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Membrane switches for highly specialized HMI applications

November 16, 2021

Source: Schurter

Design possibilities

The membrane switch has proven itself for many years as a very reliable solution for input systems. This technology still holds a strong position in many industries. Due to the adhesive layer on the back, integration is easy in carrier plates or in an enclosure. The design of a membrane switch is always customized and is possible in various shapes, sizes and designs.

There are numerous design possibilities to choose such as:

  • with or without tactility, printed switching contacts or mechanical snap domes
  • with flat or edge embossing of the touch points
  • fulfilment of IP65 degree of protection on the front side
  • design with interchangeable insert strips • selectable actuating forces
  • flexible or rigid printed circuit boards with electronics integrated on the rear side
  • carrier plates made of metal or plastic and mounting directly in the enclosure
  • with ESD and EMC shielding • printed RFID elements
  • various illumination options:
    • touch point, touch surface and backlighting
    • symbol printing in disappearing effect
    • night design (illumination modus in the dark): function keys are slightly illuminated and visible)

In combination with touchscreens

In touch panel solutions with a display, the membrane switch is a useful addition to the input system. Additional keypads next to the active touchscreen area increase user-friendliness and offer fast input with tactile feedback. Resistive touchscreens are integrated into the membrane switch structure via a viewing window using a highly transparent lamination. Depending on the requirements, various front foils with different surfaces (clear, anti-glare, scratch-resistant, UV-resistant) are available. For PCAP touchscreens with a glass surface, the installation is carried out with a window cut-out of the front foil. For use in food production, a full-surface lamination can be applied as a splinter protection film.

Challenges in demanding application areas

Medical applications

In the field of medical technology, special challenges arise for the control panels with regard to lighting options, EMC shielding, antimicrobial surfaces and chemical resistance. In order to meet these application-specific requirements, membrane switches are designed and used with optimal backlighting or solutions in night design without glare or overdriving of the lighting. Furthermore, touch point and touch surface illumination as well as symbol printing in the so-called disappearing effect are available. EMC shielding is integrated by means of an additionally printed foil that is laminated into the foil structure and contacted to the electronics. Antimicrobial surfaces are realized with films qualified for this purpose. The design and integration of chemically resistant membrane swtiches is carried out without dirty edges and facilitates the cleaning of the application.

Industrial applications

The membrane switch technology is a mature technology for industrial use and is also used in many applications in combination with resistive or capacitive touchscreens. Touch points are mainly used in HMI applications for frequently recurring input commands. Embossing the touch points allows them to be felt and makes it easier to control and set up machines and devices. The robustness of the design and the selected materials guarantee a long lifetime, ensure the IP protection rating and are thus resistant to environmental influences and aggressive media in the application.

Agricultural applications

Membrane switches for use as operator interfaces in an agricultural application are exposed to extreme conditions such as large temperature fluctuations with high humidity and other environmental influences. Suitable design solutions have been developed and qualified for these increased and special requirements. The design of these membrane switches enables qualified use in the harsh environmental conditions. This is realized by a suitable circuit structure, an additional printing of insulation layers in the relevant areas and with an optimal design of the conductor path. The penetration of liquids and aggressive media is prevented. This also allows for increased cleaning of the application.

Optimal production conditions

The number of membrane switch manufacturers, especially in the Far East, has increased considerably over the years. To ensure competitiveness, the production of high-quality input systems is carried out with automated processes. By relocating production to within Europe, a price level comparable to Asian manufacturers can be guaranteed.

Screen printing

By standardizing the print format and maximizing panel production, production time in the clean room has been minimized considerably. New equipment such as computer-to-screen (CTS) for screen production, a fully automated washing line for the screens as well as state-of-theart fully automated screen-printing lines minimize the costs for series production.

Assembly and final inspection

Production times in manufacturing are reduced through rationalized processes and automated procedures in the assembly lines. Even large quantities in series production can thus be manufactured cost-optimized in Europe. The 100% electrical and optical final inspection is carried out directly in the production line with test computers.

The perfect membrane switch solution for every application

A membrane switch is the face of your application and reflects your brand with its design. Membrane switch solutions can be customized – regardless of whether small or large quantities are involved. A high degree of automation in production ensures high quality and performance.

 

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