Laminated Ceramic Capacitor Grain Size Distribution
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Solution Overview
Problem
Achieving both high dielectric constant and high electrical insulation property in laminated ceramic capacitors becomes challenging as the thickness of the dielectric ceramic layer is reduced below 1 μm, as the number of crystal grains between internal electrodes decreases, affecting both properties negatively.
Innovation Solution
Incorporating a perovskite-type compound ABO3 with specific compositions of Ba, Ti, and accessory ingredients like La, Ce, and Si, and controlling the grain size distribution with two distinct peaks for crystal grains, where the areal percentage of larger grains is between 41% to 69%, to maintain both high dielectric constant and insulation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the dielectric ceramic layer is reduced to less than 1 μm to achieve miniaturization, then the capacity increases, but the electrical insulation property deteriorates
Solution Approach 1:
The patent applies local quality by creating a non-uniform grain size distribution within the dielectric ceramic layer. Specifically, it introduces a dual-peak grain size distribution where first crystal grains have a mean size of 0.1 to 0.3 μm and second crystal grains have sizes five times or more smaller. This local variation in grain structure optimizes different regions for different functions: larger grains contribute to dielectric constant while smaller grains maintain insulation barriers, resolving the contradiction between miniaturization and insulation property.
Solution Approach 2:
The patent employs composite material principles by combining crystal grains of two distinct size ranges within the same dielectric ceramic layer. This creates a composite microstructure where the first crystal grains (0.1 to 0.3 μm) and second crystal grains (five times or more smaller) work synergistically. The composite grain structure allows the thin dielectric layer to simultaneously achieve high dielectric constant from larger grains and high insulation resistance from the numerous smaller grains forming effective insulation barriers.
2Reliability
If the grain sizes of the crystal grains are decreased to increase the number of grains and improve insulation property, then the insulation property improves, but the dielectric constant decreases
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through spatial differentiation of grain sizes. The first crystal grains with mean size of 0.1 to 0.3 μm are distributed throughout the dielectric layer to provide high dielectric constant, while second crystal grains five times or more smaller are interspersed to create effective insulation barriers. This local quality variation allows each grain size population to fulfill its specific function without compromising the other.
Solution Approach 2:
The patent applies segmentation by dividing the crystal grain population into two distinct size categories with a five-fold or greater difference. This segmentation creates a dual-peak grain size distribution where first crystal grains (0.1 to 0.3 μm) and second crystal grains serve different functional roles. The segmented structure enables the dielectric layer to simultaneously achieve high dielectric constant from the first grains and high insulation resistance from the second grains.
Data Source
AI summary
A laminated ceramic capacitor capable of achieving both a high dielectric constant and high electrical insulation property even when the thickness of the dielectric ceramic layer is less than 1 μm, contains a plurality of laminated dielectric ceramic layers and a plurality of internal electrodes at interfaces between the dielectric ceramic layers, where dielectric ceramic layers are made of dielectric ceramic containing a perovskite-type compound represented by ABO3 as a main ingredient, and R (R is La or the like), M (M is Mn or the like) and Si as accessory ingredients. When crystal grains of the dielectric ceramic are classified into first crystal grains having grain sizes larger than one-fourth of the thickness of the dielectric ceramic layer and second crystal grains having grain sizes not larger than one-fourth of the thickness of the dielectric ceramic layer, the first crystal grains and the second crystal grains have a peak P1 and P2 of grain size distribution, and the areal percentage of the first crystal grains on a cross section of the dielectric ceramic layer is 41 to 69%.