Connector Terminal Material With Cu-Sn Barrier for High-Heat Contact Stability
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Solution Overview
Problem
Existing terminal materials for connectors face challenges in maintaining reliable electric connections at high temperatures due to diffusion of Ni into the Sn layer, leading to increased contact resistance and potential damage, and current solutions either compromise on heat resistance or are costly.
Innovation Solution
A terminal material configuration with a Ni layer, a Cu—Sn intermetallic compound layer, and an Sn layer, where the Cu—Sn intermetallic compound layer is thickened and grown uniformly to prevent Ni diffusion, and the Sn layer is optimized in thickness and crystal grain size to reduce oxidation and maintain even growth, along with a double structure of Cu3Sn and Cu6Sn5 layers to enhance barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Ni layer thickness is increased to prevent Cu diffusion, then the barrier properties improve, but the cost increases and the layer becomes more prone to cracking
Solution Approach 1:
The Ni layer is segmented into multiple thin layers (first Ni layer and second Ni layer) separated by the Cu-Sn intermetallic compound layer. This segmentation prevents cracking that would occur in a single thick Ni layer while maintaining effective Cu diffusion barrier properties through the combined thickness of multiple layers.
Solution Approach 2:
The plating structure uses a nested multi-layer configuration where the Cu-Sn intermetallic compound layer is formed between the base material and the Sn plating layer, with Ni layers positioned at specific interfaces. This nested arrangement optimizes the barrier function while controlling overall layer thickness and complexity.
2Reliability
If the Cu-Sn intermetallic compound layer is thickened to improve heat resistance, then the barrier against Ni diffusion improves, but the Sn layer thickness is reduced and heat resistance deteriorates
Solution Approach 1:
The invention optimizes the thickness parameters of both the Cu-Sn intermetallic compound layer and the Sn plating layer within specific ranges. By precisely controlling these parameters, the structure achieves adequate Ni diffusion barrier function while maintaining sufficient Sn layer thickness for heat resistance and solderability.
Solution Approach 2:
The Cu-Sn intermetallic compound layer is strategically positioned at the interface where Ni diffusion is most critical, providing localized barrier function exactly where needed. This allows the layer to be thinner overall while still effectively preventing Ni diffusion into the Sn layer, thereby preserving Sn thickness for heat resistance.
3Ease of manufacture
If the Ni layer is made thinner to reduce cost and complexity, then the manufacturing cost decreases, but Ni diffusion into the Sn layer occurs causing contact resistance increase
Solution Approach 1:
The Cu-Sn intermetallic compound layer acts as an intermediary barrier between the Ni layers and the Sn plating layer. This intermediary layer effectively blocks Ni diffusion into the Sn layer, allowing the use of thinner, more cost-effective Ni layers while maintaining contact resistance stability and preventing Sn layer contamination.
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
This configuration improves heat resistance and maintains low contact resistance even at high temperatures, while preventing Ni layer damage and reducing the risk of oxidation, thus ensuring reliable electrical connections.
Implementation Method 1
the Cu—Sn intermetallic compound layer on it has an effect of restraining diffusion of Ni to the Sn layer
Implementation Method 2
the Ni layer coating the surface of the base material restrains diffusion of Cu from the base material
Implementation Method 3
an Sn plating film formed by electrolytic plating on a surface of a base material
Implementation Method 4
an Sn plating film formed by electrolytic plating on a surface of a base material made of Cu or Cu alloy is heated, melted, and solidified
Data Source
AI summary
A terminal material having a base material in which at least a surface is made of Cu or Cu alloy; an Ni layer with at thickness of 0.1 μm to 1.0 μm inclusive on the base material; a Cu—Sn intermetallic compound layer with a thickness of 0.2 μm to 2.5 μm inclusive on the Ni layer; and an Sn layer with a thickness of 0.5 μm to 3.0 μm inclusive on the Cu—Sn intermetallic compound layer, when cross sections of the Cu—Sn intermetallic compound layer and the Sn layer are analyzed by the EBSD method with a measuring step 0.1 μm and a boundary in which misorientation between adjacent pixels is 2° or more is deemed to be a crystal boundary, an average crystal grain size Dc of the Cu—Sn intermetallic compound layer is 0.5 μm or more, and a grain size ratio Ds/Dc is five or less.