TWI843975B - Roughening of copper foil, copper-clad laminates and printed circuit boards - Google Patents

Abstract

The present invention provides a roughened copper foil, which can be used to manufacture printed circuit boards and the like that have excellent adhesion to resin, low transmission loss, and are not prone to short circuits caused by migration. The roughened copper foil of the present invention has a roughened surface on at least one side, and the roughened surface is formed with a plurality of roughened particles (1), and the surface of the roughened particles (1) is formed with bumps and depressions. Furthermore, the developed area ratio Sdr of the interface of the roughened surface measured using a three-dimensional white light interference microscope is greater than 1000% and less than 5000%, and the arithmetic mean roughness Sa of the roughened surface is greater than 0.04 μm and less than 0.6 μm.

Description

Roughening of copper foil, copper-clad laminates and printed circuit boards

The present invention relates to a roughened copper foil which can be used to manufacture printed circuit boards, etc., and a copper-clad laminate and a printed circuit board using the roughened copper foil.

A copper-clad laminate can be manufactured by pressing a copper foil and a resin substrate together. However, the adhesion between the copper foil and the resin substrate can be improved by applying a roughening treatment and pressing the resin substrate onto the roughened surface. The roughening treatment is to form roughening particles on the surface of the copper foil to roughen the surface of the copper foil.

As the height of the roughened particles (i.e., the distance between the surface of the copper foil before the roughening treatment and the front end of the roughened particles protruding from the surface of the copper foil before the roughening treatment, hereinafter also referred to as "roughening height") increases, the adhesion between the copper foil and the resin substrate can be greatly improved. However, if a copper foil with a large roughening height is used to manufacture a printed circuit board, there is a problem that the transmission loss increases due to the skin effect. In other words, the adhesion between the copper foil and the resin substrate and the transmission loss show a trade-off relationship.

On the other hand, as printed circuit boards have been developed towards high-frequency support in recent years, if the roughening height is reduced in order to reduce transmission loss, the following new problem has also emerged: migration is likely to occur when the printed circuit board is made, and the circuit of the printed circuit board becomes prone to short circuits.

Patent document 1 discloses a copper foil having high adhesion to a resin substrate, and Patent document 2 discloses a copper foil capable of manufacturing a printed circuit board with low transmission loss. However, the copper foil disclosed in Patent documents 1 and 2 still cannot satisfy both the characteristics of adhesion and transmission loss at the same time. In addition, there is a concern that a printed circuit board that is not prone to migration cannot be manufactured. [Prior technical document] (Patent document)

Patent document 1: Japanese Patent Gazette No. 6632739. Patent document 2: Japanese Patent Gazette No. 6462961.

[Problem to be solved by the invention] The problem to be solved by the present invention is to provide a roughened copper foil and a copper-clad laminate, which can produce a printed circuit board with excellent adhesion to resin, low transmission loss, and not prone to short circuits caused by migration. In addition, the problem to be solved by the present invention is to provide a printed circuit board with excellent adhesion to resin, low transmission loss, and not prone to short circuits caused by migration. [Technical means for solving the problem]

A roughened copper foil of one aspect of the present invention is a roughened copper foil having a roughened surface on at least one side, wherein the roughened surface is formed with a plurality of roughened particles. The roughened copper foil is characterized in that: projections and depressions are formed on the surface of the roughened particles, an area ratio Sdr of an interface of the roughened surface measured using a three-dimensional white light interference microscope is greater than 1000% and less than 5000%, and an arithmetic mean roughness Sa of the roughened surface is greater than 0.04 μm and less than 0.6 μm.

In addition, the copper-clad laminate of other aspects of the present invention is characterized in that it has the roughened copper foil of the above-mentioned aspect. Further, the printed circuit board of other aspects of the present invention is characterized in that it has the roughened copper foil of the above-mentioned aspect.

International Publication No. 2019/188712 and Japanese Patent Gazette No. 6430092 of the prior art disclose a copper foil, which is formed by electrolytically plating protrusions called roughly spherical protrusions on the surface of roughened particles of the copper foil, thereby forming concavities and convexities on the surface of the roughened particles. These prior arts disclose a technical feature that high mechanical strength can be obtained even if the roughened particles are small by forming concavities and convexities on the surface of the roughened particles.

However, it is believed that when electrolytic plating is used to form roughly spherical protrusions, the current will be concentrated on the top of the concentrated roughened particles for plating. As a result, there is a concern that the height of the overall roughened particles will partially increase, and the transmission characteristics will deteriorate. In addition, since International Publication No. 2019/188712 and Japanese Patent Gazette No. 6430092 do not record the transmission characteristics and the migration caused by the interface length of the close contact surface between the copper foil and the resin, it is impossible to confirm whether the problem to be solved by the present invention has been solved.

On the other hand, in the roughened copper foil of one aspect of the present invention, the formation of the unevenness on the surface of the roughened particles can be carried out by etching in a solution as described later, so that the unevenness can be formed on the surface of the roughened particles without increasing the height of the roughened particles. That is, compared with the copper foil disclosed in the above two prior arts, the roughened copper foil of one aspect of the present invention can improve the adhesion to the resin while maintaining a small transmission characteristic. In addition, by forming the unevenness on the entire surface or part of the surface of the roughened particles, the surface area of the roughened particles will also be increased, so that a printed circuit board, etc., which is not prone to short circuits caused by migration, can be manufactured. [Effect of the invention]

The roughened copper foil and copper-clad laminate of the present invention can be used to manufacture printed circuit boards that have excellent adhesion to resin, low transmission loss, and are not prone to short circuits caused by migration. The printed circuit board of the present invention has excellent adhesion to resin, low transmission loss, and is not prone to short circuits caused by migration.

An embodiment of the present invention is described. The embodiment described below is an example of the present invention. In addition, various changes or improvements can be added to the embodiment, and the form obtained by adding such changes or improvements is also included in the present invention.

A roughened copper foil of one embodiment of the present invention is a roughened copper foil having a roughened surface on at least one side, wherein the roughened surface is formed with a plurality of roughened particles, and in the roughened copper foil, projections and depressions are formed on the surfaces of the roughened particles, and an developed area ratio Sdr of the interface of the roughened surface measured using a three-dimensional white light interference microscope is greater than 1000% and less than 5000%, and an arithmetic mean roughness Sa of the roughened surface is greater than 0.04 μm and less than 0.6 μm.

With such a structure, the roughened copper foil of this embodiment can be used to manufacture printed circuit boards with excellent adhesion to resin, low transmission loss, and low risk of short circuits caused by migration. Therefore, the roughened copper foil of this embodiment can be suitably used to manufacture copper-clad laminates and printed circuit boards.

That is, the copper-clad laminate of the present embodiment has the roughened copper foil of the present embodiment. By using the roughened copper foil of the present embodiment, a copper-clad laminate having excellent adhesion to the resin can be manufactured. In addition, the printed circuit board of the present embodiment has the copper-clad laminate of the present embodiment. By using the roughened copper foil and the copper-clad laminate of the present embodiment, a printed circuit board having excellent adhesion to the resin, low transmission loss and not prone to short circuits caused by migration can be manufactured.

The roughened copper foil of this embodiment is described in detail below with reference to the drawings. The roughened copper foil of this embodiment has a roughened surface roughened by roughening treatment on at least one side. The roughening treatment is a treatment in which a plurality of roughening particles 1 are formed on the surface 3 of the raw material of the roughened copper foil (hereinafter, sometimes also described as "raw material copper foil"), and the roughened surface is formed on the surface of the roughened copper foil by the roughening treatment.

As shown in FIG. 1, the roughened particles 1 are formed in a manner protruding from the surface 3 of the raw copper foil. The distance H between the surface 3 of the raw copper foil and the front end of the roughened particles 1 is the roughening height. In addition, the surface of the roughened particles 1 is formed with concavities and convexities. In the roughened copper foil of FIG. 1, the surface of the roughened particles 1 is partially removed by etching or the like, and as a result, a plurality of convex portions 1a are formed on the surface of the roughened particles 1, thereby forming concavities and convexities.

The roughened particles 1 are preferably formed of copper or copper alloy. In addition, the shape of the roughened particles 1 may be a convex shape with a sharp tip, and specific examples include a cone, a triangular cone, a quadrangular cone, an ellipse, and a hemisphere. Alternatively, the following shapes may be included: the portion other than the tip is cylindrical or prismatic and the tip is cone, triangular cone, quadrangular cone, ellipse, or hemisphere.

The roughening height can be expressed as the arithmetic mean roughness Sa specified by ISO25178. Because the arithmetic mean roughness Sa of the roughened surface of the roughened copper foil of this embodiment is greater than 0.04 μm and less than 0.6 μm, the roughening height is small. If a copper foil with a large roughening height is used to manufacture a printed circuit board, the transmission loss will increase due to the skin effect. However, the roughening height of the roughened surface of the roughened copper foil of this embodiment is small. Therefore, as long as the roughened copper foil of this embodiment is used to manufacture a printed circuit board, even when a high-frequency signal is transmitted, the transmission loss in the circuit of the obtained printed circuit board is still small. Therefore, the roughened copper foil of this embodiment can be used to manufacture a printed circuit board with a high-frequency circuit.

In order to further reduce the transmission loss of the printed circuit board, the arithmetic mean roughness Sa of the roughened surface of the roughened copper foil of this embodiment is preferably set to be greater than 0.04μm and less than 0.45μm, more preferably set to be greater than 0.04μm and less than 0.35μm, further preferably set to be greater than 0.04μm and less than 0.3μm, and particularly preferably set to be greater than 0.1μm and less than 0.3μm.

In addition, since the surface of the roughened particle 1 is formed with irregularities, the surface area of the roughened surface becomes larger. The size of the surface area can be expressed by the interface development area ratio Sdr specified in ISO25178, and the interface development area ratio Sdr can be measured using a three-dimensional white light interference microscope. The interface development area ratio Sdr of the roughened surface measured using a three-dimensional white light interference microscope must be 1000% or more and 5000% or less.

As long as the interface development area ratio Sdr is within the above range, the surface area of the roughened surface is still large. Therefore, when the resin is layered on the roughened surface of the roughened copper foil of this embodiment, even if the roughening height is small, a sufficiently large anchoring effect can be obtained, and the adhesion between the roughened copper foil and the resin is excellent.

In addition, the inventors have devoted themselves to the research and found that the surface area of the roughened copper foil at the interface when the roughened copper foil and the resin are bonded is related to the migration. It is found that as long as the arithmetic mean roughness Sa of the roughened surface and the open area ratio Sdr of the interface are within the above range, the migration is not easy to occur. That is, if the roughening height is small, it will become easy to migrate when the printed circuit board is made, and it is easy to cause a short circuit in the circuit of the printed circuit board. However, as long as the open area ratio Sdr of the interface is within the above range, the surface area of the roughened surface is large, so the migration will become difficult to occur, and it is not easy to cause a short circuit in the circuit of the printed circuit board.

The short circuit of the circuit of the printed circuit board caused by migration is described in detail as follows. When a resin substrate is laminated on the roughened surface of the roughened copper foil when manufacturing a copper-clad laminate, the roughened particles on the roughened surface are buried in the resin. Therefore, when the roughened copper foil is removed by etching, the surface of the resin substrate opposite to the removed roughened copper foil has a replica shape, which is a transfer of the concave-convex shape of the roughened surface.

In a printed circuit board made of the copper-clad laminate, migration occurs along the resin-resin bonded interface having a replica shape of the roughened surface. However, if the roughness height of the roughened surface of the roughened copper foil is small, the migration path that may cause a short circuit will be shortened, and a short circuit caused by migration will become more likely to occur.

In addition, if the roughening height of the roughened surface of the roughened copper foil is small, the anchoring effect will be reduced, so the adhesion between the resins with the replica shape of the roughened surface will be weakened, and it will be easy to form gaps. If there are gaps between the resins, water and ions will flow into them and the copper of the circuit line will easily become ions and dissolve, making migration easy.

When the roughened copper foil of this embodiment is used to manufacture copper-clad laminates and printed circuit boards, the roughened particles of the roughened copper foil have uneven surfaces, so the surface shape of the resin having a replica of the roughened surface will also become the same shape as the roughened surface of the roughened copper foil. Therefore, even if the roughening height of the roughened surface of the roughened copper foil is small, the migration path that causes the short circuit will still be drastically extended.

Furthermore, the surface of the roughened particles of the roughened copper foil is formed with unevenness, and the surface area of the roughened surface is large, so the surface area of the surface shape of the resin having the replica shape of the roughened surface is also large. Therefore, even if the roughening height of the roughened surface of the roughened copper foil is small, the adhesion between the resin having the replica shape of the roughened surface and the resin will still be strong, and it is not easy to form gaps, so migration will become difficult to proceed.

Thus, when the roughened copper foil of this embodiment is used to manufacture copper-clad laminates and printed circuit boards, the roughened particles of the roughened copper foil will have uneven surfaces. Therefore, even if the roughening height of the roughened surface of the roughened copper foil is small, the migration path of the short circuit will be greatly lengthened, and the adhesion between the resin and the resin having the replica shape of the roughened surface will be strengthened. As a result, the short circuit of the circuit of the printed circuit board caused by migration will become less likely to occur.

In order to make the adhesion between the roughened copper foil and the resin stronger and to make the short circuit of the circuit of the printed circuit board caused by migration less likely to occur, the open area ratio Sdr of the interface of the roughened surface of the roughened copper foil of this embodiment is preferably set to be greater than 2000% and less than 5000%, and more preferably set to be greater than 3000% and less than 5000%.

The interface development area ratio Sdr and arithmetic mean roughness Sa of the roughened surface of the roughened copper foil of this embodiment can be obtained by measuring and evaluating the unevenness of the roughened surface using a three-dimensional white light interference microscope, a scanning electron microscope, an electron beam three-dimensional roughness analyzer, or the like.

As described above, the roughened copper foil of this embodiment has a small roughening height on the roughened surface and a large surface area, so it is possible to manufacture printed circuit boards that simultaneously meet the following three characteristics: excellent adhesion with resin, low transmission loss, and less prone to short circuits caused by migration.

Furthermore, the ten-point average roughness Rz of the roughened surface is preferably set to be greater than 0.6μm and less than 1.4μm. As long as the ten-point average roughness Rz of the roughened surface is set within the above range, the transmission loss can be reduced and the adhesion between the roughened copper foil and the resin can be increased. The ten-point average roughness Rz of the roughened surface can be measured using a contact surface roughness tester according to the method specified in Japanese Industrial Standard JIS B0601:2001.

In addition, in the roughened copper foil of this embodiment, a rustproofing layer can be deposited on the roughened surface, and a chemical adhesive layer can be further deposited on the rustproofing layer. With such a structure, the rustproofing layer can improve the rustproofing property of the roughened surface, and the chemical adhesive layer can further improve the adhesion between the roughened surface and the resin.

Next, an example of a method for producing the roughened copper foil of the present embodiment is described. (1) Method for producing electrolytic copper foil As the raw copper foil used in producing the roughened copper foil of the present embodiment, electrolytic copper foil and rolled copper foil having a smooth and glossy surface without coarse irregularities are preferred. Among these copper foils, electrolytic copper foil is more preferred from the viewpoint of productivity and cost, and electrolytic copper foil generally referred to as "double-sided glossy foil" and having smooth surfaces on both sides is particularly preferred.

The roughened copper foil of this embodiment can be manufactured using electrolytic copper foil as the raw material copper foil, so the manufacturing method of the electrolytic copper foil will be described first with reference to FIG. 2. The electrolytic copper foil can be manufactured, for example, using an electrolytic deposition device as shown in FIG. 2. The electrolytic deposition device of FIG. 2 includes: an insoluble electrode 12, which is composed of titanium coated with a platinum group element or its oxide; and a titanium rotating electrode 11, which is arranged opposite to the insoluble electrode 12.

Copper plating is performed using an electrolytic deposition device to deposit copper on the surface (cylindrical surface) of a cylindrical rotating electrode 11 to form a copper foil. By peeling the copper foil from the surface of the rotating electrode 11, an electrolytic copper foil can be manufactured. To be described in detail, when copper plating is performed, a current is applied using the rotating electrode 11 as a cathode and the insoluble electrode 12 as an anode. As the insoluble electrode 12, for example, a DSE (Dimensionally Stable Electrode) electrode (registered trademark) can be used. In addition, as the electrolyte 13, for example, an aqueous solution containing sulfuric acid and copper sulfate can be used. Additives such as organic additives and inorganic additives may be added to the electrolyte 13. The additives may be used alone or in combination of two or more.

When the electrolyte 13 is supplied between the rotating electrode 11 and the insoluble electrode 12 from an electrolyte supply unit (not shown) (see the blank arrow), and the rotating electrode 11 is rotated at a constant speed in the direction indicated by the dotted arrow, and a direct current is applied between the rotating electrode 11 and the insoluble electrode 12, copper is deposited on the surface of the rotating electrode 11. By peeling off the deposited copper from the surface of the rotating electrode 11 and tearing it off and continuously rolling it up in the manner indicated by the solid arrow in FIG. 2, an electrolytic copper foil 14 can be obtained.

(2) Roughening treatment Roughening treatment is applied to at least one of the two surfaces of the raw copper foil to form a roughened surface having a plurality of roughening particles. As shown in FIG. 3, a plurality of roughening particles are formed on the surface of the raw copper foil. At this time, the surface of the roughening particles has not yet formed irregularities, but presents a relatively smooth surface.

The electrolytic copper foil of general electrolytic copper foil has a smoother and glossy surface on which electrolytic deposition starts (bright surface), and the surface on the opposite side, i.e., the electrolytic deposition end surface (rough surface), generally has unevenness. In addition, in double-sided glossy foil, both the electrolytic deposition start surface and the electrolytic deposition end surface are smoother and glossier, but the electrolytic deposition end surface is smoother and glossier. It is not a problem to perform a roughening treatment on both sides of the electrolytic copper foil, but even when using any of the electrolytic copper foils, general electrolytic copper foil and double-sided glossy foil, it is better to perform a roughening treatment on the smoother and glossier side. Roughening treatment can be performed, for example, by a two-stage coating treatment as shown below. Furthermore, the second stage fixed coating process may not be performed.

(First stage: roughening coating treatment) The first stage of roughening coating treatment is a treatment to form roughening particles on at least one side of the raw copper foil. Specifically, the copper coating treatment is carried out in a copper sulfate bath. In the copper sulfate bath (roughening basic coating bath), in order to suppress the roughening particles from falling off from the surface of the raw copper foil, i.e. "powder falling", at least one of molybdenum (Mo), arsenic (As), antimony (Sb), bismuth (Bi), selenium (Se), tellurium (Te), tungsten (W), etc. can be added as an additive, and molybdenum is particularly preferred.

An example of the roughening coating treatment conditions is shown below. Copper sulfate pentahydrate concentration in the copper sulfate bath: 5 to 15 g/L in terms of copper (atomic) sulfuric acid concentration in the copper sulfate bath: 120 to 250 g/L Ammonium molybdate concentration in the copper sulfate bath: 500 to 1000 mg/L in terms of molybdenum (atomic) Temperature of the copper sulfate bath: 15 to 20°C Treatment speed: 80 m/min Current density: 5 to 55 A/ ^dm2 Treatment time: 0.5 to 5.0 seconds

(Second stage: fixed coating treatment) The second stage fixed coating treatment is to apply a smooth coating to the roughened surface formed by the above-mentioned roughening coating treatment. Specifically, the copper coating treatment is carried out in a copper sulfate bath. Generally speaking, the fixed coating treatment is used to suppress the shedding of the roughened particles, that is, to fix the roughened particles.

In the roughened copper foil of this embodiment, the fixed coating treatment is not essential, but can be performed as needed. For example, when manufacturing a copper-clad laminate and combining it with a substrate made of a flexible resin such as a hard resin such as polyimide resin, the fixed coating treatment can suppress the fall of roughened particles by performing the fixed coating treatment on the roughened surface, so it is preferable to perform the fixed coating treatment.

An example of fixed plating treatment conditions is shown below. Copper sulfate pentahydrate concentration in the copper sulfate bath: 50 to 65 g/L in terms of copper (atoms) Sulfuric acid concentration in the copper sulfate bath: 80 to 170 g/L Treatment speed: 5 to 20 m/min Current density: 1 to 7 A/dm ²

(3) Pretreatment Before performing a treatment to form irregularities on the surface of the roughened particles, a pretreatment to promote the formation of the irregularities may be performed on the roughened surface. As such a pretreatment, electroplating of zinc may be cited, for example.

If the roughened surface is slightly electroplated with zinc, an uneven zinc coating will be formed depending on the shape of the roughened particles, and a uniform zinc coating will not be formed on the surface of the copper foil. Furthermore, copper and zinc are easily alloyed to form brass, so it is believed that the alloy composition will also be uneven like the uneven zinc coating. That is, if the outermost surface of the copper foil is observed from a microscopic point of view, there will be places where zinc is exposed, places where brass is exposed, and places where brass with different composition ratios is exposed. The way these places are etched by acid is different, so as a result, it will be easy to effectively form unevenness on the surface of the roughened particles by the subsequent unevenness forming process.

Electroplating zinc coating can be performed, for example, using an alkaline zinc coating solution. The zinc concentration in the alkaline zinc coating solution is preferably 2 to 8 g/L. As long as the zinc concentration in the alkaline zinc coating solution is within the above range, the current efficiency of zinc will be appropriate, so effective zinc coating can be easily obtained, and precipitation is not easily generated in the alkaline zinc coating solution, and the stability of the alkaline zinc coating solution is excellent.

The alkaline zinc coating solution preferably contains sodium hydroxide (NaOH), and the concentration thereof is preferably 20 to 45 g/L. As long as the sodium hydroxide concentration in the alkaline zinc coating solution is within the above range, the conductivity of the alkaline zinc coating solution will be appropriate, so that an effective zinc coating amount can be easily obtained, and the coated zinc is not easily dissolved in the alkaline zinc coating solution again. If the coated zinc is dissolved in the alkaline zinc coating solution again, there is a concern that the surface of the roughened particles will not be sufficiently roughened in the subsequent roughening process. The current density during electrogalvanizing is preferably 0.1 to 1 A/dm ² , and the treatment time is preferably 1 to 5 seconds.

As other pre-treatment, there can be mentioned oxidation treatment such as natural oxidation. By slightly oxidizing the surface of the roughening particles of the roughening treatment surface, it becomes easy to effectively form the roughness on the surface of the roughening particles by the subsequent roughening treatment.

The following is an example of a natural oxidation method. After drying the copper foil, place it in the atmosphere for 12 to 48 hours to slightly oxidize the surface of the copper foil. In this method, the areas that are easily oxidized naturally also differ on the surface of the roughened particles of the copper foil, so from a microscopic point of view, different thicknesses of the oxide film will be formed. The method of etching with acid in each of these areas is different, so it is believed that as a result, it will be easy to effectively form unevenness on the surface of the roughened particles by the subsequent unevenness forming process.

As long as the natural oxidation treatment time is within the above range, an oxide film with an appropriate average thickness can be obtained, so it is less likely to cause problems in subsequent treatments. For example, if the oxidation time exceeds 48 hours, the oxidation will proceed excessively, so when the roughened copper foil is subjected to electrolytic plating for rust prevention, there is a concern that a sufficient amount of rust prevention treatment layer may not be obtained.

(4) Treatment for forming unevenness on the surface of roughened particles As treatment for forming unevenness on the surface of roughened particles, etching by chemical agents such as inorganic acids and organic acids and etching by anodic oxidation can be listed. By using etching to remove part of the surface of the roughened particles, a concave portion can be formed, and a portion with a smaller amount of removal becomes a convex portion (convex portion 1a of roughened particle 1 in Figure 1), so unevenness is formed on the surface of the roughened particles.

As an example of etching by chemical agents, for example, treatment of copper foil immersed in inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid can be cited. By immersing the copper foil in an aqueous solution of an inorganic acid of a specific concentration for several seconds to several tens of seconds, a plurality of fine asperities can be formed on the surface of the roughened particles. For example, when hydrochloric acid is used as the inorganic acid, by immersing the copper foil in hydrochloric acid at a concentration of 5 to 20 volume % for more than 2 seconds, fine asperities can be formed on the surface of the roughened particles, and the surface area of the roughened surface can be sufficiently increased.

Examples of etching other than immersion in inorganic acid include immersion in organic acid such as acetic acid and formic acid, immersion in a solution containing ferric chloride and cupric chloride, immersion in a commercially available microetchant, and electrolytic etching by anodic oxidation. These etchings may be performed alone or in combination.

FIG. 4 shows an example of a roughened surface of a roughened copper foil formed by etching to form irregularities on the surface of the roughened particles. It can be seen that the surface of the roughened particles shown in FIG. 4 has a greater number of irregularities than the surface of the roughened particles shown in FIG. 3. It can also be seen that the surface area of the roughened particles becomes larger due to the irregularities.

(5) Surface treatment The roughened surface of the roughened copper foil produced by the above method may be subjected to surface treatment as required. As the surface treatment, the following surface treatment layer may be formed on the roughened surface. That is, the following surface treatment layers can be enumerated: a base layer for suppressing the reduction in adhesion between the roughened copper foil and the resin substrate, which is caused by copper damage caused by the diffusion of copper in the roughened copper foil into the resin substrate laminated on the roughened surface of the roughened copper foil during the manufacture of the copper-clad laminate; a heat-resistant treatment layer for improving the heat resistance of the roughened copper foil; a rust-proof treatment layer for improving the rust resistance of the roughened copper foil; a chemical adhesive layer for improving the adhesion between the roughened copper foil and the resin substrate, etc. Such surface treatment layers may be deposited on the roughened surface of the roughened copper foil by depositing one type alone or by combining two or more types.

Furthermore, the thickness of the intermediate layer and the chemical adhesive layer including the heat-resistant treatment layer and the rust-proof treatment layer is very small, so it does not affect the particle shape of the roughened particles formed on the roughened surface of the roughened copper foil. The particle shape of the roughened particles is substantially determined by the particle shape of the roughened particles in the stage of formation by the roughening treatment.

In addition, the base layer, the heat-resistant treatment layer and the rust-proof treatment layer can all be formed on the roughened surface of the roughened copper foil, or only any one or two of the three layers can be formed as needed. However, when all three layers are formed, it is better to stack the base layer, the heat-resistant treatment layer and the rust-proof treatment layer in sequence from the roughened surface side.

Furthermore, when the chemical adhesive layer is laminated on the roughened copper foil, at least one of the base layer, the heat-resistant treatment layer and the rust-proof treatment layer may be inserted between the roughened copper foil and the chemical adhesive layer, or may not be inserted (that is, the chemical adhesive layer is directly formed on the roughened surface of the roughened copper foil).

When manufacturing a copper-clad laminate, copper in the roughened copper foil diffuses into a resin substrate laminated on the roughened surface of the roughened copper foil to cause copper damage, and there is a concern that the adhesion between the roughened copper foil and the resin substrate is reduced. It is preferred to form a base layer between the roughened copper foil and the chemical adhesive layer. The base layer preferably contains nickel (Ni), and is preferably formed by plating, for example, at least one selected from nickel, nickel-phosphorus (P), and nickel-zinc (Zn).

When it is necessary to improve the heat resistance of the roughened copper foil, it is preferred to form a heat-resistant treatment layer. The heat-resistant treatment layer preferably contains zinc, and is preferably formed by plating, for example, at least one selected from zinc and an alloy containing zinc. Examples of alloys containing zinc include zinc-tin (Sn) alloys, zinc-nickel alloys, zinc-cobalt (Co) alloys, zinc-copper (Cu) alloys, zinc-chromium (Cr) alloys, and zinc-vanadium (V) alloys.

When the rust resistance of the roughened copper foil needs to be improved, it is preferred to form a rust-proof treatment layer. The rust-proof treatment layer preferably contains chromium, and can be formed by, for example, chromium plating or chromate treatment.

When it is necessary to improve the adhesion between the roughened copper foil and the resin substrate, it is preferable to form a chemical adhesive layer. The chemical adhesive layer can be formed by chemical adhesive treatment using a chemical adhesive such as a silane coupling agent. For example, it can be formed by applying a chemical adhesive solution directly or through an intermediate layer on the roughened surface of the roughened copper foil, and then air drying (natural drying) or heat drying.

As long as the solvent such as water in the applied chemical adhesive solution evaporates, a chemical adhesive layer can be formed, which can improve the adhesion between the roughened copper foil and the resin substrate. If the temperature is heated and dried at 50 to 180°C, the reaction between the chemical adhesive and the roughened copper foil can be promoted, so it is appropriate.

As the silane coupling agent, it is preferred to use at least one of epoxy silane coupling agents, amino silane coupling agents, vinyl silane coupling agents, methacrylate silane coupling agents, acrylic silane coupling agents, azole silane coupling agents, styrene silane coupling agents, urea silane coupling agents, butyl silane coupling agents, sulfide silane coupling agents, and isocyanate silane coupling agents.

[Examples] The following shows examples and comparative examples, and further specifically describes the present invention. (A-1) Electrolytic copper foil Electrolytic copper foil is manufactured as raw copper foil for manufacturing roughened copper foil of Examples 1 to 17 and Comparative Examples 1 to 10. Copper plating is performed using the same apparatus as in FIG. 2 and the same operation as described above, so that copper is deposited on the surface of a rotating electrode. Furthermore, the deposited copper is torn off from the surface of the rotating electrode and continuously rolled up to produce an electrolytic copper foil (double-sided glossy foil) with a thickness of 18 μm.

As the cathode, a rotating electrode was used, which was a titanium rotating drum whose surface (cylindrical surface) roughness was adjusted by polishing with a polishing of #1000 to #2000. As the anode, an insoluble electrode was used, which was a dimensionally stable anode DSA (registered trademark). As the electrolyte, a copper sulfate aqueous solution was used, which contained 75 g/L copper, 65 g/L sulfuric acid, 20 mg/L chlorine, 2 mg/L sodium 3-hydroxy-1-propanesulfonate, 10 mg/L hydroxyethyl cellulose, and 50 mg/L low molecular weight gel (molecular weight 3000). The temperature of the electrolyte during copper plating was 50°C and the current density was 45 A/dm ² .

(A-2) Rolled copper foil As the raw copper foil for producing the roughened copper foil of Example 18 and Comparative Example 11, rolled copper foil C1020R-H manufactured by Takeuchi Metal Foil Powder Industry Co., Ltd. was used. The thickness of the rolled copper foil was 20 μm.

(B) Roughening treatment Then, the electrolytic copper foil produced by the above method is subjected to a roughening treatment on the electrolytic deposition end surface (rough surface) and one side of the rolled copper foil to form a roughened surface. The roughening treatment is carried out by performing a two-stage electroplating treatment in a roll-to-roll process.

The first stage of electroplating treatment, i.e., roughening treatment, is an electroplating treatment using a roughening basic coating bath having the following composition and at 15°C, with the current density and treatment time shown in Table 1 and a treatment speed of 15 m/min, thereby forming roughening particles of different roughening heights and shapes on the electrolytic deposition end surface of the electrolytic copper foil. Copper sulfate pentahydrate concentration in the roughening basic coating bath: 10 g/L in terms of copper (atoms) Sulfuric acid concentration in the roughening basic coating bath: 150 g/L Ammonium molybdate concentration in the roughening basic coating bath: 600 mg/L in terms of molybdenum (atoms)

[Table 1] Roughening Pre-treatment Treatment of bump formation Phase 1 Phase 2 Type Type Processing time (seconds) Current density (A/dm ² ) Processing time (seconds) Current density (A/dm ² ) Processing time (seconds) Embodiment 1 20 4 1 4 Zinc coating Hydrochloric acid pickling 14 Embodiment 2 15 4 0 0 Zinc coating Hydrochloric acid pickling 18 Embodiment 3 8 4 0 0 Zinc coating Hydrochloric acid pickling 19 Embodiment 4 30 4 2 4 Zinc coating Hydrochloric acid pickling 11 Embodiment 5 40 4 2 4 Zinc coating Hydrochloric acid pickling 10 Embodiment 6 15 4 1 4 Zinc coating Hydrochloric acid pickling 20 Embodiment 7 25 4 2 4 Zinc coating Hydrochloric acid pickling twenty four Embodiment 8 40 4 2 4 Zinc coating Hydrochloric acid pickling twenty two Embodiment 9 15 4 1 4 Zinc coating Hydrochloric acid pickling 8 Embodiment 10 25 4 2 4 Zinc coating Hydrochloric acid pickling 9 Embodiment 11 40 4 2 4 Zinc coating Hydrochloric acid pickling 6 Embodiment 12 15 4 1 4 Zinc coating Hydrochloric acid pickling 2 Embodiment 13 25 4 2 4 Zinc coating Hydrochloric acid pickling 5 Embodiment 14 40 4 2 4 Zinc coating Hydrochloric acid pickling 4 Embodiment 15 15 4 1 4 Natural oxidation Hydrochloric acid pickling 11 Embodiment 16 25 4 2 4 Natural oxidation Hydrochloric acid pickling 18 Embodiment 17 40 4 2 4 Natural oxidation Hydrochloric acid pickling 14 Embodiment 18 20 4 1 4 Zinc coating Hydrochloric acid pickling 12 Comparison Example 1 15 4 1 4 - - - Comparison Example 2 25 4 2 4 - - - Comparison Example 3 40 4 2 4 - - - Comparison Example 4 35 5 2 5 - - 0 Comparison Example 5 30 4 2 5 - - 0 Comparative Example 6 20 5 2 4 - - 0 Comparison Example 7 9.2 4.4 2.1 4.4 - Electrolytic coating 0 Comparative Example 8 50 10 20 5 Zinc coating Hydrochloric acid pickling 10 Comparative Example 9 0 0 0 0 Zinc coating Hydrochloric acid pickling 10 Comparative Example 10 20 4 1 4 Zinc coating Hydrochloric acid pickling 60 Comparative Example 11 20 4 1 4 - - 0

The second stage of electroplating treatment, i.e., fixed coating treatment, is an electroplating treatment using a fixed basic coating bath having the following composition, and the electroplating treatment is performed at a current density and treatment time shown in Table 1 and a treatment speed of 15 m/min, thereby applying a smooth coating to the electrolytic deposition end surface subjected to the roughening coating treatment to fix the roughened particles. Concentration of copper sulfate pentahydrate in the fixed basic coating bath: 55 g/L in terms of copper (atoms) Concentration of sulfuric acid in the fixed basic coating bath: 120 g/L In addition, no roughening treatment was applied to Comparative Example 9.

(C) Pretreatment Before the roughened surface of the electrolytic copper foil is subjected to a treatment for forming unevenness on the surface of the roughened particles, a pretreatment for promoting the formation of unevenness is performed. For Examples 1 to 14, 18 and Comparative Examples 7 to 10, the following electrolytic zinc plating is performed as a pretreatment. Zinc concentration in the plating bath: 2.5 g/L Sodium hydroxide concentration in the plating bath: 35 g/L Temperature of the plating bath: 20°C Current density: 0.5 A/ ^dm2 Treatment time: 1 second

In addition, for Examples 15 to 17, natural oxidation under the following conditions was performed as a pretreatment. Temperature: 23°C Humidity: 50% RH Treatment time: 12 hours Furthermore, Comparative Examples 1 to 7 and 11 were not subjected to pretreatment.

(D) Treatment of forming irregularities on the surface of roughened particles For Examples 1 to 18 and Comparative Examples 8 to 10 that had been pre-treated, treatment of forming irregularities on the surface of roughened particles was performed by immersing them in hydrochloric acid at a concentration of 10 volume % (11 volume % only for Example 3) and a temperature of 30°C. The immersion treatment time is shown in Table 1. By such treatment, roughened copper foils with different surface areas of the roughened surface were manufactured.

Although the details will be described later, no treatment for forming irregularities on the surface of the roughened particles was performed for Comparative Examples 1 to 6 and 11. Moreover, for Comparative Example 7, protrusions were formed on the surface of the roughened particles by electrolytic plating in a copper sulfate plating bath containing 9-phenylacridine (C ₁₉ H ₁₃ N), thereby forming irregularities on the surface of the roughened particles.

(E) Formation of base layer and intermediate layer Then, on the roughened surface with unevenness formed on the surface of the roughened particles, a base layer, a heat-resistant treatment layer, and a rust-proof treatment layer are sequentially deposited. The base layer is formed by nickel plating under the following conditions, the heat-resistant treatment layer is formed by zinc plating under the following conditions, and the rust-proof treatment layer is formed by chromium plating under the following conditions.

<Conditions for nickel plating> Nickel concentration in plating bath: 45 g/L Boric acid (H ₃ BO ₃ ) concentration in plating bath: 4 g/L Plating bath temperature: 20°C Plating bath pH: 3.5 Current density: 0.2 A/dm ² Treatment time: 8 seconds

<Conditions for zinc plating> Zinc concentration in plating bath: 2.5 g/L Sodium hydroxide concentration in plating bath: 35 g/L Plating bath temperature: 20°C Current density: 0.5 A/ ^dm2 Treatment time: 4 seconds

<Conditions for chromium plating> Chromium concentration in plating bath: 6 g/L Plating bath temperature: 30°C Plating bath pH: 2.3 Current density: 5 A/ ^dm2 Treatment time: 3 seconds

(F) Formation of chemical bonding agent layer Finally, a chemical bonding agent layer is deposited on the anti-rust treatment layer. In detail, a 0.2 mass % aqueous solution of 3-aminopropyltrimethoxysilane (C ₆ H ₁₇ NO ₃ Si) is applied to the anti-rust treatment layer and dried at 100°C to form a silane coupling agent layer.

(G) Description of Comparative Examples Here, Comparative Examples 1 to 11 are generally described. Comparative Examples 1 to 3 are examples in which no unevenness is formed on the surface of the roughened particles, and the treatment of forming unevenness on the surface of the roughened particles is not implemented. Comparative Examples 4 to 6 are each examples in which no unevenness is formed on the surface of the roughened particles, and the treatment of forming unevenness on the surface of the roughened particles is not implemented after the roughened particles are formed according to the method disclosed in Japanese Patent Gazette No. 6632739, Japanese Patent Gazette No. 6462961 or International Publication No. 2020/031721.

Comparative Example 7 is an example in which unevenness is formed on the surface of the roughened particles, and protrusions are formed on the surface of the roughened particles by performing electrolytic plating. Comparative Example 8 is an example in which the roughening height of the roughened surface is too large. Comparative Example 9 is an example in which roughened particles are not formed on the electrolytic deposition end surface of the copper foil, and the roughening treatment is not performed. Comparative Example 10 is an example in which the surface area of the roughened surface is too large. Comparative Example 11 is an example in which unevenness is not formed on the surface of the roughened particles, and the roughening treatment is performed on the rolled copper foil without performing the treatment to form unevenness on the surface of the roughened particles.

Here, the manufacturing method of the roughened copper foil of Comparative Example 7 is described in detail. In Comparative Example 7, roughened particles are formed on the electrolytic deposition end surface of the electrolytic copper foil by two-stage electrolytic plating. Then, the third stage of electrolytic plating is further performed to form concavities and convexities on the surface of the roughened particles. Then, the base layer, the heat-resistant treatment layer, the rust-proof treatment layer and the chemical bonding agent layer are laminated in the same manner as in the embodiment to obtain the roughened copper foil.

The manufacturing method of the roughened copper foil of Comparative Example 7 is based on the method disclosed in the embodiment of International Publication No. 2019/188712, and in the third stage of electrolytic plating, roughly spherical protrusions are formed on the surface of the roughened particles, thereby forming unevenness on the surface of the roughened particles. In the three-stage electrolytic plating, a copper sulfate solution with a copper concentration, sulfuric acid concentration, chlorine concentration, and 9-phenylacridine (9PA) concentration as described below is used as a plating bath. The conditions of the three-stage electrolytic plating are each as described below.

<Conditions for electrolytic plating in the first stage> Copper sulfate pentahydrate concentration in the plating bath: 8 g/L in terms of copper (atoms) Sulfuric acid concentration in the plating bath: 100 g/L Chlorine concentration in the plating bath: 50 ppm 9PA concentration in the plating bath: 60 ppm Temperature in the plating bath: 30°C Processing speed: 15 m/min Flow rate between electrodes in the processing direction: 15 m/min Current density: 9.2 A/ ^dm2 Processing time: 4.4 seconds

<Conditions for electrolytic plating in the second stage> Copper sulfate pentahydrate concentration in the plating bath: 69 g/L in terms of copper (atoms) Sulfuric acid concentration in the plating bath: 240 g/L Chlorine concentration in the plating bath: 0 ppm 9PA concentration in the plating bath: 0 ppm Temperature in the plating bath: 52°C Processing speed: 15 m/min Electrode flow rate in the processing direction: 15 m/min Current density: 2.1 A/ ^dm2 Processing time: 4.4 seconds

<Conditions for electrolytic plating in the third stage> Copper sulfate pentahydrate concentration in the plating bath: 13 g/L in terms of copper (atoms) Sulfuric acid concentration in the plating bath: 75 g/L Chlorine concentration in the plating bath: 35 ppm 9PA concentration in the plating bath: 139 ppm Temperature in the plating bath: 28°C Processing speed: 15 m/min Electrode flow rate in the processing direction: 15 m/min Current density: 33.6 A/ ^dm2 Processing time: 0.6 seconds

(H) Evaluation Various evaluations were performed on the copper foils of Examples 1 to 18 and Comparative Examples 1 to 11 produced in the above manner [Expanded area ratio Sdr and arithmetic mean roughness Sa of the interface of the roughened surface] The expanded area ratio Sdr and arithmetic mean roughness Sa of the interface of the roughened surface can be measured by the method specified in ISO 25178 using a three-dimensional white light interference microscope, a scanning electron microscope, an electron beam three-dimensional roughness analyzer, etc. For the copper foils of Examples 1 to 18 and Comparative Examples 1 to 11, the surface shape of the roughened surface was measured using a three-dimensional white light interference microscope Wyko ContourGT-K manufactured by BRUKER, and shape analysis was performed to obtain the interface development area ratio Sdr and arithmetic mean roughness Sa of the roughened surface.

The surface shape was measured by performing shape analysis at 5 random locations on each copper foil to obtain the interface development area ratio Sdr and arithmetic mean roughness Sa of each of the 5 locations. The average of the results obtained at the 5 locations was set as the interface development area ratio Sdr and arithmetic mean roughness Sa of each copper foil.

Shape analysis was performed using a high-resolution CCD (Charge Coupled Device) camera (resolution 1280×980 pixels) and VSI measurement method (vertical scanning interferometry). The conditions were white light, 50x measurement magnification, 96.1μm×72.1μm measurement range, 3% threshold, and Fourier filter processing after performing cylinder and tilt terms removal (Terms Removal (Cylinder and Tilt)) and data recovery (Data Restore (method: legacy, iterations 5)) filter processing.

For Fourier filtering, High Freq Pass was used as the Fourier filter, Gaussian was used in the Fourier Filter Window, and the Low Cutoff was set to 62.5 mm ^-1 in the Frequency Cutoff.

The interface development area ratio Sdr was calculated by using the hybrid mode S parameter analysis (S parameters-hybrid) to remove the tilt (Remove Tilt) as true. The arithmetic mean roughness Sa was calculated by using the height mode S parameter analysis (S parameters-height) to remove the tilt (Remove Tilt) as true. The results are shown in Table 2.

[Ten-point average roughness Rz of the roughened surface] For the roughened surfaces of the copper foils of Examples 1 to 18 and Comparative Examples 1 to 11, the ten-point average roughness Rzjis (μm) was measured in accordance with the provisions of Japanese Industrial Standards JIS B 0601:2001. As a measuring device, a contact surface roughness measuring machine Surfcorder SE1700 manufactured by Kosaka Laboratory Co., Ltd. was used. In addition, the measurement was carried out in a direction orthogonal to the length direction of the copper foil. The results are shown in Table 2. Furthermore, the so-called "longitudinal direction" refers to the MD (Machine Direction) of the electrolytic copper foil. For example, when a rotating electrode is used in manufacturing the electrolytic copper foil and the copper foil is formed on the surface of the rotating electrode by plating, it refers to the rotation direction of the rotating electrode.

[Adhesion strength] A normal peeling test was performed according to the method specified in Japanese Industrial Standard JIS C6481:1996. A resin substrate was bonded to the roughened surface of a copper foil to produce a copper-clad laminate. As the resin substrate, two sheets of low-dielectric polyphenylene ether resin films (multi-layer substrate material MEGTRON 7 manufactured by Panasonic Co., Ltd., thickness 60 μm) were bonded together. Furthermore, for the copper foils of Examples 1 to 6 and Comparative Examples 1 to 3, the copper-clad laminate was produced without performing full-surface grinding and micro-etching before bonding to the resin substrate.

Masking tape was pasted on the copper-clad laminate, and the masking tape was removed after copper chloride etching to produce a printed circuit board with a circuit line of 10 mm in width. Then, the circuit line part (copper foil part) of the printed circuit board was stretched in a 90-degree direction at a speed of 50 mm/min using a universal testing machine (Tensilon tester) manufactured by Toyo Seiki Seisakusho Co., Ltd. in a room temperature environment to peel it off from the resin substrate, and the normal peel strength was measured and set as the adhesion strength. The results are shown in Table 2. In Table 2, when the adhesion strength is 0.7N/mm or more, it is indicated as "A", when it is 0.55N/mm or more and less than 0.7N/mm, it is indicated as "B", and when it is less than 0.55N/mm, it is indicated as "C".

[Transmission loss] Using the copper foil of Examples 1 to 18 and Comparative Examples 1 to 11 and a resin substrate, i.e., a low-dielectric polyphenylene ether resin film (multi-layer substrate material MEGTRON 7 manufactured by Panasonic Co., Ltd., thickness 60 μm), a printed circuit board with strip lines was produced and the transmission characteristics were evaluated. The circuit width of the strip lines formed on the printed circuit board was 140 μm and the circuit length was 760 mm.

The transmission loss was measured by transmitting a high-frequency signal to the copper foil circuit formed on the printed circuit board using the network analyzer N5291A manufactured by Keysight Technologies. The characteristic impedance was set to 50Ω. The smaller the absolute value of the measured value of the transmission loss, the less the transmission loss, that is, the high-frequency signal can be transmitted well. The results are shown in Table 2. In Table 2, when the absolute value of the transmission loss at 30GHz is less than 28dB/760mm, it is represented as "A", when it is greater than 28dB/760mm and less than 31dB/760mm, it is represented as "B", and when it is greater than 31dB/760mm, it is represented as "C".

[Migration resistance test] The copper foils of Examples 1 to 18 and Comparative Examples 1 to 11 were bonded to a resin substrate, i.e., a low-dielectric polyphenylene ether resin film (multi-layer substrate material MEGTRON 7 manufactured by Panasonic Co., Ltd., thickness 60 μm) to produce a pressurized sample. Then, a comb-shaped circuit suitable for IPC-B-25A specification was formed on the pressurized sample to produce a printed wiring board. The line width of the comb-shaped circuit is 0.318 mm, the line spacing is 0.318 mm, and the circuit length is 22 mm.

The printed circuit boards thus manufactured were subjected to migration resistance tests in accordance with the method specified in IPC-650-TM2.5.3 using the migration tester MIG-8600B manufactured by IMV, and the migration resistance between circuit patterns was evaluated. That is, after measuring the initial resistance value of the printed circuit board in a room temperature environment (23°C and 50%RH), a 100V DC voltage was applied in a constant temperature and high humidity tank at 50°C and 90%RH for 168 hours (7 days).

After that, the printed circuit board was taken out of the constant temperature and high humidity tank, and the resistance value was measured within 1 hour. The results are shown in Table 2. In Table 2, when the resistance value measured after being taken out of the constant temperature and high humidity tank is less than 50% of the initial resistance value, it is indicated as "A", when it is more than 50% and less than 60%, it is indicated as "B", and when it is more than 60%, it is indicated as "C".

[Table 2] Interface development area ratio Sdr (%) Arithmetic mean roughness Sa (μm) Ten-point average roughness Rzjis (μm) Sealing strength Transmission loss Migration resistance Embodiment 1 3521 0.25 0.89 A A A Embodiment 2 3802 0.15 0.72 A A A Embodiment 3 3964 0.04 0.61 A A A Embodiment 4 3419 0.41 1.25 A B A Embodiment 5 3101 0.59 1.42 A B A Embodiment 6 4083 0.18 0.90 A A A Embodiment 7 4941 0.34 1.21 A B A Embodiment 8 4698 0.58 1.43 A B A Embodiment 9 2671 0.21 0.87 A A A Embodiment 10 2820 0.33 1.24 A B A Embodiment 11 2200 0.57 1.46 A B A Embodiment 12 1031 0.19 0.87 B A B Embodiment 13 1930 0.34 1.21 B B B Embodiment 14 1602 0.57 1.37 B B B Embodiment 15 3101 0.22 0.87 A A A Embodiment 16 3901 0.35 1.21 A B A Embodiment 17 3560 0.56 1.40 A B A Embodiment 18 3221 0.23 0.89 A A A Comparison Example 1 198 0.19 0.93 C A C Comparison Example 2 220 0.33 1.22 C A C Comparison Example 3 241 0.54 1.31 C A C Comparison Example 4 258 0.25 0.90 C A C Comparison Example 5 281 0.31 0.97 C A C Comparative Example 6 460 0.33 0.95 C B C Comparison Example 7 750 0.63 1.45 B C C Comparative Example 8 3561 0.96 1.80 A C B Comparative Example 9 9 0.03 0.58 C A C Comparative Example 10 5086 0.22 0.91 B A C Comparative Example 11 228 0.24 0.89 C A C

As can be seen from Table 2, the roughened copper foils of Examples 1 to 18 have an interface area ratio Sdr of the roughened surface of 1000% and below 5000%, and an arithmetic mean roughness Sa of the roughened surface of 0.04 μm or above and below 0.6 μm. Therefore, the printed circuit board made using the roughened copper foil has excellent adhesion between the resin and the roughened copper foil, low transmission loss, and is not prone to short circuits caused by migration.

In contrast, at least one of the developed area ratio Sdr and the arithmetic mean roughness Sa of the roughened surface of the copper foil of Comparative Examples 1 to 11 does not meet the above requirements. Therefore, the printed circuit board made using the copper foil is inferior to the roughened copper foil of Examples 1 to 18 in at least one of the adhesion between the resin and the copper foil, the transmission loss, and the easiness of the occurrence of short circuits due to migration.

Comparative Example 7 forms projections on the surface of the roughened particles by performing electrolytic plating, so that projections are formed on the surface of the roughened particles. Therefore, it is considered that projections are concentrated and formed near the tip of the roughened particles. Therefore, it is considered that roughened particles with increased height are partially generated by electrolytic plating, and transmission loss is increased.

In the roughened copper foils of Examples 1 to 18, the roughening process forms the unevenness on the surface of the roughened particles by etching, so the roughening height does not increase, and the unevenness is formed uniformly on the entire surface of the roughened particles. Therefore, it is believed that the transmission loss can be suppressed to a low level, the adhesion between the resin and the copper foil can be improved, and the short circuit caused by migration can also be suppressed.

1: Roughened particles 1a: Protrusions 3: Surface of raw copper foil 11: Rotating electrode 12: Insoluble electrode 13: Electrolyte 14: Electrolytic copper foil H: Distance between the surface 3 of the raw copper foil and the tip of the roughened particles 1

FIG. 1 is a schematic cross-sectional view illustrating the shape of roughened particles formed on the roughened surface of the roughened copper foil of the present embodiment and the roughening height. FIG. 2 is a view illustrating a method for manufacturing an electrolytic copper foil using an electrolytic deposition apparatus. FIG. 3 is a view illustrating a method for manufacturing a roughened copper foil of the present embodiment and is a scanning electron microscope image showing the shape of roughened particles formed by the roughening coating treatment. FIG. 4 is a view illustrating a method for manufacturing a roughened copper foil of the present embodiment and is a scanning electron microscope image showing the concavities and convexities formed on the surface of the roughened particles.

Domestic storage information (please note in the order of storage institution, date, and number) None Foreign storage information (please note in the order of storage country, institution, date, and number) None

1: Roughening particles

1a: convex part

3: The surface of raw copper foil

H: The distance between the surface 3 of the raw copper foil and the front end of the roughened particle 1

Claims (9)

A roughened copper foil, at least one of which has a roughened surface, the roughened surface is formed with a plurality of roughened particles, and the surface of the roughened particles is formed with concavities and convexities, and the interface development area ratio Sdr of the roughened surface measured by a three-dimensional white light interference microscope is greater than 1000% and less than 5000%, and the arithmetic mean roughness Sa of the roughened surface is greater than 0.04μm and less than 0.6μm. The roughened copper foil as described in claim 1, wherein the developed area ratio Sdr of the interface of the roughened surface is greater than 2000% and less than 5000%. The roughened copper foil as described in claim 1, wherein the developed area ratio Sdr of the interface of the roughened surface is greater than 3000% and less than 5000%. A roughened copper foil as described in any one of claims 1 to 3, wherein the arithmetic mean roughness Sa of the roughened surface is greater than 0.04 μm and less than 0.35 μm. A roughened copper foil as described in any one of claims 1 to 3, wherein the ten-point average roughness Rz of the roughened surface measured using a contact-type surface roughness tester is greater than 0.6 μm and less than 1.4 μm. The roughened copper foil as described in claim 4, wherein the ten-point average roughness Rz of the roughened surface measured by a contact-type surface roughness tester is greater than 0.6 μm and less than 1.4 μm. A roughened copper foil as described in any one of claim 1 to claim 3, wherein a rust-proofing layer is deposited on the roughened surface, and a chemical adhesive layer is further deposited on the rust-proofing layer. A copper-clad laminate having a roughened copper foil as described in any one of claims 1 to 7. A printed circuit board having a roughened copper foil as described in any one of claims 1 to 7.