Folded PCB LED Mounting for Narrow Bezel LCD
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Solution Overview
Problem
The existing liquid crystal display (LCD) technologies face limitations in reducing the pitch of light emitting diode (LED) packages mounted on a printed circuit board (PCB) due to manufacturing tolerances and insulating widths, making it difficult to achieve a narrow bezel and increase the number of LED packages.
Innovation Solution
The solution involves dividing the PCB into separate portions where LED packages are mounted, allowing for alternative arrangement and folding the PCB to minimize the separation distance between LED packages, eliminating the need for a minimum separation distance of 600µm, and using a guide portion to maintain the folded state and prevent light leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If LED packages are mounted on a flat PCB with standard manufacturing tolerances, then mounting reliability is ensured, but the separation distance between LED packages cannot be reduced below 600µm
Solution Approach 1:
The PCB is divided into a first PCB and a second PCB that are folded relative to each other. LED packages are mounted on opposite surfaces of these segmented PCB portions, allowing the separation distance to be reduced while maintaining manufacturing reliability through the folding structure.
Solution Approach 2:
The PCB structure transitions from a two-dimensional flat layout to a three-dimensional folded configuration. By folding the PCB, LED packages can be positioned closer together in the planar direction while maintaining adequate separation through the vertical dimension created by the fold.
2Productivity
If the pitch of LED packages is reduced to increase the number of LEDs, then the optical distance can be reduced enabling narrow bezel, but manufacturing tolerances and insulating width requirements prevent further pitch reduction
Solution Approach 1:
Dividing the PCB into folded portions allows LED packages to be mounted on opposite surfaces, effectively increasing the number of LED packages that can be accommodated in a given area while maintaining adequate separation distances for manufacturing.
Solution Approach 2:
By utilizing the vertical dimension through PCB folding, the pitch between LED packages can be reduced in the planar direction without compromising manufacturing precision, as the separation is maintained through the folded three-dimensional structure.
3Length of stationary object
If LED packages are arranged closer together, then the optical distance is reduced for narrow bezel design, but light leakage between adjacent LED packages occurs
Solution Approach 1:
The PCB is segmented into folded portions with LED packages mounted on opposite surfaces. This segmentation naturally provides physical separation and directional control of light emission, preventing light leakage between adjacent LED packages while reducing the overall optical distance.
Solution Approach 2:
The folded PCB structure utilizes the vertical dimension to separate light emission paths of adjacent LED packages. By positioning LEDs on opposite surfaces of folded PCB portions, light is directed away from adjacent packages, eliminating light leakage while maintaining compact optical distance.
Data Source
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AI summary
A liquid crystal display device includes a liquid crystal panel (110); a light guide plate (125) below the liquid crystal panel (110); first and second LED packages (210a, 210b) that are arranged alternately along a light entering surface of the light guide plate (125); a PCB (220) that includes first and second portions (220a, 220b) which face each other and which the first and second LED packages (210a, 210b) are mounted at, respectively, and a third portion (220c), in a bent state, which connects an end, in a length direction, of the first portion (220a), and an end, in a length direction, of the second portion (220b); and a first guide portion (131) that is located at an outer side of the first and second LED packages, and is interposed between and attached to the first and second portions.