Electrolytic Capacitor Resin Layer to Suppress ESR Increase
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Solution Overview
Problem
The increase in equivalent series resistance (ESR) over time in electrolytic capacitors is significant due to the reaction of acid anhydride-cured epoxy resin with water or ethylene glycol, leading to hydrolysis and elution into the electrolytic solution, which affects the capacitor's performance.
Innovation Solution
The use of phenol-based or amine-based cured epoxy resins in the resin layer, which do not contain ester bonds, prevents the reaction with water or ethylene glycol, thereby suppressing the increase in ESR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional electrolytic capacitor structure is used, then the manufacturing process is simple, but the inductance is high and frequency characteristics are poor
Solution Approach 1:
The capacitor element is divided into multiple unit capacitor elements connected in parallel. Each unit element has its own terminal, allowing independent connection to the external circuit. This segmentation reduces the overall inductance by providing multiple current paths, thereby improving frequency characteristics without significantly complicating the manufacturing process.
Solution Approach 2:
The patent transitions from a planar arrangement to a three-dimensional stacked structure where multiple capacitor elements are arranged vertically. The first and second capacitor elements are positioned at different heights along the stacking direction, with terminals extending in different spatial directions. This dimensional change enables low-inductance parallel connection while maintaining compact form factor and manageable manufacturing complexity.
2Reliability
If the capacitor element is divided into multiple unit capacitor elements, then the inductance is reduced and frequency characteristics are improved, but the manufacturing complexity increases
Solution Approach 1:
Multiple capacitor elements are nested within a single capacitor element housing. The first capacitor element is positioned in the lower portion and the second capacitor element in the upper portion of the same housing, with both elements sharing the same encapsulation space. This nesting approach reduces the number of external housings needed and simplifies assembly, offsetting the increased complexity from having multiple internal elements.
Solution Approach 2:
The common terminal serves multiple functions by being electrically connected to both the first and second capacitor elements simultaneously. This multi-functional terminal design simplifies the connection architecture, as a single terminal structure achieves what would otherwise require multiple separate connection points, thereby reducing manufacturing complexity despite the increased number of capacitor elements.
3Reliability
If multiple terminal structures are used for parallel connection, then the inductance is reduced, but the device complexity and assembly difficulty increase
Solution Approach 1:
The terminal structures are designed with asymmetric orientations to facilitate assembly. The first terminal extends in a first direction from the first capacitor element, while the second terminal extends in a second direction from the second capacitor element. This asymmetric arrangement allows terminals to be positioned optimally for parallel connection without requiring complex alignment procedures, thereby maintaining ease of assembly while achieving low inductance through proper terminal configuration.
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 electrolytic capacitors with phenol-based or amine-based cured epoxy resin layers effectively inhibit the increase in ESR over time, maintaining capacitor performance by preventing resin decomposition and elution into the electrolytic solution.
Implementation Method 1
wherein the electrolyte is impregnated in the porous layer formed on the aluminum foil
Implementation Method 2
a porous layer formed on an aluminum foil in a radial direction from a center of the aluminum foil
Data Source
Figure 1
AI summary
Provided is an electrolytic capacitor with a resin layer, in which an increase in ESR over time is suppressed. A electrolytic capacitor includes a capacitor element including an anode foil, a cathode foil, and electrolytic solution, a case housing the capacitor element, a sealing member sealing the case, and a resin layer arranged in the vicinity of the sealing member. The resin layer arranged in the vicinity of the sealing member includes epoxy resin composition without ester bond.