www.osram-os.com LEDs – Where to next? Colin Beale | 14th April 2015 | LLFY Seminar Manchester www.osram-os.com LED efficiency and performance: What are the limits? Visible LED performance and efficiency The influencing factors – Power dissipated (PD) = Forward current (IF) x Forward Voltage (VF) LED 'droop' – Flux vs. LED forward current is not linear, what if it was? Watts Current Chip LED power dissipation…... (PD = IF x VF) Internal quantum efficiency – How efficient is the process inside the chip (at the junction) at 'converting' electrons into photons? Chip extraction efficiency Package extraction efficiency – How many photons can escape from the package without getting internally reflected and absorbed by the chip and surrounding materials? Spectral power distribution (SPD) – How bright do our eyes perceive the emitted light to be? 3 LLFY Manchester – April 2015 | OS S NE | CB lumens Package – What proportion of the photons produced at the chip junction escape from the chip without getting reabsorbed? Chip theoretical limits: Thin GaN (UX3) 175mA / mm2 TJ = 85°C 3000K CRI80 4 LLFY Manchester – April 2015 | OS S NE | CB Visible LED performance and efficiency The influencing factors – Power dissipated (PD) = LED forward current (IF) x Forward Voltage (VF) LED 'droop' – Flux vs. LED forward current is not linear, what if it was? Watts Current Chip LED power dissipation…... (PD = IF x VF) Internal quantum efficiency – How efficient is the process inside the chip (at the junction) at 'converting' electrons into photons? Chip extraction efficiency Package extraction efficiency – How many photons emitted from the chip can escape from the package without getting absorbed by the chip and surrounding materials? Spectral power distribution (SPD) – How do our eyes perceive the emitted light? 5 LLFY Manchester – April 2015 | OS S NE | CB lumens Package – What proportion of the photons produced in the chip junction area escape from the chip without getting reabsorbed? Chip theoretical limits: Thin GaN (UX3) UX3 chip at 175mA / mm2 TJ = 85°C 3000K CRI80 6 LLFY Manchester – April 2015 | OS S NE | CB Forward Voltage (VF): Approaching the theoretical limit VF (350mA) V Deep Blue UX3 chip at 350mA / mm2, TJ = 25°C E(eV) = hc ÷ λ(m) hc = 1.24 x 10-6 7 LLFY Manchester – April 2015 | OS S NE | CB OSRAM OS Press release February 2015 “In view of the speed with which this first step has been implemented, we are confident that the improved process can be transferred to production by the summer of 2015. Any further reductions in forward voltage will then only be marginal owing to the laws of physics." Dr. Joachim Hertkorn – OSRAM OS 8 LLFY Manchester – April 2015 | OS S NE | CB LED 'droop' WPE (%) Impact of current density on efficiency at TJ = 25°C Current density mA / mm2 9 LLFY Manchester – April 2015 | OS S NE | CB OSRAM OS Press release September 2013 "Researchers at Osram Opto Semiconductors have now been able to demonstrate the physical effect responsible for the decrease in efficiency (droop) at typical operating current densities........" "This research provides semiconductor experts in academic institutes and in industry with a plausible roadmap for finding ways to suppress this effect." 10 LLFY Manchester – April 2015 | OS S NE | CB www.osram-os.com Cost per lumen New LED package designs The 5630 package Where to next? History – Introduced as a backlighting LED for displays and TVs. Proliferated in lighting when supply exceeded demand and soon became a 'lighting industry standard' Package size and shape – 5.6 x 3.0mm. Rectangular to suit display edge lighting applications. Large surface area to produce even light injection into light guides whilst keeping LED numbers and costs low Chip area vs. package area – At best 1:22 Package construction – Traditional over moulded silver plated lead frame with PPA or epoxy white outer moulding. Phosphor filled Silicone for volume conversion Package limitations – Reflectivity of white outer moulding reduces impacting luminous flux and accelerating lumen depreciation. Expensive due to volume of materials used 12 LLFY Manchester – April 2015 | OS S NE | CB QFN (Quad Flat No lead) Next generation LED lighting packages Why? – White outer moulding can be eliminated to increase lifetime – Reduces chip to LED surface area ratio – Reduces LED package material cost – Package extraction efficiency improved – Minimises LED footprint for high packing density What? – DURIS S2 A 2016 package with the same performance as a 5630 but with longer lifetime and lower cost – DURIS S5 and S8 Multi chip 3030 and 5050 packages with single and multiple chips – SYNIOS 2720 An LED package for industrial and automotive applications. Three chip sizes without changing package footprint – More to follow very soon..... 13 LLFY Manchester – April 2015 | OS S NE | CB QFN Multi chip packages 100 to 1800lm Why? – Minimise cost per lumen by reducing package cost – one package for multiple chips – Increase efficiency by driving chips at lower current, particularly two chip versions – Very cost effective alternative to small COB – Works well with reflectors and certain optics What – DURIS S5: 3030 package: Two series or parallel connected chips – DURIS S8: 5050 package: Six to ten series connected chips – DURIS S10: 7070 package: 18 and 24 chip arriving very soon..... 14 LLFY Manchester – April 2015 | OS S NE | CB www.osram-os.com Thank you for your time and attention Enjoy your day! We Shape the Future of Light Visit us @ www.osram-os.com
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