Membrane switch designers throw around quite a few industry terms. Some of these terms refer to design and printing technologies that serve various purposes in membrane switch design, such as digital printing and screen printing. These processes provide visual elements for the graphic overlay, aiding usability by creating visual cues and labels for different functions on the user interface.
You might also hear designers discuss conductive ink, which at first may seem like an option for the graphic overlay. But actually, conductive ink is used in the circuit layer. Here’s a closer look at these common membrane switch technologies and how they’re used.
Digital printing doesn’t refer to the use of special inks or substrates, but is a term that describes the process of sending information from a device, such as a computer or portable storage device, to the printer using digital files such as PDFs or files created by graphics software. The information is reduced to binary code for storage and reproduction.
With substantially lower production costs, digital printing has replaced traditional screen printing in many markets. The streamlined process of digital printing has enabled print-on-demand services. As there’s no need to create a screen for each color, it’s feasible to print a single copy rather than the higher production often required for screen printing.
Digital printing is ideal for membrane switch design in that it enables effects beyond those which traditional printing methods can provide, such as 3D graphics, textures, fading, and other effects. Additionally, the cost-effectiveness of this method results in lower costs to product manufacturers, which can then be passed on to end consumers.
Digital printing is an evolving field. New methods are always being tested and developed to increase the compatibility of digital printing to accommodate specific needs in various fields. It’s not a new concept; digital printing has been around for nearly three decades, but as technology advances and digital printing methodologies evolve to keep pace with market demands, it has become the printing method of choice for a great many applications. Today, laser printing has emerged as the digital printing method of choice in many cases, as color laser printers emerged in the 1990’s and 2000’s at competitive prices, making laser printing a viable option for business and consumer markets.
The screen printing process involves a woven mesh which is used to support an ink-blocking stencil to produce the desired shape. Screen printing is a printing process commonly used to apply ink to substrates such as t-shirts, vinyl, wood, and other materials.
Screen printing is a more complex process when multiple colors are involved, although several screens can be used consecutively to create a multi-colored image. This technique has been dated back to China during the Song Dynasty (960–1279 AD).
Membrane switch production traditionally relied on screen printing to print the circuit directly onto the substrate, a process which often uses silver or carbon conductive ink. Screen printing is still used in many membrane switch applications, although the rise of digital printing has offered a number of flexible alternatives and options, particularly for printing graphic overlays. Additionally, as batch volume is trending towards lower counts of 100 parts per week instead of the more traditional 1,000-part runs, screen printing poses challenges in maintaining profitability at this level of production, pushing membrane switch manufacturers towards more cost-effective digital printing options.
Still, screen printing remains a frequently used printing method in membrane switch applications. In some cases, screen printing will be used on some components, such as the circuit layer, while digital printing may be used for graphic overlays or other purposes to achieve the desired result. Both screen printing and digital printing are widely used in membrane switch applications; the ideal printing method depends largely on functional requirements, desired aesthetics and functionality, and cost considerations.
Conductive ink is commonly used in membrane switch production, so it’s a term you’ll likely encounter as you discuss membrane switch design and manufacturing options. Conductive ink, printed on a substrate, enables the resulting printed object to conduct electricity. Thus, it’s a useful material for printing the circuit components in membrane switches.
Screen printing is still the predominant printing process used to print circuits, simply because other printing methods have traditionally not been well-suited for printing viscous conductive ink. However, conductive ink is becoming increasingly compatible with varying printing methods as new techniques are tested and implemented successfully, and today, conductive ink can be used with printing methods such as flexo printing, pad printing, rotogravure, and now digital printing as well.
In 2013, for instance, a group at Georgia Tech demonstrated a method for developing inkjet-based circuits using conductive ink at dramatically lower costs and in substantially less time than the typical printing methods used with conductive ink. “The technique, called instant inkjet circuits, allows the printing of arbitrary-shaped conductors onto rigid or flexible materials and could advance the prototyping skills of non-technical enthusiasts and novice hackers,” according to the article.
There are a variety of types of conductive ink today, available commercially from several manufacturers. There are also a multitude of tutorials for do-it-yourself conductive ink brewing, such as this one and this one.
Cost-effective and easy-to-implement processes for printing circuits with conductive ink are highly valuable as conductive ink is used in a variety of applications beyond membrane switch manufacturing. Of course, lower production costs also means lower costs for producing prototypes and full runs for individual parts and complete membrane switch assemblies.
Each of these technologies plays an important role in modern membrane switch design and manufacturing. While your membrane switch design team can advise you on the best materials, substrate, and printing options for your product’s specifications and functional requirements, understanding these technologies and the role they play in the resulting membrane switch will help product manufacturers discuss design considerations with product design teams.
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