It happens all the time – you get wrapped up in an online game or watch a couple shows on your tablet – and your mobile device gets hot. You may even remember at one time owning a laptop computer with a noisy fan on the side. That heat is a result of the hundreds of microchips inside your device that make your device “smart” and pump out electricity. Those microchips must be cooled for your device to perform effectively and efficiently.
As microchips become more powerful, the chips become more, well, micro. But the power we can put in the microchips is limited without an equally advanced cooling method. When the electronics get too hot, the system performance is impacted and could even result in system failure.
Limitations in cooling “threaten to derail the technology engine which has been responsible for much of the innovation in defense and commercial microelectronic systems,” according to the Defense Advanced Research Projects Agency (DARPA) in its official description of its Inter/Intra Chip Enhanced Cooling (ICECool) program. The program is challenging its commercial, industrial and university partners to come up with new solutions using a simple premise:
Just add water.
It’s not that easy, but a core team of Lockheed Martin engineers is working on a solution to directly cool hot spots by spraying liquid right on the bottom of the chip. This technology has applications in electronic warfare, radars, high-performance computers and data servers.
“There is tremendous opportunity in new techniques in microchip cooling,” says John Ditri, the principal investigator of the Lockheed Martin team. “These solutions could result in lighter, faster and cheaper highly-sophisticated electronics.”
FINDING THE ICECool SOLUTION
Now let’s think beyond your movie-watching, game-playing mobile device. How do you cool thousands of microchips in sophisticated military systems like super computers, high-capacity data storage systems and military electronics such as radio frequency (RF) transceivers and solid-state lasers?
ICECool-Applications is a DARPA Microsystems Technoloy Office research program that could ultimately lead to dramatic improvements in cooling high-powered microchips and the commercial and military electronics that rely on them. ICECool’s goal is to enhance the performance of RF MMIC power amplifiers and embedded high performance computing systems through chip-level heat removal techniques.
“Right now, we’re limited in the power we can put into microchips,” says Ditri. “One of the biggest challenges is managing the heat. If you can manage the heat, you can use less material and that results in cost savings. If you manage the heat and use the same number of chips, you’ll get even greater performance in your system.”
Lockheed Martin experimentally verified the effectiveness of its microfluidic cooling approach, which resulted in a four-times reduction in thermal resistance. The program team also cooled a thermal demonstration electronic chip, called a die, which dissipated 1,000 watts per square centimeter area, and which contained several local hot spots dissipating over 30,000 Watts per square centimeter. To put this into perspective, this is roughly five times the heat flux found on the surface of the sun.
Lockheed Martin continues to build its Gallium Nitride (GaN) legacy by working with Qorvo to integrate its thermal solution with its high performance GaN process; a relationship that will help unleash the full potential of GaN semiconductors by removing current thermal barriers. The Lockheed Martin approach is also applicable to other current and future die technologies, such as existing Gallium Arsenide (GaAs) and future GaN on Diamond when it becomes available. Lockheed Martin’s ICECool embedded thermal management approach removes thermal barriers to harness GaN’s full RF power handling capability. In addition to revolutionizing the way GaN amplifiers are implemented, this technology will benefit any high heat flux Integrated Circuit application, including signal processing and high performance computing.
In its ongoing effort to move the technology out of the laboratory and into the field, Lockheed Martin is developing a fully functional, microfluidically cooled, transmit antenna prototype to increase the technology readiness level (TRL) of this technology. This will lay the foundation for possible insertions into future electronics systems.
“This research is taking microfluidic cooling to the next level. DARPA is moving us to the leading edge of vastly improving the performance of electronics in the civilian, commercial and defense sectors,” Ditri said.
EMPLOYEE SPOTLIGHT: DENISE LUPPA
When she was an engineering student, Denise Luppa and her female lab partner were often singled out to perform their tests again. At the time, she remembers thinking their professor simply did not believe the two women could get the correct results.
“I looked at it like a challenge,” says Denise, an advanced programs manager for Lockheed Martin. “I decided that I was going to prove him wrong.”