JP7087760B2 - Copper-clad laminate - Google Patents

Description

The present invention relates to a copper-clad laminate. More specifically, the present invention relates to a copper-clad laminate used in the manufacture of flexible printed wiring boards (FPCs) and the like.

For liquid crystal panels, notebook computers, digital cameras, mobile phones, etc., flexible printed wiring boards having a wiring pattern formed on the surface of a resin film are used. The flexible printed wiring board is manufactured from, for example, a copper-clad laminate.

The metallizing method is known as a method for manufacturing a copper-clad laminate. The production of the copper-clad laminate by the metallizing method is performed, for example, by the following procedure. First, a base metal layer made of a nickel-chromium alloy is formed on the surface of the resin film. Next, a copper thin film layer is formed on the base metal layer. Next, a copper plating film is formed on the copper thin film layer. By copper plating, the conductor layer is thickened until the film thickness is suitable for forming a wiring pattern. By the metallizing method, a copper-clad laminate of a type called a so-called two-layer substrate in which a conductor layer is directly formed on a resin film can be obtained.

A semi-additive method is known as a method for manufacturing a flexible printed wiring board using this type of copper-clad laminate. The flexible printed wiring board is manufactured by the semi-additive method according to the following procedure (see Patent Document 1). First, a resist layer is formed on the surface of the copper-plated coating of the copper-clad laminate. Next, an opening is formed in the portion of the resist layer that forms the wiring pattern. Next, electrolytic plating is performed using the copper plating film exposed from the opening of the resist layer as a cathode to form a wiring portion. Next, the resist layer is removed, and the conductor layer other than the wiring portion is removed by flash etching or the like. As a result, a flexible printed wiring board can be obtained.

In the semi-additive method, a dry film resist may be used to form a resist layer on the surface of the copper plating film. In this case, after the surface of the copper plating film is chemically polished, a dry film resist is attached. By making fine irregularities on the surface of the copper plating film by chemical polishing, the adhesion of the dry film resist due to the anchor effect is improved. However, if the surface of the copper plating film is excessively uneven, the adhesion of the dry film resist may be deteriorated.

Japanese Unexamined Patent Publication No. 2006-278950

When the copper plating film is reduced by chemical polishing, pinholes may occur in the conductor layer. The presence of pinholes in the conductor layer causes a poor appearance called "dents" in which the thickness of the wiring formed on the pinholes is partially thinned, and "chips" in which the width of the wiring is partially narrowed. Become. In the worst case, the wiring is broken.

In view of the above circumstances, it is an object of the present invention to provide a copper-clad laminate capable of suppressing the generation of pinholes after chemical polishing.

The copper-clad laminate of the present invention comprises a base film, a metal layer formed on the surface of the base film, and a copper plating film formed on the surface of the metal layer and containing chlorine as an impurity. The chlorine concentration distribution in the thickness direction of the plating film includes a plurality of chevron local distributions, and all or part of the plurality of local distributions has a chlorine concentration of 2 × measured by the secondary ion mass analysis method at the peak. It is characterized by having 10 ¹⁹ atoms / cm ³ or more .

The progress of etching of the copper plating film by chemical polishing is suppressed by the layer having a high chlorine concentration. Since the path through which etching is likely to proceed is interrupted in the high chlorine concentration layer, it is suppressed that the etching locally progresses in the thickness direction. As a result, the occurrence of pinholes can be suppressed.

It is sectional drawing of the copper-clad laminated board which concerns on one Embodiment of this invention. It is a perspective view of a plating apparatus. It is a top view of a plating tank. FIG. (A) is a graph showing the chlorine concentration distribution of the copper plating film in Example 1. FIG. (B) is a graph showing the chlorine concentration distribution of the copper plating film in Example 2. FIG. (C) is a graph showing the chlorine concentration distribution of the copper plating film in Comparative Example 1. FIG. (A) is an SEM image of the surface of the copper plating film after chemical polishing in Example 1. FIG. (B) is an SEM image of the surface of the copper plating film after chemical polishing in Example 2. FIG. (C) is an SEM image of the surface of the copper plating film after chemical polishing in Comparative Example 1.

Next, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the copper-clad laminate 1 according to the embodiment of the present invention comprises a base material 10 and a copper plating film 20 formed on the surface of the base material 10. As shown in FIG. 1, the copper plating film 20 may be formed on only one side of the base material 10, or the copper plating film 20 may be formed on both sides of the base material 10.

The base material 10 has a metal layer 12 formed on the surface of a base film 11 having an insulating property. A resin film such as a polyimide film can be used as the base film 11. The metal layer 12 is formed by, for example, a sputtering method. The metal layer 12 is composed of a base metal layer 13 and a copper thin film layer 14. The base metal layer 13 and the copper thin film layer 14 are laminated in this order on the surface of the base film 11. Generally, the base metal layer 13 is made of nickel, chromium, or a nickel-chromium alloy. Although not particularly limited, the thickness of the base metal layer 13 is generally 5 to 50 nm, and the thickness of the copper thin film layer 14 is generally 50 to 400 nm.

The copper plating film 20 is formed on the surface of the metal layer 12. Although not particularly limited, the thickness of the copper plating film 20 is generally 1 to 3 μm. The metal layer 12 and the copper plating film 20 are collectively referred to as a "conductor layer".

The copper plating film 20 is formed by electrolytic plating. The copper plating film 20 is not particularly limited, but is formed by the plating apparatus 3 shown in FIG.
The plating device 3 is a device that performs electrolytic plating on the base material 10 while transporting the long strip-shaped base material 10 by roll-to-roll. The plating device 3 has a supply device 31 for feeding out the base material 10 wound in a roll shape, and a winding device 32 for winding up the base material 10 (copper-clad laminate 1) after plating in a roll shape.

Further, the plating apparatus 3 has a pair of upper and lower endless belts 33 (the lower endless belt 33 is not shown) for transporting the base material 10. Each endless belt 33 is provided with a plurality of clamps 34 for gripping the base material 10. The base material 10 unwound from the supply device 31 has a suspended posture in which the width direction is along the vertical direction, and both edges are gripped by the upper and lower clamps 34. The base material 10 circulates in the plating device 3 by driving the endless belt 33, is released from the clamp 34, and is wound by the winding device 32.

A pretreatment tank 35, a plating tank 40, and a posttreatment tank 36 are arranged in the transport path of the base material 10. While the base material 10 is conveyed in the plating tank 40, a copper plating film 20 is formed on the surface thereof by electrolytic plating. As a result, a long strip-shaped copper-clad laminated plate 1 can be obtained.

As shown in FIG. 3, the plating tank 40 is a single horizontally long tank along the transport direction of the base material 10. The base material 10 is conveyed along the center of the plating tank 40. A copper plating solution is stored in the plating tank 40. The entire base material 10 conveyed in the plating tank 40 is immersed in a copper plating solution.

The copper plating solution contains a water-soluble copper salt. Any water-soluble copper salt generally used for the copper plating solution is used without particular limitation. Examples of the water-soluble copper salt include an inorganic copper salt, an alkane sulfonic acid copper salt, an alkanol sulfonic acid copper salt, and an organic acid copper salt. Examples of the inorganic copper salt include copper sulfate, copper oxide, copper chloride, and copper carbonate. Examples of the alkane sulfonic acid copper salt include copper methanesulfonic acid and copper propanesulfonic acid. Examples of the alkanol sulfonic acid copper salt include copper isethionic acid and copper propanol sulfonic acid. Examples of the organic acid copper salt include copper acetate, copper citrate, copper tartrate and the like.

As the water-soluble copper salt used in the copper plating solution, one type selected from inorganic copper salt, alkane sulfonic acid copper salt, alkanol sulfonic acid copper salt, organic acid copper salt and the like may be used alone, or two or more types may be used. May be used in combination. For example, when combining copper sulfate and copper chloride, two or more different types in one category selected from inorganic copper salt, alkane sulfonic acid copper salt, alkanol sulfonic acid copper salt, organic acid copper salt, etc. It may be used in combination. However, from the viewpoint of controlling the copper plating solution, it is preferable to use one kind of water-soluble copper salt alone.

The copper plating solution may contain sulfuric acid. By adjusting the amount of sulfuric acid added, the pH and sulfate ion concentration of the copper plating solution can be adjusted.

The copper plating solution contains additives that are generally added to the plating solution. Examples of the additive include a leveler component, a polymer component, a Brightner component, a chlorine component and the like. As the additive, one type selected from a leveler component, a polymer component, a Brightener component, a chlorine component and the like may be used alone, or two or more types may be used in combination.

The leveler component is composed of an amine containing nitrogen and the like. Examples of the leveler component include diallyldimethylammonium chloride, Janus Green B and the like. The polymer component is not particularly limited, but it is preferable to use one selected from polyethylene glycol, polypropylene glycol, and polyethylene glycol-polypropylene glycol copolymer alone or in combination of two or more. The Brightener component is not particularly limited, but one type selected from bis (3-sulfopropyl) disulfide (abbreviated as SPS), 3-mercaptopropane-1-sulfonic acid (abbreviated as MPS), etc. may be used alone or in two types. It is preferable to use the above in combination. The chlorine component is not particularly limited, but it is preferable to use one selected from hydrochloric acid, sodium chloride and the like alone or in combination of two or more.

The content of each component of the copper plating solution can be arbitrarily selected. However, the copper plating solution preferably contains 60 to 280 g / L of copper sulfate and 20 to 250 g / L of sulfuric acid. Then, the copper plating film 20 can be formed at a sufficient speed. The copper plating solution preferably contains a leveler component of 0.5 to 50 mg / L. Then, the protrusions can be suppressed and the flat copper plating film 20 can be formed. The copper plating solution preferably contains 10 to 1,500 mg / L of the polymer component. Then, the current concentration on the end portion of the base material 10 can be relaxed and a uniform copper plating film 20 can be formed. The copper plating solution preferably contains a Brightener component of 0.2 to 16 mg / L. Then, the precipitated crystals can be made finer and the surface of the copper plating film 20 can be smoothed. The copper plating solution preferably contains 20 to 80 mg / L of chlorine component. Then, abnormal precipitation can be suppressed. Further, since the copper plating solution contains a chlorine component, the formed copper plating film 20 contains chlorine as an impurity.

The temperature of the copper plating solution is preferably 20 to 35 ° C. Further, it is preferable to stir the copper plating solution in the plating tank 40. The means for stirring the copper plating solution is not particularly limited, but a means using a jet can be used. For example, the copper plating solution can be agitated by spraying the copper plating solution ejected from the nozzle onto the base material 10.

Inside the plating tank 40, a plurality of anodes 41 are arranged along the transport direction of the base material 10. Further, the clamp 34 that grips the base material 10 also has a function as a cathode. By passing an electric current between the anode 41 and the clamp 34 (cathode), the copper plating film 20 can be formed on the surface of the base material 10.

In the plating tank 40 shown in FIG. 3, anodes 41 are arranged on both the front and back sides of the base material 10. Therefore, if the base material 10 having the metal layers 12 formed on both sides of the base film 11 is used, the copper plating film 20 can be formed on both sides of the base film 10.

A rectifier is connected to each of the plurality of anodes 41 arranged inside the plating tank 40. Therefore, the current densities can be set to be different for each anode 41. In the present embodiment, the inside of the plating tank 40 is divided into a plurality of areas along the transport direction of the base material 10. Each area corresponds to an area in which one or more contiguous anodes 41 are located.

Each area is a low current density area LZ or a high current density area HZ. In the low current density area LZ, the current density is set to zero or a relatively low "low current density", and the base material 10 is electrolytically plated at a low current density. In the high current density area HZ, the current density is set to "high current density", which is higher than the low current density, and the substrate 10 is electrolytically plated at a high current density.

Here, it is preferable to set the current density (low current density) in the low current density area LZ to 0 to 0.29 A / dm ² . Further, it is preferable to set the current density (high current density) in the high current density area HZ to 0.3 to 10 A / dm ² .

The low current density area LZ and the high current density area HZ are alternately provided along the transport direction of the base material 10. A plurality of low current density areas LZ are provided. A plurality of high current density areas HZ are provided. The most upstream area may be the low current density area LZ or the high current density area HZ with respect to the transport direction of the base material 10. Further, the most downstream area may be a low current density area LZ or a high current density area HZ.

The current densities in the plurality of low current density areas LZ may be the same or may be different. Further, the current densities in the plurality of high current density areas HZ may be the same or may be different. However, it is preferable that the current density in the high current density area HZ is set so as to gradually increase toward the downstream side in the transport direction of the base material 10.

The base material 10 is electroplated while alternately passing through the low current density area LZ and the high current density area HZ. That is, in the plating tank 40, electrolytic plating at a low current density and electrolytic plating at a high current density are alternately and repeatedly performed on the base material 10. As a result, the copper plating film 20 is formed.

As shown in FIG. 1, the copper plating film 20 formed by such a method has a structure in which a plurality of layers formed by electrolytic plating at different current densities are laminated. Specifically, the copper plating film 20 has a structure in which high chlorine concentration layers 21 and low chlorine concentration layers 22 are alternately laminated in the thickness direction. Here, the high chlorine concentration layer 21 is formed by electrolytic plating at a low current density, and has a relatively high chlorine concentration. Further, the low chlorine concentration layer 22 is formed by electrolytic plating at a high current density, and the chlorine concentration is relatively low. It is presumed that this is because the lower the current density in electrolytic plating, the easier it is for the additive of the copper plating solution to be incorporated into the plating film.

The arrangement of the high chlorine concentration layer 21 and the low chlorine concentration layer 22 depends on the arrangement of the low current density area LZ and the high current density area HZ in the plating tank 40. There are a plurality of high chlorine concentration layers 21. There are a plurality of low chlorine concentration layers 22. The layer directly laminated on the surface of the base material 10 (the surface of the metal layer 12) may be the high chlorine concentration layer 21 or the low chlorine concentration layer 22. Further, the layer appearing on the surface of the copper plating film 20 (the surface opposite to the base material 10) may be the high chlorine concentration layer 21 or the low chlorine concentration layer 22.

The concentration of impurities contained in the copper plating film 20 can be measured by secondary ion mass spectrometry (SIMS). Since the copper plating film 20 has a structure in which high chlorine concentration layers 21 and low chlorine concentration layers 22 are alternately laminated, the chlorine concentration distribution in the thickness direction includes a plurality of chevron local distributions (FIG. 4). reference). More specifically, the chlorine concentration distribution in the thickness direction of the copper plating film 20 is such that the local distributions of the plurality of chevrons are periodically continuous. The vicinity of the peak of each local distribution corresponds to the high chlorine concentration layer 21, and the other portion corresponds to the low chlorine concentration layer 22.

For example, when a flexible printed wiring board is manufactured using a copper-clad laminate 1 by a semi-additive method, the copper plating film 20 may be reduced by chemical polishing. For example, the copper plating film 20 having a thickness of 1 to 3 μm is reduced to 0.4 to 0.8 μm. This chemical polishing may cause pinholes in the conductor layer.

On the other hand, the copper-clad laminate 1 of the present embodiment can suppress the occurrence of pinholes. The reason for this is unknown, but it is thought to be as follows. In the high chlorine concentration layer 21 containing a large amount of chlorine as an impurity, the progress of etching by the chemical polishing liquid is suppressed. The path through which etching is likely to proceed is interrupted at the high chlorine concentration layer 21. Therefore, the path through which etching is likely to proceed is not connected in the thickness direction, and the etching is suppressed from locally progressing in the thickness direction. As a result, the occurrence of pinholes can be suppressed.

The chlorine concentration (value measured by secondary ion mass spectrometry) at the peak of the local distribution contained in the chlorine concentration distribution is preferably 1 × 10 ¹⁹ atoms / cm ³ or more, and 2 × 10 ¹⁹ atoms / cm ³ or more. Is more preferable. All the local distributions included in the chlorine concentration distribution may satisfy this condition, or some local distributions may satisfy this condition. If the chlorine concentration distribution is as described above, the occurrence of pinholes can be sufficiently suppressed.

It is preferable that the full width at half maximum of the local distribution included in the chlorine concentration distribution is narrower than half of the peak interval with the adjacent local distribution. This means that the thickness of the high chlorine concentration layer 21 is thinner than the thickness of the low chlorine concentration layer 22. Since the high chlorine concentration layer 21 in which the progress of etching is suppressed is thin, it is possible to prevent the chemical polishing rate from becoming unnecessarily slow and the chemical polishing from taking a long time. All the local distributions included in the chlorine concentration distribution may satisfy the above conditions, or some local distributions may satisfy the above conditions.

Further, the presence of the high chlorine concentration layer 21 in the copper plating film 20 also has an effect that the surface of the copper plating film 20 after chemical polishing can be smoothed. The reason for this is unknown, but it is thought to be as follows. The progress of etching by the chemical polishing liquid is relatively slow in the high chlorine concentration layer 21, and relatively fast in the low chlorine concentration layer 22. Since the portion where the etching progresses slowly and the portion where the etching progresses alternately appear in the thickness direction of the copper plating film 20, the etching does not proceed locally but progresses uniformly over the entire surface. As a result, the surface of the copper plating film 20 after chemical polishing becomes smooth.

The copper plating film 20 may contain impurities other than chlorine, for example, carbon, oxygen, sulfur, etc. derived from the additive of the copper plating solution.

Next, an embodiment will be described.
(Example 1)
The substrate was prepared by the following procedure. As a base film, a polyimide film having a thickness of 35 μm (Upilex-35SGAV1 manufactured by Ube Corporation) was prepared. The base film was set in the magnetron sputtering device. A nickel-chromium alloy target and a copper target are installed in the magnetron sputtering apparatus. The composition of the nickel-chromium alloy target is 20% by mass of Cr and 80% by mass of Ni. Under a vacuum atmosphere, a base metal layer made of a nickel-chromium alloy having a thickness of 25 nm was formed on one side of the base film, and a copper thin film layer having a thickness of 100 nm was formed on the base metal layer.

Next, the copper plating solution was adjusted. The copper plating solution contains 120 g / L of copper sulfate, 70 g / L of sulfuric acid, 20 mg / L of leveler component, 1,100 mg / L of polymer component, 16 mg / L of Brightener component, and 50 mg / L of chlorine component. A diallyldimethylammonium chloride-sulfur dioxide copolymer (PAS-A-5 manufactured by Nittobo Medical Co., Ltd.) was used as a leveler component. A polyethylene glycol-polypropylene glycol copolymer (Unilube 50MB-11 manufactured by NOF CORPORATION) was used as a polymer component. Bis (3-sulfopropyl) disulfide (reagent manufactured by RASCHIG GmbH) was used as a Brightener component. Hydrochloric acid (35% hydrochloric acid manufactured by Wako Pure Chemical Industries, Ltd.) was used as the chlorine component.

The base material was supplied to the plating tank in which the copper plating solution was stored. A copper plating film having a thickness of 2.0 μm was formed on one side of the base material by electrolytic plating to obtain a copper-clad laminate. Here, the temperature of the copper plating solution was set to 31 ° C. Further, during the electrolytic plating, the copper plating solution ejected from the nozzle was sprayed substantially perpendicular to the surface of the base material to stir the copper plating solution.

In electrolytic plating, the current density was changed so that the air feeding period was included 11 times. Here, the blank feeding period means a period during which electrolytic plating is performed at a low current density, specifically 0.0 A / dm ² . The current density (high current density) other than the blank feeding period was set to 1.2 A / dm ² .

(Example 2)
A copper-clad laminate was obtained in the same procedure as in Example 1. However, in electrolytic plating, the current density was changed so that the blank feeding period was included 7 times. The other conditions are the same as in Example 1.

(Comparative Example 1)
A copper-clad laminate was obtained in the same procedure as in Example 1. However, in electrolytic plating, the current density was set to 3.2 A / dm ² , and no airborne period was provided. The other conditions are the same as in Example 1.

(Chlorine concentration measurement)
The chlorine concentration of the copper-plated coating was measured with respect to the copper-clad laminates obtained in Examples 1 and 2 and Comparative Example 1. The measurement was performed by secondary ion mass spectrometry. A quadrupole secondary ion mass spectrometer (PHI ADEPT-1010) manufactured by ULVAC FI Co., Ltd. was used as the measuring device. The measurement conditions were Cs ⁺ for the primary ion species, 5.0 kV for the primary acceleration voltage, and 96 × 96 μm for the detection region. The value of the chlorine concentration in the present specification is based on the value measured under the above conditions.

FIG. 4A shows the measurement results of the copper-clad laminate obtained in Example 1. FIG. 4B shows the measurement results of the copper-clad laminate obtained in Example 2. FIG. 4C shows the measurement results of the copper-clad laminate obtained in Comparative Example 1. The horizontal axis of each graph in FIG. 4 is the position in the thickness direction of the copper plating film. 0.0 μm is the surface on the copper thin film layer side, and 2.0 μm is the surface. The vertical axis is the chlorine concentration.

As can be seen from the graph of FIG. 4A, in the first embodiment, the chlorine concentration distribution in the thickness direction of the copper plating film consists of ten periodic chevron local distributions. Peaks near 0.2 μm correspond to the first two airborne periods. The remaining 9 peaks correspond to the following 9 airborne periods. It can be said that this copper plating film has a structure in which high chlorine concentration layers and low chlorine concentration layers are alternately laminated. Further, it can be said that this copper plating film contains 10 layers having a high chlorine concentration.

Table 1 shows the details of the chlorine concentration distribution obtained in Example 1. Here, the 10 peaks included in the chlorine concentration distribution are referred to as the 1st to 10th peaks from the surface side (2.0 μm) to the copper thin film layer side (0.0 μm), respectively. For each peak, the peak value (chlorine concentration at the peak), the full width at half maximum of the local distribution including the peak, and the half of the peak interval with the adjacent local distribution are shown. As the peak interval, the target peak and the peak adjacent to the copper thin film layer side and the interval were used. For example, the peak interval of the first peak is the interval between the first peak and the second peak.

From Table 1, it can be seen that the chlorine concentration at all 10 peaks is 1 × 10 ¹⁹ atoms / cm ³ or more. It can also be seen that the chlorine concentration in 5 of the 10 peaks is 2 × 10 ¹⁹ atoms / cm ³ or more. It can also be seen that the full width at half maximum of each peak is the same as half the peak interval, but wider than that. This means that the thickness of the high chlorine concentration layer and the thickness of the low chlorine concentration layer are about the same.

As can be seen from the graph of FIG. 4B, in Example 2, the chlorine concentration distribution in the thickness direction of the copper plating film consists of six chevron-shaped local distributions that are periodic. Peaks near 0.2 μm correspond to the first two airborne periods. The remaining 5 peaks correspond to the following 5 airborne periods. It can be said that this copper plating film has a structure in which high chlorine concentration layers and low chlorine concentration layers are alternately laminated. Further, it can be said that this copper plating film contains 6 layers having a high chlorine concentration.

Table 2 shows the details of the chlorine concentration distribution obtained in Example 2. Here, the six peaks included in the chlorine concentration distribution are referred to as the first to sixth peaks from the surface side (2.0 μm) toward the copper thin film layer side (0.0 μm), respectively. For each peak, the peak value, full width at half maximum, and half of the peak interval are shown.

From Table 2, it can be seen that the chlorine concentrations at all 6 peaks are 1 × 10 ¹⁹ atoms / cm ³ or more. It can also be seen that the chlorine concentration in 5 of the 6 peaks is 2 × 10 ¹⁹ atoms / cm ³ or more. It can also be seen that the full width at half maximum of each peak is narrower than half of the peak interval. This means that the thickness of the high chlorine concentration layer is thinner than the thickness of the low chlorine concentration layer.

As can be seen from the graph of FIG. 4C, in Comparative Example 1, the chlorine concentration is low over the entire thickness direction of the copper plating film. Specifically, the chlorine concentration is less than 1 × 10 ¹⁹ atoms / cm ³ overall. Therefore, this copper plating film does not have a structure in which high chlorine concentration layers and low chlorine concentration layers are alternately laminated.

(Chemical polishing)
The copper-clad laminates obtained in Examples 1 and 2 and Comparative Example 1 were chemically polished. As the chemical polishing solution, a solution containing sulfuric acid and hydrogen peroxide as main components (a solution obtained by diluting CPE-750 manufactured by Mitsubishi Gas Chemical Company, Inc. 10-fold) was used. The copper plating film having a thickness of 2 μm was reduced to 0.5 μm.

Table 3 shows the chemical polishing rates of each copper-clad laminate. Based on Comparative Example 1, it can be seen that the chemical polishing rate of Example 1 is 14.9% slower and that of Example 2 is 13.7% slower. The reason is unknown, but it is presumed that the thinner the high chlorine concentration layer 21 in which the progress of etching is suppressed, the faster the chemical polishing rate. From this, it was confirmed that from the viewpoint of the chemical polishing rate, it is preferable that the full width at half maximum of the local distribution contained in the chlorine concentration distribution is narrower than half of the peak interval with the adjacent local distribution (Example 2).

(Pinhole)
Next, the number of pinholes after chemical polishing was measured.
After chemical polishing, the number of pinholes was measured. The measurement was performed by irradiating a halogen lamp from the base film side and counting the number of transmitted lights existing in the field of view with a metallurgical microscope. Here, the field of view of the metallurgical microscope is 1.81 mm × 2.27 mm. The total number of transmitted lights in the three fields of view was defined as the number of pinholes.

The results are shown in Table 1. It was confirmed that Examples 1 and 2 had fewer pinholes than Comparative Example 1. From this, it was confirmed that the generation of pinholes can be suppressed if the copper-plated coating film is obtained by alternately laminating high-chlorine concentration layers and low-chlorine concentration layers. It was also confirmed that the larger the number of high chlorine concentration layers contained in the copper plating film, the more the occurrence of pinholes can be suppressed. When the number of high chlorine concentration layers contained in the copper plating film is 6 or more, the occurrence of pinholes can be sufficiently suppressed.

(Surface roughness)
The surface roughness of the copper-plated coating before chemical polishing was measured for the copper-clad laminates obtained in Examples 1 and 2 and Comparative Example 1. The results are shown in Table 5. Here, a laser microscope VK-9510 manufactured by KEYENCE Corporation was used for measuring the surface area ratio. The surface area ratio was determined from the measured surface area of the measurement area of 70 × 93 μm. The surface roughness before chemical polishing is almost the same in Examples 1 and 2 and Comparative Example 1.

Next, chemical polishing was performed on each copper-clad laminate. The conditions are the same as the above-mentioned chemical polishing. After chemical polishing, the surface roughness of the copper plating film was measured. The results are shown in Table 5.

It can be seen that in Examples 1 and 2, there is almost no change in the surface roughness before and after the chemical polishing. On the other hand, in Comparative Example 1, it can be seen that the surface of the copper plating film after chemical polishing is rough. In Examples 1 and 2, it can be confirmed that the surface of the copper plating film after chemical polishing is smoother than that in Comparative Example 1.

FIG. 5 shows an SEM image of the surface of the copper plating film after chemical polishing. FIG. 5A is an SEM image of Example 1. FIG. 5B is an SEM image of Example 2. FIG. 5C is an SEM image of Comparative Example 1. From these SEM images, it can be seen that the surface of the copper plating film after chemical polishing is smoother in Examples 1 and 2 than in Comparative Example 1.

From the above, it was confirmed that the surface of the copper-plated coating after chemical polishing can be smoothed if the copper-plated coating is obtained by alternately laminating high-chlorine concentration layers and low-chlorine concentration layers.

1 Copper-clad laminate 10 Base film 11 Base film 12 Metal layer 13 Base metal layer 14 Copper thin film layer 20 Copper plating film 21 High chlorine concentration layer 22 Low chlorine concentration layer

Claims (2)

With the base film
The metal layer formed on the surface of the base film and
A copper-plated coating formed on the surface of the metal layer and containing chlorine as an impurity is provided.
The chlorine concentration distribution in the thickness direction of the copper plating film includes a plurality of chevron local distributions.
All or part of the plurality of local distributions have a chlorine concentration of 2 × 10 ¹⁹ atoms / cm ³ or more measured by secondary ion mass spectrometry at the peak.
A copper-clad laminate characterized by this. The copper-clad laminate according to claim 1 , wherein all or a part of the plurality of local distributions has a full width at half maximum narrower than half of the peak interval with the adjacent local distributions.

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