Heat spreader

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This 120 mm-diameter vapor chamber (heat spreader) heat sink design thermal animation was created using high resolution computational fluid dynamics (CFD) analysis, and shows temperature-contoured heat sink surface and fluid flow trajectories, predicted using a CFD analysis package. CFD Vapor Chamber Heat Sink Design v1.gif
This 120 mm-diameter vapor chamber (heat spreader) heat sink design thermal animation was created using high resolution computational fluid dynamics (CFD) analysis, and shows temperature-contoured heat sink surface and fluid flow trajectories, predicted using a CFD analysis package.

A heat spreader transfers energy as heat from a hotter source to a colder heat sink or heat exchanger. There are two thermodynamic types, passive and active. The most common sort of passive heat spreader is a plate or block of material having high thermal conductivity, such as copper, aluminum, or diamond. An active heat spreader speeds up heat transfer with expenditure of energy as work supplied by an external source. [1]

Contents

A heat pipe uses fluids inside a sealed case. The fluids circulate either passively, by spontaneous convection, triggered when a threshold temperature difference occurs; or actively, because of an impeller driven by an external source of work. Without sealed circulation, energy can be carried by transfer of fluid matter, for example externally supplied colder air, driven by an external source of work, from a hotter body to another external body, though this is not exactly heat transfer as defined in physics. [2]

Exemplifying increase of entropy according to the second law of thermodynamics, a passive heat spreader disperses or "spreads out" heat, so that the heat exchanger(s) may be more fully utilized. This has the potential to increase the heat capacity of the total assembly, but the additional thermal junctions limit total thermal capacity. The high conduction properties of the spreader will make it more effective to function as an air heat exchanger, as opposed to the original (presumably smaller) source. The low heat conduction of air in convection is matched by the higher surface area of the spreader, and heat is transferred more effectively.

A heat spreader is generally used when the heat source tends to have a high heat-flux density, (high heat flow per unit area), and for whatever reason, heat can not be conducted away effectively by the heat exchanger. For instance, this may be because it is air-cooled, giving it a lower heat transfer coefficient than if it were liquid-cooled. A high enough heat exchanger transfer coefficient is sufficient to avoid the need for a heat spreader.

The use of a heat spreader is an important part of an economically optimal design for transferring heat from high to low heat flux media. Examples include:

Diamond has a very high thermal conductivity. Synthetic diamond is used as submounts for high-power integrated circuits and laser diodes.

Composite materials can be used, such as the metal matrix composites (MMCs) copper–tungsten, AlSiC (silicon carbide in aluminium matrix), Dymalloy (diamond in copper-silver alloy matrix), and E-Material (beryllium oxide in beryllium matrix). Such materials are often used as substrates for chips, as their thermal expansion coefficient can be matched to ceramics and semiconductors.

Research

In May 2022, researchers at the University of Illinois at Urbana-Champaign and University of California, Berkeley devised a new solution that could cool modern electronics more efficiently than other existing strategies. Their proposed method is based on the use of heat spreaders consisting of an electrical insulating layer of poly (2-chloro-p-xylylene) (Parylene C) and a coating of copper. This solution would also require less expensive materials. [3]

See also

Related Research Articles

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<span class="mw-page-title-main">Thermal insulation</span> Minimization of heat transfer

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<span class="mw-page-title-main">Heat transfer</span> Transport of thermal energy in physical systems

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<span class="mw-page-title-main">Heat sink</span> Passive heat exchanger that transfers the heat

A heat sink is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant, where it is dissipated away from the device, thereby allowing regulation of the device's temperature. In computers, heat sinks are used to cool CPUs, GPUs, and some chipsets and RAM modules. Heat sinks are used with high-power semiconductor devices such as power transistors and optoelectronics such as lasers and light-emitting diodes (LEDs), where the heat dissipation ability of the component itself is insufficient to moderate its temperature.

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<span class="mw-page-title-main">Heat pipe</span> Heat-transfer device that employs phase transition

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E-Material, also called E Material, is a metal matrix composite consisting of beryllium matrix with beryllium oxide particles. It has high thermal conductivity, and its thermal expansion can be adjusted to match other materials, e.g. silicon and gallium arsenide chips and various ceramics. It is chiefly used in microelectronics as substrate for power semiconductor devices and high density multi-chip modules, where it aids with removal of waste heat. E-materials have low weight and high strength, making them especially suitable for aerospace technology. Their high elastic modulus is favorable for absorbing vibrations and lowering material fatigue of attached modules and wire bonds.

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Heat exchangers are devices that transfer heat to achieve desired heating or cooling. An important design aspect of heat exchanger technology is the selection of appropriate materials to conduct and transfer heat fast and efficiently.

References

  1. ↑ Adams, M.J.; Verosky, M.; Zebarjadi, M.; Heremans, J.P. (2019-05-03). "Active Peltier Coolers Based on Correlated and Magnon-Drag Metals". Physical Review Applied. 11 (5): 054008. Bibcode:2019PhRvP..11e4008A. doi: 10.1103/physrevapplied.11.054008 .
  2. ↑ Born, M. (1949). Natural Philosophy of Cause and Chance, Oxford University Press, London, p. 44.
  3. ↑ Fadelli, Ingrid (2022-05-19). "A new solution to cool electronic devices and prevent them from overheating". Tech Xplore. Retrieved 2022-05-19.
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