New inks from DuPont Co. could pave the way for a wider range of plastic films being used in printed electronics that are crucial to consumer electronics, appliances, biomedical products and other items employing tiny electronic circuits.
DuPont Microcircuit Materials has developed electronic inks that cure rapidly at 80° C, making it possible to print the inks on films made of low-cost resins such as PVC, polystyrene, high density polyethylene and acrylics. Circuit patterns that are printed on films can act as sensors, antennas, heated surfaces and smart packaging.
Conventional electronic inks typically cure at 100° C to 140° C, according to DuPont. This has restricted the choice of plastic film substrates to expensive materials such as heat-stabilized PET, or in high temperature use, to polyethylene naphthalate or polyimide.
“It's been a big challenge,” said Steven Willoughby. Many attempts in the electronics industry to lower curing temperatures have given inks that can inconveniently cure at room temperature before they are used, or inks that lose adhesion to the substrate after printing, he said in a phone interview.
Electronic inks are applied to substrates through screen printing to create miniature circuits at the core of many modern products. The inks usually comprise three parts: a solvent, a resin that cures to a hard solid, and a conductive material such as silver or a mixture of silver and other metals. DuPont solved the cure temperature problem by adjusting the solvent and resin, Willoughby explained.
Willoughby said DuPont's low-temperature curing inks, called PE827 and PE828, offer more design flexibility and significantly lower cost because a variety of basic plastic film substrates are suitable.
“An ink that cures at 80° C is definitely useful for printed electronics, be it for plastic or other substrates [like specialty papers], as it offers more choice,” stated Peter Kallai, president and CEO of the Canadian Printable Electronics Industry Association of Nepean, Ontario, in an email correspondence. Other important film properties include transparency, printability and adhesion, he added.
“This really opens the door for application designers,” predicted DuPont Microcircuit Materials segment manager Kerry Adams. The company is looking for ways to allow electronics use to penetrate “into almost any device,” he noted in a news release.
DuPont Microcircuit Materials is based in Research Triangle Park, N.C. The 40-year-old segment's electronic inks also find use in conductive traces, capacitor and resistor elements, and dielectric and encapsulating layers. Besides plastic films, suitable substrates include glass and ceramics.
Willoughby said the new inks are being qualified by prospective customers and that they should be available in commercial quantities in about a year.