Backlight Shim for PCB Wiring Step Compensation
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Solution Overview
Problem
In EMR-based display technologies, wiring protrusions on the PCB lead to a recessed light guide plate, causing increased diffuse reflection and bright spots, which reduce the uniformity of backlight brightness and adversely affect the display effect.
Innovation Solution
A shim with a flexible layer and optional rigid layer is placed between the light guide plate and the PCB to compensate for the step difference caused by wiring protrusions, improving the flatness of the light guide plate's surface and ensuring uniform light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wiring protrusions are provided on the PCB for EMR sensing, then the EMR sensing function is enabled, but the light guide plate becomes recessed causing bright spots and non-uniform backlight brightness
Solution Approach 1:
A shim is introduced as an intermediary component between the light guide plate and the PCB. The shim compensates for the step difference created by wiring protrusions, filling the gap and preventing the light guide plate from being recessed. This mediator resolves the conflict between enabling EMR sensing (which requires wiring protrusions) and maintaining backlight uniformity (which requires a flat light guide plate surface).
Solution Approach 2:
The shim modifies the physical parameters of the assembly by changing the height compensation at specific locations. It alters the step difference parameter caused by wiring protrusions, transforming the defective state (recessed light guide plate) into a functional state (flat light guide plate surface) while preserving the EMR sensing capability.
2Length of moving object
If the light guide plate is made thinner for sleek design, then the overall device thickness is reduced, but the tolerance for surface defects and step differences becomes more critical
Solution Approach 1:
The shim acts as a compensatory intermediary that becomes increasingly important as the light guide plate thickness is reduced. Thinner light guide plates have less tolerance for surface irregularities, so the shim's role in eliminating step differences and maintaining surface flatness becomes critical for achieving both sleek design and manufacturing precision.
3Ease of operation
If wiring protrusions are added to the PCB surface, then electrical connectivity and sensing are improved, but the flatness of the assembly is compromised causing diffuse reflection
Solution Approach 1:
The shim serves as a mediator that allows the wiring protrusions to remain on the PCB for electrical connectivity while simultaneously restoring the flatness of the assembly. It fills the gap created by the protrusions, preventing light diffusion and maintaining both electrical functionality and optical performance.
Data Source
AI summary
There are provided a backlight module, a display apparatus and an electronic drawing board. The backlight module includes a light guide plate, a printed circuit board located on a side of the light guide plate facing away from a light exit side thereof and having a wiring protrusion protruding from a surface of the printed circuit board. A shim is disposed between the light guide plate and the printed circuit board and configured to partially compensate a step difference formed due to the wiring protrusion.