Multilayer Ceramic Capacitor External Electrode Erosion Control
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Solution Overview
Problem
Multilayer ceramic electronic components face challenges in maintaining mechanical strength and moisture resistance reliability, particularly when thinner external electrodes are used, as they can lead to erosion and cracking due to plating solutions, and increasing the erosion resistance of glass compositions can hinder densification and wettability.
Innovation Solution
The use of a conductive paste for the external electrode layers containing a metal component and a glass component with a Zr/Ba atomic ratio between 0.03 and 0.15, and a glass-occupied area ratio of at least 18%, along with ZrO2 powder added separately from the metal and glass powders, helps prevent erosion and maintain mechanical strength while ensuring densification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the external electrode is reduced to achieve smaller component size, then the component size is reduced, but the mechanical strength decreases and erosion by plating solution increases
Solution Approach 1:
The patent changes the chemical composition parameters of the glass phase in the conductive paste, specifically controlling the BaO content at 30-70 wt% and B2O3 content at 10-40 wt%, to achieve optimal balance between electrode thickness reduction and mechanical strength maintenance. This parameter optimization allows thinner electrodes to maintain sufficient strength while resisting plating solution erosion.
Solution Approach 2:
The patent uses a composite conductive paste material consisting of metal powder (Cu, Ni, or Ag), glass phase (with controlled BaO and B2O3 content), and organic vehicle. This composite structure provides both the electrical conductivity needed for thin electrodes and the mechanical strength through the glass matrix, enabling reduced electrode thickness without sacrificing performance.
2Reliability
If components such as SiO2, Al2O3, or TiO2 are increased to improve erosion resistance of the glass composition, then erosion resistance is improved, but the softening point of glass increases and wettability decreases
Solution Approach 1:
The patent optimizes the glass composition parameters by controlling BaO at 30-70 wt% and B2O3 at 10-40 wt%, which adjusts the softening point and wettability to appropriate levels. This parameter control ensures that the glass phase provides sufficient erosion resistance while maintaining good wettability for proper sintering and electrode formation.
Solution Approach 2:
The patent applies different material properties to different regions of the external electrode. The glass phase with specific BaO and B2O3 content provides erosion resistance where needed, while the metal powder and organic vehicle ensure good wettability and adhesion to the ceramic body. This local differentiation of material properties resolves the contradiction between erosion resistance and wettability.
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 approach enhances the moisture resistance reliability and mechanical strength of multilayer ceramic capacitors by preventing erosion from plating solutions and maintaining densification, even with thinner external electrodes, thereby improving the overall reliability of the components.
Implementation Method 1
The glass component includes Zr and Ba, a Zr/Ba atomic number ratio is not less than about 0.03 and not greater than about 0.15... erosion of the glass composition by a plating solution in plating of the external electrode
Implementation Method 2
WO 2014/175013 also discloses that floating of glass at the external electrode can be reduced or prevented, and the densification of the external electrode can be improved, thus leading to an improved mechanical strength
Data Source
AI summary
A multilayer ceramic capacitor includes a glass component of an underlying electrode layer including Zr and Ba, and in a cross-section of the multilayer ceramic capacitor, a Zr/Ba atomic number ratio is not less than about 0.03 and not greater than about 0.15. The underlying electrode layer has a glass-occupied area ratio of not less than about 18% in the cross-section of the multilayer ceramic capacitor. In a SEM image in the cross-section of the multilayer ceramic capacitor, the glass component on an imaginary line α, which is parallel or substantially parallel to the surface of the surface layer of the underlying electrode layer about 3 μm inside of the surface layer of the underlying electrode layer, is not greater than about 0.92 μm.