Self-Sealing Vent Structure for Solid Electrolytic Capacitors
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Solution Overview
Problem
Existing solid electrolytic capacitors face defects due to moisture vaporization during reflow mounting, leading to internal pressure increases and potential tombstone phenomena or positional displacement, which prior methods fail to adequately address.
Innovation Solution
A solid electrolytic capacitor with a vent structure embedded in the sealing material that includes a self-sealing valve action, melting at reflow temperatures to discharge vaporized components and solidifying to block the hole, using materials with a melting point of 240°C or lower and a thin wall portion to prevent moisture entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If holes or high water vapor permeability materials are provided in the exterior body to discharge vaporized moisture, then internal pressure during reflow mounting is reduced, but moisture and oxygen entry paths are created that facilitate deterioration and reduce capacitor life
Solution Approach 1:
The vent structure transitions from a closed state to an open state dynamically based on temperature conditions. During reflow mounting (high temperature), the material melts and forms a hole to discharge vaporized moisture. During normal operation (low temperature), the material solidifies and blocks the hole to prevent moisture and oxygen entry. This dynamic state change resolves the contradiction between pressure relief and reliability.
Solution Approach 2:
The physical state of the vent structure material changes with temperature parameter. At reflow mounting temperature, the material melts (phase change) to create an open vent for pressure relief. At operating temperature, the material solidifies to close the vent and maintain sealing. This parameter-based state transition enables both pressure discharge and moisture prevention functions.
2Ease of manufacture
If a material with melting point below reflow mounting temperature is used in the vent structure, then vaporized moisture can be discharged during reflow, but the material must be carefully selected to ensure it blocks the hole after cooling to prevent moisture entry
Solution Approach 1:
The vent structure material automatically performs both venting and sealing functions without external intervention. During reflow mounting, the material self-melts to open the vent for moisture discharge. During cooling, it self-solidifies to close the vent and prevent moisture entry. This self-service mechanism simplifies manufacturing while ensuring reliable moisture blocking.
3Speed
If the vent structure is designed with a thin wall portion, then the material can more easily melt and form a discharge hole during reflow mounting, but the structure must maintain sufficient strength to prevent premature hole formation before reflow
Solution Approach 1:
The vent structure includes a thin wall portion that is intentionally weaker than other parts, but only to the extent needed for controlled melting during reflow. The thin wall portion is localized and designed with specific dimensions (thickness 0.01-0.5mm) to ensure it melts at reflow temperature while maintaining sufficient strength during normal handling and assembly before reflow mounting.
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
Prevents defects by discharging vaporized moisture during reflow mounting, maintaining internal pressure and preventing moisture/oxygen entry, thus enhancing capacitor reliability.
Implementation Method 1
the vent structure is composed of a material that has a self-sealing valve action in which the vent structure turns into a melt at a reflow mounting temperature
Implementation Method 2
upon being cooled from the reflow mounting temperature, the melt flows and then solidifies so as to block the hole
Implementation Method 3
the melt cleaves when receiving pressure of vaporized components generated inside the sealing body
Data Source
AI summary
A solid electrolytic capacitor that includes: a capacitor element; a sealing material that seals the capacitor element to form a sealing body; and a vent structure embedded in the sealing material such that a portion of the vent structure is exposed on an outer surface of the sealing body, the vent structure being composed of a material that has a self-sealing valve action in which the vent structure turns into a melt at a reflow mounting temperature and the melt cleaves when receiving pressure of vaporized components generated inside the sealing body so as to form a hole communicating from an inside to the outer surface of the sealing body to discharge the vaporized components, and upon being cooled from the reflow mounting temperature, the melt flows and then solidifies so as to block the hole.