Stacked LED Unit Pixel Structure to Prevent Layer Cracking
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Solution Overview
Problem
Conventional LED displays face challenges in manufacturing unit pixels with stacked blue, green, and red light emitting devices, leading to increased height and risk of insulation and metal layer cracking during the manufacturing process.
Innovation Solution
The unit pixel design includes a first, second, and third light emitting stack with inclined side surfaces at angles between 30 to 70 degrees, adhesive layers with similar angles, and contact electrodes with angled sidewalls, enhancing adhesion and preventing cracking, while maintaining electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If blue, green, and red light emitting devices are stacked to form unit pixels, then the number of light emitting devices per pixel is reduced and manufacturing efficiency is improved, but the overall height of the unit pixel is increased and the risk of insulation layer or metal layer cracking is increased
Solution Approach 1:
The patent applies curvature by forming inclined side surfaces on the light emitting stacks and adhesive layers. The inclined surfaces (with angles between 30-60 degrees) replace vertical sidewalls, creating a tapered structure that distributes stress more evenly and prevents crack propagation in the insulation and metal layers during the stacking process.
Solution Approach 2:
The patent changes the geometric parameters of the light emitting stacks and adhesive layers by introducing inclination angles. The side surfaces are formed at specific angles (30-60 degrees) rather than vertical orientations, which fundamentally alters the stress distribution characteristics and prevents layer cracking during manufacturing.
2Manufacturing precision
If individual light emitting devices are arranged on each sub-pixel, then color accuracy is maintained, but the number of light emitting devices increases and mounting time increases
Solution Approach 1:
The patent merges multiple light emitting devices (blue, green, and red LEDs) into a single stacked structure called a light emitting stack. Multiple stacks are then arranged on the substrate to form unit pixels, reducing the total number of individual mounting operations while maintaining the ability to produce accurate colors through the stacked configuration.
Solution Approach 2:
The patent transitions from a two-dimensional arrangement of individual light emitting devices to a three-dimensional stacked structure. By stacking blue, green, and red light emitting devices vertically, the patent reduces the number of devices that need to be mounted on the substrate while maintaining color accuracy through the vertical integration of multiple emission wavelengths.
Data Source
AI summary
A unit pixel including a first light emitting stack; a second light emitting stack disposed under the first light emitting stack, and having an area greater than that of the first light emitting stack; a third light emitting stack disposed under the second light emitting stack, and having an area greater than that of the second light emitting stack, in which at least one of the first through third light emitting stacks includes a side surface having an inclination angle within a range of about 30 degrees to about 70 degrees with respect to a first plane parallel to a top surface of the third light emitting stack.