Multilayer Ceramic Capacitor Electrodes for Moisture and Bending Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multilayer ceramic capacitors face challenges in achieving both moisture resistance and board bending resistance, as conventional solutions either compromise on one aspect or fail to adequately address both.
Innovation Solution
A multilayer ceramic capacitor design featuring a multilayer body with dielectric and internal electrode layers, and external electrodes with a lower electrode layer having a higher glass content for strong adhesion and an upper electrode layer with a lower glass content and pores to reduce residual stresses and prevent plating solution ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the external electrode includes a lower electrode layer with high glass content for strong adhesion, then adhesion to ceramic body is improved, but residual stresses increase and board bending resistance deteriorates
Solution Approach 1:
The external electrode is divided into two distinct layers: a lower electrode layer with high glass content (15-30 mass%) for strong adhesion to the ceramic body, and an upper electrode layer with low glass content (0-10 mass%) for reduced residual stress. This segmentation allows each layer to fulfill its specific function independently, resolving the contradiction between adhesion strength and stress reduction.
Solution Approach 2:
Different regions of the external electrode are assigned different glass contents based on their functional requirements. The lower layer near the ceramic body has high glass content for maximum adhesion, while the upper layer exposed to plating solution has low glass content for stress reduction and corrosion resistance. This local quality differentiation optimizes both adhesion and stress characteristics simultaneously.
2Ease of manufacture
If water-soluble flux is used for solder-mounting, then ease of soldering is improved, but erosion of glass components increases and moisture resistance deteriorates
Solution Approach 1:
The glass content parameter in the upper electrode layer is reduced to 0-10 mass%, creating a glass-poor composition that is inherently more resistant to erosion by water-soluble flux. This parameter change maintains soldering ease while significantly improving resistance to flux attack and preventing moisture infiltration paths.
3Reliability
If glass content in external electrode is reduced for erosion resistance, then moisture resistance is improved, but adhesion to ceramic body deteriorates
Solution Approach 1:
The external electrode is segmented into two layers with different glass contents: the lower layer (15-30 mass% glass) ensures strong adhesion to the ceramic body, while the upper layer (0-10 mass% glass) provides erosion resistance. This segmentation resolves the contradiction by assigning different glass content levels to different functional zones.
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 design effectively enhances both moisture resistance by preventing moisture infiltration and board bending resistance by reducing tensile stresses during board bending, thereby improving the overall reliability of the capacitor.
Implementation Method 1
the lower electrode layers include a metal component and a glass component... structurally, the first layer has high adhesion to the ceramic body
Implementation Method 2
the upper electrode layers include a metal component and a glass component and include a plurality of pores inside... tensile stresses generated at the time of board bending can be reduced
Data Source
AI summary
A multilayer ceramic capacitor includes a multilayer body including dielectric layers, internal electrode layers, and first and second end surfaces facing each other in a length direction, a first external electrode on a side of the first end surface, and a second external electrode on a side of the second end surface. The first and second external electrodes each include lower and upper electrode layers, the lower electrode layers include a metal component and a glass component, the upper electrode layers include a metal component and a glass component, and include pores, an amount of the glass component in the upper electrode layers is less than an amount of the glass component in the lower electrode layers, and a maximum inscribed circle diameter of the pores in the upper electrode layers is greater than or equal to about 0.02 μm and less than or equal to about 0.52 μm.