Capacitor Tab Terminal UV Resin Weld Zone Whisker Suppression
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Solution Overview
Problem
Lead-free tin-plated tab terminals for electrolytic capacitors face issues with tin whisker growth at weld zones, leading to potential leakage currents and short circuits, and existing solutions using halogen-containing resins pose environmental concerns.
Innovation Solution
A tab terminal with a lead-free tin-plated surface and an aluminum core wire, where the weld zone is covered with an ultraviolet cured resin composed mainly of urethane acrylate and (meth)acrylate, and an inorganic acid salt, eliminating halogen use and preventing whisker growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-free tin plating is used on the lead wire surface, then environmental friendliness and solderability are improved, but tin whisker growth occurs at the weld zone
Solution Approach 1:
A resin coating is applied as an intermediary layer between the tin-plated lead wire and the aluminum core wire weld zone. This resin layer physically isolates the tin whiskers at the weld interface, preventing them from growing into the aluminum core wire and causing electrical shorts, while allowing the tin plating to maintain its solderability and environmental benefits
Solution Approach 2:
The resin coating is applied in advance to the weld zone before tin whisker growth can occur. This preliminary protective action prevents the harmful effect of tin whisker growth from manifesting, addressing the problem before it can cause reliability issues in the tab terminal
2Object-generated harmful factors
If heat curable resin composition is used to cover the weld zone, then tin whisker growth is suppressed, but halogen content creates environmental problems
Solution Approach 1:
The resin coating material is changed from conventional heat curable epoxy resins containing halogens to UV curable resins that are halogen-free. This parameter change in the resin composition maintains the protective function of suppressing tin whisker growth while eliminating the harmful halogen content, making the tab terminal environmentally friendly
3Object-generated harmful factors
If UV curable resin is used to cover the weld zone, then tin whisker growth is suppressed and environmental friendliness is improved, but additional manufacturing steps are required
Solution Approach 1:
The curing mechanism is changed from thermal curing (heat curable resin) to photopolymerization (UV curable resin). This substitution replaces the need for heat treatment equipment and processes with UV light curing, which can be performed at room temperature and typically requires less equipment complexity, offsetting the added step of UV irradiation
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 suppresses tin whisker growth, ensuring environmentally friendly tab terminals with improved reliability and extended service life by preventing leakage currents and maintaining capacitor performance.
Implementation Method 1
irradiating an ultraviolet curable resin composition composed mainly of a urethane acrylate and a (meth)acrylate with ultraviolet light to form a covering
Data Source
Figure 1
AI summary
Provided are a tab terminal that, even when a lead-free tin-plated lead wire as such is used in a tab terminal, does not produce tin whiskers from a weld zone and is environmentally friendly, and a method for manufacturing the same. The terminal for an electrolytic capacitor comprises a lead wire having a lead-free tin-plated surface and an aluminum core wire that has a press flattened portion and is welded to the lead wire, wherein a portion in the vicinity of a weld zone between the lead wire and the aluminum core wire is covered with an ultraviolet cured resin.