Multilayer Ceramic Capacitor Grain Gradient Side Margin Design
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Solution Overview
Problem
Multilayer ceramic capacitors face challenges in increasing capacity without enlarging size, as methods like increasing dielectric constant or reducing dielectric layer thickness degrade DC bias characteristics, and enlarging the number of layers increases capacitor size, while reducing side margin region thickness to enhance capacity can lead to cracks and reliability issues due to tensile stress.
Innovation Solution
A multilayer ceramic capacitor design with a side margin region where the average grain diameter of ceramic grains near the surface is larger than near the internal electrode layers, promoting grain growth to maintain structural integrity and reduce tensile stress, ensuring 1.5≤Db/Da≤10.0, where Da and Db are the average grain diameters within 20 μm from the edge and surface, respectively, to prevent cracking and enhance breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the side margin region is reduced to enlarge the capacity region, then the capacity of the multilayer ceramic capacitor is increased, but tensile stress concentrates in the side margin region causing cracks and reliability degradation
Solution Approach 1:
The patent applies local quality by creating a gradient in grain diameter within the side margin region. The grain diameter increases from the inner region (near internal electrodes) to the outer region (surface), with specific ratios Db/Da between 1.05-5.0. This localized structural variation allows the side margin to withstand tensile stress from capacity region expansion while maintaining overall device compactness for high capacity.
Solution Approach 2:
The patent changes the physical parameter of grain diameter distribution in the side margin region. By controlling the grain diameter ratio (Db/Da) through specific sintering conditions and additive compositions, the material structure is optimized to resist crack propagation while enabling reduced side margin thickness for higher capacity density.
2Quantity of substance
If the dielectric constant of the dielectric material is increased to enlarge capacity, then the capacity is increased, but the DC bias characteristic is degraded
Solution Approach 1:
The patent applies local quality by differentiating the grain structure in the side margin region from the capacity region. The side margin has a specific grain diameter gradient (Db/Da ratio) that optimizes mechanical stress resistance, while the capacity region maintains dielectric properties for high capacitance. This localized differentiation allows high dielectric constant materials to be used without compromising DC bias characteristics.
3Quantity of substance
If the thickness of dielectric layers is reduced to enlarge capacity, then the capacity is increased, but the electric field intensity increases causing degraded DC bias characteristic
Solution Approach 1:
The patent changes material and structural parameters including grain diameter distribution (Db/Da ratio), sintering temperature, and additive composition. These parameter changes enable the side margin region to maintain mechanical integrity even when dielectric layer thickness is reduced, allowing higher capacity density without compromising DC bias characteristics through excessive electric field intensity.
4Quantity of substance
If the number of stacking layers is increased to enlarge capacity, then the capacity is increased, but the capacitor size is enlarged
Solution Approach 1:
The patent optimizes structural parameters including grain diameter ratio (Db/Da), sintering conditions, and side margin thickness to enable reduced overall capacitor size. By improving the mechanical properties of the side margin region through grain gradient control, the patent allows for more efficient space utilization, enabling higher capacity in a compact form factor without increasing overall dimensions.
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
This design effectively suppresses cracks in the side margin region, improves breakdown voltage, and increases the volume ratio of the capacity region, achieving a larger capacity while maintaining reliability and reducing the thickness of the side margin region.
Implementation Method 1
grain growth of a surface region of a side margin region is promoted more than grain growth of an inner region of the side margin region
Data Source
AI summary
A multilayer ceramic capacitor includes: a multilayer structure in which each of a plurality of ceramic dielectric layers and each of a plurality of internal electrode layers are alternately stacked, the plurality of internal electrode layers being alternately exposed to a first edge face and a second edge face of the multilayer structure, wherein 1.5≤Db/Da≤10.0 is satisfied in a side margin region that covers edge portions to which the plurality of internal electrode layers extend toward two side faces other than the first edge face and the second edge face, when Da is an average grain diameter of a main component ceramic within 20 μm from an edge of the plurality of internal electrode layers in the side margin region and Db is an average grain diameter of a main component ceramic within 20 μm from a surface layer of the side margin region.