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  • 1. Belov, Ilja
    et al.
    Rydén, Jan
    Lindeblom, Joakim
    Zhang, Yafan
    RISE Acreo.
    Hansson, Torgny
    Bergner, Fredrik
    Leisner, Peter
    Application of CFD modelling for energy efficient humidity management of an electronics enclosure in storage under severe climatic conditions2008Conference paper (Refereed)
  • 2. Kostov, Konstantin
    et al.
    Lim, Jang-Kwon
    Zhang, Yafan
    Impact of Package Parasitics on Switching Performance2016Conference paper (Refereed)
    Abstract [en]

    The package parasitics are a serious obstacle to the high-speed switching, which is necessary in order to reduce the switching power losses or reduce the size of power converters. In order to design new packages suitable for Silicon Carbide (SiC) power transistors, it is necessary to extract the parasitics of different packages and be able to predict the switching performance of the power devices placed in these packages. This paper presents two ways of simulating the switching performance in a half-bridge power module with SiC MOSFETs. The results show that the parasitic inductances in the power module slow down the switching, lead to poor current sharing, and together with the parasitic capacitances lead to oscillations. These negative effects can cause failures, increased losses, and electromagnetic compatibility issues.

  • 3.
    Neumaier, Klaus
    et al.
    Fairchild semiconductor, Munich.
    Zhang, Yafan
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems. RISE Acreo AB, Sweden.
    Thermal, Mechanical and Electrical Design of a Power Inverter Using ANSYS Workbench2016Conference paper (Refereed)
  • 4.
    Toth-Pal, Zsolt
    et al.
    Swerea KIMAB, Sweden.
    Zhang, Yafan
    Acreo Swedish ICT, Sweden.
    Belov, I.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Bakowski, M.
    Investigation of pressure dependent thermal contact resistance between silver metallized SiC chip and DBC substrate2015In: European Conference on Silicon Carbide and Related Materials, ECSCRM 2014, Trans Tech Publications Inc., 2015, Vol. 821-823, p. 452-455Conference paper (Refereed)
    Abstract [en]

    Thermal contact resistances between a silver metallized SiC chip and a direct bonded copper (DBC) substrate have been measured in a heat transfer experiment. A novel experimental method to separate thermal contact resistances in multilayer heat transfer path has been demonstrated. The experimental results have been compared both with analytical calculations and with 3D computational fluid dynamics (CFD) simulation results. A simplified CFD model of the experimental setup has been validated. The results show significant pressure dependence of the thermal contact resistance but also a pressure independent part.

  • 5.
    Toth-Pal, Zsolt
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems. Swerea KIMAB, Sweden.
    Zhang, Yafan
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems. Swerea KIMAB, Sweden.
    Hammam, Tag
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Bakowski, Mietek
    Thermal improvement of press-pack packages: Pressure dependent thermal contact resistance with a thin silver interlayer between molybdenum substrate and silicon carbide chip2017In: 2017 IEEE International Workshop on Integrated Power Packaging, IWIPP 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7936753Conference paper (Refereed)
    Abstract [en]

    In typical press-pack, free-floating packages the thermal contact resistance between chip and substrate is a major limiting factor for the cooling ability of the power module. We report an introduction of a new, thin Silver interlayer between Molybdenum substrate and chip, and how it improves the thermal contact. The thermal contact resistances were measured with and without a Silver interlayer at different pressures. The surface roughness of the SiC chip and the Molybdenum substrate were characterized. The thermal contact resistances were measured at three different heating power levels. The results show a significant reduction of the thermal contact resistance with only a few micrometer Silver interlayer. The improved cooling effect of a Silver interlayer was also demonstrated with a fluid dynamics type of 3 D simulation comparing temperature distributions with and without a Silver interlayer. These results project a possible thermal improvement in press-pack packages.

  • 6.
    Toth-Pal, Zsolt
    et al.
    Swerea KIMAB, Sweden.
    Zhang, Yafan
    Swerea KIMAB, Sweden.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Bakowski, M.
    Investigation of pressure dependent thermal contact resistance between silver metallized SiC chip and molybdenum substrate and between molybdenum substrate and bulk copper2016In: 16th International Conference on Silicon Carbide and Related Materials, ICSCRM 2015, Trans Tech Publications, 2016, Vol. 858, p. 1061-1065Conference paper (Refereed)
    Abstract [en]

    Thermal contact resistances between a silver metallized SiC chip and a Molybdenum substrate and between the Molybdenum substrate and bulk Copper were measured in a heat transfer experiment. An experimental method to separate thermal contact resistances in a multilayer heat transfer path was used to extract the layer-specific contact resistances. The experimental results were compared with theory based calculations and also with 3-D computational fluid dynamics (CFD) simulation results. The results show significant pressure dependence of the thermal contact resistance and the results show higher thermal contact resistance per unit area between the bulk SiC chip and Molybdenum than between Molybdenum and bulk Copper.

  • 7.
    Zhang, Yafan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Multiphysics Characterization of a Novel SiC Power ModuleManuscript (preprint) (Other academic)
  • 8.
    Zhang, Yafan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems. RISE Acreo AB.
    Multiphysics Characterization of SiC Power Modules2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis proposes several novel silicon carbide power module design concepts. The goal has been to address the problems with the present designs. The electrical, thermal, and thermomechanical performances of the demonstrators have been evaluated along with presentations of methodologies of experimental and numerical characterizations.

    Compact high-temperature power modules with adequate cooling systems are attractive to automotive applications. Therefore, a novel thermal design of a double-sided liquid/air cooled silicon carbide power module (1200 V, 200 A) has been proposed. The concept integrates a dc-link capacitor, a gate driver board, and finned cooling channels. The cooling concept has been evaluated for three application scenarios based on a validated computational fluid dynamics model. Moreover, a simulation methodology has been developed to quantify the effect of different materials and thicknesses of the cold plates on the temperature of the silicon carbide power dies.

    For medium- and high-power applications, contemporary research concludes that the reliability of the existing packaging technology needs to be improved. Therefore, this work proposes a novel press-pack silicon carbide power module concept. The concept enables bondless package and allows for an order of magnitude higher clamping force on the heatsinks than what can be applied on the dies. First, experimental and numerical methodologies for thermomechanical performance characterization of a press-pack structure have been investigated. By using digital image correlation technique, the deformation of each stacked material layer has been obtained. The developed experiment has led to an analytical estimation of friction coefficients on the contact interfaces. The co-influence of the design parameters on the thermomechanical performance of the press-pack structure has been analyzed through a parametric study based on a finite element model. Second, the novel double press-pack silicon carbide power module concept has been evaluated in a demonstrator in terms of parasitic inductance, thermal resistance, and thermomechanical stress.

    Furthermore, many of the power module designs only stay at the stage of proof-of-concept due to the cost of retooling of the manufacturing facility. Embedded power modules which employ advanced printed circuit board processing and die embedding technologies, enable a solution with possibility of low cost and mass production. Therefore, a novel design concept of a three-phase embedded power module (1200 V, 20 A) has been proposed. Simulation-driven design development has been implemented and lead to a fabricated demonstrator. The electromagnetic, thermal, and thermomechanical performances of the concept have been evaluated by simulations and compared to a commercially available power module.

  • 9.
    Zhang, Yafan
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion. Jönköping University, Sweden.
    Belov, Ilja
    Bakowski, Mietek
    Lim, Jang-Kwon
    Leisner, Peter
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Investigation of a Finned Baseplate Material and Thickness Variation for Thermal Performance of a SiC Power Module2014In: 2014 15th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2014, IEEE Computer Society, 2014, article id 6813817Conference paper (Refereed)
    Abstract [en]

    A simplified transient computational fluid dynamics model of an automotive three-phase double-side liquid cooled silicon carbide power inverter, including pin-fin baseplates, has been developed and qualified for parametric studies. Effective heat transfer coefficients have been extracted from the detailed pin-fin baseplate model for two coolant volume flow rates 2 l/min and 6 l/min, at the coolant temperature 105 degrees C. The inverter model includes temperature dependent heat losses of SiC transistors and diodes, calculated for two driving cycles. Baseplate materials such as copper, aluminum-silicon carbide metal matrix composite, aluminium alloy 6061 as well as virtual materials have been evaluated in the parametric studies. Thermal conductivity, specific heat and density have been varied as well as thickness of the finned baseplates (1 to 3 mm). A trade-off between temperature of SiC chips and baseplate weight has been investigated by means of Pareto optimization. The main results of the parametric studies include a weak dependence (1 to 3 degrees C) of the chip temperature on baseplate thickness. Furthermore, switching e.g. between copper and AlSiC results in 5 to 8 degrees C increase of the chip temperature, at 65 to 70 % baseplate weight reduction.

  • 10.
    Zhang, Yafan
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion. Acreo Swedish ICT AB.
    Belov, Ilja
    Jönköpng University.
    Sarius, Niklas G.
    Sp Technical Research Institute of Sweden.
    Bakowski, Mietek
    Acreo Swedish ICT AB.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leisner, Peter
    Sp Technical Research Institute of Sweden.
    Thermal evaluation of a liquid/air cooled integrated power inverter for hybrid vehicle applications2013In: 2013 14th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2013, New York: IEEE , 2013, p. 6529944-Conference paper (Refereed)
    Abstract [en]

    A thermal design of an integrated double-side cooled SiC 50kW-1200V-200A power inverter for hybrid electric vehicle applications has been proposed to enable cooling in two different automotive operating environments: under-hood and controlled temperature environment of passenger compartment. The power inverter is integrated with air/liquid cooled cold plates equipped with finned channels. Concept evaluation and CFD model calibration have been performed on a simplified thermal prototype. Computational experiments on the detailed model of the inverter, including packaging materials, have been performed for automotive industry defined application scenarios, including two extreme and one typical driving cycles. For the studied application scenarios the case temperature of the SiC transistors and diodes have been found to be below 210°C. The maximum steady-state temperature of the DC-link capacitor has been below 127 °C for the worst-case scenario including liquid cooling, and up to 140 °C for the worst-case scenario with air-cooling.

  • 11.
    Zhang, Yafan
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems. RISE Acreo AB, Sweden.
    Hammam, Tag
    Belov, Ilja
    Sjögren, Torsten
    Bakowski, Mietek
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Thermomechanical Analysis and Characterization of a Press-Pack Structure for SiC Power Module Packaging Applications2017In: IEEE Transactions on Components, Packaging, and Manufacturing Technology, ISSN 2156-3950, E-ISSN 2156-3985, Vol. 7, no 7, p. 1089-1100Article in journal (Refereed)
    Abstract [en]

    This paper presents an experimental methodology for the characterization of thermomechanical displacement and friction properties in a free-floating press-pack structure, and evaluation of the tensile stress on the semiconductor die through simulation of different mechanical and thermal loading conditions. The press-pack structure consists of a single silver-metallized (1 μm) silicon carbide die (400 μm) in contact with rhodium-coated (0.4 μm) molybdenum square plates. The thermomechanical displacements in the press-pack structure have been obtained using the digital image correlation technique, and the mean random error has been $± $0.1 μm, which is approximately 10 ppm of the measured length (10.5 mm). The developed experimental method has led to an analytical estimation of friction coefficients on the interfaces' silicon carbide-molybdenum and molybdenum-copper. The results demonstrate that the thin silver layer behaves as a solid film lubricant. A 2-D finite-element model representing the experimental setup has been implemented. The difference in displacement between measurement and simulation is less than 8%. Furthermore, the coinfluence of the design parameters on the thermomechanical performance of the stacked structure has been analyzed through simulations. Finally, design guidelines to reduce the tensile stress on the silicon carbide die have been proposed regarding free-floating press-pack power electronics packaging.

  • 12.
    Zhang, Yafan
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems. RISE Acreo AB, Sweden.
    Neumaier, K.
    Zschieschang, O.
    Weis, G.
    Schmid, G.
    Bakowski, M.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Simulation-driven development of a novel SiC embedded power module design concept2017In: 2017 18th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7926252Conference paper (Refereed)
    Abstract [en]

    Silicon carbide embedded power modules enable a compact and cost competitive packaging solution for high-switching frequency and high-temperature operation applications. Power module packaging technologies span several engineering domains. At the early design stage, simulation-driven development is necessary to shorten the design period and reduce the design cost. This paper presents a novel design concept of a three-phase embedded power module (1200 V, 20 A, 55 mm × 36 mm × 0.808 mm) including silicon carbide metal-oxide-semiconductor field-effect transistor and antiparallel diode dies. Based on the E/CAD design data different layer built-up designs have been tested against thermal, mechanical, and electrical behavior. The obtained simulation data then have been evaluated against a commercial available power module (Motion Smart Power Module SMP33) which utilizes over mold direct bonded copper substrates with soldered semiconductor dies and bond wire contacts. Compared to the conventional module, the loop conductive interconnection parasitic inductance and resistance of the design concept (Vdc+ to Vdc-) reduces approximately by 88 % and 72 %, respectively. The average junction to case thermal resistance has been improved by approximately more than 10 % even though the total package size reduces by approximately 88 %. Furthermore, the contours of deformation and stresses have been investigated for the design concept in the thermomechanical simulation.

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