Solid Electrolytic Capacitor Conductive Polymer Layer Heat Resistance
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Solution Overview
Problem
Conventional solid electrolytic capacitors with conductive polymer layers, such as PEDT, suffer from excessive deterioration of electronic characteristics at high temperatures during the reflow process with lead-free solder, leading to insufficient heat resistance and increased impedance.
Innovation Solution
The use of a metal salt of carbon-fused bicyclic sulfonic acid as an oxidizing agent in chemical oxidization polymerization, with a molar ratio of carbon-fused bicyclic sulfonate ion to metal ion less than the stoichiometric ratio, to form a conductive polymer layer that enhances both conductivity and heat resistance without compromising leakage current or initial capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional oxidizing agents (e.g., ferric paratoluenesulfonate) are used in chemical oxidization polymerization, then the conductive polymer layer can be formed with adequate conductivity, but the heat resistance is insufficient and electronic characteristics deteriorate excessively at high temperatures during reflow process
Solution Approach 1:
The patent changes the chemical composition parameters of the oxidizing agent by using metal salts of carbon-fused bicyclic sulfonic acids (such as ferric naphthalenesulfonate or ferric tetralinesulfonate) instead of conventional oxidizing agents. This parameter change in the chemical structure of the oxidizing agent leads to improved heat resistance and suppressed electronic characteristic deterioration at high temperatures during the reflow process.
2Reliability
If the molar ratio of carbon-fused bicyclic sulfonate ion to metal ion is made less than the stoichiometric ratio, then conductivity and heat resistance of the conductive polymer layer are improved, but this requires precise control of composition ratios
Solution Approach 1:
The patent optimizes the compositional parameter by controlling the molar ratio of carbon-fused bicyclic sulfonate ion to metal ion to be less than the stoichiometric ratio (e.g., using excess metal ion). This parameter optimization achieves improved conductivity and heat resistance while providing a clear quantitative guideline for manufacturing control.
3Ease of manufacture
If lead-free solder is used for reflow process, then the soldering process can be performed without lead contamination, but the reflow temperature must be increased to 200-270°C which causes excessive deterioration of the conductive polymer
Solution Approach 1:
The patent changes the chemical composition of the oxidizing agent to metal salts of carbon-fused bicyclic sulfonic acids, which fundamentally alters the thermal stability characteristics of the conductive polymer layer. This parameter change enables the capacitor to withstand the high reflow temperatures (200-270°C) required for lead-free soldering without excessive deterioration of electronic characteristics.
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 results in a solid electrolytic capacitor with low equivalent series resistance (ESR) and high heat resistance, effectively suppressing electronic characteristic deterioration at high temperatures.
Implementation Method 1
a step of forming a conductive polymer layer by chemical oxidization polymerization of a monomer using a solution containing a metal salt of carbon-fused bicyclic sulfonic acid as an oxidizing agent
Implementation Method 2
a conductive polymer layer as a solid electrolyte... having a sufficiently low equivalent series resistance (abbreviated as ESR below)
Data Source
AI summary
The present invention provides a method of manufacturing a solid electrolytic capacitor including a step of forming a conductive polymer layer by chemical oxidization polymerization of a monomer using a solution containing a metal salt of carbon-fused bicyclic sulfonic acid as an oxidizing agent. The molar ratio X of a carbon-fused bicyclic sulfonate ion to a metal ion in the solution is less than the stoichiometric ratio Y of the metal salt of carbon-fused bicyclic sulfonic acid. This is allowed to provide a solid electrolytic capacitor with a sufficiently low equivalent series resistance (ESR) and high heat resistance.