Porous External Electrode Structure for Multilayered Capacitors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multilayered ceramic capacitors (MLCCs) face challenges in achieving stable electrical characteristics, reliability, and resistance to mechanical stress, thermal expansion, and high-temperature degradation due to external electrodes with high elasticity coefficients and materials that decompose at high temperatures.
Innovation Solution
The external electrode of the multilayered capacitor is designed with a two-layer structure, where the first layer includes a conductive metal and the second layer is an alloy of a low melting point metal with pores, reducing the elasticity coefficient and thermal expansion, and is free from materials that decompose at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external electrode with high elasticity coefficient is used, then electrical conductivity is improved, but bending strength deteriorates due to increased stress under mechanical deformation
Solution Approach 1:
The second layer of the external electrode is designed with a porous structure containing multiple voids. This porous configuration reduces the elasticity coefficient of the external electrode, thereby decreasing stress applied to the capacitor body during mechanical deformation while maintaining electrical conductivity through the conductive metal network formed by the alloy particles.
Solution Approach 2:
The external electrode employs a composite structure consisting of a first layer (solid conductive metal) and a second layer (porous alloy of conductive metal and low melting point metal). This composite design combines the high conductivity of dense metal with the stress-reducing properties of porous structure, resolving the contradiction between conductivity and bending strength.
2Ease of manufacture
If materials with large thermal expansion difference are used in the external electrode, then ease of manufacture is improved, but shape stability deteriorates due to deformation at high temperature
Solution Approach 1:
The low melting point metal undergoes a parameter change (phase transition from solid to liquid and back) during temperature cycles. This phase change allows the material to accommodate thermal expansion differences through volume changes in the porous structure, maintaining shape stability while enabling easy manufacture with conventional materials.
Solution Approach 2:
The second layer utilizes phase transitions of the low melting point metal (melting and solidification) to absorb and release thermal stress. During heating, the low melting point metal transitions to liquid state, allowing volume adjustment; during cooling, it solidifies, maintaining structural integrity. This phase transition mechanism prevents shape deformation while preserving 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
This design enhances bending strength, maintains low equivalent series resistance (ESR), and provides excellent heat resistance by minimizing stress and shape change due to mechanical deformation and temperature fluctuations.
Implementation Method 1
a second layer disposed on the first layer and including an alloy of a second conductive metal and a low melting point metal having a melting point lower than that of the second conductive metal
Implementation Method 2
since the external electrode includes no materials decomposed at a high temperature but materials no large thermal expansion difference, exhibits almost no shape change due to a temperature change
Implementation Method 3
an external electrode having a low elasticity coefficient to reduce a stress applied to the multilayered capacitor due to external mechanical deformation
Data Source
AI summary
A multilayered capacitor includes a capacitor body in which dielectric layers and internal electrodes are stacked in a first direction, and an external electrode disposed on the capacitor body. The external electrode includes a first layer including a first conductive metal, and a second layer disposed on the first layer and including an alloy of a second conductive metal and a low melting point metal having a melting point lower than that of the second conductive metal and having a plurality of pores, and an area ratio of pores in a unit area of the second layer to a unit area of the second layer is greater than or equal to about 30%.