Cu-Sn Alloy Plating for Low Insertion Force Connectors
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Solution Overview
Problem
Conductive materials for connecting parts in electrical wiring, such as connector terminals, face challenges in maintaining low insertion force, resistance to wear, and reliable electrical connection, especially in high-temperature and corrosive environments, due to the limitations of Sn plating in terms of thickness, friction coefficient, and contact resistance.
Innovation Solution
A conductive material comprising a Cu—Sn alloy covering layer with Cu content between 20 to 70 at% and an Sn covering layer, formed on a Cu strip base material, with specific thickness ranges and surface roughness, exposed portions of the Cu—Sn alloy layer to reduce friction and maintain low contact resistance, achieved through a reflow process that optimizes the surface structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Sn plating layer is rendered larger in thickness to maintain low contact resistance, then electrical connection reliability is improved, but insertion force increases due to increased adhesion force between plating layers
Solution Approach 1:
The patent applies local quality by creating a multi-layer plating structure with different properties at different depths: a Cu-Sn alloy layer (20-70 at% Sn) providing mechanical strength and controlled adhesion, and an Sn-rich surface layer (70-80 at% Sn) providing low contact resistance. This local differentiation allows the bulk to resist deformation while the surface maintains electrical conductivity.
Solution Approach 2:
The invention uses composite materials by combining Cu-Sn alloy plating with Sn-rich plating in a layered structure. The Cu-Sn alloy layer (containing 3-15 mass% Sn) provides structural integrity and controlled adhesion, while the Sn-rich surface layer provides low contact resistance, creating a composite plating system that resolves the contradiction between mechanical and electrical requirements.
2Reliability
If contact pressure is increased to maintain low contact resistance, then electrical connection is improved, but wear resistance deteriorates due to increased shearing resistance
Solution Approach 1:
The patent applies local quality by creating a multi-layer plating structure with different properties at different depths: a Cu-Sn alloy layer (20-70 at% Sn) providing mechanical strength and controlled adhesion, and an Sn-rich surface layer (70-80 at% Sn) providing low contact resistance. This local differentiation allows the bulk to resist deformation while the surface maintains electrical conductivity.
Solution Approach 2:
The invention changes material parameters by controlling the Sn content gradient through plating conditions (reflow temperature 200-300°C, plating thickness ratios). The Cu-Sn alloy layer has 3-15 mass% Sn for strength, while the surface layer has 70-80 at% Sn for conductivity, optimizing both wear resistance and electrical properties through parameter control.
3Ease of operation
If the Sn covering layer is made softer to reduce friction coefficient, then ease of insertion is improved, but resistance to slight-sliding wear deteriorates
Solution Approach 1:
The patent applies local quality by creating a multi-layer plating structure with different properties at different depths: a Cu-Sn alloy layer (20-70 at% Sn) providing mechanical strength and controlled adhesion, and an Sn-rich surface layer (70-80 at% Sn) providing low contact resistance. This local differentiation allows the bulk to resist deformation while the surface maintains electrical conductivity.
Solution Approach 2:
The invention uses composite materials by combining Cu-Sn alloy plating with Sn-rich plating in a layered structure. The Cu-Sn alloy layer (containing 3-15 mass% Sn) provides structural integrity and controlled adhesion, while the Sn-rich surface layer provides low contact resistance, creating a composite plating system that resolves the contradiction between mechanical and electrical requirements.
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 material achieves a low friction coefficient, reduced insertion force, and reliable electrical connection even in high-temperature and corrosive environments, while preventing slight-sliding wear, thus enhancing the efficiency and durability of connecting parts.
Implementation Method 1
achieved through a reflow process that optimizes the surface structure
Data Source
AI summary
There is provided a conductive material comprising a base material made up of a Cu strip, a Cu—Sn alloy covering layer formed over a surface of the base material, containing Cu in a range of 20 to 70 at.%, and having an average thickness in a range of 0.1 to 3.0 μm and an Sn covering layer formed over the Cu—Sn alloy covering layer having an average thickness in a range of 0.2 to 5.0 μm, disposed in that order, such that portions of the Cu—Sn alloy covering layer are exposed the surface of the Sn covering layer, and a ratio of an exposed area of the Cu—Sn alloy covering layer to the surface of the Sn covering layer is in a range of 3 to 75%.