UV-LED Module Design with Maximum Power Density Manfred Scholdt 1, Christian Herbold 1, Marc Schneider 2, Cornelius Neumann 1 1 e 2 Institute for Data Processing and Electronics e (LTI) KIT Universität des Landes Baden-Württemberg und nationales Forschungszentrum in der Helmholtz-Gemeinschaft www.kit.edu
High Power and UV-LEDs? High Power? LEDs? Wavelength in UV? 2 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Outline Motivation Die selection and module parameters Thermal path design Optical Measurements Summary and Outlook 3 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Motivation Field of UV application Paints, coatings, adhesives, printing or water treatment LED advantages over mercury discharge lamps: Prevention of IR radiation Narrow spectrum Instant-On Long life rating Reduced power requirements 4 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Die selection Which wavelength? gallium nitride band gap LED cluster emitting in UV range λ < 400 nm Market survey: output power sufficient for λ 365 nm 5 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Die selection Highest output power density Packing density : Packaged chips Nichia: ~ 2 dice/cm 2 Bare LED chips: Nichia NCSU033A Nichia NCSU034A Semileds SL-V-U40AC Semileds: ~ 44 dice/cm 2 packaged LED chips bare LED chips 6 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
High Power UV-LED-Module Prototype LED chips: SemiLEDs SL-V-U40AC (395 nm, 275 mw @ 350 ma) Most compact layout: narrow rhomboid pattern 98 LED chips on 2.11 cm² Emitting area: 0.92 cm² fill factor = 44% Electrical input power: up to 188 W corresponds to 88 W/cm² thermal management! 7 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Thermal management Thermal simulation of the prototype Input power: 134 W* Approx. 150 C *Datasheet value: 3,3 V, 500 ma, 17% efficiency, 98 LED chips Simulation with FloTHERM 8 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Thermal Path Thermal model LED junction LED substrate LED bonding Bonding layer PCB Thermal grease Heat sink R th 0.4 K/W R th 8.7 K/W R th 12.1 K/W R th 17.5 K/W 1. Prototype LED junction LED substrate Ag adhesive AgPt thick film printing Al 2 O 3 ceramic conductance paste Heat sink 9 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Thermal Path Thermal model LED junction LED substrate LED bonding Bonding layer PCB Thermal grease Heat sink R th 0.4 K/W R th 1.3 K/W R th 12.1 K/W R th 1.4 K/W 2. Prototype LED junction LED substrate Tin solder AgPt thick film printing Al 2 O 3 ceramic Liquid metal Heat sink 10 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Prototype 1 11 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Prototype 1 2 12 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Optical Measurement 1. Prototype Ag adhesive thermal conductance paste Max radiance: 12.9 W/cm 2 Maximum temperature: 160 C 13 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Optical Measurement Ag adhesive liquid metal LED junction LED substrate Ag adhesive AgPt thick film printing Al 2 O 3 ceramic Liquid metal Heat sink Max radiance: 17.6 W/cm 2 14 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Optical Measurement Ag adhesive liquid metal Ag adhesive liquid metal Tin solder thermal conductance paste LED junction LED substrate Tin solder AgPt thick film printing Al 2 O 3 ceramic conductance paste Heat sink Max radiance: 17.6 W/cm 2 Max radiance: 14.9 W/cm 2 15 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Optical Measurement 2. Prototype Tin solder liquid metal Max radiance: 24.6 W/cm² Maximum temperature: 82 C 16 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Radiance Prototype 1 @ 400 ma: 12.9 W/cm² Prototype 2 @ 400 ma: 20.1 W/cm² @ 600 ma: 24.6 W/cm² 17 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Optical Efficiency Prototype 1 @ 250 ma: 28.5 % @ 500 ma: 17.0 % Prototype 2 @ 200 ma: 36.2 % @ 600 ma: 27.9 % η = optical electrical output input [ W ] [ W ] 18 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Summary and Outlook Designed and manufactured an UV-LED-Module with: Radiance: 24.6 W/cm 2 @ 600 ma electrical power density: 88 W/cm 2 Electrical input power: 188 W Efficiency: 36.2 % @ 200 ma 27.9 % @ 600 ma Improve efficiency by improving thermal path AlN ceramic and water cooling 19 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Summary 20 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Questions? 21 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Thermal resistances Material λ Thickness Area R (W/mK) (µm) (mm²) (K/W) Ag adhesive 5 50 1.14 8.7 Tin solder 65 100 1.14 1.3 conductance 1.85 70 2.16 17.5 paste liquid metal 33 100 2.16 1.4 22 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Solid angle projection 23 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density
Thermal conductivities Thermal conductance paste: Chemtronics CW7250 Boron nitride filled paste thermal conductivity l = 1.85 W/(m K) Ag adhesive: Zalman ZM-STG1 Silver filled paste thermal conductivity l = 5 W/(m K) Liquid metal: Coollaboratory Liquid Pro Alloy from gallium, indium, rhodium, silver, zinc, tin, bismuth thermal conductivity l = 32.6 W/(m K) 24 01.07.2010 Manfred Scholdt UV-LED Module Design with Maximum Power Density