Surface-treated copper foil, copper-clad laminates, and printed circuit boards

Abstract

The present invention provides a surface-treated copper foil capable of improving adhesion to resin substrates, particularly resin substrates suitable for high-frequency applications. [Solution] A surface-treated copper foil having a copper foil and a surface treatment layer formed on at least one surface of the copper foil. The surface treatment layer has a change rate of Vmc represented by the following formula (1) of 23.00 to 40.00%. The rate of change of Vmc = (P2 - P1) / P2 × 100 ... (1) In the formula, P1 is Vmc calculated by applying a λs filter with a cutoff value λs of 2 μm, and P2 is Vmc calculated without applying the λs filter.

Description

[Technical Field]

[0001] This disclosure relates to surface-treated copper foil, copper-clad laminates, and printed circuit boards. [Background technology]

[0002] Copper-clad laminates are widely used in various applications, including flexible printed circuit boards. These flexible printed circuit boards are manufactured by etching the copper foil of the copper-clad laminate to form a conductor pattern (also called a "wiring pattern"), and then soldering electronic components onto the conductor pattern.

[0003] In recent years, with the increasing speed and capacity of communications in electronic devices such as personal computers and mobile terminals, electrical signals have become more high-frequency, creating a demand for flexible printed circuit boards that can handle this. In particular, as the frequency of electrical signals increases, the signal power loss (attenuation) becomes greater, making it easier for data to become unreadable, so there is a need to reduce signal power loss.

[0004] The causes of signal power loss (transmission loss) in electronic circuits can be broadly divided into two categories. The first is conductor loss, that is, loss due to copper foil, and the second is dielectric loss, that is, loss due to the resin substrate. Conductor loss occurs in the high-frequency range due to the skin effect, where current flows along the surface of the conductor. Therefore, if the copper foil surface is rough, the current will flow along a complex path. Consequently, to reduce conductor loss in high-frequency signals, it is desirable to reduce the surface roughness of the copper foil. Hereafter, in this specification, when "transmission loss" and "conductor loss" are simply referred to, they mainly mean "transmission loss of high-frequency signals" and "conductor loss of high-frequency signals."

[0005] On the other hand, dielectric loss depends on the type of resin substrate; therefore, in circuit boards where high-frequency signals flow, it is desirable to use a resin substrate made from a low-dielectric material (e.g., liquid crystal polymer, low-dielectric polyimide). Furthermore, dielectric loss is also affected by the adhesive used to bond the copper foil and the resin substrate; therefore, it is desirable to bond the copper foil and the resin substrate without using an adhesive. Therefore, in order to bond the copper foil and the resin substrate without using an adhesive, it has been proposed to form a surface treatment layer on at least one surface of the copper foil. For example, Patent Document 1 proposes a method in which a roughening treatment layer formed from roughening particles is provided on the copper foil, and a silane coupling treatment layer is formed on the outermost layer. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2012-112009 [Overview of the project] [Problems that the invention aims to solve]

[0007] The surface of copper foil on which a surface treatment layer is formed generally has minute irregularities. For example, in the case of rolled copper foil, oil pits formed by the rolling oil during rolling are formed on the surface as minute irregularities. In the case of electrolytic copper foil, polishing marks from the rotating drum formed during polishing cause minute irregularities on the rotating drum side surface of the electrolytic copper foil deposited on the rotating drum. If minute irregularities exist on the copper foil surface, for example, when forming a roughening treatment layer, current concentrates in the convex areas of the copper foil surface, causing excessive growth of roughening particles, while insufficient current is supplied to the recesses and surrounding areas of the copper foil surface, making it difficult for roughening particles to grow. As a result, large roughening particles are formed in the convex areas of the copper foil surface, while the roughening particles are too small in the recesses and surrounding areas of the copper foil surface. In particular, the adhesion of roughening particles is insufficient near the edges of oil pits, meaning that the roughening particles on the copper foil surface are not uniformly formed. In surface-treated copper foil with a large amount of large roughening particles, if a force is applied to peel the surface-treated copper foil after bonding with a resin substrate, stress concentrates in the large roughening particles, making them prone to breakage, which can reduce the adhesive strength to the resin substrate. Furthermore, in surface-treated copper foil with insufficient roughening particle size, the anchoring effect of the roughening particles is reduced, and sufficient adhesion between the copper foil and the resin substrate may not be achieved. In particular, resin substrates formed from low-dielectric materials such as liquid crystal polymers and low-dielectric polyimides are less likely to adhere to copper foil than conventional resin substrates, so there is a need to develop methods to improve the adhesion between copper foil and resin substrates. Furthermore, while silane coupling treatment layers have the effect of improving adhesion between copper foil and resin substrate, depending on the type, the effect of improving adhesion may not be sufficient.

[0008] Embodiments of the present invention have been made to solve the above-mentioned problems, and in one aspect, aim to provide a surface-treated copper foil that can improve adhesion to resin substrates, particularly resin substrates suitable for high-frequency applications. Furthermore, another aspect of the embodiments of the present invention aims to provide a copper-clad laminate with excellent adhesion between a resin substrate, particularly suitable for high-frequency applications, and a surface-treated copper foil. Furthermore, embodiments of the present invention also aim to provide a printed circuit board with excellent adhesion between a resin substrate, particularly suitable for high-frequency applications, and a circuit pattern. [Means for solving the problem]

[0009] As a result of intensive research on the surface-treated copper foil to solve the above problems, the inventors have found that by adding a trace amount of tungsten compound to the plating solution used for forming the roughened layer, overgrowth of the roughened particles formed on the convex portions of the copper foil surface can be suppressed, and roughened particles can be easily formed around the concave portions of the copper foil surface. And when the inventors analyzed the surface shape of the surface-treated copper foil thus obtained, they found that the change rate of Vmc of the surface treatment layer is closely related to this surface shape, and thus completed the embodiments of the present invention.

[0010] That is, in one aspect, an embodiment of the present invention relates to a surface-treated copper foil having a copper foil and a surface treatment layer formed on at least one surface of the copper foil, wherein the surface treatment layer has a change rate of Vmc represented by the following formula (1) of 23.00 to 40.00%. Change rate of Vmc = (P2 - P1) / P2 × 100 ···(1) In the formula, P1 is Vmc calculated by applying a λs filter with a cut-off value λs of 2 μm, and P2 is Vmc calculated without applying the λs filter.

[0011] In another aspect, an embodiment of the present invention relates to a copper-clad laminate including the surface-treated copper foil and a resin base material adhered to the surface treatment layer of the surface-treated copper foil. Furthermore, in another aspect, an embodiment of the present invention relates to a printed wiring board including a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate.

Advantages of the Invention

[0012] According to an embodiment of the present invention, in one aspect, it is possible to provide a surface-treated copper foil capable of enhancing the adhesiveness with a resin base material, particularly a resin base material suitable for high-frequency applications. Also, according to an embodiment of the present invention, in another aspect, it is possible to provide a copper-clad laminate having excellent adhesiveness between a resin base material, particularly a resin base material suitable for high-frequency applications, and a surface-treated copper foil. Furthermore, according to embodiments of the present invention, in another aspect, it is possible to provide a printed wiring board with excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and a circuit pattern. [Brief explanation of the drawing]

[0013] [Figure 1] This is a typical load curve for a surface-treated layer. [Figure 2] This is a schematic diagram illustrating the roughened particles and Vmc that constitute the surface treatment layer. [Figure 3] This is a schematic enlarged cross-sectional view of a surface-treated copper foil having a roughened layer on one side. [Modes for carrying out the invention]

[0014] Preferred embodiments of the present invention will be described below, but the present invention should not be construed as being limited thereto, and various modifications and improvements can be made based on the knowledge of those skilled in the art, without departing from the spirit of the invention. The multiple components disclosed in the following embodiments can be combined in appropriate ways to form various inventions. For example, some components may be removed from all the components shown in the following embodiments, or components from different embodiments may be combined in appropriate ways.

[0015] The surface-treated copper foil according to an embodiment of the present invention comprises a copper foil and a surface treatment layer formed on at least one surface of the copper foil. The surface treatment layer may be formed on only one side of the copper foil, or on both sides of the copper foil. If the surface treatment layer is formed on both sides of the copper foil, the types of surface treatment layers may be the same or different.

[0016] The surface shape of the surface-treated layer can be determined in accordance with ISO 25178-2:2012 by measuring the surface properties and using surface property parameters obtained by analyzing the load curve calculated from the measurement data. To explain the load curve, I will first explain the load area ratio. The load area ratio is the ratio obtained by dividing the area corresponding to the cross-section of a three-dimensional object to be measured, when cut at a certain height, by the area of ​​the measurement field of view. In this disclosure, the objects to be measured are assumed to be copper foil and the surface treatment layer of surface-treated copper foil. The load curve is a curve that represents the load area ratio at each height. The area around 0% load area ratio represents the height of the highest part of the object to be measured, and the area around 100% load area ratio represents the height of the lowest part of the object to be measured.

[0017] Next, Figure 1 shows a typical load curve for a surface-treated layer. The load curve can be used to express the physical volume and spatial volume of the surface-treated layer. The physical volume corresponds to the volume of the physical object occupied within the measurement field of view, and the spatial volume corresponds to the volume occupied by the space between the physical parts within the measurement field of view. In the load curve described in this disclosure, the load area ratio is divided into valleys, cores, and peaks, with boundaries at 10% and 80%. Referring to Figure 1, and corresponding to the surface-treated layer according to the embodiment of the present invention, Vvv represents the spatial volume in the valleys of the surface-treated layer, Vvc represents the spatial volume in the core of the surface-treated layer, Vmp represents the physical volume in the peaks of the surface-treated layer, and Vmc represents the physical volume in the core of the surface-treated layer. The peaks are the tallest parts of the object being measured. The valleys are the shortest parts of the object being measured. The core is the part of the object being measured that is not the peaks or valleys, i.e., the part with a height close to the average.

[0018] The physical volume Vmp in the peak portion is the volume of the physical material in the peak portion, i.e., the taller part of the object being measured, and represents the volume of the physical material in the particularly tall portion of the surface treatment layer. Here, the physical material in the particularly tall portion of the surface treatment layer can be interpreted as the portion caused by overgrown particles (especially roughened particles) within the particle structure. The physical volume Vmc in the core is the volume of the physical material in the core, i.e., the portion of the object being measured that is close to the average height, and represents the volume of the physical material in the portion of the surface treatment layer that is at an average height. Here, the physical material in the portion of the surface treatment layer that is at an average height can be interpreted as the portion formed on the relatively smooth part of the copper foil surface, due to particles of average size (especially roughened particles). In summary, the inventors, as a result of the analysis described above, found that in the surface-treated copper foil according to the embodiment of the present invention, Vmp correlates with the actual volume of overgrown, large particles, and Vmc correlates with the actual volume of particles of average size. It should be noted that, although the following explanation may use the case of roughened particles as an example, the particles are not limited to roughened particles.

[0019] Measurement data for measuring the surface properties of surface-treated copper foil according to the embodiment of the present invention can be acquired using a laser microscope, such as a confocal laser microscope. Here, by applying a Fourier transform to the measurement data, the measurement data can be separated into waveforms having various periods and amplitudes. The inventors believe that by applying a filter that attenuates the amplitude of waveforms within a specific frequency range to each separated waveform, and then analyzing the data obtained by synthesizing all the waveforms again, it is possible to calculate the surface property parameters of interest from the measurement data.

[0020] In analyzing surface roughness measurement data, the inventors found that by combining surface property parameters calculated by applying a λs filter with a cutoff value of λs of 2 μm and surface property parameters calculated without applying this λs filter, detailed information on the characteristic surface shape of the surface-treated layer according to the embodiment of the present invention (particularly the adhesion state of the roughened particles constituting the surface-treated layer) can be obtained. Here, the λs filter is a contour filter that significantly attenuates the amplitude of waveforms with wavelengths smaller than the cutoff value λs. The λs filter corresponds to the S filter in ISO 25178-2:2012. The magnitude of amplitude attenuation by the λs filter varies depending on the wavelength of the waveform. At wavelengths of the cutoff value λs, the amplitude is attenuated to 50% of the original value, and for waveforms with smaller wavelengths, the amplitude is attenuated more significantly. The cutoff value λs of 2 μm is a size that lies between the size of the roughening particles constituting the surface treatment layer and the size of the oil pits. The measurement data obtained by setting the cutoff value λs to 2 μm is derived from waveforms with a shorter period than the cutoff value λs, and can therefore be understood as having the data originating from the roughening particles removed. Based on this, the difference between the surface property parameters calculated without applying the λs filter with a cutoff value of λs of 2 μm and the surface property parameters calculated with this λs filter applied can be said to be information about the surface treatment layer from which the information of the oil pits has been removed, that is, information about the roughening particles constituting the surface treatment layer.

[0021] Based on the above findings, the inventors analyzed various surface property parameters obtained from the load curve and found that the rate of change of Vmc, expressed by the following equation (1) in the surface treatment layer, is closely related to the amount of roughened particles of average size adhering to the surface treatment layer. The rate of change of Vmc = (P2 - P1) / P2 × 100 ... (1) In the formula, P1 is Vmc calculated by applying a λs filter with a cutoff value λs of 2 μm, and P2 is Vmc calculated without applying the λs filter.

[0022] Here, a schematic diagram illustrating the roughened particles and Vmc constituting the surface treatment layer is shown in Figure 2. As shown in Figure 2, the surface treatment layer contains roughened particles A of average size and overgrown roughened particles B. As already explained above, Vmc corresponds to the volume of roughened particles A of average size formed on the relatively smooth portion of the copper foil surface, and is thought to correlate with the amount of roughened particles A of average size that adhere to the surface. Vmc is significantly influenced by macroscopic shapes such as oil pits, and in order to more accurately interpret the information of the surface treatment layer, it is necessary to remove the contribution of macroscopic shapes. P1 can be interpreted as the value of Vmc with information derived from roughened particles removed, or in other words, the value of Vmc with information derived from oil pits and the like remaining. Taking the difference between P2 and P1 means removing information derived from macroscopic shapes such as oil pits contained in Vmc. As a result, information correlated with the amount of roughened particles A of average size that adhere to the surface can be extracted with high accuracy. The average-sized roughened particles A formed on the relatively smooth parts of the copper foil surface are thought to be highly related to the adhesion between the resin substrate and the surface treatment layer. Overgrown (coarse) roughened particles B lead to roughening and folding, while undergrown roughened particles are thought not to penetrate the resin substrate at all. Therefore, by controlling the rate of change of the surface treatment layer Vmc, which correlates with the amount of average roughened particles A attached, to an appropriate range in the surface-treated copper foil, it is possible to improve the adhesion to the resin substrate. From this viewpoint, the surface-treated copper foil according to the embodiment of the present invention, in which the rate of change of Vmc is 23.00 to 40.00%, exhibits sufficient adhesion to the resin substrate. From the viewpoint of stably obtaining this effect, the rate of change of Vmc is preferably 23.00 to 32.00%, and more preferably 23.00 to 31.00%.

[0023] The surface treatment layer preferably has a Sku (kurtosis) of 2.50 to 4.50, calculated without applying the above-mentioned λs filter. Sku is a parameter that expresses the kurtosis (peakiness) of a histogram created using the average height as a reference. For example, if Sku = 3.00, it means that the height distribution follows a normal distribution. If Sku > 3.00, a larger value means that the height distribution is more concentrated. Conversely, if Sku < 3.00, a smaller value means that the height distribution is more dispersed.

[0024] The surface-treated copper foil according to the embodiment of the present invention has irregularities on its surface, which contribute to improving the adhesion between the copper foil and the resin substrate. The Sku of the surface-treated layer serves as an index for evaluating the height distribution of these irregularities. A surface treatment layer Sku of 2.50 to 4.50 means that the height distribution is normal or close to a normal distribution. On the other hand, a surface treatment layer Sku of less than 2.50 means that the height distribution is not biased, as there is a mix of low and high parts in the surface treatment layer (height from the copper foil surface). A surface treatment layer Sku greater than 4.50 means that the height distribution is biased, that is, the surface of the surface treatment layer has a certain height that protrudes and occupies a large portion. A normal or near-normal height distribution of the surface treatment layer means, for example, that when forming a roughening treatment layer on the surface of copper foil, there are few areas where roughening particles have overgrown on the convex parts of the copper foil surface, i.e., few areas where roughening particles have not formed around the concave parts of the copper foil surface (the edges of the convex parts). Therefore, a surface treatment layer Sku of 2.50 to 4.50 means that the overgrowth of roughening particles formed on the convex parts of the copper foil surface is suppressed, and roughening particles are also formed around the concave parts of the copper foil surface.

[0025] Both surface-treated copper foil with a high concentration of roughened particles and surface-treated copper foil with areas where roughened particles are not present are undesirable from the standpoint of adhesion to the resin substrate. For example, in the case of surface-treated copper foil with a high concentration of roughened particles, if a force is applied to peel the surface-treated copper foil after bonding with the resin substrate, stress will concentrate on the coarse roughened particles, making them prone to breakage, which is thought to actually reduce the adhesive strength to the resin substrate. Also, in the case of surface-treated copper foil with areas where roughened particles are not present, the anchoring effect by the roughened particles cannot be sufficiently secured, which is thought to reduce the adhesive strength between the surface-treated copper foil and the resin substrate. Therefore, from the viewpoint of obtaining stable adhesion to the resin substrate, the Sku of the surface treatment layer is preferably lower limit 2.90 and preferably upper limit 4.10. The Sku of the surface treatment layer can be identified by measuring the surface roughness in accordance with ISO 25178-2:2012 and analyzing the contour curve calculated from the measurement data.

[0026] The surface treatment layer preferably has a Sq (root mean square height) of 0.20 to 0.60 μm, calculated without applying the λs filter described above. Sq is a height parameter defined in ISO 25178-2:2012 and represents the variation in the height of the protrusions on the surface of the surface treatment layer. A large Sq of the surface treatment layer means that there is a large variation in the height of the protrusions on the surface of the surface treatment layer. If the Sq is too large (the variation in the height of the protrusions is too large), it may become a problem from the standpoint of quality control for industrial products. Therefore, by setting the Sq of the surface treatment layer within the above range, it is possible to ensure productivity while tolerating some variation in the height of the protrusions and performing appropriate quality control. From the viewpoint of stably obtaining such effects, the lower limit of the Sq of the surface treatment layer is preferably 0.26 μm, more preferably 0.30 μm, and even more preferably 0.34 μm, and the upper limit is preferably 0.53 μm, more preferably 0.48 μm, and even more preferably 0.43 μm. The square root of the surface treatment layer can be determined by measuring the surface roughness in accordance with ISO 25178-2:2012 and analyzing the contour curve calculated from the measurement data.

[0027] The surface treatment layer preferably has an arithmetic mean height (Sa) of 0.20 to 0.40 μm, calculated without applying the λs filter described above. Sa is a height parameter defined in ISO 25178-2:2012, and represents the average of the height differences from the mean plane. If the Sa of the surface treatment layer is large, the surface of the surface treatment layer becomes rougher, which makes it easier for the anchoring effect to be exerted when the surface-treated copper foil is bonded to the resin substrate. On the other hand, if the Sa of the surface treatment layer is too large, when a circuit board is manufactured by processing a copper-clad laminate in which the surface-treated copper foil and the resin substrate are bonded, the transmission loss increases due to the skin effect of the surface-treated copper foil. Therefore, by setting the Sa of the surface treatment layer within the above range, it is possible to ensure a balance between securing the adhesion strength of the surface-treated copper foil to the resin substrate and suppressing transmission loss. From the viewpoint of stably obtaining such effects, the lower limit of the Sa of the surface treatment layer is preferably 0.23 μm, more preferably 0.24 μm, and the upper limit is preferably 0.35 μm. Furthermore, when prioritizing the suppression of transmission loss due to the skin effect and the ease of quality control as an industrial product, it is preferable that the surface treatment layer has a Sa of 0.20 to 0.32 μm and a Sq of 0.26 to 0.40 μm. Furthermore, the Sa of the surface treatment layer can be determined by measuring the surface roughness in accordance with ISO 25178-2:2012 and analyzing the contour curve calculated from the measurement data.

[0028] The surface treatment layer preferably has an Ssk (skewness) of -1.10 to 0.60, calculated without applying the above-mentioned λs filter. Ssk is a parameter that expresses the degree of bias (skewness) of a histogram created using the average height as a reference. For example, if Ssk = 0.00, it means that the height distribution is symmetrical with respect to the average line. If Ssk > 0.00, the larger the value, the more the height distribution is skewed downwards with respect to the average line. Conversely, if Ssk < 0.00, the smaller the value, the more the height distribution is skewed upwards with respect to the average line. Therefore, Ssk of a surface treatment layer, like Sku, is an indicator for evaluating the height distribution of the surface treatment layer's irregularities. A Ssk value of -1.10 to 0.60 means, for example, that when forming a roughening treatment layer on the surface of copper foil, there are few overgrown roughening particles (i.e., coarse roughening particles) in the convex parts of the copper foil surface, and few areas around the concave parts (edges of the convex parts) where roughening particles are not formed. On the other hand, if the Ssk value is less than -1.10, there are many areas around the concave parts of the copper foil surface where roughening particles are not formed. Also, if the Ssk value is greater than 0.60, there are many overgrown roughening particles in the convex parts of the copper foil surface. From the viewpoint of obtaining stable adhesion to the resin substrate, the Ssk of the surface treatment layer preferably has an upper limit of 0.40 and a lower limit of -0.80. Furthermore, the Ssk of the surface treatment layer can be determined by measuring the surface roughness in accordance with ISO 25178-2:2012 and analyzing the contour curve calculated from the measurement data.

[0029] The type of surface treatment layer is not particularly limited, and various surface treatment layers known in the art can be used. Examples of surface treatment layers include roughening treatment layers, heat-resistant treatment layers, rust-preventive treatment layers, chromate treatment layers, and silane coupling treatment layers. These layers can be used individually or in combination of two or more. Among these, the surface treatment layer is preferably a roughening treatment layer from the viewpoint of adhesion to the resin substrate. Furthermore, if the surface treatment layer includes one or more layers selected from the group consisting of a heat-resistant treatment layer, a rust-preventive treatment layer, a chromate treatment layer, and a silane coupling treatment layer, it is preferable that these layers be provided on the roughening treatment layer.

[0030] As an example, Figure 3 shows a schematic enlarged cross-sectional view of a surface-treated copper foil having a roughened layer on one side. As shown in Figure 3, the roughening treatment layer formed on one side of the copper foil 10 includes roughening particles 20 and an overlay plating layer 30 that covers at least a portion of the roughening particles 20. The roughening particles 20 are formed not only near the center of the convex portions 11 on the surface of the copper foil 10 but also around the concave portions 12 (the ends of the convex portions 11). Furthermore, the roughening particles 20 formed on the convex portions 11 on the surface of the copper foil 10 are prevented from overgrowing by adding a small amount of tungsten compound to the plating solution. As a result, these roughening particles 20 do not overgrow into particles with large particle sizes and have a complex shape that grows in all directions. It is believed that such a structure can be achieved by controlling the rate of change of Vmc of the surface treatment layer within the above range.

[0031] The roughened particles 20 are not particularly limited, but can be formed from a single element selected from the group consisting of copper, nickel, cobalt, phosphorus, tungsten, arsenic, molybdenum, chromium, and zinc, or from an alloy containing two or more of these elements. Among these, the roughened particles 20 are preferably formed from copper or a copper alloy, particularly from copper. The overlay plating layer 30 is not particularly limited, but can be formed from copper, silver, gold, nickel, cobalt, zinc, and the like.

[0032] The roughened layer can be formed by electroplating. In particular, the roughened particles 20 can be formed by electroplating using a plating solution to which a small amount of tungsten compound has been added. The tungsten compound is not particularly limited, but for example, sodium tungstate (Na2WO4) can be used. The tungsten compound content in the plating solution is preferably 1 ppm or more. This content suppresses the overgrowth of roughened particles 20 formed on the protrusions 11 and facilitates the formation of roughened particles 20 around the recesses 12. The upper limit of the tungsten compound content is not particularly limited, but from the viewpoint of suppressing an increase in electrical resistance, it is preferably 20 ppm.

[0033] The electroplating conditions for forming the roughened layer are not particularly limited and can be adjusted according to the electroplating equipment used, but typical conditions are as follows. Each electroplating step may be performed once or multiple times. (Conditions for the formation of roughened particles 20) Plating solution composition: 5-15 g / L of Cu, 40-100 g / L of sulfuric acid, 1-6 ppm of sodium tungstate. Plating solution temperature: 20~50℃ Electroplating conditions: Current density 30-90 A / dm 2 , time 0.1~8 seconds

[0034] (Conditions for forming the overlay plating layer 30) Plating solution composition: 10-30 g / L of copper, 70-130 g / L of sulfuric acid. Plating solution temperature: 30~60℃ Electroplating conditions: Current density 4.8~15A / dm 2 , time 0.1~8 seconds

[0035] The heat-resistant layer and the rust-preventive layer are not particularly limited and can be formed from materials known in the art. Since the heat-resistant layer may also function as a rust-preventive layer, a single layer having both functions may be formed. The heat-resistant and / or rust-preventive layer may be a layer containing one or more elements selected from the group consisting of nickel, zinc, tin, cobalt, molybdenum, copper, tungsten, phosphorus, arsenic, chromium, vanadium, titanium, aluminum, gold, silver, platinum group elements, iron, and tantalum (which may be in any form such as metal, alloy, oxide, nitride, or sulfide). Among these, the heat-resistant and / or rust-preventive layer is preferably a Ni-Zn layer.

[0036] The heat-resistant and rust-preventive layers can be formed by electroplating. The conditions are not particularly limited and can be adjusted according to the electroplating equipment used, but the conditions for forming the heat-resistant layer (Ni-Zn layer) using a general electroplating equipment are as follows. Note that electroplating may be performed once or multiple times. Plating solution composition: 1-30 g / L Ni, 1-30 g / L Zn Plating solution pH: 2-5 Plating solution temperature: 30-50℃ Electroplating conditions: Current density 0.1~10A / dm 2 Time 0.1-5 seconds

[0037] The chromate treatment layer is not particularly limited and can be formed from materials known in the art. Herein, in this specification, "chromate-treated layer" means a layer formed with an anhydrous chromic acid, chromic acid, dichromate, chromate, or a solution containing a dichromate. The chromate-treated layer may be a layer containing elements such as cobalt, iron, nickel, molybdenum, zinc, tantalum, copper, aluminum, phosphorus, tungsten, tin, arsenic, and titanium (which may be in any form such as metal, alloy, oxide, nitride, or sulfide). Examples of chromate-treated layers include a chromate-treated layer treated with an anhydrous chromic acid or an aqueous solution of potassium dichromate, and a chromate-treated layer treated with a treatment solution containing anhydrous chromic acid or potassium dichromate and zinc.

[0038] The chromate-treated layer can be formed by known methods such as immersion chromate treatment and electrolytic chromate treatment. The conditions are not particularly limited, but for example, the conditions for forming a general chromate-treated layer are as follows. Note that the chromate treatment may be performed once or multiple times. Chromate solution composition: 1-10 g / L of K2Cr2O7, 0.01-10 g / L of Zn Chromate solution pH: 2-5 Chromate solution temperature: 30~55℃ Electrolysis conditions: current density 0.1~10A / dm 2 Time: 0.1-5 seconds (in the case of electrolytic chromate treatment)

[0039] The silane coupling treatment layer is not particularly limited and can be formed from materials known in the art. Herein, in this specification, "silane coupling treated layer" means a layer formed with a silane coupling agent. The silane coupling agent is not particularly limited, and any known in the art can be used. Examples of silane coupling agents include amino silane coupling agents, epoxy silane coupling agents, mercapto silane coupling agents, methacryloxy silane coupling agents, vinyl silane coupling agents, imidazole silane coupling agents, and triazine silane coupling agents. Among these, amino silane coupling agents and epoxy silane coupling agents are preferred. The above silane coupling agents can be used individually or in combination of two or more. A typical method for forming a silane coupling treatment layer involves applying a 1-3 volume percent aqueous solution of the silane coupling agent mentioned above and drying it to form the silane coupling treatment layer.

[0040] The copper foil 10 is not particularly limited and may be either electrolytic copper foil or rolled copper foil. Electrolytic copper foil is generally manufactured by electrolytically emanating copper from a copper sulfate plating bath onto a titanium or stainless steel drum. It has a flat S-surface (shine surface) formed on the rotating drum side and an M-surface (matte surface) formed on the opposite side of the S-surface. The M-surface of electrolytic copper foil generally has minute irregularities. The S-surface of electrolytic copper foil also has minute irregularities because polishing marks from the rotating drum formed during polishing are transferred to it. Furthermore, rolled copper foil has minute irregularities on its surface because oil pits are formed by the rolling oil during the rolling process.

[0041] The material of the copper foil 10 is not particularly limited, but if the copper foil 10 is rolled copper foil, high-purity copper such as tough pitch copper (JIS H3100 alloy number C1100) or oxygen-free copper (JIS H3100 alloy number C1020 or JIS H3510 alloy number C1011), which are commonly used as circuit patterns for printed circuit boards, can be used. In addition, copper alloys such as Sn-containing copper, Ag-containing copper, copper alloys with added Cr, Zr, or Mg, or Corson-type copper alloys with added Ni and Si can also be used. In this specification, "copper foil 10" is a concept that also includes copper alloy foils.

[0042] The thickness of the copper foil 10 is not particularly limited, but can be, for example, 1 to 1000 μm, 1 to 500 μm, 1 to 300 μm, 3 to 100 μm, 5 to 70 μm, 6 to 35 μm, or 9 to 18 μm.

[0043] A surface-treated copper foil having the above-described configuration can be manufactured in accordance with methods known in the art. Here, parameters such as the rate of change of Vmc of the surface-treated layer can be controlled by adjusting the formation conditions of the surface-treated layer, in particular the formation conditions of the roughened layer described above.

[0044] The surface-treated copper foil according to the embodiment of the present invention controls the rate of change of the Vmc of the surface treatment layer to 23.00 to 40.00%, thereby improving adhesion to resin substrates, especially resin substrates suitable for high-frequency applications.

[0045] A copper-clad laminate according to an embodiment of the present invention comprises the above-mentioned surface-treated copper foil and a resin substrate bonded to the surface-treated layer of the surface-treated copper foil. This copper-clad laminate can be manufactured by bonding a resin substrate to the surface treatment layer of the surface-treated copper foil described above. The resin substrate is not particularly limited, and any known in the art can be used. Examples of resin substrates include paper-based phenolic resin, paper-based epoxy resin, synthetic fiber cloth-based epoxy resin, glass cloth / paper composite-based epoxy resin, glass cloth / glass nonwoven fabric composite-based epoxy resin, glass cloth-based epoxy resin, polyester film, polyimide resin, liquid crystal polymer, and fluororesin. Among these, polyimide resin is preferred as the resin substrate.

[0046] The method for bonding the surface-treated copper foil and the resin substrate is not particularly limited and can be carried out in accordance with methods known in the art. For example, the surface-treated copper foil and the resin substrate can be laminated and then heat-pressed together. The copper-clad laminate manufactured in the manner described above can be used in the manufacture of printed circuit boards.

[0047] Because the copper-clad laminate according to the embodiment of the present invention uses the above-described surface-treated copper foil, it can improve adhesion to resin substrates, particularly resin substrates suitable for high-frequency applications.

[0048] A printed circuit board according to an embodiment of the present invention comprises a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate described above. This printed circuit board can be manufactured by etching the surface-treated copper foil of the copper-clad laminate described above to form a circuit pattern. The method for forming the circuit pattern is not particularly limited, and known methods such as the subtractive method and the semi-additive method can be used. Among these, the subtractive method is preferred for forming the circuit pattern.

[0049] When manufacturing printed circuit boards using the subtractive method, it is preferable to proceed as follows: First, a resist pattern is formed by applying a resist to the surface of the surface-treated copper foil of a copper-clad laminate, exposing it to light, and developing it. Next, the surface-treated copper foil in areas where the resist pattern is not formed (unnecessary areas) is removed by etching to form a circuit pattern. Finally, the resist pattern on the surface-treated copper foil is removed. Furthermore, the various conditions in this subtractive method are not particularly limited and can be carried out in accordance with conditions known in the relevant art.

[0050] Because the printed circuit board according to the embodiment of the present invention uses the above-mentioned copper-clad laminate, it exhibits excellent adhesion between the resin substrate, particularly a resin substrate suitable for high-frequency applications, and the circuit pattern. [Examples]

[0051] The embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these embodiments.

[0052] (Example 1) A 12 μm thick rolled copper foil (HA-V2 foil manufactured by JX Metals Corporation) was prepared. After degreasing and pickling one side, a surface-treated copper foil was obtained by sequentially forming a roughening layer, a heat-resistant layer (Ni-Zn layer), a chromate treatment layer, and a silane coupling treatment layer as surface treatment layers. The formation conditions for each treatment layer were as follows. (1) Roughened layer <Conditions for the formation of roughened particles> Plating solution composition: 11 g / L Cu, 50 g / L sulfuric acid, 5 ppm tungsten (derived from sodium tungstate dihydrate) Plating solution temperature: 27℃ Electroplating conditions: Current density 80.0 A / dm 2 , time 0.51 seconds Number of electroplating treatments: 2

[0053] <Conditions for forming the overlay plating layer> Plating solution composition: 20 g / L of Cu, 100 g / L of sulfuric acid Plating solution temperature: 50 °C Electroplating conditions: Current density 12.6 A / dm 2 , time 0.96 seconds Number of electroplating treatments: 2 times

[0054] (2) Heat-resistant treatment layer <Formation conditions of Ni-Zn layer> Plating solution composition: 23.5 g / L of Ni, 4.5 g / L of Zn Plating solution pH: 3.6 Plating solution temperature: 40 °C Electroplating conditions: Current density 0.83 A / dm 2 , time 0.49 seconds Number of electroplating treatments: 1 time

[0055] (3) Chromate treatment layer <Formation conditions of electrolytic chromate treatment layer> Chromate solution composition: 3 g / L of K₂Cr₂O₇, 0.33 g / L of Zn Chromate solution pH: 3.7 Chromate solution temperature: 55 °C Electrolysis conditions: Current density 2.20 A / dm 2 , time 0.49 seconds Number of chromate treatments: 2 times

[0056] (4) Silane coupling treatment layer A 1.2% by volume aqueous solution of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane was applied and dried to form a silane coupling treatment layer.

[0057] (Example 2) A surface-treated copper foil was obtained under the same conditions as in Example 1, except that the following conditions were changed. <Formation conditions of roughened particles> Electroplating conditions: Current density 46.8 A / dm 2 , time 1.01 seconds <Formation conditions of overlay plating layer> Electroplating conditions: Current density 9.6 A / dm 2, Time 1.44 seconds <Formation conditions of Ni-Zn layer> Electroplating condition: Current density 0.88 A / dm 2 , Time 0.73 seconds <Formation conditions of electrolytic chromate treatment layer> Electrolytic condition: Current density 1.42 A / dm 2 , Time 0.73 seconds

[0058] (Example 3) Surface-treated copper foil was obtained under the same conditions as in Example 1 except that the following conditions were changed. <Formation conditions of roughening particles> Electroplating condition: Current density 41.3 A / dm 2 , Time 1.15 seconds <Formation conditions of overlay plating layer>[[ID=2,7]] Electroplating condition: Current density 8.2 A / dm 2 , Time 1.44 seconds <Formation conditions of Ni-Zn layer> Electroplating condition: Current density 0.73 A / dm 2 , Time 0.73 seconds <Formation conditions of electrolytic chromate treatment layer> Electrolytic condition: Current density 1.51 A / dm 2 , Time 0.73 seconds

[0059] (Example 4) Surface-treated copper foil was obtained under the same conditions as in Example 1 except that the following conditions were changed. <Formation conditions of roughening particles> Electroplating condition: Current density 54.8 A / dm 2 , Time 0.90 seconds <Formation conditions of overlay plating layer> Electroplating condition: Current density 8.2 A / dm[[ID=,59]] 2 , Time 1.44 seconds <Formation conditions of Ni-Zn layer> Electroplating condition: Current density 0.73 A / dm 2 , Time 0.73 seconds <Formation conditions of electrolytic chromate treatment layer> Electrolytic condition: Current density 1.51 A / dm 2 , Time 0.73 seconds

[0060] (Example 5) A surface-treated copper foil was obtained under the same conditions as in Example 1, except that the following conditions were changed. <Conditions for forming roughened particles> Electroplating conditions: Current density 46.8 A / dm 2 , time 1.01 seconds <Conditions for forming the overlay plating layer> Electroplating conditions: Current density 9.6 A / dm 2 , time 1.44 seconds <Conditions for forming the Ni-Zn layer> Electroplating conditions: Current density 0.88 A / dm 2 , time 0.73 seconds <Conditions for forming the electrolytic chromate treatment layer> Electrolysis conditions: Current density 1.42 A / dm 2 , time 0.73 seconds

[0061] (Example 6) A rolled copper foil with a thickness of 12 μm (HG foil manufactured by JX Metals Co., Ltd.) was prepared. After degreasing and pickling one surface, a surface-treated copper foil was obtained by sequentially forming a roughened treatment layer, a heat-resistant treatment layer (Ni-Zn layer), a chromate treatment layer, and a silane coupling treatment layer as the surface treatment layer. The formation conditions for each treatment layer were as follows. (1) Roughened treatment layer <Conditions for forming roughened particles> Plating solution composition: 12 g / L of Cu, 50 g / L of sulfuric acid, 5 ppm of tungsten (derived from sodium tungstate dihydrate) Plating solution temperature: 27 °C Electroplating conditions: Current density 48.3 A / dm 2 , time 0.81 seconds Number of electroplating treatments: 2 times

[0062] <Conditions for forming the overlay plating layer> Plating solution composition: 20 g / L of Cu, 100 g / L of sulfuric acid Plating solution temperature: 50 °C Electroplating conditions: Current density 11.9 A / dm 2 , time 1.15 seconds Number of electroplating treatments: 2 times

[0063] (2) Heat-resistant treatment layer <Formation conditions of Ni-Zn layer> Plating solution composition: 23.5 g / L of Ni, 4.5 g / L of Zn pH of plating solution: 3.6 Temperature of plating solution: 40 °C Electroplating conditions: Current density 1.07 A / dm 2 , time 0.59 seconds Number of electroplating treatments: 1 time

[0064] (3) Chromate treatment layer <Formation conditions of electrolytic chromate treatment layer> Chromate solution composition: 3 g / L of K2Cr2O7, 0.33 g / L of Zn pH of chromate solution: 3.65 Temperature of chromate solution: 55 °C Electrolysis conditions: Current density 1.91 A / dm 2 , time 0.59 seconds Number of chromate treatments: 2 times

[0065] (4) Silane coupling treatment layer A 1.2% by volume aqueous solution of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane was applied and dried to form a silane coupling treatment layer.

[0066] (Comparative Example 1) The rolled copper foil (copper foil without surface treatment) used in Example 1 was used for comparison.

[0067] (Comparative Example 2) A surface-treated copper foil was obtained under the same conditions as in Example 1 except that the following conditions were changed. <Formation conditions of roughened particles> Plating solution composition: 11 g / L of Cu, 50 g / L of sulfuric acid Electroplating conditions: Current density 38.8 A / dm 2 , time 1.27 seconds <Formation conditions of overlay plating layer> Electroplating conditions: Current density 8.2 A / dm 2 , Time 1.44 seconds <Formation conditions of Ni-Zn layer> Electroplating conditions: Current density 0.59 A / dm 2 , Time 0.73 seconds <Formation conditions of electrolytic chromate treatment layer> Electrolysis conditions: Current density 1.42 A / dm 2 , Time 0.73 seconds

[0068] For the surface-treated copper foil or copper foil obtained in the above Examples and Comparative Examples, the following characteristic evaluations were performed. <Vmc, Sku, Sq, Sa and Ssk> In accordance with ISO 25178-2:2012, measurement (image capture) was performed using a laser microscope (LEXT OLS4000) manufactured by Olympus Corporation. Analysis of the captured images was performed using the analysis software of a laser microscope (LEXT OLS4100) manufactured by Olympus Corporation. For the results, the average value of the measured and analyzed values at five arbitrary locations was used. The temperature during measurement was set to 23 to 25°C. The main setting conditions for the laser microscope and analysis software are as follows. Objective lens: MPLAPON50XLEXT (Magnification: 50 times, Numerical aperture: 0.95, Immersion type: Air, Mechanical tube length: ∞, Cover glass thickness: 0, Field number: FN18) Optical zoom magnification: 1 time Scanning mode: XYZ high-precision (Height resolution: 60 nm, Number of pixels of captured data: 1024×1024) Captured image size [number of pixels]: Horizontal 257 μm × Vertical 258 μm [1024×1024] (For measurement in the horizontal direction, the evaluation length corresponds to 257 μm) DIC: Off Multi-layer: Off Laser intensity: 100 Offset: 0 Confocal level: 0 Beam diameter aperture: Off Image average: 1 time Noise reduction: On Brightness uniformity correction: On Optical noise filter: On Cutoff values: For P1(Vmc) measurements, λc=200μm and λs=2μm are applied, but λf is not. For P2(Vmc), Sku, Sq, Sa, and Ssk measurements, λc=200μm is applied, but λs and λf are not. Filter: Gaussian filter Noise reduction: Pre-measurement processing Surface (tilt) correction: Implemented Brightness: Adjust to a range of 30-50. Brightness should be set appropriately depending on the color tone of the object being measured. The above settings are appropriate when measuring the surface of surface-treated copper foil with L* set to -69 to -10, a* set to 2 to 32, and b* set to 221. Furthermore, the rate of change of Vmc was calculated according to equation (1) above. Note that the λc filter corresponds to the L filter in ISO 25178-2:2012.

[0069] <Measurement of the color tone of the object to be measured> A HunterLab MiniScan® EZ Model 4000L was used as the measuring instrument, and measurements of L*, a*, and b* in the CIE L*a*b* color system were performed in accordance with JIS Z8730:2009. Specifically, the surface-treated copper foil or the surface of the copper foil to be measured obtained in the above examples and comparative examples was pressed against the photosensitive part of the measuring instrument, and measurements were taken while preventing light from entering from the outside. In addition, the measurements of L*, a*, and b* were performed based on geometric condition C of JIS Z8722:2009. The main conditions of the measuring instrument are as follows. Optical system: d / 8°, Integrating sphere size: 63.5 mm, Observation light source: D65 Measurement method: reflection Light diameter: 25.4mm Measuring diameter: 20.0 mm Measurement wavelength / interval: 400~700nm / 10nm Light source: Pulsed xenon lamp, 1 emission / measurement Traceability standards: Calibration compliant with the National Institute of Standards and Technology (NIST), based on CIE 44 and ASTM E259. Standard observer: 10° Furthermore, the white tiles used as the measurement standard were those with the following object colors. When measured at D65 / 10°, the values ​​in the CIE XYZ color system were X: 81.90, Y: 87.02, and Z: 93.76.

[0070] <Peel strength> After bonding surface-treated copper foil to a polyimide resin substrate, a 3 mm wide circuit was formed in the MD direction (longitudinal direction of the rolled copper foil). The circuit was formed according to a standard method. Next, the strength (MD90° peel strength) when peeling the circuit (surface-treated copper foil) from the surface of the resin substrate at a speed of 50 mm / min in a 90° direction, i.e., vertically upward relative to the surface of the resin substrate, was measured in accordance with JIS C6471:1995. The measurement was performed three times, and the average value was taken as the result of the peel strength. A peel strength of 0.50 kgf / cm or higher indicates good adhesion between the circuit (surface-treated copper foil) and the resin substrate. Note that the copper foil in Comparative Example 1 could not be bonded to the polyimide resin substrate, so this evaluation was not performed.

[0071] The results of the above characteristic evaluation are shown in Table 1.

[0072] [Table 1]

[0073] As shown in Table 1, the surface-treated copper foils in Examples 1 to 6, where the change rate of the surface treatment layer Vmc was within the range of 23.00 to 40.00%, exhibited high peel strength. On the other hand, the surface-treated copper foil of Comparative Example 2, in which the rate of change of Vmc in the surface treatment layer was outside the predetermined range, had low peel strength.

[0074] Based on the above results and the consideration of the embodiments of the present invention described so far, according to the embodiments of the present invention, it is possible to provide a surface-treated copper foil that can improve adhesion to a resin substrate, particularly a resin substrate suitable for high-frequency applications. Furthermore, according to the embodiments of the present invention, it is possible to provide a copper-clad laminate with excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and the surface-treated copper foil. Moreover, according to the embodiments of the present invention, it is possible to provide a printed wiring board with excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and the circuit pattern. [Explanation of symbols]

[0075] 10 Copper foil 11 Convex part 12 recesses 20 Roughening particles 30 Overlay plating layer

Claims

1. It comprises a copper foil and a surface treatment layer formed on at least one surface of the copper foil, The surface treatment layer is a surface-treated copper foil in which the rate of change of Vmc, represented by the following formula (1), is 23.00 to 40.00%. The rate of change of Vmc = (P2 - P1) / P2 × 100 ... (1) In the formula, P1 is Vmc calculated by applying a λs filter with a cutoff value λs of 2 μm, and P2 is Vmc calculated without applying the λs filter.

2. The surface-treated copper foil according to claim 1, wherein the rate of change of Vmc is 23.00 to 32.00%.

3. The surface-treated copper foil according to claim 1, wherein the rate of change of Vmc is 23.00 to 31.00%.

4. The surface-treated copper foil according to any one of claims 1 to 3, wherein the surface-treated layer has a Sku of 2.50 to 4.50, calculated without applying the λs filter.

5. The surface-treated copper foil according to claim 4, wherein the Sku is 2.90 to 4.

10.

6. The surface-treated copper foil according to any one of claims 1 to 5, wherein the surface-treated layer has an Sq of 0.20 to 0.60 μm calculated without applying the λs filter.

7. The surface-treated copper foil according to any one of claims 1 to 6, wherein the surface-treated layer has a Sa of 0.20 to 0.40 μm, calculated without applying the λs filter.

8. The surface-treated copper foil according to any one of claims 1 to 7, wherein the surface treatment layer contains a roughening treatment layer.

9. A copper-clad laminate comprising a surface-treated copper foil according to any one of claims 1 to 8, and a resin substrate bonded to the surface-treated layer of the surface-treated copper foil.

10. A printed wiring board comprising a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate according to claim 9.

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