Multilayer Ceramic Capacitor Grain Control
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Solution Overview
Problem
Multilayer ceramic capacitors with grain diameters less than 0.5 μm exhibit low relative dielectric constant, large temperature characteristics, and short highly accelerated life time due to grain growth, leading to reliability issues.
Innovation Solution
The use of ceramic dielectric layers with barium titanate as the main component, combined with specific amounts of magnesium, manganese, and rare earth elements, and a concentration gradient of these elements within the crystal grains, along with a method of sintering at 1050° C to 1150° C, to maintain high relative dielectric constant and extended high temperature loading life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of ceramic dielectric layers is reduced to satisfy size-reduction demand, then the capacitance density increases, but the grain growth occurs more easily leading to reduced insulating property and reliability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the grain diameter to be 0.15 to 0.3 μm, which is smaller than the conventional 0.5 μm threshold. This grain size parameter control prevents grain growth while maintaining high capacitance density in thin dielectric layers (5 μm or less), thereby resolving the contradiction between size reduction and reliability
Solution Approach 2:
The patent uses composite materials by combining barium titanate powder with specific amounts of rare earth elements (0.7 to 3 molar parts per 100 molar parts of barium titanate), magnesium (0.5 to 2 molar parts), and manganese (0.2 to 0.5 molar parts). This composite composition enables the dielectric layer to maintain high insulating property and prevent grain growth even at reduced thickness, thus resolving the contradiction between capacitance density and reliability
2Volume of moving object
If the grain diameter is reduced below 0.5 μm to increase capacitance density, then the size is reduced, but the relative dielectric constant decreases and temperature characteristics worsen
Solution Approach 1:
The patent changes the grain diameter parameter to a specific range (0.15 to 0.3 μm) that is smaller than conventional values but carefully controlled to prevent excessive reduction. This parameter optimization maintains high relative dielectric constant and stable temperature characteristics while achieving high capacitance density
Solution Approach 2:
The patent applies local quality by creating a concentration gradient of rare earth elements from the grain boundary to the center of crystal grains. This non-uniform distribution of rare earth elements locally enhances the dielectric properties at the grain level, maintaining high relative dielectric constant and low temperature characteristics even with reduced grain diameter
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
Achieves a high relative dielectric constant, low temperature-dependent variation, and extended high temperature loading life even at reduced grain diameters, enhancing the reliability and performance of multilayer ceramic capacitors.
Implementation Method 1
a method of sintering at 1050° C to 1150° C
Data Source
AI summary
Disclosed is a multilayer ceramic capacitor which has a dielectric ceramic having a dielectric layer, wherein the dielectric layer mainly comprises barium titanate, contains a crystalline particle having an average crystal diameter of 0.15 to 0.3 μm, and contains Mg in an amount of 0.5 to 2 parts by mol in terms of MgO, Mn in an amount of 0.2 to 0.5 part by mol in terms of MnO, and a first rare earth element (RE) selected from Ho, Y, Er, Tm, Yb and Lu and a second rare earth element (RE) selected from Sm, Eu, Gd, Tb and Dy in a total amount of 0.7 to 3 parts by mol in terms of RE2O3 relative to 100 parts by mol of barium titanate, the crystalline particle contains the first rare earth element and the second rare earth element in such a manner that the amount of the first rare earth element is larger than that of the second rare earth element, and the density gradients of the first rare earth element and the second rare earth element in the crystalline particle as determined from the particle boundary toward the center of the crystalline particle are −0.005 to −0.05 atm %/mm and −0.0005 to −0.005 atm %/mm, respectively. Also disclosed is a method for producing the multilayer ceramic capacitor.