Capacitor Electrode Foil with Nickel Oxide Layer for Low ESR
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solid electrolytic capacitors using nickel foil as the cathode face challenges with high equivalent series resistance due to reduced effective contact area and non-uniform nickel plating, which increases costs and hinders high-frequency performance.
Innovation Solution
A capacitor electrode foil featuring a base material of valve metal aluminum with a nickel layer containing nickel and nickel oxide, where the nickel layer is deposited on the aluminum surface to enhance bonding and reduce equivalent series resistance, allowing for large capacitance and low ESR at a lower cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel foil is used as the cathode foil to increase electrostatic capacitance, then the electrostatic capacitance becomes substantially infinite, but the effective contact area between the cathode foil and solid electrolyte is reduced, generating a large equivalent series resistance
Solution Approach 1:
The cathode foil structure is segmented into multiple functional layers: a base nickel foil layer providing infinite electrostatic capacitance, and a surface treatment layer (oxide film removal + roughening + plating) that segments the surface into fine pores to increase effective contact area. This segmentation resolves the contradiction by separating the capacitance function from the contact area function.
Solution Approach 2:
The cathode foil surface is treated to create a porous structure with fine pores, increasing the effective contact area between the cathode foil and solid electrolyte. The porous structure allows the solid electrolyte to penetrate and contact the nickel foil more extensively, reducing equivalent series resistance while maintaining the infinite capacitance property of the nickel foil.
2Ease of manufacture
If electroless plating is used to plate nickel on the roughened surface, then the nickel film can be formed, but the plating film cannot be further thinned and uniformly plated into fine pores, and the oxide film hinders firm bonding
Solution Approach 1:
The oxide film is removed and the surface is roughened before plating to create a favorable surface condition. This preliminary action prepares the surface by removing barriers to bonding and creating a roughened topology that enhances plating uniformity and allows better penetration into fine pores, resolving the contradiction between ease of manufacture and manufacturing precision.
Solution Approach 2:
The surface parameters are changed through oxide film removal and roughening treatment, altering the surface energy, topology, and chemical composition. These parameter changes enable the plating process to produce uniform, thin films that can penetrate fine pores effectively, overcoming the limitations of conventional electroless plating on roughened surfaces.
3Area of stationary object
If a thick nickel plating film (1-μm) is applied to fill etching pits, then the contact area is improved, but the structure becomes more complex and cost increases
Solution Approach 1:
Instead of using a thick plating film to fill etching pits, the invention utilizes a porous surface structure that allows thin plating films to penetrate and coat the internal surfaces of the pores. This approach increases the effective contact area through surface area multiplication rather than volume addition, avoiding the need for thick films and reducing both structural complexity and cost.
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 solution results in a significant increase in capacitance and reduction of equivalent series resistance, improving high-frequency performance and corrosion resistance, while maintaining a simple and cost-effective structure.
Implementation Method 1
a nickel layer including nickel and nickel oxide, where the nickel layer is deposited on the aluminum surface
Implementation Method 2
A surface of an aluminum foil is roughened by etching
Implementation Method 3
the nickel layer forms a diffusion layer including aluminum that is valve metal, nickel, and oxygen by the heat generated during deposition of the nickel layer
Implementation Method 4
The solid electrolyte is made of conductive polymer, and is absorbed between the anode foil and the cathode foil of this element
Data Source
AI summary
A solid electrolytic capacitor that includes a cathode foil and solid electrolyte made of conductive polymer. This cathode foil is made by providing a nickel layer on a surface of a base material made of valve metal. This nickel layer includes a layer containing only nickel and a layer containing nickel oxide. Both large capacitance and low equivalent series resistance are achievable at the same time with this simple structure at low cost.