Evaluation of the thermal and hydraulic performances of a very thin sintered copper flat heat pipe for 3D microsystem packages

The reported research work presents numerical studies validated by experimental results of a flat micro heat pipe with sintered copper wick structure. The objectives of this project are to produce and demonstrate the efficiency of the passive cooling technology (heat pipe) integrated in a very thin electronic substrate that is a part of a multifunctional 3-D electronic package. The enhanced technology is dedicated to the thermal management of high dissipative microsystems having heat densities of more than 10W/cm2. Future applications are envisaged in the avionics sector. In this research 2D numerical hydraulic model has been developed to investigate the performance of a very thin flat micro heat pipe with sintered copper wick structure, using water as a refrigerant. Finite difference method has been used to develop the model. The model has been used to determine the mass transfer and fluid flow in order to evaluate the limits of heat transport capacity as functions of the dimensions of the wick and the vapour space and for various copper spheres radii. The results are presented in terms of liquid and vapour pressures within the heat pipe. The simulated results are validated by experiments and proved that the method can be further used to predict thermal performance of the heat pipe and to optimise its design.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

Mutual and self-aging effects of power semiconductors on the thermal behaviour of DC-DC boost power converter

WOS:00044822700009

Junction temperature measurements via thermo-sensitive electrical parameters and their application to condition monitoring and active thermal control of power converters

The temperature of a power semiconductor device is important for both its optimal operation and reliability. If the temperature is known during the operation of a converter, it can be used to monitor the health of power modules: a measurement of aging, scheduling of maintenance, or even implementation of active thermal control to reduce losses and increase lifetime can be performed given an accurate knowledge of temperature. Temperature measurements via thermo-sensitive electrical parameters (TSEP) are one way to carry out immediate temperature readings on fully packaged devices. However, successful implementation of these techniques during the actual operation of a device has not yet been achieved. This paper provides an overview of literature where the usage of TSEPs has been hypothesised or realised in realistic power electronic converter setups. Barriers and limitations preventing wider scale implementation of these methods are discussed. Their potential use in the aforementioned goals in condition monitoring and active thermal control is also described

Integrated cooling devices in silicon technology

Silicon technology has become a good alternative to copper for the elaboration of efficient cooling devices required in power electronics domain. Owing to its high degree of miniaturization, it is expected to provide suitable microchannels and other inlets holes that were not achievable by copper micromachining. Besides, the use of silicon technology provides a variety of bare materials (silicon dioxide, silicon nitride, silicide, etc.) which may be either insulator or conductive, with a good or bad thermal conductivity. This large choice makes it possible to built up rather complex multilayer devices with mechanical properties good enough in comparison with hybrid copper technology heat sinks. Nevertheless, the use of silicon technology, where the microchannel width may reach few tens of microns, raises fundamental features concerning the fluid displacement within such small sections. More precisely, fundamental fluid mechanics studies have to be conducted out in order to get an accurate description of the fluid boundary layers and to provide basic data on the exchange mechanisms occurring at these surfaces. In this paper, we review the operation principles of both single- and double-phase heat exchange devices elaborated in silicon technology. Forced-convection heat sinks as well as integrated micro heat pipes are analyzed. An analytical approach is adopted to evaluate their total thermal resistances as a function of several geometrical parameters. Numerical simulations are then used in order to assess the accuracy of the analytical approach and to evaluate the impact of the fluidic aspects on the whole performance. The optimum devices are then conceived thanks to an appropriate optimization procedure taken into account the several experimental constraints. Reference values of similar copper devices are reminded and the advantages of the silicon integrated approach are highlighted

A New Methodology for Early Stage Thermal Analysis of Complex Electronic Systems

Abstract-This paper presents a new methodology called Flex-CTM for Flexible Compact Thermal Modeling to build and to interface compact thermal models at different modeling levels. Each part of an electronic system is prepared to be Bou ndary Condition independent (BCI) such as to be plugged to other parts. Each part model is reduced to save memory and time consuming at the simulation stage. The resulting pluggable and reduced thermal model is called a micro-model. Therefore, a fast-to-simulate macro-model of a full microelectronic system can be obtained by assembling micro-models. The Flex-CTM is found to have numerous advantages over both current resistive models (junction-to-case and junction-toboard) and Dynamic Compact Thermal Models. The first advantage of the methodology is that multi-source and dynamic simulations of an electronic system can be performed at any design level. The second one is the control of the accuracy. The third advantage is the Boundary Condition Independence property that allows architecture exploration. Finally and the most important, micro and macro-models can be shared by teams to be reused and completed

A Busbar Like Power Module Based On 3D Chip On Chip Hybrid Integration

The paper focuses on a new generation of power modules, trying to optimize the tradeoff between thermal and EMI managements. At the same time, the packaging approach is considered in order to simplify the implementation of the power dies while improving the reliability of the structure. The approach considers the integration of the power dies, one on top of the other into a 3D Chip On Chip configuration. Thanks to this structure, the power dies can be directly inserted within electrical plates, the whole structure emulating a busbar like power module. The paper presents the characteristics and the benefits of the approach. Then, it focuses on the practical characterization of two prototypes: a buck converter structure and a single phase diode rectifier. Both of them are based on double sided thermal cooling and electro-thermal contacts are obtained by pressure. The prototypes exhibit great performances while offering really reduced parasitic and EMI coupling

Heat Pipe Integrated in Direct Bonded Copper (DBC) Technology for Cooling of Power Electronics Packaging

International audienc

Thermal aging of power module assemblies based on ceramic heat sink and multilayers pressureless silver sintering

International audienceAn assembly based on the deposition and pressureless sintering of successive silver layers on an Aluminum Nitride heat sink is studied in this paper. Sintered silver layers act as die attach, current tracks and adhesion layer on the ceramic. Compared to previous studies where silver sintering is only used as die attach, an additional degree of freedom on the sintering temperature of the ceramic adhesion and track layers is obtained. This allows the investigation of silver sintering at non-conventional temperatures (>400 °C). The presented assembly is expected to endure high operating temperature since all its constituent materials are able to withstand such temperatures. The porosity of the sintered layer is controlled by the dwell time and the sintering temperature, and porosity values between 19% and 41% are obtained. The electrical and thermal conductivities of sintered layers as functions of joint porosity are in good agreement with the literature data and the assembly presents good mechanical properties with a shear strength value higher than 18 MPa. The assembly shows a high robustness during thermal storage at 200 °C for 1000 h. The microstructure and the electrical conductivity of track layers are both stable during the whole aging period. However, a slight improvement of the thermal response and the mechanical properties of the assembly is detected after 200 h of aging followed by a stabilization until the end of the aging tests (1000 h). Such observation is correlated to the microstructure coarsening of the sintered silver under the device and it is shown that this evolution is favored by the presence of the device