TY - JOUR A1 - Liu, E A1 - Conti, Fosca A1 - Bhogaraju, Sri Krishna A1 - Signorini, Raffaella A1 - Pedron, Danilo A1 - Wunderle, Bernhard A1 - Elger, Gordon T1 - Thermomechanical stress in GaN-LEDs soldered onto Cu substrates studied using finite element method and Raman spectroscopy JF - Journal of Raman Spectroscopy N2 - Local thermomechanical stress can cause failures in semiconductor packages during long-time operation under harsh environmental conditions. This study helps to explain the packaging-induced stress in blue GaN-LEDs soldered onto copper substrates using AuSn alloy as lead-free interconnect material. Based on the finite element method, a virtual prototype is developed to simulate the thermomechanical behavior and stress in the LED and in the complete LED/AuSn/Cu assembly considering plastic and viscoplastic strain. The investigations were performed by varying the temperature between −50°C and 180°C. To validate the model, the simulation results are compared to experimental data collected with Raman spectroscopy. Studies of the urn:x-wiley:03770486:media:jrs5947:jrs5947-math-0003 phonon mode of GaN semiconductor are elaborated to understand the induced thermomechanical stress. The model enables evaluation of the stress in the interfaces of the assembly, which otherwise cannot be accessed by measurements. It serves to predict how assemblies would perform, before committing resources to build a physical prototype. UR - https://doi.org/10.1002/jrs.5947 KW - finite element method KW - gallium nitride (GaN) KW - LED KW - semiconductor KW - thermomechanical stress Y1 - 2020 UR - https://doi.org/10.1002/jrs.5947 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-9438 SN - 1097-4555 VL - 51 IS - 10 SP - 2083 EP - 2094 PB - Wiley CY - Chichester ER - TY - JOUR A1 - Conti, Fosca A1 - Saidi, Abdessamad A1 - Goldbrunner, Markus T1 - Evaluation Criteria and Benefit Analysis of Mixing Process in Anaerobic Digesters of Biogas Plants JF - Environmental and Climate Technologies N2 - A valid method to evaluate decisions of a project proposal is the so-called cost-benefit analysis. Criteria are selected and properly weighted to determine if the project is effective and feasible. The present research study is focused on methodical selection of design parameters to install two propeller mixers inside anaerobic digesters of biogas plants. A cylindrical tank of 1400 m3 was considered. For the model-based optimisation, the substrate was considered as a non-Newtonian fluid with a density of 1090 kg/m3. The Oswald-de Waele power-law model was selected to account for the rheological behaviour of the fluid. Installation parameters of the mixers were rotational angles and heights of the shafts of the two propellers. A computational model was developed to simulate the fluid dynamics depending on the mixing process inside the tank. Several configurations were analysed according to evaluating criteria such as the value of the fluid velocity, its distribution along the three spatial dimensions, and the power consumption to rotate the mixers. The maximum fluid velocity and minimum power consumption were observed when the propellers are located at intermediate height inside the tank and with the shafts perpendicular to the tank radius. With this configuration, the fluid reaches a maximum velocity of 0.28 m/s. According to the investigation, it is evident that mixing systems with propeller shafts deep-seated and parallel to the tank radius should be avoided, both in term of efficiency of the fluid mixing distribution and in term of power consumption. UR - https://doi.org/10.2478/rtuect-2020-0105 KW - Anaerobic digester KW - biomass KW - computational fluid dynamics (CFD) KW - Cost-Benefit Analysis (CBA) KW - evaluation criteria KW - flow velocity KW - full scale biogas digester KW - mixing KW - propeller Y1 - 2020 UR - https://doi.org/10.2478/rtuect-2020-0105 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-9274 SN - 2255-8837 VL - 24 IS - 3 SP - 305 EP - 317 PB - De Gruyter Poland CY - Warsaw ER - TY - JOUR A1 - Conti, Fosca A1 - Saidi, Abdessamad A1 - Goldbrunner, Markus T1 - Numeric Simulation-Based Analysis of the Mixing Process in Anaerobic Digesters of Biogas Plants JF - Chemical Engineering & Technology N2 - Stirring systems with two rotational three-bladed propellers were analyzed using computational fluid dynamics. The propellers are located at three heights and seven angles in a tank with 9 m radius. The fluid was characterized by non-Newtonian rheology and simulated by applying the k-ε turbulence model and the standard k-ω model. Reynolds numbers were estimated. High fluid speeds were obtained with the propellers located at a height of 2 m and oriented at 90° with respect to the tank radius. In the top regions of the tank, the fluid velocity was generally less intense and less affected by the angle setting. The configurations identified as good mixing systems showed power consumptions broadly distributed around 30 kW. UR - https://doi.org/10.1002/ceat.201900650 KW - Anaerobic digester KW - Biogas plant KW - Biomass KW - Fluid dynamics KW - Mixing Y1 - 2020 UR - https://doi.org/10.1002/ceat.201900650 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-9379 SN - 1521-4125 VL - 43 IS - 8 SP - 1522 EP - 1529 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Conti, Fosca A1 - Saidi, Abdessamad A1 - Goldbrunner, Markus T1 - CFD Modelling of Biomass Mixing in Anaerobic Digesters of Biogas Plants JF - Environmental and Climate Technologies N2 - Cut in greenhouse gas emissions, increment of energy from renewables and improvement in energy efficiency represent the three key targets for future energy systems. Among the available bioenergy technologies, biogas production via biodegradation and anaerobic digestion is a widely applied approach, not only to produce biofuels but also to manage industrial and domestic organic waste. Within the biogas production, a sufficient mixing of the organic mass is a crucial step to ensure high biogas yields by bacteria and enzymes. Measurements of the electric power consumption of biogas plants revealed that the electrical energy demand of the stirrer system has a high share of the total electricity consumption of a biogas plant. Investigations on real biogas digesters to optimize the mixing process are cost and time intensive. Therefore, laboratory prototypes and computational simulations represent promising alternatives to analyse and improve the efficiency of mixing systems. In this paper, a computational fluid dynamics (CFD) model is presented, which is applied to commercial stirring systems. The case of two propeller stirrers, located in diametrically opposite positions in a tank filled with ca. 1400 m3 of substrate is described in detail. For the simulation, the rheology of the fluid is adapted to a biomass with 12 wt % dry matter content and obeying the non-Newtonian generalized Ostwald-de Waele power law. The developed simulation procedure considers the rotation angle of each propeller and its height. A total of 441 mixing configurations are calculated and evaluated in terms of the technical benefit. The investigation reveals that locations of the rotors far away from the bottom and high rotational angles cause advantageous fluid dynamics. UR - https://doi.org/10.2478/rtuect-2019-0079 KW - Anaerobic digester KW - biomass KW - cellulose KW - computational fluid dynamics (CFD) KW - full scale biogas digester KW - laboratory digester KW - mixing KW - rheology KW - viscosity Y1 - 2019 UR - https://doi.org/10.2478/rtuect-2019-0079 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-9544 SN - 2255-8837 VL - 23 IS - 3 SP - 57 EP - 69 PB - RTU Press CY - Riga ER - TY - CHAP A1 - Liu, E A1 - Conti, Fosca A1 - Bhogaraju, Sri Krishna A1 - Elger, Gordon T1 - Simulations and experiments to analyze stress phenomena in soldered and sintered interconnections between silicon nitride chips and copper substrates T2 - 2021 22nd International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE) UR - https://doi.org/10.1109/EuroSimE52062.2021.9410869 KW - Performance evaluation KW - Analytical models KW - Compressive stress KW - Thermomechanical processes KW - Data models KW - Microelectronics KW - Finite element analysis Y1 - 2021 UR - https://doi.org/10.1109/EuroSimE52062.2021.9410869 SN - 978-1-6654-1373-2 PB - IEEE CY - Piscataway ER - TY - CHAP A1 - Pascucci, Jacopo A1 - Conti, Fosca A1 - Bhogaraju, Sri Krishna A1 - Signorini, Raffaella A1 - Liu, E A1 - Pedron, Danilo A1 - Elger, Gordon ED - Cheben, Pavel ED - Čtyroký, Jiří ED - Molina-Fernández, Iñigo T1 - Micro-Raman to detect stress phenomena in Si-chips bonded onto Cu substrates T2 - Integrated Optics: Design, Devices, Systems and Applications VI UR - https://doi.org/10.1117/12.2576414 Y1 - 2021 UR - https://doi.org/10.1117/12.2576414 SN - 978-1-5106-4385-7 N1 - Poster + Paper PB - SPIE CY - Bellingham ER - TY - CHAP A1 - Bhogaraju, Sri Krishna A1 - Schmid, Maximilian A1 - Hufnagel, Elias A1 - Conti, Fosca A1 - Kotadia, Hiren R. A1 - Elger, Gordon T1 - Low temperature and low pressure die-attach bonding of high power light emitting diodes with self reducing copper complex paste T2 - IEEE 71st Electronic Components and Technology Conference ECTC 2021, Proceedings UR - https://doi.org/10.1109/ECTC32696.2021.00094 KW - low temperature sintering KW - rapid sintering KW - Cu(II) formate KW - reducing binder KW - low pressure sintering KW - high bond strength Y1 - 2021 UR - https://doi.org/10.1109/ECTC32696.2021.00094 SN - 978-1-6654-4097-4 SP - 526 EP - 531 PB - IEEE CY - Piscataway ER - TY - CHAP A1 - Conti, Fosca A1 - Liu, E A1 - Bhogaraju, Sri Krishna A1 - Wunderle, Bernhard A1 - Elger, Gordon T1 - Finite Element simulations and Raman measurements to investigate thermomechanical stress in GaN-LEDs T2 - 2020 IEEE 8th Electronics System-Integration Technology Conference (ESTC) UR - https://doi.org/10.1109/ESTC48849.2020.9229843 KW - finite element method KW - gallium nitride (GaN) KW - LED KW - Raman spectroscopy KW - semiconductor KW - thermomechanical stress Y1 - 2020 UR - https://doi.org/10.1109/ESTC48849.2020.9229843 SN - 978-1-7281-6293-5 PB - IEEE CY - Piscataway ER - TY - CHAP A1 - Bhogaraju, Sri Krishna A1 - Conti, Fosca A1 - Elger, Gordon T1 - Copper die bonding using copper formate based pastes with α-terpineol, amino-2-propanol and hexylamine as binders T2 - 2020 IEEE 8th Electronics System-Integration Technology Conference (ESTC) UR - https://doi.org/10.1109/ESTC48849.2020.9229801 KW - copper inks KW - sintering KW - low temperature KW - copper nano particles KW - copper formate KW - binder KW - terpineol KW - hexylamine KW - amino-2-propanol Y1 - 2020 UR - https://doi.org/10.1109/ESTC48849.2020.9229801 SN - 978-1-7281-6293-5 PB - IEEE CY - Piscataway ER - TY - CHAP A1 - Conti, Fosca A1 - Liu, E A1 - Bhogaraju, Sri Krishna A1 - Lenz, Christoph A1 - Seitz, Roland A1 - Elger, Gordon T1 - Stress evaluations of silicon nitride chips bonded onto copper substrates via SAC soldering, AuSn soldering, and copper sintering T2 - 2020 26th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) UR - https://doi.org/10.1109/THERMINIC49743.2020.9420523 KW - Creep KW - Thermomechanical processes KW - Silicon nitride KW - Copper KW - Plastics KW - Microstructure KW - Soldering Y1 - 2021 UR - https://doi.org/10.1109/THERMINIC49743.2020.9420523 SN - 978-1-7281-7643-7 SP - 204 EP - 208 PB - IEEE CY - Piscataway ER - TY - JOUR A1 - Mokhtari, Omid A1 - Conti, Fosca A1 - Saccon, Rodolfo A1 - Bhogaraju, Sri Krishna A1 - Elger, Gordon T1 - Formic acid and formate salts for chemical vapor deposition of copper on glass substrates at atmospheric pressure JF - New Journal of Chemistry UR - https://doi.org/10.1039/D1NJ02476K Y1 - 2021 UR - https://doi.org/10.1039/D1NJ02476K SN - 1369-9261 VL - 45 IS - 43 SP - 20133 EP - 20139 PB - RSC CY - London ER - TY - JOUR A1 - Bhogaraju, Sri Krishna A1 - Kotadia, Hiren R. A1 - Conti, Fosca A1 - Mauser, Armin A1 - Rubenbauer, Thomas A1 - Bruetting, Robert A1 - Schneider-Ramelow, Martin A1 - Elger, Gordon T1 - Die-attach bonding with etched micro brass metal pigment flakes for high-power electronics packaging JF - ACS Applied Electronic Materials UR - https://doi.org/10.1021/acsaelm.1c00721 KW - sintering KW - brass flakes KW - nanostructured materials KW - self-reducing KW - etching KW - surface modifications Y1 - 2021 UR - https://doi.org/10.1021/acsaelm.1c00721 SN - 2637-6113 VL - 3 IS - 10 SP - 4587 EP - 4603 PB - ACS Publications CY - Washington ER - TY - JOUR A1 - Bhogaraju, Sri Krishna A1 - Mokhtari, Omid A1 - Conti, Fosca A1 - Elger, Gordon T1 - Die-attach bonding for high temperature applications using thermal decomposition of copper(II) formate with polyethylene glycol JF - Scripta Materialia UR - https://doi.org/10.1016/j.scriptamat.2020.02.045 Y1 - 2020 UR - https://doi.org/10.1016/j.scriptamat.2020.02.045 SN - 1359-6462 VL - 2020 IS - 182 SP - 74 EP - 80 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Bhogaraju, Sri Krishna A1 - Conti, Fosca A1 - Kotadia, Hiren R. A1 - Keim, Simon A1 - Tetzlaff, Ulrich A1 - Elger, Gordon T1 - Novel approach to copper sintering using surface enhanced brass micro flakes for microelectronics packaging JF - Journal of Alloys and Compounds UR - https://doi.org/10.1016/j.jallcom.2020.156043 KW - Metals and alloys KW - Microstructure KW - Surfaces and interfaces KW - Sintering Y1 - 2020 UR - https://doi.org/10.1016/j.jallcom.2020.156043 SN - 1873-4669 VL - 2020 IS - 844 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Mokhtari, Omid A1 - Conti, Fosca A1 - Bhogaraju, Sri Krishna A1 - Meier, Markus A1 - Schweigart, Helmut A1 - Tetzlaff, Ulrich A1 - Elger, Gordon T1 - Characterization of tin-oxides and tin-formate crystals obtained from SnAgCu solder alloy under formic acid vapor JF - New Journal of Chemistry UR - https://doi.org/10.1039/C9NJ02135C Y1 - 2019 UR - https://doi.org/10.1039/C9NJ02135C SN - 1369-9261 VL - 43 IS - 26 SP - 10227 EP - 10231 PB - RSC CY - London ER - TY - CHAP A1 - Bhogaraju, Sri Krishna A1 - Conti, Fosca A1 - Schmid, Maximilian A1 - Meier, Markus A1 - Schweigart, Helmut A1 - Elger, Gordon T1 - Development of sinter paste with surface modified copper alloy particles for die-attach bonding T2 - ETG-Fachbericht 161, CIPS 2020, 11th International Conference on Integrated Power Electronics Systems Y1 - 2020 UR - https://www.vde-verlag.de/proceedings-de/455225100.html SN - 978-3-8007-5226-3 SN - 978-3-8007-5225-6 N1 - Auch veröffentlicht auf IEEE: https://ieeexplore.ieee.org/document/9097746 SP - 582 EP - 587 PB - VDE Verlag CY - Berlin ER - TY - CHAP A1 - Elger, Gordon A1 - Liu, E A1 - Conti, Fosca A1 - Signorini, Raffaella A1 - Brugnolotto, Enrico A1 - Bhogaraju, Sri Krishna T1 - Modelling Thermo-Mechanical Stress in GaN-LEDs Soldered on Copper Substrate with Simulations Validated by Raman Experiments T2 - 2019 20th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE) UR - https://doi.org/10.1109/EuroSimE.2019.8724533 KW - Conferences KW - Microelectronics KW - Micromechanical devices Y1 - 2019 UR - https://doi.org/10.1109/EuroSimE.2019.8724533 SN - 978-1-5386-8040-7 PB - IEEE CY - Piscataway ER - TY - CHAP A1 - Elger, Gordon A1 - Mokhtari, Omid A1 - Bhogaraju, Sri Krishna A1 - Conti, Fosca A1 - Meier, Markus A1 - Schweigart, Helmut T1 - Analyse der Reaktionsprodukte von Metall-Formiaten im rückstandfreien Lötprozess T2 - GMM-Fb. 94: EBL 2020 – Elektronische Baugruppen und Leiterplatten UR - https://www.vde-verlag.de/proceedings-de/455185053.html Y1 - 2020 UR - https://www.vde-verlag.de/proceedings-de/455185053.html SN - 978-3-8007-5185-3 SN - 978-3-8007-5186-0 PB - VDE Verlag CY - Berlin ER - TY - CHAP A1 - Bhogaraju, Sri Krishna A1 - Mokhtari, Omid A1 - Pascucci, Jacopo A1 - Conti, Fosca A1 - Kotadia, Hiren R. A1 - Elger, Gordon T1 - A multi-pronged approach to low-pressure Cu sintering using surface-modified particles, substrate and chip metallization T2 - International Symposium on Microelectronics UR - https://doi.org/10.4071/2380-4505-2019.1.000387 Y1 - 2019 UR - https://doi.org/10.4071/2380-4505-2019.1.000387 SN - 2380-4505 SN - 1085-8024 VL - 2019 IS - 1 SP - 387 EP - 392 PB - IMAPS CY - Pittsburgh ER - TY - CHAP A1 - Bhogaraju, Sri Krishna A1 - Mokhtari, Omid A1 - Pascucci, Jacopo A1 - Conti, Fosca A1 - Elger, Gordon T1 - Improved sinterability of particles to substrates by surface modifications on substrate metallization T2 - Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) UR - https://doi.org/10.4071/2380-4491.2019.HiTen.000066 Y1 - 2019 UR - https://doi.org/10.4071/2380-4491.2019.HiTen.000066 SN - 2380-4491 VL - 2019 IS - HiTen SP - 66 EP - 70 PB - IMAPS CY - Pittsburgh (PA) ER -