Category Archives: Case Study

Posts related to case studies

Case Study: PCB Cooling for Telecom Application

PCB Cooling for Telecom

The layout of the PCB with the smaller but most power-dissipating component on the left and the larger, but less power-dissipating component on the right. Originally both components were covered by straight-fin heat sinks embedded with heat pipes. (Advanced Thermal Solutions, Inc.)


Engineers at Advanced Thermal Solutions, Inc. (ATS) were brought into a project to assist a client with cooling a PCB that was going to be installed in telecommunications data center. The board currently had heat sinks embedded with heat pipes covering the two hottest components but the client wanted a more reliable and cost-effective solution.

ATS engineers used the company’s patented maxiFLOW™ heat sinks to replace the heat pipes and through analytical and CFD modeling determined that by switching to maxiFLOW™ the junction temperature and case temperature would be below the maximum allowed.

Challenge: The client had a new PCB over which air could flow from either direction and two of the highest power dissipating components were on opposite sides.

Chips/Components: WinPath 3 and Vector Processor

Analysis: Analytical modeling and CFD simulations determined the junction temperature with air going from left-to-right and right-to-left and ensured it would be lower than the maximum allowable (100°C for one component and 105°C for the other).

Test Data: With air flowing from left-to-right, CFD simulation determined that the junction temperatures would be 89.3°C and 101.4°C – below the maximum temperatures of 100°C and 105°C. With air flowing from right-to-left, the junction temperature of the most power-dissipating component was 100°C, which was right at the maximum, and the second was at 87°C, which was below it.

Solution: The original heat sinks embedded with heat pipes were switched for maxiFLOW™ heat sinks, with their placement offset slightly to create a linear airflow, and the same levels of thermal performance were achieved.

PCB Cooling for Telecom

ATS engineers changed the embedded heat sinks for maxiFLOW™ heat sinks and received the same thermal performance with a more reliable and cost-effective solution. (Advanced Thermal Solutions, Inc.)

Net Result: The client received the required level of cooling in the PCB, regardless of the direction of air flow, and with a more reliable and cost-effective solution than had been previously been in use.

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.

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.

Case Study: LED Solution for Outdoor Canopy Array

Advanced Thermal Solutions, Inc. (ATS) was approached by a company interested in a new design for an outdoor LED unit that would be installed in gas station canopies. The original unit was bolted together and contained a molded plastic shroud that held the LED array, the PCB, and an extruded aluminum heat sink.

ATS engineers designed an aesthetically pleasing alternative that utilized natural convection cooling, while increasing the number of the LEDs in the array and its power. The engineers met the customer’s budget and thermal performance requirements.

Challenge: Create an outdoor canopy device that would increase the number of LED in the array, increase power to maximum of 120 watts, and increase lumens, while cooling the device through natural convection.

Chip/Component: The device had to hold an LED array and the PCB that powered it.

Analysis: Analytical modeling and CFD simulations determined the optimal fin efficiency to allow air through the device and across the heat sink, the spreading resistance. The weight of the device was also considered, as it would be outside above customers.

Solution: An aesthetically-pleasing, one-piece, casted unit with built-in electronics box for LED array and PCB was created. There was one inch of headroom between the heat sink and the canopy to allow for heat dissipation and the casting would allow heat transfer as well as allow air to flow through the system.

Net Result: The customer was able to add LEDs to the array and increase power. The new unit also simplified the manufacturing process and cut manufacturing costs.

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.

Case Study: Thermal Management in Harvard Medical School Tissue Analysis Instrumentation

Designers of today’s highly advanced medical diagnostic equipment must overcome many of the same thermal challenges common to telecommunications, industrial and information technology electronics.

In addition, medical diagnostic devices present unique design issues and boundary conditions that factor into thermal solutions. These include isothermal and cyclic temperature demands, precise test repeatability, and maintaining the patient’s safety and comfort.

These kinds of issues were presented by Harvard Medical School to the experts at Advanced Thermal Solutions, Inc. (ATS) when it needed a cooling solution for the diagnostic equipment it was relying on for the analysis and observation of human tissue samples in a controlled laboratory setting. This was the school’s Frozen Tissue Microarrayer System.

ATS engineers had to provide thermal solutions to meet a range of design goals:

• Provide long-term temperature control for tissue samples embedded in an optimum cutting temperature fluid.
• Create a cooling system to maintain tissue samples below -70°C for six hours.
• Ensure operator visibility of the samples.
• Eliminate humidity and frost within the system to prevent sample contamination.

ATS Cooling Solutions

ATS engineers developed highly effective thermal solutions to meet all the design requirements of the diagnostic equipment. A reservoir in the device holds the liquid cooling medium and tissue samples are loaded through an opening at the top. Through a duct, cool air is circulated over the top of the samples to maintain temperature and humidity requirements.

As seen in Fig. 1 (below), the diagnostic system consisted of:

• Frozen tissue coring machine (on the right in the photo)
• Tissue sample loading area at the top of the cooling system (seen on the left)
• Duct system (on both sides of system) to circulate cool air
• Ice/alcohol reservoir at the system’s bottom to contain the cooling medium

Harvard Case Study

Figure 1. Prototype system created by ATS engineers for Harvard Medical School laboratory. (Advanced Thermal Solutions, Inc.)

Conduction Cooling Design

In operation, tissue samples are loaded into removable aluminum cassettes that fit tightly into a metal receiver (top left, Figure 2). The receiver contacts the cassette on five sides which allows for cooling of the samples by conduction. The receiver is lowered into a reservoir containing a slurry of dry ice and ethyl alcohol. Here the receiver is maintained at a constant temperature until the dry ice evaporates. The reservoir is double-walled and insulated to extend the evaporation time of the dry ice.

The receiver also features integral fins that increase surface area for drawing heat downward from the base of the cassettes into the icy slurry (bottom left, Figure 2). These fins are based on the same ATS heat sink design principles used in the company’s high performance maxiFLOW™ heat sinks.

Using analytical modeling, ATS engineers determined that 10 fins were the optimal number for cooling the cassette receiver and its contents. CFD simulations also showed that the 10-fin concept resulted in an optimal design. The engineers validated their analytical and CFD results through empirical testing. It was determined that extending 10 fins into the slurry provided the cooling performance to maintain tissue sample temperatures below the -70°C threshold for 9.75 hours.

Further temperature testing using thermocouples showed only a 2.5°C difference between the coldest points at the bottom of the fins and the tissue samples in the cassette. This proved that the design overcame thermal conduction resistance and could effectively maintain the samples below their critical temperature.

Figure 2. Temperature testing with thermocouples demonstrated that the temperature difference between the bottom of the fins and the top of the cassette, through three intervening layers, was only 2.5°C. This proved that the thermal design was successful. (ATS)

Figure 2. Temperature testing with thermocouples demonstrated that the temperature difference between the bottom of the fins and the top of the cassette, through three intervening layers, was only 2.5°C. This proved that the thermal design was successful. (ATS)

Figure 3. Using a heat sink-specific thermal resistance network ATS determined that the optimal number of fins was 10. (ATS)

Figure 3. Using a heat sink-specific thermal resistance network ATS determined that the optimal number of fins was 10. (ATS)

Convection Cooling Design

The above conduction cooling design provided only part of the solution. There were additional needs to maintain the temperature at the top of the samples and to decrease the relative humidity of the cool air from the ambient air in the lab. ATS engineers designed a convection cooling system to fulfill these requirements.

A heat exchanger was installed with its fins in the dry ice/alcohol slurry and its other side extending into a duct to cool the air passing over it. This approach uses the same cooling medium for both convection and conduction to ensure there is no temperature differential throughout the sample and that the sample is as isothermal as possible.

Air is pushed by a counter-rotating fan through the duct and into the heat exchanger. The heat exchanger forms a thermal link between this air and the slurry mixture. The heat exchanger was designed with an optimum balance between its surface area and the resulting pressure drop to ensure the fan was operating with the most effectiveness.

Once the air passes the heat exchanger, it moves through the ducts and into a diffuser at the top of the system. The diffuser disperses the air over the sample creating a barrier between the tissue and the ambient environment of the lab so outside moisture and heat are not transferred in.

The ATS engineers tested this design using an array of thermocouples and ATS hotwire anemometer Candlestick Sensors connected to an ATS ATVS-2020, a temperature and air velocity scanner. They determined there was too much mixing between the air flowing over the samples and ambient air. The diffuser was redesigned with a new connection to the duct and an optimized outlet radius (see Figure 4).

In the ducts, a molecular sieve desiccant housed in a honeycomb structure was used to reduce the dew point of the air to -84.4°C, which was well below the -72°C air temperature in the duct.

Figure 4. Initial testing led to a redesign of the air diffuser to prevent ambient humidity from mixing with the air over the tissue samples. (ATS)

Figure 4. Initial testing led to a redesign of the air diffuser to prevent ambient humidity from mixing with the air over the tissue samples. (ATS)

Conclusions

ATS engineers performed a final series of tests of the Frozen Tissue Microarrayer System using Candlestick Sensors, thermocouples and the ATVS 2020 scanner. The tissue temperature stayed constant over the required six-hour period and well below the -70°C threshold. In fact, testing determined that the tissue temperature remained below the threshold for nearly eight hours before warming above a usable temperature (Figure 5). The multi-part cooling system was a success, meeting the original design objectives provided by Harvard Medical School.

Figure 5. Final testing showed that the ATS cooling design kept tissue temperature (shown in blue in the graph above) below the -70°C threshold for more than the required six hours. (ATS)

Figure 5. Final testing showed that the ATS cooling design kept tissue temperature (shown in blue in the graph above) below the -70°C threshold for more than the required six hours. (ATS)

The process of designing cooling solutions for the Frozen Tissue Microarrayer demonstrated that thermal design practices used throughout electronics cooling can be applied in the medical device industry. Fin efficiency, thermal resistance, and pressure drop calculations are standard regardless of the application. Thermal solutions should be considered early in the design process so they can be incorporated into the overall system as efficiently as possible.

The experts at ATS used traditional thermal calculations, CFD simulations, empirical testing, and its leading-edge heat sink technology to successfully design the thermal solution for this medical equipment application. The ATS design allowed Harvard Medical School to test tissue samples while meeting its strict requirements.

To learn more about the design, watch the video below:

Download a PDF of this case study at http://www.qats.com/cms/wp-content/uploads/Harvard-Medical-case-study.pdf.

Visit www.qats.com, call 781-769-2800 or email ats-hq@qats.com to learn more about ATS and its Thermal Management Analysis and Design Services.

Casting a Light on LED Cooling with Die Cast Heat Sinks

Advanced Thermal Solutions work in casting aluminum heat sinks allows us create large, rugged, and reliable heat sinks and enclosures in a single piece.  Such work carries a number of advantages including enclosures and heat sink in a single unit, reduced part count, reduced final manufacturing complexity.  ATS’s John O’Day sat down with ATS engineers Joe Gaylord and Anatoly Pikovsky regarding our engineering in cast heat sink design to discuss two specific customers projects, both in LED Lighting.   The first company is a  company focusing on LED stadium lighting and the other specializes in LED industrial lighting.

John: What kind of value add did ATS add to the stadium lighting company for their cast stadium heat sink?

Anatoly: Well, this company tried to make the casting for their Stadium LED light for almost a year. They went to many different vendors and nobody could actually build what was needed. They started to cast the first prototypes but they developed cracks. ATS was brought in to see if we could solve the technical and manufacturing problem. Our involvement made it possible for them to ship their stadium lighting on time to be installed in the University of Phoenix Stadium.

Ephesus Stadium Light

Joe: One thing we did was to change the fins a little bit to improve heat transfer and manufacturability, changed how the actual casting tool was made.

Anatoly: We also created a version of the heat sink from sheet metal as a backup, in case the casting failed.

Joe: We did CFD modeling to determine fin efficiency too. In the current design fin efficiency is very good but we thought we could improve it further, so we found that a much shorter fin version would perform just as well but this stadium LED lighting company was already down the design cycle and needed to get this product out the door. We also did work developing a version with heat pipes too, to give the customer multiple data points on what was possible.

John: So we created multiple options for the customer as backup so they could make this shipment for University of Phoenix Stadium on time. It sounds like we take partnering with our customer’s very seriously.

University of Phoenix Stadium

Joe: That’s true we do take partnering seriously and in this case there was a great deal of investment on ATS’s part.

John: So we’ve done casting for another important lighting customer too haven’t we?

Joe: That’s right, an LED company that makes several types of LED lights, some for food chillers like you might see in department stores and they also make canopy lights for gas stations. The canopy lighting LED’s were what we worked on.

Anatoly: If you ever look up while pumping gas you’ll likely see their LED lights in the overhangs above the gasoline pumps.

Joe: So the model they had previously was a molded plastic shroud with a PCB board, LED array, and extruded heat sink on the inside of the shroud of the cooling device. Essentially a big extruded aluminum heat sink, all bolted together (credit senior). Their goal was to increase the number of LED’s, power and lumens in these lights. Thermally, their target originally was 100 Watts, then it climbed to 150 Watts, then it came down to about 120 Watts.

John: So what did we do to make their design better and casting better?

Joe: Our goal was to get rid of the plastic shroud and the extruded aluminum and replace those with a cast piece. We suggested casting for this design since it would create a shroud that allowed for heat transfer. It eliminated a two piece design of heat sink with shroud allowing this LED customer to simplify manufacturing while meeting their thermal performance requirements.

John: Was it easy to come up with this design or did it take several iterations to get to the final design?

Joe: Well, as you know, ATS has a 3-Core Design Process where we do a quick analytical model of the design, move to computational modeling using Flotherm or CFdesign, and finish with an empirical model for physical testing in our thermal characterization lab. This process helps us to reduce the actual time it takes to do a proper heat transfer solution design. For this work we did a lot of thermal modeling with CFdesign.

Heat Sink Design Engineering Process, ATS

Anatoly: There were some key challenges in this design: First it required natural convection cooling. Second, we had to design to cool 120 Watts. Third, the outside ambient temperature can be up to 40 degrees C when a gas station is in the desert.

Joe: For natural convection cooling you need some headroom for the air to convect. We had designed this thermal management solution for a minimum headroom of 1-inch from the heat sink to the canopy over a gasoline pump. Allowing air to come into the heat sink and circulate out was a major challenge requiring excellent fin efficiency, a consideration for spreading resistance, and the mechanical packaging over the LED array. The weight of this casting had to be taken into account too since it would be outside in a canopy over gas pumps with people standing under it. Finally, the industrial design was an important aspect as well since it was outside and had to look attractive. We took time to carefully sculpt the heat sink fins in the final design to account for both aesthetics and thermal performance. Our final design was a machined, open enclosure with fins on all four sides, so that air flow can come up and through from all sides.

International Lighting Canopy Light

John: When we completed testing in our thermal lab with the model we had machined, did we move to casting then?

Joe: Yes we did. Our design was set to cast in two pieces so that the cost to manufacture was within the LED customer’s requirements. The end result was a powder coated single unit, with the electronics box built into the cast, that fit both the PCB and LED. All that was needed as a cover. It simplified the manufacturing process, reduced the manufacturing cost and met their requirements for overall price and thermal performance.

To learn more about ATS’s die cast heat sinks and design services, please email us ats-hq@qats.com or call us at 781-769-2800.

How to subscribe to qpedia