When it comes to industrial printing, there are a fair number of highly specialized niche areas. One of these unique applications is the printing of graphic overlays for membrane switches. A membrane switch is an electrical contact on/off switch, that when pressed, activates or de-activates an electric circuit.

Traditionally membrane switches are produced by screen printing the circuit directly onto the plastic substrate using silver or carbon conductive inks. However, developments in UV digital printing technology open up new output options within this marketplace.

Membrane switches, when coupled with components such as a tactile dome, graphic overlay, or integrated LEDs, can provide the designer with a host of capabilities to create the ideal custom user interface for their products.

Membrane Switch: Digital Printing Making its Mark

Screen printing works well when there is a need for larger volumes or high-performance, functional graphics. However, digital printing appears to be a growing option in some areas.

Ono states that even though manufacturers use screen printing to print the circuits. Other components within the membrane switch can be printed through more advanced digital technologies, and in many cases they are.

"In particular, UV printing technology is gaining popularity to print the graphic overlay of the switch. This is because digital UV offers a more streamlined workflow and is less labor-intensive than screen printing" Ono says.

"The materials may be similar, flexible substrates range from 0.005 to 0.010-inches thick. Although polyester is by far the choice for use in membrane switches, where we use polycarbonate and rigid vinyls for labels. This difference alone is significant in how the substrates are processed and techniques used to obtain maximum performance" Bolding says.

Bolding also says that while there are some similarities, companies thinking about getting involved with producing a membrane switch from outside the industry—even if they have good screen printing capability—will face significant challenges.

Switching Trends

In the U.S., the primary market for membrane switch printing is in the short- and micro-run space. This is because much of the volume of manufacturing has been moved overseas. The production of Membrane switches takes place typically close to the manufacturing hub.

Ono says that products that lend themselves to short production runs and require versatile manufacturing processes, such as custom machinery, are produced more often in the U.S. than abroad.

"Prototyping of membrane switch overlays is another profitable application for UV printing in this market,” Ono says. “One-offs and design changes are much easier to manage through digital technologies than through analog printing processes."

Ono reports that if a sign shop already has a UV-cure printer, it may be able to expand into the membrane switch printing market.

"This line expansion can work well if a shop is based in an area where technology and engineering companies are located,” Ono says. “As with any new market, the print provider will need to reach out to these businesses. He would have to offer them their capabilities."

Flatbed Options

Wood says that with print volumes becoming more specialized, some screen printers are looking at adding a flatbed to their equipment mix.

"Most of the membrane switch work is very precise,” Wood says. “By using a flatbed, they get the precision registration they need on those short run jobs without any set up costs associated with screen printing. For example, our Rastek T1000 UV flatbed printer allows them to print white at the same speed as CMYK. Plus the unit’s eight levels of grayscale enhance image quality and edge definition."

He adds that it is definitely a growing market and one that can be very profitable with proper research and investment.

Drop-On-Demand Technology

FUJIFILM Dimatix, Inc., Santa Clara, Calif., a pioneer and leading supplier of piezoelectric drop-on-demand inkjet products used for industrial applications. The company is helping drive a revolution in inkjet technology to support a new generation of products used for industrial product decoration and materials deposition.

The Santa Clara, Calif.-based company offers the Dimatix Materials Printers (DMP). This includes a line-up of materials deposition systems designed for micro-precision jetting of a variety of functional fluids onto virtually any surface. All DMP systems employ single-use cartridges that researchers can fill with their own fluid materials to minimize waste. Also, it helps in reducing the cost and complexity associated with traditional product development and prototyping.

“Our DMP-5000 and DMP-3000 printers feature a temperature-controlled vacuum platen that can accurately register, maintain and thermally manage substrates during printing,” says Chuck Griggs, vice president, Applications Engineering of FUJIFILM Dimatix, Inc. “These substrates include plastic, glass, ceramics, and silicon. As well as flexible substrates ranging from membranes, gels, and thin films to paper products.”

Substrate and Ink Trends for Membrane Switch

Bolding says that the most common inks that the manufacturers use in the industry for membrane switches are solvent inks. Primarily they use polyester or sometimes vinyl resin-based. However, this depends upon the substrate.

"However, sometimes the manufacturers also utilize UV inks. In order to obtain a good through cure, a well-designed UV curing system typically with metal halide doped mercury bulbs work best,” Bolden says. “The flexible circuitry predominantly uses thick film inks containing silver flake particles. UV curable dielectrics printing act as an insulating layer between traces that may come into contact with each other."

Bolding states that MacDermid Autotype supplies globally specialty print treated hard-coated polyester films for the graphic overlays.

"We specialize in producing films to fit the diverse applications where a membrane switch is utilized," he says. "The finish to the overlay is a chemically resistant textured finish. They offer Fine or matte textured surfaces. Also, providing finishes incorporating anti-microbial resistance for use in medical applications or in environments where surface cleanliness is critical."

One of the major ink suppliers in this area is Nazdar in Shawnee, Kan. The company was one of the first to develop viable LED-curing screen printing inks for the membrane overlay market. The inks came into existence to provide adhesion to a variety of substrates.

Nazdar Screen Ink Production

Laura Maybaum, screen-ink-product manager at Nazdar says that one trend she is seeing is the use of low heat mercury vapor curing systems. Or UV LED-curing systems that reduce or eliminate heat-related issues with the substrate, multi-layer printing, and yellowing.

"Reduced heat in the curing process, reduces heat-related issues with substrates," Maybaum says.

She adds that thanks to improvements in raw materials, the range of UV-curable inks for this market has expanded substantially. Bringing benefits such as high resolution, durability, and better workflow to the process.

"Familiarity to substrates, inks, and other process materials that manufacturer use in membrane switch may be applicable to graphics and sign applications," Maybaum says. “For example, membrane switch inks should be compatible with aggressive adhesives. This compatibility may lend itself to using printable adhesives instead of tapes or glues. Th in-molding decorating can also use some of the membrane switch inks. This process could lend itself as an alternative to thermoforming and provide a further reach into niche industrial printing.”