Dielectric Ceramic Composition for MLCC Reliability
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Solution Overview
Problem
Multilayer ceramic capacitors face challenges in maintaining high relative dielectric constant, temperature stability, and reliability while minimizing changes in electrostatic capacitance over time, particularly when dielectric layer thickness is reduced.
Innovation Solution
A dielectric ceramic with a composition of (Ba1-tCat)m(Ti1-u-xZruCux)O3, where Cu is uniformly dispersed in the primary phase grain, and accessory components like rare earth elements, metal elements, Mg, and Si are present within specific molar ratios, ensuring a high relative dielectric constant and improved temperature properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the dielectric layer is decreased to reduce size and increase capacitance, then the reduction in size and increase in capacity are achieved, but the voltage with high electric field strength causes decrease in relative dielectric constant, degradation in temperature properties, and dielectric breakdown
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of acceptor type elements and rare earth elements within the ceramic grains. The acceptor type element concentration increases from the grain center toward the grain boundary, while rare earth element concentration decreases from center to boundary. This localized compositional variation optimizes different regions of the grain for different functions: the grain boundary region with higher acceptor type element content provides improved reduction and oxidation resistance, while the overall composition maintains high relative dielectric constant and temperature stability, enabling reliable operation at reduced dielectric layer thicknesses.
2Volume of moving object
If the thickness of the dielectric layer is decreased to reduce size, then the size reduction is achieved, but the electric field strength increases causing dielectric breakdown between internal electrodes
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the dielectric ceramic. Specifically, it controls the concentration of acceptor type elements (Mn, V, Cr, Co, Fe, Cu, Ni, Mo) and rare earth elements (Ho, Sc, Y, Gd, Dy, Er, Yb, Tb, Tm, Lu) within specific ranges. The acceptor type element concentration is maintained at 0.01-10 atomic% with a gradient increasing toward grain boundaries, while rare earth element concentration is controlled at 0.01-5 atomic% with a gradient decreasing toward grain boundaries. These compositional parameter changes enhance the dielectric strength and resistance to dielectric breakdown, allowing the use of thinner dielectric layers without compromising reliability.
3Reliability
If acceptor type element concentration increases from grain center to grain boundary to improve reliability, then the reduction resistance and oxidation resistance are improved, but the rate of change in electrostatic capacitance with time increases
Solution Approach 1:
The patent applies composite materials by creating a multi-element composite ceramic system that combines barium titanate base material with acceptor type elements and rare earth elements in specific combinations and concentrations. The dielectric ceramic comprises BaTiO3 with 0.01-10 atomic% acceptor type elements and 0.01-5 atomic% rare earth elements, where both element types work synergistically. The acceptor type elements provide reduction and oxidation resistance, while the rare earth elements help stabilize the electrostatic capacitance over time. This composite approach allows the concentration gradient of acceptor type elements to improve reliability while the rare earth elements counterbalance the capacitance drift, achieving both goals simultaneously.
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 achieves a relative dielectric constant of 2,500 or more, dielectric loss less than 7%, and a rate of change in electrostatic capacitance within ±5% over time, with superior reliability and temperature stability, satisfying JIS B characteristics and withstanding high temperature load conditions.
Implementation Method 1
Cu is uniformly dispersed present in a primary phase grain forming a primary component
Implementation Method 2
a high relative dielectric constant, temperature properties of electrostatic capacitance
Implementation Method 3
performing a firing treatment on the ceramic laminate to form a multilayer sintered body
Data Source
AI summary
A dielectric ceramic includes a compound represented by the general formula: (Ba1-tCat)m(Ti1-u-xZruCux)O3 (where 0.96≦m≦1.02, 0.001≦x≦0.03, 0≦t≦0.1, and 0≦u≦0.06) as a primary component, a rare earth element Re such as Dy, a metal element M such as Mn, Mg, and Si. In the dielectric ceramic, the Cu is uniformly and dispersedly present in the primary phase grain forming the primary component, and the contents of the accessory components with respect to 100 molar parts of the primary component are 0.1 to 1.5 molar parts of Re, 0.1 to 0.6 molar parts of M, 0.1 to 1.5 molar parts of Mg and 0.1 to 2.0 molar parts of Si. Accordingly, a multilayer ceramic capacitor can be realized which has a high dielectric constant, superior temperature properties, and a high reliability, and also has a small change in electrostatic capacitance with time.