COF Input Pad Thinner Extending Portion for Metal Particle Reduction
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Solution Overview
Problem
Conventional chip on film structures for liquid crystal displays face reliability issues due to metal particles generated during the punching process, which can short circuit the chip circuit, and the existing solutions increase costs and complexity with additional tape carrier packages.
Innovation Solution
The chip on film structure features input and output pads disposed on opposite sides of the driver chip, with thinner extending portions that are cut along the cutting edge to minimize metal particle dispersion, and the output pads are positioned between the driver chip and the second cutting edge to avoid damage during punching, allowing for a simplified layout and reduced material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the chip on film structure is punched from the tape, then the driver chip can be separated and mounted, but metal particles are generated that may short circuit the chip circuit and reduce reliability
Solution Approach 1:
The harmful metal particles are removed by designing the extending portions to be thinner than the main pad body, so that when cutting occurs, less metal material is present to generate particles. The thinner extending portions are specifically extracted as sacrificial elements that minimize particle generation while maintaining electrical connectivity.
Solution Approach 2:
The extending portions are pre-designed with a thinner width before the punching process. This preliminary structural preparation ensures that when the cutting edge passes through during punching, the amount of metal material exposed and potentially generated as particles is minimized in advance, preventing the reliability issue before it occurs.
2Reliability
If additional tape carrier packages are used to avoid metal particle issues, then chip reliability is maintained, but manufacturing cost and device complexity increase
Solution Approach 1:
The input pads and output pads are integrated onto a single film substrate with the driver chip, eliminating the need for separate tape carrier packages. The extending portions of both input and output pads are designed to work together on the same substrate, simplifying the overall package structure while maintaining reliability through the thinner extending portion design.
3Object-generated harmful factors
If the extending portions of input pads are made thinner, then metal particle dispersion is reduced, but the pad structure becomes more complex
Solution Approach 1:
The pad structure employs local quality variation where the extending portions have a thinner width specifically at the regions susceptible to cutting and particle generation, while the main pad body retains its full width for electrical connectivity. This localized thickness variation reduces metal particle dispersion only where necessary without compromising overall pad functionality.
Data Source
AI summary
The chip on film structure for a liquid crystal display is disclosed. The chip on film structure includes a film substrate, a driver chip disposed on the film substrate, a plurality of the input pad, and a plurality of output pads. The input pads and the output pads are disposed on two opposite sides of the driver chip, and are electrically connect to the driver chip respectively. Each input pad comprises an extending portion extending from the input pads to a first cutting edge respectively, and a width of the extending portion is thinner than a width of the input pad, and the extending portions are cut along the first cutting edge.