Solid Electrolytic Capacitor Binder Residual Removal
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Solution Overview
Problem
Existing methods for manufacturing solid electrolytic capacitors using sintered valve metal powders often result in residual organic binder remaining on the sintered body, leading to impurities that cause leakage current, which is not effectively reduced without compromising the mechanical strength of the sintered body.
Innovation Solution
Implementing a cathode-electrolytic cleaning process in an acid solution, such as a mixed acid of hydrofluoric acid, nitric acid, and sulfuric acid, after sintering but before forming the dielectric oxide film, to efficiently remove binder residuals and enhance surface chemical polishing, thereby preventing impurities from forming in the oxide film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If binder removal is performed before sintering through dissolution cleaning, then binder residual concentration is reduced, but mechanical strength of sintered body is weakened and cracks occur
Solution Approach 1:
The patent applies preliminary action by performing dissolution cleaning of binder before sintering to reduce binder residual concentration. This removes harmful organic binder residues that would otherwise cause impurities and leakage current in the final capacitor, while the subsequent sintering process restores mechanical strength by bonding the valve metal powders.
Solution Approach 2:
The patent segments the manufacturing process into distinct stages: granulation with binder, press-molding, dissolution cleaning to remove binder, and sintering. This segmentation allows binder removal to occur when mechanical strength is not yet critical, and enables the sintering process to subsequently build the required structural strength.
2Ease of manufacture
If binder residuals remain on sintered body, then manufacturing process is simplified, but impurities form in oxide film causing leakage current
Solution Approach 1:
The dissolution cleaning step is performed as a preliminary action between press-molding and sintering to remove binder residuals before they can contaminate the oxide film formation process. This preliminary removal prevents impurity formation and leakage current issues that would otherwise require additional complex purification steps later.
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 method effectively reduces leakage current in solid electrolytic capacitors without weakening the mechanical strength of the sintered body, achieving a significant suppression of leakage current and improving the yield rate by ensuring binder residuals are removed post-sintering.
Implementation Method 1
cathode-electrolytic cleaning the sintered body to produce a cleaned sintered body
Implementation Method 2
anodizing the cleaned sintered body to form a dielectric oxide film layer thereon
Data Source
AI summary
A method for manufacturing a solid electrolytic capacitor has the steps of: mixing valve metal powders with organic binder for granulation, press-molding granulated powders embedded with a valve metal lead, sintering a press-molded compact in vacuum to produce a sintered body, and anodizing the sintered body to form a dielectric oxide film layer. The method further has a step of performing a cathode electrolytic cleaning to the sintered body before the step of forming the dielectric oxide film layer. The cathode electrolytic cleaning is performed in an acid solution, which is a mixed acid solution of hydrofluoric acid, nitric acid, and sulfuric acid.