Article about the future of classic keyboards, membrane keyboards and silicone keymats - published in PC & Industry 10/2020 Article as .pdf >>

One might think that the conventional keyboard as an input element has its golden days behind it. In the telecommunications sector, it still ekes out its existence in landline telephones, while the mobile sector has had to be handed over almost entirely to smart display technologies. Because it is precisely through the integration of multi-touch screens that mobile end devices, where the use of a mouse and keyboard is rather impractical, can exploit their full potential.
The graphic visualization options create interactive communication experiences for the user in line with the company's corporate design. Logical visualizations and clear designs make even complex menu structures easy to use.
The requirement to make the interface between man and machine uncomplicated and intuitive is also driving further and faster development in the area of gesture control, eye tracking and voice control. User-related input errors are to be eliminated and the safety of operation increased. This also makes touch displays very popular for applications in home automation, kiosk systems or plant and machine control.
Google, Siri or Alexa
It remains to be seen whether, in five or ten years, people will still need a haptic input interface as we currently understand it. It's been a long time since we've pressed the play button to listen to music or, thanks to modern smart home integration, to turn on the light switch. A small request to Google, Siri or Alexa is enough. More AI-driven technologies will set the trend in the future.
While Generation Y and older grew up with a multitude of hardware systems that today's generations only know from hearsay and see the use of a keyboard as an everyday occurrence, future generations might smile at this as nostalgic use. Just think of the further development of calculating machines in the last 50 years or the development of the first mobile telephones - all not too long ago.
Keyboard status quo
In the status quo, however, input keyboards are absolutely justified and should be used as an alternative or supplement depending on the area of application touch systems and Co. can be viewed. Especially in devices with a small number of functions, which at the same time require good visibility and are in constant user interaction, proven input components such as membrane keyboards, silicone switching mats and pushbuttons remain the preferred choice - also in terms of costs. Because the financial expense for programming a graphical user interface between man and machine is a not inconsiderable factor. The following applies: Often not everything that is technically possible is also economical.
Classic keyboards - Can be used anywhere
membrane keyboards and silicone keymats Due to their closed surface, resistance to chemicals and their tightness to liquids and dust, they are currently used in almost all industries. In the medical field, membrane keyboards can be found, for example, in nurse emergency call systems, hospital bed controls, input keyboards for diagnostic devices and defibrillators, as well as other interfaces for patient care. Many of these input devices are also operated by inexperienced users, such as older patients, so that a complex touch input solution tends to be disadvantageous.
The keyboard is also evolving
Due to constant further development, the membrane keyboard but not to be seen as a pure switching solution. Rather, it is a combination of sophisticated design, special coatings and equipment extras such as integrated LEDs or an integrated touch panel. Membrane keyboards can be used with a user-friendly and intuitive interface thanks to their diverse design options. Through the use of tools, it can take any form.
In addition to the common screen printing process, digital printing is particularly suitable for the realization of color gradients and for prototypes and small series. Specially embossed foils can even be used to achieve metallic effects such as brushed stainless steel or anodised aluminium. Another advantage compared to display solutions is that the printed surface, as well as optionally integrated LED status displays, can also be seen from a viewing angle rotated by 180°.
Flat structure of the membrane keyboard
The flat structure of a membrane keyboard consists of a composite film made up of at least four films: the decorative film, the upper and lower switching film and a spacer film. The decorative foil as the top layer of the keyboard consists of polyester or polycarbonate and is printed on the back to ensure the best possible protection against abrasion. In comparison with other flexible materials, polyester in particular is impressive with a long life cycle of over 1 million switching cycles, very high abrasion resistance and resistance to chemicals.
The front foil can be equipped with an antibacterial coating for applications in the medical sector and areas with high hygienic requirements. This antimicrobial polyester kills or inhibits bacterial growth and provides constant protection against bacterial contamination. functional elements of membrane keyboard are the lower switching foil with the printed conductors, LEDs, switching points and the connection lug located on it, as well as the upper switching foil with the contact surfaces.
Backlight for membrane keyboards
Backlight options vary depending on application-specific requirements. In darkened working environments in particular, illuminated keypads are necessary in order to find important functions without any problems. Key embossing can provide additional support here. LEDs can be integrated very easily into the existing switch membrane or, if required, be integrated into an additional LED switch membrane. Special adhesives and sealing materials are used to ensure the function of the LED even in harsh environments with strong vibrations, for example.
The backlighting of a membrane keyboard can be done by using LGF (Light Guide Film). The typical flat design and flexibility are retained. With LGF technology, LEDs are placed on the edge in a very thin (0,1 – 0,2 mm), highly refractive film. Due to the high refraction of light, depending on the size of the membrane keyboard, only very few LEDs are required for homogeneous illumination. Each key can be backlit in different colors.
In contrast to EL backlighting, LGF technology does not require a high-frequency AC voltage source. A special feature are labels with a disappearing effect. This is an inscription that cannot be seen when the keyboard is not illuminated and is only visible when it is illuminated. This allows a clear ON / OFF mode to be signaled.
Tactile feedback from a membrane keyboard
Another benefit of the membrane keyboard is the tactile feedback to the user. Snap disks provide a noticeable tactile feeling when activated and, depending on the version, an audible “crack” sound. This direct feedback reduces file entry errors. The metal snap disks are available in a wide variety of sizes, shapes and actuation forces and are preferred for applications with a high number of actuations. Membrane keypads without metal domes can also have tactile feedback using an embossed design.
The embossing can be done on the decorative foil as well as on the upper switch foil. There is the possibility of button, dome and edge embossing with which very ergonomic button shapes can be realized. Embossed keys also have the effect of finger guidance. Keys get a particularly elegant look with a high-quality epoxy coating, which gives the key a three-dimensional appearance. The combination of snap disks and button embossing is common.
Silicone surface - the hybrid keyboard
In addition to the tried-and-tested variants made of different layers of film placed one on top of the other, there is the option of replacing the upper polyester film with a silicone surface. This silicone cover with keys can be laminated onto the circuit pack of a normal membrane keyboard as a pure actuation layer. The resulting hybrid of classic membrane keyboard and silicone keymat gives scope to combine the advantages of the individual input solutions in one keyboard. With the silicone surface, a three-dimensional design can be realized, a point at which the membrane keyboard is naturally severely limited. This makes it possible to have protruding keys with free shapes, guide elements such as separate rings around a key, Braille labels or cursor keys. At the same time, the surface is visually and haptically enhanced.
Combination of membrane keyboard and touch screen
If more functionality or a more complex operating menu is desired, a combination of membrane keyboard and modern Touchscreen solutions .
An additional keypad next to the touch screen promotes user-friendly menu navigation, as input commands or preset parameters can be called up easily and clearly. With appropriate programming, the fixed keys can also assume dynamic functions appropriate to the respective menu. For the version with touch screens or displays, viewing windows are integrated into the membrane keyboard.
Depending on the requirements, these can be specified individually, including matt, scratch-resistant, UV-resistant and colored. The membrane keyboard and touch screen are connected by a highly transparent adhesive layer with a light emission level of >99%. This procedure avoids the formation of Newton's rings.
A similar combination is also with silicone keymats possible. The key layout is sprayed directly onto the plastic front frame. This creates an optimal bond between the two components. In a further processing step, the display and electronics are combined with the resulting frame. The advantage of multi-component injection molding technology is that only one component has to be designed. This leads to significantly reduced investments and effort in production and quality assurance.
silicone keymat
The single, classic silicone keymat is still one of the most common switching elements in the electronics and automotive industries. It is used millions of times every day simply by operating a remote control. However, for medical applications, where good cleanability of input elements is required, the silicone keymat consist of a closed surface.
As the central component, it triggers a direct switching function on the circuit board underneath and determines the haptics, the visual and tactile impression and the electrical behavior via the integrated contact elements. In addition, the switch mat often have a sealing function on the circuit board. Their mechanical life of up to 10 million switching cycles makes it a long-lasting and almost maintenance-free input solution. It adapts to your design and is extremely flexible and space-saving. Keycaps made of metal and plastic, different key shapes and individual key colors can be easily implemented in a mat.
Individual keys or the entire mat can be illuminated using LEDs in conjunction with transparent silicone or integrated light guides. Thanks to a very precise 2K injection molding process, multicolored keyboard lighting can also be implemented. The process enables a light channel to be integrated into each individual button. This light channel is completely isolated from the rest of the transparent button and achieves a precise bundling of the light beam. Safety mats with this technology can now not only be backlit, the individual buttons can also display status information.
The force-displacement behavior
The force-displacement behavior of a silicone keymat can be customized to the requirements of the respective application. Actuation forces from 20g to 500g and actuation distances from 0,3 to 5,0mm are possible. The implementation options for the electrical contacts range from inexpensive, yet safe carbon printing to high-quality metal contact pills with a current carrying capacity of up to 2 A. The silicone keymat can demonstrate its advantages above all when large quantities are required. The high one-off costs for the tools make small series very expensive. Compared to equipment with individual buttons, however, they are also significantly cheaper in medium series.
Vandalism-proof input buttons
In the public space or local transport, as well as in industrial machine controls continue to play vandalism-proof input buttons a role that ensures precise and reliable operation, as well as quick traceability. The buttons often take on the function of a pure command transmitter, so that signals such as start and stop or forward and reverse movement are clearly communicated. With engraved or printed lenses, colored Satus LEDs and various housing colors, pushbuttons can also be given an individual look. Multicolored lighting even allows multicolored status indications to be displayed.
The buttons are made of robust plastic or metal and built directly into a front panel and a housing. Appropriate seals give them a protection class of up to IP68 / IP69K. The service life of up to 1 million cycles also makes the buttons very reliable. Offer a longer service life Piezo button, which are made of metal.
By eliminating a mechanical stroke, wear and contamination are almost eliminated. Service life of over 50 million cycles make them very reliable and virtually maintenance-free. They are used in areas where damage from vandalism is to be expected or where they are exposed to heavy environmental stress.
Miniaturization and design of keyboards
The increasing demand for miniaturization and design orientation plays an important role in each of these proven electromechanical operating units. Buttons with low installation depths, membrane keyboards with extensive equipment and a flat structure at the same time reflect the trend. The end devices should be flatter, thinner and lighter, but miniaturization in the input area is also reaching its limits, after all the devices still have to be usable by humans. Touch screens and voice control, paired with further developments in the field of artificial intelligence (AI), are becoming increasingly present precisely because they are already an essential part of our everyday lives.
In the status quo, however, innovative control elements with a combination of the proven electromechanical control units and modern touch panels continue to ensure exciting further developments, also with regard to an increasing addition of gesture controls.
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