Surface-Treated Electrodeposited Copper Foil for Fine Pattern Wiring
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Solution Overview
Problem
Conventional electro-deposited copper foils used in printed wiring boards exhibit defects due to large waviness on the edge of fine pattern wiring, leading to insufficient resolution and performance issues in high-definition applications such as plasma display panels and monitors, where fine pitch wiring is required for high image quality and electromagnetic shielding.
Innovation Solution
A surface-treated electro-deposited copper foil with a bonding surface having a maximum waviness height of 0.05 µm to 0.7 µm, achieved through rust-proofing and/or silane coupling agent treatments, and manufactured using a sulfuric acid base copper electrolytic solution with varying electric current densities and specific additives like quaternary ammonium salt polymers and mercapto compounds, ensuring low surface roughness and improved gloss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electro-deposited copper foil is used, then it provides good electric conductivity and cost-effectiveness, but it exhibits large waviness on the edge of fine pattern wiring leading to insufficient resolution
Solution Approach 1:
The patent applies parameter changes by controlling the surface roughness (Rz) of the bonding surface to be 0.5 μm or less, and specifically controlling the waviness height (Wmax) to be 0.3 μm or less. These precise parameter specifications directly address the waviness problem while maintaining the electro-conductive properties of the copper foil.
Solution Approach 2:
The patent implements preliminary action by providing surface treatment (rust-proofing and/or silane coupling agent treatment) on the copper foil before it is used for fine pattern wiring formation. This pre-treatment ensures that the surface is properly prepared to minimize waviness and improve bonding, preventing the wiring edge defects that would otherwise occur.
2Loss of time
If thinner copper foil is used to reduce over-etching time, then etching factor is improved, but surface roughness control becomes more difficult
Solution Approach 1:
The patent maintains surface roughness (Rz) at 0.5 μm or less on the bonding surface while using thinner copper foil. This parameter control allows for reduced over-etching time because the etching process can be more precisely controlled without causing excessive material removal or surface defects.
Solution Approach 2:
The patent replaces mechanical surface finishing methods with electrochemical deposition control. By controlling the electrolysis conditions and surface treatment parameters, the desired surface roughness is achieved through chemical means rather than mechanical polishing, which is particularly effective for thin foils where mechanical processing would be difficult.
3Productivity
If high density printed wiring board is required for parts mounting, then sharing of mounting area is improved, but fine pattern wiring formation performance deteriorates due to large waviness
Solution Approach 1:
The patent controls the waviness height (Wmax) to be 0.3 μm or less and surface roughness (Rz) to be 0.5 μm or less on the bonding surface. These parameter specifications enable high density parts mounting while maintaining excellent fine pattern wiring formation, as the reduced surface irregularities prevent wiring edge defects even at high densities.
Solution Approach 2:
The patent applies surface treatment (rust-proofing and/or silane coupling agent treatment) before fine pattern wiring formation to prepare the bonding surface. This preliminary treatment ensures that the surface is optimized for both high density mounting and precise wiring formation, preventing the deterioration that would otherwise occur due to waviness.
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 surface-treated copper foil provides excellent fine pattern forming performance, reduced waviness, and enhanced bonding with insulation layers, enabling the production of high-definition printed wiring boards and electromagnetic shielding with improved straight line performance and reduced etching defects.
Implementation Method 1
a method for manufacturing the electro-deposited copper foil by depositing on a cathode surface by an electrolysis method using a sulfuric acid base copper electrolytic solution
Implementation Method 2
continuous first-step electrolysis to n-th-step electrolysis are carried out at two or more different levels of electric current density
Data Source
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AI summary
It is an object to provide a surface-treated electro-deposited copper foil which has a low profile at a level equal to or excellent than that of low-profile surface-treated electro-deposited copper foils that have conventionally been supplied to the market and in which waviness affecting the straight line performance of wiring is small, and a method for manufacturing the same. In order to achieve this object, in the surface-treated electro-deposited copper foil, the maximum waviness height (Wmax) of the bonding surface to be bonded with an insulation layer-constituting material to be 0.05 µm to 0.7 µm, the maximum peak to valley height (PV) to be 0.05 to 1.5 µm, and the surface roughness (Rzjis) to be 0.1 µm to 1.0 µm. The electro-deposited copper foil used for the manufacturing of this surface-treated electro-deposited copper foil is manufactured by using a sulfuric acid base copper electrolytic solution obtained by adding 3-mercapto-1-propanesulfonic acid or bis(3-sulfopropyl)disulfide, a quaternary ammonium salt polymer having a cyclic structure, and chlorine, and using a cathode having small surface roughness, under electrolysis conditions of carrying out continuous first-step electrolysis to n-th-step electrolysis at two or more different levels of electric current density.