High power UV-LED-clusters on ceramic substrates

Schneider, Marc; Herbold, Christian; Messerschmidt, Kay; Trampert, Klaus; Brandner, Juergen J.

doi:10.1109/ectc.2010.5490793

Cited by 3 publications

(5 citation statements)

References 3 publications

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“…It features a jet plate and micro fin design for high water flow and low thermal resistance. The second cooler is a surface micro cooler, developed and fabricated by the IMVT at KIT, which is a further development of the cooler presented in [2]. Fig.…”

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

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“…Bond pads for 98 LED chips (each 11 mm 2 ) in a rhomboid pattern are located in the center with an area of only 2.11 cm 2 . This pattern has already been used and discussed in [3]. The design enables a very tight packing of the LED chips resulting in a fill factor of 46% and the possibility to continue the pattern gapless and uninterrupted.…”

Section: Substrate Technologymentioning

confidence: 95%

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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“…1). The chip positions are identical to our former layout in [2]. With this space saving layout we are able to place 98 LED chips with a lateral dimension of 1070  1070 µm 2 on an area of 2.11 cm 2 and still have enough space for the wire bonding tool and for compensation for tolerances.…”

Section: Cluster Design and Assemblymentioning

confidence: 96%

“…9 shows a comparison of a typical commercially available UV LED module for curing applications with approximately 8 W/cm 2 and our two prototype modules on Al 2 O 3 ceramic substrates. Our first one had adhesively bonded chips using a silver filled epoxy and achieved 13.1 W/cm 2 [2]. The second one is the here described cluster.…”

Section: Optical Measurementsmentioning

confidence: 99%

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Thermal improvements for high power UV LED clusters

Schneider

Leyrer

Herbold

et al. 2011

2011 IEEE 61st Electronic Components and Technology Conference (ECTC)

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We present a high power density UV LED module for a wavelength of 395 nm with an optical power density of 27.3 W/cm 2 . The module consists of 98 densely packed LED chips soldered onto an Al 2 O 3 ceramic board. Thermal and optical measurements were conducted. The module was cooled by a forced air heat sink for the characterization experiments. A room temperature liquid gallium alloy was used as thermal interface material between substrate and heat sink with a TiN barrier layer to prevent corrosion. Further a technology to replace Al 2 O 3 ceramics by aluminum as substrate ispresented. An initial characterization shows that aluminum with a dielectric layer for electrical insulation is a competitive substrate material for efficient heat removal. IntroductionIndustrial applications using ultraviolet (UV) light are extremely progressive and gain large annual growth rates. UV light is used for curing paints, lacquers, coatings, and adhesives. Water treatment using UV light offers a large ecological benefit compared to the use of chemicals. These tasks are performed so far by high power mercury gas discharge lamps. But applications using high power UV light emitting diodes (LED) are gaining increasing attention. LED technology promises easier operation, fast switching, less power consumption, and longer lifetime than gas discharge lamps. Currently LEDs in the near UV range from 400 nm down to a wavelength of approximately 365 nm with hundreds of milliwatts optical output power per chip are available. With these LEDs compact and powerful curing solutions become possible.In contrast to gas discharge lamps, LEDs emit a narrow spectrum around a peak wavelength. Therefore applications requiring only a narrow spectral band in the near UV benefit from their use due to reduced power and cooling requirements. Another possibility to save power in non-continuous processes is the ability to switch LEDs on to full power only when needed in a cycle. In these cases many gas discharge lamps can be replaced with more energy efficient, LED based solutions [1].LEDs with much shorter wavelengths, e.g. 280 nm necessary for water purification, become more and more powerful. So the experience gathered with the construction of curing systems can be reused by exchanging the LED chips.To operate a high power UV LED source reliably some conditions have to be taken into account. The lifetime and efficiency of the system is closely associated with the junction temperature of each LED chip used. Therefore the thermal properties of the packaging are crucial for the system design.

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High power UV-LED-clusters on ceramic substrates

Cited by 3 publications

References 3 publications

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

Thermal improvements for high power UV LED clusters

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