Benefits of Extruded Aluminum Heatsinks

Using extruded aluminum heatsinks can be of enormous benefit for commercial and industrial electronic device manufacturers. Improved technology made it possible to produce heat sink extrusions that call for a lighter weight and greater strength combination. Extruded aluminum heatsinks have a higher strength-to-weight ratio than copper, brass, or steel.

Aluminum alloys are very malleable. Heat sink extrusions made from an aluminum alloy can be created in a large number of unique designs. Aluminum is a heat conductor and reflector. Those qualities make it quite useful in applications requiring heat transfer or a shield that is highly reflective. Aluminum alloys are relatively low in price. Through the processes of scraping, refining, and smelting aluminum alloys can be formed into sheets, fins, and foil used in extruded aluminum heatsinks.

Aluminum does not provide as much thermal conductivity as metals such as copper but is far easier to work into heat sink extrusions. Custom aluminum heatsink profile variations are easy to create. An extruded aluminum fin can be easily attached to a base of copper that would conduct large amounts of thermal energy to the less expensive and lighter cooling fin made of an aluminum alloy. 

Aluminum heat sink extrusions are used by electronics, medical, military, automotive, electrical, and telecommunication industries, among others. Specialty miniature extrusions are produced for a range of industries. Engineers are challenged on a routine basis to develop demanding and advanced production concepts. To do so, they need to know the essence of the needed function and the environment that the heat sink will be used.

Reasons for Using Copper Heat Pipes Instead of Vapor Chambers

Solid base fin and fan heatsinks are not always sufficient, to increase thermal efficiency, in a thermal system project design. Added fin area or a thicker base of a larger heat sink is prohibited by keep out zones. Airflow, sometimes, cannot be increased, or the enclosure size is too small. Adding a transitional copper heatsink is too heavy or may be too expensive. Density or component power makes it necessary to move heat to a remote location that is over 40 or 50 mm from the source of heat.

For all the scenarios listed above, a two-phase cooling solution is likely to be needed. Either heatpipes or vapor chambers will be used. There are thermal design considerations and structural differences between the similar, yet unique two-phase devices.

The operating principles are identical. Wick structures made of grooves, mesh screens and sintered powder are applied to the enclosure’s inside walls. The enclosure may be planar or tube shaped. Water is the usual liquid added before the device is vacuum sealed. At that point, the liquid is distributed throughout the device via the wick. The liquid turns to vapor as heat is applied. The vapor moves to lower pressure areas. There it returns to liquid as it cools. Capillary action moves the liquid back to the source of heat. In this sense, vapor chambers and heatpipes work the same way.

The most common two-phase devices are copper heat pipes that use a wick structure made of sintered copper. Water is the working liquid. Copper heat pipes have been used as the default choice for decades. The difference in cost between copper heat pipes and vapor chambers is the primary reason. They both transport heat. Lower power applications or effective heat transportation is still best accomplished by heatpipes due to design flexibility and low cost.

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Heatsink Manufacturers Design Custom Heatsinks

There is an effective cooling solution for most electronic devices. That would be custom heatsinks made of aluminum by heatsink manufacturers. Aluminum is a common alloy that is used in heatsink development. Aluminum is not the only solution for devices that need thermal management. Heatsink manufacturers can discuss custom heatsinks for your product needs.

Heatsink manufacturers can develop a custom aluminum extrusion heatsink designed to meet your specifications in a manner that is cost-effective to manufacture. For thermal dissipation needs that cannot be met by the extrusion process, a bonded fin heatsink can be manufactured.

Bonded fin heatsinks can be made with copper or aluminum bases and fins. Epoxy that has high thermal conductivity is used to attach fins to the bases of custom heatsinks. Forced air environments are the most common environments for which heatsink manufacturers develop them. Bonded fin heatsinks dissipate two to three times the heat load as extruded counterparts having the same volume. Typical applications for bonded fin heatsinks include traction drives, laser power supplies, power rectification equipment, welding units, variable speed motor controls, and uninterruptible power supplies.

Heatsink manufacturers are heat transfer experts who can help select or design a solution to solve a thermal management challenge. Industries that make use of heatsinks are consumer markets. LED lighting, telecom, power conversion, solar, transport, medical, military/aero, and test equipment. Consumer products that utilize custom heatsinks include home entertainment and gaming equipment. They are also used in the PC that sits in a home office or workplace. LED lighting in both industrial and consumer settings use heatsinks. The transmitters, amplifiers, switches, and routers of telecommunication devices, used daily, make use of heatsinks.

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How Aluminum Heatsinks Are Used in Heat Sink Extrusions

When a company orders heatsinks from a manufacturer, often the heat sink extrusions have to be customized. Customization includes the addition of plain and threaded holes, changes in the heatsink height; known as the fin height; base size changes and changes in surface finishes and treatments.

Microelectronic devices provide increased heat dissipation, and the overall form factors have been reduced. Those characteristics make thermal management an important electronic product design element. Equipment component temperatures are inversely related to the equipment’s life expectancy and performance reliability. A temperature reduction means an exponential increase in life expectancy and reliability of a silicon semi-conductor device. Controlling a device’s operating temperature, within the limits set by the manufacturer, is the way to achieve reliable performance and long life.

Extruded aluminum heatsinks enhance the dissipation of heat from a surface that is hot to an ambient that is cooler. The ambient is typically air. In most situations, the heat is transferred across the interface between the air coolant and the solid surface. The solid-air interface is the greatest heat dissipation barrier. Heat sink extrusions lower the barrier by increasing the surface area in direct contact with the air. More heat is dissipated, and the devices operating temperature is lowered. The primary purpose of extruded aluminum heatsinks is the maintenance of the device’s temperature below the allowable maximum specified by the manufacturer.

A simple heatsink mounting uses the thermal resistance concept. Heat flows through a series in the thermal circuits. It begins at the case junctions, crosses the interface of the extruded aluminum heatsinks, and is dissipated from the heat sink extrusions to the stream of air.

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BGA Heat Sinks and Bonded Grid Arrays

BGA heat sinks support demanding applications. There are a variety of heat sink styles and attachment methods available. Four primary mechanisms are used for cooling.

Natural convection heat sinks are made from cast or machine alloys, extruded aluminum, or aluminum or copper sheet. They are passive in nature. These BGA heat sinks do not rely upon local air velocity for the application of heat dissipation.

Forced air velocity is required for forced convection BGA heat sinks. The air velocity is incorporated through system level or dedicated fans to increase the thermal efficiency. Board level coolers, high fin density assemblies, or fan heat sinks are configured for impingement or cross flow environments.

Re-circulating BGA heat sinks normally employ looped heat pipes that allow heat transfer exchange through condensation and evaporation. Heat sink technologies are integrated to increase thermal efficiency when physical size restrictions or greater density requirements exist.

Channeled cold plates are used to comprise liquid cooled applications. A pump system and heat exchange are used to circulate fluids past the source of heat. Liquid cooled technology is reserved for high heat flux density applications or where phase change systems or forced convection cannot dissipate the power demanded.

In silicon die packaging, no package is considered the best package. Packaging takes up valuable space and introduces time delays. The cost increases as does the defect potential. Packaging is needed, however, to give easily damaged devices a degree of environmental and mechanical protection. Bonded grid arrays of solder balls are attached to the bottom of the carrier or package.

Plastic bonded grid arrays are the most common type. Typically, the die is wire bonded to the top of the surface of the carrier and over molded with epoxy based plastic.  Ceramic bonded grid arrays consist of a die attached to the surface top of a multilayer ceramic carrier. The die can have an active side up wire bonding or attached in a flip-flop configurations with the active side down.

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There are Pros and Cons to the Bonded Grid Arrays Used in BGA Heat Sinks

The bonded grid arrays, used in manufacturing BGA heat sinks, have advantages in a variety of applications. When designing a component, finding the appropriate device needed for a cooling system that is effective, is a major step. BGA heat sinks are available in ceramic and plastic.

The increased heat dissipation rate is an important benefit provided by bonded grid arrays. The advanced circuitry of the arrays allows quick thermal energy conveyance without high levels of resistance that often occurs when the gull wing approach is used for surface mounting. BGA heat sinks also have a great heat sink-pin count capacity that cannot be achieved with gull wing lead. The ability to auto-align, based on heat flow from the source, may be the most innovative aspect of the bonded array grids. This increases the efficiency potential and allows a greater thermal energy level to transfer through the heat sink.

A component manufacturer needs to be aware of the BGA heat sinks drawbacks before making a final decision. Standard methods of reworking and inspection cannot be used due to the joint solder complexity. Visual inspection is not possible with the bonded grid arrays. It is impossible, to individually adjust, solder joints. To ensure BGA heat sinks technology’s reliability, using x-rays has been proposed as a feasible inspection method.

Light-curable adhesives are one of the newer technologies available for corner bonding. When outside edges of BGAs are close to the edge of the array, the adhesive is very important. The adhesives are applied post-flow. They cure in seconds. The flow underneath is minimized as it is engineered to the edge of the component that is wet.

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Choosing the Right Copper Heatsinks or LED Heatsinks

Because copper has a greater thermal conductivity level, copper heatsinks are sometimes necessary for an application. Copper conducts twice the energy of its aluminum counterpart. Copper heatsinks can be put through die-casting and bound together to form plates. Copper heatsinks do have some drawbacks. They are more expensive than aluminum. They are less malleable and heavier. Extruded heatsinks cannot be produced from copper.

A big advantage to using copper is realized in the skived fin technology process. A unified heatsink is created by carving out a single block of copper. Skiving copper increases efficiency by creating an attachable heat source base that is connected to the cooling fin. The skiving solution also increases the thermal conveyance rate, making for a heatsink design that is extremely desirable.

A common alternative to heatsinks made entirely of copper is the uniting of aluminum and copper in a single heatsink. Multiple fins are affixed to a heatsink base made of copper. The copper heat source, of this design, transmits high thermal conductivity that is quickly conveyed to the fins made of aluminum. The benefits of both materials are realized. There is needed high conductivity at the base while affordable aluminum has extrusion capability.

LED heatsinks are designed to absorb and then disperse excess heat. The heat is dispersed from the LED diode to the heatsink. Active and passive air circulation around the heatsink aids in cooling it. LED phosphor is damaged by too much heat. LED heatsinks, subjected to too much heat, will have a decreased lifespan, change color, and produce a lower light output. The most common LED lighting application issue stems from having LED heatsinks or heatsinks that are too small.

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