Solid Electrolytic Capacitor Venting for Internal Pressure Relief
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Solution Overview
Problem
Existing solid electrolytic capacitors face issues with airtightness, leading to rapid internal pressure increases due to moisture evaporation during manufacturing processes, which can cause cracks and affect long-term reliability.
Innovation Solution
A solid electrolytic capacitor design featuring a sheet multilayer body with alternately stacked flat film-shaped capacitor elements and cathode electrodes, where the anode electrodes have a porous portion with a specific pore structure, and a first metal portion with a larger pore diameter than the anode electrodes, allowing for effective gas discharge and reduced internal pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capacitor elements are sealed with insulating resin to maintain airtightness, then reliability is improved, but internal pressure increases rapidly due to moisture evaporation during MSL reflow, causing cracks and LC failure
Solution Approach 1:
The anode electrode is designed with a porous structure having pores of a first diameter, while the insulating resin is formed with pores of a second diameter that is larger than the first diameter. This porous structure allows gas generated during MSL reflow to escape through the insulating resin without causing internal pressure buildup, while still maintaining airtightness against moisture intrusion during normal operation
Solution Approach 2:
The insulating resin serves as an intermediary structure between the sealed capacitor elements and the external environment. It provides a dual function: blocking moisture during normal operation while allowing gas escape during manufacturing processes through its larger pores, thus mediating between the conflicting requirements of airtightness and pressure release
2Strength
If the porous portion of the anode electrode is impregnated with insulating resin to provide structural support, then mechanical strength is improved, but gas discharge pathways are blocked, leading to crack formation
Solution Approach 1:
The patent creates an asymmetric pore structure where the insulating resin has larger pores than the porous anode electrode. This asymmetry allows the insulating resin to provide mechanical strength while simultaneously creating dedicated gas discharge pathways that are larger than the electrode pores, preventing gas blockage and subsequent crack formation
Solution Approach 2:
The insulating resin is segmented with pores of different sizes than the anode electrode pores, creating a hierarchical structure. This segmentation allows different regions to serve different functions: the anode electrode pores provide surface area for capacitance, while the larger insulating resin pores provide gas escape routes, preventing the harmful effect of gas blockage
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
This design significantly reduces the occurrence of cracks within the capacitor, enhancing its reliability by facilitating the discharge of generated gases and maintaining airtightness.
Implementation Method 1
each of the plurality of flat film-shaped capacitor elements comprising a flat film-shaped anode-electrode electrode foil having a porous portion in a predetermined depth from the surface
Implementation Method 2
the evaporation of moisture that intrudes inside during an MSL reflow may cause a rapid increase in internal pressure
Data Source
AI summary
A solid electrolytic capacitor that includes: a sheet multilayer body having a plurality of flat film-shaped capacitor elements and a plurality of flat film-shaped cathode-electrode electrode foils alternately stacked with each other, each of the plurality of flat film-shaped capacitor elements comprising a flat film-shaped anode-electrode electrode foil having a porous portion in a predetermined depth from the surface, a dielectric layer on the porous portion, and a solid electrolyte layer on the dielectric layer; a first metal portion at an end portion of the anode-electrode electrode foil; and an insulating resin sealing the sheet multilayer body, wherein a first pore diameter of the first metal portion is larger than a second pore diameter of the porous portion of the anode-electrode electrode foil.