Multi-Layer Pad Wiring Structure for COF Bonding Reliability
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Solution Overview
Problem
The existing display devices face issues with damage and disconnection of insulating layers and connection wires due to load applied during chip-on-film (COF) attachment, along with high bonding resistance between circuit components and signal wires, and cracks in insulating layers.
Innovation Solution
A display device structure is introduced with a specific configuration of insulating layers and connection wires, where at least one of the second, third, and fourth insulating layers is removed by patterning to allow connection wires to overlap, reducing the risk of damage and disconnection during COF attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If one connection wire is formed on one insulating layer, then the structure is simple, but the insulating layer and connection wire may be damaged and disconnected due to load during COF attachment
Solution Approach 1:
The patent divides the connection structure into multiple segments: multiple connection wires (first, second, third connection wires) are formed on different insulating layers (first, second insulating layers). This segmentation distributes the mechanical load during COF attachment across multiple independent connection paths, preventing single-point failure and improving overall connection reliability.
Solution Approach 2:
The patent transitions from a two-dimensional single-layer structure to a three-dimensional multi-layer structure. Connection wires are arranged on different insulating layers at different heights, creating a vertical stacking configuration. This dimensional change allows load distribution across multiple layers, enhancing mechanical strength and connection reliability during bonding processes.
2Reliability
If ACF with conductive ball is used for COF attachment, then electrical connection is achieved, but bonding resistance increases and cracks occur in insulating layer
Solution Approach 1:
The patent performs preliminary actions by forming multiple connection wires on different insulating layers before the COF attachment process. This pre-established multi-path connection structure prepares the system to distribute bonding forces and electrical currents, preventing cracks and reducing bonding resistance during the actual attachment process.
Solution Approach 2:
The multi-layer connection wire structure acts as a cushioning mechanism before the COF attachment. The distributed configuration absorbs and distributes the mechanical stress and bonding resistance, preventing concentration of forces that would cause cracks in the insulating layer or excessive bonding resistance.
3Reliability
If multiple connection wires are formed on different insulating layers, then connection reliability improves, but the structure becomes more complex
Solution Approach 1:
The patent makes each insulating layer and connection wire combination serve multiple functions: electrical connection, mechanical support, and stress distribution. This multi-functionality justifies the increased structural complexity by achieving superior connection reliability through a single integrated multi-layer design rather than separate components.
Data Source
AI summary
A display device may include a substrate, a display area, a non-display area, a bending area, a connection wire area, a pad part, and a first area included in the pad part. The first area may include: a first insulating layer disposed on the substrate; a first connection wire disposed on the first insulating layer; a second connection wire disposed on the first connection wire; a second insulating layer disposed on the second connection wire; a third connection wire disposed on the second insulating layer; and a fourth connection wire disposed on the third connection wire.