Tag Archives: heat sinks

Choosing the Right Heat Sink Attachment for Densely Populated PCB

In 1965, Fairchild Semiconductor Director of R&D and soon to be Intel co-founder Gordon Moore wrote “The Future of Integrated Electronics,” which was intended as an internal paper to define the most cost-effective number of components per integrated circuit. As he looked ahead to the next decade, Moore argued that the number of components per chip would double every year.

The paper was edited and published by Electronics in 1965 as “Cramming More Components onto Integrated Circuits”. Ten years later, Moore, then with Intel, spoke at the IEEE International Electron Devices Meeting and showed that his initial prediction was correct and estimated that the rate of increase would slow to “a doubling every two years, rather than one.”

Heat Sink Attachment

superGRIP heat sink attachment technology offer minimal addition to component footprint on densely packed PCB. (Advanced Thermal Solutions, Inc.)

This prediction has now become widely known as Moore’s law. It has become a tenet of the electronics community and continues to propel the industry forward at a time when the number of transistors on a chip (which was around 65,000 in 1975) now exceeds one billion. [1]

These high-powered components are common on printed circuit boards (PCB) in every day electronics from mobile devices to computers to automobiles. Recently, the Defense Advanced Research Program Agency (DARPA) announced that it will spend $200 million on the Electronics Resurgence Initiative to seek new materials and manufacturing techniques in expectation that Moore’s law will come to a natural end. [2]

Not only are the components themselves getting higher-powered, but increased demand for functionality in ever-smaller packages has meant that these components are increasingly being squeezed into tighter areas. A 2012 article on Tech Design Forums, based on information from Mentor Graphics’ Technology Leadership Awards, indicated that while PCB size had been “relatively constant,” the “average number of components has quadrupled in 15 years.” [3]

As the forum noted, “Despite attempts by IC (integrated circuit) suppliers to cut power dissipation, as IC speeds and densities increase so does the heat they dissipate. And putting these ICs into smaller and smaller form factors compounds the problem. This causes significant thermal management challenges that must be met at the IC package, PCB and system levels.”

OCM Manufacturing, a low- to mid-volume manufacturer of electronics products, offered a chart that detailed standard spacing of components on a PCB, but also added, “With that said, there are no hard and fast rules for component spacing. Tightly packed components may have very good yield and problems may arise only during rework.” [4]

Heat Sink Attachment

Match each component in the rows with whatever it’s adjacent to in the columns to see the preferred and minimum spacing between those two components, in millimeters. [4] (OCM Manufacturing)

Of course, all of that power will inevitably lead to increased heat across the system. Coupled with the decrease in space between components, which puts constraints on the amount of airflow across a component and leads to heat from one chip being passed on to the next, thermal management is a critical aspect of PCB design to an even greater extent than before. [5]

Heat sinks remain the most cost-effective method for cooling chips. The benefits of heat sinks, the thermal impact of different materials, and the development of new fin geometries are all discussed in depth elsewhere on this blog, but this article asks, “What is the best way to attach heat sinks, especially in a component-dense environment?”

As Dr. Kaveh Azar, founder and CEO of Advanced Thermal Solutions, Inc. (ATS), wrote in ECN Magazine, “An engineer starting the process of thermal management must first determine the cooling needed and then consider the mechanical aspects of attaching the heat sink.” [6]

He added, “The thermal consideration is foremost on our decision tree. Once we have resolved the cooling issue, including the heat sink size and the type of thermal interface material (TIM) needed, we need to ask the question of how this heat sink will be attached to the device or the PCB.”

There are several options for design engineers to consider, but each comes with its own set of challenges. Thermal tape and thermal epoxies [7] would obviously add nothing to the existing component footprint, but tape has proven better for low-powered chips and epoxies require time to cure and are essentially permanent, making potential rework more time-consuming and costly.

Push pins, threaded standoffs and z-clips are mechanical attachment technologies that are common in the electronics industry but all require expanded footprints as well as holes or anchors in the PCB, which may not be available on high-density boards. Holes and anchors also make signal routing more difficult in the design phase and there is a possibility of a standoff or solder anchor causing a short during installation that could result in damage to the board. [8]

To meet this need, ATS developed superGRIP™. The two-part attachment system features a plastic frame clip that fastens securely around the perimeter of the component and a metal spring clip that slips through the fins of a heat sink and locks to the frame clip on both ends. [9]

The system is designed to need minimal space around the component. [10] The frame clip is made of a plastic resin that allows it to be very thin but also very strong, which was demonstrated during shock and vibration testing. The interior frame profile locks securely around the bottom edge and sides of the component package. The horseshoe tabs secure the clip to ensure the proper pressure on the heat sink.

The following chart shows the superGRIP™ clearance guidelines, although custom options are available and may be needed depending on the design:

superGRIP

The required board keep-out region for ATS superGRIP heat sink attachment technology. (Advanced Thermal Solutions, Inc.)

superGRIP™ was also designed and tested to ensure maximum airflow through the heat sink. In a tightly-packed system where airflow is at a premium, superGRIP™ provides the necessary attachment security with only minimal impact on the flow. In addition, the plastic used in the frame clip stays cool in high-heat environments, rather than adding fuel to a potentially combustible situation.

superGRIP

CFD simulations with ATS superGRIP attachment demonstrating its minimal impact on airflow across a system. (Advanced Thermal Solutions, Inc.)

Unlike other attachment technologies, superGRIP™ also requires no separate tooling and can be installed or released with a common tool such as a screwdriver. [11] This makes any potential rework easier. It is important to note the direction of the airflow when placing a heat sink, so it must also be considered when placing the frame clip as well.

References
[1] http://www.computerhistory.org/siliconengine/moores-law-predicts-the-future-of-integrated-circuits/
[2] http://www.eetimes.com/document.asp?doc_id=1331974 and https://www.darpa.mil/news-events/2017-06-01
[3] http://www.techdesignforums.com/practice/technique/overcoming-increasing-pcb-complexity-with-automation/
[4] http://ocmmanufacturing.com/resources/resource/dfm-tip-spacing-components-on-a-pcb/
[5] http://www.electronicdesign.com/embedded/engineer-s-guide-high-quality-pcb-design
[6] https://www.ecnmag.com/article/2011/09/know-your-choices-mounting-heat-sinks-hot-components
[7] https://www.masterbond.com/industries/heat-sink-attachment
[8] “How the maxiGRIP™ attachment system impacts component mechanical behavior,” Qpedia Thermal eMagazine, May 2008.
[9] https://www.qats.com/cpanel/UploadedPdf/ATS_superGRIP_Launch_Release_FINAL_with_Photo_0427092.pdf
[10] https://www.qats.com/cms/wp-content/uploads/2013/12/superGRIP-Clearance-Guidelines1.pdf
[11] https://www.qats.com/cms/wp-content/uploads/2013/12/superGRIP-Installation-Guidelines.pdf

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.

Fin Optimization in Heat Sinks and Heat Exchangers

(This article was featured in an issue of Qpedia Thermal e-Magazine, an online publication produced by Advanced Thermal Solutions, Inc. (ATS) dedicated to the thermal management of electronics. To get the current issue or to look through the archives, visit http://www.qats.com/Qpedia-Thermal-eMagazine.)

In electronics cooling, often separately managed Thermal/Mechanical (TM) and Software/Electrical (SE) engineering teams are finding themselves facing common challenges, as they are being driven towards similar business goals, such as product differentiation, company growth and profitability.

More so than ever today, these teams are being directed to find ways to increase component performance, particularly on highly populated boards within complex systems, at an acceptable cost of manufacturing. They are also discovering that their goals are being held back by governing specifications, environmental conditions, mechanical limitations and budget restrictions.

Heat Exchangers

Closeup of fin array on an ATS tube-to-fin heat exchanger. (Advanced Thermal Solutions, Inc.)

TM’s design thermal solutions based on airflow, envelope size, power dissipation, etc. and migrate (as expected) to the lower cost “standard solutions” whenever possible. If adequate margin is not met, reliability implications are more apparent as engineers will have to optimize solutions. This is because, in most cases, the form factor, layout, boundary conditions, etc. are set.

Thermal solutions become the gatekeeper, and in some cases, the determining factor in product deployment.

Many leading companies design their products by using technologies that will sustain long product life cycles for increased market share and brand awareness. As products are refined through the design cycle, thermal solutions may have to be optimized and this requires many investigations to be undertaken.

As the electronics industry continues to use components dissipating more and more power, new heat sink solutions must be able to accommodate large heat fluxes while keeping the same spatial dimensions [1]. Finned heat sinks and heat exchangers are largely employed in many engineering fields, and this demand spurs researchers into devising and testing new geometries for the heat sinks.

Engineers constantly try to develop new designs to enhance the performance of heat exchangers. One such effort is the design of the wavy fins to enhance the surface area.

Figure 1 shows a close up view of an extrusion type thermal solution where the profile has a feature of undulated fins. In general, a wavy fin heat sink should perform better under natural and forced convection due to the increased surface area created by the fins. This feature can easily be manufactured with a die. The “waviness” can be adjusted to increase surface area resulting in a positive impact on thermal performance.

Heat Exchangers

Figure 1. Close-Up View of Simply Wavy Fin Geometry [1]

Theoretical models have been devised to find the pressure drop and the heat transfer from wavy fin geometries. Figure 2 shows the schematic of a wavy fin.

Heat Exchangers

Figure 2. Schematic of a Wavy Fin Geometry [2]

In this figure, the fins are assumed to have a sinusoidal geometry where

λ = Wave length (m)
H = channel width (m)
S = channel height
2A = twice the amplitude of the wave

The shape of the curve is assumed to be:

The length of the curve can be found from the following equation:

Shah and London [3] came up with the following equation for the friction and Nusselt number in channels:

Where,
F = fanning friction factor
aspect ratio

The same equation applies for a wavy fin based on the correct length:

The Nusselt number for the straight fins and wavy fins is the same as long as the correct surface area is used:

The above equations are for the low Reynolds number.

For high Reynolds number Shapiro et. al [4] derived the following equations:

Where,
Dh = hydraulic diameter (m)
Reynolds number based on hydraulic diameter
L = half length of the channel (Le/2)
Pr = prandtl number
Dh = 2SH/(S+H)

The combined asymptotic for the friction and Nusselt number is as follows:

Figure 3 compares the results of the above analytical equations with the results from Kays and London [5]. In the graph, the Colburn j factor is shown and is defined as:

The results show that the experimental values of Shah and London are within 20% band of the values obtained from the above relations. The data is for the fin type 11.44-3/8W.

Heat Exchangers

Figure 3. f and j Values as a Function of Reynolds Number.[2]

Marthinuss et al. [6] reviewed published data for air-cooled heat sinks, primarily from Compact Heat Exchangers by Kays et al [5] and concluded that for identical fin arrays consisting of circular and rectangular passages, including circular tubes, tube banks, straight fins, louvered fins, strip or lanced offset fins, wavy fins and pin fins, the optimum heat sink is a compromise among heat transfer, pressure drop, volume, weight and cost.

Figure 4 shows that if the goal is to get a higher value of heat transfer per unit of pressure drop, the straight fin is the best. Figure 5 shows that when heat transfer per unit height is of concern pin fin is the best.

Heat Exchangers

Figure 4. Profile Comparisons Based on Heat Transfer/Pressure Drop. [6]

Figure 5. Profile Comparisons Based on Heat Transfer/Volume. [6]

Sikka et al. [7] performed experiments on heat sinks with different fin geometries. Figure 6 shows 3 different categories of heat sinks tested. The conventional fins, such as straight and pin fins, are shown in (a); (b) shows the fluted fins and (c) shows the wavy fin design. The tests were done for both horizontal and vertical direction of air flow at natural convection and low Reynolds number forced flow. Table 1 shows the dimensional values of each of these heat sinks.

The last column shows the values of At/Ab (total surface area/base surface area).

Figure 6. (a) Traditional Fins, (b) Fluted Fins, (c) Wavy Fins. [7]

Table 1. Geometries and Dimensions of the Heat Sinks. [7]

The values of the Nusselt number were reported based on the following relation:

Figure 7 shows that for natural convection in the horizontal direction, the pin fin has the best performance. The fluted fins have, in general, a better performance compared to longitudinal fins. The lower graph in figure 7 shows that the wavy fins are essentially the same as the longitudinal fins.

Figure 7. Nusselt Number As a Function of Rayleigh Number for Natural Convection-Horizontal Direction. [7]

Figure 8 shows the natural convection cases for the vertical direction. The figure shows that heat transfer decreases for the pin fin, but increases for the plate fin. The pin fin still is better than the plate fin, but the difference is only 4-6%. Figure 8 also shows that the cross cut heat sink has the best performance. The bottom figure in 8 confirms that the wavy fins do not have much better heat transfer compared to plate fins.

Figure 8. Nusselt Number as a Function of Rayleigh Number for Natural Convection-Vertical Direction. [7]

Figure 9 shows the Nusselt number for forced convection over a horizontal plate as a function of Reynolds number. This figure indicates that, for very low Reynolds numbers, the cross fin is better than the pin fin; but, around Re = 2000, the situation reverses and the pin fin gets better than the cross cut heat sink. For low Reynolds numbers, the longitudinal pins are better than the wavy fins; but, at higher Reynolds numbers, the performance of the wavy fins gets better by almost 12-18%.

Figure 9. Nusselt Number as a Function of Reynolds Number for Forced Convection-Horizontal Direction. [7]

Figure 10 provides the Nusselt numbers for the vertical direction for forced flow. In comparing the results with the horizontal direction, the results are almost the same, with the difference being that the wavy fin heat sinks perform better than the plate fin heat sinks, by about 14-20%.

Figure 10. Nusselt Number as a Function of Reynolds Number for Forced Convection-Vertical Direction.[7]

The results presented in this article strengthen our understanding about how heat exchangers and heat sinks can be made more compact and efficient. The results show that the design of the fin field is still an issue and much remains to be investigated for optimization, depending on the conditions and application.

Further empirical testing is warranted for the evaluation of the effects of wavy fin heat sinks, as fine meshing and a high degree of confidence is not easily obtained through simulating these profiles using commercial CFD tools.

References:

1. Lorenzini, M., “Performance Evaluation of a Wavy-Fin Heat Sink for Power Electronics” Applied Thermal Engineering, 2007.
2. Awad, M., Muzychka, S., “Models for pressure drop and heat transfer in air cooled compact wavy fin heat exchangers”, Journal of Enhanced Heat Transfer, 18(3):191-207(2011).
3. Shah, R., London, A., “Advances in heat transfer, suppl. 1, laminar forced flow convection in ducts”, New York, Academic press, 1978
4. Shapiro, A., Sigel, R., Kline, S., “Friction factor in the laminar entry region of a smooth tube,” Proc., 2nd V.S.Nat. Congress of applied mechanics, PP. 733-741, 1954.
5. Kays, M., London,L., “Compact Heat Exchangers”, Third Edition, McGraw-Hill, 1984.
6. Marthinuss, E., Hall, G., “Air cooled compact heat exchanger design for electronics cooling”, Electronics cooling magazine, Feb 1st, 2004
7. Sikka, K., Torrance, K., Scholler, U., Salanova, I., “Heat sinks with fluted and wavy fins in natural and low-velocity forced convection”, IEEE, Intersoceity Conference, 2000.

For more information about Advanced Thermal Solutions, Inc. thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.

How Do Heat Sink Materials Impact Performance

By Michael Haskell, Thermal Engineer
and Norman Quesnel, Senior Member of Marketing Staff
Advanced Thermal Solutions, Inc.

(This article was featured in an issue of Qpedia Thermal e-Magazine, an online publication produced by Advanced Thermal Solutions, Inc. (ATS) dedicated to the thermal management of electronics. To get the current issue or to look through the archives, visit http://www.qats.com/Qpedia-Thermal-eMagazine.)

Heat Sink Materials

This article examines the difference in thermal performance between copper, aluminum, and graphite foam heat sinks. (Advanced Thermal Solutions, Inc.)

Introduction

As thermal solutions for today’s electronics grow more challenging, demand rises for novel cooling ideas or materials. As a result, the proven methods of analytical calculations, modeling and laboratory testing are sometimes bypassed for a quick “cure-all” solution. Evolutionary progress is required of the thermal industry, of course. But, despite the urgency to introduce new ideas and materials, thorough testing should be performed in determining the thermal performance of a solution before it is implemented.

This article addresses the impact of material choice on heat sink performance. First, an evaluation of different materials is made in a laboratory setting, using mechanical samples and a research quality wind tunnel. This testing compares a constant heat sink geometry made from copper, aluminum, and graphite foam. Next, an application-specific heat sink study is presented using computational fluid dynamics (CFD) software.

In this study, a heat sink was designed in 3D CAD to cool a dual core host processor. The performance of both an aluminum and copper design was then evaluated using CFD.

Laboratory Tests of Copper, Aluminum, and Graphite Foam

The stated thermal properties of engineered graphite foams have enhanced their consideration as heat sink materials. Yet, the literature is void of a true comparison of these materials with copper and aluminum. To evaluate graphite foam as a viable material for heat sinks, a series of tests were conducted to compare the thermal performance of geometrically identical heat sinks made of copper, aluminum, and graphite foam respectively.

Testing was conducted in a research quality laboratory wind tunnel where the unducted air flow was consistent with typical applications.

(The results for ducted and jet impingement flows, though similar to the unducted case, will be presented in a future article along with a secondary graphite foam material.)

Test Procedure

Earlier foam experiments by Coursey et al. [1] used solder brazing to affix a foam heat sink to a heated component. The solder method reduced the problematic interfacial resistance when using foams, due to their porous nature. Directly bonding the heat sink to a component has two potential drawbacks. First, the high temperatures common in brazing could damage the electrical component itself.

The other issue concerns the complicated replacement or rework of the component. Due to the low tensile strength of foam (Table 1) a greater potential for heat sink damage occurs than with aluminum or copper [2]. If the heat sink is damaged or the attached component needs to be serviced, direct bonding increases the cost of rework.

Table 1. Thermal and Mechanical Properties of the Heat Sink Materials. (Advanced Thermal Solutions, Inc.)

To avoid these problems, the foam heat sink can be soldered to an aluminum or copper carrier plate. This foam-and-plate assembly can then be mounted to a component in a standard fashion. The carrier plate allows sufficient pressure to be applied to the interface material, ensuring low contact resistance.

In this study, the heat sinks were clamped directly to the test component without a carrier plate as a baseline for all three materials. Shin-Etsu X23 thermal grease was used as an interface material to fill the porous surface of the foam and reduce interfacial resistance. Five J-type thermocouples were placed in the following locations: upstream of the heat sink to record ambient air temperatures, in the heater block, in the center of the heat sink base, at the edge of the heat sink base, and in the tip of the outermost fin.

Heat Sink Material

Figure 1. Test Heat Sink Drawing. (Advanced Thermal Solutions, Inc.)

A thin film heater was set at 10 watts during all testing, and the heat source area was 25 mm x 25 mm, or one quarter of the overall sink base area, as shown in Figure 1. Both cardboard and FR-4 board were used to insulate the bottom of the heater, The estimated value of Ψjb is 62.5°C/W. Throughout testing, the value of Ψjb was 36–92 times greater than that of Ψja.

Results

As expected, the traditional copper and aluminum heat sinks performed similarly. The main difference was due to the higher thermal conductivity of copper, which reduced spreading resistance. During slow velocity flow conditions, the lower heat transfer rate means that convection thermal resistance makes up a large portion of the overall Θja.

Heat Sink Materials

Table 2. Test Heat Sink Geometry. (Advanced Thermal Solutions, Inc.)

Heat Sink Materials

Figure 2. Experimental Heater and Measurement Setup. (Advanced Thermal Solutions, Inc.)

As flow speed increases, the convection resistance decreases, and the internal heat sink conduction resistance is more of a factor in the overall Θja value. This behavior is evident in the table below, and when comparing the different heat sink materials. The graphite heat sink’s thermal performance was only 12% lower than aluminum at low flow rates. However, the performance difference increased to 25-30% as the flow rate increased (Table 3).

Heat Sink Materials

Table 3. Specific Thermal Test Results. (Advanced Thermal Solutions, Inc.)

Due to the lack of a solder joint, the foam heat sink experienced a larger interfacial resistance when compared to the solid heat sinks. This difference can be seen when comparing ΨHEATER-BASE in Table 3. To decouple the effect of interfacial resistance ΨBASE-AIR can be calculated. When ignoring interfacial resistance in this manner foam performs within 1% of aluminum at 1.5 m/s, and within 15% at 3.5 m/s.

Heat Sink Materials

Figure 3. Heat Sink Thermal Resistance as a Function of Velocity. (Advanced Thermal Solutions, Inc.)

Graphite foam-derived heat sinks show promise in specific applications, but exhibit several drawbacks in mainstream electronics cooling. Due to the frail nature of graphite foam, unique precautions must be taken during the handling and use of these heat sinks. When coupled to a copper base plate, graphite foam can perform with acceptably small spreading resistances.

However, the foam’s lower thermal conductivity reduces thermal performance at high flow velocities compared to a traditional copper heat sink.

The mechanical attachment needed to ensure acceptable thermal interface performance without soldering or brazing also hinders foam-based heat sinks from being explored in mainstream applications. Despite these challenges, the thermal performance-to-weight ratio of foam is very attractive and well-suited to the aerospace and military industries, where cost and ease of use come second to weight and performance.

Thermal Software Comparison of Aluminum and Copper Heat Sinks

A challenging thermal application was considered. This involved the use of a dual core host processor on a board with limited footprint area for a heat sink of sufficient size. A heat sink with a stepped base was designed to clear onboard components. It provided sufficient surface area to dissipate heat (Figure 4).

Due to the complexity of the heat sink, machining a test sample from each material was not practical. Instead, CFD was used to predict the performance difference between the two materials and determine if the additional cost of copper was warranted.

Heat Sink Materials

Figure 4. Stepped Base maxiFLOW™ Heat Sink (ATS). (Advanced Thermal Solutions, Inc.)

Because of the stepped base and a long heat conduction path, spreading resistance was a major factor in the overall thermal resistance. The effect of copper in place of aluminum due to its higher thermal conductivity (400 and 180 W/m*K respectively) is shown in Table 4. The CFD software predicted a 21% improvement using copper in place of aluminum. More importantly, it reduced the processor case temperature below the required goal of 95°C.

The performance improvement with copper is due to the reduced spreading resistance from the processor die to the heat sink fins. This effect is shown in Figure 5, where the base temperatures of both heat sinks are obtained from the CFD analysis and plotted together. The aluminum heat sink shows a hotter center base temperature and a more pronounced drop off in temperature along the outer fins. The copper heat sink spreads the heat to all fins in a more even fashion, increasing the overall efficiency of the design. This temperature distribution can be seen in Figures 6 and 7, which were created using CFDesign software.

Heat Sink Materials

Figure 5. Effect of Heat Sink Material on Temperature Distribution. (Advanced Thermal Solutions, Inc.)

Heat Sink Materials

Figure 6. Aluminum Stepped Base maxiFLOW™ Heat Sink Simulation. (Advanced Thermal Solutions, Inc.)

Heat Sink Materials

Figure 7. Copper Stepped Base maxiFLOW™ Heat Sink Simulation. (Advanced Thermal Solutions, Inc.)

Conclusion

Design engineers have many materials at their disposal to meet the challenging thermal needs of modern components. Classic materials such as aluminum and copper are joined by new technologies that bring improvements in cost, weight, or conductivity. The choice between a metallic, foam or plastic heat sink can be difficult because thermal conductivity provides the only available information to predict performance.

The first method for determining material selection is a classic thermodynamics problem: what effect does conductivity have on the overall thermal resistance in my system? Only once this is answered can the benefits of cost, weight, and manufacture be addressed.

References

1. Coursey, J., Jungho, K., and Boudreaux, P. Performance of Graphite Foam Evaporator for Use in Thermal Management, Journal of Electronics Packaging, June 2005.
2. Klett, J., High Conductivity Graphitic Foams, Oak Ridge National Laboratory, 2003.

For more information about Advanced Thermal Solutions, Inc. thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.

#WeOwnTheBoard: ATS Has Thermal Solutions to Cover the Whole Board

We Own The Board

Advanced Thermal Solutions, Inc. (ATS) has an extensive line of heat sinks and board level thermal solutions that allow ATS engineers to work with industry-leading components and solve the industry’s toughest thermal challenges. (Advanced Thermal Solutions, Inc.)

Advanced Thermal Solutions, Inc. (ATS) has an extensive product line of innovative, off-the-shelf and custom heat sinks and attachments that provides the broadest range of designs to meet the demanding thermal challenges presented by today’s high-powered electronics. Led by its patented maxiFLOW™, which provides the highest thermal performance for physical volume it occupies compared to other heat sinks on the market, ATS has a solution to meet any thermal problem.

In addition, ATS engineers have world-renowned expertise in thermal management and are capable of designing liquid and air cooling solutions using heat sinks, heat pipes, heat exchangers, fans, and cold plates. ATS has more than two decades of solving the industry’s toughest thermal challenges and have a proven record of success in handling the industry’s leading components.

From the latest generation of Intel processors to Altera’s high-powered Stratix FPGA to Qualcomm’s ARM processors to Texas Instruments, Nvidia, NXP, Cavium, and many more, ATS has the experience, the analytical capability, and the products to provide you with the necessary thermal management.

Board Level Solutions

maxiFLOW™ – maxiFLOW™ heat sink design provides the highest thermal performance for the physical volume that it occupies as compared to other heat sink designs. maxiFLOW™ heat sinks are ideally suited to meet the thermal requirements of a broad range of electronics packages, including: BGA, QFP, LCC, LGA, CLCC, TSOP, DIPs and LQFP.

Straight Fin – ATS offers a large variety of high performance Straight fin heat sinks that can be used in many applications where the direction of the airflow is clearly defined. The straight fin heat sink can be utilized in areas where the maxiFLOW™ flair-fanned cannot be used, providing an excellent alternative for cooling thermally sensitive devices.

Cross-Cut – Electronics packages are numerous and range from BGA, QFP, LCC, LGA, CLCC, TSOP, DIPs, LQFP and many others. ATS offers a large variety of cross cut heat sinks that can be used in a variety of applications where the direction of the airflow is ambiguous. The cross cut allow for the heat sink to receive air from any direction.

Pin Fin – Electronics packages are numerous and range from BGA, QFP, LCC, LGA, CLCC, TSOP, DIPs, LQFP and many others. ATS offers a large variety of cross cut heat sinks that can be used in a variety of applications where the direction of the airflow is ambiguous. The cross cut tape on allow for the heat sink to receive air from any direction and can be easily attached to the device by a thermally conductive tape.

fanSINK™ – In many electronic systems, such as telecomm and datacom chassis, or 1U, 2U servers and blades, the system air flow rate is not adequate for cooling of high power devices. Therefore, additional air flow introduced at the device level is required. ATS offers a large family of fanSINK™ products for applications where FPGA or ASICs in BGA packages are deployed. ThefanSINK™ can be either clipped on to the device by maxiGRIP™ or superGRIP™ heat sink attachment technologies or taped on.

Power Brick – DC/DC power converters are an essential part of PCB design and their performance requires a stable temperature for optimum performance. ATS has produced a broad array of high performance power brick heat sinks, based off of the patented maxiFLOW™ design, to effectively cool DC/DC power converters and power modules deployed in a host of electronics applications. ATS’ power brick heat sinks are available in full, half, quarter and eighth packaging.

pushPIN™ – With over 108K different push pin heat sink assembly configurations, ATS offers the largest push pin heat sink offering in the market. Select from fine and ultra-fine pitch heat sinks designed for high velocity air flows and coarse pitch heat sinks for low velocity air flow conditions. Offered in straight fin, cross-cut and the ultra performance maxiFLOW™ fin geometries, ATS pushPIN™ heat sink line is suited to meet a wide variety of applications for components ranging in size from 25mm-70mm. Push pins are offered in brass and plastic and are packaged with different compression springs to achieve precise force required for secure attachment.

blueICE™ (Ultra Low Profile) – In many electronics systems, such as Telecomm, Datacomm, Biomedical equipment and others, card-to-card spacing is small, yet stringent thermal requirements remain the same. Electronics packages such as BGA, QFP, LCC, LGA, CLCC, TSOP, DIP, LQFP are commonly used with stringent thermal requirements in a tight space with limited airflow. Ultra low profile heat sinks offered by ATS range from 2 to 7mm in height and are ideally suited for tight-space application electronics since they offer the best thermal performance. Their thermal resistance is as low as 1.23° C/W within an air velocity of 600 ft/min.

Standard Board Level – ATS’ high quality, low cost, aluminum stamped heat sinks are ideal for low power thermal management solutions. The simple design and manufacturing of these heat sinks allows high volume manufacturing and reducing assembly costs. Stamped heat sinks are ideally used for TO packages and other power devices.

Extrusions – Aluminum extrusions are the most cost-effective solutions for the majority of electronic cooling applications. ATS offers a wide variety of aluminum profiles used for heat sink fabrication and other aluminum applications. Whether you are seeking a standard extrusion profile or the expertise from our design team to create a new and innovative profile, ATS has the capabilities and expertise to meet your requirements.

Heat Sink Attachments

superGRIP™ – superGRIP™ is a two component attachment system which quickly and securely mounts heat sinks to a wide range of components, without needing to drill holes in the PCB. superGRIP™ provides a strong, even attachment force with minimal space required around the components perimeter, making it ideal for densely populated PCBs. superGRIP™ is available with ATS maxiFLOW™ heat sink and straight fin heat sinks.

maxiGRIP™ – maxiGRIP™ is a unique, two component attachment system which quickly and securely mounts heat sinks to a wide range of components, without needing to drill holes in the PCB. The steady, even attachment force provided by maxiGRIP™ allows the heat sink and thermal interface material to achieve maximum thermal performance. maxiGRIP™ is available with ATS maxiFLOW™, straight fin, fanSINK™ and device specific heat sinks.

Thermal Tape
– The interface material plays a pivotal role in transporting the heat from the component to the heat sink. The tape is applied to the base of the heat sink and then the heat sink is attached to the component. For tape to work well, proper cleaning of the component surface and the base of heat sink is required. Also, it is usually necessary to apply the tape with a certain amount of pressure.

Power Brick: #GoldStandard Heat Sinks for DC/DC Converters

Power Brick

ATS Power Brick heat sinks are the #GoldStandard for cooling eighth, quarter, half, and full brick DC/DC power converters. (Advanced Thermal Solutions, Inc.)


Advanced Thermal Solutions, Inc. (ATS) has a line of Power Brick heat sinks (available through Digi-Key Electronics and Arrow) that are specially designed to cool eighth-, quarter-, half-, and full-sized DC to DC power converters and power modules. Power Brick heat sinks feature ATS’ patented maxiFLOW™ design, which reduces the air pressure drop and provides greater surface area for more effective convection cooling.

Power Brick heat sinks are a critical component for the optimal thermal management of electronic devices because DC/DC power converters are used in many applications and across a number of industries, including communications, health care, computing, and more.

DC/DC converters are electronic circuits that convert direct current (DC) from one voltage to another. Converters protect electronic devices from power sources that are too strong or step up the level of the system input power to ensure it runs properly. The process works by way of a switching element that turns the initial DC signal into a square wave, which is alternating current (AC), and then passes it through a second filter that converts it back to DC at the necessary voltage.

As explained in an article on MaximIntegrated.com, “Switching power supplies offer higher efficiency than traditional linear power supplies. They can step-up, step-down, and invert. Some designs can isolate output voltage from the input.”

When converting electrical input to the proper voltage, DC/DC converters operate at a specified efficiency level, with some energy lost to heat. ATS Power Brick heat sinks provide the necessary step of dissipating that heat away from the converter to lower the junction temperature. This will optimize the performance of the component and ensure the longevity of the converter.

Anodization boosts Power Brick heat transfer capability

The pleasing gold color that has made Power Brick one of the most popular lines of heat sinks for DC/DC converters stems from the anodization process that ATS uses for its heat sinks. Anodization, as noted in an earlier blog post on this site, “changes the microscopic texture of a metal, making the surface durable, corrosion- and weather-resistant.”

Surface anodization works by turning the metal into the anode (positive electrode) of an electrolytic circuit. By passing an electric current through an acidic electrolytic solution, hydrogen is released at the cathode (negative electrode) and oxygen is released at the anode. The oxygen on the surface of the metal anode forms a deposit of metal oxide of varying thickness – anywhere from 1.8-25 microns.

The previous article explained, “The advantages of surface anodizing are the dielectric isolation of the cooling components from their electronics environment, and the significant increase in their surface emissivity.”

The emissivity coefficient of an anodized surface is typically 0.83-0.86, which is a significant boost from the standard coefficient of aluminum (0.04-0.06). By increasing the emissivity of the metal, there is also a significant enhancement of the metal’s radiant heat transfer coefficient.

The eye-catching gold color of ATS Power Brick heat sinks is added during the anodization process.

maxiFLOW™ design gives Power Brick an edge

Anodization of heat sinks is a standard practice to ensure that the metal components can withstand the rigors of dissipating heat from high-powered components. The feature that gives an ATS Power Brick heat sink the significant edge on its competitors is its patented maxiFLOW™ fin geometry, which has higher thermal performance for the physical volume it occupies compared to other heat sink designs.

maxiFLOW™ design is a low-profile, spread-fin array, which offers greater surface area for convection cooling. While it offers more surface area, it does not require additional space within the electronics package. This is an important feature in today’s electronics devices, which have an ever-increasing component density and in which space is always at a premium. This is an especially important feature for designers that want to cool DC/DC converters but are limited in the amount of available room.

Independent testing at Northeastern University of various heat sink designs demonstrated that maxiFLOW™ had the lowest thermal resistance for natural and forced convection, particularly when air flow velocity was below two meters per second. For heat sinks with the same base dimensions and fin height, maxiFLOW™ performed the best.

Testing has demonstrated that maxiFLOW™ can produce 20 percent lower junction temperatures and 40 percent lower thermal resistance than other heat sink designs. Utilizing maxiFLOW™ allows ATS Power Brick heat sinks to meet the industry standard base plate temperature of 100°C.
For more information about maxiFLOW™, watch the video below:

Power Brick meets industry standards

In the DC/DC market, there are a number of standard footprints that manufacturers use to offer flexibility for designers in choosing a vendor and in laying out a PCB. ATS has addressed the industry standard footprints with its Power Brick heat sinks. This will facilitate the use of the heat sinks for thermal management.

By optimizing the thermal management and meeting industry standards, Power Brick heat sinks can provide cost savings and reduce MTBF. Rather than having to over-design a system or a layout, engineers can turn to Power Brick as a thermal solution.

It is not only the industry standard footprints that Power Brick heat sinks have matched but also the standard hole patterns, which meet the standards set by the Distributed-power Open Systems Alliance (DOSA) to make assembly easy. The three millimeter holes (and soon 3.5 mm) match up to sizes commonly used in power brick manufacturing to ensure the proper connection for the heat sink (to avoid increasing the thermal resistance) and also to avoid using additional space in the tight confines of a PCB.

For the above reasons, Power Brick heat sinks are the “gold standard” for cooling DC/DC converters. Learn more in the video below:

For more information about Advanced Thermal Solutions, Inc. thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.

References

i http://uk.rs-online.com/web/generalDisplay.html?file=automation/dc-converters-overview&id=infozone
ii https://www.maximintegrated.com/en/app-notes/index.mvp/id/2031
iii https://www.qats.com/cms/2010/11/09/how-heat-sink-anondization-improves-thermal-performance-part-1-of-2/
iv https://www.qats.com/cms/wp-content/uploads/2013/09/Qpedia_Oct08_How-Air-Velocity-Affects-HS-Performance.pdf