Chip Resistor Electrode Design for Sulfidizing Gas Reliability

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Solution Overview

Problem

Conventional chip resistors experience disconnection issues in sulfidizing gas environments due to silver sulfide precipitation, and existing solutions either fail to prevent disconnection or lead to delamination problems with nickel-plated layers.

Innovation Solution

A chip resistor design featuring a substrate with a resistor layer, a first upper electrode layer, and a second upper electrode layer composed of 75-85% silver particles by weight with an average diameter of 0.3-2 μm and 1-10% carbon, which prevents silver sulfide precipitation and ensures strong adhesion to nickel-plated layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a silver electrode is used to prevent disconnection, then conductivity is improved, but silver sulfide precipitates in sulfidizing gas environments causing disconnection

Engineering Contradiction:

Improveconnection stabilityVSAvoidsilver sulfide precipitation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies composite materials by combining silver particles (75-85% by weight) with carbon particles (15-25% by weight) to form a second upper electrode layer. This composite structure maintains the high conductivity of silver while the carbon component prevents silver sulfide precipitation in sulfidizing gas environments, thereby resolving the contradiction between conductivity and corrosion resistance.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the compositional parameters of the electrode layer by specifying precise weight percentages of silver (75-85%) and carbon (15-25%), along with particle diameter ranges (silver: 0.3-2 μm, carbon: 0.1-1 μm). These parameter optimizations ensure both electrical conductivity and resistance to sulfidizing gas, preventing the silver sulfide precipitation problem while maintaining connection stability.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a nickel-based resin is used as the second upper electrode layer, then corrosion resistance is improved, but it becomes difficult to determine the presence of the nickel-plated layer

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidnickel layer identification

Core Design Contradiction:

ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent applies local quality by creating a distinct second upper electrode layer with specific local composition (silver and carbon particles in resin) that differs from the nickel-plated layer beneath it. This localized compositional differentiation allows the nickel-plated layer to be identified through cross-sectional observation or eddy current testing, as the second upper electrode layer has distinct electromagnetic and physical properties.

Inventive Principle:

Principle #3Local quality

3Reliability

If carbon-based conductive material is used as the second upper electrode layer, then conductivity is maintained, but the nickel-plated layer has weak adhesion and delaminates

Engineering Contradiction:

Improveelectrical conductivityVSAvoidadhesion strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies composite materials by combining silver particles with carbon particles in a resin matrix to form the second upper electrode layer. This composite structure provides both electrical conductivity (from silver and carbon) and strong adhesion to the nickel-plated layer, preventing delamination while maintaining conductivity.

Inventive Principle:

Principle #40Composite materials

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

The solution effectively prevents disconnection in sulfidizing gas environments and maintains conductivity without silver sulfide precipitation on the surface, while ensuring strong adhesion and preventing delamination.

Implementation Method 1

When the electronic device to which the chip resistor is mounted is used in an atmosphere where sulfidizing gas is contained and humidity is high, such as a hot-spring area, sulfidizing gas enters into the gap to react with upper electrode layer 2 to form silver sulfide

Methodology Applied

Scientific EffectSulfidization resistance: Oxidation

Implementation Method 2

The second upper electrode layer includes between 75% by weight and 85% by weight (inclusive) of silver particles with an average particle diameter ranging from 0.3 μm to 2 μm

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS9245672B2Chip resistor and method of producing same

Publication Date: 2016.01.26 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

An object of the disclosure is to provide a chip resistor without causing the disconnection in atmosphere of sulfidizing gas and without precipitating silver sulfide on its surface. The chip resistor of the present disclosure includes a resistor layer disposed on a top surface of a substrate; a first upper electrode layer disposed at both sides of the resistor layer and being electrically connected to the resistor layer; and a second upper electrode layer disposed on the first upper electrode layer and including between 75% by weight and 85% by weight (inclusive) of silver particles with an average particle diameter ranging from 0.3 um to 2 um, between 1% by weight and 10% by weight (inclusive) of carbon, and a resin.