Copper Diffusion Joint for Press-Fit Terminal Fatigue
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The connection strength between press fit terminals and substrates in electronic apparatuses is compromised by variations in friction coefficient, leading to potential disconnection under external forces, and conventional diffusion joining methods result in reduced fatigue life due to the presence of tin and copper-tin alloy layers.
Innovation Solution
The electronic apparatus employs a metallurgical joint between copper-based connection portions using oxide films on the surfaces of the first and second connection portions, which are reduced to form a direct copper joint, eliminating the need for tin or copper-tin alloy layers and thereby enhancing fatigue life and connection strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the diameter of the through hole is reduced to increase spring reaction force, then connection strength is improved, but damage to connection portions enlarges and connection reliability falls
Solution Approach 1:
The patent introduces a plating film as an intermediary layer between the base material and the contact interface. This plating film undergoes diffusion joining to create a metallurgical bond, which strengthens the connection without requiring increased mechanical pressure that would damage the connection portions. The plating film acts as a mediator that enables strong bonding while protecting the base materials from damage.
Solution Approach 2:
The patent changes the chemical composition parameters by applying different plating films (tin, nickel, or zinc) with controlled thicknesses (0.1-5.0 μm). This parameter change enables diffusion joining that creates strong metallurgical bonds without requiring high mechanical pressure, thereby maintaining connection reliability while achieving sufficient connection strength.
2Strength
If tin plating is used for diffusion joining, then connection strength is improved, but fatigue life is reduced due to formation of copper-tin alloy layers
Solution Approach 1:
The patent employs thin plating films (0.1-5.0 μm) that are intentionally designed to be sacrificial layers. These plating films undergo diffusion joining and form alloy layers that are acceptable to be consumed during the bonding process, achieving strong connections without compromising the fatigue life of the base materials. The plating film serves as a disposable intermediary that enables strong bonding.
Solution Approach 2:
The patent creates a composite structure consisting of the base material and the plating film layer. This composite material approach allows the plating film to provide the necessary diffusion joining functionality while the base material maintains its fatigue resistance. The controlled thickness and composition of the plating film ensure that the composite structure achieves both strength and durability.
3Strength
If mechanical connection is performed with high spring reaction force, then connection strength is improved, but damage to connection portions increases
Solution Approach 1:
The patent replaces purely mechanical connection (relying on spring reaction force and friction) with a metallurgical bonding system based on diffusion joining. This substitution allows the connection to achieve sufficient strength through chemical bonding at the atomic level, eliminating the need for high mechanical pressure that would cause damage to the connection portions.
Solution Approach 2:
The patent performs preliminary plating of the base material surfaces before the connection process. This preliminary action creates a controlled interface layer that facilitates diffusion joining and ensures that the subsequent mechanical pressing (if any) does not cause damage to the connection portions, as the bonding has already been established through the plating film diffusion.
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 solution strengthens the connection while reducing the risk of damage during mechanical assembly and significantly improves the fatigue life of the joint portion by eliminating fatigue-prone layers, ensuring reliable retention power and reduced spring reaction force.
Implementation Method 1
oxide films on the surfaces of the first and second connection portions, which are reduced to form a direct copper joint
Data Source
AI summary
An electronic apparatus includes a connection target member that has a first connection portion including copper or copper alloy, a connection terminal that has a second connection portion including copper or copper alloy, the second connection portion mechanically connecting with the first connection portion by spring reaction force of the connection terminal, and a joint portion that is provided with a contact point between the first connection portion and the second connection portion. At least one of the first connection portion and the second connection portion includes an oxide film at a periphery of the joint portion on a surface thereof, the oxide film including copper oxide. The joint portion directly joints copper included in the first connection portion and copper included in the second connection portion metallurgically.