Multilayer Ceramic Capacitor Electrode Layers for Moisture Reliability
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Solution Overview
Problem
Multilayer ceramic capacitors require improved reliability, particularly in ultra-small and ultra-high-capacitance versions used in fields requiring high reliability, such as electric vehicles, due to challenges in maintaining contact with internal electrodes and resistance to corrosion and moisture.
Innovation Solution
The external electrode of the multilayer ceramic capacitor is composed of at least two layers with different glass compositions, where the lower layer includes aluminum in an amount of 0 to 8 atom % and the upper layer includes aluminum in an amount of 10 to 20 atom %, along with other components like lithium, sodium, and iron, to enhance contact and corrosion resistance, and the thickness ratio of the corner portion to the central portion is maintained between 0.1 to 0.5 to improve moisture endurance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of dielectric layer and internal electrode layer is reduced to achieve miniaturization and ultra-high capacitance, then the capacitance increases and size decreases, but the reliability deteriorates
Solution Approach 1:
The external electrode is divided into a lower layer and an upper layer with different glass compositions. The lower layer contains 0-8 atom % Al and provides excellent contact with internal electrodes, while the upper layer contains 10-20 atom % Al and provides corrosion resistance and moisture endurance. This segmentation allows each layer to be optimized for its specific function, resolving the contradiction between reliability and structural complexity.
Solution Approach 2:
Different regions of the external electrode are given different glass compositions tailored to their functional requirements. The lower layer near the internal electrodes uses low-Al glass for optimal electrical contact, while the upper layer exposed to environment uses high-Al glass for protection. This local quality approach ensures each part has the properties needed for its specific role, improving overall reliability without requiring complex overall restructuring.
2Reliability
If a single-layer external electrode structure is used, then the manufacturing process is simple, but the contact with internal electrodes and corrosion resistance are insufficient
Solution Approach 1:
The external electrode is segmented into two functional layers: a lower layer with 0-8 atom % Al for optimal contact with internal electrodes, and an upper layer with 10-20 atom % Al for corrosion resistance and moisture endurance. This segmentation enables each layer to perform its specific function effectively, resolving the contradiction between reliability and structural complexity.
Solution Approach 2:
The external electrode uses a composite structure combining two different glass compositions. The lower layer uses glass with lower Al content for electrical contact optimization, while the upper layer uses glass with higher Al content for environmental protection. This composite material approach allows simultaneous achievement of good contact quality and corrosion resistance without requiring a single complex material.
Data Source
AI summary
A multilayer ceramic capacitor and a method of manufacturing the same. The multilayer ceramic capacitor includes a capacitor body including a dielectric layer and an internal electrode layer; and an external electrode disposed outside the capacitor body. The external electrode includes a lower layer positioned on a cross-section of the capacitor body to be electrically connected to the internal electrode layer, and an upper layer to cover the lower layer and positioned on the lower layer. The lower layer includes a first glass including aluminum (Al) in an amount of more than 0 atom % to 8 atom % or less with respect to a total amount of components of the first glass. The upper layer includes a second glass including aluminum (Al) in an amount of 10 atom % or more to 20 atom % or less with respect to a total amount of components of the second glass.