Stacked LED Display Panel for Reliable Via-Bonded Pixel Connections
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Solution Overview
Problem
The challenge lies in achieving reliable electrical connections between small-sized LEDs and circuit boards in display apparatuses, particularly in compact devices like smart watches or AR glasses, where the thermal expansion mismatch between the circuit board and the substrate can lead to defective connections, and the small size makes replacement difficult, and the limited area reduces sub-pixel luminance, affecting brightness.
Innovation Solution
A display panel design featuring a circuit board with pads and pixel regions, where each pixel includes a stack of LEDs with bonding layers and through-vias connected to the pads, allowing for independent electrical connection and light emission, and a reflection layer to enhance light extraction, eliminating the need for LED transfer and optimizing sub-pixel area for improved brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LEDs are transferred from a support substrate to a circuit board in groups, then productivity is improved, but reliability deteriorates due to thermal expansion mismatch causing defective electrical connections
Solution Approach 1:
The patent divides the pixel structure into separate stacked LED components (first LED stack, second LED stack, third LED stack) rather than transferring complete pixel groups. Each stack is independently mounted and electrically connected to the circuit board through separate bonding layers and through-vias, eliminating the thermal expansion mismatch problem associated with group transfer while maintaining productivity through systematic assembly procedures
Solution Approach 2:
The patent introduces intermediate bonding layers (first bonding layer, second bonding layer, third bonding layer) and through-vias as intermediary elements between the LED stacks and the circuit board. These intermediaries provide stable electrical connections that compensate for thermal expansion differences, ensuring reliable connectivity without direct substrate-to-board contact that causes defects
2Area of stationary object
If sub-pixel area is reduced to fit more pixels in a restricted area, then device compactness is improved, but brightness deteriorates due to reduced luminous area
Solution Approach 1:
The patent transitions from a two-dimensional lateral arrangement of sub-pixels to a three-dimensional stacked configuration. Multiple LED stacks are arranged vertically along the light emission direction, allowing the pixel to maintain a compact footprint while increasing total luminous area through the third dimension. This enables more pixels to fit in restricted areas without sacrificing brightness, as each pixel's brightness is determined by its vertical stack height rather than lateral sub-pixel area
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 solution ensures reliable electrical connections and increased sub-pixel area, enhancing the brightness and reliability of LED displays in compact devices by integrating LEDs directly onto the circuit board, preventing transfer-related issues and maintaining high light emission efficiency.
Implementation Method 1
a first LED stack disposed on the circuit board, a first bonding layer disposed between the first LED stack and the circuit board, a second LED stack disposed on the first LED stack, a third LED stack disposed on the second LED stack
Data Source
AI summary
A display panel including a circuit board having pads thereon, and a plurality of pixel regions arranged on the circuit board, each of the pixel regions including a first LED stack disposed on the circuit board, a first bonding layer disposed between the first LED stack and the circuit board, a second LED stack disposed on the first LED stack, a third LED stack disposed on the second LED stack, first through-vias passing through the first LED stack and the first bonding layer, second through-vias passing through the second LED stack, and third through-vias passing through the third LED stack, in which the first through-vias pass through the first LED stack and the first bonding layer, and are connected to the pads of the circuit board.