Since the first microwave ovens appeared in the 1960s, membrane switch overlays have become a ubiquitous part of our daily lives.
Though we seldom think about them they are present on standard household appliances, phones and computers, and found in medical, machinery and automotive applications - in fact pretty much everything which requires the pressure of a finger to activate it. You use them to enter function commands and they then flex back to their original position, once you release the pressure.
Today, membrane switches are manufactured globally, and are in use everywhere on a daily basis. They are unique because the manufacturing process requires both circuit printing and graphics printing .
Substrates common to the industry are predominantly Industrial PET (polyester) foils for the circuit layers and for high demand professional membrane switch overlays. For low cost, less demanding applications polycarbonate is used as a lower cost alternative for the graphic overlays, The membrane switch overlays are reverse printed on the rear side of the industrial film.
After all ink layers have been applied, switches are assembled, and physical components are attached and connected to complete the final switch assembly, which can contain electronic and graphic printed layers.
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Océ Product Manager for Display Graphics, Steven Badger, with a membrane printed on the Océ Arizona flatbed series. |
Screen printing has been the print method of choice for many years because of its accuracy and ability to handle the delicate substrates involved. This is slowly changing though, with many manufacturers faster and less expensive digital solutions, offering additional options. True flatbed printing is mandatory, given that several layers are printed on top of each other, calling for precise, repeatable thicknesses, which makes accurate positioning of the substrate critical. Hybrid or roll-to-roll printers, which move the overlay film while printing, can’t deliver this accuracy.
Océ Product Manager for Display Graphics, Steven Badger, says that cost comparisons conducted in Europe show that membrane switch overlays printed on the company’s flagship Océ Arizona flatbed printers can be produced up to 40% faster than by normal screen methods and around 16% cheaper.
“Océ began looking into MSO printing after it received expressions of interest from a number of MSO suppliers in Europe. Given the possible market opportunities, this led Océ to conduct MSO printing trials with the Océ Arizona UV flatbed.
“As the printer uses a vacuum system to hold the substrate firmly on the table during the printing, this was initially a quite difficult process. The thin substrates were pulled out of shape by the existing vacuum, which was designed for far more robust surfaces, such as cardboard and polystyrene. Further trials remedied this and the thin membranes now sit absolutely flat on the printing table while remaining firm and allowing the extremely accurate printing process to proceed.”
The Océ Arizona is ideal for small to mid level production runs around 2,000 pieces, able to print all layers digitally with up to 50,000 switch actuations. While this would be insufficient for some applications, a combination of screen and digital, able to perform more than a million actuations, is also practical with the same speed advantages and reduced costs.
Says Badger: “”Using digital production small and mid-size production runs can be produced faster and more cost effectively, with a significant reduction in the turnaround of jobs. Prototyping can also be offered faster and more cheaply.
“Digital printing meets the industry’s demand for extended graphical demands, such as more colors, gradients and the possibility of using images, logos and pictures
“Additionally digital printing is done unattended, freeing up operators for other tasks and is environmentally more friendly than screen printing. The digital inks used for MSO production are Océ IJC256 which provide excellent adhesion and meet the ASTM F1842-20 standard.
Badger says that Océ now has nearly a dozen MSO customers internationally and believes there is a strong market for MSO in Australia.
“We have the results of international tests which prove the speed and cost advantages over screen printing available for producers to study to see if those same advantages could be duplicated in their own manufacturing processes. In one significant test, using 300 overlays in seven layers with five colours and two white flood fill layers, the screen process was compared to the digital process.
“The digital process, using the Arizona, on the same sample production took fewer overlays, took only 70% of the time and 84% of the cost. A hybrid process, using both screen and digital was even less expensive.
“I think this is an idea whose time has come,”
Océ Australia
www.oce.com.au
