Dielectric Ceramic Composition for X8R Multilayer Capacitors
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Solution Overview
Problem
Existing multilayer ceramic capacitors using barium titanate-based ferroelectric materials face challenges in achieving guaranteed X8R temperature characteristics and reliability, particularly due to limitations in temperature coefficient of capacitance (TCC) at high temperatures and deterioration of insulation resistance.
Innovation Solution
A dielectric ceramic composition is developed with a barium titanate-based base material and minor components, including specific ratios of calcium and rare-earth elements, which are sintered to form a fine structure with controlled crystal grain content and cross-sectional area ratios, optimizing the pyrochlore phase ratio to achieve X8R characteristics and improved reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If barium titanate-based ferroelectric materials are used to achieve high capacitance, then the dielectric constant at room temperature is improved, but the temperature coefficient of capacitance deteriorates at high temperatures and insulation resistance decreases
Solution Approach 1:
The patent employs a composite dielectric material system consisting of barium titanate (BaTiO3) as the base material combined with calcium titanate (CaTiO3) and rare-earth element additives (Y2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3, or Lu2O3). This composite approach allows the material to achieve high capacitance through the ferroelectric properties of BaTiO3 while the CaTiO3 and rare-earth additives work synergistically to stabilize the temperature coefficient of capacitance and maintain insulation resistance at high temperatures, thereby resolving the contradiction between high capacitance and reliable temperature characteristics
Solution Approach 2:
The patent systematically optimizes the compositional parameters of the dielectric material, specifically controlling the molar ratios of BaTiO3, CaTiO3, and rare-earth oxides within defined ranges. By adjusting these compositional parameters and corresponding sintering conditions, the material achieves optimal balance between high capacitance and stable temperature characteristics, transforming the trade-off into a controllable parameter optimization problem that simultaneously improves both capacitance and reliability
2Ease of manufacture
If calcium content is increased to improve sinterability and grain growth, then the sintering process is improved, but the temperature coefficient of capacitance deteriorates and X8R characteristics cannot be achieved
Solution Approach 1:
The patent applies local quality by creating a non-uniform calcium distribution within the dielectric material structure. The calcium content is controlled to be in the specific range of 0.02-0.15 mol, which provides sufficient calcium for improved sinterability and grain growth while preventing excessive calcium that would deteriorate the temperature coefficient of capacitance. The rare-earth elements are also distributed to locally stabilize the crystal structure and maintain X8R characteristics, achieving differentiated functional zones that simultaneously satisfy sinterability and electrical performance requirements
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 effectively satisfies X8R temperature characteristics and enhances the reliability of multilayer ceramic capacitors by maintaining low dissipation factor and high insulation resistance, even at high temperatures, while improving temperature coefficient of capacitance and withstand voltage.
Implementation Method 1
the dielectric ceramic composition is sintered to form a sintered body having a fine structure
Data Source
AI summary
There is provided a dielectric ceramic composition including: a major component (a barium titanate-based base material); and a minor component, wherein the dielectric ceramic composition is sintered to form a sintered body having a fine structure, the fine structure includes first crystal grains in which a Ca content is lower than 2.5 mol % and second crystal grains in which a Ca content is between 2.5 mol % to 13.5 mol %, and the second crystal grains have a cross-sectional area ratio of 30% to 80% on the basis of 100% of an overall cross-sectional area of the fine structure.