Display Panel Input Pad Spacing for Thermal Expansion Alignment

Solution Overview

Problem

The misalignment of input and output pads during the bonding process in display panels due to differing thermal expansion coefficients between the flexible circuit board and the display panel substrate affects the bonding yield.

Innovation Solution

The display panel and flexible circuit board designs feature input and output pads arranged in a specific pattern with varying spacings and extensions, allowing for gradual and uniform spacing adjustments to match thermal expansion, ensuring accurate alignment and bonding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the flexible circuit board and display panel substrate are bonded using conventional uniform pad spacing, then the bonding process is simple, but thermal expansion mismatch causes misalignment between input and output pads

Engineering Contradiction:

Improvepad alignment precisionVSAvoidpad spacing pattern complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies local quality by varying the spacing between adjacent pads in different regions of the pad array. Specifically, the spacing between pads is adjusted locally to compensate for thermal expansion differences, creating a non-uniform spacing pattern that matches the thermal deformation characteristics of the flexible circuit board relative to the display panel substrate.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the spacing parameter between adjacent pads from a uniform value to a variable value that depends on the position in the pad array. This parameter change allows the pad spacing to adapt to thermal expansion effects, maintaining alignment between input and output pads after bonding under thermal conditions.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the pad spacing is adjusted to compensate for thermal expansion, then misalignment is reduced, but the fabrication process becomes more complex

Engineering Contradiction:

Improvebonding yieldVSAvoidfabrication process simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent implements preliminary action by pre-calculating and pre-setting the non-uniform pad spacing pattern during the design and fabrication stage. This preliminary adjustment accounts for the expected thermal expansion mismatch before bonding occurs, so that when thermal expansion happens during operation, the pads remain aligned without requiring additional real-time adjustments or complex fabrication processes.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If uniform pad spacing is used, then the fabrication process is straightforward, but thermal expansion causes misalignment affecting bonding yield

Engineering Contradiction:

Improvebonding yieldVSAvoidpad arrangement complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies local quality by varying the spacing between adjacent pads in different regions of the pad array. Specifically, the spacing between pads is adjusted locally to compensate for thermal expansion differences, creating a non-uniform spacing pattern that matches the thermal deformation characteristics of the flexible circuit board relative to the display panel substrate.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the spacing parameter between adjacent pads from a uniform value to a variable value that depends on the position in the pad array. This parameter change allows the pad spacing to adapt to thermal expansion effects, maintaining alignment between input and output pads after bonding under thermal conditions.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design effectively reduces misalignment and improves bonding yield by matching the spacing variations of thermally expanded pads, aligning input and output pads in a one-to-one correspondence, enhancing the reliability of the bonding process.

Implementation Method 1

a thermal expansion coefficient of the flexible circuit board is different from a thermal expansion coefficient of a substrate of the display panel, which causes a misalignment between an input pad and an output pad during the bonding process

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS10897819B2Display panel, flexible circuit board and display device

Publication Date: 2021.01.19 XIAMEN TIANMA MICRO ELECTRONICS

AI summary

A display panel, a flexible circuit board and a display device are provided. The display panel includes a substrate, and at least one row of a plurality of input pads including at least one first-input pad disposed in the middle of the input pads and a plurality of second-input pads disposed on both sides of the first input pad. Each input pad includes a first end and a second end that are oppositely disposed, and a spacing between any adjacent two input pads includes a first spacing between adjacent two first ends and a second spacing between adjacent two second ends. The first spacing and the second spacing between any adjacent two second-input pads are not equal. Along a direction from the first-input pad to the second-input pad, starting from adjacent first-input and second-input pads, the first spacing and the second spacing successively and gradually increases, respectively.