UV/EB curing has numerous advantages for manufacturers, and this is also true for flexible and printed electronics. UV/EB curing is finding a home in numerous applications, including structural electronics and Li-ion batteries, as well as additive manufacturing.

RadTech 2022, which is being held from May 9-12 at the Hyatt Regency Orlando, is holding a session on Flexible and Structural Electronics. During this session, four speakers discussed new energy-curable technologies for the electronics field.

Dr. Sage Schissel, applications specialist, PCT Ebeam and Integration, opened the session with “Electrons In, Electrons Out: Electron Beam for Battery Production.” Dr. Schissel noted that Li-ion battery demand is predicted to grow exponentially for electric vehicle and energy storage applications, from 526 GWh now to 9300 GWh by 2030.

The challenge is to scale up manufacturing, and electron beam (EB) could be the key.

“The way we produce Li-ion batteries should be sustainable, and we also have to be able to meet this demand,” said Dr. Schissel. “Conventional Li-ion batteries use thermal drying to create the electrodes.”

Working with Oak Ridge National Laboratories, PCT is testing EB for Li-ion battery production.

“The idea is to use an EB-curable pre-polymer as a more sustainable alternative to the conventional NMP/PVDF,” said Dr. Schissel. “The result is a crosslinked polymer coating, and you don’t have the production of VOCs since it is solvent-free. There are a lot of advantages. It also offers a compact footprint and is an instant cure process. All of these advantages result in cost savings. During the test run on the pilot line, when fully cured, EB electrodes had similar performance to the conventional NMP/PVDF system.”

Jonathan Shaw of allnex USA Inc. followed with “UV Curable Resins for Use in Structural Electronics.” Shaw observed that productivity is the primary benefit for roll-to-roll electronics, and UV curing takes seconds to cure vs. minutes or hours.

“Roll-to-roll printing techniques are often used, and can include gravuve, laser etched plates in flexo and screen printing, which is good for thick pastes found with some conductive inks,” said Shaw.

Shaw then discussed how modifications of the resin can improve performance.

“Shifting the catalyst creates a large difference in dielectric strength, and the addition of an acidic monomer increases dielectric strength a bit,” said Shaw. “Changes to the resins, such as catalyst swaps or the addition of polar materials, can change the degree but still remain in the realm of an insulator. Resins with isocyanate functionality are being used for conformal coatings. We are investigating methods to increase conductivity, such as adding carbon nanotubes.”

Donald Herr of Sartomer discussed “Dielectric Performance of UV-Curable Piezo-Inkjet Resins for Dielectric Coating Applications.”

“We used UV cure on a section of material and screenprinted conductive inks on both sides of the substrate,” said Herr. “Two piezo-ejectable inkjet resins have been dielectrically quantified to showcase their applicability to be used in a dielectric substrate application. These examples demonstrate how electronic properties can be improved by optimizing the chemistry, polarity and polarizability of the resin.”

Christian Gorsche of Cubicure GmbH is a 3D printing sp[ecialist, closed the Flexible and Structural Electronics session with “Hot Lithography – High Precision 3D Printing of Flame Retardant Photopolymers for the Electronics Industry.”

Gorsche noted that he saw no impairment with liquid flame retardants, but solid flame retardants reduced curing depth as well as leading to a rougher surface. This led to Cubicure developing its new printing systems, such as Caligma for prototyping and Cerion for production, to meet faster production levels.

“Our Caligma 3D printer can produce 280 parts per day,” Gorsche said. “We had to rethink the stereolithography process by developing our Cerion mobile printhead – it has resin exposed via scrolling DLP, has continuous coating and peeling during printing and multiple synchronized moving sequences. Scaling up is possible – we can do 2,000 flame retardant connectors in two hours and up to 20,000 parts per day.”