Copper Foil Composite Bending Properties via Grain Size Control
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Solution Overview
Problem
Current copper foil composites for electromagnetic shielding and flexible printed circuits lack sufficient bending properties, particularly in severe folding applications, as they fail to demonstrate excellent results in 180-degree intimate bend tests.
Innovation Solution
A copper foil composite is developed with specific composition, texture orientation, and grain size, including elements like Sn, Mn, Cr, Zn, Zr, Mg, Ni, Si, and Ag at controlled concentrations, along with a resin layer, to enhance bending properties by ensuring a tensile strength of 100 to 180 MPa, a degree of aggregation I200/I 0 200 of 30 or more, and an average grain size of 10 to 400 µm, which improves deformation transmission and ductility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the copper foil thickness is increased to ensure electromagnetic shielding properties, then the shielding effectiveness is improved, but the bending properties and formability deteriorate
Solution Approach 1:
The invention changes the microstructural parameters of the copper foil, specifically controlling the grain size to 10-400 μm and the degree of aggregation I200/I0200 to 30 or more, while maintaining thickness of several μm or more. This allows the foil to achieve both adequate shielding effectiveness and improved bending properties through optimized crystallographic structure rather than simply increasing thickness.
Solution Approach 2:
The invention creates a composite structure by laminating a resin film on the copper foil. This composite material approach allows the copper foil to maintain its shielding function while the resin layer provides mechanical support and flexibility, improving the overall bending properties of the assembly without compromising electromagnetic shielding effectiveness.
2Ease of operation
If the copper foil is made thinner to improve flexibility, then the formability is improved, but the electromagnetic shielding properties deteriorate
Solution Approach 1:
The invention optimizes the copper foil thickness to several μm or more, which is thin enough to provide flexibility but thick enough to maintain electromagnetic shielding properties. The key is changing the microstructural parameters (grain size 10-400 μm and degree of aggregation ≥30) to enable the foil to achieve adequate shielding effectiveness at this optimized thickness without requiring excessive thickness that would compromise flexibility.
3Strength
If the grain size is reduced to improve strength, then the tensile strength is improved, but the bending properties and ductility deteriorate
Solution Approach 1:
The invention identifies an optimal grain size range of 10-400 μm that balances tensile strength and bending properties. This is a specific parameter change that avoids both extremely fine grains (which would improve strength but reduce ductility and bending properties) and extremely coarse grains (which would improve bending but reduce strength). The degree of aggregation I200/I0200 ≥30 is also controlled to optimize the crystallographic orientation for both strength and formability.
4Ease of operation
If the degree of aggregation is increased to improve formability, then the drawing formability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The invention sets the degree of aggregation I200/I0200 to 30 or more, which is a specific parameter change that promotes favorable crystallographic orientation for formability. This level of aggregation improves drawing formability while remaining achievable through conventional manufacturing processes like controlled rolling and annealing, thus not requiring excessive manufacturing precision beyond standard industrial capabilities.
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 foil composite exhibits enhanced bending properties and drawing formability, allowing for severe bending without cracking, as demonstrated by improved results in W-bending and 180-degree intimate bending tests, and increased ductility, making it suitable for space-saving applications in mobile devices.
Implementation Method 1
recrystallization annealing after a cold rolling step is performed
Implementation Method 2
an average grain size viewed from a plate surface of the copper foil being 10 to 400 μm, which improves deformation transmission and ductility
Data Source
Figure 1
AI summary
A copper foil composite comprising a copper foil and a resin layer laminated, the copper foil containing at least one selected from the group consisting of Sn, Mn, Cr, Zn, Zr, Mg, Ni, Si and Ag at a total of 30 to 500 mass ppm, a tensile strength of the copper foil having of 100 to 180 MPa, a degree of aggregation I200/I0200 of a (100) plane of the copper foil being 30 or more, and an average grain size viewed from a plate surface of the copper foil being 10 to 400 µm.