Roughened copper foil, copper foil having carrier, copper-clad laminate, and printed wiring board

Abstract

Provided is a roughened copper foil with which it is possible to obtain excellent transmission characteristics when used in a copper-clad laminate or a printed wiring board. The roughened copper foil has a roughened surface. The surface C / Cu ratio, which is the ratio of the C concentration (at%) of the roughened surface to the Cu concentration (at%) of the roughened surface, is 20-350, the Cu concentration of the roughened surface and the C concentration of the roughened surface being respectively the atomic concentration of Cu and the atomic concentration of C obtained by performing elemental analysis of C, N, O, Si, Cr, Ni, Cu, Zn, Mo, W, and Co on the roughened surface by X-ray photoelectron spectroscopy (XPS).

Description

Roughened copper foil, copper foil with carrier, copper-clad laminates, and printed circuit boards

[0001] This disclosure relates to roughened copper foil, copper foil with carrier, copper-clad laminates, and printed circuit boards.

[0002] In the manufacturing process of printed circuit boards, copper foil is widely used in the form of copper-clad laminates, which are bonded to an insulating resin substrate. In this regard, it is desirable that the copper foil and the insulating resin substrate have high adhesion to prevent delamination of the wiring during the manufacturing of printed circuit boards. Therefore, in the case of copper foil for the manufacturing of conventional printed circuit boards, the bonding surface of the copper foil is roughened to create irregularities made of fine copper particles, and these irregularities are pressed into the interior of the insulating resin substrate by a pressing process to create an anchoring effect and improve adhesion.

[0003] Incidentally, with the increasing sophistication of portable electronic devices in recent years, signals, whether digital or analog, are becoming higher frequency in order to process large amounts of data at high speed, and printed circuit boards suitable for high-frequency applications are in demand. For such high-frequency printed circuit boards, it is desirable to reduce transmission loss in order to transmit high-frequency signals without degradation. A printed circuit board consists of copper foil processed into a wiring pattern and an insulating substrate, and the main losses in transmission loss are conductor loss due to the copper foil and dielectric loss due to the insulating substrate.

[0004] Conductor loss can increase due to the skin effect of copper foil, which becomes more pronounced at higher frequencies. Therefore, to suppress transmission loss in high-frequency applications, it is necessary to refine the roughened particles to reduce the skin effect of copper foil. As an example of copper foil having such fine roughened particles, Patent Document 1 (WO2014 / 133164A1) discloses a surface-treated copper foil having a black roughened surface formed by attaching copper particles (e.g., substantially spherical copper particles) with a particle size of 10 nm to 250 nm. Patent Document 2 (JP 2011-168887) discloses a roughened copper foil having a roughened surface with a surface roughness Rz of 1.1 μm or less after roughening treatment, as a copper foil with excellent transmission characteristics in the high-frequency range. Furthermore, Patent Document 3 (WO2022 / 209989A1) discloses controlling the roughness slope tanθ and the minute roughening projected area, which are calculated based on the average height Rc and the average length RSm of the contour curve elements, respectively, to a predetermined range on the surface of roughened copper foil. It is stated that copper-clad laminates or printed circuit boards manufactured using such roughened copper foil can achieve both excellent transmission characteristics and high peel strength.

[0005] WO2014 / 133164A1 Japanese Patent Publication No. 2011-168887 WO2022 / 209989A1

[0006] As described above, various attempts have been made to improve the transmission characteristics (high-frequency characteristics) of roughened copper foil, but further improvements in transmission characteristics are desired.

[0007] The present inventors have now discovered that by controlling the surface C / Cu ratio, which is the ratio of the C concentration on the roughened surface to the Cu concentration on the roughened surface, to 20 to 350 in a roughened copper foil having a roughened surface, excellent transmission characteristics can be achieved in copper-clad laminates or printed circuit boards manufactured using this.

[0008] Therefore, the object of the present invention is to provide a roughened copper foil that can achieve excellent transmission characteristics when used in copper-clad laminates or printed circuit boards.

[0009] The following embodiments are provided according to this disclosure: [Embodiment 1] A roughened copper foil having a roughened surface, wherein the surface C / Cu ratio, which is the ratio of the C concentration (at%) of the roughened surface to the Cu concentration (at%) of the roughened surface, is 20 or more and 350 or less, and the Cu concentration and C concentration of the roughened surface are, respectively, the atomic concentrations of Cu and C obtained when C, N, O, Si, Cr, Ni, Cu, Zn, Mo, W, and Co are elementally analyzed on the roughened surface by X-ray photoelectron spectroscopy (XPS). [Embodiment 2] The roughened copper foil according to Embodiment 1, wherein the surface C / Cu ratio is 20 or more and 100 or less. [Embodiment 3] The roughened copper foil according to Embodiment 1 or 2, wherein the interface development area ratio Sdr, measured in accordance with ISO 25178, on the roughened surface is 2.9% or less. [Aspect 4] The roughened copper foil according to any one of aspects 1 to 3, wherein the developed area ratio Sdr of the interface on the surface opposite to the roughened surface of the roughened copper foil, as measured in accordance with ISO 25178, is 2.5% or less. [Aspect 5] The roughened surface comprises a plurality of roughened particles, the internal C / Sdr ratio, which is the ratio of the C concentration (at%) of the roughened particles to the developed area ratio Sdr (%) of the interface of the roughened surface, is 0.1 or more and 2.9 or less, Sdr is a value measured in accordance with ISO 25178, and the C concentration of the roughened particles is the atomic concentration of C measured at a depth position where the total concentration of Si, Cr, Ni, Zn, Mo, W, and Co is less than 2.0 at%, when elemental analysis of C, N, O, Si, Cr, Ni, Cu, Zn, Mo, W, and Co is performed from the roughened surface toward the depth direction of the roughened copper foil by XPS. The roughened copper foil according to any one of aspects 1 to 4. [Aspect 6] The roughened copper foil according to any one of aspects 1 to 5, further comprising a rust-preventive treatment layer and / or a silane coupling agent layer on the roughened surface. [Aspect 7] A copper foil with a carrier, comprising a carrier, a release layer provided on the carrier, and a roughened copper foil according to any one of aspects 1 to 6 provided on the release layer with the roughened surface facing outward. [Aspect 8] A copper-clad laminate comprising the roughened copper foil according to any one of aspects 1 to 6. [Aspect 9] A printed circuit board comprising the roughened copper foil according to any one of aspects 1 to 6.

[0010] This is a schematic cross-sectional view showing an example of the roughened copper foil of this disclosure. This is a schematic cross-sectional view showing an example of a conventional roughened copper foil. This is a schematic cross-sectional view showing an example of a roughened copper foil in which the roughened particles in the roughened copper foil of Figure 2 have been further refined.

[0011] Definitions The following are definitions of terms and parameters used to specify this invention.

[0012] In this specification, "interface development area ratio Sdr" or "Sdr" is a parameter measured in accordance with ISO 25178, which expresses as a percentage (%) how much the development area (surface area) of the defined region has increased relative to the area of ​​the defined region. A smaller value indicates a surface shape that is closer to flat, with a perfectly flat surface having an Sdr of 0%. On the other hand, a larger value indicates a surface shape with more irregularities. For example, if the Sdr of a surface is 2.0%, it indicates that the surface area of ​​this surface has increased by 2.0% compared to a perfectly flat surface.

[0013] Sdr can be calculated by measuring the surface profile of a predetermined measurement area on the surface of a roughened copper foil using a commercially available laser microscope. In this specification, Sdr is measured under conditions without cutoff using S filters and L filters. Preferred measurement and analysis conditions for the surface profile using a laser microscope are shown in the examples below.

[0014] In this specification, "C concentration of roughened particles" means the atomic concentration (at%) of carbon (C) measured at a depth position where the total atomic concentration of Si, Cr, Ni, Zn, Mo, W, and Co is less than 2.0 at%, when elemental analysis of C, N, O, Si, Cr, Ni, Cu, Zn, Mo, W, and Co is performed from the roughened surface of the roughened copper foil toward the depth direction of the roughened copper foil by X-ray photoelectron spectroscopy (XPS). In other words, the roughened surface of the roughened copper foil may contain Si, Cr, Ni, Zn, Mo, W, and Co as elements derived from various surface treatments (e.g., silane coupling agent treatment and rust prevention treatment) in its surface layer. Therefore, when the above surface treatment is applied to the roughened surface, if elemental analysis is performed by XPS while sputtering down from the roughened surface (outermost surface) of the roughened copper foil toward the depth direction (the surface opposite the roughened surface), the total atomic concentration of elements derived from the above surface treatment will be 2.0 at% or more near the surface, and as sputtering progresses, this total atomic concentration will decrease until there is a depth position where it falls below 2.0 at%. For this reason, when measuring the C concentration inside the roughened area, in order to minimize the influence of the above surface treatment, elemental analysis in the depth direction by XPS will be performed, and the first depth position where the total atomic concentration of elements derived from the above surface treatment falls below 2.0 at% will be considered as the depth position indicating the constituent elements inside the roughened area. In addition, in the elemental analysis at the above depth position, due to the waviness of the copper foil and the unavoidable non-uniformity of sputtering, etc., the analysis may include some information on the constituent elements of the copper foil body (untreated) in addition to the information on the constituent elements of the roughened particles. In this regard, in this specification, the above configuration is acceptable, assuming that the information on the constituent elements of the roughened particles is sufficiently reflected. The preferred measurement and analysis conditions for elemental analysis using XPS are shown in the examples described below.

[0015] In this specification, "Cu concentration on the roughened surface" and "C concentration on the roughened surface" refer to the atomic concentrations (at%) of copper (Cu) and carbon (C) (at%), respectively, when elemental analysis of C, N, O, Si, Cr, Ni, Cu, Zn, Mo, W, and Co is performed on the roughened surface of the roughened copper foil by XPS. That is, unlike the C concentration of the roughened particles described above, the Cu concentration and C concentration on the roughened surface are atomic concentrations obtained by elemental analysis of the roughened surface (outermost surface) of the roughened copper foil by XPS without performing sputtering. In elemental analysis by XPS, the constituent elements in a depth region of several nm from the roughened surface are measured due to the depth to which photoelectrons generated by incident X-rays escape from the sample surface (penetration depth). However, since disturbance factors such as silanes that may be present on the surface of the roughened particles are faint relative to the penetration depth of XPS, their influence can be said to be suppressed. Preferred measurement and analysis conditions for elemental analysis by XPS are shown in the examples described later.

[0016] In this specification, "internal C / Sdr ratio" means the ratio of the C concentration of the roughened particles to the Sdr ratio of the developed area of ​​the interface on the roughened surface. Also, in this specification, "surface C / Cu ratio" means the ratio of the C concentration on the roughened surface to the Cu concentration on the roughened surface.

[0017] In this specification, the "electrode surface" of electrolytic copper foil refers to the surface that was in contact with the cathode during the manufacturing of the electrolytic copper foil. In this specification, the "deposition surface" of electrolytic copper foil refers to the surface on which electrolytic copper is deposited during the manufacturing of the electrolytic copper foil, that is, the surface that is not in contact with the cathode.

[0018] Figure 1 schematically shows an example of the roughened copper foil of this disclosure. The roughened copper foil 10 shown in Figure 1 has a roughened surface. Typically, the roughened surface comprises a plurality of roughened particles 10a. The surface C / Cu ratio, which is the ratio of the C concentration (at%) of the roughened surface to the Cu concentration (at%) of the roughened surface, is 20 or more and 350 or less. In this way, by controlling the surface C / Cu ratio, which is the ratio of the C concentration of the roughened surface to the Cu concentration of the roughened surface, to 20 or more and 350 or less in the roughened copper foil 10 having a roughened surface, excellent transmission characteristics (high frequency characteristics) can be achieved in copper-clad laminates or printed circuit boards manufactured using this.

[0019] The mechanism by which superior transmission characteristics can be achieved by controlling the surface C / Cu ratio within a predetermined range is not entirely clear, but it is thought to be as follows. Here, Figure 2 shows an example of a conventional roughened copper foil. The roughened copper foil 110 shown in Figure 2 has roughened particles 110a, and the roughened particles 110a contain carbon (C). That is, as mentioned above, in order to suppress transmission loss in high-frequency applications, it is necessary to miniaturize the roughened particles in order to reduce the skin effect of the copper foil. In order to manufacture roughened copper foil with such fine roughened particles in an efficient manner, it is necessary to include additives (organic substances) in the electrolyte during the roughening process. In other words, carbon derived from the additives is inevitably present in the miniaturized roughened particles.

[0020] Here, in order to further improve the transmission characteristics, it is conceivable to further refine the fine roughened particles 110a (for example, further reduce the Sdr of the roughened surface). However, it was found that simply refining the roughened particles further did not unexpectedly improve the transmission characteristics. Figure 3 shows an example of a roughened copper foil with further refined roughened particles. In the roughened copper foil 210 shown in Figure 3, because the roughened particles 210a are extremely small, although it contains the same amount of carbon as the conventional roughened particles 110a, the carbon density in the roughened particles 210a is higher than that of the roughened particles 110a. Here, the dielectric loss tangent (Df), which contributes greatly to the high-frequency characteristics, will increase (worsen) due to the presence of polar organic matter. In this regard, even if the additive contained in the electrolyte during the roughening treatment does not have polar groups (for example, 9-phenylacridine), it is expected that there will be a charge imbalance when considering the three-dimensional structure of the additive. Therefore, if the carbon concentration of the roughened particles is high, even if the roughened particles are extremely fine, it is unlikely that the transmission characteristics (high-frequency characteristics) will be improved.

[0021] In contrast, the roughened copper foil 10 of this disclosure has a surface C / Cu ratio, which is the ratio of the C concentration on the roughened surface to the Cu concentration on the roughened surface, controlled to be small, between 20 and 350. Since the surface C / Cu ratio is obtained by dividing the carbon concentration by the copper concentration of the base material, it is possible to accurately evaluate the effect of the carbon contained in the roughened particles 10a on the dielectric loss tangent, taking into account the size of the roughened particles 10a. Furthermore, the Cu concentration and C concentration on the roughened surface reflect the information of the constituent elements at the outermost surface of the roughened particles 10a, and therefore, it is possible to reflect the information of the constituent elements in the smallest roughened particles 10a without omission. In this respect, as shown in Figure 1, the roughened copper foil 10 in which the surface C / Cu ratio is controlled within the above predetermined range has finely milled roughened particles 10a, and the amount of carbon contained in the roughened particles 10a is also small, so it can be said that the density of carbon in the roughened particles is controlled to be low. Thus, by suppressing the deterioration of the dielectric loss tangent due to the presence of organic matter (carbon), it is thought that the improvement of transmission characteristics (reduction of the skin effect) through the miniaturization of roughened particles can be effectively achieved.

[0022] Therefore, the roughened copper foil 10 has a surface C / Cu ratio of 20 to 350, preferably 20 to 250, more preferably 20 to 150, even more preferably 20 to 100, and particularly preferably 20 to 80.

[0023] The roughened copper foil 10 preferably has an internal C / Sdr ratio, which is the ratio of the C concentration (at%) of the roughened particles to the developed area ratio Sdr (%) of the interface of the roughened surface, of 0.1 to 2.9, more preferably 0.1 to 1.5, even more preferably 0.1 to 1.0, and particularly preferably 0.1 to 0.5. As mentioned above, the C concentration of the roughened particles reflects the information of the constituent elements inside the roughened particles 10a. By using the internal C / Sdr ratio, which has Sdr as the denominator (the rate of increase in surface area), as an indicator, the influence of carbon contained in the roughened particles 10a on the dielectric loss tangent can be accurately evaluated, taking into account the size of the roughened particles 10a. Furthermore, by controlling the internal C / Sdr ratio within the above range, even better transmission characteristics can be achieved when the roughened copper foil 10 is used in a copper-clad laminate or printed circuit board.

[0024] The Sdr of the roughened surface in the roughened copper foil 10 is preferably 2.9% or less, more preferably 0.1% to 2.9%, even more preferably 0.1% to 1.5%, and particularly preferably 0.1% to 1.0%. This makes it possible to more effectively suppress transmission loss by miniaturizing the roughened particles 10a.

[0025] The Sdr on the surface of the roughened copper foil 10 opposite to the roughened surface is preferably 2.5% or less, more preferably 0.1% to 2.0%, even more preferably 0.1% to 1.8%, particularly preferably 0.1% to 1.5%, and most preferably 0.1% to 1.0%. By doing so, even better transmission characteristics can be achieved when the roughened copper foil 10 is used in printed wiring boards or the like on which striplines are formed.

[0026] The thickness of the roughened copper foil 10 is not particularly limited, but is preferably 0.1 μm to 210 μm, and more preferably 0.5 μm to 70 μm. The roughened copper foil 10 is not limited to ordinary copper foil with a roughened surface, but may also be a copper foil with a carrier attached with a roughened surface.

[0027] The roughened copper foil 10 can preferably be manufactured by roughening a smooth copper foil surface (for example, the deposition surface of an electrolytic copper foil (smooth foil)) under desired low roughening conditions to form fine roughened particles 10a. Therefore, according to a preferred embodiment of this disclosure, the roughened copper foil 10 is an electrolytic copper foil, and the roughened surface is located on the deposition surface side of the electrolytic copper foil. The roughened copper foil 10 may have roughened surfaces on both sides, or it may have a roughened surface on only one side. The roughened surface comprises a plurality of roughened particles 10a, and it is preferable that each of these plurality of roughened particles 10a is made of copper particles. The copper particles may be made of metallic copper or a copper alloy.

[0028] The aforementioned smooth electrolytic copper foil can preferably be produced by electrolytic manufacturing using a sulfuric acid-based copper electrolyte containing, for example, a sulfonate of an active sulfur compound (e.g., bis(3-sulfopropyl) disulfide) and / or a quaternary ammonium salt polymer having a cyclic structure (e.g., diallyldimethylammonium chloride polymer) as an additive. Furthermore, from the viewpoint of smoothing the electrode surface of the electrolytic copper foil, it is preferable to adjust the surface roughness by polishing the surface of the rotating cathode used in electrolytic manufacturing of the copper foil with a buff of a predetermined grit. That is, by transferring the surface profile of the rotating cathode thus adjusted to the electrode surface of the electrolytic copper foil, it becomes easier to control the Sdr on the surface opposite to the roughened surface (i.e., the electrode surface) to a desired range when the deposited surface of the electrolytic copper foil is roughened. Preferred buff grits are #1000 to #5000, more preferably #1000 to #3000, and even more preferably #1000 to #2500.

[0029] The roughening treatment is performed in a copper sulfate solution having a copper concentration of 5 g / L or more and 20 g / L or less, a sulfuric acid concentration of 15 g / L or more and 100 g / L or less (more preferably 50 g / L or more and 100 g / L or less, still more preferably 70 g / L or more and 100 g / L or less), a 9-phenylacridine concentration of 100 mg / L or more and 200 mg / L or less (more preferably 100 mg / L or more and 150 mg / L or less, still more preferably 120 mg / L or more and 150 mg / L or less), and a chlorine concentration of 20 mg / L or more and 100 mg / L or less (more preferably 20 mg / L or more and 50 mg / L or less, still more preferably 30 mg / L or more and 40 mg / L or less), at a temperature of 25°C or higher and 44°C or lower (more preferably 25°C or higher and 40°C or lower, still more preferably 30°C or higher and 35°C or lower), and a current density of 25 A / dm ２ or more and 70 A / dm ２ or less (more preferably 30 A / dm ２ or more and 50 A / dm ２ or less, still more preferably 35 A / dm ２ or more and 45 A / dm ２ or less). During electrolytic deposition, it is preferable to perform electrolytic deposition under the following formula: F Ｃｕ =F ＣｕＳＯ４ ×C Ｃｕ / S (wherein F Ｃｕ is the interelectrode copper supply rate [(g·m) / (min·L)], F ＣｕＳＯ４ is the flow rate of the copper sulfate solution (m ３ / min), C Ｃｕ is the copper concentration of the copper sulfate solution (g / L), S is the cross-sectional area between the anode and the cathode (m ２ ), that is, the area of the space between the electrodes calculated by the product of the electrode length and the interelectrode distance when the electrodes (anode and cathode) are viewed in cross-section) is preferably 5.0 [(g·m) / (min·L)] or less, more preferably 2.5 [(g·m) / (min·L)] or less, and still more preferably 0.5 [(g·m) / (min·L)] or less. A lower interelectrode copper supply rate is preferable, and for example, it may be 0.0 [(g·m) / (min·L)]. By performing the roughening treatment under such conditions, the carbon content in the roughening particles 10a is controlled to a desired range, and a roughened copper foil 10 having a roughened surface in which the internal C / Sdr ratio and / or the surface C / Cu ratio is controlled within a predetermined range can be preferably formed.

[0030] Optionally, the roughened copper foil 10 may be subjected to rust prevention treatment, forming a rust prevention layer. The rust prevention treatment preferably includes a zinc plating treatment. The zinc plating treatment may be either zinc plating or zinc alloy plating, with zinc-nickel alloy plating being particularly preferred. The zinc-nickel alloy plating treatment may include at least Ni and Zn, and may further include other elements such as Sn, Cr, Co, and Mo. For example, by further including Mo in addition to Ni and Zn in the rust prevention layer, the treated surface of the roughened copper foil 10 will have better adhesion to the resin, chemical resistance and heat resistance, and less etching residue will remain. The Ni / Zn adhesion ratio in zinc-nickel alloy plating is preferably 1.2 to 10 by mass ratio, more preferably 2 to 7, and even more preferably 2.7 to 4. Furthermore, the rust prevention treatment preferably includes a chromate treatment, and it is even more preferable that this chromate treatment is performed on the surface of the zinc-containing plating after the zinc plating treatment. This further improves rust prevention. A particularly preferred rust prevention treatment is a combination of zinc-nickel alloy plating and subsequent chromate treatment.

[0031] If desired, the roughened copper foil 10 may be treated with a silane coupling agent on its surface, forming a silane coupling agent layer. This improves moisture resistance, chemical resistance, and adhesion to adhesives, etc. The silane coupling agent layer can be formed by appropriately diluting the silane coupling agent, applying it, and drying it. Examples of silane coupling agents include epoxy-functional silane coupling agents such as 4-glycidylbutyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane; amino-functional silane coupling agents such as 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-3-(4-(3-aminopropoxy)butoxy)propyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane; mercapto-functional silane coupling agents such as 3-mercaptopropyltrimethoxysilane; olefin-functional silane coupling agents such as vinyltrimethoxysilane and vinylphenyltrimethoxysilane; acrylic-functional silane coupling agents such as 3-methacryloxypropyltrimethoxysilane and 3-acryloxypropyltrimethoxysilane; imidazole-functional silane coupling agents such as imidazolesilane; and triazine-functional silane coupling agents such as triazinesilane.

[0032] For the reasons stated above, it is preferable that the roughened copper foil 10 further comprises a rust-preventive treatment layer and / or a silane coupling agent layer on the roughened surface, and more preferably both the rust-preventive treatment layer and the silane coupling agent layer. The rust-preventive treatment layer and the silane coupling agent layer may be formed not only on the roughened surface side of the roughened copper foil 10, but also on the side where the roughened surface is not formed. When the roughened copper foil 10 further comprises a rust-preventive treatment layer and / or a silane coupling agent layer, the elemental analysis by XPS for measuring the C concentration of the roughened particles and the Cu and C concentrations of the roughened surface shall be performed on the roughened surface after these layers have been formed (i.e., the outermost surface of the roughened copper foil 10).

[0033] Copper Foil with Carrier As mentioned above, the roughened copper foil 10 of the present disclosure may be provided in the form of a copper foil with a carrier. That is, according to a preferred embodiment of the present disclosure, there is provided a copper foil with a carrier, comprising a carrier, a release layer provided on the carrier, and the roughened copper foil 10 provided on the release layer with the roughened surface facing outward. However, the copper foil with a carrier can adopt a known layer structure except for using the roughened copper foil 10 of the present disclosure.

[0034] The carrier is a support for supporting the roughened copper foil 10 and improving its handling properties, and a typical carrier comprises a metal layer. Examples of such a carrier include aluminum foil, copper foil, stainless steel (SUS) foil, resin films and glass whose surfaces are metal-coated with copper or the like, and copper foil is preferred. The copper foil may be either rolled copper foil or electrolytic copper foil, and is preferably electrolytic copper foil. The thickness of the carrier is typically 250 µm or less, and preferably 7 µm or more and 200 µm or less.

[0035] It is preferred that the surface of the carrier on the release layer side is smooth. That is, in the manufacturing process of the copper foil with a carrier, an extremely thin copper foil (before roughening treatment) is formed on the surface of the carrier on the release layer side. Therefore, by smoothing the surface of the carrier on the release layer side, the outer surface of the extremely thin copper foil can also be smoothed, and by performing roughening treatment on the smooth surface of the extremely thin copper foil, it becomes easier to achieve a roughened surface having a desired Sdr. A smooth carrier can be preferably produced, for example, by performing electrolytic foil production in accordance with the aforementioned production conditions for a smooth electrolytic copper foil.

[0036] The release layer is a layer that weakens the peel strength of the carrier, ensures the stability of that strength, and further suppresses the mutual diffusion that may occur between the carrier and the copper foil during high-temperature press molding. The release layer is generally formed on one side of the carrier, but it may also be formed on both sides. The release layer may be either an organic release layer or an inorganic release layer. Examples of organic components used in the organic release layer include nitrogen-containing organic compounds, sulfur-containing organic compounds, and carboxylic acids. Examples of nitrogen-containing organic compounds include triazole compounds and imidazole compounds, among which triazole compounds are preferred because they tend to have stable release properties. Examples of triazole compounds include 1,2,3-benzotriazole, carboxybenzotriazole, N',N'-bis(benzotriazolylmethyl)urea, 1H-1,2,4-triazole, and 3-amino-1H-1,2,4-triazole. Examples of sulfur-containing organic compounds include mercaptobenzothiazole, thiocyanuric acid, and 2-benzimidazolethiol. Examples of carboxylic acids include monocarboxylic acids and dicarboxylic acids. On the other hand, examples of inorganic components used in the inorganic exfoliation layer include Ni, Mo, Co, Cr, Fe, Ti, W, P, Zn, and chromate-treated films. The exfoliation layer can be formed by contacting a solution containing the exfoliation layer components with at least one surface of the carrier and fixing the exfoliation layer components to the surface of the carrier. When contacting the carrier with the solution containing the exfoliation layer components, this contact can be performed by immersion in the solution, spraying the solution, or letting the solution flow down. In addition, methods for forming a film of the exfoliation layer components by vapor deposition or sputtering can also be employed. Furthermore, the exfoliation layer components can be fixed to the carrier surface by adsorption or drying of the solution containing the exfoliation layer components, or by electrodeposition of the exfoliation layer components in the solution. The thickness of the exfoliation layer is typically 1 nm to 1 μm, preferably 5 nm to 500 nm.

[0037] If desired, another functional layer may be provided between the release layer and the carrier and / or the roughened copper foil 10. Examples of such other functional layers include an auxiliary metal layer. The auxiliary metal layer is preferably made of nickel and / or cobalt. Forming such an auxiliary metal layer on the surface side of the carrier and / or the surface side of the roughened copper foil 10 can suppress mutual diffusion that may occur between the carrier and the roughened copper foil 10 during high-temperature or long-time hot press molding, and ensure the stability of the peeling strength of the carrier. The thickness of the auxiliary metal layer is preferably 0.001 μm or more and 3 μm or less.

[0038] The roughened copper foil 10 of this disclosure is preferably used in the manufacture of copper-clad laminates for printed circuit boards. That is, according to a preferred embodiment of this disclosure, a copper-clad laminate equipped with roughened copper foil 10 is provided. By using the roughened copper foil 10 of this disclosure, it is possible to achieve both excellent transmission characteristics and high reliability in the copper-clad laminate. This copper-clad laminate comprises roughened copper foil 10 and a resin layer provided in close contact with the roughened surface of the roughened copper foil 10. The roughened copper foil 10 may be provided on one side of the resin layer or on both sides. The resin layer comprises a resin, preferably an insulating resin. The resin layer is preferably a prepreg and / or a resin sheet. A prepreg is a general term for a composite material obtained by impregnating a substrate such as a synthetic resin plate, glass plate, glass woven fabric, glass nonwoven fabric, or paper with a synthetic resin. Preferred examples of insulating resins include epoxy resins, cyanate resins, bismaleimide triazine resins (BT resins), polyphenylene ether resins, and phenolic resins. Examples of insulating resins constituting the resin sheet include epoxy resins, polyimide resins, polyester resins, liquid crystal polymer resins (LCPs), and polytetrafluoroethylene resins (PTFEs). The resin layer may also contain filler particles made of various inorganic particles such as silica and alumina to improve insulation properties. The thickness of the resin layer is not particularly limited, but is preferably 1 μm to 1000 μm, more preferably 2 μm to 400 μm, and even more preferably 3 μm to 200 μm. The resin layer may be composed of multiple layers. The resin layer, such as a prepreg and / or resin sheet, may be provided on the roughened copper foil 10 via a primer resin layer that is applied to the copper foil surface in advance.

[0039] The roughened copper foil 10 of this disclosure is preferably used in the manufacture of printed circuit boards. That is, according to a preferred embodiment of this disclosure, a printed circuit board equipped with the roughened copper foil 10 is provided. By using the roughened copper foil 10 of this disclosure, both excellent transmission characteristics and high reliability can be achieved in the printed circuit board. The printed circuit board according to this embodiment includes a layer structure in which a resin layer and a copper layer are laminated. The copper layer is a layer derived from the roughened copper foil 10 of this disclosure. The resin layer is as described above with respect to copper-clad laminates. In any case, a known layer structure can be used for the printed circuit board. Specific examples of printed circuit boards include single-sided or double-sided printed circuit boards in which a circuit is formed on a laminate formed by bonding the roughened copper foil 10 to one or both sides of a prepreg and curing it, and multilayer printed circuit boards made by layering these. Other specific examples include flexible printed circuit boards, COF, TAB tapes, etc., in which a circuit is formed by forming the roughened copper foil 10 on a resin film. Further specific examples include a build-up wiring board in which a resin-coated copper foil (RCC) is formed by applying the above-mentioned resin layer to a roughened copper foil 10, the resin layer is laminated onto the above-mentioned printed circuit board as an insulating adhesive layer, and then a circuit is formed using methods such as the modified semi-additive method (MSAP) or subtractive method with the roughened copper foil 10 as all or part of the wiring layer; a build-up wiring board in which the roughened copper foil 10 is removed and a circuit is formed using the semi-additive method (SAP); and a direct build-up on wafer in which the lamination of resin-coated copper foil and circuit formation are alternately repeated on a semiconductor integrated circuit.

[0040] The present invention will be further described in detail by the following examples. However, the present invention is not limited to the following examples.

[0041] Examples 1-4: Roughened copper foil was prepared as follows.

[0042] (1) Preparation of electrolytic copper foil A copper sulfate solution with the composition shown below was used as the copper electrolyte. A rotating titanium electrode, polished with a buff of the grit shown in Table 1 to adjust the surface roughness, was used, and a DSA (dimensionally stable anode) was used as the anode. The solution temperature was 45°C and the current density was 55 A / dm². ２Electrolysis was performed to obtain electrolytic copper foil with a thickness of 35 μm. <Composition of sulfuric acid-acidified copper sulfate solution> - Copper concentration: 80 g / L - Sulfuric acid concentration: 260 g / L - Bis(3-sulfopropyl) disulfide concentration: 30 mg / L - Diallyldimethylammonium chloride polymer concentration: 50 mg / L - Chlorine concentration: 40 mg / L

[0043] (2) Roughening Treatment Of the electrode surface and deposition surface of the electrolytic copper foil described above, the deposition surface was subjected to a one-step roughening treatment. This roughening treatment was carried out by electrolysis using solutions with the copper concentration, sulfuric acid concentration, 9-phenylacridine concentration, and chlorine concentration shown in Table 1, under the conditions of solution temperature, current density, and inter-electrode copper supply amount shown in Table 1, followed by washing with water. The copper concentration was appropriately adjusted within the range of 5 g / L to 20 g / L.

[0044]

[0045] (3) Anti-corrosion treatment was performed on the electrolytic copper foil after roughening treatment. Specifically, both sides of the electrolytic copper foil after roughening treatment were subjected to anti-corrosion treatment consisting of inorganic anti-corrosion treatment and chromate treatment. First, as inorganic anti-corrosion treatment, a pyrophosphate bath was used with a potassium pyrophosphate concentration of 80 g / L, a zinc concentration of 0.2 g / L, a nickel concentration of 2 g / L, a liquid temperature of 40°C, and a current density of 0.5 A / dm ２ A zinc-nickel alloy was treated with a rust-preventive coating. Subsequently, a chromate layer was formed on top of the treated zinc-nickel alloy as a chromate treatment. This chromate treatment was performed with a chromic acid concentration of 1 g / L, pH 11, solution temperature of 25°C, and current density of 1 A / dm². ２ I went there.

[0046] (4) Silane coupling agent treatment The copper foil that had undergone the above rust prevention treatment was washed with water, and then immediately treated with a silane coupling agent to adsorb the silane coupling agent onto the chromate layer on the roughened surface. This silane coupling agent treatment was carried out by spraying a solution of the silane coupling agent with pure water as the solvent onto the roughened surface using a showering method for adsorption. 3-aminopropyltrimethoxysilane was used as the silane coupling agent. The concentration of the silane coupling agent was 3 g / L. After the adsorption of the silane coupling agent, the water was finally evaporated using an electric heater to obtain roughened copper foil of a predetermined thickness.

[0047] The following evaluations were performed on the roughened copper foil that was manufactured for evaluation.

[0048] (a) Surface properties parameters: Surface roughness analysis was performed on both sides of the roughened copper foil using a laser microscope in accordance with ISO 25178. The specific measurement conditions are shown in Table 2. The surface profiles of the roughened copper foil obtained were analyzed according to the conditions shown in Table 2, and the developed area ratio Sdr of the interface between the roughened surface and the surface opposite the roughened surface was calculated. The results are shown in Table 3.

[0049]

[0050] (b) Elemental analysis Elemental analysis was performed by XPS on the roughened surface (outermost surface) of the roughened copper foil using an ion gun, while drilling in the depth direction (towards the surface opposite the roughened surface). This elemental analysis was performed using a scanning dual X-ray photoelectron spectroscopy (XPS) analyzer (ULVAC-PHI, PHI Quantes) under the following measurement conditions: (Measurement conditions) - X-ray beam diameter: 200 μmφ - X-ray output: 50 W - X-ray type: monochromatic Al Kα rays - Ion gun settings: ion type Ar gas, acceleration voltage 2 kV, irradiation area 2 mm × 2 mm - Sputtering rate (SiO ２ Conversion: 5.5 nm / min - Measured elements and orbitals: C 1s, N 1s, O 1s, Si 2s, Cr 3p, Ni 2p ３／２ Cu 2p ３／２ , Zn 2p ３／２ , Mo 3d, W 4f, Co 2p １／２

[0051] The C / Sdr ratio was determined by considering the C concentration (at%) at a depth position where the total atomic concentration of Si, Cr, Ni, Zn, Mo, W, and Co—elements derived from silane and anti-corrosion metals in the roughened surface layer—was less than 2.0 at%. This C concentration represented the internal roughening information (i.e., the C concentration of the roughened particles). For Examples 1-3, the depth position was 50 nm from the outermost surface of the roughened copper foil, and for Example 4, it was 100 nm from the outermost surface of the roughened copper foil. The C atomic concentration (at%) at these depth positions was calculated for each example. All measured elements were used in the calculation of atomic concentration (at%). The internal C / Sdr ratio was then determined by dividing the obtained C concentration of the roughened particles by the Sdr of the roughened surface calculated in (a) above. The results are shown in Table 3.

[0052] Surface C / Cu Ratio In the elemental analysis described above, the atomic concentrations of C (at%) and Cu (at%) were calculated on the roughened surface (outermost surface) of roughened copper foil that had not undergone sputtering. All elements measured were used in the calculation of atomic concentrations (at%). The surface C / Cu ratio was then determined by dividing the obtained C concentration on the roughened surface by the Cu concentration on the roughened surface. The results are shown in Table 3.

[0053] (c) Transmission characteristics As part of the evaluation of transmission characteristics, evaluation substrates with microstrip lines and evaluation substrates with strip lines were fabricated, and the transmission loss was measured for each evaluation substrate. Specifically, the details are as follows.

[0054] A high-frequency substrate (TU943SR, manufactured by Taiwan Union Technology Corporation) was prepared as the insulating resin substrate for the microstrip lines. Roughened copper foil was laminated to both sides of this insulating resin substrate so that the roughened side was in contact with the insulating resin substrate. Using a vacuum press, the lamination was performed at a temperature of 220°C for 120 minutes to obtain a copper-clad laminate with an insulating thickness of 136 μm. Subsequently, the copper-clad laminate was etched to form microstrip lines with a characteristic impedance of 50 Ω ± 2 Ω, obtaining a transmission loss measurement substrate. The transmission loss (dB / cm) at 50 GHz was measured on the obtained transmission loss measurement substrate using a network analyzer (N5225B, manufactured by Keysight Technologies). The obtained transmission losses were graded and evaluated according to the following criteria. The results are shown in Table 3. <Transmission Loss Evaluation Criteria> - Evaluation A (Best): Transmission loss of -0.324 dB / cm or more - Evaluation B (Good): Transmission loss of -0.328 dB / cm or more and less than -0.324 dB / cm - Evaluation C (Poor): Transmission loss of less than -0.328 dB / cm

[0055] A high-frequency substrate (Panasonic, MEGTRON7) was prepared as the stripline insulating resin substrate. Roughened copper foil was laminated to both sides of this insulating resin substrate so that the roughened side of the foil was in contact with the insulating resin substrate. Using a vacuum press, the lamination was performed at a temperature of 190°C and a pressing time of 120 minutes to obtain two copper-clad laminates with an insulating thickness of 136 μm. Subsequently, one of the two copper-clad laminates obtained (hereinafter referred to as the "first copper-clad laminate") was etched on one side of the copper foil to form a conductive circuit on one side. The first copper-clad laminate with the circuit formed and the copper-clad laminate without the circuit formed (hereinafter referred to as the "second copper-clad laminate") were each treated with an adhesion treatment agent (Atotech, Bond Film HF1000). A separate insulating resin substrate identical to the high-frequency substrate described above was prepared to a thickness of 136 μm. A first copper-clad laminate was laminated onto one surface of this insulating resin substrate so that its conductor circuit side surface was in contact with it, and a second copper-clad laminate was laminated onto the other surface of the insulating resin substrate. Then, using a vacuum press, the substrate was pressed at a temperature of 190°C for a pressing time of 120 minutes to obtain a four-layer copper-clad laminate with four copper layers (insulation thickness between copper layers: 136 μm). The obtained four-layer copper-clad laminate was subjected to a circuit formation process for measurement, and a transmission loss measurement substrate was obtained by forming striplines so that the characteristic impedance was 67 Ω ± 2 Ω. The transmission loss (dB / cm) at 50 GHz was measured on the obtained transmission loss measurement substrate using a network analyzer (Keysight Technologies, N5227B). The transmission characteristics of the obtained transmission loss were evaluated based on the evaluation criteria below. The results are shown in Table 3. <Transmission Loss Evaluation Criteria> - Evaluation A (Best): Transmission loss of -0.516 dB / cm or more - Evaluation B (Good): Transmission loss greater than -0.518 dB / cm but less than -0.516 dB / cm - Evaluation C (Poor): Transmission loss of -0.518 dB / cm or less

[0056]

[0057] 10, 110, 210: roughened copper foil, 10a, 110a, 210a: roughened particles, C: carbon

Claims

1. A roughened copper foil having a roughened surface, wherein the surface C / Cu ratio, which is the ratio of the C concentration (at%) of the roughened surface to the Cu concentration (at%) of the roughened surface, is 20 or more and 350 or less, and the Cu concentration and C concentration of the roughened surface are the atomic concentrations of Cu and C, respectively, obtained when C, N, O, Si, Cr, Ni, Cu, Zn, Mo, W, and Co are elementally analyzed on the roughened surface by X-ray photoelectron spectroscopy (XPS).

2. The roughened copper foil according to claim 1, wherein the surface C / Cu ratio is 20 or more and 100 or less.

3. The roughened copper foil according to claim 1 or 2, wherein the interface development area ratio Sdr of the roughened surface, measured in accordance with ISO 25178, is 2.9% or less.

4. The roughened copper foil according to claim 1 or 2, wherein the interface development area ratio Sdr, measured in accordance with ISO 25178, on the surface of the roughened copper foil opposite to the roughened surface is 2.5% or less.

5. The roughened surface comprises a plurality of roughened particles, the internal C / Sdr ratio, which is the ratio of the C concentration (at%) of the roughened particles to the developed area ratio Sdr (%) of the interface of the roughened surface, is 0.1 or more and 2.9 or less, Sdr is a value measured in accordance with ISO 25178, and the C concentration of the roughened particles is the atomic concentration of C measured at a depth position where the total concentration of Si, Cr, Ni, Zn, Mo, W, and Co is less than 2.0 at%, when elemental analysis of C, N, O, Si, Cr, Ni, Cu, Zn, Mo, W, and Co is performed from the roughened surface toward the depth direction of the roughened copper foil by XPS.

6. The roughened copper foil according to claim 1 or 2, further comprising a rust-preventive treatment layer and / or a silane coupling agent layer on the roughened surface.

7. A copper foil with a carrier, comprising a carrier, a release layer provided on the carrier, and a roughened copper foil according to claim 1 or 2 provided on the release layer with the roughened surface facing outward.

8. A copper-clad laminate comprising the roughened copper foil described in claim 1 or 2.

9. A printed circuit board comprising the roughened copper foil described in claim 1 or 2.

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