The performance, quality and cost-effectiveness of printed electronics are directly impacted by the printing techniques chosen, making their selection an essential process. A variety of factors, including the ink's properties (conductive, dielectric or semiconductive), the substrate's compatibility (e.g., paper, glass, plastic), and the required output velocity, dictate the optimal printing process.
Screen printing
Screen printing has quickly become one of the most common and effective ways to imprint designs and functional inks onto various materials. It's also used to make functional circuits, which results in high-quality images. Let's take a look at screen printing for electronics and learn about its advantages.
The term "stenciling" describes the first step of screen printing, which entails using a squeegee to force ink through a mesh screen. A printed picture or pattern is produced when the ink clings to the material. Aligning the screen and placing fiducials (markers) in the four corners of the screen accurately are two of the most critical steps in this process. Consistent and accurate results are guaranteed by layer-to-layer positioning throughout the substrate.
Gravure printing
Standard ink on paper printing requires the same setup as electronic printing using gravure printing. In gravure printing, a steel-coated copper cylinder is utilized for structural support. Surfaces are often etched with cells of varying widths and depths using an electromechanical or laser method. The next step is to fill the cells with ink and then contact the outside of the cylinder with a doctor's blade to scrape out any excess. After that, the cells are pressed onto a substrate in order to make an imprint. Because the typical approach applies too much pressure when printing on hard substrates or glass, an offset gravure process may be necessary for specific kinds of printable electronics.
Inkjet printing
Practically every printer in a household or small business uses inkjet printing. Digital nature is one of the key selling points of inkjet as a prototyping tool for additive electronics devices. This makes it possible to print the updated design immediately upon making a change to the design without the need for additional tooling, which speeds up the iteration process. Because it is digital, inkjet prints any pattern on a substrate by rapidly ejecting small droplets from a print head's hundreds of tiny nozzles. The exact process by which the droplets are generated differs throughout the various inkjet types. To print on household items, any type of inkjet will do; however, not all inkjets work with additive electronics. The two most common methods for applying inkjet are thermal and piezo.
Flexography printing
Printed electronics made using flexography printing technology are among the most fascinating and game-changing innovations of the last several years. There are multiple critical processes involved in the process of flexography printed electronics. Using CAD software, the initial step is to create a layout of the electronic circuit. The arrangement of components, conductive channels and other crucial aspects are all part of its design. Using the schematic as a guide, a photopolymer or other flexible printing plate is manufactured. After that, a printing cylinder is used to attach the plate. According to the specifications needed for the printed electronics, conductive inks made of metallic nanoparticles or conductive polymers are used. Adhesion, conductivity and flexibility are all carefully considered in the formulation of these inks.
Ink is applied to the printing plate, and a sequence of rollers transfers the design to the substrate. Flexible polymers, paper or even cloth can all serve as substrates. The ink is cured after printing using heat or ultraviolet (UV) light, among other processes, to make sure it sticks and conducts properly. Then, it is tested. The next step is to check the operation and performance of the printed circuit boards.
Offset lithography printing
Offset lithography is a widely used printing technique that operates on the principle of oil and water repelling each other. It involves transferring an inked image from a printing plate to a rubber blanket, which then presses the image onto the substrate, such as paper or flexible films. This indirect transfer, or "offset," ensures better print quality and extends the life of the printing plate. Offset lithography is particularly known for its ability to produce high-resolution, detailed patterns, making it ideal for applications requiring precision, such as printed electronics.
Aerosol jet printing
It is a promising printing technique for printed electronics known for its precision and versatility. It can print extremely fine lines (down to 10 microns), making it ideal for detailed applications like microelectronics and antennas. As a non-contact method, aerosol jet printing minimizes the risk of damaging substrates, allowing for printing on various surfaces, including curved ones. It supports a wide range of inks, including conductive and dielectric materials, and enables high aspect ratio printing, enhancing the performance of electronic circuits. While typically slower than traditional methods, this technology is scalable for both prototyping and low-to-medium volume production, making it a valuable option in the field of 3D-printed electronics.
Conclusion
A range of printing processes can be employed in the production of printed electronics, such as inkjet printing, screen printing, flexography and gravure printing. In practical terms, nearly any industrial printing method can be leveraged to fabricate printed electronics. Printed electronics enable the utilization of flexible substrates, thereby reducing production costs and facilitating the fabrication of mechanically flexible circuits.
