Copper Foil Composite with Cr Oxide Layer for Formability
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Solution Overview
Problem
Copper foil composites used in flexible printed circuits and electromagnetic shielding materials face issues with severe deformation, leading to potential breakage and compromised corrosion resistance and electric contact properties when subjected to complex deformation modes, such as those encountered in press-forming processes.
Innovation Solution
The solution involves a copper foil composite with a resin layer, where the deformation behavior of the resin layer is transmitted to the copper foil, enhancing ductility and preventing cracking, while a Cr oxide layer and optionally a Ni or Ni alloy layer provide corrosion resistance and stable electric contact properties. The composite is designed to satisfy specific stress and adhesion strength ratios, ensuring the copper foil and resin layer work together under tensile strain, and the Cr oxide layer is applied at a surface not laminated with the resin to enhance corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the copper foil composite is press-formed to achieve complex deformation and tailored product shapes, then formability and adaptability are improved, but the copper foil may break due to severe deformation
Solution Approach 1:
The patent uses a composite structure consisting of a copper foil layer and a resin layer. The resin layer has superior ductility and can undergo complex deformation without breaking, while the copper foil provides electrical conductivity. When the copper foil composite is press-formed, the resin layer absorbs and distributes the deformation stress, preventing the copper foil from breaking while still achieving the desired complex shape.
2Ease of operation
If the copper foil composite is designed for uniaxial flex deformation (MIT/IPC flexibility), then bending properties are improved, but it cannot withstand severe complex deformation modes
Solution Approach 1:
The patent changes the material parameters by selecting a resin layer with specific mechanical properties (high ductility, appropriate stiffness) that differ from traditional flexible circuit board materials. This resin layer can accommodate complex multi-axial deformation modes during press-forming, enabling the copper foil composite to withstand severe deformation while maintaining structural integrity.
3Device complexity
If the copper foil surface is left exposed to achieve simplicity, then manufacturing complexity is reduced, but corrosion resistance and electric contact properties deteriorate
Solution Approach 1:
The patent applies a thin Cr oxide coating layer on the copper foil surface. This thin coating provides excellent corrosion resistance and stable electric contact properties at minimal cost and with simple processing. The Cr oxide layer is thin enough that it does not significantly increase complexity or cost, yet it effectively protects the copper foil from corrosion and ensures reliable electrical contact over long periods.
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 results in a copper foil composite with excellent formability, preventing breakage during complex deformation, maintaining long-term corrosion resistance, and ensuring stable electric contact properties, making it suitable for applications requiring severe forming and three-dimensional molding.
Implementation Method 1
a Cr oxide layer is formed at an coating amount of 5 to 100 μg/dm2 is formed on a surface of the copper foil
Data Source
AI summary
A copper foil composite comprising a copper foil and a resin layer laminated thereon, satisfying an equation 1: (f3×t3)/(f2×t2)=>1 wherein t2 (mm) is a thickness of the copper foil, f2 (MPa) is a stress of the copper foil under tensile strain of 4%, t3 (mm) is a thickness of the resin layer, f3 (MPa) is a stress of the resin layer under tensile strain of 4%, and an equation 2: 1<=33f1/(F×T) wherein f1 (N/mm) is 180° peeling strength between the copper foil and the resin layer, F(MPa) is strength of the copper foil composite under tensile strain of 30%, and T (mm) is a thickness of the copper foil composite, wherein a Cr oxide layer is formed at an coating amount of 5 to 100 μg/dm2. is formed on a surface of the copper foil on which the resin layer is not laminated.