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 - Kober, Markus A1 - Kühhorn, Arnold A1 - Rademann, Jörg A1 - Mück, Bernhard T1 - Nonlinear topology optimization of centrifugally loaded aero-engine part with newly developed optimality-criteria based algorithm T2 - Aerospace Science and Technology N2 - In this paper a successful topology optimization of a centrifugally loaded aero-engine part is presented. For the topology optimization, which is a nonlinear problem due to several contact regions, a self-developed topology optimization algorithm in combination with a commercial FE-solver is used. The goal of the optimization was the reduction of stresses in the structure. ©2014 Rolls-Royce Deutschland Ltd & Co. KG. Published by Elsevier Masson SAS. All rights reserved. KW - Topology optimization KW - Optimality criteria KW - Aero-engine KW - Centrifugal loading Y1 - 2014 UR - http://www.sciencedirect.com/science/article/pii/S1270963814001783 U6 - https://doi.org/10.1016/j.ast.2014.09.005 VL - Vol. 39 SP - 705 EP - 711 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 -