LGF Backlit Membrane Keypad Switch Design Guide

LGF Backlit Membrane Keyboard Switch Design Guide

Light Guide Film (LGF) Technology is a key component in the design of membrane keypad switches, enabling efficient backlighting. By guiding the light from side-emitting LEDs through a film, LGF achieves uniform light distribution across the keypad surface and can produce multiple color changes. This technology is especially suitable for compact, lightweight devices that cannot accommodate significant increases in thickness. Moving forward, as material sciences advance and manufacturing costs decrease, LGF technology is expected to find broader applications in various devices and smart home products.

Additionally, through WeGlow’s technology, LGF light guide films can be integrated with capacitive touch switches to offer more diversified solutions.

What is an LGF?

LGF is an optical film that directs light from LEDs to areas requiring backlighting. It can be designed in any shape to meet the lighting needs of keys and logos. Various LED colors can achieve unique lighting effects. LGF can be manufactured through printing or laser processes. WeGlow engineers can assist you in selecting the appropriate LGF light guide film.

Key Considerations and Design Points for LGF Membrane Keypad Switches:

• LGF sometimes causes light leakage and bright spots, but these issues can be addressed through engineering design changes.

• A single light source LED cannot provide different color changes to all keys in a backlight keypad simultaneously. If different keys require individual illumination or multiple color changes, each key must be equipped with its own LED.

• Typically, LGF light guide film layers slightly affect the tactile feel of keys, but this impact is minimal and can be mitigated through design modifications.

• In addition to keys, other patterns such as logos can also be illuminated with backlight. • There should be a significant distance between keys and between LEDs and keys.

• The illuminated area should be more than 5mm away from the circuit tail and the edge of the shape.

• Side-emitting or right-angle LEDs are recommended.

WeGlow engineers will assist you in designing the perfect backlight product.

Choice of Light Source:

LED Light Source: LEDs are the most commonly used LGF light sources due to their small size, low energy consumption, and long lifespan. LEDs can cover a large backlight area with minimal units, which not only saves costs but also enhances energy efficiency.

EL Light Source: Electroluminescent (EL) lighting is another common light source, suitable for environments that require continuous backlighting. However, its colors are typically limited, and brightness decreases over time.

Fiber Optic Lighting: Although not commonly used in backlight membrane keyboard switches, fiber optic lighting provides uniform backlighting suitable for large-area applications but at a higher cost and greater structural complexity. Learn more about backlight membrane keyboard switch products. Contact WeGlow for engineering assistance.

Testing and Verification:

After the prototype backlight keypad switch samples are manufactured, they undergo a series of inspections and tests such as light intensity, consistency, and uniformity checks. Environmental and physical strength tests are also performed.


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