Dielectric Ceramic Composition for X8R Multilayer Capacitors
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Solution Overview
Problem
Existing high capacitance multilayer ceramic capacitors using barium titanate (BaTiO3) materials face limitations in achieving X8R temperature characteristics up to 150°C and ensuring reliability, particularly in maintaining capacitance and insulation resistance at elevated temperatures.
Innovation Solution
A dielectric ceramic composition is developed, comprising a base powder mixture of (1−a)[(1−x)BaTiO3−xBi(Mg0.5Ti0.5)O3] + a[(1−y)BaTiO3−yBi(Mg0.5Ti0.5)O3], where x, y, and a satisfy specific ratios, allowing for improved temperature stability and reliability by incorporating Bi(Mg0.5Ti0.5)O3 with BaTiO3 at different ratios, along with accessory components like Mn and Si to enhance sintering and high-temperature withstand voltage properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If barium titanate (BaTiO3) based dielectric materials are used to achieve high capacitance, then room temperature dielectric constant is improved, but temperature characteristics and reliability at elevated temperatures deteriorate
Solution Approach 1:
The patent employs a composite dielectric material system consisting of BaTiO3 as the primary ferroelectric phase combined with specific amounts of Bi(Mg0.5Ti0.5)O3 (BMT) and barium zirconate (BaZrO3). This composite approach leverages the high dielectric constant of BaTiO3 while using BMT and BaZrO3 to stabilize the crystal structure at elevated temperatures, thereby achieving both high capacitance and improved temperature characteristics up to 150°C
Solution Approach 2:
The patent systematically optimizes the compositional parameters of the dielectric material, specifically controlling the ratios of BaTiO3, BMT, and BaZrO3 within defined ranges. By adjusting these compositional parameters, the material achieves a balance between room temperature capacitance and high temperature stability, enabling X8R temperature characteristics
2Quantity of substance
If barium titanate (BaTiO3) based materials are used for high capacitance, then dielectric constant at room temperature is improved, but withstand voltage at high temperature deteriorates
Solution Approach 1:
The composite dielectric system combines BaTiO3 with BMT and BaZrO3 to achieve both high dielectric constant and high withstand voltage. The BMT component contributes to maintaining dielectric properties at elevated temperatures, while BaZrO3 enhances the breakdown strength and electrical insulation performance, resulting in improved withstand voltage characteristics at high temperatures
Solution Approach 2:
The patent introduces local compositional variations within the dielectric material by incorporating specific amounts of BMT and BaZrO3 in different regions of the material structure. This local quality adjustment allows different regions to contribute differently to the overall performance, with some regions optimized for high dielectric constant and others for enhanced withstand voltage at operating temperatures
3Ease of manufacture
If traditional BaTiO3 materials are used, then manufacturing process is simple, but temperature coefficient of capacitance (TCC) control deteriorates
Solution Approach 1:
The patent achieves precise TCC control by optimizing the compositional parameters of the multi-component system. By carefully controlling the ratios of BaTiO3, BMT, and BaZrO3 within specific ranges, the material exhibits improved temperature stability and TCC characteristics that meet X8R specifications, while maintaining compatibility with conventional manufacturing processes
Data Source
AI summary
A dielectric ceramic composition may include a base powder represented by (1−a)[(1−x)BaTiO3−xBi(Mg0.5Ti0.5)O3]+a[(1−y)BaTiO3−yBi(Mg0.5Ti0.5)O3](wherein x, y, and a satisfy 0≦x≦0.05, 0.05≦y≦0.5, a≧0, and 0.01−x≦a≦1−y) and formed by mixing a first powder represented by [(1−x)BaTiO3−xBi(Mg0.5Ti0.5)O3] with a second powder represented by [(1−y)BaTiO3−yBi(Mg0.5Ti0.5)O3]. Each of the first powder and the second powder contains a first main component represented by BaTiO3 and a second main component represented by Bi(Mg0.5Ti0.5)O3, but at different ratios.