Conductive Member With Cu-Sn Intermetallic Compound Layer
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Solution Overview
Problem
Conductive members used in connectors experience increased contact resistance and separation issues due to thermal diffusion of Sn and Cu, leading to Kirkendall voids, especially at high temperatures, and poor adhesiveness between base plated layers, which results in increased inserting and drawing forces.
Innovation Solution
A conductive member with a Cu-Sn intermetallic compound layer and Sn-based surface layer formed on a Cu-based substrate through an Ni-based base layer, featuring a two-layer structure of Cu 3 Sn and Cu 6 Sn 5 layers with recessed and projected portions, and an optional Fe-based base layer to enhance heat resistance and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a three-layer plated structure of Ni, Cu, and Sn is formed to improve electrical connection, then electrical conductivity is improved, but adhesiveness between the base plated layer and Cu is poor causing separation
Solution Approach 1:
The chemical composition and structure of the base layer are changed from a simple Ni layer to an Ni-based alloy layer with specific compositional parameters. This parameter change enhances the chemical affinity and bonding strength between the base layer and the Cu-based substrate, preventing separation while maintaining the electrical conductivity function.
2Adaptability or versatility
If multipolarization of connectors is implemented to increase circuit integration, then circuit integration is improved, but inserting force during assembly increases
Solution Approach 1:
The surface layer is designed with local quality characteristics - an Sn-based surface layer with specific microstructural properties that reduce friction and inserting force. This localized optimization of the surface layer's mechanical properties allows multipolarized connectors to be assembled with reduced force while maintaining high circuit integration.
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 stabilizes contact resistance, prevents separation, and reduces inserting and drawing forces by controlling the thickness and coverage of the Cu-Sn intermetallic compound layers and the Fe-based base layer, effectively addressing thermal diffusion and adhesiveness issues.
Implementation Method 1
prolonged exposure to such a high temperature leads to mutual thermal diffusion of Sn and Cu
Implementation Method 2
performing heating and a reflow treatment on the plated layers so as to sequentially form an Ni-based base layer, a Cu-Sn intermetallic compound layer
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
[Object] To provide a conductive member which has a stable contact resistance, is difficult to be separated, and also decreases the inserting and drawing force when used for a connector. [Means to Solve Problems] A Cu-Sn intermetallic compound layer 3 and an Sn-based surface layer 4 are formed in this order on the surface of a Cu-based substrate 1 through an Ni-based base layer 2, and, furthermore, the Cu-Sn intermetallic compound layer 3 is composed of a Cu3Sn layer 5 arranged on the Ni-based base layer 2 and a Cu6Sn5 layer 6 arranged on the Cu3Sn layer 5; the Cu-Sn intermetallic compound layer 3 obtained by bonding the Cu3Sn layer 5 and the Cu6Sn5 layer 6 is provided with recessed and projected portions on the surface which is in contact with the Sn-based surface layer 4; thicknesses X of the recessed portions 7 are set to 0.05 µm to 1.5 µm, the area coverage of the Cu3Sn layer 5 with respect to the Ni-based base layer 2 is 60% or higher, the ratio of the thicknesses of the projected portions 8 to the thicknesses Y of the recessed portions 7 in the Cu-Sn intermetallic compound layer 3 is 1.2 to 5, and the average thickness of the Cu3Sn layer 5 is 0.01 µm to 0.5 µm.