Backlight Unit Metal PCB Fixing Protrusion Prevents Separation
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Solution Overview
Problem
Edge type backlight units in liquid crystal display devices suffer from light leakage, uneven brightness, and damage to the light guide plate due to separation of the metal printed-circuit-board (PCB) from the bottom cover caused by heat generated during LED operation, leading to malfunction.
Innovation Solution
A backlight unit design that includes a metal PCB with a fixing protrusion projecting from its upper surface, which is fastened to a panel guide combined with the bottom cover, preventing the PCB from separating and ensuring secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the metal PCB is fastened to the bottom cover using adhesive, then the assembly is simple, but the PCB separates due to heat generated by LEDs
Solution Approach 1:
The bottom cover is divided into a cover body and a separate panel guide component. The panel guide includes recesses that receive and secure the metal PCB, creating a segmented structure where the PCB is mechanically interlocked rather than merely adhered. This segmentation allows the PCB to be firmly held while maintaining assembly simplicity.
Solution Approach 2:
The panel guide acts as an intermediary component between the bottom cover and the metal PCB. It provides a mechanical interface with recesses that physically secure the PCB, mediating the connection and preventing direct thermal contact while maintaining firm attachment. This intermediary structure resolves the contradiction by providing reliable mechanical fastening without requiring complex adhesive applications.
2Device complexity
If the metal PCB separates from the bottom cover, then assembly is simple, but light leakage and uneven brightness occur
Solution Approach 1:
The panel guide is pre-formed with recesses that precisely position the metal PCB and LEDs before final assembly. This preliminary structuring ensures that when the PCB is installed, the LEDs are automatically aligned in uniform intervals, preventing light leakage and uneven brightness without requiring complex adjustment mechanisms during assembly.
3Temperature
If the metal PCB separates due to heat, then thermal expansion occurs, but the light guide plate is damaged
Solution Approach 1:
The panel guide serves as a thermal intermediary, providing a mechanical connection structure that prevents direct thermal contact between the heat-generating LEDs and the light guide plate. The recesses in the panel guide secure the PCB while maintaining thermal isolation, preventing heat-induced damage to the light guide plate.
Solution Approach 2:
The design converts the harmful thermal expansion effect into a beneficial mechanical interlocking effect. The panel guide's recesses are designed to accommodate and secure the PCB in a way that utilizes thermal movement to enhance the mechanical connection, transforming the potential harm of thermal expansion into a feature that ensures firm attachment while protecting the light guide plate.
Data Source
AI summary
A backlight unit adapted to improve uneven brightness and reliability is disclosed. The backlight unit includes: a bottom cover; at least one metal PCB disposed on one side surface of the inner side of the bottom cover; a plurality of light emission diodes arranged at a fixed interval on the metal PCB; and at least one fixing protrusion projecting from an upper surface of the metal PCB and fastened to a panel guide which is combined with the bottom cover, in order to prevent the metal PCB from separating.