Matthew Modoono/Northeastern University 

Engineers at Northeastern University have created a novel type of ceramic that can be shaped into tiny, intricate shapes, opening up a wide range of new uses in electronics.

The innovative materials, known as thermoformable ceramics, were created by "accident" in a lab but had potential applications, including more effective and long-lasting heat sinks.

Published in Advanced Materials on September 4, Northeastern University professor Randall Erb and Ph.D. student Jason Bice's discovery suggests that all-ceramic that can be compression-molded into complex parts could transform the design and construction of heat-emitting electronics, including cellphones and other radio components.

“Our research group’s lives are very much situated at the bleeding edge of technology,” says Erb in the statement, an associate professor of mechanical and industrial engineering who heads the DAPS Lab at Northeastern.

“Things break a lot, and every once in a while, one of those breaks turns out to be good fortune.”

Erb and Bice were in his Northeastern lab in July of last year when things seemed to go awry. They were putting an experimental ceramic material to the test as part of a hypersonic project for an industry partner.

Matthew Modoono/Northeastern University   

“We blasted it with a blowtorch, and while we were loading it, it unexpectedly deformed and fell out of the fixture,” Erb added. “We looked at the sample on the floor thinking that it was a failure.”

When ceramics are subjected to abrupt temperature changes and mechanical loading, they frequently shatter (or even explode) from thermal shock. However, their sample had distorted.

“We tried it a few more times and realized that we could control the deformation,” Erb says. “And then we started compression-molding the material and found that it was a very fast process.”

Its underlying microstructure enables the all-ceramic to transmit heat and flow during the molding process effectively. At room temperature, the ceramic can be formed into exquisite geometries and exhibits impressive mechanical strength and thermal conductivity.

“It’s unique: Thermoformable ceramics, from what we’ve seen and read, don’t really exist,” Bice says. “So it’s a new frontier in materials.”

The new product has the potential to bring two industry improvements, the first of which is its efficiency as a heat conductor capable of cooling high-density electronics.

Cell phones and other electronics are generally outfitted with a thick layer of aluminum to draw heat away from the unit.

“Our material can be less than a millimeter thick, which presents a low-profile solution,” Bice says. “It can be molded to conform to the surface that you’re trying to cool.”

According to Erb, the phononic crystal-based ceramic enables heat to move without electron transport. It doesn't interact with other systems or the radio frequencies (RF) used by telephones.

“If you put an aluminum heatsink into an RF component, you’ve basically introduced a series of antennae to interact with the RF signal,” Erb says. “Instead, we can put our boron nitride-based material in and around an RF component, and it is essentially invisible to the RF signal.”

Erb and Bice believe they will be able to shape the all-ceramic materials to fit a wide range of electrical components. The ceramic will be thinner, lighter, and more efficient than current metals.

Thermoforming processing, traditionally reserved for thermoplastic polymers and sheet metals, is extended here to boron-based all-ceramics. Specifically, sintered boron nitride composite sheets manufactured via a combined vibration and tape-casting photopolymerization process exhibit a highly oriented microstructure that allows these preform sheets to flow as viscous Bingham pseudoplastics during compression molding. These sintered all-ceramic preforms are thermoformed into thin, complex parts with features down to 200 µm. Further, a new workflow is leveraged to generate bespoke all-ceramic heat spreaders that can be press-fit onto printed circuit boards and outperform metal heat sinks as a low-profile thermal management solution. This work offers a route for other all-ceramics that may be thermoformed through first fabricating pre-forms with highly-ordered anisotropic microstructures.

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