Multilayer Ceramic Capacitor External Electrodes Cu3Sn Adhesion
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Solution Overview
Problem
Multilayer ceramic capacitors with thermosetting resin layers suffer from weak adhesion between the resin and electrode layers, leading to moisture ingress and degradation of moisture resistance and electrical characteristics.
Innovation Solution
A multilayer ceramic capacitor design featuring a laminated body with internal electrodes and external electrodes comprising a base electrode layer, a metallic interlayer with a Cu3Sn alloy, and a conductive resin layer, where the metallic interlayer enhances the adhesion between the base electrode and conductive resin layers, improving mechanical strength and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thermosetting resin layer is used in the external electrode, then mechanical strength is improved, but adhesion to the electrode layer deteriorates
Solution Approach 1:
A metallic interlayer is introduced between the base electrode layer and the conductive resin layer to serve as an intermediary that enhances adhesion. The metallic interlayer forms strong metallurgical bonds with both the base electrode layer (through Cu diffusion) and the conductive resin layer (through Sn bonding), thereby resolving the adhesion problem while maintaining the mechanical strength benefits of the resin layer.
Solution Approach 2:
The external electrode is designed as a composite structure comprising a base electrode layer, a metallic interlayer, and a conductive resin layer. This composite structure combines the advantages of each material: the Cu-based base electrode provides electrical conductivity, the metallic interlayer provides strong adhesion, and the conductive resin provides mechanical strength and flexibility.
2Adaptability or versatility
If a thermosetting resin layer is used in the external electrode, then substrate bendability is improved, but moisture resistance deteriorates
Solution Approach 1:
The metallic interlayer acts as a barrier and bonding interface that prevents moisture from penetrating between the base electrode layer and the conductive resin layer. By forming strong metallurgical bonds and providing a dense metallic structure, it blocks moisture ingress pathways while allowing the conductive resin layer to maintain substrate bendability.
3Strength
If the metallic interlayer thickness is increased, then adhesion strength is improved, but manufacturing precision control becomes difficult
Solution Approach 1:
The thickness of the metallic interlayer is optimized to a specific range (0.1-23.7 μm) to achieve the desired adhesion strength while maintaining manufacturability. This parameter optimization ensures that the interlayer is thick enough to provide sufficient bonding area and strength, but thin enough to be controlled within manufacturing tolerances and to minimize overall electrode thickness.
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 enhanced adhesion and mechanical strength improve moisture resistance reliability and electrical characteristics, while the conductive resin layers provide substrate bendability and drop impact resistance.
Implementation Method 1
a metallic interlayer containing a Cu3Sn alloy provided on the surface of the base electrode layer
Data Source
AI summary
A multilayer ceramic capacitor includes a laminated body including ceramic layers and internal electrodes, and a pair of external electrodes on both end surfaces of the laminated body to be electrically connected to the internal electrodes, and each external electrode includes a base electrode layer containing Cu and provided on the surface of the laminated body, a metallic interlayer containing a Cu3Sn alloy and provided on the surface of the base electrode layer, and a conductive resin layer provided on the surface of the metallic interlayer.