The colour of white LEDs can be very inconsistent, although manufacturers have narrowed their binning ranges. White LEDs with the same correlated colour temperature can have different colour tints perceptible to the human eye.
Fabricating LEDs is a complex high-temperature process involving the growth of crystalline layers across the surface of a semiconductor wafer. The quality of these layers determines the properties of the LED. Reproducibility is difficult to achieve across a single wafer, or from wafer to wafer, or from day to day. Some LEDs processed from a wafer will yield high-quality devices, while others from the same wafer will have much lower quality and will end up in low-end applications such as children’s toys.
LEDs open up many new design options, some of which were previously inconceivable.
LEDs do not contain mercury and in many cases steps are being taken to replace lead-containing solders (used mainly to fix LEDs to circuit boards) with the lead-free material, in line with European directives. The energy-efficient nature of LEDs also makes them environmentally friendly.
LEDs are low-voltage light sources, generally requiring a constant DC voltage or current to operate optimally. Designing and implementing an effective driver is key to obtain all the benefits of LEDs.
In general, there is a gap in understanding between the LED manufacturers and the lighting community. The former group do not include the latter in their product development activities and do not provide information that is directly comparable to the information available for competing for light sources. The latter do not understand a huge amount about LEDs and are unfamiliar with crucial issues such as thermal management, or why white LED performance is not highly consistent.