Conductive Polymer Coating for Stable ESR in Solid Electrolytic Capacitors
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Solution Overview
Problem
Existing solid electrolytic capacitors face challenges in achieving improved equivalent series resistance (ESR) stability and reduced leakage, particularly under high temperature and high humidity conditions, due to issues with conductive polymer layer bonding and dopant solubility.
Innovation Solution
A dual function coating layer comprising aromatic sulfonate and carboxylic acid compounds, or phosphorus-containing compounds, is applied after the last conductive polymer layer, providing a more uniform distribution and enhancing ESR thermal stability and high temperature high humidity leakage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If additives are incorporated into the conductive polymer layer during formation, then ESR thermal stability is improved, but the additives alter the layer surface which is detrimental to bonding with subsequent layers
Solution Approach 1:
The patent divides the additive application into two separate stages: (1) incorporating additives into the conductive polymer layer during formation to improve ESR thermal stability, and (2) applying a separate bonding promoter layer containing silane or titanate compounds to restore and enhance interlayer bonding. This segmentation allows each function to be optimized independently without compromising the other.
Solution Approach 2:
The patent introduces bonding promoter compounds (silane or titanate-based additives) as an intermediary layer between the conductive polymer layer and subsequent layers. This intermediary layer specifically targets the interface to improve adhesion without affecting the bulk properties of the conductive polymer, thereby resolving the surface alteration issue while maintaining bonding strength.
2Reliability
If multiple purification steps are performed to remove ionic impurities from the conductive polymer, then polymer quality is improved, but the purification steps reduce the amount of dopant which negatively impacts ESR
Solution Approach 1:
The patent modifies the purification process parameters by reducing the number of washing steps and adjusting the purification severity. This parameter change allows retention of more dopant in the conductive polymer layer, improving ESR stability, while still removing harmful ionic impurities through optimized purification conditions that balance quality and dopant retention.
3Stability of the object's composition
If a stabilizer is applied as a separate layer on the conductive polymer, then ESR thermal stability is improved, but the solubility of the stabilizer makes it difficult to form coatings with sufficient coverage
Solution Approach 1:
The patent creates a composite stabilizer system by combining the stabilizer compound with solubility-enhancing additives or using composite stabilizer formulations. This composite approach maintains the ESR thermal stability benefits while improving the solubility and coating uniformity, allowing sufficient coverage to be achieved during the coating process.
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
The dual function coating layer improves ESR thermal stability and reduces high temperature high humidity leakage by ensuring even distribution and direct interaction with subsequent cathode components, overcoming limitations of previous methods.
Implementation Method 1
a dual function additive applied to the external surface of the conductive polymer layer wherein the dual function additive provides superior doping to the conductive polymer
Data Source
AI summary
Provided is an improved method for preparing an electrolytic capacitor comprising:forming an anode with a dielectric on the anode;forming a conductive polymer layer on the dielectric wherein the forming of the conductive polymer layer comprises sequential applying multiple layers of a conductive polymer on the dielectric;applying a treatment to the conductive polymer layer wherein the treatment comprises applying a dopant wherein the dopant comprises:a carboxylic acid compound defined by the formula:R2—(C(O)OX3)m; anda compound selected from the group consisting of:an aromatic sulfonate compound defined by the formula:R1—(S(O)2OX1)n and a phosphorus containing compound defined by:R3—(OxP(O)(OX4)2)p wherein all groups are defined.