Ceramic Electrode Intermediate Layers for Silver-Free Varistors

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Solution Overview

Problem

Conventional varistor electrode components face issues with environmental pollution, high production costs due to precious silver usage, low bonding strength, high-resistance ohmic contact, and poor corrosion resistance, particularly with lead-free soldering, leading to reliability concerns.

Innovation Solution

The electrode component features intermediate layers formed by sputtering metal materials like nickel, vanadium, chromium, or aluminum on a ceramic substrate, with electrode layers sprayed using metal materials like zinc, copper, or nickel, eliminating the need for organic silver paste and enhancing bonding strength and corrosion resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If organic silver paste is used to form the electrode layer, then good electrical conductivity is achieved, but high production cost and environmental pollution occur due to precious silver material and toxic substances

Engineering Contradiction:

Improveelectrical conductivityVSAvoidenvironmental pollution and production cost

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent changes the material composition parameter by replacing organic silver paste with inorganic metal materials (such as aluminum, zinc, or nickel) and their alloys, thereby eliminating toxic organic substances and reducing precious metal consumption while maintaining electrical conductivity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes expensive silver material with cheaper inorganic metal materials, reducing production cost while achieving the required electrical conductivity through optimized material composition and layer structure

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If thick silver layer is adopted to increase surge-withstanding capability, then better electrical performance is achieved, but high production cost and poor bonding strength occur

Engineering Contradiction:

Improvesurge-withstanding capabilityVSAvoidbonding strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent uses composite inorganic metal layer structures (such as aluminum-zinc-nickel combinations) that provide both excellent electrical conductivity and strong bonding to the ceramic substrate, eliminating the need for thick silver layers while improving surge-withstanding capability

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The inorganic metal layers serve as an intermediary between the ceramic substrate and the external environment, providing both electrical conductivity and mechanical bonding strength through direct metallurgical bonding to the ceramic surface

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If lead-free solder is used for soldering, then environmental protection is improved, but poor corrosion resistance and electrode detachment occur due to high mutual solubility of tin and silver

Engineering Contradiction:

Improveenvironmental protectionVSAvoidcorrosion resistance

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent replaces silver-based electrodes with inorganic metal electrodes that are resistant to solder corrosion, allowing the use of lead-free solder without the risk of electrode detachment or melting

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent changes the electrode material composition to inorganic metals with low solubility in solder alloys, fundamentally altering the chemical interaction between the electrode and solder to prevent corrosion and detachment

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 solution reduces heat generation, prolongs operation duration, and improves electrical characteristics by eliminating the use of precious silver, minimizing pollution, and providing enhanced solder erosion protection, resulting in improved durability and reliability.

Implementation Method 1

Each intermediate layer is formed by a metal material selected from one of nickel, vanadium, chromium, aluminum, and zinc or a combination thereof

Methodology Applied

Scientific EffectSputtering: Sputtering

Data Source

PatentUS9583239B2Electrode component with electrode layers formed on intermediate layers

Publication Date: 2017.02.28 THINKING ELECTRONIC IND CO LTD

AI summary

An electrode component with electrode layers formed on intermediate layers includes a ceramic substrate, two intermediate layers formed on two opposite surfaces of the ceramic substrate, two electrode layers respectively formed on the two intermediate layers, two lead wires respectively connected to the electrode layers, and an insulating layer enclosing the ceramic substrate, the intermediate layers, the electrode layers, and portions of the two lead wires. The intermediate layer formed between the ceramic substrate and the electrode layer replaces the fabrication means for conventional silver electrode layer to provide good binding strength between the ceramic substrate and the electrode layer. Besides same electrical characteristics for original products, the electrode component can get rid of the use of precious silver in screen printed silver electrode and avoid pollution caused by evaporation and thermal dissolution of organic solvent while lowering the ohmic contact resistance between the electrode layer and the ceramic substrate.