Copper Alloy Plate for Connectors Resolving Strength-Conductivity Trade-off
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Solution Overview
Problem
Current copper alloys for terminal and connector materials face challenges in achieving a balance between high tensile strength, electric conductivity, and other essential properties like stress corrosion resistance and solderability, while also being economically efficient and environmentally friendly, due to limitations in existing materials such as beryllium copper, phosphor bronze, nickel silver, and brass.
Innovation Solution
A copper alloy sheet with specific compositions of Zn, Sn, P, Ni, and optionally Co and Fe, which are cold-rolled to achieve a balance of crystal grain size and precipitate distribution, enhancing tensile strength, electric conductivity, and stress relaxation characteristics, while maintaining excellent bending workability and solderability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If beryllium copper is used to achieve high strength, then tensile strength is improved, but manufacturing cost and environmental safety deteriorate
Solution Approach 1:
The patent replaces expensive beryllium copper with a cost-effective copper-Zinc-Sn-P-Ni alloy system. The invention uses common, inexpensive elements (Zn, Sn, P, Ni) in specific combinations to achieve high strength without requiring costly beryllium materials or specialized dissolution facilities, making the material economically viable for mass production
Solution Approach 2:
The patent creates a composite alloy system combining Cu with Zn, Sn, P, and Ni elements that work synergistically. The specific composition ranges (Zn: 3-12%, Sn: 0.1-1.0%, P: 0.01-0.08%, Ni: 0.2-0.85%) create a multi-phase microstructure that achieves beryllium-copper-level strength through composite strengthening mechanisms rather than relying on a single expensive element
2Strength
If phosphor bronze or nickel silver is used to achieve high strength, then tensile strength is improved, but productivity and manufacturing efficiency deteriorate
Solution Approach 1:
The patent optimizes the chemical composition parameters within specific ranges (Zn: 3-12%, Sn: 0.1-1.0%, P: 0.01-0.08%, Ni: 0.2-0.85%) to achieve a microstructure that is highly amenable to hot rolling and cold rolling processes. This parameter optimization enables high productivity through conventional manufacturing methods while maintaining high strength, eliminating the need for transverse continuous casting
Solution Approach 2:
The patent introduces localized precipitates of specific phases (such as Ni3P, Ni2P, or intermetallic compounds) within the copper matrix at controlled distributions. These localized strengthening phases provide high strength while maintaining good hot and cold workability, allowing the material to be processed through high-productivity rolling operations
3Strength
If strength is increased in copper alloy, then tensile strength is improved, but electric conductivity deteriorates
Solution Approach 1:
The patent introduces localized precipitates of specific phases (such as Ni3P, Ni2P, or intermetallic compounds) within the copper matrix at controlled distributions. These localized strengthening phases provide high strength while maintaining good hot and cold workability, allowing the material to be processed through high-productivity rolling operations
Solution Approach 2:
The patent creates a composite alloy system combining Cu with Zn, Sn, P, and Ni elements that work synergistically. The specific composition ranges (Zn: 3-12%, Sn: 0.1-1.0%, P: 0.01-0.08%, Ni: 0.2-0.85%) create a multi-phase microstructure that achieves beryllium-copper-level strength through composite strengthening mechanisms rather than relying on a single expensive element
4Strength
If crystal grain size is reduced to improve strength, then tensile strength is improved, but manufacturing complexity increases
Solution Approach 1:
The patent incorporates alloying elements (P, Ni, Zn, Sn) that automatically promote fine grain formation during standard hot rolling and cold rolling processes. The composition is designed so that precipitates form naturally during conventional manufacturing steps, pre-establishing a fine-grained microstructure without requiring additional grain-refining operations or complex process controls
Solution Approach 2:
The alloying elements in the patent (particularly P and Ni in combination with Zn and Sn) self-organize during cooling and rolling to form fine precipitates and a refined grain structure. The material essentially self-regulates its microstructure development during standard processing, eliminating the need for external grain-refining interventions or complex manufacturing sequences
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 copper alloy sheet exhibits improved tensile strength, proof stress, electric conductivity, and stress corrosion crack resistance, with a balance of properties suitable for high-performance applications in connectors and terminals, while being economically viable and environmentally responsible.
Implementation Method 1
which are cold-rolled to achieve a balance of crystal grain size and precipitate distribution
Implementation Method 2
superior stress relaxation characteristics
Data Source
AI summary
A copper alloy sheet for terminal and connector materials contains 4.5 mass % to 12.0 mass % of Zn, 0.40 mass % to 0.9 mass % of Sn, 0.01 mass % to 0.08 mass % of P, and 0.20 mass % to 0.85 mass % of Ni with a remainder being Cu and inevitable impurities, a relationship of 11≤[Zn]+7.5×[Sn]+16×[P]+3.5×[Ni]≤19 is satisfied, a relationship of 7≤[Ni]/[P]≤40 is satisfied in a case in which the content of Ni is in a range of 0.35 mass % to 0.85 mass %, an average crystal grain diameter is in a range of 2.0 μm to 8.0 μm, an average particle diameter of circular or elliptical precipitates is in a range of 4.0 nm to 25.0 nm or a proportion of the number of precipitates having a particle diameter in a range of 4.0 nm to 25.0 nm in the precipitates is 70% or more, an electric conductivity is 29% IACS or more, a percentage of stress relaxation is 30% or less at 150° C. for 1000 hours as stress relaxation resistance, bending workability is R/t≤0.5 at W bending, solderability is excellent, and a Young's modulus is 100×103 N/mm2 or more.