Rolled Copper Foil Crater Control via Base Plating
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Solution Overview
Problem
Conventional rolled copper or copper-alloy foils with roughened surfaces face issues such as crater formation due to inclusions, impaired adhesion with resin, reduced etchability, and inadequate acid resistance, making them unsuitable for fine pattern formation on flexible printed circuit boards.
Innovation Solution
A rolled copper or copper-alloy foil with a roughened surface is treated with a copper base plating layer of 0.15 μm to 0.30 μm thickness and copper fine grains of 0.25 μm to 0.45 μm size, followed by a Co—Ni—Cu fine-grain layer with specific composition, to inhibit crater formation and enhance adhesion, etchability, and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If roughening treatment is performed on electrolytic copper foil to improve adhesion with resin, then adhesive strength is improved, but etchability is significantly impaired causing undercutting
Solution Approach 1:
The patent applies preliminary roughening treatment to create a specific surface profile before etching, controlling the roughness to optimize both adhesion and etchability. The roughening is performed to a controlled extent (not excessive) to prevent undercutting while maintaining adequate adhesive strength
Solution Approach 2:
The patent optimizes the roughness parameters of the copper foil surface, specifically controlling the arithmetic mean roughness (Ra) within a specific range. By adjusting the roughness parameters appropriately, the patent achieves a balance between adhesion improvement and etchability maintenance
2Manufacturing precision
If low profiling treatment is applied to electrolytic copper foil to reduce roughness and control undercutting, then etchability is improved, but adhesion strength with polyimide layer is reduced
Solution Approach 1:
The patent identifies and optimizes the critical roughness parameters (Ra, Rz, etc.) to find the optimal range that provides sufficient adhesion while preventing undercutting. The roughness is controlled within specific numerical ranges to balance both requirements
Solution Approach 2:
The patent applies a moderate level of roughening treatment - not too light to lose adhesion, not too heavy to cause undercutting. The roughening is performed to a precisely controlled extent to achieve the optimal balance
3Strength
If rolled copper-alloy foil is plated with copper to form fine copper grains for roughening, then strength is improved, but crater formation occurs due to inclusions
Solution Approach 1:
The patent performs preliminary cleaning and surface preparation of the rolled copper-alloy foil before copper plating to remove inclusions and contaminants. This preliminary treatment prevents crater formation during the subsequent roughening process
Solution Approach 2:
The patent optimizes the plating parameters including current density, plating time, and solution composition to achieve uniform fine copper grain formation without crater defects. The plating conditions are carefully controlled to ensure high surface quality
4Manufacturing precision
If conventional roughening treatment is applied to achieve fine pattern formation, then etching can be performed, but acid resistance and tin plating solution resistance are reduced
Solution Approach 1:
The patent optimizes the roughness parameters and plating conditions to create a surface structure that provides adequate etchability while maintaining acid resistance. The roughness is controlled within specific ranges to prevent excessive acid attack
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 solution effectively reduces crater formation, improves adhesive strength, acid resistance, and peel strength, while maintaining high glossiness and etchability, making the foil suitable for fine pattern formation on flexible printed circuit boards.
Implementation Method 1
a copper base plating layer is provided between the copper roughened layer and the rolled copper or copper-alloy foil
Implementation Method 2
subjected to roughening treatment with copper fine grains wherein copper fine grains of the copper roughened layer obtained by roughening treatment with the copper fine grains have a size between 0.25 μm and 0.45 μm inclusive
Data Source
AI summary
Provided is a rolled copper or copper-alloy foil having a roughened surface, the rolled copper or copper-alloy foil subjected to roughening treatment with copper fine grains wherein a copper base plating layer is provided between the copper roughened layer and the rolled copper or copper-alloy foil. An object of the present invention is to provide a roughened rolled copper-alloy foil having fewer craters, the presence of which is a serious disadvantage unique to a rolled copper-alloy foil having a roughened surface. In particular, provided is a rolled copper or copper-alloy foil in which the development of craters caused by inclusions present in or near a surface of the base material can be controlled.