Micro-LED Backplate Bonding Structure for Repair Without Remelting
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Solution Overview
Problem
Current metal bonding processes for LED chips in micro-LED display backplates face challenges in achieving high yield due to the melting of primary bonded LED chips during secondary repair bonding, leading to batch deviations and damage.
Innovation Solution
A backplate design with distinct bonding layers for primary and repair bonding, where the first bonding layer has a higher melting point than the second, ensuring that the primary bonded LEDs are not affected during the repair process, using multi-layer structures of single-metal layers with controlled thickness ratios and materials to maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the same kind of solder is deposited on pads for primary bonding and repair bonding, then the repair bonding process can be simplified, but the bonding temperature will cause primary bonded LED chips to melt again or partially, resulting in batch deviation or damage
Solution Approach 1:
The bonding layer is segmented into two distinct layers: a first bonding layer with higher melting point for primary bonding and a second bonding layer with lower melting point for repair bonding. This segmentation allows each layer to serve its specific function without interfering with the other, enabling repair operations without remelting primary bonds
Solution Approach 2:
Different regions of the bonding structure are given different material properties. The first bonding layer uses materials with higher melting points (e.g., Au, Ag, Cu) while the second bonding layer uses materials with lower melting points (e.g., Sn, Pb, In). This local differentiation in material quality enables selective bonding and repair without affecting other regions
2Strength
If a higher bonding temperature is used for primary bonding to ensure strong adhesion, then the primary bonding strength is improved, but it becomes difficult to perform repair bonding without affecting the primary bonded chips
Solution Approach 1:
The melting point parameter of the bonding layer is changed by creating a bimodal distribution with two distinct melting point ranges. The first bonding layer operates at higher temperatures (e.g., 800-1000°C for Au/Ag) to ensure strong primary bonding, while the second bonding layer operates at lower temperatures (e.g., 183-250°C for Sn/Pb/In) to enable easy repair without affecting primary bonds
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 ensures the stability of primary bonded LEDs during repair bonding, preventing batch deviations and achieving high mass-production yield by controlling the bonding temperatures of the multi-layer metal structures.
Implementation Method 1
a bonding temperature of the first bonding layer is higher than that of the second bonding layer
Implementation Method 2
heating of the second bonding layer would not affect LEDs which have been bonded
Implementation Method 3
the solder is heated by heating and bonded to form metallurgically bonded connections
Data Source
AI summary
A display panel, and light-emitting elements and a backplate used for display panels are provided. The backplate is provided thereon a first pad and a second pad serving as a repair pad. The first pad includes a first adhesive layer and a first bonding layer. The second pad includes a second adhesive layer and a second bonding layer. Each of the first and second bonding layers is a multi-layer structure including multiple single-metal layers. A bonding temperature of the first bonding layer is higher than that of the second bonding layer. The multiple single-metal layers are formed on both first and second pads by evaporation, so that a purity of each single-metal layer is ensured, facilitating alloys with different melting points are formed subsequently. When the second pad is heated to solder a LED chip for repairing, a first alloy on the first pad cannot be melted.