Core-Shell Dielectric Powder for High-Voltage MLCC Insulation
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Solution Overview
Problem
Existing multilayer ceramic capacitors face challenges in achieving high insulation resistance and withstand voltage characteristics due to the use of dielectric materials that require expensive conductors like Pd or Ag-Pd, and when using Cu or Ni, they struggle with low dielectric constant and rapid degradation during sintering, making it difficult to implement large capacity and high voltage capacitors for x-EV power conversion circuits.
Innovation Solution
A dielectric powder composition is formulated with a non-stoichiometric dielectric base material coated with a glass powder to form a core-shell structure, combined with transition metal oxides, using a rapid heat-treatment process to enhance insulation resistance and withstand voltage, resulting in a dielectric constant of 38 to 45 and insulation resistance of 1000 G-ohm or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a dielectric with reduction-resistance is applied to achieve high-capacity MLCC, then the dielectric constant is low (28-32), but this causes deterioration in withstand voltage characteristics
Solution Approach 1:
The patent uses a composite material system consisting of (Ca, Sr)(Ti, Zr)O3 dielectric powder combined with specific glass compositions (B2O3-SiO2 system) to achieve both high dielectric constant and excellent withstand voltage characteristics. The composite structure allows the dielectric to maintain high capacitance while the glass phase improves insulation and breakdown voltage properties.
Solution Approach 2:
The patent changes the chemical composition parameters of the dielectric system by incorporating Zr into the (Ca, Sr)(Ti, Zr)O3 structure and adjusting the glass composition ratios (B2O3:SiO2 = 1:3 to 1:6). These parameter changes enable the material to achieve both high dielectric constant (38-45) and high withstand voltage characteristics simultaneously.
2Quantity of substance
If a thin layer design of dielectric layer is required for high-capacity MLCC, then capacitance increases, but insulation resistance deteriorates
Solution Approach 1:
The patent employs a composite material system where (Ca, Sr)(Ti, Zr)O3 dielectric particles are combined with B2O3-SiO2 glass. The glass phase forms a matrix that provides high insulation resistance while the dielectric particles provide high capacitance, allowing thin-layer design to achieve both high capacity and high insulation resistance simultaneously.
Solution Approach 2:
The patent adjusts the glass composition parameters (B2O3 content at 30-60 wt%, SiO2 at 40-70 wt%) to optimize the balance between dielectric constant and insulation resistance. This parameter optimization enables thin dielectric layers to maintain high insulation resistance (1000 G-ohm or more) while achieving high capacitance.
3Reliability
If expensive Pd or Ag-Pd is used as conductor for internal electrode layer, then electrical conductivity improves, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive precious metal conductors (Pd, Ag-Pd) with cheaper base metals (Cu, Ni) for the internal electrode layer. While base metals have lower inherent conductivity, the optimized dielectric composition compensates for this, providing sufficient electrical performance at lower cost, making the capacitor more economically viable for mass production.
Solution Approach 2:
The patent changes the conductor material parameters from precious metals to base metals, and simultaneously optimizes the dielectric composition to compensate for the lower conductivity of base metals. This parameter substitution achieves cost reduction while maintaining acceptable electrical performance for the intended application.
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
The solution provides high-capacity and high-voltage multilayer ceramic capacitors with excellent insulation breakdown voltage and temperature stability, ensuring reliability and stability in x-EV power conversion systems.
Implementation Method 1
performing heat-treatment of the mixture
Implementation Method 2
glass powder coated on an outer periphery of the dielectric base material powder to form a core-shell structure
Implementation Method 3
adding transition metal powder to the heat-treated dielectric ceramic powder to improve insulation resistance at a high temperature
Implementation Method 4
rapidly heat-treating the mixture using a roller hearth kiln (RHK) electric furnace during heat-treatment
Implementation Method 5
sintered in a reduction-resistant atmosphere
Data Source
AI summary
Provided are a dielectric powder composition for multilayer ceramic capacitors. The dielectric powder composition includes 93 to 98.5 wt % of a main ingredient composed of dielectric base material powder, 1.0 to 5.0 wt % of a first sub-ingredient including glass powder coated on an outer periphery of the dielectric base material powder to form a core-shell structure, and 0.5 to 2.0 wt % of a second sub-ingredient made of a transition metal oxide mixed with the core-shell structure powder, wherein the main ingredient is non-stoichiometrically represented as [(BaxCaySr1-x-y)O]m[(TizZr1-z)O2](where x: 0.22 to 0.42, y: 0.10 to 0.35, z: 0.03 to 0.08, and m ranges from 0.85 to 1.05), the first sub-ingredient includes an alkaline earth metal compound including (Ba, Sr, Ca), SnO2, B2O3 and SiO2, and the second sub-ingredient includes at least two selected from the group consisting of manganese oxide (Mn3O4), tungsten oxide (WO3), and aluminum oxide (Al2O3).