Overlapping Chip-on-Film Packages for Display Resolution
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Solution Overview
Problem
The increasing number of chip-on-film (COF) packages around ultra-high definition flat panel displays reduces the pitch between adjacent packages, exceeding the production capabilities, leading to lower bonding yield and increased manufacturing costs, which hinders the achievement of higher resolution and better image quality.
Innovation Solution
A COF package structure comprising two overlapping COFs with increased inner leads, allowing for easier bonding and reduced production costs, while expanding the distance between adjacent COF packages to comply with manufacturing requirements, thereby enhancing bonding yield and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of COF packages is increased to achieve higher resolution, then the image quality is improved, but the pitch between adjacent packages becomes too small, reducing bonding yield and productivity
Solution Approach 1:
The patent divides a single COF package into two separate COF packages (first COF and second COF), each handling a portion of the pixel electrodes. This segmentation allows the packages to be spaced further apart while still achieving the required resolution, as each package independently connects to its designated pixel region without requiring minimal pitch with adjacent packages.
2Reliability
If the number of leads on COF package is increased to improve electrical connection, then the bonding quality is improved, but the pitch between leads becomes excessively small, failing to comply with manufacturing requirements
Solution Approach 1:
The patent segments the lead connections by dividing them into inner leads and outer leads with distinct functions. The inner leads connect to pixel electrodes while outer leads connect to common electrodes. This functional segmentation allows each lead type to be optimized for its specific purpose with appropriate pitch, avoiding the need for excessively small pitch across all leads while maintaining reliable electrical connections.
Solution Approach 2:
The patent applies different lead configurations to different regions of the COF package. Inner leads are concentrated near the pixel electrode connection region with appropriate pitch for high-density signaling, while outer leads are positioned at the periphery with larger pitch suitable for common electrode connections and manufacturing processes.
3Measurement precision
If the distance between adjacent COF packages is reduced to increase the number of packages, then the resolution is improved, but the distance becomes too small for production apparatus, lowering productivity
Solution Approach 1:
By segmenting the display into multiple COF packages with clear spatial separation, the patent enables each package to be positioned at locations that maintain adequate distance for manufacturing equipment. The segmented architecture allows resolution to be achieved through the combined coverage of multiple packages rather than through excessive miniaturization of package spacing.
Data Source
AI summary
A chip-on-film (COF) package structure includes a first COF and a second COF. The first COF includes a first flexible substrate having a first external terminal and a first internal terminal opposite to each other, first outer leads disposed at the first external terminal, first inner leads disposed at the first internal terminal, and a first chip disposed between the first external terminal and the first internal terminal. The second COF includes a second flexible substrate having a second external terminal and a second internal terminal opposite to each other, second outer leads disposed at the second external terminal, second inner leads disposed at the second internal terminal, and a second chip disposed between the second external terminal and the second internal terminal. The first COF is partially overlapped with the second COF. A display device having the COF package structure is also provided.