Cu-Sn Layered Conductive Material for Low-Pressure Terminal Contact
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conductive materials used in automotive terminals face challenges in maintaining low contact resistance under low contact pressure, high dynamic friction coefficient, and sufficient heat resistance, especially with the downsizing of on-vehicle terminals.
Innovation Solution
A conductive material composed of a copper or copper alloy base material, an underlayer of Ni, Co, or Fe, a Cu—Sn alloy layer, and a Sn layer, with a part of the Cu—Sn alloy exposed on the Sn layer-side surface, and specific surface roughness parameters to ensure low contact resistance and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the terminal is downsized to reduce vehicle size, then the contact pressure decreases, but the contact resistance increases
Solution Approach 1:
The patent applies local quality by creating a multi-layer structure with different materials (Cu-Sn alloy layer, Sn layer, underlayer) having distinct properties. The Cu-Sn alloy layer provides low friction coefficient, the Sn layer provides oxidation resistance, and the underlayer provides adhesion to the base material. This layered approach allows each layer to contribute its specific local properties to solve the overall problem of maintaining low contact resistance under reduced contact pressure.
Solution Approach 2:
The patent uses composite materials by combining multiple layers with different compositions and properties. The conductive material consists of a base material, an underlayer, a Cu-Sn alloy layer, and a Sn layer. This composite structure leverages the advantages of each material: copper's conductivity, Sn's oxidation resistance, and the Cu-Sn alloy's low friction coefficient, thereby maintaining reliable electrical contact even when terminal size and contact pressure are reduced.
2Ease of operation
If the Cu-Sn alloy layer is exposed on the surface to reduce dynamic friction coefficient, then the friction decreases, but the contact resistance may increase due to surface irregularities
Solution Approach 1:
The patent applies parameter changes by precisely controlling the surface roughness parameters of the Cu-Sn alloy layer. Specifically, it sets the arithmetic mean height (Sa) within 0.03-0.5 μm and the maximum height (Sz) within 0.12-2.0 μm. By optimizing these surface topology parameters, the patent achieves a balance between maintaining low dynamic friction coefficient (through exposure of the Cu-Sn alloy layer) and ensuring low contact resistance (by limiting excessive surface irregularities).
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 low contact resistance, low dynamic friction coefficient, and sufficient heat resistance, while providing fretting wear resistance, even under low contact pressure.
Implementation Method 1
a conductive material to be used for a terminal needs to have a low dynamic friction coefficient from the viewpoint of reducing a load on an operator and preventing errors in fitting
Implementation Method 2
a conductive material that exhibits high conductivity even at a low contact pressure (that is, exhibits low contact resistance) is required
Data Source
AI summary
A conductive material includes a base material composed of copper or a copper alloy; an underlayer being one or more layers composed of one or more selected from the group consisting of Ni, Co and Fe; a Cu—Sn alloy layer; and a Sn layer in this order. A part of the Cu—Sn alloy layer is exposed on a Sn layer-side surface of the conductive material, and an arithmetic mean height evaluated with a cut-off value of 25 μm is 0.03 μm or more in a 250 μm square region containing 50 area % or more of the Sn layer in the Sn layer-side surface of the conductive material.