CN111655908B

CN111655908B - Surface-treated copper foil, and copper-clad laminate and printed wiring board using same

Info

Publication number: CN111655908B
Application number: CN201880078041.9A
Authority: CN
Inventors: 斋藤贵广
Original assignee: Furukawa Electric Co Ltd
Current assignee: Furukawa Electric Co Ltd
Priority date: 2017-12-05
Filing date: 2018-12-04
Publication date: 2022-03-29
Anticipated expiration: 2038-12-04
Also published as: JPWO2019111914A1; TWI746910B; KR102390417B1; WO2019111914A1; CN111655908A; TW201932648A; KR20200094740A; JP6623320B2

Abstract

The surface copper foil of the present invention is a surface-treated copper foil having a surface-treated film containing a roughened layer formed by forming roughened particles on at least one surface of a copper foil substrate, wherein when a cross section of the surface-treated copper foil is observed by a Scanning Electron Microscope (SEM), the average value of the particle height (h) of the roughened particles is 0.05 to 0.30 [ mu ] m, the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the roughened particles is 0.7 to 5.0, and the linear coverage (c) of the roughened particles is 15 to 60% as calculated by the following formula (1): c = d × W × 100(%) · (1).

Description

Surface-treated copper foil, and copper-clad laminate and printed wiring board using same

Technical Field

The present invention relates to a surface-treated copper foil, and more particularly to a surface-treated copper foil suitable for a printed wiring board used in a high frequency band (high frequency band region). The present invention also relates to a copper-clad laminate and a printed wiring board using the surface-treated copper foil.

Background

In recent years, high frequency counterparts such as over 50GHz have been developed. However, when a high-frequency signal having a frequency exceeding 50GHz band is transmitted to a conductor circuit, the depth of the skin through which a current flows is about 0.3 μm or less, and the current flows only through the outermost layer of the conductor. Therefore, when the surface irregularities of the conductor are large, the transmission path of the conductor (i.e., the transmission path of the skin portion) becomes long, and the transmission loss increases. Therefore, in the copper-clad laminate used for the high-frequency-compatible device, in order to suppress an increase in transmission loss, it is desirable to reduce the surface irregularities of the copper foil.

In addition, in general, a copper foil used for a printed wiring board is required to have high adhesion to a resin base material in addition to transmission characteristics. In general, as a technique (technique) for improving adhesion between a resin base material and a copper foil surface, a technique is mentioned in which a roughened layer (a layer having roughened particles formed thereon) is formed on the surface by plating, etching, or the like, and a physical adhesion effect (anchor effect) with the resin base material is obtained to improve adhesion. However, if the particle size of the roughening particles formed on the surface of the copper foil is increased in order to effectively improve the adhesion between the surface of the copper foil and the resin substrate, the transmission loss increases as described above.

However, printed wiring boards that are compatible with high frequencies have recently been developed in fields where higher reliability is required. For example, printed wiring boards for mobile communication devices, such as printed wiring boards for vehicles, are required to have high reliability that can withstand even severe environments, such as high-temperature environments. In order to meet the high reliability requirement, it is necessary to further improve the adhesion between the copper foil and the resin substrate, and for example, it is necessary to have an adhesion that can withstand a severe test at 150 ℃ for 1000 hours. Therefore, the conventional techniques as described above cannot satisfy adhesion (heat-resistant adhesion) under a severe high-temperature environment which has been required in recent years.

In addition, in order to improve adhesion to a resin substrate, a technique of applying chemical adhesion to a resin substrate by treating the surface of a copper foil with a silane coupling agent is used in addition to forming the roughened layer. However, in order to improve chemical adhesion between the silane coupling agent and the resin substrate, the resin substrate needs to have a large substituent having a certain degree of polarity. However, when a low dielectric substrate in which the amount of polar bulky substituent is reduced is used as a resin substrate in order to suppress dielectric loss, it is difficult to obtain chemical adhesion even if the surface of the copper foil is treated with a silane coupling agent, and it is difficult to ensure sufficient adhesion between the copper foil and the resin substrate.

As described above, in the copper-clad laminate, the suppression of the transmission loss and the improvement of the adhesion between the copper foil and the resin substrate, particularly the improvement of the normal adhesion and the heat-resistant adhesion (improvement of the durability) are in a trade-off relationship with each other. Therefore, conventionally, various techniques have been studied for a copper foil used for a copper-clad laminate, in order to achieve both suppression of transmission loss and normal adhesion to a resin substrate and heat-resistant adhesion.

For example, patent document 1 proposes a technique for increasing the specific surface area by fine irregularities, patent document 2 proposes a technique for forming roughened particles into a special shape, patent document 3 proposes a technique for forming fine roughened particles by plating with an alloy of nickel, cobalt or the like, and patent document 4 proposes a technique for forming fine roughened particles and covering the upper surface thereof with an oxidation-resistant layer containing molybdenum and cobalt.

However, the above-mentioned techniques are still insufficient from the viewpoint of suppressing the transmission loss in a higher frequency band or further improving the normal adhesion and the heat-resistant adhesion to the resin substrate.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 6182584;

patent document 2: japanese patent No. 5972486;

patent document 3: japanese patent laid-open publication No. 2015-61939;

patent document 4: japanese patent No. 6083619.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a surface-treated copper foil which can satisfactorily achieve both excellent transmission characteristics in a high frequency band (hereinafter, may be simply referred to as "high frequency characteristics") and excellent normal adhesion and heat-resistant adhesion to a resin base material, particularly when used for a conductor circuit of a printed wiring board.

Means for solving the problems

The present inventors have conducted intensive studies and, as a result, have found that a surface-treated copper foil having a surface-treated film comprising a roughened layer formed of roughened particles on at least one side of a copper foil substrate, wherein, when a cross section of the surface-treated copper foil is observed with a Scanning Electron Microscope (SEM), the average value of the particle height (h) of the roughened particles is 0.05 to 0.30 μm, the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the roughened particles is 0.7 to 5.0, and the linear coverage (c) of the roughened particles is 15 to 60% with respect to the surface of the surface-treated film, can provide a surface-treated copper foil which can achieve both excellent high-frequency characteristics and excellent normal-state adhesion and heat resistance particularly in the case of being used for a conductor circuit of a printed wiring board, thus, the present invention has been completed.

That is, the main configuration of the present invention is as follows.

[1] A surface-treated copper foil having a surface-treated film containing a roughened layer formed by forming roughened particles on at least one surface of a copper foil substrate,

when the cross section of the surface-treated copper foil is observed by a Scanning Electron Microscope (SEM), the surface of the surface-treated film,

the average value of the particle height (h) of the coarsening particles is 0.05 to 0.30 μm,

the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the coarsened particles is 0.7 to 5.0, and

the coarse particles have a linear coverage (c) of 15 to 60% as calculated by the following formula (1):

c=d×W×100 (%) ···(1)

in the above formula (1), c is the line coverage (c), d is the line density (d) [ pieces/μm ] of the coarse particles calculated from the number of the coarse particles present in each 2.5 μm region in the width direction of the observation field, and W is the average value of the particle widths (W) of the coarse particles in the region.

[2] The surface-treated copper foil according to the above [1], wherein a value calculated from each of values of the 20-degree specular gloss Gs (20 °), the 60-degree specular gloss Gs (60 °), and the 85-degree specular gloss Gs (85 °) of the surface-treated film by the following formula (2) is 0 to 10:

(Gs(85°)﹣Gs(60°))/Gs(20°) ···(2)。

[3] the surface-treated copper foil according to the above [1] or [2], wherein the surface-treated film has a 20-degree specular gloss Gs (20 °) of 0.5 to 120%, a 60-degree specular gloss Gs (60 °) of 5 to 200%, and an 85-degree specular gloss Gs (85 °) of 75 to 120%.

[4] The surface-treated copper foil according to any one of the above [1] to [3], wherein the average value of the particle widths (w) of the roughening particles is 0.02 to 0.15 μm.

[5] The surface-treated copper foil according to any one of the above [1] to [4], wherein the surface-treated film has a ten-point average roughness Rzjis value of 0.5 to 2.0 μm.

[6] A copper-clad laminate formed using the surface-treated copper foil according to any one of the above [1] to [5 ].

[7] A printed wiring board formed using the copper-clad laminate according to [6 ].

Effects of the invention

According to the present invention, there is provided a surface-treated copper foil having a surface-treated film containing a roughened layer formed by forming roughened particles on at least one surface of a copper foil substrate, wherein when a cross section of the surface-treated copper foil is observed by a Scanning Electron Microscope (SEM), with respect to the surface of the surface-treated film, the average value of the particle height (h) of the coarsening particles is 0.05 to 0.30 μm, the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the coarsened particles is 0.7 to 5.0, and the linear coverage (c) of the coarsened particles is 15 to 60%, thus, a surface-treated copper foil which can achieve both excellent high-frequency characteristics and excellent normal adhesion and heat-resistant adhesion particularly when used for a conductor circuit of a printed wiring board can be provided. Further, according to the surface-treated copper foil of the present invention, for example, even when a high-frequency signal exceeding 50GHz is transmitted, a printed wiring board excellent in durability under severe conditions can be obtained while highly suppressing transmission loss and maintaining high adhesion to a resin base material (resin layer) at high temperatures.

Drawings

Fig. 1 is an example of SEM images each of which is obtained by observing the state of the surface-treated film of the surface-treated copper foil of the present invention from the right above and from the processed cross section.

FIG. 2 is an example of a procedure for image analysis of an SEM image of a processed cross section of a surface-treated copper foil.

Fig. 3 is a view for explaining an example of a measuring method of the coarsened particles.

Fig. 4 is a view for explaining a method of measuring coarsened particles having a special shape or the like.

Fig. 5 is a view for explaining an example of a method of measuring roughened particles having a special shape, particularly roughened particles having a protrusion.

Detailed Description

Preferred embodiments of the surface-treated copper foil of the present invention will be described in detail below.

The surface-treated copper foil according to the present invention is characterized in that at least one surface of a copper foil substrate has a surface-treated film containing a roughened layer formed by forming roughened particles, and when a cross section of the surface-treated copper foil is observed by a Scanning Electron Microscope (SEM), the average value of the particle height (h) of the roughened particles is 0.05 to 0.30 [ mu ] m, the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the roughened particles is 0.7 to 5.0, and the linear coverage (c) of the roughened particles is 15 to 60% as calculated by the following formula (1):

c=d×W×100 (%) ···(1)

The surface-treated copper foil of the present invention has a copper foil substrate and a surface-treated coating film containing a roughened layer formed by forming roughened particles on at least one surface of the copper foil substrate. The surface of the surface-treated film as described above is at least one of the outermost surfaces (front and back surfaces) of the surface-treated copper foil, and is a roughened surface having a fine uneven surface shape reflecting the state of formation of roughened particles formed on at least one surface of the copper foil substrate, the particle shape, and the like. The surface of the surface-treated film (hereinafter referred to as "roughened surface") may be, for example, the surface of a roughened layer formed on a copper foil substrate, the surface of a silane coupling agent layer directly formed on the roughened layer, or the surface of a silane coupling agent layer formed on the roughened layer via an intermediate layer such as a Ni-containing base layer, a Zn-containing heat-resistant layer, and a Cr-containing rust-proofing layer. In the case where the surface-treated copper foil of the present invention is used, for example, for a conductor circuit of a printed wiring board, the roughened surface is a surface (bonding surface) for bonding a laminated resin base material.

Here, fig. 1(a) and (b) show the state of the roughened surface of the surface-treated copper foil of the present invention. Fig. 1(a) is an example of an SEM image obtained by observing the roughened surface of the surface-treated copper foil of the present invention from directly above with a Scanning Electron Microscope (SEM), and fig. 1(b) is an example of an SEM image obtained by performing cross-sectional processing using an ion milling apparatus from the surface side of the surface-treated copper foil and observing the processed cross-section with a Scanning Electron Microscope (SEM). As shown in fig. 1(a) and (b), the roughened surface of the surface-treated copper foil of the present invention is sparsely formed with very fine roughened particles.

As for the evaluation of the shape of the roughened particles on the special roughened surface as described above, in the conventional general technique for observing the roughened surface, for example, in the observation by a laser microscope or a white interference microscope, since the particle size is below the limit of resolution (about 0.1 μm at present), it is difficult to perform accurate evaluation, and since the difference in height of the roughened particles cannot be clearly determined only by an optical technique such as specular gloss measurement, sufficient evaluation cannot be performed. Therefore, in the conventional technique, strict evaluation of the roughened surface is limited in terms of cost and technique. Therefore, in the present invention, as one technique of the method for evaluating the roughened surface, as shown in fig. 1(b), the state of formation of the roughened particles on the roughened surface is analyzed from the cross section of the surface-treated copper foil, and the characteristics of the roughened surface are specified and evaluated. Specifically, the following technique is used.

First, a cross-sectional work was performed from the surface side of the surface-treated copper foil using an ion milling apparatus, and a secondary electron image with a magnification of 5 ten thousand times was observed on the worked cross-section at an acceleration voltage of 3kV by SEM. In the SEM observation, the surface-treated copper foil was horizontally fixed on a smooth support table, and the surface-treated copper foil was adjusted so that the surface-treated copper foil was horizontal in the cross-sectional SEM photograph, taking care that the surface-treated copper foil did not warp or loosen.

Further, the size of the coarsened particles on the coarsened surface was measured by performing image analysis on the SEM photograph obtained in the SEM observation described above. An example of a procedure for image analysis is shown in fig. 2. First, a cross-sectional SEM photograph was obtained at a magnification of 5 ten thousand as shown in fig. 2 (a). Then, the sectional SEM photograph is subjected to image processing to extract a contour line of the sectional shape shown in fig. 2 (b). Then, only the contour line of the cross-sectional shape in the same machining cross-section as shown in fig. 2(c) is finally extracted. The image processing described above can be performed by using known processing software such as "Photoshop", "imageJ" and "Real World Paint", which are general image editing software. Specifically, the following examples are described.

Next, based on the contour line of the extracted cross-sectional shape and fig. 2(c), the coarsened particles were identified and various sizes were measured. Note that the measurement as described above can be performed using known processing software such as "WinROOF", "Photo Ruler", or the like, which is general image measurement software. Specifically, the following examples are described. Hereinafter, an example of the simplest method of measuring the coarsened particles is shown in fig. 3.

First, as shown in fig. 3(a), for the convex portion (coarsened particle) to be measured existing on the contour line, a line L passing through the apex V of the convex portion is drawn in the growth direction of the particle. Next, as shown in fig. 3 b, a rectangle (including a square) Sq having upper and lower sides perpendicular to the line L is drawn. The upper side of the rectangle Sq intersects the vertex V, and any angle of the lower side intersects one of the base portions of the convex portions which is far from the vertex (this angle is referred to as "R1"). The other corner of the lower side of the rectangle Sq (this corner is referred to as "R2") is orthogonal to the side extending parallel to the line L from the upper side direction, and the other side of the base of the convex portion is located on this side (this point is referred to as "R2"). Next, as shown in fig. 3 c, among the sides of the rectangle Sq, the size of the side parallel to the line L is defined as the particle height (h) of the roughening particles, and the size of the side perpendicular to the line L is defined as the particle width (w) of the roughening particles. In addition to the following specific examples, all the convex portions obtained by measuring while drawing the rectangle Sq are regarded as one coarsened particle.

Next, an example in which the measurement is not performed as the coarse particles and a method of measuring the coarse particles having a special shape will be described with reference to fig. 4 and 5 as necessary.

First, although not particularly shown, among the convex portions measured according to the above standard, the convex portions having a particle height (h) of less than 0.02 μm do not affect the adhesiveness and high-frequency characteristics of interest in the present invention, and are difficult to measure accurately, and therefore, are not targets for measurement, and such a case is not included in the "coarsened particles" of the present invention.

In addition, as shown in fig. 4(a), among the convex portions measured according to the above-mentioned standard, since the convex portions having a ratio (h/w) of the particle height (h) to the particle width (w) of less than 0.40 do not affect the adhesiveness and the high-frequency characteristics focused on by the present invention, they are not observed and are not included in the "coarsened particles" of the present invention.

Fig. 4(b) shows a measurement example of a convex portion having 2 or more vertexes. In this case, as shown in fig. 4(b), it is sufficient to perform measurement on each vertex as if it is a particle based on the above definition.

Fig. 4(c) shows a measurement example in which a convex portion having 2 steps or more is formed near the root. In this case, the determination of the root is made in accordance with the viewpoint of which part of the convex part the adhesiveness and the high-frequency characteristics are affected, which is the concern of the present invention. That is, an angle R1 intersecting with a side away from the apex at the root of the convex portion is set as the position of the lowest stage of the root. In this case, the growth direction of the particles is determined as the whole particles.

Fig. 4(d) is a measurement example of the case where there are other convex portions on the convex portion where the root portion is relatively blurred and the size ratio (h/w) is less than 0.40 as shown in fig. 4 (a). In this case, the blurred root is not targeted for measurement, but measurement may be performed based on the above definition by focusing on the convex portion having a distinguishable root. This is because the gentle convex portion having the blurred root portion does not affect the adhesiveness and the high-frequency characteristics to which the present invention is directed.

In addition, as shown in fig. 5(a), when the convex portion to be measured has a main portion a and a protrusion portion B branched from the main portion a, the measurement is performed as follows. First, as shown in fig. 5(b), for the convex portion as the main portion a,the particle height (h) and the particle width (w) were measured according to the above criteria, and the particles were identified as coarsened particles according to the above criteria. Next, as shown in fig. 5(c), the projection B branched from the main portion a is projected from a base position R1 of the projection B_BLine L with main part A_AA vertical straight line, and the intersection is R1_BLA. Here, on line L_AUpward, from the root side of the main portion a to a point R1_BLAIs set as height h_ABAt a height h_ABParticle height h as principal portion A_AWhen the number of the protrusions B is 1/4 or more, the protrusions B are not a measurement target and are not included in the "coarsened particles" of the present invention. In addition, at the height h_ABParticle height h lower than main portion A_A1/4, the protrusions B were measured for particle height (h) and particle width (w) according to the above criteria and treated as coarsened particles different from the main portion A.

Although not particularly shown, when there are a plurality of projections branching from the main portion, the determination is individually made for each projection in accordance with the above criteria.

In addition, for the coarsened particles having a shape other than the above, the particle height (h) and the particle width (w) are appropriately measured in accordance with the above criteria, taking into consideration the effects of the adhesiveness and the high-frequency characteristics that are focused on in the present invention.

Further, since the determination and measurement of the coarsened particles become the determination of the contour line, some errors occur depending on the measurement person. However, the error described above can be sufficiently minimized by averaging the measurement results of a large number of coarse particles. Specifically, at least 5 or more, preferably 10 or more photographs of the cross section are analyzed on an arbitrary observation cross section, and the average value of the respective measured values is evaluated as the measured value of each surface-treated copper foil.

That is, first, for each cross-sectional photograph, based on the above criteria, the particle height (h) and the particle width (w) of the coarsened particles and the number of the coarsened particles (observation target particles) present in each 2.5 μm region in the width direction of the observation field are measured. Based on these values, the average values of the particle height (h), the particle width (w), and the ratio (h/w) of the particle height (h) to the particle width (w), and the line density (d) and the line coverage (c) of the coarsened particles described later were calculated, respectively. Then, the values calculated for each cross-sectional photograph were combined and averaged with the total number of observed cross-sections to obtain the measured value of each surface-treated copper foil. More specific measurement methods and calculation methods will be described in the examples below.

Hereinafter, the characteristics of the roughened particles on the roughened surface of the surface-treated copper foil of the present invention will be described separately.

The average particle height (h) of the roughened particles on the roughened surface is 0.05 to 0.30 μm, preferably 0.05 to 0.20 μm, and more preferably 0.10 to 0.20 μm. By setting the above range, excellent high-frequency characteristics and excellent normal adhesion and heat-resistant adhesion can be achieved at the same time. When the average particle height (h) of the coarse particles is less than 0.05. mu.m, the heat resistant adhesion tends to be low, and when it exceeds 0.30. mu.m, the high frequency characteristics tend to be low.

The average width (w) of the coarsened particles is preferably 0.02 to 0.15 μm, more preferably 0.02 to 0.10 μm, and even more preferably 0.02 to 0.08 μm. In particular, the heat-resistant adhesion can be further improved by setting the average value of the widths (w) of the coarsened particles to 0.10 μm or less.

The average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the coarsened particles is 0.7 to 5.0, preferably 1.0 to 5.0, more preferably 1.0 to 4.0, and further preferably 1.0 to 3.0. By setting the above range, excellent high-frequency characteristics and excellent normal adhesion and heat-resistant adhesion can be achieved at the same time. If the average value of the ratio (h/w) is less than 0.7, the heat resistant adhesion tends to be lowered. In addition, by setting the average value of the ratio (h/w) to 1.0 or more, the normal adhesion can be further improved. Even if the average value of the ratio (h/w) exceeds 5.0, it is not particularly significant, but rather, a powder falling defect may occur, and the strength of the coarsened particles is lowered by heating, so that the adhesiveness (particularly, heat-resistant adhesiveness) tends to be lowered.

The linear density (d) of the roughened particles on the roughened surface is preferably 2.0 particles/μm or more, more preferably 3.0 particles/μm or more, and still more preferably 4.0 particles/μm or more. In particular, by setting the linear density (d) of the coarse particles to 2.0 pieces/μm or more, sufficient normal state adhesion can be secured. The line density (d) of the coarsened particles is a value calculated from the number of coarsened particles (observation target particles) present in each 2.5 μm region in the width direction of the observation field, and indicates the number density of particles per unit line region (width region).

The roughened surface has a linear coverage (c) of the roughened particles calculated by the following formula (1) of 15 to 60%, preferably 20 to 50%, more preferably 25 to 50%, and still more preferably 25 to 45%. By setting the above range, excellent high-frequency characteristics and excellent normal adhesion and heat-resistant adhesion can be achieved at the same time. When the line coverage (c) of the coarse particles exceeds 60%, the high-frequency characteristics are deteriorated due to an excessive increase in the surface area. In addition, the heat resistant adhesion tends to be lowered even when the content is less than 15% or more than 60%. In particular, by setting the line coverage (c) of the coarsened particles to 25% or more, the heat-resistant adhesion can be further improved.

c=d×W×100 (%) ···(1)

Here, it is considered that the reason why the heat resistant adhesion is lowered when the line coverage (c) of the roughened particles is less than 15% is simply due to insufficient physical adhesion effect (anchor effect) of the resin base material to the roughened surface. However, from the viewpoint of the physical adhesion effect described above, when the line coverage (c) of the coarsened particles exceeds 60%, a stronger adhesion effect is expected, and it is expected that the heat-resistant adhesion is further improved. However, when the line coverage (c) of the coarsened particles actually exceeds 60%, the heat-resistant adhesion is lowered. Although the detailed mechanism for generating the phenomenon described above is not known, the following mechanism is considered as one of the reasons.

That is, if the roughened particles are excessively dense on the roughened surface (the surface to be bonded to the resin substrate) on which the roughened particles are formed at a very fine level as in the surface-treated copper foil of the present invention, it is considered that the fine roughened particles act as dicing lines on the resin substrate to be peeled off by a certain stress. Therefore, the resin layer having reduced ductility particularly in a high-temperature environment is likely to be broken by aggregation along the tips of the coarse particles, and is considered to have reduced heat-resistant adhesion.

From the viewpoint of the density of the coarsened particles as described above, the linear density (d) and the linear coverage (c) of the coarsened particles on the coarsened surface can also be regarded as the same index. However, the effect of the above-described scribe line is more correlated with the line coverage (c) than with the line density (d) of the coarse particles.

For example, even in the case of a roughened surface having the same linear density (d), when the particle width of the roughened particles is small, that is, when the linear coverage (c) is small, the number of portions where the roughened particles are not present is increased, and therefore, it is considered that the effect of the above-described dicing line is reduced. On the other hand, when the particle width of the roughened particles is large, that is, when the wire coverage (c) is large, the portion where the roughened particles are not present is reduced, and therefore, the effect of the above-described dicing line is considered to be improved.

That is, the effect of the scribe line is not simply a concentration of the number of the roughening particles per unit line region, but is considered to be a large influence of the thinning in the sense that there is an appropriate gap between the roughening particles (a portion where the roughening particles are not present). Therefore, it is considered that, in the surface-treated copper foil according to the present invention, it is desirable that the roughened particles are appropriately dispersed on the roughened surface (the surface to be bonded to the resin substrate) on which the roughened particles are formed at a very fine level in order to suppress the effect of the above-described dicing lines.

In addition, the surface-treated copper foil of the present invention preferably has a specular gloss on the roughened surface in the range of not more than the range of each light-receiving angle measured according to JIS Z8741-1997.

In general, the measurement of specular gloss is generally evaluated by a single light-receiving angle, but since the roughened surface of the surface-treated copper foil of the present invention has a complicated shape due to the formation of roughened particles, it is difficult to sufficiently evaluate the surface shape characteristics thereof by a single light-receiving angle. Therefore, the surface shape of the roughened surface of the surface-treated copper foil of the present invention can be evaluated in more detail by measuring the specular gloss using the following 3 types of light-receiving angles.

In the surface-treated copper foil of the present invention, the average value of the height (h) of the roughening particles, the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the roughening particles, and the evaluation of the linear coverage (c) of the roughening particles are given priority, but since the specular gloss tends to be a certain degree, the fine shape characteristics of the roughening particles on the roughened surface of the copper foil of the present invention can be evaluated in more detail by adding the evaluation of the specular gloss using the following 3 types of light-receiving angles in addition to the above evaluations.

It is to be noted that, as described above, the measurement of the specular gloss of the roughened surface is not the measurement on a smooth surface, and therefore the measurement values at 3 types of light-receiving angles do not have a simple proportional relationship.

Particularly, from the viewpoint of satisfying both high-frequency characteristics and heat-resistant adhesion, the 20-degree specular gloss Gs (20 °) is preferably 0.5 to 120%, more preferably 0.5 to 100%, even more preferably 5 to 100%, and even more preferably 15 to 100%.

Particularly, from the viewpoint of satisfying both high-frequency characteristics and heat-resistant adhesion, the 60-degree specular gloss Gs (60 °) is preferably 5 to 200%, more preferably 10 to 200%, even more preferably 20 to 200%, and even more preferably 20 to 150%.

Particularly, from the viewpoint of satisfying both the high-frequency characteristics and the heat-resistant adhesion, the 85-degree specular gloss Gs (85 °) is preferably 75 to 120%, more preferably 75 to 115%, even more preferably 80 to 115%, and even more preferably 85 to 115%.

The surface-treated copper foil of the present invention preferably has a value calculated by the following formula (2) based on each value of 20-degree specular gloss Gs (20 °), 60-degree specular gloss Gs (60 °), and 85-degree specular gloss Gs (85 °) on the roughened surface of 0 to 10, more preferably 0 to 9, and even more preferably 0 to 5. By setting the above range, excellent high-frequency characteristics and heat-resistant adhesion properties can be more reliably achieved at the same time. When the value calculated by the following formula (2) is less than 0, the heat resistant adhesion tends to be low, and when it exceeds 10, the high frequency characteristics tend to be low.

(Gs(85°)﹣Gs(60°))/Gs(20°) ···(2)

The detailed measurement conditions are described in the examples described below.

In addition, the surface-treated copper foil of the present invention has a ten-point average roughness Rzjis value of preferably 0.5 to 2.0 μm, more preferably 0.5 to 1.5 μm on the roughened surface. In particular, by setting the thickness to 2.0 μm or less, the transmission loss can be more reliably suppressed, and the high-frequency characteristics can be improved. Further, when the thickness is 0.5 μm or more, the productivity is also good. The detailed measurement conditions are described in the examples described below.

Further, according to the surface-treated copper foil of the present invention, when it is used for a conductor circuit of a printed wiring board, it is possible to highly suppress transmission loss when a high-frequency signal in a GHz band is transmitted, and it is possible to obtain a printed wiring board excellent in durability under severe conditions by maintaining good adhesion between the surface-treated copper foil and a resin base material (resin layer) even at high temperatures.

< method for producing surface-treated copper foil >

Next, an example of a preferable production method of the surface-treated copper foil of the present invention will be described. In the present invention, it is preferable to perform roughening treatment for forming roughened particles on the surface of the copper foil substrate.

(copper foil base)

As the copper foil substrate, an electrolytic copper foil or a rolled copper foil having a smooth and glossy surface free from rough irregularities is preferably used. Among these, electrolytic copper foil is preferably used from the viewpoint of productivity and cost, and particularly electrolytic copper foil having both smooth surfaces, which is generally called "double-sided gloss foil", is more preferably used.

In view of normally forming the fine roughened particles of the present invention on the surface of the copper foil substrate as described above, it is desirable that the 20-degree specular gloss Gs (20 °), the 60-degree specular gloss Gs (60 °), and the 85-degree specular gloss Gs (85 °) on the surface of the copper foil substrate are 50% or more.

In the electrolytic copper foil, as a smooth and glossy surface, for example, an S (shiny) surface in a general electrolytic copper foil, and both an S surface and an M (mat) surface in a double-sided glossy foil are provided, but a smoother and glossy surface is an M surface. In the present invention, when any electrolytic copper foil is used, it is preferable to perform roughening treatment described later on a smoother and glossy surface.

However, the electrolytic copper foil has minute irregularities on the smooth surface as described above. The irregularities described above are derived from the surface shape of the cathode surface when the electrolytic copper foil is produced. In general, the cathode surface of titanium or the like is kept smooth by polishing, but a slight polishing mark remains. Therefore, the S-surface formed with the cathode surface as the deposition surface has a shape copied with the polishing trace of the cathode surface transferred thereto, and the M-surface has a surface shape following or affected by the polishing trace of the cathode surface. On the S-side and M-side of the electrodeposited copper foil as described above, striped projections or recesses derived from the polishing traces on the cathode side were formed. However, when the striped projections or recesses on the S-plane and M-plane are compared with the particle size of the coarse particles to be formed in the present invention, the sizes are very large and different. Therefore, the striped projections and recesses as described above have a ripple on the base line of the roughened surface, but do not affect the shape of the roughened particles formed thereon. Therefore, although not described in the above definition, it is needless to say that the large irregularities such as the corrugation pattern of the roughened surface are not the target of measurement of the roughened particles in the present invention.

However, as described above, the striped projections and recesses on the S-and M-surfaces of the electrodeposited copper foil cause waviness in the base line of the roughened surface, and therefore, there is a possibility that the value of the ten-point average roughness Rzjis on the roughened surface of the surface-treated copper foil is affected. Therefore, the ten-point average roughness Rzjis value of the surface subjected to the roughening treatment described later is preferably 0.5 to 2.0 μm, and more preferably 0.5 to 1.5 μm, from the viewpoint of controlling the predetermined ten-point average roughness Rzjis value on the roughened surface to be in a predetermined range. The measurement method was the same as the measurement on the roughened surface. The detailed measurement conditions are described in the examples described below.

(roughening treatment)

The roughening treatment is preferably carried out by roughening plating treatment (1) as shown below. The plating treatment (2) may be combined as necessary.

Roughening plating treatment (1)

The roughening plating treatment (1) is a treatment for forming roughening particles on at least one surface of the copper foil substrate. Specifically, the plating treatment is performed in a copper sulfate bath. In the copper sulfate bath (basic bath for roughening plating solution) described above, conventionally known additives such As molybdenum (Mo), arsenic (As), antimony (Sb), bismuth (Bi), selenium (Se), tellurium (Te), and tungsten (W) may be added to prevent the removal of the roughened particles, i.e., "dusting", and molybdenum (Mo) is particularly preferably added. The present inventors have conducted extensive studies and, as a result, have found that the following factors affect the surface properties of a surface-treated copper foil, and have found that the required properties of high-frequency characteristics and adhesiveness (normal adhesiveness and heat-resistant adhesiveness) which are the effects of the present invention can be satisfied at a high level by setting the conditions thereof skillfully.

First, when the copper concentration of the copper sulfate bath in the roughening plating treatment (1) is less than 5g/L, the formation of the roughening particles itself becomes difficult, and the wire coverage (c) of the roughening particles becomes too small, so that the heat-resistant adhesion tends to deteriorate. When the copper concentration of the plating bath exceeds 13g/L, diffusion of copper ions is promoted to densely form coarse particles, and the wire coverage (c) of the coarse particles becomes too large. In this case, since copper ions are efficiently supplied to the vicinity of the coarsened particles grown on the crystal, the coarsened particles growing require more copper ions and the force to spread to a distant place, that is, the force to grow in the height direction is weakened, and the height (h) of the coarsened particles and the ratio (h/w) of the particle height (h) to the particle width (w) of the coarsened particles are reduced. As a result, the heat-resistant adhesion tends to deteriorate. Therefore, the copper concentration is preferably set to 5 to 13 g/L.

Next, the additive to be added to the copper sulfate bath will be described by taking, for example, molybdenum (Mo) as an example. If the molybdenum (Mo) concentration is less than 500mg/L, the formation of coarse particles may be concentrated on large striped projections of the copper foil substrate, and the uniformity of coarse formation may be deteriorated. Further, it is difficult to miniaturize the coarse particles while keeping the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the coarse particles focused on in the present invention at a predetermined value, and it tends to be difficult to achieve both of the adhesiveness and the high frequency characteristics. When the molybdenum (Mo) concentration exceeds 1000mg/L, the generation density of nuclei that become starting points of generation of the coarsened particles becomes too high, and the linear coverage (c) of the coarsened particles becomes too high, and therefore the heat resistant adhesion tends to deteriorate. Therefore, the concentration of molybdenum (Mo) is preferably 500 to 1000 mg/L.

Next, electrolytic conditions and the like of the roughening plating treatment (1) will be described.

In the present invention, for example, in terms of mass production and production cost, the plating treatment is preferably performed in a roll-to-roll (roll-to-roll) manner.

The conditions for the plating treatment may be appropriately adjusted depending on the treatment method, and particularly, from the viewpoint of suppressing the diffusion of copper ions, it is preferable to set the conditions under which the stirring of the plating solution is difficult. Therefore, in the roll-to-roll system, it is preferable that the treatment direction (the direction of the treatment speed) and the flow direction of the plating solution between the electrodes (the direction of the inter-electrode flow velocity) are aligned. In addition, in the roll-to-roll system, it is desirable to perform the treatment in a stationary bath state, and it is preferable that stirring is not performed in the plating treatment.

However, in both the roll-to-roll system and the other systems, gas may be generated during the plating process, and stirring may occur due to the floating (floating) of the generated gas.

For example, in the case of a plating treatment other than the batch type roll-to-roll method, the treatment of the present invention is completed in a very short time of about 3 seconds at the maximum, and therefore, it is not necessary to take special consideration of stirring due to the gas generation as described above.

However, in the case of the roll-to-roll system, since the continuous process is performed, gas is continuously generated in the processing bath, and the continuously generated gas is sequentially floated, so that the flow of the plating solution is generated in the floating direction. In addition, in the case of the roll-to-roll system, since the copper foil base is continuously supplied to the plating solution, the flow of the plating solution occurs in the transport direction of the copper foil base. In the case where these two flows are identical, there is little need to consider the generation of the above-mentioned gas. However, when these two flows are in opposite directions, an unnecessary stirring force is generated on the treatment surface, and the diffusion of copper ions may be promoted. Therefore, when the plating treatment is performed by the roll-to-roll method, it is preferable to select a reaction tank for performing the plating treatment so that the floating direction of the gas coincides with the conveying direction of the copper foil base (the treatment direction of the plating treatment).

In the roll-to-roll plating process described above, if the absolute value of the difference between the processing speed and the inter-electrode flow velocity of the plating solution flowing in the processing direction (hereinafter referred to as "inter-electrode flow velocity in the processing direction") exceeds 1.0 m/min, an unnecessary stirring force is generated on the processing surface, and the diffusion of copper ions is promoted. As described above, promoting the diffusion of copper ions affects the line coverage of the coarsened particles and the ratio (h/w) of the particle height (h) to the particle width (w) of the coarsened particles, and tends to deteriorate the heat-resistant adhesion. Therefore, the absolute value of the difference between the processing speed and the inter-electrode flow velocity in the processing direction is preferably set to less than 1.0 m/min.

In addition, if the current density (A/dm)²) The product (= S) of the sum of the processing time (seconds) is set to be less than 10{ (A/dm)²) Second }, it becomes difficult to obtain sufficient normal adhesion required in the present invention. When the product S exceeds 80{ (A/dm)²) Second }, the coarsened particles grow excessively, and it becomes difficult to obtain the desired good high frequency characteristics of the present invention. Therefore, the product S is preferably 10 to 80{ (A/dm)²) Second }.

In addition, when the ratio (= S/Mo concentration) of the product S of the current density and the processing time to the molybdenum (Mo) concentration is set to be less than 0.02[ { (a/dm) }²) Second }/(mg/L)]The generation density of nuclei that become starting points of generation of the coarsened particles becomes too high, and the linear coverage of the coarsened particles becomes too high, and therefore the heat-resistant adhesion tends to deteriorate. In addition, if the S/Mo concentration exceeds 0.10[ { (A/dm)²) Second }/(mg/L)]The formation of coarse particles is concentrated in the copper foilIn the case of large striped protrusions of the matrix, in addition to the deterioration in uniformity of the roughening formation, it is difficult to finely form the roughened particles while maintaining the shape having the desired characteristics of the present invention, and it tends to be difficult to achieve both of the adhesiveness and the high-frequency characteristics. Therefore, the S/Mo concentration is preferably 0.02 to 0.10[ { (A/dm)²) Second }/(mg/L)]。

Fixed plating treatment (2)

The fixed plating treatment (2) is a treatment of performing smooth cover plating on the copper foil base subjected to the surface treatment in the roughening plating treatment (1). Specifically, the plating treatment is performed in a copper sulfate bath. In general, this treatment is performed to prevent the coarsened particles from falling off, i.e., to fix the coarsened particles. In the present invention, the fixing plating treatment (2) is not essential, but may be performed as needed, and for example, in the case of combining with a flexible substrate using a hard resin such as a polyimide resin in the production of a copper-clad laminate, it is preferable to perform the fixing plating treatment in order to adjust the roughened surface to the hard resin.

The electrolytic conditions and the like of the fixed plating treatment (2) will be described.

The plating treatment is preferably performed in a roll-to-roll manner, for example, from the viewpoint of mass production and production cost. When the fixed plating treatment is performed in a roll-to-roll manner, if the absolute value of the difference between the treatment speed and the inter-electrode flow rate is less than 9 m/min, it becomes difficult to perform normal fixed plating, and dusting tends to occur. When the particle size exceeds 24 m/min, the root portions of the coarse particles are easily buried, and it becomes difficult to increase the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the coarse particles, and the heat resistant adhesion tends to be deteriorated. Therefore, the absolute value of the difference between the processing speed and the interelectrode flow rate is preferably set to 9 to 24 m/min. In the fixed plating treatment, the flow direction of the treatment speed (treatment direction) and the flow direction of the inter-electrode flow velocity may not coincide with each other, and when the flow directions are opposite to each other, one flow velocity is calculated as a negative flow velocity with respect to the other flow velocity.

Further, if the ratio [ (K/S) × 100] (%) of the product K of the current density and the treatment time of the fixed plating treatment (2) to the product S of the current density and the treatment time of the rough plating treatment (1) exceeds 50%, it becomes difficult to maintain the shape of the rough particles obtained in the rough plating treatment (1), and it becomes difficult to maintain various properties such as heat-resistant adhesion well. Therefore, the above ratio [ (K/S). times.100 ] is preferably 50% or less.

The conditions of the plating treatment and the method of controlling the shape of the roughened particles on the roughened surface have been described above, but the method of controlling the specular gloss on the roughened surface is also roughly as described above.

That is, in the surface-treated copper foil of the present invention, the specular gloss on the roughened surface is a value that comprehensively reflects the particle shape characteristics of the roughened particles represented by the average value of the height (h) of the roughened particles, the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the roughened particles, the line coverage (c) of the roughened particles, and the like, and particularly, is a value that approximately correlates with the product of the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the roughened particles and the line coverage (c) of the roughened particles. Therefore, it is difficult to control the surface properties of the roughened surface by using only the specular gloss on the roughened surface as a determination index, but by appropriately controlling the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the roughened particles and the linear coverage (c) of the roughened particles in consideration of the above-mentioned correlation, a desired specular gloss can be obtained.

Hereinafter, one example of the composition and the electrolytic conditions of the plating solution for the roughening plating treatment is shown. The following conditions are preferred examples, and the type and amount of the additive and the electrolysis conditions may be appropriately changed or adjusted as necessary within a range not to impair the effects of the present invention.

< Condition for roughening plating treatment (1) >

Copper sulfate pentahydrate (5-13 g/L) converted into copper (atom)

100-250 g/L sulfuric acid

Ammonium molybdate (500-1000 mg/L) converted into molybdenum (atom)

The processing speed is 5-20 m/min

Flow velocity between electrodes in the treatment direction of 5-20 m/min

Current density of 5-50A/dm²

Treatment time 0.5-3.0 seconds

Bath temperature 15-20 DEG C

< Condition of fixed plating treatment (2) >

Copper sulfate pentahydrate (50-70 g/L) converted into copper (atom)

Sulfuric acid 80-160 g/L

The processing speed is 5-20 m/min

Flow rate between electrodes 1-30 m/min

Current density of 1-5A/dm²

Treatment time 1-10 seconds

Bath temperature 50-70 DEG C

The surface-treated copper foil of the present invention may have a roughened layer having a predetermined fine uneven surface shape formed by electrodeposition of roughened particles on at least one surface of a copper foil substrate, and a silane coupling layer may be further formed on the roughened layer directly or through an intermediate layer such as a nickel (Ni) -containing base layer, a zinc (Zn) -containing heat-resistant layer, and a chromium (Cr) -containing rust-proofing layer. Since the intermediate layer and the silane coupling agent layer have extremely small thicknesses, the particle shape of the roughened particles on the roughened surface of the surface-treated copper foil is not affected. The particle shape of the roughened particles on the roughened surface of the surface-treated copper foil is substantially determined by the particle shape of the roughened particles on the surface of the roughened layer corresponding to the roughened surface.

Further, as a method for forming the silane coupling agent layer, for example, a method of forming a layer by applying a silane coupling agent solution directly or through an intermediate layer on the uneven surface of the roughened layer of the surface-treated copper foil and then air-drying (natural drying) or heat-drying the layer is exemplified. The effect of the present invention is sufficiently exhibited by forming a silane coupling agent layer if water in the solution evaporates with respect to the applied coupling agent solution. The heating and drying at 50 to 180 ℃ is preferable in promoting the reaction between the silane coupling agent and the copper foil.

The silane coupling agent layer preferably contains at least one of epoxy silane, amino silane, vinyl silane, methacrylic silane, acrylic silane, styrene silane, ureide silane, mercapto silane, sulfide silane, and isocyanate silane.

In another embodiment, it is preferable that at least 1 intermediate layer selected from a base layer containing Ni, a heat-resistant treated layer containing Zn, and a rust-preventive treated layer containing Cr is provided between the roughening-treated layer and the silane coupling agent layer.

In the case where copper (Cu) in the copper foil substrate or the roughened layer diffuses to the resin substrate side to cause copper damage and the adhesion is sometimes reduced, for example, the Ni-containing base layer is preferably formed between the roughened layer and the silane coupling agent layer. The Ni-containing underlayer is preferably formed of at least 1 selected from nickel (Ni), nickel (Ni) -phosphorus (P), and nickel (Ni) -zinc (Zn).

The heat-resistant treatment layer containing Zn is preferably formed in a case where further improvement in heat resistance is required. The heat-resistant treatment layer containing Zn is preferably formed, for example, of zinc or an alloy containing zinc, that is, an alloy containing zinc selected from at least 1 of zinc (Zn) -tin (Sn), zinc (Zn) -nickel (Ni), zinc (Zn) -cobalt (Co), zinc (Zn) -copper (Cu), zinc (Zn) -chromium (Cr), and zinc (Zn) -vanadium (V).

The rust-preventive treatment layer containing Cr is preferably formed when further improvement in corrosion resistance is required. Examples of the rust-preventive treatment layer include a chromium layer formed by chromium plating and a chromate layer formed by chromate treatment.

When all three layers are formed, the base layer, the heat-resistant treated layer, and the rust-preventive treated layer are preferably formed in this order on the roughened treated layer, and either one or both layers may be formed depending on the application and the intended characteristics.

[ production of surface-treated copper foil ]

The method for producing the surface-treated copper foil of the present invention is summarized below.

In the present invention, the surface-treated copper foil is preferably produced by the following formation steps (S1) to (S5).

(S1) roughening layer Forming step

A roughened layer having a fine uneven surface is formed on a copper foil substrate by electrodeposition of roughened particles.

(S2) base layer Forming Process

On the roughened layer, a base layer containing Ni is formed as necessary.

(S3) Process for Forming Heat-resistant treatment layer

A heat-resistant treated layer containing Zn is formed on the roughened layer or the base layer as necessary.

(S4) anticorrosive treatment layer Forming step

If necessary, a rust-preventive layer containing Cr is formed on the roughened layer or on the base layer and/or the heat-resistant layer formed on the roughened layer.

(S5) Process for Forming silane coupling agent layer

The silane coupling agent layer is formed directly on the roughened layer, or is formed by an intermediate layer in which at least 1 of the base layer, the heat-resistant layer, and the rust-preventive layer is formed.

In addition, the surface-treated copper foil of the present invention is suitably used for the production of a copper-clad laminate. The copper-clad laminate as described above is suitable for use in the production of a printed wiring board having high adhesiveness and excellent high-frequency transmission characteristics, and exhibits excellent effects. The surface-treated copper foil of the present invention is particularly suitable for use as a printed wiring board for high-frequency bands of 40GHz or more, particularly 60GHz or more.

The copper-clad laminate can be formed by a known method using the surface-treated copper foil of the present invention. For example, a copper-clad laminate can be produced by laminating and bonding a surface-treated copper foil and a resin base material (insulating substrate) so that the roughened surface (bonding surface) of the surface-treated copper foil faces the resin base material. Examples of the insulating substrate include a flexible resin substrate and a rigid resin substrate, and the surface-treated copper foil of the present invention is particularly suitable for a combination with a rigid resin substrate.

In the case of producing a copper-clad laminate, a surface-treated copper foil having a silane coupling agent layer and an insulating substrate may be laminated by hot pressing. The same effects as those of the present invention are also obtained in a copper-clad laminate produced by applying a silane coupling agent to an insulating substrate and laminating the insulating substrate applied with the silane coupling agent and a surface-treated copper foil having an anticorrosive treatment layer on the outermost surface by hot pressing.

The printed wiring board can be formed by a known method using the above copper-clad laminate.

The embodiments of the present invention have been described above, but the above embodiments are merely examples of the present invention. The invention encompasses the concept of the invention and all solutions contained in the claims, which can be varied within the scope of the invention.

Examples

The present invention will be described in more detail below based on examples, but the following is an example of the present invention.

Preparation example preparation of copper foil substrate

A roll-shaped electrolytic copper foil (double-sided glossy foil) having a ten-point average roughness Rzjis of 0.9 to 1.8 [ mu ] M on the M-plane, a 20-degree specular gloss Gs (20 DEG) of 179.0 to 195.2%, a 60-degree specular gloss Gs (60 DEG) of 365.8 to 412.1%, an 85-degree specular gloss Gs (85 DEG) of 121.5 to 125.7% and a thickness of 18 [ mu ] M was produced as a copper foil base to be a base material to be subjected to roughening treatment by using a copper sulfate electrolyte having the following composition and the following electrolytic conditions. The ten-point average roughness Rzjis and the specular gloss on the M-plane of the electrodeposited copper foil are measured under the same conditions as those of the surface-treated copper foil described later. More specifically, the following description will be made in the evaluation method column.

< cathode and anode >

Cathode: a titanium drum having roughness adjusted by polishing and grinding of #1000 to #2000

Anode: dimensional stability anode DSA (registered trademark)

< composition of electrolyte >

Cu：80g/L

H₂SO₄：70g/L

Chlorine concentration: 25mg/L

(additives)

Sodium 3-mercapto-1-propanesulfonate: 2mg/L

Hydroxyethyl cellulose: 10mg/L

Low molecular weight gum (molecular weight 3000): 50mg/L

< electrolytic conditions >

Bath temperature: 55 deg.C

Current density: 45A/dm²

(example 1)

In example 1, the following steps [1] to [3] were performed to obtain a surface-treated copper foil. The following description is made in detail.

[1] Formation of roughened layer

The electrolytic copper foil produced in the above preparation example, in which the ten-point average roughness Rzjis on the M-plane was 0.9 μ M, the 20-degree specular gloss Gs (20 °) was 188.7%, the 60-degree specular gloss Gs (60 °) was 385.7%, and the 85-degree specular gloss Gs (85 °) was 121.5%, was used as a copper foil base, and the M-plane was subjected to a roughening plating treatment in a roll-to-roll manner. The roughening plating treatment is performed by a two-stage plating treatment as necessary. The rough plating treatment (1) was carried out by using the following basic bath composition of the rough plating solution, in which the copper concentration and the molybdenum (Mo) concentration were set as shown in table 1 below, and the treatment speed, the inter-electrode flow rate in the treatment direction, the current density, and the treatment time were set as shown in table 1 below. The molybdenum (Mo) concentration was adjusted by adding and dissolving disodium molybdenum (VI) acid dihydrate in the roughening plating solution base bath. When the fixed plating treatment (2) is continued, the following fixed plating solution composition is used, and the treatment speed, the inter-electrode flow rate, the current density, and the treatment time are set as shown in table 1 below. In the case where the fixed plating treatment is not performed, the process proceeds to the following step [2 ].

< basic bath composition and bath temperature of roughening plating solution >

H₂SO₄：150g/L

Bath temperature: 18 deg.C

< composition of plating solution to be fixed, bath temperature >

Cu：60g/L

H₂SO₄：120g/L

Bath temperature: 60 deg.C

[2] Formation of a metallization layer

Next, on the surface of the roughened layer formed in [1], a metal plating was performed in the order of Ni, Zn, and Cr under the following conditions to form a metal-treated layer (intermediate layer).

< Ni plating Condition >

Ni：40g/L

H₃BO₃：5g/L

Bath temperature: 20 deg.C

pH：3.6

Current density: 0.2A/dm²

Treatment time: 10 seconds

< Zn plating Condition >

Zn：2.5g/L

NaOH：40g/L

Bath temperature: 20 deg.C

Current density: 0.3A/dm²

Treatment time: 5 seconds

< Cr plating Condition >

Cr：5g/L

Bath temperature: 30 deg.C

pH：2.2

Current density: 5A/dm²

Treatment time: 5 seconds

[3] Formation of silane coupling agent layer

Finally, an aqueous solution of 3-glycidylpropyltrimethoxysilane was applied at a concentration of 0.2 mass% to the metal-treated layer (particularly, the Cr-plated layer on the outermost surface) formed by [2], and dried at 100 ℃ to form a silane coupling agent layer.

(examples 2 to 9 and comparative examples 1 to 7)

Examples 2 to 9 and comparative examples 1 to 7 in the step [1] of forming a roughened layer, a surface-treated copper foil was obtained by the same method as in example 1, except that the electrolytic copper foil of the above preparation example having an M surface with ten-point average roughness Rzjis and specular gloss shown in table 1 was used as the copper foil substrate, and the conditions of the roughening treatment (1) and the fixed plating treatment (2) were set as described in table 1.

[ evaluation ]

The surface-treated copper foils of the examples and comparative examples were subjected to the following property evaluations.

The evaluation conditions for each property are as follows, and unless otherwise specified, each measurement is performed at normal temperature (20 ℃. + -. 5 ℃). The results are shown in table 2.

[ Cross-sectional Observation ]

The cross-section of the surface-treated copper foil was observed by image analysis according to the following procedure steps (i) to (iii).

First, (i) a surface-treated copper foil of 5mm square was cut out, cut perpendicularly to the roughened surface from the roughened surface side of the surface-treated copper foil, and the cut surface was precision-polished for 30 minutes using an ion milling apparatus ("IM 4000") under conditions of a table mode of C1 (oscillating angle: ± 15 °, oscillating speed: 6 reciprocation/min) and an acceleration voltage of 6 kV. A scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, "SU 8020") was used to observe a secondary electron image of 5 ten thousand times at an acceleration voltage of 3kV from a direction perpendicular to the processed surface of the surface-treated copper foil exposed on the processed surface of the prepared measurement sample, and a cross-sectional photograph (SEM image, length 1.89 μm × width 2.54 μm) of the vicinity of the roughened surface was prepared.

Next, (ii) image processing for emphasizing the outline of the coarsened particles is performed on the cross-sectional photograph using image editing software ("Real World Paint"), the outline of the cross-sectional shape is extracted, and finally only the outline of the cross-sectional shape in the same machining cross-section is extracted. Then, (iii) the particle height (h) and the particle width (w) of the coarsened particles in the contour line, and the number of the coarsened particles (observation target particles) present in each observation visual field (2.5 μm in the width direction) region arbitrarily were measured using image measurement software (Photo Ruler), respectively.

Based on the above measurement values, the average values of the particle height (h) and the particle width (w) of the coarsened particles, and the ratio (h/w) of the particle height (h) to the particle width (w) of the coarsened particles in the 2.5 μm region in the width direction of the observation field, and the linear density (d) and the linear coverage (c) of the coarsened particles were obtained, respectively.

The same surface-treated copper foil was analyzed at 10 portions of an arbitrary cross section. Then, based on the respective measured values of the cross-sectional photographs totaling 10 sheets, the average value of the particle height (h) of the coarsened particles, the average value of the particle width (w), the average value of the ratio (h/w) of the particle height (h) to the particle width (w), the respective average values of the linear density (d) and the linear coverage (c) were calculated, and the respective average values were set as the measured values of the surface-treated copper foil to be observed. The measured values of the surface-treated copper foils of the examples and comparative examples are shown in table 2.

[ specular gloss ]

The roughened surface of the surface-treated copper foil was measured for 20-degree specular gloss Gs (20 degrees), 60-degree specular gloss Gs (60 degrees) and 85-degree specular gloss Gs (85 degrees) according to JIS Z8741-1997 using a gloss meter (VG 7000, manufactured by Nippon Denshoku industries Co., Ltd.). For each light-receiving angle, 3 measurements were performed in a direction perpendicular to the longitudinal direction (conveying direction) of the surface-treated copper foil, and all the measured values (N =3) were averaged to obtain the specular gloss corresponding to each light-receiving angle.

The specular gloss of the M-side of the electrodeposited copper foil produced in the above preparation example was measured under the same conditions.

[ ten-point average roughness ]

On the roughened surface of the surface-treated copper foil, a contact surface roughness meter ("Surfcorder SE 1700", manufactured by shinka corporation) was used to measure the roughness of the roughened surface of the surface-treated copper foil in a direction perpendicular to the longitudinal direction (conveying direction) of the surface-treated copper foil, in accordance with JIS B0601: 2001, the ten point average roughness Rzjis (μm).

The ten-point average roughness Rzjis (μ M) of the M-plane of the electrodeposited copper foil produced in the above preparation example was also measured under the same conditions.

[ evaluation of high frequency characteristics ]

As evaluation of high-frequency characteristics, transmission loss in a high-frequency band was measured. The details are described below.

The roughened surface of the surface-treated copper foil was bonded to both surfaces of a laminate of MEGTRON7 (thickness: 60 μm) as a polyphenylene ether-based low dielectric constant resin substrate, manufactured by 2 Xtensiles, by pressing at 200 ℃ for 2 hours under a surface pressure of 3.5MPa, to produce a double-sided copper-clad laminate. The obtained copper-clad laminate was subjected to circuit processing to produce a circuit board on which a microstrip line having a transmission line width of 300 μm and a length of 70mm was formed. The transmission loss was measured by transmitting a high-frequency signal to a transmission path of the circuit board using a network analyzer (manufactured by Keysight Technologies, "N5247A"). The characteristic impedance is set to 50 Ω.

The smaller the absolute value of the measured value of the transmission loss is, the smaller the transmission loss is, the better the high-frequency characteristics are. The high-frequency characteristics were evaluated based on the following evaluation criteria using the obtained measurement values as indices.

O: the absolute value of the transmission loss at 60GHz is lower than 3.5dB, and the absolute value of the transmission loss at 100GHz is lower than 6 dB;

and (delta): the absolute value of the transmission loss at 60GHz is lower than 3.5dB, and the absolute value of the transmission loss at 100GHz is more than 6 dB;

x: the absolute value of the transmission loss at 60GHz is 3.5dB or more.

[ evaluation of Normal adhesion ]

As evaluation of normal adhesion, based on JIS C6481: 1996, peel test was performed. The details are described below.

A copper-clad laminate was produced by the same method as described in [ evaluation of high-frequency characteristics ] above, and the copper foil portion (surface-treated copper foil) of the obtained copper-clad laminate was masked with a tape having a width of 10 mm. After copper chloride etching was performed on the copper-clad laminate, the tape was removed, and a circuit wiring board having a width of 10mm was produced. The peel strength of the circuit wiring board was measured by a tensile tester manufactured by Toyo Seiki Seisaku-Sho K.K., in the case of peeling a 10 mm-wide circuit wiring portion (copper foil portion) from a resin base material at a speed of 50 mm/min in a 90-degree direction. The adhesion was evaluated based on the following evaluation criteria using the obtained measurement values as indices.

< evaluation criteria for Normal adhesion >

O: the peel strength is more than 0.55 kN/m;

and (delta): a peel strength of 0.50kN/m or more and less than 0.55 kN/m;

x: the peel strength is less than 0.50 kN/m.

[ evaluation of Heat-resistant adhesion ]

As evaluation of heat resistant adhesion, based on JIS C6481: 1996, peel test after heat treatment. The details are described below.

A copper-clad laminate was produced by the same method as described in [ evaluation of high-frequency characteristics ] above, and the copper foil portion of the resulting copper-clad laminate was masked with a tape having a width of 10 mm. After copper chloride etching was performed on the copper-clad laminate, the tape was removed, and a circuit wiring board having a width of 10mm was produced. The circuit wiring board was heated in a heating furnace at 300 ℃ for 1 hour, and then cooled to room temperature with natural air. Then, the peel strength of the circuit wiring portion (copper foil portion) having a width of 10mm of the circuit wiring board was measured by a tensile tester manufactured by Toyo Seiki Seisaku-Sho K.K., at a speed of 50 mm/min in a 90-degree direction from the resin substrate. The heat-resistant adhesion was evaluated based on the following evaluation criteria using the obtained measurement values as indices.

< evaluation criteria for Heat-resistant adhesion >

O: the peel strength is more than 0.50 kN/m;

and (delta): a peel strength of 0.40kN/m or more and less than 0.50 kN/m;

x: the peel strength is less than 0.40 kN/m.

[ comprehensive evaluation ]

All of the above-mentioned high-frequency characteristics, normal adhesion and heat-resistant adhesion were combined and evaluated comprehensively based on the following evaluation criteria. In this example, a and B were set as the pass levels in the comprehensive evaluation.

< evaluation criteria for comprehensive evaluation >

A (excellent): all evaluations were ∘;

b (qualified): there was no x evaluation in all evaluations;

c (fail): at least 1 was evaluated as ×.

As shown in table 2, when SEM observation was performed on the cross section of the surface-treated copper foils of examples 1 to 9, it was confirmed that: the roughened surface is controlled so that the average particle height (h) of the roughened particles is 0.05 to 0.30 [ mu ] m, the average particle height (h) to particle width (w) ratio (h/w) of the roughened particles is 0.7 to 5.0, and the linear coverage (c) of the roughened particles is 15 to 60%, and therefore, the roughened surface is excellent in high-frequency characteristics and exhibits high adhesiveness (normal adhesiveness and heat-resistant adhesiveness).

In contrast, with respect to the surface-treated copper foils of comparative examples 1 to 7, it was confirmed that: the average value of the particle height (h) of the coarse particles on the coarse surface is 0.05-0.30 [ mu ] m, the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the coarse particles is 0.7-5.0, and the linear coverage (c) of the coarse particles is at least one of 15-60%, so that one or both of the high-frequency characteristics and the adhesiveness (particularly, the heat-resistant adhesiveness) are inferior to those of the surface-treated copper foils of examples 1-9.

Claims

1. A surface-treated copper foil having a surface-treated film containing a roughened layer formed by forming roughened particles on at least one surface of a copper foil substrate,

c=d×W×100 (%) ···(1)

2. The surface-treated copper foil according to claim 1, wherein the surface-treated film has a 20-degree specular gloss Gs (20 °) of 0.5 to 120%, a 60-degree specular gloss Gs (60 °) of 5 to 200%, and an 85-degree specular gloss Gs (85 °) of 75 to 120%,

a value calculated from each value of the 20-degree specular gloss Gs (20 °), the 60-degree specular gloss Gs (60 °), and the 85-degree specular gloss Gs (85 °) by the following equation (2) is 0 to 10:

(Gs(85°)﹣Gs(60°))/Gs(20°) ···(2)。

3. the surface-treated copper foil according to claim 1 or 2, wherein the average value of the particle width (w) of the roughening particles is 0.02 to 0.15 μm.

4. The surface-treated copper foil according to claim 1 or 2, wherein the linear density (d) of the roughening particles is 2.0 particles/μm or more.

5. The surface-treated copper foil according to claim 1 or 2, wherein the surface treatment film has a ten-point average roughness Rzjis value of 0.5 to 2.0 μm on the surface thereof.

6. A copper-clad laminate formed using the surface-treated copper foil according to any one of claims 1 to 5.

7. A printed wiring board formed using the copper-clad laminate according to claim 6.