Porous Electrode Foil Layout to Prevent Winding Cracks
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Solution Overview
Problem
The existing electrode foils for electrolytic capacitors suffer from low folding endurance and breakage when wound due to stress, particularly along the separation parts with narrow groove widths, leading to cracks and breakage during the winding process.
Innovation Solution
The electrode foil features a metal foil with a porous portion and a core portion, where the porous portion has recessed portions with specific diameter and spacing arrangements, distributed in a dot pattern, to mitigate stress and prevent breakage by forming controlled cracks between the recessed portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If separation parts with narrow groove width are provided to increase pushing depth, then the Erichsen value increases, but the folding endurance decreases and cracks form along the separation parts
Solution Approach 1:
The electrode foil is divided into multiple regions by providing separation parts that extend in the width direction. These separation parts segment the foil structure, creating distinct zones that can independently handle stress, thereby preventing crack propagation across the entire foil while maintaining local pushing depth
Solution Approach 2:
The separation parts are designed with specific groove widths (50 μm or less, including 0) at specific locations to locally enhance pushing depth where needed, while the overall foil structure maintains sufficient folding endurance. The local modification of groove width allows targeted improvement of Erichsen value without compromising overall reliability
2Ease of manufacture
If the electrode foil is wound to form the capacitor, then the capacitor structure is formed, but stress generates cracks extending from end to end in the width direction causing breakage
Solution Approach 1:
The separation parts divide the electrode foil into multiple segments that can flex independently during winding. This segmentation prevents stress concentration from propagating across the entire foil width, thereby preventing end-to-end cracks while still allowing the foil to be successfully wound into the capacitor structure
Solution Approach 2:
The separation parts are pre-formed in the electrode foil before the winding process. This preliminary structural preparation ensures that when winding stress is applied, the foil already has built-in stress relief pathways, preventing crack formation during the manufacturing process
Data Source
AI summary
An electrode foil for an electrolytic capacitor includes a metal foil that includes a porous portion and a core portion continuous to the porous portion. The metal foil has a main surface in which pores in the porous portion are open. The porous portion includes a plurality of recessed portions that are open in the main surface and distributed in a dot pattern in an in-plane direction of the metal foil. The pores in the porous portion have an opening diameter smaller than 2 μm, recessed portions that are adjacent to each other have an opening diameter D1 μm and an opening diameter D2 μm, respectively, and are spaced apart from each other by a distance L μm, and the opening diameter D1 and the distance L satisfy 2≤D1 and 2≤L/D1≤50. The opening diameter D2 and the distance L satisfy 2≤D2 and 2≤L/D2≤50.