Chip on Film Switchable Output Units Reduce Pad Count

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Solution Overview

Problem

The increasing number of gate transmission signals in display devices, such as OLEDs, leads to a higher number of output pads on chip-on-film (COF) structures, causing misalignment errors and increased manufacturing costs due to the need for wider COFs and more complex bonding processes.

Innovation Solution

A COF design with switchable output units, including multiplexers and demultiplexers, that selectively outputs gate transmission signals and data to reduce the number of output pads by utilizing a first and second switchable output unit to share output pads, thereby reducing the total number of pads required.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the number of gate transmission signals is increased, then the display device functionality is improved, but the number of output pads increases causing misalignment errors and increased manufacturing costs

Engineering Contradiction:

Improvedisplay device functionalityVSAvoidbonding alignment accuracy

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent makes output pads multi-functional by enabling them to alternately serve as gate transmission signal outputs and data outputs through switchable output units. This allows the same physical pads to handle different signal types at different times, effectively reducing the total number of pads needed while maintaining full functionality for both gate signals and data transmission

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent introduces dynamic switching capability through switchable output units that can change the function of output pads in real-time. The output pads can dynamically alternate between transmitting gate signals and data signals based on operational requirements, enabling adaptive signal routing without increasing pad count

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If the number of output pads is increased, then more gate transmission signals can be output, but the horizontal width of COF increases leading to higher manufacturing costs

Engineering Contradiction:

Improvegate transmission capabilityVSAvoidCOF horizontal width

Core Design Contradiction:

Adaptability or versatilityVSLength of stationary object

Solution Approach 1:

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the gate signal output function and data output function into the same physical output pads. By combining these functions temporally through switching, the patent reduces the total number of pads required, thereby maintaining COF width within acceptable limits while providing full gate transmission capability

Inventive Principle:

Principle #5Merging (Combining)

3Manufacturing precision

If additionally divided source PCBs are used to overcome misalignment error, then bonding alignment is improved, but the number of operations increases leading to increased tact time and manufacturing costs

Engineering Contradiction:

Improvebonding alignment accuracyVSAvoidassembly efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent extracts the misalignment problem from the bonding process by reducing the number of pads that need to be bonded. By making output pads multi-functional and reducing their total count, the patent removes the need for complex PCB division and connector assembly, thereby maintaining high bonding precision while simplifying the overall assembly process

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS10726787B2Chip on film and display device including the same

Publication Date: 2020.07.28 LG DISPLAY CO LTD

AI summary

A chip on film and a display device including the same selectively outputs gate transmission signals and data outputs to reduce the number of output pads in a data driving IC. The COF includes first to third groups of data input pads, gate input pads, and output pads. A data driving IC includes first to third groups of output buffers, a first switchable output unit configured to selectively supply gate transmission signals and an output of the first group of output buffers to the first group of output pads, and a second switchable output unit configured to selectively supply the gate transmission signals and an output of the third group of output buffers to the third group of output pads. An output of the second group of output buffers is supplied to the second group of output pads between the first and the third groups of output pads.