CN117441039A

CN117441039A - Roughened copper foil, copper-clad laminate and printed circuit board

Info

Publication number: CN117441039A
Application number: CN202280039573.8A
Authority: CN
Inventors: 加藤翼; 立冈步; 杨博钧; 川口彰太
Original assignee: Mitsui Mining and Smelting Co Ltd
Current assignee: Mitsui Mining and Smelting Co Ltd
Priority date: 2021-06-03
Filing date: 2022-06-01
Publication date: 2024-01-23

Abstract

Provided is a roughened copper foil which has excellent transfer characteristics and circuit linearity and can achieve high peel strength when used in a copper-clad laminate and/or a printed circuit board. The roughened copper foil has a roughened surface on at least one side. The ratio Rdc/Rku of the cross-sectional height difference Rdc of the roughness curve of the roughened surface to the kurtosis Rku of the roughness curve is 0.180 μm or less, and the maximum cross-sectional height Wt of the waviness curve is 2.50 μm or more and 10.00 μm or less. Rku and Wt are values measured in accordance with JIS B0601-2013, and Rdc is a value obtained as a difference in height c of a cross section in a height direction between a load length ratio of 20% and a load length ratio of 80% in accordance with JIS B0601-2013.

Description

Roughened copper foil, copper-clad laminate and printed circuit board

Technical Field

The present invention relates to roughened copper foil, copper-clad laminate and printed circuit board.

Background

In the process of manufacturing a printed wiring board, copper foil is widely used in the form of a copper-clad laminate laminated with an insulating resin base material. In this regard, in order to prevent peeling of the wiring from occurring at the time of manufacturing the printed circuit board, it is desirable to have a high adhesion force between the copper foil and the insulating resin base material. Therefore, in a copper foil for manufacturing a general printed circuit board, roughness is formed on the surface of the copper foil to be bonded, and the roughness is bitten into the inside of the insulating resin base material by press working to exert an anchor effect, thereby improving adhesion.

As a copper foil subjected to such roughening treatment, for example, patent document 1 (japanese unexamined patent publication No. 2018-172785) discloses a surface-treated copper foil having a copper foil and a roughening treatment layer on at least one surface of the copper foil, wherein the arithmetic average roughness Ra of the roughening treatment layer side surface is 0.08 μm or more and 0.20 μm or less, and the glossiness of the roughening treatment layer side surface in the TD (width direction) is 70% or less. According to such a surface-treated copper foil, the occurrence of wrinkles and streaks when the surface-treated copper foil is bonded to an insulating substrate can be favorably suppressed while the falling-off of roughened particles provided on the surface of the copper foil is favorably suppressed.

However, with the recent increase in functionality of portable electronic devices and the like, in order to process large-capacity data at high speed, there is a demand for printed circuit boards suitable for high-frequency applications, in which high frequencies of signals are being developed, regardless of whether digital signals or analog signals are being processed. In such a high-frequency printed circuit board, it is desirable to reduce transmission loss in order to enable transmission of high-frequency signals without degradation. The printed wiring board includes a copper foil processed into a wiring pattern and an insulating base material, but as a main loss among transmission losses, there are a conductor loss due to the copper foil and a dielectric loss due to the insulating base material.

In this regard, a roughened copper foil realizing reduction of transmission loss is proposed. For example, patent document 2 (japanese patent application laid-open No. 2015-148011) discloses a surface-treated copper foil having a small signal transmission loss, a laminate using the surface-treated copper foil, and the like, in which the degree of deviation Rsk according to JIS B0601-2001 on the surface of the copper foil is controlled to be in a predetermined range of-0.35 or more and 0.53 or less by surface treatment.

Prior art literature

Patent literature

Patent document 1 Japanese patent application laid-open No. 2018-172785

Patent document 2 Japanese patent application laid-open No. 2015-148011

Disclosure of Invention

As described above, in recent years, improvement of the transmission characteristics (high frequency characteristics) of printed circuit boards has been demanded. In order to meet such a demand, attempts have been made to roughen the surface of the copper foil to be bonded to the insulating resin base material more finely. That is, in order to reduce irregularities on the surface of the copper foil, which is a factor of increasing transmission loss, it is considered to subject the surface of the copper foil having a small waviness (for example, the surface of a double-sided smooth foil, and electrode surfaces of an electrolytic copper foil) to fine roughening treatment. Further, it is considered that the use of the roughened copper foil having a small waviness improves the linearity of the wiring pattern (hereinafter referred to as circuit linearity) at the time of forming the circuit. However, when such roughened copper foil is used for processing a copper-clad laminate and/or manufacturing a printed wiring board, there generally occurs a problem that the peel strength between the copper foil and the base material is low and the adhesion reliability is poor.

The inventors have now obtained the following insight: the roughened copper foil surface is excellent in transfer characteristics and circuit linearity and can realize high peel strength by controlling the ratio Rdc/Rku of the cross-sectional height difference Rdc to the kurtosis Rku and the maximum cross-sectional height Wt within predetermined ranges, and a copper-clad laminate and/or a printed wiring board manufactured using the roughened copper foil surface.

Accordingly, an object of the present invention is to provide a roughened copper foil which is excellent in transfer characteristics and circuit linearity and can achieve high peel strength when used in a copper-clad laminate and/or a printed circuit board.

According to the present invention, the following manner is provided.

Mode 1

A roughened copper foil having a roughened surface on at least one side,

the ratio Rdc/Rku of the cross-sectional height difference Rdc of the roughness curve of the roughened surface to the kurtosis Rku of the roughness curve is 0.180 μm or less, and the maximum cross-sectional height Wt of the waviness curve is 2.50 μm or more and 10.00 μm or less,

the Rku is a value measured according to JIS B0601-2013 under the conditions that the magnification is 200 times, the cutoff wavelength based on the cutoff value λs is 0.3 μm and the cutoff wavelength based on the cutoff value λc is 5 μm,

The Rdc is a value obtained as a difference (c (Rmr 1) -c (Rmr 2)) in a height direction section height c between a load length ratio (Rmr 1) 20% and a load length ratio (Rmr 2) 80% in a roughness curve measured according to JIS B0601-2013 under a condition that the multiplying power is 200 times, the cutoff wavelength based on the cutoff value λs is 0.3 μm and the cutoff wavelength based on the cutoff value λc is 5 μm,

the Wt is a value measured under the conditions that the magnification is 20 times, the cutoff wavelength based on the cutoff value λc is 5 μm, and the cutoff based on the cutoff value λf is not performed in accordance with JIS B0601-2013.

Mode 2

The roughened copper foil according to embodiment 1, wherein the maximum cross-sectional height Wt of the roughened surface is 2.90 μm or more and 10.00 μm or less.

Mode 3

The roughened copper foil according to embodiment 1 or 2, wherein the cross-sectional height difference Rdc of the roughened surface is 0.45 μm or less.

Mode 4

The roughened copper foil according to any one of modes 1 to 3, wherein the maximum peak height Wp of the waviness curve of the roughened surface is 1.00 μm or more and 6.00 μm or less, the Wp being a value measured under conditions that the magnification is 20 times, the cutoff wavelength based on the cutoff value λc is 5 μm, and the cutoff based on the cutoff value λf is not performed according to JIS B0601-2013.

Mode 5

The roughened copper foil according to any one of aspects 1 to 4, wherein the roughness curve element of the roughened surface has an average height Rc of 0.70 μm or less, the Rc being a value measured according to JIS B0601-2013 under conditions of a magnification of 200 times, a cutoff wavelength of 0.3 μm based on a cutoff value λs, and a cutoff wavelength of 5 μm based on a cutoff value λc.

Mode 6

The roughened copper foil according to any one of modes 1 to 5, wherein a cross-sectional height difference Wdc of the roughened surface in a height direction of a waviness curve obtained as a difference (c (Wmr 1) -c (Wmr 2)) between 20% of a load length ratio (Wmr 1) and 80% of a load length ratio (Wmr 2) in the waviness curve measured under conditions that the magnification is 20 times, a cutoff wavelength based on a cutoff value λc is 5 μm, and the cutoff based on the cutoff value λf is not performed in accordance with JIS B0601-2013 is 1.20 μm or more and 3.10 μm or less.

Mode 7

The roughened copper foil according to any one of aspects 1 to 6, wherein the roughness profile of the roughened surface has a root mean square height Rq of 0.290 μm or less, the Rq being a value measured according to JIS B0601-2013 under conditions of a magnification of 200 times, a cutoff wavelength of 0.3 μm based on a cutoff value λs, and a cutoff wavelength of 5 μm based on a cutoff value λc.

Mode 8

The roughened copper foil according to any one of aspects 1 to 7, wherein the kurtosis Rku of the roughened surface is 1.30 or more and 8.00 or less.

Mode 9

The roughened copper foil according to any one of aspects 1 to 8, which comprises a rust-preventive treatment layer and/or a silane coupling agent treatment layer on the roughened surface.

Mode 10

The roughened copper foil according to any one of aspects 1 to 9, wherein the roughened copper foil is an electrolytic copper foil, and the roughened surface is present on the deposition surface side of the electrolytic copper foil.

Mode 11

A copper-clad laminate comprising the roughened copper foil according to any one of modes 1 to 10.

Mode 12

A printed wiring board comprising the roughened copper foil according to any one of modes 1 to 10.

Drawings

Fig. 1 is a diagram for explaining a load curve of a roughness curve determined in accordance with JIS B0601-2013.

Fig. 2 is a diagram for explaining a load length ratio Rmr (c) determined in accordance with JIS B0601-2013.

Fig. 3 is a diagram for explaining a cross-sectional height difference Rdc determined in accordance with JIS B0601-2013.

Fig. 4 is a view for explaining that the surface irregularities of the roughened copper foil contain a roughening particle component and a waviness component.

Fig. 5 is a schematic view showing an example of the roughened copper foil of the present invention.

Detailed Description

Definition of the definition

The following illustrates definitions of terms and/or parameters used to define the invention.

In the present specification, the "load curve of roughness curve" is a curve determined in accordance with JIS B0601-2013, representing the proportion of solid portions occurring when the roughness curve is cut at the section height c as a function of c, as shown in fig. 1. That is, the load curve of the roughness curve can be said to be a curve representing the height of the load length ratio Rmr (c) from 0% to 100%. The load length ratio Rmr (c) is a parameter indicating the ratio of the load length of the roughness curve element at the section height c to the evaluation length, which is determined in accordance with JIS B0601-2013, as shown in fig. 2.

In the present specification, the "cross-sectional height difference Rdc of the roughness curve", "cross-sectional height difference Rdc", or "Rdc" is a parameter indicating the difference (c (Rmr 1) -c (Rmr 2)) in the height direction between 2 load length ratios Rmr1 and Rmr2 (where Rmr1 < Rmr 2) in the load curve of the roughness curve measured in accordance with JIS B0601-2013, as shown in fig. 3. In this specification, rdc is calculated by designating Rmr1 as 20% and Rmr2 as 80%.

In the present specification, "root mean square height Rq of roughness curve", "root mean square height Rq", or "Rq" is a parameter indicating the root mean square of the roughness curve at an arbitrary position x at a reference length Z (x) measured in accordance with JIS B0601-2013.

In the present specification, "kurtosis Rku", or "Rku" of the roughness curve is a parameter indicating the fourth-order root of Z (x) at a reference length nondimensionized from the fourth-order root mean square height Rq, measured in accordance with JIS B0601-2013. Rku refers to sharpness as a measure of surface sharpness, representing sharp corners (sharpness) of a height distribution. Rku=3 means that the height distribution is normal, and Rku > 3 means that the height distribution is sharp, and Rku < 3 means that the height distribution is flattened.

In the present specification, "Rdc/Rku" is a parameter indicating a ratio of the cross-sectional height difference Rdc to the kurtosis Rku.

In the present specification, "average height Rc" or "Rc" of the roughness curve elements is a parameter indicating the average of the heights of the roughness curve elements at the reference length measured in accordance with JIS B0601-2013. The roughness curve element refers to a set of adjacent peaks and valleys in the roughness curve. Among peaks and/or valleys constituting the roughness curve elements, a minimum height and a minimum length are defined, and the height is 10% or less of the maximum height Rz or 1% or less of the reference length, and the peaks and/or valleys are considered as noise, and are considered as a part of the successive valleys and/or peaks.

In the present specification, "maximum cross-sectional height Wt", or "Wt" of the waviness profile is a parameter indicating the sum of the maximum value of the peak height and the maximum value of the valley depth of the waviness profile under the evaluation length measured in accordance with JIS B0601-2013.

In the present specification, "maximum peak height Wp", or "Wp" of the waviness curve is a parameter indicating the maximum value of the peak height of the waviness curve at the reference length measured in accordance with JIS B0601-2013.

In the present specification, the "load curve of the waviness curve" is a curve determined in accordance with JIS B0601-2013, which represents the proportion of the solid portion occurring when the waviness curve is cut at the section height c as a function of c. That is, the load curve of the waviness curve can be said to be a curve representing the height of the load length ratio Wmr (c) from 0% to 100%. The load length ratio Wmr (c) is a parameter indicating the ratio of the load length to the evaluation length of the waviness curve element at the section height c, which is determined in accordance with JIS B0601-2013.

In the present specification, "the cross-sectional height difference Wdc of the waviness profile", "the cross-sectional height difference Wdc", or "Wdc" is a parameter indicating the difference (c (Wmr 1) -c (Wmr)) in the height direction of the cross-sectional height c between 2 load length ratios Wmr1 and Wmr2 (where Wmr1 < Wmr) in the load profile of the waviness profile, measured in accordance with JIS B0601-2013. In this specification, pdc was calculated by designating Wmr1 as 20% and Wmr2 as 80%.

Rdc, rq, rku, rc, wt, wp and Wdc can be calculated by measuring the surface profile of a predetermined measurement length on the roughened surface by a commercially available laser microscope. In the present specification, rdc, rq, rku and Rc as roughness parameters are measured under the conditions that the magnification is 200 times, the cutoff wavelength based on the cutoff value λs is 0.3 μm, and the cutoff wavelength based on the cutoff value λc is 5 μm. In addition, the reference length and the evaluation length used in the calculation of the roughness parameters were 5 μm and 25 μm, respectively. On the other hand, wt, wp, and Wdc as waviness parameters were measured under the conditions that the magnification was 20 times, the cutoff wavelength based on the cutoff value λc was 5 μm, and the cutoff based on the cutoff value λf was not performed. The reference length and the evaluation length used for calculation of the waviness parameter are the same as the measured length of the roughened surface. In the examples described later, the waviness parameters were measured in the region of 643.973 μm in the longitudinal direction and 643.393 μm in the transverse direction on the roughened surface, but the reference length and the evaluation length in this case were 643.973 μm in the longitudinal direction and 643.393 μm in the transverse direction. When both the objective lens and the optical zoom are used in the measurement by the laser microscope, the above-mentioned magnification corresponds to a value obtained by multiplying the magnification of the objective lens by the magnification of the optical zoom. For example, in the case where the objective magnification is 100 times and the optical zoom magnification is 2 times, the magnification is 200 times (=100×2). In addition, preferable measurement conditions and analysis conditions concerning the surface profile by a laser microscope are shown in examples described later.

In the present specification, the "electrode surface" of the electrolytic copper foil means a surface on a side contacting with a cathode in the production of the electrolytic copper foil.

In the present specification, the "deposition surface" of the electrolytic copper foil means a surface on the deposition side of the electrolytic copper, that is, a surface on the side not in contact with the cathode in the production of the electrolytic copper foil.

Roughened copper foil

The copper foil of the present invention is a roughened copper foil. The roughened copper foil has a roughened surface on at least one side. The ratio Rdc/Rku of the cross-sectional height difference Rdc of the roughness curve of the roughened surface to the kurtosis Rku of the roughness curve is 0.180 μm or less. The maximum section height Wt of the waviness curve of the roughened surface is 2.50 μm or more and 10.00 μm or less. As can be seen from this, by controlling Rdc/Rku and maximum cross-sectional height Wt to predetermined ranges on the surface of the roughened copper foil, the copper-clad laminate and/or printed wiring board manufactured using the same is excellent in transmission characteristics (high frequency characteristics) and circuit linearity, and can realize high peel strength.

It is originally difficult to achieve both excellent transfer characteristics and high peel strength, and also excellent circuit linearity and high peel strength. This is because: in order to improve the transfer characteristics and/or the circuit linearity, it is required to reduce the irregularities on the surface of the copper foil, and to obtain high peel strength, it is required to increase the irregularities on the surface of the copper foil, both of which are in a relationship of cancellation (trade off). As shown in fig. 4, the irregularities on the surface of the roughened copper foil include a "roughened particle component" and a "waviness component" having a longer period than the roughened particle component. In general, in order to improve the transfer characteristics and/or the circuit linearity, it is considered to form small roughened particles by performing fine roughening treatment on the surface of a copper foil having a small waviness (for example, the surface of a double-sided smooth foil or the electrode surface of an electrolytic copper foil), but when a copper-clad laminate and/or a printed wiring board is manufactured using such roughened copper foil, the peel strength between the copper foil and the substrate is generally lowered.

In order to solve this problem, the inventors studied the influence of the roughness particles and waviness on the surface of the copper foil on the transmission characteristics, the circuit linearity and the peel strength. As a result, it was found that the waviness component of the copper foil was not liable to affect the transmission characteristics, and that the size of the roughened particles was mainly liable to affect the transmission characteristics. The inventors have found that the protrusion (roughened particle) is made finer for improving the transmission characteristics, and insufficient adhesion is compensated by the waviness of the copper foil having a small influence on the transmission characteristics, thereby achieving both excellent transmission characteristics and adhesion reliability due to high peel strength. In addition, it has been found that by controlling the waviness of the copper foil within a predetermined range, excellent circuit linearity and high peel strength can be achieved in a balanced manner. Specifically, it was found that the shape of minute projections (roughened particles) affecting the transmission characteristics can be accurately reflected by using Rdc/Rku obtained by dividing the cross-sectional height difference Rdc by the kurtosis Rku, and that excellent transmission characteristics can be achieved by controlling Rdc/Rku to 0.180 μm or less. Further, it was found that the maximum cross-sectional height Wt can accurately reflect the waviness component on a wide range of roughened surfaces, and that by setting this Wt to 2.50 μm or more and 10.00 μm or less, it was also found that the circuit linearity was excellent and that the waviness of the copper foil was used to achieve high peel strength between copper foil and substrate.

The roughened particle component and waviness component of the copper foil surface affecting the transmission characteristics, circuit linearity or peel strength can be distinguished by distinguishing the measurement magnification using a laser microscope, and the cut-off values λs, λc and λf. Specifically, by measuring the roughened surface at a high magnification of 200 times, fine irregularities of the roughened surface affecting the transfer characteristics can be accurately evaluated. Further, by using a roughness curve obtained by measuring the roughened surface under the condition that the cutoff wavelength is 0.3 μm based on the cutoff value λs and the cutoff wavelength is 5 μm based on the cutoff value λc, it is possible to calculate a roughness parameter in which the influence of the waviness component is suppressed. Therefore, it can be said that the roughness parameters Rdc, rku, rdc/Rku, rc and Rq in the present invention are parameters that accurately reflect the roughened particle components on the copper foil surface, and by using these indices, the transmission characteristics can be accurately evaluated. In contrast, by measuring the roughened surface at a low magnification of 20 times, the height (waviness) of the entire roughened surface, which affects the linearity and adhesion reliability of the circuit, can be widely evaluated. Further, by using a waviness curve obtained by measuring the roughened surface under the conditions that the cutoff wavelength is 5 μm based on the cutoff value λc and the cutoff is not performed based on the cutoff value λf, it is possible to obtain a waviness parameter in which the influence of the roughened particle component is suppressed. Therefore, the waviness parameters Wt, wp, and Wdc in the present invention can be said to be parameters that appropriately reflect the waviness components on the copper foil surface, and by using these indices, the circuit linearity and peel strength can be accurately evaluated.

The maximum cross-sectional height Wt of the waviness curve of the roughened surface of the roughened copper foil is 2.50 μm or more and 10.00 μm or less, preferably 2.90 μm or more and 10.00 μm or less, more preferably 3.10 μm or more and 9.00 μm or less, still more preferably 3.30 μm or more and 7.00 μm or less. When Wt is within the above range, excellent circuit linearity and high peel strength can be achieved in a balanced manner while ensuring excellent transfer characteristics.

The Rdc/Rku of the roughened surface of the roughened copper foil is 0.180 μm or less, preferably 0.015 μm or more and 0.150 μm or less, more preferably 0.030 μm or more and 0.110 μm or less, and still more preferably 0.045 μm or more and 0.080 μm or less. When Rdc/Rku is within the above range, excellent transfer characteristics can be achieved while achieving excellent circuit linearity and high peel strength.

The cross-sectional height difference Rdc of the roughened surface of the roughened copper foil is preferably 0.45 μm or less, more preferably 0.04 μm or more and 0.40 μm or less, still more preferably 0.08 μm or more and 0.35 μm or less, particularly preferably 0.12 μm or more and 0.30 μm or less. When Rdc is in the above range, rdc/Rku is easily controlled in the above range, and more excellent transmission characteristics can be achieved.

The kurtosis Rku of the roughness curve of the roughened surface of the roughened copper foil is preferably 1.30 to 8.00, more preferably 1.50 to 5.50, even more preferably 2.00 to 4.50, and particularly preferably 2.50 to 3.20. When Rku is within the above range, rdc/Rku can be easily controlled within the above range, and more excellent transmission characteristics can be realized.

The maximum peak height Wp of the waviness curve of the roughened surface of the roughened copper foil is preferably 1.00 μm or more and 6.00 μm or less, more preferably 1.20 μm or more and 5.00 μm or less, still more preferably 1.30 μm or more and 4.30 μm or less, and particularly preferably 1.40 μm or more and 3.70 μm or less. When Wp is within the above range, excellent circuit linearity and high peel strength can be achieved more uniformly while ensuring excellent transfer characteristics.

The average height Rc of the roughness curve elements of the roughened surface of the roughened copper foil is preferably 0.70 μm or less, more preferably 0.06 μm or more and 0.60 μm or less, still more preferably 0.12 μm or more and 0.50 μm or less, and particularly preferably 0.18 μm or more and 0.50 μm or less. When Rc is in the above range, more excellent transfer characteristics can be achieved while achieving excellent circuit linearity and high peel strength.

The cross-sectional height difference Wdc of the roughened surface of the roughened copper foil is preferably 1.20 μm or more and 3.10 μm or less, more preferably 1.20 μm or more and 2.70 μm or less, still more preferably 1.30 μm or more and 2.30 μm or less, and particularly preferably 1.60 μm or more and 2.00 μm or less. When Wdc is within the above range, excellent circuit linearity and high peel strength can be achieved more uniformly while ensuring excellent transmission characteristics.

The root mean square height Rq of the roughness curve of the roughened surface of the roughened copper foil is preferably 0.290 μm or less, more preferably 0.030 μm or more and 0.260 μm or less, still more preferably 0.060 μm or more and 0.220 μm or less, particularly preferably 0.090 μm or more and 0.200 μm or less. When Rq is in the above range, more excellent transfer characteristics can be achieved while achieving excellent circuit linearity and high peel strength.

The thickness of the roughened copper foil is not particularly limited, but is preferably 0.1 μm or more and 210 μm or less, more preferably 0.3 μm or more and 105 μm or less, still more preferably 7 μm or more and 70 μm or less, and particularly preferably 9 μm or more and 35 μm or less. The roughened copper foil of the present invention is not limited to the surface roughening treatment of a normal copper foil, and may be the surface roughening treatment and/or fine roughening treatment of a copper foil with a carrier copper foil.

Fig. 5 shows an example of the roughened copper foil of the present invention. As shown in fig. 5, the roughened copper foil of the present invention can be preferably produced by roughening the surface of a copper foil having a predetermined waviness (e.g., the deposition surface of an electrolytic copper foil) under a desired low roughening condition to form fine roughened particles. Therefore, according to a preferred embodiment of the present invention, the roughened copper foil is an electrolytic copper foil, and the roughened surface is present on the deposition surface side of the electrolytic copper foil. The roughened copper foil may be a copper foil having roughened surfaces on both sides, or may be a copper foil having roughened surfaces on only one side. The roughened surface is typically provided with a plurality of roughened particles, which are preferably each formed from copper particles. The copper particles may be formed of metallic copper or a copper alloy.

The roughening treatment for forming the roughened surface may be more preferably performed by forming roughened particles on the copper foil with copper or a copper alloy. The copper foil before roughening treatment may be a copper foil without roughening treatment or a copper foil subjected to pre-roughening treatment. The surface of the roughened copper foil preferably has a ten-point average roughness Rz of 1.30 μm or more and 10.00 μm or less, more preferably 1.50 μm or more and 8.00 μm or less, as measured in accordance with JIS B0601-1994. Within the above range, the roughened surface is easily given with the surface profile required for the roughened copper foil of the present invention.

The roughening treatment is preferably performed in a copper sulfate solution containing, for example, copper in a concentration of 7g/L to 17g/L inclusive, sulfuric acid in a concentration of 50g/L to 200g/L inclusive, at a temperature of 20 ℃ to 40 ℃ inclusive, at a concentration of 10A/dm inclusive ² Above and 50A/dm ² Electrolytic deposition was performed as follows. The electrolytic deposition is preferably performed for 0.5 seconds to 30 seconds, more preferably for 1 second to 30 seconds, and still more preferably for 1 second to 3 seconds. Of course, the roughened copper foil according to the present invention is not limited to the above method, and can be produced by any method。

In the electrolytic deposition, the following formula is shown:

R _L ＝L/D _C

(wherein R is _L The liquid resistance index (mm.L/mol), L is the distance (mm) between electrodes (anode and cathode), D _C Density of charge carrier (mol/L)

Defined liquid resistance index R _L Preferably 9.0 mm.L/mol or more and 20.0 mm.L/mol or less, more preferably 11.0 mm.L/mol or more and 17.0 mm.L/mol or less. It can be seen that by increasing R _L The voltage of the whole system becomes large, and the voltage at the time of the bump formation reaction becomes large. This affects the shape of the protrusions, and as a result, it is possible to preferably form the protrusions suitable for imparting the shape of the surface profile required for the roughened copper foil of the present invention. The charge carrier density D _C The product of the individual ion concentrations and the valence numbers of all ions present in the plating solution can be summed up. For example, in the case of using a copper sulfate solution as the plating solution, the charge carrier density D _C Calculated by the following equation.

Dc＝[H ⁺ ]×1+[Cu ²⁺ ]×2+[SO ₄ ^2- ]×2

(wherein, [ H ] ⁺ ]Is the concentration (mol/L) of hydrogen ions in the solution, [ Cu ] ²⁺ ]Is the concentration (mol/L) of copper ions in the solution, [ SO ] ₄ ^2- ]Concentration of sulfate ion in solution (mol/L)

To liquid resistance index R _L The relationship with voltage is explained as follows. First, the following equation is derived from ohm's law.

V＝ρ×L×I/S

(where V is the voltage, ρ is the resistivity, L is the inter-electrode distance, I is the current, and S is the cross-sectional area of the inter-electrode).

That is, the voltage V is proportional to the resistivity ρ, the inter-electrode distance L, and the current density (=i/S). And the resistivity ρ and the charge carrier density D _C Inversely proportional. Therefore, when the current density is constant, the current density is increased (proportional to the inter-electrode distance L, and proportional to the charge carrier density D _C Inversely proportional toAnd the liquid resistance index, the voltage also becomes large. Therefore, it can be said that the liquid resistance index is an index related to the resistance of the solution.

If desired, the roughened copper foil may be subjected to an anti-rust treatment to form an anti-rust treatment layer. The rust inhibitive treatment preferably includes a plating treatment using zinc. The plating treatment using zinc may be any one of a zinc plating treatment and a zinc alloy plating treatment, and the zinc alloy plating treatment is particularly preferably a zinc-nickel alloy treatment. The zinc-nickel alloy may be a plating treatment containing at least Ni and Zn, and may further contain other elements such as Sn, cr, co, mo. For example, when the rust inhibitive treatment layer further contains Mo in addition to Ni and Zn, the treated surface of the roughened copper foil is more excellent in adhesion to resin, chemical resistance and heat resistance, and is less likely to have etching residues.

The ratio of the Ni adhering amount to the total amount of Zn adhering amount and Ni adhering amount, i.e., ni/(zn+ni), in the zinc-nickel alloy plating is preferably 0.3 or more and 0.9 or less, more preferably 0.4 or more and 0.9 or less, and still more preferably 0.4 or more and 0.8 or less in terms of mass ratio. In addition, the total adhesion amount of Zn and Ni in the zinc-nickel alloy plating is preferably 8mg/m ² 160mg/m of the above ² Hereinafter, it is more preferably 13mg/m ² 130mg/m of the above ² Hereinafter, it is more preferably 19mg/m ² 80mg/m of the above ² The following is given. On the other hand, the ratio of Ni/(zn+ni+mo), which is the ratio of the Ni adhering amount to the total amount of Zn adhering amount, ni adhering amount and Mo adhering amount, in the zinc-nickel-molybdenum alloy plating is preferably 0.20 or more and 0.80 or less, more preferably 0.25 or more and 0.75 or less, and still more preferably 0.30 or more and 0.65 or less in terms of mass ratio. In addition, the total adhesion amount of Zn, ni and Mo in the zinc-nickel-molybdenum alloy plating is preferably 10mg/m ² 200mg/m of the above ² Hereinafter, it is more preferably 15mg/m ² Above 150mg/m ² Hereinafter, it is more preferably 20mg/m ² Above and 90mg/m ² The following is given. The respective adhesion amounts of Zn, ni and Mo may be determined by dissolving a prescribed area (for example, 25cm ² ) The concentration of each element in the solution obtained by the ICP emission spectrometry was calculated 。

The rust inhibitive treatment preferably further comprises a chromate treatment, and the chromate treatment is more preferably performed on the surface of the zinc-containing plating layer after the plating treatment using zinc. Thus, rust inhibitive performance can be further improved. Particularly preferred rust inhibitive treatments are zinc-nickel alloy plating treatments (or zinc-nickel-molybdenum alloy plating treatments) and combinations of chromate treatments thereafter.

If desired, the roughened copper foil may be subjected to a silane coupling agent treatment on the surface to form a silane coupling agent layer. This can improve moisture resistance, chemical resistance, adhesion to adhesives, and the like. The silane coupling agent layer can be formed by coating and drying a silane coupling agent by appropriately diluting the agent. Examples of the silane coupling agent include epoxy functional silane coupling agents such as 4-glycidyl butyl trimethoxysilane and 3-glycidoxypropyl trimethoxysilane; or amino-functional silane coupling agents such as 3-aminopropyl triethoxysilane, N- (2-aminoethyl) -3-aminopropyl trimethoxysilane, N-3- (4- (3-aminopropoxy) butoxy) propyl-3-aminopropyl trimethoxysilane, and N-phenyl-3-aminopropyl trimethoxysilane; or mercapto-functional silane coupling agents such as 3-mercaptopropyl trimethoxy silane or olefin-functional silane coupling agents such as vinyl trimethoxy silane and vinyl phenyl trimethoxy silane; or an acryl-functional silane coupling agent such as 3-methacryloxypropyl trimethoxysilane and 3-acryloxypropyl trimethoxysilane; or imidazole functional silane coupling agents such as imidazole silane; or a triazine functional silane coupling agent such as a triazine silane.

For the above reasons, the roughened copper foil is preferably further provided with an anti-rust treatment layer and/or a silane coupling agent layer on the roughened surface, and more preferably with both an anti-rust treatment layer and a silane coupling agent layer. In the case where the roughened surface is formed with the rust inhibitive treatment layer and/or the silane coupling agent treatment layer, the respective values of the roughness parameter and the waviness parameter in the present specification refer to values obtained by measuring the surface of the roughened copper foil after the formation of the rust inhibitive treatment layer and/or the silane coupling agent treatment layer. The rust inhibitive treatment layer and the silane coupling agent layer may be formed not only on the roughened surface side of the roughened copper foil but also on the side where the roughened surface is not formed.

Copper-clad laminate

The roughened copper foil of the present invention is preferably used for producing a copper-clad laminate for a printed wiring board. That is, according to a preferred embodiment of the present invention, there is provided a copper-clad laminate provided with the roughened copper foil. The use of the roughened copper foil of the present invention enables both excellent transfer characteristics and high peel strength to be achieved in the copper-clad laminate. The copper-clad laminate is provided with: the roughened copper foil of the present invention, and a resin layer provided in close contact with the roughened surface of the roughened copper foil. The roughened copper foil may be provided on one side or both sides of the resin layer. The resin layer contains a resin, preferably an insulating resin. The resin layer is preferably a prepreg and/or a resin sheet. The prepreg is a generic term for a composite material in which a base material such as a synthetic resin sheet, a glass woven fabric, a glass nonwoven fabric, or paper is impregnated with a synthetic resin. Preferable examples of the insulating resin include epoxy resin, cyanate resin, bismaleimide triazine resin (BT resin), polyphenylene ether resin, and phenol resin. Examples of the insulating resin constituting the resin sheet include insulating resins such as epoxy resin, polyimide resin, and polyester resin. In addition, from the viewpoint of improving insulation and the like, filler particles containing various inorganic particles such as silica and alumina may be contained in the resin layer. The thickness of the resin layer is not particularly limited, but is preferably 1 μm or more and 1000 μm or less, more preferably 2 μm or more and 400 μm or less, and still more preferably 3 μm or more and 200 μm or less. The resin layer may be composed of a plurality of layers. The resin layer such as prepreg and/or resin sheet may be provided on the roughened copper foil through a primer resin layer that is pre-applied to the surface of the copper foil.

Printed circuit board with improved heat dissipation

The roughened copper foil of the present invention is preferably used for the manufacture of printed circuit boards. That is, according to a preferred embodiment of the present invention, there is provided a printed wiring board comprising the roughened copper foil. The roughened copper foil of the present invention can provide a printed wiring board having both excellent transmission characteristics and high peel strength. The printed circuit board according to the present embodiment includes a layer structure in which a resin layer and a copper layer are laminated. The copper layer is a layer derived from the roughened copper foil of the present invention. In addition, the resin layer is as described above for the copper-clad laminate. In any case, the printed circuit board may adopt a known layer structure. Specific examples of the printed wiring board include a single-sided or double-sided printed wiring board obtained by bonding the roughened copper foil of the present invention to one or both sides of a prepreg, curing the bonded copper foil to form a laminate, and then forming a circuit, and a multilayer printed wiring board obtained by layering the laminate and the double-sided printed wiring board. Further, as other specific examples, there are flexible printed circuit boards, COFs, TAB tapes, and the like in which the roughened copper foil of the present invention is formed on a resin film to form a circuit. As still another specific example, there may be mentioned: forming a resin-coated copper foil (RCC) having the resin layer coated on the roughened copper foil of the present invention, laminating the resin layer as an insulating adhesive material layer on the printed circuit board, and forming a laminated circuit board of a circuit by a modified semi-additive Method (MSAP), subtractive method or the like using the roughened copper foil as all or a part of the wiring layer; a laminated circuit board in which the roughened copper foil is removed and a circuit is formed by a half-additive method (SAP); and a direct lamination wafer (direct build up on wafer) in which lamination of the resin-coated copper foil and circuit formation are alternately repeated on the semiconductor integrated circuit.

Examples

The invention is more specifically illustrated by the following examples.

Examples 1 to 11

The roughened copper foil of the present invention was produced as follows.

(1) Production of electrolytic copper foil

An acidic copper sulfate solution having the composition shown below was used as the copper electrolyte, and titanium was used as the cathodeThe prepared electrode, anode using DSA (dimensionally stable anode), had a current density of 55A/dm at a solution temperature of 45 DEG C ² Next, electrolysis was performed to obtain an electrolytic copper foil having a thickness shown in Table 1. In this case, as the cathode, an electrode whose surface was polished with a polishing wheel having a particle size shown in table 1 to adjust the surface roughness was used.

Composition of sulfuric acid copper sulfate solution

Copper concentration: 80g/L

Sulfuric acid concentration: 300g/L

-gum concentration: 5mg/L

Chlorine concentration: 30mg/L

(2) Roughening treatment

Among the electrode surfaces and deposition surfaces of the electrolytic copper foil, examples 1 to 6 and 11 were subjected to roughening treatment on the deposition surface side, and examples 7 to 10 were subjected to roughening treatment on the electrode surface side. Ten-point average roughness Rz measured according to JIS B0601-1994 using a contact surface roughness meter in the deposition surfaces of the electrolytic copper foils used in examples 1 to 6 and 11 and the electrode surfaces of the electrolytic copper foils used in examples 7 to 10 are shown in table 1.

Regarding examples 1 to 8, the roughening treatment (first roughening treatment) shown below was performed. The roughening treatment was performed as follows: in the copper electrolytic solution for roughening treatment (copper concentration: 7g/L to 17g/L, sulfuric acid concentration: 50g/L to 200g/L, liquid temperature: 30 ℃ C.), electrolysis and water washing were carried out under the conditions of the liquid resistance index, current density and time shown in Table 1.

With respect to examples 9 to 11, the first roughening treatment, the second roughening treatment, and the third roughening treatment shown below were sequentially performed.

The first roughening treatment proceeds as follows: in a copper electrolytic solution for roughening treatment (copper concentration: 7g/L to 17g/L, sulfuric acid concentration: 50g/L to 200g/L, liquid temperature: 30 ℃ C.), electrolysis and water washing were carried out under the conditions of liquid resistance index, current density and time shown in Table 1.

The second roughening treatment is carried out as follows: in a copper electrolytic solution for roughening treatment having the same composition as the first roughening treatment, electrolysis and water washing were performed under the conditions of the liquid resistance index, current density and time shown in table 1.

The third roughening treatment proceeds as follows: in a copper electrolytic solution for roughening treatment (copper concentration: 65g/L to 80g/L, sulfuric acid concentration: 50g/L to 200g/L, liquid temperature: 45 ℃ C.), electrolysis and water washing were carried out under the conditions of liquid resistance index, current density and time shown in Table 1.

(3) Rust-proof treatment

The electrodeposited copper foil after the roughening treatment was subjected to rust inhibitive treatment as shown in Table 1. As the rust inhibitive treatment, regarding examples 1 and 5 to 8, the roughened surface of the electrolytic copper foil was treated with a pyrophosphoric acid bath at a potassium pyrophosphate concentration of 100g/L, a zinc concentration of 1g/L, a nickel concentration of 2g/L, a molybdenum concentration of 1g/L, a liquid temperature of 40℃and a current density of 0.5A/dm ² Rust inhibitive treatment a (zinc-nickel-molybdenum rust inhibitive treatment) was performed. The surface of the electrolytic copper foil which was not roughened was treated with a pyrophosphoric acid bath having a potassium pyrophosphate concentration of 80g/L, a zinc concentration of 0.2g/L, a nickel concentration of 2g/L, a liquid temperature of 40℃and a current density of 0.5A/dm ² To perform rust inhibitive treatment B (zinc-nickel based rust inhibitive treatment). On the other hand, regarding examples 2 to 4 and 9 to 11, the rust inhibitive treatment B was performed on both sides of the electrolytic copper foil under the same conditions as those of the surfaces of the electrolytic copper foils in examples 1 and 5 to 8 on which the roughening treatment was not performed.

(4) Chromate treatment

The chromate treatment is performed on both surfaces of the electrodeposited copper foil subjected to the rust inhibitive treatment, and a chromate layer is formed on the rust inhibitive treated layer. The chromate treatment was carried out at a chromic acid concentration of 1g/L, pH11, a liquid temperature of 25℃and a current density of 1A/dm ² Is carried out under the condition of (2).

(5) Silane coupling agent treatment

The chromate treated copper foil is washed with water, and immediately thereafter, a silane coupling agent is treated to adsorb the silane coupling agent on the chromate layer of the roughened surface. The silane coupling agent treatment is performed by spraying a solution of the silane coupling agent in pure water as a solvent on the roughened surface in a spray manner to perform adsorption treatment. As the silane coupling agent, 3-aminopropyl trimethoxysilane was used in examples 1, 3, 4 and 6 to 8, and 3-glycidoxypropyl trimethoxysilane was used in examples 2, 5 and 9 to 11. The concentration of the silane coupling agent was set to 3g/L. After the silane coupling agent is adsorbed, the water is evaporated by an electric heater, and a roughened copper foil of a predetermined thickness is obtained.

TABLE 1

Evaluation

The roughened copper foil thus produced was subjected to various evaluations shown below.

< surface texture parameter of roughened surface >)

The roughened surface of the roughened copper foil was measured according to JIS B0601-2013 by analyzing the surface roughness by using a laser microscope (OLS-5000, manufactured by Olympic Co., ltd.). At this time, the roughness parameters (Rdc, rku, rc and Rq) were measured at 200 times (the objective magnification is 100 times×the optical zoom is 2 times) as shown in table 2, and the waviness parameters (Wdc, wt and Wp) were measured at 20 times (the objective magnification is 20 times) as shown in table 3. Other specific measurement conditions are shown in tables 2 and 3. The surface profile of the obtained roughened surface was analyzed under the conditions shown in tables 2 and 3, and Rdc, rku, rc, rq, wdc, wt and Wp were calculated. In addition, rdc/Rku is calculated based on the obtained values of Rdc and Rku. The results are shown in Table 4.

TABLE 2

TABLE 3

TABLE 3 Table 3

< measurement of element adhesion in anti-rust treated layer >)

The area of the roughened surface of the copper foil was 25cm by acid dissolution roughening treatment ² In the region (5 cm. Times.5 cm), the Zn deposition amount, ni deposition amount and Mo deposition amount were measured from the respective concentrations of Zn, ni and Mo in the solution obtained by the analysis of ICP emission spectrometry. The results are shown in Table 4.

< fabrication of copper-clad laminate >

Two sheets of prepregs (thickness 100 μm) containing polyphenylene ether, triallyl isocyanurate and bismaleimide resin as main components were prepared and stacked as insulating substrates. The surface-treated copper foil thus produced was laminated on the prepreg of the stack so that the roughened surface thereof was in contact with the prepreg, and was laminated on the prepreg of the stack at a thickness of 32kgf/cm ² A copper-clad laminate of 34 cm. Times.34 cm was produced by pressing at 205℃for 120 minutes.

Circuit linearity

The circuit linearity was evaluated in the following manner. First, in examples 4 to 7, the copper foil side surface of the copper-clad laminate was etched until the thickness of the copper foil was 12 μm. In examples 1 to 11, a dry film was adhered to the copper foil side surface of the copper-clad laminate, and the film was exposed to light and developed to form a resist. Copper is dissolved and removed from the resist by treatment with a copper chloride etching solution, whereby 3 linear circuits (6 total) each having a circuit width of 300 μm, a circuit height of 12 μm, and a length of 10cm or 15cm are formed. The linear circuits thus obtained were observed with an optical microscope, 30 sites of each circuit were randomly selected, and the circuit width was measured. For the obtained 30 circuit width data sets, an average value and a standard deviation were calculated, and a variation coefficient (%) for each circuit was calculated by dividing the standard deviation by the average value. An average value of the variation coefficients of 6 circuits was obtained as a circuit width variation coefficient in each example. The quality of the circuit width variation coefficient obtained based on the following reference evaluation was evaluated. The results are shown in Table 4.

Circuit Width variation coefficient evaluation criterion

Good: the circuit width variation coefficient is less than 1.50%

-poor: the variation coefficient of the circuit width is more than 1.50 percent

< peel Strength between copper foil and substrate >

To evaluate the adhesion between the roughened copper foil and the insulating substrate, the normal peel strength was measured as follows. First, in examples 4 to 7, the copper foil side surface of the copper-clad laminate was etched until the thickness of the copper foil was 12 μm. In examples 1 to 11, circuit formation was performed on a copper-clad laminate by etching to produce a test substrate having a linear circuit with a width of 3 mm. The thus obtained linear circuit was peeled off from the insulating substrate in accordance with method A (90 DEG peeling) of JIS C5016-1994 to measure the normal peel strength (kgf/cm). The normal peel strength obtained was evaluated based on the following criteria. The results are shown in Table 4.

< normal peel Strength evaluation criterion >

Good: the normal peel strength is 0.30kgf/cm or more

-poor: peel strength at normal state of less than 0.30kgf/cm

(c) Transmission characteristics

A high-frequency substrate (MEGTRON 6N manufactured by Panasonic) was prepared as an insulating resin substrate. The roughened copper foil was laminated on both surfaces of the insulating resin base material so that the roughened surface thereof was in contact with the insulating resin base material, and the laminate was laminated under the conditions of 190 ℃ and a pressing time of 120 minutes using a vacuum press, to obtain a copper-clad laminate having an insulating thickness of 136 μm. Then, the copper-clad laminate was subjected to etching to obtain a transmission loss measurement substrate having microstrip lines formed so as to have a characteristic impedance of 50Ω. The transmission loss (dB/cm) of 28GHz was measured on the obtained substrate for measuring transmission loss by using a network analyzer (N5225B, manufactured by Keysight Technologies Co.). The quality of the transmission loss obtained was evaluated based on the following criteria. The results are shown in Table 4.

< Transmission loss evaluation criterion >)

Good: the transmission loss is more than-0.33 dB/cm

-poor: the transmission loss is less than-0.33 dB/cm

TABLE 4

Claims

1. A roughened copper foil having a roughened surface on at least one side,

2. The roughened copper foil according to claim 1, wherein the maximum cross-sectional height Wt of the roughened surface is 2.90 μm or more and 10.00 μm or less.

3. The roughened copper foil according to claim 1 or 2, wherein the cross-sectional height difference Rdc of the roughened surface is 0.45 μm or less.

4. The roughened copper foil according to claim 1 or 2, wherein the maximum peak height Wp of the waviness curve of the roughened surface is 1.00 μm or more and 6.00 μm or less, the Wp being a value measured according to JIS B0601-2013 under the condition that the magnification is 20 times, the cutoff wavelength based on the cutoff value λc is 5 μm, and the cutoff based on the cutoff value λf is not performed.

5. The roughened copper foil according to claim 1 or 2, wherein the roughness curve element of the roughened surface has an average height Rc of 0.70 μm or less, the Rc being a value measured according to JIS B0601-2013 under the conditions of a magnification of 200 times, a cutoff wavelength of 0.3 μm based on a cutoff value λs, and a cutoff wavelength of 5 μm based on a cutoff value λc.

6. The roughened copper foil according to claim 1 or 2, wherein a section height difference Wdc of the roughened surface in the height direction of a waviness curve is 1.20 μm or more and 3.10 μm or less, the Wdc being a value obtained as a difference (c (Wmr 1) -c (Wmr)) in the form of a section height c in the height direction of a load length ratio (Wmr 1) of 20% and a load length ratio (Wmr 2) of 80%, in the waviness curve measured according to JIS B0601-2013 with a magnification of 20 times, a cutoff wavelength of 5 μm based on a cutoff value λc, and without performing cutoff based on the cutoff value λf.

7. The roughened copper foil according to claim 1 or 2, wherein the roughness profile of the roughened surface has a root mean square height Rq of 0.290 μm or less, the Rq being a value measured according to JIS B0601-2013 under conditions of a magnification of 200 times, a cutoff wavelength of 0.3 μm based on a cutoff value λs, and a cutoff wavelength of 5 μm based on a cutoff value λc.

8. The roughened copper foil according to claim 1 or 2, wherein the kurtosis Rku of the roughened surface is 1.30 or more and 8.00 or less.

9. The roughened copper foil according to claim 1 or 2, which comprises an anti-rust treatment layer and/or a silane coupling agent treatment layer on the roughened surface.

10. The roughened copper foil according to claim 1 or 2, wherein the roughened copper foil is an electrolytic copper foil, and the roughened surface is present on the deposition surface side of the electrolytic copper foil.

11. A copper-clad laminate comprising the roughened copper foil according to claim 1 or 2.

12. A printed wiring board comprising the roughened copper foil according to claim 1 or 2.