Stacked LED Sub-Pixel Structure for Higher Brightness Displays
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Solution Overview
Problem
Existing LED displays face challenges in increasing the area of each sub-pixel within a restricted pixel area, reducing the time required for the mounting process, and enhancing production yield while maintaining brightness.
Innovation Solution
A light emitting device with a stacked structure of multiple LED stacks, including transparent electrodes and bump pads, where each LED stack emits different colors, allowing for increased luminous area without increasing pixel size, and optimizing the manufacturing process to prevent damage to transparent electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If individual LED chips are arranged on a two-dimensional plane to provide blue, green, and red light for each sub-pixel, then the display can realize various colors, but the number of LED chips increases and the mounting process time increases
Solution Approach 1:
The patent transitions from a two-dimensional arrangement of individual LED chips to a three-dimensional stacked structure where multiple LED stacks are vertically arranged. This vertical stacking enables multiple colors (blue, green, red) to be integrated within a single pixel column, dramatically reducing the number of chips per pixel and simplifying the mounting process while maintaining full color display capability.
Solution Approach 2:
The patent merges multiple LED stacks (first, second, and third LED stacks emitting different colors) into a single integrated structure that functions as one pixel unit. By combining the blue, green, and red LED stacks vertically with shared electrode structures, the design reduces the total chip count and streamlines manufacturing while preserving the ability to display various colors through sub-pixel combination.
2Productivity
If the area of each sub-pixel is reduced to arrange sub-pixels in a restricted area, then more sub-pixels can fit in the display, but the luminous area of sub-pixels is reduced and brightness deteriorates
Solution Approach 1:
The patent utilizes the vertical dimension by stacking multiple LED stacks (first, second, and third LED stacks) within each pixel column. This three-dimensional arrangement increases the effective luminous area available for light emission without expanding the horizontal pixel footprint, thereby maintaining brightness while enabling higher pixel density in restricted display areas.
Solution Approach 2:
The patent segments each pixel into multiple sub-pixels arranged vertically (first sub-pixel, second sub-pixel, third sub-pixel), where each sub-pixel contains dedicated LED stacks for specific colors. This segmentation allows efficient utilization of vertical space, increasing the number of functional sub-pixels within a compact pixel area while maintaining adequate luminous area for brightness.
3Reliability
If transparent electrodes are used to interpose between LED stacks for electrical connection, then electrical connectivity is achieved, but the transparent electrodes may be damaged during the manufacturing process
Solution Approach 1:
The patent employs a multi-layer electrode structure where transparent electrodes are sandwiched between robust conductive layers (first electrode pad, lower second electrode pad, bump pads). This layered configuration provides mechanical protection and structural support to the fragile transparent electrodes during manufacturing processes, preventing damage while ensuring reliable electrical connectivity between the stacked LED structures.
Solution Approach 2:
The patent creates a composite electrode system combining transparent conductive materials with opaque conductive materials and bonding structures (bump pads). This composite structure leverages the electrical transparency of the transparent electrodes for light transmission while utilizing the mechanical strength of the surrounding conductive layers and bump pads to protect against manufacturing damage, achieving both reliability and durability.
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 enhances the luminous area of each sub-pixel, reduces manufacturing time, and improves production yield by preventing damage to transparent electrodes during the manufacturing process.
Implementation Method 1
a first transparent electrode interposed between the first LED stack and the second LED stack
Implementation Method 2
each LED stack emits different colors
Implementation Method 3
individual LED chips emitting blue, green and red light
Data Source
AI summary
A light emitting device for a display including a circuit board, a plurality of light emitting units arranged on the circuit board, each light emitting unit comprising a first LED stack including a first conductivity type semiconductor layer, a second conductivity type semiconductor layer, a first electrode disposed on the first conductivity type semiconductor layer, and a second electrode disposed on the second conductivity type semiconductor layer, a plurality of bump pads disposed between the plurality of light emitting units and the circuit board, and a bonding layer disposed between the second electrode and the circuit board, in which the second electrode has a side surface recessed inwardly with respect to a side surface of the light emitting unit to define a recessed portion, and the bonding layer is filled in the recessed portion.