Case Study: Thermal Comparison of Copper and Aluminum Heat Sinks

Advanced Thermal Solutions, Inc. (ATS) engineers were tasked by a client to find a more cost-effective and lighter solution for a custom-designed copper heat sink that dissipated heat from four components on a PCB. ATS engineers compared the thermal performance of the copper heat sink to custom aluminum heat sinks embedded with heat pipes.

Aluminum Heat Sinks

ATS engineers worked on a comparison of a copper heat sink with an aluminum heat sink that had embedded heat pipes running underneath the components. Analysis showed that the aluminum heat sink nearly matched the thermal performance of the copper and was within the margin required by the client. (Advanced Thermal Solutions, Inc.)

Using analytical modeling and CFD simulations, the ATS engineers determined that switching to an aluminum heat sink with heat pipes that run underneath the components yielded case temperatures that were greater than 4.35%, on average, of those achieved with the copper heat sink. The largest difference between the two heat sinks was 9.2°C, over a single component.

Challenge: The client wanted a redesign of a custom copper heat sink to an equivalent or better aluminum heat sink with embedded copper heat pipes.

Chips/Components: Two Inphi (formerly ClariPhy) Lightspeed-II CL20010 DSPs at 96 watts and two Xilinx 100G Gearboxes at 40 watts each.

Analysis: Analytical modeling and CFD simulations determined the junction temperatures between the four components when covered by a copper heat sink (Design 1), by an aluminum heat sink with heat pipes that stop in front of the components (Design 2), and by an aluminum heat sink with heat pipes that run underneath the components (Design 3). The analysis demonstrated the difference between the heat sink designs in relation to thermal performance.

Test Data: CFD analysis showed an average component case temperature of 158.8°C with the original copper heat sink design, 158.3°C with Design 2, and 152°C with Design 3. The average difference in temperature between Design 1 and Design 2 was 0.5°C and the average temperature difference between Design 1 and Design 3 was 6.8°C.

Here is a CFD simulation from the top of the aluminum heat sink with the air hidden, showing the temperature gradient through the heat sink. (Advanced Thermal Solutions, Inc.)

Solution: The client was shown that aluminum heat sinks with heat pipes provided nearly the same thermal performance as the original copper heat sink design and at much lower cost and weight. The component junction temperature differences between Design 1 and Design 3 were well within the margin set by the client.

o The simulated air velocity is lower and the airflow cross section is larger than in the actual application, meaning absolute temperatures are higher than the customer has seen in their testing.

Net Result: Despite using conservative thermal conductivity calculations, aluminum heat sinks with heat pipes were shown to be a more cost-effective solution for achieving the client’s thermal needs than copper.

CLICK HERE FOR A TECHNICAL DISCUSSION OF THIS PROJECT.

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.

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