MLCC Outer Electrode Layers for Moisture and Hydrogen Blocking
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Solution Overview
Problem
The reliability of multilayer ceramic capacitors is compromised due to the dissolution of glass material and diffusion of hydrogen during the formation of a plating film, which deteriorates their performance.
Innovation Solution
The use of a sulfur-including layer on barium-boron-silicon-based glass and a tin layer on copper exposed at the surface of the outer electrode, preventing moisture and hydrogen diffusion, respectively, while maintaining a reduced film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a plating film is formed using a plating solution, then the wettability of solder is improved, but the glass material in the outer electrode dissolves and hydrogen diffuses into the outer electrode, causing reliability deterioration
Solution Approach 1:
The outer electrode is segmented into multiple functional layers: a glass material layer (barium-boron-silicon-based glass) that provides moisture barrier function, and a metal layer (copper) that provides electrical conductivity and solder wettability. This segmentation allows each layer to perform its specific function without interfering with the other, preventing both moisture ingress and hydrogen diffusion while maintaining solderability.
Solution Approach 2:
The outer electrode uses a composite structure combining glass material (barium-boron-silicon-based glass) and metal (copper). The glass material provides chemical stability and moisture resistance, while the metal layer provides electrical conductivity and solder wettability. This composite material approach resolves the contradiction by combining materials with complementary properties to achieve both reliability and ease of soldering.
2Length of moving object
If the outer electrode structure is made thinner, then the device size is reduced, but moisture and hydrogen can more easily penetrate through the thinner structure, worsening reliability
Solution Approach 1:
The invention changes the material parameters of the outer electrode by using barium-boron-silicon-based glass with specific compositional ratios (BaO: 40-70 wt%, B2O3: 20-40 wt%, SiO2: 5-20 wt%). This parameter optimization provides superior moisture barrier properties and chemical stability, allowing the outer electrode to maintain thin dimensions while achieving adequate moisture and hydrogen resistance through enhanced material performance rather than increased 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
Enhances the reliability of multilayer ceramic capacitors by preventing moisture and hydrogen ingress, ensuring sufficient moisture resistance even with a thinner outer electrode structure.
Implementation Method 1
a sulfur-including layer is located on at least a portion of the surface of the glass exposed at the surface of the outer electrode
Implementation Method 2
a tin layer is located on at least a portion of the surface of a copper exposed at the surface of the outer electrode
Data Source
AI summary
In a multilayer ceramic capacitor, an outer electrode includes at least one of barium-boron-silicon-based glass, strontium-boron-silicon-based glass, or barium-strontium-boron-silicon-based glass, which serves as glass, and copper, the glass and the copper being exposed at a surface of the outer electrode, a sulfur-including layer is provided on at least a portion of the surface of the glass exposed at the surface of the outer electrode, and a tin layer is provided on at least a portion of the surface of the copper exposed at the surface of the outer electrode.