Porous Electrolytic Capacitor Anode for High Capacitance and Low ESR
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Solution Overview
Problem
Existing electrolytic capacitors face challenges in achieving sufficient capacitance and low equivalent series resistance (ESR) due to limitations in tantalum powder composition and pore distribution, which affect handling characteristics and electrolyte solution permeability.
Innovation Solution
The electrolytic capacitor features an anode body with a porous structure formed by sintering a mixture of first and second particles, where the average particle diameter of the first particles is smaller than the second particles, resulting in a volume-based pore diameter distribution with peaks below and above 0.5 μm, enhancing specific surface area and conductive path formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single particle size is used for the anode body, then the manufacturing process is simple, but the capacitance and ESR performance cannot be optimized simultaneously
Solution Approach 1:
The anode body is segmented into multiple regions with different particle sizes: a first region containing fine particles (average diameter 0.5-5 μm) for high capacitance, and a second region containing coarse particles (average diameter 5-20 μm) for low ESR. This segmentation allows each region to contribute its optimal properties to the overall capacitor performance.
Solution Approach 2:
Different regions of the anode body are assigned different particle size characteristics tailored to their functional requirements. The first region near the dielectric layer uses fine particles to maximize surface area and capacitance, while the second region uses coarse particles to reduce resistance and improve conductivity. This local optimization resolves the contradiction between capacitance and ESR performance.
2Quantity of substance
If only fine particles are used, then the specific surface area and capacitance increase, but the ESR increases and handling characteristics deteriorate
Solution Approach 1:
Fine particles are localized in the first region where they provide high specific surface area for capacitance formation, while coarse particles are placed in the second region where they reduce ESR and improve handling. This spatial differentiation allows fine particles to contribute capacitance without causing excessive ESR or handling problems throughout the entire anode body.
Solution Approach 2:
The anode body uses a composite structure combining two different particle size distributions in specific regions. The fine particles (0.5-5 μm) provide high surface area for capacitance, while the coarse particles (5-20 μm) provide low resistance pathways and good handling characteristics, creating a composite material system that balances opposing properties.
3Object-generated harmful factors
If only coarse particles are used, then the ESR decreases and handling is improved, but the capacitance is insufficient
Solution Approach 1:
The anode body is divided into two functional regions: the first region with fine particles provides the necessary capacitance through high surface area, while the second region with coarse particles reduces ESR and improves handling. This segmentation ensures that coarse particles do not uniformly reduce capacitance while still achieving low ESR in the overall structure.
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 configuration enables the electrolytic capacitor to achieve favorable capacitance and low ESR, balancing electrostatic capacity and conductivity by creating a well-defined pore structure within the anode body.
Implementation Method 1
The anode body is formed by sintering a molded body of metal particles
Implementation Method 2
a dielectric layer formed on the surface of the anode body
Data Source
AI summary
An electrolytic capacitor includes an anode body having a porous structure, an anode lead partially embedded in the anode body, a dielectric layer formed on a surface of the anode body, and a cathode part that covers at least part of the dielectric layer. The anode body has a first region in which first particles sintered together and a second region in which second particles sintered together. The average particle diameter D1 of the first particles is smaller than the average particle diameter D2 of the second particles. The volume-based pore diameter distribution of the anode body with the dielectric layer has a first peak in a range of less than or equal to 0.5 μm in pore diameter, and a second peak in a range of more than 0.5 μm in pore diameter.