Solid-state Light Emitting Diodes (LEDs) produce light when an electrical current flows from the positive (anode) side to the negative (cathode) side. Like other solid-state devices, LEDs offer a long lifetime if used properly.
UV LEDs are one small, though important, part of a UV light source, but the rest of the system must also be taken into account when discussing the lifetime. This includes the internal control circuitry plus the cooling system to ensure the LEDs remain within their operating specifications, as well as the housing to protect the LEDs from environmental factors.
Phoseon’s patented and proprietary systems use thermal management, sealing techniques, optical enhancements, and control circuitry to maximize performance without sacrificing lifetime.
UV LED solutions produce light by generating a voltage to join positive holes with negative electrons emitting energy in the form of photons. If engineered correctly, these semiconductor devices last beyond 40,000 hours of operating time unlike traditional UV lamps. Traditional lamps produce light by generating an electric arc inside an ionized gas (typically mercury) chamber to excite atoms, which then decay, emitting photons.
Additionally, the European Commission (EC) through its Restriction on Hazardous Substances (RoHS) guidelines has continually monitored the rapid progress of UV LED’s capability. Many in the industry predict the EC will begin limiting traditional lamp usage, starting first with smaller systems then working towards larger systems in ensuing years.Combining energy generation of today’s UV LED light sources and the right formulation of UV curable resins, photoinitiators, and additives, it is possible to surpass current process capabilities for a variety of applications.
Phoseon works with a large number of third party formulators to develop materials specifically formulated for UV LED technology.
Two major factors that affect the lifetime of LEDs are temperature and current. As LEDs convert electricity into light, heat generates within the p-n junction, known as the junction temperature. For a diode to achieve maximum life expectancy, the junction temperature has to remain in a safe operating zone. The UV Power output of a diode increases with input current but decreases with junction temperature. At any fixed input current, the cooler the junction temperature remains, the more UV output the diode will provide.
The normal ‘failure mode’ of an LED is gradual degradation of the light output. Many commercial LED lighting systems define failure at 70% of the original operating output, also known as L70. Phoseon light sources are designed to ensure an L80 lifetime (80% of original output) of at least 20,000 hours, but have shown to provide L80 at as much as 70,000 hours. Figure is actual data gathered by Phoseon Technology of a continuously operated light source.