Micro LED Bump Structure for Stable Step-Embedded Mounting
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Solution Overview
Problem
Micro LED displays face reduced luminous efficiency due to non-radiative recombination at the side walls of the active layer, which is not effectively addressed by existing technologies.
Innovation Solution
The proposed LED module features a unique bump structure with different thickness regions to embed a step portion between the cathode and anode electrodes, using low-melting-point solder to form bumps that fill and stabilize the LED chip's step portion, ensuring a stable electrical connection and enhanced light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional micro LED structure is used with uniform electrode heights, then the manufacturing process is simple, but the mounting stability is poor due to the step portion between cathode and anode electrodes
Solution Approach 1:
The patent applies asymmetry by making the cathode electrode height different from the anode electrode height. Specifically, the cathode electrode includes a first height portion and a second height portion at different levels, creating an asymmetric structure that accommodates the step portion of the LED chip. This asymmetric design improves mounting stability by providing better mechanical interlocking with the chip's step portion.
Solution Approach 2:
The patent introduces height variation in the electrode structure by creating multiple height portions (first height portion and second height portion) in the cathode electrode. This dimensional change from a uniform plane to a multi-level structure allows the electrode to embed into the step portion of the LED chip, enhancing mechanical stability without complicating the overall device architecture.
2Reliability
If bumps are made with uniform thickness, then the manufacturing process is simple, but voids and creep fractures occur at the step portion, reducing connection reliability
Solution Approach 1:
The patent applies local quality by creating bumps with different thicknesses at different locations. The first bump has a first thickness that fills the step portion, while the second bump has a second thickness. This localized variation in bump thickness ensures complete filling of the step portion to prevent voids and creep fractures, while maintaining manufacturability through a controlled multi-layer formation process.
Solution Approach 2:
The patent segments the bump structure into multiple parts with different thicknesses. The first bump is divided into a first thickness portion and a second thickness portion, allowing each segment to serve a specific function: the thicker portion fills the step portion while the thinner portion provides electrical connection. This segmentation prevents defects while maintaining ease of manufacture through systematic layer formation.
3Reliability
If the distance between electrode and cathode is reduced, then the electrical connection is improved, but the mounting stability deteriorates due to insufficient embedding of the step portion
Solution Approach 1:
The patent applies the nesting principle by having the first bump embed into the step portion of the cathode electrode. The first thickness portion of the first bump is positioned to fill the step portion, creating a nested structure where the bump is partially embedded within the electrode structure. This nesting provides both mechanical stability and good electrical contact by ensuring intimate contact between the bump and electrode surfaces.
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 improves the mounting stability and light extraction efficiency of micro LEDs by embedding the step portion with bumps of varying thickness, preventing voids and creep fractures, thereby enhancing the overall performance of micro LED displays.
Implementation Method 1
using low-melting-point solder to form bumps that fill and stabilize the LED chip's step portion
Implementation Method 2
heating the first bump and the second bump to electrically connect the LED chip to the first electrode and the second electrode
Data Source
AI summary
An LED module includes a first electrode and a second electrode disposed on the substrate, an LED chip disposed on the first electrode and the second electrode, and a first bump between the LED chip and the first electrode, and a second bump between the LED chip and the second electrode. The LED chip includes a cathode electrode facing the first electrode, an anode electrode facing the second electrode, and a step portion between the cathode electrode and the anode electrode, a distance between the first electrode and the cathode electrode is larger than a distance between the second electrode and the anode electrode, and the first bump is disposed to embed the step portion.