PCB Base Material Etching Accuracy via Copper Layer Composition
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Solution Overview
Problem
The existing base materials for printed circuit boards, which use a nickel-chromium alloy layer between the base film and copper layer, face challenges in etching due to the difficulty in etching nickel and chromium, leading to longer etching times and reduced accuracy, making it hard to form fine circuits.
Innovation Solution
A base material with a metal layer primarily composed of copper, where the content of Cr and Ni within 100 nm of the interface is less than 0.1 mg/m2, and an arithmetic mean roughness of the surface is less than 0.10 μm, allowing for easier etching and high accuracy, and incorporating sintered copper particles fixed to the base film, eliminating the need for expensive vacuum equipment and separate etching steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nickel-chromium alloy layer is used between the base film and copper layer, then migration resistance is improved, but etching difficulty increases and etching accuracy deteriorates
Solution Approach 1:
The patent extracts and removes the nickel-chromium alloy layer from the structure, replacing it with a copper-based metal layer having specific compositional characteristics. This eliminates the etching difficulty caused by nickel and chromium while maintaining migration resistance through controlled copper content and composition in the metal layer directly on the base film.
Solution Approach 2:
The patent changes the compositional parameters of the metal layer, specifying that copper content is 80 mass% or more, and controlling the content of Cr and Ni to be 0.01 mg/m2 or less within 100 nm from the interface. This parameter change transforms the material from a nickel-chromium alloy system to a copper-dominated system that is much easier to etch accurately.
2Reliability
If a nickel-chromium alloy layer is used between the base film and copper layer, then migration resistance is improved, but etching time increases
Solution Approach 1:
By removing the nickel-chromium alloy layer and replacing it with a copper-based metal layer, the patent eliminates the need for separate, time-consuming etching steps for nickel and chromium. The simplified composition allows for faster, single-step etching processes while maintaining sufficient migration resistance.
Solution Approach 2:
The compositional parameters are changed to copper-rich (80 mass% or more) with minimal Cr and Ni (0.01 mg/m2 or less within 100 nm from interface), which fundamentally alters the etching characteristics from difficult and time-consuming to easy and rapid, reducing total etching time while preserving migration resistance.
3Reliability
If a nickel-chromium alloy layer is used, then migration resistance is improved, but device complexity increases due to separate etching steps
Solution Approach 1:
The patent extracts the nickel-chromium alloy layer that necessitates complex multi-step etching processes. By removing this layer and using a copper-based metal layer instead, the etching process is simplified to a single step, reducing device complexity in the manufacturing process while maintaining migration resistance through controlled composition.
Solution Approach 2:
The patent merges the functions of migration resistance and etchability into a single copper-based metal layer with controlled composition, eliminating the need for separate etching steps for different materials. This consolidation simplifies the overall etching process from multiple sequential steps to a single unified step.
4Ease of manufacture
If sputtering method is used to form seed layer, then metal layer is formed on base film, but expensive vacuum equipment is required
Solution Approach 1:
The patent replaces the expensive sputtering process with a cost-effective electroless plating method to form the metal layer. This substitution uses inexpensive chemical solutions and standard plating equipment instead of costly vacuum sputtering systems, making the manufacturing process more accessible and economical while achieving the same functional result of forming a copper-based metal layer on the base film.
Solution Approach 2:
The patent substitutes the mechanical/physical sputtering process (requiring vacuum equipment) with a chemical electroless plating process. This replacement eliminates the need for complex vacuum systems and uses chemical reactions in solution to deposit the metal layer, significantly reducing equipment complexity and cost.
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
Enables the formation of fine circuits with high etching accuracy and reduced manufacturing costs by simplifying the etching process and eliminating the need for separate etching of nickel and chromium, while maintaining sufficient migration resistance.
Implementation Method 1
incorporating sintered copper particles fixed to the base film
Data Source
AI summary
According to the present invention, a base material for a printed circuit board includes: an insulating base film; and a metal layer that is layered on at least one surface of the base film and that includes copper as a main component, wherein in a content per unit area in a region of 100 nm or less from an interface of the metal layer with the base film, Cr<0.1 mg/m2, and Ni<0.1 mg/m2, wherein an arithmetic mean roughness (Sa) of the surface of the base film on which the metal layer is layered is less than 0.10 μm.