Press-fit Terminal Alloy Layer Friction and Holding Force
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Solution Overview
Problem
Press-fit terminals face challenges in suppressing scraping and reducing insertion/withdrawal load while maintaining a high holding force, as existing metal layer configurations on both the terminal and the through hole are insufficient to prevent unintended disengagement.
Innovation Solution
A press-fit terminal connection structure featuring a surface alloy containing layer with a tin-palladium alloy and a tin layer on the through hole's inner peripheral surface, optimizing surface hardness and friction coefficients to balance scraping suppression and holding force, without using contact oil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hard metal layer is provided on the surface of the board connecting portion to suppress scraping and reduce insertion/withdrawal load, then surface friction is reduced and scraping is suppressed, but the holding force of the press-fit terminal in the inserted state deteriorates
Solution Approach 1:
The invention applies different metal layer configurations to different locations: the board connecting portion surface has a hard metal layer (Cu3Sn or Cu6Sn5 alloy layer) to reduce friction during insertion/withdrawal, while the through hole inner peripheral surface has a tin layer to provide high holding force through tin-tin adhesion. This local differentiation allows simultaneous achievement of easy operation and high reliability.
Solution Approach 2:
The invention uses a composite metal layer structure consisting of multiple layers with different properties: a hard metal layer (Cu3Sn or Cu6Sn5 alloy) on the press-fit terminal surface combined with a tin layer on the through hole surface. The combination of these different metal materials enables both low friction during movement and high adhesion for holding.
2Reliability
If a tin plating layer is provided on the board connecting portion surface, then electrical connection is ensured, but scraping occurs during insertion into the through hole affecting electrical connection
Solution Approach 1:
The invention changes the material parameter of the surface layer from pure tin (soft, prone to scraping) to a Cu-Sn alloy layer with higher hardness. The Cu3Sn or Cu6Sn5 alloy layer maintains electrical conductivity while providing sufficient hardness to resist scraping during insertion, thus preventing the generation of tin scrapings that would harm electrical connection.
Solution Approach 2:
The invention converts the inherent softness of tin (which causes scraping) into a benefit by using Cu-Sn intermetallic compounds that form a harder surface layer. This harder layer prevents scraping and tin exposure, while the underlying tin layer still provides good electrical conductivity and adhesion to the base material.
3Ease of operation
If only the configuration of the metal layer on the press-fit terminal surface is considered, then scraping suppression and load reduction are improved, but the holding force in the inserted state cannot be sufficiently improved
Solution Approach 1:
The invention expands the solution from considering only the press-fit terminal surface (one dimension) to considering both the terminal surface and the through hole inner peripheral surface (two dimensions). By optimizing the metal layer configuration on both surfaces, the invention achieves simultaneous improvement in friction reduction and holding force enhancement.
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 structure effectively reduces dynamic friction for easy insertion and withdrawal while enhancing static friction for a strong holding force, eliminating the need for contact oil and improving workability and connection reliability.
Implementation Method 1
it is possible to reduce surface friction during the insertion and withdrawal of the terminal and suppress scraping
Implementation Method 2
exhibit a high holding force to prevent the press-fit terminal from easily coming out from the through hole
Data Source
AI summary
It is aimed to provide a press-fit terminal connection structure in which a board connecting portion of a press-fit terminal is press-fit into a through hole provided in a printed circuit board and which can combine the suppression of scraping of a surface layer and a reduction of a necessary load when the press-fit terminal is inserted into and withdrawn from the through hole and an improvement of a holding force for keeping the press-fit terminal inserted in the through hole. In the press-fit terminal connection structure, the press-fit terminal includes, at least on a surface of the contact point portion, an alloy containing layer mainly containing tin and palladium, and the through hole includes a tin layer on an outermost surface of an inner peripheral surface including at least the contact point portion.