Lumileds Germany GmbH

Aachen, Germany

Lumileds Germany GmbH

Aachen, Germany
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Tolhurst T.M.,University of Saskatchewan | Strobel P.,Ludwig Maximilians University of Munich | Schmidt P.J.,Lumileds Germany GmbH | Schnick W.,Ludwig Maximilians University of Munich | Moewes A.,University of Saskatchewan
Journal of Physical Chemistry C | Year: 2017

A large band gap is a prerequisite for efficient emissions from a rare earth doped phosphor and is consequently a prerequisite for its application in high-quality lighting. We present a detailed characterization of luminescent materials Li2Ca2[Mg2Si2N6]:Eu2+ and Ba[Li2(Al2Si2)N6]:Eu2+ using soft X-ray spectroscopy and density functional theory calculations, including a rigorous experimental determination, and theory-based elucidation, of their band gaps. The band gap of Li2Ca2[Mg2Si2N6]:Eu2+ is determined to be 4.84 ± 0.20 eV, while that of Ba[Li2(Al2Si2)N6]:Eu2+ is 4.82 ± 0.20 eV. The origin of the band gaps is discussed in the context of the calculated DOS of each material and compared to benchmark luminescent materials Sr[LiAl3N4]:Eu2+ and Sr[Mg3SiN4]:Eu2+. Critically, the elements determining the band gaps are identified using the calculated density of states, as well as experimental resonant X-ray emission measurements. This allows for predictive power when searching for new nitridosilicates and related host structures, which upon doping with rare earth elements, may find application in the next-generation of phosphor converted light emitting diodes. © 2017 American Chemical Society.

Timinger A.,Lumileds Germany GmbH | Spinger B.,Lumileds Germany GmbH
Optics InfoBase Conference Papers | Year: 2017

Styling requires compact headlamps, where the size of the source is limiting the quality of the bundle. Managing the luminance distribution of the source gives optics designers degrees of freedom to answer these challenges. © OSA 2017.

Strobel P.,Ludwig Maximilians University of Munich | Weiler V.,Lumileds Germany GmbH | Hecht C.,Lumileds Germany GmbH | Schmidt P.J.,Lumileds Germany GmbH | Schnick W.,Ludwig Maximilians University of Munich
Chemistry of Materials | Year: 2017

The nitridomagnesosilicates Li2Ca2[Mg2Si2N6]:Eu2+ and Li2(Ca1.88Sr0.12)[Mg2Si2N6]:Eu2+ show narrow-band red emission at 638 and 634 nm, respectively, with an emission bandwidth of 62 nm (∼1513 cm-1) after excitation in the blue spectral region. Ce3+-doped samples show luminescence in the green spectral range (λem = 540 nm). The compounds were synthesized via solid-state metathesis reaction in Li melts. Refinement of single-crystal X-ray diffraction data revealed that Li2(Ca1.88Sr0.12)[Mg2Si2N6] crystallizes isomorphic to Li2Ca2[Mg2Si2N6]: C2/m [Z = 2, a = 5.5744(2), b = 9.8439(3), c = 6.0170(2) Å, β = 97.2520(10)°, R1 = 0.021, wR2 = 0.047]. Crystal composition was checked by EDS and ICP-OES measurements and luminescence properties are compared to state of the art narrow-band red emitting luminophors. On the basis of its narrow-band emission, application of the novel red luminophor in high CRI white pcLEDs is promising. © 2017 American Chemical Society.

Hanss A.,Ingolstadt University of Applied Sciences | Liu E.,Ingolstadt University of Applied Sciences | Schmid M.,Ingolstadt University of Applied Sciences | Muller D.,Ingolstadt University of Applied Sciences | And 3 more authors.
Proceedings - Electronic Components and Technology Conference | Year: 2017

A high reliability of light emitting diode (LED) light sources is essential for general and automotive lighting applications, where exchange of LED components is expensive. Thermal management of modern high power LEDs is crucial for their lifetime. An important aspect is the thermal path for heat conduction. Many different defects can have an influence on this path of an electronic system: on the one hand process failures during production, e.g. voids inside the solder joint, on the other hand typical failures induced by thermo-mechanical stress during their lifetime, like cracks in the solder joint or delamination in the package. The transient thermal analysis (TTA) is a powerful tool to detect changes in the thermal path. Due to improvements in the TTA method during the last years, not only cracks can be detected but also failure modes can be separated, and the root cause can be analyzed by support of transient finite element analysis. In this paper, transient thermal testing is applied and further developed, to monitor the structural integrity of new wafer level LED packages during thermal stress testing. Failure modes are defined and separated. For failure analysis the different defects are simulated by transient finite element analysis and correlated to the TTA results. The simulation results, that solder cracks increase the peak height of the derivative of the transient thermal curves (b(z)). A delamination of an inner layer of the LED package creates additionally to the increase of the peak height also a separation of the b(z) curves between 1 μs and 5 μs. Therefore a transient thermal measurement equipment with a dead time © 2017 IEEE.

Elger G.,Ingolstadt University of Applied Sciences | Kandaswamy S.V.,Ingolstadt University of Applied Sciences | Liu E.,Ingolstadt University of Applied Sciences | Hanss A.,Ingolstadt University of Applied Sciences | And 3 more authors.
Microelectronics Journal | Year: 2015

An innovative sensitive test method is developed to detect solder joint cracking for high power LED packages. The method is based on transient thermal analysis and can fully replace the still dominating light-on test. For experimental application of the model, test groups of LED packages were soldered with two different lead free solders (SnAgCu305 and Innolot FL-640) on Aluminum Insulated Metal Substrate (Al-IMS) and exposed to temperature cycles. Transient thermal measurements were performed directly after assembly and after specific cycle numbers. After data processing the increase of the relative thermal resistance between the initial signal at "0" cycles and ". n" cycles is obtained and correlated with cracks in the solder joint by cross sections. Based on the CAD and material data of the LED package a finite element (FE) model is set up. The time-resolved temperature curves are properly reproduced by transient thermal simulation. The measured "0" cycle curves are fitted using the FE model by adjusting a few material parameters within their allowed tolerance range. A parameter sensitivity analysis is performed. The impact of a crack in the solder joint between package and printed circuit board (PCB) on the time resolved temperature curve is simulated. The simulated crack propagates from the corner of the package to its center. The experimental measured curves are reproduced. Based on the simulation a failure criteria is defined, representing a crack length between 20% and 30% of the solder joint area, and Weibull curves are calculated. A higher creep resistance for the test group soldered with Innolot FL-640 compared to the test group soldered with SAC305 is observed. © 2015 Elsevier Ltd.

Marchuk A.,Ludwig Maximilians University of Munich | Wendl S.,Ludwig Maximilians University of Munich | Imamovic N.,Ludwig Maximilians University of Munich | Tambornino F.,Ludwig Maximilians University of Munich | And 3 more authors.
Chemistry of Materials | Year: 2015

The isotypic nitridophosphates Ba3P5N10X (X = Cl, I) have been synthesized by high-temperature reaction under pressures between 1 and 5 GPa. The crystal structures of both compounds were solved and refined using single-crystal X-ray diffraction data. Accuracy of the structure determination as well as phase purity of the products were confirmed by Rietveld refinement and FTIR spectroscopy. The band gap values (4.0-4.3 eV) for the direct transitions were determined from UV-vis data using the Kubelka-Munk function and were confirmed by DFT calculations. Both compounds crystallize in the Ba3P5N10Br structure type (space group Pnma (No. 62), Z = 8; Ba3P5N10Cl, a = 12.5182(5) Å, b = 13.1798(5) Å, c = 13.7676(6) Å, R1 = 0.0214, wR2 = 0.0526; Ba3P5N10I, a = 12.6311(7) Å, b = 13.2565(8) Å, c = 13.8689(8) Å, R1 = 0.0257, wR2 = 0.0586) with a tetrahedra network being analogous to the topology of the JOZ zeolite structure type. The crystal structure is built up of all-side vertex-sharing PN4 tetrahedra leading to a zeolite-like framework with three-dimensional achter-ring channels containing alternately Ba and respective halide atoms. The condensed dreier-, vierer-, and sechser-rings form two different composite building units made up of 344286-cages. Upon being doped with Eu2+, the title compounds exhibit intriguing luminescence properties, which were compared with that of Ba3P5N10Br:Eu2+. Upon excitation by near-UV light, nonsaturated color luminescence from multiple emission centers was observed in the orange (X = Cl) and cyan to amber (X = I) spectral range of the visible spectrum. © 2015 American Chemical Society.

Strobel P.,Ludwig Maximilians University of Munich | Schmiechen S.,Ludwig Maximilians University of Munich | Siegert M.,Ludwig Maximilians University of Munich | Tucks A.,Lumileds Germany GmbH | And 2 more authors.
Chemistry of Materials | Year: 2015

Eu2+- as well as Ce3+-doped Ba[Li2(Al2Si2)N6] and its related Mg-substituted compounds Ba[(Mg2-xLix) (Al4-xSix)N6]:Eu2+ (x = 0-2) with x = 1.6, 1.8 have been synthesized by metathesis reactions in tantalum ampules. Crystal structures were solved and refined from single-crystal X-ray diffraction data. All three compounds crystallize in tetragonal space group P4/ncc (no. 130) (Z = 4, Ba[Li2(Al2Si2)N6]:Eu2+: a = 7.8282(4), c = 9.9557(5) Å, R1 = 0.0144, wR2 = 0.0366). Their crystal structures, exhibiting the novel framework topology whj, consist of a highly condensed anionic tetrahedra network of disordered (Li/Mg)N4 and (Al/Si)N4 units connected to each other by common edges and corners. The degree of condensation (i.e., atomic ratio (Al,Li,Mg,Si):N) is κ = 1. The Ba2+-position is coordinated eight-fold by N3- in form of a truncated square pyramid. Upon doping with Eu2+, narrow-band emission in the green to yellow spectral range is observed (λem = 532-562 nm, fwhm ≈ 1962 cm-1). Ce3+-doped crystals of Ba[Li2(Al2Si2)N6] show blue emission (λem = 468; 507 nm). According to the tunability of the narrow-band green emission, application in LED-backlight liquid crystal displays appears promising. (Figure Presented). © 2015 American Chemical Society.

Durach D.,Ludwig Maximilians University of Munich | Neudert L.,Ludwig Maximilians University of Munich | Schmidt P.J.,Lumileds Germany GmbH | Oeckler O.,University of Leipzig | Schnick W.,Ludwig Maximilians University of Munich
Chemistry of Materials | Year: 2015

Due to the relationship between structure and luminescence properties, detailed crystal structure determination for microcrystalline phosphors is necessary for a profound understanding of materials properties. The yellow phosphor La3BaSi5N9O2:Ce3+ (λmax = 578 nm; fwhm ∼4700 cm-1) was characterized by a combination of transmission electron microscopy (TEM) and synchrotron microfocus diffraction as only agglomerates of crystals with a maximum size of a few μm could be obtained yet. La3BaSi5N9O2:Ce3+ was synthesized from LaF3, La(NH2)3, BaH2, Si(NH)2, and CeF3 in a radio frequency furnace. It crystallizes in space group Pmn21 (no. 31) with a = 9.5505(8), b = 19.0778(16), c = 12.1134(9) Å, and Z = 8. Its interrupted three-dimensional tetrahedra network contains zehner and dreier rings of vertex-sharing SiN4 and SiN2O2 tetrahedra. The crystal structure was confirmed by high-resolution TEM and Z-contrast scanning TEM. The element distribution was derived by bond-valence sum calculations. The infrared spectrum proves the absence of N-H bonds (Figure Presented). © 2015 American Chemical Society.

Wagatha P.,Ludwig Maximilians University of Munich | Pust P.,Ludwig Maximilians University of Munich | Weiler V.,Lumileds Germany GmbH | Wochnik A.S.,Ludwig Maximilians University of Munich | And 4 more authors.
Chemistry of Materials | Year: 2016

Highly efficient red-emitting luminescent materials deliver the foundation for next-generation illumination-grade white light-emitting diodes (LEDs). Recent studies demonstrate that the hardly explored class of nitridoaluminates comprises intriguing phosphor materials, e.g., Sr[LiAl3N4]:Eu2+ or Ca[LiAl3N4]:Eu2+. Here, we describe the novel material Ca18.75Li10.5[Al39N55]:Eu2+ with highly efficient narrow-band red emission (λem ≈ 647 nm, full width at half-maximum, fwhm ≈ 1280 cm-1). This compound features a rather uncommon crystal structure, comprising sphalerite-like T5 supertetrahedra that are composed of tetrahedral AlN4 units that are interconnected by additional AlN4 moieties. The network charge is compensated by Ca2+ and Li+ ions located between the supertetrahedra. The crystal structure was solved and refined from single-crystal and powder X-ray diffraction data in the cubic space group Fd3m (No. 227) with a = 22.415(3) Å and Z = 8. To verify the presence of Li, transmission electron microscopy (TEM) investigations including electron energy-loss spectroscopy (EELS) were performed. Based on the intriguing luminescence properties, we proclaim high potential for application in high-power phosphor-converted white LEDs. (Figure Presented). © 2016 American Chemical Society.

Bhardwaj J.,Trimble | Peddada R.,Trimble | Spinger B.,Lumileds Germany GmbH
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

High power LEDs were introduced in automotive headlights in 2006-2007, for example as full LED headlights in the Audi R8 or low beam in Lexus. Since then, LED headlighting has become established in premium and volume automotive segments and beginning to enable new compact form factors such as distributed low beam and new functions such as adaptive driving beam. New generations of highly versatile high power LEDs are emerging to meet these application needs. In this paper, we will detail ongoing advances in LED technology that enable revolutionary styling, performance and adaptive control in automotive headlights. As the standards which govern the necessary lumens on the road are well established, increasing luminance enables not only more design freedom but also headlight cost reduction with space and weight saving through more compact optics. Adaptive headlighting is based on LED pixelation and requires high contrast, high luminance, smaller LEDs with high-packing density for pixelated Matrix Lighting sources. Matrix applications require an extremely tight tolerance on not only the X, Y placement accuracy, but also on the Z height of the LEDs given the precision optics used to image the LEDs onto the road. A new generation of chip scale packaged (CSP) LEDs based on Wafer Level Packaging (WLP) have been developed to meet these needs, offering a form factor less than 20% increase over the LED emitter surface footprint. These miniature LEDs are surface mount devices compatible with automated tools for L2 board direct attach (without the need for an interposer or L1 substrate), meeting the high position accuracy as well as the optical and thermal performance. To illustrate the versatility of the CSP LEDs, we will show the results of, firstly, a reflector-based distributed low beam using multiple individual cavities each with only 20mm height and secondly 3x4 to 3x28 Matrix arrays for adaptive full beam. Also a few key trends in rear lighting and impact on LED light source technology are discussed. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.

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