Solid Electrolytic Capacitor Polymer Coating Edge Coverage
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Solution Overview
Problem
Existing methods for forming conductive polymer coatings on capacitors often result in inadequate edge and corner coverage, leading to reliability issues and increased equivalent series resistance (ESR) under high humidity conditions, due to the use of crosslinkers that can contaminate the polymer dispersion and cause delamination.
Innovation Solution
A method involving the application of a monoamine and a weak acid with a conductive polymer, followed by a high temperature and high humidity treatment to fuse the polymer layers, enhancing edge and corner coverage without crosslinking the polymer dispersion, thereby improving bonding and reducing ESR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If crosslinker solution is applied between conductive polymer dispersion dipping cycles to improve polymer coverage of corners and edges, then coverage is improved, but the crosslinker contaminates the conductive polymer dispersion causing viscosity increase and requiring additional manufacturing steps
Solution Approach 1:
The invention extracts and removes the harmful crosslinker contamination from the system by implementing a water wash step between dipping cycles. This eliminates the viscosity increase problem and removes the need for complex ion exchange processes while maintaining improved corner and edge coverage through the controlled application of crosslinker solutions.
Solution Approach 2:
The invention changes the chemical parameters of the dispersion by controlling the pH level and ionic strength through buffered solutions. This allows the dispersion to maintain stability and appropriate viscosity even after crosslinker application, enabling improved coverage without requiring complex manufacturing steps to restore dispersion properties.
2Manufacturing precision
If crosslinker solution is applied to improve polymer coverage, then coverage is improved, but additional washing or ion exchange steps are required to remove contamination
Solution Approach 1:
The invention uses a simple, inexpensive water wash step instead of complex ion exchange processes. This disposable washing approach effectively removes crosslinker contamination and restores dispersion properties without requiring expensive equipment or multiple complex manufacturing steps, thereby maintaining productivity while achieving improved coverage.
3Manufacturing precision
If solid particles are mixed with conductive polymer dispersion to improve coverage, then coverage may be improved, but the coating layer becomes brittle and residual leakage and ESR increase
Solution Approach 1:
The invention changes the chemical composition parameters of the dispersion by adding specific additives and buffers that modify the polymer matrix properties. This creates a flexible, adhesive coating layer that maintains good electrical performance and low ESR while achieving improved coverage, avoiding the brittleness problem associated with solid particle additions.
4Manufacturing precision
If conductive polymer dispersion retreats from edges and corners during drying, then coverage in these areas is insufficient, but increasing coating thickness to compensate increases material usage and cost
Solution Approach 1:
The invention applies preliminary treatment to the substrate or dispersion before the main coating process to prevent retreat during drying. This might include applying a primer layer, modifying surface energy, or adjusting dispersion composition in advance, allowing thin, uniform coatings to achieve complete edge and corner coverage without requiring excessive material.
Solution Approach 2:
The invention modifies the physical and chemical parameters of the dispersion such as surface tension, viscosity, and drying rate by adding surfactants or buffers. This prevents the dispersion from retracting from edges and corners during drying, enabling complete coverage with optimal material usage and reducing overall polymer consumption.
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 provides improved coverage and stability of capacitors, maintaining low ESR and leakage current even under harsh conditions, eliminating the need for additional washing steps and reducing manufacturing complexity.
Implementation Method 1
followed by a high temperature and high humidity treatment to fuse the polymer layers
Implementation Method 2
Solid electrolytic capacitors with conductive polymers as the cathode are widely used in the electronics industry because of their low equivalent series resistance (ESR)
Data Source
AI summary
A method for forming a capacitor, a capacitor formed thereby and an improved composition for a conductive coating are described. The method includes providing an anode, forming a dielectric on the anode and forming a cathode layer over the dielectric by applying an amine, a weak acid and a conductive polymer.