阅读说明：本技术 表面处理铜箔、使用了该表面处理铜箔的覆铜层叠板以及印刷电路板 (Surface-treated copper foil, and copper-clad laminate and printed wiring board using same ) 是由 佐野惇郎 于 2020-03-19 设计创作，主要内容包括：本发明的目的在于,提供一种特别是在用于印刷电路板的导体电路的情况下,能实现传输特性、密合性、耐热性以及基板耐湿可靠性,并且无落粉的表面处理铜箔、使用了该表面处理铜箔的覆铜层叠板以及印刷电路板。该表面处理铜箔具有包含在铜箔基体的至少一个面形成粗化粒子而成的粗化处理层的表面处理被膜,在通过扫描电子显微镜(SEM)对该表面处理铜箔的剖面进行观察时,在该表面处理被膜的宽度方向75μm的区域中,该粒子的粒子高度的平均值为0.8～2.0μm,该粗化粒子的该粒子高度(h)与粒子宽度(w)之比(h/w)的平均值为1.5～4.5,该粗化粒子中,满足必要条件(I)～(IV)的粗化粒子(P)存在1～60个。(The present invention aims to provide a surface-treated copper foil which can realize transmission characteristics, adhesion, heat resistance and substrate moisture resistance reliability and is free from powder falling particularly when used for a conductor circuit of a printed circuit board, and a copper-clad laminate and a printed circuit board using the surface-treated copper foil. The surface-treated copper foil has a surface-treated film comprising a roughened layer formed by forming roughened particles on at least one surface of a copper foil substrate, wherein when the surface-treated copper foil is observed by a Scanning Electron Microscope (SEM) on a cross section thereof, the average particle height of the particles is 0.8 to 2.0 [ mu ] m, the average particle height (h/w) of the roughened particles is 1.5 to 4.5, and the roughened particles have 1 to 60 roughened particles (P) satisfying the requirements (I) to (IV) in a region of 75 [ mu ] m in the width direction of the surface-treated film.)

1. A surface-treated copper foil comprising: a surface treatment film comprising 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 was observed by a Scanning Electron Microscope (SEM), in a region of 75 μm in the width direction of the surface-treated film,

the average value of the particle height h of the coarsening particles is 0.8 to 2.0 μm,

the average value of the ratio h/w of the particle height h to the particle width w of the coarsening particles is 1.5 to 4.5,

among the coarse particles, 1 to 60 coarse particles P satisfying the following requirements I to IV exist,

requirement I: the height h of the coarsening particles is 1.5-3.5 μm;

requirement II: the ratio h/w of the height h to the width w of the coarsened particles is 2.5 to 15;

requirement III: the number of branches of the coarsening particles is 10-25;

requirement IV: the shortest root pitch between the coarsened particles and other coarsened particles which are closest to the coarsened particles and have a particle height of more than 1.5 mu m is 0.7-10.0 mu m.

2. The surface-treated copper foil according to claim 1,

the linear density d of the coarsening particles is 1.0-1.8 particles/mu m.

3. The surface-treated copper foil according to claim 1 or 2,

the surface treatment film has an extended area ratio Sdr of 300 to 380% as measured by a three-dimensional white interference microscope.

4. A copper-clad laminate formed using the surface-treated copper foil according to any one of claims 1 to 3.

5. A printed circuit board formed using the copper-clad laminate according to claim 4.

Technical Field

The present invention relates to a surface-treated copper foil, and a copper-clad laminate and a printed wiring board using the surface-treated copper foil.

Background

In recent years, high frequency compliant devices exceeding 1GHz, such as servers, routers, and smart phones, have increased, and copper foils through which high frequency signals actually flow are also required to have excellent transmission characteristics. Meanwhile, it has been required that the peel strength, which is an index of reliability, is a certain level or more, and that the transmission characteristics and the peel strength (hereinafter referred to as "adhesion") are compatible at a high level.

Generally, as a method for improving the adhesion between the resin base material and the surface of the copper foil, the following methods are mentioned: a roughened layer (a layer having roughened particles formed thereon) is formed on the surface thereof by plating, etching, or the like, and a physical adhesion effect (anchor effect) with the resin base material is obtained, thereby improving the 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 (adhesion) between the surface of the copper foil and the resin base material, the transmission loss increases due to the skin effect.

In this way, in the copper-clad laminate, the improvement of the adhesion between the copper foil and the resin base material and the suppression of the transmission loss are in a trade-off relationship.

Therefore, in the copper foil used in the copper-clad laminate, both improvement of adhesion between the copper foil and the resin base material and suppression of transmission loss have been studied. For example, patent documents 1 to 4 propose techniques for improving adhesion between a copper foil and a resin base material mainly by appropriately controlling the shape of roughening particles.

However, in the above-described conventional technique, since the specific surface area is increased by forming fine irregularities on the roughened surface, when the resin substrate is bonded to the resin substrate, filling defects of the roughened surface with the resin may occur depending on the type of the resin substrate. In this case, a gap is formed between the resin base material and the copper foil, which leads to a problem that heat resistance and substrate moisture resistance reliability are deteriorated.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-515456

Patent document 2: japanese patent laid-open publication No. 2017-520558

Patent document 3: japanese patent laid-open No. 2015-147978

Patent document 4: japanese patent laid-open publication No. 2018-172790

Disclosure of Invention

Problems to be solved by the invention

Accordingly, an object of the present invention is to provide a surface-treated copper foil which can realize excellent transmission characteristics, adhesion, heat resistance and substrate moisture resistance reliability particularly when used for a conductor circuit of a printed wiring board and which is free from powder falling, and a copper-clad laminate and a printed wiring board using the surface-treated copper foil.

Means for solving the problems

As a result of intensive studies, the present inventors have found that a surface-treated copper foil having a surface-treated film including a roughened layer formed by forming roughened particles on at least one surface of a copper foil substrate can be provided with a structure that can realize excellent transmission characteristics, adhesion, heat resistance and substrate moisture resistance reliability particularly when used for a conductor circuit of a printed wiring board, and have completed the present invention by: when the surface-treated copper foil is observed in a cross section thereof by a Scanning Electron Microscope (SEM), in a region of 75 [ mu ] m in the width direction of the surface-treated film, the average value of the particle height (h) of the roughening particles is 0.8 to 2.0 [ mu ] m, the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the roughening particles is 1.5 to 4.5, and 1 to 60 of the roughening particles (P) satisfying the following requirements (I) to (IV) are present among the roughening particles.

Requirement (I): the height (h) of the coarsened particles is 1.5 to 3.5 μm.

Requirement (II): the ratio (h/w) of the particle height (h) to the particle width (w) of the coarsened particles is 2.5 to 15.

Requirement (III): the number of branches of the coarsened particles is 10-25.

Requirement (IV): the shortest root pitch between the coarsened particles and other coarsened particles which are closest to the coarsened particles and have a particle height of more than 1.5 mu m is 0.7-10.0 mu m.

That is, the gist of the present invention is as follows.

[1] A surface-treated copper foil having a surface-treated film comprising 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 0.8 to 2.0 [ 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 1.5 to 4.5, and 1 to 60 of the roughened particles (P) satisfying the following requirements (I) to (IV) are present among the roughened particles.

Requirement (I): the height (h) of the coarsened particles is 1.5 to 3.5 μm.

Requirement (II): the ratio (h/w) of the particle height (h) to the particle width (w) of the coarsened particles is 2.5 to 15.

Requirement (III): the number of branches of the coarsened particles is 10-25.

Requirement (IV): the shortest root pitch between the coarsened particles and other coarsened particles which are closest to the coarsened particles and have a particle height of more than 1.5 mu m is 0.7-10.0 mu m.

[2] The surface-treated copper foil according to the above [1], wherein the linear density (d) of the roughening particles is 1.0 to 1.8 particles/μm.

[3] The surface-treated copper foil according to the above [1] or [2], wherein the surface-treated film has an extended area ratio (Sdr) of 300 to 380% as measured by a three-dimensional white interference microscope.

[4] A copper-clad laminate formed using the surface-treated copper foil according to any one of the above [1] to [3 ].

[5] A printed wiring board formed using the copper-clad laminate according to [4 ].

Effects of the invention

According to the present invention, a surface-treated copper foil which can realize excellent transmission characteristics, adhesion, heat resistance and substrate moisture resistance reliability particularly when used for a conductor circuit of a printed wiring board and which is free from powder falling, a copper-clad laminate using the surface-treated copper foil, and a printed wiring board can be provided.

Drawings

In fig. 1, (a) in fig. 1 is an example of an SEM image obtained by observing the surface of the surface treatment film of the surface-treated copper foil of the present invention from directly above in an original state, fig. 1(b) is an example of an SEM image obtained by observing the surface of the surface treatment film of the surface-treated copper foil of the present invention from a processing section in an original state, and fig. 1 (c) is an example of an SEM image obtained by observing the surface of the surface treatment film of the surface-treated copper foil of the present invention from a processing section after resin embedding processing.

Fig. 2 shows an example of the procedure for image analysis of an SEM image of a processed cross section of a surface-treated copper foil.

Fig. 3 is a diagram for explaining an example of a method for measuring coarse particles.

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

Fig. 5 is a diagram for explaining a method of measuring the number of coarsened particle branches of the coarsened particles.

Fig. 6 is a diagram for explaining an example of a method for measuring the shortest root pitch between the coarsened particle and another coarsened particle having a particle height of 1.5 μm or more closest to the coarsened particle.

Detailed Description

The surface-treated copper foil of the present invention, and a copper-clad laminate and a printed wiring board using the surface-treated copper foil will be described in detail below.

< surface-treated copper foil >

The surface-treated copper foil is characterized by comprising a surface-treated coating film comprising 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 0.8-2.0 [ 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 1.5-4.5, and 1-60 roughened particles (P) satisfying the following requirements (I) - (IV) are present in the roughened particles.

Requirement (I): the height (h) of the coarsened particles is 1.5 to 3.5 μm.

Requirement (II): the ratio (h/w) of the particle height (h) to the particle width (w) of the coarsened particles is 2.5 to 15.

Requirement (III): the number of branches of the coarsened particles is 10-25.

Requirement (IV): the shortest root pitch between the coarsened particles and other coarsened particles which are closest to the coarsened particles and have a particle height of more than 1.5 mu m is 0.7-10.0 mu m.

The surface-treated copper foil of the present invention comprises: a copper foil substrate; and a surface-treated film comprising a roughened layer formed by forming roughened particles on at least one surface of the copper foil substrate. The surface of such a surface-treated film 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 and the particle shape formed on at least one surface of the copper foil substrate. The surface of such a 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 formed directly on the roughened layer, or the surface of a silane coupling agent layer formed on the roughened layer with an intermediate layer such as a Ni-containing base layer, a Zn-containing heat-resistant layer, and a Cr-containing rust-proofing layer interposed therebetween. In the case where the surface-treated copper foil of the present invention is used for a conductor circuit of a printed wiring board, for example, the roughened surface serves as a surface (bonding surface) for bonding a laminated resin base material.

Here, fig. 1 (a), 1(b) and 1 (c) show the case 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) in the original state (without processing such as resin embedding), and fig. 1(b) is an example of an SEM image obtained by cutting the surface-treated copper foil in the original state perpendicularly to the roughened surface, precision-polishing the cut surface with an ion milling device (ion milling device), and observing the processed cut surface with a Scanning Electron Microscope (SEM). Fig. 1 (c) is an example of an SEM image obtained by performing resin embedding processing on the surface side of the surface-treated copper foil, then cutting the surface perpendicularly to the roughened surface, performing precision polishing processing on the cross section using an ion milling apparatus, and observing the processed cross section with a Scanning Electron Microscope (SEM).

As is apparent from fig. 1(b), in particular, the roughened surface of the surface-treated copper foil of the present invention has roughened particles having a certain number of side surfaces with a protruding shape (hereinafter referred to as "branches").

In the evaluation of the shape of the roughened particles in such a special roughened surface, when the surface of the roughened surface is observed by a contact roughness measuring instrument or an optical microscope, only the branches of the outermost surface are observed in the principle of measurement, and the shape of the entire growth direction of each roughened particle cannot be observed. Therefore, in the present invention, as one method of evaluating the roughened surface, a method of defining and evaluating the characteristics of the roughened surface by analyzing the state of formation of the roughened particles in the roughened surface from the cross section of the surface-treated copper foil as shown in fig. 1(b) is employed. Specifically, the method is performed as follows.

First, the surface-treated copper foil was cut perpendicularly to the roughened surface, the cross section was precision-polished using an ion milling apparatus, and a secondary electron image of ten thousand times the magnification of the processed cross section was observed at an acceleration voltage of 3kV under SEM. In the SEM observation, attention was paid to horizontally fixing the surface-treated copper foil on a smooth support table so that the surface-treated copper foil does not warp or sag, and adjusting the surface-treated copper foil to be horizontal in the cross-sectional SEM photograph.

The observation sample for taking a cross-sectional SEM photograph may be a surface-treated copper foil as it is, or a surface-treated copper foil in which the observation surface is embedded with a resin, if necessary.

Further, the measurement of the size of the roughened particles in the roughened surface is performed by image analysis of the SEM photograph obtained by the SEM observation. Fig. 2 shows an example of the sequence of image analysis. First, a cross-sectional SEM photograph was obtained at ten thousand times magnification as shown in fig. 2 (a). Next, the cross-sectional SEM photograph is subjected to image processing, and a contour line of the cross-sectional shape as shown in fig. 2 (b) is extracted. 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. Such image processing may be performed by known processing software such as "Photoshop", "imageJ", "Real World Paint", which is a general image editing software. Specifically, the following examples are given.

This image processing is performed to extract the roughened shape of the outermost surface from the cross-sectional SEM photograph of the surface-treated copper foil. Therefore, when a cross section of a test piece subjected to resin embedding processing on the front surface side of the copper foil or a cross section of a circuit board bonded to a resin base material is observed, the above-described processing is not necessary.

Next, based on the extracted outline of the cross-sectional shape and fig. 2 (c), coarse particles were identified and various sizes were measured. The measurement can be performed by known processing software such as "WinROOF" and "Photo Ruler" which are general image measurement software. Specifically, the following examples are given. Fig. 3 shows an example of the simplest method for measuring coarse particles.

First, as shown in fig. 3 (a), a line L passing through the apex V of the projection is drawn in the particle growth direction for the projection (coarsened particle) to be measured located on the contour line. Next, as shown in fig. 3 (b), a rectangle (including a square) Sq having upper and lower sides perpendicularly intersecting the line L is drawn. The upper side of the rectangle Sq intersects the vertex V, and any corner of the lower side intersects the base of the projection farther from the vertex (this corner is referred to as "R1"). Further, the other corner of the lower side of the rectangle Sq (this corner is referred to as "R2") is an orthogonal point of the lower side and a side extending parallel to the line L from the upper side direction. The one side is drawn so as to pass through the other side of the root of the projection (this point is referred to as "R2'"). As shown in fig. 3 (c), the dimension of one side of the rectangle Sq parallel to the line L is defined as the particle height (h) of the roughening particles, and the dimension of one 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 measured while drawing the rectangle Sq are regarded as one coarsened particle.

In the case of observing the cross section of a test piece having a surface side of a copper foil subjected to resin embedding processing or the cross section of a circuit board bonded to a resin base material, the cross section can be observed without extracting the contour line, but in this case, the coarsened particles existing obliquely inside the cross section are partially cut and reflected on the observed cross section. Such roughened particles appear to float from the surface-treated copper foil in the observation cross section, and are not the object of measurement.

Further, an example of the measurement without the coarse particles and a method of measuring the coarse particles having a special shape will be described with reference to fig. 4 as necessary.

First, although not particularly shown, particles having a particle height (h) of less than 0.2 μm in the projections measured with the above-described reference do not affect the transmission characteristics and adhesion of the present invention, and it is difficult to accurately measure them, and therefore, they are not the object of 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 projections measured in the above-described reference, the projections having a ratio (h/w) of the particle height (h) to the particle width (w) of less than 0.40 do not affect the transmission characteristics and the adhesion which are important in the present invention, and therefore are not observed and are not included in the "coarsened particles" in the present invention.

Fig. 4 (b) shows a measurement example in which two or more convex portions are provided at the apex. As shown in fig. 4 (b), each vertex may be regarded as one particle and measured based on the above definition.

Fig. 4 (c) shows an example of measurement of a projection having two or more steps near the root. In this case, the determination of the root is made in a point that the transmission characteristics and the adhesion, which are important in the present invention, are affected by which part of the projection is determined. That is, the angle R1 intersecting the base of the projection farther from the apex is the position of the lowest stage of the base. In this case, the growth direction of the particles is determined by the whole particles.

Fig. 4 (d) is a measurement example in the case where there are other projections on the projection having less unclear root parts and having a size ratio (h/w) of less than 0.40 as in fig. 4 (a). In this case, the unknown root is not to be measured, and the measurement may be performed based on the above definition by focusing attention on the projection having a distinguishable root. This is because the gentle convex portion having an undefined root portion does not originally affect the transmission characteristics and the adhesion which are important in the present invention.

In addition, regarding 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 in consideration of the effects of the transmission characteristics and the adhesion which are important in the present invention.

Further, based on the particle height (h), the particle width (w) and the number of the coarse particles measured as described above, the average values of the particle height (h), the particle width (w), the ratio (h/w) of the particle height (h) to the particle width (w) in a region of 75 μm in the width direction of the observation field, and the linear density (d) of the coarse particles were calculated.

Furthermore, among the coarse particles observed in a region of 75 μm in the width direction of the observation field, those satisfying the following requirements (I) to (IV) were identified as specific coarse particles (P), and the number thereof was measured.

Requirement (I): the height (h) of the coarsened particles is 1.5 to 3.5 μm.

Requirement (II): the ratio (h/w) of the particle height (h) to the particle width (w) of the coarsened particles is 2.5 to 15.

Requirement (III): the number of branches of the coarsened particles is 10-25.

Requirement (IV): the shortest root pitch between the coarsened particles and other coarsened particles which are closest to the coarsened particles and have a particle height of more than 1.5 mu m is 0.7-10.0 mu m.

Hereinafter, a method for identifying the specific coarsening particles (P) will be described in detail.

First, as the coarse particles (p), the coarse particles satisfying the requirements (I) and (II) among the coarse particles observed in a region of 75 μm in the width direction of the observation field are extracted. The coarsened particles (p) do not fall off powder, and contribute to improvement of adhesion.

Next, the coarsened particles satisfying the requirement (III) among the coarsened particles (p) are extracted as coarsened particles (p'). Since the coarsened particles (p') more effectively exhibit the anchoring effect, the peel strength is improved, which cannot be fully exhibited only by the effect based on the particle height (h) and the ratio (w) of the particle height to the particle width.

Hereinafter, a method for measuring the number of branches of the coarse particles (hereinafter, may be simply referred to as "coarse particle branches") defined in the requirement (III) will be described with reference to fig. 5.

First, as shown in fig. 5 (a), the apex V, the line L, the point R1, the point R2, and the point R2' are identified for the coarse particles (p) to be measured according to the above method. Next, as shown in fig. 5 (b), a straight line k perpendicular to the line L of the coarse particles (p) to be measured is drawn₁、k₂、......、k_nFrom a line k passing through the root R2₁The projections are drawn out at 0.05 μm intervals in the direction of the apex V. Then, as shown in fig. 5 (c), the straight line k is followed₁、k₂、......、k_nEach of the particles (p) is determined as a common portion with a region surrounded by the outline of the coarsened particle (p), and the size (t) of the common portion is measured₁、t₂、...、t_n. Note that, the dimension t₁、t2、......、t_nNot necessarily the size of a continuous line, e.g. k₂₉That is aligned with the straight line k₂₉When there are two or more common portions (2), the sum of the two or more line segments is measured as a dimension t₂₉. Then, based on the measured dimensions t_nM satisfying the following formula (i) is obtained, and the number of m is obtained as the number of coarsened particle branches of the coarsened particles (p).

(t_m-t_m-1)×(t_m+1-t_m)＜0(m＝2，3，......，n-1)......(i)

The coarse particles (p) are extracted from the coarse particles (p) in which the number of coarse particle branches is 10 to 25.

Among the coarse particles (P'), those satisfying the requirement (IV) are identified as specific coarse particles (P).

Next, a method for measuring the shortest root pitch of another coarsened particle that is closest to the particle and has a particle height of 1.5 μm or more, which is defined in requirement (IV), will be described with reference to fig. 6.

First, as shown in fig. 6, the other coarsened particles closest to the coarsened particle having a particle height of 1.5 μm or more existing on the left side of the coarsened particle (p') to be measured are determined as coarsened particles (q1), and the coarsened particles are measuredAmong the coarsened particles having a particle height of 1.5 μm or more existing on the right side of the seed (p'), the closest other coarsened particle is determined as a coarsened particle (q 2). Then, two points R1 at the root of the coarsened particle (p')_p’、R2’_p’Two points R1 at the root of any one of the coarse particles (q1)_q1、R2’_q1Of the four line segments connected to each other, the line segment having the smallest size is the size of the line segment of the combination (R1 in fig. 6)_p’-R2’_q1Dimension (d) was measured as the left shortest root pitch (x 1). Similarly, two points R1 at the root of the coarsened particle (p')_p’、R2_p’Two points R1 at the root of any one of the coarse particles (q2)_q2、R2’_q2The size of the line segment (R2 'in the case of FIG. 6) of the combination of the four line segments connected to each other and having the smallest size'_p’-R1_q2Dimension (d) was measured as the right shortest root pitch (x 2). Then, the shorter one of x1 and x2 is defined as the shortest root pitch (x) between the coarsened particles and the other coarsened particles having a particle height of 1.5 μm or more closest to the coarsened particle (p'). When no coarsened particle (q1) or coarsened particle (q2) is present in the observation field, the shortest root pitch (x) is set to be the dimension of one of x1 and x2 that can be measured.

As shown in fig. 6, other coarse particles having a particle height of less than 1.5 μm may be present between the coarse particles (p ') and the coarse particles (q1) or between the coarse particles (p') and the coarse particles (q 2).

In the present invention, among the coarse particles (P'), the coarse particles having the shortest root pitch (x) of 0.7 to 10.0 μm are determined as the specific coarse particles (P).

The above-mentioned roughened particles (p') themselves contribute to the improvement of adhesion, but the adhesion can be further improved by further providing other roughened particles having a particle height of 1.5 μm or more in the proximity distance (within 10.0 μm in terms of root pitch). However, if the other roughening particles having a particle height of 1.5 μm or more are too close to the roughening particles (p '), there is a tendency that a gap is generated between the resin base material and the copper foil when the resin of the resin base material is not sufficiently filled around the roughening particles (p') in the production of the copper-clad laminate.

Therefore, among the roughened particles (P') satisfying the requirements (I) to (III), the roughened particles satisfying the requirement (IV) which have particularly excellent anchoring effect and hardly generate a gap between the resin base material and the copper foil are considered as the specific roughened particles (P) in the present invention.

Since the determination and measurement of the above-described various types of coarse particles are the determination of the contour line, a slight error occurs depending on the measurement person. However, such an error can be sufficiently minimized by observing a region 75 μm in the width direction and averaging the measurement results of a plurality of coarse particles.

Specifically, the particle height (h) and the particle width (w) of the coarse particles are measured for each sectional photograph based on the above criteria, and the number of coarse particles (particles to be observed) existing in the observation field corresponding to 75 μm in each width direction and the number of specific coarse particles (P) are measured.

Although it depends on the size of the cross-sectional photograph, for example, when the observation field of view is 12.5 μm in the width direction for each cross-sectional photograph, the total of 6 arbitrary spots (6 cross-sectional photographs) is set as the observation result of the region of 75 μm in the width direction. In addition, although it depends on the size and number of the cross-sectional photographs, when the total of the observation visual fields is 75 μm or more in the width direction, the observation result is obtained by converting the measured values to values of 75 μm or more in the width direction.

More specific measurement methods and calculation methods are described in the examples below.

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

The average particle height (h) of the roughened particles in the roughened surface is 0.8 to 2.0 μm, preferably 0.8 to 1.4 μm, and more preferably 1.0 to 1.4 μm. By setting the above range, excellent transmission characteristics, adhesion, heat resistance, and substrate moisture resistance reliability can be achieved. When the average particle height (h) of the coarse particles is less than 0.8 μm, the adhesion, heat resistance and substrate moisture resistance reliability tend to be lowered, and when it exceeds 2.0 μm, the transmission characteristics tend to be lowered.

The average width (w) of the coarsened particles is preferably 0.2 to 1.0 μm, more preferably 0.2 to 0.6 μm, and even more preferably 0.3 to 0.5 μm. In particular, the average value of the widths (w) of the roughening particles is 0.5 μm or less, whereby the heat resistance can be further improved.

The average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the coarsened particles is 1.5 to 4.5, preferably 1.6 to 4.0, more preferably 2.0 to 4.0, and further preferably 2.4 to 4.0. By setting the above range, no powder falling occurs, and excellent adhesion, heat resistance, and substrate moisture resistance reliability can be achieved. In particular, when the average value of the ratio (h/w) is 2.0 or more, the adhesion can be further improved. The average value of the ratio (h/w) is not particularly limited if it exceeds 4.5, but rather, a powder falling failure tends to occur.

The linear density (d) of the roughened particles in the roughened surface is preferably 0.5 to 2.5 particles/μm, more preferably 0.8 to 2.1 particles/μm, and still more preferably 1.0 to 1.8 particles/μm. In particular, when the linear density (d) of the coarse particles is 0.8 pieces/μm or more, more excellent adhesion and heat resistance can be achieved. Further, by setting the linear density (d) of the coarsened particles to 2.1 pieces/μm or less, more excellent transfer characteristics can be realized. The line density (d) of the coarse particles is a value calculated from the number of coarse particles (particles to be observed) existing in the observation field corresponding to 75 μm per width direction, and is a particle number density per unit line region (width region).

The number of the specific roughening particles (P) in the roughened surface is 1 to 60, preferably 3 to 60, more preferably 3 to 48, and still more preferably 3 to 36. By setting the above range, excellent transmission characteristics, heat resistance, and substrate moisture resistance reliability can be achieved. When the number of the specific roughening particles (P) is 0, the heat resistance and the substrate moisture resistance reliability tend to be lowered, and when it exceeds 60, the transmission characteristics tend to be lowered.

In addition, conventionally, ten-point average roughness Rzjis is generally used as a parameter indicating the surface shape of the copper foil, but the ten-point average roughness Rzjis includes only information in the height direction of the two-dimensional cross-sectional shape with respect to the surface, and thus sufficient evaluation cannot be performed. On the other hand, the extended area ratio (Sdr) includes three-dimensional information of the surface, and therefore more appropriate characteristic evaluation can be performed.

The spread area ratio (Sdr) is a ratio of the surface area increased by the surface properties based on an ideal plane having the size of the measurement region, and is defined by the following formula (iii).

In the above formula (iii), x and y are plane coordinates, and z is a coordinate in the height direction. z (x, y) represents the coordinate of a certain point, and the slope at the coordinate point is obtained by differentiating the coordinate. Further, a is a plane area of the measurement region.

The spread area ratio (Sdr) can be obtained by measuring and evaluating the difference in roughness of the surface of the copper foil by, for example, a three-dimensional white interference microscope, a Scanning Electron Microscope (SEM), an electron beam three-dimensional roughness analyzer, or the like. In general, the spread area ratio (Sdr) tends to increase as the spatial complexity of the surface properties increases, regardless of the change in the surface roughness (Sa).

In the present invention, by measuring the spread area ratio (Sdr) as average information of a plurality of roughened particles on the roughened surface, more appropriate characteristic evaluation can be performed.

The spread area ratio (Sdr) of the surface-treated copper foil of the present invention on the roughened surface, as measured by a three-dimensional white interference microscope, is preferably 250 to 400%, more preferably 290 to 390%, and still more preferably 300 to 380%. In particular, when the spreading area ratio (Sdr) is 290% or more, more excellent adhesion and heat resistance can be achieved. Further, by setting the spreading area ratio (Sdr) of the coarsened particles to 390% or less, more excellent transmission characteristics can be realized.

Further, according to the surface-treated copper foil of the present invention, by using it for a conductor circuit of a printed wiring board, the following printed wiring board can be obtained: the surface-treated copper foil can highly suppress transmission loss when transmitting a high-frequency signal having a frequency of, for example, 1GHz or higher, and can maintain good adhesion between the surface-treated copper foil and the resin base even under high temperature and high humidity, and has excellent durability under severe conditions.

< method for producing surface-treated copper foil >

Next, a preferred method for producing the surface-treated copper foil of the present invention will be described as an example. 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 coarse unevenness is preferably used. Among these, electrolytic copper foil is preferably used from the viewpoint of productivity and cost, and in particular, electrolytic copper foil with smooth both surfaces, which is generally called "double-sided glossy foil", is more preferably used.

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

In addition, in the electrolytic copper foil, there are also some irregularities on the smooth surface as described above. Such unevenness is caused by 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 and grinding, but grinding marks remain slightly. Therefore, the S-surface formed by using the cathode surface as the deposition surface has a shape transferred with the polishing marks of the cathode surface, and the M-surface has a surface shape following or affected by the polishing marks of the cathode surface. On the S-side and M-side of the electrodeposited copper foil, stripe-shaped projections and recesses are formed, which are derived from the polishing marks on the cathode side. However, the striped projections and recesses of the S-plane and the M-plane are very large compared with the particle size of the roughening particles to be formed in the present invention, and have different specifications. Therefore, the stripe-shaped projections and recesses give undulation to the base line of the roughened surface, but do not affect the shape of the roughened particles formed thereon. Therefore, although not specifically described in the above definition, it is needless to say that, in the present invention, the large irregularities such as the undulations of the roughened surface are not targeted for the measurement of the roughened particles.

(roughening treatment)

The roughening treatment is preferably performed by roughening plating treatment (1) described below, for example. The fixed plating treatment (2) may be combined as necessary, and it is more preferable to perform the fixed plating treatment (2) as described below after the roughening plating treatment (1).

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 using a copper sulfate bath. In such a copper sulfate bath (roughening plating solution basic bath), additives known hitherto such As molybdenum (Mo), arsenic (As), antimony (Sb), bismuth (Bi), selenium (Se), tellurium (Te), and tungsten (W) can be added for the purpose of preventing the roughening particles from falling off, that is, "powder falling". 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 that by skillfully setting these conditions, powder falling can be suppressed, and the transmission characteristics, adhesion, heat resistance, and substrate moisture resistance reliability can be satisfied at high levels.

First, when the copper concentration of the copper sulfate bath in the roughening plating treatment (1) is less than 10g/L, the shape of the roughened particles becomes too fine, that is, the value of the ratio (h/w) becomes too large, and powder falling tends to occur easily. Further, when the copper concentration of the plating bath exceeds 30g/L, copper ions are efficiently supplied in the vicinity of the coarsened particles in which crystals are growing, and therefore, the coarsened particles that are growing need more copper ions and the force trying to extend to a far place, that is, the force trying 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 respectively reduced. Further, when the copper concentration of the plating bath is high, diffusion of copper ions is promoted, and thus the coarse particles are densely formed, and the linear density (d) of the coarse particles tends to be too high. As a result, the heat resistance tends to be poor. Therefore, the copper concentration is preferably 10 to 30 g/L.

In particular, in the present invention, it is preferable to adopt a structure in which a plurality of (for example, three or more) anodes connected to one rectifier and having a size in the copper foil transport direction that is gradually increased are arranged in the copper foil transport direction (hereinafter referred to as "grid-shaped anodes").

By using such a grid-shaped anode, the area of the anode gradually increases in the roughening treatment step of roughening treatment plating (1), and the current density gradually decreases, and the plating treatment can be periodically performed. As a result, the starting point of nucleation of the roughening plating is generated not only on the surface of the copper foil substrate but also on the side surface of the generated roughening particles, and therefore, a plurality of protrusions are formed on the side surface, and roughening particles having a specific number of branches of the roughening particles can be formed.

For example, the anode 1 (width d) is provided in the order of copper foil passing₀Length d in the direction of copper foil transport₁Current density J₁) Anode 2 (width d)₀Length d in the direction of copper foil transport₂Current density J₂) Anode 3 (width d)₀Length d in the direction of copper foil transport₃Current density J₃). At this time, the length d of each anode in the copper foil transport direction is set to be longer₁、d₂And d₃The ratio is set as d₁∶d₂∶d₃1: 2: 3, the current density J of each anode₁、J₂And J₃The ratio of J to J₁∶J₂∶J₃3: 2: 1. The specific dimensions of each anode may be adjusted as appropriate so as to obtain the average current density as in the examples.

The average current density is obtained by averaging the current density values of a plurality of anodes having different dimensions in the copper foil conveyance direction by the number of anodes. That is, the apparatus configuration of the above exampleIn the case of (2), the average current density is [ (J)₁+J₂+J₃)/3]。

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

In the present invention, the plating treatment is preferably performed by a roll-to-roll (roll) plating method, for example, from the viewpoint of mass production and production cost.

The average current density (A/dm)²) Charge density (C/dm) of product of processing time (sec)²) Less than 65C/dm²It is difficult to obtain sufficient adhesion required in the present invention. Further, when the charge density exceeds 220C/dm²The coarsened particles grow excessively, and it is difficult to obtain the good transmission characteristics required by the present invention. Therefore, the charge density is preferably 65 to 220C/dm²。

Fixed plating treatment (2)

The fixed plating treatment (2) is a treatment of performing smooth cover plating on the copper foil substrate subjected to the surface treatment in the roughening plating treatment (1). Specifically, the plating treatment is performed using a copper sulfate bath. In general, this treatment is performed to prevent the coarse particles from falling off, that is, to fix the coarse particles.

For example, the plating treatment is preferably performed by a roll-to-roll plating method from the viewpoint of mass production and production cost.

An example of the composition of the plating solution for rough plating and the electrolysis conditions will be described below. The following conditions are preferred examples, and the type, amount, and electrolysis conditions of the additive may be appropriately changed and adjusted as necessary within a range not to impair the effects of the present invention.

< Condition for roughening plating treatment (1) >

Copper sulfate pentahydrate: 10 to 30g/L in terms of copper (atom);

sulfuric acid: 100-250 g/L;

anode: a grid-shaped anode;

the processing speed is as follows: 5-15 m/min;

average current density: 20 to 80A/dm²；

Treatment time: 1.0-3.0 seconds;

bath temperature: 30 to 50 ℃.

< Condition of fixed plating treatment (2) >

Copper sulfate pentahydrate: 50-70 g/L in terms of copper (atom);

sulfuric acid: 80-160 g/L;

the processing speed is as follows: 5-15 m/min;

current density: 1 to 5A/dm²；

Treatment time: 1.0-5.0 seconds;

bath temperature: 50-70 ℃.

Further, 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 agent layer may be further formed on the roughened layer directly or through an intermediate layer such as a base layer containing nickel (Ni), a heat-resistant treated layer containing zinc (Zn), and a rust-proof treated layer containing chromium (Cr). The intermediate layer and the silane coupling agent layer are extremely thin, and therefore do not affect the particle shape of the roughened particles in the roughened surface of the surface-treated copper foil. The particle shape of the roughened particles in 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 silane coupling agent layer by applying a silane coupling agent solution directly or via 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 applied solution is exemplified. The silane coupling agent solution applied can form a silane coupling agent layer as long as water in the solution evaporates, thereby sufficiently exhibiting the effects of the present invention. It is preferable to heat-dry the copper foil at 50 to 180 ℃ in order to accelerate the reaction between the silane coupling agent and the copper foil.

The silane coupling agent layer preferably contains a silane coupling agent selected from one or more of epoxy silane, amino silane, vinyl silane, methacrylic silane, acrylic silane, styrene silane, ureido silane, mercapto silane, thioether silane, and isocyanate silane.

In another embodiment, it is preferable that at least one intermediate layer selected from the group consisting of a base layer containing Ni, a heat-resistant treated layer containing Zn, and a rust-proof treated layer containing Cr is provided between the roughened layer and the silane coupling agent layer.

The base layer containing Ni is preferably formed between the roughened layer and the silane coupling agent layer, for example, when copper (Cu) in the copper foil base or the roughened layer diffuses to the resin base material side and adhesion is reduced by copper damage. The Ni-containing underlayer is preferably formed of at least one 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 of, for example, zinc or an alloy containing zinc, that is, an alloy containing zinc, at least one kind selected from the group consisting 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 of the 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 two layers may be formed depending on the application and the desired 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, a surface-treated copper foil is produced according to 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

If necessary, a base layer containing Ni is formed on the roughened layer.

(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

An anticorrosive layer containing Cr is formed as necessary on the roughened layer or on the base layer and/or the heat-resistant treated layer formed on the roughened layer as necessary.

(S5) Process for Forming silane coupling agent layer

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

< copper-clad laminate and printed wiring board >

The surface-treated copper foil of the present invention is preferably used for manufacturing a copper-clad laminate. Such a copper-clad laminate is preferably used for producing a printed wiring board having high adhesion and excellent high-frequency transmission characteristics, and exhibits excellent effects. In particular, the surface-treated copper foil of the present invention is suitable for use as a printed wiring board for high frequency bands, for example, in a frequency band of 1GHz or more, preferably 10GHz to 40 GHz.

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

In the case of producing a copper-clad laminate, a surface-treated copper foil having a silane coupling agent layer may be produced by bonding a resin base material to a surface-treated copper foil by hot pressing. The effect equivalent to that of the present invention is also obtained in a copper-clad laminate produced by applying a silane coupling agent to a resin base material and laminating the resin base material applied with the silane coupling agent to a surface-treated copper foil having an anticorrosive treated 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 present invention encompasses the concept of the invention and all the aspects contained in the claims, and various changes can be made within the scope of the present invention.

Examples

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

Production example preparation of copper foil substrate

As a copper foil substrate to be a substrate for roughening treatment, a roll-shaped electrolytic copper foil (double-sided glossy foil) having a thickness of 12 μm was produced under the following electrolytic conditions using a copper sulfate electrolytic solution having the following composition using a cathode and an anode described below.

< cathode and anode >

Cathode: a titanium rotary drum with 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: 25 mg/L.

(additives)

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

hydroxyethyl cellulose: 10 mg/L;

low molecular weight gum (molecular weight 3000): 50 mg/L.

< electrolytic conditions >

Bath temperature: 55 ℃;

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 details will be described below.

[1] Formation of roughened surface

The electrolytic copper foil produced in the above production example was used as a copper foil base, and the M-side of the copper foil base was subjected to roughening plating treatment by a roll-to-roll method. The roughening plating treatment is performed by two stages of plating treatment. The roughening plating treatment (1) was carried out using the following roughening plating solution basic bath composition, with the copper concentration being as shown in table 1 below, and with the treatment speed, whether or not a plurality of anodes (grid-shaped anodes were used) having a length ratio of the copper foil in the conveying direction of 1: 2: 3 were used, the bath temperature, the average current density, the treatment time, and the charge density being as shown in table 1 below. The fixed plating treatment (2) was performed using the following fixed plating solution composition, with the current density, treatment rate, treatment time, and charge density set as shown in table 1 below.

< basic bath composition of roughening plating solution >

H₂SO₄：150g/L

< composition of plating solution for fixation and bath temperature >

Cu：60g/L

H₂SO₄：120g/L

Bath temperature: 60 deg.C

[ Table 1]

[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 ℃;

pH：3.6；

current density: 0.2A/dm²；

Treatment time: for 10 seconds.

< Zn plating Condition >

Zn：2.5g/L；

NaOH：40g/L；

Bath temperature: 20 ℃;

current density: 0.3A/dm²；

Treatment time: for 5 seconds.

< Cr plating Condition >

Cr：5g/L；

Bath temperature: 30 ℃;

pH：2.2；

current density: 5A/dm²；

Treatment time: for 5 seconds.

[3] Formation of silane coupling agent layer

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

(examples 2 to 9 and comparative examples 1 to 6)

In examples 2 to 9 and comparative examples 1 to 6, a surface-treated copper foil was obtained in the same manner as in example 1 except that in the step [1] of forming a roughened layer, the conditions of the roughening plating treatment (1) and the fixed plating treatment (2) were set as described in table 1 above.

[ 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-section Observation >

The cross-sectional observation of the surface-treated copper foil was performed by image analysis in the following steps (i) to (iii).

First, (i) a test piece of 5mm square was cut out of the obtained surface-treated copper foil, the surface-treated copper foil was cut perpendicularly to the roughened surface from the roughened surface side, and the cut surface was precision-polished for 30 minutes under the conditions of a flat table mode (stage mode) C1 (swing angle: ± 15 °, swing speed: 6 round trips/min) and an acceleration voltage of 6kV using an ion milling apparatus ("IM 4000" manufactured by hitachi High-Technologies). A secondary electron image was observed by a scanning electron microscope (SU 8020, hitachi High-Technologies) at an accelerating voltage of 3kV at ten thousand times from a direction perpendicular to the processed surface of the surface-treated copper foil exposed on the surface of the prepared measurement sample, and a cross-sectional photograph (SEM image, vertical 9.5 μm × horizontal 12.5 μm) of the vicinity of the roughened surface was prepared.

Next, (ii) the image processing for emphasizing the outline of the coarsened particles is performed on the cross-sectional photograph using image editing software ("Real World Paint"), and 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 coarsened particles (particles to be observed) present in an arbitrary observation field are measured using image measurement software (Photo Ruler). Then, the number of the coarsened particle branches and the shortest root pitch of the coarsened particles corresponding to the coarsened particles (p) are further measured.

Based on the measured values, the average values of the particle height (h) and the particle width (w) of the coarse particles, the average value of the ratio (h/w) of the particle height (h) to the particle width (w), the linear density (d) of the coarse particles, and the number of the specific coarse particles (P) are obtained.

The analysis up to this point was performed on the same surface-treated copper foil in a field of view of 75 μm in total in the width direction with 6 arbitrary sections. Then, based on the measured values of 6 sectional photographs in total, the average value of the particle height (h) of the roughened 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), and the average value of the linear density (d) were calculated, and the average values were set as the measured values of the surface-treated copper foil to be observed. Then, the number of the specific roughened particles (P) observed in each cross-sectional photograph was summed up, and the value was used as a measured value 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.

[ extended area ratio (Sdr) ]

The spread area ratio (Sdr) was measured by measuring the surface shape of the roughened surface of the surface-treated copper foil using a white light interference optical microscope (Wyko ContourGT-K, BRUKER Co., Ltd.), and further performing shape analysis.

The surface shape measurement was performed by using a high-density CCD (charge coupled device) camera in a VSI (vertical scanning interferometry) measurement method under the following conditions: the zoom lens magnification was 1 times, the objective lens magnification was 50 times, the measurement area was 96.1 μm × 72.1 μm, the light source was a white light source, the lateral sampling (lateral sampling) was 0.075 μm, the velocity (speed) was 1 time, the back scan (backscan) was 10 μm, the length (length) was 10 μm, and the threshold (threshold) was 3%.

Further, as the shape analysis, the data were restored (1) by item removal (cylinder and tilt), (2) by data restoration (manner: acquisition, iteration: 5, restored edge: unselected), (3) by truncation frequency of Fourier transform of 62.5mm^-1The gaussian high-pass filter of (1) performs a filtering process in this order, and then performs a data process.

The spread area ratio (Sdr) is measured at any 10 points on the roughened surface of one surface-treated copper foil, and the obtained value (N ═ 10) is averaged to obtain the spread area ratio (Sdr) of the surface-treated copper foil.

[ evaluation of falling powder ]

First, a test piece of about 80mm × 50mm square was cut out from the surface-treated copper foil and fixed to a plastic plate having a flat surface with its roughened surface facing upward. Then, two kinds of filter papers (manufactured by ADVANTEC corporation) specified in JIS P3801-. In this case, the contact surface between the filter paper and the weight was a circular shape having a diameter of 30 mm.

Subsequently, the filter paper was stretched in the horizontal direction for 5 seconds by 100mm with the weight placed thereon. Then, the weight was removed, and the filter paper on the surface-treated copper foil was gently peeled off in the vertical direction to recover the filter paper.

The filter paper was visually checked, and the case where the adhesion of the copper particle powder was not confirmed was evaluated as "no powder falling", and the case where the adhesion of the copper particle powder was confirmed was evaluated as "presence of powder falling".

< evaluation of Transmission characteristics >

The transmission loss in the high frequency band was measured and evaluated as the transmission characteristics. The details will be described below.

A polyphenylene ether resin base material (MEGTRON 6, manufactured by Panasonic electric appliances, Inc., having a thickness of 60 μm) having a low dielectric constant was bonded to the surface-treated copper foil to prepare a substrate for transmission characteristic measurement. The substrate was configured in a strip line (stripe) configuration, and the conductor length was 400mm, the conductor thickness was 18 μm, the conductor width was 0.14mm, the overall thickness was 0.39mm, and the characteristic impedance was 50 Ω. The surface-treated copper foil and the resin base material were laminated so that the roughened surface faced the resin base material, and the laminate was pressed under a surface pressure of 3.1MPa and at 200 ℃ for 2 hours.

The transmission loss at 40GHz was measured using a vector network analyzer E8364C (KEYSIGHT TECHNOLOGIES).

The smaller the absolute value of the measured value of the transmission loss, the smaller the transmission loss, which means that the transmission characteristics are good. The obtained measurement values were used as indices, and the transmission characteristics were evaluated according to the following evaluation criteria.

A: the absolute value of the transmission loss at conductor length 400mm at 40GHz is less than 32 dB.

B: the absolute value of the transmission loss at a conductor length of 400mm at 40GHz is 32dB or more and 36dB or less.

C: the absolute value of the transmission loss at conductor length 400mm at 40GHz is greater than 36 dB.

[ evaluation of adhesion ]

Evaluation of adhesion was made in accordance with JIS C6481: 1996 peel test. The details will be described below.

The roughened surface of the surface-treated copper foil was bonded to one surface of two stacked polyphenylene ether-based low-dielectric-constant resin substrates (MEGTRON 7, manufactured by sons electric corporation, thickness: 60 μm) by pressing under a surface pressure of 3.5MPa at 200 ℃ for 2 hours, to produce a copper-clad laminate. 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 foil laminate, the tape was removed, and a circuit wiring board having a width of 10mm was manufactured. The peel strength of the circuit wiring board was measured by using a Tensilon tester manufactured by Toyo Seiki Seiko 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 50mm/min in a 90-degree direction. The obtained measurement values were used as indices, and the adhesion (normal adhesion) was evaluated according to the following evaluation criteria.

< evaluation criteria for adhesion >

A: the peel strength is 0.60kN/m or more.

B: the peel strength is 0.50kN/m or more and less than 0.60 kN/m.

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

[ evaluation of Heat resistance ]

The presence or absence of swelling at the interface between the copper foil and the resin substrate after reflow was evaluated as an evaluation of heat resistance. The details will be described below.

First, a surface-treated copper foil was laminated on both surfaces of two pieces of a polyphenylene ether-based low-dielectric-constant resin base material (MEGTRON 7, manufactured by panasonic electric corporation, having a thickness of 60 μm) so that the roughened surfaces were opposed to the resin base material, respectively, and the copper foil was laminated by pressing under a surface pressure of 3.5MPa at 200 ℃ for 2 hours to produce a double-sided copper-clad laminate.

The obtained copper-clad laminate was cut into three pieces with a size of 100mm × 100mm, and the pieces were used as test pieces.

Subsequently, the prepared test piece was passed through a reflow furnace 10 times under a heating condition of a maximum temperature of 260 ℃ for 10 seconds.

The surface of the test piece heated under the above conditions on the copper foil side was observed to investigate the presence or absence of swelling. It was confirmed that a bulge was generated from the surface, the center of the bulged region was cut, and the cross section was observed with a microscope to confirm whether or not interlayer peeling occurred between the copper foil and the resin base material. The test piece in which the interlayer peeling was confirmed was regarded as a test piece in which the copper foil-resin base material interface was swollen. From the above observation results, the heat resistance was evaluated based on the following evaluation criteria.

< evaluation criteria for Heat resistance >

A: in none of the three test pieces, the copper foil-resin base material interface was raised.

B: in the three test pieces, one test piece had a bulge at the interface between the copper foil and the resin base material.

C: among the three test pieces, two or more test pieces had a bulge at the interface between the copper foil and the resin base material.

[ evaluation of substrate moisture resistance reliability ]

As an evaluation of the reliability of the substrate moisture resistance, after PCT (pressure cooker test), the presence or absence of the bulge between the resin base material and the resin base material after float welding (retainer float) was evaluated. The details will be described below.

First, a double-sided copper-clad laminate was produced by the same method as that described in [ evaluation of heat resistance ]. The copper foils on both sides of the double-sided copper-clad laminate were etched entirely and removed, and on both sides after etching, a piece of polyphenylene ether-based low-dielectric-constant resin base material (MEGTRON 7, manufactured by panasonic electric corporation, thickness 60 μm) was stacked, and further, on each surface of the stacked resin base material, a piece of surface-treated copper foil was stacked so that the roughened surfaces were opposed to each other, and pressing was performed under a surface pressure of 3.5MPa and 200 ℃ for 2 hours to bond the resin base materials to each other and the resin base material to the copper foil, thereby obtaining a laminate. Further, the copper foils on both sides of the laminate were etched and removed to obtain a resin base laminate in which four resin bases were stacked.

The resin base material laminate was cut into three pieces with a size of 100mm × 100mm, and the pieces were used as test pieces.

Then, using the prepared test piece, pct (pressure cookie test) was performed under the following conditions, and after taking out, a float-welding test was performed under the following conditions within 1 hour.

PCT was carried out using a highly accelerated life test HAST device (PC-422R8, manufactured by Hill corporation) at a temperature of 121 ℃ and a humidity of 100% RH for 48 hours.

The float-welding test was carried out by repeating 10 times the operation of floating the test piece in a solder bath heated to 288 ℃ for 10 seconds and then leaving the test piece at room temperature for 10 seconds.

The surface of the test piece after the float test was observed to visually determine whether or not the bulge was present. From the observation results, the substrate moisture resistance reliability was evaluated based on the following evaluation criteria.

< evaluation criteria for substrate moisture resistance reliability >

A: in none of the three test pieces, no bulge was generated.

B: among the three test pieces, one test piece was raised.

C: among the three test pieces, two or more test pieces were raised.

[ comprehensive evaluation ]

The powder falling, the transmission characteristics, the adhesion, the heat resistance, and the substrate moisture resistance reliability were all comprehensively evaluated based on the following evaluation criteria. In the present example, S, A and B were defined as the pass levels in the overall evaluation.

< evaluation criteria for comprehensive evaluation >

S (optimal): all the evaluations of no powder falling, transmission characteristics, adhesion, heat resistance, and substrate moisture resistance reliability were a evaluation.

A (excellent): no powder falling, no C evaluation was made in all evaluations of transmission characteristics, adhesion, heat resistance and substrate moisture resistance reliability, and any of these evaluations was a B evaluation.

B (good): no powder falling, no C evaluation was made in all evaluations of transmission characteristics, adhesion, heat resistance and substrate moisture resistance reliability, and any two or more of these evaluations were given by B evaluation.

C (fail): the evaluation of the presence of powder falling or the reliability of transmission characteristics, adhesion, heat resistance, and moisture resistance of the substrate is evaluated by C.

As shown in table 2, the roughened surface of the surface-treated copper foils of examples 1 to 9 was controlled to be as follows when the cross section thereof was observed by SEM: in a region of 75 μm in the width direction, the average value of the particle height (h) of the coarsened particles is 0.8 to 2.0 μm, the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the coarsened particles is 1.5 to 4.5, and 1 to 60 specific coarsened particles (P) are present, so that no powder drop is confirmed, and particularly in the case of a conductor circuit used for a printed circuit board, excellent transmission characteristics, adhesion, heat resistance, and substrate moisture resistance reliability can be realized.

On the other hand, the roughened surfaces of the surface-treated copper foils of comparative examples 1 to 6 did not satisfy at least one of the following: the average particle height (h) of the coarsened particles in a region of 75 μm in the width direction is 0.8 to 2.0 μm, the average value of the ratio (h/w) of the particle height (h) to the particle width (w) of the coarsened particles is 1.5 to 4.5, and 1 to 60 specific coarsened particles (P) are present. Therefore, it was confirmed that the copper foil was inferior to the surface-treated copper foils of examples 1 to 9 in the characteristics evaluated at least in one of the transmission characteristics, adhesion, heat resistance, substrate moisture resistance reliability, and powder falling.