Multilayer External Electrodes for Low-ESR Electrolytic Capacitors
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Solution Overview
Problem
Existing methods for forming external electrodes on resin molded bodies in electrolytic capacitors face challenges in achieving high adhesion between the resin and the electrode layer, leading to increased production costs and elevated Equivalent Series Resistance (ESR).
Innovation Solution
The proposed solution involves forming external electrodes with a multilayer structure, including an inner plating layer, a resin electrode layer containing a resin component and metals like Ni, Cu, or Ag, and an outer plating layer, with a total number of layers limited to four or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a five-layer external electrode structure (Ni/Ag/Ni/Sn) is formed to improve adhesion and prevent oxidation, then reliability is improved, but device complexity and production cost increase
Solution Approach 1:
The patent extracts and removes the Ag plating layer from the traditional five-layer Ni/Ag/Ni/Sn structure, simplifying it to a four-layer Ni/Ni/Sn structure. This extraction eliminates the oxidation prevention function of the Ag layer while maintaining adhesion performance through optimized Ni plating parameters and resin electrode layer composition, thereby reducing production cost and manufacturing complexity without significantly compromising reliability
Solution Approach 2:
The patent merges the functions of multiple layers by using a thickened Ni plating layer (3-10 μm) that simultaneously provides both adhesion to the anode/cathode and oxidation resistance. The resin electrode layer containing metal particles (Ni, Cu, or Ag) is combined with the Ni plating layer to create a composite structure that achieves both mechanical adhesion and chemical stability in fewer layers
2Reliability
If multiple electrode layers are formed to improve adhesion, then reliability is improved, but Equivalent Series Resistance (ESR) increases
Solution Approach 1:
By removing the Ag plating layer from the electrode structure, the patent reduces the number of interfaces between layers. Fewer interfaces mean fewer potential contact resistances, thereby lowering the overall Equivalent Series Resistance while maintaining adequate adhesion through the optimized Ni plating and resin electrode layer combination
3Reliability
If a resin electrode layer with metal particles is used to improve adhesion, then reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise parameter ranges for the resin electrode layer, including metal particle content (60-95 wt%), resin component content (5-40 wt%), and particle size distribution. By controlling these parameters within defined ranges rather than requiring exact values, the patent achieves reliable adhesion while making the manufacturing process more robust and less sensitive to minor variations
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 enhances adhesion between the resin molded body and the electrode layer, thereby reducing production costs and minimizing the increase in ESR, while maintaining the performance of the electrolytic capacitor.
Implementation Method 1
forming an inner plating layer in direct contact with a cathode or an anode
Implementation Method 2
a resin electrode layer for preventing cracking of the external electrode... containing a resin component and at least one metal selected from the group consisting of Ni, Cu, and Ag
Implementation Method 3
forming a Ni plating layer on the surface of the resin electrode layer, followed by forming a Sn plating layer on the surface of the Ni plating layer
Data Source
AI summary
An electrolytic capacitor that includes: a cuboid resin molded body having a first end surface and a second end surface opposite to each other; a first external electrode on the first end surface and electrically connected to an exposed end of an anode; and a second external electrode on the second end surface and electrically connected to an exposed end of a cathode, wherein at least one of the first and second external electrodes has a multilayer structure including: an inner plating layer; and a resin electrode layer on the inner plating layer and containing a resin component and at least one metal selected from Ni, Cu, and Ag, and a total number of layers defining each of the first and second external electrodes is four or less.