Metal Layer Step Structure for Micro LED Adhesion Reliability
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Solution Overview
Problem
The adhesion between the metal layer and the organic insulating layer in micro LED display devices is weak, leading to peeling issues during heat treatment, which affects the reliability of the display device.
Innovation Solution
Incorporating a convex or recessed portion in the organic insulating layer with a metal layer that covers it, including a step portion along the side surface, to relax the stress and improve bonding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal layer is formed over an organic insulating layer in a micro LED display device, then electrical connectivity and structural support are improved, but adhesion between the layers is weak leading to peeling during heat treatment
Solution Approach 1:
The patent introduces a step portion in the metal layer that creates a vertical dimension change, allowing the metal layer to wrap around and cover the side surface of the convex portion of the organic insulating layer. This three-dimensional configuration increases the bonding interface area and mechanical interlocking, thereby improving adhesion strength and preventing peeling during heat treatment.
Solution Approach 2:
The convex portion of the organic insulating layer introduces a curved surface geometry instead of a flat interface. The metal layer conforms to this curved surface and wraps around it, creating a stepped configuration that enhances mechanical interlocking and adhesion between the metal and organic insulating layers.
2Strength
If heat treatment is applied to bond the light emitting element, then bonding strength is improved, but peeling occurs at the interface between metal and organic insulating layers
Solution Approach 1:
The patent pre-forms a convex portion in the organic insulating layer before depositing the metal layer. This convex structure creates a stepped configuration that anticipates and prevents peeling during subsequent heat treatment by providing mechanical interlocking and stress distribution, cushioning against the harmful peeling effect before it occurs.
Solution Approach 2:
By introducing the step portion that wraps around the convex portion, the patent adds a vertical dimension to the bonding interface. This three-dimensional configuration distributes thermal stress more effectively during heat treatment and prevents peeling by creating mechanical interlocking, thereby cushioning against the harmful effects of thermal processing.
3Area of stationary object
If the metal layer is made thicker to improve coverage, then coverage and electrical conductivity are improved, but stress in the metal layer increases leading to more peeling
Solution Approach 1:
Instead of increasing metal layer thickness uniformly, the patent creates a stepped configuration where the metal layer wraps around the convex portion. This three-dimensional structure provides adequate coverage and electrical conductivity while distributing stress across multiple interfaces, preventing excessive stress concentration that would lead to peeling.
Solution Approach 2:
The metal layer is segmented into different levels or steps rather than being a single continuous thick layer. This segmentation allows each step to independently manage stress, providing sufficient coverage and conductivity while reducing overall stress accumulation that would cause peeling at the interface.
Data Source
AI summary
A display device includes a substrate, an organic insulating layer over the substrate, a metal layer over the organic insulating layer, and a light emitting element over the metal layer. The organic insulating layer includes a convex portion that overlaps the light emitting element. The metal layer covers the convex portion and includes a step portion along a side surface of the convex portion.