Membrane switches – customized

Folientastatur mit Display

For over 20 years we have been realizing customer-specific membrane keyboards and decorative foils for all industries and applications. We advise you comprehensively on the equipment requirements, the technical features and offer active support in the construction. In addition to the single membrane keyboard, we also manufacture complete input solutions with touch displays and carrier plates or suitable plastic housings.

Due to the extraordinary variety of design options, membrane switches can be used in almost every type of electronic device. There are nearly no limits to the ergonomic and design requirements. Membrane switches are used in areas, where dirt and water resistance or easy cleanability are required. They are also used when a compact design or a small number of items is required, due to comparatively low tool costs. You can choose from a variety of constructions of varying tactility and a wide range of viewing windows, screens and lighting options. In addition, we offer the patented Duraswitch technology.

Laser cutting for small quantities and development samples


For short-term requirements parallel to series production or functional development samples, we offer the production of membrane keyboards without tools by using laser cutting.
Without the tools, the delivery time is halved to 3 weeks. Even smaller special series and individualized printing of existing variants can be implemented flexibly and promptly. Laser cutting offers the perfect complement to the established punching process as the standard for medium and large series productions.
 
 

ReferencesAdvantagesConstructionOptionsDesign

References

Advantages

  • low weight, space saving
  • backprinting of the film for a robust, individual design
  • individual tactility
  • easy integration of LEDs, buzzers, sliders, controllers, rotary encoders
  • Integration of viewing windows for combination with displays
  • dustproof and water resistant, resistant to chemicals (solvents)
  • easy to clean, hygienically closed user interface
  • over 1 million life-time cycles
  • EMC shielding possible
Construction
Aufbau einer Folientastatur

A keypad consisting of a plurality of individual layers which are superposed on each other.  By default, there is a membrane keyboard from 5 basic foils: decorative foil, upper & lower switching foil,  a spacer film and a adhesive foil.

The decorative foil is made of polyester or polycarbonate and ensures the highest possible protection against abrasion. For applications in the medical field and areas with high hygienic requirements, the front foil can be equipped with an antibacterial coating. Also UV-resistant polyester for outdoor use is possible.

Functional elements are the lower circuit foil with the conductor tracks, switching points and the terminal lug located thereon, as well as the upper switching foil with the contact surfaces which lie opposite the switching points on the lower foil. The upper switching foil can be dispensed if it is replaced by metal domes, or the contact surfaces are printed directly on the decorative foil.

For special applications and complex circuits, the lower switching foil is made of polyimide (Kapton) instead of polyester. A hard printed circuit board made of FR4 is suitable for circuit design and at the same time acts as a carrier plate with mounting screws or sockets. The spacer foil as an insulator separates the upper and lower switching foil; in a version with metal domes, it has the task of fixing foil.

 
Tactility

Metal dome


Metallschnappscheiben für eine Taktile Rückmeldung
Metal Domes different sizes and shapes

For a striking tactility and higher actuation force metal domes can be used. When the metal dome is actuated, it snaps downwards and establishes contact between two printed circuits.

Metal domes can be used for more precise tactility and higher actuation force. When the metal dome is actuated, it snaps down and establishes contact between two conductor tracks. Metal domes have different sizes and shapes. The actuation force is 40g – 700g depending on the model, higher forces are possible on request. The service life is up to 10 million cycles.

For illuminated membrane switches, metal domes with a central recess are used. The LED is placed directly under the recess.

A special metal dome construction is available for double actuation. Double-action metal domes have two actuation forces and can also close two circuits. The first closing is done by pressing lightly, which does not yet give any tactile feedback. The second closure takes place when the metal dome is pressed again with corresponding tactile feedback. An example would be the focusing of a camera when the shutter button is lightly pressed and the eventual shutter release when the button is pressed all the way down.

 

Embossing


Prägungen einer Folientastatur
Embossing Styles

Membrane switches without metal domes may also have tactile feedback using dome embossing design. The dome embossing can be done in the decorative film as well as in the upper switching film. For a stronger operating force and tactility, even both of the two films can be shaped.

  • Dome embossing: This embossing is not only suitable for round, but also for square buttons.
  • Frame embossing: A raised edge is formed around the key surface.
  • Terrace embossing: The entire button surface is raised. This embossing is usually used for small buttons.
 
Protection
Folientastatur mit Sichtfenster und partieller EMV-Abschirmung
Membrane keyboard with viewing window and partial EMC shielding

EMC protection:
All keyboards can be provided with appropriately printed masks to comply with the requirements for electromagnetic shielding.

IP ratings:

To ensure use in extreme environments that are dust or water-intensive, IP67 rated protection is required.

Lighting Options

LEDs can be easily integrated into membrane keyboards by the integration of an additional LED switching foil. Special adhesives and sealing materials are used to control the function of the LED even in a harsher environment with e.g. ensure strong vibration.

Folientastatur mit LGF Hinterleuchtung

Backlighting of membrane switch can be done by using LGF (Light Guide Film). The typical flat design and flexibility are retained. In the LGF technology, LEDs are used on the edge in a very thin (0.1 – 0.2 mm), highly refractive film. Due to the high refraction of light, only very few LEDs are required for homogeneous illumination. The backlighting of each button can be done in different colors.

Folientastatur mit LGF Beleuchtung
Backlighting of membrane switch with LGF

Also with the LGF technology, a “disappearance effect” can be realized. The keyboard symbols are only visible when the HMI device is switched on.

Folientastatur mit Verschwindeeffekt
Memebrane Switch with disappearance effect
 
Rotary encoders / signal transmitters / capacitive control
Folientastatur mit Drehgeber und Piezo-Buzzer
Membrane witchwith rotary encoder and piezo buzzers

The Duraswitch technology enables the integration of pushbuttons with tactile feedback, rotary encoders (rotary encoders and analog potentiometers), and cursor controls. Compared to separate solutions, the integrated solution is much more cost-effective.

In addition, very flat piezo buzzers can be integrated into the membrane keyboards.

Senso-Touch: Kapazitive Lösung für Folientastaturen
Senso-Touch: capacitive solution for membrane switches

A capacitive solution with a closed surface is recommended for hygiene-sensitive areas. Controllers, rotary encoders, and cursor keys can be implemented in this way and replace the classic mouse as an input unit. Another advantage is an increased service life since there is no mechanical wear. The user can experience acoustic or optical feedback through the integration of LEDs or signal transmitters. An integrated solution can be more cost-effective than separate solutions, as there are no wiring and soldering processes and the assembly time is reduced.

 
Touch Panel & Windows
Folientastatur mit Display
Membrane Switch with Display

With a combination of modern display and proven keyboard technology, the advantages of both worlds can be played out effectively and economically.
There are various realization techniques for the integration of displays. The simplest variant is to punch out the display area, another is to integrate a viewing window into the membrane switch. Depending on the requirements and optical design, versions such as glossy, matt, anti-reflective, scratch-resistant, UV-resistant, and colored can be individually specified.
If there is a touch panel under the viewing window, a highly transparent adhesive layer with a light transmittance > 99% is used. This special process avoids the formation of Newton’s rings. The bonding is carried out in a cleanroom.

 
Metal plate
Folientastatur-mit-Display-auf-Frontplatte
Membrane keyboard with display on aluminum carrier plate

The membrane switch can be mounted on tailor-made carrier plates for reinforcement. Aluminum plates are used as standard, possibly with press-in bolts for easy assembly. The membrane keyboard is glued to the carrier plate over its entire surface. A complete assembly with display and printed circuit board is also possible. Depending on the installation situation, seals can also be integrated directly.

Silk Screen & Digital Printing
Muster von kundenspezifischen Folientastaturen
In addition to the screen printing process, there is also digital printing, which is preferably used for color gradients. In addition, it is particularly suitable for the production of prototypes and one-offs as well as for small series, as there are no costs for the production of the screens.
 
Silicone keys / rubber design
Folientastatur mit Silikonabdeckung und Epoxy Coating
Membrane switch with silicone keys / rubber design and Epoxy Coating

The membrane switch is as usual provided with a polyester decorative film, but the buttons are made of silicone. The keys have a grippy key surface, which gives the feeling of a high-quality keyboard. The key shape can be realized in various geometries. Alternatively, the decorative film is completely replaced by a silicone layer. This allows for outstanding buttons with free shaping, guide elements such as offset rings around a key, Braille lettering or cursor keys. At the same time, the surface is upgraded visually and haptically.

 
Epoxy Coatings
Folientastatur mit Epoxy-Tasten (Doming-Technologie)
Membrane Switch with epoxy keys (Doming-Technology)

High-quality three-dimensional design elements can be realized with epoxy. Instead of a “normal” embossing, epoxy material is applied to the button, which creates a particularly high-quality and glossy surface due to its transparency. The epoxy design can be used with most membrane keyboards.

 
Surface Finish

Membrane switches can take on a variety of surface structures.
In addition to high gloss and satin matt, metal look effects such as brushed stainless steel or anodised aluminum are also possible thanks to specially embossed foils

Folientastatur in Metall-Optik
Metal-look membrane switch
Folientastatur mit Hochglanzoberfläche im Vergleich zu Matt
High gloss surface and matte surface

 


Folientastatur Maschinensteuerung Membrane switch for a machine control
 
 

Suitable housing, cable assembly, display?

In addition to the membrane keyboard as an input element, we also supply suitable housings, cable assembly, and the pcb , etc. – True to our guideline – single source supply !