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Composite Metal Heat Spreaders in Handheld Electronics Design

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Overview: Composite metal solutions provide design opportunities for improved heat spreading and mechanical rigidity in space-constrained consumer devices. Utilizing composites in the design of structural components allows existing device features, such as frames and EMI shields, to dissipate thermal loads from high power heat sources without the need for secondary heat spreaders. Design considerations and materials performance properties are discussed with an eye toward cooler, stiffer devices.

Who should attend our webinar:
Thermal engineers and designers of consumer electronic devices. Engineers looking for light weighting opportunities.

Aaron VodnickAaron Vodnick
Aaron Vodnick joined Materion in 2012, bringing years of experience in advanced materials and product development. At Materion, Aaron leads global market and product development initiatives for composite metal systems, specifically unconventional thermal and structural materials for consumer devices. Aaron has a Bachelor’s Degree in Materials Engineering from the University of Minnesota Twin Cities, and a Ph.D. in Materials Engineering from Cornell University. With knowledge of materials performance, design, and characterization, Aaron’s primary responsibility is to help engineers understand materials’ behaviors and identify the best solutions.

The following are questions presented to the speaker by the attendees during the webinar, along with answers to each.

What’s the maximum practical thickness for a composite stack?
Answer: Over 2-3mm in thickness making coils of high stiffness composite metals becomes challenging, but there is no fundamental limit to the thickness of these composites. Current equipment limitations (in October 2015) cap the maximum thickness of eStainless at 0.8mm. However, work is in process to increase this thickness range to 2mm, so check back with Materion soon to learn about updated capabilities.

Was annealled pyrolytic graphite considered? The inplane conductivity is considerably higher.
Answer: Though pyrolitic graphite has impressive thermal conductivity values, the performance of graphite heat spreaders is limited by the micron-scale thicknesses. As the thickness of these graphite materials increase to carry more heat, the thermal conductivity performance suffers. Graphite is also a notoriously expensive material to use in electronics design. The advantage of the clad laminates is the ability to use the bulk conductivity of low-cost metals to outperform micron-scale graphite films, while simultaneously providing structural rigidity. (Graphite is not a structural material).

Is it machinable?
Answer: Yes. Just as Steel and Aluminum are machinable, the composite can be processed using the same equipment.

Can the material be processed like sheet metal into a 3D shape?
Answer: Yes. The eStainless composite is produced in large coils of sheet metal and is compatible with high speed stamping operations. Formability directly follows the temper of the steel used in the skins (Typically annealed Stainless 304, though other stainless steel grades have been used), and the composite is capable of forming sharp bends and deep draws.

Have you used any dielectric material layer?
Answer: The challenge with incorporating dielectrics is the composite metals must be stamped and drawn into finished components, and good dielectrics layers are generally relatively brittle. We do see opportunities here and have some ideas for how to incorporate dielectrics, especially adding them to the surface after the components have been stamped. Contact us if there is interest, and we would be happy to explore the options together.

Have you examined latent heat storage (phase change materials) to manage transient heat loads?
Answer: Yes, but one advantage of eStainless is actually just the opposite mechanism: The low heat capacity of Aluminum increases the thermal diffusivity of the composite, and helps to rapidly move heat away from the heat source during thermal spikes. There may be opportunities to incorporate phase change materials into composites to absorb thermal excursions, but heat spreading (rather than absorption) is a critical function to promote heat dissipation to the ambient in consumer devices. Through this improved heat dissipation, composite materials will help to increase the possible computational power and reduce the need for expensive, bulky, active thermal management components such as fans and heat pipes.