Electrolytic Capacitor Feedthrough Pin for Laser-Safe Sealing
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Solution Overview
Problem
Existing electrical feedthroughs in electrolytic capacitors face issues such as loosening due to thermal expansion or mechanical impact, risk of short circuits from laser welding, difficulty in establishing stable electrical contacts, and challenges in maintaining insulation and hermetic sealing, particularly with aluminum electrolytic capacitors.
Innovation Solution
The feedthrough pin features circumferential protrusions to protect casting substances from laser welding and ensure stable anchoring, combined with grooves and protrusions in the feedthrough flange for secure positioning, and a method involving galvanic deposition for reliable electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser welding is used to establish electrical contact to the feedthrough pin, then electrical contact is established, but the epoxy resin insulation is burned causing short circuit and loss of hermetic sealing
Solution Approach 1:
The feedthrough pin is divided into functionally distinct sections: a lower insulation section coated with epoxy-resistant material for hermetic sealing, and an upper contact section with laser-absorbing coating for reliable electrical contact. This segmentation allows different portions to have different properties optimized for their specific functions.
Solution Approach 2:
Different surface coatings are applied to different sections of the feedthrough pin. The lower section has epoxy-resistant coating to prevent insulation degradation, while the upper section has laser-absorbing coating to enable welding. This local differentiation resolves the contradiction between needing laser welding and protecting the epoxy resin.
2Adaptability or versatility
If the feedthrough pin is made from valve metal (aluminum, niobium, tantalum, zirconium), then it is compatible with the electrode material, but it is not appropriate for laser welding
Solution Approach 1:
A laser-absorbing coating is applied to the upper section of the feedthrough pin, serving as an intermediary layer that absorbs laser energy and enables welding. This coating acts as a mediator between the valve metal substrate (which is incompatible with direct laser welding) and the laser welding process, allowing electrical contact establishment without compromising material compatibility.
3Ease of manufacture
If the feedthrough pin position is not precisely controlled during epoxy resin casting, then the casting process is simple, but the insulation distances may be underrun requiring discarding of capacitors
Solution Approach 1:
The feedthrough pin is pre-positioned in the feedthrough opening using precise mechanical features (protrusions fitting into grooves, positioning elements) before the epoxy resin casting process. This preliminary positioning ensures that the pin remains in the correct location during casting, guaranteeing adequate insulation distances without requiring complex casting control mechanisms.
4Reliability
If the connection between epoxy resin and aluminum surface is made, then insulation is provided, but the connection is mechanically instable
Solution Approach 1:
The feedthrough pin combines valve metal (aluminum, niobium, tantalum, or zirconium) with specialized surface coatings. The epoxy-resistant coating on the lower section creates a composite structure that prevents epoxy resin degradation and enhances mechanical stability of the connection, while maintaining the electrical and chemical compatibility of the base metal with the electrode.
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 provides stable electrical contacts, prevents short circuits and electrolyte leakage, and ensures durable insulation, enhancing the reliability and longevity of electrolytic capacitors.
Implementation Method 1
if the feedthrough pin is contacted by or joined with an outside electric conductor, e.g., a wire or a ribbon, via laser welding, the additional risk exists that the laser light burns the epoxy resin
Implementation Method 2
a method involving galvanic deposition for reliable electrical connections
Data Source
AI summary
The invention relates, amongst others, to a feedthrough pin of an electrolytic capacitor for contacting an electrode of the electrolytic capacitor and providing an electrical contact of the electrolytic capacitor on an outside of the electrolytic capacitor, the feed-through pin comprising a longitudinally extending body. According to an aspect of the invention, a first circumferential protrusion is arranged between a first section of the longitudinally extended body and a second section of the longitudinally extended body, wherein the first circumferential protrusion runs around a longitudinal axis of the longitudinally extended body and extends radially outwards over an outer contour of the first section of the longitudinally extended body and an outer contour of the second section of the longitudinally extended body.