Backlit Switch PCB Spatial Arrangement
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Solution Overview
Problem
Backlit switches in devices often compromise either the uniformity of light transmission or the press feeling of the button, affecting user experience due to the placement of the tact switch and light source on the same side of the PCB.
Innovation Solution
A backlit switch design where the light source and tact switch are mounted on opposite sides of the PCB, with a dome-type button that moves to trigger the tact switch and allow light transmission through a dedicated light transmitting portion, ensuring both uniform light and proper button press feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the tact switch and light source are mounted on the same side of the PCB, then the device complexity is reduced, but either the uniformity of light transmission or the press feeling of the button is compromised
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement (both components on the same side of the PCB) to a three-dimensional spatial arrangement (components on opposite sides of the PCB). The light source is mounted on one side of the PCB while the tact switch is mounted on the other side, allowing light to pass through the button perpendicular to the PCB plane. This dimensional change enables both components to be centered relative to the button without spatial interference, achieving uniform light transmission while maintaining proper button press feedback.
2Manufacturing precision
If the light source is centered with respect to the button, then the light transmission uniformity is improved, but the press feeling of the button is compromised
Solution Approach 1:
By moving the tact switch to the opposite side of the PCB from the light source, the patent creates separate spatial zones for optical functionality and mechanical feedback. The light source centered on one side provides uniform illumination through the button, while the tact switch centered on the other side provides proper mechanical feedback. The PCB acts as a spatial separator that allows both centering requirements to be satisfied simultaneously without compromise.
3Ease of operation
If the tact switch is centered with respect to the button, then the button press feedback is improved, but the light transmission uniformity is compromised
Solution Approach 1:
The patent resolves this contradiction by utilizing the third dimension (depth relative to the PCB) to separate the optical path from the mechanical actuation path. The light source on one side of the PCB and tact switch on the other side are both centered relative to the button's projection, but occupy different depths. This allows the light to pass uniformly through the button while the tact switch remains properly positioned for mechanical feedback, eliminating the trade-off between these two requirements.
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
This design enhances user experience by maintaining both uniform light transmission and proper button press feedback without compromising either, improving the overall functionality of backlit switches in devices.
Implementation Method 1
a light source mounted on a first side of the PCB... The light source is enclosed within the hollow space of the button... transmit light through the light transmitting portion of the button
Data Source
AI summary
Example of backlit switches are described. In an example, a backlit switch includes a printed circuit board (PCB) and a dome-type button coupled to the PCB. The dome-type button has a light transmitting portion. A light source is mounted on a first side of the PCB, and a tact switch is mounted on a second side of the PCB that is opposite to the first side. Further, a projection is provided to trigger the tact switch, in response to pressing of the dome-type button.