Heat spreader
Encyclopedia
A heat spreader is most often simply a copper plate, having high thermal conductivity
. Functionally, it is a heat exchanger
that moves heat
between a heat source and a secondary heat exchanger whose surface area and geometry are more favorable. By definition, the heat is "spread out", such that the secondary heat exchanger increases the heat capacity of the assembly. These properties make it a better match for an air heat exchanger, since the low heat conduction for air in convection is matched with higher surface area.
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 secondary 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:
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
. Functionally, it is a heat exchanger
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...
that moves heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
between a heat source and a secondary heat exchanger whose surface area and geometry are more favorable. By definition, the heat is "spread out", such that the secondary heat exchanger increases the heat capacity of the assembly. These properties make it a better match for an air heat exchanger, since the low heat conduction for air in convection is matched with higher surface area.
A heat spreader is generally used when the heat source tends to have a high heat-flux density
Flux density
-Formal Statement:The flux density is simply defined as the amount of flux passing through a unit-area. -Mathematical Statement:The flux density would essentially be the number of field lines passing through a defined unit-area...
, (high heat flow per unit area), and for whatever reason, heat can not be conducted away effectively by the secondary 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.
- A copper-clad bottom on a stove-top cooking container made of steelSteelSteel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
or stainless steelStainless steelIn metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass.... - Air-cooling integrated circuitIntegrated circuitAn integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
s such as a microprocessorMicroprocessorA microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and... - Air-cooling a photovoltaic cell in a concentrated photovoltaicsConcentrated photovoltaicsConcentrated photovoltaic technology uses optics such as lenses to concentrate a large amount of sunlight onto a small area of solar photovoltaic materials to generate electricity...
system