Heat Sinks and Thermal Solutions for Server Computer Industry Applications

The server industry offers a large variety of products ranging from 1U servers and blade servers, to mainframes all posing challenging and interesting thermal problems. The processors used typically dissipate a large amount of power yet have limited space for the heat sink. Other heat sources within the system often cause additional problems and require cooling as well. The servers are often required to work at elevated ambient temperatures and utilize system airflow for component and heat sick cooling. Because of this, often times, heat sinks must be custom designed for the application.

Heat Sinks and Thermal Solutions for Server Computers

Server heat sinks range from large extruded heat sinks or bonded fin heat sinks, to heat pipe embedded heat sinks measuring 10mm tall. Heat pipes provide an excellent method of improving the performance of a heat sink, either by improving the heat spreading across the base, or by carrying the heat to a more open area for improved heat dissipation. Additionally, in case of tall heat sink fins, heat pipes can be used to increase heat sink fin efficiency providing better performing thermal solution.

1U server heat sinks can be particularly difficult to design because they often need to cool high end CPUs, while limiting the heat sink height to less than 1 inch. In most server applications heat sinks use system airflow for cooling, while in rare occasions heat sinks have fans mounted directly to them. Depending on the application, some heat sinks must continue to work after partial fan failures.

1U servers often pose an interesting thermal challenge to system and heat sink designers. 1U servers are compact (approximately 43mm thick), and rack mountable limiting the space for heat sink integration. They typically use 40mm axial fans or compact blowers to force air through the system or a heat sink. 1U servers are available with virtually any type of processor, from budget desktop, to power conservative mobile CPUs, to high end 32 bit and 64 bit processors hence a vide variety of heat sinks are used in these applications.

To meet the challenging 1U server thermal requirements, many types of heat sinks are available on the market. For low power CPUs, extruded aluminum heat sinks are often capable of dissipating the heat. If better performance is required, an all copper 1U heat sink may be necessary. Copper 1U heat sinks are typically either machined or skived, to achieve thin fins and high surface area. However, copper 1U heat sinks typically have high pressure drops, which may require ducted airflow through the heat sink from the system fans.

Heat pipes can also be integrated into 1U heat sinks, which offers several advantages to the heat sink design. First, heat pipes allow the heat to be carried to open areas, or areas of high airflow increasing the heat dissipating capacity of heat sink design. In the cramped 1U systems, system layout can be very difficult, and heat pipes can simplify heat sink design and ease of manufacturing. Heat pipes can also improve the performance of a direct mounted 1U heat sink, by spreading the heat effectively in the heat sink base.

For higher heat sink performance, it may be necessary to use an active heat sink, which has fans mounted directly to the heat sink. 1U active heat sinks offer high performance, without depriving the rest of the system of forced airflow. Also, these heat sinks can give greater flexibility in the system design by allowing greater freedom in component placement. However, fans are often viewed as a high point of failure. For this reason, most of the 1U servers utilize system airflow for component and heat sink cooling.

Blade servers cause even more challenging thermal problems. Most blade servers utilize high end, high power dissipating processors in a very compact chassis with limited space for a heat sink. These servers are often rack mounted often causing additional thermal problems.

Enertron has a long history of supporting server industry. For more information regarding Enertron's support of Server Computer market, please contact one or our applications engineers.

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