Electrolytic Capacitor Solid Electrolyte Layer with Sorbitol
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Solution Overview
Problem
Solid electrolytic capacitors face challenges in maintaining high withstand voltage characteristics at high temperatures and during lead-free reflow soldering, with issues related to ESR (Equivalent Series Resistance) and heat stability, particularly when using conductive polymers like PEDOT, which can lead to reduced performance and lifespan.
Innovation Solution
The formation of an electrolyte layer using a conductive polymer compound dispersion containing sorbitol and polyalcohol, impregnated into the capacitor element and filled with an electrolytic solution containing ethylene glycol, prevents the mixing of reaction residues and improves ESR and withstand voltage characteristics, ensuring stability at high temperatures and during lead-free reflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conductive polymer solid electrolyte layer is formed by polymerization reaction in the capacitor element, then the capacitor achieves small size and large capacity, but reaction residues remain mixed in the electrolyte layer causing reduced withstand voltage characteristics
Solution Approach 1:
The patent extracts and removes reaction residues from the solid electrolyte layer through washing processes using solvents. The electrolyte layer is washed to eliminate polymerization byproducts and residues, thereby improving withstand voltage characteristics while preserving the conductive polymer's capacity-enhancing properties.
Solution Approach 2:
The patent changes the chemical composition parameters of the solid electrolyte layer by incorporating specific additives (carboxylic acid or sulfuric acid compounds) during the polymerization process. This modifies the electrolyte's properties to enhance withstand voltage characteristics while maintaining low ESR and high capacity.
2Reliability
If the ESR is reduced by using conductive polymer, then the capacitor performance is improved, but the heat stability at high temperatures deteriorates
Solution Approach 1:
The patent creates a composite solid electrolyte layer by combining conductive polymer with specific carboxylic acid or sulfuric acid compounds. This composite structure maintains the low ESR properties of the conductive polymer while the additive components provide heat stability, preventing degradation at high temperatures and ensuring stable performance.
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 electrolytic capacitors with reduced ESR, extended lifespan at high temperatures, and improved withstand voltage characteristics, even under high-temperature and lead-free reflow conditions, enhancing their performance and reliability.
Implementation Method 1
promote polymerization reaction in the capacitor element and generate the solid electrolyte layer composed of a conductive polymer such as PEDOT
Implementation Method 2
a voltage is applied in an aqueous solution such as ammonium borate so as to form an oxide coating layer which is as a dielectric (chemical conversion)
Implementation Method 3
a surface of the anode foil made of a valve-action metal such as aluminum is roughened by electrochemical etching processing in an aqueous chloride solution so as to form a large number of etching pits
Data Source
AI summary
Provided are an electrolytic capacitor with high withstand voltage capable of preventing deterioration of withstand voltage characteristics caused by lead-free reflow or the like and improving ESR characteristics, and a manufacturing method thereof. The electrolytic capacitor is obtained by impregnating a capacitor element in which an anode electrode foil and a cathode electrode foil are wound with a separator interposed, with a dispersion containing: particles of a conductive polymer; sorbitol or sorbitol and polyalcohol; and a solvent so as to form a solid electrolyte layer containing 60 to 92 wt% of the sorbitol or the sorbitol and polyalcohol, and by filling an electrolytic solution containing ethylene glycol in a gap portion in the capacitor element on which the solid electrolyte layer is formed.