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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