Advantages of membrane keypads in the food, laboratory and medical sectors

Membrane keyboards are still justified

Specialist articles also in the electronics industry 08/2020: Article as .pdf >>

In the food, laboratory, and medical sectors, membrane keypads continue to play an important role today due to their closed surface, chemical resistance, and impermeability to liquids and dust. N&H Technology, based in Willich, Germany, has been manufacturing membrane keypads for all industries for over 20 years.

Preferred choice not only in the medical field

Especially in devices with a small number of functions, which at the same time require good visibility and are in constant user interaction membrane keypads the preferred choice. In the medical field, these are, for example, 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 is rather disadvantageous.

Design options for membrane keypads

membrane keypads can through the diverse design options with a user-friendly and intuitive interface By using tools, the membrane keypad can take on almost any shape. In addition to the conventional 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 metallic effects , for example, brushed stainless steel or anodized aluminum. Another advantage over display solutions is that the printed surface and optionally integrated LED status indicators can also be viewed from a 180° angle.

Membrane keyboards impress with their flat design

The flat structure of a membrane keypad consists of a film composite made up of at least four films: the decorative film, the upper and lower switching film and a spacer film. The decorative film is the top layer of the keyboard and is made of polyester or polycarbonate. It is printed on the back to ensure the highest possible protection against abrasion.

Compared to other flexible materials, polyester is particularly convincing with a long life cycle of over one million switching cycles, very high abrasion resistance and very good resistance to chemicals.

For applications in the medical field and areas with high hygiene requirements, the front film can be coated with an antibacterial coating. This antimicrobial polyester kills or inhibits bacterial growth and provides constant protection against bacterial contamination.

Functional elements of a membrane keypad

The functional elements of the membrane keypad are the lower circuit membrane with the printed conductors, LEDs, switching points and the connection lug located on it, as well as the upper circuit membrane with the contact surfaces. The spacer foil acts as an insulator, separating the upper and lower switching foils or, in the case of a version with metal snap-action discs, acts as a fixing foil.

Illuminated membrane keypads

Backlighting options vary depending on the application requirements. Illuminated keypads are particularly necessary in the often darkened working environments of the medical field, allowing key functions to be easily located. LEDs can be easily integrated into the existing keypad or, if necessary, incorporated into an additional LED keypad.

Special adhesives and sealing materials are used to ensure the functionality of the LED even in harsh environments with, for example, strong vibrations. Backlighting of a membrane keypad can be achieved through the use of LGF (Light Guide Film) The typical flat design and flexibility are retained. With LGF technology, LEDs are placed on the edge of a very thin (0,1 to 0,2 mm), highly refractive film.. Due to the high light refraction, depending on the size of the membrane keypad, very few LEDs for homogeneous illumination are required for operation.

The Backlighting of each key can be done in various colors. Unlike EL backlighting, LGF technology does not require a high-frequency AC voltage source. A special feature is the disappearing lettering. This is a lettering that is invisible when the keyboard is unlit and only becomes visible when illuminated. This allows a clear on/off mode to be signaled.

Tactile feedback

Another benefit of the membrane keypad is the tactile feedback of the key function to the user. Snap domes ensure Actuation for a noticeable tactile feeling and, depending on the design, an audible click. This direct feedback can help reduce file entry errors. The metal snap domes are available in various sizes, shapes, and actuation forces and are preferred for applications with a high number of actuations.