Multilayer Ceramic Capacitor Grain Size Distribution
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Solution Overview
Problem
Increasing the stack number of dielectric layers in multilayer ceramic capacitors to enhance capacity leads to structural defects like delamination and cracks due to differences in crystal grain diameters and mechanical strengths between regions.
Innovation Solution
A multilayer ceramic capacitor design with a specific grain size distribution in the end margin region, where the D20% diameter is smaller and the D80% diameter is larger than in the capacity region, or the ratio 1/(log D80−log D20) is greater, to reduce mechanical strength differences and suppress defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the stack number of dielectric layers is increased to enhance capacity, then the capacitor capacity is improved, but structural defects such as delamination and cracks occur due to differences in crystal grain diameters and mechanical strengths between regions
Solution Approach 1:
The patent applies local quality by creating different grain size distributions in different regions of the dielectric layer. Specifically, the end margin region has a wider grain size distribution (smaller D20% diameter and/or larger D80% diameter compared to the capacity region) to enhance mechanical strength and suppress delamination, while the capacity region maintains a narrower grain size distribution for optimal capacitance. This regional differentiation resolves the contradiction by allowing high capacity in the main body while ensuring structural reliability at critical margins.
Solution Approach 2:
The patent changes the grain size distribution parameters (D20% diameter, D80% diameter, and the ratio 1/(log D80−log D20)) in the end margin region compared to the capacity region. By adjusting these parameters, the mechanical strength of the end margin region is enhanced to match or exceed that of the capacity region, preventing delamination and cracks that would otherwise occur when increasing the stack number for higher capacity.
2Volume of moving object
If the thickness of dielectric layers is reduced to achieve small size, then the capacitor size is decreased, but the mechanical strength difference between regions increases leading to more defects
Solution Approach 1:
The patent addresses this contradiction by applying local quality enhancement to the end margin region through controlled grain size distribution. Even when dielectric layer thickness is reduced for miniaturization, the end margin region maintains adequate mechanical strength through its wider grain size distribution, preventing delamination and cracks that would be more likely in thinner structures.
Data Source
AI summary
A multilayer ceramic capacitor includes: a first and a second external electrodes; internal electrode layers that are alternately connected to the first and the second external electrodes; and dielectric layers including a ceramic material as a main component, wherein a D20% diameter of the ceramic material of an end margin region, in which internal electrode layers connected to one of the first external electrode and the second external electrode face with each other and does not face with internal electrode layers connected to the other, is smaller than that of a capacity region in which internal electrode layers connected to different external electrodes face with each other and a D80% diameter of the ceramic material of the end margin region is larger than that of the capacity region, or 1/(log D80−log D20) of the ceramic material of the capacity region is larger than that of the end margin region.