Ceramic Electronic Device External Electrode Stress Management
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Solution Overview
Problem
Ceramic electronic devices, such as multilayer ceramic capacitors, often experience cracks at the edge parts due to thermal expansion coefficient differences between the dielectric body and external electrodes, leading to reliability issues and difficulties in the plating process.
Innovation Solution
A ceramic electronic device with a multilayer chip structure where external electrodes have a thinner thickness on the corner portions and a larger thickness on areas where internal electrode layers are extracted, with a crook shape to reduce stress and improve adhesion, and a manufacturing method involving specific adjustments to the wettability of conductive pastes and cover layers to achieve this configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of co-material in the paste for the external electrode is increased to improve adhesiveness and reduce contraction difference, then adhesion between external electrode and dielectric body is improved, but it becomes difficult to perform the plating process
Solution Approach 1:
The paste composition is made non-uniform by concentrating co-material in specific regions (corner portions and areas adjacent to internal electrode layers) rather than distributing it uniformly throughout the external electrode, allowing localized adhesion enhancement without compromising overall plating processability
Solution Approach 2:
The concentration of co-material is varied spatially across different regions of the external electrode, with higher concentrations in areas requiring enhanced adhesion and lower concentrations in areas requiring good plating characteristics
2Object-affected harmful factors
If the thickness of the paste for the external electrode is reduced on the edge part to reduce stress during firing and suppress cracks, then crack suppression is improved, but the thickness of the external electrode becomes smaller on the edge face, degrading reliability
Solution Approach 1:
The external electrode is designed with spatially varying thickness and composition: thinner with higher co-material concentration in corner portions for crack suppression, and thicker with appropriate composition in areas adjacent to internal electrode layers for maintaining adhesion and reliability
Solution Approach 2:
The external electrode is formed as a composite structure combining different paste compositions in different regions, with co-material enriched zones strategically placed to provide both crack suppression and adhesion enhancement functions simultaneously
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 design effectively suppresses cracks and enhances the reliability of ceramic electronic devices by managing stress distribution and maintaining adequate electrode thickness, ensuring robustness and functionality.
Implementation Method 1
adjusting a difference between wettability of an area of the two edge faces where the conductive paste for forming internal electrode layers is provided and wettability of a corner portion of the cover sheet
Implementation Method 2
forming dielectric layers, internal electrode layers, cover layers and external electrodes from the dielectric green sheets, the conductive pastes for forming internal electrode layers, the cover sheets and the conductive pastes for forming external electrodes by firing the ceramic multilayer structure and the conductive paste for forming external electrodes
Data Source
AI summary
A ceramic electronic device includes: a multilayer chip including a multilayer structure and cover layers, the multilayer structure having a structure in which each of a plurality of dielectric layers and each of a plurality of internal electrode layers are alternately stacked and are alternately exposed to two edge faces of the multilayer chip, a main component of the plurality of dielectric layers being a ceramic, the cover layers being provided on an upper face and a lower face of the multilayer structure in a stacking direction; and a pair of external electrodes that are formed on the two edge faces, wherein each of the external electrodes has a smaller thickness on a corner portion of the cover layers, has a crook toward the internal electrode layers, and has a larger thickness on an area of the two edge faces where the internal electrode layers are extracted.