Method for measuring surface parameter of copper foil, and method for sorting copper foil

A method for measuring a surface parameter of copper foil, the method comprising:

• (a) utilizing a microscope to measure a surface profile on a treated surface of a surface-treated copper foil as a reference for setting a filter condition;
• (b) setting a cutoff value for an L filter based on the surface profile, wherein the cutoff value satisfies:
• (i) Sa1, which is an arithmetical mean height Sa after processing with the L filter, being 0.5 μm or less, and
• (ii) a percent change of developed interfacial area ratio Sdr before and after processing with the L filter being 80% or less, the percent change of Sdr being represented by a formula (|Sdr0−Sdr1|/Sdr0)×100, wherein Sdr0 is an Sdr before processing with the L filter, and Sdr1 is an Sdr after processing with the L filter, or
• (ii′) a percent change of a value before and after processing with the L filter being set to be 80% or less, the percent change of a value being represented by a formula (|α0−α1|/α0)×100, wherein α0 is an α value before processing with the L filter, and α1 is an α value after processing with the L filter;
• the α value being obtained by dividing a core material volume Vmc by a core height Sk to obtain a quotient and multiplying the quotient by a developed interfacial area ratio Sdr, that is, obtained by a formula (Vmc/Sk)× Sdr;
• and
• the Sa, the Sdr, the Vmc and the Sk being surface parameters defined by ISO25178;
• (c) utilizing the microscope to measure a surface profile on a treated surface of a surface-treated copper foil as a measurement object, the surface-treated copper foil as the measurement object being produced or treated under the same condition as the surface-treated copper foil as the reference;
• (d) subjecting the acquired surface profile of the surface-treated copper foil as the measurement object to filter processing, the filter processing including processing using an L filter with the cutoff value;
• and
• (e) calculating at least one of surface parameters defined in ISO25178 on the treated surface of the surface-treated copper foil as the measurement object based on the surface profile after the filter processing.