Surface-treated copper foil, copper-clad laminate, and printed wiring board

Abstract

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. The surface treatment layer has a variation in Vmp represented by the following formula (1) of 0.0010 to 0.0110 μm 3 / μm 2 The variation in Vmp = P2 - P1 (1) In the formula, P1 is the Vmp calculated using a λs filter having a cutoff value λs of 2 μm, and P2 is the Vmp calculated without using the λs filter.

Description

Technical Field

[0001] This invention relates to a surface-treated copper foil, a copper-clad laminate, and a printed wiring board. Background Technology

[0002] Copper-clad laminates are widely used in various applications such as flexible printed circuit boards. These flexible printed circuit boards are manufactured by etching the copper foil of the copper-clad laminate to form conductor patterns (also known as "wiring patterns"), and then using solder to connect and mount electronic components onto the conductor patterns.

[0003] In recent years, with the increasing speed and capacity of communication in electronic devices such as personal computers and mobile terminals, electrical signals have become increasingly high-frequency, requiring flexible printed circuit boards (PCBs) to accommodate them. In particular, the higher the frequency of the electrical signal, the greater the signal power loss (attenuation), and the more difficult it is to read data. Therefore, it is necessary to reduce signal power loss.

[0004] The causes of signal power loss (transmission loss) in electronic circuits can be broadly divided into two types. One is conductor loss, which is the loss caused by the copper foil, and the other is dielectric loss, which is the loss caused by the resin substrate.

[0005] Conductor loss exhibits the following characteristics: at high frequencies, the skin effect exists, and current flows along the conductor surface. Therefore, if the copper foil surface is rough, the current will flow along a complex path. Thus, to reduce conductor loss in high-frequency signals, it is ideal to reduce the surface roughness of the copper foil. Hereinafter, in this specification, when simply referred to as "transmission loss" and "conductor loss," the terms primarily refer to "transmission loss of high-frequency signals" and "conductor loss of high-frequency signals."

[0006] On the other hand, dielectric loss depends on the type of resin substrate. Therefore, in circuit boards where high-frequency signals flow, it is ideal to use a resin substrate formed of a low-dielectric material (such as liquid crystal polymer or low-dielectric polyimide). Furthermore, dielectric loss is also affected by the adhesive between the copper foil and the resin substrate. Therefore, it is ideal to bond the copper foil and the resin substrate without using an adhesive.

[0007] Therefore, in order to bond the copper foil to the resin substrate without using an adhesive, it is proposed to form a surface treatment layer on at least one side of the copper foil. For example, Patent Document 1 proposes a method in which a roughening treatment layer formed of roughening particles is provided on the copper foil, and a silane coupling treatment layer is formed on the outermost layer.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2012-112009 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] The surface of the copper foil to which the surface treatment layer is formed generally has tiny unevenness. For example, in the case of rolled copper foil, oil pits formed by the rolling oil during rolling will form on the surface in the form of tiny unevenness. Also, in the case of electrolytic copper foil, the grinding stripes formed by the rotating drum during grinding will cause tiny unevenness to be deposited on the rotating drum side surface of the electrolytic copper foil formed on the rotating drum.

[0013] If there are minute irregularities on the surface of the copper foil, for example, during the formation of a roughening layer, current concentration occurs at the protrusions, leading to excessive growth of roughened particles. Conversely, insufficient current is supplied to the recesses and their surrounding areas, hindering particle growth. This results in a situation where large roughened particles form on the protrusions, while the particles in the recesses and their surrounding areas are too small, particularly near the ends of the oil pits, where adhesion is insufficient, meaning the roughened particles on the copper foil surface are not uniformly formed. Copper foil with many large roughened particles may, after bonding with a resin substrate, experience stress concentration on the large particles when peeled off, leading to breakage and reduced adhesion to the resin substrate. Furthermore, copper foil with insufficiently sized roughened particles may exhibit reduced anchoring effect due to the particles, resulting in inadequate adhesion between the copper foil and the resin substrate.

[0014] In particular, resin substrates formed from low-dielectric materials such as liquid crystal polymers and low-dielectric polyimides are more difficult to bond with copper foil than conventional resin substrates. Therefore, it is desirable to develop a method to improve the adhesion between copper foil and resin substrates.

[0015] Furthermore, although the silane coupling treatment layer can improve the adhesion between the copper foil and the resin substrate, the improvement effect is sometimes insufficient, depending on the type of silane coupling treatment layer.

[0016] The embodiments of the present invention were made to solve the problems described above. In one embodiment, the aim is to provide a surface-treated copper foil that can improve adhesion to resin substrates, especially resin substrates suitable for high-frequency applications.

[0017] Furthermore, in another embodiment of the present invention, the aim is to provide a copper-clad laminate with excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and a surface-treated copper foil.

[0018] Furthermore, in another embodiment of the present invention, the aim is 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.

[0019] Technical solutions to the problem

[0020] To solve the aforementioned problems, the inventors conducted in-depth research on surface-treated copper foil and obtained the following insights: by adding a trace amount of tungsten compound to the plating solution used to form the roughening treatment layer, excessive growth of roughening particles forming on the convex portions of the copper foil surface is suppressed, and roughening particles are easily formed around the concave portions of the copper foil surface. Furthermore, after analyzing the surface shape of the surface-treated copper foil thus obtained, the inventors discovered that the change in Vmp of the surface-treated layer is closely related to its surface shape, thereby completing the embodiment of the present invention.

[0021] That is, in one embodiment of the present invention, there is a surface-treated copper foil having a copper foil and a surface-treated layer formed on at least one side of the copper foil, wherein the variation of Vmp of the surface-treated layer, expressed by the following formula (1), is 0.0010 to 0.0110 μm. 3 / μm 2 .

[0022] The change in Vmp = P2 - P1···(1)

[0023] In the formula, P1 is Vmp calculated by applying a λs filter with a cutoff value of 2μm, and P2 is Vmp calculated without applying the above λs filter.

[0024] Furthermore, in another embodiment of the present invention, there is a copper-clad laminate comprising the aforementioned surface-treated copper foil and a resin substrate adjoining the aforementioned surface-treated layer to the aforementioned surface-treated copper foil.

[0025] Furthermore, in another embodiment of the present invention, there is a printed wiring board having a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate.

[0026] The effects of the invention

[0027] According to an embodiment of the present invention, in one embodiment, a surface-treated copper foil capable of improving adhesion to resin substrates, particularly resin substrates suitable for high-frequency applications, can be provided.

[0028] According to an embodiment of the present invention, in another embodiment, a copper-clad laminate with excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and a surface-treated copper foil can be provided.

[0029] Furthermore, according to an embodiment of the present invention, in another embodiment, a printed wiring board with excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and a circuit pattern can be provided. Attached Figure Description

[0030] [ Figure 1 [This is a typical load curve for a surface treatment layer.]

[0031] [ Figure 2 This is a schematic diagram used to illustrate the roughened particles and Vmp that constitute the surface treatment layer.

[0032] [ Figure 3 This is a schematic enlarged cross-sectional view of a surface-treated copper foil with a roughening treatment layer on one side.

[0033] Explanation of reference numerals in the attached figures

[0034] 10: Copper foil

[0035] 11:convex part

[0036] 12: concave part

[0037] 20: Coarsened particles

[0038] 30: Coating. Detailed Implementation

[0039] The preferred embodiments of the present invention will be described in detail below, but the present invention should not be limited thereto. Various modifications and improvements can be made based on the knowledge of those skilled in the art without departing from the spirit of the present invention. The various constituent elements disclosed in the following embodiments can be appropriately combined to form various inventions. For example, some constituent elements can be deleted from all the constituent elements shown in the following embodiments, or constituent elements from different embodiments can be appropriately combined.

[0040] The surface-treated copper foil of the present invention has a copper foil and a surface-treated layer formed on at least one side of the copper foil.

[0041] The surface treatment layer may be formed on only one side of the copper foil or on both sides. When 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.

[0042] The surface shape of the surface treatment layer can be specified using surface property parameters, which are determined according to ISO 25178-2:2012 and obtained by analyzing the load curve calculated from the self-measured data.

[0043] When explaining the load curve, the load area ratio is explained first.

[0044] The load area ratio refers to the ratio obtained by dividing the area of ​​the cross-section of the object being measured (equivalent to a three-dimensional object cut at a certain height) by the area of ​​the measurement field of view. Furthermore, in this invention, copper foil or a surface treatment layer of surface-treated copper foil is used as the object being measured. The load curve is a curve representing the load area ratio at various heights. A load area ratio near 0% indicates the height of the highest part of the object being measured, while a load area ratio near 100% indicates the height of the lowest part of the object being measured.

[0045] Next, Figure 1 This represents a typical load curve for a surface treatment layer. The load curve can be used to represent the solid portion volume and the spatial portion volume of the surface treatment layer. The solid portion volume corresponds to the volume of the solid part of the object being measured within the field of view, while the spatial portion volume corresponds to the volume of the space between the solid parts within the field of view. In the load curve described in this invention, the load area ratio is divided into valley, core, and mountain sections, with the 10% and 80% marks as boundaries. (Refer to...) Figure 1 The surface treatment layer of the present invention will be described accordingly. Vvv refers to the volume of the space portion at the valley of the surface treatment layer, Vvc refers to the volume of the space portion at the core of the surface treatment layer, Vmp refers to the volume of the solid portion at the mountain of the surface treatment layer, and Vmc refers to the volume of the solid portion at the core of the surface treatment layer.

[0046] Furthermore, the so-called "mountain section" refers to the highest part of the object being measured. The so-called "valley section" refers to the lowest part of the object being measured. The so-called "core section" refers to the part of the object being measured other than the mountain and valley sections, that is, the part with a height close to the average.

[0047] The solid volume Vmp at the mountain-like part refers to the volume of the solid part at the highest point of the measured object, specifically the volume of the solid part at the particularly high point of the surface treatment layer. Here, the solid part at the particularly high point of the surface treatment layer can be interpreted as the portion caused by excessively grown particles (especially coarsened particles).

[0048] The volume Vmc of the solid portion at the core is the volume of the solid portion at the portion of the object whose height is close to the average height. It refers to the volume of the solid portion at the portion of the average height of the surface treatment layer. Here, the solid portion at the portion of the average height of the surface treatment layer can be interpreted as the portion caused by the average-sized particles (especially coarsened particles) formed on the relatively smooth portion of the copper foil surface.

[0049] In summary, based on the analysis conducted by the inventors in the above manner, the following conclusions were drawn: In the surface-treated copper foil of the embodiments of the present invention, Vmp is related to the solid volume of the excessively grown large particles, and Vmc is related to the solid volume of the average-sized particles. Furthermore, the following explanation will take the case where the coarsened particles are particles as an example, but it should be noted that the particles are not limited to coarsened particles.

[0050] The measurement data used to determine the surface properties of the surface-treated copper foil according to the embodiments of the present invention can be obtained, for example, using a laser microscope such as a confocal laser microscope. Here, a Fourier transform is performed on the measurement data, thereby separating the measurement data into waveforms with 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 of the separated waveforms, and then synthesizing all the waveforms again and analyzing the synthesized data, the surface property parameters of note can be calculated from the measurement data.

[0051] In the analysis of surface roughness measurement data, the inventors obtained the following insights: by combining the surface characteristic parameters calculated by applying a λs filter with a cutoff value of 2 μm and the surface characteristic parameters calculated without applying the λs filter, detailed information on the characteristic surface shape of the surface treatment layer of the embodiment of the present invention (in particular, the adhesion state of the roughening particles constituting the surface treatment layer) can be obtained.

[0052] Here, the λs filter is a profile filter that significantly attenuates the amplitude of waveforms with wavelengths smaller than the cutoff value λs. The λs filter is equivalent 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 with the cutoff value λs, the amplitude is attenuated to 50% of its original value; at wavelengths smaller than this, the amplitude can be attenuated even more significantly.

[0053] The 2μm cutoff value λs represents the size between the size of the coarsened particles constituting the surface treatment layer and the size of the oil pits. Measurement data obtained by setting the cutoff value λs to 2μm originates from waveforms with shorter periods than the cutoff value λs; therefore, it can be understood as data obtained after removing information originating from the coarsened particles. Based on this, it can be said that the difference between the surface characteristic parameters calculated without applying a λs filter with a 2μm cutoff value and the surface characteristic parameters calculated using that λs filter represents the information of the surface treatment layer after removing the information from the oil pits, i.e., the information of the coarsened particles constituting the surface treatment layer.

[0054] Based on the above insights, the inventors analyzed various surface property parameters obtained from the self-loading curve and found that the change in Vmp of the surface treatment layer, expressed by the following formula (1), is closely related to the amount of overgrown coarsened particles attached.

[0055] The change in Vmp = P2 - P1···(1)

[0056] In the formula, P1 is Vmp calculated by applying a λs filter with a cutoff value of 2μm, and P2 is Vmp calculated without applying the above λs filter.

[0057] Here, Figure 2 This is a schematic diagram illustrating the roughened particles and Vmp that constitute the surface treatment layer. (Example) Figure 2 As shown, the surface treatment layer contains coarsened particles A of average size and excessively grown coarsened particles B. As explained above, Vmp can be considered related to the volume of the portion of the excessively grown coarsened particles B on the copper foil surface whose height is higher than that of the average-sized coarsened particles A. Vmp is significantly affected by macroscopic shapes such as oil pits. To more accurately read the information of the surface treatment layer, the influence of macroscopic shapes needs to be removed. P1 can be interpreted as the Vmp value after removing information originating from coarsened particles; in other words, it is the Vmp value retaining information originating from oil pits, etc. Taking the difference between P2 and P1 represents removing information from macroscopic shapes such as oil pits contained in Vmp. As a result, information related to the excessively grown coarsened particles B can be extracted with high precision.

[0058] Surface-treated copper foil with a controlled variation in Vmp related to the amount of overgrown coarsened particles B can improve adhesion to the resin substrate. It can be considered that for surface-treated copper foil with a high amount of overgrown coarsened particles B, after bonding with the resin substrate, if a force is applied to peel the surface-treated copper foil, the stress concentrates on the overgrown coarsened particles B, making them prone to breakage, resulting in reduced adhesion. Conversely, for surface-treated copper foil with the overgrown coarsened particles B controlled within an appropriate range, the stress is distributed among the coarsened particles, centered on the average-sized coarsened particles A. As a result, the coarsened particles are less likely to break, and the adhesion to the resin substrate is improved.

[0059] Based on the above viewpoint, the variation of Vmp is 0.0010–0.0110 μm. 3 / μm 2 The surface-treated copper foil of the embodiment of the present invention exhibits sufficient adhesion to the resin substrate. From the viewpoint of achieving the above-mentioned effect through self-stabilization, the variation in Vmp is preferably 0.0020 to 0.0100 μm. 3 / μm 2 More preferably, it is 0.0052–0.0088 μm. 3 / μm 2 .

[0060] The Ssk (skex) calculated without applying the above-mentioned λs filter for the surface treatment layer is preferably -1.10 to 0.60.

[0061] Ssk is a parameter representing the skewness (skewness) of a histogram of heights created based on the average height. For example, when Ssk = 0.00, it means the height distribution is symmetrical relative to the average line. When Ssk > 0.00, a larger value indicates a more downward skewed height distribution relative to the average line. Conversely, when Ssk < 0.00, a smaller value indicates a more upward skewed height distribution relative to the average line. Therefore, Ssk of a surface treatment layer is an indicator for evaluating the height distribution of the surface treatment layer's unevenness.

[0062] For example, when a roughening layer is formed on the surface of copper foil, a Ssk value of -1.10 to 0.60 indicates that there are excessively grown roughened particles (i.e., large roughened particles) on the convex parts of the copper foil surface, or that there are few areas where roughened particles have not formed around the concave parts (the ends of the convex parts) of the copper foil surface. On the other hand, if it is less than -1.10, it indicates that there are many areas where roughened particles have not formed around the concave parts of the copper foil surface. Furthermore, if Ssk exceeds 0.60, it indicates that there are many excessively grown roughened particles on the convex parts of the copper foil surface.

[0063] From the perspective of adhesion to resin substrates, both surface-treated copper foils with a high concentration of coarse particles and those with areas where no particles have formed are undesirable. For example, with surface-treated copper foils containing a high concentration of coarse particles, it is believed that after bonding with the resin substrate, if a force is applied to peel the surface-treated copper foil, the stress will concentrate on the coarse particles, making it prone to breakage. As a result, the adhesion to the resin substrate is actually reduced. Furthermore, with surface-treated copper foils in areas where no particles have formed, it is believed that the anchoring effect caused by the particles cannot be adequately ensured, thus reducing the adhesion between the surface-treated copper foil and the resin substrate.

[0064] From the viewpoint of achieving self-stable adhesion to the resin substrate, the upper limit of the surface treatment layer Ssk is preferably 0.40, and the lower limit is preferably -0.80.

[0065] Furthermore, the surface roughness of the SSK surface treatment layer can be measured according to ISO 25178-2:2012, and the profile curve calculated from the self-measured data can be analyzed to determine its specificity.

[0066] The Sa (arithmetic mean height) calculated without applying the above-mentioned λs filter for the surface treatment layer is preferably 0.20 to 0.40 μm. Sa is a parameter in the height direction specified by ISO 25178-2:2012, representing the average value of the height difference from the mean surface.

[0067] If the Sa value of the surface treatment layer is large, the surface of the surface treatment layer becomes rough, thus making it easier to exhibit an anchoring effect when bonding the surface-treated copper foil to the resin substrate. On the other hand, if the Sa value of the surface treatment layer is too large, when processing a copper-clad laminate formed by bonding the surface-treated copper foil to the resin substrate to manufacture a circuit board, the transmission loss will increase due to the skin effect of the surface-treated copper foil. Therefore, by setting the Sa value of the surface treatment layer within the above-mentioned range, a balance can be ensured between ensuring the adhesion of the surface-treated copper foil to the resin substrate and suppressing transmission loss. From the viewpoint of achieving the above-mentioned effects through self-stabilization, the lower limit value of the Sa value of the surface treatment layer is preferably 0.23 μm, more preferably 0.24 μm, and the upper limit value is preferably 0.35 μm.

[0068] Furthermore, the surface roughness of the surface treatment layer, Sa, can be determined according to ISO 25178-2:2012, and the profile curve calculated from the self-measured data can be analyzed to determine its specificity.

[0069] The root mean square height (Sq) of the surface treatment layer, calculated without applying the aforementioned λs filter, is preferably 0.20–0.60 μm. Sq is a height-direction parameter specified in ISO 25178-2:2012, representing the deviation of the height of the protrusions on the surface of the surface treatment layer.

[0070] A large Sq in a surface treatment layer refers to a large deviation in the height of the protrusions on the surface of the surface treatment layer. If Sq is too large (the deviation in protrusion height is too large), it can sometimes become a problem from the perspective of quality management of industrial products. Therefore, by making the Sq of the surface treatment layer within the above-mentioned range, it is possible to slightly tolerate the deviation in protrusion height to ensure productivity, while also allowing for appropriate quality management. From the viewpoint of consistently achieving the above-mentioned 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.

[0071] Furthermore, when it is important to suppress transmission loss caused by the skin effect and to facilitate quality management of industrial products, the Sa of the surface treatment layer is preferably 0.20 to 0.32 μm, and the Sq is preferably 0.26 to 0.40 μm.

[0072] Furthermore, the surface roughness Sq of the surface treatment layer can be determined according to ISO 25178-2:2012, and the profile curve calculated from the self-measured data can be analyzed to determine its specificity.

[0073] The Sku (kurtosis) calculated without applying the above-mentioned λs filter for the surface treatment layer is preferably 2.50 to 4.50.

[0074] When SKU is used to create a histogram of heights based on the average height, it represents the sharpness (sharpness) of that histogram. For example, an SKU of 3.00 indicates a normal height distribution. Furthermore, when SKU > 3.00, a larger value indicates a more concentrated height distribution. Conversely, when SKU < 3.00, a smaller value indicates a more dispersed height distribution. Therefore, the SKU of a surface treatment layer is an indicator for evaluating the height distribution of its unevenness.

[0075] A surface treatment layer with an SKU of 2.50–4.50 indicates a normal or near-normal height distribution. Conversely, an SKU below 2.50 indicates a mixed distribution of height (height from the copper foil surface), resulting in an unbiased height distribution. An SKU greater than 4.50 indicates a biased height distribution, where a certain height portion of the surface treatment layer prominently occupies multiple areas.

[0076] The height distribution of the surface treatment layer is a normal distribution or close to this distribution, meaning that, for example, when a roughening treatment layer is formed on the copper foil surface, there are fewer areas where particles excessively grow on the convex parts of the copper foil surface (i.e., large particles) or where no particles are formed in the periphery of the concave parts (ends of the convex parts). Therefore, a SKU of 2.50 to 4.50 for the surface treatment layer means that excessive growth of particles formed on the convex parts of the copper foil surface is suppressed, and roughened particles are also formed in the periphery of the concave parts of the copper foil surface. Thus, the uniform formation of roughened particles on the copper foil surface is considered to indicate good adhesion between the copper foil and the resin substrate.

[0077] Therefore, from the viewpoint of achieving self-stabilized adhesion to the resin substrate, the lower limit of the Sku of the surface treatment layer is preferably 2.90, and the upper limit is preferably 4.10.

[0078] Furthermore, the SKU of the surface treatment layer can be determined according to ISO 25178-2:2012 to measure the surface roughness, and the profile curve calculated from the self-measured data can be analyzed to determine its specificity.

[0079] The type of surface treatment layer is not particularly limited, and various surface treatment layers known in the art can be used.

[0080] Examples of surface treatment layers include roughening treatment layers, heat-resistant treatment layers, rust-proof treatment layers, chromate treatment layers, and silane coupling treatment layers. These layers can be used individually or in combination of two or more. From the viewpoint of adhesion to the resin substrate, a roughening treatment layer is preferred among the surface treatment layers.

[0081] Furthermore, when the surface treatment layer contains 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, the layer is preferably disposed on the roughening treatment layer.

[0082] Here, Figure 3 This is a schematic enlarged cross-sectional view of a surface-treated copper foil with a roughening layer on one side, as an example.

[0083] like Figure 3 As shown, a roughening treatment layer formed on one side of the copper foil 10 includes roughening particles 20 and a coated layer 30 covering at least a portion of the roughening particles 20. The roughening particles 20 are formed not only near the center of the protrusions 11 on the surface of the copper foil 10, but also around the recesses 12 (the ends of the protrusions 11). Furthermore, the excessive growth of the roughening particles 20 formed on the protrusions 11 on the surface of the copper foil 10 is suppressed by adding a trace amount of tungsten compound to the plating solution. Therefore, the roughening particles 20 do not excessively grow into large particles, but have a complex shape growing in all directions. It is believed that this structure can be obtained by controlling the variation of the surface treatment layer's Vmp within the aforementioned range.

[0084] The coarsening particles 20 are not particularly limited and 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. Preferably, the coarsening particles 20 are formed from copper or copper alloys, particularly copper.

[0085] The coating 30 is not particularly limited and can be formed from copper, silver, gold, nickel, cobalt, zinc, etc.

[0086] The roughening layer can be formed by electroplating. In particular, the roughening particles 20 can be formed by electroplating using a plating solution with trace amounts of tungsten compound added.

[0087] There are no particular limitations on the tungsten compound used; for example, sodium tungstate (Na2WO4) can be used.

[0088] The content of tungsten compound in the plating solution is preferably 1 ppm or more. At this content, excessive growth of coarsened particles 20 formed on the protrusions 11 can be suppressed, and coarsened particles 20 are easily formed around the recesses 12. Furthermore, the upper limit of the tungsten compound content is not particularly limited, but from the viewpoint of suppressing increased resistance, 20 ppm is preferred.

[0089] The electroplating conditions for forming the roughening layer can be adjusted according to the electroplating equipment used, and are not particularly limited. Typical conditions are as follows. Furthermore, each electroplating step can be performed once or multiple times.

[0090] (Conditions for the formation of coarsened particles 20)

[0091] Plating solution composition: 5–15 g / L Cu, 40–100 g / L sulfuric acid, 1–6 ppm sodium tungstate

[0092] Plating solution temperature: 20~50℃

[0093] Electroplating conditions: Current density 30~90A / dm 2 Time: 0.1 to 8 seconds

[0094] (Conditions for the formation of the coating 30)

[0095] Plating solution composition: 10-30 g / L Cu, 70-130 g / L sulfuric acid

[0096] Plating solution temperature: 30~60℃

[0097] Electroplating conditions: Current density 4.8~15A / dm 2 Time: 0.1 to 8 seconds

[0098] The heat-resistant treatment layer and the rust-proof treatment layer are not particularly limited and can be formed from materials known in the art. Furthermore, the heat-resistant treatment layer sometimes also functions as a rust-proof treatment layer, so it is also possible to form a single layer that functions as both a heat-resistant treatment layer and a rust-proof treatment layer.

[0099] As a heat-resistant and / or rust-proof layer, it can be formed into 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 (or any form of metal, alloy, oxide, nitride, sulfide, etc.). The heat-resistant and / or rust-proof layer is preferably a Ni-Zn layer.

[0100] The heat-resistant and rust-proof treatment layers can be formed by electroplating. The conditions can be adjusted depending on the electroplating equipment used and are not particularly limited. The conditions for forming the heat-resistant layer (Ni-Zn layer) using general electroplating equipment are as follows. Furthermore, electroplating can be performed once or multiple times.

[0101] Plating solution composition: 1-30 g / L Ni, 1-30 g / L Zn

[0102] pH value of plating solution: 2-5

[0103] Plating solution temperature: 30~50℃

[0104] Electroplating conditions: Current density 0.1~10A / dm 2 Time: 0.1 to 5 seconds

[0105] The chromate treatment layer is not particularly limited and can be formed from materials known in the art.

[0106] Here, the term "chromate-treated layer" in this specification refers to a layer formed from a liquid containing chromic anhydride, chromic acid, dichromic acid, chromate, or dichromate. The chromate-treated layer may contain elements such as cobalt, iron, nickel, molybdenum, zinc, tantalum, copper, aluminum, phosphorus, tungsten, tin, arsenic, and titanium (or any form of metal, alloy, oxide, nitride, or sulfide). Examples of chromate-treated layers include those treated with an aqueous solution of chromic anhydride or potassium dichromate, and those treated with a solution containing chromic anhydride, potassium dichromate, and zinc.

[0107] A chromate-treated layer can be formed by well-known methods such as chromate impregnation or electrolytic chromate treatment. The conditions for these methods are not particularly limited; for example, the conditions for forming a general chromate-treated layer are as follows. Furthermore, chromate treatment can be performed once or multiple times.

[0108] The chromate solution composition is: 1–10 g / L K₂Cr₂O₇, 0.01–10 g / L Zn

[0109] pH of chromate solution: 2-5

[0110] Chromate solution temperature: 30~55℃

[0111] Electrolysis conditions: Current density 0.1~10A / dm³ 2 The time is 0.1 to 5 seconds (for electrolytic chromate treatment).

[0112] The silane coupling treatment layer is not particularly limited and can be formed from materials known in the art.

[0113] Here, "silane coupling treatment layer" in this specification refers to a layer formed by a silane coupling agent.

[0114] The silane coupling agent is not particularly limited, and those known in the art can be used. Examples of silane coupling agents include amino-based silane coupling agents, epoxy-based silane coupling agents, mercapto-based silane coupling agents, methacryloxy-based silane coupling agents, vinyl-based silane coupling agents, imidazole-based silane coupling agents, and triazine-based silane coupling agents. Among these, amino-based silane coupling agents and epoxy-based silane coupling agents are preferred. Two or more of the above-mentioned silane coupling agents can be used alone or in combination.

[0115] A representative method for forming a silane coupling treatment layer is to form the silane coupling treatment layer by coating a 1-3 vol% aqueous solution of the aforementioned silane coupling agent and then drying it.

[0116] The copper foil 10 is not particularly limited and can be either electrolytic copper foil or rolled copper foil.

[0117] Electrolytic copper foil is generally manufactured by electrolytically extracting copper from a copper sulfate plating bath onto a titanium or stainless steel roller. It has a flat S-side (polished surface) formed on the side of the rotating roller and an M-side (matte surface) formed on the opposite side of the S-side. The M-side of the electrolytic copper foil typically has minute irregularities. Furthermore, the S-side of the electrolytic copper foil has minute irregularities due to the transfer of abrasive stripes from the rotating roller formed during the grinding process.

[0118] Furthermore, rolled copper foil has tiny unevenness on its surface because oil pits are formed on the surface during the rolling process due to the rolling oil.

[0119] The material of copper foil 10 is not particularly limited. When copper foil 10 is rolled copper foil, high-purity copper such as refined 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 for circuit patterns on printed wiring boards, can be used. Furthermore, for example, copper alloys such as Sn-doped copper, Ag-doped copper, copper alloys with added Cr, Zr, or Mg, or Carson-based copper alloys with added Ni and Si can also be used. Moreover, in this specification, "copper foil 10" also includes the concept of copper alloy foil.

[0120] The thickness of the copper foil 10 is not particularly limited. For example, it can be set to 1-1000μm, or 1-500μm, or 1-300μm, or 3-100μm, or 5-70μm, or 6-35μm, or 9-18μm.

[0121] The surface-treated copper foil having the above-described structure can be manufactured according to methods known in the art. Here, parameters such as the variation in Vmp of the surface-treated layer can be controlled by adjusting the formation conditions of the surface-treated layer, particularly the formation conditions of the roughening treatment layer described above.

[0122] In the embodiment of the present invention, the surface-treated copper foil controls the variation of Vmp of the surface-treated layer to be 0.0010–0.0110 μm. 3 / μm 2 Therefore, it can improve adhesion to resin substrates, especially resin substrates suitable for high-frequency applications.

[0123] The copper-clad laminate of the present invention comprises the above-described surface-treated copper foil and a resin substrate to which a surface-treated layer is attached.

[0124] The copper-clad laminate can be manufactured by attaching a resin substrate to the surface treatment layer of the aforementioned surface-treated copper foil.

[0125] The resin substrate is not particularly limited, and those known in the art can be used. Examples of resin substrates include paper-based phenolic resins, paper-based epoxy resins, synthetic fiber cloth-based epoxy resins, glass cloth-paper composite substrate epoxy resins, glass cloth-glass nonwoven fabric composite substrate epoxy resins, glass cloth-based epoxy resins, polyester films, polyimide resins, liquid crystal polymers, fluororesins, etc. Among these, polyimide resins are preferred.

[0126] The bonding method between the surface-treated copper foil and the resin substrate is not particularly limited, and can be carried out according to methods known in the art. For example, the surface-treated copper foil and the resin substrate can be laminated and then thermo-pressed together.

[0127] The copper-clad laminate manufactured in the above manner can be used in the manufacture of printed wiring boards.

[0128] The copper-clad laminate of the present invention, by using the above-described surface-treated copper foil, can improve adhesion to resin substrates, especially resin substrates suitable for high-frequency applications.

[0129] The printed wiring board of the present invention includes a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate.

[0130] This printed circuit board can be manufactured by etching the surface-treated copper foil of the aforementioned copper-clad laminate to form a circuit pattern. The method for forming the circuit pattern is not particularly limited, and well-known methods such as subtractive or semi-additive methods can be used. However, the subtractive method is preferred.

[0131] When manufacturing printed wiring boards using a subtractive process, the following method is preferred: First, a resist is applied to the surface of the surface-treated copper foil of the copper-clad laminate, and then exposed and developed to form a specific resist pattern. Next, the portion of the surface-treated copper foil where the resist pattern is not formed (the excess portion) is etched away to form a circuit pattern. Finally, the resist pattern on the surface-treated copper foil is removed.

[0132] Furthermore, the various conditions in this subtraction method are not particularly limited and can be carried out according to conditions known in the technical field.

[0133] The printed wiring board of the embodiment of the present invention, due to the use of the above-mentioned copper-clad laminate, exhibits excellent adhesion between the resin substrate, especially a resin substrate suitable for high-frequency applications, and the circuit pattern.

[0134] [Example]

[0135] The embodiments of the present invention will be described in more detail below through examples, but the present invention is not limited to the examples described.

[0136] (Example 1)

[0137] A 12μm thick rolled copper foil (HA-V2 foil manufactured by JX Metals Co., Ltd.) was prepared. After degreasing and pickling one side, a roughening treatment layer, a heat-resistant treatment layer (Ni-Zn layer), a chromate treatment layer, and a silane coupling treatment layer were sequentially formed as surface treatment layers to obtain a surface-treated copper foil. The formation conditions of each treatment layer are as follows.

[0138] (1) Roughening treatment layer

[0139] <Conditions for the formation of coarsened particles>

[0140] The plating solution consists of 11 g / L Cu, 50 g / L sulfuric acid, and 5 ppm tungsten (derived from sodium tungstate dihydrate).

[0141] Plating solution temperature: 27℃

[0142] Electroplating conditions: Current density 74.8 A / dm 2 Time: 0.58 seconds

[0143] Electroplating treatment times: 2 times

[0144] <Conditions for the formation of the coating>

[0145] Plating solution composition: 20 g / L Cu, 100 g / L sulfuric acid

[0146] Plating solution temperature: 50℃

[0147] Electroplating conditions: Current density 11.0 A / dm 2 Time: 1.10 seconds

[0148] Electroplating treatment times: 2 times

[0149] (2) Heat-resistant treatment layer

[0150] <Conditions for the formation of Ni-Zn layers>

[0151] Plating solution composition: 23.5 g / L Ni, 4.5 g / L Zn

[0152] pH value of plating solution: 3.6

[0153] Plating solution temperature: 40℃

[0154] Electroplating conditions: Current density 0.68 A / dm 2 Time: 0.56 seconds

[0155] Electroplating treatment times: 1 time

[0156] (3) Chromate-treated layer

[0157] <Conditions for the formation of the electrolytic chromate treatment layer>

[0158] The chromate solution composition is: 3 g / L K₂Cr₂O₇, 0.33 g / L Zn

[0159] Chromate solution pH: 3.7

[0160] Chromate solution temperature: 55℃

[0161] Electrolysis conditions: Current density 1.90 A / dm³ 2 Time: 0.56 seconds

[0162] Chromate treatment times: 2 times

[0163] (4) Silane coupling treatment layer

[0164] A 1.2 vol% aqueous solution of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane was coated and dried to form a silane coupling treatment layer.

[0165] (Example 2)

[0166] Except for the following changes, the surface-treated copper foil was obtained under the same conditions as in Example 1.

[0167] <Conditions for the formation of coarsened particles>

[0168] Plating solution composition: 11 g / L Cu, 50 g / L sulfuric acid, 6 ppm tungsten (derived from sodium tungstate dihydrate).

[0169] Electroplating conditions: Current density 38.8 A / dm 2 Time: 1.27 seconds

[0170] <Conditions for the formation of the coating>

[0171] Electroplating conditions: Current density 8.2 A / dm 2 Time: 1.44 seconds

[0172] <Conditions for the formation of Ni-Zn layers>

[0173] Electroplating conditions: Current density 0.59 A / dm 2 Time: 0.73 seconds

[0174] <Conditions for the formation of the electrolytic chromate treatment layer>

[0175] Electrolysis conditions: Current density 1.42 A / dm³ 2 Time: 0.73 seconds

[0176] (Example 3)

[0177] Except for the following changes, the surface-treated copper foil was obtained under the same conditions as in Example 1.

[0178] <Conditions for the formation of coarsened particles>

[0179] Electroplating conditions: Current density 46.8 A / dm 2 Time: 1.01 seconds

[0180] <Conditions for the formation of the coating>

[0181] Electroplating conditions: Current density 9.6 A / dm 2 Time: 1.44 seconds

[0182] <Conditions for the formation of Ni-Zn layers>

[0183] Electroplating conditions: Current density 0.88 A / dm 2 Time: 0.73 seconds

[0184] <Conditions for the formation of the electrolytic chromate treatment layer>

[0185] Electrolysis conditions: Current density 1.42 A / dm³ 2 Time: 0.73 seconds

[0186] (Example 4)

[0187] A 12μm thick rolled copper foil (HG foil manufactured by JX Metals Co., Ltd.) was prepared. After degreasing and pickling one side, a roughening treatment layer, a heat-resistant treatment layer (Ni-Zn layer), a chromate treatment layer, and a silane coupling treatment layer were sequentially formed as surface treatment layers to obtain a surface-treated copper foil. The formation conditions of each treatment layer are as follows.

[0188] (1) Roughening treatment layer

[0189] <Conditions for the formation of coarsened particles>

[0190] Plating solution composition: 12 g / L Cu, 50 g / L sulfuric acid, 5 ppm tungsten (derived from sodium tungstate dihydrate).

[0191] Plating solution temperature: 27℃

[0192] Electroplating conditions: Current density 48.3 A / dm 2 Time: 0.81 seconds

[0193] Electroplating treatment times: 2 times

[0194] <Conditions for the formation of the coating>

[0195] Plating solution composition: 20 g / L Cu, 100 g / L sulfuric acid

[0196] Plating solution temperature: 50℃

[0197] Electroplating conditions: Current density 11.9 A / dm 2 Time: 1.15 seconds

[0198] Electroplating treatment times: 2 times

[0199] (2) Heat-resistant treatment layer

[0200] <Conditions for the formation of Ni-Zn layers>

[0201] Plating solution composition: 23.5 g / L Ni, 4.5 g / L Zn

[0202] pH value of plating solution: 3.6

[0203] Plating solution temperature: 40℃

[0204] Electroplating conditions: Current density 1.07 A / dm 2 Time: 0.59 seconds

[0205] Electroplating treatment times: 1 time

[0206] (3) Chromate-treated layer

[0207] <Conditions for the formation of the electrolytic chromate treatment layer>

[0208] The chromate solution composition is: 3 g / L K₂Cr₂O₇, 0.33 g / L Zn

[0209] Chromate solution pH: 3.65

[0210] Chromate solution temperature: 55℃

[0211] Electrolysis conditions: Current density 1.91 A / dm³ 2 Time: 0.59 seconds

[0212] Chromate treatment times: 2 times

[0213] (4) Silane coupling treatment layer

[0214] A 1.2 vol% aqueous solution of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane was coated and dried to form a silane coupling treatment layer.

[0215] (Comparative Example 1)

[0216] The rolled copper foil (untreated copper foil) used in Example 1 was used as a comparison.

[0217] (Comparative Example 2)

[0218] Except for the following changes, the surface-treated copper foil was obtained under the same conditions as in Example 1.

[0219] <Conditions for the formation of coarsened particles>

[0220] Plating solution composition: 11 g / L Cu, 50 g / L sulfuric acid

[0221] Electroplating conditions: Current density 38.8 A / dm 2 Time: 1.27 seconds

[0222] <Conditions for the formation of the coating>

[0223] Electroplating conditions: Current density 8.2 A / dm 2 Time: 1.44 seconds

[0224] <Conditions for the formation of Ni-Zn layers>

[0225] Electroplating conditions: Current density 0.59 A / dm 2 Time: 0.73 seconds

[0226] <Conditions for the formation of the electrolytic chromate treatment layer>

[0227] Electrolysis conditions: Current density 1.42 A / dm³ 2 Time: 0.73 seconds

[0228] The surface-treated copper foil or copper foil obtained in the above embodiments and comparative examples were evaluated for the following characteristics.

[0229] <Vmp, Ssk, Sa, Sq and Sku>

[0230] Measurements (image capture) were performed using a laser microscope (LEXTOLS4000) manufactured by Olympus Corporation, in accordance with ISO 25178-2:2012. Image analysis was performed using the analysis software of a laser microscope (LEXT OLS4100) manufactured by Olympus Corporation. The results were calculated by averaging the values ​​measured and analyzed at any five locations. Furthermore, the measurement temperature was set to 23–25°C. The main settings for the laser microscope and analysis software are as follows.

[0231] Objective lens: MPLAPON 50XLEXT (Magnification: 50x, Numerical aperture: 0.95, Immersion type: Air, Mechanical barrel length: ∞, Cover glass thickness: 0, Field of view number: FN18)

[0232] Optical zoom ratio: 1x

[0233] Scanning mode: XYZ high precision (height resolution: 60nm, number of pixels for data acquisition: 1024×1024)

[0234] Image dimensions [pixels]: 257μm (width) × 258μm (height) [1024×1024]

[0235] (Since the measurement was taken in the transverse direction, the estimated length is equivalent to 257 μm.)

[0236] DIC: Close

[0237] Multilayer: Off

[0238] Laser intensity: 100

[0239] Compensation: 0

[0240] Confocal grade: 0

[0241] Beam diameter stop: Closed

[0242] Take the average value of the image: 1 time

[0243] Noise Reduction: On

[0244] Uneven brightness correction: On

[0245] Optical noise filter: On

[0246] Cutoff: When measuring P1 (Vmp), use λc = 200 μm and λs = 2 μm, and do not use λf. When measuring P2 (Vmp), Ssk, Sa, Sq, and Sku, use λc = 200 μm, and do not use λs and λf.

[0247] Filter: Gaussian filter

[0248] Noise Removal: Pre-measurement Processing

[0249] Surface (slope) correction: implementation

[0250] Brightness: Adjust to the range of 30-50.

[0251] Brightness should be set appropriately according to the hue of the object being measured. The above settings are suitable when measuring the surface of surface-treated copper foil with L* = -69 to -10, a* = 2 to 32, and b* = 221.

[0252] Furthermore, for Vmp, the change in Vmp is calculated according to the above formula (1).

[0253] Furthermore, the λc filter is equivalent to the L filter in ISO 25178-2:2012.

[0254] <Determination of the hue of the object being measured>

[0255] The MiniScan EZ Model 4000L (registered trademark) manufactured by HunterLab was used as the measuring instrument to measure L*, a*, and b* of the CIE L*a*b* colorimetric system according to JIS Z8730:2009. Specifically, the surface-treated copper foil or the object surface of the copper foil obtained in the above embodiments and comparative examples was pressed against the photosensitive part of the measuring instrument, and the measurement was performed without light entering from the outside. Furthermore, the measurement of L*, a*, and b* was performed based on geometric condition C of JIS Z8722:2009. The main conditions of the measuring instrument are as follows.

[0256] Optical system: d / 8°, integrating sphere size: 63.5mm, observation light source: D65

[0257] Measurement method: Reflectance

[0258] Illumination diameter: 25.4mm

[0259] Measured diameter: 20.0 mm

[0260] Measurement wavelength and interval: 400–700 nm, 10 nm

[0261] Light source: Pulsed xenon lamp, single emission / measurement

[0262] Traceability Standards: Correction based on CIE 44 and ASTM E259 standards from the National Institute of Standards and Technology (NIST).

[0263] Standard observer: 10°

[0264] Furthermore, the white ceramic tile used as the benchmark for measurement uses the following object color.

[0265] When measured at D65 / 10°, the values ​​in the CIE XYZ colorimetric system are: X: 81.90, Y: 87.02, Z: 93.76.

[0266] <Peel strength>

[0267] After bonding the surface-treated copper foil to the polyimide resin substrate, a circuit with a width of 3 mm is formed along the MD direction (the direction of the long side of the rolled copper foil). The circuit formation is carried out according to conventional methods. Next, the peel strength (MD90° peel strength) of the circuit (surface-treated copper foil) relative to 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, is measured according to JIS C6471:1995. The measurement is performed three times, and the average value is taken as the peel strength result. If the peel strength is 0.50 kgf / cm or higher, it can be said that the adhesion between the circuit (surface-treated copper foil) and the resin substrate is good.

[0268] Furthermore, the copper foil of Comparative Example 1 was not evaluated as it could not be bonded to the polyimide resin substrate.

[0269] The results of the above characteristic evaluation are shown in Table 1.

[0270] [Table 1]

[0271]

[0272]

[0273] As shown in Table 1, the variation of Vmp of the surface treatment layer is 0.0010–0.0110 μm. 3 / μm 2 The surface-treated copper foils of Examples 1-4 within the range exhibit high peel strength.

[0274] On the other hand, the surface-treated copper foil of Comparative Example 2, whose peel strength is low, has a variation in Vmp of the surface-treated layer that is outside a specific range.

[0275] Referring to the above results and the examination of the embodiments of the present invention described so far, according to the embodiments of the present invention, surface-treated copper foil capable of improving adhesion to resin substrates, especially resin substrates suitable for high-frequency applications, can be provided. Furthermore, according to the embodiments of the present invention, copper-clad laminates with excellent adhesion between resin substrates, especially resin substrates suitable for high-frequency applications, and surface-treated copper foil can be provided. Moreover, according to the embodiments of the present invention, printed wiring boards with excellent adhesion between resin substrates, especially resin substrates suitable for high-frequency applications, and circuit patterns can be provided.

Claims

1. A surface-treated copper foil, comprising a copper foil and a surface-treated layer formed on at least one side of the copper foil. The variation of Vmp of this surface treatment layer, expressed by the following formula (1), is 0.0052–0.0088 μm. 3 / μm 2 Without using a λs filter with a cutoff value of 2 μm, Sa is calculated to be 0.23–0.32 μm; Sq is calculated to be 0.29–0.40 μm; Ssk is calculated to be -0.53–0.28; and Sku is calculated to be 3.16–4.

04. The change in Vmp = P2 - P1...(1) In the formula, P1 is Vmp calculated by applying the λs filter, and P2 is Vmp calculated without applying the λs filter; When measuring P1, P2, Ssk, Sa, Sq, and Sku, a λc filter with a cutoff value of λc = 200 μm is used.

2. The surface-treated copper foil as described in claim 1, wherein, This surface treatment layer contains a roughening treatment layer.

3. A copper-clad laminate comprising a surface-treated copper foil as described in claim 1 or 2 and a resin substrate adhering to the surface-treated copper foil and the surface-treated layer thereof.

4. A printed wiring board having a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate as claimed in claim 3.

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