Multilayer Ceramic Capacitor Grain Doping Gradient
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Solution Overview
Problem
Multilayer ceramic capacitors with dielectric layers thinner than 0.8 μm face challenges in achieving excellent life characteristics while minimizing leak current, as existing compositions either fail to adequately improve life characteristics or lead to excessive leak current due to uneven distribution of donor and acceptor elements.
Innovation Solution
A multilayer ceramic capacitor design where the ratio of donor element (Nb, Mo, Ta, W) to acceptor element (Mg, Mn) concentration varies within the ceramic grain, with higher donor element concentration at the center and higher acceptor element concentration at the edge, optimizing life characteristics and reducing leak current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the dielectric layer is reduced to increase the number of layers and capacitance, then the capacitance increases, but the voltage applied per unit thickness increases which shortens the service life of the dielectric layer
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of donor elements within the ceramic grain structure. The center part of the ceramic grain has a higher concentration of donor elements (Nb, Mo, Ta, or W) compared to the outer edge part. This localized concentration gradient allows the center region to provide sufficient electrons for suppressing oxygen defects and improving service life, while the outer edge region maintains lower electron concentration to suppress leak current, thus resolving the contradiction between improving reliability and maintaining low leak current in thin dielectric layers.
2Reliability
If donor elements such as Mo are added to improve service life by suppressing oxygen defect, then the service life improves, but the electron concentration increases which leads to excessive leak current
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through spatially differentiated donor element concentration. The center part of the ceramic grain contains a higher concentration of donor elements (Nb, Mo, Ta, or W) to provide sufficient electrons for suppressing oxygen defects and improving service life. Meanwhile, the outer edge part contains a lower concentration of donor elements to reduce electron concentration and suppress leak current. This non-uniform distribution allows both requirements to be satisfied simultaneously in different regions of the same ceramic grain.
3Reliability
If the concentration of additive elements increases from the center of the core toward the shell to improve reduction resistance, then the reduction resistance improves, but the volume of high concentration regions is limited which reduces the effectiveness for life characteristics improvement
Solution Approach 1:
The patent applies inversion by reversing the conventional concentration gradient of additive elements. Instead of increasing concentration from the center toward the shell as in prior art, this patent creates a configuration where the center part of the ceramic grain has a higher concentration of donor elements (Nb, Mo, Ta, or W) than the outer edge part. This inverted concentration distribution ensures that the region with high donor element concentration (which improves life characteristics by suppressing oxygen defects) has sufficient volume, while still maintaining effective reduction resistance through the overall presence of additive elements throughout the grain structure.
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 specified concentration ratio effectively enhances the life characteristics of multilayer ceramic capacitors while suppressing leak current, even at dielectric layer thicknesses of 0.8 μm or less, by ensuring sufficient donor element concentration for improved life and acceptor element distribution for reduced electron concentration at the edge.
Implementation Method 1
the donor element is believed to improve life characteristics by suppressing oxygen defect
Implementation Method 2
the acceptor element is made richer at the outer edge part in order to lower the electron concentration at the outer edge part and thereby suppress leak current
Data Source
AI summary
A multilayer ceramic capacitor has a laminate comprising dielectric layers stacked alternately with internal electrode layers of different polarities, wherein: the dielectric layers contain ceramic grains whose primary component is BaTiO3; the ceramic grains contain at least one type of donor element (D) selected from the group that includes Nb, Mo, Ta, and W, and at least one type of acceptor element (A) selected from the group that includes Mg and Mn; and the ratio of the concentration of the donor element (D) and that of the acceptor element (A) (D/A) is greater than 1 at the center parts of the ceramic grains, while the D/A ratio is less than 1 at the outer edge parts of the ceramic grains (if A=0, then D/A=∞ and D=A=0 never occurs).