Energie-Umweltmanagement

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    A fast test technique for life time estimation of ultrasonically welded Cu-Cu interconnects
    (Elsevier, 2010-09)
    Czerny, Bernhard 
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    Khatibi, Golta 
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    Weiss, Brigitte 
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    Licht, T. 
    In this research the quality of the interconnects of the ultrasonically welded Cu terminals to the Cu substrate in the IGBT-module has been investigated. An ultrasonic resonance fatigue system in combination with a laser Doppler vibrometer and a special specimen design was used for shear fatigue testing of these large ultrasonic Cu-Cu welds (about 0.5 cm2). Fatigue life curves up to 109 loading cycles were obtained in a very short period of time. Using this technique it was possible to evaluate the fatigue strength of these interconnects for the first time. The microstructural features of the interconnects were characterized and their crack growth behaviour was studied. Fracture analysis of the fatigued specimen shows that failure occur due to the propagation of the crack beneath the welding interface into the copper substrate. Additionally performed finite element simulations offer an insight into the stress and strain concentrations during the mechanical fatigue tests. As this method is not restricted to the welding geometry, material joints with larger interconnects can be tested likewise. Thus this new technique can be used as a practical and valid fatigue testing method for evaluation of various interconnects.
      51  2Scopus© Citations 1
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    A New Algebraic Reynolds Stress Turbulence Model for Prediction of Wall-Affected Three Dimensional Room Airflows
    (E. Weber, 2008)
    Heschl, Christian 
    In the past various experimental investigations about room airflows were published. But most investiagtions are limited regarding measurements positions (restricted gflow patttern) and the availability of turbulent quantities (Reynolds-Stresses, entrainment, macroscopic instabilities etc.) based on the avaiable experimental data a targeted improvement of turbulence models is difficult. Therefore a complex three dimensional room airflow situation was investigatedwith three-dimensional Particle Image Velocmetry. Detailed informatiom of the floww, the Reynolds-stress distribution and the entertainment are presented. Based on the experimental results the behaviour of RANS-based turbulence models in predicting roomairflow is discussed. In this context, it is shown that intensive anisotropic Reynolds stresses near the wall arise and influences the airflow pattern. For this reason a new algebraic Reynolds stress turbulence model - which can in princible reproduce the turbulence anisotropic behaviour- is proposed. Compared with the linear eddy viscoity turbulence models the new nonlinear model agrees clearly better with the presented experimental findings.
      128  1
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    A new approach for evaluation of fatigue life of al wire bonds in power electronics
    (Elsevier, 2014-02-16)
    Czerny, Bernhard 
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    Khatibi, Golta 
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    Lederer, Martin 
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    Kotas, Agnieszka Betzwar 
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    Weiss, Brigitte 
    Ultrasonically bonded A1 wire bonds on A1 metallization pads are widely used in power semiconductors. The required long time reliability of the devices is highly dependent on the interfacial quality of A1 wire and the bond pad. Reliability of wire bonds is commonly assessed by thermal and power cycling tests. Accelerated mechanical fatigue testing can be used as an alternative to these time consuming procedures. In the present study, lifetime of thick A1 wedge bonds on Si substrates was investigated using a novel mechanical fatigue testing technique operating at high frequencies and elevated temperatures. The influence of microstructure, testing temperature and frequency on lifetime of A1 wire bonds was investigated. Finite element analysis was applied to calculate the stress distribution at the interfacial region and to establish life time prediction curves. The results of mechanical isothermal fatigue curves were compared and correlated with thermal cycling data of Al wire bonds. Copyright © 2014 by The Minerals, Metals & Materials Society.
      73  1Scopus© Citations 2
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    A New Approach for Evaluation of Fatigue Life of Al Wire Bonds in Power Electronics
    (Elsevier, 2014-03)
    Czerny, Bernhard 
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    Khatibi, Golta 
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    Kotas, Agnieszka Betzwar 
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    Weiss, Brigitte 
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    Lederer, Martin 
    Ultrasonically bonded Al wire bonds on Al metallization pads are widely used in power semiconductors. The required long time reliability of the devices is highly dependent on the interfacial quality of Al wire and the bond pad. Reliability of wire bonds is commonly assessed by thermal and power cycling tests. Accelerated mechanical fatigue testing can be used as an alternative to these time consuming procedures. In the present study, lifetime of thick Al wedge bonds on Si substrates was investigated using a novel mechanical fatigue testing technique operating at high frequencies and elevated temperatures. The influence of microstructure, testing temperature and frequency on lifetime of Al wire bonds was investigated. Finite element analysis was applied to calculate the stress distribution at the interfacial region and to establish life time prediction curves. The results of mechanical isothermal fatigue curves were compared and correlated with thermal cycling data of Al wire bonds. © 2014 The Minerals, Metals & Materials Society.
      46  1Scopus© Citations 6
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    A novel approach for evaluation of material interfaces in electronics
    (2016-03-05)
    Czerny, Bernhard 
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    Khatibi, Golta 
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    Lassnig, Alice 
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    Lederer, Martin 
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    Nicolics, Johann 
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    Magnien, Julien 
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    Suhir, Ephraim 
    The rapid technological advancements and market demands in electronic sector requires application of highly accelerated, still practice relevant reliability assessment methods. At present, accelerated power and temperature cycling tests count as the state of the art for qualification of the devices. However due to physical characteristics of the devices, there are limitations to accelerated thermal and power cycling tests. Further acceleration by exceeding a critical temperature or time reduction may result in occurrence of failure mechanisms other than those encountered in real application or suppressing these failures. An alternative approach for further acceleration of the testing procedures is based on the application of isothermal mechanical fatigue testing at high frequencies (AMT). The principle idea of this approach is replacement of thermally induced strains by means of equivalent mechanical strains. Based on a physics of failure approach, the relevant failure modes in the material interfaces are induced enabling detection of weak sites of the devices in a very short duration of time. In addition of time saving factor a further advantage of mechanical fatigue testing is the possibility of decoupling of thermal, mechanical and environmental stress factors for a more effective investigation and diagnosis. This paper presents an overview of our recent reliability studies on different types of electronic components by using the proposed methodology with the aim to give an insights into the advantages and some restrictions of AMT for qualification of electronic devices.
      64  1Scopus© Citations 4
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    A novel linear predictive control approach for auxiliary energy supply to a solar thermal combistorage
    (Elsevier, 2014)
    Pichler, Martin Felix 
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    Lerch, Werner 
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    Heinz, Andreas 
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    Görtler, Gregor 
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    Schranzhofer, Hermann 
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    Rieberer, René 
    This paper presents and investigates a novel, hybrid model predictive approach to control the auxiliary heating for a combistorage. Faulty design, as well as suitable design schemes cause situations in which solar energy supply has to “compete against” the auxiliary energy supply. This research demonstrates a feasible method to remedy such situations with the utilization of weather forecast data. The developed approach is modular and expandable to be used with additional heat sources. A suitable disturbance-prediction, which approximates the expected solar energy flux into the storage, in connection with a linear model predictive control (MPC), can prevent the auxiliary system to switch on at an early stage and thus reduce the auxiliary energy demand and keep storage capacity for solar thermal energy supply. Results obtained through simulations for selected months show a reduction of auxiliary energy demand up to 40%, when facilitating this approach for a solar thermal combisystem for a single family house. Monthly solar fractions (Fs) increase by approximately 4% points or 5% with respect to the base case.
      68  1Scopus© Citations 17
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    A rapid test for reliability of heavy wire bonds
    (Konradin-Verl. Kohlhammer, 2019-04-17)
    Czerny, Bernhard 
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    Seidl, Siegfried 
    Bond-Drahtverbindungen müssen über mehrere Dekaden und unter hohen thermomechanischen Belastungen zuverlässig halten. Dafür sorgt ein Bondtester mit einem extrem schnellen automatischen Qualitätstest zur Lebensdauerbestimmung der Bond-Drahtverbindungen.
      60  1
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    A Thermal Flow Sensor Based on Printed Circuit Technology in Constant Temperature Mode for Various Fluids
    (MDPI, 2019)
    Glatzl, Thomas 
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    Beigelbeck, Roman 
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    Cerimovic, Samir 
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    Steiner, Harald 
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    Wenig, Florian 
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    Sauter, Thilo 
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    Treytl, Albert 
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    Keplinger, Franz 
    We present a thermal flow sensor designed for measuring air as well as water flow velocities in heating, ventilation, and air conditioning (HVAC) systems. The sensor is designed to integrate the flow along the entire diameter of the pipe also quantifying the volume flow rate of the streaming fluid where the calorimetric principle in constant temperature operation is utilized as a readout method. In the constant temperature mode, a controller keeps a specific excess temperature between sensing elements at a constant level resulting in a flow dependent heater voltage. To achieve cost-effective sensors, the fabrication of the transducer is fully based on printed circuit board technology allowing low-cost mass production with different form factors. In addition, 2D-FEM simulations were carried out in order to predict the sensor characteristic of envisaged setups. The simulation enables a fast and easy way to evaluate the sensor’s behaviour in different fluids. The results of the FEM simulations are compared to measurements in real environments, proving the credibility of the model.
      452  1Scopus© Citations 8
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    Absorption von Sauerstoff mit chemischer Reaktion
    (Wiley, 2005)
    Siebenhofer, Matthaeus 
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    Kracker-Semler, Gunther 
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    Vorbach, Martin 
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    Zapfel, Wilhelm 
    Die Absorption von Gasen kann durch eine chemische Reaktion der absorbierten Komponente im Absorbens beschleunigt werden. Um den Einfluss der chemischen Reaktion auf die Absorption von Gasen quantifizieren zu können, wurde eine Fallfilmabsorptionsanlage entwickelt und damit die komplexe Wechselwirkung zwischen der Absorption von SO2, der Absorption von O2 und der Oxidation von Sulfit/Hydrogensulfit untersucht. Einer der Schwerpunkte war die Modellierung der Absorption von Sauerstoff mit chemischer Reaktion.
      60  1
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    Accelerated mechanical fatigue interconnect testing method for electrical wire bonds
    (2018-04-25)
    Czerny, Bernhard 
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    Khatibi, Golta 
    Every new development in device performance and packaging design, can drastically affect the reliability of devices due to implementation of new materials and design changes. High performance and high reliability demands in power electronics over several decades and a short time to market development, raise the need for very fast reliability testing methods. In this study a mechanical fatigue testing method is presented for evaluating the interfacial fatigue resistance of heavy Al wire bonded interconnects in high power modules. By separating the concurrent thermal, mechanical and environmental failure mechanisms a selective investigation of the desired failure mode is possible. The setup is designed to reproduce the thermo-mechanical shear stresses by mechanical means, while provoking the same lift-off failure mode as in power cycling tests. With a frequency variable test setup of a few Hz up to several kHz, measurements from 103 up to 108 loading cycles and determining the influence of the testing frequency on the fatigue life are possible. A semi-automated bond wire fatigue tester operating at 60 kHz is presented which is suitable for rapid screening and qualification of a variety of wire bonds at the stages of development and during the production. © 2018 Walter de Gruyter GmbH, Berlin/Boston.
      65  1Scopus© Citations 19
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    Accelerated mechanical fatigue interconnect testing method for heavy wire bonds in power modules
    (2017-05-11)
    Czerny, Bernhard 
    Every new development in device performance and packaging design, due to new materials and design changes can influence the device reliability drastically. High performance and high reliability demands in power electronics over several decades and a short time to market development, raise the need for very fast reliability testing methods. In this study a mechanical fatigue testing method is presented for evaluating the interfacial fatigue resistance of heavy Al wire bonded interconnects in high power modules. By separating the concurrent thermal, mechanical and environmental failure mechanisms a selective investigation of the desired failure mode is possible. The setup is designed to reproduce the thermo-mechanical shear stresses by mechanical means, while provoking the same lift-off failure mode as in power cycling tests. With a frequency variable test setup of a few Hz up to several kHz, measurements from 1E3 up to 1E8 and determining the influence of the testing frequency on the fatigue life were possible.
      55  1
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      107  1
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      101  1
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      63  1Scopus© Citations 22
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    Aerosol-assisted nanoscale Fe/silica particles for dechlorination of trichloroethylene
    (AIChE, 2007-11-07)
    Zheng, Tonghua 
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    Zhan, Jingjing 
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    Piringer, Gerhard 
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    McPherson, Gary L. 
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    Lu, Yunfeng 
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    John, Vijay T. 
    Nanoscale iron particles are a preferred option for the reductive dehalogenation of trichloroethylene (TCE) due to their environmentally benign nature, high efficiency and low cost. However, nanoscale zerovalent iron (ZVI) particles aggregate and in in-situ remediation technologies, it is difficult to transport these particles to the source of contamination. This study describes a novel approach to the preparation of ZVI nanoparticles that are efficient and effectively transport to contaminant sites. We describe the synthesis of silica supported iron nanoparticles using aerosol technology. While the encapsulated iron nanoparticles are reactive for groundwater trichloroethylene remediation, environmentally benign silica particles serve as effective carriers for nanoiron transport through soil. Encapsulation of iron into submicron silica particles protects ferromagnetic iron nanoparticles from aggregation and may increase their mobility through sedimentation. Additionally, the presence of surface silanol groups on silica particles allows control of surface properties via silanol modification using organic functional groups. Aerosol silica particles with functional groups such as ethyl tails on the surface preferentially adsorb hydrophobic TCE during environmental remediation. This increases the local concentration of TCE in the vicinity of iron nanoparticles, thus promoting the degradation of TCE by iron. These nanoscale iron/silica aerosol particles with controlled surface properties have the potential to be efficiently applied for in-situ remediation and permeable reactive barriers construction.
      58  1
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    An Integrated Framework for Building’s Energy Management based on Deep Learning
    (Leykam, 2020-11-26)
    Meintanis, I. 
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    Monios, N. 
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    Livieris, I.E. 
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    Kampourakis, M. 
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    Fourakis, S. 
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    Kyriakoulis, N. 
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    Kokkorikos, S. 
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    Chondronasios, A. 
    Forecasting the building energy consumption constitutes a significant factor for a wide variety of applications including planning, management and optimization. Nowadays, research is focused towards the development of more efficient and sustainable energy management systems which focus on minimising energy waste. These systems are based on intelligent models, which provide accurate predictions of future energy demand/load, both at aggregate and individual site level. In this work, we present a holistic integrated solution for the buildings’ energy management systems using deep learning methods. The proposed solution is based on efficient deep-learning forecasting models for short-term local weather parameters and energy load consumption. The developed forecasting models are integrated into the smart energy management system of the building for taking the proper decisions to ensure efficient utilization of energy resources.
      163  397
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    Application of in-situ non-invasive failure detection methods for wire bonds
    (2020-09-15)
    Czerny, Bernhard 
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    Chavan, Vinayak 
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    Gasser, Christoph 
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    Rosc, Jördis 
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    Khatibi, Golta 
    Two in-situ failure detection methods by measuring acoustic emissions and transducer responses are presented to investigate the wire bond degradation failure during a highly accelerated mechanical fatigue test. This BAMFIT fatigue test is used to induce cyclic shear stresses in the bond interface until wire bond lift-off, operating at 60 kHz. The task was to incorporate non-invasive failure detection to identify the degree of degradation prior to end of life as an extension to the BAMFIT method and a possible quality control method. The acoustic emission investigations uses a Fabry Perot interferometer to detect high frequency emissions in the vicinity of the wire bond and detecting changes in the first three harmonics to identify a bond degradation. The transducer response approach observes systematic changes in the vibration and the damping behavior of the coupled resonance system by using the transducer as a piezo sensor. The results have shown that defective bond interconnect can be identified as early as ~50% of end of life, using high power but very short vibration pulses, and at ~80% for low power and completely non-invasive pulses. The obtained responses from the presented methods were correlated to the degree of degradation of the bond wire interface, by completing BAMFIT tests until end of life, cross section analysis as well as non-destructive X-ray computer tomography.
      68  1Scopus© Citations 2
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      261  1588