Backlit Keyboard Light Guide Metal Layer EMI Shielding
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Solution Overview
Problem
In backlit keyboards, metal reflecting layers used to increase light usage also cause electromagnetic interference (EMI) and short circuits due to their conductivity, leading to instability and performance issues.
Innovation Solution
A light guide module with a metal layer that reflects light back into the guide plate while shielding electromagnetic waves, using an insulation layer with ground windows to connect the metal layer to a ground level, reducing EMI and preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a metal reflecting layer is used to increase light usage, then light reflection efficiency is improved, but electromagnetic interference and short circuit risks increase
Solution Approach 1:
The metal layer is segmented into multiple isolated metal islands instead of a continuous layer. This segmentation maintains light reflection functionality while breaking the conductive path that causes EMI and short circuits, directly resolving the contradiction between light usage efficiency and system stability
Solution Approach 2:
The patent applies different properties to different regions: the metal islands provide local reflection functionality, while the insulating material between them provides local electrical isolation. This local differentiation allows simultaneous achievement of high light usage and system reliability
2Illumination intensity
If a continuous metal layer is used for reflection, then light reflection is enhanced, but electromagnetic wave propagation and short circuits occur
Solution Approach 1:
The continuous metal layer is divided into discrete metal islands that are electrically isolated from each other by insulating material. This segmentation maintains sufficient light reflection intensity from each island while preventing electromagnetic wave propagation through the broken conductive paths
Solution Approach 2:
An insulating material is introduced as an intermediary between metal regions. This intermediary maintains the reflective function by allowing light interaction with metal while blocking electromagnetic interference and preventing short circuits between conductive elements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively reduces electromagnetic interference and increases the stability of the device by electrically connecting the metal layer to the ground level, enhancing light extraction and preventing short circuits.
Implementation Method 1
When light is incident onto the upper surface of the metal layer, the light is reflected back into the light guide plate
Implementation Method 2
When an electromagnetic wave reaches the lower surface of the metal layer, the metal layer shields the electromagnetic wave from propagating
Implementation Method 3
an adhesive layer disposed between the light guide plate and the metal layer so that the metal layer is attached to the light guide plate
Data Source
AI summary
A backlit keyboard includes a keyboard module having a plurality of key units and a light guide module including a light guide plate, a metal layer, and an insulation layer. The light guide plate has a light-exit surface and a bottom surface. The metal layer has an upper surface and a lower surface, wherein the upper surface is attached to the bottom surface of the light guide plate. When light is incident onto the upper surface of the metal layer, the light will be reflected back into the light guide plate. When electromagnetic wave reaches the lower surface of the metal layer, the metal layer will shield the electromagnetic wave from propagating. The insulation layer substantially covers the lower surface of the metal layer, wherein at least one ground window is formed in the insulation layer to expose the metal layer.