How graphene is changing PCBs
3.5 minutes | 04 Feb 2020
As far as compounds go, graphene is relatively new on the scene. Manchester University researchers discovered it in 2004, going on to win a Nobel Prize for their efforts.The potential uses of graphene seem endless across every sector, not just electronics. If you don’t know, graphene is a thin layer of pure carbon –one atom thick, in fact. it’s the thinnest compound known to man and offers three advantages:
- Strength: It might be thin, but graphene is up to 300 times stronger than steel and harder than its carbon cousin, the diamond. Graphene can be twisted, folded, crumpled, etc, and it still won’t lose its strength.
- Flexibility: Its flexibility is due to its thinness. If you stretch graphene, it’ll extend to 20% of its original length.
- Conductivity: One of the best conductors of heat and electricity, making it an ideal alternative to silicon and copper.
Products with graphene are just now starting to appear on the market: smart health watches, mobiles, supercars, audio interconnects such as headphones and ear buds – even memory-foam pillows that help maintain body temperature.
The cost is coming down
The reason it’s taken so long to bring products to market has been the cost of mass producing graphene. At one time, it cost $800 just to get a usable gram of graphene made. Scientists have now solved the long-standing challenge of an efficient process for large-scale production. The price of graphene depends on the quality, but to give you a general idea, one seller currently advertises the product for €99 a ml, which converts to $115 a gram, as of this writing. The price has come down considerably.
What does graphene mean for PCBs?
Back in 2011, IBM demonstrated a “proof-of-concept” by building an analogue graphene integrated circuit with a broadband frequency mixer. However, the performance of the graphene transistor (transistors are the core of micro-processors) was inevitably degraded due to harsh fabrication processes.
Since then, IBM scientists have focused on improving device performance for modern wireless communications. The demonstrated performance is 10,000 times better than previously reported efforts for graphene integrated circuits and is a major step forward in true graphene technology, which will potentially provide higher performance and lower cost wireless communication systems.
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Wearable, washable circuits
In January, researchers at the Iowa State University in the U.S. developed flexible, water-repellent graphene circuits for washable electronics. New graphene printing technology can produce electronic circuits that are low-cost, flexible, highly conductive and water repellent.
"We're taking low-cost, inkjet-printed graphene and tuning it with a laser to make functional materials," said Jonathan Claussen, an assistant professor in mechanical the corresponding author of the paper recently featured on the cover of the journal Nanoscale.
The paper describes how Claussen and the nanoengineers in his research group use inkjet printing technology to create electric circuits on flexible materials. In this case, the ink is flakes of graphene. The printed flakes, however, aren't highly conductive and have to be processed to remove non-conductive binders and weld the flakes together, boosting conductivity and making them useful for electronics or sensors.
That post-print process typically involves heat or chemicals, but the research group developed a rapid-pulse laser process that treats the graphene without damaging the printing surface, even when it’s paper. Now they've found another application of their laser processing technology: taking graphene-printed circuits that can hold water droplets and turning them into circuits that repel water.
Another stunning advancement has come from a team of researchers from Northwestern University, The University of Texas at Dallas, University of Illinois at Urbana-Champaign, and University of Central Florida.
In a study published in the journal Nature Communications, the team found that a graphene-based transistor could actually work better than silicon transistors used in today’s computers.This is radical.
Microprocessors built using silicon transistors have been stuck at processing speeds mostly in the 3 to 4 gigahertz range for over a decade now. Quite simply, there’s a limit to the rate of signals and power these transistors can handle, mostly due to silicon’s resistance. The researchers, however, found a way through this barrier by using graphene instead of silicon.
Electrons pass through graphene with almost no resistance and generate very little heat. Graphene itself is a good thermal conductor that dissipates heat quickly. Due to their superior performance, electronics made from graphene run much faster. The research team built a logic gate series that uses less power but could work 1,000 times faster than ones with silicon.
An all-carbon computing system still exists only on the drawing board, says co-author Joseph S. Friedman of University of Texas at Dallas, but Friedman and his collaborators are currently working on a prototype.
Bye, bye silicon?
The development of silicon electronic materials appears to be fading. Graphene is the flavor of the month. The reason: carbon nanotubes and graphenes have smaller size and better electrical properties than those of silicon devices. They are likely to replace silicon materials in the future.
The future of graphene
Researchers aspired to use graphene as an unconventional transistor material, an idea that eluded the scientific world for quite some time. The main reason graphene failed as a transistor material is because it has a zero bandgap, which is the energy difference between the valence and the conduction bands in semiconductors and conductors. This made graphene more of a conductor than a semiconductor. But as we’ve seen in recent developments, scientists have overcome this hurdle.
Graphene is thought of as a wonder material, but as reflected in prices, quality of the material varies. Because of this, final application-level results are influenced by many parameters. This includes graphene morphology, formulation/compounding technique and conditions. Graphene is still in its infancy, but it’s looking more and more like the next generation of electronics.
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