CN115038818A

CN115038818A - Roughened copper foil, copper foil with carrier, copper-clad laminate, and printed wiring board

Info

Publication number: CN115038818A
Application number: CN202180012212.XA
Authority: CN
Inventors: 细川真; 高梨哲聪; 沟口美智; 平冈慎哉
Original assignee: Mitsui Mining and Smelting Co Ltd
Current assignee: Mitsui Kinzoku Co Ltd
Priority date: 2020-02-04
Filing date: 2021-01-20
Publication date: 2022-09-09
Anticipated expiration: 2041-01-20
Also published as: TWI756038B; CN115038818B; KR20220106199A; KR102832557B1; TW202134482A; JP7177956B2; WO2021157363A1; JPWO2021157363A1

Abstract

Provided is a roughened copper foil which can achieve both excellent high-frequency characteristics and high shear strength in processing a copper-clad laminate and/or in manufacturing a printed wiring board. The roughened copper foil has a roughened surface on at least one side. The roughened surface has an interfacial spreading area ratio Sdr of 0.50% to 7.00% as measured according to ISO25178 under the conditions that the S filter has a cutoff wavelength of 0.55 μm and the L filter has a cutoff wavelength of 10 μm. The roughened copper foil has a peak top density Spd of 2.00X 10 measured in accordance with ISO25178 under the conditions of a cut-off wavelength of 3.0 μm for an S filter and a cut-off wavelength of 10 μm for an L filter ⁴ mm ^‑2 Above and 3.30X 10 ⁴ mm ^‑2 The following.

Description

Roughened copper foil, copper foil with carrier, copper-clad laminate, and printed wiring board

Technical Field

The invention relates to a roughened copper foil, a copper foil with a carrier, a copper-clad laminate and a printed circuit board.

Background

In recent years, MSAP (modified semi additive process) has been widely used as a manufacturing method of a printed circuit board suitable for miniaturization of a circuit. The MSAP method is a method suitable for forming an extremely fine circuit, and is performed using a copper foil with a carrier in order to utilize the characteristics thereof. For example, as shown in fig. 1 and 2, an extra thin copper foil 10 is pressed and adhered to an insulating resin substrate 11 by using a prepreg 12 and a primer layer 13, the insulating resin substrate 11 having a lower circuit 11b on a base substrate 11a (step (a)); after the carrier (not shown) is peeled off, via holes 14 are formed by laser punching as necessary (step (b)). Next, electroless copper plating 15 is performed (step (c)), and then, exposure and development using the dry film 16 are performed to mask a predetermined pattern (step (d)), thereby performing electrolytic copper plating 17 (step (e)). After the dry film 16 is removed to form the wiring portion 17a (step (f)), unnecessary extra thin copper foil or the like between the

adjacent wiring portions

17a and 17a is removed from the entire thickness thereof by etching (step (g)), and the wiring 18 formed in a predetermined pattern is obtained. Here, in order to improve physical adhesion between the circuit and the substrate, the surface of the ultra-thin copper foil 10 is generally subjected to roughening treatment.

Actually, some copper foils with a carrier, which are excellent in fine circuit formability by MSAP method and the like, have been proposed. For example, patent document 1 (international publication No. 2016/117587) describes a carrier-attached copper foil provided with an extra thin copper foil in which the average distance between peaks on the surface on the release layer side is 20 μm or less and the maximum height difference of waviness on the surface opposite to the release layer side is 1.0 μm or less, and according to this aspect, both fine circuit formability and laser processability can be achieved. Further, patent document 2 (jp 2018-26590 a) discloses a copper foil with a carrier, in which a ratio Sp/Spk of a maximum peak height Sp to a projected peak height Spk according to ISO25178 on a surface of an extra thin copper layer side is 3.271 or more and 10.739 or less, for the purpose of improving a fine circuit formability.

In addition, with the recent development of higher functions of portable electronic devices and the like, signals are becoming higher in frequency for high-speed processing of large amounts of information, and printed wiring boards suitable for high-frequency applications are being sought. In such a high-frequency printed circuit board, it is desirable to reduce transmission loss so that transmission can be performed without degrading the quality of a high-frequency signal. The printed wiring board includes a copper foil processed into a wiring pattern and an insulating resin base material, and the transmission loss mainly comes from a conductor loss caused by the copper foil and a dielectric loss caused by the insulating resin base material.

In this regard, a roughened copper foil is known for the purpose of reducing transmission loss. For example, patent document 3 (japanese patent No. 6462961) relates to a surface-treated copper foil having a roughening treatment layer, an antirust treatment layer, and a silane coupling layer laminated in this order on at least one surface of the copper foil, and discloses that the interfacial spreading area ratio Sdr measured from the surface of the silane coupling layer is 8% or more and 140% or less, the root-mean-square slope Sdq is 25 ° or more and 70 ° or less, and the aspect ratio Str of the surface property is 0.25 or more and 0.79 or less. The surface-treated copper foil can be used to manufacture a printed wiring board having low transmission loss of high-frequency electric signals and excellent adhesion during reflow soldering.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2016/117587

Patent document 2: japanese patent laid-open publication No. 2018-26590

Patent document 3: japanese patent No. 6462961

Disclosure of Invention

As described above, from the viewpoint of high-frequency transmission, a copper foil with less transmission loss (that is, a copper foil with excellent high-frequency characteristics) is required as a material for forming circuit wiring of a flow communication signal. It is considered that the transmission loss can be suppressed by smoothing the copper foil and miniaturizing the roughening particles, but the physical adhesion force between the copper foil and the substrate resin or the like is reduced.

Here, one of the indexes of physical adhesion between the circuit and the substrate is shear strength (shear strength), and in order to improve the physical adhesion between the circuit and the substrate (hereinafter, sometimes simply referred to as circuit adhesion), it is required to keep the shear strength at a constant level or more. However, in order to secure a certain or more shear strength, the roughened particles of the copper foil have to be increased, and there is a problem that it is difficult to achieve both high-frequency characteristics and circuit adhesion. In this regard, as described above, patent document 3 discloses a surface-treated copper foil that achieves both high-frequency characteristics and adhesion, but in order to obtain more excellent high-frequency characteristics, it is required to ensure circuit adhesion even when a smoother copper foil is used.

The inventors have obtained the following findings this time: in the roughened copper foil, by providing a surface profile in which the interface spread area ratio Sdr and the peak top density Spd defined in ISO25178 are controlled to be within predetermined ranges, excellent high-frequency characteristics and high shear strength can be achieved at the same time in the processing of a copper-clad laminate and/or the production of a printed wiring board.

Accordingly, an object of the present invention is to provide a roughened copper foil which can achieve both excellent high-frequency characteristics and high shear strength in processing a copper-clad laminate and/or in manufacturing a printed wiring board.

According to one embodiment of the present invention, there is provided a roughened copper foil having a roughened surface on at least one side,

the roughened surface has an interfacial expansion area ratio Sdr of 0.50% or more and 7.00% or less as measured under the conditions of a cut-off wavelength of 0.55 [ mu ] m by an S filter and a cut-off wavelength of 10 [ mu ] m by an L filter in accordance with ISO25178, and a peak top density Spd of 2.00X 10 in accordance with ISO25178 as measured under the conditions of a cut-off wavelength of 3.0 [ mu ] m by an S filter and a cut-off wavelength of 10 [ mu ] m by an L filter ⁴ mm ^-2 Above and 3.30X 10 ⁴ mm ^-2 The following.

According to another aspect of the present invention, there is provided a copper foil with a carrier, including: a carrier, a release layer provided on the carrier, and the roughened copper foil provided on the release layer with the roughened surface as the outer side.

According to another aspect of the present invention, there is provided a copper-clad laminate including the roughened copper foil.

According to another aspect of the present invention, there is provided a printed wiring board comprising the roughened copper foil.

Drawings

Fig. 1 is a process flow chart for explaining the MSAP method, and is a diagram showing the first half process (processes (a) to (d)).

FIG. 2 is a process flow chart for explaining the MSAP method, and is a diagram showing the latter half of the processes (e) to (g)).

Fig. 3 is a diagram for explaining a load curve and a load area ratio determined in accordance with ISO 25178.

Fig. 4 is a diagram for explaining a load area ratio Smr1 separating the projected ridge portions from the center portion, a load area ratio Smr2 separating the projected valley portions from the center portion, and a level difference Sk of the center portion, which are determined in accordance with ISO 25178.

Fig. 5 is a schematic diagram for explaining a method of measuring shear strength.

Detailed Description

Definition of

The following shows definitions of terms and/or parameters used to define the present invention.

In the present specification, the "interface spread area ratio Sdr" means: a parameter indicating how much the extended area (surface area) of a defined area increases relative to the area of the defined area, measured according to ISO 25178. In the present specification, the interfacial expansion area ratio Sdr is expressed as an increase (%) in surface area. The smaller this value, the closer to a flat surface shape, and the Sdr of the completely flat surface is 0%. On the other hand, the larger the value, the more uneven the surface shape. For example, a surface with an Sdr of 40% indicates that the surface represents a 40% increase in surface area from a perfectly flat surface.

In the present specification, the "peak top density Spd" is a parameter indicating the number of peak tops per unit area measured in accordance with ISO25178, and is counted only for peak tops larger than 5% of the maximum amplitude of the contour curved surface. A large value teaches a large number of contact points with other objects.

In the present specification, "load curve of a plane" (hereinafter simply referred to as "load curve") means: curve representing the load area ratio from 0% to 100% height, determined according to ISO 25178. The load area ratio is a parameter indicating the area of a region having a certain height c or more as shown in fig. 3. The load area ratio at height c is equivalent to smr (c) in fig. 3. As shown in fig. 4, a secant line of the load curve is drawn along the load curve with the difference in load area ratio being 40% from the load area ratio being 0%, the secant line of the load curve is moved from the load area ratio being 0%, and the position where the slope of the secant line is most gentle is referred to as the center portion of the load curve. The straight line having the smallest sum of squares of deviations from the longitudinal axis direction with respect to the central portion is referred to as an equivalent straight line. A portion included in a range of the height of the load area ratio of the equivalent straight line from 0% to 100% is referred to as a center portion. The portions higher than the central portion are referred to as projecting crests, and the portions lower than the central portion are referred to as projecting troughs.

In the present specification, the "horizontal difference Sk in the center portion" is a value obtained by subtracting the minimum height from the maximum height of the center portion measured in accordance with ISO25178, and is a parameter calculated from a height difference between 0% and 100% of the load area ratio of the equivalent straight line as shown in fig. 4.

In the present specification, "maximum height Sz" is a parameter indicating the distance from the highest point to the lowest point of a surface measured in accordance with ISO 25178.

In the present specification, the "aspect ratio Str of the surface texture" is a parameter indicating isotropy and/or anisotropy of the surface texture measured in accordance with ISO 25178. Str ranges from 0 to 1, and strong isotropy is generally indicated by Str >0.5, whereas strong anisotropy is indicated by Str < 0.3.

The interfacial expansion area ratio Sdr, the peak top density Spd, the level difference Sk of the central portion, the maximum height Sz, and the aspect ratio Str of the surface texture can be determined by measuring a predetermined area (for example, 16384 μm) of the roughened surface with a commercially available laser microscope ² Two-dimensional region) of the surface profile is measured and calculated. In the present specification, the numerical values of the interfacial expansion area ratio Sdr, the level difference Sk in the central portion, the maximum height Sz, and the aspect ratio Str of the surface property are values measured under the condition that the cutoff wavelength by the S filter is 0.55 μm and the cutoff wavelength by the L filter is 10 μm. In the present specification, the numerical value of the peak top density Spd is a value measured under the condition that the cutoff wavelength by the S filter is 3 μm and the cutoff wavelength by the L filter is 10 μm.

In the present specification, the "electrode surface" of the carrier refers to the surface that is in contact with the cathode during production of the carrier.

In the present specification, the "deposition surface" of the carrier refers to a surface on which electrolytic copper is deposited at the time of production of the carrier, that is, a surface not in contact with the cathode.

Roughened copper foil

The copper foil of the present invention is a roughened copper foil. The roughened copper foil has a roughened surface on at least one side. The surface-roughened surface has an interfacial spread area ratio Sdr of 0.50% or more and 7.00% or less, and a peak top density Spd of 2.00X 10 ⁴ mm ^-2 Above and 3.30X 10 ⁴ mm ^-2 The following. In this way, by providing the roughened copper foil with a surface profile in which the interface spread area ratio Sdr and the peak top density Spd are controlled to be within predetermined ranges, it is possible to achieve both excellent high-frequency characteristics and high shear strength in processing of the copper-clad laminate and/or manufacturing of the printed circuit board.

Excellent high-frequency characteristics and high shear strength are inherently difficult to achieve at the same time. This is because, as described above, it is generally required to reduce the size of the roughening particles in order to obtain excellent high-frequency characteristics, and it is generally required to increase the size of the roughening particles in order to improve the shear strength of the circuit. In particular, the shear strength is not simply proportional to the specific surface area, the roughening height, and the like used in the conventional evaluation, and it is difficult to control the shear strength. In this regard, the present inventors have found that it is effective to evaluate the combination of the interface expansion area ratio Sdr and the peak top density Spd in order to obtain a correlation with physical properties such as high-frequency characteristics and shear strength. Specifically, it was found that a roughened copper foil having a fine surface with excellent high-frequency characteristics and having a protrusion height and a protrusion density suitable for ensuring high shear strength and a specific surface area can be obtained by controlling the interface spread area ratio Sdr to a very small range to make the surface of the roughened copper foil remarkably smooth and controlling the peak top density Spd to a relatively small value. That is, first, when the interfacial spreading area ratio Sdr is to be controlled to a specific range, if the variation in the size of the roughening particles on the surface of the roughened copper foil is large, the number of extremely small particles which do not contribute much to the shear strength is increased, and thus the peak top density Spd tends to be large. In contrast, with the roughened copper foil of the present invention, by adhering the roughened particles of an appropriate size contributing to the shear strength to the roughened surface without variation, the peak top density Spd can be controlled to a relatively small value even when the interface spread area ratio Sdr is controlled to a very small range. Thus, the roughened copper foil of the present invention can realize excellent high-frequency characteristics and high shear strength (and further high circuit adhesion in terms of shear strength).

From the viewpoint of achieving excellent high-frequency characteristics and high shear strength in a well-balanced manner, the roughened surface of the roughened copper foil has an interfacial spreading area ratio Sdr of 0.50% or more and 7.00% or less, preferably 0.50% or more and 4.00% or less, and more preferably 0.50% or more and 2.00% or less. Within such a range, even if the surface is a fine surface (roughened height) having excellent high-frequency characteristics, a sufficient adhesion area to the resin to be laminated can be secured in the production of the copper-clad laminate and/or the printed wiring board, and the circuit adhesion in terms of shear strength is improved.

Excellent high-frequency characteristics and high impedance are realized in good balanceFrom the viewpoint of shear strength, the peak-to-peak density Spd of the roughened surface of the roughened copper foil was 2.00X 10 ⁴ mm ^-2 Above and 3.30X 10 ⁴ mm ^-2 Hereinafter, it is preferably 2.00X 10 ⁴ mm ^-2 Above and 2.80X 10 ⁴ mm ^-2 Hereinafter, more preferably 2.00X 10 ⁴ mm ^-2 Above and 2.45X 10 ⁴ mm ^-2 The following. Within such a range, sufficient adhesion points with the laminated resin can be secured at the time of manufacturing the copper-clad laminate and/or the printed circuit board, and the transmission path of the high-frequency signal can be suppressed from becoming long, thereby reducing the transmission loss.

The roughened copper foil preferably has a peak top density Spd (mm) of the roughened surface ^-2 ) Spd/Sdr, which is the ratio of the area ratio Sdr (%) to the interfacial expansion, is 7000 or more, more preferably 8000 or more and 15000 or less, and still more preferably 9000 or more and 12000 or less. By controlling the ratio of the interfacial expansion area ratio Sdr to the peak top density Spd to be in the above range, the roughened surface can be configured to have further roughened particles of an appropriate size contributing to the shear strength adhere to the roughened surface, and thus, the respective roughened particles constituting the roughened surface can be easily and uniformly embedded in the resin. As a result, even in the case of excellent high-frequency characteristics, higher shear strength can be ensured.

Maximum height Sz (mum) of roughened surface of roughened copper foil and peak top density Spd (mm) ^-2 ) Sz × Spd is preferably 20000 or more, more preferably 24000 or more and 65000 or less, and further preferably 25000 or more and 35000 or less. In the roughened copper foil, by setting the spread area ratio Sdr to be within the above range and controlling Sz × Spd to be within the above range, smoothness of the roughened copper foil can be ensured and a state in which relatively large protrusions (roughening particles) are present at a high density on the roughened surface can be highly balanced, and adhesion to a resin can be further improved while maintaining excellent high-frequency characteristics. As a result, even in the case of excellent high-frequency characteristics, higher shear strength can be ensured. In addition, from furtherFrom the viewpoint of realizing a fine surface having excellent high-frequency characteristics, the maximum height Sz of the roughened surface of the roughened copper foil is preferably 1.3 μm or less, more preferably 0.1 μm or more and 0.9 μm or less, and still more preferably 0.4 μm or more and 0.9 μm or less.

The aspect ratio Str of the surface properties of the roughened surface of the roughened copper foil is preferably 0.90 or less, more preferably 0.30 or more and 0.90 or less, and still more preferably 0.50 or more and 0.90 or less. Within such a range, the roughened surface has a waviness suitable for adhesion to the resin to some extent, and has isotropy favorable for high-frequency characteristics. As a result, high shear strength can be ensured and more excellent high-frequency characteristics can be realized.

From the viewpoint of achieving excellent high-frequency characteristics and high shear strength with a good balance, the level difference Sk in the center of the roughened surface of the roughened copper foil is preferably 0.05 μm or more and 0.30 μm or less, more preferably 0.05 μm or more and 0.20 μm or less, and still more preferably 0.05 μm or more and 0.15 μm or less. Within such a range, even if the surface is a fine surface (height of roughening) excellent in high-frequency characteristics, the respective roughened particles constituting the roughened surface can be uniformly embedded in the resin, and as a result, the adhesion to the resin is further improved. That is, if there is unevenness in the roughening treatment, the unevenness is considered to be a projecting peak on the roughened surface. However, such unevenness (projecting peak portion) is hardly helpful in improving circuit adhesion in the viewpoint of shear strength. In this regard, the maximum height Sz and the like used in the conventional evaluation are parameters including the projecting ridge portion. Therefore, when the circuit adhesion is to be improved based on such parameters, the roughening height is likely to be increased, and the high-frequency characteristics are likely to be degraded. In contrast, the level difference Sk in the center portion is a parameter not including the projecting peak as described above. Therefore, by using the level difference Sk in the center portion as an evaluation index, the adhesion to the resin can be further improved, and as a result, the increase in the roughening height can be suppressed.

The thickness of the roughened copper foil is not particularly limited, but is preferably 0.1 μm or more and 35 μm or less, more preferably 0.5 μm or more and 5.0 μm or less, and still more preferably 1.0 μm or more and 3.0 μm or less. The roughened copper foil is not limited to one obtained by roughening the surface of a normal copper foil, and may be one obtained by roughening the surface of a copper foil with a carrier. Here, the thickness of the roughened copper foil is a thickness not including the height of the roughened particles formed on the surface of the roughened surface (the thickness of the copper foil itself constituting the roughened copper foil). The copper foil having a thickness in the above range may be referred to as an extra thin copper foil.

The roughened copper foil has a roughened surface on at least one side. That is, the roughened copper foil may have roughened surfaces on both sides, or may have roughened surfaces on only one side. The roughened surface is typically provided with a plurality of roughened particles (projections), and each of the plurality of roughened particles is preferably formed of copper particles. The copper particles may be formed of metallic copper or a copper alloy.

The roughening treatment for forming the roughened surface may be more preferably performed by forming roughened particles on the copper foil with copper or a copper alloy. For example, the roughening treatment is preferably performed by a method including at least 2 plating steps including: a baking and plating step of depositing and adhering fine copper particles on the copper foil; and a coating plating step for preventing the fine copper particles from falling off. In this case, the firing step preferably includes: specifically disclosed is an electrodeposition method wherein a copper sulfate solution containing a copper concentration of 5-20 g/L inclusive and a sulfuric acid concentration of 180-240 g/L inclusive contains 20-29 ppm inclusive of Carboxybenzotriazole (CBTA). In addition, the coating plating step preferably includes: in a copper sulfate solution containing a copper concentration of 50g/L to 100g/L inclusive and a sulfuric acid concentration of 200g/L to 250g/L inclusive, at a temperature of 40 ℃ to 60 ℃ inclusive at 2A/dm ² Above and 4A/dm ² Electrodeposition is performed as follows. In particular, by adding carboxybenzotriazole in the above concentration range to the plating solution in the baking step, copper can be roughened while maintaining the etching properties close to those of pure copperThe foil is configured such that the developed area ratio Sdr is controlled to be in a very small range and that the roughening particles having an appropriate size contributing to the shear strength are attached to the roughened surface without variation, and further, the peak density Spd can be controlled to be a relatively small value. That is, it becomes easy to form projections suitable for satisfying the above surface parameters on the processed surface. Further, in the baking and plating step and the coating and plating step, by performing electrodeposition with a reduced current density as compared with the conventional method, projections suitable for satisfying the above-described surface parameters can be more easily formed on the treated surface.

The roughened copper foil may be subjected to rust-proofing treatment to form a rust-proofing layer, as desired. The rust-preventive treatment preferably includes a plating treatment using zinc. The plating treatment using zinc may be any of a zinc plating treatment and a zinc alloy plating treatment, and the zinc alloy plating treatment is particularly preferably a zinc-nickel alloy treatment. The zinc-nickel alloy treatment may be a plating treatment including at least Ni and Zn, and may further include other elements such as Sn, Cr, and Co. The Ni/Zn adhesion ratio in the zinc-nickel alloy plating is preferably 1.2 or more and 10 or less, more preferably 2 or more and 7 or less, and further preferably 2.7 or more and 4 or less in terms of a mass ratio. In addition, the rust preventing treatment preferably further includes chromate treatment, and the chromate treatment is more preferably performed on the surface of the plating layer including zinc after the plating treatment using zinc. In this way, the rust prevention property can be further improved. A particularly preferred rust inhibiting treatment is a combination of a zinc-nickel alloy plating treatment followed by a chromate treatment.

The roughened copper foil may be treated with a silane coupling agent on the surface to form a silane coupling agent layer, if desired. This improves moisture resistance, chemical resistance, adhesion to adhesives and the like. The silane coupling agent layer can be formed by appropriately diluting the silane coupling agent, applying the diluted silane coupling agent, and drying the silane coupling agent. Examples of the silane coupling agent include epoxy-functional silane coupling agents such as 4-glycidoxybutyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane, amino-functional silane coupling agents such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N-3- (4- (3-aminopropyloxy) butoxy) propyl-3-aminopropyltrimethoxysilane and N-phenyl-3-aminopropyltrimethoxysilane, mercapto-functional silane coupling agents such as 3-mercaptopropyltrimethoxysilane, olefin-functional silane coupling agents such as vinyltrimethoxysilane and vinylphenyltrimethoxysilane, acrylic-functional silane coupling agents such as 3-methacryloxypropyltrimethoxysilane, acrylic-functional silane coupling agents such as, And imidazole-functional silane coupling agents such as imidazole silane and triazine-functional silane coupling agents such as triazine silane.

For the above reasons, the roughened copper foil preferably further includes a rust-preventive treatment layer and/or a silane coupling agent layer on the roughened surface, and more preferably includes both a rust-preventive treatment layer and a silane coupling agent layer. The rust-preventive treatment layer and the silane coupling agent layer may be formed not only on the roughened surface side of the roughened copper foil but also on the side where the roughened surface is not formed.

Copper foil with carrier

As described above, the roughened copper foil of the present invention can be provided in the form of a copper foil with a carrier. That is, according to a preferred aspect of the present invention, there is provided a copper foil with a carrier, comprising: the copper foil includes a carrier, a release layer provided on the carrier, and the roughened copper foil provided on the release layer with the roughened surface as the outer side. Of course, the copper foil with a carrier may be formed of a known layer, other than the roughened copper foil of the present invention.

The carrier is a support for supporting the roughened copper foil to improve the handling property thereof, and typically includes a metal layer. Examples of such a carrier include an aluminum foil, a copper foil, a stainless steel (SUS) foil, a resin film having a surface coated with a metal such as copper, and glass, and a copper foil is preferable. The copper foil may be any of a rolled copper foil and an electrolytic copper foil. Preferably an electrolytic copper foil. The thickness of the support is typically 250 μm or less, preferably 9 μm or more and 200 μm or less.

The surface of the carrier on the release layer side is preferably smooth. That is, in the process for producing the copper foil with carrier, the surface on the release layer side of the carrier is formed (roughened)Pre-treatment) ultra thin copper foil. When the roughened copper foil of the present invention is used in the form of a copper foil with a carrier, the roughened copper foil can be obtained by subjecting such an extra thin copper foil to a roughening treatment. Therefore, the surface on the release layer side of the carrier is smoothed in advance, so that the outer surface of the extra thin copper foil can be smoothed, and the roughened surface having the interfacial spreading area ratio Sdr within the predetermined range and the level difference Sk between the central portion can be easily realized by roughening the smoothed surface of the extra thin copper foil. In order to smooth the surface of the carrier on the release layer side, for example, the surface roughness can be adjusted by polishing the surface of the cathode used in the electrolytic foil formation of the carrier with a polishing wheel of a predetermined type. That is, the surface profile of the cathode thus adjusted is transferred to the electrode surface of the carrier, and the extra thin copper foil is formed on the electrode surface of the carrier through the release layer, whereby a smooth surface condition in which the roughened surface is easily achieved can be provided to the outer surface of the extra thin copper foil. The model number of the polishing wheel is preferably #2000 or more and #3000 or less, more preferably #2000 or more and #2500 or less. In addition, from the viewpoint of making the extra thin copper foil a smoother copper foil and making it easier to control the spreading area ratio Sdr of the obtained roughened copper foil to the above range, it is preferable to set the conditions for electrolytic foil formation of the carrier to the conditions for using the additives as described below. Namely, a sulfuric acid-based copper electrolytic solution is used in which the copper concentration is 60g/L to 100g/L inclusive, the sulfuric acid concentration is 50g/L to 150g/L inclusive, the concentration of a sulfonate of an active sulfur compound as an additive is 5mg/L to 1g/L inclusive, the concentration of a quaternary ammonium salt polymer having a cyclic structure is 5mg/L to 500mg/L inclusive, and the chlorine concentration is 10mg/L to 100mg/L inclusive, and DSA (dimensionally stable anode) is used as an anode, and the current density is 30A/dm inclusive at a liquid temperature of 40 ℃ to 60 ℃ inclusive ² Above and 100A/dm ² By performing electrolysis as follows, an electrolytic copper foil having a smoother surface can be preferably obtained. Examples of the sulfonate of the active sulfur compound used as the additive include 3-mercapto-1-propane sulfonate and bis (3-sulfopropyl) disulfide, and the likeExamples of the quaternary ammonium salt polymer having a cyclic structure include diallyl dimethyl ammonium chloride polymers.

The release layer is a layer having the following functions: the peeling strength of the carrier is weakened, the stability of the strength is ensured, and interdiffusion which can be caused between the carrier and the copper foil during press forming at high temperature is inhibited. The release layer is usually formed on one surface of the carrier, but may be formed on both surfaces. The release layer may be any of an organic release layer and an inorganic release layer. Examples of the organic component used in the organic release layer include nitrogen-containing organic compounds, sulfur-containing organic compounds, carboxylic acids, and the like. Examples of the nitrogen-containing organic compound include a triazole compound and an imidazole compound, and among them, a triazole compound is preferable in that the releasability is easily stabilized. Examples of the triazole compound include 1,2, 3-benzotriazole, carboxybenzotriazole, N' -bis (benzotriazolylmethyl) urea, 1H-1,2, 4-triazole, and 3-amino-1H-1, 2, 4-triazole. Examples of the sulfur-containing organic compound include mercaptobenzothiazole, trithiocyanuric acid, and 2-benzimidazolethiol. Examples of the carboxylic acid include monocarboxylic acid and dicarboxylic acid. On the other hand, examples of the inorganic component used in the inorganic release layer include Ni, Mo, Co, Cr, Fe, Ti, W, P, Zn, chromate-treated films, and the like. The release layer can be formed by bringing a solution containing a release layer component into contact with at least one surface of a carrier to fix the release layer component to the surface of the carrier. In the case of contacting the carrier with the release layer component-containing solution, the contacting may be performed by immersion in the release layer component-containing solution, spraying of the release layer component-containing solution, flowing down of the release layer component-containing solution, or the like. Further, a method of forming a film of a release layer component by a vapor phase method such as vapor deposition or sputtering may be employed. The release layer component can be fixed to the surface of the support by adsorption of a release layer component-containing solution, drying, electrodeposition of the release layer component in the release layer component-containing solution, or the like. The thickness of the release layer is typically 1nm or more and 1 μm or less, and preferably 5nm or more and 500nm or less.

Other functional layers may be provided between the peeling layer and the carrier and/or the roughening-treated copper foil as desired. As an example of such another functional layer, an auxiliary metal layer may be mentioned. The auxiliary metal layer is preferably formed of nickel and/or cobalt. By forming such an auxiliary metal layer on the surface side of the carrier and/or the surface side of the roughened copper foil, interdiffusion that may occur between the carrier and the roughened copper foil during hot press forming at high temperature or for a long time can be suppressed, and stability of the peel strength of the carrier can be ensured. The thickness of the auxiliary metal layer is preferably 0.001 μm or more and 3 μm or less.

Copper-clad laminated board

The roughened copper foil of the present invention is preferably used for producing a copper-clad laminate for a printed wiring board. That is, according to a preferred embodiment of the present invention, there is provided a copper-clad laminate including the roughened copper foil. By using the roughened copper foil of the present invention, excellent high-frequency characteristics and high shear strength can be achieved at the same time in the processing of the copper-clad laminate. The copper-clad laminate comprises: the invention provides a roughened copper foil and a resin layer closely arranged on the roughened surface of the roughened copper foil. The roughened copper foil may be provided on one side or both sides of the resin layer. The resin layer contains a resin, preferably an insulating resin. The resin layer is preferably a prepreg and/or a resin sheet. The prepreg is a generic name of a composite material in which a base material such as a synthetic resin plate, a glass woven fabric, a glass nonwoven fabric, or paper is impregnated with a synthetic resin. Preferred examples of the insulating resin include epoxy resin, cyanate resin, bismaleimide triazine resin (BT resin), polyphenylene ether resin, and phenol resin. Examples of the insulating resin constituting the resin sheet include insulating resins such as epoxy resin, polyimide resin, and polyester resin. In addition, the resin layer may contain filler particles containing various inorganic particles such as silica and alumina, from the viewpoint of improving insulation properties. The thickness of the resin layer is not particularly limited, but is preferably 1 μm or more and 1000 μm or less, more preferably 2 μm or more and 400 μm or less, and further preferably 3 μm or more and 200 μm or less. The resin layer may be composed of a plurality of layers. The resin layer such as a prepreg and/or a resin sheet may be provided on the roughened copper foil through a primer resin layer applied to the surface of the copper foil in advance.

Printed circuit board

The roughened copper foil of the present invention is preferably used for the production of printed wiring boards. That is, according to a preferred embodiment of the present invention, there is provided a printed wiring board including the roughened copper foil. By using the roughened copper foil of the present invention, excellent high-frequency characteristics and high shear strength can be achieved at the same time in the production of printed wiring boards. The printed wiring board of the present embodiment has a layered structure in which a resin layer and a copper layer are stacked. The copper layer is a layer derived from the roughened copper foil of the present invention. In addition, as for the resin layer, as described above with respect to the copper-clad laminate. In any case, the printed wiring board may be constituted by a known layer, except for using the roughened copper foil of the present invention. Specific examples of the printed wiring board include a single-sided or double-sided printed wiring board obtained by bonding the roughened copper foil of the present invention to one or both sides of a prepreg, curing the copper foil to form a laminate, and then forming a circuit, a multilayer printed wiring board obtained by multilayering the laminate, and the like. Further, as other specific examples, a flexible printed wiring board, COF, TAB tape, and the like, in which the roughened copper foil of the present invention is formed on a resin film to form a circuit, can be cited. As other specific examples, there may be mentioned: the resin-coated copper foil (RCC) in which the resin layer is coated on the roughened copper foil of the present invention is formed, the resin layer is laminated on the printed circuit board as an insulating adhesive layer, the roughened copper foil is used as all or part of the wiring layer to form a build-up wiring board of a circuit by a method such as a modified semi-additive (MSAP) method or a subtractive method, the roughened copper foil is removed to form a build-up wiring board of a circuit by a semi-additive method, and a direct build-up wafer (direct build-up on wafer) in which the resin-coated copper foil is laminated on a semiconductor integrated circuit and the circuit is formed is alternately repeated. As a more developed specific example, there are an antenna element formed by laminating the resin-attached copper foil on a substrate to form a circuit, an electronic material for panel and display, an electronic material for window glass, and the like, in which a pattern is formed by laminating glass or a resin film via an adhesive layer, and an electromagnetic wave shielding film and the like obtained by coating a conductive adhesive on the roughened copper foil of the present invention. In particular, the printed wiring board including the roughened copper foil of the present invention is suitable for use as a high-frequency substrate for applications such as an automobile antenna, a mobile phone base station antenna, a high-performance server, and a radar bumper used in a high-frequency band having a signal frequency of 10GHz or higher. In particular, the roughened copper foil of the present invention is suitable for MSAP process. For example, when a circuit is formed by the MSAP method, the configuration shown in fig. 1 and 2 can be adopted.

Examples

The present invention will be described more specifically by the following examples.

Examples 1,2,4 and 7

A copper foil with a carrier having a roughened copper foil was produced and evaluated as follows.

(1) Preparation of the vector

A copper electrolytic solution having the composition shown below, a cathode, and DSA (dimensionally stable anode) as an anode were used at a solution temperature of 50 ℃ and a current density of 70A/dm ² Electrolytic copper foil with a thickness of 18 μm was produced as a carrier by electrolysis. At this time, as the cathode, an electrode whose surface roughness was adjusted by polishing the surface with a polishing wheel of #2000 was used.

< composition of copper electrolyte >

-copper concentration: 80g/L

-sulfuric acid concentration: 300g/L

-chlorine concentration: 30mg/L

-gum concentration: 5mg/L

(2) Formation of a Release layer

The electrode surface of the carrier subjected to the acid washing treatment was immersed in a CBTA aqueous solution containing 1g/L of Carboxybenzotriazole (CBTA), 150g/L of sulfuric acid and 10g/L of copper at a liquid temperature of 30 ℃ for 30 seconds to adsorb the CBTA component to the electrode surface of the carrier. Thus, a CBTA layer was formed as an organic release layer on the electrode surface of the carrier.

(3) Formation of an auxiliary metal layer

The carrier having the organic release layer formed thereon was immersed in a solution containing nickel at a concentration of 20g/L prepared using nickel sulfate, and the solution temperature was 45 ℃, pH3, and current density was 5A/dm ² Nickel was attached to the organic release layer in an amount corresponding to 0.001 μm thick. Thus, a nickel layer was formed as an auxiliary metal layer on the organic peeling layer.

(4) Formation of ultra-thin copper foil

The carrier having the auxiliary metal layer formed thereon was immersed in a copper solution having a composition shown below, and the solution temperature was 50 ℃ and the current density was 5A/dm ² Above and 30A/dm ² Next, electrolysis was performed to form an extra thin copper foil having a thickness of 1.5 μm on the auxiliary metal layer.

< composition of solution >

-copper concentration: 60g/L

-sulfuric acid concentration: 200g/L

(5) Roughening treatment

The surface of the extra thin copper foil thus formed is roughened to form a roughened copper foil, thereby obtaining a copper foil with a carrier. The roughening treatment is composed of the following steps: a baking and plating step of depositing and adhering fine copper particles on the extra thin copper foil; and a coating plating step for preventing the fine copper particles from falling off. In the baking plating step, Carboxybenzotriazole (CBTA) was added at a concentration shown in Table 1 to an acidic copper sulfate solution containing copper at a bath temperature of 25 ℃ and a sulfuric acid concentration of 10g/L and 200g/L, and then subjected to roughening treatment at a current density shown in Table 1. In the subsequent coating plating step, electrodeposition was performed under smooth plating conditions at a bath temperature of 52 ℃ and a current density shown in Table 1 using an acidic copper sulfate solution containing copper at a concentration of 70g/L and sulfuric acid at a concentration of 240 g/L. At this time, the CBTA concentration and current density in the firing step and the current density in the coating step were appropriately changed as shown in table 1, thereby producing various samples having different characteristics of the roughened surface.

(6) Anti-rust treatment

The roughened surface of the obtained copper foil with a carrier is subjected to rust-proofing treatment including zinc-nickel alloy plating treatment and chromate treatment. First, a solution containing 1g/L zinc, 2g/L nickel and 80g/L potassium pyrophosphate was used at a liquid temperature of 40 ℃ and a current density of 0.5A/dm ² The surface of the roughening treatment layer and the support is subjected to zinc-nickel alloy plating treatment. Next, an aqueous solution containing 1g/L chromic acid was used at a pH of 12 and a current density of 1A/dm ² The surface subjected to zinc-nickel alloy plating treatment is subjected to chromate treatment under the conditions of (1).

(7) Silane coupling agent treatment

The surface of the copper foil with the carrier on the roughened copper foil side was adsorbed with an aqueous solution containing a commercially available silane coupling agent, and water was evaporated by an electric heater, thereby performing the silane coupling agent treatment. At this time, the carrier side was not treated with a silane coupling agent.

(8) Evaluation of

The thus obtained copper foil with a carrier was evaluated for various properties as follows.

(8a) Surface property parameters of roughened surface

The roughened surface of the roughened copper foil was measured in accordance with ISO25178 by surface roughness analysis using a laser microscope (ollympus Corporation, OLS 5000). Specifically, the area 16384 μm of the roughened surface of the roughened copper foil was measured with the above laser microscope using a lens 100 times the aperture ratio (N.A.) of 0.95 ² The surface profile of the area (d) is determined. After the noise removal and the first order linear surface tilt correction (first-order linear surface tilt correction) were performed on the surface profile of the obtained roughened surface, the maximum height Sz, the interface expansion area ratio Sdr, the aspect ratio Str of the surface property, the level difference Sk of the central portion, and the peak top density Spd were measured by the surface property analysis. In this case, the measurement of Sz, Sdr, Str, and Sk was performed with the cutoff wavelength of the S filter set to 0.55 μm and the cutoff wavelength of the L filter set to 10 μm. On the other hand, for the determination of Spd, theThe measurement was performed with the cutoff wavelength of the S filter set to 3 μm and the cutoff wavelength of the L filter set to 10 μm. The results are shown in Table 1.

(8b) Sealing property (shear strength) of plating circuit

The obtained copper foil with a carrier was used to produce a laminate for evaluation. That is, a roughened copper foil of a copper foil with a carrier was laminated on the surface of an insulating resin substrate via a prepreg (manufactured by Mitsubishi gas chemical corporation, GHPL-830NSF, thickness 0.1mm), thermocompression-bonded at a pressure of 4.0MPa and a temperature of 220 ℃ for 90 minutes, and then the carrier was peeled off to obtain a copper-clad laminate as a laminate for evaluation. The dry film was bonded to a laminate for evaluation, and exposure and development were performed. After a copper layer having a thickness of 14 μm was deposited by pattern plating on the laminate masked with the developed dry film, the dry film was peeled off. The exposed copper portion was etched with a sulfuric acid-hydrogen peroxide etching solution to prepare a circuit sample for measuring shear strength (a laminate 134 having a circuit 136 formed therein shown in FIG. 5) having a height of 15 μm, a width of 10 μm and a length of 200 μm. The shear strength when the circuit 136 was pushed from the side of the circuit sample for shear strength measurement and deflected was measured using a joint strength tester (4000 Plus bond tester, manufactured by Nordson DAGE corporation). That is, as shown in fig. 5, the laminate 134 having the electric circuit 136 formed thereon is placed on the movable stage 132, and moved in the arrow direction in the drawing together with the stage 132, and the electric circuit 136 is pressed against the detector 138 fixed in advance, whereby a lateral force is applied to the side surface of the electric circuit 136, the electric circuit 136 is shifted in the lateral direction, and the force (gf) at that time is measured by the detector 138 and used as the shear strength. In this case, the test type was a fracture test, and the test height was 5 μm, the lowering speed was 0.050 mm/sec, the test speed was 200 μm/sec, the tool movement amount was 0.05mm, and the fracture identification point was 10%. The obtained shear strength was evaluated in a graded manner according to the following criteria, and a case of evaluation as a or B was judged as passed. The results are shown in Table 1.

< evaluation criteria for shear Strength >

-evaluation a: a shear strength of 12.50gf or more

-evaluation B: the shear strength is more than 11.50gf and less than 12.50gf

-evaluation C: shear strength of less than 11.50gf

(8c) High frequency characteristics

The obtained copper foil with a carrier was used to produce a copper-clad laminate. That is, a roughened copper foil of the copper foil with a carrier is laminated on a surface of a substrate (dielectric loss tangent Df at 30GHz is 0.005) and thermocompression bonded, and then the carrier is peeled off to produce a copper-clad laminated board. This copper-clad laminate was subjected to formation of a microstrip line having a circuit length of 300mm by the same method as in (8b) (dry film lamination, exposure and development, pattern plating, and etching after dry film peeling) to prepare a substrate for measuring transmission characteristics. The transmission characteristics of the substrate for transmission characteristics measurement were measured using a network analyzer (N5225B, manufactured by Keysight corporation) at a frequency of 10MHz to 50GHz and a characteristic impedance of 50 Ω ± 5 Ω, and a transmission characteristic S21 was measured. The obtained loss amounts of 26GHz to 30GHz were averaged and evaluated in a classification manner according to the following criteria. Then, the case where the high frequency characteristic is evaluated as a or B is judged as pass. The results are shown in Table 1.

< evaluation criteria for high frequency characteristics >

-evaluation a: the loss amount is less than 0.320dB/cm

-evaluation B: the loss amount is more than 0.320dB/cm and less than 0.350dB/cm

-evaluation C: the loss amount exceeds 0.350dB/cm

Examples 3 and 5

The production and evaluation of the copper foil with carrier were carried out in the same manner as in example 1 except for the following a) to c). The results are shown in Table 1.

a) Preparation of the carrier was carried out according to the procedure shown below.

b) Instead of the electrode surface of the carrier, a release layer, an auxiliary metal layer and an extra thin copper foil are formed in this order on the deposition surface of the carrier.

c) The CBTA concentration and current density in the firing step and the current density in the coating step were changed to the values shown in table 1.

(preparation of the support)

The sulfuric acid copper sulfate solution having the composition shown below was usedAs the copper electrolytic solution, a titanium electrode having a surface roughness Ra of 0.20 μm was used as a cathode, and a DSA (dimensionally stable anode) was used as an anode, and the solution temperature was 45 ℃ and the current density was 55A/dm ² Then, electrolysis was carried out to obtain an electrolytic copper foil having a thickness of 12 μm as a carrier.

< composition of sulfuric acid-acid copper sulfate solution >

-copper concentration: 80g/L

-free sulfuric acid concentration: 140g/L

-bis (3-sulfopropyl) disulfide concentration: 30mg/L

-diallyl dimethyl ammonium chloride polymer concentration: 50mg/L

-chlorine concentration: 40mg/L

Example 6 (comparative)

The production and evaluation of the copper foil with carrier were carried out in the same manner as in example 3 except that the roughening treatment of the extra thin copper foil was carried out by the following black plating step instead of the baking plating step and the coating plating step. The results are shown in Table 1.

(Black plating step)

The surface of the ultra-thin copper foil was treated with a black roughening copper electrolytic solution having a composition shown below at a solution temperature of 30 ℃ and a current density of 50A/dm ² And electrolysis was carried out for 4 seconds to perform black graining.

< composition of copper electrolytic solution for black roughening >

-copper concentration: 13g/L

-sulfuric acid concentration: 70g/L

-chlorine concentration: 35mg/L

Sodium polyacrylate concentration: 400ppm of

[ Table 1]

Claims

1. A roughened copper foil having a roughened surface on at least one side,

the roughened surface has an interfacial expansion area ratio Sdr of 0.50% or more and 7.00% or less, as measured according to ISO25178 under conditions of a cut-off wavelength of 0.55 [ mu ] m for an S-filter and a cut-off wavelength of 10 [ mu ] m for an L-filter, and a peak top density Spd of 2.00 × 10, as measured according to ISO25178 under conditions of a cut-off wavelength of 3.0 [ mu ] m for an S-filter and a cut-off wavelength of 10 [ mu ] m for an L-filter ⁴ mm ^-2 Above and 3.30X 10 ⁴ mm ^-2 The following.

2. The roughened copper foil according to claim 1, wherein the interfacial spreading area ratio Sdr is 0.50% or more and 4.00% or less.

3. The roughened copper foil according to claim 1 or 2, wherein the peak top density Spd (mm) ^-2 ) Spd/Sdr, which is the ratio of the area ratio Sdr (%) to the interfacial expansion, is 7000 or more.

4. The roughened copper foil according to any one of claims 1 to 3, wherein the roughened surface has a maximum height Sz (μm) and the peak top density Spd (mm) measured according to ISO25178 under a condition that the S-filter-based cutoff wavelength is 0.55 μm and the L-filter-based cutoff wavelength is 10 μm ^-2 ) The product of (A) Sz × Spd is 20000 or more.

5. The roughened copper foil according to any one of claims 1 to 4, wherein the roughened surface has an aspect ratio Str of 0.90 or less in surface properties as measured according to ISO25178 under conditions that the S-filter has a cutoff wavelength of 0.55 μm and the L-filter has a cutoff wavelength of 10 μm.

6. The roughened copper foil according to any one of claims 1 to 5, wherein the roughened surface has a level difference Sk of 0.05 μm or more and 0.30 μm or less in the central portion, as measured in accordance with ISO25178 under the conditions that the S-filter has a cutoff wavelength of 0.55 μm and the L-filter has a cutoff wavelength of 10 μm.

7. The roughened copper foil according to any one of claims 1 to 6, wherein the maximum height Sz of the roughened surface, as measured in accordance with ISO25178 under the conditions that the S-filter-based cutoff wavelength is 0.55 μm and the L-filter-based cutoff wavelength is 10 μm, is 1.3 μm or less.

8. The roughened copper foil according to any one of claims 1 to 7, further comprising an antirust treatment layer and/or a silane coupling agent layer on the roughened surface.

9. A copper foil with a carrier, comprising: a carrier, a release layer provided on the carrier, and the roughened copper foil according to any one of claims 1 to 8 provided on the release layer with the roughened surface as an outer side.

10. A copper-clad laminate comprising the roughened copper foil according to any one of claims 1 to 8.

11. A printed wiring board comprising the roughened copper foil according to any one of claims 1 to 8.