TW202014067A - Copper-coated laminate capable of making surface of copper-plated film being smooth after chemical polishing - Google Patents

Abstract

The present invention provides a copper-coated laminate, which may make the surface of copper-plated film being smooth after chemical polishing. The copper-coated laminate 1 comprises a substrate 11, a metal layer 12 formed on the surface of the substrate 11, and a copper-plated film 20 formed on the surface of the metal 12 as dopant and containing chlorine. The average diameter of the crystal particles of the copper-plated film 20 is below 300nm. The copper-plate film 20 is preferably composed by alternately laminating a high chlorine concentration layer 21 having a higher chlorine concentration with a low chlorine concentration layer 22 having a lower chlorine concentration.

Description

Copper clad laminate

The invention relates to a copper-clad laminate. In more detail, the present invention relates to a copper-clad laminate used in the manufacture of flexible printed circuit boards (FPC) and the like.

In a liquid crystal panel, a notebook computer, a digital camera, a mobile phone, etc., a flexible printed circuit board having a wiring pattern formed on the surface of a resin film is used. The flexible printed circuit board is made of, for example, a copper-clad laminate.

As a method of manufacturing a copper-clad laminate, a metal spray method is known. The production of the copper-clad laminate using the metal spraying method is performed, for example, as follows. First, a base metal layer containing 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 it becomes a film thickness suitable for forming a wiring pattern. By a metal spraying method, a so-called copper-clad laminate in which a conductor layer is directly formed on a resin film is called a two-layer substrate.

As a method of manufacturing a flexible printed circuit board using such a copper-clad laminate, a semi-additive process (Semi-additive Process) is known. The manufacturing of the flexible printed circuit board by the semi-additive method is performed according to the following procedure (refer to Patent Document 1). First, a resist layer is formed on the surface of the copper-plated film of the copper-clad laminate. Next, an opening is formed in the portion of the resist layer where the wiring pattern is formed. Next, the copper plating film exposed from the opening of the resist layer is used as a cathode for electrolytic plating to form a wiring portion. Then, the resist layer is removed, and the conductor layer other than the wiring portion is removed by flash etching or the like. Thereby, a flexible printed circuit board is obtained.

In the semi-additive method, when a resist layer is formed on the surface of the copper plating film, a dry film resist is sometimes used. In this case, after the surface of the copper-plated coating is chemically polished, the dry film resist is adhered. By chemical polishing, fine irregularities are formed on the surface of the copper-plated coating, thereby improving the adhesion of the dry film resist due to the anchoring effect. However, if there are too many irregularities on the surface of the copper plating film, on the contrary, the adhesion of the dry film resist may deteriorate.

[Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2006-278950.

[Summary of the invention]

The surface roughness of the copper-plated coating after chemical polishing is affected by the size of the crystal grains of the copper-plated coating. It is said that the smaller the crystal grains, the smoother the surface of the copper-plated coating after chemical polishing, and the larger the crystal grains, the rougher the surface of the copper-plated coating after chemical polishing.

In view of the above circumstances, the present invention aims to provide a copper-clad laminate capable of smoothing the surface of a copper plating film after chemical polishing.

The copper-clad laminate of the first invention is characterized by comprising a base film, a metal layer formed on the surface of the base film, and a copper-plated coating film formed on the surface of the metal layer and containing chlorine as an impurity, and the plated The average particle diameter of the crystal grains of the copper film is 300 nm or less.

The copper-clad laminate of the second invention is characterized in that in the first invention, the copper plating film is formed by alternately laminating a high chlorine concentration layer with a high chlorine concentration and a low chlorine concentration layer with a low chlorine concentration.

The copper clad laminate of the third invention is characterized in that in the second invention, the chlorine concentration of the high chlorine concentration layer measured by secondary ion mass spectrometry is 1×10 ¹⁹ atoms/cm ³ or more, and the low chlorine The concentration of chlorine in the concentration layer measured by secondary ion mass spectrometry is less than 1×10 ¹⁹ atoms/cm ³ .

According to the present invention, since the particle size of the crystal grains of the copper-plated coating is 300 nm or less, the crystal grains are small enough to smooth the surface of the copper-plated coating after chemical polishing.

1‧‧‧Copper laminate

10‧‧‧ Base material

11‧‧‧ Base film

12‧‧‧Metal layer

13‧‧‧ Base metal layer

14‧‧‧Copper film layer

20‧‧‧Coated with copper

21‧‧‧High chlorine concentration layer

22‧‧‧Low chlorine concentration layer

FIG. 1 is a cross-sectional view of a copper-clad laminate according to an embodiment of the present invention.

Fig. 2 is a perspective view of a plating apparatus.

Fig. 3 is a plan view of a plating bath.

The graph (A) in FIG. 4 is a graph showing the chlorine concentration distribution of the copper-plated coating in Example 1. FIG. Figure (B) is a graph showing the chlorine concentration distribution of the copper-plated coating in Example 2.

The graph (A) in FIG. 5 is a graph showing the chlorine concentration distribution of the copper plating film in Comparative Example 1. Figure (B) is a graph showing the chlorine concentration distribution of the copper-plated coating in Comparative Example 2.

FIG. 6 (A) is an SEM image of a cross section of the copper-clad laminate in Example 1. FIG. Figure (B) is an SEM image of a cross section of the copper-clad laminate in Example 2.

FIG. 7 (A) is a SEM image of a cross section of the copper-clad laminate in Comparative Example 1. FIG. Figure (B) is a SEM image of a cross section of the copper-clad laminate in Comparative Example 2.

Fig. 8(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-plated coating after chemical polishing in Example 2. FIG.

FIG. 9 (A) is an SEM image of the surface of the copper-plated coating after chemical polishing in Comparative Example 1. FIG. FIG. (B) is an SEM image of the surface of the copper-plated coating after chemical polishing in Comparative Example 2. FIG.

[Form for carrying out the invention]

Hereinafter, an embodiment of the present invention will be described based on the drawings.

As shown in FIG. 1, a copper-clad laminate 1 according to an embodiment of the present invention includes a base 10 and a copper-plated coating 20 formed on the surface of the base 10. As shown in FIG. 1, the copper plating film 20 may be formed only on one side of the substrate 10, or the copper plating film 20 may be formed on both sides of the substrate 10.

The base material 10 is a base material in which the metal layer 12 is formed on the surface of the insulating base film 11. As the base film 11, a resin film such as a polyimide film can be used. The metal layer 12 is formed by a sputtering method, for example. The metal layer 12 includes 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 deposited on the surface of the base film 11 in this order. Generally, the base metal layer 13 contains 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. In addition, the metal layer 12 and the copper plating film 20 are collectively called "conductor layer".

The average particle diameter of the crystal grains of the copper plating film 20 is 300 nm or less. Since the crystal grains are small enough, the surface of the copper plating film 20 after chemical polishing can be smoothed. The surface roughness of the copper plating film 20 after chemical polishing is affected by the size of the crystal grains of the copper plating film 20. The smaller the crystal grains, the smoother the surface of the copper-plated coating film 20 after chemical polishing, and the larger the crystal grains, the rougher the surface of the copper-plated coating film 20 after chemical polishing. Although the reason is still unclear, it is considered as follows. The crystal grain boundary is more difficult to etch than in the crystal grain. Therefore, the size of the crystal grains is reflected in the surface roughness of the copper plating film 20 after chemical polishing. As a result, the smaller the crystal grains, the smoother the surface of the copper plating film 20 after chemical polishing.

In addition, the average particle diameter of the crystal grains of the copper plating film 20 is preferably 100 nm or more. In general, the film formed by copper plating gradually grows larger as the recrystallization proceeds. Therefore, it is difficult to maintain fine crystal grains having an average particle diameter of less than 100 nm. If the copper plating film 20 is composed of crystal grains with an average particle diameter of 100 nm or more, it can be stably manufactured.

The copper plating film 20 is formed by electrolytic plating. The copper plating film 20 is not particularly limited, but is formed by the electroplating device 3 shown in FIG. 2.

The electroplating device 3 is a device that transports a long strip-shaped base material 10 using a roll-to-roll (Roll-to-Roll), and performs electrolytic plating on the base material 10. The electroplating device 3 includes a supply device 31 that sends out the substrate 10 wound into a roll shape, and a winding device 32 that winds the substrate 10 after plating (copper-clad laminate 1) into a roll shape.

In addition, the electroplating apparatus 3 includes a pair of endless belts 33 (the lower endless belt 33 not shown) above and below the transport substrate 10. Each endless belt 33 is provided with a plurality of jigs 34 that sandwich the base material 10. The base material 10 sent out from the supply device 31 is in a hanging posture in the width direction along the vertical direction, and both edges are sandwiched by the upper and lower jigs 34. After the base material 10 is circulated in the electroplating device 3 by the drive of the endless belt 33, it is released by the jig 34 and taken up by the take-up device 32.

In the transport path of the base material 10, a pre-treatment tank 35, a plating tank 40, and a post-treatment tank 36 are arranged. The base material 10 is transported into the plating tank 40 on one side, and the copper plating film 20 is formed on the surface by electrolytic plating. Thus, a long strip-shaped copper-clad laminate 1 is obtained.

As shown in FIG. 3, the electroplating tank 40 is a horizontally elongated single tank along the conveyance direction of the base material 10. The base material 10 is transported along the center of the plating tank 40. A copper plating solution is stored in the plating tank 40. The entire substrate 10 transported in the plating tank 40 is immersed in the copper plating solution as a whole.

The copper plating solution contains water-soluble copper salts. It is not particularly limited as long as it is a water-soluble copper salt commonly used in copper plating solutions. Examples of water-soluble copper salts include inorganic copper salts, alkane sulfonic acid copper salts, alkanol sulfonic acid copper salts, and organic acid copper salts. Examples of inorganic copper salts include copper sulfate, copper oxide, copper chloride, and copper carbonate. Examples of the copper salt of alkanesulfonic acid include copper methanesulfonate and copper propanesulfonate. Examples of the copper salt of alkanolsulfonic acid include copper isethionate and copper propanesulfonate. Examples of copper salts of organic acids include copper acetate, copper citrate, and copper tartrate.

As the water-soluble copper salt used in the copper plating solution, one kind selected from inorganic copper salt, copper alkanesulfonate, copper alkanesulfonate, organic acid copper salt, etc. may be used alone, or two kinds may be used in combination the above. For example, two or more different types in the same category selected from inorganic copper salt, copper alkanesulfonate, copper alkanosulfonate, organic acid copper salt, etc. can be combined as in the case of combining copper sulfate and copper chloride Use in combination. However, from the viewpoint of easy management of the copper plating solution, it is preferable to use a 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 usually added to the plating solution. Examples of the additives include leveling agent components, polymer components, brightener components, and chlorine components. As the additive, one kind selected from leveling agent components, polymer components, brightener components, chlorine components, and the like may be used alone, or two or more kinds may be used in combination.

The leveling agent component is composed of nitrogen-containing amine and the like. As the leveling agent component, diallyl dimethyl ammonium chloride, Janus Green B (Janus Green B), etc. may be mentioned. The polymer component is not particularly limited, but preferably, one kind selected from polyethylene glycol, polypropylene glycol, and polyethylene glycol-polypropylene glycol copolymer may be used alone, or two or more kinds may be used in combination. The brightener component is not particularly limited, but it is preferably used alone selected from bis(3-sulfopropyl) disulfide (abbreviated as SPS), 3-mercaptopropane-1-sulfonic acid (abbreviated as MPS), etc. One of them, or two or more in combination. The chlorine component is not particularly limited, but it is preferable to use one kind selected from hydrochloric acid, sodium chloride and the like alone or to use two or more kinds in combination.

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. If so, the copper plating film 20 can be formed at a sufficient speed. The copper plating solution preferably contains 0.5 to 50 mg/L of a leveling agent component. If this is the case, the protrusions are suppressed, and the flat copper plating film 20 can be formed. The copper plating solution preferably contains 10 to 1500 mg/L of polymer component. If this is the case, the concentration of current to the end of the base material 10 will be relaxed, and a uniform copper plating film 20 can be formed. The copper plating solution preferably contains 0.2 to 16 mg/L of brightener component. If this is the case, the precipitated crystals will be made fine, and the surface of the copper plating film 20 can be smoothed. The copper plating solution preferably contains 20 to 80 mg/L of a chlorine component. If so, abnormal precipitation can be suppressed. In addition, 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. In addition, 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 means using jet flow can be used. For example, by spraying the copper plating liquid sprayed from the nozzle onto the base material 10, the copper plating liquid can be stirred.

In the interior of the plating tank 40, a plurality of anodes 41 are arranged along the conveyance direction of the base material 10. In addition, the jig 34 holding the base material 10 also has a function as a cathode. By flowing current between the anode 41 and the jig 34 (cathode), the copper-plated coating 20 can be formed on the surface of the base material 10.

In addition, 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 material 10.

A plurality of anodes 41 arranged inside the plating tank 40 are connected by rectifiers. Therefore, it is possible to set a different current density for each anode 41. In this embodiment, the inside of the plating tank 40 is divided into a plurality of regions along the conveyance direction of the base material 10. Each region corresponds to a region where one or a plurality of consecutive anodes 41 are arranged.

Each zone is a low current density zone LZ or a high current density zone HZ. In the low current density region LZ, the current density is set to zero or a relatively low "low current density", and the substrate 10 is subjected to electrolytic plating at a low current density. In the high current density region HZ, the current density is set to a “high current density” higher than the low current density, and the substrate 10 is subjected to electrolytic plating at a high current density.

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

The low current density region LZ and the high current density region HZ are alternately arranged along the conveyance direction of the base material 10. The number of low current density regions LZ may be one, or plural. The number of high current density regions HZ may be one or plural. Using the transport direction of the base material 10 as a reference, the most upstream region may be a low current density region LZ or a high current density region HZ. In addition, the most downstream region may be a low current density region LZ or a high current density region HZ.

When a plurality of low current density regions LZ are arranged in the plating tank 40, the current density in the plurality of low current density regions LZ may be the same or different. In addition, when a plurality of high current density regions HZ are arranged in the plating tank 40, the current density in the plurality of high current density regions HZ may be the same or different. However, the current density in the high current density region HZ is preferably set to increase toward the downstream side in the conveyance direction of the base material 10 in steps.

The base material 10 is electrolytically plated while alternately passing through the low current density region LZ and the high current density region 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.

The copper plating film 20 formed by this method has a structure in which a plurality of layers are formed by electrolytic plating at different current densities as shown in FIG. 1. Specifically, the copper plating film 20 has a structure in which the high-chlorine concentration layer 21 and the low-chlorine concentration layer 22 are alternately stacked in the thickness direction. Here, the high chlorine concentration layer 21 is formed by electrolytic plating at a low current density, and the relative chlorine concentration is high. On the other hand, the low chlorine concentration layer 22 is formed by electrolytic plating at a high current density, and the relative chlorine concentration is low. This is presumed to be that the lower the current density in electrolytic plating, the easier the additives of the copper plating solution are sucked in by 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 region LZ and the high current density region HZ in the plating tank 40. The number of high-chlorine concentration layers 21 may be one, or plural. The number of low chlorine concentration layers 22 may be one, or plural. The layer directly deposited 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. In addition, the layer appearing on the surface of the copper plating film 20 (the surface on the side 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: Secondary Ion Mass Spectrometry). The chlorine concentration of the high-chlorine concentration layer 21 measured by secondary ion mass spectrometry is preferably 1×10 ¹⁹ atoms/cm ³ or more. The chlorine concentration of the low chlorine concentration layer 22 measured by secondary ion mass spectrometry is preferably less than 1×10 ¹⁹ atoms/cm ³ .

In general, the crystal grains of the copper plating film 20 gradually become larger as the recrystallization after the plating process progresses. On the other hand, in the copper plating film 20 of this embodiment, the stress relief is blocked by the high chlorine concentration layer 21, and the progress of recrystallization is suppressed. Therefore, the crystal grains of the copper plating film 20 can be maintained in a fine state. Specifically, the average particle diameter of the crystal grains can be maintained at 300 nm or less.

In addition, the copper plating film 20 may contain impurities other than chlorine, for example, carbon, oxygen, sulfur, etc. from additives of the copper plating solution.

[Example]

Hereinafter, Examples will be described.

(Example 1)

Follow the steps below to prepare the substrate. As the base film, a polyimide film having a thickness of 35 μm (manufactured by Ube Industries, Inc., Upilex-35SGAV1) was prepared. Install the base film in the magnetron sputtering device. A nickel-chromium alloy target and a copper target are provided in the magnetron sputtering device. The composition of the nickel-chromium alloy target is 20% by mass of Cr and 80% by mass of Ni. Under a vacuum environment, a base metal layer containing a nickel-chromium alloy with a thickness of 25 nm was formed on one side of the base film, and a copper thin film layer with a thickness of 100 nm was formed thereon.

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

The base material is supplied to an electroplating bath storing the aforementioned copper plating solution. A copper-clad laminate was obtained by depositing a copper-plated coating with a thickness of 2.0 μm on one side of the substrate by electrolytic plating. Here, the temperature of the copper plating solution is set to 31°C. In addition, during the electrolytic plating, the copper plating liquid sprayed from the nozzle is sprayed substantially perpendicularly to the surface of the base material, thereby stirring the copper plating liquid.

In electrolytic plating, the current density is changed so as to include 11 air-delivery periods. Here, the air-delivery period means a period when electrolytic plating is performed at a low current density, specifically, 0.0 A/dm ² . The current density (high current density) outside the air-feeding period was 1.2 A/dm ² .

(Example 2)

In the same manner as in Example 1, a copper-clad laminate was obtained. However, in electrolytic plating, the current density is changed so as to include seven idle periods. Other conditions are the same as in Example 1.

(Comparative example 1)

The 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 air feed period was provided. Other conditions are the same as in Example 1.

(Comparative example 2)

The copper-clad laminate was obtained in the same procedure as in Example 1. However, in electrolytic plating, the current density was set to 0.33A/dm ² and no air-delivery period was provided. Other conditions are the same as in Example 1.

(Determination of chlorine concentration)

For the copper-clad laminates obtained in Examples 1 and 2 and Comparative Examples 1 and 2, the chlorine concentration of the copper plating film was measured. The measurement is performed by secondary ion mass spectrometry. As a measuring device, a quadrupole secondary ion mass spectrometer (PHI ADEPT-1010) of ULVAC-PHI Inc. was used. The measurement conditions are such that the primary ion type is Cs ⁺ , the primary acceleration voltage is 5.0 kV, and the detection area is 96×96 μm. In addition, the value of the chlorine concentration in this specification is based on the value measured under the aforementioned conditions.

The measurement results of the copper-clad laminate obtained in Example 1 are shown in FIG. 4(A). The measurement results of the copper-clad laminate obtained in Example 2 are shown in FIG. 4(B). The measurement results of the copper-clad laminate obtained in Comparative Example 1 are shown in FIG. 5(A). The measurement results of the copper-clad laminate obtained in Comparative Example 2 are shown in FIG. 5(B). The horizontal axis of each graph 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. 4(A), in Example 1, the chlorine concentration distribution in the thickness direction of the copper-plated coating has a periodic distribution of 10 peaks. The peak near 0.2 μm corresponds to the first two air feed periods. The remaining 9 peaks correspond to the following 9 air-delivery periods. The chlorine concentration of each peak is 1×10 ¹⁹ atoms/cm ³ or more. Moreover, the lower limit between peaks is less than 1×10 ¹⁹ atoms/cm ³ . Therefore, it can be said that this copper-plated coating is a structure in which a high-chlorine concentration layer and a low-chlorine concentration layer are alternately stacked. In addition, it can be said that the copper plating film contains 10 high-chlorine concentration layers.

From the graph of FIG. 4(B), it can be seen that in Example 2, the chlorine concentration distribution in the thickness direction of the copper-plated coating has a periodic distribution of six peaks. The peak near 0.2 μm corresponds to the first two air feed periods. The remaining 5 peaks correspond to the subsequent 5 air-delivery periods. The chlorine concentration of each peak is 1×10 ¹⁹ atoms/cm ³ or more. Moreover, the lower limit between peaks is less than 1×10 ¹⁹ atoms/cm ³ . Therefore, it can be said that this copper-plated coating is a structure in which a high-chlorine concentration layer and a low-chlorine concentration layer are alternately stacked. In addition, it can be said that this copper-plated coating contains 6 layers of high chlorine concentration.

As can be seen from the graph of FIG. 5(A), in Comparative Example 1, the overall chlorine concentration in the thickness direction of the copper plating film was low. Specifically, the chlorine concentration is less than 1×10 ¹⁹ atoms/cm ^{3 as a whole} . Therefore, this copper plating film does not have a structure in which a high-chlorine concentration layer and a low-chlorine concentration layer are alternately stacked.

As can be seen from the graph of FIG. 5(B), in Comparative Example 2, compared with Comparative Example 1, the chlorine concentration is higher in the entire thickness direction of the copper-plated coating. Although this copper plating film does not have a structure in which a high-chlorine concentration layer and a low-chlorine concentration layer are alternately stacked, it contains a high-concentration chlorine as a whole.

(Crystal grain)

The copper-clad laminates obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were observed in cross section 7 days after the plating process. The SEM image of the cross section of Example 1 is shown in FIG. 6(A). The SEM image of the cross section of Example 2 is shown in FIG. 6(B). The SEM image of the cross section of Comparative Example 1 is shown in FIG. 7(A). The SEM image of the cross section of Comparative Example 2 is shown in FIG. 7(B). It can be seen from these SEM images that the crystal grains of the copper-plated coating are finer in Examples 1 and 2 than in Comparative Examples 1 and 2.

The average particle diameter of the crystal grains of the copper plating film was calculated using each SEM image. The steps are as follows. First, the SEM image is subjected to image processing to identify each crystal grain contained in the copper-plated coating. Next, the equivalent circle diameter is calculated from the area of each crystal grain. Next, the frequency distribution of the calculated diameter is obtained. Here, the number of stages is divided on a scale of 10 nm, and the number frequency in each stage is calculated. Next, the diameter of each stage is converted into an area, and then the number frequency is multiplied by the area to calculate the area frequency. The average particle diameter is calculated from the obtained area frequency.

The results are shown in Table 1. It was confirmed that in Examples 1 and 2, the average particle diameter of the crystal grains was smaller than in Comparative Examples 1 and 2. In Examples 1 and 2, the crystal grains are small, and it is considered that the copper plating film has a structure in which a high-chlorine concentration layer and a low-chlorine concentration layer are alternately stacked. It is presumed that since the copper plating film contains a high chlorine concentration layer, the progress of recrystallization can be suppressed, and the crystal grains can be maintained in a fine state.

In Example 1, the average particle size of the crystal grains is smaller than that in Example 2. The copper-plated coating of Example 1 includes 10 high-chlorine concentration layers, and the copper-plated coating of Example 2 includes 6 high-chlorine concentration layers. From this, it can be said that the greater the number of high-chlorine concentration layers contained in the copper-plated coating, the smaller the average particle diameter of the crystal grains.

(Surface roughness)

For the copper-clad laminates obtained in Examples 1 and 2 and Comparative Examples 1 and 2, the surface roughness of the copper-plated coating before chemical polishing was measured. Here, for the measurement of the surface area ratio, a laser microscope VK-9510 manufactured by Keyence Corporation was used. The surface area ratio was obtained from the measurement surface area of the measurement area of 70×93 μm.

The results are shown in Table 1. The surface roughness before chemical polishing was almost the same in Examples 1, 2 and Comparative Example 1. Comparative Example 2 is slightly rougher than Examples 1, 2 and Comparative Example 1.

Next, each copper-clad laminate was chemically polished. As the chemical polishing liquid, a liquid containing sulfuric acid and hydrogen peroxide as a main component (a liquid in which CPE-750 manufactured by Mitsubishi Gas Chemical Co., Ltd. was diluted 10 times) was used. The copper plating film with a thickness of 2 μm was reduced to 0.5 μm. After chemical polishing, the surface roughness of the copper-plated coating was measured.

The results are shown in Table 1. It can be seen that in Examples 1 and 2, the surface roughness hardly changed before and after chemical polishing. On the other hand, it can be seen that in Comparative Examples 1 and 2, the surface of the copper plating film after chemical polishing became rough. It can be confirmed that the surfaces of the copper-plated coating after chemical polishing in Examples 1 and 2 are smooth compared to Comparative Examples 1 and 2.

For each copper-clad laminate, the surface of the copper plating film after chemical polishing was observed. 8(A) is an SEM image of Example 1. FIG. 8(B) is an SEM image of Example 2. FIG. 9(A) is an SEM image of Comparative Example 1. FIG. 9(B) is an SEM image of Comparative Example 2. It can also be seen from these SEM images that the surfaces of the copper-plated coatings after chemical polishing in Examples 1 and 2 were smooth compared to Comparative Examples 1 and 2.

It can be seen from Table 1 that in Example 2 where the average particle diameter of the crystal grains of the copper-plated coating is 251 nm, it can be said that the surface of the copper-plated coating after chemical polishing is smooth. On the other hand, in Comparative Example 2 in which the average particle diameter of the crystal grains of the copper-plated coating was 376 nm, the surface of the copper-plated coating after chemical polishing was rough. Therefore, if the average particle diameter of the crystal grains of the copper plating film is 300 nm or less, it is considered that the surface of the copper plating film after chemical grinding can be smoothed.

[Table 1]

1‧‧‧Copper laminate

10‧‧‧ Base material

11‧‧‧ Base film

12‧‧‧Metal layer

13‧‧‧ Base metal layer

14‧‧‧Copper film layer

20‧‧‧Coated with copper

21‧‧‧High chlorine concentration layer

22‧‧‧Low chlorine concentration layer

Claims (3)

A copper-clad laminate, characterized by: Basement membrane, 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, On the other hand, the average particle diameter of the crystal grains of the copper plating film is 300 nm or less. As in the copper clad laminate of claim 1, where, The copper plating film is formed by alternately stacking a high chlorine concentration layer with a high chlorine concentration and a low chlorine concentration layer with a low chlorine concentration. As in the copper clad laminate of claim 2, where, The chlorine concentration measured by the secondary ion mass spectrometry of this high chlorine concentration layer is 1×10 ¹⁹ atoms/cm ³ or more, The chlorine concentration of this low chlorine concentration layer measured by secondary ion mass spectrometry is less than 1×10 ¹⁹ atoms/cm ³ .

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