Multilayer Ceramic Capacitor Structure for Crack and Moisture Resistance
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Solution Overview
Problem
Existing multilayer ceramic capacitors face challenges in reducing size while minimizing the occurrence of cracks and improving moisture resistance, as seen in Japanese Unexamined Patent Application Publication No. 2019-16781.
Innovation Solution
The multilayer ceramic capacitor design includes an inner-layer portion with first dielectric layers and first inner electrodes, and outer-layer portions with second dielectric layers and second inner electrodes, where the second inner electrodes have reduced dimensions and porosity, and are combined with a conductive-resin layer to provide stress relief and moisture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the multilayer ceramic capacitor is downsized to reduce electronic device size, then the size of the multilayer ceramic capacitor is reduced, but the occurrence of cracks increases due to susceptibility to stresses
Solution Approach 1:
The patent applies local quality by creating a porosity gradient within the dielectric layers, where the porosity varies from the inner-layer portion to the outer-layer portions. This localized variation in porosity allows different regions to have different mechanical properties, with higher porosity regions providing stress relief while maintaining overall compact dimensions, thereby reducing crack occurrence in the downsized capacitor
Solution Approach 2:
The patent changes the physical parameter of porosity within the dielectric layers to resolve the contradiction. By controlling and varying the porosity parameter across different regions (inner-layer vs outer-layer portions), the capacitor achieves both reduced size and improved reliability, as the porosity gradient enables stress management without increasing overall dimensions
2Reliability
If a conductive-resin layer is disposed on the outer electrode to relax stresses and reduce cracks, then the occurrence of cracks is reduced, but the device complexity and manufacturing complexity increase
Solution Approach 1:
The patent extracts the stress-relief function from a separate conductive-resin layer and integrates it directly into the dielectric layers through porosity control. This eliminates the need for an additional conductive-resin layer while maintaining the stress-relief effect, thereby reducing device complexity and the number of manufacturing steps
Solution Approach 2:
The patent merges the stress-relief function with the dielectric layers by creating porosity gradients within them. Instead of having separate dielectric layers and conductive-resin layers, the stress-management capability is combined into the dielectric structure itself, simplifying the overall device architecture
3Reliability
If additional reinforcing members are added to prevent cracks and improve moisture resistance, then the reliability and moisture resistance are improved, but the size of the multilayer ceramic capacitor increases
Solution Approach 1:
The patent applies local quality by creating regions with different porosity levels within the dielectric layers. The inner-layer portion has different porosity characteristics than the outer-layer portions, providing localized moisture resistance and stress management without requiring additional reinforcing members that would increase overall capacitor size
Solution Approach 2:
The patent uses composite material structures within the dielectric layers, combining regions of different porosity to create a multi-functional material that provides both mechanical strength and moisture resistance. This internal composite structure eliminates the need for external reinforcing members
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 reduces the occurrence of cracks, minimizes size, and enhances moisture resistance by utilizing the porosity gradient and conductive-resin layer to manage stress and moisture, without the need for additional reinforcing members.
Implementation Method 1
When each outer-layer portion is divided into two equal regions in the lamination direction, a porosity of a region near the inner-layer portion is smaller than a porosity of a region farther from the inner-layer portion
Implementation Method 2
The conductive-resin layer can relax stresses and thereby reduce the occurrence of cracks in the multilayer ceramic capacitor
Implementation Method 3
The conductive-resin layer also can provide reliable moisture resistance
Data Source
AI summary
A multilayer ceramic capacitor includes a multilayer body and outer electrodes on two surfaces of the multilayer body. The multilayer body includes an inner-layer portion and two outer-layer portions. The inner-layer portion includes first dielectric layers laminated in the lamination direction and a first inner electrode between the first dielectric layers. Each outer-layer portion includes at least one second dielectric layer and a second inner electrode in contact with the at least one second dielectric layer. A length of the second inner electrode is less than a length of the first inner electrode, or a width of the second inner electrode is less than a width of the first inner electrode. When each outer-layer portion is divided into two equal regions, a porosity of a region near the inner-layer portion is less than a porosity of a region farther from the inner-layer portion.