Multilayer Ceramic Capacitor External Electrode Thermal Expansion Control

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Solution Overview

Problem

The existing methods for forming external electrodes in multilayer ceramic capacitors often result in cracks due to sintering shrinkage differences between the external electrode paste and the ceramic structure, and excessive addition of ceramic additives hampers the plating process.

Innovation Solution

A multilayer ceramic capacitor design where the external electrodes have a plated layer on a ground layer with a metal or alloy component having a higher thermal expansion coefficient than the ceramic, and the ceramic additive is chosen to satisfy a specific thermal expansion coefficient relationship, minimizing stress and allowing for effective plating without excessive additive use.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a large amount of ceramic additive is added to the external electrode paste to reduce sintering shrinkage difference and suppress crack occurrence, then crack suppression is improved, but it becomes difficult to form a plated layer on the ground layer

Engineering Contradiction:

Improvecrack suppressionVSAvoidplating process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies local quality by creating a multilayer external electrode structure where different layers have different compositions and functions. The ground layer contains ceramic additive for adhesion and shrinkage control, while the plated layer provides electroconductivity and corrosion resistance. This local differentiation allows each layer to optimize its specific function without compromising the other.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining metal particles (Ni, Cu, Pd, Pt, Ag) with ceramic additives in the external electrode paste to form a ground layer that exhibits both metallic properties (electroconductivity, thermal expansion) and ceramic properties (adhesion to dielectric layer, shrinkage control). This composite approach enables simultaneous achievement of crack suppression and plating compatibility.

Inventive Principle:

Principle #40Composite materials

2Strength

If the thermal expansion coefficient of the metal in the ground layer is larger than that of the ceramic dielectric layer, then adhesion to the dielectric layer is improved, but stress during sintering increases

Engineering Contradiction:

Improveadhesion to dielectric layerVSAvoidsintering stress

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The patent applies parameter changes by carefully selecting and controlling the thermal expansion coefficient of the metal component in the ground layer. The thermal expansion coefficient is designed to be larger than that of the ceramic dielectric layer to ensure good adhesion, but the ceramic additive content is optimized to control the overall sintering shrinkage and reduce excessive stress during the sintering process.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the external electrode paste is sintered together with the ceramic multilayer structure, then manufacturing efficiency is improved, but crack occurrence in the dielectric layer near the sintered external electrode increases

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidcrack occurrence

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent introduces the ground layer as an intermediary between the ceramic dielectric layer and the plated layer. This ground layer, containing ceramic additive and metal particles, acts as a buffer that accommodates sintering shrinkage differences and reduces stress concentration at the interface, thereby preventing crack formation while enabling simultaneous sintering of the external electrode with the ceramic multilayer structure.

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 approach suppresses crack occurrence and maintains the integrity of the plating process by aligning the thermal expansion coefficients of the ground layer, cover layers, and dielectric layers, reducing stress and ensuring efficient manufacturing.

Implementation Method 1

a thermal expansion coefficient of the metal being larger than that of a main ceramic component of the dielectric layer

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

sintering the ceramic multilayer structure after the coating

Methodology Applied

Scientific EffectSintering: Sintering

Data Source

PatentUS10475581B2Multilayer ceramic capacitor and manufacturing method of multilayer ceramic capacitor

Publication Date: 2019.11.12 TAIYO YUDEN KK

AI summary

A multilayer ceramic capacitor includes: a multilayer chip in which each of dielectric layers and each of internal electrode layers are alternately stacked and are alternately exposed to two edge faces thereof; and external electrodes formed on the two edge faces; wherein: the external electrodes have a structure in which a plated layer is formed on a ground layer whose main component is a metal or an alloy, a thermal expansion coefficient of the metal being larger than that of a main ceramic component of the dielectric layer, the ground layer including a ceramic additive; outermost layers of the multilayer chip are cover layers whose main component is a main component of the dielectric layer; and thermal expansion coefficients satisfy a relationship of, the main component of the ground layer>the main component of the cover layers>the ceramic additive.