Dummy Terminal Equalizes Etching Loading Effect on Display Driver IC

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Solution Overview

Problem

The reliability of the outermost terminal in liquid crystal display devices is compromised due to the 'loading effect' during etching, where the width of through holes becomes wider, leading to potential conduction failures from moisture or oxygen exposure, especially since the cap metal is not adequately protected.

Innovation Solution

A display device design where a dummy terminal is formed on the outer side of the outermost IC terminal, with a through hole and covered by ITO, but not connected to the interconnection, to equalize the loading effect with other IC terminals, ensuring consistent reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the outermost terminal is formed without a dummy terminal, then the device complexity is reduced, but the reliability deteriorates due to the loading effect causing wider through holes and potential conduction failures

Engineering Contradiction:

Improveterminal connection reliabilityVSAvoidterminal structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The terminal structure is segmented into functional terminals (connected to interconnections) and dummy terminals (not connected to interconnections). The dummy terminal is separated from the functional terminal by a gap, allowing independent formation and function. This segmentation enables the dummy terminal to specifically address the loading effect problem without complicating the functional terminal structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The dummy terminal acts as an intermediary element that mediates the loading effect between the etching process and the functional terminal. By positioning the dummy terminal adjacent to the outermost functional terminal, it serves as a buffer that equalizes the etching conditions, preventing the harmful widening of through holes in the functional terminal while maintaining overall device functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a dummy terminal is formed on the outer side of the outermost IC terminal, then the reliability is improved by equalizing the loading effect, but the manufacturing precision requirement increases to ensure proper positioning and spacing

Engineering Contradiction:

Improveoutermost terminal reliabilityVSAvoiddummy terminal positioning precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The dummy terminal is formed in advance during the same manufacturing process as the functional terminals, specifically during the through hole formation step. By preparing the dummy terminal structure beforehand with predetermined spacing, the loading effect is equalized before the actual connection terminals are completed, ensuring consistent etching conditions without requiring post-manufacturing adjustments.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If the through hole width increases due to loading effect, then the ease of manufacture is improved by simpler etching, but the reliability deteriorates due to moisture and oxygen exposure causing conduction failures

Engineering Contradiction:

Improveetching process simplicityVSAvoidconduction reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The loading effect, which normally causes harmful widening of through holes and reliability degradation, is converted into a beneficial equalizing force. By intentionally adding a dummy terminal that experiences the same loading effect, the etching conditions are equalized across all terminals. The harmful widening is distributed uniformly, and the cap metal protection becomes effective, transforming the previously harmful loading effect into a consistent manufacturing condition that maintains reliability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 configuration maintains the reliability of the outermost terminal similar to other terminals, preventing conduction failures by controlling the etching effect and protecting the terminal metal from moisture and oxygen.

Implementation Method 1

a terminal metal is covered with an inorganic passivation film

Methodology Applied

Scientific EffectPhysical barrier protection:

Implementation Method 2

the through hole is covered with ITO

Methodology Applied

Scientific EffectProtective coating: Coatings

Data Source

PatentUS9865579B2Display device having driver IC directly connected to substrate

Publication Date: 2018.01.09 MAGNOLIA WHITE CORP

AI summary

In a display device connected with an IC driver, particularly the reliability of connection between an IC terminal located on the outermost side and the IC driver is improved. IC terminals and flexible wiring board terminals are formed on a terminal region of a TFT substrate. A plurality of the IC terminals are formed at a predetermined pitch. The reliability of an outermost IC terminal is degraded as compared with the reliability of the other IC terminals caused by the loading effect in etching a protection insulating film. In order to prevent this degradation, a dummy terminal is formed on the outer side of the outermost IC terminal, and the loading effect on the outermost IC terminal is made equal to the loading effect on the other IC terminals. Accordingly, degradation in the reliability of the outermost IC terminal is prevented.