Copper Wiring Electrode Corrosion Prevention

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Solution Overview

Problem

Thin-film devices with copper electrodes in rewiring layers suffer from corrosion due to halogen ions from solder flux, leading to increased electric resistance and unfavorable appearance, as the insulating resin layer allows moisture and halogen ions to reach the electrodes, causing oxidation.

Innovation Solution

A thin-film device configuration with a rewiring layer featuring a copper wiring electrode covered by a passivating first close-contact layer and optionally a second close-contact layer, made of materials like titanium, chrome, or aluminum, which prevents halogen ions from reaching the electrode, and an insulating resin layer that covers the close-contact layers to maintain insulation and protect against moisture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an insulating resin layer is formed to cover wiring electrodes, then insulation is improved, but the resin layer allows moisture and halogen ions to pass through, causing corrosion

Engineering Contradiction:

Improveinsulation performanceVSAvoidmoisture and halogen ion penetration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies a composite protective structure consisting of multiple layers: a base insulating resin layer combined with a fluororesin coating layer. This composite material system leverages the insulation properties of the resin layer while the fluororesin layer provides superior moisture and halogen ion barrier properties, preventing corrosion of the copper wiring electrodes.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent uses a thin fluororesin film coating applied over the insulating resin layer to create a protective barrier. This thin film structure effectively blocks moisture and halogen ions from reaching the wiring electrodes while maintaining the overall insulation performance and not significantly increasing device thickness.

Inventive Principle:

Principle #30Flexible shells and thin films

2Reliability

If copper wiring electrodes are used in rewiring layers, then conductivity is improved, but the copper electrodes are susceptible to oxidation and corrosion from halogen ions

Engineering Contradiction:

Improveelectrical conductivityVSAvoidoxidation and corrosion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a fluororesin coating layer as an intermediary protective barrier between the copper wiring electrodes and the corrosive environment. This intermediate layer prevents direct contact between halogen ions and copper, eliminating the chemical reaction that would otherwise cause corrosion and maintain electrical conductivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The fluororesin coating creates an inert protective environment around the copper wiring electrodes, shielding them from reactive substances like halogen ions and moisture. This inert barrier prevents oxidation and corrosion reactions, allowing the copper electrodes to maintain their conductive properties over time.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

3Ease of manufacture

If halogen from solder flux reaches the copper electrode, then soldering is achieved, but copper-halogen compounds form causing increased resistance and discoloration

Engineering Contradiction:

Improvesoldering capabilityVSAvoidelectrical resistance control

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The fluororesin coating serves as a selective barrier that allows controlled interaction during soldering while preventing harmful reactions. During the soldering process, the coating permits necessary thermal and chemical interactions for proper solder joint formation, but subsequently prevents halogen ions from migrating to and reacting with the copper electrodes, thereby maintaining electrical resistance within specifications.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively suppresses corrosion of the wiring electrodes, reducing electric resistance and maintaining the device's functionality while improving its appearance by preventing halogen-copper compound formation and moisture ingress.

Implementation Method 1

The first close-contact layer is made of a material that becomes passivated. The first close-contact layer is in direct contact with the wiring electrode and has a shape covering, in a continuous manner, a second region of the first main surface of the wiring electrode

Methodology Applied

Scientific EffectPassivation:

Data Source

PatentUS11587734B2Thin-film device having a close-contact layer covering part of a wiring electrode, and method of manufacturing thin-film device

Publication Date: 2023.02.21 MURATA MFG CO LTD

AI summary

A thin-film device that includes a wiring electrode which contains copper. A terminal electrode is formed on a first region of the first main surface of the wiring electrode. A first close-contact layer made of a material different from copper and that has a shape covering, in a continuous manner, a second region of the first main surface of the wiring electrode, the second region being adjacent to the first region, and the side surface of the wiring electrode that is continuous with the second region.