TY - CHAP A1 - May, Daniel A1 - Fritsche, S. A1 - Cardoso, A. A1 - Schacht, Ralph A1 - Wunderle, Bernhard T1 - IR Pulse Thermography as Failure Analytical Tool Applied to Die Attach Processes T2 - 21st International Workshop on Thermal Investigations of ICs and Systems, Sept. 30 2015 - Oct. 2 2015 N2 - New die attach technologies are necessary to meet the demand for faster and more reliable power electronic devices.Technologies based on sintering such as silver sintering and silver sinter adhesives are currently in the focus of technology development because of their high strength and very high thermal performance. To ensure the reliability of such a die attach reliable, fast and non-destructive failure analysis (FA) are needed. Transient thermal methods (TTM) provide techniques for detection of different types of defects such as delaminations of interfaces, cracks , electrical short circuits and voids in die attach layer [1]–[3]. In this work, pulse thermography (PT), one of the TTMs, was successfully used for nondestructive testing of the die attach layers under industrial conditions. We have studied the physical principles and presented fundamental possibilities and limitations given by formulas, nomograms and parameter sensitivity studies. Finally, we demonstrate the PT as accompanying FA to process qualification of a sintered silver adhesive process. KW - IR Thermography KW - Non-Destrutive Failuer Analysis Y1 - 2015 UR - http://ieeexplore.ieee.org/document/7389622/ SN - 978-1-4673-9705-6 PB - IEEE CY - Piscataway, NJ ER - TY - CHAP A1 - Abo Ras, Mohamad A1 - May, Daniel A1 - Schacht, Ralph A1 - Bast, M. A1 - Eisle, R. A1 - Michel, Bernd A1 - Winkler, Thomas A1 - Rzepka, Sven A1 - Wunderle, Bernhard T1 - "LaTIMA" an Innovative Test Stand for Thermal and Electrical Characterization of Highly Conductive Metals, Die Attach, and Substrate Materials T2 - 21st International Workshop on Thermal Investigations of ICs and Systems, Sept. 30 2015 - Oct. 2 2015 N2 - This paper deals with the development of an innovative test stand for the measurement of thermal and electrical conductivity of metals, semiconductors, highly conductive die attaches and substrates using the steady state technique for thermal characterization and four-terminal sensing with pulse delta technique for electrical characterization. We present a systematic study of sintered silver in order to investigate the influence of sintering conditions on thermal and electrical properties. Several sintered silver samples have been prepared under sintering temperature variation between 200°C and 270°C and sintering pressure variation between 5 MPa and 25 MPa. The characterization results diversify up to 200% for thermal conductivity and up to 330% for electrical conductivity. The Wiedemann-France law describes the relationship between electrical and thermal conductivities for bulk metals. We proved that this law applies not only for bulk metal but also for porous sintered metal. KW - Thermal characterization KW - electrical characterization KW - highly conductive metals KW - die attach KW - substrate materials Y1 - 2015 UR - www.therminic2015.eu SN - 978-1-4673-9705-6 N1 - Best paper award PB - IEEE CY - Piscataway, NJ ER - TY - GEN A1 - Schacht, Ralph A1 - Hausdorf, Alexander A1 - Wunderle, Bernhard T1 - Feasibility and Design Study of a Frictionless Air Mover for Thermal Management of Electronics T2 - Journal of Physics: Conference Series N2 - A frictionless air mover concept will be introduced. As opposed to a piezoelectric driven fan, the air mover is based on a flexible blade whose vibration is driven by means of a magnetic field. The blade material is based on a polymer material. The paper presents the results of feasibility and an on-going comprehensive design study. The results are compared with a comparable piezoelectric fan [1, 2]. The performance of the feasibility study amounted to 65% to the piezoelectric fan. To enhance the performance, two different blade materials as well as the influence of the coil shape and value were under investigation. A further goal is to reduce the size and to investigate the influence of a cabinet. The design study results in a prototype of a size of 50 x 14 x 35 mm² incl. a cabinet. The performance could be doubled. A volume flow rate of V̊ ~14 l/min and static pressure of Ƿstat = 3 Pa could be reached. KW - firctionless cooling KW - air mover KW - miniturized fan Y1 - 2014 U6 - https://doi.org/10.1088/1742-6596/525/1/012026 SN - 1742-6596 SN - 1742-6588 VL - 525 SP - 012026 ER - TY - CHAP A1 - Schacht, Ralph A1 - Hausdorf, Alexander A1 - Wunderle, Bernhard A1 - Rzepka, Sven A1 - Michel, Bernd T1 - Efficiency optimization for a frictionless air flow blade fan – design study T2 - 14th IEEE ITHERM Conference, Orlando(Fl), USA, May 30th, 2014 N2 - This paper resumes the frictionless fan concept which was introduced at itherm 2012 [1]. This concept was based on a flexible polymer blade, the vibration of which is, as opposite to the piezoelectric driven fan principle, driven by means of a magnetic field. This type of fan can be of interest in regions where otherwise the fluid flow would be stagnant. This paper presents the results of a further in depth design study to reduce power loss and form factor as well as to optimize fan efficiency. Therefore, different blade materials and shapes, different sheet materials for the inductive stimulation as well as the influence of coil shape, value and number were under investigation. As a result, the size could be reduced by half and the efficiency could be doubled. A maximum flow rate of 14 l/min and a static pressure of 3 Pa at 240 mW fan power could be reached. KW - frictionless cooling KW - reliable air flow fan KW - thermal management KW - nearly noiseless cooling Y1 - 2014 SN - 978-1-4799-5267-0 SP - 1019 EP - 1026 PB - IEEE CY - Piscataway, NJ ER - TY - GEN A1 - Wunderle, Bernhard A1 - May, Daniel A1 - Heilmann, Jens A1 - Arnold, Jörg A1 - Hirscheider, Josef A1 - Lee, Yi A1 - Bauer, Jörg A1 - Schacht, Ralph A1 - Abo Ras, Mohamad T1 - Accelerated Pump Out Testing for Thermal Greases T2 - 20th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE) N2 - Thermal greases allow a low stress bond at low bond line thicknesses (BLT) at medium thermal conductivities and simple application, all of which make it an alternative to solders, thermal adhesives or pads. It is widely used in power and microprocessor applications, most of which involve large areas to be used for heat transfer. However, for years thermal overload failure of power modules and chips has been a pressing problem due to pump-out of thermal grease as a die or module thermal interface material (TIM): Most thermal greases are Bingham fluids and thus not solids, so they can be squeezed out from in between the gap, driven by thermo-mechanical action of the adjacent layers as e.g. DCB substrate or silicon chip with the heat sink. Today, thermal greases have to be qualified in lengthy stress tests in a product relevant environment which consumes substantial resources as often a system test is required. Therefore, a fast test is necessary which accelerates testing and thus allows a fast screening of commercial greases on one hand, and guidelines for material development on the other. For that purpose this paper addresses this topic in a combined simulative and experimental way, where at the same time a novel test procedure is proposed for accelerated grease pump-out testing (GPOT) in the framework of a completely new approach, combining loading with in-situ failure analytical techniques and decoupling thermal from mechanical loading. This allows for the first time a realistic loading of greases during accelerated testing with testing times below one hour. The method is demonstrated on various commercial and custom greases, varying their composition and structure, and benchmarked against industry standard thermal cycling tests. Further, two fundamental failure mechanisms have been identified being at work simultaneously, notably fluid transport (which constitutes actually a pump-in phenomenon) and air entrapment. We were able to identify key properties of the materials and loading variables, on which their intensity depends. KW - Thermal Grease, Pump out Y1 - 2019 SN - 978-1-5386-8040-7 SN - 978-1-5386-8039-1 SN - 978-1-5386-8041-4 U6 - https://doi.org/10.1109/EuroSimE.2019.8724540 PB - IEEE ER - TY - GEN A1 - Schacht, Ralph A1 - Gruen, Tobias A1 - Nowak, Torsten A1 - Arnold, Jörg A1 - May, Daniel A1 - Wunderle, Bernhard T1 - Experimental investigation of pumped two-phase flow boiling using different finned and pin finned structures on interchangeable heater modules T2 - 29th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) N2 - This paper introduces an industry-grade, multipurpose closed loop flow boiling cooler test stand for rapid experimental characterization and parameter variation. A flow boiling chamber with interchangeable plug-in heater module was designed that allows for the investigation of different finned cooler structures and surface topologies and chemistry respectively to enhance small bubble formation and release. In this experimental investigation a finned and a pin finned cooler structure using mm-size dimensions were used. It could be shown that the pin finned and finned cooler structure show for low flow rates at low pressure drop the same performance. Furthermore, it could be observed that the heat transfer coefficient could be increased for both cooler structure in the two-phase regime as opposed to single-phase convective liquid cooling. KW - Mini channel liquid cooler KW - Pumped two-phase flow boiling KW - Industrial-grade flow boiling cooler test stand KW - Liquid cooling Y1 - 2023 U6 - https://doi.org/10.1109/THERMINIC60375.2023.10325896 ER - TY - GEN A1 - Kettelgerdes, Marcel A1 - Mezmer, Peter A1 - Haeussler, Michael J. A1 - Böttger, Gunnar A1 - Tavakolibasti, Majid A1 - Pandey, Amit A1 - Erdogan, Hüseyin A1 - Elger, Gordon A1 - Schacht, Ralph A1 - Wunderle, Bernhard T1 - Realization, multi-field coupled simulation and characterization of a thermo-mechanically robust LiDAR front end on a copper coated glass substrateier den Haupttitel eintragen N2 - The thermo-mechanical robustness of Advanced Driving Assistance Systems is crucial to leverage the growing market of automated driving. Especially in case of optical sensors, such as camera and Light Detection and Ranging (LiDAR) sensors, the thermo-mechanical state of the sensor front end is closely coupled with its optical performance. Deformations in the optical path, consisting of the lens elements and imager, can cause major performance degradation like defocus. Additionally, the big Coefficient of Thermal Expansion (CTE) mismatch between the commonly used FR4 substrate and large silicon (time-off light) imagers, leads to extraordinary mechanical stress in the respective interconnects if operated under harsh automotive temperature conditions. Hence, within this work, an optical LiDAR front end on glass is realized in the form of reduced complexity modules (RCMs) of the transmitter and receiver path. The transmitter RCM, consisting of a variety of small glass mounted high power Vertical Cavity Surface Emitting Laser (VCSEL) diodes is tested and evaluated with respect to lifetime reliability, whereas the receiver RCM, consisting of a glass mounted large-scale imager, is firstly investigated with regard to cooling under high temperature operation. Y1 - 2023 U6 - https://doi.org/10.1109/ECTC51909.2023.00131 ER - TY - GEN A1 - Panahandeh, Sara A1 - May, Daniel A1 - Grosse-Kockert, Corina A1 - Schacht, Ralph A1 - Abo Ras, Mohamad A1 - Wunderle, Bernhard T1 - Pulsed infrared thermal imaging as inline quality assessment tool T2 - Microelectronics Reliability N2 - Pulsed infrared thermography (PIRT) is a very fast and non-destructive technique for testing various types of specimens. This makes PIRT interesting for 100 %-inspections in industrial production lines. Especially for the die attach interface inspection of sintered and soldered electronic components and layer-to-layer interfaces in fiber-reinforced plastic (FRP), the industry is looking for alternatives to cost intensive X-ray methods and the time-consuming scanning acoustic microscopy (C-SAM). A big challenge to use the PIRT technology for inspections in industrial production lines is the low emissivity of the surface of the device under test (DUT). This work will present a PIRT system including a vacuum foil lamination setup to avoid the necessary spray coating of DUTs with low emissivity surfaces in failure analyses. This system can be used as inline quality assessment tool with an integrated technique to perform reliable component inspections on a wide range of different specimens. KW - Pulsed infrared thermography; Non-destructive technique; Sintered and soldered electronic components; Production line; Failure analysis Y1 - 2023 U6 - https://doi.org/10.1016/j.microrel.2023.114910 SN - 0026-2714 VL - 2023 IS - Volume 142 SP - 1 EP - 11 ER - TY - GEN A1 - Schacht, Ralph A1 - Majed, Jihed Ben A1 - Grün, Tobias A1 - May, Daniel A1 - Ras, Mohamad Abo A1 - Wunderle, Bernhard T1 - Closed-loop flow boiling cooler test stand for investigations on future power package designs T2 - 2024 30th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) N2 - In this work, flow boiling heat transfer to water is investigated experimentally. Flow boiling heat transfer is a topic that is of interest for the cooling of power electronics, high performance computing in automotive applications, and other electronic packages with particularly high heat flux. To investigate cooling solutions for new electronic packages a closed-loop two-phase flow boiling cooling test stand for rapid experimental characterization and parameter variation is introduced. In order to have a proof of concept for the test stand and to demonstrate comparability with the test setups described in the literature, first, different cooler structures in the mm range are investigated, using copper heater modules driven by heater cartridges. Secondly, the integration of flow boiling cooling together with an industry-oriented electronic power package is demonstrated. A heat transfer coefficient of 24 kW/m²K (242 W/cm² at 1.5 kW on a chip area of 24.9 x 24.9 mm²) was achieved for a plain silicon chip surface at a volume flow rate of 1 l/min using dielectric water as cooling fluid. The chip temperature and the differential pressure were measured to 137 °C and 8 kPa. KW - Closed-loop two-phase flow boiling, future application-oriented flow boiling cooler concept, HPC, electronic power package, automotive Y1 - 2024 U6 - https://doi.org/10.1109/THERMINIC62015.2024.10732089 SP - 1 EP - 8 PB - IEEE ER - TY - CHAP A1 - Schacht, Ralph A1 - Majed, Ben A1 - Gruen, Tobias A1 - May, Daniel A1 - Wunderle, Bernhard T1 - Multi-purpose thermal test vehicle for experimental investigation on pumped two-phase cooling T2 - 2024 25th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE) N2 - Flow boiling heat transfer to water of different cooler surface topologies is experimentally investigated. To have the possibility for investigations of new electronic packages that supports cooling solutions by two-phase flow boiling, a multipurpose closed two-phase flow boiling cooling test stand for rapid experimental characterization and parameter variation is designed. The designed test vehicle holds interchangeable, plug-in heating module that offers the possibility to investigate different cooler structures and surface topologies/chemistry to improve the formation and release of small bubbles. In order to have a proof of concept for the test stand and to show its reproducible to those given in the literature, initially, the investigation is limited to a plain-and dimpled-surface and a pin fin and finned cooler structure in the mm range. KW - Pins KW - Micromechanical devices KW - Cooling KW - Water heating KW - Packaging KW - Electronic packaging thermal management KW - Topology Y1 - 2024 U6 - https://doi.org/10.1109/EuroSimE60745.2024.10491533 SP - 1 EP - 7 PB - IEEE ER - TY - GEN A1 - Schacht, Ralph A1 - Majed, Jihed Ben A1 - Grün, Tobias A1 - May, Daniel A1 - Ras, Mohamad Abo A1 - Wunderle, Bernhard T1 - Integration of two-phase flow boiling in future power packages T2 - 2025 41st Semiconductor Thermal Measurement, Modeling & Management Symposium (SEMI-THERM) N2 - Flow boiling heat transfer is a topic that is of interest for the cooling of power electronics, highperformance computing in automotive applications, and other electronic packages with particularly high heat flux. Based on the investigations from [Schacht 2024], in which the effects on the high performance computing (HTC) with regard to the wetting behavior of de-ionised water (DI water) on silicon (SI) and gold (Au) surfaces during two-phase flow boiling were investigated, an initial design for the integration of two-phase cooling together with the power electronics in one housing (e.g. HPC or automotive) was introduced and the requirements for a controlled two-phase cooling system were discussed. In this paper, the use of a Glycol-DI water mixture instead of DI water as a coolant is experimentally investigated with regard to heat transfer performance. In addition, the influence of the surface properties of matte and polished silicon on the heat transfer coefficient performance is investigated. Glycol-DI-water mixture is used as a coolant in applications where ambient temperatures can be below 0°C (e.g. in the automotive industry) and which has no negative impact on global warming and is explosion-proof in useWith Glycol-DI-water mixture as coolant a maximum heat transfer coefficient HTC ~ 4.4 kW (m2K) at a volume flow rate of 𝒗􁈶 = 0.5 l/min (Tin = 60°C) with a maximum wall heat flux of 𝒒􁈶 𝒘𝒂𝒍𝒍 ~ 38 W/cm² and a wall temperature of Twall ~ 165°C could be achieved. An influence between matte and polished silicon surfaces on the heat transfer could not be determined. KW - Closed-loop two-phase flow boiling KW - Future application-oriented flow boiling cooler concept KW - HPC KW - Electronic power package Y1 - 2025 UR - https://ieeexplore.ieee.org/document/10970682 SN - 978-1-7355325-5-4 SP - 7 EP - 12 PB - IEEE CY - Piscataway, NJ ER - TY - GEN A1 - Wu, Yanan A1 - Pareek, Kaushal Arun A1 - May, Daniel A1 - Zajaczkowski, Marek A1 - Grosse-Kockert, Corinna A1 - Ras, Mohamad Abo A1 - Schacht, Ralph A1 - Wunderle, Bernhard T1 - Failure analysis for electronic packaging materials : a comparative study of pulsed thermography and lock-in thermography T2 - 31st International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) N2 - Electronic packaging plays a critical role in ensuring the reliability and performance of electronic systems. As various materials are used in these systems, each with distinct properties, failure analysis of each is key to improving overall system reliability. This paper presents a comparative study of two non-destructive testing (NDT) methods—pulsed thermography (PT) and lock-in thermography (LIT) — for failure analysis in electronic packaging materials. The study focuses on defect detection in copper (Cu), aluminum (AI), and polymer, which are widely used in electronic packaging due to their distinct thermal characteristics. Experimental results are evaluated using signal-to-background contrast (SBC). To enhance thermal contrast, three post-processing techniques—pulse phase thermography (PPT), principal component thermography (PCT), and thermographic signal reconstruction (TSR)—were applied to the PT results. These results were then compared with the optimal performance of LIT. The findings demonstrate that both methods have distinct advantages and limitations: PT offers faster detection, while LIT provides higher sensitivity for materials with higher thermal diffusivity. This study enhances the understanding of how these techniques can be effectively applied in electronic packaging failure analysis. KW - Failure Analysis KW - Non-destructive Testing KW - Pulsed Thermography KW - Lock-in Thermography KW - Electronic Packaging Material Y1 - 2025 SN - 979-8-3315-9486-2 U6 - https://doi.org/10.1109/THERMINIC65879.2025.11216883 SP - 1 EP - 6 PB - IEEE CY - Piscataway, NJ ER -