WO2020158140A1

WO2020158140A1 - Surface-treated copper foil, copper-cladded laminate plate, and printed wiring board

Info

Publication number: WO2020158140A1
Application number: PCT/JP2019/046454
Authority: WO
Inventors: 郁浩五刀; 敦史三木; 宣明宮本
Original assignee: Ｊｘ金属株式会社
Priority date: 2019-01-30
Filing date: 2019-11-27
Publication date: 2020-08-06
Also published as: TWI716210B; TW202028484A; JP2020122189A; JP7114499B2

Abstract

A surface-treated copper foil comprising a copper foil and a surface-treating layer formed on at least one surface of the copper foil. In the surface-treated copper foil, the average length RSm of the surface-treating layer is 3.3 to 5.2 μm. Additionally, a copper-cladded laminate plate comprising a surface-treated copper foil and a resin base material bonded to a surface-treating layer of the surface-treated copper foil.

Description

Surface treated copper foil, copper clad laminates and printed wiring boards

The present disclosure relates to surface-treated copper foil, copper-clad laminate, and printed wiring board.

Copper-clad laminates are widely used in various applications such as flexible printed wiring boards. This flexible printed wiring board is formed by etching a copper foil of a copper-clad laminate to form a conductor pattern (also referred to as "wiring pattern"), and mounting electronic components on the conductor pattern by soldering. Manufactured.

In recent years, in electronic devices such as personal computers and mobile terminals, the frequency of electric signals has been increasing with the increase in communication speed and capacity, and there is a demand for flexible printed wiring boards that can handle this. In particular, with respect to the frequency of the electric signal, the higher the frequency, the larger the loss (attenuation) of the signal power, and it becomes difficult to read the data.

The loss of signal power (transmission loss) in an electronic circuit can be roughly divided into two. One is a conductor loss, that is, a loss due to a copper foil, and the second is a dielectric loss, that is, a loss due to a resin base material.
The conductor loss has a skin effect in a high frequency range and has a characteristic that the current flows on the surface of the conductor. Therefore, if the surface of the copper foil is rough, the current will follow a complicated path. 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, in this specification, when simply referred to as “transmission loss” and “conductor loss”, it mainly means “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 resin base material, it is preferable to use a resin base material formed of a low dielectric material (for example, liquid crystal polymer or 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 bonds the copper foil and the resin base material, it is desirable to bond the copper foil and the resin base material without using the adhesive.
Therefore, in order to bond the copper foil and the resin base material without using an adhesive, it has been proposed to form a surface treatment layer on at least one surface of the copper foil. For example, Patent Document 1 proposes a method of providing a roughening treatment layer formed of roughening particles on a copper foil and forming a silane coupling treatment layer on the outermost surface layer.

Japanese Patent Laid-Open No. 2012-112009

The roughening treatment layer can increase the adhesiveness between the copper foil and the resin base material by the anchoring effect of the roughening particles, but may increase the conductor loss due to the skin effect. It is desirable to reduce the number of roughening particles to be electrodeposited. On the other hand, if the roughening particles to be electrodeposited on the surface of the copper foil are reduced, the anchoring effect of the roughening particles is reduced, and the adhesiveness between the copper foil and the resin substrate cannot 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 bond 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. Development of a method to raise it is desired.
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 its type.

The embodiment of the present invention is made to solve the above problems, and is a surface-treated copper foil capable of enhancing the adhesiveness with a resin substrate, particularly a resin substrate suitable for high frequency applications. The purpose is to provide.
Further, an embodiment of the present invention aims to provide 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.
Further, an embodiment of the present invention aims 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.

As a result of intensive studies to solve the above problems, the present inventors have found that the average length RSm of the surface-treated layer of the surface-treated copper foil is the adhesiveness between the surface-treated copper foil and the resin base material. Based on the finding that they are closely related, by controlling the average length RSm of the surface-treated layer of the surface-treated copper foil within a specific range, the adhesiveness between the surface-treated copper foil and the resin base material is increased. They have found that they can obtain it, and have completed an embodiment of the present invention.

That is, the 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 average length RSm of the surface treatment layer is 3.3 to 5.2 μm. Which is a surface-treated copper foil.
Further, an embodiment of the present invention is 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 is a printed wiring board including a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate.

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 substrate, particularly a resin substrate suitable for high frequency applications.
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 adhesiveness between a resin substrate, particularly a resin substrate suitable for high frequency use and a circuit pattern.

Hereinafter, preferred embodiments of the present invention will be specifically described, but the present invention should not be construed as being limited thereto, and is based on the knowledge of those skilled in the art without departing from the gist of the present invention. , Various changes and improvements can be made. A plurality of constituent elements disclosed in this embodiment can form various inventions by an appropriate combination. For example, some components may be deleted from all the components shown in this embodiment, 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. That is, 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 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 average length RSm of 3.3 to 5.2 μm.
Here, the average length RSm represents the average of the lengths of the contour curve elements in the reference length (that is, the average interval of the uneven shape of the surface), and is measured according to JIS B0601:2013. .. RSm of the surface treatment layer is an index representing the density of the uneven shape of the surface treatment layer (in particular, the density of the roughened particles in the roughened particle layer). It can be expected that the smaller the RSm of the surface treatment layer, the higher the density of the uneven shape of the surface treatment layer, and the easier the anchor effect will be exhibited when the surface-treated copper foil is bonded to the resin substrate. However, if RSm is too small (the density of the concavo-convex shape of the surface treatment layer is remarkably increased), it cannot be denied that the transmission loss may be increased. Therefore, from the viewpoint of ensuring a balance between securing the anchor effect and suppressing the transmission loss, the RSm of the surface treatment layer is controlled to 3.3 to 5.2 μm, preferably 3.3 μm or more and less than 5.0 μm.

The root mean square height Sq of the surface-treated layer is preferably 0.33 to 0.55 μm.
Here, the root mean square height Sq represents a parameter (standard deviation of height) corresponding to the standard deviation of the distance from the average surface, and is measured according to ISO 25178. Sq of the surface treatment layer is an index showing the variation in height of the convex portions on the surface of the surface treatment layer. When the Sq of the surface-treated layer is large, variations in height of the protrusions on the surface of the surface-treated layer become large, and the anchor effect is easily exhibited when the surface-treated copper foil is bonded to the resin base material. However, if Sq is too large (variation in height of convex portions is too large), it may cause a problem from the viewpoint of quality control as an industrial product. Therefore, from the viewpoint of ensuring the balance between the anchor effect and the viewpoint of quality control, the Sq of the surface treatment layer is preferably controlled to 0.33 to 0.55 μm, and more preferably 0.40 to 0.55 μm.

The surface-treated layer preferably has an arithmetic average roughness Ra of 0.25 to 0.40 μm.
Here, the arithmetic average roughness Ra represents the average of Z(x) in the reference length of the roughness curve, and is measured according to JIS B0601:2013. Ra of the surface treatment layer is an index representing the average roughness of the surface of the surface treatment layer. When Ra of the surface-treated layer is large, the surface of the surface-treated layer becomes rough, so that the anchor effect is easily exhibited when the surface-treated copper foil is adhered to the resin base material, while the transmission loss increases due to the skin effect. Therefore, from the viewpoint of securing a balance between securing the anchor effect and suppressing the transmission loss, Ra of the surface treatment layer is preferably controlled to 0.25 to 0.40 μm, more preferably 0.28 to 0.35 μm.

The surface-treated layer preferably has an arithmetic average height Sa of 0.25 to 0.40 μm.
Here, the arithmetic mean height Sa is a three-dimensionally expanded parameter of Ra, which is a two-dimensional parameter, and is measured in accordance with ISO 25178. Sa of the surface treatment layer is an index showing the average roughness of the surface of the surface treatment layer, like Ra. When the surface treatment layer has a large Sa, the surface of the surface treatment layer becomes rough, so that the anchor effect is easily exhibited when the surface treated copper foil is adhered to the resin base material, while the transmission loss increases due to the skin effect. Therefore, from the viewpoint of ensuring the balance between securing the anchor effect and suppressing the transmission loss, the Sa of the surface treatment layer is controlled to preferably 0.25 to 0.40 μm, and more preferably 0.30 to 0.40 μm.

The surface treatment layer preferably has a maximum height roughness Rz of 2.3 to 5.1 μm.
Here, the maximum height roughness Rz represents the sum of the maximum value of the peak height and the maximum value of the valley depth of the contour curve in the reference length, and is measured according to JIS B0601:2013. The Rz of the surface treatment layer is an index indicating the presence or absence of protrusions and depressions (peaks and valleys) on the surface of the surface treatment layer. When the surface treatment layer has a large Rz, the surface treatment layer has protrusions and depressions, so that the anchor effect is easily exhibited when the surface-treated copper foil is bonded to the resin substrate, while the skin effect causes transmission loss. Will grow. Therefore, from the viewpoint of securing a balance between securing the anchor effect and suppressing the transmission loss, Rz of the surface treatment layer is preferably controlled to 2.3 to 5.1 μm, more preferably 2.5 to 3.5 μm.

The maximum height Sz of the surface-treated layer is preferably 4.4 to 7.4 μm.
Here, the maximum height Sz is a parameter obtained by expanding the two-dimensional parameter Rz in three dimensions, and is measured according to ISO 25178. Similar to Rz, Sz of the surface treatment layer is an index indicating the presence or absence of protruding irregularities on the surface of the surface treatment layer. If the surface treatment layer has a large Sz, the surface treatment layer has irregularities protruding, so that the anchor effect is easily exhibited when the surface-treated copper foil is bonded to the resin base material, while the skin effect causes a transmission loss. Will grow. Therefore, from the viewpoint of securing a balance between securing the anchor effect and suppressing the transmission loss, the Sz of the surface treatment layer is controlled to preferably 4.4 to 7.4 μm, more preferably 5.0 to 6.5 μm.

The surface treatment layer preferably has a minimum autocorrelation length Sal of 1.2 to 1.7 μm.
Here, the minimum autocorrelation length Sal represents the closest lateral distance at which the surface autocorrelation decays to the correlation value s (0≦s<1), and is measured according to ISO 25178. Sal of the surface treatment layer is an index indicating the presence or absence of a portion where the height of the convex portion is rapidly changing on the surface of the surface treatment layer. The Sal of the surface treatment layer increases as the surface of the surface treatment layer becomes flat, and decreases as the number of protrusions increases. Therefore, from the viewpoint of securing the balance between securing the anchor effect and suppressing the transmission loss, the Sal of the surface treatment layer is preferably controlled to 1.2 to 1.7 μm, more preferably 1.3 to 1.7 μm.

The surface treatment layer preferably has a load area ratio SMr1 for separating the protruding peak portion and the core portion from 11.5 to 16.0%.
Here, the load area ratio SMr1 that separates the protruding peak portion and the core portion represents the number of protruding peak portions, and is measured according to ISO 25178. If the SMr1 of the surface treatment layer is large, the protruding peaks of the surface treatment layer increase, so that the anchor effect is easily exhibited when the surface-treated copper foil is bonded to the resin substrate, while the skin effect causes a large transmission loss. Become. Therefore, from the viewpoint of ensuring the balance between securing the anchor effect and suppressing the transmission loss, the SMr1 of the surface treatment layer is preferably controlled to 11.5 to 16.0%, more preferably 12.0 to 15.5 μm. ..

The surface treatment layer preferably has a load area ratio SMr2 for separating the protruding valley portion and the core portion from 86.5 to 91.0%.
Here, the load area ratio SMr2 for separating the protruding valley portion and the core portion represents the number of protruding valley portions, and is measured in accordance with ISO 25178. When the SMr2 of the surface treatment layer is large, the number of protruding troughs of the surface treatment layer increases, so when the surface treated copper foil is bonded to the resin base material, the anchor effect is easily exhibited, while the skin effect causes a large transmission loss. Become. Therefore, from the viewpoint of ensuring the balance between securing the anchor effect and suppressing the transmission loss, the SMr2 of the surface treatment layer is controlled to preferably 86.5 to 91.0%, more preferably 88.0 to 91.0 μm. ..

The surface treatment layer preferably has a protruding peak height Spk of 0.41 to 1.03 μm.
Here, the protruding peak height Spk is measured in accordance with ISO 25178. If the surface treatment layer has a large Spk, the height of the protruding peak portion of the surface treatment layer is large, so that the anchor effect is easily exhibited when the surface treated copper foil is bonded to the resin substrate, while the skin effect causes a transmission loss. Will grow. Therefore, from the viewpoint of ensuring the balance between securing the anchor effect and suppressing the transmission loss, the Spk of the surface treatment layer is preferably controlled to 0.41 to 1.03 μm, more preferably 0.55 to 1.00 μm.

The surface-treated layer preferably has a root mean square slope RΔq of 37 to 70°.
Here, the root mean square slope RΔq represents the root mean square of the local slope dz/dx in the reference length of the roughness curve, and is measured according to JIS B0601:2013. RΔq of the surface treatment layer is an index representing the slope of the unevenness on the surface of the surface treatment layer. The RΔq of the surface-treated layer increases when the growth of the surface-treated layer (particularly, the roughened particles of the roughened layer) in the z direction is large, and an anchor effect is exhibited when the surface-treated copper foil is bonded to a resin substrate. However, the skin loss increases the transmission loss. Therefore, from the viewpoint of ensuring a balance between securing an appropriate anchor effect and suppressing transmission loss, RΔq of the surface treatment layer is preferably controlled to 37 to 70°, more preferably 45 to 65°.

The type of 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-resistant treatment layer, a rust-prevention treatment layer, a chromate treatment layer, and a silane coupling treatment layer. These layers may be used alone or in combination of two or more. Among them, the surface treatment layer preferably has a roughening treatment layer from the viewpoint of adhesiveness to the resin substrate.
Here, in the present specification, the "roughening treatment layer" is a layer containing roughening particles, and the "roughening particles" are particles having various shapes such as spherical, elliptical, rod-shaped, and dendritic. .. The formation of roughened particles is called roughening treatment, which is generally performed by electroplating, especially so-called burn plating. In the roughening treatment, normal copper plating or the like may be performed as a pretreatment, or as a finishing treatment, normal copper plating or the like may be performed to prevent the roughened particles from falling off. The "roughening treatment layer" in the specification includes a layer formed by these pretreatments and finishing treatments.

The roughening particles are not particularly limited, but are formed from any single substance selected from the group consisting of copper, nickel, cobalt, phosphorus, tungsten, arsenic, molybdenum, chromium and zinc, or an alloy containing at least one of them. can do. Further, after forming the roughened particles, a roughening treatment of providing secondary particles and tertiary particles with a simple substance of nickel, cobalt, copper, zinc or an alloy can be further performed.

The roughening treatment layer can be formed by electroplating. The conditions are not particularly limited as long as they can be adjusted according to the electroplating apparatus used, but typical conditions are as follows. The electroplating may be performed in two steps. It should be noted that the following conditions are conditions in a beaker test in which a cylindrical cathode wound with a copper foil is arranged in the center and an anode is provided around the cathode in a certain interval to perform electroplating. Is.
Plating solution composition: 11-30 g/L Cu, 50-150 g/L sulfuric acid Plating solution temperature: 25-50°C
Electroplating conditions: current density 38.4-48.5 A/dm ² , time 1-10 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 functions of the heat-resistant treatment layer and the rust-prevention treatment layer should be formed as the heat-treatment treatment layer and the rust-prevention treatment layer. Good.
As the heat-resistant treatment layer and/or the anticorrosion treatment 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 (which may be any form of metal, alloy, oxide, nitride, sulfide, etc.). Among them, the heat resistant treatment layer and/or the rustproof treatment layer is preferably a Ni—Zn layer or a Zn layer. In particular, if the Ni content is smaller than the Zn content, that is, the Ni—Zn layer or the Zn layer does not contain Ni, the conductor loss can be reduced without significantly reducing the heat resistance effect and the rust prevention effect. Which is preferable.

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

In particular, it is preferable to form the Ni—Zn layer under the following conditions because it is possible to reduce the conductor loss without significantly reducing the heat resistance effect and the rust preventive effect.
Plating solution composition: 23.5 g/L Ni, 4.5 g/L Zn
Plating solution pH: 3.6
Plating solution temperature: 40°C
Electroplating conditions: current density 1.1 A/dm ² , time 0.7 seconds

The chromate treatment layer is not particularly limited and can be formed of a material known in the art.
Here, in the present specification, the "chromate-treated layer" means a layer formed by a liquid containing chromic anhydride, chromic acid, dichromic acid, chromate or dichromate. The chromate treatment layer is made of any element (metal, alloy, oxide, nitride, sulfide, etc.) such as cobalt, iron, nickel, molybdenum, zinc, tantalum, copper, aluminum, phosphorus, tungsten, tin, arsenic, and titanium. Can be a morphology). Examples of the chromate-treated layer include a chromate-treated layer treated with an aqueous solution of chromic 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 a known method such as immersion chromate treatment or electrolytic chromate treatment. Although those conditions are not particularly limited, for example, the conditions for forming a general immersion chromate treatment layer are as follows.
Chromate solution composition: 1 to 10 g/L K ₂ Cr ₂ O ₇ , 0.01 to 10 g/L Zn
Chromate pH: 2-5
Chromate temperature: 30-55℃

The silane coupling treatment layer is not particularly limited and can be formed of a material known in the art.
Here, in the present specification, the “silane coupling treatment layer” 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 silane coupling agents, epoxy silane coupling agents, mercapto silane coupling agents, methacryloxy silane coupling agents, vinyl silane coupling agents, imidazole 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 preferable. The above-mentioned silane coupling agents can be used alone or in combination of two or more kinds.
A typical method for forming a silane coupling treatment layer is a 1.2% by volume aqueous solution of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (KBM603 manufactured by Shin-Etsu Chemical Co., Ltd.) (pH: 10). ) Is applied and dried to form a silane coupling treatment layer.

The copper foil is not particularly limited, and may be electrolytic copper foil or rolled copper foil. An electrolytic copper foil is generally manufactured by electrolytically depositing copper from a copper sulfate plating bath on a titanium or stainless drum, and a flat S surface (shine surface) formed on the drum side and an S surface And an M surface (mat surface) formed on the opposite side. Generally, since the M surface of the electrolytic copper foil has irregularities, a surface treatment layer is formed on the M surface of the electrolytic copper foil, and the surface treatment layer is adhered to a resin base material to form the surface treatment layer and the resin. Adhesiveness with a base material can be improved.

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

The thickness of the copper foil 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. ..

The surface-treated copper foil having the above configuration can be manufactured according to a method known in the art. Here, RΔq, Ra, Sa, Rz, Sz, Sq, Sal, SMr1, SMr2, Spk and RSm of the surface treatment layer adjust the conditions for forming the surface treatment layer, particularly the conditions for forming the roughening treatment layer. It can be controlled by

The copper-clad laminate can be manufactured by adhering a resin base material 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 material epoxy resin, glass cloth/paper composite base material epoxy resin, glass cloth/glass non-woven composite base material epoxy resin, glass. Examples include cloth-based epoxy resin, polyester film, polyimide film, liquid crystal polymer, and fluororesin.

The method for adhering the surface-treated copper foil and the resin base material is not particularly limited, and it 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 printed wiring boards. The method for manufacturing the printed wiring board is not particularly limited, and a known method such as a subtractive method or a semi-additive method can be used. Among them, the copper clad laminate according to the embodiment of the present invention is most suitable for use in the subtractive method.

When a printed wiring board is manufactured by the subtractive method, it is preferably performed 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 in the portion (unnecessary portion) where the resist pattern is not formed is removed by etching. Finally, the resist pattern 20 on the surface-treated copper foil 1 is removed.
The various conditions in the subtractive method are not particularly limited and can be performed according to the conditions known in the art.

Hereinafter, the embodiments of the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples.

(Example 1)
By preparing a rolled copper foil (HA-V2 foil manufactured by JX Metals Co., Ltd.) having a thickness of 12 μm, degreasing and pickling one surface, and then successively forming a roughening treatment layer and a chromate treatment layer as a surface treatment layer. A surface-treated copper foil was obtained. The conditions for forming each layer are as follows.

<Roughening layer>
A roughened layer was formed by arranging a cylindrical cathode wound with a copper foil in the center, and providing an anode around the cathode at a constant interval and performing electroplating. The electroplating conditions are as follows.
Plating liquid composition: 11 g/L Cu, 50 g/L sulfuric acid
Plating solution temperature: 25°C
Electroplating conditions: current density 48.5 A/dm ² , time 1 second x 2 times

<Chromate treatment layer>
A chromate-treated layer was formed by the following immersion chromate treatment or electrolytic chromate treatment. That is, the chromate-treated layer was formed by immersion chromate treatment during the preparation of the sample for measuring the peel strength described later. On the other hand, when preparing a sample for measuring transmission loss, which will be described later, a chromate-treated layer was formed by electrolytic chromate treatment.
(Immersion chromate treatment)
Chromate composition: 3.0 g/L K ₂ Cr ₂ O ₇ , 0.33 g/L Zn
Chromate solution pH: 3.65
Chromate temperature: 55℃
(Electrolytic chromate treatment)
Chromate composition: 3.0 g/L K ₂ Cr ₂ O ₇ , 0.33 g/L Zn
Chromate solution pH: 3.65
Chromate temperature: 55℃
Electroplating conditions: current density 2.1 A/dm ² , time 1.4 seconds

(Example 2)
Under the conditions for forming the roughening treatment layer, a surface-treated copper foil was obtained under the same conditions as in Example 1 except that the plating solution composition was changed to 15 g/L Cu and 75 g/L sulfuric acid.

(Example 3)
Under the same conditions as in Example 1, except that the plating solution composition was changed to 20 g/L Cu, 100 g/L sulfuric acid, and the current density was changed to 38.4 A/dm ^{2 under the} conditions for forming the roughening treatment layer. A surface-treated copper foil was obtained.

(Example 4)
A surface-treated copper foil was obtained under the same conditions as in Example 1 except that the plating solution composition was changed to 20 g/L Cu and 100 g/L sulfuric acid under the roughening treatment layer forming conditions.

(Example 5)
Except that the plating solution composition was changed to 20 g/L Cu, 100 g/L sulfuric acid, the plating solution temperature was 35° C., and the current density was 38.4 A/dm ^{2 under the} conditions for forming the roughening treatment layer. A surface-treated copper foil was obtained under the same conditions as in Example 1.

(Example 6)
Under the conditions for forming the roughening treatment layer, the surface-treated copper was treated under the same conditions as in Example 1 except that the plating solution composition was changed to 20 g/L Cu, 100 g/L sulfuric acid, and the plating solution temperature was changed to 35°C. Got foil.

(Example 7)
Except that the plating solution composition was changed to 20 g/L Cu, 100 g/L sulfuric acid, the plating solution temperature was changed to 50° C., and the current density was changed to 38.4 A/dm ^{2 under the} conditions for forming the roughening treatment layer. A surface-treated copper foil was obtained under the same conditions as in Example 1.

(Example 8)
Under the conditions for forming the roughening treatment layer, the surface-treated copper was treated under the same conditions as in Example 1 except that the plating solution composition was changed to 20 g/L Cu, 100 g/L sulfuric acid, and the plating solution temperature was changed to 50°C. Got foil.

(Example 9)
Under the conditions for forming the roughening treatment layer, the surface-treated copper was treated under the same conditions as in Example 1 except that the plating solution composition was changed to 30 g/L Cu, 150 g/L sulfuric acid, and the plating solution temperature was changed to 35°C. Got foil.

(Comparative Example 1)
A surface-treated copper foil was obtained under the same conditions as in Example 1 except that the current density was changed to 33.3 A/dm ^{2 under the} roughening treatment layer forming conditions.

(Comparative example 2)
Under the same conditions as in Example 1, except that the composition of the roughening layer was changed to 20 g/L of Cu, 100 g/L of sulfuric acid, and the current density to 33.3 A/dm ^2. A surface-treated copper foil was obtained.

(Comparative example 3)
A surface-treated copper foil was obtained under the same conditions as in Example 1 except that the plating solution composition was changed to 40 g/L of Cu and 200 g/L of sulfuric acid under the roughening treatment layer forming conditions.

The following evaluations were performed on the surface-treated copper foils obtained in the above Examples and Comparative Examples.
<RΔq, Ra, Sa, Rz, Sz, Sq, Sal, SMr1, SMr2, Spk, RSm of the surface treatment layer>
Images were taken using a laser microscope (LEXT OLS4000) manufactured by Olympus Corporation. The photographed image was analyzed using analysis software of a laser microscope (LEXT OLS 4100) manufactured by Olympus Corporation. RΔq, Ra, Rz, and RSm were measured according to JIS B0601:2013, and Sa, Sz, Sq, Sal, SMr1, SMr2, and Spk were measured according to ISO 25178, respectively. In addition, for these measurement results, the average value of the values measured at any three locations 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: 50 times, numerical aperture: 0.95, liquid immersion type: air, mechanical barrel length: ∞, cover glass thickness: 0, field of view: FN18)
Optical zoom magnification: 1 time Scanning mode: XYZ high precision (height resolution: 10 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 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 averaging: 1 time Noise reduction: On Luminance unevenness correction: On Optical noise filter: On Cutoff: None (no λc, λs, λf)
Filter: Gaussian filter Noise removal: Pre-measurement processing Surface (tilt) correction: Implementation Minimum height identification value: 10% of ratio to Rz
Cutting level difference: Rmr1 20%
Rmr2 80%
Relative load length ratio RMr: Cutting level C ₀ : 1 μm below the highest point
Cutting level difference: 1 μm below the cutting level C ₀

<Peel strength>
The 90 degree peel strength was measured in accordance with JIS C6471:1995. Specifically, the width of the circuit (surface-treated copper foil) is set to 3 mm, and a commercially available resin base material (LCP: liquid crystal polymer resin (hydroxybenzoic acid (ester) and hydroxynaphthoic acid) at a speed of 50 mm/min at an angle of 90 degrees is used. (Copolymer with (ester)) film (Vecstar (registered trademark) CTZ manufactured by Kuraray Co., Ltd.; thickness 50 μm)) and the surface-treated copper foil were peeled off, and the strength was measured. The measurement was performed twice, and the average value was used as the peel strength result. If the peel strength is 0.5 kgf/cm or more, it can be said that the adhesion between the circuit and the resin base material is good.
The circuit width was adjusted by a usual subtractive etching method using a copper chloride etching solution.

<Transmission loss>
A resin base material (LCP: liquid crystal polymer resin (copolymer of hydroxybenzoic acid (ester) and hydroxynaphthoic acid (ester)) film (Vecstar (registered trademark) CTZ manufactured by Kuraray Co., Ltd.; thickness 50 μm) ), a microstrip line is formed by etching to have a characteristic impedance of 50Ω, and the transmission coefficient is measured using a network analyzer N5247A manufactured by Agilent Technology Co., Ltd. (currently Keysight Technology Co., Ltd.). , And the transmission loss at a frequency of 30 GHz was obtained. It can be said that the transmission loss is good when it is within −6.0 dB/10 cm.

The above evaluation results are shown in Table 1.

As shown in Table 1, the surface-treated copper foils of Examples 1 to 9 having RSm of the surface-treated layer of 3.3 to 5.2 μm had high peel strength and little transmission loss.
On the other hand, the surface-treated copper foils of Comparative Examples 1 to 3 in which the RSm of the surface-treated layer exceeded 5.2 μm had a small transmission loss but a low peel strength.
In addition, in the above-mentioned examples, when a heat-resistant treatment layer such as a Zn—Ni layer and/or a rust-proof treatment layer is provided, it can be expected that the heat resistance and/or the resistance to rust is improved. In this case, it is preferable that the heat resistant treatment layer and/or the rust prevention treatment layer be formed by smooth plating. Further, when the silane coupling treatment layer is provided, it can be expected that the bonding strength with the resin base material is improved.

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 substrate, particularly a resin substrate suitable for high frequency applications. .. 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 adhesiveness between a resin substrate, particularly a resin substrate suitable for high frequency use and a circuit pattern.

Claims

Copper foil, having a surface treatment layer formed on at least one surface of the copper foil,
A surface-treated copper foil in which the average length RSm of the surface-treated layer is 3.3 to 5.2 μm.
The surface-treated copper foil according to claim 1, wherein the root-mean-square height Sq of the surface-treated layer is 0.33 to 0.55 μm.
The surface-treated copper foil according to claim 1, wherein the surface-treated layer has an arithmetic average roughness Ra of 0.25 to 0.40 μm.
The surface-treated copper foil according to any one of claims 1 to 3, wherein the arithmetic average height Sa of the surface-treated layer is 0.25 to 0.40 μm.
The surface-treated copper foil according to any one of claims 1 to 4, wherein the maximum height roughness Rz of the surface-treated layer is 2.3 to 5.1 µm.
The surface-treated copper foil according to any one of claims 1 to 5, wherein the maximum height Sz of the surface-treated layer is 4.4 to 7.4 μm.
The surface-treated copper foil according to any one of claims 1 to 6, wherein a minimum autocorrelation length Sal of the surface-treated layer is 1.2 to 1.7 μm.
The surface-treated copper foil according to any one of claims 1 to 7, wherein a load area ratio SMr1 for separating the protruding peak portion and the core portion of the surface-treated layer is 11.5 to 16.0%.
The surface-treated copper foil according to any one of claims 1 to 8, wherein a load area ratio SMr2 for separating the protruding valley portion and the core portion of the surface-treated layer is 86.5 to 91.0%.
The surface-treated copper foil according to any one of claims 1 to 9, wherein the protruding peak height Spk of the surface-treated layer is 0.41 to 1.03 μm.
The surface-treated copper foil according to any one of claims 1 to 10, wherein a root mean square slope RΔq of the surface-treated layer is 37 to 70°.
12. The surface treatment layer according to claim 1, wherein the surface treatment layer has at least one layer selected from the group consisting of a roughening treatment layer, a heat treatment treatment layer, an anticorrosion treatment layer, a chromate treatment layer and a silane coupling treatment layer. The surface-treated copper foil according to any one of claims.
A roughening treatment layer is provided on the copper foil, a Ni—Zn layer is provided on the roughening treatment layer, a chromate treatment layer is provided on the Ni—Zn layer, and a silane cup is provided on the chromate treatment layer. The surface-treated copper foil according to any one of claims 1 to 12, which has a ring-treated layer.
The surface-treated copper foil according to any one of claims 1 to 13, wherein the copper foil is a rolled copper foil.
A copper clad laminate comprising the surface-treated copper foil according to any one of claims 1 to 14 and a resin base material adhered to a 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 15.