WO2022153580A1

WO2022153580A1 - Surface-treated copper foil, copper-clad laminate, and printed wiring board

Info

Publication number: WO2022153580A1
Application number: PCT/JP2021/026045
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: 2021-01-15
Filing date: 2021-07-09
Publication date: 2022-07-21
Also published as: TW202229651A; JPWO2022154102A1; WO2022154102A1; KR20230104700A

Abstract

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 an Sku of from 2.50 to 4.50 and an Str of from 0.20 to 0.40.

Description

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

This disclosure relates to surface-treated copper foil, 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 mounted by etching the copper foil of a copper-clad laminate to form a conductor pattern (also called a "wiring pattern") and connecting electronic components on the conductor pattern with solder. Manufactured.

In recent years, in electronic devices such as personal computers and mobile terminals, the frequency of electric signals has been increasing along with the increase in communication speed and capacity, and a flexible printed wiring board capable of coping with this has been required. In particular, as the frequency of the electric signal becomes higher, the loss (attenuation) of the signal power becomes larger and the data tends to be unreadable. Therefore, it is required to reduce the loss of the signal power.

The causes of signal power loss (transmission loss) in electronic circuits can be broadly divided into two. The first is the conductor loss, that is, the loss due to the copper foil, and the second is the dielectric loss, that is, the loss due to the resin base material.
The conductor loss has a skin effect in the high frequency region and has the characteristic that the current flows on the surface of the conductor. Therefore, if the surface of the copper foil is rough, the current will flow along a complicated path. Therefore, in order to reduce the conductor loss of the high frequency signal, it is desirable to reduce the surface roughness of the copper foil. Hereinafter, when the terms "transmission loss" and "conductor loss" are simply used in the present specification, they mainly mean "transmission loss of high frequency signal" and "conductor loss of high frequency signal".

On the other hand, since the dielectric loss depends on the type of the resin base material, it is possible to use a resin base material formed of a low dielectric material (for example, a liquid crystal polymer or a low dielectric polyimide) in a circuit board through which a high frequency signal flows. desirable. Further, since the dielectric loss is also affected by the adhesive that adheres between the copper foil and the resin base material, it is desirable to adhere between the copper foil and the resin base material 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 base material without using an adhesive. For example, Patent Document 1 proposes a method of providing a roughening treatment layer formed of roughened particles on a copper foil and forming a silane coupling treatment layer on the outermost surface layer.

Japanese Unexamined Patent Publication No. 2012-112009

The surface of the copper foil on which the surface treatment layer is formed generally has minute irregularities. For example, in the case of rolled copper foil, oil pits formed by rolling oil during rolling are formed on the surface as minute uneven portions. Further, in the case of the electrolytic copper foil, the polishing streaks of the rotating drum formed during polishing cause minute uneven portions on the surface of the electrolytic copper foil on the rotating drum side, which are deposited and formed on the rotating drum.
If the copper foil has minute irregularities, for example, when forming the roughening treatment layer, the current is concentrated in the convex portions and the roughened particles are overgrown, while the current is not sufficiently supplied in the concave portions. It becomes difficult for the roughened particles to grow. As a result, coarse roughened particles are formed in the convex portion of the copper foil, while the roughened particles are too small in the concave portion of the copper foil, that is, the roughened particles on the surface of the copper foil are uniformly formed. It will be in a non-existent state. In the surface-treated copper foil having many coarse coarse particles, if a force for peeling the surface-treated copper foil is applied after bonding with the resin base material, stress is concentrated on the coarse roughened particles and the resin is easily broken. Adhesive strength to the substrate may decrease. Further, in the surface-treated copper foil in which the size of the roughened particles is insufficient, the anchor effect due to the roughened particles is lowered, and the adhesiveness between the copper foil and the resin base material may not be sufficiently obtained.
In particular, a resin base material formed of a low dielectric material such as a liquid crystal polymer or a low dielectric polyimide is more difficult to adhere to a copper foil than a conventional resin base material, so that the adhesiveness between the copper foil and the resin base material is improved. It is desired to develop a method to enhance it.
Further, although the silane coupling treatment layer has an effect of improving the adhesiveness between the copper foil and the resin base material, the effect of improving the adhesiveness may not be sufficient depending on the type.

The embodiment of the present invention has been made to solve the above-mentioned problems, and in one aspect, it is possible to enhance the adhesiveness with a resin base material, particularly a resin base material suitable for high frequency applications. It is an object of the present invention to provide a surface-treated copper foil.
Further, in another aspect, the embodiment of the present invention provides a copper-clad laminate having excellent adhesion between a resin base material, particularly a resin base material suitable for high-frequency applications, and a surface-treated copper foil. The purpose.
Further, an embodiment of the present invention aims to provide a printed wiring board having excellent adhesion between a resin base material, particularly a resin base material suitable for high frequency applications, and a circuit pattern, in another aspect. ..

As a result of diligent research on the surface-treated copper foil in order to solve the above problems, the present inventors have added a trace amount of tungsten compound to the plating solution used for forming the roughening-treated layer to obtain the copper foil. It was found that the overgrowth of the roughened particles formed in the convex portion can be suppressed and the roughened particles can be easily formed in the concave portion of the copper foil. Then, the present inventors analyzed the surface shape of the surface-treated copper foil thus obtained, and found that the Sku and Str of the surface-treated layer are closely related to this surface shape. We have found and completed the embodiment of the present invention.

That is, the embodiment of the present invention has a copper foil and a surface-treated layer formed on at least one surface of the copper foil on one side surface, and the surface-treated layer has Sku of 2.50 to 2.50. It relates to a surface-treated copper foil having 4.50 and a Str of 0.20 to 0.40.
In another aspect, an embodiment of the present invention relates to a copper-clad laminate comprising the surface-treated copper foil and a resin base material adhered to the surface-treated layer of the surface-treated copper foil.
Further, an embodiment of the present invention relates to a printed wiring board having a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate on another side surface.

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

It is a schematic enlarged sectional view of the surface-treated copper foil which has a roughening treatment layer on one surface of a copper foil.

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 shall be based on the knowledge of those skilled in the art as long as the gist of the present invention is not deviated. , Various changes and improvements can be made. The plurality of components disclosed in the following embodiments can form various inventions by appropriate combinations. For example, some components may be deleted from all the components shown in the following embodiments, or components of different embodiments may be combined as appropriate.

The surface-treated copper foil according to the embodiment of the present invention has a copper foil and a surface-treated layer formed on at least one surface of the copper foil.
The surface treatment layer may be formed on only one surface of the copper foil, or may be formed on both surfaces of the copper foil. When the surface treatment layer is formed on both surfaces of the copper foil, the type of the surface treatment layer may be the same or different.

The surface treatment layer has a Sku (Kurtosis) of 2.50 to 4.50. Sk is defined in ISO 25178-2: 2012. Sk is a parameter that expresses the degree of kurtosis (kurtosis) of the histogram when a histogram of height is created with reference to the average height. For example, when Sk = 3.00, it means that the height distribution is a normal distribution. Further, when Sk> 3.00, the larger the value, the more concentrated the height distribution. On the contrary, when Sk <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 irregularities on the surface, and the irregularities contribute to the improvement of the adhesiveness between the copper foil and the resin base material. The Sk of the surface treatment layer is an index for evaluating the height distribution of the unevenness.
When the Sku of the surface treatment layer is 2.50 to 4.50, it means that the height distribution is a normal distribution or a distribution state close to it. On the other hand, the fact that the Sk of the surface treatment layer is less than 2.50 is a result of various mixing of low and high heights of the surface treatment layer (height from the copper foil surface), resulting in a height distribution. Means that is an unbiased distribution. The fact that the Sk of the surface treatment layer is larger than 4.50 means that the height distribution is uneven, that is, the surface of the surface treatment layer is in a state where a certain height portion protrudes and occupies a large part. Means that
The height distribution of the surface-treated layer is a normal distribution or a distribution state close to that, for example, when a roughened-treated layer is formed on the surface of the copper foil, the roughened particles overgrown in the convex portion of the copper foil, that is, coarse particles. This means that there are few roughened particles or recesses of the copper foil where the roughened particles are not formed. 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 portion of the copper foil is suppressed, and the roughened particles are also suppressed on the concave portion of the copper foil. Means the state in which is formed.

Neither a surface-treated copper foil having a large amount of coarse roughened particles nor a surface-treated copper foil having a portion where roughened particles are formed is preferable from the viewpoint of adhesiveness to a resin base material. For example, in a surface-treated copper foil having many coarse roughened particles, if a force is applied to peel off the surface-treated copper foil after bonding with a resin base material, stress is concentrated on the coarse roughened particles and the particles are easily broken. On the contrary, it is considered that the adhesive force to the resin base material is reduced. Further, in the surface-treated copper foil in which the roughened particles are not formed, the anchor effect due to the roughened particles cannot be sufficiently secured, and the adhesive force between the surface-treated copper foil and the resin base material is lowered. Conceivable. As a result of measuring and analyzing the peel strength of the surface-treated copper foils of Examples and Comparative Examples described later, the present inventors have found that Sk of the surface-treated layer is involved in the adhesiveness with the resin substrate. rice field.
From the viewpoint of stably obtaining the adhesive force to the resin base material, the Sku of the surface treatment layer is preferably 2.80 to 4.00, and more preferably 2.90 to 3.75.
The Sk of the surface treatment layer is measured in accordance with 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 isotropic. Str is in the range of 0 to 1, and the closer it is to 0, the stronger the anisotropy (for example, the larger the streaks). On the contrary, the closer the Str is to 1, the stronger the isotropic property.
When the Str of the surface treatment layer is 0.20 to 0.40, the surface of the surface treatment layer has an appropriate anisotropy. This state means that the surface treatment layer is uniformly formed along the minute uneven portions on the surface of the copper foil. Therefore, for example, when the roughening treatment layer is formed on the surface of the copper foil, it means that there are few roughened particles overgrown in the convex portions and few roughened 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 the roughened particles formed in the convex portion of the copper foil is suppressed, and the roughened particles are also formed in the concave portion of the copper foil. It means the state of being done. As a result, the anchoring effect of the roughened particles can be sufficiently ensured, so that the adhesive force between the surface-treated copper foil and the resin base material is increased. From the viewpoint of stably obtaining such an effect, the 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 a 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.
If the Sa of the surface-treated layer is too 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 the resin base material. 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 (that is, a rough surface) and a resin base material are bonded to each other, the skin of the surface-treated copper foil is formed. The effect increases the transmission loss. Therefore, by setting Sa of the surface-treated layer in the above range, it is possible to secure a balance between securing the adhesive force of the surface-treated copper foil to the resin base material and suppressing transmission loss. From the viewpoint of stably obtaining such an effect, the lower limit value of Sa of the surface treatment layer is preferably 0.20 μm, more preferably 0.24 μm, and the upper limit value is preferably 0.40 μm, more preferably 0. It is .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 a variation in the height of the convex portion on the surface of the surface treatment layer.
When the Sq of the surface-treated layer is large, the height of the convex portion on the surface of the surface-treated layer varies widely, and the anchor effect is likely to be exhibited when the surface-treated copper foil is adhered to the resin base material. However, if Sq is too large (the height variation of the convex portion is too large), it may cause 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 ensuring the anchor effect and the viewpoint of quality control. From the viewpoint of stably obtaining such an effect, the lower limit value of Sq of the surface treatment layer is preferably 0.30 μm, more preferably 0.34 μm, and the upper limit value is preferably 0.48 μm, more preferably 0. It is .43 μm.
When the suppression of transmission loss due to the skin effect and the ease of quality control as an industrial product are emphasized, the surface treatment layer has a Sa of 0.20 to 0.32 μm and an Sq of 0.26 to 0. It is preferably .40 μm.

The surface treatment layer preferably has an Sdr (developed interface area ratio) of 38 to 79%. Sdr is a composite parameter defined in ISO 25178-2: 2012 and represents the rate of increase in the surface. In other words, it represents the rate of increase in the actual surface area with respect to the area when a surface is viewed in a plan view.
If the Sdr of the surface-treated layer is too large, the surface of the surface-treated layer becomes dense and undulating, so that the anchor effect is likely to be exhibited when the surface-treated copper foil is adhered to the resin base material, while transmission is performed by the skin effect. The loss will be large. Therefore, by setting the Sdr of the surface treatment layer within the above range, it is possible to secure a balance between ensuring the anchor effect and suppressing transmission loss.

The type of the surface treatment layer is not particularly limited, and various surface treatment layers known in the art can be used.
Examples of the surface treatment layer include a roughening treatment layer, a heat resistance treatment layer, a rust prevention treatment layer, a chromate treatment layer, a silane coupling treatment layer and the like. These layers can be used alone or in combination of two or more. Among them, the surface treatment layer preferably contains a roughening treatment layer from the viewpoint of adhesiveness to the resin base material.
When the surface treatment layer contains one or more layers selected from the group consisting of a heat resistant treatment layer, a rust prevention treatment layer, a chromate treatment layer and a silane coupling treatment layer, these layers are roughened treatment layers. It is preferably provided on top.

Here, as an example, FIG. 1 shows a schematic enlarged cross-sectional view of a surface-treated copper foil having a roughening-treated layer on one surface of the copper foil.
As shown in FIG. 1, the roughening-treated layer formed on one surface of the copper foil 10 includes roughened particles 20 and a cover plating layer 30 that covers at least a part of the roughened particles 20. The roughened particles 20 are formed not only in the convex portion 11 of the copper foil 10 but also in the concave portion 12. Further, overgrowth of the roughened particles 20 formed on the convex portion 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 Sk and Str of the surface treatment layer within the above range.

The roughened 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 the containing alloy. Among them, the roughened particles 20 are preferably formed of copper or a copper alloy, particularly copper.
The cover plating layer 30 is not particularly limited, but can be formed 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 to which a trace amount of tungsten compound is added.
The tungsten compound is not particularly limited, but for example, sodium tungstate (Na ₂ WO ₄ ) or the like can be used.
The content of the tungsten compound in the plating solution is preferably 1 ppm or more. With such a content, it is possible to suppress the overgrowth of the roughened particles 20 formed in the convex portion 11 and facilitate the formation of the roughened particles 20 in the concave portion 12. The upper limit of the content of the tungsten compound is not particularly limited, but is preferably 20 ppm from the viewpoint of suppressing an increase in electrical resistance.

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

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

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

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

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

The chromate-treated layer can be formed by a known method 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-treated layer are as follows. The chromate treatment may be performed once or a plurality of times.
Chromate solution composition: 1 to 10 g / L K ₂ Cr ₂ O ₇ , 0.01 to 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 (in the case of electrolytic chromate treatment)

The silane coupling treatment layer is not particularly limited, and can be formed from a material known in the art.
Here, the term "silane coupling-treated layer" as used herein means a layer formed of 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, metharoxy-based silane coupling agents, vinyl-based silane coupling agents, and imidazole-based silane coupling agents. , Triazine-based silane coupling agent and the like. Among these, amino-based silane coupling agents and epoxy-based silane coupling agents are preferable. The above silane coupling agent can be used alone or in combination of two or more.
As a typical method for forming a silane coupling treatment layer, a method of forming a silane coupling treatment layer by applying a 1 to 3% by volume aqueous solution of the above-mentioned silane coupling agent and drying it can be mentioned.

The copper foil 10 is not particularly limited, and may be either an electrolytic copper foil or a rolled copper foil.
Electrolytic copper foil is generally manufactured by electrolytically depositing copper on a titanium or stainless steel drum from a copper sulfate plating bath, but a flat S surface (shine surface) formed on the rotating drum side and an S surface. It has an M surface (matte surface) formed on the opposite side of the surface. The M surface of the electrolytic copper foil generally has minute uneven portions. Further, the S surface of the electrolytic copper foil has minute uneven portions because the polishing streaks of the rotating drum formed during polishing are transferred.
Further, the rolled copper foil has minute uneven portions on the surface because oil pits are formed by rolling oil during rolling.

The material of the copper foil 10 is not particularly limited, but when the copper foil 10 is a rolled copper foil, tough pitch copper (JIS H3100 alloy number C1100) and oxygen-free copper (JIS H3100) usually used as a circuit pattern of a printed wiring board are used. High-purity copper such as alloy number C1020 or JIS H3510 alloy number C1011) can be used. Further, for example, copper alloys such as Sn-containing copper, Ag-containing copper, copper alloys to which Cr, Zr, Mg and the like are added, and Corson-based copper alloys to which Ni and Si and the like are added can also be used. In addition, in this specification, "copper foil 10" is a concept including copper alloy foil.

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

The surface-treated copper foil having the above-mentioned structure can be produced according to a method known in the art. Here, parameters such as Sku and Str of the surface treatment layer can be controlled by adjusting the formation conditions of the surface treatment layer, particularly the above-mentioned formation conditions of the roughening treatment layer.

The surface-treated copper foil according to the embodiment of the present invention has a tungsten content of 1.0 × when it is acid-decomposed to a solution and the tungsten content in the solution is measured by inductively coupled plasma mass spectrometry. It is preferably 12 / t to 4.0 × 12 / t [ppm] (t is the thickness of the copper foil 10). If the content of tungsten is within such a range, the Sku and Str of the surface treatment layer can be controlled within the above range.
The copper foil 10 is a processed copper alloy to which high-purity copper such as tough pitch copper and oxygen-free copper, which is usually used as a circuit pattern of a printed wiring board, and Sn, Ag, Cr, Zr, Mg, etc. are added. In some cases, the copper foil 10 usually does not contain W. Therefore, by performing a calculation considering the thickness of the copper foil 10 based on the amount of tungsten obtained by analyzing the solution of the surface-treated copper foil containing the copper foil 10, the tungsten of the surface-treated layer can be obtained. The content can be estimated. The above formula is the estimation method.
The solution 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).

In the surface-treated copper foil according to the embodiment of the present invention, the Sku of the surface-treated layer is controlled to 2.50 to 4.50 and the Str is controlled to 0.20 to 0.40. It is possible to enhance the adhesiveness with a resin base material suitable for the above.

The copper-clad laminate according to the embodiment of the present invention includes the above-mentioned surface-treated copper foil and a resin base material adhered to the surface-treated layer of the surface-treated copper foil.
This copper-clad laminate can be manufactured by adhering a resin base material to the surface-treated layer of the above-mentioned surface-treated copper foil.
The resin base material is not particularly limited, and those known in the art can be used. Examples of resin base materials include paper base material phenol resin, paper base material epoxy resin, synthetic fiber cloth base material epoxy resin, glass cloth / paper composite base material epoxy resin, glass cloth / glass non-woven composite base material epoxy resin, and glass. Examples thereof include cloth-based epoxy resin, polyester film, polyimide resin, liquid crystal polymer, and fluororesin. Among these, the resin base material is preferably a polyimide resin.

The method for adhering the surface-treated copper foil to the resin base material is not particularly limited, and can be performed according to a method known in the art. For example, the surface-treated copper foil and the 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 above-mentioned surface-treated copper foil, it is possible to improve the adhesiveness to a resin base material, particularly a resin base material suitable for high-frequency applications.

The printed wiring board according to the 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 manufactured by etching the surface-treated copper foil of the copper-clad laminate to form a circuit pattern. The method for forming the circuit pattern is not particularly limited, and a known method such as a subtractive method or a semi-additive method can be used. Among them, the subtractive method is preferable as the method for forming the circuit pattern.

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

Since the printed wiring board according to the embodiment of the present invention uses the above-mentioned copper-clad laminate, it is excellent in adhesiveness between a resin base material, particularly a resin base material suitable for high-frequency applications, and a circuit pattern. ..

Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Example 1)
A rolled copper foil (thickness 12 μm) is prepared, and one surface is degreased and pickled, and then a roughening treatment layer is used as a surface treatment layer, a Ni—Zn layer is used 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 formation conditions of each treatment layer were as follows.
(1) Roughening treatment layer <Conditions for forming roughened particles>
Plating solution composition: 11 g / L Cu, 50 g / L sulfuric acid, 1 ppm tungsten (derived from sodium tungstate dihydrate)
Plating liquid temperature: 27 ° C
Electroplating conditions: Current density 38.8 A / dm ² , time 1.3 seconds Number of electroplating processes: 2 times

<Conditions for forming the 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 processes: 2 times

(2) Heat-resistant treatment 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 liquid 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 solution composition: 3 g / L K ₂ Cr ₂ O ₇ , 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 Treatment Layer A silane coupling treatment layer was formed by applying a 1.2% by volume aqueous solution of N-2- (aminoethyl) -3-aminopropyltrimethoxysilane and drying it.

(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 plating solution composition was changed to 2 ppm under the conditions for forming the roughened 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 plating solution composition was changed to 3 ppm under the conditions for forming the roughened 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 plating solution composition was changed to 4 ppm under the conditions for forming the roughened 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 plating solution composition was changed to 5 ppm under the conditions for forming the roughened 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 plating solution composition was changed to 6 ppm under the conditions for forming the roughened particles.

(Example 7)
The same rolled copper foil as in Example 1 was prepared, and after degreasing and pickling one surface, a roughening treatment layer was used 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 formation conditions of each treatment layer were as follows.
(1) Roughening treatment layer <Conditions for forming roughened particles>
Plating solution composition: 11 g / L Cu, 50 g / L sulfuric acid, 5 ppm tungsten (derived from sodium tungstate dihydrate)
Plating liquid temperature: 27 ° C
Electroplating conditions: Current density 46.8 A / dm ² , time 1.0 seconds Number of electroplating processes: 2 times

(2) Heat-resistant treatment 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 liquid 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 solution composition: 3 g / L K ₂ Cr ₂ O ₇ , 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 under the conditions for forming the cover plating layer.

(Example 9)
The current density was set to 46.0 A / dm ² under the conditions for forming the roughened particles, the current density was set to 9.6 A / dm ² under the conditions for forming the cover plating layer, and the current density was set to 0 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 the values were changed to 9 A / dm ² .

(Comparative Example 1)
The rolled copper foil (copper foil without surface treatment) used in Example 1 was used as a 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 plating solution composition was 0 ppm (sodium tungstate was not added) under the conditions for forming the roughened particles.

The following characteristic evaluations were performed on the surface-treated copper foils or copper foils obtained in the above Examples and Comparative Examples.
<Sku, Str, Sa, Sq and Sdr>
Images were taken using a laser microscope (LEXT OLS4000) manufactured by Olympus Corporation. The captured image was analyzed using the analysis software of a laser microscope (LEXT OLS4100) manufactured by Olympus Corporation. Measurements of Sku, Str, Sa, Sq and Sdr were performed in accordance with ISO 25178-2: 2012, respectively. Further, as these measurement results, the average value of the values measured at any five places was used as the measurement result. The temperature at the time of measurement was 23 to 25 ° C. The main setting conditions for the laser microscope and analysis software are as follows.
Objective lens: MPLAPON50XLEXT (magnification: 50x, numerical aperture: 0.95, immersion type: air, mechanical lens barrel length: ∞, cover glass thickness: 0, field of view: 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]: 257 μm wide x 258 μm long [1024 x 1024]
(Since it is measured in the lateral direction, the evaluation length is equivalent to 257 μm)
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, no λs and λf Filter: Gaussian filter Noise reduction: Pretreatment surface (tilt) ) Correction: Implementation Brightness: Adjust so that it is in the range of 30 to 50. Brightness is a value that should be set appropriately according to the color tone of measurement symmetry. The above setting is an appropriate value when measuring the surface of the surface-treated copper foil in which L * is −69 to −10, a * is 2 to 32, and b * is 221.

<Measurement of color tone of measurement target>
Using MiniScan (registered trademark) EZ Model 4000L manufactured by HunterLab as a measuring instrument, CIE L * a * b * color system L *, a * and b * were measured in accordance with JIS Z8730: 2009. .. Specifically, the surface-treated copper foil or the surface to be measured of the copper foil obtained in the above Examples and Comparative Examples was pressed against the photosensitive portion of the measuring instrument, and the measurement was performed while preventing light from entering from the outside. Further, the measurements of L *, a * and b * were performed based on the 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: Reflective illumination diameter: 25.4 mm
Measurement diameter: 20.0 mm
Measurement wavelength / interval: 400-700 nm / 10 nm
Light source: Pulse xenon lamp, 1 emission / measurement Traceability standard: Based on CIE 44 and ASTM E259, National Institute of Standards and Technology (NIST) compliant calibration Standard observer: 10 °
In addition, as the white tile used as the measurement standard, the one with the following object color was used.
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 acid-decomposed to form a solution, and the content of tungsten in the solution was measured by inductively coupled plasma mass spectrometry. The conditions such as solution formation were as described above.
Since the W concentration in the surface-treated layer of Examples 7 to 9 is considered to be the same as that of Example 5, this evaluation was not performed.

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

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-treated layer were within a predetermined range had high peel strength.
On the other hand, although the Sa of the surface-treated layer was equivalent to that 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 out of the predetermined range had a low peel strength. In general, considering that the larger the Sa of the surface treatment layer, the better the adhesiveness with the resin base material, this result, that is, the peel strength is improved by controlling the Sku and Str while the Sa is almost the same. The result was amazing.
Comparing the surface-treated copper foils of Examples 1 to 9 with the copper foils of Comparative Example 1, it can be seen that Str is a very close value. The surface-treated copper foils of Examples 1 to 9 have already been described in view of the fact that the copper foil of Comparative Example 1 is surface-treated and that Str exhibits surface anisotropy and isotropic properties. As described above, in the surface-treated copper foil according to the embodiment of the present invention, the surface-treated layer, particularly the roughened particle layer, is uniformly formed along the minute uneven portion (oil pit in the case of rolled copper foil) on the surface of the copper foil. You can see that it has been done. If the roughened particle layer is not formed along the minute uneven portion, the Str value should be significantly different before and after the surface treatment.
Although the W content of Comparative Example 2 is 0.4 ppm, this is unintentionally applied to any of the plating solutions used for forming the surface-treated layer when the surface-treated copper foil of Comparative Example 2 is manufactured. It is considered that the cause was that W remained. The present inventors consider that W did not remain in the plating solution for forming the roughening treatment layer, but remained in the plating solution for forming the other surface treatment layer.

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 enhancing the adhesiveness with a resin base material, particularly a resin base material suitable for high frequency applications. .. Further, according to the embodiment of the present invention, it is possible to provide a surface-treated copper foil in which roughened particles are formed along minute 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 adhesiveness between a resin base material, particularly a resin base material suitable for high-frequency applications and a surface-treated copper foil. Further, according to the embodiment of the present invention, it is possible to provide a printed wiring board having excellent adhesion between a resin base material, particularly a resin base material suitable for high frequency applications, and a circuit pattern.

10 Copper foil 11 Convex part 12 Concave part 20 Roughened particles 30 Cover plating layer

Claims

It has 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 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-treated layer has Sa of 0.20 to 0.32 μm and 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-treated layer has an Sdr of 38 to 79%.
When the surface-treated copper foil was acid-decomposed to form a solution and the tungsten content in the solution was measured by inductively coupled plasma mass analysis, the tungsten content was 1.0 × 12 / t to 4. The surface-treated copper foil according to any one of claims 1 to 6, wherein 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-treated layer contains a roughened-treated layer.
A copper-clad laminate comprising the surface-treated copper foil according to any one of claims 1 to 8 and a resin base material adhered to the surface-treated layer of the surface-treated copper foil.
A printed wiring board having a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate according to claim 9.