Membrane keyboard manufacturing

Membrane keyboard

The membrane keyboard is a popular HMI solution in the modern electronics industry.

It is a widespread and popular design option for switching and control units in the fields of instrumentation, medical technology, automotive and automation.

Advantages over other traditional solutions:

Excellent for use in extreme conditions. Extreme applications include outdoor, high-altitude and humid environments. They withstand extreme temperature and pressure fluctuations.
It is easy to install (strong self-adhesive layer can be attached to most surfaces), and takes up little space on the front of the device (total thickness can be implemented from 0.5 mm).
The design of an electrical control panel is simplified by the internal circuit layout of the keypad.
Cost-effective solution for large and medium series production.
It provides a hygienic, easy-to-clean user interface.
Long lifespan, 1 million - 5 million keystrokes.

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Gallery

General structures

Basic type 'A' (snap-on contact, embossed)

One of the most common designs. The click effect of the buttons provides clear switching feedback, and thanks to the embossing, they are easy to touch for the user.

Buttons: 'Click' effect buttons, equipped with metal snap contacts. Switching force can be set between 1N-4N.
Switching type: Resistive.
Embossing types: Frame or surface embossing (see embossing).
Thickness: from 0.55 mm.
Illuminated buttons: No.
LED installation possible: Yes.
Connector type: Any (see connections).

Basic type 'B' (snap-on contact, no embossing)

Similar design to type 'A', except that the buttons are not embossed.

Buttons: 'Click' effect buttons, equipped with metal snap contacts. Switching force can be set between 1N-4N.
Switching type: Resistive.
Embossing types: No embossing.
Thickness: From 0.85 mm.
Illuminated buttons: No.
LED installation possible: Yes.
Connector type: Any (see connections).

Basic type 'C' (touch type)

Its design is very similar to resistive touch panels. When touched, the conductive layer on the top decor foil closes the circuit of the contact foil. Modern looking, extremely thin, light-transmitting and affordable design.

Buttons: Touch buttons.
Embossing types: No embossing.
Thickness: from 0.5 mm.
Light-transmitting buttons: Yes.
LED installation possible: Yes.
Connector type: Any (see connections).

'D' basic type (dome embossed, foil-switch contact)

The thick decorative foil has dome embossed buttons that provide a tactile feel. This solution saves on metal snap-on contact elements, which can be a significant cost element for large-scale and high-button-count products.

Buttons: ‘Click’ effect, arc-embossed buttons. Switching force can be set to around ~1N.
Embossing types: Dome embossing.
Thickness: from 0.5 mm.
Illuminated buttons: Yes.
LED installation possible: Yes.
Connector type: Any (see connections).

'E' base type (capacitive keyboard)

One of the biggest advantages of capacitive keyboards is that they are extremely resistant and vandal-proof, as they do not contain any moving parts. Different types of capacitive sensors are integrated into the keyboard, the changes in their capacitance can be decoded with an appropriate circuit.

Buttons: Touch, capacitive sensors.
Embossing types: None.
Thickness: From 0.4 mm.
Backlit buttons: Yes.
LED installation possible: Yes.
Connector type: Any (see connections).

Graphic solutions

Graphic design is made using screen printing and digital printing technology. Design foils can be created with a wide variety of surface structures.

Foil types, according to their surface

- Foils with a matte-velvet surface structure

- Fine-structured foils

- Glossy foils
- Anti-glare or anti-reflective films

Overlay foils can also have high scratch and chemical resistance, UV stability and an 'anti newton ring' coating.

Display windows, LED windows

- Clear transparent

- Matte transparent

- Colored

- Darkened

Or a combination of these.

Unique QR and barcode

Printing serial numbers, QR codes, bar codes, and other unique identifiers on keypads, instrument front panels, and industrial labels.

Embossing

It is possible to emboss buttons or other design elements. Embossing can be a design element or a functional solution. Embossing is done by special thermoforming using unique clichés and tools.
Characteristic types:

Pillow embossing

The height of the embossing is typically 0.3 mm (this is already easy to feel, easy to implement, and can be implemented with a basic keyboard structure), which can be modified based on customer requirements.

Arc embossing

The height of the embossing is typically 0.5 mm (this is already easy to touch, easy to implement, can be implemented with a basic keyboard structure, and provides a suitable switching feel), which can be modified based on customer requirements.

Frame embossing

Designs according to IP protection

The IP protection of the keyboards is significantly influenced by the adhesive layer on the back and the design of the outlet. These IP protections are for informational purposes only and represent the maximum available level!
The level of protection also depends significantly on the type of self-adhesive and carrier surface and their compatibility, surface preparation, insulation of the inlet cutout after installation, and correct installation.
Basic designs influencing IP rating:

IP63 design

A filling foil is mounted under the outlet. This design ensures cost-effective production, however, there are 2 gaps (0.3-0.6 mm) at the junction of the flexible outlet of the keyboard and the edge of the keyboard. These gaps can be closed by building a recessed, precisely fitting nest, thus improving the IP protection degree.

IP67 design

The flexible cable of the keyboard is passed through the bottom adhesive layer and is led out. This involves additional manufacturing steps, but significantly improves the IP protection of the product.

IP68 design

The design is the same as the IP67, with the difference that the entire keyboard gets an additional frame that closes the edges 100%, thus maximizing IP protection.

Built-in LED and backlighting in the membrane keyboard

It is possible to install various LEDs in the keyboards. This saves drilling the enclosure, integrating LEDs into the PCB, fixing the PCB to the cover with spacers, and other additional assembly work.
We also offer special, low-voltage, ultra-thin homogeneous backlight solutions!

Connector types

The membrane keyboard can be connected to the control electronics via its electrical terminal. When selecting the connector type, the available space, possible mechanical stress and the cost-effectiveness appropriate for the given series must be taken into account.

FFC connector

One of the most common solutions. Cost-effective and takes up little space. Can be plugged into a suitable PCB-built FFC-ZIF connector. Pitch can be achieved from as little as 0.5 mm!

2.54 pitch connector housing

Crimped, 2.54 mm pitch female header. Available in lead or gold plated versions.
Easily connects to any 2.54 mm pitch pin header.

Ribbon cable

Possible termination type for PCB and FPC based keyboards. Its advantage is that it can be soldered directly to the control electronics, making it a space and cost-saving solution.

Soldered connector

This design is possible for PCB and FPC based keyboards. It is an advantageous solution to have a detachable connection for assembly and service.

Pocket membrane keyboards

You can insert a regular paper label into pocket keyboards, allowing you to individually configure the keyboard and modify its labels.

Bottom adhesives

Choosing the right adhesive is very important. If you choose the wrong one, the keyboard may detach from the surface and the expected IP protection will not be achieved. Main considerations:

Surface energy of the substrate surface
- Low surface energy materials: e.g. polyethylene, polypropylene, powder coated surfaces. (recommended adhesive: 3M 300LSE) - Medium surface energy materials: e.g. polyester, polycarbonate, ABS, etc. (recommended adhesives: Ritrama, Lohman, 3M 467MP, 3M 468MP) High surface energy materials: e.g. Aluminum, copper, steel, etc. (recommended adhesives: Ritrama, Lohman, 3M 467MP, 3M 468MP)

Roughness of the substrate surface
It is necessary to select a self-adhesive film with a thickness appropriate to the roughness. If the Rz value is low (shiny, mirror surface), then a 10 micron self-adhesive film is sufficient. (recommended self-adhesive: Ritrama, Lohman (3M 300LSE for LSE)) In case of a higher Rz value, a self-adhesive film with a thickness of up to 130 microns may be necessary. (recommended self-adhesive: Lohman, 3M 467MP, 3M 468 MP (3M 300LSE for LSE))

Removal/replacement frequency
Some adhesives can be removed without leaving any adhesive residue, while others leave an extremely stubborn adhesive residue on the substrate that is very difficult to remove.

Our company stocks products from the following self-adhesive manufacturers:

Electrical characteristics

Membrane keyboards can be implemented with any circuit, however the required number of layers can be a significant factor affecting the price. Typically, the following connections, or a combination of these, are used:

Matrix circuit

This is a common connection for keyboards with many buttons. The advantage is that a large number of buttons can be handled with relatively few connection points, meaning the width of the terminal will be smaller, and this solution is more space-saving. The number of terminals = number of rows + number of columns, the number of buttons = number of rows * number of columns. The disadvantage is that jumpers or a multi-layer keyboard must be created, which increases production costs.

Common point circuit

Each button is connected to 1 common point, and each button has an independent connection point. Number of terminals = number of buttons + 1. Recommended for keyboards with a smaller number of buttons. The advantage is that the keyboard is cheaper to build due to the simpler structure.

Independent circuit

Each button is wired and routed separately, independently of each other. It is only recommended if the buttons need to be completely isolated from each other, there should be no common potential.

Basic electrical properties
These parameters may differ and be modified after prior consultation.

R s (switching resistance) < 100 Ohm
I max (maximum load capacity) 100 mA
U max (maximum voltage) 50V
P max (maximum dissipated power) 1 Watt
Built-in LED current: < 20mA

Download membrane keyboard technical data sheet and user manual: