Flexible Circuit Board Multi-Layer Conductive Patterns

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Solution Overview

Problem

Conventional chip-on-film (COF) flexible circuit boards require multiple printed circuit boards to connect a display panel to a main board, increasing device thickness and limiting miniaturization due to bonding failures and adhesive layer reliability issues.

Innovation Solution

A flexible circuit board design with multiple conductive pattern layers on a single substrate, including inner and extension lead patterns, and plating layers, allows direct connection between the display panel and main board, reducing the number of necessary substrates and enhancing reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple printed circuit boards are used to connect display panel and main board, then connection reliability is improved, but device thickness increases

Engineering Contradiction:

Improveconnection reliabilityVSAvoiddevice thickness

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The patent combines multiple printed circuit board functions into a single flexible circuit board by integrating multiple conductive pattern layers (first, second, and third conductive pattern parts) on one substrate. This merging eliminates the need for multiple separate boards while maintaining reliable electrical connections between the display panel and main board, thereby reducing device thickness without sacrificing connection reliability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent transitions from a planar arrangement of multiple separate printed circuit boards to a multi-layered flexible circuit board structure where conductive patterns are stacked in the thickness direction. By utilizing the Z-axis dimension for layer stacking rather than requiring multiple separate boards in the X-Y plane, the design achieves reliable multi-path connections while minimizing overall device thickness.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If multiple printed circuit boards are used, then connection reliability is improved, but device size increases

Engineering Contradiction:

Improveconnection reliabilityVSAvoiddevice size

Core Design Contradiction:

ReliabilityVSArea of moving object

Solution Approach 1:

The patent merges multiple circuit board functions into a single flexible substrate with multiple conductive pattern layers, eliminating the need for multiple separate boards. This integration consolidates the spatial footprint, reducing the overall device area while maintaining reliable electrical connections through the multi-layer conductive structure.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If multiple printed circuit boards are used, then connection reliability is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveconnection reliabilityVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple printed circuit board manufacturing processes into a single flexible circuit board fabrication process. By integrating multiple conductive pattern layers on one substrate rather than assembling multiple separate boards, the manufacturing process is simplified, reducing the number of bonding steps and potential failure points while maintaining connection reliability.

Inventive Principle:

Principle #5Merging (Combining)

4Manufacturing precision

If COF scheme is used to mount chips on flexible substrate, then fine pitch implementation is achieved, but direct connection between display panel and main board is prevented

Engineering Contradiction:

Improvefine pitch capabilityVSAvoidnumber of printed circuit boards

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent makes the flexible circuit board universal by enabling it to perform multiple functions: it maintains the COF scheme's fine pitch chip mounting capability while simultaneously providing direct connection between the display panel and main board. The multi-layer conductive pattern structure allows the single flexible substrate to replace multiple separate circuit boards, achieving both fine pitch implementation and direct connectivity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11089682B2Flexible circuit board, chip package including the same, and electronic device including the chip package

Publication Date: 2021.08.10 LG INNOTEK CO LTD

AI summary

According to an embodiment, a flexible circuit board includes: a first substrate; a second substrate disposed on the first substrate and including an opening; a first conductive pattern part disposed on a bottom surface of the first substrate; a second conductive pattern part disposed on a top surface of the second substrate; a third conductive pattern part disposed between the first substrate and the second substrate; and an upper protective layer partially disposed on the second conductive pattern part and including a first open region, wherein the third conductive pattern part includes: a first inner lead pattern part disposed in the opening of the second substrate; and a first extension pattern part connected to the first inner lead pattern part, the second conductive pattern part includes: a second inner lead pattern part disposed in the first open region of the upper protective layer; and a second extension pattern part connected to the second inner lead pattern part, and a number of first inner lead pattern parts is greater than a number of second inner lead pattern parts.