Cu-Sn Alloy Connector Terminal Fretting Resistance
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Solution Overview
Problem
Connectors for motor vehicles face issues with fretting phenomenon due to the brittleness of tin-based plating layers, leading to oxidation and abrasion, which affects electrical conductivity, especially in high-temperature environments and during insertion/extraction processes, where reduced contact pressure exacerbates the problem.
Innovation Solution
A connector design featuring an alloy layer of Cu—Sn on the surface, with a concentration of Cu decreasing towards the surface, and Sn or its alloys diffused in an island shape, forming a gradation structure to prevent fretting and maintain conductivity, and including a Ni or Cu underlayer to prevent diffusion and oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plating layer of Sn is used on the terminal surface, then electrical connectability is improved, but the plating layer is easily oxidized and worn away in high-temperature environments, leading to fretting phenomenon and deterioration of connection
Solution Approach 1:
The patent applies a composite plating structure consisting of multiple layers: a Sn plating layer for electrical conductivity, a Cu plating layer as intermediate layer, and a Ni plating layer as barrier layer. This composite structure combines the advantages of each material - Sn provides excellent electrical connectability, Cu offers ductility and oxidation resistance, and Ni prevents diffusion and provides additional corrosion protection. The composite plating system resolves the contradiction by distributing functional requirements across different material layers.
Solution Approach 2:
The patent optimizes the thickness parameters of each plating layer to achieve the desired balance. The Sn layer is maintained at a specific thickness range to ensure electrical conductivity while the Cu and Ni layers are sized to provide adequate protection against oxidation and fretting. By carefully controlling these dimensional parameters, the patent achieves both excellent electrical connectability and resistance to environmental degradation.
2Ease of operation
If contact pressure between terminals is reduced to ease insertion and extraction, then ease of operation is improved, but fretting phenomenon occurs more easily between contact faces
Solution Approach 1:
The composite plating structure with Cu and Ni layers provides enhanced mechanical strength and ductility to the terminal surface. The Cu layer specifically contributes to ductility, allowing the terminal to withstand repeated insertion and extraction cycles without permanent deformation. This structural reinforcement enables reduced contact pressure while maintaining resistance to fretting, as the composite plating system can accommodate the mechanical stresses of operation without failing.
Solution Approach 2:
The patent applies different material properties to different functional zones of the terminal. The Sn-rich outer surface provides electrical conductivity and smooth contact, while the Cu and Ni layers provide mechanical strength and ductility. This local differentiation of material properties allows the terminal to exhibit both ease of operation and resistance to fretting simultaneously - the surface is soft enough for easy insertion while the underlying structure provides the strength needed to resist fretting under reduced contact pressure.
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 Cu—Sn alloy layer reduces fretting and oxidation, enhancing the stability of electrical connectivity and reducing the force required for insertion and extraction, while maintaining conductivity and corrosion resistance.
Implementation Method 1
Sn or its alloys diffused in an island shape, forming a gradation structure to prevent fretting and maintain conductivity
Implementation Method 2
including a Ni or Cu underlayer to prevent diffusion and oxidation
Implementation Method 3
the Cu—Sn alloy layer reduces fretting and oxidation, enhancing the stability of electrical connectivity
Data Source
AI summary
A connector includes a male terminal and a female terminal. At least one of the male terminal and the female terminal has an outermost surface layer formed of a metallic material as an alloy layer of Cu—Sn. The alloy layer of Cu—Sn has a concentration of Cu decreasing gradually toward a surface thereof. The metallic material for the connector includes the outermost surface layer formed of the alloy layer of Cu—Sn. The alloy layer of Cu—Sn has the concentration of Cu decreasing gradually toward the surface thereof.