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

Abstract

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

Description

[Technical Field]

[0001] This invention relates to roughened copper foil, copper-clad laminates, and printed circuit boards. [Background technology]

[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] As an example of copper foil subjected to such roughening treatment, Patent Document 1 (Japanese Patent Application Publication No. 2018-172785) discloses a surface-treated copper foil having a roughening treatment layer on at least one surface of the copper foil, wherein the arithmetic mean roughness Ra of the roughening treatment layer side surface is 0.08 μm or more and 0.20 μm or less, and the glossiness in the TD (width direction) of the roughening treatment layer side surface is 70% or less. With such a surface-treated copper foil, the shedding of roughening particles provided on the copper foil surface is well suppressed, and the occurrence of wrinkles and streaks when bonded to an insulating substrate is well suppressed.

[0004] 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.

[0005] In this regard, roughened copper foil designed to reduce transmission loss has been proposed. For example, Patent Document 2 (Japanese Patent Publication No. 2015-148011) discloses a method for controlling the skewness Rsk of the copper foil surface, based on JIS B0601-2001, to a predetermined range of -0.35 to 0.53 by surface treatment, with the aim of providing a surface-treated copper foil with low signal transmission loss and a laminate using the same. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-172785 [Patent Document 2] Japanese Patent Publication No. 2015-148011 [Overview of the project]

[0007] As mentioned above, in recent years there has been a demand to improve the transmission characteristics (high-frequency characteristics) of printed circuit boards. To meet these demands, finer roughening treatments have been attempted on the bonding surface of copper foil with insulating resin substrate. Specifically, in order to reduce the unevenness of the copper foil surface, which is a factor that increases transmission loss, it is conceivable to perform fine roughening treatment on copper foil surfaces with small waviness (for example, the surface of double-sided smooth foil or the electrode surface of electrolytic copper foil). Furthermore, by using roughened copper foil with small waviness, it is conceivable to improve the linearity of the wiring pattern during circuit formation (hereinafter referred to as circuit linearity). However, when copper-clad laminates are processed or printed circuit boards are manufactured using such roughened copper foil, problems can generally arise such as low peel strength between the copper foil and the substrate, and poor adhesion reliability.

[0008] The present inventors have now found that by controlling the ratio of Rdc / Rku (the difference in cutting level Rdc to the kurtosis Rku) and the maximum cross-sectional height Wt within a predetermined range on the surface of roughened copper foil, copper-clad laminates or printed circuit boards manufactured using this method can exhibit excellent transmission characteristics and circuit linearity, as well as high peel strength.

[0009] Therefore, an object of the present invention is to provide a roughened copper foil that has excellent transmission characteristics and circuit linearity and can achieve high peel strength when used in a copper-clad laminate or a printed wiring board.

[0010] According to the present invention, the following aspects are provided. [Aspect 1] A roughened copper foil having a roughened surface on at least one side, where the roughened surface has a ratio of the cut-off level difference Rdc of the roughness curve to the kurtosis Rku of the roughness curve, Rdc / Rku, of 0.180 μm or less, and the maximum cross-sectional height Wt of the waviness curve is 2.50 μm or more and 10.00 μm or less, where the Rku is a value measured under the conditions of a magnification of 200 times, a cut-off wavelength of 0.3 μm based on the cut-off value λs, and a cut-off wavelength of 5 μm based on the cut-off value λc in accordance with JIS B0601-2013, where the Rdc is a value obtained as the difference (c(Rmr1) - c(Rmr2)) in the height direction between the load length ratio (Rmr1) of 20% and the load length ratio (Rmr2) of 80% in the roughness curve measured under the conditions of a magnification of 200 times, a cut-off wavelength of 0.3 μm based on the cut-off value λs, and a cut-off wavelength of 5 μm based on the cut-off value λc in accordance with JIS B0601-2013, where the Wt is a value measured under the conditions of a magnification of 20 times, a cut-off wavelength of 5 μm based on the cut-off value λc, and no cut-off based on the cut-off value λf in accordance with JIS B0601-2013, the roughened copper foil. [Aspect 2] The roughened copper foil according to Aspect 1, where the maximum cross-sectional height Wt is 2.90 μm or more and 10.00 μm or less. [Aspect 3] The roughened copper foil according to Aspect 1 or 2, where the cut-off level difference Rdc is 0.45 μm or less. [Aspect 4] The roughened surface has a maximum peak height Wp of the waviness curve of 1.00 μm or more and 6.00 μm or less, and the Wp is a value measured under the conditions of a magnification of 20 times, a cut-off wavelength of 5 μm by a cut-off value λc, and no cut-off by a cut-off value λf in accordance with JIS B0601-2013. The roughened copper foil according to any one of Aspects 1 to 3. [Aspect 5] The roughened surface has an average height Rc of roughness curve elements of 0.70 μm or less, and the Rc is a value measured under the conditions of a magnification of 20, a cut-off wavelength of 0.3 μm by a cut-off value λs, and a cut-off wavelength of 5 μm by a cut-off value λc in accordance with JIS B0601-2013. The roughened copper foil according to any one of Aspects 1 to 4. [Aspect 6]<{ The roughened surface has a cut-off level difference Wdc of the waviness curve of 1.20 μm or more and 3.10 μm or less, and the Wdc is a difference (c(Wmr1) - c(Wmr2)) in the height direction between a load length ratio (Wmr1) of 20% and a load length ratio (Wmr2) of 80% in the waviness curve measured under the conditions of a magnification of 20 times, a cut-off wavelength of 5 μm by a cut-off value λc, and no cut-off by a cut-off value λf in accordance with JIS B0601-2013. The roughened copper foil according to any one of Aspects 1 to 5. [Aspect 7] The roughened surface has a root mean square height Rq of the roughness curve of 0.290 μm or less, and the Rq is a value measured under the conditions of a magnification of 200 times, a cut-off wavelength of 0.3 μm by a cut-off value λs, and a cut-off wavelength of 5 μm by a cut-off value λc in accordance with JIS B0601-2013. The roughened copper foil according to any one of Aspects 1 to 6. [Aspect 8] The roughened surface has the kurtosis Rku of 1.30 or more and 8.00 or less. The roughened copper foil according to any one of Aspects 1 to 7. [Aspect 9] The roughened surface is provided with a rust preventive treatment layer and / or a silane coupling agent treatment layer. The roughened copper foil according to any one of Aspects 1 to 8. [Aspect 10] The roughened copper foil according to any one of embodiments 1 to 9, wherein the roughened copper foil is an electrolytic copper foil, and the roughened surface is located on the deposition surface side of the electrolytic copper foil. [Aspect 11] A copper-clad laminate comprising roughened copper foil according to any one of embodiments 1 to 10. [Aspect 12] A printed circuit board comprising roughened copper foil according to any one of embodiments 1 to 10. [Brief explanation of the drawing]

[0011] [Figure 1] This diagram illustrates the load curve of the roughness curve determined in accordance with JIS B0601-2013. [Figure 2] This diagram illustrates the load length ratio Rmr(c) determined in accordance with JIS B0601-2013. [Figure 3] This diagram illustrates the cutting level difference Rdc determined in accordance with JIS B0601-2013. [Figure 4] This diagram illustrates that the surface irregularities of roughened copper foil consist of roughened particle components and undulation components. [Figure 5] This is a schematic diagram showing an example of the roughened copper foil of the present invention. [Modes for carrying out the invention]

[0012] definition The following are definitions of terms and parameters used to specify the present invention.

[0013] In this specification, the "load curve of the roughness curve" is, as shown in FIG. 1, a curve representing the ratio of the solid part that appears when the roughness curve is cut at a cut-off level c as a function of c, determined in accordance with JIS B0601-2013. That is, the load curve of the roughness curve can also be said to be a curve representing the height at which the load length ratio Rmr(c) ranges from 0% to 100%. The load length ratio Rmr(c) is, as shown in FIG. 2, a parameter representing the ratio of the load length of the roughness curve element at the cut-off level c to the evaluation length, determined in accordance with JIS B0601-2013.

[0014] In this specification, the "cut-off level difference Rdc of the roughness curve", "cut-off level difference Rdc", or "Rdc" is, as shown in FIG. 3, a parameter representing the difference (c(Rmr1) - c(Rmr2)) in the cut-off level c in the height direction between two load length ratios Rmr1 and Rmr2 (where Rmr1 < Rmr2) in the load curve of the roughness curve, measured in accordance with JIS B0601-2013. In this specification, Rmr1 is specified as 20% and Rmr2 as 80% to calculate Rdc.

[0015] In this specification, the "root mean square height Rq of the roughness curve", "root mean square height Rq", or "Rq" is a parameter representing the root mean square of Z(x) (where Z(x) represents the height of the roughness curve at an arbitrary position x) at the reference length, measured in accordance with JIS B0601-2013.

[0016] In this specification, the "kurtosis Rku of the roughness curve", "kurtosis Rku", or "Rku" is a parameter representing the fourth moment of Z(x) at the reference length, dimensionless by the fourth power of the root mean square height Rq, measured in accordance with JIS B0601-2013. Rku means the sharpness, which is a measure of the sharpness of the surface, and represents the sharpness (sharpness) of the height distribution. Rku = 3 means that the height distribution is a normal distribution. When Rku > 3, the height distribution is sharp, and when Rku < 3, it means that the height distribution has a flattened shape.

[0017] In this specification, "Rdc / Rku" is a parameter representing the ratio of the cleavage level difference Rdc to the crustosis Rku.

[0018] In this specification, "average height Rc of roughness curve elements," "average height Rc," or "Rc" refers to a parameter that represents the average height of roughness curve elements at a given length, measured in accordance with JIS B0601-2013. A roughness curve element refers to a pair of adjacent peaks and valleys in a roughness curve. Peaks and valleys constituting a roughness curve element have defined minimum heights and minimum lengths. Those with a height of 10% or less of the maximum height Rz, or a length of 1% or less of the given length, are considered noise and are included as part of the preceding and succeeding valleys or peaks.

[0019] In this specification, "maximum cross-sectional height Wt of the undulation curve," "maximum cross-sectional height Wt," or "Wt" is a parameter that represents the sum of the maximum peak height and the maximum valley depth of the undulation curve at the evaluation length, measured in accordance with JIS B0601-2013.

[0020] In this specification, "maximum peak height Wp of the undulation curve," "maximum peak height Wp," or "Wp" is a parameter that represents the maximum value of the peak height of the undulation curve at a reference length, measured in accordance with JIS B0601-2013.

[0021] In this specification, the "load curve of the wobble curve" is a curve that represents the proportion of the actual body that appears when the wobble curve is cut at cutting level c, as a function of c, as determined in accordance with JIS B0601-2013. In other words, the load curve of the wobble curve can also be said to be a curve that represents the height at which the load length ratio Wmr(c) ranges from 0% to 100%. The load length ratio Wmr(c) is a parameter that represents the ratio of the load length of the wobble curve element at cutting level c to the evaluation length, as determined in accordance with JIS B0601-2013.

[0022] In this specification, the "waviness curve cutting level difference Wdc", "cutting level difference Wdc", or "Wdc" refers to a parameter representing the difference (c(Wmr1) - c(Wmr2)) in the height direction of the cutting level c between two load length ratios Wmr1 and Wmr2 (where Wmr1 < Wmr2) in the load curve of the waviness curve, measured in accordance with JIS B0601-2013. In this specification, it is assumed that Wmr1 is specified as 20% and Wmr2 as 80% to calculate Wdc.

[0023] Rdc, Rq, Rku, Rc, Wt, Wp, and Wdc can be calculated by measuring the surface profile of a predetermined measurement length on the roughened surface with a commercially available laser microscope. In this specification, the roughness parameters Rdc, Rq, Rku, and Rc are measured under the conditions of a magnification of 200 times, a cut-off wavelength of 0.3 μm by the cut-off value λs, and a cut-off wavelength of 5 μm by the cut-off value λc. Also, the reference length and evaluation length used for calculating the roughness parameters are 5 μm and 25 μm, respectively. On the other hand, the waviness parameters Wt, Wp, and Wdc are measured under the conditions of a magnification of 20 times, a cut-off wavelength of 5 μm by the cut-off value λc, and no cut-off by the cut-off value λf. Also, the reference length and evaluation length used for calculating the waviness parameters are both the same as the measurement length of the roughened surface. In the examples described later, the waviness parameters are measured for a region of 643.973 μm in length and 643.393 μm in width on the roughened surface. In such a case, the reference length and evaluation length are 643.973 μm in the longitudinal direction and 643.393 μm in the transverse direction. In the measurement by a laser microscope, when both the objective lens and the optical zoom are used, the above magnification corresponds to the value obtained by multiplying the magnification of the objective lens by the magnification of the optical zoom. For example, when the objective lens magnification is 100 times and the optical zoom magnification is 2 times, the magnification is 200 times (= 100 × 2). Other preferred measurement conditions and analysis conditions for the surface profile by a laser microscope are shown in the examples described later.

[0024] 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.

[0025] In this specification, the "deposited 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.

[0026] Roughened copper foil The copper foil of the present invention is a roughened copper foil. This roughened copper foil has a roughened surface on at least one side. On this roughened surface, the ratio of Rdc / Rku, which is the difference in cutting level Rdc of the roughness curve to the crustosis Rku of the roughness curve, is 0.180 μm or less. Furthermore, the maximum cross-sectional height Wt of the waviness curve of the roughened surface is 2.50 μm or more and 10.00 μm or less. By controlling Rdc / Rku and the maximum cross-sectional height Wt within a predetermined range on the surface of the roughened copper foil in this way, it is possible to achieve excellent transmission characteristics (high frequency characteristics) and circuit linearity, as well as high peel strength, in copper-clad laminates or printed circuit boards manufactured using this foil.

[0027] Achieving both excellent transmission characteristics and high peel strength, as well as excellent circuit linearity and high peel strength, is inherently difficult. This is because improving transmission characteristics or circuit linearity requires reducing surface irregularities on the copper foil, while obtaining high peel strength requires increasing surface irregularities on the copper foil; these are trade-offs. As shown in Figure 4, the surface irregularities of roughened copper foil consist of "roughened particle components" and "undulation components" with longer periods than the roughened particle components. Generally, to improve transmission characteristics or circuit linearity, it is conceivable to perform a fine roughening treatment on a copper foil surface with small undulations (for example, the surface of a double-sided smooth foil or the electrode surface of an electrolytic copper foil) to form small roughened particles. However, when copper-clad laminates or printed circuit boards are manufactured using such roughened copper foil, the peel strength between the copper foil and the substrate is generally low.

[0028] To address this problem, the inventors investigated the effects of roughening particles and undulations on the surface of copper foil on transmission characteristics, circuit linearity, and peel strength. As a result, contrary to expectations, the undulation component of the copper foil had little effect on transmission characteristics, and it was found that the size of the roughening particles primarily influenced the transmission characteristics. The inventors then discovered that by miniaturizing the bumps (roughening particles) to improve transmission characteristics, and compensating for the resulting lack of adhesion with the undulations of the copper foil, which have little impact on transmission characteristics, it is possible to achieve both excellent transmission characteristics and high adhesion reliability due to high peel strength. Furthermore, they found that by controlling the undulations of the copper foil within a predetermined range, a good balance between excellent circuit linearity and high peel strength can be achieved. Specifically, they found that using Rdc / Rku, obtained by dividing the cutting level difference Rdc by the kurtosis Rku, accurately reflects the shape of minute bumps (roughening particles) that affect transmission characteristics, and that controlling Rdc / Rku to 0.180 μm or less enables the realization of excellent transmission characteristics. Furthermore, we discovered that the maximum cross-sectional height Wt can accurately reflect the waviness component in a wide range of roughened surfaces, and that by setting this Wt to ​​between 2.50 μm and 10.00 μm, it is possible to achieve high peel strength between the copper foil and the substrate while maintaining excellent circuit linearity by utilizing the waviness of the copper foil.

[0029] The roughening particle components and waviness components on the copper foil surface that affect transmission characteristics, circuit linearity, or peel strength can be distinguished by using different measurement magnifications and cutoff values ​​λs, λc, and λf in a laser microscope. Specifically, by measuring the roughened surface at a high magnification of 200x, the fine irregularities of the roughened surface that affect transmission characteristics can be accurately evaluated. Furthermore, by using the roughness curves obtained by measuring the roughened surface under conditions of a cutoff wavelength of 0.3 μm using the cutoff value λs and a cutoff wavelength of 5 μm using the cutoff value λc, roughness parameters with the influence of waviness components removed can be calculated. Therefore, the roughness parameters in this invention, namely Rdc, Rku, Rdc / Rku, Rc, and Rq, can be said to accurately reflect the roughening particle components on the copper foil surface, and transmission characteristics can be accurately evaluated by using these indices. In contrast, by measuring the roughened surface at a low magnification of 20x, the overall height (undulation) of the roughened surface, which affects circuit linearity and adhesion reliability, can be evaluated over a wide range. Furthermore, by using the undulation curves obtained by measuring the roughened surface under conditions where no cutoff is applied, using a cutoff wavelength of 5 μm with a cutoff value λc, and also using a cutoff value λf, it is possible to calculate undulation parameters that are free from the influence of roughened particle components. Therefore, the undulation parameters in this invention, namely Wt, Wp, and Wdc, are parameters that accurately reflect the undulation components on the copper foil surface, and circuit linearity and peel strength can be accurately evaluated using these indicators.

[0030] The roughened surface of the roughened copper foil has a maximum cross-sectional height Wt of the undulation curve of 2.50 μm or more and 10.00 μm or less, preferably 2.90 μm or more and 10.00 μm or less, more preferably 3.10 μm or more and 9.00 μm or less, and even more preferably 3.30 μm or more and 7.00 μm or less. When Wt is within the above range, it is possible to achieve a good balance between excellent circuit linearity and high peel strength while ensuring excellent transmission characteristics.

[0031] The roughened surface of the roughened copper foil has an Rdc / Rku of 0.180 μm or less, preferably 0.015 μm to 0.150 μm, more preferably 0.030 μm to 0.110 μm, and even more preferably 0.045 μm to 0.080 μm. An Rdc / Rku within the above range allows for excellent transmission characteristics while maintaining excellent circuit linearity and high peel strength.

[0032] The roughened surface of the roughened copper foil preferably has a cutting level difference Rdc of 0.45 μm or less, more preferably 0.04 μm to 0.40 μm, even more preferably 0.08 μm to 0.35 μm, and particularly preferably 0.12 μm to 0.30 μm. Having an Rdc within the above range makes it easier to control Rdc / Rku within the range described above, and enables the realization of even better transmission characteristics.

[0033] The roughened surface of the roughened copper foil preferably has a kurtosis Rku of 1.30 to 8.00, more preferably 1.50 to 5.50, even more preferably 2.00 to 4.50, and particularly preferably 2.50 to 3.20. Having an Rku within the above range makes it easier to control Rdc / Rku within the aforementioned range and enables the realization of even better transmission characteristics.

[0034] The roughened surface of the roughened copper foil preferably has a maximum peak height Wp of the undulation curve of 1.00 μm or more and 6.00 μm or less, more preferably 1.20 μm or more and 5.00 μm or less, even more preferably 1.30 μm or more and 4.30 μm or less, and particularly preferably 1.40 μm or more and 3.70 μm or less. When Wp is within the above range, it is possible to achieve an even better balance between excellent circuit linearity and high peel strength while ensuring excellent transmission characteristics.

[0035] The roughened surface of the roughened copper foil preferably has an average height Rc of 0.70 μm or less of roughness curve elements, more preferably 0.06 μm to 0.60 μm, even more preferably 0.12 μm to 0.50 μm, and particularly preferably 0.18 μm to 0.50 μm. When Rc is within the above range, it is possible to achieve even better transmission characteristics while maintaining excellent circuit linearity and high peel strength.

[0036] The roughened surface of the roughened copper foil preferably has a cutting level difference Wdc of undulation curve of 1.20 μm to 3.10 μm, more preferably 1.20 μm to 2.70 μm, even more preferably 1.30 μm to 2.30 μm, and particularly preferably 1.60 μm to 2.00 μm. A Wdc within the above range allows for a better balance between excellent circuit linearity and high peel strength while ensuring excellent transmission characteristics.

[0037] The roughened surface of the roughened copper foil preferably has a root mean square height Rq of the roughness curve of 0.290 μm or less, more preferably 0.030 μm to 0.260 μm, even more preferably 0.060 μm to 0.220 μm, and particularly preferably 0.090 μm to 0.200 μm. When Rq is within the above range, it is possible to achieve even better transmission characteristics while maintaining excellent circuit linearity and high peel strength.

[0038] The thickness of the roughened copper foil is not particularly limited, but is preferably 0.1 μm to 210 μm, more preferably 0.3 μm to 105 μm, even more preferably 7 μm to 70 μm, and particularly preferably 9 μm to 35 μm. The roughened copper foil of the present invention 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 or finely roughened surface.

[0039] An example of the roughened copper foil of the present invention is shown in Figure 5. As shown in Figure 5, the roughened copper foil of the present invention can be preferably manufactured by roughening a copper foil surface having a predetermined undulation (for example, the deposition surface of an electrolytic copper foil) under desired low roughening conditions to form fine roughened particles. Therefore, according to a preferred embodiment of the present invention, the roughened copper foil is an electrolytic copper foil, and the roughened surface is located on the deposition surface side of the electrolytic copper foil. The roughened copper foil may have roughened surfaces on both sides, or it may have a roughened surface on only one side. The roughened surface typically comprises a plurality of roughened particles, and it is preferable that each of these plurality of roughened particles is made of copper particles. The copper particles may be made of metallic copper or a copper alloy.

[0040] The roughening treatment to form a roughened surface can preferably be carried out by forming roughened particles of copper or a copper alloy on a copper foil. The copper foil before the roughening treatment may be an unroughened copper foil or one that has undergone preliminary roughening. The surface of the copper foil to be roughened preferably has a ten-point average roughness Rz of 1.30 μm to 10.00 μm, measured in accordance with JIS B0601-1994, and more preferably 1.50 μm to 8.00 μm. Within this range, it is easier to impart the surface profile required for the roughened copper foil of the present invention to the roughened surface.

[0041] The roughening treatment is performed in a copper sulfate solution containing, for example, a copper concentration of 7 g / L to 17 g / L and a sulfuric acid concentration of 50 g / L to 200 g / L, at a temperature of 20°C to 40°C, at a rate of 10 A / dm 2 More than 50A / dm 2 It is preferable to perform electrolytic extraction as described below. This electrolytic extraction is preferably performed for 0.5 seconds to 30 seconds, more preferably for 1 second to 30 seconds, and even more preferably for 1 second to 3 seconds. However, the roughened copper foil according to the present invention is not limited to the above method and may be manufactured by any method.

[0042] When the above electrical analysis is performed, the following formula is used: R L = L / D C (where R L is the liquid resistance index (mm·L / mol), L is the distance between the electrodes (anode - cathode) (mm), and D C is the charge carrier density (mol / L)) The liquid resistance index R L defined by is preferably 9.0 mm·L / mol or more and 20.0 mm·L / mol or less, and more preferably 11.0 mm·L / mol or more and 17.0 mm·L / mol or less. By increasing the liquid resistance index R L in this way, the voltage in the entire system increases, and the voltage during the nodule formation reaction also increases. As a result, this affects the nodule shape, and nodules of a shape suitable for imparting the surface profile required for the roughened copper foil of the present invention can be preferably formed. Note that the charge carrier density D C can be calculated by summing the product of the concentration and valence of each ion for all ions present in the plating solution. For example, when using a copper sulfate solution as the plating solution, the charge carrier density D C is given by the following formula: Dc = [H + ×1 + [Cu 2+ ×2 + [SO4 2- ×2 (where [H + is the hydrogen ion concentration (mol / L) in the solution, [Cu 2+ is the copper ion concentration (mol / L) in the solution, and [SO4 2- is the sulfate ion concentration (mol / L) in the solution) and is calculated by.

[0043] The relationship between the liquid resistance index R L and the voltage is explained as follows. First, according to Ohm's law, the following formula: V = ρ×L×I / S (where V is the voltage, ρ is the specific resistance, L is the electrode distance, I is the current, and S is the cross-sectional area between the electrodes) is derived. That is, the voltage V is proportional to the specific resistance ρ, the electrode distance L, and the current density (= I / S). And the specific resistance ρ is the charge carrier density D C [described above]]It is inversely proportional to (the distance L between poles and the charge carrier density D). Therefore, when the current density is constant, (it is proportional to the distance L between poles and the charge carrier density D C Increasing the liquid resistance index (which is inversely proportional to the voltage) also increases the voltage. Therefore, the liquid resistance index can be considered an indicator that correlates with the resistance of the solution.

[0044] If desired, the roughened copper foil may be treated with a rust-preventive coating to form a rust-preventive coating layer. The rust-preventive coating 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-preventive coating layer, the treated surface of the roughened copper foil will have better adhesion to the resin, chemical resistance and heat resistance, and less etching residue will remain.

[0045] In zinc-nickel alloy plating, the ratio of Ni deposition to the total amount of Zn deposition, Ni / (Zn+Ni), is preferably 0.3 to 0.9 by mass, more preferably 0.4 to 0.9, and even more preferably 0.4 to 0.8. Furthermore, the total amount of Zn and Ni deposition in zinc-nickel alloy plating is 8 mg / m². 2 More than 160mg / m 2 The following is preferred, and more preferably, 13 mg / m² 2 More than 130mg / m 2 More preferably, 19 mg / m² 2 More than 80mg / m 2 The following applies. On the other hand, in zinc-nickel-molybdenum alloy plating, the ratio of Ni deposition to the total amount of Zn deposition, Ni deposition, and Mo deposition, Ni / (Zn+Ni+Mo), is preferably 0.20 to 0.80 by mass ratio, more preferably 0.25 to 0.75, and even more preferably 0.30 to 0.65. Furthermore, the total deposition amount of Zn, Ni, and Mo in zinc-nickel-molybdenum alloy plating is 10 mg / m². 2More than 200mg / m 2 The following is preferred, and more preferably, 15 mg / m² 2 More than 150mg / m 2 More preferably 20 mg / m² 2 More than 90mg / m 2 The following applies: The amount of Zn, Ni, and Mo attached to a predetermined area (e.g., 25 cm²) on the roughened surface of the roughened copper foil. 2 This can be calculated by dissolving the substance in acid and analyzing the concentration of each element in the resulting solution based on ICP emission spectrometry.

[0046] The rust prevention treatment preferably includes a chromate treatment, and this chromate treatment is more preferably performed on the surface of the zinc-containing plating after the zinc-based plating treatment. This further improves rust prevention. A particularly preferred rust prevention treatment is a combination of zinc-nickel alloy plating (or zinc-nickel-molybdenum alloy plating) followed by a chromate treatment.

[0047] If desired, the roughened copper foil may be treated with a silane coupling agent on its surface, forming a silane coupling agent treated layer. This improves moisture resistance, chemical resistance, and adhesion to adhesives, etc. The silane coupling agent treated 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.

[0048] For the reasons stated above, it is preferable that the roughened copper foil has a rust-preventive treatment layer and / or a silane coupling agent treatment layer on the roughened surface, and more preferably both the rust-preventive treatment layer and the silane coupling agent treatment layer. When the rust-preventive treatment layer and / or the silane coupling agent treatment layer is formed on the roughened surface, the numerical values ​​of the roughness parameter and waviness parameter in this specification refer to the numerical values ​​obtained by measuring the surface of the roughened copper foil after the rust-preventive treatment layer and / or the silane coupling agent treatment layer have been formed. The rust-preventive treatment layer and the silane coupling agent treatment layer may be formed not only on the roughened surface side of the roughened copper foil, but also on the side where the roughened surface is not formed.

[0049] Copper-clad laminate The roughened copper foil of the present invention is preferably used in the manufacture of copper-clad laminates for printed circuit boards. That is, according to a preferred embodiment of the present invention, a copper-clad laminate equipped with the roughened copper foil is provided. By using the roughened copper foil of the present invention, it is possible to achieve both excellent transmission characteristics and high peel strength in the copper-clad laminate. This copper-clad laminate comprises the roughened copper foil of the present invention and a resin layer provided in close contact with the roughened surface of the roughened copper foil. The roughened copper foil may be provided on one side 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 resin, cyanate resin, bismaleimide triazine resin (BT resin), polyphenylene ether resin, and phenolic resin. Examples of insulating resins that constitute the resin sheet include epoxy resins, polyimide resins, and polyester resins. The resin layer may also contain filler particles made of various inorganic particles such as silica and alumina to improve insulation. 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 via a primer resin layer that is applied to the copper foil surface in advance.

[0050] Printed circuit board The roughened copper foil of the present invention is preferably used in the manufacture of printed circuit boards. That is, according to a preferred embodiment of the present invention, a printed circuit board equipped with the roughened copper foil is provided. By using the roughened copper foil of the present invention, both excellent transmission characteristics and high peel strength 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 of the present invention. 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 circuits are formed on a laminate formed by bonding the roughened copper foil of the present invention 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 circuits are formed by forming the roughened copper foil of the present invention 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 the roughened copper foil of the present invention, 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 as all or part of the wiring layer; a build-up wiring board in which the roughened copper foil is removed and a circuit is formed using the semi-additive method (SAP); and a direct build-up on a wafer in which the lamination of resin-coated copper foil and circuit formation are alternately repeated on a semiconductor integrated circuit. [Examples]

[0051] The present invention will be further described in detail by the following examples.

[0052] Examples 1-11 The roughened copper foil of the present invention was manufactured as follows.

[0053] (1) Manufacturing of electrolytic copper foil A sulfuric acid-acidified copper sulfate solution with the following composition was used as the copper electrolyte, a titanium electrode was used as the cathode, and a dimensionally stable anode (DSA) was used as the anode, with a solution temperature of 45°C and a current density of 55 A / dm². 2 Electrolysis was performed to obtain electrolytic copper foil of the thickness shown in Table 1. At this time, an electrode was used as the cathode, whose surface roughness was adjusted by polishing the surface with a buff of the grit shown in Table 1. <Composition of sulfuric acid-acidified copper sulfate solution> - Copper concentration: 80g / L - Sulfuric acid concentration: 300g / L - Glue concentration: 5 mg / L - Chlorine concentration: 30 mg / L

[0054] (2) Roughening treatment Of the electrode surface and deposition surface of the electrolytic copper foil described above, roughening treatment was performed on the deposition surface side for Examples 1-6 and 11, and on the electrode surface side for Examples 7-10. The ten-point average roughness Rz measured using a contact-type surface roughness meter in accordance with JIS B0601-1994 for the deposition surface of the electrolytic copper foil used in Examples 1-6 and 11, and the electrode surface of the electrolytic copper foil used in Examples 7-10, is shown in Table 1.

[0055] For Examples 1 to 8, the roughening treatment (first roughening treatment) described below was performed. This roughening treatment was carried out by electrolysis in a copper electrolytic solution for roughening treatment (copper concentration: 7 g / L to 17 g / L, sulfuric acid concentration: 50 g / L to 200 g / L, liquid temperature: 30°C) under the conditions of liquid resistance index, current density, and time shown in Table 1 for each example, followed by washing with water.

[0056] For Examples 9-11, the first, second, and third roughening treatments shown below were performed in this order. - The first roughening treatment was performed by electrolysis in a copper electrolytic solution for roughening (copper concentration: 7 g / L to 17 g / L, sulfuric acid concentration: 50 g / L to 200 g / L, solution temperature: 30°C) under the conditions of liquid resistance index, current density, and time shown in Table 1, followed by washing with water. - The second roughening treatment was performed by electrolysis in a copper electrolytic solution for roughening treatment with the same composition as the first roughening treatment, under the conditions of liquid resistance index, current density, and time shown in Table 1, followed by washing with water. - The third roughening treatment was performed by electrolysis in a copper electrolytic solution for roughening (copper concentration: 65 g / L to 80 g / L, sulfuric acid concentration: 50 g / L to 200 g / L, solution temperature: 45°C) under the conditions of solution resistance index, current density, and time shown in Table 1, followed by washing with water.

[0057] (3) Rust prevention treatment The electrolytic copper foil after roughening was subjected to the rust prevention treatment shown in Table 1. For this rust prevention treatment, in Examples 1 and 5-8, a pyrophosphate bath was used on the roughened surface of the electrolytic copper foil, with a potassium pyrophosphate concentration of 100 g / L, a zinc concentration of 1 g / L, a nickel concentration of 2 g / L, a molybdenum concentration of 1 g / L, a liquid temperature of 40°C, and a current density of 0.5 A / dm². 2 Anti-corrosion treatment A (zinc-nickel-molybdenum-based anti-corrosion treatment) was performed. Furthermore, a pyrophosphate bath was used on the unroughened surface of the electrolytic copper foil, 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 / dm². 2 For example, rust prevention treatment B (zinc-nickel rust prevention treatment) was performed. On the other hand, for Examples 2-4 and 9-11, rust prevention treatment B was performed on both sides of the electrolytic copper foil under the same conditions as the side of the electrolytic copper foil that had not undergone roughening treatment in Examples 1 and 5-8.

[0058] (4) Chromate treatment Chromate treatment was performed on both sides of the electrolytic copper foil that had undergone the above rust prevention treatment, forming a chromate layer on top of the rust prevention treatment layer. This chromate treatment was performed with a chromic acid concentration of 1 g / L, pH 11, liquid temperature of 25°C, and current density of 1 A / dm². 2 It was carried out under these conditions.

[0059] (5) Silane coupling agent treatment The copper foil subjected to the above chromate 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 performed by showering a solution of the silane coupling agent, with pure water as the solvent, onto the roughened surface for adsorption. As the silane coupling agent, 3-aminopropyltrimethoxysilane was used in Examples 1, 3, 4 and 6-8, and 3-glycidoxypropyltrimethoxysilane was used in Examples 2, 5 and 9-11. The concentration of the silane coupling agent was 3 g / L in all cases. After the adsorption of the silane coupling agent, the water was finally evaporated using an electric heater to obtain roughened copper foil of the predetermined thickness.

[0060] [Table 1]

[0061] evaluation The following evaluations were performed on the manufactured roughened copper foil.

[0062] <Surface properties parameters of roughened surfaces> Surface roughness analysis of the roughened surface of roughened copper foil was performed in accordance with JIS B0601-2013 using a laser microscope (Olympus Corporation, OLS-5000). For roughness parameters (Rdc, Rku, Rc, and Rq), the measurement magnification was 200x (objective lens magnification 100x × optical zoom 2x) as shown in Table 2, and for waviness parameters (Wdc, Wt, and Wp), the measurement magnification was 20x (objective lens magnification 20x) as shown in Table 3. Other specific measurement conditions are shown in Tables 2 and 3. The obtained surface profiles of the roughened surfaces were analyzed according to the conditions shown in Tables 2 and 3 to calculate Rdc, Rku, Rc, Rq, Wdc, Wt, and Wp. Furthermore, Rdc / Rku was calculated based on the obtained Rdc and Rku values. The results are shown in Table 4.

[0063] [Table 2]

[0064] [Table 3]

[0065] <Measurement of elemental adhesion in rust-preventive treatment layer> Area of ​​the roughened surface of the roughened copper foil: 25 cm² 2 A (5cm × 5cm) area was dissolved with acid, and the concentrations of Zn, Ni, and Mo in the resulting solution were analyzed by ICP emission spectrometry to measure the amounts of Zn, Ni, and Mo deposited. The results are shown in Table 4.

[0066] <Fabrication of copper-clad laminates> Two prepregs (100 μm thick) mainly composed of polyphenylene ether, triallyl isocyanurate, and bismaleimide resin were prepared as insulating substrates and stacked. On these stacked prepregs, the manufactured surface-treated copper foil was laminated so that its roughened surface was in contact with the prepreg, and a load of 32 kgf / cm² was applied. 2 A 34cm x 34cm copper-clad laminate was fabricated by pressing it at 205℃ for 120 minutes.

[0067] <Circuit linearity> The linearity of the circuits was evaluated as follows. First, for Examples 4-7, etching was performed on the copper foil side surface of the copper-clad laminate described above until the copper foil thickness reached 12 μm. For Examples 1-11, a dry film was attached to the copper foil side surface of the copper-clad laminate, exposed to light, and developed to form an etching resist. By treating with a copper chloride etching solution, copper was dissolved and removed from between the resists, forming three linear circuits (a total of six) with a circuit width of 300 μm, a circuit height of 12 μm, and a length of 10 cm or 15 cm. The resulting linear circuits were observed with an optical microscope, and the circuit width was measured at 30 random locations per circuit. The mean and standard deviation were calculated for each set of 30 circuit width data points, and the coefficient of variation (%) for each circuit was calculated by dividing the standard deviation by the mean. The average of the coefficients of variation for the six circuits was found and used as the circuit width variation coefficient for each example. The quality of the obtained circuit width variation coefficients was evaluated according to the following criteria. The results are shown in Table 4. <Evaluation Criteria for Circuit Width Variation Coefficient> - Good: Circuit width variation coefficient is 1.50% or less. - Defect: Circuit width variation coefficient exceeds 1.50%

[0068] <Peel strength between copper foil and substrate> To evaluate the adhesion between the roughened copper foil and the insulating substrate, the normal peel strength was measured as follows. First, for Examples 4 to 7, etching was performed on the copper foil side surface of the copper-clad laminate described above until the copper foil thickness was 12 μm. For Examples 1 to 11, circuits were formed on the copper-clad laminate by etching, and test substrates with 3 mm wide straight circuits were manufactured. The resulting straight circuits were peeled off from the insulating substrate in accordance with Method A (90° peel) of JIS C 5016-1994, and the normal peel strength (kgf / cm) was measured. The quality of the obtained normal peel strength was evaluated according to the following criteria. The results are shown in Table 4. <Criteria for evaluating peel strength under normal conditions> - Good: Normal peel strength is 0.30 kgf / cm or higher. - Defective: Peel strength under normal conditions is less than 0.30 kgf / cm

[0069] (c) Transmission characteristics A high-frequency substrate (Panasonic, MEGTRON6N) was prepared as the insulating resin substrate. 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 190°C and a pressing time of 120 minutes to obtain a copper-clad laminate with an insulation thickness of 136 μm. Subsequently, the copper-clad laminate was etched to form microstrip lines with a characteristic impedance of 50 Ω, obtaining a transmission loss measurement substrate. The transmission loss (dB / cm) at 28 GHz was measured on the obtained transmission loss measurement substrate using a network analyzer (Keysight Technologies, N5225B). The quality of the obtained transmission loss was evaluated according to the following criteria. The results are shown in Table 4. <Transmission Loss Evaluation Criteria> - Good: Transmission loss of -0.33 dB / cm or higher - Failure: Transmission loss less than -0.33 dB / cm

[0070] [Table 4]

Claims

1. A roughened copper foil having a roughened surface on at least one side, The roughened surface has a ratio of Rdc / Rku, which is the difference in cutting level Rdc of the roughness curve to the crustosis Rku of the roughness curve, of 0.180 μm or less, and a maximum cross-sectional height Wt of the waviness curve of 2.50 μm or more and 10.00 μm or less. The aforementioned Rku is a value measured in accordance with JIS B0601-2013 under the conditions of a magnification of 200x, a cutoff wavelength of 0.3 μm with a cutoff value λs, and a cutoff wavelength of 5 μm with a cutoff value λc. The aforementioned Rdc is a value obtained as the difference in the cutting level c in the height direction between a load length ratio (Rmr1) of 20% and a load length ratio (Rmr2) of 80% in a roughness curve measured under conditions of a magnification of 200x, a cutoff wavelength of 0.3 μm with a cutoff value λs, and a cutoff wavelength of 5 μm with a cutoff value λc, in accordance with JIS B0601-2013. The aforementioned Wt is a value measured in accordance with JIS B0601-2013 under conditions of 20x magnification, a cutoff wavelength of 5 μm using the cutoff value λc, and no cutoff using the cutoff value λf, and is a roughened copper foil.

2. The roughened surface has a maximum cross-sectional height Wt of 2.90 μm or more and 10.00 μm or less, as described in claim 1.

3. The roughened surface has a cutting level difference Rdc of 0.45 μm or less, as described in claim 1 or 2.

4. The roughened surface has a maximum peak height Wp of the waviness curve of 1.00 μm or more and 6.00 μm or less, and Wp is a value measured in accordance with JIS B0601-2013 under conditions of magnification of 20x, a cutoff wavelength of 5 μm with cutoff value λc, and no cutoff with cutoff value λf, as described in claim 1 or 2.

5. The roughened surface has an average height Rc of roughness curve elements of 0.70 μm or less, and Rc is a value measured in accordance with JIS B0601-2013 under the conditions of a magnification of 200x, a cutoff wavelength of 0.3 μm with a cutoff value λs, and a cutoff wavelength of 5 μm with a cutoff value λc, as described in claim 1 or 2.

6. The roughened surface has a cutting level difference Wdc of the waviness curve of 1.20 μm or more and 3.10 μm or less, and Wdc is a value obtained as the difference in the height cutting level c (c(Wmr1) - c(Wmr2)) between a load length ratio (Wmr1) of 20% and a load length ratio (Wmr2) of 80% in a waviness curve measured under conditions of JIS B0601-2013, with a magnification of 20x, a cutoff wavelength of 5 μm due to a cutoff value λc, and no cutoff due to a cutoff value λf, as described in claim 1 or 2.

7. The roughened surface has a root mean square height Rq of the roughness curve of 0.290 μm or less, and Rq is a value measured in accordance with JIS B0601-2013 under the conditions of a magnification of 200x, a cutoff wavelength of 0.3 μm with a cutoff value λs, and a cutoff wavelength of 5 μm with a cutoff value λc, as described in claim 1 or 2.

8. The roughened surface has a kurtosis Rku of 1.30 or more and 8.00 or less, according to claim 1 or 2.

9. The roughened copper foil according to claim 1 or 2, wherein the roughened surface is provided with a rust-preventive treatment layer and / or a silane coupling agent treatment layer.

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

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

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

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