Barrier-Coated Solid Electrolytic Capacitor for Moisture and Oxygen Blocking
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Solution Overview
Problem
Conventional solid electrolytic capacitors face issues with high leakage current and delamination due to moisture and oxygen diffusion, especially at high temperatures, leading to reduced electrical performance and mechanical stability.
Innovation Solution
A solid electrolytic capacitor design featuring a porous anode body, dielectric, and solid electrolyte, encapsulated with a casing material and a barrier coating containing a polymeric material with a glass transition temperature of 10° C. to 120° C. and thermal decomposition temperature of 200° C. to 300° C., which includes a fluorinated and non-fluorinated component to prevent delamination and oxygen diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional solid electrolytic capacitors use in situ polymerized polymers or PEDOT:PSS dispersions, then low ESR and non-burning failure mode are achieved, but high leakage current and delamination occur at high temperatures
Solution Approach 1:
The patent uses a composite polymer electrolyte consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(styrene sulfonic acid) (PSS) in a specific ratio range (70:30 to 30:70). This composite material combines the beneficial electrical properties of PEDOT with the structural stability of PSS, achieving both low ESR and high temperature reliability without delamination or excessive leakage current.
2Strength
If the capacitor element is encapsulated with casing material for mechanical stability, then protection from exterior environment is provided, but micro-cracks form and delamination occurs at high temperatures
Solution Approach 1:
The patent specifies precise glass transition temperature ranges for the casing material (−50°C to 0°C or 0°C to 50°C) and controlled moisture content (0.1% to 5.0%). By controlling these physical parameters, the casing maintains mechanical stability while preventing micro-crack formation and delamination during high-temperature reflow processing.
3Ease of manufacture
If high temperatures are used during capacitor manufacture, then sintering and anodizing processes are completed, but residual moisture vaporizes causing micro-cracks and delamination
Solution Approach 1:
The patent applies a barrier coating to the capacitor element before encapsulation with the casing material. This preliminary protective layer prevents moisture ingress and protects against thermal stress during subsequent high-temperature sintering and anodizing processes, eliminating the root cause of micro-crack formation and delamination.
Solution Approach 2:
The patent controls the glass transition temperature of the barrier coating material to be within specific ranges (−50°C to 0°C or 0°C to 50°C), ensuring the coating remains flexible and adherent during high-temperature manufacturing processes while preventing moisture-related defects.
4Reliability
If oxygen diffusion into the cathode is prevented, then electrical property degradation is reduced, but additional barrier layers increase device complexity
Solution Approach 1:
The patent employs a composite barrier coating system consisting of the polymer electrolyte layer and the barrier coating material working together. This composite structure provides effective oxygen and moisture barrier properties without requiring multiple separate layers, thus preventing electrical property degradation while maintaining relatively simple device architecture.
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 capacitor exhibits improved electrical performance and mechanical stability, with reduced leakage current and equivalent series resistance, maintaining capacitance and ESR stability even at high temperatures and humidity levels, as demonstrated by compliance with stringent moisture and reflow sensitivity tests.
Implementation Method 1
a barrier coating that covers at least a portion of the capacitor element and is in contact with the casing material. The coating contains a polymeric material that includes a fluorinated component and a non-fluorinated component
Implementation Method 2
high temperatures that are often used during manufacture of the capacitor (e.g., reflow) can cause residual moisture to vaporize as steam, which may exit the case with considerable force and cause micro-cracks to form in the casing material
Implementation Method 3
The polymeric material has a glass transition temperature of from about 10° C. to about 120° C. and a thermal decomposition temperature of about 200° C. to about 300° C.
Implementation Method 4
The polymeric material has a glass transition temperature of from about 10° C. to about 120° C. and a thermal decomposition temperature of about 200° C. to about 300° C.
Implementation Method 5
The coating contains a polymeric material that includes a fluorinated component and a non-fluorinated component
Data Source
AI summary
A solid electrolytic capacitor comprising a capacitor element, anode lead extending from a surface of the capacitor element, an anode termination that is in electrical connection with the anode lead, a cathode termination that is in electrical connection with the solid electrolyte, and a casing material that encapsulates the capacitor element and anode lead is provided. A barrier coating is disposed on at least a portion of the capacitor element and is in contact with the casing material. The coating contains a polymeric material that includes a fluorinated component and a non-fluorinated component. The polymeric material has a glass transition temperature of from about 10° C. to about 120° C. and a thermal decomposition temperature of about 200° C. to about 300° C.