The use of vapor chambers in the thermal management of electronics has grown exponentially since Advanced Thermal Solutions, Inc. (ATS) first wrote seven years ago about their ability to spread heat uniformly across the base of a heat sink, reducing the spreading resistance and enhancing the heat sink’s heat transfer capabilities when applied to high-powered components.
In a two-part series published originally in 2010 and based on an article from Qpedia Thermal eMagazine entitled, “Vapor Chambers and Their Use in Thermal Management,” it was explained that “a vapor chamber (VC) is basically a flat heat pipe that can be part of the base of a heat sink. It is vacuumed and then injected with just enough liquid (e.g. water) to wet the wick.” [1]
Similar to heat pipes, “The heat source causes the liquid to vaporize on the evaporator side. The resulting pressure increase in this area forces the vapor into the condenser side, which is the base of the heat sink. Here, the vapor transfers the heat to the heat sink, and it then condenses back to liquid. The liquid is pumped back to the base through the capillary action of the wick structure.”
In Fig. 1, two heat sinks are shown. One has a solid base and the other has a vapor chamber in its base and it is clear from the temperature distribution that the vapor chamber spreads out the heat across the base and distributes heat to a larger portion of the heat sink.
As the original article explained, “The very high equivalent thermal conductivity of the vapor chamber has spread the heat uniformly, leading to more efficiency from the heat sink.”
Figure 1. Schematic View of Heat Sinks with (a) Solid Base and (b) Vapor Chamber Base. [1]
The second article runs through some of the equations that define the effective thermal conductivity of the wicking structure inside the vapor chamber and the impact that changing the wick material can have on its efficiency.
“This article shows that while a vapor chamber presents exciting technology, some calculations should be made to justify its use,” it continued. “In some situations, a solid copper block might provide better thermal performance than a vapor chamber. To use a vapor chamber instead of solid copper must be justified, for example, to reduce weight.
Another issue with vapor chambers presented by the article was that “some vapor chambers have a power limit of 500 watts. Exceeding this value might cause a dry out, as with a heat pipe, and could increase the vapor temperature and the pressure. The increase in internal pressure can deform the VC surfaces, or cause leakage from the welded joints.”
The study of vapor chambers has developed in the past seven years and, although some of the same issues remain, they are now thinner and lighter than ever and engineers are finding many new ways of incorporating them into cooling systems. Vapor chambers are now frequently used in applications ranging from hard drive disk cooling, PC cooling (not just for gamers and overclockers, but also for office computers), graphic card cooling, server cooling, high heat flux chips (IGBT and MOSFET), LED, and in consumer products (particularly mobile devices such as cell phones and tablets).
In addition to the benefits explained above, vapor chambers are critical in applications where height is limited, which is an increasing problem in today’s era of miniaturization, and where power densities are high. Vapor chambers are also important in applications where there are hotspots, where weight is a concern, and where there is a high ambient temperature or low airflow.
Hard Drive Disk Cooling
Several manufacturers in the hard drive market have turned to vapor chambers because of increases in spindle speed. In the past, many manufacturers and designers limited the thermal management of hard drives to using the aluminum case as a heat sink to dissipate the excess heat from the device, but as drives began working at 7,200 RPM and higher another option was required to ensure the reliability and longevity of the drive. [2]
A 2013 study that was published in International Communications in Heat and Mass Transfer explored the use of vapor chambers to cool hard drives in personal computers. The researchers found that adding vapor chambers to the cooling system could reduce the hard drive temperature by as much as 15.21%. [3]
Gaming, Overclocking, Personal Computing
The gaming and overclocking community has turned towards liquid cooling in recent years, as evidenced by a recent survey from KitGuru that showed 51% of its readers had already or would shortly be using liquid cooling for their personal computers. [4] While there is a trend in that direction, just under half (49%) of the respondents were also sticking with convection cooling options and many companies are incorporating vapor chamber technology in elaborate cooling devices (many with fans and heat pipes) for the PC market.
Cooler Master has introduced the V8 GTS CPU Air Cooler, which strongly resembles a car engine and has a horizontal vapor chamber and eight heat pipes. [5] The vapor chamber spreads the heat evenly from hotspots in the CPU and the heat pipes draw that heat into the tower’s heat sink.
The Cooler Master GTS V8 has a distinct car engine look and uses vapor chambers, heat pipes, and heat sinks to cool PCs. (Cooler Master/YouTube)
ID Cooling has introduced several products that boast vapor chamber technology, including the HUNTER, and FI (which stands for Finland) Series CPU coolers. [6] Even gaming systems have gotten into the act with the recently announced, high-powered Xbox One Scorpio expected to include a vapor chamber array as part of its thermal management. [7] Microsoft’s announcement that it was using vapor chambers in Project Scorpio was not surprising because of the technology’s ability to fit into the tight confines of the gaming system.
Microsoft’s Project Scorpio introduced a new, higher-powered gaming system that required an array of vapor chambers to keep it cool. (Microsoft)
Also, the increasing capabilities and power of next-generation graphics cards has led to a trend in the industry to use vapor chambers as part of a package to cool these components. Nvidia is one of the biggest names in graphic cards and for both the Titan X and the GeForce GTX 1080 (each launched in 2016) vapor chamber are used with a blower to dissipate the increased power of the devices. [8]
It is not only the gaming community that is benefiting from vapor chamber cooling. Hewlett Packard (HP) has also explored using vapor chambers for multiple purposes. HP released a white paper last year about using 3-D vapor chambers in its Z Coolers to enhance their thermal efficiency as well as reduce the acoustic impact of the fans. [9] Also last year, HPE Labs released a study of vapor chambers for cooling multiple chip modules dissipating 250 W and operating temperatures up to 45°C and found that “VC (vapor chamber) performs better for: high power, power density, off center or asymmetric heat sources.” [10]
Server Cooling
Much like in graphic cards or gaming systems, vapor chambers are increasingly used in server cooling applications because their size and weight allows them to fit into tight spaces, particularly in applications with high component density. For example, Rugged has released an M120 1-U server rack that includes vapor chambers to spread the heat evenly and high-speed fans to pull the heat out of the system. [11]
A study by Aavid Thermacore from the 2007 ASME InterPACK Conference explained that in blade processors that need to dissipate 100-300 W with heat sinks lower than 30 mm, vapor chambers could be used as the base of the heat sink to improve effective spreading and improve performance by 25-30%. [12] Radian’s Intel Skylake heat sink that is intended for server chips installed in a 1-U chassis put this into practice with a vapor chamber in its base that enhances the effective thermal conductivity of the stamped aluminum fins. [13]
Radian’s Intel Skylake heat sink uses a vapor chamber in the base to evenly spread the heat and improve the heat transfer through the fins of the heat sink. (Radian)
For more on the topic of vapor chambers as heat sink bases, read https://www.qats.com/cms/2017/07/26/vapor-chambers-solid-material-base-high-power-devices.
LED Cooling
A more recent development in the use of vapor chambers is their inclusion in LED packages. A 2016 study from the 37th International Electronic Manufacturing Technology Conference outlined the use of vapor chambers along with finned heat sinks in the thermal management of LED to enhance the thermal performance and provide a “more economical” process than making the heat sink larger or using more expensive materials. [14]
Advanced Cooling Technologies (ACT) also released a case study about cooling high-powered LED applications, such as ultraviolet (UV) cutting devices, which said, “Vapor Chambers are an important tool in LED thermal management, since they act as flux transformers, spreading the high input heat flux over the entire surface of the vapor chamber. This allows the heat to be removed from the vapor chamber by conventional cooling methods.” [15] ACT added that it developed C.T.E matched vapor chambers that allow for direct bonding with the LED and “dissipate heat fluxes as high as 700 W/cm2 and 2kW overall.”
Vapor chambers are also being used in automotive LED applications to prevent failures by spreading the heat quickly from the source. A study from the 2011 International Heat Pipe Symposium found that a vapor chamber with distilled water dropped the LED temperature from 112.7°C to 80.7°C, reduced thermal resistance by 56%, and reached steady state faster than conventional systems. [16]
Mobile Devices
The most obvious market for vapor chambers is mobile devices. Last fall, the news was filled with stories about Samsung cell phone batteries reaching thermal runaway and airplane passengers being forced to turn off the phones for concern about a midair fire. With their thin design and low weight, vapor chambers can be used to spread the heat quickly from batteries or high-powered processors in phones, laptops, tablets, etc. and reduce the risk for catastrophic failures.
A 2016 study from the International Journal of Heat and Mass Transfer described vapor chambers being used to reduce hotspots to improve the comfort of users, which is a problem unique to mobile devices. [17] The researchers proposed a “biporous condenser-side wick design” that “facilitates a thicker vapor core, and thereby reduces the condenser surface peak-to-mean temperature difference by 37% relative to a monolithic wick structure.”
A recent story from EE Times noted that the combined shipments of mobile devices was expected to decline in 2017, marking the third straight year of reduced shipments [18], but with companies expending resources to develop 5G technology there is still a need for superior cooling options moving forward and vapor chambers appear to be a perfect fit in mobile thermal management systems.
References
[1] “Vapor Chambers in Thermal Management”, Qpedia Thermal eMagazine, Sept. 2007.
[2] http://www.pcguide.com/ref/hdd/op/packCooling-c.html
[3] P. Naphon. S. Wongwises, and S. Wiriyasart, “Application of two-phase vapor chamber technique for hard disk drive cooling of PCs,” International Communications in Heat and Mass Transfer, January 2013.
[4] https://www.kitguru.net/components/cooling/andrzej/majority-of-kitguru-readers-now-planning-on-liquid-cooling/
[5] http://www.coolermaster.com/cooling/cpu-air-cooler/v8-gts/
[6] http://www.idcooling.com/Product/series/category_parent/25/name/AIR%20COOLING
[7] https://www.youtube.com/watch?v=RE2hNrq1Zxs
[8] http://www.pcworld.com/article/3102027/components-graphics/nvidias-monstrous-new-titan-x-graphics-card-stomps-onto-the-scene-powered-by-pascal.html and https://www.nvidia.com/en-us/geforce/products/10series/geforce-gtx-1080/
[9] http://www8.hp.com/h20195/v2/getpdf.aspx/4AA6-1205ENW.pdf?ver=2.0
[10] https://www.labs.hpe.com/techreports/2016/HPE-2016-85.pdf
[11] http://www.coresystemsusa.com/filedata/prod/443m120_1u_rugged_rackmount_computer.pdf
[12] http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1595384
[13] https://www.radianheatsinks.com/intel-skylake-heatsink/
[14] K.S. Ong, C.F. Tan, K.C. Lai, K.H. Tan, and R. Singh, “Thermal management of LED with vapor chamber and thermoelectric cooling,” 37th International Electronic Manufacturing Technology Conference, 2016.
[15] https://www.1-act.com/led-thermal-management-case-study-cte-matched-vapor-chamber/
[16] Ji Won Yeo, Hyun Jik Lee, Soo Jung Ha, et al., “Development of Cooling System of LED Headlamp for Vehicle Using Vapor Chamber Type Heat Pipe,” 10th International Heat Pipe Symposium, November 2011.
[17] GauravPatankar, Justin A.Weibel, and Suresh V.Garimella, “Patterning the condenser-side wick in ultra-thin vapor chamber heat spreaders to improve skin temperature uniformity of mobile devices,” International Journal of Heat and Mass Transfer, October 2016.
For more information about Advanced Thermal Solutions, Inc. (ATS) thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.