ATS and Future Facilities have announced a hands-on workshop on Wednesday, Sept. 12 at the ATS headquarters (89 Access Rd. Norwood, MA). “A Comprehensive Approach to Thermal Design and Validation” will teach engineers how to tackle thermal challenges in modern electronics from concept to final validation. Click here to learn more and to register for this workshop. Sign up today because space is limited.
Posted in Thermal Design
Tagged 6SigmaET, Analytical Modeling, CFD, Empirical Modeling, Future Facilties
Marketing Communications Specialist Josh Perry sat down with Product Engineering Manager Greg Wong to discuss the process that Advanced Thermal Solutions, Inc. (ATS) engineers go through to create a heat sink and find a thermal solution for customers.
Watch the full conversation in the video below and scroll down to read the transcript of the interview.
JP: Greg, thanks again for joining us here in marketing to explain what it is that goes into designing a heat sink for a customer. So, how does that process begin?
GW: We usually start with a few basic parameters; we call them boundary conditions. So, we start with a few boundary conditions, basics like how much airflow we have, how much space constraint we have around a heat sink, and how much power we’re dissipating, as well as the ambient temperature of the air coming into the heat sink.
So, those are the real basic parts that we need to start out with and sometimes the customer has that information and they give it to us, and usually we double-check too, and then other times the customer has parts of the information, like they know what fan they want to use and they know what kind of chassis they’re putting it in and we take that information and we come up with some rough calculations so we can arrive at those things like air flow and stuff like that.
JP: When you get the data from the customer, how do you determine what the problem is, so that way you can move forward?
GW: We usually start out with an analytical analysis. So, we put pen to paper and we start out with basic principles of heat transfer and thermal resistance and stuff like that so we can understand if what we’re trying to achieve is even feasible and we can come up with some basic parameters just using that analytical analysis.
Like we can calculate what kind of heat sink thermal resistance we need or we can calculate how much air flow we need or, if we have several components in a row, we can calculate what the rough air temperature rise is going to be along that chain of parts. So, there’s a lot we can do when we get the basic information from the customer just on pen and paper.
JP: What’s the next step beyond analytical?
GW: Well, we can do some lab testing or a lot of times we also use CFD simulations and, if our customer has a model they can supply us, we can plug that into the CFD simulations and we can come up with an initial heat sink design and we can put that into the simulations as well and then we set those up and run them.
The great thing, having done these analytical analyses beforehand, we know what to expect from CFD simulations. So that way, if the simulations don’t run quite right, we already have an understanding of the problem, we know what to expect, because CFD is not 100 percent reliable.
I mean, you can go and plug all this stuff in there but you really have to understand the problem to know if the CFD is giving you a good result. So, oftentimes that’s the next stage of the process and from there we can actually produce low-volume prototypes right here in Norwood (Mass.), in our factory. We have CNC machines and manual milling machines, lathes, all that kind of stuff, and we can produce the prototypes and test them out here in our labs.
JP: How much of a benefit is it to be able to create a prototype and to be able to turn one around quickly like that?
GW: Oh, it’s great. I mean, if we had to wait to get parts from China it will take weeks to get. We can turn them around here in a few days and the great thing about that is we can test them in our labs and, you know, when it comes to getting results nothing beats the testing.
I mean, you can do analytical analysis, you can do CFD simulations, but when you actually test the part in a situation that is similar to what the actual thing is going to be that’s where the real meat comes down.
ATS engineers take customer data and using analytical modeling and CFD simulations can design the right cooling solution to meet the customer’s specific thermal needs. (Advanced Thermal Solutions, Inc.)
JP: So, we test the prototypes before sending them out to the customer? We do the testing here or do we send it to them first?
GW: It all depends on what the customer requires. Sometimes the customer has a chassis that we really can’t simulate in our labs, so we might send the prototype heat sinks to the customer and the customer will actually put them into their system to test them out.
Other times, a customer might have a concept and they don’t actually have a product yet, so we’ll mock something up in our labs and we’ll test it and it all just depends what the customer needs and also how complex the problem is.
If it’s a simple heat sink and pretty simple airflow, we might not need to test that because we understand that pretty well, but the more complex the chassis is and how the airflow bends and stuff like that, the greater benefits we get out of lab testing.
JP: Well, I appreciate it Greg. Thank you for taking us through the process of making a heat sink and solving thermal problems for our customers.
GW: Sure Josh. We love seeing new thermal challenges and coming up with ways of keeping stuff cool.
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.
Posted in CFD, Chassis, Consulting, Engineering, heat sink, heat sink design, Heat Sinks, PCB, Thermal Design
Tagged Analytical Modeling, CFD, Greg Wong, heat sink design, Josh Perry
An Advanced Thermal Solutions, Inc. (ATS) client was planning on upgrading an existing board by adding Altera’s high-powered Stratix 10 FPGAs, with estimates of as many as 90 watts of power being dissipated by two of the components and 40 watts from a third. The client was using ATS heat sinks on the original iteration of the board and wanted ATS to test whether or not the same heat sinks would work with higher power demands.
In the end, the original heat sinks proved to be effective and lowered the case temperature below the required maximum. Through a combination of analytical modeling and CFD simulations, ATS was able to demonstrate that the heat sinks would be able to cool the new, more powerful components.
ATS Field Application Engineer Vineet Barot recently spoke with Marketing Director John O’Day and Marketing Communications Specialist Josh Perry about the process he undertook to meet the requirements of the client and to test the heat sinks under these new conditions.
JP: Thanks again for sitting down with us to talk about the project Vineet. What was the challenge that this client presented to us?
VB: They had a previous-generation PCB on which they were using ATS heat sinks, ATS 1634-C2-R1, and they wanted to know if they switched to the next-gen design with three Altera Stratix 10 FPGAs, two of them being relatively high-powered, could they still use the same heat sinks?
The board that was given to ATS engineers to determine whether the original ATS heat sinks would be effective with new, high-powered Stratix 10 FPGA from Altera. (Advanced Thermal Solutions, Inc.)
They don’t even know what the power of the FPGAs is exactly, but they gave us these parameters: 40°C ambient with the junction temperatures to be no more than 100°C. Even though the initial package is capable of going higher, they wanted this limit. That translates to a 90°C case temperature. You have the silicon chip, the actual component with the gates and everything, and you have a package that puts all that together and there’s typically a thermal path that it follows to the lid that has either metal or plastic. So, there’s some amount of temperature lost from the junction to the case.
The resistance is constant so you know for any given power what the max will be. The power that they wanted for FPGAs 1 and 2, which are down at the bottom, was 90 watts, again this is an estimate, and the third one was 40 watts.
JP: How did you get started working towards a solution?
VB: Immediately we tried to identify the worst-case scenario. Overall the board lay-out is pretty well done because you have nice, linear flow. The fans are relatively powerful, lots of good flow going through there. It’s a well-designed board and they wanted to know what we could do with it.
I said, let’s start with the heat sinks that you’re already using, which are the 1634s, and then go from there. Here are the fan specs. They wanted to use the most powerful fan here in this top curve here. This is flow rate versus pressure. The more pressure you have in front of a fan, the slower it can pump out the air and this is the curve that determines that.
Fan operating points on the board, determined by CFD simulations. (Advanced Thermal Solutions, Inc.)
This little area here is sometime called the knee of the fan curve. Let’s say we’re in this area, the flow rate and pressure is relatively linear, so if I increase my pressure, if I put my hand in front of the fan, the flow rate goes down. If I have no pressure, I have my maximum flow rate. If I increase my pressure then the flow rate goes down. What happens in this part, the same thing. In the knee, a slight increase in pressure, so from .59 to .63, reduces the flow rate quite a bit.
CFD simulations showed that the fans were operating in the “knee” where it is hard to judge the impact of pressure changes on flow rate and vice versa. (Advanced Thermal Solutions, Inc.)
So, for a 0.1 difference in flow rate (in cubic meters per second) it took 0.4 inches of water pressure difference, whereas here for a 0.1 difference in flow rate it only took a .04 increase in pressure. That’s why there’s a circle there. It’s a danger area because if you’re in that range it gets harder to predict what the flow will be because any pressure-change, any dust build-up, any change in estimated open area might change your flow rate.
The 1634 is what they were using previously. It’s a copper heat pipe, straight-fin, mounted with a hardware kit and a backing plate that they have. It’s a custom heat sink that we made for them and actually the next –gen, C2-R1, we also made for them for the previous-gen of their board, they originally wanted us to add heat pipes to this copper heat sink, but I took the latest version and said, let’s see what this one will do. For the third heat sink, I went and did some analytical modeling to see what kind of requirement would be needed and I chose one of our off-the-shelf pushPIN™ heat sinks to work because it was 40 watts.
JO: Is the push pin heat sink down flow from the 1634, so it’s getting preheated air?
VB: Yes. This is a pull system, so the air is going out towards the fans.
CFD simulations done with FloTherm, which uses a recto-linear grid. (Advanced Thermal Solutions, Inc.)
This is the CFD modeling that ATS thermal engineer Sridevi Iyengar did in FloTherm. This is a big board. There are a lot of different nodes, a lot of different cells and FloTherm uses recto-linear grids to avoid waviness. You can change the shape of the lines depending on where you need to be. Sri’s also really good at modeling. She was able to turn it around in a day.
Flow vectors at the cut plane, as determined by CFD simulations. (Advanced Thermal Solutions, Inc.)
These are the different fans and she pointed out what the different fan operating curves. Within this curve, she’s able to point out where the different fans are and she’s pointing out that fan 5 is operating around the knee. If you look at all the different fans they all operate around this are, which is not the best area to operate around. You want to operate down here so that you have a lot of flow. If you look at the case temperatures, remember the max was 90°C, we’re at 75°C. We’re 15°C below, 15° margin of error. This was a push pin heat sink on this one up here and 1634s on the high-powered FPGAs down here.
JP: Was there more analysis that you did before deciding the original heat sinks were the solution?
VB: I calculated analytical models using the flow and the fan operating curves from CFD because it’s relatively hard to predict what the flow is going to be. Using that flow and doing a thermal analysis using HSM (heat sink modeling tool), we were within five percent. What Sri simulated with FloTherm was if a copper heat sink with the heat pipe was working super well, let’s try copper without the heat pipe and you can see the temperature increased from 74° to 76°C here, still way under the case temperature. Aluminum with the heat pipe was 77°; aluminum without the heat pipe was 81°, so you’re still under.
Basically there were enough margins for error, so you could go to smaller fans because there’s some concern about operating in the knee region, or you can downgrade the heat sink if the customer wanted. We presented this and they were very happy with the results. They weren’t super worried about operating in the knee region because there’s going to be some other things that might shift the curve a little bit and they didn’t want to downgrade the heat sink because of the power being dissipated.
Final case temperatures determined by CFD simulations and backed up by analytical modeling. (Advanced Thermal Solutions, Inc.)
JO: What were some of the challenges in this design work that surprised you?
VB: The biggest challenges were translating their board into a board that’s workable for CFD. It’s tricky to simplify it without really removing all of the details. We had to decide what are the details that are important that we need to simulate. The single board computer and power supply, this relatively complex looking piece here with the heat sink, and we simplified that into one dummy heat sink to sort of see if it’s going to get too hot. It all comes with it, so we didn’t have to work on it.
The power supply is even harder, so I didn’t put it in there because I didn’t know what power it would be, didn’t know how hot it would be. I put a dummy component in there to make sure it doesn’t affect the air flow too much but that it does have some effect so you can see the pressure drop from it but thermally it’s not going to affect anything.
JO: It really shows that we know how to cool Stratix FPGAs from Altera, we have clear solutions for that both custom and off-the-shelf and that we understand how to model them in two different ways. We can model them with CFD and analytical modeling. We have pretty much a full complement of capabilities when dealing with this technology.
JP: Are there times when we want to create a TLB (thermal load board) or prototype and test this in a wind tunnel or in our lab?
VB: For the most part, customers will do that part themselves. They have the capability, they have the rack and if it’s a thing where they have the fans built into the rack then they can just test it. On a single individual heat sink basis, it’s not necessary because CFD and analytical modeling are so established. You want two independent solutions to make sure you’re in the right ballpark but it’s not something you’re too concerned that the result will be too far off of the theoretical. For another client, for example, we had to make load boards, but even then they did all the testing.
To learn more about Advanced Thermal Solutions, Inc. consulting services, visit https://www.qats.com/consulting or contact ATS at 781.769.2800 or ats-hq@qats.com.
Posted in Analysis, CFD, Chassis, Consulting, Heat Sinks, Modeling, PCB, Simulation, Thermal Analysis
Tagged Advanced Thermal Solutions, altera, Analytical Modeling, ATS, CFD, Consulting, FLOTHERM, FPGA, heat sinks, Josh Perry, Sridevi Iyengar, Straight-Fin Heat Sink, Stratix 10, thermal management, Vineet Barot
Getting to markets faster and in the most cost-effective way is the primary goal of today’s product development process. Choosing a thermal design engineering partner that understands that goal makes a company’s product realization process simpler and faster. There are number of strategies a company’s project engineers can use to save time and money in the design of an electronics cooling solution. Two of the most efficient methods are Virtual Engineering Demos (VED) and Thermal Load Boards (TLB).
VEDs make it possible for project engineers to remotely see an instrument, how it operates, ask questions about how it works, and, if the project is included in the demo, get data in real time about a design. In this method, a live demo is setup at a thermal design engineering partner’s laboratory. Whether the project is a PCB, a system, or another product type, it can be included in the VED and be run through the lab set-up.
ATS engineer Greg Wong gives a live, online demonstration from the ATS research lab to a potential customer. (John O’Day/Advanced Thermal Solutions, Inc.)
ATS engineer Greg Wong sets up to demonstrate the ATVS-2020, Candlestick Sensors and StageVIEW Data Acquisition Software (DAQ) for measuring and analyzing temperature for an electronics board in this VED. (Advanced Thermal Solutions, Inc.)
Equipment setup and live camera feeds are all part of a VED setup. (Advanced Thermal Solutions, Inc.)
As the project is analyzed, data is shown on the engineering partner’s computer screen, which is in turn broadcast in real time to the project engineers via a live video feed. The video feed simultaneously shows the demo and the software’s operation, while allowing bi-directional conversation between the engineering partner and the project engineers in one or more locations.
Screenshot showing data being recorded in stageVIEW. This information is available to the remote team. (Advanced Thermal Solutions, Inc.)
The advantages of this strategy to project engineers are:
• Quick evaluation of a design to determine if there is a need for new equipment in a project.
• No lag time in talking with a thermal design engineering partner about how to approach the thermal measurement of project
• Reducing the need to travel to a thermal design engineering partner’s lab.
• Faster response on lab testing, shortening the design cycle.
A Thermal Load Board (TLB) is another strategy for reducing the cost of a design, while getting a product to market faster. TLBs are created by a thermal engineering partner using a simple one- or two- layer non-populated PCB, heat sinks, thermally equivalent mock semiconductors and other mock components created with a 3-D printer.
Using these components a populated board is created that allows the testing of the heat sinks chosen for the project work and measurement of the airflow over the components and through the board. (Advanced Thermal Solutions, Inc.)
The thermal engineering partner is effectively creating a mock version of the functional board. The design of the TLB is based on the size and placement of the semiconductors and other components on the actual board, which is provided by the project engineers, and provides a cheaper and quicker means of producing a prototype for testing. The data from that testing will in turn expedite the design process and time to market.
This can be a very cost-effective method for doing heat sink characterization for the following reasons:
• It reduces electronic system development cost.
o A system developer can focus on thermal issues very quickly instead of waiting for an expensive prototype to come out of the factory.
o Rather than using a potentially expensive project, testing on prototypes can determine design flaws without requiring a significant
cost.
o Because prototypes are less expensive, each iteration of a design can quickly go through an initial series of tests.
• It reduces time to market.
o Valuable resources can be applied to engineering the best solution because a load board can generally be created in 1-2 weeks and at a
fraction of the cost of a full PCB.
• It allows a physical testing very early in the design.
o Many times components on a PCB will obstruct air flow, requiring either costly design changes during NPI (new product introduction) or
requiring engineers to over-design a board and the thermal management solution, putting the product outside its cost objective.
After a thermal load board is created, the board is ready to be used:
A completed load board ready for testing. (Advanced Thermal Solutions, Inc.)
The heaters on the board can be powered up to dissipate the same level of power as the semiconductors they are meant to represent. Heat sinks can then be applied based on initial analysis done via integral modeling, mathematical modeling or through CFD (computational fluid dynamics). To test just air flow, heat sinks can even be created by 3-D printing.
Once populated with heat sinks, the board can be tested in a wind tunnel to see if the air flow will be sufficient. Wind tunnel testing methods include smoke flow visualization or water tunnel testing in order to examine air flow and ensure the most functional and cost-effective design is applied.
Getting to market faster and with the best possible design is very important in today’s product development process. Working with a thermal engineering partner, such as Advanced Thermal Solutions, Inc. (ATS), that offers Virtual Engineering Demos (VED) and Thermal Load Boards (TLB) will benefit a project’s bottom line and ensure a project’s successful completion. Project engineers will know that their design has proper thermal management early in the process, meaning that they will not have to over-design the project, which will save time and money in the long run.
Learn more about ATS and its capabilities as a thermal engineering partner for your next project by visiting www.qats.com or by calling 781-769-2800.
References:
http://www.3dsystems.com/learning-center/case-studies/lowering-cost-and-reducing-production-time-projet-3d-printing-lets