WO2023281774A1

WO2023281774A1 - Surface-treated copper foil, copper-clad laminate and printed wiring board

Info

Publication number: WO2023281774A1
Application number: PCT/JP2022/001217
Authority: WO
Inventors: 佑樹松岡; 翔平岩沢; 郁浩五刀; 誓哉中島; 敦史三木
Original assignee: Ｊｘ金属株式会社
Priority date: 2021-07-09
Filing date: 2022-01-14
Publication date: 2023-01-12
Also published as: KR20230110591A; CN116745468A; TW202302918A; JPWO2023281774A1

Abstract

The present invention provides a surface-treated copper foil which comprises a copper foil and a surface treatment layer that is formed on at least one surface of the copper foil. The surface treatment layer has a change ratio of Vmc of 23.00% to 40.00%, the change ratio of Vmc being represented by formula (1).　(1): (Change ratio of Vmc) = (P2 – P1)/P2 × 100 In the formula, P1 is the value of Vmc as calculated, while applying a λs filter having a cut-off value λs of 2 µm; and P2 is the value of Vmc as calculated without applying the λs filter.

Description

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

The present disclosure relates to surface-treated copper foils, copper-clad laminates, and printed wiring boards.

Copper-clad laminates are widely used in various applications such as flexible printed wiring boards. This flexible printed wiring board is made by etching the copper foil of a copper-clad laminate to form a conductor pattern (also called a "wiring pattern"), and mounting electronic components on the conductor pattern by connecting them with solder. manufactured.

In recent years, in electronic devices such as personal computers and mobile terminals, the frequency of electrical signals has increased as the speed and capacity of communication have increased, and there is a demand for flexible printed wiring boards that can handle this. In particular, the higher the frequency of an electrical signal, the greater the loss (attenuation) of signal power, making it more likely that data cannot be read. Therefore, it is desired to reduce the loss of signal power.

The causes of loss of signal power (transmission loss) in electronic circuits can be roughly divided into two. The first is conductor loss, that is, loss due to copper foil, and the second is dielectric loss, that is, loss due to resin substrate.
Conductor loss has a skin effect in a high frequency range, and current has the property of flowing on the surface of the conductor. Therefore, in order to reduce the conductor loss of high frequency signals, it is desirable to reduce the surface roughness of the copper foil. Hereinafter, the terms "transmission loss" and "conductor loss" in this specification mainly mean "transmission loss of high-frequency signals" and "conductor loss of high-frequency signals".

On the other hand, since the dielectric loss depends on the type of resin base material, it is possible to use a resin base material made of a low dielectric material (eg, liquid crystal polymer, low dielectric polyimide) in a circuit board through which high frequency signals flow. desirable. In addition, since the dielectric loss is also affected by the adhesive that bonds the copper foil and the resin substrate together, it is desirable to bond the copper foil and the resin substrate without using an adhesive.
Therefore, it has been proposed to form a surface treatment layer on at least one surface of the copper foil in order to bond the copper foil and the resin substrate without using an adhesive. For example, Patent Literature 1 proposes a method of providing a roughening treatment layer formed of roughening particles on a copper foil and forming a silane coupling treatment layer on the outermost layer.

Japanese Unexamined Patent Application Publication No. 2012-112009

The surface of the copper foil on which the surface treatment layer is formed generally has fine irregularities. For example, in the case of rolled copper foil, oil pits formed by rolling oil during rolling are formed on the surface as fine irregularities. In the case of electrolytic copper foil, polishing streaks formed on the rotating drum during polishing cause fine irregularities on the surface of the electrolytic copper foil on the rotating drum side deposited and formed on the rotating drum.
If there is a minute unevenness on the copper foil surface, for example, when forming a roughening treatment layer, the current concentrates on the unevenness of the copper foil surface, and the roughening particles overgrow. In and around these areas, the current is not sufficiently supplied, making it difficult for the roughened particles to grow. As a result, while coarse roughening particles are formed in the convex portions of the copper foil surface, the roughening particles are too small in the concave portions of the copper foil surface and the concave portions in the vicinity thereof, especially near the end of the oil pit. Insufficient adhesion of the roughening particles, that is, roughening particles on the copper foil surface are not uniformly formed. In the surface-treated copper foil, which has a large number of coarse roughened particles, when a force is applied to peel off the surface-treated copper foil after bonding to the resin base material, stress concentrates on the coarse roughened particles, making it easier to break. Adhesion to substrates may be reduced. In addition, in a surface-treated copper foil with roughened particles having an insufficient size, the anchoring effect of the roughened particles is reduced, and sufficient adhesiveness between the copper foil and the resin substrate may not be obtained.
In particular, resin substrates made from low-dielectric materials such as liquid crystal polymers and low-dielectric polyimides are more difficult to adhere to copper foils than conventional resin substrates. It is desired to develop a method to increase the
In addition, although the silane coupling treatment layer has the effect of improving the adhesion between the copper foil and the resin base material, the effect of improving the adhesion may not be sufficient depending on the type.

The embodiments of the present invention have been made to solve the above problems, and in one aspect, it is possible to improve the adhesiveness to resin substrates, particularly resin substrates suitable for high frequency applications. An object of the present invention is to provide a surface-treated copper foil that is superior in quality.
In another aspect, an embodiment of the present invention provides a copper-clad laminate having excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and a surface-treated copper foil. aim.
Furthermore, in another aspect, an object of the embodiments of the present invention is to provide a printed wiring board having excellent adhesion between a resin substrate, particularly a resin substrate suitable for high frequency applications, and a circuit pattern. .

The present inventors have made intensive research on surface-treated copper foils to solve the above problems. As a result, the copper foil surface is It was found that the overgrowth of the roughening particles formed on the convex portions of the copper foil can be suppressed and the roughening particles can be easily formed around the concave portions of the copper foil surface. The present inventors analyzed the surface shape of the surface-treated copper foil thus obtained, and found that the rate of change in Vmc of the surface-treated layer is closely related to the surface shape. and completed the embodiment of the present invention.

That is, in one aspect, an embodiment of the present invention has a copper foil and a surface treatment layer formed on at least one surface of the copper foil, and the surface treatment layer is represented by the following formula (1) It relates to a surface-treated copper foil having a Vmc change rate 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 cutoff value λs of 2 μm, and P2 is Vmc calculated without applying the λs filter.

In another aspect, the embodiments of the present invention relate to a copper-clad laminate comprising the surface-treated copper foil and a resin substrate adhered to the surface treatment layer of the surface-treated copper foil.
Furthermore, in another aspect, the 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.

According to an embodiment of the present invention, in one aspect, it is possible to provide a surface-treated copper foil capable of enhancing adhesiveness to a resin substrate, particularly a resin substrate suitable for high frequency applications.
Further, according to an embodiment of the present invention, in another aspect, there is provided a copper-clad laminate having excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and a surface-treated copper foil. be able to.
Furthermore, according to the embodiment of the present invention, in another aspect, it is possible to provide a printed wiring board having excellent adhesion between a resin substrate, particularly a resin substrate suitable for high frequency applications, and a circuit pattern. .

It is a typical load curve of a surface treatment layer. FIG. 4 is a schematic diagram for explaining roughening particles and Vmc that constitute the surface treatment layer. 1 is a schematic enlarged cross-sectional view of a surface-treated copper foil having a roughened layer on one surface of the copper foil; FIG.

Hereinafter, preferred embodiments of the present invention will be specifically described, but the present invention should not be construed as being limited to these, and as long as it does not depart from the gist of the present invention, , various modifications, improvements, etc. may be made. A plurality of constituent elements disclosed in the following embodiments can be combined appropriately to form various inventions. For example, some constituent elements may be deleted from all the constituent elements shown in the following embodiments, or constituent elements of different embodiments may be combined as appropriate.

A surface-treated copper foil according to an embodiment of the present invention has 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 only on one surface of the copper foil, or may be formed on both surfaces of the copper foil. When surface treatment layers are formed on both surfaces of the copper foil, the types of surface treatment layers may be the same or different.

The surface profile of the surface treatment layer can be specified using surface texture parameters obtained by measuring the surface texture and analyzing the load curve calculated from the measured data in accordance with ISO 25178-2:2012.
Before explaining the load curve, the load area ratio will be explained first.
The load area ratio is a ratio obtained by dividing a region corresponding to a cross section of a three-dimensional measurement object cut along a plane of a certain height by the area of the measurement visual field. In the present disclosure, the object to be measured is assumed to be a copper foil, a surface-treated layer of a surface-treated copper foil, or the like. The load curve is a curve representing the load area ratio at each height. The height near 0% of the load area ratio represents the height of the highest portion of the object to be measured, and the height near 100% of the load area ratio represents the height of the lowest portion of the object to be measured.

Next, FIG. 1 shows a typical load curve of the surface treatment layer. The load curve can be utilized to express the volume of the body portion and the volume of the space portion of the surface treatment layer. The volume of the entity portion corresponds to the volume of the portion occupied by the entity of the object to be measured in the field of view for measurement, and the volume of the space portion corresponds to the volume occupied by the space between the portions of the entity in the field of view to be measured. The load curve described in this disclosure is divided into a trough portion, a core portion and a peak portion, with the positions where the load area ratio is 10% and 80% as boundaries. With reference to FIG. 1, when describing the surface treatment layer according to the embodiment of the present invention, Vvv is the volume of the space at the valley of the surface treatment layer, Vvc is the volume of the space at the core of the surface treatment layer, Vmp and Vmc respectively mean the volume of the substance in the peaks of the surface treatment layer and the volume of the substance in the core of the surface treatment layer.
It should be noted that the mountain portion is a high portion of the object to be measured. A trough is a portion having a low height in the object to be measured. The core portion is a portion of the object to be measured other than the peaks and valleys, that is, the portion having a height close to the average.

The actual volume Vmp at peaks is the volume of the peaks, i.e., the volume of the substantial portion in the high portion of the object to be measured, and means the volume of the substantial portion in the particularly high portion of the surface treatment layer. . Here, the substantial portion in the portion of the surface treatment layer having a particularly high height can be interpreted as a portion resulting from overgrown grains (especially roughened grains) among grains.
The volume Vmc of the core portion is the volume of the core portion, that is, the volume of the body portion in the portion of the object to be measured that has a height close to the average, and the volume of the body portion in the portion of the surface treatment layer that has the average height. means Here, the substantial part in the portion of the average height of the surface treatment layer is caused by particles of average size (especially roughened particles) formed on the relatively smooth portion of the copper foil surface. It can be interpreted as the part that
In summary, as a result of the above analysis by the present inventors, in the surface-treated copper foil according to the embodiment of the present invention, Vmp is the volume of the overgrown large grains, and Vmc is the volume of the average size. It was found that each correlates with the volume of the solid part of the particle. It should be noted that although roughened particles are used as examples of particles in the following description, it should be noted that the particles are not limited to roughened particles.

Measurement data for measuring the surface properties of the surface-treated copper foil according to the embodiment of the present invention can be obtained using a laser microscope such as a confocal laser microscope. Here, by subjecting the measured data to Fourier transform, the measured data can be separated into waveforms having various periods and amplitudes. After applying a filter that attenuates the amplitude of the waveform in a specific range to each waveform after separation, the surface properties to be noticed from the measurement data are analyzed by synthesizing all the waveforms again. The inventors thought that the parameters could be calculated.

In the analysis of surface roughness measurement data, the present inventors found that surface texture parameters calculated by applying a λs filter with a cutoff value λs of 2 μm and surface texture parameters calculated without applying this λs filter By using a combination of rice field.
Here, the λs filter is a profile filter that greatly 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 amount by which the λs filter attenuates the amplitude depends on the wavelength of the waveform. At wavelengths with a cutoff value λs, the amplitude is attenuated to 50% of its original value, and at waveforms with shorter wavelengths, the amplitude is attenuated more.
The cutoff value λs of 2 μm is a size positioned between the size of the roughening particles forming the surface treatment layer and the size of the oil pit. Since the measurement data obtained by setting the cutoff value λs to 2 μm is data derived from a waveform with a period shorter than the cutoff value λs, it is understood that the data derived from roughening particles are removed. can. Based on this, the difference between the surface texture parameter calculated without applying the λs filter with a cutoff value λs of 2 μm and the surface texture parameter calculated using this λs filter is the oil pit information. It can be said that it is the information of the removed surface treatment layer, that is, the information of the roughening particles constituting the surface treatment layer.

Based on the above knowledge, the present inventors analyzed various surface property parameters obtained from the load curve, and found that the change rate of Vmc represented by the following formula (1) in the surface treatment layer was It was found to be closely related to the adhesion amount of average-sized roughening particles forming the treated layer.
Change rate 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.

Here, FIG. 2 shows a schematic diagram for explaining the roughening particles and Vmc that constitute the surface treatment layer. As shown in FIG. 2, the surface treatment layer includes average-sized roughening particles A and overgrown roughening particles B. As shown in FIG. As already explained above, Vmc corresponds to the volume of the average-sized roughened particles A formed on the relatively smooth portion of the copper foil surface, and the average-sized roughened particles It is considered to be correlated with the amount of A adhered. Vmc is not a little affected by macroscopic shapes such as oil pits, and in order to read the information of the surface treatment layer more accurately, it is necessary to remove the contribution of macroscopic shapes. P1 can be interpreted as a value of Vmc from which information derived from roughening particles has been removed, in other words, a value of Vmc from which information derived from oil pits or the like remains. Taking the difference between P2 and P1 means removing information derived from macroscopic shapes such as oil pits included in Vmc. As a result, it is possible to accurately extract information correlated with the adhesion amount of the roughening particles A having an average size.
It is considered that the average-sized roughened particles A formed on the relatively smooth portion of the copper foil surface have a great relationship with the adhesive strength between the resin substrate and the surface treatment layer. It is thought that overgrown (coarse) roughened particles B lead to roughening breakage, and excessively small roughened particles do not bite into the resin substrate in the first place. Therefore, by using a surface-treated copper foil in which the change rate of Vmc of the surface-treated layer, which correlates with the average adhesion amount of roughening particles A, is controlled within an appropriate range, adhesion to the resin substrate is improved. becomes possible.
From this point of view, the surface-treated copper foil according to the embodiment of the present invention having a rate of change in Vmc of 23.00 to 40.00% exhibits sufficient adhesion to resin substrates. From the viewpoint of stably obtaining this effect, the rate of change of Vmc is preferably 23.00 to 32.00%, more preferably 23.00 to 31.00%.

The surface treatment layer preferably has an Sku (kurtosis) of 2.50 to 4.50 calculated without applying the λs filter.
Sku is a parameter that expresses the sharpness (kurtosis) of a height histogram created based on the average height. For example, Sku=3.00 means that the height distribution is a normal distribution. Also, in the case of Sku>3.00, the larger the numerical value, the more concentrated the height distribution. Conversely, when Sku<3.00, the smaller the value, the more dispersed the height distribution.

The surface-treated copper foil according to the embodiment of the present invention has unevenness on the surface, and the unevenness contributes to the improvement of adhesion between the copper foil and the resin substrate. The Sku of the surface treatment layer serves as an index for evaluating the height distribution of the unevenness.
The Sku of the surface treatment layer being 2.50 to 4.50 means that the height distribution is a normal distribution or a distribution state close thereto. On the other hand, if the Sku of the surface treatment layer is less than 2.50, the height distribution means that the distribution is unbiased. If the Sku of the surface treatment layer is greater than 4.50, it means that the height distribution is uneven, that is, the surface of the surface treatment layer has a portion with a certain height that protrudes and occupies a large portion. means that
The height distribution of the surface treatment layer is a normal distribution or a distribution state close to it. It means that there are few roughening particles and there are few places where roughening particles are not formed around the recesses (ends of the protrusions) on the copper foil surface. Therefore, when the Sku of the surface treatment layer is 2.50 to 4.50, the overgrowth of the roughened particles formed on the convex portions of the copper foil surface is suppressed, and also around the concave portions on the copper foil surface. It means a state in which roughened particles are formed.

A surface-treated copper foil with a large number of roughened particles and a surface-treated copper foil with portions where no roughened particles are formed are not preferable from the viewpoint of adhesiveness to a resin substrate. For example, in a surface-treated copper foil with a large number of roughening particles, when a force is applied to peel off the surface-treated copper foil after bonding to the resin base material, stress concentrates on the coarser roughening particles and makes them easier to break. It is thought that the adhesive force to the resin substrate is lowered. In addition, in the surface-treated copper foil where roughening particles are not formed, the anchoring effect of the roughening particles cannot be sufficiently secured, and the adhesive strength between the surface-treated copper foil and the resin substrate decreases. Conceivable.
Therefore, from the viewpoint of stably obtaining adhesive strength to the resin substrate, the lower limit of Sku of the surface treatment layer is preferably 2.90, and the upper limit is preferably 4.10.
The Sku of the surface treatment layer can be specified by measuring the surface roughness and analyzing the contour curve calculated from the measurement data in accordance with ISO 25178-2:2012.

The surface treatment layer preferably has an Sq (root mean square height) of 0.20 to 0.60 μm calculated without applying the λs filter. Sq is a parameter in the height direction defined in ISO 25178-2:2012, and represents the height variation of the protrusions on the surface of the surface treatment layer.
A large Sq of the surface treatment layer means that the height of the protrusions on the surface of the surface treatment layer varies greatly. If Sq is too large (variation in the height of the convex portion is too large), it may pose a problem from the viewpoint of quality control as an industrial product. Therefore, by setting the Sq of the surface treatment layer within the above range, it is possible to perform appropriate quality control while ensuring productivity by allowing some variation in the height of the protrusions. From the viewpoint of stably obtaining such effects, the Sq of the surface treatment layer preferably has a lower limit of 0.26 μm, more preferably 0.30 μm, still more preferably 0.34 μm, and an upper limit of preferably 0. 0.53 μm, more preferably 0.48 μm, even more preferably 0.43 μm.
The Sq of the surface treatment layer can be specified by measuring the surface roughness and analyzing the contour curve calculated from the measurement data in accordance with ISO 25178-2:2012.

The surface treatment layer preferably has an Sa (arithmetic mean height) of 0.20 to 0.40 μm calculated without applying the λs filter. Sa is a parameter in the height direction defined in ISO 25178-2:2012 and represents the average height difference from the average plane.
If the Sa of the surface-treated layer is large, the surface of the surface-treated layer becomes rough, so that the anchor effect is likely to be exhibited when the surface-treated copper foil is adhered to a resin base material. On the other hand, if the Sa of the surface-treated layer is too large, when a circuit board is fabricated by processing a copper-clad laminate in which the surface-treated copper foil and the resin substrate are bonded, transmission loss will occur due to the skin effect of the surface-treated copper foil. becomes larger. 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 of the surface-treated copper foil to the resin substrate and suppressing the transmission loss. From the viewpoint of stably obtaining such effects, the lower limit of Sa in the surface treatment layer is preferably 0.23 μm, more preferably 0.24 μm, and the upper limit is preferably 0.35 μm.
In addition, when emphasizing the suppression of transmission loss due to the skin effect and the ease of quality control as an industrial product, the surface treatment layer has a Sa of 0.20 to 0.32 μm and an Sq of 0.26 to 0. 0.40 μm is preferred.
The Sa of the surface treatment layer can be specified by measuring the surface roughness and analyzing the contour curve calculated from the measurement data according to ISO 25178-2:2012.

The surface treatment layer preferably has an Ssk (skewness) of −1.10 to 0.60 calculated without applying the λs filter.
Ssk is a parameter that expresses the degree of deviation (skewness) of a height histogram created with the average height as a reference. For example, Ssk=0.00 means that the height distribution is symmetrical about the mean line. Moreover, when Ssk>0.00, the larger the numerical value, the more the height distribution is biased downward with respect to the average line. Conversely, when Ssk<0.00, the smaller the value, the more the height distribution is biased upward with respect to the average line. Therefore, Ssk of the surface treatment layer serves as an index for evaluating the height distribution of unevenness of the surface treatment layer, like Sku.
The fact that Ssk is -1.10 to 0.60 means that, for example, when a roughening treatment layer is formed on the surface of the copper foil, roughening particles overgrown on the convex portions of the copper foil surface, that is, coarse roughness It means that there are few roughening particles and there are few places where roughening particles are not formed around the recesses (ends of the protrusions) on the copper foil surface. On the other hand, when it is less than -1.10, there are many places where the roughening particles are not formed around the recesses on the copper foil surface. Moreover, when Ssk is more than 0.60, a large number of overgrown roughened particles are present in the convex portions of the copper foil surface.
From the viewpoint of stably obtaining adhesive strength to the resin substrate, the upper limit of Ssk of the surface treatment layer is preferably 0.40, and the lower limit is preferably -0.80.
The Ssk of the surface treatment layer can be specified by measuring the surface roughness in accordance with ISO 25178-2:2012 and analyzing the contour curve calculated from the measurement data.

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 resistance treatment layers, rust prevention treatment layers, chromate treatment layers, silane coupling treatment layers, and the like. These layers can be used singly or in combination of two or more. Among them, the surface treatment layer preferably contains a roughening treatment layer from the viewpoint of adhesion to the resin substrate.
In addition, when the surface treatment layer contains one or more layers selected from the group consisting of a heat-resistant treatment layer, an antirust treatment layer, a chromate treatment layer and a silane coupling treatment layer, these layers are roughening treatment layers. It is preferably provided above.

Here, as an example, FIG. 3 shows a schematic enlarged cross-sectional view of a surface-treated copper foil having a roughened layer on one surface of the copper foil.
As shown in FIG. 3 , the roughening treatment layer formed on one surface of copper foil 10 includes roughening particles 20 and covering plating layer 30 covering at least part of 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 (ends of the protrusions 11). Moreover, overgrowth of the roughening particles 20 formed on the convex portions 11 of the copper foil 10 is suppressed by adding a small amount of a tungsten compound to the plating solution. Therefore, the roughened particles 20 do not overgrow into particles having a large particle size, and have a complicated shape that grows in each direction. It is considered that such a structure can be obtained by controlling the change rate of Vmc of the surface treatment layer within the above range.

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

The roughened layer can be formed by electroplating. In particular, the roughened particles 20 can be formed by electroplating using a plating solution containing a trace amount of tungsten compound.
Although the tungsten compound is not particularly limited, for example, sodium tungstate (Na ₂ WO ₄ ) can be used.
The content of the tungsten compound in the plating solution is preferably 1 ppm or more. With such a content, overgrowth of roughening particles 20 formed on convex portions 11 can be suppressed, and roughening particles 20 can be easily formed around concave portions 12 . Although the upper limit of the content of the tungsten compound is not particularly limited, it is preferably 20 ppm from the viewpoint of suppressing an increase in electrical resistance.

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

(Conditions for forming cover plating layer 30)
Plating solution composition: 10-30 g/L Cu, 70-130 g/L sulfuric acid Plating solution temperature: 30-60°C
Electroplating conditions: current density 4.8-15 A/dm ² , time 0.1-8 seconds

The heat-resistant layer and the rust-proof layer are not particularly limited, and can be formed from materials known in the art. In addition, since the heat-resistant treatment layer may also function as a rust-preventive treatment layer, a single layer having the functions of both the heat-resistant treatment layer and the rust-preventive treatment layer is formed as the heat-resistant treatment layer and the rust-preventive treatment layer. good too.
As the heat-resistant layer and/or rust-proof layer, nickel, zinc, tin, cobalt, molybdenum, copper, tungsten, phosphorus, arsenic, chromium, vanadium, titanium, aluminum, gold, silver, platinum group elements, iron, tantalum It can be a layer containing one or more elements selected from the group of (any form of metal, alloy, oxide, nitride, sulfide, etc.). Among them, the heat-resistant layer and/or the rust-proof layer is preferably a Ni—Zn layer.

The heat-resistant layer and the rust-proof layer can be formed by electroplating. The conditions may be adjusted according to the electroplating apparatus to be used, and are not particularly limited, but the conditions for forming the heat-resistant layer (Ni—Zn layer) using a general electroplating apparatus are as follows. be. Electroplating may be performed once or multiple times.
Plating solution composition: 1 to 30 g/L Ni, 1 to 30 g/L Zn
Plating solution pH: 2-5
Plating solution temperature: 30-50°C
Electroplating conditions: current density 0.1 to 10 A/dm ² , time 0.1 to 5 seconds

The chromate treatment layer is not particularly limited, and can be formed from materials known in the technical field.
As used herein, the term "chromate treatment layer" means a layer formed of a liquid containing chromic anhydride, chromic acid, dichromic acid, chromate, or dichromate. The chromate treatment layer contains elements such as cobalt, iron, nickel, molybdenum, zinc, tantalum, copper, aluminum, phosphorus, tungsten, tin, arsenic, titanium, etc. (any metal, alloy, oxide, nitride, sulfide, etc.) morphology). Examples of the chromate-treated layer include a chromate-treated layer treated with an aqueous solution of chromic acid anhydride or potassium dichromate, a chromate-treated layer treated with a treatment liquid containing chromic anhydride or potassium dichromate and zinc, and the like.

The chromate treatment layer can be formed by known methods such as immersion chromate treatment and electrolytic chromate treatment. These conditions are not particularly limited, but, for example, the conditions for forming a general chromate treatment layer are as follows. The chromate treatment may be performed once or multiple times.
Chromate liquid composition: 1-10 g/L K ₂ Cr ₂ O ₇ , 0.01-10 g/L Zn
Chromate solution pH: 2-5
Chromate liquid temperature: 30-55°C
Electrolytic conditions: current density 0.1 to 10 A/dm ² , time 0.1 to 5 seconds (for electrolytic chromate treatment)

The silane coupling-treated layer is not particularly limited, and can be formed from materials known in the art.
Here, the term "silane coupling treated layer" as used herein means a layer formed with a silane coupling agent.
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, and imidazole-based silane coupling agents. , triazine-based silane coupling agents, and the like. Among these, amino-based silane coupling agents and epoxy-based silane coupling agents are preferred. Said silane coupling agent can be used individually or in combination of 2 or more types.
A representative method for forming a silane coupling-treated layer includes a method of forming a silane coupling-treated layer by applying a 1 to 3% by volume aqueous solution of the above-mentioned silane coupling agent and drying it.

The copper foil 10 is not particularly limited, and may be either an electrolytic copper foil or a rolled copper foil.
Electrodeposited copper foil is generally produced by electrolytically depositing copper from a copper sulfate plating bath onto a titanium or stainless steel drum. and an M surface (matte surface) formed on the opposite side of the . The M side of the electrolytic copper foil generally has minute unevenness. In addition, the S side of the electrolytic copper foil has fine irregularities because polishing streaks formed on the rotary drum during polishing are transferred to the S side.
In addition, the rolled copper foil has oil pits formed by the rolling oil during rolling, so that the rolled copper foil has minute irregularities on its surface.

The material of the copper foil 10 is not particularly limited. High-purity copper such as alloy number C1020 or JIS H3510 alloy number C1011) can be used. Copper alloys such as Sn-containing copper, Ag-containing copper, copper alloys containing Cr, Zr, Mg, etc., and Corson copper alloys containing Ni, Si, etc. can also be used. In addition, in this specification, the "copper foil 10" is a concept including a copper alloy foil.

The thickness of the copper foil 10 is not particularly limited. can.

The surface-treated copper foil having the configuration as described above can be produced according to a method known in the technical field. Here, parameters such as the rate of change of Vmc of the surface treatment layer can be controlled by adjusting the conditions for forming the surface treatment layer, particularly the conditions for forming the above-described roughening treatment layer.

Since the surface-treated copper foil according to the embodiment of the present invention controls the Vmc change rate of the surface-treated layer to 23.00 to 40.00%, it is suitable for resin substrates, especially for high-frequency applications. can enhance the adhesion with.

A copper-clad laminate according to an embodiment of the present invention includes the surface-treated copper foil described above and a resin substrate adhered to the surface-treated layer of the surface-treated copper foil.
This copper-clad laminate can be produced by adhering a resin substrate to the surface-treated layer of the surface-treated copper foil.
The resin substrate is not particularly limited, and those known in the art can be used. Examples of resin base materials include paper base phenol resin, paper base epoxy resin, synthetic fiber cloth base epoxy resin, glass cloth/paper composite base epoxy resin, glass cloth/glass nonwoven cloth composite base epoxy resin, glass Examples include cloth-based epoxy resins, polyester films, polyimide resins, liquid crystal polymers, and fluorine resins. Among these resin substrates, polyimide resin is preferable.

The method for bonding the surface-treated copper foil and the resin substrate is not particularly limited, and can be performed according to a method known in the art. For example, a surface-treated copper foil and a resin base material may be laminated and thermocompression bonded.
The copper-clad laminate manufactured as described above can be used for manufacturing a printed wiring board.

Since the copper-clad laminate according to the embodiment of the present invention uses the surface-treated copper foil described above, it is possible to improve the adhesiveness to resin substrates, particularly resin substrates suitable for high-frequency applications.

A printed wiring board according to an embodiment of the present invention includes a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate.
This printed wiring board can be produced by etching the surface-treated copper foil of the copper-clad laminate to form a circuit pattern. A method for forming a circuit pattern is not particularly limited, and known methods such as a subtractive method and a semi-additive method can be used. Among them, the subtractive method is preferable as the method of forming the circuit pattern.

When manufacturing a printed wiring board by a subtractive method, it is preferable to carry out as follows. First, a predetermined resist pattern is formed by applying a resist to the surface of the surface-treated copper foil of the copper clad laminate, exposing and developing the resist. Next, the circuit pattern is formed by removing the surface-treated copper foil from the portion where the resist pattern is not formed (unnecessary portion) by etching. Finally, the resist pattern on the surface-treated copper foil is removed.
Various conditions in this subtractive method are not particularly limited, and can be carried out according to conditions known in the technical field.

Since the printed wiring board according to the embodiment of the present invention uses the above copper clad laminate, it has excellent adhesion between the resin substrate, particularly the resin substrate suitable for high frequency applications, and the circuit pattern. .

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

(Example 1)
Prepare a rolled copper foil (HA-V2 foil manufactured by JX Metals Co., Ltd.) with a thickness of 12 μm, degreasing and pickling one side, roughening treatment layer as a surface treatment layer, heat treatment layer (Ni-Zn layer ), a chromate-treated layer and a silane coupling-treated layer were sequentially formed to obtain a surface-treated copper foil. The conditions for forming each treated layer were as follows.
(1) Roughened layer <Conditions for forming roughened particles>
Plating solution composition: 11 g/L Cu, 50 g/L sulfuric acid, 5 ppm tungsten (from sodium tungstate dihydrate)
Plating solution temperature: 27°C
Electroplating conditions: current density 80.0 A/dm ² , time 0.51 seconds Number of electroplating treatments: 2 times

<Conditions for Forming Cover Plating Layer>
Plating solution composition: 20 g/L Cu, 100 g/L 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

(2) Heat-resistant layer <Conditions for forming Ni—Zn layer>
Plating solution composition: 23.5 g/L Ni, 4.5 g/L 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

(3) Chromate-treated layer <Conditions for forming electrolytic chromate-treated layer>
Chromate liquid composition: ₃ g/L _K2Cr2O7 , _0.33 g/L Zn
Chromate solution pH: 3.7
Chromate liquid temperature: 55°C
Electrolysis conditions: current density 2.20 A/dm ² , time 0.49 seconds Number of chromate treatments: 2 times

(4) Silane Coupling Treated Layer A 1.2% by volume aqueous solution of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane was applied and dried to form a silane coupling treated layer.

(Example 2)
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 cover plating layer>
Electroplating conditions: current density 9.6 A/dm ² , time 1.44 seconds <Conditions for Ni—Zn layer formation>
Electroplating conditions: current density 0.88 A/dm ² , time 0.73 seconds <Conditions for forming electrolytic chromate treatment layer>
Electrolysis conditions: current density 1.42 A/dm ² , time 0.73 seconds

(Example 3)
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 41.3 A/dm ² , time 1.15 seconds <Conditions for forming cover plating layer>
Electroplating conditions: current density 8.2 A/dm ² , time 1.44 seconds <Conditions for Ni—Zn layer formation>
Electroplating conditions: current density 0.73 A/dm ² , time 0.73 seconds <Conditions for forming electrolytic chromate treatment layer>
Electrolysis conditions: current density 1.51 A/dm ² , time 0.73 seconds

(Example 4)
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 of 54.8 A/dm ² , time of 0.90 seconds <Conditions for forming cover plating layer>
Electroplating conditions: current density 8.2 A/dm ² , time 1.44 seconds <Conditions for Ni—Zn layer formation>
Electroplating conditions: current density 0.73 A/dm ² , time 0.73 seconds <Conditions for forming electrolytic chromate treatment layer>
Electrolysis conditions: current density 1.51 A/dm ² , time 0.73 seconds

(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 cover plating layer>
Electroplating conditions: current density 9.6 A/dm ² , time 1.44 seconds <Conditions for Ni—Zn layer formation>
Electroplating conditions: current density 0.88 A/dm ² , time 0.73 seconds <Conditions for forming electrolytic chromate treatment layer>
Electrolysis conditions: current density 1.42 A/dm ² , time 0.73 seconds

(Example 6)
A rolled copper foil (HG foil manufactured by JX Metals Co., Ltd.) with a thickness of 12 μm is prepared, one side is degreased and pickled, and then a roughened layer and a heat-resistant layer (Ni—Zn layer) are formed as surface treatment layers. A surface-treated copper foil was obtained by sequentially forming a chromate-treated layer and a silane coupling-treated layer. The conditions for forming each treated layer were as follows.
(1) Roughened layer <Conditions for forming roughened particles>
Plating solution composition: 12 g/L Cu, 50 g/L sulfuric acid, 5 ppm tungsten (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

<Conditions for Forming Cover Plating Layer>
Plating solution composition: 20 g/L Cu, 100 g/L 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

(2) Heat-resistant layer <Conditions for forming Ni—Zn layer>
Plating solution composition: 23.5 g/L Ni, 4.5 g/L Zn
Plating solution pH: 3.6
Plating solution temperature: 40°C
Electroplating conditions: current density 1.07 A/dm ² , time 0.59 seconds Number of electroplating treatments: 1 time

(3) Chromate-treated layer <Conditions for forming electrolytic chromate-treated layer>
Chromate liquid composition: ₃ g/L _K2Cr2O7 , _0.33 g/L Zn
Chromate solution pH: 3.65
Chromate liquid temperature: 55°C
Electrolysis conditions: current density 1.91 A/dm ² , time 0.59 seconds Number of chromate treatments: 2 times

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

(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.
<Conditions for Forming Roughened Particles>
Plating solution composition: 11 g/L of Cu, 50 g/L of sulfuric acid Electroplating conditions: current density of 38.8 A/dm ² , time of 1.27 seconds <Conditions for forming overlying plating layer>
Electroplating conditions: current density 8.2 A/dm ² , time 1.44 seconds <Conditions for Ni—Zn layer formation>
Electroplating conditions: current density 0.59 A/dm ² , time 0.73 seconds <Conditions for forming electrolytic chromate treatment layer>
Electrolysis conditions: current density 1.42 A/dm ² , time 0.73 seconds

The surface-treated copper foils or copper foils obtained in the above examples and comparative examples were evaluated for the following properties.
<Vmc, Sku, Sq, Sa and Ssk>
In accordance with ISO 25178-2:2012, measurement (image photography) was performed using a laser microscope (LEXT OLS4000) manufactured by Olympus Corporation. The captured images were analyzed using analysis software for a laser microscope (LEXT OLS4100) manufactured by Olympus Corporation. The average value of the values measured and analyzed at any five locations was used as the result. The temperature during the measurement was 23 to 25°C. Main setting conditions for the laser microscope and analysis software are as follows.
Objective lens: MPLAPON50XLEXT (magnification: 50x, numerical aperture: 0.95, liquid immersion type: air, mechanical barrel length: ∞, cover glass thickness: 0, field number: FN18)
Optical zoom magnification: 1x Scanning mode: XYZ high precision (height resolution: 60 nm, number of pixels of captured data: 1024 x 1024)
Captured image size [Number of pixels]: Horizontal 257 μm × Vertical 258 μm [1024 × 1024]
(Since it is measured in the horizontal direction, it corresponds to 257 μm as an evaluation length)
DIC: Off Multilayer: Off Laser intensity: 100
Offset: 0
Confocal level: 0
Beam diameter aperture: OFF Image average: 1 time Noise reduction: ON Brightness unevenness correction: ON Optical noise filter: ON Cutoff: For P1 (Vmc) measurement, λc = 200 µm and λs = 2 µm are applied, and λf is Not applicable. When measuring P2 (Vmc), Sku, Sq, Sa and Ssk, λc=200 μm is applied and λs and λf are not applied.
Filter: Gaussian filter Noise removal: Pre-measurement processing Surface (tilt) correction: Implemented Brightness: Adjust to be in the range of 30 to 50 Brightness should be appropriately set according to the color tone to be measured. The above settings are appropriate values when measuring the surface of a surface-treated copper foil with L* of -69 to -10, a* of 2 to 32, and b* of 221.
As for Vmc, the change rate of Vmc was calculated according to the above formula (1).
Note that the λc filter corresponds to the L filter in ISO 25178-2:2012.

<Measurement of color tone of measurement target>
Using HunterLab's MiniScan (registered trademark) EZ Model 4000L as a measuring instrument, L*, a* and b* of the CIE L*a*b* color system were measured in accordance with JIS Z8730:2009. . Specifically, the measurement target surface of the surface-treated copper foil or copper foil obtained in the above examples and comparative examples was pressed against the photosensitive part of the measuring device, and the measurement was performed while preventing light from entering from the outside. In addition, L*, a* and b* were measured 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 Illumination diameter: 25.4mm
Measurement diameter: 20.0mm
Measurement wavelength/interval: 400 to 700 nm/10 nm
Light source: pulsed xenon lamp, 1 emission/measurement Traceability standard: National Institute of Standards and Technology (NIST) compliant calibration based on CIE 44 and ASTM E259 Standard observer: 10°
In addition, the following object colors were used for the white tiles used as the measurement standard.
When measured at D65/10°, the values in the CIE XYZ color system are X: 81.90, Y: 87.02, Z: 93.76

<Peel strength>
After bonding the surface-treated copper foil to the polyimide resin substrate, a circuit with a width of 3 mm was formed in the MD direction (longitudinal direction of the rolled copper foil). Formation of the circuit was carried out according to the usual method. Next, the circuit (surface-treated copper foil) is peeled off from the surface of the resin base material at a speed of 50 mm/min in a 90° direction, that is, vertically upward with respect to the surface of the resin base material. The thickness (MD90° peel strength) was measured according to JIS C6471:1995. The measurement was performed three times, and the average value was taken as the result of the peel strength. If the peel strength is 0.50 kgf/cm or more, it can be said that the adhesion between the circuit (surface-treated copper foil) and the resin substrate is good.
This evaluation was not performed for the copper foil of Comparative Example 1 because it could not be attached to the polyimide resin substrate.

Table 1 shows the results of the above characteristic evaluation.

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

With reference to the above results and the discussion of the embodiments of the present invention described so far, according to the embodiments of the present invention, it is possible to increase the adhesion to resin substrates, particularly resin substrates suitable for high frequency applications. A surface-treated copper foil can be provided. Further, according to the embodiment of the present invention, it is possible to provide a copper-clad laminate having excellent adhesion between a resin substrate, particularly a resin substrate suitable for high frequency applications, and the surface-treated copper foil. Furthermore, according to the embodiment of the present invention, it is possible to provide a printed wiring board having excellent adhesiveness between a resin substrate, particularly a resin substrate suitable for high frequency applications, and a circuit pattern.

REFERENCE SIGNS LIST 10 Copper foil 11 Convex portion 12 Concave portion 20 Roughened particles 30 Cover plating layer

Claims

Having a copper foil and a surface treatment layer formed on at least one surface of the copper foil,
The surface-treated layer is a surface-treated copper foil having 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 cutoff value λs of 2 μm, and P2 is Vmc calculated without applying the λs filter.
The surface-treated copper foil according to claim 1, wherein the change rate of Vmc is 23.00 to 32.00%.
The surface-treated copper foil according to claim 1, wherein the change rate of Vmc is 23.00 to 31.00%.
The surface-treated copper foil according to any one of claims 1 to 3, wherein the surface-treated layer has an Sku of 2.50 to 4.50 calculated without applying the λs filter.
The surface-treated copper foil according to claim 4, wherein the Sku is 2.90 to 4.10.
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.
The surface-treated copper foil according to any one of claims 1 to 6, wherein the surface-treated layer has an Sa calculated without applying the λs filter of 0.20 to 0.40 µm.
The surface-treated copper foil according to any one of claims 1 to 7, wherein the surface treatment layer contains a roughening treatment layer.
A copper-clad laminate comprising the surface-treated copper foil according to any one of claims 1 to 8 and a resin substrate adhered to the surface treatment layer of the surface-treated copper foil.
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.