Electrolytic Capacitor Nickel Cathode Grain Control
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Solution Overview
Problem
Conventional solid electrolytic capacitors experience a reduction in capacitance and an increase in Equivalent Series Resistance (ESR) due to unintentional formation of metal oxide films on the cathode aluminum foil during heat treatment, which affects their high-frequency impedance characteristics.
Innovation Solution
A nickel layer with crystal grains of 50 nm or more in length is formed on the surface of aluminum foil using a vacuum deposition method followed by heat treatment, preventing the formation of unwanted capacitance components and reducing ESR by creating a low-resistance nickel layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nickel layer is formed on the aluminum foil surface to prevent capacitance component generation, then the high-frequency impedance characteristic is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent changes the physical parameters of the nickel layer, specifically controlling the crystal grain size to be 50 nm or more in length. This parameter control is achieved by adjusting deposition conditions (vacuum deposition) and heat treatment parameters (temperature and time), which transforms the nickel layer structure to prevent capacitance component formation while maintaining manufacturing feasibility
Solution Approach 2:
The patent creates a composite structure by forming a nickel layer on the aluminum foil surface. This composite material approach combines the properties of aluminum (base electrode) with nickel (protective low-resistance layer), where the nickel layer serves multiple functions: preventing oxidation and reducing ESR, while the specific crystal grain structure prevents unwanted capacitance generation
2Reliability
If the nickel layer crystal grain size is increased to 50 nm or more to reduce ESR, then the electrical conductivity is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent establishes specific parameter ranges for crystal grain size (50 nm or more) and controls them through standardized vacuum deposition and heat treatment processes. By defining this parameter threshold and controlling it through process parameters (deposition temperature, time, heat treatment conditions), the patent achieves low ESR while maintaining manufacturing precision through controllable parameters rather than uncontrolled variables
3Reliability
If conventional chemical conversion treatment is applied to the cathode foil to prevent oxidation, then the protective function is improved, but the capacitance component generation increases
Solution Approach 1:
Instead of applying chemical conversion treatment to the cathode foil as done with the anode, the patent inverts the approach by applying vacuum deposition of nickel to the cathode surface. This inverted method achieves oxidation protection without forming the thick aluminum oxide layer that creates unwanted capacitance components, thereby solving the contradiction between protection and capacitance generation
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 approach effectively suppresses the generation of unwanted capacitance components and lowers the ESR of solid electrolytic capacitors, enabling downsizing and increasing capacitance while maintaining excellent high-frequency characteristics.
Implementation Method 1
A nickel layer with crystal grains of 50 nm or more in length is formed on the surface of aluminum foil using a vacuum deposition method
Implementation Method 2
followed by heat treatment, preventing the formation of unwanted capacitance components and reducing ESR by creating a low-resistance nickel layer
Data Source
AI summary
An electrolytic capacitor includes an anode body formed with a dielectric layer on a surface thereof, a cathode body formed with a nickel layer on a surface thereof, and a solid electrolyte formed between the anode body and the cathode body. The solid electrolyte contains a conductive polymer. The nickel layer contains a nickel crystal grain whose length in a direction perpendicular to a thickness direction of the nickel layer in a cross section taken in the thickness direction is 50 nm or more.