Philips Lumileds Develops a Low-Cost, High-Power, Warm-White LED Package
With the help of DOE funding, Philips Lumileds has developed a low-cost, high-power, warm-white LED package for general illumination. During the course of the two-year project, this package was used to commercialize a series of products with correlated color temperatures (CCTs) ranging from 2700 to 5700 K, under the product name LUXEON M. A record efficacy of nearly 125 lm/W was demonstrated at a flux of 1023 lumens, a CCT of 3435 K, and a color rendering index (CRI) of more than 80 at room temperature in the productized package. In an R&D package, a record efficacy of more than 133 lm/W at a flux of 1015 lumens, a CCT of 3475 K, and a CRI greater than 80 at room temperature were demonstrated.
The new high-power LED is a die-on-ceramic surface-mountable LED package. It has four 2mm2 InGaN pump dice, flip-chip attached to a ceramic submount in a 2x2 array configuration. The submount design combines a high-thermal-conductivity ceramic core for die attachment and a low-cost, low-thermal-conductivity ceramic frame for mechanical support and carrying the optical lens. The LED package has a thermal resistance of approximately 1.25 kelvin per watt.
The efficacy performance goal was achieved through progress in high-efficiency royal blue pump LED development, thanks to active region design and epitaxial growth quality improvement. Improvement in extraction efficiency from the LED package was achieved by improving InGaN-die-level and package-level optical extraction efficiency. Phosphor system efficiency was improved by improving phosphor-package interactions.
The high-power warm-white LED product developed has been proven to have good reliability through extensive reliability tests.