Thermal dissipation in power electronics systems is becoming an extremely important issue with the continuous growth of power density in their components. The primary cause of failure in this equipment is excessive temperatures in the critical components, such as semiconductors and transformers. This problem is particularly important in power electronic systems for space applications. These systems are usually housed in completely sealed enclosures for safety reasons. The effective management of heat removal from a sealed enclosure poses a major thermal-design challenge since the cooling of these systems primarily rely on natural convection. In this context, the presented paper treats the heat pipes as effective heat transfer devices that can be used to raise the thermal conductive path in order to spread a concentrated heat source over a larger surface area. As a result, the high heat flux at the heat source can be reduced to a smaller and manageable level that can be dissipated through conventional cooling methods. The objective of our work is to describe the feasibility of a cooling system with miniature heat pipes embedded in a direct bonded copper (DBC) structure. The advantage of this type of heat pipe is the possibility for implementation of the component layout on the heat pipe itself, which eliminates the existence of a thermal interface between the device and the cooling system

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

Investigation of Multiphase Coupled-Inductor Buck Converters in Point-of-Load Applications

Thermal issues in the design of high-power and small-size non-isolated Point of Load (POL) converters have been significant and are becoming more so. If a heat sink is dispensed with, then a large area of multi-layer PCB material with significant amounts of copper is required for necessary cooling. A high-rate cooling fan is also necessary. So what at first seems like a small and elegant converter becomes bulky and challenging to position in the overall system when its thermal management is taken into account. This work finds a solution to these problems and investigates the use of Low- Temperature Co-fired Ceramic (LTCC) for integrating the inductor with the active stage. A buck POL is used to demonstrate these methodologies. The end result is a POL converter that can achieve full 20 A output current with no need for an external heat sink and no need for a cooling fan while providing a large step-down of 5 V to 1.2 V. High light- load efficiency of 92.2% is achieved and a high power density of 156 W/in3 including all the necessary thermal management, in natural convection condition, has been demonstrated.

System design of a 3D integrated non-isolated Point Of Load converter

As the power densities of power components continue to grow, thermal issues are becoming extremely important and vital for the product quality. The primary causes of failures in electronic equipment are the excessive temperatures of the critical components, such as semiconductors and transformers. Power systems for space application are usually housed in completely sealed enclosures due to safety reasons. Since the cooling of these systems primarily relies on natural convection, the effective management of the heat removal from a sealed enclosure poses a major thermal-design challenge. In this context heat pipes are very effective heat transfer devices and can be used to raise the thermal conductive path in order to spread a concentrated heat source over a much larger surface area. As a result, the high heat flux at the heat source can be reduced to a much smaller and manageable level that can be dissipated through conventional cooling methods. The objective of this work, presented in this paper is to describe the feasibility of a cooling system with miniature heat pipes embedded in a direct bonded copper structure (DBC). The advantage of this kind of heat pipe is the integration of the electronic component layout directly on the heat pipe itself, which eliminates the existence of a thermal interface between the device and the cooling system

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

A honeycomb porous microchannel cooling system for electronics cooling was proposed in this article. The design, fabrication, and test system configuration of the microchannel heat sink were summarized. Preliminary experimental investigation was conducted to understand the characteristics of heat transfer and cooling performance under steady single-phase flow. In the experiments, a brass microchannel heat sink was attached to a test heater with 8 cm2 area. The experimental results show that the cooling system is able to remove 18.2 W/cm2 of heat flux under 2.4 W pumping power, while the junction wall temperature is 48.3°C at the room temperature of 26°C. Extensive experiments in various operation conditions and parameters for the present cooling system were also conducted. The experimental results show that the present cooling system is able to perform heat dissipation well.

A Honeycomb Microchannel Cooling System for Microelectronics Cooling

Between two insulating DBC substrates (Al/sub 2/O/sub 3/ or AlN) there are structured copper foils bonded together by DBC technology, to build a three dimensional system of micro channels The large internal surface of the highly conductive copper allows an extremely efficient cooling of the DBC substrates The DBC layout is customer specified and both DBCs are mounted to the top and the bottom of the water cooler This compact cooling system designed to the customer's requirements gives four times the system offered efficient cooling of conventional module assemblies with liquid cooling Due to the low weight and the relatively small dimensions the water cooled DBC substrate is an ideal solution for very high power applications In detail we describe the following items: (i) the 3D MCI cooler; (ii) water for cooling; measurement of heat dissipation and flow rates; (iii) results of water flow measurement; and (iv) results of thermal dissipation measurement

K. Exel

Papers

Water cooled DBC direct bonded copper substrates