Heat sink
344123
224241654
2008-07-07T23:22:35Z
Ham Pastrami
4245638
dab note
{{otheruses4|a device that prevents machines from overheating|the environmental phenomenon|urban heat island}}
[[Image:AMD heatsink and fan.jpg|thumb|CPU heat sink with fan attached and a smaller heat sink on the [[Northbridge (computing)|Northbridge]].]]
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). Heat sinks are used in a wide range of applications wherever efficient heat dissipation is required; major examples include [[refrigeration]], [[heat engines]], [[Thermal management of electronic devices and systems|cooling electronic devices]] and [[laser]]s.
==Principle==
<div style="float:right; clear:right;">
[[Image:Flow-vector-heat-sink-fluid-WBG.jpg|thumb|none|Radial Heat Sink with Thermal Profile and Swirling Forced Convection Flow Trajectories (using CFD analysis)]]
[[Image:Liquid-heat-sink-fluid-WBG.jpg|thumb|none|Liquid Cooled Heat Sink with Forced Convection Flow Trajectories (using CFD analysis)]]
[[Image:Natural-convection-heat-sink-fluid-WBG.jpg|thumb|none|Pin Fin Heat Sink with Thermal Profile and Dione Convection Flow Trajectories (using CFD analysis)]]
[[Image:Copper_heat_sink_with_pipes.jpg|thumb|none|Heat sink in a workstation computer]]
[[Image:Heatsink_povray.png|thumb|none|A [[motherboard]] heat sink]]
[[Image:Nelson_tulsa_test.jpg|thumb|none|[[Fire test]] where the [[steel]] [[pipe]] [[penetrant]]s clearly act to absorb and conduct heat from the [[furnace]], through to the unexposed side.]]
</div>
Heat sinks function by efficiently transferring [[thermal energy]] ("heat") from an object at high temperature to a second object at a lower temperature with a much greater [[heat capacity]]. This rapid transfer of thermal energy quickly brings the first object into [[thermal equilibrium]] with the second, lowering the temperature of the first object, fulfilling the heat sink's role as a cooling device. Efficient function of a heat sink relies on rapid transfer of thermal energy from the first object to the heat sink, and the heat sink to the second object.
The most common design of a heat sink is a metal device with many fins. The high [[thermal conductivity]] of the metal combined with its large surface area result in the rapid transfer of thermal energy to the surrounding, cooler, air. This cools the heat sink and whatever it is in direct thermal contact with. Use of [[fluid]]s (for example coolants in refrigeration) and [[thermal interface material]] (in cooling electronic devices) ensures good transfer of thermal energy to the heat sink. Similarly a fan may improve the transfer of thermal energy from the heat sink to the air.
==Performance==
Heat sink performance (including free convection, forced convection, liquid cooled, and any combination thereof) is a function of material, geometry, and overall surface heat transfer coefficient. Generally, forced convection heat sink thermal performance is improved by increasing the thermal conductivity of the heat sink materials, increasing the surface area (usually by adding extended surfaces, such as fins or foam metal) and by increasing the overall area heat transfer coefficient (usually by increase fluid velocity, such as adding fans, pumps, etc.).
Online heat sink calculators from companies such as Novel Concepts, Inc., can accurately estimate forced convection heat sink performance. For more complex heat sink geometries, and/or heat sinks with multiple materials, and/or heat sinks with multiple fluids, computation fluid dynamics (CFD) analysis is recommended (see graphics on this page).
==Use in electronics==
===Explanation===
In common use, it is a [[metal]] object brought into contact with an [[electronics|electronic]] component's hot surface — though in most cases, a thin [[thermal interface material]] mediates between the two surfaces. [[Microprocessor]]s and power handling [[semiconductor]]s are examples of electronics that need a heat sink to reduce their temperature through increased [[thermal mass]] and heat dissipation (primarily by [[heat conduction|conduction]] and [[convection]] and to a lesser extent by [[thermal radiation|radiation]]). Heat sinks are widely used in [[electronics]], and have become almost essential to modern [[integrated circuits]] like [[microprocessors]], [[digital signal processor|DSP]]s, [[Graphics processing unit|GPU]]s, and more.
===Construction and materials===
A heat sink usually consists of a base with one or more flat surfaces and an array of comb or fin-like protrusions to increase the heat sink's surface area contacting the air, and thus increasing the heat dissipation rate. While a heat sink is a static object, a [[fan (mechanical)|fan]] often aids a heat sink by providing increased airflow over the heat sink — thus maintaining a larger temperature [[gradient]] by replacing the warmed air more quickly than passive convection achieves alone — this is known as a forced air system.
Heat sinks are made from a good thermal conductor such as [[copper]] or [[aluminum]] alloy. Copper (401 W/(m·K) at 300 K) is significantly more expensive than aluminum (237 W/(m·K) at 300 K) but is also roughly twice as efficient as a [[thermal conductor]]. Aluminum has the significant advantage that it can be easily formed by [[extrusion]], thus making complex cross-sections possible. The heat sink's contact surface (the base) must be flat and smooth to ensure the best thermal contact with the object needing cooling. Frequently, a [[thermal grease|thermally conductive grease]] is used to ensure optimal thermal contact; such grease usually contains ceramic materials such as [[beryllium oxide]] and [[aluminium nitride]], but may alternatively contain finely divided metal particles, e.g. [[colloidal silver]].<ref name="apmag">{{cite journal | author=Greg Becker, Chris Lee, and Zuchen Lin | title=Thermal conductivity in advanced chips — Emerging generation of thermal greases offers advantages | journal=Advanced Packaging | month=Jul | year=2005 | pages=pp.2–4 | url=http://www.apmag.com/ | accessdate=2008-03-04 }}</ref> Further, a clamping mechanism, screws, or thermal adhesive hold the heat sink tightly onto the component, but specifically without pressure that would crush the component.
===PC marketplace===
Due to recent technological developments and public interest, the retail heat sink market has reached an all time high. In the early 2000s, [[CPU]]s were produced that emitted more heat than ever before, escalating requirements for quality cooling systems.
[[Overclocking]] has always meant greater cooling needs, and the inherently hotter chips meant more concerns for the enthusiast. Efficient heat sinks are vital to [[overclocking|overclocked]] computer systems because the higher a microprocessor's cooling rate, the faster the computer can operate without instability; generally, faster operation leads to higher performance. Many companies now compete to offer the best heat sink for [[Personal computer|PC]] overclocking enthusiasts.
===In soldering===
Temporary heat sinks were sometimes used while [[soldering]] circuit boards, preventing excessive heat from damaging sensitive nearby electronics. In the simplest case, this means partially gripping a component using a heavy metal [[crocodile clip]] or similar clamp. Modern semiconductor devices, which are designed to be assembled by [[reflow soldering]], can usually tolerate soldering temperatures without damage. On the other hand, electrical components such as magnetic [[reed switch]]es can malfunction if exposed to higher powered soldering irons, so this practice is still very much in use. [http://www.eleinmec.com/article.asp?23]
===Recent developments===
More recently, [[synthetic diamond]] cooling sinks are being researched to provide better cooling. Also, some heat sinks are constructed of multiple materials with desirable characteristics, such as [[phase change material]]s, which can store a great deal of energy due to their [[heat of fusion]].
==As a problem in firestopping and fireproofing==
A heat sink is rarely a desired thing in [[passive fire protection]]. Rather, it is usually a problem that must be overcome to maintain [[fire-resistance rating]]s. The proven ability to ''overcome'' heat sinks in construction is subject to [[building code]] and fire code regulations.
===Firestopping===
*'''Problem''' - Metallic [[penetrant]]s and [[Sleeve (construction)|sleeves]], at a density of 7.9 kg/L are more dense than common [[firestop]]s or [[concrete]]. Consequently, during a fire, they will absorb more [[photon]]s and seek to conduct these to the unexposed side of a fire barrier (thus ''"cooling"'' the exposed side at the expense of the unexposed side), such as the cold side of a [[firewall (construction)|firewall]]. This is undesirable. Even if the fire is stopped by the barrier, one must keep the unexposed side cool to prevent autoignition of combustibles on the unexposed side of a fire barrier. The unexposed side may very well be an [[area of refuge]], which must be safeguarded to comply with the building code. Greater penetrant and sleeve conductivity leads to lower [[Fire-resistance rating|T-ratings]]. Higher [[density]] firestops, such as [[Mortar (firestop)|firestop mortars]] act as a heat sink to absorb heat away from small penetrants, such as [[cable]]s, thus increasing T-ratings.
*'''Benefit''' - a rare exception where heat sinks are ''beneficial'' in firestops is where [[intumescent]]s must be activated, such as in a firestop containing a [[plastic]] [[pipe]]. Heat sinks such as wire mesh and extra metallic sleeving may be used to carry heat to intumescents to activate expansion such as to choke off a melting plastic pipe or melting pipe covering, such as foamed plastic or fibreglass.
===Fireproofing===
In [[fireproofing]] of [[structural steel]] as well as providing [[circuit integrity]] to [[cable]]s, [[cable tray]]s, [[junction box]]es and [[electrical conduit]], the metallic items that are protected by the fireproofing measures act as a heat sink. Fireproofing methods are used to ''defeat'' the heat sink properties of the items they protect. In the case of circuit integrity measures, electrical services will fuse and [[short circuit]] above 140° C.
==See also==
*[[Active cooling]]
*[[Computer cooling]]
*[[Heat pipe]]
*[[Heat pump]]
*[[Radiator]]
*[[Thermal management of electronic devices and systems]]
*[[Thermal resistance in electronics]]
==References==
{{Refimprove|date=March 2008}}
<references/>
==External links==
*[http://www.sems.com.my/ SEMS Sdn Bhd: Heat Sink, Automation & Robots, Metal Stamping]
*[http://www.novelconceptsinc.com/ Online Heat Sink Calculators]
*[http://www.frostytech.com/articlesearch.cfm?SearchValue=&Search=Search&Category=198&CategorySearch=Get+Listing Over 350 reviews of CPU heatsinks with synthetic thermal test apparatus] ([[FrostyTech]])
*[http://www.madshrimps.be/gotoartik.php?articID=389 Hundreds of CPU heatsink tests in real world conditions] ([[Madshrimps]])
*[http://www.heatsink-guide.com/heatsinkinfo-2.shtml Overview of different manufacturing methods to produce a heat sink]
*[http://www.tomshardware.com/2001/09/17/hot_spot/index.html Tom's hardware test: What happens when the processor heat sink is removed]
[[Category:Computer hardware cooling]]
[[Category:Passive fire protection]]
[[de:Kühlkörper]]
[[es:Disipador]]
[[fr:Dissipateur thermique]]
[[it:Dissipatore (elettronica)]]
[[he:צלעות קירור]]
[[lt:Radiatorius (elektronikoje)]]
[[nl:Koelvin]]
[[ja:ヒートシンク]]
[[pl:Radiator]]
[[pt:Dissipador]]
[[ru:Кулер]]
[[sk:Chladič (elektronika)]]
[[th:ฮีตซิงก์]]
[[zh:散热片]]