Digital printing offers a number of new alternatives in membrane switch technology

Membrane Switch Printing

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 plastic substrate using silver or carbon conductive inks. However, developments in UV digital printing technology open up new output options within this marketplace.

This complex looking membrane panel integrates a touch-switch domed key pad, membrane switches and touch-screen technology. (Image courtesy of Hoffmann and Krippner and MacDermid Autotype)

The technology was first introduced for use in microwave ovens as an alternative to bulky mechanical switch assemblies. Over the past two decades, membrane switches have evolved to become highly sophisticated and complex, electronic components. They now encompass multiple circuit layers, integrated display windows, embedded devices such as LED displays, high-definition graphics as well as touch screen technologies. They can be constructed with multiple circuit layers, and more elaborate graphic design features, such as domed key embossing, and are used in a broad range of products such as consumer appliances, vending machines, office equipment, and medical devices. 

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.

Digital Printing Making its Mark

Screen printing works well when larger volumes are required or high-performance, functional graphics are needed, but digital printing appears to be a growing option in some areas. 

“In the past few years digital printing technology continues to have a major impact on this market,” says G. Scott Wood, product manager at EFI VUTEk, Meredith, N.H. “There are a couple of factors that are driving that industry in the digital direction. More and more, the traditional users of those products are going to ‘just-in-time manufacturing,’ which is driving batch size down. So instead of batch runs of 1,000, they are now making 100 parts each week. With that print volume, it’s harder to make it profitable using screen printing systems. With digital technology, you can also run multiple jobs on one sheet, so you can optimize both the print surface and print time.”

The DMP-5000 is a large-format, non-contact, fluid deposition system capable of jetting a wide range of functional fluids using multiple FUJIFILM Dimatix fluid deposition printheads interchangeably. (Image courtesy of FUJIFILM Dimatix)

“Within a membrane switch, there are different components that need to be printed, including the underlying circuits, their casing and the graphics display on top,” says Hiroshi Ono, group product manager, Roland DGA Corp., Irvine, Calif. “To print directly on the underlying circuits, typically screen printing processes are employed. In fact, traditional screen printers have dominated this market. This is because the inks used to print the metallic, conductive items within the switch are very specialized, high viscosity inks that are not well suited for inkjet printing.”

Ono states that even though screen printing is most often used 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. 

“UV-cure printing technology is also used because it supports such a wide array of substrates, including the clear polycarbonates and clear polyester films used to produce membrane switch overlays,” he says. “Using a digital UV-cure printing device, you can achieve great image quality on these overlays while eliminating the manual labor and materials involved in screen printing.” 

This complex marine control panel uses an outdoor durable textured polyester overlay. (Image courtesy of Electronic Imaging, NZ and MacDermid Autotype)

“The bulk of membrane switch overlays are printed on a flatbed or cylinder press,” says Neil Bolding, manager, quality, technical and marketing at MacDermid Autotype Inc., Rolling Meadows, Ill. He points out that the business sector most closely related to this market from a signage perspective are labels and graphic overlays. 

“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 polycarbonate and rigid vinyls are used 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. 

“Additional resources and knowledge are required, for example design and electrical engineers, additional test equipment and possibly new production equipment,” Bolding says. “Manufacturing a membrane switch is more than printing a good looking graphic. What sets this business apart from most flat stock graphics is the print requires the long-term functionality associated with electrical circuits.”

These ruggedized control panels for use in mines employ textured polyester overlays (Image courtesy of Rowland Automation and MacDermid Autotype)

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 manufacturing has been moved overseas. Membrane switches are typically produced 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 and offer them their capabilities.”  

For membrane switch printing, he says that the UV-cure printer should feature white ink to support the clear media used for the overlays. 

Membrane panel printing with a digital printer allows for some versioning, as can be seen with these metal panels. (Image courtesy of Bex Design Services and MacDermid Autotype) 

“For example, Roland’s VersaUV line of UV-LED printers and printer/cutters features CMYK, white and clear inks, and is offered in a dual-white ink configuration for even brighter white text and graphics,” Ono says. “Roland’s VersaUV LEJ-640 64-inch UV-LED printer supports both roll and flat media substrates up to a half-inch thick, ranging from thin films to foam board and corrugated packaging materials. Having this broad media support can open up new markets for your business. In short, the more versatile your digital printing business is, the better positioned you are to branch out into new, profitable applications.”

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. 

“Just think about the number of products out there with overlays or touch pads on them,” Wood says.

The EFI Rastek T1000 UV flatbed printer provides solutions in specialty application markets like the membrane switch market where CMYK plus white printing are essential. (Image courtesy of EFI)

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, 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), which 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 and reduce 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.” 

Early in 2012, FUJIFILM announced added support for their Q-Class platform of drop-on-demand inkjet Emerald and Sapphire printheads to the range of printheads available for both the DMP-3000 and DMP-5000. This broadens the scope of the fluid deposition systems to support applications requiring precise large-feature fluid deposition such as conductive and non-conductive patterning and coating large surfaces with functional fluids from UV-curable light-emitting polymers to conductive and dielectric inks.

Textured polyester rolls ready for processing. (Image courtesy of MacDermid Autotype)

“By adding support for Emerald and Sapphire printheads on our floor-standing Dimatix Materials Printers creates new opportunities for applying inkjet technology to a broad spectrum of applications that were not previously feasible,” Griggs says. “The scalability of Dimatix Q-Class printheads, along with their excellent dot placement accuracy, channel-to-channel uniformity, low cross talk, and high productivity, adds an exciting and new dimension to the field of large-feature fluid deposition. These and other advances will allow manufacturers to apply the many advantages of piezo drop-on-demand inkjet technology to tap into the rapidly growing markets for printed, thin film and organic electronics, among many others.”

Substrate and Ink Trends

Bolding says that the most commonly used inks in the industry for membrane switches are solvent inks, primarily polyester or sometimes vinyl resin based, depending on the substrate being used. 

“However, UV inks are also widely utilized and 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 are printed 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. Fine or matte textured surfaces are offered, as well as 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 were developed to provide adhesion to a variety of substrates.

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 used 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. Some membrane switch inks can also be used for in-mold decorating. This process could lend itself as an alternative to thermoforming and provide a further reach into niche industrial printing.”

For shops looking to enter the market, Maybaum offers this advice: “Learn the requirements for the market, qualify the process carefully, and use the appropriate products. This more specialized market has very established players with a high level of competency. The ink is the small cost of the finished piece, so the entire construction has to be very thought out and of a high, consistent quality,” she says.