LCD Backlight PCB Layout With Thixotropic LED Molding
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Solution Overview
Problem
The existing backlight units in display apparatuses face challenges with low light extraction efficiency due to the difference in density between the air and the light-emitting layer, leading to increased manufacturing costs and difficulty in making the light source plate thin, while also experiencing luminance unevenness (Mura) and high production costs.
Innovation Solution
A display apparatus with a light source plate that includes a printed circuit board with power wiring and PSR layers, flip chip type LED chips mounted in a COB method, and molding members made of thixotropic materials such as silicone or epoxy resin, surrounded by a reflective sheet with openings to position the molding members inside, enhancing light efficiency and preventing luminance unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional packaging methods or CSP methods are used to manufacture the light source plate, then the light extraction efficiency can be improved, but the manufacturing cost increases and the light source plate thickness cannot be reduced
Solution Approach 1:
The patent uses a simple planar substrate instead of expensive packaged LED modules or CSP structures. The LED chips are directly mounted on the substrate without requiring complex packaging structures, walls, or encapsulation materials, significantly reducing manufacturing cost while maintaining light extraction efficiency through the planar configuration and optical diffuser layer
Solution Approach 2:
The light source plate is divided into multiple LED chips mounted on a planar substrate, with each chip having its own optical diffuser layer. This segmentation allows for better light extraction from each individual chip while maintaining overall cost-effectiveness through simplified manufacturing processes compared to pre-packaged solutions
2Loss of energy
If traditional packaging methods or CSP methods are used to manufacture the light source plate, then the light extraction efficiency can be improved, but the light source plate thickness cannot be reduced
Solution Approach 1:
The patent extracts the essential light extraction function from complex packaged structures and implements it through a simplified planar substrate with directly mounted LED chips and optical diffuser layers. This eliminates the need for thick packaging structures, walls, and encapsulation materials, reducing the overall light source plate thickness while maintaining effective light extraction
Solution Approach 2:
The patent transitions from three-dimensional packaged LED structures to a two-dimensional planar substrate configuration. The LED chips are mounted flat on the substrate with optical diffuser layers, eliminating the vertical thickness required by traditional packaging methods while maintaining light extraction efficiency through the planar optical path
3Manufacturing precision
If molding material is dispensed to surround LED chips, then uniform molding member shapes can be achieved, but the material must have specific thixotropic properties to prevent spreading
Solution Approach 1:
The patent specifies that the molding material must possess thixotropic properties, meaning its viscosity changes with shear rate or time. This parameter change allows the material to be easily dispensed during manufacturing and then maintain a stable, uniform shape after application, preventing unwanted spreading while achieving precise molding member geometry
Solution Approach 2:
The patent employs molding materials that combine thixotropic properties with appropriate optical characteristics. This composite material approach ensures both the structural uniformity needed for precise molding member formation and the optical performance required for effective light diffusion, while maintaining manufacturing precision
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
The solution increases light efficiency, reduces manufacturing costs, and minimizes luminance unevenness by maintaining uniform molding member shapes, widening the beam angle of LED chips, and reducing the thickness of the display apparatus.
Implementation Method 1
a plurality of molding members formed of a molding material including a material having thixotropy that is dispensed to respectively surround the plurality of LED chips
Implementation Method 2
a reflective sheet including a plurality of openings formed to correspond to positions of the plurality of molding members of the light source plate so that while the reflective sheet is between the liquid crystal panel and the light source plate the plurality of molding members of the light source plate are respectively positionable inside the plurality of openings
Data Source
AI summary
A display device comprising: a light source plate behind a liquid crystal panel to provide light to the liquid crystal panel. The light source plate comprises: a printed circuit board including a power wiring layer and a photo solder resist (PSR) layer; a plurality of LED chips mountable directly on the printed circuit board; and a plurality of molding parts formed of a molding material comprising a material having thixotropy to respectively surround the plurality of LED chips. A reflective sheet includes a plurality of openings formed to correspond to positions of the plurality of molding parts so that while the reflective sheet is between the liquid crystal panel and the light source plate, the plurality of molding parts are respectively positionable inside the plurality of openings with the plurality of molding members spaced apart from an inner circumferential surfaces of each of the plurality of openings.