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Cooling Wide-Bandgap Materials in Power Electronics

Engineers are always looking for an edge in their designs to extract as much power and performance as possible from a system, while attempting to meet industry trends in miniaturization. In the power electronics industry, this has required an examination of the materials being used to overcome inherent limitations from heat, voltage, or switching speed.

Cooling Wide-bandgap materials

Engineers are using wide-bandgap materials to expand the capabilities of power electronics, pushing them beyond the thermal and electrical limits of silicon-based components.(Background image created by Xb100 – Freepik.com)

For years, silicon was the answer for the power electronics market, but in the past decade there has been a growing movement towards wide-bandgap materials, particularly silicon carbide (SiC) and gallium nitride (GaN). Wide-bandgap materials have higher breakdown voltage and perform more efficiently at high temperatures than silicon-based components. [1] Recent research indicated, “For commercial applications above 400 volts, SiC stands out as a viable near-term commercial opportunity especially for single-chip current ratings in excess of 20 amps.” [2] This efficiency allows systems to consume less power, charge faster, and convert energy at a higher rate.

A recent article from Electronic Design explained that SiC power devices “operate at higher switching speeds and higher temperatures with lower losses than conventional silicon.” SiC has an internal resistance that is 100 times lower than silicon and a breakdown electric field of 2.8 MV/cm, which is far higher than silicon’s 0.3 MV/cm, meaning that SiC components can handle the same level of current in smaller packages. [3]

Engineers use the new material to produce systems with higher power-density and energy efficiency. While some industries have adopted new materials quicker than others, recent research from Yole Développement, a semiconductor and advanced packaging company based in France, indicated that there has been a significant growth in the SiC market in recent years. The research placed the market at $200 million as of 2015 and said that the market would reach an inflection point in 2017. [4]

New Electronics wrote that silicon carbide technology had reached a “tipping point” where engineers would focus more attention on new materials than on silicon, “pushed by the space, weight and efficiency requirements of electric vehicles and hybrids and by some particular industrial applications.” [5] All About Circuits added, based on the Yole research, that SiC was the material of choice for “power factor correction (PFC) power supplies, chargers, photovoltaic inverters, and trains.” [6]

As evidence of the industry’s acceptance of wide-bandgap materials, JEDEC Solid State Technology Association, a leader in standards development for the microelectronics industry, announced in September that it formed a committee on Wide Bandgap Power Electronic Conversion Semiconductors with sub-committees for SiC and GaN. “GaN and SiC technologies are poised to benefit from the development of standards focused on quality and reliability, datasheets, and test methods,” said Tim McDonald, Senior Director, GaN Applications and Marketing at Infineon Technologies. [7]

Industry leaders such as Texas Instruments (TI), Infineon, and Wolfspeed have signed on to the JEDEC committee and have already established products based on SiC technology. For instance, Infineon has released CoolSiC™ semiconductor solutions that include MOSFET, Schittky diodes, and hybrid modules. [8] ROHM Semiconductor recently announced that it had produced full SiC power modules that it claims reduces switching losses by 64 percent at 150°C. The company also announced that it is supplying power modules for the Venturi Formula E racing team. [9]

At the recent APEC 2018 show in San Antonio, sponsored by the PSMA (Power Sources Manufacturers Association), TI unveiled a new reference design (pictured below) for an HEV/EV onboard charger that used SiC-isolated gate drivers. [10]

ATS cold plates were on display at the TI booth, as a thermal solution for a new TI design. (Advanced Thermal Solutions, Inc.)

Thermal Management Concerns for SiC

SiC (and GaN) is clearly not just the future of semiconductor technology, it is also the present, but while wide-bandgap material allows components to perform at higher temperatures, there are thermal management concerns that engineers need to consider when designing the devices into a system. While SiC and other wide-bandgap materials may be able to withstand high temperatures, there are potential performance issues, such as higher rates of switching losses, and researchers still recommend that SiC dies operate at temperatures lower than 100°C for best efficiency. [11]

Higher temperature limits mean that, in theory, less complex cooling systems are required, which also means that SiC component packaging can be smaller since it no longer needs to account for larger, more intricate thermal management designs. It also means potential cost- and energy-savings for designers. But, the higher heat loads and the desire for smaller packaging mean passive, air cooling techniques are unlikely to accommodate the thermal management needs of the system. Liquid cooling is usually required, particularly the use of liquid cold plates to increase the rate of heat transfer to the ambient.

A recent presentation by SatCon Applied Technology showed that, despite higher power outputs, SiC components required smaller thermal contact areas and suggests the use of cold plates (copper in this particular example) to achieve the necessary cooling. [12] This was backed up by research from the European Research Council, which reported that active thermal management systems improved the performance of power electronics systems. [13]

Research from Cal Tech and the Jet Propulsion Laboratory (Pasadena, Calif.) explored the use of novel thermoelectric (TEC) microcoolers at the device level that provided spot cooling at higher heat fluxes than standard passive heat sinks. [14] According to researchers, the use of diamond or aluminum substrates enhanced the thermal performance of the microcoolers and thick-film coolers were able to achieve power densities greater than 100 W/cm2.

As noted in a research report by the National Renewable Energy Lab, while wide-bandgap materials can withstand much higher junction temperatures, those high heat loads can have a detrimental effect on other components in a system. Increasing the temperature of the system as a whole can lead to more failures, switching losses, and other issues for components that are not built to withstand high-temperature operation. Therefore, cooling needs to take not only a device-level but also system-level outlook. [15]

The NREL research suggested the following tactics for cooling SiC: using thermal interface material (TIM) that has low thermal resistance and is “reliable at functional temperatures,” using microchannels in cold plates to lower device junction temperatures, enhancing the surface and including “turbulence promoters” in the module, and incorporating both advanced manufacturing techniques and “multiple mode cooling” at the system level.

This slide from the presentation by the NREL explains how thermal management of wide-bandgap materials encompassed device-level, module-level, and system-level solutions. (NREL)

SiC has found a niche in the automotive world where the material is frequently mentioned in reports of new designs for electric vehicle batteries, as well as brake components and other components in high-heat environments. Some recent studies have gone beyond standard liquid cooling to include jet impingement cooling, which demonstrated significant thermal enhancement. According to a 2015 study, simulations demonstrated that a commercial, off-the-shelf (COTS) cold plate reduced the junction temperature of an SiC power module operating at a design heat load of 151 W from 290°C to 215°C. A COTS microchannel heat exchanger reduced the junction temperature to 215°C and a jet impingement-cooled heat exchanger lowered the junction temperature to 169°C at the same flow rate. [16]

The European Commission’s Community Research and Development Information Service (CORDIS) recently closed its SMARTPOWER project that brought together 15 partners from seven countries to examine the use of SiC and GaN technologies in industrial power devices. [17] The research led to the creation of forced cooling solutions with TEC modules to enhance heat sink thermal performance by as much as 200%, dropping device junction temperature from 250°C to 125°C. The research also developed enhanced TIM composed of vertically-aligned carbon nanotubes that increased heat transfer away from the devices, as part of novel 3-D packaging solutions.

Advanced Thermal Solutions, Inc. (ATS) continues to work on thermal solutions to meet the latest developments in power electronics. ATS recently released a new line of high-performance liquid cold plates that provide 30% improved performance compared to other commercially-available cold plates. An innovative, internal fin array with an optimized aspect ratio makes ATS cold plates, available in aluminum or copper and easily customizable to meet specific size or thermal requirements, the perfect choice for cooling high-powered electronics, including wide-bandgap devices.

ATS cold plates are the perfect solution for cooling high-powered electronics, such as IGBT modules. (Advanced Thermal Solutions, Inc.)

ATS cold plates provide uniform surface temperature across an IGBT or other high-powered device and can be fitted to a variety of components including Semikron SemiTRANS® Case D56, Infineon 62 mm, Fuji Semiconductor M127, M234, and M235, Powerex 62 mm, Mitsubishi 62 mm, and Vincotech 62 mm packages among many others.

As wide-bandgap materials proliferate across the power industry, ATS has liquid cooling solutions that will ensure optimal thermal management. For example, the TI reference design mentioned above used a customized ATS cold plate to provide the necessary cooling.

Learn more about ATS liquid cold plates and its array of liquid cooling solutions at https://www.qats.com/Products/Liquid-Cooling/Cold-Plates.

1. https://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/50531/1/04267750.pdf
2. http://jss.ecsdl.org/content/2/8/N3055.short
3. http://www.electronicdesign.com/analog/making-jump-wide-bandgap-power
4. https://www.i-micronews.com/compound-semi-expertise/8113-yole-analysis-the-sic-power-electronics-market-will-reach-an-inflection-point-in-2017-but-growth-brings-supply-chain-worries.html
5. http://www.newelectronics.co.uk/electronics-technology/silicon-carbide-technology-reaches-tipping-point/151641/
6. https://www.allaboutcircuits.com/news/sic-chips-kickstart-a-new-era-in-power-electronics/
7. https://www.jedec.org/news/pressreleases/new-jedec-committee-set-standards-wide-bandgap-power-semiconductors
8. https://www.infineon.com/cms/en/product/power/silicon-carbide-sic/
9. http://www.rohm.com/web/global/groups/-/group/groupname/SiC%20

10. https://www.qats.com/cms/2018/04/19/ats-power-solutions-on-display-at-apec-2018/
11. https://hal.archives-ouvertes.fr/hal-01473614/file/REYNES_Thermal%20Management%20Optimization.pdf
12. http://www.sandia.gov/ess/docs/pr_conferences/2005/Casey.pdf
13. https://www.sciencedirect.com/science/article/pii/S0026271414002650
14. https://pdfs.semanticscholar.org/ef32/8d5d3e0f617ada86cc02d

15. https://www.nrel.gov/docs/fy15osti/63002.pdf
16. https://www.researchgate.net/publication/273394047_Liquid_Jet_Impingement

17. https://cordis.europa.eu/project/rcn/99996_en.html

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

ATS Power Solutions on Display at APEC 2018

Advanced Thermal Solutions, Inc. (ATS) recently attended APEC 2018 in San Antonio to showcase the company’s thermal solutions for power electronics, meet with industry representatives, and learn the latest trends in the power industry.

ATS has been a member of the PSMA (Power Sources Manufacturers Association), which is the sponsoring organization for APEC, for the past three years because ATS has a strong connection to the power industry and extensive expertise in keeping the industry cool.

ATS Power Solutions

Product Engineering Manager is interviewed about ATS cold plates by Alix Paultre, the Power Editor at Aspencore, in the ATS booth at APEC 2018 in San Antonio. (Advanced Thermal Solutions, Inc.)

Vice-President of Sales and Business Development Steve Nolan and Product Engineering Manager Greg Wong manned the ATS booth during the show and took visits from sales representatives, distributors, and engineers from across the industry, some were familiar faces and some were learning about ATS expertise in thermal management of power electronics for the first time.

The highlighted products were ATS liquid cold plates, which boast 30% better thermal performance than comparable products on the market and are easily customizable to meet a variety of applications, and the line of ATS high-performance round and flat heat pipes, which is expanding by the end of 2018 to give ATS the broadest offering of off-the-shelf heat pipes on the market.

“When people start having thermal issues, it’s because they’re dissipating a lot of power and then you start to need things like heat pipes and liquid cold plates,” said Wong. “In most of these applications, people are talking about custom designs, which is where we have a lot of strength working with the customer and designing these custom applications.”

ATS cold plates were also featured in the Texas Instruments (TI) booth as part of a “98.5% efficiency, 6.6-kW Totem-Pole PFC Reference Design for HEV/EV Onboard Charger.” The base of the design was silicon carbide (SiC) MOSFETs with a C2000 microcontroller with SiC-isolated gate drivers, according to information presented by TI.

Underneath the prototype that was on display at the TI booth was a custom ATS cold plate to meet the charger’s thermal requirements.

ATS cold plates were on display at the TI booth, as a thermal solution for a new TI design. (Advanced Thermal Solutions, Inc.)

“It’s a great example of how we can customize our cold plates to meet a particular application,” Wong added. “A lot of people were taking pictures of that piece at the TI booth and a lot of people were talking with TI about it. The booth was mobbed every time I went over there.” 

ATS participation in the TI booth at APEC 2018 is a continuation of the strong working relationship between the two companies. ATS has also been a key reference design supplier of heat sink solutions for TI’s audio evaluation module.

Wong and Nolan also learned a lot about the future of power electronics, including the prevalence of SiC and gallium nitride (GaN) components in the industry and the increasing popularity of liquid cooling, to keep ATS current on industry trends and ensure that the innovative thermal solutions that ATS provides can meet ever-rising power demands.

While there is a lot that is new in the industry, IGBT designs continue to be popular and the standard IGBT footprint matches perfectly with ATS off-the-shelf cold plates to make an easy fit for engineers designing liquid cooling solutions.

“If people are still making devices in that IGBT footprint then it will bolt directly to the cold plate, which is good news because that package is very popular, so it’s good to have those standard products,” Wong explained.

Watch the video below as Greg Wong of ATS was interviewed by Alix Paultre of Power Electronics News at APEC 2018 about ATS heat pipes and cold plates.

ATS has the expertise, products, and resources to provide off-the-shelf and customized thermal solutions for the power electronics industry. Learn more about the full line of products at https://www.qats.com or contact ATS at ats-hq@qats.com.

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

We Cover 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.

ARM Microprocessors and ATS superGRIP: Attached at the Clip

Advanced Thermal Solutions, Inc., (ATS), has introduced a line of heat sinks compatible with the Sitara ARM Microprocessor family from Texas Instruments.

AM1707 from Texas Instruments

AM1707 from Texas Instruments

The Sitara ARM Microprocessors feature ARM Cortex-8 and ARM9 MPUs, which are used in a wide variety of Industrial, Medical, and Consumer Electronics applications.

The AM17x family consists of low-power ARM microprocessors that enable OEMs and ODMs to maximize product offerings by providing high processing performance life, advanced operating systems and rich user interfaces. Compatible operating systems include Neutrino, Integrity, Windows, Embedded CE, Linux, VXWorks and Android.

ATS patented maxiFLOW heat sinks with superGRIP clip attachment ensure long-term product reliability and maximum performance from the Sitara ARM Microprocessors. maxiFLOW high performance BGA heat sinks feature a low profile, spread fin array that maximizes surface area for more effective convection air cooling. The unique maxiFLOWTM design provides thermal performance that is 30-200% better than conventional heat sinks.

ATS' maxiFLOW Heat Sink with superGRIP Attachment

ATS’ maxiFLOW Heat Sink with superGRIP Attachment

maxiFLOW is available with pre-assembled phase change material, maxiGRIP clip attachments, and superGRIP clip attachments. The superGRIP attachment system features a plastic frame clip that fastens securely around the perimeter of a component and a metal spring clip that slips through a heat sinks fin field and locks securely to both ends of the plastic frame. The resulting superGRIP assembly applies steady even pressure to the component throughout the product lifecycle, improving thermal performance and long-term reliability. The ATS superGRIP heat sink attachment system permits the use of high performance phase changing thermal interface materials that improves heat transfer by as much as 20 times more than typical double-sided adhesive thermal tapes. It also allows for the heat sink to be detached and reattached without damaging the component or the PCB, an important feature for applications where PCB rework and ease of assembly and disassembly are important. The full range of ATS products compatible with Texas Instruments products can be viewed in the new heat sink selection tool on http://qats.com/Distributor/AE-Dist.php

To learn more about maxiFLOW heat sinks and the superGRIP clip attachment, please visit www.qats.com, email ats-hq@qats.com, or call 781-769-2800.