MicroLED Bonding Layer Structure for Uneven Laser Heating
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Solution Overview
Problem
The mass transfer technique for microLEDs in display panels often results in poor connections to the array substrate, leading to reduced production yield due to uneven bonding temperatures caused by surface spot laser irradiation, which can lead to either short circuits or poor bonding.
Innovation Solution
The use of a display panel design with a bonding layer featuring discrete bonding portions, where the first bonding portions in the center region include a first intermetallic compound and the second bonding portions in the edge region include a combination of a first metal and a second intermetallic compound with a lower melting point, allowing for controlled melting and bonding through surface spot laser irradiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If surface spot laser irradiation is used for mass transfer of microLEDs, then bonding speed is improved, but bonding temperature uniformity deteriorates causing poor connection quality
Solution Approach 1:
The bonding layer is segmented into multiple discrete bonding portions with different material compositions. Each bonding portion contains different metal elements with different melting points, allowing localized temperature control during laser irradiation. This segmentation enables the center region and edge region to bond at different temperature ranges simultaneously, resolving the temperature uniformity issue while maintaining fast bonding speed.
Solution Approach 2:
Different regions of the bonding layer are given different local qualities through varying metal element compositions. The center region bonding portions contain metal elements suitable for higher temperature bonding, while edge region bonding portions contain metal elements with lower melting points. This local quality differentiation ensures optimal bonding at each region under uniform laser irradiation, solving the temperature uniformity problem.
2Strength
If high temperature laser bonding is used, then bonding strength is improved, but short circuit risk increases due to excessive melting
Solution Approach 1:
The bonding layer uses metal elements with different melting points to create a temperature gradient tolerance. When laser irradiation occurs, the metal elements melt at different temperatures, allowing the bonding process to complete successfully without excessive melting that would cause short circuits. This parameter variation in material properties enables strong bonding while maintaining reliability.
Solution Approach 2:
The bonding layer is constructed as a composite material system with multiple metal elements having different thermal properties. This composite structure allows the bonding layer to withstand the laser bonding process without uniform overheating, as different components respond differently to thermal input, preventing the excessive melting that leads to short circuits while still achieving strong bonding.
3Reliability
If low temperature laser bonding is used, then short circuit risk is reduced, but bonding quality deteriorates due to insufficient melting
Solution Approach 1:
By incorporating metal elements with lower melting points in the bonding layer composition, the bonding process can occur at lower temperatures that prevent short circuits. The phase change behavior of these metal elements at lower temperatures ensures adequate melting and bonding quality without requiring high temperature irradiation that would cause reliability issues.
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 improves the production yield by reducing the risk of short circuits and ensuring reliable bonding between microLEDs and the array substrate, maintaining the structural integrity and display performance of the panel.
Implementation Method 1
The array substrate and the temporary substrate are irradiated by using a surface spot laser
Implementation Method 2
all first metal portions and second metal portions irradiated by a center region of the surface spot laser melt
Implementation Method 3
all first metal portions and second metal portions irradiated by a center region of the surface spot laser melt and all second metal portions irradiated by an edge region of the surface spot laser melt
Implementation Method 4
The bonding layer includes multiple discrete bonding portions. A bonding portion connects a light-emitting diode and a corresponding first electrode
Data Source
AI summary
Provided are a display panel, a manufacturing method thereof, a display device, and an array substrate. The display panel includes an array substrate, light-emitting diodes, and a bonding layer including bonding portions. A first bonding portion of the bonding portions includes a first intermetallic compound portion. A second bonding portion of the bonding portions includes a first metal portion and a second intermetallic compound portion that are stacked. The first intermetallic compound portion includes a first metal element and a second metal element. The first metal portion includes the first metal element, and the second intermetallic compound portion includes the second metal element. The melting point of a pure metal or an alloy formed from the second metal element is lower than that of a pure metal or an alloy formed from the first metal element.