Stacked RGB LED Package Structure for Small-Pitch Displays
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Solution Overview
Problem
Existing package structures for RGB LEDs in display devices face challenges in achieving small-pitch operation due to limitations in package technology, particularly in adopting chip-on-board technology, which hinders the integration of mini LEDs and micro LEDs for efficient and environmentally friendly display panels.
Innovation Solution
A package structure with vertically stacked light-emitting layers, including a substrate, transparent adhesive layers, LED chips, redistribution layers, and planarization layers, allowing for the vertical arrangement of LED chips with different colors, and a method for transferring LED chips from a source wafer to a target substrate, optimizing space utilization and simplifying the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional surface mounted device package technology is used for RGB LEDs, then the package structure can be implemented with existing processes, but small-pitch operation cannot be achieved due to process limits
Solution Approach 1:
The patent transitions from conventional planar (2D) LED chip arrangement to a vertically stacked (3D) configuration where multiple LED chips are arranged in different layers above the substrate. This dimensional change enables smaller pixel pitches by utilizing the vertical space rather than being constrained by horizontal placement limits, thereby achieving high-resolution displays while maintaining manufacturability through established chip-on-board processes adapted for vertical stacking.
2Productivity
If mini LEDs and micro LEDs are integrated using chip-on-board technology, then small-pitch operation and energy efficiency are improved, but the package structure complexity increases
Solution Approach 1:
The patent divides the LED package into multiple discrete layers, with each layer containing LED chips of specific sizes (mini LEDs or micro LEDs) mounted on transparent adhesive layers. This segmentation allows independent optimization of each layer and simplifies the integration process, enabling high pixel integration density while managing complexity through modular assembly rather than monolithic structure.
Solution Approach 2:
The patent introduces transparent adhesive layers as intermediary elements between the substrate and LED chips, and between different LED chip layers. These adhesive layers serve multiple functions: mechanical support, optical transparency to allow light extraction, and electrical isolation. This intermediary approach simplifies the overall package structure by providing a standardized interface for mounting various LED chip types without requiring complex direct bonding processes.
3Area of stationary object
If vertically stacked LED chips are arranged in a single pixel, then pixel area is reduced and resolution is enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent employs preliminary wafer-level preparation where LED chips are fabricated and pre-assembled in vertical stacks on a source wafer before being transferred to the final substrate. This preliminary action allows the complex vertical stacking to be performed once at the wafer level, simplifying the subsequent chip transfer process to a single-step operation and reducing manufacturing complexity while achieving small pixel areas through compact vertical arrangement.
Data Source
AI summary
A package structure is provided. The package structure has a light-emitting region and a non-light-emitting region that is adjacent to the light-emitting region, and includes a substrate, a first light-emitting layer, a second light-emitting layer and a third light-emitting layer. The first light-emitting layer, the second light-emitting layer and the third light-emitting layer are sequentially stacked on the substrate. Each of the first light-emitting layer, the second light-emitting layer and the third light-emitting layer includes a transparent adhesive layer disposed in the light-emitting region, a light-emitting diode (LED) chip disposed on the transparent adhesive layer, a redistribution layer formed on the LED chip and extending from the light-emitting region to the non-light-emitting region, and a planarization layer disposed on the LED chip and the redistribution layer.