it is an advantage to use LED membrane switches because
it allows for simpler product sourcing and final assembly. These embedded LED PCBs are best suited for low-light environments, consumer devices, appliances, medical devices, light to medium industrial applications, and some aviation and marine applications. No matter the application the benefits of the embedded LED PCB are many, including:

• Lightweight, low profile
• Lower cost backlit membrane switch
• Dust and moisture resistant
• Easy to integrate into complex interface assemblies
• Efficient low power consumption
• Available in a wide variety of sizes, colors, and intensities
• May be used in silver flex membrane switches and copper flex membrane switches

When the LED is embedded in the PCB, it is easier to then combine the LED membrane switch with keypads, touch screens, and other types of membrane switches. The embedded LED PCBs yield more freedom of design, even when creating complex back-lit switch assemblies. The thinness of an LED membrane switch helps to reduce the overall footprint of those complex switch interfaces. Oftentimes, designers and engineers choose embedded LED PCBs when revising and upgrading products.
Overall, embedded LED PCBs deliver the most affordable backlighting for membrane switches. They sometimes are a better choice for backlighting small icons and symbols, as uniform backlighting of larger icons and symbols is not as easy to achieve with embedded LED PCBs.