Cu-Ni-Si Alloy Plate Ni Gradient for High-Temp Reliability
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Solution Overview
Problem
Conventional Cu—Ni—Si based copper alloy plates fail to maintain balanced performance in contact electric resistance, solder wettability, and heat-peeling resistance under high-temperature environments, which is critical for reliable electrical connections in automotive applications.
Innovation Solution
The Cu—Ni—Si based copper alloy plate is designed with a controlled Ni concentration gradient in the surface layer, where the surface Ni concentration is 70% or less of the center Ni concentration, to suppress oxidation and Ni diffusion into the plating film, thereby enhancing electrical connection reliability and solder wettability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the Ni concentration is increased to improve strength, then the strength increases, but the contact electric resistance increases and solder wettability deteriorates under high-temperature environments
Solution Approach 1:
The patent applies local quality by creating a non-uniform Ni concentration distribution within the copper alloy plate. The surface layer contains lower Ni concentration (0.01-3.0 mass%) to maintain low contact electric resistance and good solder wettability, while the interior contains higher Ni concentration (0.5-5.0 mass%) to provide sufficient strength. This spatial variation in composition allows different regions to optimize for their specific functions.
Solution Approach 2:
The patent transitions from a single-dimensional uniform composition to a multi-dimensional composition profile by controlling Ni concentration as a gradient through the thickness direction. This dimensional approach allows simultaneous optimization of surface properties (electrical contact) and bulk properties (mechanical strength) that would be conflicting in a uniform composition.
2Strength
If the Ni concentration is increased to improve strength, then the strength increases, but the adhesiveness of the plating film deteriorates due to Ni diffusion into the plating film
Solution Approach 1:
The patent creates a low-Ni surface layer (0.01-3.0 mass%) that acts as a protective barrier, preventing excessive Ni diffusion into the plating film while maintaining overall high strength through the interior Ni concentration (0.5-5.0 mass%). This local composition optimization resolves the conflict between strength and plating adhesiveness.
Solution Approach 2:
The patent performs preliminary action by pre-establishing the controlled Ni concentration distribution before plating. The surface layer is designed with lower Ni content in advance to prevent harmful Ni diffusion during subsequent plating and heat treatment processes, ensuring good plating adhesiveness from the outset.
3Object-affected harmful factors
If the surface Ni concentration is increased to suppress oxidation, then the oxidation resistance improves, but the contact electric resistance increases
Solution Approach 1:
The patent inverts the conventional approach by not relying on high surface Ni concentration for oxidation resistance. Instead, it uses a controlled low-Ni surface layer combined with appropriate atmosphere control during service to maintain low contact electric resistance while achieving sufficient oxidation resistance through the overall alloy composition and surface treatment.
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 approach effectively reduces contact resistance, improves solder wettability, and enhances the adhesiveness of the plating film under high-temperature conditions, ensuring reliable electrical connections.
Implementation Method 1
suppress oxidation and Ni diffusion into the plating film
Data Source
AI summary
A Cu—Ni—Si based copper alloy containing Ni and Si: in a center portion in a plate thickness direction, containing 0.4% by mass or more and 5.0% by mass or less of Ni, 0.05% by mass or more and 1.5% by mass or less of Si, and the balance Cu and inevitable impurities; where an Ni concentration on a plate surface is 70% or less of a center Ni concentration in the thickness center portion; a surface layer portion having a depth from the plate surface to be 90% of the center Ni concentration; in the surface layer portion, the Ni concentration increases from the plate surface toward the thickness center portion at 5.0% by mass/μm or more and 100% by mass/μm or less of a concentration gradient; to improve the electric connection reliability under high-temperature environment.