JP6705094B2 - Copper foil with release film and method for producing copper foil with release film - Google Patents

Description

The present invention relates to a copper foil with a release film which is preferably used for printed wiring board applications and a method for producing the same.

2. Description of the Related Art In recent years, semiconductor integrated circuit devices (hereinafter, sometimes referred to as “semiconductor devices”) used as microprocessors of computers have been improved in performance and multifunction. Therefore, the pitch between terminals of the semiconductor element is required to be narrowed, and the wiring board is also required to have a finer wiring pattern, which is a printed wiring board on which the semiconductor element is mounted.

The method of forming a wiring pattern of a printed wiring board has been manufactured by etching a copper layer of a copper clad laminate. The processing method by etching includes, for example, a subtractive method and a semi-additive method. The subtractive method is a method of removing unnecessary copper layer parts from a copper clad laminate to form a circuit.Apply ink or paint to the part you want to leave as wiring, cover it, and etch the copper layer with a metal corrosive chemical. This is a method of forming a required circuit. On the other hand, the semi-additive method is a method of adding a circuit pattern to the insulating layer substrate afterwards, and is a method of forming a pattern by forming a resist on a portion where the pattern is not formed and plating.

Printed wiring boards to be mounted on electronic devices and the like that have been reduced in size and weight in recent years have been required to form a fine pitch circuit because they are arranged in a narrow area with improved component mounting density.

Copper foil is preferably used as a wiring material, and it has been required to reduce the thickness of the copper foil in order to meet this demand. However, the thinner the copper foil is, the more difficult it is to handle the copper foil and the more easily defects such as wrinkles occur. If the copper foil has wrinkles or pinholes, cracks will form from the wrinkles of the copper foil during press molding, and the fluidized insulating layer resin will exude from the cracks, and the surface of the copper-clad laminate will be contaminated. May damage the flatness of the. These defects of the copper-clad laminate cause the short-circuit or disconnection of the wiring circuit formed in the subsequent manufacturing process of the printed wiring board.

Roll laminating when manufacturing a flexible type copper-clad laminate, even when using a method different from press processing such as casting method, the wrinkles present in the copper foil remain even after the state of the copper-clad laminate. Remains as unevenness on the surface, causing the same problem.

Further, the adhesion strength between the copper foil and the insulating layer resin becomes a problem. If the adhesion strength between the copper foil and the insulating layer resin is low, wiring peeling occurs when the above etching is performed. The finer the pitch of the circuit, the smaller the grounding area of the copper foil and the resin of the insulating layer, and the more easily the wiring peels off. Adhesive strength of 0.5 N/mm or more is required to prevent the peeling of the wiring.

Various proposals have been made to solve this problem. For example, a copper foil with a carrier sheet has been proposed (for example, Patent Document 1). In this method, a metal layer and a carbon layer are formed on a copper foil carrier sheet, and a copper foil is formed on the metal layer and carbon layer by copper plating. By using a carrier sheet, the problem of handling a thin copper foil is solved and a thin copper foil of 3 to 5 μm is realized. In this method, the carrier sheet can be peeled off even after heating at a high temperature of 300° C. or higher.

There is also a carrier using an organic film (for example, Patent Document 2). This is a method in which electroless plating and electrolytic plating are laminated in this order on a resin film. By this method, an ultrathin copper layer having a surface roughness Rz of 2.0 to 4.0 μm is obtained on the resin film.

Further, there is a copper foil whose surface is roughened in order to obtain close contact with a resin by using a copper foil as a carrier (for example, Patent Document 3). It is a method of forming an ultrathin copper layer on a copper foil and roughening it by a plating method. The adhesion strength is obtained by controlling the crystal grain size of the surface roughening.

There is also a carrier using an organic film (for example, Patent Document 4). In this method, copper is formed by a physical vapor deposition method using a plastic film as a support and any one of a cellulose resin, a water-soluble polyester resin and a water-soluble acrylic resin for a release layer. In this method, since the surface roughness depends on the plastic film, the surface roughness Ra of 0.09 μm or less can be obtained.

JP, 2008-255462, A JP, 2000-141542, A JP, 2015-24515, A JP, 2009-231790, A

However, in recent years, a wiring board capable of transmitting a high frequency signal has been required in order to realize a high speed operation in a circuit system. Generally, when a high frequency signal is transmitted to a conductor layer of a wiring board, a skin effect in which a current concentrates near the conductor surface occurs, and as the frequency increases, the conductor loss increases due to the effect of the skin effect. When the surface of the conductor layer is rough, the electric current flows intensively through the uneven portion of the conductor surface due to the skin effect, so that the conductor loss increases remarkably. Therefore, in order to manufacture a wiring board capable of transmitting high frequency signals, it is necessary to use a smooth copper foil having a surface roughness Ra of 0.10 μm or less. However, while satisfying this surface roughness, it was not possible to obtain adhesion strength with the insulating layer resin used for high frequency applications.

In the case of copper foil with a carrier as in Patent Documents 1 to 3, after forming a release layer on a metal foil or an organic film, a copper seed layer is formed by electroless plating or a sputtering method, and then an electrolytic plating method. To form a copper foil. In the electrolytic plating method, it is difficult to satisfy the surface roughness while satisfying the film thickness uniformity required for wiring. Generally, the surface roughness Ra of the copper foil is generally 0.20 μm or more, and even if the leveling property is improved by changing the composition of the plating solution, a copper foil having a surface roughness Ra of 0.10 μm or less is produced. It's difficult. Further, if the surface roughness is reduced, the adhesion strength with the insulating layer resin will be reduced.

In the case of the film with a copper film as in Patent Document 4, the copper layer is formed by physical vapor deposition. When forming a copper layer by the physical vapor deposition method, the surface condition depends on the surface of the base material, so a copper film with a small surface roughness can be formed by selecting a base material with a small surface roughness. .. Therefore, it is possible to produce a copper film having a surface roughness Ra of 0.09 μm or less, which is suitable for high frequency applications. However, if the method of simply reducing the surface roughness is used, the adhesion strength with the insulating layer resin becomes low, and the wiring peels off when the wiring is formed.

Therefore, in the present invention, a copper layer is formed by a physical vapor deposition method using an organic film to finely roughen the surface while maintaining the surface roughness Ra of 0.10 μm or less, thereby improving the adhesion strength with the insulating layer resin. The purpose was to produce a copper foil with a release film that can be secured.

As a result of intensive studies in view of the above problems, the present inventors formed fine crystallites of copper having a thickness of 5 nm or more and 50 nm or less on the surface, thereby maintaining a surface roughness Ra of 0.10 μm or less and closely adhering to an insulating layer resin. We have obtained a copper foil with a release film that has improved strength.

That is, the present invention is a release film-attached copper foil having a release layer on at least one surface of a film, and a copper layer on the release layer, wherein the copper layer has a thickness of 0.5 μm or more. It relates to a copper foil with a release film, which is 3.0 μm or less, and the surface of the copper layer contains crystal grains of 5 nm or more and 50 nm or less in an area ratio of 65% or more.
A preferred embodiment is a copper foil with a release film, wherein the surface of the copper layer contains 80% or more of crystal grains of 5 nm or more and 50 nm or less.

A preferred embodiment relates to a copper foil with a release film, wherein the surface roughness Ra of the copper layer is 0.01 μm or more and 0.10 μm or less.
A preferred embodiment relates to a copper foil with a release film, wherein the release layer is a carbon layer having a thickness of 0.5 nm or more and 5.0 nm or less.

A preferred embodiment relates to a method for producing a copper foil with a release film, which comprises forming the copper layer by a vacuum deposition method and then forming the copper layer by a sputtering method.

The copper foil with a release film of the present invention has a thin thickness and a smooth surface, and can be peeled off even after the heat treatment at 160° C. to 220° C. used for heat treatment such as vacuum hot pressing and vacuum laminating. A copper clad laminate having a smooth copper layer surface can be obtained by laminating the release film-attached copper foil and the insulating layer sheet. By etching this copper-clad laminate, it is possible to obtain a printed wiring board having a high adhesion strength between the copper layer and the insulating layer resin. This copper-clad laminate can be suitably used for high frequency applications.

It is an AFM observation image of the copper layer surface of Example 1 in this invention. It is an AFM differential image of the copper layer surface of Example 1 in this invention. It is an AFM observation image of the copper layer surface of the comparative example 1 in this specification. It is an AFM differential image of the copper layer surface of the comparative example 1 in this specification.

The present invention will be described in detail below.

The copper foil with a release film of the present invention has a release layer and a copper layer formed in this order on one surface of the film.

The film used in the present invention is a thin film formed by molding a polymer such as a synthetic resin.

The copper layer in the present invention is preferably formed on the release layer on one surface of the polymer film by the vacuum vapor deposition method in the physical vapor deposition method and then by the sputtering method.

The thickness of the copper layer in the present invention is preferably 0.5 μm or more and 3.0 μm or less. If it exceeds 3.0 μm, the warp of the copper layer itself may cause spontaneous peeling from the base film. Further, the amount of heat applied to the base material during vapor deposition also increases, and the base material may be thermally deformed. If the thickness is less than 0.5 μm, pinholes and voids in the copper layer will increase.

The vacuum evaporation method includes an induction heating evaporation method, a resistance heating evaporation method, a laser beam evaporation method, an electron beam evaporation method, and the like. Although any vapor deposition method may be used, the electron beam vapor deposition method is preferably used from the viewpoint of having a high film formation rate. During vapor deposition, vapor deposition may be performed while cooling the film so that the temperature of the substrate does not rise.

The vapor deposition film formed using the physical vapor deposition method is affected by heat as the vapor deposition film becomes thicker. In the present invention, the thickness of the copper layer is preferably 0.5 μm or more and 3.0 μm or less. Therefore, if a film is formed to this thickness only by the vacuum deposition method, crystal grains may grow and increase to 100 nm or more. The copper foil having a crystal grain of 100 nm or more on the surface is smooth, has no anchor effect, and has low adhesion strength with the insulating layer. Therefore, in order to obtain adhesion strength, it is preferable to form crystal grains of 5 nm or more and 50 nm or less on the crystal grains of 100 nm or more to form a finely roughened surface that contributes to adhesion. In order to form small crystal grains of 5 nm or more and 50 nm or less on the crystal grains of 100 nm or more, for example, a sputtering method can be used. Although it can be formed by a vacuum vapor deposition method, it is necessary to successively perform vacuum vapor deposition in order to further form small crystal grains of 5 nm or more and 50 nm or less after forming crystal grains of 100 nm or more. If vacuum deposition is continuously performed, only crystal grains grow, and it is difficult to form small crystal grains on the surface. Therefore, it is not simple because it is necessary to divide the process into two times or to have two vapor deposition equipments in the apparatus. The sputtering method can be preferably used because a device can be provided relatively easily, and the sputtering method can be performed in one step by sequentially performing the vapor deposition on the same line.

The thickness of the copper layer obtained by the sputtering method is about 10 nm to 20 nm, which is very thin with respect to the thickness of the copper layer formed by the vacuum deposition method. The thickness of the copper layer formed by the vacuum evaporation method is a value close to the thickness of the copper layer of the copper foil with a release film of the present invention.

The small crystal grain formed on the crystal grain of 100 nm or more in the present invention is preferably 5 nm or more and 50 nm or less. When crystal grains smaller than 5 nm are formed, the influence of fine roughening is small and the adhesion strength does not increase so much. On the other hand, if it is larger than 50 nm, the roughening is not fine and the adhesion strength becomes small. Therefore, the thickness is preferably 5 nm or more and 50 nm or less, and more preferably 10 nm or more and 50 nm or less.

In the present invention, the ratio of crystal grains of 5 nm or more and 50 nm or less is preferably 65% or more in area ratio. If the area ratio is less than 65%, the effect of fine roughening is small and the adhesion strength does not increase. The area ratio is preferably 65% or more, more preferably 80% or more.

When the area ratio is 80% or more, it is presumed that a dense and stable copper oxide film is formed on the copper layer surface, which is preferable. It is considered that this thin oxide film functions as a protective film even in a high temperature environment and suppresses the progress of oxidation. Therefore, when the area ratio is 80% or more, it is not necessary to perform the rustproofing treatment. In general rust prevention treatment, a thin organic film such as benzotriazole is formed on the copper surface to suppress contact with oxygen and prevent oxidation, but to prevent adhesion with resin, it is necessary to attach it before bonding with resin. Need to be removed. On the other hand, a dense, thin and stable copper oxide film is preferable because it is assumed to be bonded to the terminal groups of the resin via the oxygen in the film and the adhesive force is further increased.

In the present invention, forming a copper layer on a film by roll-to-roll by a vacuum deposition method is preferably exemplified. In that case, the film is exposed to heat during deposition. The film is cooled by the cooling roll in contact with the back surface, but if the heat resistant temperature of the film is low or the heat shrinkage of the film is large at this time, it will float from the cooling roll due to the deformation of the film and the cooling will be sufficient. If not melted, holes will be created due to melting. Therefore, it is preferable that the heat resistant temperature is high and the heat shrinkage is small. It is assumed that the temperature on the film during vapor deposition when forming the copper layer by the electron beam method is about 100 to 120°C. Therefore, it is preferable that the heat-resistant temperature is 120° C. or higher, and the thermal shrinkage at 120° C. is 2.0% or less in both the longitudinal direction (also referred to as MD direction) and the width direction (also referred to as TD direction) of the film. . When it exceeds 2.0%, it is difficult to control the deformation of the film by changing the tension or cooling the roll, and when the thickness of the copper layer is tried to be formed, the film separates from the roll and the temperature of the film rises to melt the holes. May be empty. The heat shrinkage ratio is more preferably 1.8% or less, still more preferably 1.5% or less. The heat shrinkage rate of the film can be obtained from the dimensional change rate before and after the film is treated at a predetermined temperature for 30 minutes.

The copper foil with a release film of the present invention may have a heat treatment step in the step of attaching it to the insulating layer resin, and in that case, heat resistance is required. Here, the insulating layer resin contains a thermosetting resin such as an epoxy resin, and the resin needs to be cured at the time of bonding, so that vacuum heat pressing or the like is required. Although this temperature condition varies depending on the type of insulating layer resin, a temperature condition of about 220° C. is required at a place where fine wiring is required. Therefore, the melting point of the film is preferably 220° C. or higher. More preferably, it is 230° C. or higher.

As the film preferably used in the present invention, for example, a polyimide film, a syndiotactic polystyrene film, an aromatic polyamide film, a modified polyphenylene ether film, a fluorine-based film, a liquid crystal polymer film can be used. Of these, a polyimide film is more preferably used. These films may be used alone or in combination. Further, as long as the temperature condition of the bonding step is satisfied, a resin coated surface may be used.

The thickness of the film is preferably 25 μm or more and 150 μm or less. If the thickness of the film is less than 25 μm, the film may be deformed or torn due to the stress generated during vapor deposition. On the other hand, if the thickness exceeds 150 μm, the film cannot be controlled by the tension and winding misalignment or the like may occur, and the amount that can be charged in one vapor deposition decreases and the productivity deteriorates. It is more preferably 35 μm or more and 125 μm or less.

In the present invention, the release layer is provided on at least one surface of the film. The film and the release layer are sometimes called a release film. The release layer is sufficient if a copper layer can be formed on the release layer, and after the copper layer is formed, the insulating layer sheet and the copper foil surface of the release film-attached copper foil are bonded together, and then the film and the copper foil are attached. It just needs to be peeled off. The release layer after peeling may be attached to either the film or the copper foil.

A melamine resin, a cellulose resin, a carbon layer and the like are preferably used for the release layer in the present invention. Although any release layer may be used, a carbon layer is preferably used. While the melamine resin and the cellulose resin are formed by coating in a film shape, the carbon layer can be formed by the sputtering method or the CVD method, so that the carbon layer can be formed simultaneously with the formation of the copper layer in one apparatus. Therefore, the carbon layer is preferably used.

In the present invention, when the vapor deposition is performed by using, for example, the electron beam method, the film and the release layer are affected by the electron beam. It is assumed that the molecular chains are broken by the electron beam or the cut molecules are cross-linked. For this reason, the film itself may be deteriorated, or the film and the release layer may be chemically bonded to each other and may not be peeled off. Therefore, a carbon layer having a large number of bonds is preferably used as the release layer in the present invention.

Further, as a method of forming such a release layer, there are a method by vapor deposition and a method of electrically depositing a carbon film from an organic solvent. Examples of the vapor deposition method include an arc ion plating method, a magnetron sputtering method, a high frequency plasma CVD method, a pulse type direct current plasma CVD method, an ionization vapor deposition method, and a plasma ion implantation film forming method. A magnetron sputtering vapor deposition method that can be relatively easily realized as an apparatus is preferably used.

The thickness of the carbon layer is preferably 0.5 nm or more and 5.0 nm or less. If it is less than 0.5 nm, the carbon layer is thin and the film and copper cannot be separated well. Further, the layer is thin, and when a plurality of bonds are broken by the influence of the electron beam, the molecular chains are easily broken. On the other hand, if it exceeds 5.0 nm, the peeling force between the carbon layer and the copper layer becomes weak, and peeling may occur during vapor deposition conveyance. More preferably, it is 1.0 nm or more and 4.0 nm or less.

It is difficult to directly measure the thickness of such a carbon layer, but from the transmittance, Lambert-Beer's law described later is used.

Can be calculated using. Here, I ₀ is the amount of light before passing through the thin film, I is the amount of light after passing through the thin film, α is the extinction coefficient, Z is the film thickness, k is the extinction coefficient, and λ is the wavelength.

When a melamine resin or a cellulose resin is used for the release layer in the present invention, the thickness of the release layer is not particularly limited, but the release layer is prepared by diluting the resin with a solvent and coating the film surface to dry the solvent. Form the layers. Therefore, it is preferable that the thickness is 0.1 μm or more and 2.0 μm or less. If it is less than 0.1 μm, it is difficult to adjust the film thickness, and if it exceeds 2.0 μm, it takes a long time to dry because the amount of solvent diluted increases. It is more preferably 0.2 μm or more and 1.0 μm or less.

In the copper foil with a release film of the present invention, it is preferable that the surface roughness Ra of the copper layer which is not in contact with the release layer is 0.01 μm or more and 0.10 μm or less. If it exceeds 0.10 μm, the surface is rough and the conductor effect increases due to the influence of the skin effect, which makes it difficult to use for high frequency applications. It is more preferably 0.05 μm or less, still more preferably 0.03 μm or less.

Moreover, the copper layer of the copper foil with a release film of the present invention depends on the surface roughness of the film. For this reason, also in the film, at least the surface roughness Ra of the surface in contact with the release layer is preferably 0.10 μm or less. It is more preferably 0.05 μm or less, still more preferably 0.03 μm or less.

The copper foil obtained in the present invention can be peeled off even after heat treatment up to 220° C. such as vacuum hot pressing or vacuum laminating, and a copper clad laminate having a smooth copper layer surface can be obtained by attaching the copper foil to an insulating layer sheet. By etching this copper clad laminate, it is possible to obtain a printed wiring board having a good circuit pattern with few defects on the wiring. Further, this copper clad laminate can be suitably used for high frequency applications.

The copper foil obtained in the present invention is mainly used for circuits, but is not limited to this. For example, it can be used for shields of electromagnetic waves, transfer foils of touch panels and the like.

It should be noted that the present invention is not limited to the configurations described above, and various modifications are possible, and the present invention is also applicable to embodiments obtained by appropriately combining the technical means disclosed in different embodiments. It is included in the technical scope of the invention.

Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to these Examples.

(Measurement of surface roughness)
The surface roughness Ra is the arithmetic average roughness defined in JIS B 0601-1994, and the reference roughness (l) is extracted from the roughness curve in the direction of the average line, and the direction of the average line of this extracted portion. Is the value obtained by the following formula when the X-axis is taken as the vertical axis and the Y-axis is taken in the direction orthogonal to the X-axis and the roughness curve is expressed as y=f(x).

The surface of the film and the copper foil with the release film were observed with a laser microscope (VK-8500 manufactured by KEYENCE) and the surface was observed in accordance with JIS B0601-1994. The analysis was performed using the analysis application software VK-H1W manufactured by Keyence Corporation, and the cutoff value was 0.25 μm. In the software, the surface roughness Ra was determined by designating a length of 100 μm. The measurement was performed in one direction of the sample and in a direction perpendicular thereto, and the larger value was taken as the surface roughness Ra.

(Measurement of copper layer thickness)
The thickness of the copper layer of the copper foil with the release film was measured by a fluorescent X-ray film thickness meter (SFT9400 manufactured by SSI Nanotechnology).

(Carbon layer thickness)
The transmittance of the carbon layer formed on the film was measured with a transmittance meter, and from the obtained values, Lambert-Beer's law

The film thickness was calculated from Here, I ₀ is the amount of light before passing through the thin film, I is the amount of light after passing through the thin film, α is the extinction coefficient, Z is the film thickness, k is the extinction coefficient, and λ is the wavelength. The value of the extinction coefficient of 0.047 when the wavelength was 632.8 nm was adopted with I/I ₀ as the transmittance, and the value was used as the thickness of the carbon layer.

(Peeling test after vacuum press)
The release film-attached copper foil was cut into a size of 340 mm×340 mm, and laminated with Adfrema NC0204 (manufactured by NAMICS Corporation). The bonding was performed at 110° C. for 30 minutes and 0.5 MPa, and then vacuum pressing was performed at 220° C. for 105 minutes and 3.0 MPa. The vacuum condition was 16 torr. When the film was able to be peeled smoothly after bonding, it was marked as ◎, and it was peelable, but when the film was torn during peeling or when it was difficult to peel partly, it was marked as ○ and could not be peeled. Things were marked as x.

In addition, the copper clad product that was stuck was cut into a size of 150 mm×20 mm. A part of the film was peeled from the copper layer via the release layer and fixed to Tensilon, and the film was peeled at 180° peeling, and the value obtained was converted to a peeling force per 1 mm to obtain a peeling force. A peeling force of 0.1×10 ⁻² N/mm or more and less than 9.0×10 ⁻² N/mm is defined as ◎ in a good range, and 9.0×10 ⁻² N/mm or more and 1.5× A range of 10 ⁻¹ N/mm or less was marked as ◯ in a peelable range, and other than that was marked as ×.

(Adhesion strength with resin)
The copper portion of the copper-clad laminate having the release film-attached copper foil and the insulating layer sheet bonded together was plated to a copper thickness of up to 20 μm. After that, the sample was cut into a width of 10 mm and fixed to an acrylic plate with a double-sided tape. Then, it was peeled off at a speed of 50 mm/min with a Tensilon tester to measure the adhesion strength. Adhesion strength of 0.7 N/mm or more was evaluated as ⊚ when the adhesion strength was good, and that of 0.4 N/mm or more and less than 7.0 N/mm was evaluated as ◯ when the adhesion strength was sufficient.

(Crystal grain diameter and number, area ratio)
The copper layer side surface of the copper foil with a release film was observed using an atomic force microscope (AFM5200S manufactured by Hitachi High-Tech Science). The observation is performed at 1 μm×1 μm, and after edge enhancement is performed with the image enhanced software “LucisPro MT/R” (manufactured by Mitani Corp.), the image is analyzed using the image analysis/measurement software “WinROOF2015 Standard” (manufactured by Mitani Corp.). The crystal grain size and the number of grains were counted, and the area ratio of the crystal grains was calculated.

(About surface oxidation resistance)
Using a clean oven, the copper foil with release film was heat-treated as it was in the air atmosphere at 140° C. for 1 hour, and the oxidation resistance was judged by the degree of discoloration after the heat treatment. The case where the surface color has changed to blue is marked with X, and the case where the copper color can be maintained without discoloring is marked with ○.

(Example 1)
A carbon layer was formed by magnetron sputtering on a biaxially oriented polyimide film having a thickness of 50 μm (trade name “Kapton” type: 200EN manufactured by Toray DuPont Co., Ltd.) to form a release film. The surface roughness Ra of the film was 0.06 μm.

As the sputtering conditions for forming the carbon layer, a target having a size of 50 mm×550 mm was used, the degree of vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 2 kw using a DC power supply. The transmittance of the carbon layer was 99.91%, and the carbon layer thickness calculated from the conversion formula was 1.0 nm.

Copper was vacuum-deposited to a thickness of 2.0 μm at a film forming rate of 2.0 μm·m/min and a line speed of 1.0 m/min on the carbon layer forming surface of this release film by an electron beam evaporation method, and then magnetron sputtering method. Then, copper microcrystals were formed to produce a copper foil with a release film. As the conditions for forming the copper microcrystals under the sputtering conditions, a target of 50 mm×550 mm size was used, the vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 5.0 kw using a DC power supply. The copper layer had a thickness of 2.06 μm and a surface roughness Ra of 0.06 μm. The AFM observation image of this copper layer surface is as shown in FIG. 1, and the differential image is as shown in FIG. The area ratio of the crystal grains of 5 nm or more and 50 nm or less was 88.8%.

When it was laminated with a resin by a vacuum press, it could be peeled well even after pressing, and the peeling force of the film after pressing was 0.9×10 ⁻² N/mm. The adhesion strength between the copper foil and the resin after this bonding was 0.87 N/mm.

Further, the release film-coated copper foil was heat-treated as it was in the air atmosphere at 140° C. for 1 hour, but the surface of the copper foil was not discolored.

(Example 2)
A carbon layer was formed by a magnetron sputtering method on a biaxially oriented polyimide film having a thickness of 50 μm (trade name “UPILEX-S” type: 50S, manufactured by Ube Industries, Ltd.) to prepare a release film. The surface roughness Ra of the film was 0.21 μm.

As the sputtering conditions for forming the carbon layer, a target having a size of 50 mm×550 mm was used, the vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 3 kw using a DC power supply. The transmittance of the carbon layer alone was 99.86%, and the carbon layer thickness calculated from the conversion formula was 1.5 nm.

Copper was vacuum-deposited to a thickness of 2.0 μm at a film forming rate of 2.0 μm·m/min and a line speed of 1.0 m/min on the carbon layer forming surface of this release film by an electron beam evaporation method, and then magnetron sputtering method. Then, copper microcrystals were formed to produce a copper foil with a release film. As the copper microcrystal formation conditions under the sputtering conditions, a target of 50 mm×550 mm size was used, the vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 1.2 kw using a DC power supply. The copper layer had a thickness of 2.01 μm and a surface roughness Ra of 0.21 μm. The area ratio of crystal grains of 5 nm or more and 50 nm or less on the surface of the copper layer was 68.2%.

When it was laminated with a resin by a vacuum press, it could be peeled well even after pressing, and the peeling force of the film after pressing was 0.65×10 ⁻² N/mm. The adhesion strength between the copper foil and the resin after this bonding was 0.41 N/mm.

Further, the release film-coated copper foil was heat-treated as it was in an air atmosphere at 140° C. for 1 hour, but the copper foil surface turned blue.

(Example 3)
A carbon layer was formed by magnetron sputtering on a biaxially oriented polyimide film having a thickness of 50 μm (trade name “Kapton” type: 200EN manufactured by Toray DuPont Co., Ltd.) to form a release film. The surface roughness Ra of the film was 0.05 μm.

As the sputtering conditions for forming the carbon layer, a target having a size of 50 mm×550 mm was used, the degree of vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 2 kw using a DC power supply. The transmittance of the carbon layer alone was 99.91%, and the carbon layer thickness calculated from the conversion formula was 1.0 nm.

Copper was vacuum-deposited to a thickness of 2.0 μm at a film forming speed of 2.0 μm·m/min and a line speed of 1.0 m/min on the carbon layer forming surface of this release film by a resistance heating evaporation method, and then magnetron sputtering method. Then, copper microcrystals were formed to produce a copper foil with a release film. As the copper microcrystal formation conditions under the sputtering conditions, a target having a size of 50 mm×550 mm was used, the vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 2.5 kw using a DC power supply. The copper layer had a thickness of 2.03 μm and a surface roughness Ra of 0.05 μm. The area ratio of crystal grains of 5 nm or more and 50 nm or less on the surface of the copper layer was 79.4%.

When a part of the copper foil with release film, which has not been peeled off, was attached to the resin by a vacuum press, the copper foil was peeled off well after pressing and the peeling force of the film after pressing was 0.90×10 ^−. It was ² N/mm. The adhesive strength between the copper foil and the resin after the bonding was 0.61 N/mm.

Further, the release film-coated copper foil was heat-treated as it was in an air atmosphere at 140° C. for 1 hour, but the copper foil surface turned blue.

(Example 4)
A carbon layer was formed by magnetron sputtering on a biaxially oriented polyimide film having a thickness of 50 μm (trade name “Kapton” type: 200EN manufactured by Toray DuPont Co., Ltd.) to form a release film. The surface roughness Ra of the film was 0.06 μm.

As the sputtering conditions for forming the carbon layer, a target having a size of 50 mm×550 mm was used, the degree of vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 0.4 kw using a DC power supply. The transmittance of the carbon layer alone was 99.96%, and the carbon layer thickness calculated from the conversion formula was 0.4 nm.

Copper was vacuum-deposited on the carbon layer-formed surface of the release film by induction heating vapor deposition to a thickness of 2.0 μm at a film forming rate of 2.0 μm·m/min and a line speed of 1.0 m/min, followed by magnetron sputtering. Then, copper microcrystals were formed to produce a copper foil with a release film. As the copper microcrystal formation conditions under the sputtering conditions, a target having a size of 50 mm×550 mm was used, the degree of vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 5.0 kw using a DC power supply. The copper layer had a thickness of 2.02 μm and a surface roughness Ra of 0.06 μm. The area ratio of crystal grains of 5 nm or more and 50 nm or less on the surface of the copper layer was 87.9%.

When it was attached to the resin by a vacuum press, some parts were difficult to peel off after pressing. The peeling force and the adhesion strength with the resin were measured by utilizing the part which can be peeled off well. The peeling force of the film after pressing was 1.8×10 ⁻² N/mm. The adhesive strength between the copper foil and the resin after this bonding was 0.86 N/mm.

Further, the release film-coated copper foil was heat-treated as it was in the air atmosphere at 140° C. for 1 hour, but the surface of the copper foil was not discolored.

(Example 5)
A carbon layer was formed by magnetron sputtering on a biaxially oriented polyimide film having a thickness of 50 μm (trade name “Kapton” type: 200EN manufactured by Toray DuPont Co., Ltd.) to form a release film. The surface roughness Ra of the film was 0.06 μm.

As the sputtering conditions for forming the carbon layer, a target having a size of 50 mm×550 mm was used, the degree of vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 2 kw using a DC power supply. The transmittance of the carbon layer was 99.91%, and the carbon layer thickness calculated from the conversion formula was 1.0 nm.

Copper was vacuum-deposited to a thickness of 2.0 μm at a film forming rate of 2.0 μm·m/min and a line speed of 1.0 m/min on the carbon layer forming surface of this release film by an electron beam evaporation method, and then magnetron sputtering method. Then, copper microcrystals were formed to produce a copper foil with a release film. As the conditions for forming copper microcrystals by the sputtering conditions, a target of 50 mm×550 mm size was used, the vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 8.0 kw using a DC power supply. The copper layer had a thickness of 2.06 μm and a surface roughness Ra of 0.06 μm. The AFM observation image of this copper layer surface is as shown in FIG. 1, and the differential image is as shown in FIG. The area ratio of the crystal grains of 5 nm or more and 50 nm or less was 78.9%.

When it was laminated with a resin by a vacuum press, it could be peeled well even after pressing, and the peeling force of the film after pressing was 0.90×10 ⁻² N/mm. The adhesive strength between the copper foil and the resin after this bonding was 0.54 N/mm.

Further, the release film-coated copper foil was heat-treated as it was in an air atmosphere at 140° C. for 1 hour, but the copper foil surface turned blue.

(Example 6)
A carbon layer was formed by a magnetron sputtering method on a biaxially oriented polyimide film having a thickness of 50 μm (trade name “UPILEX-S” type: 50S, manufactured by Ube Industries, Ltd.) to prepare a release film. The surface roughness Ra of the film was 0.21 μm.

As the sputtering conditions for forming the carbon layer, a target having a size of 50 mm×550 mm was used, the vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 3 kw using a DC power supply. The transmittance of the carbon layer alone was 99.86%, and the carbon layer thickness calculated from the conversion formula was 1.5 nm.

Copper was vacuum-deposited to a thickness of 1.0 μm at a film forming rate of 2.0 μm·m/min and a line speed of 2.0 m/min on the carbon layer forming surface of this release film by an electron beam evaporation method, and then magnetron sputtering method. Then, copper microcrystals were formed to produce a copper foil with a release film. As the copper microcrystal formation conditions under the sputtering conditions, a target of 50 mm×550 mm size was used, the vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 5 kW using a DC power supply. The copper layer had a thickness of 0.98 μm and a surface roughness Ra of 0.21 μm. The area ratio of crystal grains of 5 nm or more and 50 nm or less on the surface of the copper layer was 79.4%.

When it was laminated with a resin by a vacuum press, it could be peeled well even after pressing, and the peeling force of the film after pressing was 0.65×10 ⁻² N/mm. The adhesion strength between the copper foil and the resin after this bonding was 0.60 N/mm.

(Example 7)
A carbon layer was formed by magnetron sputtering on a biaxially oriented polyimide film having a thickness of 50 μm (trade name “Kapton” type: 200EN manufactured by Toray DuPont Co., Ltd.) to form a release film. The surface roughness Ra of the film was 0.05 μm.

As a sputtering condition for forming the carbon layer, a target having a size of 50 mm×550 mm was used, a vacuum achievement was 1×10 ⁻² Pa or less, and a sputtering output was 10 kW using a DC power supply. The transmittance of the carbon layer alone was 99.42%, and the carbon layer thickness calculated from the conversion formula was 6.2 nm.

Copper was vacuum-deposited on the carbon layer forming surface of the release film by a resistance heating vapor deposition method at a film forming rate of 3.0 μm·m/min and a line speed of 5.0 m/min to a thickness of 0.6 μm, and then magnetron sputtering method. Then, copper microcrystals were formed to produce a copper foil with a release film. Part of the copper layer and the film peeled off during the transportation. As the copper microcrystal formation conditions under the sputtering conditions, a target of 50 mm×550 mm size was used, the degree of vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 6 kW using a DC power supply. The copper layer had a thickness of 0.63 μm and a surface roughness Ra of 0.05 μm. The area ratio of crystal grains of 5 nm or more and 50 nm or less on the surface of the copper layer was 68.3%.

When the copper foil with the release film was used for bonding with a resin by using a non-peeled portion, the film could be peeled well after pressing and the peeling force of the film after pressing was 0.3×10 ^−. It was ² N/mm. The adhesion strength between the copper foil and the resin after this bonding was 0.42 N/mm.

(Comparative Example 1)
A carbon layer was formed by magnetron sputtering on a biaxially oriented polyimide film having a thickness of 50 μm (trade name “Kapton” type: 200EN manufactured by Toray DuPont Co., Ltd.) to form a release film. The surface roughness Ra of the film was 0.06 μm.

As the sputtering conditions for forming the carbon layer, a target having a size of 50 mm×550 mm was used, the degree of vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 2 kw using a DC power supply. The transmittance of the carbon layer alone was 99.91%, and the carbon layer thickness calculated from the conversion formula was 1.0 nm.

The release film was formed by vacuum-depositing copper on the carbon layer-formed surface of the release film by an electron beam evaporation method to a thickness of 2.0 μm at a film forming rate of 2.0 μm·m/min and a line speed of 1.0 m/min. An attached copper foil was produced. Copper microcrystals were not formed by sputtering. The copper layer had a thickness of 1.99 μm and a surface roughness Ra of 0.06 μm. The AFM observation image of the copper layer surface is as shown in FIG. 3, and the differential image is as shown in FIG. The area ratio of the crystal grains of 5 nm or more and 50 nm or less was 61.4%.

When it was laminated with a resin by a vacuum press, it could be peeled well even after pressing, and the peeling force of the film after pressing was 0.9×10 ⁻² N/mm. The adhesive strength between the copper foil and the resin after the bonding was 0.21 N/mm.

Further, the release film-coated copper foil was heat-treated as it was in an air atmosphere at 140° C. for 1 hour, but the copper foil surface turned blue.

(Comparative example 2)
A carbon layer was formed by magnetron sputtering on a biaxially oriented polyimide film having a thickness of 50 μm (trade name “Kapton” type: 200EN manufactured by Toray DuPont Co., Ltd.) to form a release film. The surface roughness Ra of the film was 0.06 μm.

As the sputtering conditions for forming the carbon layer, a target having a size of 50 mm×550 mm was used, the degree of vacuum achievement was 1×10 ⁻² Pa or less, and the sputtering output was 2 kw using a DC power supply. The transmittance of the carbon layer alone was 99.91%, and the carbon layer thickness calculated from the conversion formula was 1.0 nm.

Copper was vacuum-deposited on the carbon layer-formed surface of this release film by an electron beam evaporation method to a thickness of 5.0 μm at a film-forming speed of 2.0 μm·m/min and a line speed of 0.4 m/min. The copper foil was peeled off during the film formation, and the copper foil with the release film could not be produced.

Claims (5)

A copper foil with a release film, having a release layer on at least one surface of a film, and having a copper layer on the release layer, wherein the copper layer has a thickness of 0.5 μm or more and 3.0 μm or less. A copper foil with a release film, wherein the surface of the copper layer contains crystal grains of 5 nm or more and 50 nm or less obtained by the following, in an area ratio of 65% or more.
(Crystal grain)
The atomic force microscope (AFM5200S manufactured by Hitachi High-Tech Science) is used to observe the surface of the copper foil with the release film on the copper layer side. The observation is performed at 1 μm×1 μm, and after edge enhancement is performed with the image enhanced software “LucisPro MT/R” (manufactured by Mitani Corp.), the image is analyzed using the image analysis/measurement software “WinROOF2015 Standard” (manufactured by Mitani Corp.). The crystal grain size and the number of grains are counted, and the area ratio of the crystal grains is calculated. The copper foil with a release film according to claim 1, wherein the surface of the copper layer contains 80% or more of crystal grains of 5 nm or more and 50 nm or less. The copper foil with a release film according to claim 1 or 2, wherein the surface roughness Ra of the copper layer is 0.01 µm or more and 0.10 µm or less. The copper foil with a release film according to claim 1, wherein the release layer is a carbon layer having a thickness of 0.5 nm or more and 5.0 nm or less. It is a manufacturing method of the copper foil with a release film in any one of Claims 1-4, Comprising: After forming this copper layer by a vacuum evaporation method, it forms on it further by a sputtering method, It is characterized by the above-mentioned. A method for producing a copper foil with a release film.