Multilayer Ceramic Capacitor Ca Diffusion Grain Boundary
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Solution Overview
Problem
Multilayer ceramic capacitors face challenges in maintaining reliable dielectric constant-temperature characteristics and high-temperature reliability as the thickness of dielectric ceramic layers decreases, leading to deteriorated electrical performance under high electric fields.
Innovation Solution
The use of a perovskite compound in dielectric ceramic layers containing Ba, Ti, and Ca, with controlled Ca diffusion depth and increased Ca concentration, along with rare earth elements, to enhance the electrical characteristics and reliability of multilayer ceramic capacitors, particularly when the dielectric ceramic layers have a thickness of 0.8 μm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of dielectric ceramic layers is decreased to reduce the size and increase capacitance, then the capacitance increases, but the reliability and dielectric constant-temperature characteristics deteriorate due to increased electric field intensity
Solution Approach 1:
The patent applies local quality by creating a diffusion phase with distinct composition around the main component phase. The auxiliary component elements (Ca, Si, Al, Na, K) are concentrated in this diffusion phase, forming a protective region at the grain boundaries that locally enhances reliability without affecting the overall capacitance of the dielectric layer.
Solution Approach 2:
The patent uses composite materials by combining the main component phase (barium titanate) with a diffusion phase containing auxiliary component elements. This composite structure creates a multi-phase ceramic where the diffusion phase provides protective properties while the main phase maintains high dielectric constant, resolving the contradiction between capacitance and reliability.
2Volume of moving object
If the thickness of dielectric ceramic layers is decreased, then the device size reduces, but the electric field intensity increases causing deterioration of dielectric constant-temperature characteristics
Solution Approach 1:
The diffusion phase is created with specific local quality to stabilize dielectric constant-temperature characteristics. The auxiliary component elements are strategically concentrated at grain boundaries in this diffusion phase, providing local stabilization that compensates for the increased electric field intensity resulting from reduced layer thickness.
Solution Approach 2:
The auxiliary component elements are pre-distributed to form the diffusion phase during the sintering process before the capacitor is put into service. This preliminary formation of the protective diffusion phase ensures that the dielectric constant-temperature characteristics are stabilized in advance, preventing deterioration under high electric field conditions.
3Reliability
If auxiliary component elements are added to improve electrical characteristics, then the reliability improves, but the crystal grain morphology and dielectric constant-temperature characteristics may deteriorate
Solution Approach 1:
The patent resolves this contradiction by localizing the auxiliary component elements in the diffusion phase at grain boundaries, rather than uniformly distributing them throughout the crystal grains. This localized concentration improves reliability by protecting grain boundaries while minimizing the negative impact on the dielectric constant-temperature characteristics of the bulk material.
Solution Approach 2:
The patent controls the concentration parameters of auxiliary component elements in the diffusion phase within specific ranges. By optimizing these concentration parameters, the patent achieves improved reliability while maintaining acceptable dielectric constant-temperature characteristics, resolving the trade-off between these two properties.
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 maintains a high relative dielectric constant, suppresses electric field dependence, and ensures satisfactory lifetime characteristics, resulting in a small, stable, high-quality multilayer ceramic capacitor with improved capacitance and reliability.
Implementation Method 1
a diffusion phase around the main component phase, wherein variations in the average diffusion depth of the dielectric particles have CV in the range of 5% to 30%, and the average diffusion depth refers to the average depth at which an auxiliary component element in the diffusion phase diffuses from the surface of the diffusion phase toward the center of each of the dielectric particles
Data Source
AI summary
A dielectric ceramic that forms dielectric ceramic layers of a multilayer ceramic capacitor contains a Ba and Ti containing perovskite compound, Ca, R (R denotes a rare earth element, such as La), M (M denotes Mn or the like), and Si. The Ca content ranges from 0.5 to 2.5 molar parts, the R content ranges from 0.5 to 4 molar parts, the M content ranges from 0.5 to 2 molar parts, and the Si content ranges from 1 to 4 molar parts, based on 100 molar parts of Ti. In perovskite crystal grains, the Ca diffusion depth is 10% or less of the average grain size of the crystal grains, and the Ca concentration in a Ca diffusion region is 0.2 to 5 molar parts higher than the Ca concentration near the center of each of the crystal grains.