Tech Briefs Magazine - June 2021 - 34

Electrical/Electronics
Polymer-Based Electrical Insulation for Circuits
The new material could help put more power in smaller microchips.
University of Virginia, Charlottesville and Northwestern University, Evanston, Illinois
ll of our most-used electronic devices
rely on increasingly smaller micro -
chips. One of the biggest hurdles to putting
more circuits and power onto a
smaller chip is managing the heat. As
chips become smaller, heat increases
exponentially. Not only are there more
transistors in a given area - which generates
more heat in a small space - but
they also are closer together, making it
harder for heat to dissipate.
A research team explored an emerging
type of material with the potential to
keep chips cool as they continue shrinking
in size. Called " low-k " dielectrics,
electrical insulation materials minimize
electrical crosstalk in chips. By steering
current to eliminate signal interference,
low-k dielectrics make all electronics
A
possible. Ideally, this material type also
could pull damaging, electrical currentgenerated
heat away from the circuitry.
But because low-k materials have very
low thermal conductivity, they have been
previously unable to manage heat.
Scientists have been in search of a lowk
dielectric material that can handle the
heat transfer and space issues inherent
at much smaller scales. Using two-dimen -
sional (2D) covalent organic frameworks
(COFs), the team developed high-quality,
porous COF thin films that finally
solve the heat problem. Not only is the
material low-k but it also has high thermal
conductivity. The team is currently
applying this new material class to meet
the requirements of miniaturizing transistors
on a dense chip.
The team took sheets of polymer that
are one atom thick - called 2D - and
controlled their properties by layering the
sheets in a specific architecture. COFs
show both low-k properties and thermal
conductivity as a consequence of their 2D
layer architectures and porous structures.
The researchers are exploring this
new class of materials for applications
such as chemical sensing. The materials
can be used to determine (or sense)
what chemicals and how much of those
chemicals are in the air. Knowing about
the chemicals in the air, researchers can
optimize food storage, transport, and
distribution to reduce global food waste.
For more information, contact Wende
Whitman at wende@virginia.edu; 434-8069326.
Large
Integrated Circuits Produced in a Printing Press
Complete integrated circuits with more than 1,000 organic electrochemical transistors
can be screen-printed.
Linköping University, Linköping, Sweden
esearchers have printed
complete integrated circuits
with more than 1,000
organic electrochemical transistors.
Printing electronic
circuits with a line width of
approximately 100 micrometers
places high demands on
print technology. To solve the
problem, the team de veloped
screen-printing frames with
meshes that can print ex -
tremely fine lines and printing
ink with the right properties.
The material used is the
polymer PEDOT:PSS.
At least three challenges
have been dealt with: reducing
the circuit size, increasing
the quality such that the probability
that all transistors in the
circuit work lie as close to
100% as possible, and solving integration
with the silicon-based circuits needed to
process signals and communicate with the
surroundings.
R
34
Cov
Large-scale integrated circuits (LSI) can be used, for example, to power an
electrochromic display, itself manufactured as printed electronics. (Credit:
Thor Balkhed)
Printed circuits were used to create an
interface with traditional silicon-based electronic
components. Several types of printed
circuits based on organic electrochemical
transistors were built. One of these is a
shift-register, which can form an interface
and deal with the contact between the silicon-based
circuit and other electronic
www.techbriefs.com
ToC
components such as sensors
and displays. This results in a
silicon chip with fewer contacts,
which needs a smaller
area and is less expensive.
The development of ink to
print the thin lines and im -
provements of the screenprinting
frames contributed
not only to the miniaturization
process but also to achieving
higher quality. More than
1,000 organic electrochemical
transistors can be placed on an
A4-sized plastic substrate and
can be connected in different
ways to create different types
of printed integrated circuits.
These large-scale integrated
circuits (LSI) can be used, for
example, to power an electrochromic
display - itself
manufactured as printed electronics - or
another part of the online electronic
world that the Internet of Things brings.
For more information, contact Magnus
Berggren at magnus.berggren@liu.se; +46 11
36 36 37.
Tech Briefs, June 2021
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Tech Briefs Magazine - June 2021

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