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Encyclopedia > Thermal grease
Silicone thermal compound
Silicone thermal compound
Metal (silver) thermal compound
Metal (silver) thermal compound
Metal thermal grease applied to a chip
Metal thermal grease applied to a chip
Surface imperfections
Surface imperfections
Xenon processor with remaining thermal grease

Thermal grease (also called thermal compound, heat paste, thermal paste, or heat sink compound) is a substance that increases thermal conductivity between the surfaces of two or more objects. In electronics, it is often used to aid a component's thermal dissipation via a heat sink. Image File history File links Beschreibung: handelsübliche Wärmeleitpaste von Arctic Cooling / Thermal compound / grease / paste Fotograf: Darkone, 23. ... Image File history File links Beschreibung: handelsübliche Wärmeleitpaste von Arctic Cooling / Thermal compound / grease / paste Fotograf: Darkone, 23. ... Image File history File links Download high resolution version (2287x590, 74 KB) The silver based thermal compound. ... Image File history File links Download high resolution version (2287x590, 74 KB) The silver based thermal compound. ... ImageMetadata File history File links Thermalgrease. ... ImageMetadata File history File links Thermalgrease. ... ImageMetadata File history File links Cpuimperfections. ... ImageMetadata File history File links Cpuimperfections. ... Image File history File links IBMxenon. ... Image File history File links IBMxenon. ... Not to be confused with the Intel Xeon. ... K value redirects here. ... This article is about the engineering discipline. ... CPU heat sink with fan attached A heat sink (or heatsink) is an environment or object that absorbs and dissipates heat from another object using thermal contact (either direct or radiant). ...

Contents

Basic types

Thermal greases use one or more different thermally conductive substances:

  • Ceramic-based (often zinc oxide) thermal grease has generally good thermal conductivity and is usually suspended in a liquid or gelatinous silicone compound (hence the term 'grease'). If a product is described as a 'silicone paste' or a generic silicone thermal compound. It is usually white in colour (since the two most used ceramics, aluminum oxide and zinc oxide, are white in powder form).
  • Metal based thermal grease contain solid metal particles (usually silver). It has a better thermal conductivity (and is more expensive) than zinc oxide based grease. It is also more electrically conductive which can cause problems if it contacts the electrical connections of an integrated circuit.
  • Liquid metal based. Some thermal pastes are made of liquid metal alloys of gallium. Rare and expensive.

All but the last classification of compound usually use silicone grease as a medium, a heat conductor in itself, though some manufacturers prefer use of fractions of mineral oil. [citation needed] Zinc oxide is a chemical compound with formula ZnO. It is nearly insoluble in water but soluble in acids or alkalis. ... This article is about metallic materials. ... This article is about the chemical element. ... Integrated circuit of Atmel Diopsis 740 System on Chip showing memory blocks, logic and input/output pads around the periphery Microchips with a transparent window, showing the integrated circuit inside. ... This article needs to be cleaned up to conform to a higher standard of quality. ... General Name, Symbol, Number gallium, Ga, 31 Chemical series poor metals Group, Period, Block 13, 4, p Appearance silvery white   Standard atomic weight 69. ... Silicones (more accurately called polymerized siloxanes or polysiloxanes) are inorganic-organic polymers with the chemical formula [R2SiO]n, where R = organic groups such as methyl, ethyl, and phenyl. ... Mineral oil or liquid petrolatum is a by-product in the distillation of petroleum to produce gasoline. ...


Purpose

Thermal grease is primarily used in the electronics and computer industries to assist a heatsink to draw heat away from a semiconductor component such as an integrated circuit or transistor . A large copper heatsink. ... A semiconductor is a solid whose electrical conductivity is in between that of a conductor and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ... Integrated circuit of Atmel Diopsis 740 System on Chip showing memory blocks, logic and input/output pads around the periphery Microchips with a transparent window, showing the integrated circuit inside. ... Assorted discrete transistors A transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. ...


Thermally conductive paste improves the efficiency of a heatsink by filling air gaps that occur when the irregular surface of a heat generating component is pressed against the irregular surface of a heatsink, air being approximately 8000 times less efficient at conducting heat (see Thermal Conductivity) than, for example, aluminium, a common heatsink material.[1] Surface imperfections inherently arise from limitations in manufacturing technology and range in size from visible and tactile flaws such as machining marks or casting irregularities to sub-microscopic ones not visible to the naked eye. K value redirects here. ...


Both high power handling transistors, like those in a conventional audio amplifier, and high speed integrated circuits, such as the central processing unit (CPU) of a personal computer, generate sufficient heat to require the use of thermal grease in addition to the heatsink. High temperatures cause semiconductors to change their switching properties to the point of failure while CPU power dissipation overheating causes logic errors as heat raises electrical resistance on the multi-nanometer wide circuits of the CPU core.[2] Mission Cyrus 1 Hi Fi integrated audio amplifier An audio amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 hertz to 20,000 hertz, the human range of hearing) to a level suitable for driving loudspeakers and is the final stage... CPU redirects here. ... CPUs (Central processing units) in their various incarnations consume some amount of electric power. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... A nanometre (American spelling: nanometer) is 1. ...


Properties

The thermal grease's most important property is its thermal conductivity, measured in watts per metre-kelvin (W/(m·K)). Typical thermal conductivity for silicone and zinc oxide thermal compounds is 0.7 to 0.9 W/(m·K). (In comparison, the thermal conductivity of copper is 401 W/(m·K) and of aluminum 237.) Silver thermal compounds may have the conductivity of 2 to 3 W/(m·K) or more. The compound must also be smooth so that it is easy to apply in a very thin layer. In physics, thermal conductivity, λ, is the quantity of heat transmitted, due to unit temperature gradient, in unit time under steady conditions in a direction normal to a surface of unit area, when the heat transfer is dependent only on the temperature gradient thermal conductivity = heat flow rate / (distance × temperature... General Name, symbol, number zinc, Zn, 30 Chemical series transition metals Group, period, block 12, 4, d Appearance bluish pale gray Standard atomic weight 65. ... An oxide is a chemical compound containing at least one oxygen atom and other elements. ... Copper has played a significant part in the history of mankind, which has used the easily accessible uncompounded metal for nearly 10,000 years. ... Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ...


In compounds containing suspended particles, the properties of the fluid may well be the most important. As seen by the thermal conductivity measures above, the conductivity is closer to that of the fluid components rather than the ceramic or metal components. Other properties of fluid components that are important for thermal grease might be:

  1. How well it fills the gaps and conforms to the component's uneven surfaces and the heat sink
  2. How well it adheres to those surfaces
  3. How well it maintains its consistency over the required temperature range
  4. How well it resists drying out or flaking over time
  5. How well it insulates electrically
  6. Whether it degrades with oxidation or breaks down over time

Applying and removing

For computer CPU applications the grease is often applied on both surfaces with a small plastic spatula or credit card.


Because thermal grease's thermal conductivity is poorer than the metals they couple, it is important to use no more than is necessary to exclude air gaps. Excess grease separating the metal surfaces further will only degrade conductivity.


The preferred way to remove typical silicone oil based thermal grease from a component or heat sink is by using isopropyl alcohol. Isopropyl alcohol (also isopropanol or rubbing alcohol) is a common name for propan-2-ol, a colorless, flammable chemical compound with a strong odor. ...


See also

Computer cooling is the process of removing heat from computer components. ... Arctic Silver 3 thermal compound Arctic Silver Inc. ... A Phase Change Material (PCM) is a substance with a high heat of fusion which, melting and solidifying at certain temperatures, is capable of storing or releasing large amounts of energy. ... In computing and electronics, thermal pads are commonly found on the underside of heatsinks to aid the conduction of heat away from the component being cooled (such as a CPU or chip) and into the heatsink (usually made from aluminium or copper). ... Thermal adhesive is a type of thermally conductive glue used for electronic components and heatsinks. ...

References

  1. ^ [1]
  2. ^ Intel - Nanotechnology

External links


  Results from FactBites:
 
Thermal grease - Wikipedia, the free encyclopedia (574 words)
Thermal grease (also called thermal compound, thermal paste, or heat sink compound) is a substance that increases thermal conductivity between the surfaces of two or more objects.
Silicone-based thermal grease has moderate thermal conductivity, is usually white, and is often shipped with CPU heat sinks.
Thermal grease's primary purpose in electronics is to mediate small surface imperfections between an integrated circuit (also known as a chip) and a heat sink.
Interface Material - Thermal Grease Interface Materials from Thermaflo (271 words)
Thermal greases are manufactured by dispersing thermally conductive fillers (ceramics, Boron Nitride, Alumina, etc.) in either a silicone or hydrocarbon oil carrier to form a paste of varying viscosities.
Thermal greases achieve performance increases through their ability to conform and level to both the contours of the heat sink and the device package, not typically due to higher bulk thermal conductivity.
Thermal conductivity is maximized by using a minimum amount of material and achieving the minimum distance between the heat sink and package.
  More results at FactBites »

 
 

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