Display Panel Pad Overlap Layout for Reliable Micro LED Bonding
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Solution Overview
Problem
In the production of Micro LED/Mini LED display panels, the small size of LED chips leads to issues with electrode bonding, resulting in virtual welding and poor contact, which reduces product yield and affects display quality due to the small contact areas and low push-pull forces between LED chips and their corresponding pads on the driver backplate.
Innovation Solution
The display panel design includes a substrate with pad groups where the first and second pads overlap the corresponding metal elements, ensuring a consistent overlapping area ratio of no more than 5%, which helps maintain flatness and stability, preventing height differences and improving bonding success rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the distance between LED chips is reduced to increase density, then the resolution is improved, but the contact area between pins and pads becomes smaller leading to virtual welding and poor contact
Solution Approach 1:
The pad structure is segmented into multiple layers including a first pad layer and a second pad layer, with each layer providing bonding contact. This segmentation allows the bonding function to be distributed across multiple interfaces, compensating for the reduced contact area at each individual interface while maintaining overall bonding reliability.
Solution Approach 2:
The bonding structure transitions from a single-plane contact to a multi-layer three-dimensional structure. By stacking pad layers vertically, the bonding interface is extended into the depth dimension, increasing the total contact area and bonding strength without increasing the horizontal footprint, thus accommodating higher chip density while maintaining reliable connections.
2Measurement precision
If the size of LED chips is reduced to increase density, then the resolution is improved, but the push-pull forces become lower leading to poor bonding
Solution Approach 1:
The force transmission path is segmented across multiple pad layers and metal element layers. Instead of relying on a single bonding interface to withstand all mechanical stresses, the multi-layer structure distributes the push-pull forces across multiple interfaces, with each layer contributing to the overall mechanical strength and force bearing capacity.
Solution Approach 2:
The bonding structure employs composite construction with alternating layers of conductive materials (metal elements) and insulating materials (dielectric layers). This composite structure provides both electrical connectivity and mechanical strength, creating a robust bonding system that can withstand the reduced push-pull forces associated with smaller LED chips while maintaining electrical functionality.
Data Source
AI summary
A display panel and a display device are provided. The display panel includes a substrate; light-emitting devices, pad groups on a side of the substrate, and first metal elements and second metal elements at a side of the pad groups close to the substrate. Each pad group includes a first pad and a second pad, and at least one pad group corresponds to one light-emitting device. In one pad group corresponding to one same light-emitting device, along a direction perpendicular to a plane of the substrate, the first pad at least partially overlaps the first metal elements with an overlapping area of S1 and the second pad at least partially overlaps the second metal elements with an overlapping area of S2 where |S1−S2|/S1≤5%, or the first pad does not overlap the first metal elements and the second pad does not overlap the second metal elements.