Tag Archives: thermal cooling

ATS Expands in the COTS Market with its Wind Tunnel Sale to the US Navy

ATS has continued to expand in the COTS industry because of its expertise in resolving thermal challenges through its consulting services, cooling solutions, and thermal test instruments. Most recently, the CWT-107 open loop wind tunnel was sold to the United States Navy for use in their Research Development Labs.



CWT-107 Open Loop Wind Tunnel

The CWT-107 is a research quality wind tunnel designed for multiple PCB and component level testing. It is used in air flow characterization and flow visualization, thermal resistance measurements and generation of P-Q curves. The large test section (24″ x 2″ x 7″) is designed to accommodate multiple PCBs, as seen in a typical ATCA chassis. The wind tunnel can also be used to characterize different heat sink sizes for natural and forced convection cooling. Additionally, multiple heat sinks can be tested side by side to determine their thermal performance in the same environment.

The following video is a brief demonstration and walk through of the CWT-107 Open Loop Wind Tunnel:

To learn more about the CWT-107 and how ATS products can be utilized in COTS applications, please visit www.qats.com.

Want to keep up to date on ATS products, services, free engineering webinars and our monthly Qpeda Thermal eMagazine? Subscribe to ATS

Latest Qpedia Now Available for Download

Qpedia Thermal eMagazine June 2013

Qpedia Thermal eMagazine June 2013

Qpedia Thermal eMagazine, Volume 7, Issue 6, has just been released and can be downloaded at: http://www.qats.com/Qpedia-Thermal-eMagazine/Back-Issues.

This month’s featured articles include:

Enhancing Heat Sink Performance Using Thermoelectric Coolers

With the increase in the power dissipation of components and the parallel reduction of their size, engineers and researchers across the globe have been predicting that the era of air cooling might come to an end. Even though in some applications, with very high power dissipations such as IGBTs, air cooling may not be adequate and liquid cooling is a must; air cooling will continue to be the first choice for most electronic cooling applications for many years to come. Advances in air cooling continue to extend its use and the implementation of thermoelectric coolers (TECs) in heat sink applications is one such effort.

Immersion Liquid Cooling for Servers in Data Centers

Data center designers and operators have invented many ways to improve the data center’s thermal efficiency, such as optimizing the rack layout and air conditioner location, separating cold aisles and hot aisles, optimizing the configuration of pipes and cables in under-floor plenum, introducing liquid cooling to high-power severs. While the above methods can improve the data center heat load management, they cannot dramatically reduce the Power Usage Effectiveness (PUE). This article reviews two relatively new solutions: active single-phase immersion cooling technology proposed by Green Revolution Cooling (GRC) and a passive two-phase immersion cooling technology proposed by the 3M Company.

Industry Developments: Piezoelectric Cooling

Piezoelectric fans and jets must overcome various materials, thermal and mechanical challenges to become widely used in electronics cooling, but because they consume just 1/150 of the electricity of circular fans, run with little noise and have no parts that will wear out, they remain of great interest. In this article, a number of issues are addressed, including the inverse effect of the piezoelectric phenomena and dual piezoelectric cooling jets.

Technology Review: Innovative Cold Plate Designs, 2007 – 2012

In this issue our spotlight is on innovative cold plate designs. There is much discussion about its deployment in the electronics industry, and these patents show some of the salient features that are the focus of different inventors.

& Cooling News featuring the latest product releases and buzz from around the electronics cooling industry.

Download the issue now.

Not a Qpedia subscriber? Subscribe Now for free at: http://www.qats.com/Qpedia-Thermal-eMagazine/Subscribe-to-Qpedia and see why over 18,000 engineers read Qpedia.

Did you know Qpedia also publishes a book series? The five volume set contains 248 in-depth articles, researched and written by veteran engineers. They address the most critical areas of electronics cooling, with a wide spectrum of topics and thorough technical explanation. Order Now.

Thermal Resistance and Component Temperature

To maintain operation, the heat must flow out of a semiconductor as such a rate as to ensure acceptable junction temperatures. This heat flow encounters resistance as it moves from the junction throughout the device package, much like electrons face resistance when flowing through a wire. In thermodynamic terms, this resistance is known as conduction resistance and consists of several parts. From the junction, heat can flow toward the case of the component, where a heat sink may be located. This is referred to as ÎJC, or junction to case thermal resistance. Heat can also flow away from the top surface of the component and into the board. This is known as junction to board resistance, or ΘJB.

Source: JESD51-2, Integrated Circuits Thermal Test Method – Natural Convection, JEDEC, March 1999.

ΘJB is defined as the temperature difference between the junction and the board divided by the power when the heat path is from junction to board only. To measure ΘJB, the top of the device is insulated and a cold plate is attached to the board edge (Figure 1). This is the true thermal resistance, which is the characteristic of the device. The only problem is that, in a real application one does not know how much power is being transmitted from different paths.

Due to the multiple heat transfer paths within a component, a single resistance cannot be used to accurately calculate the junction temperature. The thermal resistance from junction to ambient must be broken down further into a network of resistances to improve the accuracy of junction temperature prediction. A simplified resistor network is shown in Figure 2.

As board layouts become denser, there is a need to design optimized thermal solutions that use the least amount of space possible. Simply put, there is no margin to allow for over-designed heat sinks with tight component spacing. Accounting for the effect of board coupling is an important part of this optimization. The possibility for using an oversized heat sink exists only if the junction to case heat transfer path is considered.

To ensure a 105°C junction temperature at 55°C ambient a typical component (see Table 1) needs a heat sink resistance of 2.05°C/W (if we ignore board conduction). When board conduction is taken into account, the actual junction temperature could be as low as 74°C, assuming the board temperature is the same as the air temperature. This indicates a heat sink that is larger than necessary.

From this example, it is clear that all heat transfer paths from the component junction must be considered. Using just the ΘJC and ΘCA values can lead to a larger than optimal heat sink and may not accurately predict operating junction temperatures. Using the proposed correlation can also predict junction temperature when the board temperature is known from experimentation, as shown in Figure 3.



New Hardcover Collection of Qpedia Electronics Thermal Management Articles Now Available from ATS