TWI734976B - Surface treatment copper foil, copper clad laminate and printed circuit board - Google Patents

Abstract

The present invention provides a surface-treated copper foil that has fine wiring processability that can form fine wiring with L&S of, for example, 30 µm/30 µm or less using a subtractive method with excellent process cost, and has excellent adhesion to a resin substrate. The present invention is a surface-treated copper foil having a surface based on the roughened surface is formed using the roughening treated copper foil and a foil thickness of 10 μm or less, and the vertex curvature of the roughened surface arithmetic mean Ssc of 0.7 μm ^{- 1} or more and 3.8 µm ^-1 or less. In addition, when the cross-section was analyzed by electron beam backscatter diffraction method after heating at 200°C for 2 hours, among the crystal grains with a grain size of 0.5 µm or more, the crystal grains had a grain size of 0.5 µm or more and less than 1.0 µm. The ratio R1 of the number of grains is 0.51 or more and 0.97 or less, the ratio of the number of crystal grains having a grain size of 1.0 µm or more and less than 3.0 µm, R2 is 0.03 or more and 0.42 or less, and the grain size is 3.0 µm or more The ratio R3 of the number of crystal grains is 0.07 or less.

Description

Surface treatment copper foil, copper clad laminates and printed circuit boards

The present invention relates to a surface-treated copper foil, and copper-clad laminates and printed circuit boards using the surface-treated copper foil. The surface-treated copper foil is suitable for the fineness of printed circuit boards with high-density wiring circuits (fine patterns), etc. Excellent wiring processability and adhesion to resin substrates.

As the copper foil used for the copper-clad laminated board and the printed wiring board, the electrolytic copper foil obtained by peeling the copper foil deposited to the drum of the electrolysis extraction apparatus from the drum is used. The electrolytic copper foil obtained by peeling from the drum has a relatively smooth start surface (smooth surface. Hereinafter referred to as "S surface"), which is the end surface of the electrolytic copper foil on the opposite side (rough surface. Hereinafter, referred to as “M-face”) usually has unevenness. A resin substrate is placed on the M surface of the electrolytic copper foil and thermocompression bonding is performed to manufacture a copper-clad laminate, and the M surface is roughened by roughening treatment to improve the adhesion to the resin substrate.

Recently, in the industry, an adhesive resin such as epoxy resin is preliminarily applied to the roughened surface of copper foil, and the adhesive resin becomes an insulating resin layer in a semi-cured state (stage B) to form a copper foil with resin. The copper foil with resin is used as the copper foil for surface circuit formation, and the side of the insulating resin layer of the copper foil is thermocompression bonded to the insulating substrate to manufacture printed circuit boards (especially build-up circuit boards). For build-up circuit boards, various electronic parts are expected to be highly integrated. Corresponding to this, high-density wiring patterns are also required. Therefore, wiring patterns that require fine line widths and spacing between lines, so-called fine Patterned printed circuit board. For example, as multilayer substrates used in servers, routers, communication base stations, automotive substrates, etc., or multilayer substrates for smartphones, printed circuit boards with high-density and fine wiring are required (hereinafter referred to as "high-density circuit boards") ).

High-density circuit boards of any level (AnyLayer) (using laser vias with high configuration freedom to connect between layers) are mainly used for the motherboards of smart phones. However, in recent years, the miniaturization of wiring has continued to advance, requiring line width and line spacing. The distance between each other (hereinafter referred to as "L&S") shall be 30 µm or less for wiring. High-density circuit boards were previously manufactured by printed circuit board manufacturers using the subtractive method using photoresistance. However, if the L&S becomes narrower, the cross-sectional shape of the wiring will collapse. Therefore, the high-density circuit can be made in a large area over 500 mm square. When the board is packaged and molded, it is difficult to form wiring with an L&S of 30 µm/30 µm (line width (L) is 30 µm, and line spacing (S) is 30 µm) or less.

Therefore, recently, in order to form wiring with an L&S of 30 µm/30 µm or less in high-density circuit boards, the introduction of the MSAP method (Modified Semi Additive Process) has been advancing. However, the MSAP method has a higher process cost than the subtractive method, so there is a problem that the burden on the circuit board manufacturer is heavy. In addition, when forming fine wiring, it is effective to reduce the surface roughness of the copper foil. On the other hand, if the surface roughness of the copper foil is reduced, the adhesion between the resin substrate and the copper foil may decrease.

Patent Document 1 discloses a technique for forming fine wiring by minimizing the average crystal grain size of the entire ultra-thin copper layer. However, if the crystal grain size is too small, side etching (lateral etching of the wiring section) may occur. It may not be possible to obtain a high etching factor due to influence. In addition, Patent Document 2 discloses a copper foil with excellent adhesion to a high heat-resistant resin, but the roughened particles with sharp shapes tend to dissolve and remain (root residues) during etching, and the fine wiring processability becomes insufficient. Yu.

[Prior Technical Literature] (Patent Document) Patent Document 1: Japanese Patent No. 6158573 Patent Document 2: Japanese Patent Application Laid-Open No. 2010-236058

[The problem to be solved by the invention] The problem of the present invention is to provide a surface-treated copper foil that has fine wiring processability that can be used to form fine wiring with L&S of 30 µm/30 µm or less, for example, by a subtractive method with excellent process cost, and adhesiveness with a resin substrate Excellent. In addition, the problem of the present invention is to provide a copper-clad laminate having the above-mentioned fine wiring processability and a printed wiring board with high-density ultra-fine wiring.

[Technical Means to Solve the Problem] The main purpose of the surface-treated copper foil of one aspect of the present invention is that it is a surface-treated copper foil having a roughened surface formed by roughening treatment on the surface, and the foil thickness is 10 µm or less, The arithmetic mean Ssc of the apex curvature of the roughened surface is 0.7 µm ^-1 or more and 3.8 µm ^-1 or less. When the cross section is analyzed by electron beam backscatter diffraction method after heating at 200°C for 2 hours, the crystal grain size is 0.5 µm Among the above crystal grains, the ratio R1 of the number of crystal grains with a grain size of 0.5 µm or more and less than 1.0 µm is 0.51 or more and 0.97 or less, and the ratio of the number of crystal grains with a crystal grain size of 1.0 µm or more and less than 3.0 µm The ratio R2 of the number is 0.03 or more and 0.42 or less, and the ratio R3 of the number of crystal grains with a crystal grain size of 3.0 µm or more is 0.07 or less.

In addition, another aspect of the copper-clad laminated board of the present invention is mainly aimed at: the surface-treated copper foil of the above-mentioned aspect and the resin substrate laminated on the roughened surface of the surface-treated copper foil. Furthermore, the main purpose of the printed circuit board of another aspect of the present invention is to provide the copper clad laminate board of the other aspect described above.

[Effects of the invention] The surface-treated copper foil of the present invention has fine wiring processability that can form fine wiring of 30 µm/30 µm or less by using a subtractive method with excellent process cost, and has excellent adhesion to a resin substrate. In addition, the copper-clad laminated board of the present invention has the fine wiring processability as described above. Furthermore, the printed wiring board of the present invention has high-density ultra-fine wiring.

An embodiment of the present invention will be described. In addition, the embodiment described below shows an example of the present invention, and the present invention is not limited to this embodiment. In addition, various changes or improvements can be added to this embodiment, and such changes or improvements can also be included in the present invention.

The inventors of the present invention conducted diligent studies and found that the fine wiring processability of copper foil is highly influenced by the distribution of crystal grains with a crystal grain size of 0.5 µm or more in the copper foil. In general, it is known that in the etching process of fine wiring, the grain boundaries of the crystal grains are dissolved preferentially compared to the crystal grains. The crystal grain boundary is equivalent to the boundary of crystal grains with different plane orientations. There are many mismatches and defects in the arrangement of atoms, so it is in an energy-active state, so it is easy to dissolve in etching. Therefore, it can be considered that the finer the crystal grains in the copper foil, the greater the number of crystal grain boundaries and the faster the dissolution rate.

Investigating the factors that affect the improvement of copper foil's fine wiring processability, the results show that when the crystal grains of 0.5 µm or more and less than 1.0 µm are in a fixed ratio after heating at 200°C for 2 hours, the longitudinal dissolution during etching The speed increases and the etching factor increases. However, on the other hand, it was found that if the ratio of crystal grains of this size is too large, on the contrary, dissolution in the lateral direction of the top side of the cross section of the wiring pattern (hereinafter, the upper part of the pattern is referred to as the top and the lower part of the pattern is referred to as the bottom) preferentially proceeds. The etching factor is reduced.

Specifically, when the cross-section is analyzed by the electron beam backscattering diffraction method after heating at 200°C for 2 hours, among the crystal grains with a crystal grain size of 0.5 µm or more, if the crystal grain size is 0.5 µm or more and less than 1.0 If the ratio R1 of the number of µm crystal grains is 0.51 or more and 0.97 or less, the etching factor increases. However, if the ratio R1 is greater than 0.97, etching on the top side is preferentially performed and the fine wiring processability is reduced. If the ratio R1 is less than 0.51, the etching rate in the thickness direction of the copper foil becomes slower and the fine wiring processing decreases.

In addition, if the crystal grain size is 3.0 µm or more, the area of the grain boundary relative to the volume of the crystal grains is small and it is easy to dissolve and remain. Therefore, the wiring pattern is likely to be tailed due to the decrease in the etching rate. Specifically, when the cross-section is analyzed by electron beam backscatter diffraction method after heating at 200°C for 2 hours, among the crystal grains with a grain size of 0.5 µm or more, one of the crystal grains with a crystal grain size of 3.0 µm or more When the ratio R3 of the number is 0 or exceeds 0 and is in the range of 0.07 or less, the fine wiring processability is improved, but if the ratio R3 is greater than 0.07, the influence of the dissolved residue of large crystal grains increases and the fine wiring processability decreases.

The details will be described later, and the distribution of the crystal grains as described above can be controlled by making the current density imparted to the electrolyte solution uniform when manufacturing the electrolytic copper foil. Furthermore, in the process of investigating the factors that contribute to the processability of fine wiring, it was found that the arithmetic mean of the curvature of the part near the ridge of the roughened particle of the copper foil (arithmetic mean of the curvature of the apex of the roughened surface) Ssc has a strong influence. Specifically, when the arithmetic mean Ssc of the vertex curvature is 0.7 µm ^-1 or more and 3.8 µm ^-1 or less, the etching factor increases. The arithmetic mean Ssc of vertex curvature is the average peak curvature of various mountain structures and is expressed by the following formula. In the following formula, z(x, y) is the height coordinate of the x and y coordinates, and N is the number of vertices of the coarsened particles.

[Formula 1]

When there is arithmetic mean Ssc of apex curvature in this range, the degree of curvature of the apex of the roughened particles on the roughened surface of the copper foil is in a moderate state. Therefore, it can be considered that no root residue will occur during etching (the tip of the roughened particle dissolves and remains) State) and easy to dissolve, the tailing of the copper foil is suppressed and the etching factor rises.

When the arithmetic mean Ssc of the apex curvature is greater than 3.8 µm ^-1 , the apex of the roughened particles has a strong degree of curvature. Therefore, the roughened particles penetrate deeply into the resin substrate, resulting in root residue during etching and tailing of the copper foil. It becomes longer and the etching factor decreases. When the arithmetic mean Ssc of vertex curvature is less than 0.7 µm ^-1 , the degree of curvature of the apex of the roughened particles is gentle, so the degree of immersion of the roughened particles into the resin substrate is poor (weak anchoring effect), and the adhesion between the resin substrate and the copper foil reduce.

The details will be described later. The arithmetic mean Ssc of the apex curvature can be reduced by dissolving the apex of the roughened particle. Therefore, if the copper foil is immersed in a copper sulfate aqueous solution after the pulse plating and roughening treatment, Method to dissolve the apex of the coarsened particle, the arithmetic mean Ssc of the apex curvature can be controlled.

That is, the surface-treated copper foil of one embodiment of the present invention is a surface-treated copper foil having a roughened surface formed by a roughening treatment on the surface, and the foil thickness is 10 µm or less, and the arithmetic mean Ssc of the apex curvature of the roughened surface It is 0.7 µm ^-1 or more and 3.8 µm ^-1 or less. In addition, when the cross-section was analyzed by electron beam backscatter diffraction method after heating at 200°C for 2 hours, among the crystal grains with a grain size of 0.5 µm or more, the crystal grains had a grain size of 0.5 µm or more and less than 1.0 µm. The ratio R1 of the number of grains is 0.51 or more and 0.97 or less, the ratio of the number of crystal grains having a grain size of 1.0 µm or more and less than 3.0 µm, R2 is 0.03 or more and 0.42 or less, and the grain size is 3.0 µm or more The ratio R3 of the number of crystal grains is 0.07 or less. That is, crystal grains with a crystal grain size of 3.0 µm or more are optional components, and the ratio R3 is 0 or more than 0 and less than 0.07.

In the surface-treated copper foil of one embodiment of the present invention, it is more preferable that the arithmetic mean Ssc of the apex curvature of the roughened surface is 1.0 µm ^-1 or more and 2.5 µm ^-1 or less. In addition, it is preferable that when the cross-section is analyzed by electron beam backscatter diffraction method after heating at 200°C for 2 hours, the crystal grain size is 0.5 µm or more, and the crystal grain size is 0.5 µm or more and less than 1.0. The ratio R1 of the number of µm crystal grains is 0.59 or more and 0.96 or less, the ratio R2 of the number of crystal grains 1.0 µm or more and less than 3.0 µm is 0.04 or more and 0.41 or less, and the crystal particle size is 3.0 The ratio R3 of the number of crystal grains above µm is 0.

The above-mentioned surface-treated copper foil of this embodiment has fine wiring processability that can form L&S fine wiring of, for example, 30 µm/30 µm or less by a subtractive method with excellent process cost, and has excellent adhesion to a resin substrate. Therefore, the surface-treated copper foil of this embodiment can be preferably used to manufacture copper-clad laminates and printed circuit boards, and can manufacture printed circuit boards with high-density ultra-fine wiring.

In the surface-treated copper foil of this embodiment, the foil thickness is 10 µm or less. If the thickness of the surface-treated copper foil exceeds 10 µm, the dissolution time of the copper foil may become longer and the etching factor may decrease. In addition, in the surface-treated copper foil of this embodiment, the Rpm of the roughened surface (10 points average of the maximum mountain height of the roughness curve) can also be set to 0.5 µm or more and 3.5 µm or less. If the Rpm of the roughened surface is less than 0.5 µm, there is a risk that the adhesiveness with the resin substrate may decrease. On the other hand, if the Rpm of the roughened surface exceeds 3.5 µm, there is a risk that the etching factor will decrease.

Furthermore, in the surface-treated copper foil of this embodiment, the tensile strength under normal conditions can also be set to 400 MPa or more and 780 MPa or less, and the tensile strength measured at room temperature after heating at 220°C for 2 hours can also be set as Above 300 MPa. If the tensile strength under normal conditions is 400 MPa or more and 780 MPa or less, the handling and etching properties of the surface-treated copper foil are good. In addition, when the tensile strength measured at room temperature after heating at 220°C for 2 hours is 300 MPa or more, the etching properties are good.

In addition, in the present invention, the "crystal grain size" refers to a circle equivalent diameter. In addition, in the present invention, the so-called "normal state" refers to a state where the surface-treated copper foil has not undergone thermal history such as heat treatment and is left at room temperature (that is, about 25°C). The tensile strength under normal conditions can be measured at room temperature by the method according to IPC-TM-650. In addition, the tensile strength after heating can be measured by heating the surface-treated copper foil to 220°C and keeping it for 2 hours, then cooling it to room temperature naturally, and measuring the tensile strength at room temperature by the same method as that under normal conditions.

Hereinafter, the surface-treated copper foil of this embodiment will be described in more detail. First, the manufacturing method of surface-treated copper foil is demonstrated. (1) About the manufacturing method of electrolytic copper foil The electrolytic copper foil can be manufactured using, for example, an electrolytic extraction device as shown in FIG. 1. The electrolysis extraction device of FIG. 1 includes: an insoluble anode 104, which contains titanium coated with a platinum group element or its oxide; a titanium cathode drum 102, which is arranged opposite to the insoluble anode 104; and a polishing wheel 103, which is opposite The cathode drum 102 is polished to remove the oxide film generated on the surface of the cathode drum 102.

The electrolyte 105 (sulfuric acid-copper sulfate aqueous solution) is supplied between the cathode drum 102 and the insoluble anode 104, while the cathode drum 102 is rotated at a fixed speed, a direct current is applied between the cathode drum 102 and the insoluble anode 104. In this way, copper is deposited on the surface of the cathode drum 102. The deposited copper is peeled off from the surface of the cathode drum 102 and continuously wound up, thereby obtaining an electrolytic copper foil 101.

The inventors of the present invention conducted diligent studies and found that, compared to the previous method of stirring the electrolyte by a pump, the current between the cathode drum 102 and the insoluble anode 104 is increased by generating a strong turbulence in the electrolyte 105 The density is more uniform than that of general electrolytic foil, so that the distribution of crystal grains in copper foil can be controlled. As an example of a method for generating a strong turbulent flow in the electrolyte 105, the introduction of gas such as air can be cited. If a gas inlet device is installed in the electrolysis extraction device, and the gas is supplied to the electrolyte 105 while adjusting the flow rate to make the electrolyte 105 bubble, the bubbles in the electrolyte 105 move randomly to generate a strong turbulent flow.

Specifically, if the gas flow rate is set to 2 L/min or more and 8 L/min or less, the current density can be made uniform, and it is easy to obtain the electron beam backscattered diffraction after heating at 200°C for 2 hours. The distribution of crystal grains when analyzing the cross section by the method is the same electrolytic copper foil as the surface-treated copper foil of this embodiment described above. If the gas flow rate is less than 2 L/min, a region with low current density is locally generated, and coarse crystal grains are easily formed, so the etching factor may decrease. On the other hand, if the gas flow rate exceeds 8 L/min, the ratio R1 becomes larger and side etching becomes an advantage, so there is a possibility that the etching factor may decrease.

In addition, as another embodiment, continuous unevenness may be formed on the surface of the insoluble anode. In the vicinity of the bumps, the flow rate of the electrolyte is slow. On the other hand, between the insoluble anode and the cathode, the flow rate of the electrolyte becomes faster, resulting in a speed difference. It is found that strong turbulence is generated due to the speed difference, and the current density distribution is more uniform compared to the previous electrolytic foil, so that the distribution of crystal grains in the copper foil can be controlled.

Specifically, with an interval of 60 mm along the circumferential direction of the anode, convex portions with a height of 0.5 mm to 1.5 mm and a width of 10 mm to 70 mm are continuously formed to generate turbulent flow, which is easy to obtain at 200°C. After heating for 2 hours, the distribution of crystal grains when the cross-section was analyzed by the electron beam backscattering diffraction method was the same electrolytic copper foil as the surface-treated copper foil of this embodiment described above.

When manufacturing electrolytic copper foil, additives may be added to the electrolyte 105. The type of additives is not particularly limited, and examples include ethylene thiourea, polyethylene glycol, tetramethyl thiourea, and polypropylene amide. Here, by increasing the addition amount of ethylene thiourea and tetramethyl thiourea, the tensile strength under normal conditions and the tensile strength measured at room temperature after heating at 220°C for 2 hours can be improved.

If the tensile strength under normal conditions is 400 MPa or more and 780 MPa or less, the handling and etching properties of the surface-treated copper foil are good. If the tensile strength under normal conditions is less than 400 MPa, since the surface-treated copper foil is a thin foil product, wrinkles may occur during transportation and the workability may deteriorate. On the other hand, if the tensile strength in the normal state is greater than 780 MPa, the copper foil deposited to the drum may be easily broken when the copper foil is manufactured using the electrolytic extraction device and is not suitable for manufacturing.

In addition, when the tensile strength measured at room temperature after heating at 220°C for 2 hours is 300 MPa or more, the crystal grains are also heated in the step of laminating the surface-treated copper foil and the resin substrate to produce a copper-clad laminate. It is thin and has good etching properties. If the tensile strength measured at room temperature after heating at 220°C for 2 hours does not reach 300 MPa, the crystal grains will change due to the heating in the step of manufacturing the copper-clad laminate by laminating the surface-treated copper foil and the resin substrate. It is large and hard to dissolve in etching, so there is a risk that the etching property will decrease.

In addition, molybdenum may be added to the electrolyte 105. By adding molybdenum, the etching properties of copper foil can be improved. Generally, in the electrolytic solution, the copper concentration of the electrolyte 105 (the concentration of only copper without considering the sulfuric acid component in copper sulfate) is 13 g/L to 72 g/L, and the sulfuric acid concentration of the electrolyte 105 is 26 g/L to 133 g/L, the temperature of the electrolyte 105 is 18°C to 67°C, the current density is 3 A/dm ² to 67 A/dm ² , and the treatment time is 1 second or more and 1 minute 55 seconds or less.

(2) About the surface treatment of electrolytic copper foil >Roughening treatment> It is known that for the purpose of improving the adhesion to the resin substrate, the surface of the electrolytic copper foil is roughened to form a roughened surface, but generally speaking, if it is roughened with high adhesion, it is easy to etch. Root residue is generated, and the etching factor is easy to decrease. The inventors conducted diligent studies and found that by slightly dissolving the apex of the roughened particles and reducing the strength of the curvature of the apex (the arithmetic mean Ssc of the apex curvature of the roughened surface is reduced), it is difficult to produce roots during etching. Remains and the etching factor increases. The method of dissolving the apex of the roughened particle is not particularly limited, and examples include: a method of dissolving it by pulse plating using a moderate reverse current, and immersing the copper foil in an aqueous solution of copper sulfate after the roughening treatment. The method of top dissolution.

In addition, it was found that if the arithmetic mean Ssc of the apex curvature of the roughened surface is 0.7 µm ^-1 or more and 3.8 µm ^-1 or less, and it is heated at 200°C for 2 hours, the crystal is analyzed by the electron beam backscatter diffraction method. The distribution of the grains is as described above (that is, when the cross-section is analyzed by electron beam backscatter diffraction method after heating at 200°C for 2 hours, the grain size is 0.5 µm or more in the crystal grains. The ratio R1 of the number of crystal grains above and less than 1.0 µm is 0.51 or more and 0.97 or less, and the ratio R2 of the number of crystal grains above 1.0 µm and less than 3.0 µm is 0.03 or more and 0.42 or less, The ratio R3 of the number of crystal grains with a grain size of 3.0 µm or more is 0, or when the cross-section is analyzed by electron beam backscatter diffraction after heating at 200°C for 2 hours, the crystal grain size is 0.5 µm or more Among the crystal grains, the ratio R1 of the number of crystal grains with a grain size of 0.5 µm or more and less than 1.0 µm is 0.51 or more and 0.97 or less, and the number of crystal grains with a crystal grain size of 1.0 µm or more and less than 3.0 µm If the ratio R2 is 0.03 or more and 0.42 or less, and the ratio R3 of the number of crystal grains with a crystal grain size of 3.0 µm or more is more than 0 and 0.07 or less), the etching factor of the copper foil specifically increases.

It can be considered that this is caused by a good balance between the dissolution rate in the vertical direction (the direction from the top side of the wiring to the bottom side) in the copper foil and the dissolution rate in the roughened surface (the horizontal direction, that is, the width direction of the wiring). Effect. For example, when the dissolving speed of the roughened surface (dissolving in the horizontal direction) is faster than that of the copper foil (dissolving in the vertical direction), an undercut will occur (the dissolution of the roughened surface in the horizontal direction is much faster than that of copper foil. The state).

>Formation of nickel layer, zinc layer and chromate treatment layer> In the surface-treated copper foil of this embodiment, it is also possible to form a nickel layer and a zinc layer in order on the roughened surface formed by the roughening treatment. The zinc layer plays the role of preventing the deterioration of the resin substrate caused by the reaction between the surface-treated copper foil and the resin substrate when the surface-treated copper foil and the resin substrate are thermally compressed, and the surface-treated copper foil The surface is oxidized to improve the adhesion between the surface-treated copper foil and the resin substrate. In addition, the nickel layer prevents the zinc in the zinc layer from thermally diffusing into the surface-treated copper foil when the surface-treated copper foil and the resin substrate are thermocompression-bonded. That is, the nickel layer functions as a base layer of the zinc layer for effectively performing the above-mentioned functions of the zinc layer.

Furthermore, the nickel layer and zinc layer can be formed by applying well-known electrolytic plating methods and electroless plating methods. In addition, the nickel layer may be formed of pure nickel, or may be formed of a phosphorus-containing nickel alloy. In addition, if chromate treatment is further performed on the zinc layer, an anti-oxidation layer is formed on the surface of the surface-treated copper foil, which is preferable. As the chromate treatment to be applied, a well-known method may be used. For example, the method disclosed in Japanese Patent Application Laid-Open No. 60-86894 can be cited. By attaching chromium oxide and its hydrates, which are converted to a chromium amount of about 0.01 mg/dm ² to 0.3 mg/dm ² , an excellent anti-oxidation function can be imparted to the surface-treated copper foil.

>Silane treatment> The surface treated with chromate can also be treated with silane coupling agent (silane treatment). By using the surface treatment with silane coupling agent, the surface of the surface-treated copper foil (the surface of the bonding side with the resin substrate) is given a functional group that has a strong affinity with the adhesive. Therefore, the surface treatment of the copper foil and the resin substrate The adhesion is further improved, and the rust resistance, moisture absorption and heat resistance of the surface-treated copper foil are further improved.

The type of silane coupling agent is not particularly limited. Examples include vinyl silane, epoxy silane, styrene silane, methacrylic silane, acrylic silane, amino silane, ureido silane, chloropropyl It is silane, mercapto-based silane, sulfide-based silane, isocyanate-based silane, etc. These silane coupling agents are usually used as an aqueous solution with a concentration of 0.001% by mass or more and 5% by mass or less. The aqueous solution is applied to the surface of the surface-treated copper foil and then heated and dried, thereby enabling silane treatment. Furthermore, instead of silane coupling agents, coupling agents such as titanate-based and zirconate-based coupling agents can also be used to obtain the same effect.

(3) About the manufacturing method of copper clad laminates and printed circuit boards First, on one or both surfaces of an electrically insulating resin substrate made of glass epoxy resin, polyimide resin, etc., surface-treated copper foils are placed on top of each other. At this time, the roughened surface of the surface-treated copper foil was opposed to the resin substrate. Then, while heating the laminated resin substrate and surface-treated copper foil, pressure in the lamination direction is applied to join the resin substrate and the surface-treated copper foil to obtain a copper-clad laminate with or without a carrier. Since the surface-treated copper foil of this embodiment has high tensile strength in normal conditions and after heating, it can be adequately dealt with even without a carrier.

Next, the surface of the copper foil of the copper clad laminate is irradiated with a CO ₂ gas laser to make holes. That is, the surface of the copper foil on which the laser absorption layer is formed is irradiated with a CO ₂ gas laser to form a through hole that penetrates the surface-treated copper foil and the resin substrate. Then, a circuit such as a high-density wiring circuit is formed on the surface-treated copper foil by a conventional method, so that a printed circuit board can be obtained.

[Example] Hereinafter, examples and comparative examples are shown to explain the present invention more specifically. (A) Manufacturing of electrolytic copper foil Using the electrolytic extraction device shown in FIG. 1, the sulfuric acid-copper sulfate aqueous solution was used as the electrolyte, and the electrolytic copper foil was manufactured by the following operations. That is, since the electrolyte is supplied between the anode and the cathode drum disposed opposite to the anode, while air is introduced into the electrolyte and the cathode drum is rotated at a fixed speed, a direct current is applied between the anode and the cathode drum, As a result, copper is deposited on the surface of the cathode drum. Then, the deposited copper is peeled off from the surface of the cathode drum and continuously wound up, thereby manufacturing an electrolytic copper foil.

The copper concentration, sulfuric acid concentration, and chlorine concentration in the electrolyte are shown in Table 1. In a part of Example 1 to Example 14 and Comparative Example 1 to Comparative Example 5, as shown in Table 1, as additives, ethylene thiourea, polyethylene glycol, tetramethyl thiourea, And 2 kinds of glue (molecular weight 20000), the concentration of these additives is shown in Table 1. In addition, the temperature, current density, and air flow rate of the electrolyte during the manufacture of electrolytic copper foil are shown in Table 1. Furthermore, in Example 13 and Example 14, the protrusions having a height of 1.0 mm and a width of 60 mm were continuously formed at intervals of 60 mm along the circumferential direction of the anode.

[Table 1]

(B) Coarse treatment Next, the S surface or the M surface (refer to Table 2) of the electrolytic copper foil was subjected to a roughening treatment to make the surface a roughened surface to produce a surface-treated copper foil. Specifically, electroplating (pulse plating) in which fine copper particles are electrodeposited on the surface of the electrolytic copper foil is performed as a roughening treatment, thereby forming a roughened surface with fine irregularities formed by the copper particles. The plating solution used for electroplating contains copper, sulfuric acid, molybdenum, and nickel. The copper concentration, sulfuric acid concentration, molybdenum concentration, and nickel concentration are shown in Table 2.

In addition, the conditions of the roughening treatment, that is, the pulse plating (the surface to be roughened (treated surface), electrolysis conditions, plating treatment time, and plating solution temperature) are shown in Table 2. Under the electrolysis conditions in Table 2, Ion1 represents the pulse current density at the first stage, Ion2 represents the pulse current density at the second stage, ton1 represents the pulse current application time at the first stage, and ton2 represents the pulse current application time at the second stage , Toff represents the time to set the current between the pulse current in the second stage and the pulse current in the first stage to zero.

In addition, regarding Example 11, Example 12, and Comparative Example 1, normal plating was performed instead of pulse plating. Under the electrolysis conditions in Table 2, I is the current density of the electroplating implemented in Example 11, Example 12 and Comparative Example 1. Furthermore, regarding Example 11 and Example 12, the obtained surface-treated copper foil was further immersed in a copper sulfate bath (copper sulfate aqueous solution), thereby dissolving the apexes of the fine protrusions formed on the surface of the electrolytic copper foil. Round, adjust the arithmetic mean Ssc of the vertex curvature of the roughened surface. The copper concentration, sulfuric acid concentration, and immersion time of the copper sulfate bath are shown in Table 2.

[Table 2]

(C) Formation of nickel layer (base layer) Next, electrolytic plating is performed on the roughened surface of the surface-treated copper foil under the Ni plating conditions shown below, thereby forming a nickel layer (Ni deposit 0.06 mg/dm ² ). The plating solution for nickel plating contains nickel sulfate, ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ), boric acid (H ₃ BO ₃ ), the concentration of nickel is 5.0 g/L, and the concentration of ammonium persulfate is 40.0 g/L, the concentration of boric acid is 28.5 g/L. In addition, the temperature of the plating solution is 28.5°C, the pH is 3.8, the current density is 1.5 A/dm ² , and the plating treatment time is 1 second to 2 minutes.

(D) Formation of zinc layer (heat-resistant treatment layer) Furthermore, electrolytic plating is performed on the nickel layer under the Zn plating conditions shown below, thereby forming a zinc layer (the adhesion amount of Zn is 0.05 mg/dm ² ) . The plating solution used for zinc plating contains zinc sulfate heptahydrate and sodium hydroxide. The concentration of zinc is 1 g/L to 30 g/L, and the concentration of sodium hydroxide is 10 g/L to 300 g/L. In addition, the temperature of the plating solution is 5°C to 60°C, the current density is 0.1 A/dm ² to 10 A/dm ² , and the plating treatment time is 1 second to 2 minutes.

(E) Formation of chromate treatment layer (anti-rust treatment layer) Furthermore, electrolytic plating is performed on the zinc layer under the Cr plating conditions shown below, thereby forming a chromate treatment layer (Cr adhesion The amount is 0.02 mg/dm ² ). The plating solution used for chromium plating contains chromic anhydride (CrO ₃ ) with a chromium concentration of 2.5 g/L. In addition, the temperature of the plating solution is 15°C to 45°C, the pH is 2.5, the current density is 0.5 A/dm ² , and the plating treatment time is 1 second to 2 minutes.

(F) Formation of silane coupling agent layer Furthermore, the following treatment was performed to form a silane coupling agent layer on the chromate treatment layer. That is, methanol or ethanol is added to the silane coupling agent aqueous solution and adjusted to a predetermined pH to obtain a treatment solution. The treatment liquid is applied to the chromate treatment layer of the surface-treated copper foil, and after keeping it for a predetermined time, it is dried with hot air, thereby forming a silane coupling agent layer.

(G) Evaluation As described above, the surface-treated copper foils of Example 1 to Example 14 and Comparative Example 1 to Comparative Example 5 were respectively manufactured. The foil thickness of these surface-treated copper foils is shown in Table 3. Various evaluations were performed for each of the obtained surface-treated copper foils.

>Tensile Strength> The surface-treated copper foils of Examples 1 to 14 and Comparative Examples 1 to 5 obtained in the above manner were cut into short strips with a width of 12.7 mm and a length of 130 mm as tensile test pieces. Measure the tensile strength of the tensile test piece under normal conditions by the method according to IPC-TM-650. As the measuring device, a 1122 tensile tester made by Instron was used, and the measuring temperature was set to normal temperature. In addition, after heating the tensile test piece at 220°C for 2 hours, it was naturally cooled to normal temperature. The tensile strength of the tensile test piece after the thermal history is given is measured in the same way as the tensile strength under normal conditions. The results are shown in Table 3.

>Etching Factor> By the subtractive method, a resist pattern with an L&S of 30 µm/30 µm was formed on the surface-treated copper foils of Example 1 to Example 14 and Comparative Example 1 to Comparative Example 5. Then, etching is performed to form a wiring pattern. As the resist, a dry resist film was used, and as the etching solution, a mixed solution containing copper chloride and hydrochloric acid was used. Then, the etching factor (Ef) of the obtained wiring pattern was measured. The etching factor refers to the value expressed by the following formula when the thickness of the copper foil is set to H, the bottom width of the formed wiring pattern is set to B, and the top width of the formed wiring pattern is set to T. Ef=2H/(B-T) In the present embodiment and the comparative example, the test piece with an etching factor of 2.5 or more is regarded as a good product, and the test piece with an etching factor of less than 2.5 is regarded as a defective product.

If the etching factor is small, the verticality of the sidewalls in the wiring pattern will collapse. In the case of fine wiring patterns with narrow line widths, there is a risk of dissolving copper foil between adjacent wiring patterns, causing a short circuit, and causing the risk of disconnection. sex. In this experiment, the bottom width B and top width T are measured with a microscope for the wiring pattern when it becomes the timely etching position (the position of the resist end is aligned with the position of the bottom of the wiring pattern), and the etching factor is calculated. The results are shown in Table 3.

[Adhesion] A resin substrate was bonded to the roughened surface of the copper foil to produce a sample for measurement. The resin substrate uses a commercially available polyphenylene ether resin (the ultra-low transmission loss multilayer substrate material MEGTRON6 manufactured by Matsushita Co., Ltd.). The curing temperature during bonding is 210°C and the curing time is 2 hours.

After etching the copper foil of the prepared measurement sample into a circuit wiring with a width of 10 mm, fix the resin substrate side to the stainless steel plate with a double-sided tape, and move the circuit wiring in a 90-degree direction at a speed of 50 mm/min. It was stretched and peeled, and the adhesiveness (kN/m) was measured. The adhesion is measured using a universal material testing machine (Tensilon manufactured by A&D Co., Ltd.). In the present example and the comparative example, the case where the adhesion is 0.4 kN/m or more is regarded as a good product, and the case where the adhesion is less than 0.4 kN/m is regarded as a defective product.

[Operability: Number of defective wrinkles] The surface-treated copper foils of Example 1 to Example 14 and Comparative Example 1 to Comparative Example 5 were cut into a square shape with a side of 200 mm, and pressure-bonded to the substrate FR4 to produce a copper-clad laminate. The bonding conditions are 170°C temperature, 1.5 MPa pressure, and pressure time 1 hour. For each surface-treated copper foil, 30 pieces of copper-clad laminates were produced, and the wrinkles of the copper foil were visually confirmed, and the number of copper-clad laminates that produced wrinkles on the copper foil (the number of defective wrinkles) was counted. The operability of the surface-treated copper foil was evaluated by the number of defective wrinkles. When the number of wrinkle defects was 3 or less, it was regarded as pass, and when it was 4 or more, it was regarded as unacceptable. The results are shown in Table 3.

[Arithmetic mean of vertex curvature Ssc, Rpm] Using the three-dimensional white light interference microscope Wyko ContourGT-K of BRUKER, the surface shape of the roughened surface of the surface-treated copper foil of Example 1 to Example 14 and Comparative Example 1 to Comparative Example 5 was measured, and shape analysis was performed to obtain The arithmetic mean Ssc and Rpm of vertex curvature. The shape analysis system uses a high-resolution CCD (charge coupled device) camera with a VSI (Virtual Switch Interface) measurement method. The conditions are as follows: the light source is white light, the measurement magnification is 10 times, the measurement range is 477 µm×357.8 µm, the lateral sampling (Lateral Sampling) is 0.38 µm, the speed (speed) is 1, the backscan height (Backscan) is 10 µm , Length is 10 µm, Threshold is 3%, item removal (Terms Removal) (Cylinder and Tilt), data recovery (Data Restore) (method: legacy, iteration (iterations) 5), statistics After filtering (Statistic Filter) (Filter Size: 3, Filter Type: Median), data processing is performed. The results are shown in Table 3.

[Distribution of crystal grains] Using the EBSD (Electron Back Scatter Diffraction) camera Hikari/DC5.2/A5.2 of TSL Solutions Co., Ltd. and the scanning electron microscope JSM-7001FA of JEOL, Measure the crystal grains of the roughened surface of the surface-treated copper foil under the conditions of 5000 times magnification and 0.05 beam step. In the measurement of crystal grains by EBSD, a crystal grain boundary with an azimuth difference of 15° or more is set, and the area surrounded by the crystal grain boundary is a crystal grain.

At this time, the cut surface of the surface-treated copper foil was polished by CP (Cross Section Polisher), and the portion of the polished surface in the range shown in Figure 2 was measured by EBSD. That is, when the foil thickness of the surface-treated copper foil is set to t, as shown in Figure 2, the vertical (length in the thickness direction) contacting the surface on the opposite side of the roughened surface is 0.8 t and the horizontal (normal to the thickness direction) The length of the cross direction) 1.6 t rectangle range, carry out the EBSD measurement. For example, when the foil thickness t is 10 µm, it becomes a rectangular range of 8.0 µm in length and 16.0 µm in width, and when the foil thickness t is 6 µm, it becomes a rectangular range of 4.8 µm in length and 9.6 µm in width, and the foil thickness t is 4 µm. At this time, it becomes a rectangular area with a length of 3.2 µm and a width of 6.4 µm. Based on the data of GRAIN SIZE of EBSD (Electron Beam Backscattering Diffraction), calculate the ratio of the aforementioned crystal grains R1, R2, R3. The results are shown in Table 3.

[table 3]

Comparative Example 1 is a copper foil manufactured under the known foil manufacturing conditions (Example 2 of Japanese Patent No. 4583149). However, since the ratio R3 of the number of crystal grains is large, the etching factor (Ef) is small and cannot Make L&S thinner. Compared with Example 3, Comparative Example 2 has a lower inlet flow rate. Therefore, the ratio of the number of crystal grains R2 and R3 becomes larger, and L&S cannot be made finer.

In Comparative Example 3, since the inlet flow rate was too large, the ratio R1 of the number of crystal grains became large, and the L&S could not be made finer. Compared with Example 1, in Comparative Example 4, the reverse current was not applied with the pulse current of the roughening treatment, and the roughened particles were not dissolved, so the etching factor was lowered. In Comparative Example 5, since the current of the roughening treatment was large, the roughened particles became coarse, which caused root residues to be easily generated during etching, and the etching factor was reduced.

101‧‧‧Electrolytic Copper Foil 102‧‧‧Cathode drum 103‧‧‧Polishing wheel 104‧‧‧Insoluble anode 105‧‧‧Electrolyte

Fig. 1 is a diagram illustrating a method of manufacturing an electrolytic copper foil using an electrolytic extraction device. Figure 2 is a diagram illustrating the method for measuring the distribution of crystal grains.

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Claims (7)

A surface-treated copper foil, which is a surface-treated copper foil having a roughened surface formed by roughening treatment on the surface, and the foil thickness is 10 μm or less, and the arithmetic mean Ssc of the apex curvature of the roughened surface is 0.7 μm ^-1 or more and 3.8μm ^-1 or less, when the cross-section is analyzed by electron beam backscattering diffraction method after heating at 200°C for 2 hours, the crystal grain size is 0.5μm or more, and the crystal grain size is 0.5μm or more and less than The ratio R1 of the number of crystal grains of 1.0 μm is 0.51 or more and 0.97 or less, the ratio of the number of crystal grains of 1.0 μm or more and less than 3.0 μm R2 is 0.03 or more and 0.42 or less, and the crystal particle size is The ratio R3 of the number of crystal grains of 3.0 μm or more is 0.07 or less. The surface-treated copper foil according to claim 1, wherein the arithmetic mean Ssc of the apex curvature of the roughened surface is 1.0 μm ^-1 or more and 2.5 μm ^-1 or less, the aforementioned ratio R1 is 0.59 or more and 0.96 or less, and the aforementioned ratio R2 It is 0.04 or more and 0.41 or less, and the aforementioned ratio R3 is zero. The surface-treated copper foil according to claim 1, wherein the Rpm of the roughened surface is 0.5 μm or more and 3.5 μm or less. The surface-treated copper foil according to claim 2, wherein the Rpm of the roughened surface is 0.5 μm or more and 3.5 μm or less. The surface-treated copper foil according to any one of claims 1 to 4, wherein the tensile strength under normal conditions is 400 MPa or more and 780MPa or less, the tensile strength measured at room temperature after heating at 220°C for 2 hours is 300MPa or more. A copper-clad laminated board comprising the surface-treated copper foil described in any one of items 1 to 5 in the scope of the patent application, and a resin substrate laminated on the roughened surface of the surface-treated copper foil. A printed circuit board is provided with a copper clad laminate as described in item 6 of the scope of patent application.

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