Chip on Film Pattern Branching for GIP Pad Reduction

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Solution Overview

Problem

The increasing number of gate-in-panel (GIP) input pads in chip on film (COF) structures for display devices, such as OLEDs, leads to narrowed input pad pitch, misalignment errors during bonding, and increased manufacturing costs, as well as complex assembly processes.

Innovation Solution

A pattern branching structure is implemented on the COF, reducing the number of GIP input pads from 2N to N by dividing GIP wirings into 2N transmission paths, with separate connection lines at different layers and via holes for efficient signal transmission, independent of data signal paths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the number of GIP input pads is increased to accommodate more GIP driving signals, then the number of GIP driving signals is improved, but the input pad pitch is narrowed

Engineering Contradiction:

Improvenumber of GIP driving signalsVSAvoidinput pad pitch

Core Design Contradiction:

Quantity of substanceVSLength of moving object

Solution Approach 1:

The patent divides the COF into two separate COFs, each handling N GIP input pads, thereby segmenting the total 2N pads into two manageable groups. This segmentation allows each COF to maintain adequate pad pitch while collectively supporting the required number of GIP driving signals

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from a single-row pad arrangement to a two-dimensional layout by positioning N GIP input pads at the left side and N GIP input pads at the right side of the circuit film, utilizing both lateral dimensions to accommodate more pads without narrowing pitch

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Quantity of substance

If the number of input pads of COF is increased, then the number of GIP driving signals is improved, but misalignment error occurs during bonding process

Engineering Contradiction:

Improvenumber of GIP input padsVSAvoidalignment accuracy

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

By segmenting the 2N input pads into two separate COFs with N pads each, the patent reduces the complexity of alignment during bonding. Each COF requires alignment of only N pads, which is more manageable and achieves better alignment accuracy compared to bonding a single COF with 2N pads

Inventive Principle:

Principle #1Segmentation

3Quantity of substance

If the horizontal width of COF is increased to accommodate more input pads, then the number of GIP driving signals is improved, but manufacturing costs are increased

Engineering Contradiction:

Improvenumber of GIP input padsVSAvoidmanufacturing cost

Core Design Contradiction:

Quantity of substanceVSEase of manufacture

Solution Approach 1:

The patent segments the COF into two separate COFs, each with N input pads. This segmentation allows using standard-width COFs with established manufacturing processes, avoiding the need to manufacture wider COFs with 2N pads, thereby controlling manufacturing costs

Inventive Principle:

Principle #1Segmentation

4Manufacturing precision

If source PCBs are divided into two pieces to overcome misalignment error, then alignment accuracy is improved, but the number of operations in bonding and assembly process is increased

Engineering Contradiction:

Improvealignment accuracyVSAvoidtact time

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

Instead of dividing the PCB and increasing assembly complexity, the patent inverts the approach by using two separate COFs that can be independently bonded to a single PCB. This reduces the assembly operations compared to connecting multiple PCB pieces through connectors and flexible cables

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS10546807B2Chip on file display device including the same

Publication Date: 2020.01.28 LG DISPLAY CO LTD

AI summary

Disclosed are a chip on film (COF) and a display device including the same, for reducing the number of input pads using a pattern branching structure. The COF is connected to gate-in-panel (GIP) output pads using a structure formed via branching of GIP wirings connected to the GIP input pads in a data driving integrated circuit (IC) or a circuit film to reduce the number of GIP input pads.