Designers of embedded systems–from boards and modules used in the latest telecom and networking equipment to a variety of cutting-edge designs–face a growing thermal-management challenge. Newer semiconductor devices are dissipating higher amounts of power, so that they run ever hotter and give off more heat within the system.
If the space available for cooling these components were also increasing, designers might make do with the usual approaches to cooling. However, the space allocated in new designs for thermal management isn't growing. At best, it's at a stand still.
In many cutting-edge embedded applications, this thermal-management dilemma is forcing designers to replace aluminum heat sinks (one innovative example is shown Figure 1 ) with much smaller, but heavier, copper heat sinks. Designers are finding that even large-sized aluminum heat sinks are often inadequate in these applications because these heat sinks have a limited ability to spread the heat, which restricts the overall heat sink's performance.
Because copper has nearly double the thermal conductivity than aluminum, copper heat sinks are much more effective at heat spreading. Copper also has 40% higher heat capacity, meaning devices with transient heat loads or spikes will have better temperature regulation when mated with a copper heat sink.
Nevertheless, copper heat sinks have two notable drawbacks–they're significantly heavier and more expensive than aluminum heat sinks. Fortunately, there is a third option that provides the heat spreading of copper heat sinks, yet is less expensive and significantly lighter. Hybrid heat sinks employ a hybrid copper-and-aluminum construction that combines the advantages of copper and aluminum, providing a superior cooling solution for a wide array of embedded applications.
The heat loads associated with state-of-the-art semiconductors in embedded applications demand heat sinks with substantial cooling capability. Typically, that means the heat sinks need to have large amounts of surface area. One way to achieve greater surface area would be to build heat sinks with taller fins. But that's not an option in many cases since popular standards such as PCI Express, Compact PCI, and ATCA impose height constraints on board-level components. So heat sinks need to be low profile.
To achieve large surface areas in low-profile environments, the footprint must be increased rather than the overall height. This leads to very large footprints for the heat sinks.
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