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). In Thermodynamics, a Thermodynamic system is said to be in thermal contact with another system if it can exchange energy with it through the process of Heat Heat sinks are used in a wide range of applications wherever efficient heat dissipation is required; major examples include refrigeration, heat engines, cooling electronic devices and lasers. Refrigeration is the process of removing Heat from an enclosed space or from a substance and moving it to a place where it is unobjectionable A heat engine is a physical or theoretical device that converts Thermal energy to mechanical output Heat generated by Electronic devices and Circuitry must be dissipated to improve Reliability and prevent premature Failure. A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission.
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Principle
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. Thermal energy is the sum of the sensible energy and latent energy. Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the Temperature of a unit quantity 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. In Thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium Mechanical equilibrium, and 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. In Physics, thermal conductivity, k is the property of a material that indicates its ability to conduct Heat. This cools the heat sink and whatever it is in direct thermal contact with. Use of fluids (for example coolants in refrigeration) and thermal interface material (in cooling electronic devices) ensures good transfer of thermal energy to the heat sink. FLUID ( F ast L ight '''U'''ser '''I'''nterface D esigner is a graphical editor that is used to produce FLTK Source code A Thermal Interface Material or Mastic (aka TIM) is used to fill the gaps between Thermal transfer surfaces such as between Microprocessors and Heatsinks 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 electronic component's hot surface — though in most cases, a thin thermal interface material mediates between the two surfaces. The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical A Thermal Interface Material or Mastic (aka TIM) is used to fill the gaps between Thermal transfer surfaces such as between Microprocessors and Heatsinks Microprocessors and power handling semiconductors are examples of electronics that need a heat sink to reduce their temperature through increased thermal mass and heat dissipation (primarily by conduction and convection and to a lesser extent by radiation). A microprocessor incorporates most or all of the functions of a Central processing unit (CPU on a single Integrated A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that Heat conduction or thermal conduction is the spontaneous transfer of thermal energy through matter from a region of higher Temperature to a region of lower Convection in the most general terms refers to the movement of molecules within Fluids (i Thermal radiation is Electromagnetic radiation emitted from the surface of an object which is due to the object's Temperature. Heat sinks are widely used in electronics, and have become almost essential to modern integrated circuits like microprocessors, DSPs, GPUs, and more. Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside A microprocessor incorporates most or all of the functions of a Central processing unit (CPU on a single Integrated A digital signal processor ( DSP or DSP micro) is a specialized Microprocessor designed specifically for Digital signal processing, generally
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 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. A mechanical fan is an electrically powered device used to produce an airflow for the purpose of creature comfort (particularly in the heat ventilation, exhaust In Vector calculus, the gradient of a Scalar field is a Vector field which points in the direction of the greatest rate of increase of the scalar
Heat sinks are made from a good thermal conductor such as copper or aluminum alloy. Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 WikipediaNaming 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. In Physics, thermal conductivity, k is the property of a material that indicates its ability to conduct Heat. Aluminum has the significant advantage that it can be easily formed by extrusion, thus making complex cross-sections possible. Extrusion is a process used to create objects of a fixed cross-sectional profile 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 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. Thermal grease (also called thermal compound, heat paste, heat transfer compound, thermal paste, or Beryllium oxide ( BeO) is a white crystalline oxide It is notable as it is an electrical insulator with a thermal conductivity higher than any other non-metal that actually Aluminium nitride ( Al[[Nitrogen N]] is a Nitride of Aluminium. g. colloidal silver. Colloidal silver is a Liquid suspension of Microscopic particles of Silver. [1] 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, CPUs 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 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 PC overclocking enthusiasts. A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated
In soldering
Temporary heat sinks were sometimes used while soldering circuit boards, preventing excessive heat from damaging sensitive nearby electronics. Soldering is a process in which two or more Metal items are joined together by melting and flowing a filler metal into the joint the filler metal having a relatively low In the simplest case, this means partially gripping a component using a heavy metal crocodile clip or similar clamp. A crocodile clip (or spring clip is a temporary Electrical connector, named for its resemblance to a Crocodile 's jaws Modern semiconductor devices, which are designed to be assembled by reflow soldering, can usually tolerate soldering temperatures without damage. Reflow soldering is a process in which a Solder paste (a sticky mixture of powdered solder and flux) is used to temporarily hold the components to their attachment On the other hand, electrical components such as magnetic reed switches can malfunction if exposed to higher powered soldering irons, so this practice is still very much in use. The reed switch is an electrical switch operated by an applied Magnetic field. [1]
Recent developments
More recently, synthetic diamond cooling sinks are being researched to provide better cooling. Synthetic diamond (also known variously as lab-created, manufactured, lab-grown or cultured diamond) is a term used to describe Diamond Also, some heat sinks are constructed of multiple materials with desirable characteristics, such as phase change materials, which can store a great deal of energy due to their heat of fusion. A phase change material ( PCM) is a substance with a high Heat of fusion which melting and solidifying at a certain temperature is capable of storing and releasing The standard Enthalpy of fusion (symbol \Delta{}H_{fus} also known as the heat of fusion or specific melting heat, is the amount of
As a problem in firestopping and fireproofing
A heat sink is rarely a desired thing in passive fire protection. Passive fire protection (PFP is an integral component of the three components of structural Fire protection and fire safety in a Building. Rather, it is usually a problem that must be overcome to maintain fire-resistance ratings. A fire-resistance rating typically means the duration for which a Passive fire protection System can withstand a standard fire resistance test. The proven ability to overcome heat sinks in construction is subject to building code and fire code regulations. A building code, or building control, is a set of rules that specify the minimum acceptable level of safety for constructed objects such as Buildings and Nonbuilding
Firestopping
- Problem - Metallic penetrants and sleeves, at a density of 7. In Construction, a sleeve is used both by the electrical and mechanical trades to create a penetration. 9 kg/L are more dense than common firestops or concrete. A firestop is a Passive fire protection System of various components used to seal openings and joints in fire-resistance rated wall Concrete is a construction material composed of Cement (commonly Portland cement) as well as other cementitious materials such as Fly ash and Slag Consequently, during a fire, they will absorb more photons 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. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena In Construction, a firewall is a fire-resistance rated Wall assembly intended to slow the 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. An Area of refuge is a location in a Building designed to hold occupants during a Fire or other Emergency, when evacuation may not be safe or Greater penetrant and sleeve conductivity leads to lower T-ratings. A fire-resistance rating typically means the duration for which a Passive fire protection System can withstand a standard fire resistance test. Higher density firestops, such as firestop mortars act as a heat sink to absorb heat away from small penetrants, such as cables, thus increasing T-ratings. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different Firestop mortars are most typically used to Firestop large openings in walls and floors required to have a Fire-resistance rating. A cable is one or more Wires or Optical fibers bound together typically in a common protective jacket or sheath
- Benefit - a rare exception where heat sinks are beneficial in firestops is where intumescents must be activated, such as in a firestop containing a plastic pipe. An intumescent is a substance which swells as a result of Heat exposure thus increasing in Volume, and decreasing in Density. Plastic is the general common term for a wide range of synthetic or semisynthetic organic solid materials suitable for the manufacture of industrial products 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 cables, cable trays, junction boxes and electrical conduit, the metallic items that are protected by the fireproofing measures act as a heat sink. "Fireproof" redirects here For the album see Fireproof (album. Structural steel is Steel construction Material, a profile, formed with a specific Shape or cross section and certain standards of Circuit integrity refers to the operability of electrical circuits during a Fire. A cable is one or more Wires or Optical fibers bound together typically in a common protective jacket or sheath A cable tray system according to the US National Electrical Code is "a unit or assembly of units or sections and associated fittings forming a rigid structural system used to An electrical junction box is a container for electrical junctions usually intended to conceal them from sight and to An electrical conduit is a purpose-designed electrical Piping System used for protection and routing of Electrical wiring. 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. Short Circuit is a 1986 comedy Science fiction film starring Ally Sheedy and Steve Guttenberg and directed by
See also
- Active cooling
- Computer cooling
- Heat pipe
- Heat pump
- Radiator
- Thermal management of electronic devices and systems
- Thermal resistance in electronics
References
- ^ Greg Becker, Chris Lee, and Zuchen Lin (Jul 2005). Computer cooling is the process of removing heat from computer components Computer cooling is the process of removing heat from computer components A heat pipe is a heat transfer mechanism that can transport large quantities of heat with a very small difference in Temperature between the hotter and colder interfaces A heat pump is a machine or device that moves Heat from one location (the 'source' to another location (the 'sink' or 'heat sink' using work. Radiators and convectors are types of Heat exchangers designed to transfer Thermal energy from one medium to another for the purpose of cooling Heat generated by Electronic devices and Circuitry must be dissipated to improve Reliability and prevent premature Failure. Thermal resistance is the Temperature difference across a structure when a unit of Heat energy flows through it in unit Time. "Thermal conductivity in advanced chips — Emerging generation of thermal greases offers advantages". Advanced Packaging: pp. 2-4.
External links
- SEMS Sdn Bhd: Heat Sink, Automation & Robots, Metal Stamping
- Online Heat Sink Calculators
- Over 350 reviews of CPU heatsinks with synthetic thermal test apparatus (FrostyTech)
- Hundreds of CPU heatsink tests in real world conditions (Madshrimps)
- Overview of different manufacturing methods to produce a heat sink
- Tom's hardware test: What happens when the processor heat sink is removed
Dictionary
heat sink
-noun
- An object or system that absorbs and dissipates heat in order to protect heat-sensitive components.
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