CN110740568A

CN110740568A - Copper-clad laminated board

Info

Publication number: CN110740568A
Application number: CN201910640844.5A
Authority: CN
Inventors: 渡边智治; 小川茂树; 下地匠; 西山芳英
Original assignee: Sumitomo Metal Mining Co Ltd
Current assignee: Sumitomo Metal Mining Co Ltd
Priority date: 2018-07-18
Filing date: 2019-07-16
Publication date: 2020-01-31
Anticipated expiration: 2039-07-16
Also published as: JP7103006B2; CN110740568B; JP2020011441A; KR20230152633A; TW202014067A; KR20200010033A; TWI793350B

Abstract

The present invention provides kinds of copper-clad laminated sheets capable of smoothing the surface of a copper-clad film after chemical polishing, wherein the copper-clad laminated sheet (1) comprises a base film (11), a metal layer (12) formed on the surface of the base film (11), and a copper-clad film (20) formed on the surface of the metal layer (12) and containing chlorine as an impurity, the average grain size of the crystal grains of the copper-clad film (20) is 300nm or less, and preferably the copper-clad film (20) has a structure in which a high-chlorine-concentration layer (21) having a high chlorine concentration and a low-chlorine-concentration layer (22) having a low chlorine concentration are alternately laminated.

Description

Copper-clad laminated board

Technical Field

The present invention relates to kinds of copper-clad laminates, and more particularly, to kinds of copper-clad laminates used for manufacturing flexible printed circuit boards (FPCs) and the like.

Background

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

As a method for producing a copper-clad laminate, a metal spraying method is known. The copper-clad laminate produced by the metallization method is produced, for example, by the following procedure. First, a base metal layer made of nichrome is formed on the surface of the resin film. Then, 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. The conductor layer is made thick by copper plating until a film thickness suitable for forming a wiring pattern is obtained. A copper-clad laminate of a type called a 2-layer substrate in which a conductor layer is directly formed on a resin film is obtained by a metallization method.

As a method for manufacturing a flexible printed wiring board using such a copper-clad laminate, a semi-additive method is known. The production of a flexible printed wiring board by the semi-additive method is performed according to the following procedure (see patent document 1). First, a resist layer is formed on the surface of the copper plating film of the copper-clad laminate. Next, an opening is formed in a portion of the resist layer where the wiring pattern is formed. Next, the copper plating film exposed through the opening of the resist layer is subjected to electrolytic plating using the copper plating film as a cathode 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 wiring board was obtained.

In the semi-additive method, a dry film resist is sometimes used when forming a resist layer on the surface of the copper plating film. In this case, the surface of the copper-plated film is chemically polished and then a dry film resist is attached. The surface of the copper-plated film is formed with fine irregularities by chemical polishing, thereby improving the adhesion to the dry film resist due to the anchor effect. However, when the surface of the copper plating film has too many irregularities, the adhesiveness of the dry film resist is rather deteriorated.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2006-278950.

Disclosure of Invention

The surface roughness of the copper plating film after chemical polishing is affected by the size of crystal grains of the copper plating film. The surface of the copper-plated film after chemical polishing is smoother as the crystal grains are smaller, and rougher as the crystal grains are larger.

The present invention has been made in view of the above problems, and an object thereof is to provide kinds of copper-clad laminated boards capable of smoothing the surface of a copper-clad film after chemical polishing.

The th invention of the present invention is a type copper-clad laminate, comprising a base film, a metal layer formed on the surface of the base film, and a copper-clad film formed on the surface of the metal layer and containing chlorine as an impurity, wherein the average grain size of crystal grains of the copper-clad film is 300nm or less.

A second aspect of the present invention is the -type copper-clad laminate, wherein the -type copper-clad laminate is formed by alternately laminating a high-chlorine-concentration layer having a high chlorine concentration and a low-chlorine-concentration layer having a low chlorine concentration.

The third invention of the present invention is kinds of copper-clad laminates, wherein in the copper-clad laminate according to the second invention, the chlorine concentration of the high chlorine concentration layer as measured by secondary ion mass spectrometry is 1 × 10¹⁹Atom/cm³As described above, the chlorine concentration of the low chlorine concentration layer measured by secondary ion mass spectrometry is less than 1X 10¹⁹Atom/cm³。

According to the present invention, since the grain size of the crystal grains of the copper plating film is 300nm or less, the crystal grains are sufficiently small, and the surface of the copper plating film after chemical polishing can be made smooth.

Drawings

Fig. 1 is a cross-sectional view of copper-clad laminates according to embodiments of the present invention.

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

FIG. 3 is a plan view of the plating tank.

FIG. 4 is a graph showing the chlorine concentration distribution of the copper-plated film in example 1. FIG. B is a graph showing the chlorine concentration distribution of the copper-plated film in example 2.

FIG. 5(A) is a graph showing the chlorine concentration distribution of the copper-plated film in comparative example 1. FIG. B is a graph showing the chlorine concentration distribution of the copper-plated film in comparative example 2.

Fig. 6(a) is an SEM image of a cross section of the copper-clad laminate in example 1. Fig. (B) is an SEM image of a cross section of the copper-clad laminate in example 2.

Fig. 7(a) is an SEM image of a cross section of the copper-clad laminate in comparative example 1. Fig. (B) is an 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-plated film after chemical polishing in example 1. FIG. B is an SEM image of the surface of the copper-plated film after chemical polishing in example 2.

FIG. 9(A) is an SEM image of the surface of the copper-plated film after chemical polishing in comparative example 1. FIG. B is an SEM image of the surface of the copper-plated film after chemical polishing in comparative example 2.

Wherein the reference numerals are explained as follows:

1: a copper-clad laminate; 10: a substrate; 11: a base film; 12: a metal layer; 13: a base metal layer; 14: a copper thin film layer; 20: a copper plating film; 21: a high chlorine concentration layer; 22: a low chlorine concentration layer.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings.

As shown in fig. 1, the copper-clad laminate 1 according to the embodiments of the present invention is composed of a base material 10 and a copper-clad film 20 formed on the surface of the base material 10, the copper-clad film 20 may be formed only on one surface of the base material 10 as shown in fig. 1, or the copper-clad film 20 may be formed on both surfaces of the base material 10.

The base material 10 is a base material having a metal layer 12 formed on the surface of a base film 11 having insulation properties, the base film 11 may be a resin film such as a polyimide film, the metal layer 12 may be formed by, for example, a sputtering method, the metal layer 12 may be 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 may be sequentially laminated on the surface of the base film 11, the base metal layer 13 may be generally composed of nickel, chromium, or a nickel-chromium alloy, and although not particularly limited, the thickness of the base metal layer 13 is generally 5 to 50nm, 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, and the metal layer 12 and the copper plating film 20 are collectively referred to as "conductor layer".

The average grain size of the crystal grains of the copper-plated film 20 is 300nm or less. Since the crystal grains are sufficiently small, the surface of the copper plating film 20 after chemical polishing can be made smooth. The surface roughness of the copper plating film 20 after chemical polishing is affected by the size of crystal grains of the copper plating film 20. The surface of the copper-plated film 20 after chemical polishing tends to be smoother as the crystal grains become smaller, and the surface of the copper-plated film 20 after chemical polishing tends to be rougher as the crystal grains become larger. Although the reason for this is not clear, it is considered that the following is true. Etching is difficult to progress at the grain boundaries as compared to within the grains. Therefore, the surface roughness of the copper plating film 20 after chemical polishing reflects the size of crystal grains. As a result, the surface of the copper plating film 20 after chemical polishing becomes smoother as the crystal grains become smaller.

Further, the average grain size of the crystal grains of the copper plating film 20 is preferably 100nm or more, and shows that the crystal grains gradually increase as the film formed by copper plating progresses with recrystallization, and therefore, it is difficult to maintain fine crystal grains having an average grain size of less than 100nm, and a copper plating film 20 composed of crystal grains having an average grain size of 100nm or more can be stably produced.

The copper-plated film 20 is formed by electrolytic plating. The copper-plated film 20 is not particularly limited, and is formed by the plating apparatus 3 shown in fig. 2.

The plating apparatus 3 is an apparatus for conveying a long strip-shaped substrate 10 by Roll-to-Roll (Roll-to-Roll) and electrolytically plating the substrate 10. The plating apparatus 3 includes: a supply device 31 for feeding out the roll-wound base material 10; and a winding device 32 for winding the plated substrate 10 (copper-clad laminate 1) into a roll shape.

The plating apparatus 3 includes endless belts 33 (not shown on the lower side) for conveying pairs of upper and lower of the substrates 10, each endless belt 33 is provided with a plurality of clamps 34 for clamping the substrates 10, the substrates 10 fed from the supply apparatus 31 are in a suspended posture with their width directions along the vertical direction, both edges are clamped by the upper and lower clamps 34, and the substrates 10 are circulated in the plating apparatus 3 by driving of the endless belts 33, and thereafter released by the clamps 34 and taken up by the take-up apparatus 32.

A pretreatment tank 35, a plating tank 40, and a post-treatment tank 36 are disposed in the transport path of the substrate 10. The base material 10 is conveyed into the plating tank 40, and a copper plating film 20 is formed on the surface thereof by electrolytic plating. Thereby, a long strip-shaped copper-clad laminate 1 was obtained.

As shown in FIG. 3, the plating tank 40 is a tank of sheet extending in the transverse direction of the conveyance direction of the base material 10, the base material 10 is conveyed along the center of the plating tank 40, the plating bath 40 stores the copper plating solution, and the base material 10 conveyed in the plating tank 40 is entirely immersed in the copper plating solution.

The copper plating solution contains a water-soluble copper salt. The water-soluble copper salt generally used in the copper plating solution is not particularly limited. Examples of the water-soluble copper salt include inorganic copper salts, copper alkane sulfonates, copper alkanol sulfonates, and copper organic acid salts. Examples of the inorganic copper salt include copper sulfate, copper oxide, copper chloride, and copper carbonate. Examples of the copper alkane sulfonate salt include copper methane sulfonate and copper propane sulfonate. Examples of the Copper salt of an alkanol sulfonic acid include Copper isethionate (Copper isethionate) and Copper propanol sulfonate. Examples of the organic copper salt include copper acetate, copper citrate, and copper tartrate.

The water-soluble copper salt used in the copper plating solution may be kinds selected from inorganic copper salts, copper alkane sulfonates, copper alkanol sulfonates, copper organic acid salts and the like, singly or two or more kinds selected from the group consisting of copper sulfate and copper chloride, for example, in the case of a combination of copper sulfate and copper chloride, two or more different kinds selected from the same group selected from inorganic copper salts, copper alkane sulfonates, copper alkanol sulfonates, copper organic acid salts and the like may be used in combination.

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

The copper plating solution usually contains additives to be added to the plating solution, examples of the additives include a leveler component, a polymer component, a brightener component, a chlorine component, and kinds selected from the leveler component, the polymer component, the brightener component, the chlorine component, and the like can be used alone or in combination of two or more.

The leveling agent component is composed of nitrogen-containing amine, etc. examples of the leveling agent component include diallyldimethylammonium chloride, janus Green b (janus Green b), etc. as the polymer component, there is no particular limitation, it is preferable to use species selected from polyethylene glycol, polypropylene glycol, and polyethylene glycol-polypropylene glycol copolymer alone, or two or more species in combination.

The content of each component of the copper plating solution can be selected arbitrarily. However, the copper plating solution preferably contains 60 to 280g/L of copper sulfate and 20 to 250g/L of sulfuric acid. Thus, the copper plating film 20 can be formed at a sufficient speed. The copper plating solution preferably contains 0.5 to 50mg/L of leveling agent component. Thus, a flat copper-plated film 20 can be formed while suppressing the protrusion. The copper plating solution preferably contains 10 to 1500mg/L of a polymer component. This can alleviate the concentration of the current on the end of the base material 10, and can form a uniform copper plating film 20. The copper plating solution preferably contains 0.2 to 16mg/L of brightener component. This can make the precipitated crystal fine and smooth the surface of the copper plating film 20. The copper plating solution preferably contains 20 to 80mg/L of chlorine component. Thus, abnormal precipitation can be suppressed. Since the copper plating solution contains chlorine, the formed copper plating film 20 contains chlorine as an impurity.

The temperature of the copper plating solution is preferably 20-35 ℃. 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, and a means using a jet flow can be used. For example, the copper plating solution can be stirred by spraying the copper plating solution discharged from the nozzle onto the base material 10.

Inside the plating tank 40, a plurality of anodes 41 are arranged along the conveying direction of the substrate 10. The jig 34 for holding the substrate 10 also functions as a cathode. By passing a current between the anode 41 and the jig 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 disposed on both the front and back sides of the substrate 10. Therefore, when the base material 10 having the metal layers 12 formed on both surfaces of the base film 11 is used, the copper-plated films 20 can be formed on both surfaces of the base material 10.

Since the plurality of anodes 41 disposed inside the plating tank 40 are connected to the rectifier, respectively, different current densities can be set for each anode 41, in the present embodiment, the inside of the plating tank 40 is divided into a plurality of regions in the transport direction of the substrate 10, each region corresponding to a region where or a plurality of continuous anodes 41 are disposed.

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

Here, it is preferable that the current density (low current density) in the low current density zone LZ is set to 0 to 0.29A/dm², it is preferable that the current density (high current density) in the high current density zone HZ is set to 0.3 to 10A/dm²。

The number of the low current density zones LZ may be or a plurality of the low current density zones LZ, and the number of the high current density zones HZ may be or a plurality of the high current density zones HZ, the uppermost zone may be the low current density zone LZ or the high current density zone HZ., and the lowermost zone may be the low current density zone LZ or the high current density zone HZ, with respect to the transport direction of the substrate 10.

When a plurality of low current density zones LZ are disposed in the plating tank 40, the current densities in the plurality of low current density zones LZ may be the same or different. In the case where a plurality of high current density regions HZ are arranged in the plating tank 40, the current densities in the plurality of high current density regions HZ may be the same or different. However, it is preferable that the current density in the high current density region HZ be set to increase stepwise toward the downstream side in the transport direction of the base material 10.

The base material 10 is electrolytically plated while alternately passing through the low current density zone LZ and the high current density zone HZ, &lttttransfer = one "&gtt-one &ltt/t &gtt &inthe plating tank 40, that is, the base material 10 is alternately and repeatedly subjected to electrolytic plating at a low current density and electrolytic plating at a high current density, thereby forming the copper plated film 20.

The copper plating film 20 formed by this method has a structure in which a plurality of layers are stacked as shown in fig. 1, the layers being formed by electrolytic plating performed at different current densities, and specifically, the copper plating film 20 has a structure in which a high chlorine concentration layer 21 and a low chlorine concentration layer 22 are alternately stacked in the thickness direction, the high chlorine concentration layer 21 is formed by electrolytic plating performed at a low current density and the relative chlorine concentration is high, and is considered that the low chlorine concentration layer 22 is formed by electrolytic plating performed at a high current density and the relative chlorine concentration is low.

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 zone LZ and the high current density zone HZ in the plating bath 40. the number of the high chlorine concentration layers 21 may be , or a plurality thereof, the number of the low chlorine concentration layers 22 may be , or a plurality thereof, the layer directly laminated on the surface of the substrate 10 (the surface of the metal layer 12) may be the high chlorine concentration layer 21, or the low chlorine concentration layer 22, and the layer present on the surface of the copper plating film 20 (the surface on the opposite side of the substrate 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). The chlorine concentration measured by the secondary ion mass spectrometry of the high chlorine concentration layer 21 is preferably 1X 10¹⁹Atom/cm³The above. The chlorine concentration measured by secondary ion mass spectrometry of the low-chlorine concentration layer 22 is preferably less than 1X 10¹⁹Atom/cm³。

, the crystal grains of the copper plating film 20 gradually grow larger as the recrystallization after the plating treatment progresses, whereas in the copper plating film 20 of the present embodiment, the stress relaxation is blocked by the high chlorine concentration layer 21, and the progress of recrystallization is suppressed, so the crystal grains of the copper plating film 20 can be kept fine, specifically, the average grain size of the crystal grains can be kept at 300nm or less.

The copper plating film 20 may contain impurities other than chlorine, such as carbon, oxygen, and sulfur, which are additives derived from the copper plating solution.

Examples

Next, examples will be explained.

(example 1)

The substrate was prepared as follows. A polyimide film (Upliex-35 SGAV1, product of Updex corporation, Updex) having a thickness of 35 μm was prepared as a base film. The base film is placed in a magnetron sputtering device. A nickel-chromium alloy target and a copper target are arranged in the magnetron sputtering device. The composition of the nichrome target was 20 mass% Cr and 80 mass% Ni. A base metal layer made of a nickel-chromium alloy having a thickness of 25nm was formed on one surface of a base film in a vacuum atmosphere, and a copper thin film layer having a thickness of 100nm was formed thereon.

Next, a copper plating solution was prepared. The copper plating solution contained 120g/L of copper sulfate, 70g/L of sulfuric acid, 20mg/L of leveler component, 1100mg/L of polymer component, 16mg/L of brightener component, and 50mg/L of chlorine component. As the leveling agent component, A diallyldimethylammonium chloride-sulfur dioxide copolymer (PAS-A-5, manufactured by Nittobo medical Co., Ltd.) was used. As the polymer component, a polyethylene glycol-polypropylene glycol copolymer (manufactured by Nichii oil Co., Ltd., Unilube 50MB-11) was used. As the brightener component, bis (3-sulfopropyl) disulfide (a reagent manufactured by RASHIG GmbH) was used. Hydrochloric acid (35% hydrochloric acid manufactured by Wako pure chemical industries, Ltd.) was used as the chlorine component.

The base material is supplied to a plating tank storing the copper plating solution. A copper-clad laminate was obtained by forming a copper-clad coating having a thickness of 2.0 μm on one surface of a substrate by electrolytic plating. Here, the temperature of the copper plating solution was 31 ℃. Further, during the electrolytic plating, the copper plating solution discharged from the nozzle is sprayed substantially perpendicularly to the surface of the base material, thereby stirring the copper plating solution.

In the electrolytic plating, the current density was varied so as to include 11 idle periods. Here, the idle transmission period is a period at a low current density, specifically, 0.0A/dm²During the electrolytic plating. The current density (high current density) outside the idle transmission period was 1.2A/dm²。

(example 2)

A copper-clad laminate was obtained in the same manner as in example 1. In the electrolytic plating, the current density was changed so as to include 7 idle periods. Other conditions were the same as in example 1.

Comparative example 1

A copper-clad laminate was obtained in the same manner as in example 1. Wherein the current density in the electrolytic plating was 3.2A/dm²No idle period is set. Other conditions were the same as in example 1.

Comparative example 2

A copper-clad laminate was obtained in the same manner as in example 1. Wherein the current density in the electrolytic plating is set to 0.33A/dm²No idle period is set. Other conditions were the same as in example 1.

(measurement of chlorine concentration)

The copper-clad laminates obtained in examples 1 and 2 and comparative examples 1 and 2 were subjected to measurement of the chlorine concentration of the copper plating film, measurement was performed by secondary ion mass spectrometry, and a quadrupole secondary ion mass spectrometer (PHI ADEPT-1010) manufactured by department of obstetrics and gynecology (ULVAC-PHI inc., アルバック, ファイ) was used as a measurement device under the condition of a secondary ion species of Cs⁺The -time acceleration voltage was 5.0kV, and the detection field was 96X 96 μm, and the chlorine concentration in this specification was determined based on the value measured under the above-mentioned conditions.

Fig. 4(a) shows the measurement result of the copper-clad laminate obtained in example 1. Fig. 4(B) shows the measurement result of the copper-clad laminate obtained in example 2. Fig. 5(a) shows the measurement result of the copper-clad laminate obtained in comparative example 1. Fig. 5(B) shows the measurement result of the copper-clad laminate obtained in comparative example 2. The horizontal axis of each graph indicates the position in the thickness direction of the copper-plated film. 0.0 μm is the surface on the copper thin film layer side, and 2.0 μm is the surface. The vertical axis represents chlorine concentration.

As is clear from the graph of fig. 4(a), in example 1, the chlorine concentration distribution in the thickness direction of the copper-plated film is a distribution having 10 peaks with periodicity. The peak around 0.2 μm corresponds to the first 2 idle periods. The remaining 9 peaks correspond to the following 9 empty periods. The chlorine concentration of each peak was 1X 10¹⁹Atom/cm³The above. And the lower limit between peaks is less than 1X 10¹⁹Atom/cm³. Therefore, the copper-plated film can be said to have a structure in which a high-chlorine-concentration layer and a low-chlorine-concentration layer are alternately laminated. The copper plating film can be said to contain 10 high chlorine concentration layers.

As is clear from the graph of fig. 4(B), in example 2, the chlorine concentration distribution in the thickness direction of the copper-plated film was a distribution having 6 periodic peaks. The peak around 0.2 μm corresponds to the first 2 idle periods. The remaining 5 peaks correspond to the following 5 empty periods. The chlorine concentration of each peak was 1X 10¹⁹Atom/cm³The above. And the lower limit between peaks is less than 1X 10¹⁹Atom/cm³. Therefore, the copper plating film can be said to have a high chlorine concentrationThe layers and the low chlorine concentration layer are alternately stacked. The copper plating film can be said to contain 6 high chlorine concentration layers.

As is clear from the graph of fig. 5(a), in comparative example 1, the chlorine concentration was low throughout the thickness direction of the copper plating film. Specifically, the chlorine concentration is less than 1X 10 as a whole¹⁹Atom/cm³. Therefore, the copper-plated film does not have a structure in which a high-chlorine-concentration layer and a low-chlorine-concentration layer are alternately stacked.

As is clear from the graph of fig. 5(B), in comparative example 2, the chlorine concentration was higher throughout the thickness direction of the copper plating film than in comparative example 1. This copper plating film does not have a structure in which high-chlorine-concentration layers and low-chlorine-concentration layers are alternately stacked, but contains chlorine at a high concentration as a whole.

(Crystal grain)

The copper-clad laminates obtained in examples 1 and 2 and comparative examples 1 and 2 were observed for their cross section after 7 days from the plating treatment. Fig. 6(a) shows an SEM image of a cross section of example 1. Fig. 6(B) shows an SEM image of a cross section of example 2. Fig. 7(a) shows an SEM image of a cross section of comparative example 1. Fig. 7(B) shows an SEM image of a cross section of comparative example 2. From these SEM images, it was found that the crystal grains of the copper plating films of examples 1 and 2 were finer than those of comparative examples 1 and 2.

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

The results are shown in Table 1. It was confirmed that the average particle size of the crystal grains was smaller in examples 1 and 2 than in comparative examples 1 and 2. The small crystal grains in examples 1 and 2 are considered to be due to the copper plating film having a structure in which a high chlorine concentration layer and a low chlorine concentration layer are alternately stacked. It is presumed that the inclusion of the high chlorine concentration layer in the copper plating film can suppress the progress of recrystallization and keep the crystal grains in a fine state.

In example 1, the average particle size of the crystal grains was smaller than that in example 2. The copper plating film of example 1 included 10 high-chlorine-concentration layers, and the copper plating film of example 2 included 6 high-chlorine-concentration layers. From this fact, it can be said that the larger the number of high chlorine concentration layers contained in the copper plating film, the smaller the average grain size of the crystal grains.

(surface roughness)

The surface roughness of the copper-plated film before chemical polishing was measured for the copper-clad laminates obtained in examples 1 and 2 and comparative examples 1 and 2. The surface area ratio was measured using a laser microscope VK-9510 manufactured by Keyence Corporation. The surface area ratio was determined from the measurement surface area of the measurement region of 70X 93. mu.m.

The results are shown in Table 1. Examples 1 and 2 and comparative example 1 are substantially the same in terms of surface roughness before chemical polishing. The surface of comparative example 2 was slightly rough compared to 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 main components (a liquid obtained by diluting CPE-750 manufactured by Mitsubishi Gas Chemical co., Ltd) by 10 times) was used. The thickness of the copper plating film was reduced to 0.5. mu.m. After the chemical polishing, the surface roughness of the copper plating film was measured.

The results are shown in Table 1, it is clear that the surface roughness before and after chemical polishing hardly changed in examples 1 and 2, and , it is clear that the surface of the copper-plated film after chemical polishing was roughened in comparative examples 1 and 2, and it is confirmed that the surface of the copper-plated film after chemical polishing was smooth in examples 1 and 2 as compared with comparative examples 1 and 2.

The surface of the copper-plated film after chemical polishing was observed for each copper-clad laminate. Fig. 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. From these SEM images, it is clear that the surfaces of the copper plating films after chemical polishing were smooth in examples 1 and 2 as compared with comparative examples 1 and 2.

As is apparent from Table 1, it can be said that the surface of the copper plating film after chemical polishing was smooth in example 2 in which the average grain size of the crystal grains of the copper plating film was 251nm, and , the surface of the copper plating film after chemical polishing was rough in comparative example 2 in which the average grain size of the crystal grains of the copper plating film was 376 nm.

TABLE 1

Claims

1, A copper-clad laminate, comprising:

a base film;

a metal layer formed on a 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 average grain size of the crystal grains of the copper plating film is 300nm or less.

2. The copper-clad laminate according to claim 1,

the copper-plated film is formed by alternately laminating a high-chlorine-concentration layer having a high chlorine concentration and a low-chlorine-concentration layer having a low chlorine concentration.

3. The copper-clad laminate according to claim 2,

the chlorine concentration of the high chlorine concentration layer measured by secondary ion mass spectrometry was 1X 10¹⁹Atom/cm³In the above-mentioned manner,

the low chlorine concentration layer has a chlorine concentration of less than 1X 10 as measured by secondary ion mass spectrometry¹⁹Atom/cm³。