Dissipateur thermique

Un dissipateur thermique est un dispositif destiné à évacuer la chaleur résultante de l'effet Joule dans un élément semi-conducteur d'électronique de puissance. Il s'agit de dispositifs généralement munis d'ailettes, qui doivent de préférence être montées verticalement pour faciliter le refroidissement par convection. Loi d'Ohm thermique thumb|upright|Transistor en boîtier plastique et dissipateur adapté Types thumb|upright|left|Dissipateurs anodisés noir en aluminium De nombreux types de dissipateurs thermiques sont proposés par les constructeurs : dissipateur s'adaptant aux boîtiers ronds des transistors de petite et moyenne puissance, dissipateurs plats avec des ailettes plus ou moins grandes, pour le montages des éléments de puissance (diodes, transistors, thyristors, triacs). L'élément de puissance est fixé au refroidisseur avec une vis, un clip ou une colle conductrice de la chaleur. Certains dissipateurs sont livrés « au mètre », l'utilisateur coupant la longueur

Flow Boiling of R134a in a Multi-Microchannel Heat Sink with Hotspot Heaters for Energy-Efficient Microelectronic CPU Cooling Applications

Etienne Costa-Patry, Yassir Madhour, Bruno Michel, Jonathan Olivier, John Richard Thome

This paper focuses on two-phase flow boiling of refrigerant R134a inside a copper multi-microchannel heat sink for microelectronic central processing unit cooling applications. The heat sink is composed of 100 parallel microchannels, 100 mu m wide, 680 mu m high, and 15 mm long, with 72-mu m-thick fins separating the channels. The base heat flux was varied from 2.57 to 189 W/cm(2) and the mass flux from 205 to 1000 kg/m(2)s, at a nominal saturation temperature of 63 degrees C. Over 40 000 local heat transfer coefficients were measured at 35 locations using local heaters and temperature sensors, for which different heat transfer trends were identified. The main ones were that the heat transfer coefficient increased with heat flux and was independent of mass flow rate. Heat transfer coefficients as high as 270 000 W/m(2)K (relative to the base area) were reached, keeping the chip under 85 degrees C with a maximum of 94 kPa of pressure drop, for no inlet subcooling and a coolant flow rate of 1000 kg/m(2)s.

2011

Diamond on GaN integration for power semiconductor devices with efficient thermal management

Reza Soleiman Zadeh Ardebili

The international actions against global warming demands reductions in carbon emission and more efficient use of energy. Energy efficiency in the conversion and use of electricity, as an important form of energy in the modern life, has strong environmental and economical impacts. Power electronic devices determining roles in the overall system efficiency in many applications such as power converters and inverters. Gallium Nitride (GaN) devices have emerged as an superior alternative to the silicon devices and enabled unprecedented efficiencies. GaN-based high electron-mobility transistors (HEMTs) offer excellent characteristics such as high switching speed, low switching and conduction losses, small device size and high power density capabilities. However, such significant increases in the power density and the reduction of device size comes at the price of dramatic increases in the heat fluxes and appearance of hot spots in the device footprint that cannot be addressed using conventional methods. The integration of diamond and GaN has been highly pursued for thermal management purposes as well as combining their exceptional complementary properties for power electronics applications and novel semiconductor heterostructures. In this thesis, we discuss the key hindrances towards realisation of diamond on GaN substrates and devices, and we propose novel solutions for improving the feasibility of diamond-on-GaN integration for efficient thermal management of hot spots in GaN devices and development of diamond devices integrated with GaN devices in the same chip.The growth of diamond on GaN is challenging due to the high lattice and thermal expansion mismatches. The weak adhesion of diamond to GaN and high residual stresses after the deposition often result in the diamond film delamination or development of cracks, which prevents the subsequent device fabrication. In this thesis, a new seed dibbling method is presented for seeding and growing high-quality diamond films on cost-effective GaN-on-Si substrates, which result in significantly larger diamond grains and lower residual stresses (as low as 0.2 GPa) compared to conventional methods. Moreover, the excellent adhesion obtained by this method enabled a reliable polishing of the as-grown diamond films on GaN-on-Si without any delamination, resulting in smooth diamond-on-GaN substrates with sub-nanometer roughness. The high temperature hot spots in GaN devices are addressed by the near-junction heat spreaders using diamond films deposited on GaN. An analytical model for the heat spreading is presented to analyse the performance and optimize the heat spreaders, considering the geometry and thermal conductivity of the heat spreader and the substrate. Experimental demonstration of diamond heat spreaders on vertical GaN diodes together with the thermal characterization of their behaviour shows significant reduction of thermal spreading resistances, hot spot temperatures and temperature gradients from the device footprint, which highlights the impact of such heat spreaders for the thermal management of high power density GaN devices.The diamond films deposited on GaN were also used to demonstrate high-performance diamond transistors integrated on AlGaN/GaN-on-Si substrates with characteristics such as high breakdown voltage, high current density, and high on/off ratio, which opens many new possibilities for the development of power ICs with complementary logics, gate drivers and power

EPFL2021

Diamond on GaN integration for power semiconductor devices with efficient thermal management

Reza Soleiman Zadeh Ardebili

EPFL2021

Flow Boiling of R134a in a Multi-Microchannel Heat Sink with Hotspot Heaters for Energy-Efficient Microelectronic CPU Cooling Applications

Diamond on GaN integration for power semiconductor devices with efficient thermal management

Single Sink with non-simultaneous Demand

Flow Boiling of R134a in a Multi-Microchannel Heat Sink with Hotspot Heaters for Energy-Efficient Microelectronic CPU Cooling Applications

Diamond on GaN integration for power semiconductor devices with efficient thermal management

Single Sink with non-simultaneous Demand