Multilayer Capacitor Electrode Structure for Thermal Shock Resistance

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Solution Overview

Problem

Ceramic electronic components face issues with mechanical strength and increased electric resistance due to differences in thermal expansion coefficients between the ceramic and substrate, leading to potential cracking and malfunction, especially when using base metal internal electrodes and resin-coated noble metal electrodes.

Innovation Solution

A ceramic electronic component configuration with internal electrodes made of base metals like Ni, external electrodes having a base metal first layer, a noble metal second layer, and a conductive resin layer containing noble metals, enhancing bonding and mechanical strength while preventing oxidation and cracking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a base metal electrode layer is formed immediately below the resin layer, then cost is reduced, but the electric resistance increases due to oxidation when the resin layer absorbs water

Engineering Contradiction:

Improveelectric resistance stabilityVSAvoidcost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The external electrode is divided into multiple layers: a base metal layer (first electrode layer) for cost reduction and bonding, a noble metal layer (second electrode layer) for oxidation resistance, and a conductive resin layer. This segmentation allows each layer to perform its specific function, preventing oxidation while maintaining low cost.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A noble metal layer is introduced as an intermediary between the base metal layer and the conductive resin layer. This intermediate noble metal layer prevents direct contact between the base metal and the resin, blocking the oxidation pathway while allowing electrical conduction to pass through.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a noble metal electrode layer is used below the resin layer, then oxidation resistance is improved, but bonding strength to base metal internal electrodes deteriorates

Engineering Contradiction:

Improveoxidation resistanceVSAvoidbonding strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The electrode structure is segmented into a base metal layer for strong bonding to internal electrodes and a separate noble metal layer for oxidation resistance. This segmentation allows the base metal layer to provide mechanical strength and adhesion while the noble metal layer provides chemical stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different parts of the electrode structure have different material properties: the base metal layer (first electrode layer) has high bonding strength for attachment to internal electrodes, while the noble metal layer (second electrode layer) has high oxidation resistance. Each layer is optimized for its local function.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If the ceramic electronic component and substrate have different coefficients of thermal expansion, then mounting is simplified, but deflection and cracking occur due to thermal shock

Engineering Contradiction:

Improvemounting easeVSAvoidcrack resistance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The conductive resin layer acts as a flexible element that can accommodate thermal expansion differences between the ceramic component and substrate. This resin layer absorbs the stress from thermal shock, preventing cracks in the rigid ceramic and metal structures.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The conductive resin layer is designed in advance to absorb and cushion the thermal stress that will occur during operation. This pre-planned cushioning mechanism prevents cracks before they can form in the ceramic or metal layers during thermal cycling.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 reduces costs, prevents cracking from thermal shock, and suppresses the increase in electric resistance by improving bonding and oxidation resistance, ensuring reliable operation.

Implementation Method 1

When the substrate with the ceramic electronic component thereon is subjected to a thermal shock due to a sudden temperature change, the ceramic electronic component and substrate expand and contract according to their respective coefficients of thermal expansion

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

if the resin layer absorbs water, the surface of the electrode layer of the base metal immediately below the resin layer will oxidize

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentUS7304831B2Ceramic electronic component and multilayer capacitor

Publication Date: 2007.12.04 TDK CORP

AI summary

A multilayer capacitor comprises a ceramic sintered body, an internal electrode disposed in the ceramic sintered body, and an external electrode disposed on an external surface of the ceramic sintered body. The external electrode has a first electrode layer formed on the external surface of the ceramic sintered body, a second electrode layer formed on the first electrode layer, and a conductive resin layer formed on the second electrode layer. The internal electrode and the first electrode layer consist primarily of a base metal. The second electrode layer consists primarily of a noble metal or a noble metal alloy. The conductive resin layer contains a noble metal or a noble metal alloy as a conductive material.