Method for measuring surface parameter of copper foil, and method for sorting copper foil
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.
1. 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.
2. The method for measuring a surface parameter of copper foil according to claim 1 , wherein, in (d), the filter processing is conducted without using an S filter.
3. The method for measuring a surface parameter of copper foil according to claim 1 , wherein the Sa1 is 0.3 μm or less, and the percent change of Sdr is 70% or less.
4. The method for measuring a surface parameter of copper foil according to claim 1 , wherein the Sa1 is 0.3 μm or less, and the percent change of a value is 70% or less.
5. The method for measuring a surface parameter of copper foil according to claim 1 , wherein, in (b), a second order differential of a surface parameter defined in ISO25178 is calculated to set the cutoff value for the L filter.
6. A method for selecting copper foil, comprising:
measuring a surface parameter of copper foil using the method according to claim 1 , wherein the surface parameter is at least one selected from the group consisting of an arithmetical mean height Sa, a root mean square height Sq, a maximum height Sz, a developed interfacial area ratio Sdr, a core material volume Vmc, and a core height Sk defined by ISO25178; and
selecting, as a copper foil suitable for a printed-wiring board for high frequency application, a copper foil having a surface in which the Sa is 1.2 μm or less, the Sq is 2.5 μm or less, the Sz is 14 μm or less, the Sdr is 60% or less, the Vmc is 1.5 μm 3 or less, and/or the Sk is 4 μm or less.
7. A method for producing a printed-wiring board for high frequency application, comprising the step of producing a printed-wiring board for high frequency application using a copper foil obtained by the method according to claim 6 .
8. The method of claim 1 , wherein the microscope comprises at least one from among: an atomic force microscope, a contact-type surface roughness measuring device, and a non-contact-type surface roughness measuring device.
9. The method of claim 1 , wherein the microscope comprises a laser microscope.
10. The method of claim 1 , wherein the microscope comprises at least one from among a confocal chromatic probe, a phase-shifting interferometric microscope, a coherence scanning interferometer, a point autofocus probe, a focus variation microscope, and a confocal microscope.
11. The method of claim 1 , wherein the microscope comprises a coherence scanning interferometer.