Thermal improvements for high power UV LED clusters

Schneider, Marc; Leyrer, Benjamin; Herbold, Christian; Trampert, Klaus; Brandner, Juergen J.

doi:10.1109/ectc.2011.5898731

Cited by 5 publications

(9 citation statements)

References 1 publication

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“…The UV LED module built on an Al 2 O 3 ceramic substrate is already described in [1]. It consists of 98 densely packed UV LED chips of the type SL-V-U40AC from SemiLEDs Inc. Each chip emits typically 250-300 mW of optical power at a wavelength of 390-395 nm and a current of 350 mA.…”

Section: Ceramic Substratementioning

confidence: 99%

Index matched fluidic packaging of high power UV LED clusters on aluminum substrates for improved optical output power

Schneider¹,

Leyrer²,

Herbold³

et al. 2012

2012 IEEE 62nd Electronic Components and Technology Conference

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We present an improved cooling for a high power density UV LED module for a wavelength of 395 nm. The module consists of 98 LED chips soldered on a thick film printed alumina substrate on an area of 2.11 cm 2 . We investigated cooling by a commercial water cooler as well as by a surface micro cooler developed by our own.Further we describe a technology to replace alumina by aluminum as substrate material. A module consisting of 25 UV LEDs was optically characterized without and with liquid encapsulation.Finally we conducted numerical studies to develop an easily producible, sufficiently powerful, and robust water cooler. Based on the results we present a water cooler design with cooling channels embedded in the aluminum substrate of an LED module, removing the interface between LED substrate and heat sink. IntroductionMany industrial applications today use UV light. It is used to cure paints, lacquers, coatings, and adhesives with low emissions and timesaving. Waste water treatment with UV light offers an important ecological advantage compared to chemical treatment. Currently these applications use high power gas discharge lamps. But high power UV LED sources are gaining increased attention. LED technology promises easier operation, faster switching, lower power consumption, variable light output, and longer lifetime than gas discharge lamps. UV LED chips for the near UV spectral range at wavelengths between 400 nm and 365 nm are currently available with several hundred milliwatt of optical output power. These LEDs enable powerful UV LED light sources.Applications needing just a small spectral band benefit from lower power and cooling demands, because in contrast to gas discharge lamps LEDs emit only in the required spectral band and no light has to be filtered out. Additional power can be saved through an efficient control in non-continuous processes due to the instantaneous light output after switching on the LEDs.As lifetime, efficiency, and reliability of LED systems is closely associated with the junction temperature of every single LED, the thermal properties of the packaging and the cooling system are crucial issues.We present substantial improvements in the cooling of an LED cluster built on a ceramic substrate using a high performance microstructured water cooler. Additionally we show a novel LED cluster built on a thick aluminum substrate with thick film printed dielectrics and silver traces. The LEDs are

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Section: Ceramic Substratementioning

confidence: 99%

Index matched fluidic packaging of high power UV LED clusters on aluminum substrates for improved optical output power

Schneider¹,

Leyrer²,

Herbold³

et al. 2012

2012 IEEE 62nd Electronic Components and Technology Conference

Self Cite

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“…Blue emitting LED chips were used in current investigations in contrast to former research studies [1,2] where modules using UV-LED chips emitting in the near ultraviolet range were investigated. The results are transferable to other emission wavelengths as the main challenge is the cooling of the LED chips.…”

Section: Introductionmentioning

confidence: 97%

“…Blue emitting LED chips were used in current investigations in contrast to former research studies [1,2] where modules using UV-LED chips emitting in the near ultraviolet…”

Section: Introductionmentioning

confidence: 98%

“…On that account, a layout with a very high possible chip density on a substrate and enough space to wire bond between the chips and compensate for fabrication tolerances was developed [1]. The evolution of the packaging technology includes two aspects, a new substrate material and a new technology for bonding the LED chips onto the substrate.…”

Section: Introductionmentioning

confidence: 99%

“…The evolution of the packaging technology includes two aspects, a new substrate material and a new technology for bonding the LED chips onto the substrate. All combinations of these LED modules with new and old substrate materials and different bonding technologies were fabricated and characterized.Blue emitting LED chips were used in current investigations in contrast to former research studies [1,2] where modules using UV-LED chips emitting in the near ultraviolet …”

mentioning

confidence: 98%

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High power density LED modules with silver sintering die attach on aluminum nitride substrates

Schneider

Leyrer

Herbold

et al. 2014

2014 IEEE 64th Electronic Components and Technology Conference (ECTC)

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Current research studies deal with the investigation of the thermal and optical properties of four LED modules on different substrate materials. The LED modules consist of arrays of 98 blue emitting LEDs with an emission wavelength of 457 nm within an area of 2.11 cm 2 . The modules are based on aluminum oxide or aluminum nitride substrates and the LED chips are attached by using a soldering or a pressureless silver sintering process. The modules are mounted on a high performance microstructured heat exchanger. By using the water driven cooler a maximum optical power density of 106.2 W/cm 2 at a forward current of 2100 mA and 837.5 W electrical input power is achieved. A saturation of the optical power density over the input current due to thermal degradation is not observed. IntroductionLight engines consisting of a large number of densely packed high-power LED chips require sophisticated heat management for efficient and high performance operation. It is quite easy to achieve high optical power densities with small arrays of rows of LED chips just two chips wide due to the simple electrical connection on both sides of the rows and the possibility to spread the generated heat. For large area light sources with high optical power densities this design is unsuitable because of the inhomogeneous light emitting area. With regard to a small optical system with beam forming a small light emitting area is beneficial. These light sources could be used for flood lights in stadiums, TV studios, architectural lighting or automotive head lamps. But larger areas of tightly packed LED chips with high light densities present a technological challenge, because of the integration of a sufficient heat spreading technology for cooling, the required high fill factor of LEDs, and their electrical connections between the chips.On that account, a layout with a very high possible chip density on a substrate and enough space to wire bond between the chips and compensate for fabrication tolerances was developed [1]. The evolution of the packaging technology includes two aspects, a new substrate material and a new technology for bonding the LED chips onto the substrate. All combinations of these LED modules with new and old substrate materials and different bonding technologies were fabricated and characterized.Blue emitting LED chips were used in current investigations in contrast to former research studies [1,2] where modules using UV-LED chips emitting in the near ultraviolet

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Experimental investigation of microheat pipes for high‐power light‐emitting diode modules

Luo

Liu

Zou

et al. 2013

Micro & Nano Letters

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A light-emitting diode (LED) is a novel electronic light source that provides a direct conversion of electrical energy into light. A typical LED power package has a heat flux of 100 W/cm 2 , thus high power LEDs face severe thermal challenges because of their small size and general lack of a proper thermal path. The advantage of microheat pipes (MHPs) which are largely used in heat dissipation of microdevices is based on phase change. With the trend of using a silicon wafer as the substrate in LED manufacturing, a silicon-glass MHP was fabricated for the quick spread of heat from the LEDs. Flat plate grooved MHPs are introduced. The grooves were fabricated on the silicon wafer and followed by bonding with Pyrex 7740 glass. Water was selected as the working liquid and the charge rate was 40%. The temperature test experiments were carried out to test the feasibility of the MHPs in LED heat conduction, and the preliminary experimental results indicate that the heat conductivity of MHPs without a vapour chamber is better than that of MHPs with a vapour chamber, which is even better than that of the silicon wafer.

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Thermal improvements for high power UV LED clusters

Cited by 5 publications

References 1 publication

Index matched fluidic packaging of high power UV LED clusters on aluminum substrates for improved optical output power

Index matched fluidic packaging of high power UV LED clusters on aluminum substrates for improved optical output power

High power density LED modules with silver sintering die attach on aluminum nitride substrates

Experimental investigation of microheat pipes for high‐power light‐emitting diode modules

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