WO2023281759A1

WO2023281759A1 - Surface-treated copper foil, copper-clad laminate, and printed wiring board

Info

Publication number: WO2023281759A1
Application number: PCT/JP2021/026044
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: 2021-07-09
Publication date: 2023-01-12
Also published as: CN117120670A; WO2023281773A1

Abstract

This surface-treated copper foil has a copper foil and a surface-treated layer formed on at least one surface of the copper foil. The surface-treated layer has an Sku of 2.50-4.50 and an Str of 0.20-0.40.

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 the copper foil has minute unevenness, for example, when forming a roughening treatment layer, the current concentrates on the projections and the roughened particles grow overgrown, while the current is not sufficiently supplied to the depressions. It becomes difficult for roughening particles to grow. As a result, while coarse roughening particles are formed in the convex portions of the copper foil, the roughening particles are too small in the concave portions of the copper foil. be in a state of non-existence. 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 studies on surface-treated copper foils to solve the above problems. The present inventors have found that it is possible to suppress overgrowth of roughened particles formed in the convex portions and facilitate the formation of roughened particles in the concave portions of the copper foil. When the present inventors analyzed the surface shape of the surface-treated copper foil thus obtained, they found that the Sku and Str of the surface-treated layer are closely related to the surface shape. The headline led to the completion of 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 has an Sku of 2.50 to 4.50, relating to surface-treated copper foils having a Str of 0.20 to 0.40.
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. .

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 treatment layer has an Sku (Kurtosis) of 2.50 to 4.50. Sku is defined in ISO 25178-2:2012. 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 in the recesses of the copper foil. Therefore, when the Sku of the surface treatment layer is 2.50 to 4.50, the overgrowth of the roughening particles formed in the convex portions of the copper foil is suppressed, and the roughening particles are also formed in the concave portions of the copper foil. is formed.

A surface-treated copper foil with a large number of coarse roughened particles and a surface-treated copper foil with portions where no roughened particles are formed are not preferable from the viewpoint of adhesion to the resin base material. For example, in a surface-treated copper foil with many coarse roughened particles, when a force is applied to peel off the surface-treated copper foil after bonding to the resin base material, the stress concentrates on the coarse roughened particles, making it easier to break. On the contrary, it is considered 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. The present inventors measured and analyzed the peel strength of the surface-treated copper foils of Examples and Comparative Examples, which will be described later, and found that the Sku of the surface-treated layer is involved in the adhesion to the resin substrate. rice field.
The Sku of the surface treatment layer is preferably 2.80 to 4.00, more preferably 2.90 to 3.75, from the viewpoint of stably obtaining adhesive strength to the resin substrate.
The Sku of the surface treatment layer is measured according to ISO 25178-2:2012.

The surface treatment layer has a Str (texture aspect ratio) of 0.20 to 0.40. Str is a spatial parameter defined in ISO 25178-2:2012 and represents the strength of surface anisotropy and isotropy. Str is in the range of 0 to 1, and the closer it is to 0, the stronger the anisotropy (for example, the greater the streaks). Conversely, the closer Str is to 1, the stronger the isotropy.
When the Str of the surface treatment layer is 0.20 to 0.40, the surface of the surface treatment layer is moderately anisotropic. This state means that the surface treatment layer is uniformly formed along the minute irregularities on the surface of the copper foil. Therefore, for example, when a roughening treatment layer is formed on the surface of a copper foil, it means that there are few overgrown roughening particles in the convex portions and few portions in which the roughening particles are not formed in the concave portions. That is, when the Str of the surface treatment layer is 0.20 to 0.40, the overgrowth of roughening particles formed in the convex portions of the copper foil is suppressed, and the roughening particles are also formed in the concave portions of the copper foil. means that the As a result, the anchoring effect of the roughening particles can be sufficiently ensured, so that the adhesive strength between the surface-treated copper foil and the resin substrate is increased. From the viewpoint of stably obtaining such effects, Str of the surface treatment layer is preferably 0.26 to 0.35.
The Str of the surface treatment layer is measured according to ISO 25178-2:2012.

The surface treatment layer preferably has an Sa (arithmetic mean height) of 0.18 to 0.43 μm. Sa is a parameter in the height direction defined in ISO 25178-2:2012 and represents the average height difference from the average plane.
When the Sa of the surface treatment layer is too large, the surface of the surface treatment layer becomes rough, so that the anchor effect is likely to be exhibited when the surface treatment copper foil is adhered to the resin substrate. On the other hand, when a circuit board is produced by processing a copper-clad laminate in which a surface-treated copper foil having a large Sa of a surface-treated layer (that is, a rough surface) is bonded to a resin base material, the surface of the surface-treated copper foil The effect increases the transmission loss. 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 Sa of the surface treatment layer preferably has a lower limit of 0.20 µm, more preferably 0.24 µm, and an upper limit of preferably 0.40 µm, more preferably 0. .35 μm.

The surface treatment layer preferably has an Sq (root mean square height) of 0.26 to 0.53 μm. 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.
When the Sq of the surface treatment layer is large, the height of the protrusions on the surface of the surface treatment layer varies greatly, and the anchor effect is likely to be exhibited when the surface treatment copper foil is adhered to the resin base material. However, 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 secure a balance between securing the anchoring effect and the viewpoint of quality control. From the viewpoint of stably obtaining such effects, the Sq of the surface treatment layer preferably has a lower limit of 0.30 μm, more preferably 0.34 μm, and an upper limit of preferably 0.48 μm, more preferably 0. .43 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 surface treatment layer preferably has an Sdr (spread interface area ratio) of 38 to 79%. Sdr is a composite parameter defined in ISO 25178-2:2012 and represents the rate of surface increase. In other words, it represents the increase ratio of the actual surface area to the area when a certain surface is viewed in plan.
If the Sdr of the surface treatment layer is too large, the surface of the surface treatment layer will be dense and undulating. Therefore, when the surface-treated copper foil is adhered to a resin base material, the anchor effect will be more likely to be exhibited, while the skin effect will cause transmission. loss increases. Therefore, by setting the Sdr of the surface treatment layer within the above range, it is possible to secure a balance between securing the anchor effect and suppressing the transmission loss.

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. 1 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. 1 , 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 on the convex portions 11 of the copper foil 10 but also on the concave portions 12 . Further, overgrowth of the roughening particles 20 formed on the convex portions 11 of the copper foil 10 is suppressed by adding a trace 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 parameters such as Sku and Str of the surface treatment layer within the above ranges.

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 the roughening particles 20 formed in the convex portions 11 can be suppressed, and the roughening particles 20 can be easily formed in the 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 0.1-10 A/dm ² , time 0.1-5 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 chromating 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, the parameters such as Sku and Str of the surface treatment layer can be controlled by adjusting the conditions for forming the surface treatment layer, particularly the conditions for forming the roughening treatment layer described above.

The surface-treated copper foil according to the embodiment of the present invention is dissolved by acid decomposition treatment, and when the content of tungsten in the solution is measured by inductively coupled plasma mass spectrometry, the content of tungsten is 1.0 × It is preferably 12/t to 4.0×12/t [ppm] (t is the thickness of the copper foil 10). With the content of tungsten in such a range, the Sku and Str of the surface treatment layer can be controlled within the above ranges.
The copper foil 10 is processed from high-purity copper such as tough-pitch copper or oxygen-free copper, or a copper alloy added with Sn, Ag, Cr, Zr, Mg, or the like, which is usually used as a circuit pattern for a printed wiring board. In some cases, copper foil 10 typically does not contain W. Therefore, based on the amount of tungsten obtained by analyzing the solution of the surface-treated copper foil containing the copper foil 10, by performing a calculation considering the thickness of the copper foil 10, the amount of tungsten in the surface treatment layer content can be estimated. The above calculation formula is the estimation method.
Solutionization by acid decomposition treatment is carried out by dissolving a 10 cm square surface-treated copper foil in a mixed solution of nitric acid and hydrofluoric acid and diluting the solution.
Inductively coupled plasma mass spectrometry can be performed using an inductively coupled plasma mass spectrometer (ICP-MS).

Since the surface-treated copper foil according to the embodiment of the present invention controls the Sku of the surface treatment layer to 2.50 to 4.50 and the Str to 0.20 to 0.40, it is suitable for resin substrates, especially for high frequency applications. It is possible to increase the adhesiveness with the resin substrate suitable for.

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)
A rolled copper foil (thickness 12 μm) is prepared, and one side is degreased and pickled, then a roughening treatment layer as a surface treatment layer, a Ni-Zn layer as a heat treatment layer, a chromate treatment layer, and a silane coupling treatment. A surface-treated copper foil was obtained by sequentially forming layers. 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, 1 ppm tungsten (from sodium tungstate dihydrate)
Plating solution temperature: 27°C
Electroplating conditions: current density 38.8 A/dm ² , time 1.3 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 8.2 A/dm ² , time 1.4 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 0.6 A/dm ² , time 0.7 seconds

(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 1.4 A/dm ² , time 0.7 seconds

(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 amount of tungsten in the composition of the plating solution was changed to 2 ppm in the conditions for forming roughening particles.

(Example 3)
A surface-treated copper foil was obtained under the same conditions as in Example 1, except that the amount of tungsten in the composition of the plating solution was changed to 3 ppm in the conditions for forming roughening particles.

(Example 4)
A surface-treated copper foil was obtained under the same conditions as in Example 1, except that the amount of tungsten in the composition of the plating solution was changed to 4 ppm in the conditions for forming roughening particles.

(Example 5)
A surface-treated copper foil was obtained under the same conditions as in Example 1, except that the amount of tungsten in the composition of the plating solution was changed to 5 ppm in the conditions for forming roughening particles.

(Example 6)
A surface-treated copper foil was obtained under the same conditions as in Example 1, except that the amount of tungsten in the composition of the plating solution was changed to 6 ppm in the formation conditions of the roughened particles.

(Example 7)
Prepare the same rolled copper foil as in Example 1, degreasing and pickling one side, roughening treatment layer as surface treatment layer, Ni-Zn layer as heat treatment layer, chromate treatment layer, and silane coupling treatment A surface-treated copper foil was obtained by sequentially forming layers. 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 46.8 A/dm ² , time 1.0 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 0.7 A/dm ² , time 0.7 seconds

(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 1.5 A/dm ² , time 0.7 seconds

(Example 8)
A surface-treated copper foil was obtained under the same conditions as in Example 7, except that the current density was changed to 9.6 A/dm ² in the formation conditions of the covering plating layer.

(Example 9)
The current density was set to 46.0 A/dm ² under the conditions for forming the roughened particles, at 9.6 A/dm 2 under the conditions for forming the covering plating layer, and at 0.0 A/dm ² under the conditions for forming the Ni—Zn layer. A surface-treated copper foil was obtained under the same conditions as in Example 7, except that it was changed to 9 A/dm ² .

(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 amount of tungsten in the composition of the plating solution was set to 0 ppm (sodium tungstate was not added) in the conditions for forming roughening particles.

The surface-treated copper foils or copper foils obtained in the above examples and comparative examples were evaluated for the following characteristics.
<Sku, Str, Sa, Sq and Sdr>
Images were captured 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. Sku, Str, Sa, Sq and Sdr were measured according to ISO 25178-2:2012. Moreover, these measurement results were obtained by averaging the values measured at arbitrary five locations. 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: λc = 200 µm, λs and λf are not used Filter: Gaussian filter Noise removal: Pre-measurement processing Surface (tilt ) Correction: Implemented Brightness: Adjusted to be in the range of 30 to 50 Brightness is a value that 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.

<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

<Content of tungsten (W)>
The surface-treated copper foil or copper foil was subjected to acid decomposition treatment to form a solution, and the content of tungsten in the solution was measured by inductively coupled plasma mass spectrometry. Conditions such as dissolution were as described above.
For Examples 7 to 9, the W concentration in the surface treatment layer was considered to be equivalent to that of Example 5, so this evaluation was not performed.

<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 surface-treated copper foils of Examples 1 to 9, in which the Sku and Str of the surface treatment layer were within the predetermined ranges, had high peel strength.
On the other hand, although the Sa of the surface treatment layer was equivalent to those of the surface treated copper foils of Examples 1 to 9, the surface treated copper foil of Comparative Example 2, in which the Sku was outside the predetermined range, had low peel strength. In general, the larger the Sa of the surface treatment layer, the more the adhesiveness to the resin substrate improves. As a result, the peel strength is improved by controlling the Sku and Str while the Sa is approximately the same. The result was astonishing.
Comparing the surface-treated copper foils of Examples 1 to 9 and the copper foil of Comparative Example 1, it can be seen that Str values are very close. Considering that the surface-treated copper foils of Examples 1 to 9 are obtained by subjecting the copper foil of Comparative Example 1 to surface treatment, and that Str represents the anisotropy and isotropy of the surface, the above-mentioned As described above, in the surface-treated copper foil according to the embodiment of the present invention, a surface-treated layer, particularly a roughened particle layer is uniformly formed along the fine irregularities (oil pits in the case of rolled copper foil) on the surface of the copper foil. It can be seen that If the roughened particle layer were not formed along the minute unevenness, the Str value would be greatly different before and after the surface treatment.
Although the W content in Comparative Example 2 is 0.4 ppm, this was unintentionally added to any of the plating solutions used to form the surface treatment layer when the surface-treated copper foil of Comparative Example 2 was produced. It is considered that the reason for this is that W remained. The present inventors believe that W did not remain in the plating solution for forming the roughened layer, but remained in the plating solutions for forming other surface treatment layers.

As can be seen from the above results, according to the embodiment of the present invention, it is possible to provide a surface-treated copper foil capable of improving adhesion to a resin substrate, particularly a resin substrate suitable for high frequency applications. . Moreover, according to the embodiment of the present invention, it is possible to provide a surface-treated copper foil in which roughening particles are formed along fine irregularities on the surface of the copper foil. 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 an Sku of 2.50 to 4.50 and a Str of 0.20 to 0.40.
The surface-treated copper foil according to claim 1, wherein the Sku is 2.80 to 4.00 and the Str is 0.26 to 0.35.
The surface-treated copper foil according to claim 1 or 2, wherein the surface-treated layer has a Sa of 0.18 to 0.43 µm.
The surface-treated copper foil according to any one of claims 1 to 3, wherein the surface-treated layer has an Sq of 0.26 to 0.53 µm.
The surface-treated copper foil according to claim 1 or 2, wherein the surface treatment layer has an Sa of 0.20 to 0.32 µm and an Sq of 0.26 to 0.40 µm.
The surface-treated copper foil according to any one of claims 1 to 5, wherein the surface treatment layer has an Sdr content of 38 to 79%.
When the surface-treated copper foil is acid-decomposed to form a solution, and the content of tungsten in the solution is measured by inductively coupled plasma mass spectrometry, the content of tungsten is found to be 1.0×12/t to 4.0×12/t. The surface-treated copper foil according to any one of claims 1 to 6, which is 0 × 12/t [ppm] (t is the thickness of the copper foil).
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.