Low-roughness surface-treated copper foil with low bending deformation, copper foil laminates and printed circuit boards containing the same.

Abstract

The present invention relates to a surface-treated copper foil that has excellent adhesive strength with a resin substrate, exhibits low bending deformation after bonding with the resin substrate, and has low transmission loss, and is therefore suitable as a high-frequency foil, and to a copper foil laminate and a printed wiring board including the same. The present invention relates to a surface-treated copper foil including a surface treatment layer formed on at least one side of an original copper foil, and an oxidation prevention layer formed on the surface treatment layer, wherein at least one side of the surface-treated copper foil contains fine copper particles having an average particle size of 100 nm or less, and the surface-treated copper foil has a deformation value (Y) of 5 or less, as expressed by the following formula: deformation value (Y) = tensile strength deformation value (Y1) + elongation deformation value (Y2) (where Y1 = (T1 - T2) / (kgf / mm 2 ), Y2=(E2-E1) / %, T2 and E2 are the tensile strength and elongation measured after heat treatment at a pressure of 4.9 MPa and a temperature of 220°C for 90 minutes, respectively, and T1 and E1 are the tensile strength and elongation measured at room temperature, respectively.

Description

[Technical Field]

[0001] The present invention relates to surface-treated copper foil, and more particularly to surface-treated copper foil that exhibits excellent adhesive strength to resin substrates, low bending deformation after bonding to resin substrates, and low transmission loss, making it suitable as a high-frequency foil, as well as to copper foil laminates and printed circuit boards containing the same. [Background technology]

[0002] As the miniaturization and weight reduction of electrical and electronic devices accelerates, printed circuits formed on substrates are becoming smaller, more integrated, and more compact. This, in turn, demands a variety of physical properties from the copper foil used in printed circuit boards.

[0003] The composite materials used in the manufacture of flexible substrates, multilayer substrates for high-density mounting, high-frequency circuit boards, etc. (hereinafter collectively referred to as "circuit boards" or "printed wiring boards") consist of a conductor (copper foil) and an insulating substrate (including film) that supports it. The insulating substrate ensures insulation between the conductors and has sufficient strength to support the components.

[0004] Conventionally, to increase the adhesive strength to insulating substrates, methods have been employed that increase the current flowing during surface treatment and increase the amount of granular copper deposited during surface treatment, thereby increasing the ten-point average roughness Rz. However, while such methods are suitable for improving adhesive strength, over-treating the copper foil surface to increase adhesive strength can increase interference factors for high-frequency signal transmission, potentially adversely affecting signal transmission. Therefore, these methods are not suitable for circuit boards that require consideration of high-frequency characteristics.

[0005] On the other hand, in recent years, the trend towards thinner and more integrated electronic product substrates has led to a decrease in the thickness of insulators. When copper foil is laminated onto such thin insulating substrates under pressure and heat, bending deformation occurs in the resulting copper-clad laminate (CCL). This bending deformation problem will likely become more serious as the thickness of the insulating substrate and / or copper-clad laminate decreases.

[0006] To address these issues, U.S. Patent Publication No. 6194056 presents a method for producing high-strength copper foil using various additives to minimize changes in the physical properties of the copper foil. However, the copper foil produced in this way still has a high surface roughness, making it difficult to use as high-frequency foil, and there is no consideration for reducing bending deformation after lamination. [Overview of the project] [Problems that the invention aims to solve]

[0007] To solve the problems of the conventional technology described above, the inventors of the present invention discovered that changes in the physical properties of copper foil before and after lamination affect the occurrence of bending in the copper foil laminate after lamination.

[0008] Therefore, the present invention aims to provide a surface-treated copper foil suitable as a high-frequency foil that has excellent adhesive strength to a resin substrate while suppressing bending before and after lamination pressing, a copper foil laminate containing the same, and a printed circuit board containing the same. [Means for solving the problem]

[0009] To solve the above technical problems, the present invention provides a surface-treated copper foil comprising a surface treatment layer formed on at least one surface of a copper base foil and an oxidation-preventive layer formed on the surface treatment layer, wherein at least one surface of the surface-treated copper foil contains fine copper particles with an average particle size of 100 nm or less, and the surface-treated copper foil has a deformed value (Y) expressed by the following formula of 5 or less;

[0010] Deformation value (Y) = Tensile strength deformation value (Y1) + Elongation deformation value (Y2)

[0011] (Here, Y1 = (T1 - T2) / (kgf / mm) 2 ) where Y2 = (E2 - E1) / %, T2 and E2 are the tensile strength and elongation measured after heat treatment at a pressure of 4.9 MPa and a temperature of 220°C for 90 minutes, respectively, and T1 and E1 are the tensile strength and elongation measured at room temperature, respectively.

[0012] In the present invention, when the surface-treated copper foil is bonded to a low-dielectric resin (low DK Prepreg), polyimide (PI), hydrocarbon, or polytetrafluoroethylene (PTFE) film to produce a copper foil laminate, the bending deformation may be 0.5 mm or less.

[0013] Furthermore, in the present invention, the ten-point average roughness of at least one surface of the surface-treated copper foil may be 0.5 μm or less, and the glossiness may be 200 or more.

[0014] Furthermore, in the present invention, the surface-treated copper foil may have an adhesive strength of 0.5 kgf / cm or more with respect to a low-dielectric resin, polyimide, hydrocarbon, or polytetrafluoroethylene film.

[0015] In the present invention, the surface-treated copper foil may have a transmission loss (S21) of 3.0 dB / 100 mm or less at 20 GHz.

[0016] In the present invention, the antioxidant layer may contain at least one element selected from the group consisting of nickel, cobalt, zinc, nickel, tin, and phosphorus, and preferably contains nickel and phosphorus.

[0017] Furthermore, in order to achieve the other technical challenges mentioned above, the present invention provides a copper foil laminate in which the aforementioned surface-treated copper foil is laminated on a resin substrate.

[0018] Furthermore, in order to achieve the other technical challenges mentioned above, the present invention provides a printed circuit board formed using the aforementioned copper foil laminate. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a surface-treated copper foil that is suitable as a high-frequency foil that suppresses bending before and after pressing while having excellent adhesion strength to a resin substrate, a copper foil laminate including the same, and a printed wiring board including the same.

Brief Description of Drawings

[0020] [Figure 1A] FIG. 1A is an electron micrograph observing the surfaces of a surface-treated copper foil specimen before and after surface treatment (after formation of an antioxidant layer) manufactured in an example. [Figure 1B] FIG. 1B is an electron micrograph observing the surfaces of a surface-treated copper foil specimen before and after surface treatment (after formation of an antioxidant layer) manufactured in an example.

[0021] [Figure 2A] FIG. 2A is an electron micrograph photographing crystal grain changes in a specimen cross-section with a focused ion beam (Focused Ion Beam, FIB) equipment before and after high-temperature pressing of a surface-treated copper foil specimen manufactured in an example. [Figure 2B] FIG. 2B is an electron micrograph photographing crystal grain changes in a specimen cross-section with a focused ion beam (Focused Ion Beam, FIB) equipment before and after high-temperature pressing of a surface-treated copper foil specimen manufactured in an example.

[0022] [Figure 3A] FIG. 3A is an electron micrograph observing the surfaces of a surface-treated copper foil specimen before and after surface treatment manufactured in Comparative Example 1. [Figure 3B] FIG. 3B is an electron micrograph observing the surfaces of a surface-treated copper foil specimen before and after surface treatment manufactured in Comparative Example 1

[0023] [Figure 4A] FIG. 4A is an electron micrograph photographing crystal grain changes in a specimen cross-section with a focused ion beam equipment before and after high-temperature pressing of a surface-treated copper foil specimen manufactured in Comparative Example 1. [Figure 4B]Figure 4B shows electron microscope images of the crystal grain changes in the cross-section of a surface-treated copper foil specimen manufactured in Comparative Example 1, taken with a focused ion beam before and after high-temperature pressing.

[0024] [Figure 5A] Figure 5A shows electron microscope images of the surface of the surface-treated copper foil specimen produced in Comparative Example 2, observed before and after surface treatment. [Figure 5B] Figure 5B shows electron microscope images of the surface of the surface-treated copper foil specimen produced in Comparative Example 2, observed before and after surface treatment. [Modes for carrying out the invention]

[0025] The embodiments and configurations shown in the drawings described herein represent only one of the most preferred embodiments of the present invention and do not represent the entire technical concept of the invention. Therefore, it should be understood that there are various equivalents and modifications that can substitute for them at the time of filing. Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0026] The surface-treated copper foil of the present invention comprises a base foil, a surface treatment layer on at least one surface of the base foil, and an oxidation-preventive layer on the surface treatment layer. The base foil, surface treatment layer, and oxidation-preventive layer of the present invention will be described in detail below.

[0027] A. Original foil

[0028] one According to concrete examples, untreated copper foil is electrolytic copper With foil It's okay to have it.

[0029] In the present invention, the thickness of the base foil is not particularly limited, but when surface-treated copper foil is used in a printed circuit board, the thickness of the base foil may be, for example, 6 to 35 μm, preferably 7 to 17 μm.

[0030] In this invention, the raw foil is 35 kgf / mm 2 ~60kgf / mm 2, 35 kgf / mm 2 ~50 kgf / mm 2 、or 35 kgf / mm 2 ~45 kgf / mm 2 Preferably, it has a tensile strength of

[0031] In addition, in the present invention, it is preferable that the mechanical properties of the raw foil are kept constant before and after high-temperature pressing in the joining process with a prepreg for forming a copper foil laminate or a printed wiring board. In the present invention, the change in crystal grains of the raw foil before and after pressing is very small.

[0032] For example, the change rate of the tensile strength value of the raw foil after heat treatment at a pressure of 4.9 Mpa and a temperature of 220°C for a predetermined time with respect to the tensile strength value at room temperature may be less than 5%, or less than 3%. Also, the change rate of the elongation of the raw foil after heat treatment at a pressure of 4.9 Mpa and a temperature of 220°C for a predetermined time with respect to the elongation at room temperature may be less than 5% or less than 3%.

[0033] B. Surface treatment layer

[0034] In the present invention, the surface treatment layer may be formed on one or both surfaces of the raw foil. The surface treatment method for forming the surface treatment layer of the present invention is not particularly limited. For example, it can be formed by electrolytic plating of the raw foil. As the electrolytic solution, an aqueous solution containing 5 - 60 g / L of copper salt and 50 - 200 g / L of additive can be used, for example, adjusted to pH 1 - 8 (for example, 6 - 7). Examples of the type of copper salt include copper sulfate (CuSO4), copper nitrate (Cu(NO3)2), copper chloride (CuCl2), copper acetate (Cu(CH3COO)2), etc., and examples of the additive include citric acid (C6H8O7), ethylenediaminetetraacetic acid (C[[ID=!25]] 10 H 16At least one of the following can be used, but is not limited to, N2O8, nitrilotriacetic acid (C6H9NO6), sodium citrate (C6H5Na3O7), and tartaric acid (C4H6O6). Electrolytic plating is performed, for example, by immersing an insoluble electrode as the anode and an untreated raw foil as the cathode in the electrolyte, at a liquid temperature of 25-45°C and an A / dm² of 0.5-10A / dm². 2 At the current density, the electrolysis may be carried out for, for example, 5 to 20 seconds, but is not limited to this.

[0035] C. Antioxidant layer

[0036] In the present invention, an antioxidant layer may be formed on the surface treatment layer. The antioxidant layer may contain nickel (Ni) and phosphorus (P). In addition to nickel and phosphorus, the antioxidant layer may further contain zinc (Zn), cobalt (Co), titanium (Ti), tin (Sn), etc., as needed.

[0037] The amount of the antioxidant layer applied is, for example, 30-300 mg / m². 2 Other examples include 50-120 mg / m². 2 This may be the case, but it is not limited to this.

[0038] In the present invention, the method for forming the oxidation prevention layer is not particularly limited, but for example, it can be formed by electroplating a copper foil containing a surface treatment layer. For example, as the electrolyte, an aqueous solution containing 3 to 15 g / L of nickel salt and 15 to 60 g / L of phosphoric acid (H3PO4) can be used. Electroplating is performed, for example, by immersing an insoluble electrode as the anode and a copper foil containing a surface treatment layer as the cathode in the electrolyte, at a liquid temperature of 25 to 45°C and an A / dm² of 1 to 5 A / dm². 2 The electrolysis may be carried out for, for example, 5 to 20 seconds at the specified current density, but is not limited thereto. Examples of nickel salts include, but is not limited to, nickel sulfate (NiSO4), nickel nitrate (Ni(NO3)2), nickel chloride (NiCl2), and nickel acetate (C4H6NiO4).

[0039] As described above, the present invention provides a surface-treated copper foil comprising a surface treatment layer formed on at least one surface of a copper base foil and an oxidation prevention layer formed on the surface treatment layer. In this case, it is preferable that the surface on which the surface treatment layer of the surface-treated copper foil is formed contains fine copper particles with an average particle size of 100 nm or less. For example, the fine copper particles on the surface of the surface-treated copper foil may have an average particle size of 10 to 100 nm, 20 to 100 nm, or 50 to 100 nm. In the present invention, the average particle size of the copper particles can be calculated by obtaining a scanning electron microscope (SEM) image of the surface-treated layer and measuring the particle size of the copper particles by image analysis, or it may be calculated by averaging the measured values ​​of a total of 100 particles. When the average particle size of the fine copper particles of the surface-treated layer is within this range, it has excellent adhesion strength to the resin substrate and low transmission loss, making it suitable as a high-frequency foil.

[0040] Furthermore, in the present invention, it is preferable that the surface-treated copper foil has a deformed value (Y) expressed by the following formula 1 that is 5 or less.

[0041] (Equation 1)

[0042] Deformation value (Y) = Tensile strength deformation value (Y1) + Elongation deformation value (Y2)

[0043] Here, Y1 = (T1 - T2) / (kgf / mm) 2 The deformation value (Y) is given by Y2 = (E2 - E1) / %, where T2 and E2 are the tensile strength and elongation (percentage) measured after heat treatment at a pressure of 4.9 MPa and a temperature of 220°C for 90 minutes, respectively, and T1 and E1 are the tensile strength and elongation measured at room temperature, respectively. Therefore, the deformation value (Y) is unitless. In this case, the tensile strength and elongation of the surface-treated copper foil may be measured using a tensile testing machine in accordance with the IPC-TM-650 2.4.18B standard.

[0044] Within the range satisfying the aforementioned deformation value, the surface-treated copper foil of the present invention exhibits little change in crystal grain before and after pressing, thus providing an effect of suppressing bending deformation that occurs when bonding with a thin prepreg. More preferably, the deformation value (Y) may be 4.5 or less, 4.0 or less, or 3.5 or less.

[0045] In the present invention, when the surface-treated copper foil is bonded to a low-dielectric resin, polyimide, hydrocarbon, or polytetrafluoroethylene film to produce a copper foil laminate, its bending deformation is 0.5 mm or less, more preferably 0.4 mm or less. In this case, the bending deformation can be evaluated by measuring the degree to which the copper foil curls up (mm) with a steel ruler after a 50 mm x 50 mm cross-shaped cut in the center of the copper foil laminate.

[0046] In the present invention, the ten-point average roughness Rz of the surface-treated copper foil may be 0.4 μm or less, 0.5 μm or less, 0.6 μm or less, or 0.7 μm or less. Alternatively, the ten-point average roughness Rz may be 0.2 μm or more, or 0.3 μm or more.

[0047] Furthermore, the glossiness (Gs 60°) of the surface-treated copper foil may be 200 or higher, 250 or higher, or 300 or higher, and may be less than 400 or less than 500.

[0048] Within this range, it exhibits excellent adhesion strength to resin substrates and low transmission loss, making it suitable as a high-frequency foil. Here, "ten-point average roughness Rz" refers to the ten-point average roughness Rz defined in JIS B 0601-1994 "Definition and indication of surface roughness" 5.1 Definition of ten-point average roughness, and "glossiness (Gs 60°)" refers to the value measured based on JIS Z 874, where measurement light is irradiated onto the copper foil surface at an incident angle of 60° and the intensity of the light reflected at a reflection angle of 60° is measured. For example, the ten-point average roughness Rz of surface-treated copper foil may be 0.25~0.5μm, or as another example, 0.3~0.45μm, and the glossiness (Gs 60°) may be, for example, 200~400, or as another example, 220~380, but is not limited to these values.

[0049] In the present invention, the surface-treated copper foil may have an adhesive strength of 0.5 kgf / cm or more with respect to a low-dielectric resin, polyimide, hydrocarbon, or polytetrafluoroethylene film. Here, the adhesive strength may be the adhesive strength measured according to the JIS C6481 standard. For example, the adhesive strength of the surface-treated copper foil with respect to a low-dielectric resin, polyimide, hydrocarbon, or polytetrafluoroethylene film may be 0.5 to 1.0 kgf / cm, 0.5 to 2.0 kgf / cm, 0.5 to 3.0 kgf / cm, 0.5 to 4.0 kgf / cm, or 0.5 to 7.0 kgf / cm, but is not limited thereto.

[0050] In the present invention, the surface-treated copper foil may have a transmission loss (S21) of 3.0 dB / 100 mm or less at 20 GHz. Here, the transmission loss (S21) at "20 GHz" refers to the transmission loss at 20 GHz measured using a network analyzer after the surface-treated copper foil has been bonded to both sides of a polytetrafluoroethylene resin, and a microstrip line has been formed so that the characteristic impedance is 50 Ω. For example, the transmission loss (S21) at 20 GHz of the surface-treated copper foil may be 0.5 to 3.0 dB / 100 mm, 1.0 to 3.0 dB / 100 mm, or 1.5 to 2.5 dB / 100 mm.

[0051] The surface-treated copper foil described above can be used as a copper foil laminate by laminating it onto a resin substrate, and such a copper foil laminate may be used to manufacture printed circuit boards. [Examples]

[0052] The present invention will be described in more detail below with reference to examples. However, these are presented as preferred examples of the present invention and should not be construed as limiting the present invention in any way.

[0053] Examples

[0054] <Example 1>

[0055] For the production of copper foil by electroplating, a 2L capacity electrolytic cell system capable of circulating at 20L / min was prepared. The temperature of the copper electrolyte was maintained at a constant 45°C. A 10mm thick, 10cm x 10cm DSE (Dimensionally Stable Electrode) plate was used as the anode, and a titanium plate of the same size and thickness as the anode was used as the cathode.

[0056] To produce the final 12 μm thick electrolytic copper foil, a 11 μm thick pre-treatment base foil was first prepared. A copper electrolyte consisting of 100 g / L copper, 150 g / L sulfuric acid, 30 ppm chloride ions, 30 ppm polyethylene glycol, 40 ppm bis-(3-sulfopropyl)-disulfide, 40 ppm sodium 3-(benzothiazoly-2-mercapto)-propyl-sulfonate, and 2 ppm diethylthiourea was used, with a current density of 35 A / dm². 2 The raw foil was prepared before surface treatment.

[0057] Next, the surface treatment involves immersion in an aqueous solution containing 5 g / L of copper and 200 g / L of disodium ethylenediaminetetraacetate, at a liquid temperature of 25°C, pH 7, and current density of 3 A / dm². 2 Plating was performed for 10 seconds under these conditions.

[0058] Subsequently, the surface-treated copper foil was subjected to an aqueous solution composed of 5 g / L nickel and 20 g / L phosphoric acid at a temperature of 40°C, pH 4, and current density of 1 A / dm². 2 An antioxidant layer was formed under these conditions.

[0059] <Comparative Example 1>

[0060] In the production of the raw foil before surface treatment, the raw foil before surface treatment was prepared by plating with a copper electrolyte consisting only of 250-400 g / L of copper, 80-150 g / L of sulfuric acid, and 1 ppm of chloride ions, except that the surface-treated copper foil was produced using the same method as in Example 1.

[0061] <Comparative Example 2>

[0062] A copper electrolyte consisting of 25 g / L of copper and 150 g / L of sulfuric acid was used, with an electrolyte temperature of 30°C and a current density of 15 A / dm². 2 Surface-treated copper foil was manufactured using the same method as in Example 1, except that it was plated for 10 seconds under the specified conditions.

[0063] <Evaluation of physical properties>

[0064] The physical properties of each surface-treated copper foil sample produced in the examples and comparative examples were measured. The physical property evaluation items and measurement methods are as follows.

[0065] a. Tensile strength and elongation

[0066] - Measurement of tensile strength and elongation at room temperature: Tensile strength and elongation were measured using a tensile testing machine in accordance with the IPC-TM-650 2.4.18B standard.

[0067] - Measurement of high-temperature tensile strength and elongation

[0068] After pressing the surface-treated copper foil with a press at a pressure of 4.9 MPa and a temperature of 220°C for 90 minutes, the tensile strength and elongation were measured using a tensile testing machine in accordance with the IPC-TM-650 2.4.18B standard.

[0069] b. Ten point average roughness R z (Unit: μm)

[0070] Based on the JIS B0601 standard, the average roughness of ten points after surface treatment of copper foil using a surface roughness measuring instrument is measured R. z We measured it.

[0071] c. Average particle size of copper particles (unit: nm)

[0072] SEM images were taken of the surface of the copper foil after surface treatment using an electron scanning microscope, and the particle size of 100 copper particles within a 100 μm × 100 μm area was measured, and the average value was calculated.

[0073] d. Glossiness (Gs 60°)

[0074] The glossiness of the copper foil surface after surface treatment was measured according to the JIS Z 8741 standard.

[0075] e. Adhesive strength (unit: kgf / cm)

[0076] The adhesive strength of surface-treated copper foil was measured according to the JIS C 6481 standard. The insulator used was Panasonic's product name MEGTRON (R-5785), with a thickness of 40 μm.

[0077] f. Transmission loss (S 21 (Unit: dB / 100 mm)

[0078] After laminating a 12μm thick surface-treated copper foil to both sides of a 12μm thick polytetrafluoroethylene resin (AGC), a microstrip line was formed to achieve a characteristic impedance of 50Ω. The transmission loss at 20GHz was then determined using an HP network analyzer. A value of S21 closer to 0 indicates lower transmission loss, making it suitable for high-speed transmission.

[0079] g. Thermal discoloration evaluation

[0080] After heat treatment at 220°C for 2 hours using an oven, the presence or absence of discoloration was observed visually. The presence or absence of discoloration was classified as O (occurred) or X (not occurred).

[0081] h. Evaluation of copper foil bending deformation

[0082] A test specimen was manufactured by bonding a surface-treated copper foil to a Panasonic MEGTRON (R-5785) insulator, which has a thickness of 40 μm, using a press at a pressure of 4.9 MPa and a temperature of 220°C for 90 minutes. After that, a 50 mm x 50 mm cross-shaped cut was made in the center of the specimen using a cutting tool, and the degree of curling (mm) of the copper foil was measured with a steel ruler.

[0083] Figures 1A and 1B are electron microscope images of the surface of the surface-treated copper foil specimens produced in the example, observed before surface treatment and after surface treatment and the formation of the anti-oxidation layer, respectively.

[0084] Referring to Figures 1A and 1B, it can be seen that the surface of the specimen in the example is smooth before surface treatment (Figure 1A), and after surface treatment (Figure 1b), fine copper particles of 100 nm or less are generated on the surface of the specimen.

[0085] Figures 2A and 2B are electron microscope images, respectively, of the changes in crystal grain size in the cross-section of surface-treated copper foil specimens manufactured in the examples, taken using FIB before and after high-temperature pressing.

[0086] Referring to Figures 2A and 2B, it can be seen that the specimens in the example show no significant changes in the shape or size of the crystal grains before (Figure 2A) and after (Figure 2B) pressing.

[0087] On the other hand, Figures 3A and 3B are electron microscope images of the surface of the surface-treated copper foil specimen produced in Comparative Example 1, before surface treatment and after surface treatment and oxidation prevention layer formation, respectively. Figures 4A and 4B are electron microscope images of the surface-treated copper foil specimen produced in Comparative Example 1, taken using FIB before and after high-temperature pressing to capture changes in the crystal grain of the specimen cross-section.

[0088] First, referring to Figures 3A and 3B, it can be seen that the specimen of Comparative Example 1 shows a relatively higher roughness before surface treatment (Figure 3A) compared to Example (Figure 1A), and it can be confirmed that fine copper particles were generated after surface treatment (Figure 3B). Furthermore, referring to Figures 4A and 4B, it can be seen that the crystal grain size of the specimen of Comparative Example 1 grew significantly after pressing (Figure 4B) compared to before pressing (Figure 4A).

[0089] Figures 5A and 5B are electron microscope images of the surface of the surface-treated copper foil specimen produced in Comparative Example 2, observed before surface treatment (Figure 5A) and after surface treatment and oxidation prevention layer formation (Figure 5B), respectively. As shown in the figures, it can be seen that coarse copper particles are formed on the surface of the specimen from Comparative Example 2 after surface treatment and oxidation prevention layer formation (Figure 5B).

[0090] Table 1 summarizes the calculation results of the change values ​​(Y) for the specimens produced in Example 1, Comparative Example 1, and Comparative Example 2, and Table 2 summarizes the results of the physical property evaluation of the specimens produced in Example 1, Comparative Example 1, and Comparative Example 2.

[0091] [Table 1]

[0092] [Table 2]

[0093] Referring to Tables 1 and 2, it can be seen that the examples and Comparative Example 2 with low deformation values ​​(Y) before / after high-temperature pressing exhibit less bending deformation compared to Comparative Example 1. Furthermore, referring to Table 2 and Figures 2 to 4 above, it can be seen that the examples with low bending deformation values, unlike the specimens of Comparative Example 1, show less change in crystal grains before and after pressing, indicating that the bending deformation is related to the change in crystal grain shape during the high-temperature pressing process. In addition, unlike Comparative Examples 1 and 2, the specimens of the examples surface-treated with high gloss and small copper particles demonstrate high adhesive strength and low transmission loss at 20 GHz, despite their very low roughness, confirming their suitability as high-frequency copper foil.

[0094] Furthermore, it can be seen that although the specimen of Comparative Example 1 has a higher surface roughness compared to the specimen of the Example, it exhibits a phenomenon where the adhesive strength decreases due to the decrease in strength after pressing.

[0095] On the other hand, while Comparative Example 2 showed higher adhesive strength compared to the example, it was confirmed that its transmission loss characteristics were inferior due to the relatively large copper particles and high roughness.

[0096] On the other hand, although not separately organized, it was confirmed that all of the examples and comparative examples 1 and 2 treated with an oxidation-preventive layer were in good condition in terms of thermal discoloration evaluation.

[0097] Although preferred embodiments of the present invention have been described in detail above, those with ordinary skill in the art to which the present invention pertains will understand that various modifications are possible to the above embodiments without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments described, but should be defined by the claims and equivalents described below. [Industrial applicability]

[0098] This invention can be used in electrolytic copper foil, copper foil laminates, and printed circuit boards.

Claims

1. A surface-treated copper foil comprising a surface treatment layer formed on at least one surface of a copper base foil and an oxidation-preventive layer formed on the surface treatment layer, The raw foil has a tensile strength value at room temperature with a change rate of less than 5% or less than 3% after heat treatment with a pressure of 4.9 MPa and a temperature of 220°C for 90 minutes, and the raw foil has a change rate of elongation at room temperature with a change rate of less than 5% or less than 3% after heat treatment with a pressure of 4.9 MPa and a temperature of 220°C for 90 minutes, The aforementioned base foil is prepared from a copper electrolyte containing polyethylene glycol, bis-(3-sulfopropyl)-disulfide, sodium 3-(benzothiazoly-2-mercapto)-propyl-sulfonate, and diethylthiourea. At least one surface of the surface-treated copper foil contains fine copper particles with an average particle size of 100 nm or less. The aforementioned surface-treated copper foil is characterized in that the deformed value (Y) expressed by the following formula is 5 or less; Deformation value (Y) = Tensile strength deformation value (Y1) + Elongation deformation value (Y2) (Here, Y1 = (T1 - T2) / (kgf / mm2), Y2 = (E2 - E1) / %, where T2 and E2 are the tensile strength and elongation measured after heat treatment at a pressure of 4.9 MPa and a temperature of 220°C for 90 minutes, respectively, and T1 and E1 are the tensile strength and elongation measured at room temperature, respectively.)

2. The surface-treated copper foil according to claim 1, characterized in that the ten-point average roughness of at least one surface of the surface-treated copper foil is 0.5 μm or less, and the glossiness is 200 or more.

3. The surface-treated copper foil according to claim 1, characterized in that the transmission loss (S21) at 20 GHz is 3.0 dB / 100 mm or less.

4. The surface-treated copper foil according to claim 1, characterized in that the oxidation-preventive layer contains at least one element selected from the group consisting of nickel, cobalt, zinc, nickel, tin, and phosphorus.

5. The surface-treated copper foil according to claim 4, characterized in that the oxidation-preventive layer contains nickel and phosphorus.

6. A copper foil laminate in which a surface-treated copper foil according to any one of claims 1 to 5 is laminated on a resin substrate.

7. A printed circuit board formed using the copper foil laminate described in claim 6.

Images