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

Abstract

Provided is a roughened copper foil simultaneously achieving excellent transmission characteristics and high peel strength when used in a copper-clad laminated board or a printed wiring board. This roughened copper foil has a roughened surface on at least one side. The microparticle tip volume of the roughened surface is 1.300 μm3 / particle or less, as calculated by the formula (Vmp + Vmc) / Spd, where Vmp is the material volume of a protruding peak portion, Vmc is the material volume of a core portion, and Spd is the density of peaks, and the cut level difference Rdc is 0.95 μm or greater. Vmp, Vmc and Spd are values measured in compliance with ISO 25178, and Rdc is a value obtained as the difference in the cut level c in the height direction at load length ratios of 20% and 80% in compliance 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, attempts have been made to perform finer roughening treatments on the bonding surface of copper foil with insulating resin substrates. In other words, 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 undulations (for example, the surface of double-sided smooth foil or the electrode surface of electrolytic copper foil). 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 actual volume Vmp of the protruding peaks, the actual volume Vmc of the core, the volume of minute tip particles calculated based on the peak apex density Spd, and the cutting level difference Rdc on the surface of roughened copper foil to a predetermined range, it is possible to achieve both excellent transmission characteristics and high peel strength in copper-clad laminates or printed circuit boards manufactured using this method.

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

[0010] The present invention provides the following embodiments. [Aspect 1] A roughened copper foil having a roughened surface on at least one side, The roughened surface has a total volume Vmp (μm) of protruding peaks per unit area. 3 / μm 2 ), the actual volume Vmc(μm) of the core per unit area 3 / μm 2 ), and the density of mountain peaks per unit area Spd (peaks / μm 2 Based on this, the minute tip particle volume is calculated using the formula (Vmp + Vmc) / Spd, which is 1,300 μm. 3 The number is less than or equal to / , and the cleavage level difference Rdc is 0.95 μm or more. The aforementioned Vmp, Vmc, and Spd are values ​​measured in accordance with ISO 25178 under conditions of 200x magnification, a cutoff wavelength of 0.3 μm using an S filter, and a cutoff wavelength of 5 μm using an L filter. The aforementioned Rdc is a roughened copper foil, obtained as the difference in cutting levels c in the height direction at load length ratio (Rmr1) 20% and load length ratio (Rmr2) 80% in a roughness curve measured under conditions of JIS B0601-2013, with a magnification of 20x, no cutoff by cutoff value λs, and a cutoff wavelength of 320 μm using cutoff value λc. [Aspect 2] The roughened surface is a roughened copper foil according to Embodiment 1, wherein the cutting level difference Rdc is 1.10 μm or more and 20.00 μm or less. [Aspect 3] The roughened surface has a core volume Vmc per unit area of ​​0.360 μm². 3 / μm 2 The roughened copper foil according to embodiment 1 or 2, which is as follows: [Aspect 4] The roughened surface is such that Vmp + Vmc, which is the sum of the solid volume Vmp of the protruding mountain portion and the solid volume Vmc of the core portion, is 0.380 μm 3 / μm 2 The roughened copper foil according to any one of Aspects 1 to 3, wherein the above is satisfied. [Aspect 5] The roughened copper foil according to any one of Aspects 1 to 4, wherein the roughened surface has a developed area ratio Sdr of 70% or less, and the Sdr is a value measured under the conditions of a magnification of 200 times, a cut-off wavelength of 0.3 μm by an S filter, and a cut-off wavelength of 5 μm by an L filter in accordance with ISO25178. [Aspect 6] The roughened copper foil according to any one of Aspects 1 to 5, wherein the roughened surface has a level difference Sk of the core portion of 1.50 μm or more, and the Sk is a value measured under the conditions of a magnification of 20 times, no cut-off by an S filter, and a cut-off wavelength of 320 μm by an L filter in accordance with ISO25178. [Aspect 7] The roughened copper foil according to any one of Aspects 1 to 6, wherein the roughened surface has a peak height Sxp of 1.10 μm or more, and the Sxp is a value measured under the conditions of a magnification of 20 times, no cut-off by an S filter, and a cut-off wavelength of 320 μm by an L filter in accordance with ISO25178. [Aspect 8] The roughened surface has a peak density Spd per unit area of 0.12 pieces / μm 2 or more and 0.46 pieces / μm 2 or less. The roughened copper foil according to any one of Aspects 1 to 7. [Aspect 9] The roughened copper foil according to any one of Aspects 1 to 8, further comprising a rust prevention treatment layer and / or a silane coupling agent treatment layer on the roughened surface. [Aspect 10] The roughened copper foil according to any one of Aspects 1 to 9, wherein the roughened copper foil is an electrolytic copper foil and the roughened surface is present on the deposition surface side of the electrolytic copper foil. [Aspect 11] A copper-clad laminate comprising the roughened copper foil according to any one of Aspects 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 figure illustrates the surface load curve and load area ratio Smr(c) determined in accordance with ISO 25178. [Figure 5] This diagram illustrates the load area ratio Smr1 that separates the protruding peaks and the core, the load area ratio Smr2 that separates the protruding valleys and the core, and the level difference Sk of the core, all determined in accordance with ISO 25178. [Figure 6] This diagram illustrates the actual volume Vmp of the protruding peak and the actual volume Vmc of the core, as determined in accordance with ISO 25178. [Figure 7] This is a diagram illustrating the pole height Sxp, which is determined in accordance with ISO 25178. [Figure 8] This diagram illustrates that the surface irregularities of roughened copper foil consist of roughened particle components and undulation components. [Figure 9] This is a schematic cross-sectional view of roughened particles, intended to illustrate the volume of minute tip particles. [Figure 10] 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 definitions of the terms or parameters used to identify the present invention are shown below.

[0013] As used herein, the "load curve of the roughness curve" is a curve representing, as a function of c, the ratio of the solid part that appears when the roughness curve is cut at the cut-off level c, determined in accordance with JIS B0601 - 2013, as shown in FIG. 1. 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 a parameter representing, as shown in FIG. 2, the ratio of the load length of the roughness curve elements at the cut-off level c to the evaluation length, determined in accordance with JIS B0601 - 2013.

[0014] As used herein, the "cut-off level difference Rdc" or "Rdc" is a parameter representing, as shown in FIG. 3, the difference (c(Rmr1) - c(Rmr2)) in the cut-off level c in the height direction at 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% for calculating Rdc.

[0015] As used herein, the "load curve of the surface" refers to a curve representing the height at which the load area ratio ranges from 0% to 100%, determined in accordance with ISO25178. The load area ratio is a parameter representing, as shown in FIG. 4, the area of the region above a certain height c. The load area ratio at height c corresponds to Smr(c) in FIG. 4. As shown in FIG. 5, the secant line of the load curve obtained by subtracting the difference in the load area ratio by 40% along the load curve from 0% of the load area ratio is moved from 0% of the load area ratio, and the position where the slope of the secant line becomes the gentlest is called the central part of the load curve of the surface. For this central part, the straight line with the minimum sum of the squares of the deviations in the vertical axis direction is called the equivalent line. The part included in the range of the height from 0% to 100% of the load area ratio of the equivalent line is called the core part. The part higher than the core part is called the protruding peak part, and the part lower than the core part is called the protruding valley part.

[0016] In this specification, "Load area ratio Smr1 separating the protruding peak and the core" is a parameter that represents the load area ratio at the intersection of the height of the upper part of the core and the load curve of the surface, as determined in accordance with ISO 25178, as shown in Figure 5 (i.e., the load area ratio that separates the core and the protruding peak). In this specification, "Load area ratio Smr2 separating the protruding valley and the core" is a parameter that represents the load area ratio at the intersection of the height of the lower part of the core and the load curve, as determined in accordance with ISO 25178, as shown in Figure 5 (i.e., the load area ratio that separates the core and the protruding valley).

[0017] In this specification, "core level difference Sk" or "Sk" refers to the value obtained by subtracting the minimum height from the maximum height of the core, measured in accordance with ISO 25178, and is a parameter calculated from the difference in height between the load area ratios of 0% and 100% of the equivalent straight line, as shown in Figure 5.

[0018] In this specification, "actual volume Vmp of the protruding peak" or "Vmp" is a parameter representing the volume of the protruding peak, measured in accordance with ISO 25178, as shown in Figure 6. Similarly, in this specification, "actual volume Vmc of the core" or "Vmc" is a parameter representing the volume of the core, measured in accordance with ISO 25178, as shown in Figure 6. In this specification, Vmp and Vmc are calculated by specifying a load area ratio Smr1 separating the core and the protruding peak as 10%, and a load area ratio Smr2 separating the core and the protruding valley as 80%.

[0019] In this specification, "peak density Spd" or "Spd" is a parameter that represents the number of peaks per unit area, measured in accordance with ISO 25178. Spd can be calculated by dividing the number of peaks included in the contour surface by the projected area of ​​the contour surface. In this specification, Spd is calculated by counting only peaks that are greater than 5% of the maximum amplitude in the contour surface.

[0020] In this specification, "micro-tip particle volume" refers to the actual volume Vmp (μm) of the protruding peak per unit area.3 / μm 2 ), the actual volume Vmc(μm) of the core per unit area 3 / μm 2 ), and the density of mountain peaks per unit area Spd (peaks / μm 2 Based on this specification, the parameter is calculated by the formula (Vmp + Vmc) / Spd. In this specification, "Vmp + Vmc" refers to the actual volume Vmp (μm) of the protruding peak per unit area. 3 / μm 2 ) and the actual volume Vmc(μm) of the core per unit area 3 / μm 2 This refers to the parameter calculated by the sum of ).

[0021] In this specification, "pole height Sxp" or "Sxp" is a parameter that represents the difference between the heights of load area ratio p% and load area ratio q%, as measured in accordance with ISO 25178, as shown in Figure 7. Sxp represents the difference between the average surface and the surface height after removing particularly high peaks from the surface. In this specification, Sxp is calculated by specifying a load area ratio p of 2.5% and a load area ratio q of 50%.

[0022] In this specification, "interface development area ratio Sdr" or "Sdr" is a parameter measured in accordance with ISO 25178, which represents the percentage increase in the development area (surface area) of the defined region 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%. Conversely, a larger value indicates a surface shape with many irregularities.

[0023] Rdc can be calculated by measuring the surface profile of a predetermined measurement length on the roughened surface using a commercially available laser microscope. Vmp, Vmc, Spd, Sdr, Sk, and Sxp can each be calculated by measuring the surface profile of a predetermined measurement area on the roughened surface using a commercially available laser microscope. In this specification, Vmp, Vmc, Spd, and Sdr are to be measured under conditions of 200x magnification, a cutoff wavelength of 0.3 μm using an S filter, and a cutoff wavelength of 5 μm using an L filter. On the other hand, Rdc is to be measured under conditions of 20x magnification, no cutoff using the cutoff value λs, and a cutoff wavelength of 320 μm using the cutoff value λc, while Sk and Sxp are to be measured under conditions of 20x magnification, no cutoff using an S filter, and a cutoff wavelength of 320 μm using an L filter. When using both an objective lens and optical zoom in laser microscope measurements, the above magnification corresponds to the value obtained by multiplying the objective lens magnification by the optical zoom magnification. For example, if the objective lens magnification is 100x and the optical zoom magnification is 2x, the magnification will be 200x (=100 × 2). Other preferred measurement and analysis conditions for surface profiles using 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. This roughened surface has a total volume Vmp (μm) of protruding peaks per unit area. 3 / μm 2 ), the actual volume Vmc(μm) of the core per unit area 3 / μm 2), and the density of mountain peaks per unit area Spd (peaks / μm 2 Based on this, the minute tip particle volume is calculated using the formula (Vmp + Vmc) / Spd, which is 1,300 μm. 3 The number of particles is less than or equal to one particle. Furthermore, the roughened surface has a cutting level difference Rdc of 0.95 μm or more. By controlling the volume of minute tip particles and the cutting level difference Rdc within a predetermined range on the surface of the roughened copper foil in this way, it is possible to achieve both excellent transmission characteristics (high frequency characteristics) and high peel strength (e.g., normal peel strength and moisture-resistant peel strength) in copper-clad laminates or printed circuit boards manufactured using this foil.

[0027] Excellent transmission characteristics and high peel strength are inherently difficult to achieve simultaneously. This is because, in order to obtain excellent transmission characteristics, it is necessary to reduce the surface irregularities of the copper foil, while in order to obtain high peel strength, it is necessary to increase the surface irregularities of the copper foil; the two are in a trade-off relationship. As shown in Figure 8, the surface irregularities of roughened copper foil consist of "roughened particle components" and "undulation components" with a longer period than the roughened particle components. Generally, in order to obtain excellent transmission characteristics, 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 influence of roughening particles and undulations on the surface of copper foil on transmission characteristics 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 affected 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 effect on transmission characteristics, it is possible to achieve both excellent transmission characteristics and high adhesion reliability due to high peel strength. Specifically, the minute tip particle volume related to the volume of minute bumps (roughening particles) that affect transmission characteristics was set to 1,300 μm. 3 We found that excellent transmission characteristics can be achieved by keeping the number of particles below a certain limit. Furthermore, we discovered that by setting the cutting level difference Rdc to 0.95 μm or more under measurement conditions that reflect the height of a wide range of roughened surfaces, high peel strength between the copper foil and the substrate can be achieved by utilizing the undulation of the copper foil, even with small roughened particles that would otherwise be difficult to ensure peel strength.

[0029] The mechanism by which transmission characteristics can be improved by controlling the volume of minute tip particles is not entirely clear, but it is thought to be as follows. Here, Figure 9 shows a schematic cross-sectional view of a bump (roughened particle) in which the boundary between the core and the protruding valley is separated. As shown in Figure 9, the volume of the part of the bump that combines the core and the protruding peak (the part of the bump that excludes the lower part of the bump corresponding to the protruding valley from the entire bump) per unit area corresponds to Vmp + Vmc. The peak density Spd represents the number of bumps per unit area, so as shown in Figure 9, Vmp + Vmc divided by Spd (= (Vmp + Vmc) / Spd) corresponds to the volume of minute tip particles per bump. In this respect, if we consider two types of roughened surfaces with the same Spd (i.e., the same number of bumps per unit area) but different Vmp + Vmc, the roughened surface with smaller Vmp + Vmc will have smaller bumps, and therefore will have superior transmission characteristics. On the other hand, if we consider two types of roughened surfaces with the same Vmp+Vmc (i.e., the same volume of bumps per unit area) but different Spd values, the roughened surface with a larger Spd value will have superior transmission characteristics because the same volume is distributed among many bumps, meaning the size of each bump is smaller. Therefore, it is possible to improve transmission characteristics by controlling the volume of minute tip particles to a small value.

[0030] The roughened particle components and waviness components on the copper foil surface that affect transmission characteristics or peel strength can be distinguished by using different measurement magnifications in a laser microscope, as well as by using S-filters and L-filters, or cutoff values ​​λs and λc. 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 measuring under conditions of a cutoff wavelength of 0.3 μm with an S-filter and a cutoff wavelength of 5 μm with an L-filter, parameters of the roughened particle component with the influence of waviness components removed can be obtained. Therefore, the minute tip particle volume, Vmp, Vmc, Vmp+Vmc, Spd, and Sdr in this invention accurately reflect the parameters of roughened particles on the copper foil surface, and transmission characteristics can be accurately evaluated by using these indicators. In contrast, by measuring the roughened surface at a low magnification of 20x, the overall height (waviness) of the roughened surface that affects adhesion reliability can be evaluated over a wide range. Furthermore, by measuring the roughened surface under conditions of a cutoff wavelength of 320 μm using a cutoff value λc or L filter, without using a cutoff value λs or an S filter, it is possible to obtain parameters for the entire roughened surface that reflect the influence of both the roughened particle component and the waviness component. Therefore, Rdc, Sk, and Sxp in this invention are parameters that reflect not only the roughened particle component of the copper foil surface but also the waviness component, and by using these indices, the peel strength can be accurately evaluated.

[0031] The roughened surface of the roughened copper foil has a cutting level difference Rdc of 0.95 μm or more, preferably 1.10 μm to 20.00 μm, more preferably 1.15 μm to 12.00 μm, even more preferably 1.20 μm to 6.00 μm, and particularly preferably 1.25 μm to 4.00 μm. When Rdc is within the above range, the anchoring effect is effectively exerted while ensuring excellent transmission characteristics, thereby achieving high peel strength.

[0032] The roughened surface of the roughened copper foil has a fine tip particle volume of 1,300 μm.3 The particle size is less than or equal to one particle, preferably 0.300 μm. 3 / pcs or more 1.300μm 3 / piece or less, more preferably 0.400 μm 3 / pcs or more 1.300μm 3 / piece or less, more preferably 0.500 μm 3 / pcs or more 1.300μm 3 / or less, particularly preferably 0.500 μm 3 / pcs or more 1.200μm 3 The number is less than or equal to / . Within the above range, the volume of minute tip particles allows for high peel strength while achieving excellent transmission characteristics.

[0033] The roughened surface of the roughened copper foil has a core volume Vmc per unit area of ​​0.360 μm². 3 / μm 2 Preferably, it is less than or equal to 0.040 μm, and more preferably 0.040 μm 3 / μm 2 More than 0.320μm 3 / μm 2 More preferably 0.070 μm 3 / μm 2 More than 0.290μm 3 / μm 2 The following is particularly preferred: 0.100 μm 3 / μm 2 More than 0.260μm 3 / μm 2 Below, most preferably 0.130 μm 3 / μm 2 More than 0.230μm 3 / μm 2 The following applies: When Vmc is within the above range, it becomes easier to control the volume of minute tip particles within the aforementioned range, and even better transmission characteristics can be achieved while maintaining high peel strength.

[0034] The roughened surface of the roughened copper foil has a volume Vmp + Vmc, which is the sum of the actual volume Vmp of the protruding peaks and the actual volume Vmc of the core, of 0.380 μm. 3 / μm 2 Preferably, it is less than or equal to 0.050 μm, and more preferably 0.050 μm 3 / μm 2 More than 0.340μm 3 / μm 2 More preferably 0.090 μm 3 / μm 2 More than 0.310μm 3 / μm 2 The following is particularly preferred: 0.130 μm 3 / μm 2 More than 0.280μm 3 / μm 2 Below, most preferably 0.140 μm 3 / μm 2 More than 0.250μm 3 / μm 2 The following applies: When Vmp+Vmc is within the above range, it becomes easier to control the volume of minute tip particles within the aforementioned range, enabling the realization of even better transmission characteristics while maintaining high peel strength.

[0035] The roughened surface of the roughened copper foil has a peak density (Spd) of 0.12 peaks / μm per unit area. 2 More than 0.46 pieces / μm 2 Preferably, the following, and more preferably, 0.13 particles / μm 2 More than 0.44 pieces / μm 2 More preferably, 0.14 particles / μm 2 More than 0.37 pieces / μm 2 The following is particularly preferred: 0.15 particles / μm 2 More than 0.31 pieces / μm 2 Below, most preferably 0.16 particles / μm 2 More than 0.28 pieces / μm 2 The following applies: When the Spd is within the above range, it becomes easier to control the volume of the minute tip particles within the range described above, and even better transmission characteristics can be achieved while maintaining high peel strength.

[0036] The roughened surface of the roughened copper foil preferably has an interface development area ratio (Sdr) of 70% or less, more preferably 5% to 65%, even more preferably 10% to 60%, particularly preferably 15% to 55%, and most preferably 20% to 50%. An Sdr within the above range results in a surface rich in irregularities, which is advantageous for achieving even better transmission characteristics while ensuring high peel strength.

[0037] The roughened surface of the roughened copper foil preferably has a core level difference Sk of 1.50 μm or more, more preferably 1.58 μm to 20.00 μm, even more preferably 1.65 μm to 12.00 μm, particularly preferably 1.70 μm to 8.00 μm, and most preferably 2.00 μm to 6.00 μm. With a Sk within the above range, excellent transmission characteristics can be achieved while the anchoring effect is effectively exerted, resulting in even higher peel strength.

[0038] The roughened surface of the roughened copper foil preferably has a pole height Sxp of 1.10 μm or more, more preferably 1.20 μm to 20.00 μm, even more preferably 1.30 μm to 12.00 μm, particularly preferably 1.40 μm to 8.00 μm, and most preferably 1.70 μm to 6.00 μm. When the pole height Sxp is within the above range, excellent transmission characteristics can be achieved while the anchoring effect is effectively exerted, resulting in even higher peel strength.

[0039] The thickness of the roughened copper foil is not particularly limited, but is preferably 0.1 μm to 210 μm, and more preferably 0.3 μm to 105 μm. The roughened copper foil of the present invention is not limited to ordinary copper foil whose surface has been roughened, but may also be a copper foil with a carrier whose surface has been roughened or finely roughened.

[0040] An example of the roughened copper foil of the present invention is shown in Figure 10. As shown in Figure 10, 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.

[0041] 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 1.50 μm to 20.00 μm, measured in accordance with JIS B0601-1994, and more preferably 2.00 μm to 10.00 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.

[0042] 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.

[0043] 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 defined by L 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 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 L can be calculated by summing the products of the concentration and valence of each ion for all the ions present in the plating solution. For example, when a copper sulfate solution is used as the plating solution, the charge carrier density D C is given by the following formula: C Dc = [H × 1 + [Cu + × 2 + [SO4 2+ × 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) is calculated by

[0044] 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 distance between the electrodes, 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 distance between the electrodes L, and the current density (= I / S). And the specific resistance ρ is the charge carrier density D described above​C 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.

[0045] Optionally, the roughened copper foil 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 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 further includes a chromate treatment, and this chromate treatment is more preferably performed on the surface of the zinc-containing plating after the zinc plating treatment. This further improves corrosion resistance. A particularly preferred corrosion prevention treatment is a combination of zinc-nickel alloy plating followed by chromate treatment.

[0046] 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.

[0047] For the reasons stated above, it is preferable that the roughened copper foil further comprises 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. 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.

[0048] 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.

[0049] 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]

[0050] The present invention will be further described in detail by the following examples.

[0051] Examples 1-15 The roughened copper foil of the present invention was manufactured as follows.

[0052] (1) Manufacturing of electrolytic copper foil For Examples 1-9 and 11-15, 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 DSA (dimensionally stable anode) 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 A with the thickness shown in Table 1. At this time, an electrode whose surface roughness was adjusted by polishing the surface with a #1000 buff was used as the cathode. <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

[0053] On the other hand, for Example 10, a sulfuric acid-acidified copper sulfate solution with the composition shown below was used as the copper electrolyte to obtain electrolytic copper foil B with the thickness shown in Table 1. At this time, all conditions other than the composition of the sulfuric acid-acidified copper sulfate solution were the same as those for electrolytic copper foil A. <Composition of sulfuric acid-acidified copper sulfate solution> - Copper concentration: 80g / L - Sulfuric acid concentration: 260g / L - Bis(3-sulfopropyl) disulfide concentration: 30 mg / L - Diallyldimethylammonium chloride polymer concentration: 50 mg / L - Chlorine concentration: 40 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, 10, and 12-15, and on the electrode surface side for Examples 7-9 and 11. 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, 10, and 12-15, and the electrode surface of the electrolytic copper foil used in Examples 7-9 and 11, 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 9-15, the first, second, and third roughening treatments shown below were performed in that 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 Examples 1-5, 7, and 8, the roughened surface of the electrolytic copper foil was treated using a pyrophosphate bath with a potassium pyrophosphate concentration of 100 g / L, zinc concentration of 1 g / L, nickel concentration of 2 g / L, molybdenum concentration of 1 g / L, liquid temperature of 40°C, and current density of 0.5 A / dm². 2 A zinc-nickel-molybdenum-based rust prevention 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. 2For the first example, a zinc-nickel rust-preventive treatment was performed. On the other hand, for Examples 6 and 9-15, a zinc-nickel rust-preventive treatment was performed on both sides of the electrolytic copper foil under the same conditions as the unroughened side of the electrolytic copper foil in Examples 1-5, 7, and 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 and 3-8, and 3-glycidoxypropyltrimethoxysilane was used in Examples 2 and 9-15. 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] (a) Surface properties parameters of the roughened surface Surface roughness analysis of the roughened surface of roughened copper foil was performed using a laser microscope (Olympus Corporation, OLS-5000) in accordance with ISO 25178 or JIS B0601-2013. For Spd, Vmp, Vmc, and Sdr, the measurement magnification was 200x (objective lens magnification 100x × optical zoom 2x) as shown in Table 2, while for Rdc, Sk, and Sxp, 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 Spd, Vmp, Vmc, Sdr, Rdc, Sk, and Sxp. Furthermore, based on the obtained values ​​of Spd, Vmp, and Vmc, Vmp + Vmc and the volume of the micro-tip particle (= (Vmp + Vmc) / Spd) were calculated. The results are shown in Table 4.

[0063] [Table 2]

[0064] [Table 3]

[0065] (b) Peel strength between copper foil and substrate To evaluate the adhesion of roughened copper foil to insulating substrates under normal temperature and high humidity conditions, the normal peel strength and moisture-resistant peel strength were measured as follows.

[0066] (b-1) Peeling strength under normal conditions 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. 2Copper-clad laminates were manufactured by pressing at 205°C for 120 minutes. Next, circuits were formed on these copper-clad laminates by etching to produce test substrates with 3 mm wide linear circuits. For Examples 1, 2, and 12, copper plating was performed on the copper foil side surface of the copper-clad laminate until the copper foil thickness reached 18 μm before circuit formation. For Examples 4-6, 14, and 15, etching was performed on the copper foil side surface of the copper-clad laminate until the copper foil thickness reached 18 μm before circuit formation. The resulting linear circuits were peeled off 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 0.40 kgf / cm or higher. - Defective: Peel strength under normal conditions is less than 0.40 kgf / cm

[0067] (b-2) Moisture peel strength Prior to measuring the peel strength, the moisture-resistant peel strength (kgf / cm) was measured using the same procedure as described above for measuring the peel strength under normal conditions, except that the test substrate equipped with a linear circuit was immersed in boiling water for 2 hours. The quality of the obtained moisture-resistant peel strength was evaluated according to the following criteria. The results are shown in Table 4. <Moisture Peeling Strength Evaluation Criteria> - Good: Moisture peel strength of 0.40 kgf / cm or higher - Defect: Moisture peel strength is less than 0.40 kgf / cm

[0068] (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

[0069] [Table 4]

Claims

1. A roughened copper foil having a roughened surface on at least one side, The roughened surface has a total volume Vmp (μm) of protruding peaks per unit area. ３ / μm ２ ), the actual volume Vmc (μm) of the core per unit area ３ / μm ２ ), and the density of mountain peaks per unit area Spd (peaks / μm ２ Based on this, the minute tip particle volume is calculated using the formula (Vmp + Vmc) / Spd, which is 1,300 μm. ３ The number of particles is less than or equal to the number of particles, and the cutting level difference Rdc is 0.95 μm or more. The aforementioned Vmp, Vmc, and Spd are values ​​measured in accordance with ISO 25178 under conditions of 200x magnification, a cutoff wavelength of 0.3 μm using an S filter, and a cutoff wavelength of 5 μm using an L filter. The aforementioned Rdc is a value obtained as the difference in the cutting level c in the height direction (c(Rmr1) - c(Rmr2)) in the roughness curve measured under the conditions of a magnification of 20x, no cutoff by the cutoff value λs, and a cutoff wavelength of 320 μm by the cutoff value λc, in accordance with JIS B0601-2013, at a load length ratio (Rmr1) of 20% and a load length ratio (Rmr2) of 80%, wherein the roughened copper foil is a value obtained as such.

2. The roughened surface has a cutting level difference Rdc of 1.10 μm or more and 20.00 μm or less, as described in claim 1.

3. The roughened surface has a core volume Vmc per unit area of ​​0.360 μm ３ / μm ２ The roughened copper foil according to claim 1 or 2, which is as follows:

4. The roughened surface is such that Vmp + Vmc, which is the sum of the solid volume Vmp of the protruding ridge portion and the solid volume Vmc of the core portion, is 0.380 μm ３ / μm ２ The roughened copper foil according to claim 1 or 2, wherein the above is true.

5. The roughened surface has an interface development area ratio Sdr of 70% or less, and the Sdr is a value measured in accordance with ISO 25178 under conditions of a magnification of 200x, a cutoff wavelength of 0.3 μm with an S filter and a cutoff wavelength of 5 μm with an L filter, as described in claim 1 or 2.

6. The roughened surface has a core level difference Sk of 1.50 μm or more, and the Sk is a value measured in accordance with ISO 25178 under conditions of 20x magnification, no cutoff by an S filter, and a cutoff wavelength of 320 μm by an L filter.

7. The roughened surface has a pole height SXp of 1.10 μm or more, and SXp is a value measured in accordance with ISO 25178 under conditions of 20x magnification, no cutoff by an S filter, and a cutoff wavelength of 320 μm by an L filter.

8. The roughened surface has a peak density Spd of 0.12 peaks / μm per unit area. ２ 0.46 pieces / μm or more ２ The roughened copper foil according to claim 1 or 2, which is as follows:

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

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