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Webinar on Limits of Air Cooling in March

Advanced Thermal Solutions, Inc. (ATS) is hosting a series of monthly, online webinars covering different aspects of the thermal management of electronics. This month’s webinar will be held on Thursday, March 28 from 2-3 p.m. ET and will cover the limits of air cooling and the role of liquid cooling in . Learn more and register at https://qats.com/Training/Webinars.

Low-profile thermal solutions required for cooling high-density boards

Advancements in the telecommunications, Internet of Things (IoT), broadcast, biomedical, and other industries demand more power, more data processing, and more capabilities. Engineers have been required to fill boards to the brim in order to meet the ever-increasing call for more and this high-density board design requires creative thermal management solutions.

Low-profile solutions
With today’s high-density boards, low-profile solutions are required to ensure proper thermal management even in tight spaces. (Advanced Thermal Solutions, Inc.)

Standard heat sink sizes are too large for many telecom systems, module and blade servers, or IoT gateways, where card-to-card and internal spacing is limited, and may not be designed to handle the lower airflow that is the result of numerous components packed into tight spaces. With space and airflow at a premium, engineers need low-profile solutions that are lightweight, compact, and will not sacrifice thermal performance.

Advanced Thermal Solutions, Inc. (ATS) has several low-profile heat sink options that will give engineers greater flexibility in designing boards and systems while still managing heat.

Ultra-Low-Profile blueICE™ Heat Sinks

ATS blueICE™ heat sinks are specially designed for low airflow systems where space is limited. The heat sinks range in height from 2-7 mm and the spread-fin array maximizes surface area to enhance thermal performance even in low airflow systems. Their thermal resistance is as low as 1.23 °C/W within an air velocity of 600 ft/min.

Ultra-low-profile blueICE heat sinks are specially designed for high thermal performance in tight spaces and low airflow. (Advanced Thermal Solutions, Inc.)

The heat sinks are lightweight, ranging from 4-30 grams, and no mechanical attachment is required. Thermal tape is all that is needed to attach blueICE™ heat sinks to a component, which further reduces weight and assembly time and saves valuable space on the board.

In systems where boards are packed tightly together, low-profile heat sinks can provide the necessary thermal performance without significantly adding to the height of the components on the board. Also, the design of blueICE™ heat sinks removes heat from devices even with lower airflow.

Low-Profile maxiFLOW™ Heat Sinks

ATS has also made low-profile versions of its ultra-high-performance maxiFLOW™ heat sinks, available with either maxiGRIP™ or superGRIP™ mechanical attachments. The low-profile, spread-fin array maximizes surface area and enhances convection cooling, while attachment technology offers secure hold without a significant increase in footprint or the need to drill holes in the board.

Low-profile maxiFLOW heat sinks with superGRIP attachment technology maximizes surface area for higher thermal performance. (Advanced Thermal Solutions, Inc.)

Low-profile maxiFLOW™ heat sinks are designed for component heights ranging from 1.5-2.99 mm and the specially-designed fin array increases the surface area to provide the highest thermal performance per volume occupied when compared to other heat sinks on the market.

Using maxiGRIP™ or superGRIP™ heat sink attachment technology also gives design engineers more flexibility because of their easy assembly and removal. There is no damage to the board, which is important because of dense PCB routing and the potential need for rework.

Heat Pipes and Vapor Chambers  

In situations where low-profile heat sinks will not fit, ATS has heat pipes and vapor chambers that will transport heat away from a component and can be attached to a heat sink or the system chassis/enclosure to dissipate the heat to the ambient. These innovative cooling solutions will meet even the toughest thermal challenges.

Heat pipes can be used to move heat from devices to heat sinks, the chassis, or system enclosure to remove the heat to the ambient. (Advanced Thermal Solutions, Inc.)

ATS has expanded its line of high-performance, off-the-shelf round and flat heat pipes to provide the broadest offering on the market. Engineers can avoid the extra cost of custom lengths by selecting from the more than 350 product numbers that ATS has created. Flat heat pipes are available in lengths of 70-500 mm, with widths of 4.83-11.41 mm, and heights of 2-6.5 mm.

Vapor chambers are essentially flat heat pipes and provide another low-profile option for spreading heat. (Advanced Thermal Solutions, Inc.)

Vapor chambers are essentially flat heat pipes that can be used in the base of heat sinks to spread heat. ATS has expertise designing vapor chambers and heat pipes into electronics systems to improve thermal management, especially with limited space and airflow. Their high thermal conductivity can move a lot of heat from devices and they can be easily attached to heat sinks to form cooling assemblies.

See how low-profile solutions are needed in IoT sensor-level infrastructure in the following video:

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.

Technical Discussion: Designing Heat Sinks for Cooling QSFP Optical Transceivers

During a recent project designing a thermal solution for a customer’s PCB (printed circuit board) layout, Advanced Thermal Solutions, Inc. (ATS) Field Application Engineer Peter Konstatilakis also analyzed the thermal properties of a series of SFP (small form-factor pluggable) optical transceivers on the edge of the board.

QSFP Optical Transceivers

ATS engineer Peter Konstatilakis holds the heat sinks that he designed for cooling QSFP optical transceivers. (Advanced Thermal Solutions, Inc.)

From that project came the idea of examining the thermal challenges presented by SFP and QSFP (quad SFP) and designing a heat sink solution that future customers could use to solve potential issues that stem from the increased power requirements of the compact transceivers that are frequently used in the transmission of data.

After conducting an analytical analysis, running computer simulations, and testing the heat sinks in the state-of-the-art ATS labs, Peter demonstrated a new heat sink design and optimized layout sequence that showed 30 percent improvement on QSFP heat sinks currently on the market.

In addition, he showed that having heat sinks with fewer fins upstream and heat sinks with more fins downstream provided a near isothermal relationship between the first and last QSFP, an important consideration for QSFP arrangements.

Peter recently sat down with ATS Vice-President of Marketing and eCommerce Rebecca O’Day and Marketing Communications Specialist Josh Perry to discuss the project, his research, and the successful design of the new QSFP cooling solution.

JP: What prompted the work on QSFP heat sinks? Why did we start looking into this technology?
PK: Optics are pretty big now with all the higher information rates, 400 gigabyte cards, which is 400 gigabytes of throughput and that’s a lot. They need these multiple high-powered SFP or QSFP to do that. So, higher power demands call for ATS expertise in thermal management.

RO: Optics are really expanding. It’s not just routers and things like that, but they’re also used in storage, array networks, video…so this kind of thing could really be able to expand.
PK: Anywhere that you are transferring data, which is basically everywhere – the Cloud, big servers, the internet itself. They’re being used a ton.

JP: Was the impetus for designing QSFP heat sinks something that was prompted by a customer or did we think about the technology and recognize that it needed to be cooled?
PK: We had worked on SFP cooling for a customer first, so that helped us understand the area a bit more. Also, from what we were hearing from customers, QSFP that were being designed had higher throughput, which means higher power. And it is also good to have products that we can market, even if it isn’t for every customer, and show that we can handle the optical transceiver arena.

JP: What was the first step in designing the heat sinks? Did you know a lot about QSFP or did you have to do a lot of research?
PK: There is definitely a lot to think about. You can’t use a TIM (thermal interface material) because the QSFP isn’t fixed in the cage; it can be hot swapped. After a few insertions and removals, it will gunk up the TIM.

JP: Was that something you knew before?
PK: It was something I knew before, but there is also a specification document for this technology written by the SFF (Small Form Factor) Committee, which is a standard controlled document that engineers design to for this form factor and it stated in there not to use a TIM. When we looked at it with the customer, it made sense and when we asked the customer they agreed.

RO: If there is no TIM, how does the interface work? Is it a direct interface? Is it flat enough?
PK: You have to specify a good enough flatness and surface roughness, within cost means, that will still have a low contact resistance. That was one of the challenges as well as understanding the airflow of typical QSFP arrangements because you have four in a row, so you’re going to have preheated air going into the fourth QSFP.

JP: When designing the heat sinks, what were the issues that you needed to consider?
PK: One consideration was getting as much surface area as we can, so that required extending the heat sink off the edge of the cage and we also had fins on the bottom of the heat sink. Usually, you only have fins above the cage but there was some room underneath, about 10 mm depending on what components are around, which provides additional surface area.

We also found that when you extend the surface the spreading resistance becomes an issue as well, so you need to increase the thickness of the base to help spread the heat to the outer extremities of the heat sink. You want the first QSFP and the last QSFP case temperatures’ to be isothermal due to laser performance (an electrical parameter), whereas each individual heat sink should be isothermal to get the most out of all the heat sink surface area (a heat transfer parameter).

‘Cold’ spots insinuate a lack of heat transfer to that location and thus poor use of that surface area. Then it was about the airflow and having the front heat sinks be shorter with fewer fins and the back two to be taller with denser fin arrays.

ATS heat sinks designed specifically for cooling QSFP optical transceivers. (Advanced Thermal Solutions, Inc.)

JP: Was the difference in fin arrays between upstream and downstream heat sinks how you optimized the design to account for the preheated air?
PK: What is really important is to keep each QSFP at the same temperature, within reason, because they all work together. So, if one is a higher temperature than another, the laser performance is going to be affected and it will affect the stack. You want to have them as isothermal as you can; the case temperature from the first QSFP to the last.

We figured when we were going through the design, you could have a shorter heat sink up front with fewer fins to help the airflow pass to the downstream QSFP. The upstream QSFP wouldn’t need as much cooling because they’re getting the fresher air and faster airflow. So, if you relax the front heat sinks and make the ones in the back more aggressive, then you’re going to get better cooling downstream.

What happens is the front heat sinks aren’t as effective. This is fine as long as the upstream QSFP case temperatures are lower than the downstream QSFP. The overall effect is that the upstream QSFP temperatures will be closer to the temperature of the downstream QSFP, keeping the stack as isothermal as possible.

This is where the limit lies. Minimizing the upstream QSFP heat sinks, which in turn minimizes the amount of preheat to the downstream QSFP and allows as much airflow to enter downstream QSFP. At the same time ensuring the upstream QSFP temperatures are equal to or just lower than the downstream QSFP. This keeps the downstream QSFP temperatures at a minimum, while also keeping the transceiver stack close to isothermal.

JP: Were there any unexpected challenges that you had to account for?
PK: There was a challenge in testing and making sure that the thermocouples (which you can see in the picture below) contact the heat sink surface correctly and all of them at the same point. I had to glue it, so it may touch the case of the heat sink or it may not, depending on how the glue set, so I had to put a little thermal grease inside the pocket just to have the thermocouple make good contact with the heater block itself.

The test setup to measure cooling performance of individual heat sinks on a QSFP connector cage when airflow is from one side only. (Advanced Thermal Solutions, Inc.)

The metal piece (heater block) mimics the QSFP and we put a cartridge heater in the middle to heat it up and then we put a groove where the thermocouple is attached as I just explained.

Other than that…it was really just the flatness. It was hard to test and get reliable data between several heat sinks because there is going to be some flatness variation between them. Sometimes there isn’t enough to show a variation, but if I’m seeing different data with a different heat sink on the same heater block then the flatness and surface roughness is affecting it.

RO: On the flatness issue, in theory someone could spend a lot of money and make sure that it was completely flat but there’s a certain point where it has to be flat enough.
PK: Obviously there are diminishing returns after a certain point, so you have to find that line. There are no calculations that explain flatness and surface roughness, so at the end of the day it comes down to testing.

RO: I find it interesting that the testing was a challenge because it appears to us on the outside that this is a standard approach but then you get into it and have to ask how are we going to measure the temperature accurately:
PK: There is always something that comes up which you didn’t think about until you start doing the testing and you have to make a change and modify it to make it work. That is where experience comes in handy. The more testing you do, the more you’ve seen and you can take care of the problem before it arises.

RO: It’s a good example of what we can do at ATS. We don’t have to test with a full, expensive board or the full optical arrangement, instead we can come up with inexpensive (low startup cost) ways to test that will provide quick, accurate data to help the customer get to market.

JP: So, we tested three different arrangements for the heat sinks?
PK: Yeah. There were two different designs with changes in the density of the fins. Based on the CFD (computational fluid dynamics) and in the lab, the best outcome was having the less dense fins in front for the first two heat sinks and having the denser fin arrays downstream. As we expected, more airflow was able to make it to the back heat sinks and were able to cool them more effectively.

QSFP Heat Sinks

This graph shows the difference in temperature between the ATS heat sinks at various air flows. (Advanced Thermal Solutions, Inc.)

We were seeing less than a degree difference, especially at higher airflows, between the first heat sink and the last and that was pretty impressive. That configuration also provided the lowest temperature for the final two QSFP. Those are going to be the limiting factors; they’re going to be the highest temperature components no matter what since they’re receiving preheated air. That’s why it’s important to minimize the preheated air and maximize the airflow downstream by designing shorter, low fin-density heat sinks upstream.

If you put a dense heat sink up front, you’re going to restrict airflow downstream and you’re going to pull more heat out of the component because it is a better heat sink. With this you’re going to dump more heat into the air and send it to the downstream QSFP. So, it is worth keeping some heat in the upstream components, which has a double effect of keeping all of the QSFP temperatures as isothermal as possible. As long as the upstream components aren’t going over the case temperature of the last component, then you’re fine.

RO: It’s almost counter-intuitive. The general thermal design says to pull as much heat away from the component as quickly as possible and dissipate it, but you’re saying it was better to leave some of the heat in place.
PK: For the upstream QSFP, absolutely. There is margin because it is receiving so much fresh air.

That is really because we’re working in a system environment where choices upstream affect the airflow downstream. If it wasn’t a system and you’re looking at a single component, then sure you want to get rid of all the heat. And again, leaving heat in also allows the QSFP components to be as isothermal as possible.

JP: It sounds like it worked the way that you expected going in?
PK: Yeah it did. I’m not going to sit here and pretend it always happens that way but what we thought would happen did happen and we were able to design it analytically before we went into CFD and testing.

JP: Were there certain calculations that you use when working with a system?
PK: We can look at the fan curve. Each heat sink has its own pressure drop and the way you use a fan curve is to analyze the four heat sinks, add the pressure drops together, and then examine the fan curve (the amount of airflow varies with the pressure that the fan sees) with the higher the pressure, the less airflow. So, we’re able to estimate the amount of airflow across the system based on the total pressure drop.

We also use Q=mCpΔT and that way we can determine, based on the amount of power coming from the component, what is the air temperature that is leaving the heat sink. It is a little conservative because we’re saying that all of the heat is going into the next heat sink, which isn’t true because a little is escaping to other locations, but being conservative doesn’t make a difference when comparing designs.

Analyzing the airflow into each heat sink and the temperature into each heat sink lets us know what we have to design for; just because you’re putting more surface area doesn’t mean you have a good solution.

RO: This is a good example of how thermal management is more than just removing the heat, but also analyzing how the heat travels and thinking about it as a system. It’s much more complicated.

JP: How important is for ATS to be able to see potential thermal challenges in new technology, like this, and work through the problem even if it isn’t for a specific design or customer?
PK: It always helps to have more experience. It’s knowledge for the future. We’ve already seen it, we’ve already dealt with it, and we can save time and cost for the customer.

Whenever we run into this issue, we can say we tested that in the lab and explain the solution that we found. We don’t need to do more analysis, but provide the customer with a solution.

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.

Case Study: High-Powered Altera Stratix 10 FPGAs

Altera Stratix 10 FPGAs`

Advanced Thermal Solutions, Inc. engineers designed a solution to cool a board that contained high-powered Altera Stratix 10 FPGAs. (Advanced Thermal Solutions, Inc.)


Engineers at Advanced Thermal Solutions, Inc. were asked to test the layout of a PCB that was using Altera Stratix 10 FPGAs (field-programmable gate arrays) with fans on one side pulling air across the board. The client used ATS heat sinks on the original iteration of the PCB and wanted to ensure those heat sinks would provide the necessary cooling for this iteration as well.

Through a combination of analytical modeling and CFD simulations, ATS engineers determined that the heat sinks already being used would provide enough cooling for the more powerful components.

Challenge: ATS conducted thermal analysis of a system with Altera Stratix 10 FPGA units when using ATS 1634-C2-R1 and ATS FPX06006025-C1-R0 heat sinks. Two of the FPGAs would be running at 90 watts and one at 40 watts and there were fans on one side of the PCB that would pull air across the board.

Chip/Component: Altera Stratix 10 FPGAs

Analysis: Analytical models and CFD simulations were run with ATS 1634-C2-R1 heat sinks and several other options, including copper and aluminum heat sinks with and without embedded heat pipes. CFD simulations also created fan curves for all six of the Mechtronics MD4028V fans being used.

Test Data: The data showed that even with the additional power of the new chips that the original heat sinks would keep the case temperature below 80°C. The other heat sinks showed similar case temperatures mostly below 80°C as well. Fan curves showed that the fans were operating near the knee, which the client was notified about.

Solution: ATS engineers recommended staying with the ATS 1634-C2-R1 heat sink because it was able to cool the high-powered FPGAs below the maximum case temperature. The ATS FPX06006025-C1-R0 was recommended for the lower power FPGA.

Altera Stratix 10 FPGAs

CFD simulation with the case temperatures of the three FPGA using the original ATS heat sinks.
(Advanced Thermal Solutions, Inc.)

Net Result: The customer was able to continue using the same heat sinks that had worked on the prior iteration of the PCB.

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.

National Thermal Engineer Day at ATS

July 24th is the hottest day of the year, so naturally that is the perfect day to celebrate the contributions thermal engineers make to everyday life. You don’t know what thermal engineers do? Sadly enough, you are not alone. Thermal engineers are often overshadowed in society by electrical and software engineers when in reality, the thermal engineers are enabling electronics to function.

Thermal engineers work with heat energy and its transfer between different mediums and also into other usable forms of energy. Without thermal engineering, the electronics we use every day would not function.

ATS decided it was time for thermal engineers to gain recognition, thus, National Thermal Engineer Day was started. It is now recognized every year on July 24th. We celebrated the second annual National Thermal Engineer Day here at ATS on Friday, July 22nd, 2016. It was a success celebrating the work done by thermal engineers.

 

President, CEO, and founder of ATS, Kaveh Azar, shared his input on the importance of thermal engineers, “We make things happen in the electronics industry. We have a very tough job but as a result of the position, we never get recognized. We are doing the bulk of the work. We are making these things happen. We are making the electronics function.”

 

ATS employees spent the afternoon enjoying a barbecue and playing games, taking in the warmth of the sun on one of the hottest days of the year.

 

Cassandra Moore of our Sales Order Management team took a break from working with customer’s to enjoy the awesome food.

 

Sharon Koss, ATS’s Vice-President for Operations and Business Development, Dahra, Engineering Intern and Diane Chalmers, of our Sales Order Management Team, found the grilled steak and chicken to be great dishes for ATS’s National Thermal Engineer Day outing.

 

ATS’s Chief Technology Officer, Dr. Bahman Tavassoli, enjoying some rare time out of the lab.

 

Arlain Cherry from our Engineering team was happy to break away from his current project just long enough to enjoy some sunshine, food and good laughs.

 

Pete Clonda, Sr. Director of Operations Logistics, and Brent Bennett, Manufacturing Team, enjoying a friendly (but competitive!) game of bean bag toss.  Peter Konstatilakis chases after a frisbee.

 

Many of you reading this have likely seen one of Greg Wong’s many “how to” videos including “how to make a thermocouple” and “how to apply thermal interface material: thermal tape”.  He took a break from Engineering to celebrate National Thermal Engineer Day.

 

Marketing Specialist Becca Leonard took a break from graphics and web design to Celebrate National Thermal Engineer Day by taking the amazing photographs in this blog post!

 

What celebration would be complete without a cake?  Our National Thermal Engineer Day Cake was a delicious hit, courtesy of Whole Foods Markets.

 

Celebrate with us next year and every year after that! July 24th is National Thermal Engineer Day.  Learn more and sign up for a pin at this link:  National Thermal Engineer Day.

 

See you all next year at National Thermal Engineer Day, July 24th, 2017!