Compact, cost-effective and endlessly customisable!
No wonder the membrane switches can be found in almost all areas of application, whether in private households or in industrial applications. Various functions can be easily supplemented with a wide range of additional components: bright lighting, complex electronics, modern touch screen, robust carrier plates or elegant domed key features (GT technology).
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The classic membrane switches with contact spring (also called switching contact or clicker) ensures reliable, low-bounce switching behavior, regardless of the type of key actuation. The shape of the contact spring guarantees reliable contact with clear feedback. Various pressure points from 2N to 10N can be used, completely customised to your application.
The pressure point may vary depending on the technical design of the membrane switches.
If tactile feedback is not important for the application, a membrane switches can also be used without contact springs. We are then talking about a so-called silver-silver switches. Two layers of film printed with conductive silver trigger the function when the button is pressed.
Components and options
Assembly of a membrane switch
A membrane switch consists of several film layers and additional components that can be customized. The standard assembly of our flexible membrane switches always consists of 6 individual layers:
- Decorative film
- Dome retainer
- Circuit layer
The decorative film is made of durable polyester that is reverse printed with a custom design. The film can be enhanced with our GT technology or various embossing forms. The GT domes and embossing provide the user with easy finger guidance. For outdoor use or applications in medical technology, special polyester films with UV protection or antimicrobial properties can be used.
A wide variety of adhesives in variable thicknesses and adhesive properties are selected depending on the area of application of the membrane switch.
The dome retainer holds the contact springs (or metal domes) to the circuit layer so that they remain permanently in place. The underlying spacer optimally compensates for the height of the contact springs.
The circuit layer is the actual heart of the membrane switch. The entire electrical function is located on this layer: the printed conductor paths according to an individual circuit diagram, the assembled contact springs and LEDs.
The printed circuits on film can also be replaced by a printed circuit board if desired.
Carrier plates or housings give membrane switches more stability and can be easily added upon request.
Membrane switches with metal effect: light, durable, elegant!
Go for more individuality with the control unit of your application. A membrane switch is lightweight, reliable, durable and with the right design, it can be transformed into a elegant control unit.
The textured and reflective film surface resembles brushed metal and blends perfectly with other metal surfaces.
Dead front effect
A clean and slim design for your control panel.
Some HMIs control extensive functions and are therefore equipped with many keys, symbols and LEDs.
The so-called “dead front effect” ensures a clean user interface without having to sacrifice functions. A special printing process can be used to hide non-illuminated areas on the surface and display only actively illuminated areas.
Illuminated membrane switches
For the illumination of our membrane switches we use so-called SideLEDs (LEDs emitting light from the side). LED technology combined with a sophisticated switch design, allows us to illuminate large areas and individual keys in a variety of colors. This technology stands out above all with enormous brightness and long service life.
With our lighting technology we reduce installation depth for our customers to a minimum. With a keypad structure of 2.2 mm, the LED technology requires only slightly more space than an EL film. An optional light partition between the individual keys even allows each key to be illuminated separately. The use of bi-color or RGB LEDs also providesa virtually unlimited color selection. Since the assembly must take place on a printed circuit board, its unused back can be used for the assembly of series resistors and ICs or even the entire customer-specific circuit electronics.
Additional features for the decorative layer such as embossing or dispensed key domes (GT technology) are of course still an option. Capacitive keys are also illuminated with our SideLED technology.
SMD LEDs are used to integrate status LEDs in membrane keypads. These LEDs can be mounted on flexible film as well as on printed circuit boards. For integration on film, the LEDs are glued and held in place on the circuit layer. With an overall height of 0.35 mm, the LEDs can be easily integrated into the flexible assembly. Choose from an extensive color palette between mono, bi-color and RGB LEDs.
Only for areas of application with frequent vibrations, e.g. in vehicles, we advise against glued LEDs on film. Depending on the strength of the shock, the adhesive may come loose and the LED may lose its grip. In this case, we recommend mounting the LEDs on a printed circuit board.
Membrane switches with printed circuit board
A printed circuit board serves as a carrier for the membrane switch and replaces the circuit layer on film used for a flexible assembly. It is made of epoxy FR4 material and can be used as single/ double sided or multilayer PCB. The PCB gives the keyboard assembly more stability and the possibility to add more electronic components, both front and back.
We develop custom solutions with integrated microcontrollers and direct connection to the desired interface.
We specialize in the following interfaces:
- RS232, RS485
- CAN bus
- Profibus, Profinet (Gateway)
- I2C, SPI
- USB (generic HID)
- GSM (data connection via mobile radio)
- Analog digital interface (PWM, 0-10V, 4-20mA,…)
Carrier plates and housings made of metal or plastic
Membrane switches can be mounted on or recessed into carrier plates and housings. Preferably, the carriers are made of aluminum, stainless steel or plastic.
Front panels can be effortlessly integrated into the front of the device or machine by attaching self-clinching fasteners or holes. Customized housings protect sensitive electronics and complete the input system.
The surface of the carrier plate or housing can also be customized to your application: bare, anodized, chromated or brushed. A milled groove for seals ensures that your device is optimally protected from dirt or liquids.
You can also find out more about carrier plates and enclosures from TES Frontdesign, a member of our HK technology network, or from our partner OKW Gehäusesysteme.
Membrane switches with touchscreen
The tactile feedback of a membrane switch can be combined with a touch-sensitive touchscreen. Both resistive and capacitive touchscreens can be integrated into the switch design. The touchscreen is connected to the membrane switch assembly via an adhesive frame or full-surface OCA bonding.
Membrane switches with slide-in strips
If the same membrane switches is used in different countries, the labeling can be solved using slide-in strips in different languages. So-called slide-in pockets are integrated into the switch assembly for this purpose. Via these pockets, the corresponding slide-in strips can be easily exchanged.
Membrane switches with double contact funcion
High safety requirements for control systems demand maximum reliability of the HMI. For example, a speed function (slow/fast) controlling a crane requires two distinctly different switching functions. Hoffmann + Krippner ensures this so-called double contact function. While the first switching level is activated at a pressure of approx. 7 N, the second level switches only at approx. 13 N. This means that two different actuating forces can be realized in one key.
Dispensed domes on the membrane surface on top of the keys (GT technology) reinforce the tactile feedback of both switching levels.
Membrane switches with key domes
We give flat membrane keypads domed key tops. This allows you to feel where the keys are located even during blind operation. For this purpose, we dispense a high-gloss plastic compound in the shape of a dome to the surface of the film, precisely above the keys. Our GT technology (GT= casting technology) gives the pre-printed design an additional elegant, glossy look.
Advantages of our GT technology:
- Extremely high mechanical resistance
- Pressure marks from hard objects “heal” without damage
- creative design possibilities, e.g. company logos, displays, LEDs
- user-friendly haptics with optimal finger guidance
- good tactile feedback
Membrane switches with embossing
For optimum finger guidance, film surfaces can be embossed up to 0.4 mm high in addition to GT technology. In the case of membrane switches with embossing, the decorative film is formed into the desired shape using appropriate tools, a vacuum and temperature.
You can choose from the following embossing shapes:
- Surface embossing
- Frame embossing
Integrated EMI shielding prevents radiation generated in the device from penetrating to the outside and influencing surrounding devices and interfering with their function. The penetration of external interference radiation into the interior of the device is also prevented by the EMI shielding.
To make our input systems electromagnetically compatible, an electrically conductive layer is integrated into the assembly of the membrane switch. For this purpose, a polyester film is printed with silver polymer and insulation over its entire surface, and one or more contact areas are printed with graphite. The EMI shielding is contacted via a separate connector, e.g. to the ground connection of the device.
For integrated displays, the radiation that occurs must be collected by transparent conductive layers. Thin metal grids cast into Plexiglas or conductive vaporized films or filter discs are suitable for this purpose.
Improved technology for less EMI radiation!
For some years now, electronics has evolved to the point where:
- almost no more radiation is emitted due to improved components and design rules in the configuration and PCB layout
- Newer displays do not produce significant radiation
- Control electronics of capacitive touch systems are already radiation-minimized
This means that subsequently added EMI shielding is hardly needed nowadays due to the further development of technology.
Sealed membrane switches
To ensure that no water or dirt can penetrate into the interior of the device, we use precisely dispensed gaskets. For this purpose, we use silicone-containing, silicone-free or conductive sealing materials.
Sealing of cable outlets is also possible. By spraying the cable outlet with silicone, no water or dirt can get into the inside of the membrane keypad.
More information about our gaskets.
UV protection for membrane switches
For devices that are exposed to UV rays in outdoor use, among other things, we recommend a UV-stabilized polyester film. This special film material prevents discoloration and fading colors.
The UV-stable film has a slight yellow tint. Therefore, color deviations may occur.
Antimicrobial film surface – hygienic for life
For hygienically demanding environments such as in medical and dental technology or in the food industry, we offer a specially developed antimicrobial film for the sustainable protection of membrane keypads against bacterial contamination.
This innovative film material combines
antimicrobial properties with a durable surface. The antimicrobial protection is directly integrated into the textured hard coating. This ensures an even distribution of the antimicrobial agent over the entire surface of the keypad, for its entire service life.
When microorganisms come into contact with the film surface, their cell walls are penetrated by the film’s protective agents. Cell functions are interrupted, and cell growth and reproduction are prevented.
We realize your design wishes using digital or screen printing. You can choose from a wide range of colors according to RAL-classic, Pantone or HKS. Even metallic colors for a very special effect can be easily implemented. We offer transparent viewing windows for displays or 7-segment displays, either clear or slightly textured.
The mechanics of the membrane switches are completely customised to your field of application. Anything from button sizes and positions, to connector tape options and mounting options, to tolerance specifications are individually coordinated with you.
You decide on the connection option for your membrane switches. Cable, connector, number of contacts and wiring diagram will be fully customised to your device.
You want electronics assembly?
We create circuit diagrams, PCB layouts and bill of materials for you or you can provide us your files.
Facts and figures
- Temperature: – 40 °C to 70 °C
- Switching current: (max.) 100 mA
- Service life: up to 1 million switching cycles
All technical data are not guaranteed properties, but may deviate depending on the customer-specific design.
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