Overlay foil manufacturing

Overlay foils

The overlay foil is a possible alternative to the membrane keyboard.

Their external appearance is similar to membrane keyboards.

The overlay foils consist of a special material graphic part and a spacer/self-adhesive layer. They hermetically seal the switch unit, thereby protecting the electronics, which often consist of microswitches mounted on the panel.

Advantages:

The favorable price and the protection provided by the outer foil.
Provides an aesthetic appearance.
With its mechanical protection, it increases the service life of the switch panel.
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 0.2 mm).
It provides a hygienic, easy-to-clean user interface.

Gallery

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.

Overlay foils with conductive layer on the back

A conductive layer (can be silver, carbon or a combination of the two) can be applied directly to the back of the front panel foils. This allows the front panel to directly connect the comb contact formed on the PCB without an integrated switching element.

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 cliches and tools.
Characteristic types:

Terassenprägung

Die Höhe der Prägung beträgt typischerweise 0,3 mm (dies ist bereits gut fühlbar, einfach umzusetzen und mit einer einfachen Tastaturstruktur umsetzbar), kann aber je nach Kundenwunsch angepasst werden.

Domprägung

Die Höhe der Prägung beträgt typischerweise 0,5 mm (dies ist bereits angenehm haptisch, einfach umzusetzen, mit einer einfachen Tastaturstruktur umsetzbar und vermittelt ein passendes Schaltgefühl), welche je nach Kundenwunsch angepasst werden kann.

Rahmenprägung

Die Höhe der Prägung beträgt typischerweise 0,3 mm (dies ist bereits gut fühlbar, einfach umzusetzen und mit einer einfachen Tastaturstruktur realisierbar), kann aber je nach Kundenwunsch angepasst werden.

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.