LED Substrate Electrode Layers for Crack-Resistant Mass Transfer
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Solution Overview
Problem
Conventional methods of transferring light-emitting diodes onto circuit substrates result in erroneously transferred or adversely affected diodes, leading to poor display quality due to difficulties in cleaning conductive adhesive and repairing individual pixels.
Innovation Solution
A light-emitting diode substrate design with specific electrode layers, including a first conductive layer with high adhesion to the semiconductor stack, a barrier layer, and a metal layer with a low melting point, allowing for improved bonding and reduced cracking during the transfer process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conductive adhesive is formed on the circuit substrate in a large area for mass transfer, then the light-emitting diode can be transferred onto the circuit substrate, but it becomes difficult to clean up the conductive adhesive and time-consuming to form adhesive only in specific small regions during repair
Solution Approach 1:
The patent segments the bonding interface by introducing a metal layer with low melting point (below 260°C) that can be selectively melted and removed. This allows the bonding structure to be divided into permanent adhesion layers (first conductive layer with high adhesion to semiconductor stack) and removable bonding layers (metal layer), enabling easy cleanup during repair without affecting the underlying adhesion structure
Solution Approach 2:
The patent changes the thermal parameter of the bonding interface by using a metal layer with melting point below 260°C. This parameter change allows selective melting and removal of the metal layer during repair processes, while the first conductive layer maintains strong adhesion to the semiconductor stack. The barrier layer prevents diffusion during heating, enabling controlled parameter changes without compromising structural integrity
2Device complexity
If conventional electrode structures are used during transfer, then the structure is simple, but cracks occur at the bonding place between light-emitting diode and circuit substrate
Solution Approach 1:
The patent uses composite material structure for the electrode consisting of multiple layers: first conductive layer (high adhesion to semiconductor stack), barrier layer (prevents diffusion), and metal layer (low melting point for selective removal). This composite structure provides both strong bonding reliability during transfer and controlled removability during repair, preventing cracks by distributing stress across different functional layers
Solution Approach 2:
The barrier layer acts as an intermediary between the first conductive layer and the metal layer. During heating processes, it prevents diffusion of metal atoms into the conductive layer, mediating the interaction between the low-melting-point metal and the high-adhesion conductive layer, thereby preventing crack formation at the bonding interface
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
Enhances the bonding between light-emitting diodes and circuit substrates, reducing cracks and improving the reliability and efficiency of the display device fabrication process.
Implementation Method 1
The metal layers of one of the light-emitting diodes are eutectically bonded to two of the pads
Implementation Method 2
the barrier layer shields metal atoms in the metal layer from being diffused to the first conductive layer
Data Source
AI summary
A display device includes a circuit substrate and a light-emitting diode. Two electrodes of the light-emitting diode are connected to two pads of the circuit substrate. Each electrode of the light-emitting diode includes a first conductive layer, a barrier layer, and a metal layer. The first conductive layer is connected to a semiconductor stack layer of the light-emitting diode. The barrier layer is electrically connected to the semiconductor stack layer of the light-emitting diode through the first conductive layer. The adhesion of the material selected for the first conductive layer to the semiconductor stack layer is greater than the adhesion of the material selected for the barrier layer to the semiconductor stack layer. The metal layer electrically connects the barrier layer to the corresponding one of the pads. The melting point of the metal layer is lower than 260 degrees Celsius.