Chip to System Levels Thermal Needs and Alternative Thermal Technologies for High Brightness LEDS

2007 ◽  
Vol 129 (3) ◽  
pp. 328-338 ◽  
Author(s):  
Mehmet Arik ◽  
Anant Setlur ◽  
Stanton Weaver ◽  
Deborah Haitko ◽  
James Petroski
Keyword(s):  
Integrated Circuits ◽  
Thermal Management ◽  
Heat Fluxes ◽  
Electrical Currents ◽  
System Architectures ◽  
High Brightness ◽  
Light Emitting ◽  
Optical Extraction ◽  
Address System ◽  
Light Color

Light emitting diodes (LEDs) historically have been used for indicators and produced low amounts of heat. The introduction of high brightness LEDs with white light and monochromatic colors has allowed them to penetrate specialty and general illumination applications. The increased electrical currents used to drive the LEDs have resulted in higher heat fluxes than those for average silicon integrated circuits (i.e., ICs). This has created a need to focus more attention on the thermal management engineering of LED power packages. The output of a typical commercial high brightness, 1mm2, LED has exceeded 100lm at drive levels approaching 3W. This corresponds to a heat flux of up to 300W∕cm2. Novel thermal solutions need to address system architectures, packaging, phosphors for light color conversion, and encapsulants and fillers for optical extraction. In this paper, the effect of thermal management on packaging architectures, phosphors, encapsulants, and system design are discussed. Additionally, discussions of microscopic defects due to packaging problems as well as chip active layer defects are presented through experimental and computational findings.

Thermal Needs and Challenges for the Solid State Lighting Devices: Materials to Packages

2005 ◽  
Author(s):  
Mehmet Arik ◽  
Stanton Weaver ◽  
Anant Setlur ◽  
Deborah Haitko
Keyword(s):  
Heat Flux ◽  
Thermal Management ◽  
Electronics Packaging ◽  
Luminous Efficiency ◽  
Heat Fluxes ◽  
Solid State Lighting ◽  
Electrical Currents ◽  
High Brightness ◽  
Light Emitting ◽  
Experimental Findings

Light emitting diodes historically have been used for indicators and produced low amounts of heat. The introduction of high brightness LEDs with white light and monochromatic colors have led to a movement towards specialty and general illumination applications. The increased electrical currents used to drive the LEDs have focused more attention on the thermal paths in the LED packages and developments in LED power packaging. The luminous efficiency of LEDs is soon expected to reach over 80 Lumens/Watt that is approximately 6 times more than a conventional tungsten bulb. The thermal challenges include but not limited to chip architecture, packaging, phosphors for light conversion, encapsulants and fillers for optical transparency, interconnects for both electrical and thermal reasons. A typical LED power-package has a 1mm2 surface area with a total heat generation of 1 W. This corresponds to a heat flux of 100 W/cm2, which is much higher than heat fluxes at the current electronics packaging. In this paper, effect of the thermal management on packaging architectures, as well as phosphor and encapsulants are discussed. Discussions on the microscopic defects due to packaging problems as well as chip active layer defects are presented through experimental findings.

scholarly journals High-brightness lasing at submicrometer enabled by droop-free fin light-emitting diodes (LEDs)

2020 ◽  
Vol 6 (33) ◽  
pp. eaba4346
Author(s):  
Babak Nikoobakht ◽  
Robin P. Hansen ◽  
Yuqin Zong ◽  
Amit Agrawal ◽  
Michael Shur ◽  
...  
Keyword(s):  
Output Power ◽  
Light Emitting Diodes ◽  
Efficiency Droop ◽  
Light Extraction Efficiency ◽  
Electrical Currents ◽  
High Brightness ◽  
Light Emitting ◽  
Recombination Processes ◽  
Current Densities ◽  
New Generation

“Efficiency droop,” i.e., a decline in brightness of light-emitting diodes (LEDs) at high electrical currents, limits the performance of all commercial LEDs and has limited the output power of submicrometer LEDs and lasers to nanowatts. We present a fin p-n junction LED pixel that eliminates efficiency droop, allowing LED brightness to increase linearly with current. With record current densities of 1000 kA/cm2, the LEDs transition to lasing, with brightness over 20 μW. Despite a light extraction efficiency of only 15%, these devices exceed the output power of any previous electrically driven submicrometer LED or laser pixel by 100 to 1000 times while showing comparable external quantum efficiencies. Modeling suggests that spreading of the electron-hole recombination region in fin LEDs at high injection levels suppresses the nonradiative Auger recombination processes. Further refinement of this design is expected to enable a new generation of high-brightness LED and laser pixels for macro- and microscale applications.

Embedded Cooling for Wide Bandgap Power Amplifiers: A Review

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
A. Bar-Cohen ◽  
J. J. Maurer ◽  
D. H. Altman
Keyword(s):  
Integrated Circuits ◽  
Thermal Management ◽  
Power Amplifiers ◽  
Electronic Materials ◽  
Jet Impingement ◽  
Wide Bandgap ◽  
Heat Fluxes ◽  
Rf Power Amplifiers ◽  
Rf Power ◽  
Baseline Design

Successful utilization of the inherent capability of wide bandgap materials and architectures for radio frequency (RF) power amplifiers (PAs) necessitates the creation of an alternative thermal management paradigm. Recent “embedded cooling” efforts in the aerospace industry have focused on overcoming the near-junction thermal limitations of conventional electronic materials and enhancing removal of the dissipated power with on-chip cooling. These efforts, focusing on the use of diamond substrates and microfluidic jet impingement, are ushering in a new generation (Gen3) of thermal packaging technology. Following the introduction of a modified Johnson's figure-of-merit (JFOM-k), which includes thermal conductivity to reflect the near-junction thermal limitation, attention is turned to the options, challenges, and techniques associated with the development of embedded thermal management technology (TMT). Record GaN-on-Diamond transistor linear power of 11 W/mm, transistor power fluxes in excess of 50 kW/cm2, and heat fluxes, above 40 kW/cm2, achieved in Defense Advanced Research Projects Agency (DARPA)'s near-junction thermal transport (NJTT) program, are described. Raytheon's ICECool demonstration monolithic microwave integrated circuits (MMICs), which achieved 3.1× the CW RF power output and 4.8× the CW RF power density relative to a baseline design, are used to illustrate the efficacy of Gen3 embedded cooling.

THERMAL MANAGEMENT SOLUTIONS FOR THE LED MARKET

2010 ◽  
Vol 2010 (1) ◽  
pp. 000151-000155
Author(s):  
K. Andrew Kintz ◽  
Sara N. Paisner ◽  
M. Shane Thompson
Keyword(s):  
Thermal Management ◽  
Heat Dissipation ◽  
Epoxy Adhesive ◽  
High Brightness ◽  
Light Emitting ◽  
New Class ◽  
High Adhesion ◽  
Die Attach ◽  
Low Modulus ◽  
Thermal Grease

High-brightness light emitting diodes (LEDs) are challenged with thermal management issues due to increased power and reduced surface area. This has led to the need for new materials with higher thermal conductivity that can quickly remove the heat from the active layer. LORD Corporation has developed two new thermal management materials, a “no pump-out” thermal grease and a low modulus die attach adhesive, as solutions to the heat dissipation problems facing LED manufacturers. These innovative technologies will help engineers solve complex fundamental thermal management problems. A new 4 W/mK silicone thermal grease has been developed with significant resistance to in-package bleed-out or pump-out eliminating the reliability problem most commonly encountered with traditional thermal greases. A new 10–20 W/mK thermal epoxy adhesive has also been developed creating a new class of flexible adhesives with high adhesion. This combination allows the new LORD die attach adhesive to not only effectively transfer heat out of the package, but also to dissipate the stress caused by thermal expansion and contraction during thermal cycling thereby affording improved package reliability.

scholarly journals Compact Modelling of Electrical, Optical and Thermal Properties of Multi-Colour Power LEDs Operating on a Common PCB

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1286
Author(s):  
Krzysztof Górecki ◽  
Przemysław Ptak
Keyword(s):  
Integrated Circuits ◽  
Optical Model ◽  
Printed Circuit Board ◽  
Circuit Board ◽  
Junction Temperature ◽  
Optical Parameters ◽  
Spice Simulation ◽  
Light Emitting ◽  
Proposed Model ◽  
Good Agreement

This paper concerns the problem of modelling electrical, thermal and optical properties of multi-colour power light-emitting diodes (LEDs) situated on a common PCB (Printed Circuit Board). A new form of electro-thermo-optical model of such power LEDs is proposed in the form of a subcircuit for SPICE (Simulation Program with Integrated Circuits Emphasis). With the use of this model, the currents and voltages of the considered devices, their junction temperature and selected radiometric parameters can be calculated, taking into account self-heating phenomena in each LED and mutual thermal couplings between each pair of the considered devices. The form of the formulated model is described, and a manner of parameter estimation is also proposed. The correctness and usefulness of the proposed model are verified experimentally for six power LEDs emitting light of different colours and mounted on an experimental PCB prepared by the producer of the investigated devices. Verification was performed for the investigated diodes operating alone and together. Good agreement between the results of measurements and computations was obtained. It was also proved that the main thermal and optical parameters of the investigated LEDs depend on a dominant wavelength of the emitted light.

High-brightness perovskite quantum dot light-emitting devices using inkjet printing

2021 ◽  
Vol 93 ◽  
pp. 106168
Author(s):  
Chunbo Zheng ◽  
Xin Zheng ◽  
Chen Feng ◽  
Songman Ju ◽  
Zhongwei Xu ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Inkjet Printing ◽  
High Brightness ◽  
Light Emitting ◽  
Light Emitting Devices

scholarly journals Pyridinyl-Carbazole Fragments Containing Host Materials for Efficient Green and Blue Phosphorescent OLEDs

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4615
Author(s):  
Dovydas Blazevicius ◽  
Daiva Tavgeniene ◽  
Simona Sutkuviene ◽  
Ernestas Zaleckas ◽  
Ming-Ruei Jiang ◽  
...  
Keyword(s):  
Current Efficiency ◽  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
Power Efficiency ◽  
Triplet Energy ◽  
New Host ◽  
High Brightness ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Host Materials

Pyridinyl-carbazole fragments containing low molar mass compounds as host derivatives H1 and H2 were synthesized, investigated, and used for the preparation of electro-phosphorescent organic light-emitting devices (PhOLEDs). The materials demonstrated high stability against thermal decomposition with the decomposition temperatures of 361–386 °C and were suitable for the preparation of thin amorphous and homogeneous layers with very high values of glass transition temperatures of 127–139 °C. It was determined that triplet energy values of the derivatives are, correspondingly, 2.82 eV for the derivative H1 and 2.81 eV for the host H2. The new derivatives were tested as hosts of emitting layers in blue, as well as in green phosphorescent OLEDs. The blue device with 15 wt.% of the iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,C2′]picolinate (FIrpic) emitter doping ratio in host material H2 exhibited the best overall characteristics with a power efficiency of 24.9 lm/W, a current efficiency of 23.9 cd/A, and high value of 10.3% of external quantum efficiency at 100 cd/m2. The most efficient green PhOLED with 10 wt% of Ir(ppy)3 {tris(2-phenylpyridine)iridium(III)} in the H2 host showed a power efficiency of 34.1 lm/W, current efficiency of 33.9 cd/A, and a high value of 9.4% for external quantum efficiency at a high brightness of 1000 cd/m2, which is required for lighting applications. These characteristics were obtained in non-optimized PhOLEDs under an ordinary laboratory atmosphere and could be improved in the optimization process. The results demonstrate that some of the new host materials are very promising components for the development of efficient phosphorescent devices.

Thermal Characterization of Interlayer Microfluidic Cooling of Three-Dimensional Integrated Circuits With Nonuniform Heat Flux

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Yoon Jo Kim ◽  
Yogendra K. Joshi ◽  
Andrei G. Fedorov ◽  
Young-Joon Lee ◽  
Sung-Kyu Lim
Keyword(s):  
Integrated Circuits ◽  
Mass Flow Rate ◽  
Thermal Management ◽  
Mass Flow ◽  
Flow Rate ◽  
Single Phase ◽  
Hot Spot ◽  
Three Dimensional ◽  
Two Phase ◽  
Two Phase Cooling

It is now widely recognized that the three-dimensional (3D) system integration is a key enabling technology to achieve the performance needs of future microprocessor integrated circuits (ICs). To provide modular thermal management in 3D-stacked ICs, the interlayer microfluidic cooling scheme is adopted and analyzed in this study focusing on a single cooling layer performance. The effects of cooling mode (single-phase versus phase-change) and stack/layer geometry on thermal management performance are quantitatively analyzed, and implications on the through-silicon-via scaling and electrical interconnect congestion are discussed. Also, the thermal and hydraulic performance of several two-phase refrigerants is discussed in comparison with single-phase cooling. The results show that the large internal pressure and the pumping pressure drop are significant limiting factors, along with significant mass flow rate maldistribution due to the presence of hot-spots. Nevertheless, two-phase cooling using R123 and R245ca refrigerants yields superior performance to single-phase cooling for the hot-spot fluxes approaching ∼300 W/cm2. In general, a hybrid cooling scheme with a dedicated approach to the hot-spot thermal management should greatly improve the two-phase cooling system performance and reliability by enabling a cooling-load-matched thermal design and by suppressing the mass flow rate maldistribution within the cooling layer.

High-Brightness Blue-Green Light-Emitting Diodes on ZnSe Substrates

1995 ◽  
Vol 187 (2) ◽  
pp. 467-470 ◽  
Author(s):  
W. C. Harsch ◽  
G. Cantwell ◽  
J. F. Schetzina
Keyword(s):  
Light Emitting Diodes ◽  
Green Light ◽  
High Brightness ◽  
Light Emitting
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