Stacked LED Sub-Pixel Structure for Larger Luminous Area
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Solution Overview
Problem
Existing LED display technologies face challenges in increasing the area of each sub-pixel within a restricted pixel area, reducing the time required for the mounting process, and improving production yield.
Innovation Solution
A light emitting device for a display is designed with a stack structure of multiple LEDs, including a first, second, and third LED stack, with transparent electrodes interposed between the stacks for efficient light emission and a common bump pad for electrical connection.
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 sub-pixels, then the display can show 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 configuration. Multiple LED chips emitting different colors (blue, green, red) are vertically stacked and bonded together, allowing color display functionality while reducing the number of separate mounting operations required.
Solution Approach 2:
The patent combines multiple individual LED chips into a single integrated stack structure. The stacked LED chips are electrically and physically bonded together, merging what would otherwise be separate mounting operations into one unified assembly, thereby reducing mounting process time while maintaining color display capability.
2Area of stationary object
If sub-pixels are arranged on a two-dimensional plane in a restricted area, then the display can fit within the pixel area, but the luminous area of each sub-pixel is reduced and brightness deteriorates
Solution Approach 1:
The patent utilizes the third dimension (vertical stacking) to increase the effective luminous area within a restricted two-dimensional pixel footprint. By stacking LED chips vertically, the luminous area of each sub-pixel is expanded without requiring additional horizontal space, thereby maintaining or improving brightness within the same pixel area.
3Adaptability or versatility
If multiple individual LED chips are used for each sub-pixel, then color display is achieved, but the device complexity and mounting process complexity increase
Solution Approach 1:
The patent merges multiple individual LED chips into a single stacked assembly that functions as an integrated unit. This consolidation reduces device complexity by eliminating the need to handle and mount separate chips individually, while still achieving full color display capability through the combined emission of the stacked chips.
4Area of moving object
If the area of each sub-pixel is reduced to fit more sub-pixels in a restricted area, then the pixel density increases, but the luminous area is reduced and brightness deteriorates
Solution Approach 1:
The patent compensates for reduced sub-pixel area by extending into the third dimension through vertical stacking. This allows the luminous area to be maintained or increased through the stack height, thereby preserving brightness even when the horizontal footprint of each sub-pixel is reduced to increase pixel density.
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 allows for an increased luminous area of each sub-pixel without expanding the pixel area, reduces the time and complexity of the mounting process, and enhances production yield by preventing damage to electrodes during manufacturing.
Implementation Method 1
each of the first to third LED stacks includes a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer
Implementation Method 2
a first transparent electrode interposed between the first LED stack and the second LED stack, and being in ohmic contact with a lower surface of the first LED stack
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.