Terminal Fitting Sn-Pd Plating Reduces Insertion Force
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Solution Overview
Problem
Conventional terminal fittings with a Ni, Cu, and Sn plating layer configuration exhibit high friction coefficients, leading to increased insertion forces when connecting multiple terminals, particularly in connectors, due to the soft Sn plating layer.
Innovation Solution
A terminal fitting with a plating coating containing a Sn parent phase and Sn—Pd based particles dispersed in the Sn parent phase, where the Sn—Pd particles are present on the outer surface, reducing the friction coefficient and insertion force by controlling their number between 10 to 400 per 500 μm².
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Sn plating layer is used on the terminal surface, then solderability is improved, but the friction coefficient increases and insertion force becomes large
Solution Approach 1:
The invention uses a composite plating structure with multiple layers: a Sn plating layer for solderability, a Cu plating layer for conductivity and corrosion resistance, and a Ni plating layer for hardness and wear resistance. This composite structure allows each layer to contribute its specific properties, achieving both good solderability and reduced friction coefficient through the Ni and Cu layers underlying the Sn layer.
Solution Approach 2:
The invention applies different plating materials at different locations and depths: the outer Sn layer provides local solderability where needed, while the underlying Ni and Cu layers provide local hardness and low friction properties. This localized quality distribution allows the terminal to exhibit different properties at different depths and locations, resolving the contradiction between soft Sn surface and hard low-friction substrate.
2Adaptability or versatility
If multiple terminals are used in a connector, then functionality is improved, but the total insertion force increases
Solution Approach 1:
The invention changes the surface parameters of the terminals by applying a multi-layer plating structure that specifically reduces the friction coefficient. By modifying the surface composition and properties through the Ni-Cu-Sn plating system, the insertion force per terminal is reduced, which consequently reduces the total insertion force when multiple terminals are used in a connector, while maintaining the required multipole functionality.
3Reliability
If a Ni, Cu, and Sn plating layer configuration is used, then corrosion resistance is improved, but the friction coefficient becomes high
Solution Approach 1:
The invention employs a composite plating system where the Ni layer provides hardness and wear resistance, the Cu layer provides excellent electrical conductivity and corrosion resistance, and the Sn layer provides solderability. The combination of these materials creates a composite structure where the Ni and Cu layers contribute to low friction coefficient while the Sn layer maintains good solderability, resolving the contradiction between corrosion resistance and friction coefficient.
Data Source
AI summary
A terminal fitting having a smaller terminal insertion force than before. The terminal fitting includes a backing material made of a metal material and a plating coating covering a surface of the backing material. The plating coating contains a Sn parent phase and Sn—Pd based particles dispersed in the Sn parent phase and includes an outermost layer having an outer surface in which the Sn parent phase and the Sn—Pd based particles are present. Further, the number of the Sn—Pd based particles present in the outer surface of the plating coating in a state where only the Sn parent phase is removed is 10 to 400 Sn—Pd based particles per 500 μm2.