Laser-Welded Solid Electrolytic Capacitor With Reflective Layer
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Solution Overview
Problem
Conventional solid organic electrolytic capacitors face issues with laser welding due to the close proximity of the laser to the anode wire and termination, leading to potential deflection and carbonization of the organic solid electrolyte, resulting in poor electrical properties such as high leakage current.
Innovation Solution
A solid electrolytic capacitor design that includes a light reflective layer with particles having an index of refraction of 1.7 or more, applied over the solid organic electrolyte layer to reflect incident laser light and prevent carbonization, along with a conductive polymer layer and a dielectric layer overlying the anode body, allowing for laser welding without compromising electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser welding is used to connect the anode wire to the termination, then the electrical connection is improved, but the organic solid electrolyte may be carbonized due to laser deflection, leading to high leakage current
Solution Approach 1:
A reflective coating layer is applied to the anode wire and termination components to act as an intermediary that redirects the laser beam. This coating has high reflectivity at the laser wavelength, causing the laser energy to reflect away from the organic solid electrolyte rather than being absorbed and causing carbonization, thus enabling safe laser welding
Solution Approach 2:
The optical properties of the welding components are modified by applying a reflective coating with specific optical parameters (high reflectivity at laser wavelength). This parameter change allows the components to interact differently with the laser beam, redirecting it away from sensitive areas while maintaining the welding function
2Volume of moving object
If the case size is reduced, then the capacitor becomes more compact, but the laser must be positioned closer to the anode wire and termination, increasing the risk of electrolyte carbonization
Solution Approach 1:
The reflective coating serves as a protective intermediary on the anode wire and termination, enabling compact design by allowing laser welding to proceed safely even when the laser is positioned close to the electrolyte. The coating prevents harmful energy transfer to the electrolyte
Solution Approach 2:
The reflective coating is applied selectively to specific components (anode wire and termination) that are in the path of the laser beam, providing localized protection where needed while leaving the rest of the capacitor structure unchanged
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 solution effectively minimizes contact between the laser and the organic solid electrolyte, reducing carbonization and resulting in capacitors with low equivalent series resistance (ESR) and low leakage currents, maintaining excellent electrical properties.
Implementation Method 1
a light reflective layer overlying the solid organic electrolyte layer. The light reflective layer contains a plurality of reflective particles having an index of refraction of about 1.7 or more
Data Source
AI summary
A solid electrolytic capacitor that is capable of withstanding laser welding without a significant deterioration in its electrical performance is provided. The capacitor contains an anode body, dielectric layer overlying the anode body, and a solid organic electrolyte layer overlying the dielectric layer. Furthermore, the capacitor of the present invention also employs a light reflective layer that overlies the solid organic electrolyte layer. The present inventors have discovered that such a light reflective layer may help reflect any light that inadvertently travels toward the capacitor element during laser welding. This results in reduced contact of the solid organic electrolyte with the laser and thus minimizes defects in the electrolyte that would have otherwise been formed by carbonization. The resultant laser-welded capacitor is therefore characterized by such performance characteristics as relatively low ESR and low leakage currents.