Monolithic LED Micro-Display Flip-Chip Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional LED micro-displays face limitations in array dimensions, pixel brightness, and light efficiency due to low field effect mobility of thin film transistor materials and passive address schemes, resulting in poor illumination uniformity and low resolution.
Innovation Solution
A monolithic LED micro-display is manufactured using flip-chip technology on an active matrix panel, with a substrate having overlaying layers, a current spreading layer, and a metal multilayer configuration that allows independent control of each LED via active control circuit chips, enabling improved heat dissipation and light efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If thin film transistor materials are used in conventional LED micro-displays, then device complexity is reduced, but field effect mobility is low resulting in poor pixel brightness and non-uniform illumination
Solution Approach 1:
The patent segments the control circuitry into separate active matrix panels that are bonded to the LED array. This allows the use of high-performance thin film transistors in the control panels without compromising the LED pixel performance, resolving the contradiction between device complexity and illumination intensity.
Solution Approach 2:
The patent introduces an active matrix panel as an intermediary between the control circuitry and the LED array. This intermediary contains the thin film transistor switches that control current flow to each LED, enabling low-complexity control while maintaining high pixel brightness through proper transistor design and material selection.
2Device complexity
If passive address schemes are used in conventional LED micro-displays, then device complexity is reduced, but array dimensions and resolution are limited
Solution Approach 1:
The patent inverts the conventional approach by using active matrix control panels instead of passive addressing. The active matrix panels provide independent control of each pixel through addressed scanning, enabling high resolution displays while maintaining manageable device complexity through standardized panel architectures.
3Ease of manufacture
If bottom-emitting configuration is used, then ease of manufacture is improved, but aperture is limited resulting in low light efficiency
Solution Approach 1:
The patent transitions from bottom-emitting to top-emitting LED configuration. This dimensional change in light emission direction allows for larger apertures and improved light extraction efficiency, as the light is emitted from the top surface where the LED chip is mounted, rather than being constrained by the bottom-emitting geometry.
4Ease of manufacture
If individually packaged LED devices are used, then ease of manufacture is improved, but array dimensions and pixel density are limited
Solution Approach 1:
The patent merges multiple LED chips onto a single substrate or closely spaced arrays, eliminating the need for individual packaging of each LED device. This merging approach enables higher pixel density and larger array dimensions while maintaining manufacturing simplicity through standardized chip mounting processes.
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
This approach allows for high-resolution, uniformly illuminated LED micro-displays with independent control of each pixel, enhancing light efficiency and overcoming the limitations of previous technologies by using flip-chip bonding and active matrix control.
Implementation Method 1
combining the LED micro-array panel with the AM panel, which includes a plurality of active control circuit chips fixed thereon, the plurality of active control circuit chips being provided with conductive solder material thereon
Implementation Method 2
providing a plurality of overlaying layers of material on a surface of the substrate, the plurality of overlaying layers of material being configured in combination to emit light when activated
Data Source
AI summary
A high-resolution, Active Matrix (AM) programmed monolithic Light Emitting Diode (LED) micro-array is fabricated using flip-chip technology. The fabrication process includes fabrications of an LED micro-array and an AM panel, and combining the resulting LED micro-array and AM panel using the flip-chip technology. The LED micro-array is grown and fabricated on a sapphire substrate and the AM panel can be fabricated using CMOS process. LED pixels in a same row share a common N-bus line that is connected to the ground of AM panel while p-electrodes of the LED pixels are electrically separated such that each p-electrode is independently connected to an output of drive circuits mounted on the AM panel. The LED micro-array is flip-chip bonded to the AM panel so that the AM panel controls the LED pixels individually and the LED pixels exhibit excellent emission uniformity. According to this constitution, incompatibility between the LED process and the CMOS process can be eliminated.