Filtered Copper Foil Surface Measurement for High-Frequency Correlation
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Solution Overview
Problem
Conventional methods for measuring surface roughness of copper foil do not adequately correlate with high frequency characteristics, requiring excessive working hours and materials for evaluation.
Innovation Solution
Set a cutoff value for an L filter based on a surface profile of surface-treated copper foil to process it, ensuring Sa1 is 0.5 μm or less and percent change of Sdr or α value is 80% or less, allowing for the calculation of surface parameters with high correlation to high frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods for measuring surface roughness are used, then surface parameters can be obtained, but the correlation with high frequency characteristics is insufficient
Solution Approach 1:
The invention changes the measurement parameters by specifying particular filter cutoff values (L filter: 0.003mm, S filter: 0.5μm or 0.8μm) and measurement area sizes (10μm×10μm to 100μm×100μm) to optimize the correlation between surface roughness parameters and high frequency characteristics. This parameter optimization resolves the contradiction by making the measurement more relevant to actual performance while maintaining technical measurability.
Solution Approach 2:
The invention performs preliminary filtering of the surface profile data using specified L filters and S filters before calculating surface parameters. This preliminary processing action removes irrelevant frequency components and enhances the correlation between measured parameters and high frequency characteristics, thereby resolving the measurement precision issue.
2Measurement precision
If actual evaluation of high frequency characteristics is performed by producing surface-treated copper foil, then accurate high frequency characteristics can be obtained, but excessive working hours and materials are required
Solution Approach 1:
The invention creates a simplified measurement model that copies the essential features of actual high frequency performance evaluation through surface parameter measurement. By measuring surface roughness with optimized parameters and filtering, the invention obtains a proxy indicator that correlates with high frequency characteristics without requiring actual production and testing of copper foil samples, thus dramatically reducing time and material consumption.
Solution Approach 2:
The invention replaces the mechanical process of producing and physically testing copper foil samples with a non-contact optical measurement system (laser microscope) that measures surface topography. This substitution eliminates the need for actual production and high frequency testing, reducing evaluation time from days to minutes while maintaining measurement precision through optimized measurement parameters.
3Strength
If surface treatment is applied to increase adhesiveness, then adhesive strength improves, but surface roughness increases which may deteriorate high frequency characteristics
Solution Approach 1:
The invention applies different evaluation criteria to different aspects of surface quality: for adhesiveness, it evaluates overall surface roughness parameters (Sa, Sq, Sz), while for high frequency characteristics, it evaluates filtered surface parameters that exclude certain wavelength components. This local differentiation of quality assessment allows understanding of how different surface features affect different performance aspects.
Solution Approach 2:
The invention introduces dynamic filtering with adjustable cutoff values that can adapt to different surface treatment conditions and frequency requirements. By dynamically selecting appropriate L filter and S filter cutoff values, the evaluation system can balance the trade-off between adhesiveness (requiring rougher surfaces) and high frequency performance (requiring smoother surfaces at certain scales).
Data Source
AI summary
A measurement method capable of acquiring, in a simple manner, a surface parameter of copper foil exhibiting high correlation with high frequency characteristics, the method including: (a) acquiring a surface profile of surface-treated copper foil as a reference; (b) setting a cutoff value for an L filter, the cutoff value satisfies: (i) an arithmetical mean height Sa after processing with the L filter, being 0.5 μm or less, and (ii) a percent change of Sdr or α value after processing with the L filter being 80% or less; (c) acquiring a surface profile of surface-treated copper foil as a measurement object; (d) subjecting the acquired surface profile of the copper foil as the measurement object to filter processing; and (e) calculating at least one of surface parameters defined in ISO25178 on the copper foil as the measurement object based on the surface profile after the filter processing.