Interfacial Coating in Solid Electrolytic Capacitors for Reflow Stability
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Solution Overview
Problem
Solid electrolytic capacitors face issues with micro-cracks and rapid deterioration of electrical properties due to vaporized moisture during high-temperature manufacturing, leading to delamination and instability.
Innovation Solution
A solid electrolytic capacitor design with a specific distance ratio between the anode lead connection region and the front surface, combined with an interfacial coating on the anode and/or cathode terminations, enhances mechanical stability and maintains electrical properties under high humidity and temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high temperatures are used during capacitor manufacture (e.g., reflow), then manufacturing efficiency is improved, but residual moisture vaporizes as steam causing micro-cracks in the casing material and delamination
Solution Approach 1:
A moisture barrier layer is introduced as an intermediary between the capacitor element and the casing material. This layer prevents moisture from vaporizing into the casing during high-temperature reflow, eliminating micro-cracks and delamination while allowing the reflow process to proceed at high temperatures for manufacturing efficiency
2Ease of manufacture
If the capacitor is exposed to high temperatures, then manufacturing process is completed, but electrical properties deteriorate rapidly due to moisture vaporization
Solution Approach 1:
The moisture barrier layer is applied in advance before the reflow process. This preliminary protective action prevents moisture vaporization during the subsequent high-temperature exposure, maintaining electrical property stability while allowing the manufacturing process to be completed
3Strength
If casing material encapsulates the capacitor element, then mechanical stability is improved, but moisture trapped inside causes steam expansion and micro-crack formation at high temperatures
Solution Approach 1:
The moisture barrier layer serves as an intermediary between the capacitor element and the encapsulating casing material. It allows the casing to provide mechanical stability through encapsulation while simultaneously blocking moisture from vaporizing and causing steam expansion that would create micro-cracks
Data Source
AI summary
A solid electrolytic capacitor containing a capacitor element is provided. The capacitor element contains a sintered porous anode body, a dielectric that overlies the anode body, and a solid electrolyte that overlies the dielectric. An anode lead extends from the front surface of the capacitor element in the longitudinal direction. An anode termination is in contact with the anode lead at a connection region, wherein the ratio of the distance between the connection region and the front surface of the capacitor element to the length of the capacitor is 0.13 or more. A cathode termination is in electrical connection with the solid electrolyte and a casing material encapsulates the capacitor element and anode lead. Further, an interfacial coating that is disposed on at least a portion of the anode termination and/or cathode termination and is in contact with the casing material.