Multilayer Ceramic Capacitor External Electrode Resin Layer
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Solution Overview
Problem
Multilayer ceramic capacitors (MLCCs) face challenges in ensuring high reliability due to residual stress, degradation of chemical resistance, and moisture sensitivity when using pastes containing Cu, glass frit, and thermoplastic resin, which affect their mechanical and thermal performance.
Innovation Solution
A multilayer ceramic capacitor design featuring external electrodes with an intermediate layer of a first intermetallic compound and a conductive resin layer containing metal particles and a second intermetallic compound, applied using a low melting point paste, which enhances moisture resistance, reduces equivalent series resistance (ESR), and improves mechanical stress resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a paste containing Cu, glass frit, and thermoplastic resin is used to form the conductive resin layer, then the external electrode can be formed with basic conductivity, but residual stress remains in the capacitor and chemical resistance properties are degraded
Solution Approach 1:
The paste composition is changed by replacing glass frit with specific metal particles (Cu, Ag, Ni) and using a thermosetting resin instead of thermoplastic resin. The metal particle size is controlled at 0.1-3.0 μm and content is optimized at 30-70 wt%, which fundamentally changes the physical and chemical properties to eliminate residual stress and improve chemical resistance.
Solution Approach 2:
The conductive resin layer is formed as a composite material containing metal particles (Cu, Ag, Ni), intermetallic compounds (Cu6Sn5, Ag3Sn, Ni3Sn4), and thermosetting resin. This composite structure provides both conductivity and mechanical strength while eliminating the harmful effects of glass frit, achieving high reliability and stress resistance simultaneously.
2Strength
If the conductive resin layer is formed with traditional paste materials, then basic electrical conductivity is achieved, but bending impacts are transmitted to the ceramic body and mechanical stress resistance is reduced
Solution Approach 1:
The mechanical properties are improved by changing the resin type from thermoplastic to thermosetting and optimizing metal particle content to 30-70 wt%. The thermosetting resin forms a cross-linked network structure that provides high mechanical strength and flexibility, absorbing bending impacts without transmitting them to the ceramic body.
Solution Approach 2:
The conductive resin layer acts as an intermediary buffer layer between the rigid external electrode and the ceramic body. The optimized composite structure with metal particles and thermosetting resin absorbs mechanical stress and bending impacts, protecting the ceramic body from damage while maintaining electrical conductivity.
3Reliability
If glass frit is used in the paste formulation, then the paste can be applied and dried easily, but moisture absorption increases and reliability under thermal and mechanical impact is reduced
Solution Approach 1:
The paste formulation is changed by replacing glass frit with metal particles of specific size (0.1-3.0 μm) and using thermosetting resin. This change eliminates moisture absorption issues while the paste maintains good applicability and forms a dense, uniform layer after drying and curing, achieving high moisture resistance without compromising manufacturability.
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 proposed design improves the reliability of MLCCs by reducing residual stress, enhancing moisture resistance, and lowering ESR, while maintaining mechanical strength and chemical resistance, as evidenced by improved capacitance and dissipation factor values compared to traditional methods.
Implementation Method 1
curing the dried paste through a heat treatment to form an intermediate layer and a conductive resin layer
Implementation Method 2
applying a paste having a low melting point to the electrode layer, drying the paste, and curing the dried paste through a heat treatment to form an intermediate layer and a conductive resin layer
Data Source
AI summary
A multilayer ceramic capacitor includes a body including a dielectric layer and first and second internal electrodes, and external electrodes disposed on at least one surface of the body. The external electrodes each includes an electrode layer in contact with the first or second internal electrodes, an intermediate layer disposed on the electrode layer and including a first intermetallic compound, and a conductive resin layer disposed on the intermediate layer and including a plurality of metal particles, a second intermetallic compound and a base resin.