Multilayer Copper Foil Structure for Thinness and Grain Control
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Solution Overview
Problem
Thin electrodeposited copper foils used in electronic circuits and secondary batteries face challenges with mechanical strength due to reduced thickness, necessitating a technique to enhance stability while maintaining control over grain sizes.
Innovation Solution
A multilayer copper foil is manufactured with a recrystallization active layer and a recrystallization suppressing layer alternately stacked to inhibit grain growth, using varying current densities in electroplating to achieve a lamellar structure with high strength and controlled thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of electrodeposited copper foil is reduced to improve degree of integration of secondary battery, then the thickness decreases, but the mechanical strength is weakened and stability deteriorates
Solution Approach 1:
The copper foil is divided into multiple layers with different recrystallization characteristics (recrystallization active layers and recrystallization suppressing layers) stacked alternately. This segmentation allows each layer to contribute differently to the overall structure, enabling thin foil design while maintaining strength through the composite layered architecture.
Solution Approach 2:
The invention uses a composite structure combining copper layers with different recrystallization behaviors. The recrystallization active layers provide ductility and formability, while the recrystallization suppressing layers maintain dimensional stability and prevent excessive grain growth, creating a composite material system that achieves both thinness and high strength.
2Volume of moving object
If thin copper foils are manufactured to improve degree of integration, then the thickness decreases, but grain size control becomes difficult and mechanical properties deteriorate
Solution Approach 1:
Different regions of the copper foil (different layers) are given different local qualities regarding recrystallization behavior. The recrystallization suppressing layers contain higher impurity concentrations or specific microstructures that locally inhibit grain growth, while the active layers allow controlled recrystallization. This local differentiation enables precise grain size control throughout the thin foil structure.
Solution Approach 2:
The invention controls grain size by changing parameters such as impurity concentration, layer thickness ratios, and recrystallization temperatures across different layers. By adjusting these parameters in the recrystallization suppressing layers, the grain growth in the active layers can be effectively controlled even in thin foils, achieving precise microstructural control.
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 multilayer copper foil achieves high strength and small thickness, suitable for secondary battery applications, with the recrystallization suppressing layer effectively inhibiting grain growth and enhancing mechanical properties.
Implementation Method 1
the recrystallization active layer may be formed through electroplating that is performed in a manner that a first external power having a current density value calculatable from a first reaction surface area between the substrate and a plating solution being equal to a predetermined first current density value, is applied to cause electrical conduction in the plating solution
Implementation Method 2
a first external power having a current density value calculatable from a first reaction surface area between the substrate and a plating solution being equal to a predetermined first current density value, is applied to cause electrical conduction in the plating solution
Data Source
AI summary
The multilayer copper foil includes: a recrystallization active layer disposed on a surface of a substrate; and a recrystallization suppressing layer disposed on a surface of the recrystallization active layer to inhibit recrystallization of the recrystallization active layer, wherein a concentration of impurities within the recrystallization suppressing layer is greater than a concentration of impurities within the recrystallization active layer.