Micro LED Array Substrate Bonding Adhesive Gap Filling
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Solution Overview
Problem
Flip-chip type micro LEDs have a small electrode area, resulting in low adhesion to the array substrate, making them prone to failure under conditions like high temperatures, high humidity, or thermal shock, and the increased thermal expansion during bonding limits bonding accuracy.
Innovation Solution
An array substrate with a larger contact area is created by placing a bonding adhesive between the electrodes of the micro LEDs, using solder materials with higher melting temperatures than the adhesive, and applying a bonding adhesive with a specific composition and thickness to enhance the connection between the micro LEDs and the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If flip-chip type micro LEDs are used to simplify later processes, then manufacturing complexity is reduced, but adhesion strength to the array substrate deteriorates due to small electrode area
Solution Approach 1:
The patent introduces a bonding adhesive as an intermediary substance between the micro LED electrodes and the array substrate. The adhesive fills the gap between the first and second electrodes, creating a mechanical interlocking structure that significantly enhances adhesion strength while maintaining the simplified flip-chip bonding process.
Solution Approach 2:
The patent transitions from relying solely on point-contact electrode adhesion to a distributed areal adhesion by filling the gap between electrodes with bonding adhesive. This dimensional expansion from point to area contact dramatically increases the total bonding interface and adhesion strength.
2Productivity
If the one-time transferring area of micro LEDs is increased, then productivity is improved, but bonding accuracy deteriorates due to increased thermal expansion during bonding
Solution Approach 1:
The patent modifies the bonding process parameters by introducing bonding adhesive with specific thermal and rheological properties. The adhesive remains in a semi-fluid state during bonding, accommodating thermal expansion, then cures to lock the expanded position, thereby maintaining bonding accuracy despite large-scale transferring.
Solution Approach 2:
The bonding adhesive acts as a cushioning medium that anticipates and absorbs the thermal expansion that occurs during bonding. By pre-filling the gap with a material that can accommodate volume changes, the system prevents expansion-induced misalignment and maintains bonding precision.
3Quantity of substance
If the electrode area of micro LEDs is kept small, then device integration density is improved, but reliability deteriorates due to insufficient adhesion under high temperature and humidity conditions
Solution Approach 1:
The patent employs a composite bonding structure combining the micro LED electrodes, bonding adhesive, and array substrate. This composite approach leverages the complementary properties of each material: the conductive electrodes for electrical connection, the adhesive for mechanical bonding and environmental sealing, and the substrate for structural support, thereby achieving both high density and high reliability.
Solution Approach 2:
The bonding adhesive provides beforehand protection against environmental stressors by filling and sealing the gap between electrodes and substrate. This pre-established protective barrier prevents moisture and contaminant ingress, and accommodates thermal stress, ensuring operational reliability under high temperature and humidity conditions.
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 increases the contact area between micro LEDs and the array substrate, improving product yield by preventing failures under adverse conditions and enhancing bonding accuracy.
Implementation Method 1
curing the bonding adhesive so that the micro LED is connected to the substrate through the bonding adhesive
Implementation Method 2
at least a first solder material is further disposed between the positive electrode and the first electrode, and at least a second solder material is further disposed between the negative electrode and the second electrode
Data Source
AI summary
An array substrate and a method of fabricating the array substrate are disclosed. The array substrate includes a substrate including a plurality of pixel units arranged in an array. Each of the pixel units has a first electrode and a second electrode, and a first gap is provided between the first electrode and the second electrode. A bonding adhesive is disposed at the first gap. A micro light-emitting diode is disposed on the first electrode, the second electrode, and the bonding adhesive to prevent a failure of the micro light-emitting diode and improve product yield.