Composite Copper Foil Surface Protrusions for Adhesion
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Solution Overview
Problem
Existing copper foils for printed wiring boards face conflicting requirements of adhesion and surface smoothness, with existing surface treatment methods either enhancing adhesion at the cost of roughness or vice versa, and there is a need for a method that balances these properties effectively.
Innovation Solution
A composite copper foil with protrusions on its surface, formed by oxidizing and then plating a copper foil with a metal like Sn, Ag, or Ni, where the protrusions are 10 nm to 1000 nm in height and the copper content is 80% or less at a depth of 6 nm, and 90% or more without oxygen, achieving a uniform layer with enhanced adhesion and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface of copper foil is roughened by etching to enhance adhesion, then the physical adhesive strength is improved, but the surface smoothness deteriorates
Solution Approach 1:
The copper foil surface is pre-oxidized before plating to create copper oxide protrusions. This preliminary oxidation action prepares the surface topology that will later be selectively plated, allowing the protrusions to serve as adhesion-enhancing features while the overall surface remains relatively smooth for integration requirements
Solution Approach 2:
The plating process is applied selectively to protrude regions rather than uniformly across the entire surface. This creates local metal particle distributions concentrated at protrusion tips and sides, providing enhanced adhesion at critical contact points while maintaining smoother areas in between, thus resolving the contradiction between adhesion needs and surface smoothness requirements
2Shape
If oxidation and reduction steps are used to adjust surface roughness, then the surface roughness is controlled, but the process complexity increases
Solution Approach 1:
The invention extracts and eliminates the reduction step from the conventional oxidation-reduction process. By using only oxidation followed by selective plating, the process complexity is reduced while still achieving the desired surface roughness control and adhesion enhancement, as the plating step alone can selectively deposit metal on oxidized protrusions without requiring a subsequent reduction step
Solution Approach 2:
The oxidation conditions (such as oxidizing agent concentration, temperature, and exposure time) are optimized to control the formation of copper oxide protrusions with specific height ranges (10-1000 nm). By adjusting these oxidation parameters, the surface roughness is controlled to achieve both adhesion enhancement and compatibility with integrated circuit requirements, simplifying the overall process compared to multi-step oxidation-reduction methods
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 composite copper foil achieves a balance of tight adhesion and moderate surface roughness, suitable for printed wiring boards and secondary batteries, with improved heat resistance and peel strength, while maintaining a low surface roughness, thus addressing the conflicting demands of adhesion and smoothness.
Implementation Method 1
immersing it in a chemical solution containing an oxidizing agent to oxidize its surface
Implementation Method 2
immersing the copper foil in a chemical solution containing a reducing agent to reduce the copper oxide to adjust the protrusions and depressions on its surface
Implementation Method 3
a method of forming, by plating, a film having discretely distributed metal particles on the surface of a copper conductor pattern
Data Source
AI summary
[Problem] An object is to provide novel composite copper foils. [Means to solve the problem] A composite copper foil comprises a copper foil and a layer of metal other than copper, the metal layer being formed on at least a part of a surface of the copper foil, wherein at least a part of the composite copper foil has protrusions on a surface thereof, and each protrusion has a height of 10 nm or more but 1000 nm or less in a cross-section of the composite copper foil.