Laminated Ceramic Capacitor Stress Relieving Layer
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Solution Overview
Problem
Laminated ceramic capacitors with high dielectric constant materials face structural defects such as cracks due to electrostriction and increased stress during firing, limiting design flexibility and breakdown voltage when the number of lamination layers is increased.
Innovation Solution
Incorporating a stress relieving layer with ceramic dielectric layers and dummy inner electrode layers between capacitance forming layers, along with capacitance-formation-preventing inner electrode layers, to absorb and relieve stress, with specific thickness and area ratios to prevent crack generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of lamination layers is increased to increase capacity, then the capacitance is improved, but stress imposed on the ceramic dielectric layers increases causing crack generation and reduction in breakdown voltage
Solution Approach 1:
The capacitor is divided into multiple lamination layers with alternating capacitance-forming layers and stress-relieving layers. This segmentation allows the total stress to be distributed across multiple interfaces rather than concentrated in a single thick layer, enabling increased total capacity while maintaining breakdown voltage through progressive stress management.
Solution Approach 2:
Different layers are assigned different functional qualities: capacitance-forming layers with high dielectric constant materials for maximum capacitance, and stress-relieving layers with optimized thickness and material composition specifically for stress management. This local differentiation allows each layer to perform its specialized function optimally.
2Stress or pressure
If the thickness of the intermediate layer is increased to relieve stress from electrostriction, then the stress relief is improved, but crack generation in the intermediate layer occurs due to contraction difference during firing
Solution Approach 1:
The thickness of stress-relieving layers is precisely controlled within the range of 1-10 μm, and the dielectric constant of these layers is optimized to be lower than adjacent capacitance-forming layers. These parameter changes enable the layer to provide sufficient stress relief while maintaining contraction compatibility during firing to prevent cracking.
Solution Approach 2:
The capacitor uses composite material composition where stress-relieving layers contain dielectric materials with specifically selected properties (lower dielectric constant, optimized thickness) that differ from the capacitance-forming layers. This composite structure enables simultaneous achievement of stress relief and crack prevention through material property differentiation.
3Quantity of substance
If the dielectric constant of the ceramic material is increased to improve capacitance, then the capacitance is improved, but stress imposed on the ceramic dielectric layers increases causing structural defects
Solution Approach 1:
High dielectric constant materials are selectively applied only in capacitance-forming layers where maximum capacitance is required, while stress-relieving layers use materials with optimized (lower) dielectric constants. This local quality differentiation allows high capacitance in functional layers while preventing stress-induced defects in stress-management layers.
Solution Approach 2:
Stress-relieving layers act as intermediary layers between high-stress capacitance-forming layers. These intermediary layers with lower dielectric constants serve as buffers that reduce the transmission of stress from high-dielectric layers to adjacent structures, preventing crack generation while allowing high capacitance materials to be used.
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 enhances breakdown voltage and withstand-voltage performance by effectively managing stress and contraction differences, preventing cracks and structural defects even with high dielectric constant materials and increased lamination layers.
Implementation Method 1
stress is imposed on the ceramic dielectric layers due to electrostriction (inverse piezoelectric effect) that causes mechanical displacement by voltage
Implementation Method 2
The capacitance forming layers having the inner electrode layers greatly contract during firing
Data Source
AI summary
A laminated ceramic capacitor has a high breakdown voltage and excellent withstand-voltage performance, and prevents cracks generated during firing even when the number of lamination layers constituted by ceramic layers and inner electrode layers is increased. The laminated ceramic capacitor includes capacitance forming layers in which ceramic dielectric layers and capacitance-forming inner electrode layers are laminated, and a stress relieving layer. The stress relieving layer is disposed between the capacitance forming layers. In the stress relieving layer, ceramic dielectric layers, dummy inner electrode layers (split electrodes) that do not contribute to the formation of electrostatic capacitance, and capacitance-formation-preventing inner electrode layers that prevent capacitance from being formed between the capacitance-forming inner electrode layers and the dummy inner electrode layers are laminated. The thickness of the stress relieving layer is in the range of about 100 μm to about 300 μm inclusive. The plane area of the dummy inner electrode layers is about 60% or more of that of the capacitance-forming inner electrode layers. The dummy inner electrode layers are undivided or are divided into two or three parts in a single layer. With this structure, stress caused by electrostriction is relieved.