Solid Electrolytic Capacitor Dual-Layer Resin Stress Reduction
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Solution Overview
Problem
Conventional solid electrolytic capacitors experience increased leakage current due to stress transmission from the anode lead to the dielectric layer during the molding process, leading to defects and cracks, which existing methods fail to adequately address.
Innovation Solution
A solid electrolytic capacitor design incorporating a resin layer with a softer first resin layer and a harder second resin layer, covering the exposed portion and connecting parts of the anode lead, to reduce stress transmission and enhance mechanical reinforcement, thereby minimizing dielectric layer cracks and leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the anode lead is rigidly held by thermosetting resin, then stress transmission to the dielectric layer is reduced, but the resin cannot sufficiently suppress cracks and leakage current due to direct contact between pouring resin and anode lead
Solution Approach 1:
The resin layer is divided into two distinct segments: a first resin layer that is softer and directly contacts the anode lead, and a second resin layer that is harder and covers the first resin layer. This segmentation allows each layer to perform its specific function - the softer first layer absorbs stress while the harder second layer provides structural support, collectively preventing stress transmission to the dielectric layer and reducing leakage current.
Solution Approach 2:
Different regions of the resin layer are assigned different mechanical properties. The first resin layer in direct contact with the anode lead has softer, more compliant properties to absorb local stress concentrations. The second resin layer has harder, more rigid properties to provide overall structural support. This local differentiation of material properties optimizes stress distribution and prevents crack formation.
2Reliability
If only the root of the anode lead is covered with thermosetting resin, then some stress is reduced, but stress from the anode terminal is still transmitted through the anode lead to the dielectric layer
Solution Approach 1:
The solution extends from a one-dimensional point contact (root coverage) to a two-dimensional surface coverage by forming the resin layer to cover not only the root but also the exposed portion and connecting part of the anode lead. This dimensional expansion ensures comprehensive stress absorption along the entire vulnerable path of the anode lead, preventing stress transmission from any point along its length.
Solution Approach 2:
The resin layer acts as an intermediary substance between the anode lead and the external environment (pouring resin and anode terminal). By positioning the resin layer to cover the exposed portion and connecting part, it serves as a stress-absorbing mediator that isolates the anode lead from harmful external stresses, protecting the dielectric layer from crack formation.
3Object-affected harmful factors
If the resin layer covers the exposed portion, anode lead end, and connecting part, then stress transmission is sufficiently reduced, but the dual-layer structure increases manufacturing complexity
Solution Approach 1:
The invention changes the physical parameters of the resin layer by creating two layers with different hardness values. The first resin layer has a softer consistency (lower hardness parameter) to maximize stress absorption, while the second resin layer has a harder consistency (higher hardness parameter) to provide structural integrity. This parameter differentiation resolves the contradiction by allowing each layer to optimize its function within the combined structure.
Data Source
AI summary
A solid electrolytic capacitor includes at least one capacitor element in which the other end of an anode lead extends beyond an exposed portion of an electrolyte layer exposed from a cathode layer. The solid electrolytic capacitor further includes: an anode terminal connected to the other end of the anode lead, a cathode terminal connected to the cathode layer, a resin layer and a resin outer package covering the capacitor element and the resin layer. The resin layer covering the exposed portion of the electrolyte layer, the other end of the anode lead, and a connecting part between the other end of the anode lead and the anode terminal. The resin layer includes a first resin layer covering the exposed portion and a second resin layer covering the first resin layer, the first resin layer being softer than the second resin layer.