Terminal Plating with Intermediate Silver Layer for Crack Resistance
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Solution Overview
Problem
Existing terminal plating technologies face issues with wear resistance against micro-sliding and bendability, leading to increased contact electrical resistance and reduced connection reliability due to cracking and adhesion of silver-tin alloy layers.
Innovation Solution
A metal plate with a two-layer plating film structure, where a soft intermediate silver layer is layered on a base material and a harder silver-tin alloy layer is exposed, with the intermediate silver layer being thinner than the alloy layer to alleviate strain and impact, preventing cracks and improving wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a base plating made of nickel or copper is used under a silver coating layer, then the wear resistance can be improved, but cracks may appear due to strain or impact when the base plating is bent
Solution Approach 1:
The plating film is segmented into three distinct layers: a base material layer, an intermediate Ag layer, and an Ag-Sn alloy layer. This segmentation allows each layer to perform its specific function - the intermediate Ag layer absorbs bending strain while the Ag-Sn alloy layer provides wear resistance, preventing cracks from propagating through the entire structure.
Solution Approach 2:
The invention uses a composite plating structure combining different materials (Ag and Ag-Sn alloy) with complementary properties. The intermediate Ag layer provides ductility and strain absorption, while the Ag-Sn alloy layer provides hardness and wear resistance, creating a composite system that overcomes the limitations of single-material plating.
2Strength
If a silver-tin alloy layer is used to reduce coefficient of friction, then the wear resistance can be improved, but the contact electrical resistance is likely to increase when micro-sliding is applied
Solution Approach 1:
The invention creates local quality differentiation within the plating film by positioning the Ag-Sn alloy layer specifically at the outermost surface where wear occurs, while the intermediate Ag layer closer to the base material provides excellent electrical conductivity. This local optimization allows the surface to have high wear resistance while maintaining overall low electrical resistance.
Solution Approach 2:
The invention addresses the contradiction by adding a dimensional aspect - creating a vertical gradient in material properties through the thickness of the plating film. The composition and properties vary through the depth of the plating, with the Ag-Sn alloy concentrated at the surface for wear resistance and pure Ag in the intermediate layer for electrical conductivity, effectively resolving the contradiction in the third dimension.
Data Source
AI summary
A metal plate for a terminal and a terminal in which cracks in a plating film due to bending or the like can be suppressed, and a terminal pair that is wear resistant against micro-sliding. The metal plate includes a base material and, a plating film that covers the entire surface of the base material. The plating film includes an intermediate Ag layer that is layered on the base material, and an Ag—Sn alloy layer that is layered on the intermediate Ag layer and is exposed on the outermost surface. The terminal is made from the metal plate and has a protruding contact projecting from the surrounding region and is configured to come into contact with a corresponding terminal. The plating film is arranged at least on the protruding contact.