Solid Electrolytic Capacitor Termination Coatings for Humidity Stability
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Solution Overview
Problem
Solid electrolytic capacitors face rapid deterioration in electrical properties when exposed to high humidity due to micro-cracks in anode and cathode terminations, which absorb moisture and oxidize the conductive polymer electrolyte, especially during high-temperature manufacturing processes.
Innovation Solution
A capacitor assembly with a sintered porous anode body, dielectric, and solid electrolyte, where the anode and cathode terminations are coated with organometallic compounds to enhance adhesion and reduce micro-crack formation, and encapsulated in a casing material to protect against moisture, maintaining electrical properties even at high humidity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high temperatures are used during capacitor manufacture (e.g., reflow), then the capacitor can be surface mounted and integrated into circuits, but micro-cracks form in the anode and cathode terminations
Solution Approach 1:
The patent applies a coating containing an organometallic compound to the anode and cathode terminations before the high-temperature reflow process. This preliminary coating action creates a protective layer that prevents micro-crack formation during subsequent thermal processing, allowing the capacitor to withstand surface mounting temperatures while maintaining termination integrity.
2Ease of manufacture
If micro-cracks are present in the terminations, then the capacitor structure can be formed, but moisture absorption leads to oxidation of the conductive polymer solid electrolyte
Solution Approach 1:
The organometallic compound coating acts as an intermediary barrier between the termination and the moisture environment. This intermediate layer prevents moisture from penetrating into micro-cracks and reaching the conductive polymer solid electrolyte, thereby preventing oxidation and maintaining electrical property stability while allowing the capacitor to be assembled.
3Adaptability or versatility
If the capacitor is exposed to high humidity levels, then it can operate in various environmental conditions, but the conductive polymer solid electrolyte oxidizes and deteriorates rapidly
Solution Approach 1:
The organometallic compound coating creates a protective environment around the termination, effectively isolating the conductive polymer solid electrolyte from the humid external atmosphere. This inert barrier prevents moisture-induced oxidation, allowing the capacitor to operate in high humidity conditions without deterioration of electrical properties.
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 assembly exhibits low equivalence series resistance, minimal capacitance loss, and high wet-to-dry capacitance percentage, maintaining performance for extended periods at high humidity and temperature conditions.
Implementation Method 1
a first coating is disposed on at least a portion of the anode termination that contains an organometallic compound and a second coating is disposed on at least a portion of the cathode termination that contains an organometallic compound
Implementation Method 2
a casing material encapsulates the capacitor element and leaves exposed a mounting surface of the anode termination and the cathode termination
Data Source
Figure 1
AI summary
A capacitor assembly that is capable of performing well under the conditions of high humidity (e.g., 60% relative humidity) is provided. The capacitor assembly comprises a solid electrolytic capacitor element that contains a sintered porous anode body, a dielectric that overlies the anode body, and a solid electrolyte that overlies the dielectric. An anode termination is in electrical connection with the anode body and a cathode termination is in electrical connection with the solid electrolyte. A first coating is disposed on at least a portion of the anode termination that contains an organometallic compound and a second coating is disposed on at least a portion of the cathode termination that contains an organometallic compound. Further, a casing material encapsulates the capacitor element and leaves exposed a mounting surface of the anode termination and the cathode termination.