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Sankt Stefan ob Leoben, Austria

Langer G.,Austria Technology and Systemtechnik AG | Leitgeb M.,Austria Technology and Systemtechnik AG | Nicolics J.,Vienna University of Technology | Unger M.,Vienna University of Technology | And 2 more authors.
IPC APEX EXPO 2014 | Year: 2014

With increasing power loss of electrical components, thermal performance of an assembled device becomes one of the most important quality factors in electronic packaging. Due to the rapid advances in semiconductor technology, particularly in the regime of high-power components, the temperature dependence of the long-term reliability is a critical parameter and has to be considered with highest possible care during the design phase. Two main drivers in the electronics industry are miniaturization and reliability. Whereas there is a continuous improvement concerning miniaturization of conductor tracks (lines / spaces have been reduced continuously over the past years), miniaturization of the circuit carrier itself, however, has mostly been limited to decreased layer-counts and base material thicknesses. This can lead to significant component temperature and therewith to accelerated system degradation. Enhancement of the system reliability is directly connected to an efficient thermal management on the PCB-level. There are several approaches, which can be used to address this issue: Optimization of the board-design, use of base materials with advanced thermal performance and use of innovative buildup concepts. The aim of this paper is to give a short overview about standard thermal solutions like thick copper, thermal vias, plugged vias or metal core based PCBs. Furthermore, attention will be turned on the development of copper filled thermal vias in thin board constructions. In another approach advanced thermal management solutions will be presented on the board level, exploring different buildup concepts (e.g. cavities). Advantages of cavity solutions in the board will be shown, which not only decrease the thermal path leading from the high power component through the board to the heat sink, but also have an impact concerning the mechanical miniaturization of the entire system (reduction of z-axis). Such buildups serve as packaging solution and show an increase in mechanical and thermal reliability. Moreover, thermal simulations will be conducted and presented in this paper in order to reduce production efforts and to offer optimized designs and board buildups. Source

Wenzl F.P.,Joanneum Research | Sommer C.,Joanneum Research | Hartmann P.,Joanneum Research | Pachler P.,Tridonic Jennersdorf GmbH | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

Color constancy and color maintenance are key issues in the context of the utilization of light-emitting diodes (LEDs) for general lighting applications. For a systematic approach to improve the white light quality of phosphor converted LEDs and to fulfill the demands for color temperature reproducibility and constancy, it is imperative to understand how compositional, optical and thermal properties of the color conversion elements (CCE), which typically consist of a phosphor particles embedded in a transparent matrix material, affect the correlated color temperature of a white LED source. Based on a combined optical and thermal simulation procedure, in this contribution we give a comprehensive discussion on the underlying coherences of light absorption, quantum efficiency and thermal conductivity and deduce some strategies to minimize the temperature increase within the CCE in order to maintain acceptable color variations upon device operation. © 2012 SPIE. Source

Langer G.,Austria Technology and Systemtechnik AG | Satzinger V.,Joanneum Research | Schmidt V.,Joanneum Research | Schmid G.,Vienna University of Technology | Leeb W.R.,Vienna University of Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

The increasing demand for miniaturization and design flexibility of polymer optical waveguides integrated into electrical printed circuit boards (PCB) calls for new coupling and integration concepts. We report on a method that allows the coupling of optical waveguides to electro-optical components as well as the integration of an entire optical link into the PCB. The electro-optical devices such as lasers and photodiodes are assembled on the PCB and then embedded in an optically transparent material. A focused femtosecond laser beam stimulates a polymerization reaction based on a two-photon absorption effect in the optical material and locally increases the refractive index of the material. In this way waveguide cores can be realized and the embedded components can be connected optically. This approach does not only allow a precise alignment of the waveguide end faces to the components but also offers a truly 3-dimensional routing capability of the waveguides. Using this technology we were able to realize butt-coupling and mirror-coupling interface solutions in several demonstrators. We were also manufacturing demonstrator boards with fully integrated driver and preamplifier chips, which show very low power consumption of down to 10 mW for about 2.5 Gbit/s. Furthermore, demonstrators with interconnects at two different optical layers were realized. Source

Krivic P.,Vienna University of Technology | Wenzl F.-P.,Joanneum Research | Sommer C.,Joanneum Research | Langer G.,Austria Technology and Systemtechnik AG | And 4 more authors.
Proceedings of the International Spring Seminar on Electronics Technology | Year: 2012

The reliability and long-term stability of solid-state lighting devices strongly depend on successful thermal management. It is well known that junction temperature instability negatively impacts the lightning properties of LED illuminators. However, for prediction of life time and longterm stability the temperature distribution also inside the color converter must be known. A deeper understanding of these demanding thermal issues is provided in our paper on the base of measurements and simulations also taking into account the spatial power loss distribution due to absorption of light and Stokes shift within the color converter. For this purpose 3-dimensional models were set-up and examined to thermally characterize high-power LED assemblies. Two different types of set-ups were investigated. Moreover, an efficient solution is presented where a junction-to-case thermal resistance below 10 K/W is achieved. © 2012 IEEE. Source

Unger M.,Vienna University of Technology | Nicolics J.,Vienna University of Technology | Langer G.,Austria Technology and Systemtechnik AG | Wenzl F.-P.,Joanneum Research | And 3 more authors.
Proceedings of the 5th Electronics System-Integration Technology Conference, ESTC 2014 | Year: 2014

The long-term stability of the optical properties of high-power LEDs like spectral emissivity and total luminous efficacy is still one of the big technical challenges in solid-state lighting. A basic requirement to guarantee the promised lifetime is to keep the maximum temperature during operation reliably below the specified value. With this respect, the thermal performance of innovative LED-sub mounts based on a thin bismaleimide triazine (BT) substrate with copper filled thermal vias for the direct attachment of high-power LEDs is investigated. The influence of the arrangement of the thermal vias and the copper structure as well as the impact of the degree of imperfectness of solder joints on the junction-to-case thermal resistance are revealed by thermal simulation. The thermal model is verified experimentally using a demonstrator set-up with a thermal resistance of ca. 11 K/W. © 2014 IEEE. Source

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