Patterned sapphire substrate (PSS) technology is an effective approach to improving efficacy and reducing cost of LEDs and has gained wide use in mid-power LEDs. With the help of DOE funding, Lumileds has developed and industrialized PSS and epitaxy technology for high-power flip-chip LEDs, to bring these benefits to a broader range of applications and accelerate adoption.
The objective of this project was to establish and industrialize a low-cost PSS high-power LED fabrication process with demonstrated epitaxial growth of InGaN layers capable of producing best-in-class lm/$ and lm/W performance when combined with low-cost packaging methods. Lumileds’ InGaN high-power LED architecture involves fabricating a thin-film flip-chip device (TFFC) supported by a metalized ceramic submount, which entails a series of steps to enable efficient light extraction. The alternative approach developed by this project involves leaving the InGaN layers on their sapphire substrate to simplify the die fabrication process and enable simpler packages that utilize the sapphire as mechanical support, thereby reducing the LED package cost.
PSS geometries were designed for highly efficient light extraction in a flip-chip architecture and high-volume manufacturability, and corresponding sapphire patterning and epitaxy manufacturing processes were integrally developed. Concurrently, device and package architectures were developed to take advantage of the PSS flip-chip die in different types of products that meet application needs. An efficacy of 131 lm/W was demonstrated at a CCT of 3000K with CRI > 80, and a PSS-based chip-scale package white LED was achieved with 26% lower cost than a TFFC LED with the same die size. The developed PSS and epitaxy technology has been fully implemented in manufacturing and incorporated into illumination-grade LED products that have been successfully introduced to the market, including LUXEON Q and LUXEON FlipChip White. (May 2016)
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