Silver-Plated Electrical Terminal With Anti-Tarnish Intermetallic Layer
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Solution Overview
Problem
Silver-containing electrical connectors tend to tarnish and are susceptible to environmental degradation, requiring passivation which can be inconsistent, and silver alloys are difficult to manufacture and control in stoichiometry, necessitating improved connectors with enhanced stability and simplified manufacturing.
Innovation Solution
A silver-based electrical connector with an intermetallic phase of silver and indium, gallium, or tin, or a bismuth layer, which protects the silver from tarnishing and environmental effects, and a barrier layer to prevent silver diffusion, allowing for reduced insertion forces and enhanced longevity, manufactured through a process involving deposition and tempering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver is used as contact plating, then high conductivity and ductility are achieved, but tarnishing and environmental degradation occur
Solution Approach 1:
A passivation layer comprising indium, gallium, or tin is applied over the silver contact plating to act as a protective intermediary. This layer prevents direct exposure of silver to environmental factors, thereby stopping tarnishing while preserving the underlying silver's high conductivity and ductility properties.
Solution Approach 2:
The electrical connector employs a composite structure combining silver contact plating with a passivation layer of indium, gallium, or tin. This composite material system leverages the high conductivity of silver while the outer passivation layer provides resistance to tarnishing and environmental degradation.
2Object-affected harmful factors
If passivation layer is applied over silver, then protection from corrosion is achieved, but manufacturing consistency is difficult to ensure
Solution Approach 1:
The patent specifies precise parameter ranges for the passivation layer including thickness (0.1-5.0 µm), composition ratios, and deposition conditions. By controlling these parameters within defined ranges, the manufacturing process achieves greater consistency and repeatability while maintaining effective corrosion protection.
3Object-affected harmful factors
If silver alloys are used, then resistance to environmental degradation is improved, but stoichiometry control becomes difficult
Solution Approach 1:
Instead of creating a homogeneous silver alloy with difficult-to-control stoichiometry, the invention segments the protective structure into distinct layers: a silver contact plating layer and a separate passivation layer comprising indium, gallium, or tin. This segmentation allows independent control and optimization of each layer's composition and properties, simplifying manufacturing precision.
4Force
If soft metals like indium are used to reduce insertion forces, then PCB damage is reduced, but manufacturing complexity increases
Solution Approach 1:
The passivation layer comprising indium, gallium, or tin serves multiple functions simultaneously: it protects the silver from tarnishing, provides corrosion resistance, and reduces insertion forces to prevent PCB damage. This multi-functionality eliminates the need for separate components or processes, thereby reducing overall manufacturing complexity despite the advanced material properties.
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 electrical connectors with high conductivity and resistance to tarnishing and environmental effects, reducing manufacturing complexity and ensuring consistent performance, while allowing for efficient raw material use and stable insertion forces.
Implementation Method 1
The metallic conductive layer comprises either: a silver layer and an intermetallic phase of silver and one or a combination of indium or gallium
Implementation Method 2
a silver layer and a bismuth layer, wherein the silver layer is located between the substrate and the bismuth layer
Implementation Method 3
The barrier layer prevents diffusion of the silver into the substrate
Data Source
Figure 1
Figure 2
AI summary
An electrical terminal 2, 4 comprising a substrate 6 and a metallic conductive layer 8 provided on the substrate 12. The electrical terminal may be a male or female electrical terminal. The metallic conductive layer 8 has either: a silver layer 14 and an intermetallic phase 10 of silver 14 and any one or a combination of the group comprising: indium 16, gallium or tin, or; a silver layer and a bismuth layer. The intermetallic phase 10 or bismuth layer protects the silver from environmental degradation. A method of manufacturing the male or female electrical terminals 2, 4 is also disclosed.