Why screen printers should care about the development of apparel infused with electronic sensors and circuitry.
In May 2014, FlexTech Alliance and Drs. Xiaoying Rong and Malcolm Keif of the Graphic Communication Department at Cal Poly State University completed a screen-printing study for printed electronics applications. Their report, “Characterizations of Screen Printing Low Viscosity Ink, Thin Film and Small Features for Printed Electronics Applications,” explored whether screen-printing processes could produce fine features (30 microns or less) and thin ink films (a few microns to submicron) while using inks with much lower viscosity than typical screen-printing inks. The study also investigated the impact of mesh technologies, ink rheology, and printing conditions on feature quality measured in width, thickness, and electrical resistance.
“Screen printing is a widely used process for the electronics industry,” noted Michael Ciesinski, president and CEO of FlexTech Alliance. “If screen printing can produce finer features and utilize thinner ink films, it will help the industry replace more expensive processes and expand existing screen-printing lines for new printed electronic products.”
The study concluded that ink rheological properties play a significant role in printing fine features. “With optimized printing parameters, fine features can be screen printed with commercially available inks, mesh, and emulsion,” Dr. Rong explained. “The conclusion of this study supports screen printing as a cost-effective production method that can simplify the fabrication processes while utilizing existing technology and equipment to service the printed electronics industry.”
Greenwood agrees that ink rheology really matters and urges his clients to understand the rheology of every component involved in printed electronics. For example, the shape and texture of particles can be just as critical to ink rheology as particle size. He notes that screen printing can handle inks with very difficult ink rheologies as well as acids, caustics, and electrolytic materials.
As the demand for thin-film flexible electronics grows, some types of applications might be better suited for production with industrial inkjet printers, gravure, flexo, or offset printing equipment. Each printing process has certain strengths and limitations that can be adapted for specific types of applications. For example, industrial inkjet printers might be used to customizing the final wearable products or applying adhesives to irregular surfaces and complex geometries such as athletic shoes.
Did you enjoy this article? Click here to subscribe to the magazine.