Aluminum Electrolytic Capacitor Separator Thickness Ratio
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Solution Overview
Problem
Conventional aluminum electrolytic capacitors face issues with low tensile strength of separators leading to short circuits and decreased capacitance due to stress from electrode leads, and increased separator thickness deteriorates ESR characteristics.
Innovation Solution
The capacitors employ a laminated structure with a specific ratio of total thickness of first and second separators before and after winding, along with an acid component and non-protic solvent in the electrolyte solution, to minimize stress and improve reliability and ESR characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a low-density separator is used to improve ESR characteristics, then ESR decreases, but tensile strength decreases leading to ruptures and short circuits
Solution Approach 1:
The patent employs a composite separator structure consisting of a base separator made of low-density material (such as polyolefin) combined with a reinforcement layer made of high-strength material (such as aramid or glass fiber). This composite structure maintains the low ESR characteristics of the low-density base separator while the reinforcement layer provides the necessary tensile strength to prevent ruptures and short circuits during winding and operation.
2Strength
If separator thickness is increased to improve strength, then tensile strength increases, but volume of electrode foils decreases and ESR characteristics deteriorate
Solution Approach 1:
The composite separator structure allows a thin base separator (maintaining low ESR) to be reinforced with a high-strength layer. This enables achieving the required tensile strength without significantly increasing the overall separator thickness, thereby preserving the volume available for electrode foils and maintaining good ESR characteristics.
Solution Approach 2:
The reinforcement layer is applied selectively to specific regions of the separator where mechanical strength is most needed (such as areas subject to winding stress or lead connection stress), rather than uniformly increasing thickness throughout. This localized reinforcement maintains overall separator thinness while providing necessary strength.
3Reliability
If separator thickness is increased to prevent short circuits, then short-circuit resistance improves, but capacitance increases difficult due to decreased electrode foil area
Solution Approach 1:
The composite separator provides enhanced short-circuit resistance through the high-strength reinforcement layer without requiring increased overall thickness. This maintains the electrode foil area necessary for achieving high capacitance values, as the reinforcement layer provides mechanical protection against short circuits rather than relying on increased separator thickness.
Data Source
AI summary
An aluminum electrolytic capacitor having an excellent short-circuit resistance, high capacitance, long life, and low equivalent series resistance (ESR) is provided. For this purpose, the aluminum electrolytic capacitor includes a capacitor element having a positive electrode foil, a first separator, a negative electrode foil, and a second separator, which are sequentially laminated one on another and wound together. After the capacitor element is impregnated with a driving electrolyte solution and housed in a metallic case, an open end of the metallic case is sealed with a sealing material. A ratio of B/A, i.e. a ratio of total thickness B of the first and second separators after winding with respect to total thickness A of the first and second separators before winding, is set in the range from 0.5 to 0.8.