A heat spreader transfers energy as heat from a hotter source to a colder

heat sink A heat sink (also commonly spelled heatsink) 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 thermal management (electronics), ...

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 The thermal conductivity of a material is a measure of its ability to heat conduction, conduct heat. It is commonly denoted by k, \lambda, or \kappa and is measured in W·m−1·K−1. Heat transfer occurs at a lower rate in materials of low ...

, such as

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

, aluminum, or diamond. An active heat spreader speeds up heat transfer with expenditure of energy as work supplied by an external source. 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. 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 Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...

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: * A copper-clad bottom on a

steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...

stainless steel Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chromi ...

stove-top cooking container * Air-cooling

integrated circuit An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...

s such as a

microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...

* Air-cooling a

photovoltaic cell A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

in a concentrated photovoltaics system 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 Beryllium is a chemical element; it has Symbol (chemistry), symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with ...

matrix). Such materials are often used as substrates for chips, as their thermal expansion coefficient can be matched to ceramics and semiconductors. Corsair CM2X1024-6400C5DHX 20080221.jpg, Two memory modules encased in

aluminum Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

heat spreaders Comparison of Intel and AMD Microprocessor Integrated Heatspreaders.JPG, Side-by-side comparison of AMD (center) and Intel (sides) integrated heatspreaders (IHS) common on their microprocessors AMD Athlon 64 X2 6000+ (ADA6000IAA6CZ), heat spreader removed.jpg, AMD Athlon 64 X2 6000+ (ADA6000IAA6CZ, Windsor), having its heat spreader removed (known as decapping or delidding). This particular CPU core is soldered to the heat spreader, causing the CPU to be destroyed during the removal or making removal more difficult.

Research

In May 2022, researchers at the University of Illinois at Urbana-Champaign and

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a Public university, public Land-grant university, land-grant research university in Berkeley, California, United States. Founded in 1868 and named after t ...

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.

References

{{Reflist Computer hardware cooling Heat transfer Residential heating appliances

Research

See also

References