Copper Alloy Strip Microstructure for Strength-Conductivity Balance
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Solution Overview
Problem
Existing copper alloys used in lead frames for integrated circuits face challenges in achieving high strength, electrical conductivity, surface flatness, and uniform residual stress distribution, particularly in etched products, due to issues with residual stress control and surface quality.
Innovation Solution
A copper alloy strip composition with controlled amounts of Cr, Si, and optional elements like Fe, Ti, Zr, Ag, Zn, and Sn, combined with a specific microstructure and manufacturing process including casting, homogenizing annealing, hot rolling, solid solution treatment, cold rolling, aging treatment, and low-temperature annealing, to achieve dispersed second-phase particles and controlled texture ratios, enhancing mechanical and electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Cr content is increased to improve strength through precipitation strengthening, then tensile strength is improved, but electrical conductivity deteriorates and surface roughness increases
Solution Approach 1:
The patent optimizes the Cr content parameter to a specific range (0.01-1.0 wt%) to achieve the best balance between strength and electrical conductivity. It also controls the ratio of fine to coarse second-phase particles (A/B ≥ 3) and adjusts aging treatment parameters (temperature and time) to precipitate fine particles that strengthen the material without excessively increasing resistivity.
Solution Approach 2:
The patent creates a non-uniform distribution of second-phase particles with different sizes, where fine particles (≤5 nm) are dispersed throughout the matrix for strengthening, while controlling the number of coarse particles (≥100 nm) to minimize their harmful effects on conductivity and surface quality. This local differentiation of particle quality optimizes both strength and electrical properties.
2Strength
If Cr content is increased to improve strength, then tensile strength is improved, but surface flatness deteriorates
Solution Approach 1:
The patent controls Cr content within 0.01-1.0 wt% and optimizes the aging treatment parameters (temperature and time) to precipitate fine second-phase particles uniformly distributed in the matrix. This controlled parameter adjustment ensures strength improvement while maintaining surface flatness by avoiding excessive coarse particle formation.
Solution Approach 2:
The patent promotes uniform dispersion of fine second-phase particles throughout the alloy matrix while controlling the distribution and size of coarse particles. This local quality control ensures that strengthening occurs without creating surface irregularities, as fine particles provide strength without the surface roughening effect of large particles.
3Manufacturing precision
If etching process is used to achieve fine lead pitch, then manufacturing precision is improved, but residual stress control becomes more difficult
Solution Approach 1:
The patent controls the Cr content (0.01-1.0 wt%) and aging treatment parameters to precipitate fine second-phase particles that evenly distribute residual stress throughout the material. This parameter optimization ensures that the copper alloy strip maintains uniform residual stress after etching, enabling fine lead pitch manufacturing with controlled stress levels.
Solution Approach 2:
The patent creates a uniform distribution of fine second-phase particles throughout the alloy matrix, which acts as stress distribution points that evenly disperse residual stress during etching. This local quality uniformity prevents stress concentration and maintains residual stress uniformity even when achieving fine lead pitch through etching processes.
4Strength
If aging treatment is performed to precipitate second-phase particles for strengthening, then tensile strength is improved, but electrical conductivity is reduced
Solution Approach 1:
The patent optimizes aging treatment parameters (temperature and time) to control the size and distribution of precipitated second-phase particles. By maintaining Cr content within 0.01-1.0 wt% and controlling the aging process, fine particles are precipitated that provide strengthening with minimal impact on electrical conductivity, achieving the best balance between these two properties.
Solution Approach 2:
The patent promotes the precipitation of fine second-phase particles (≤5 nm) dispersed uniformly throughout the matrix, which provide strengthening through interaction with dislocations while having minimal scattering effect on electrons. The patent controls the number of coarse particles (≥100 nm) to minimize their harmful scattering effect on electrical conductivity, thus achieving local quality optimization for both strength and conductivity.
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 strip exhibits high tensile strength, excellent electrical conductivity, and uniform residual stress distribution, with improved surface flatness, meeting the requirements of etched and half-etched products like lead frames.
Implementation Method 1
Cr is dissolved into a copper matrix through solid solution treatment to form a supersaturated solid solution
Implementation Method 2
then second-phase particles are precipitated through aging treatment
Implementation Method 3
the precipitated second-phase particles interact violently with the dislocations, which greatly increases the dislocation density in the alloy matrix, thereby improving the strength of the alloy
Implementation Method 4
hot rolling, solid solution treatment, cold rolling, aging treatment, and low-temperature annealing
Implementation Method 5
homogenizing annealing
Implementation Method 6
low-temperature annealing
Data Source
AI summary
The invention provides a copper alloy strip, wherein the copper alloy comprises the following components in percentage by mass: 0.1 wt %-1.0 wt % of Cr, 0.01 wt %-0.2 wt % of Si, 0.01 wt %-1.0 wt % of X and the balance of Cu and inevitable impurities, wherein X is at least one of Fe, Ti, Zr, Ag, Zn and Sn; on a section of the copper alloy strip perpendicular to a rolling direction, the number of second-phase particles having a particle size of 5 nm or below 5 nm is A, the number of second-phase particles having a particle size of 100 nm or above 100 nm is B, and A/B is greater than or equal to 3.