Finely roughened electrolytic copper foil, method for manufacturing the same, and copper foil substrate containing the finely roughened electrolytic copper foil

Abstract

This invention provides a finely roughened electrolytic copper foil, a method for manufacturing the same, and a copper foil substrate containing the finely roughened electrolytic copper foil, which meet the requirements of high-frequency and high-speed transmission. [Solution] The finely roughened electrolytic copper foil comprises a main layer, a roughening plating layer, and a fixing plating layer. The main layer has a basically flat surface, the roughening plating layer is formed on the basically flat surface and has a plurality of fine copper bumps, and the fixing plating layer is formed between the roughening plating layer and the basically flat surface to fix the plurality of fine copper bumps. The plurality of fine copper bumps are uniformly distributed on the basically flat surface, the maximum particle diameter of each of the fine copper bumps is less than 100 nm, and the surface roughness Rz of the finely roughened electrolytic copper foil is less than 0.8 μm.

Description

[Technical Field]

[0001] This invention relates to electrolytic copper foil, and more particularly to finely roughened electrolytic copper foil that meets the requirements of high-frequency and high-speed transmission. [Background technology]

[0002] With the rapid development of the electronics and information industries, high-frequency and high-speed signal transmission has become a major consideration in the design and manufacture of copper foil. As is well known, the roughness (smoothness) of copper foil is a crucial factor affecting high-frequency and high-speed signal transmission. The rougher the copper foil, the slower the signal transmission speed and the worse the accuracy. Furthermore, excessively high roughness can cause signal transmission loss, affecting the transmission stability of high-frequency signals. Therefore, those skilled in the art related to copper foil usually pay attention to and control the roughness of the copper foil to ensure that the desired performance levels are reliably achieved in various applications.

[0003] However, in practical applications, a certain peel strength is required between the copper foil and the resin substrate to prevent delamination of the copper foil substrate (copper clad laminate, CCL) during subsequent processing and use. Generally, reducing the surface roughness of the copper foil also weakens the peel strength between the copper foil and the resin substrate, indicating that surface roughness and peel strength are inverse indicators.

[0004] Therefore, overcoming the aforementioned drawbacks by improving the structural design to achieve extremely low roughness that approximates a smooth surface on the copper foil, while simultaneously maintaining peel strength between the copper foil and the resin substrate, is one of the important challenges for this project. [Overview of the project] [Problems that the invention aims to solve]

[0005] The technological problem that this invention aims to solve is to provide a finely roughened electrolytic copper foil, a method for manufacturing the same, and a copper foil substrate containing the finely roughened electrolytic copper foil, in response to the shortcomings of the prior art. The finely roughened electrolytic copper foil of this invention can achieve low roughness while ensuring a certain level of peel strength. Furthermore, the finely roughened electrolytic copper foil of this invention is suitable for the manufacture of copper foil substrates, and printed circuit boards with high adhesion and excellent high-frequency transmission characteristics can be manufactured using the obtained copper foil substrate. [Means for solving the problem]

[0006] To solve the above technical problems, one of the technical means employed by the present invention is to provide a finely roughened electrolytic copper foil. The finely roughened electrolytic copper foil includes a main body layer, a roughening plating layer, and a fixing plating layer. The main body layer has a basically flat surface, and the roughening plating layer is formed on the basically flat surface and has a plurality of fine copper bumps. The fixing plating layer is formed between the roughening plating layer and the basically flat surface to fix the plurality of fine copper bumps. In the present invention, the plurality of fine copper bumps are uniformly distributed on the basically flat surface, the maximum particle diameter of each of the fine copper bumps is less than 100 nm, and the surface roughness Rz of the finely roughened electrolytic copper foil is less than 0.8 μm.

[0007] To solve the above technical problems, another technical means employed by the present invention is to provide a method for manufacturing finely roughened electrolytic copper foil. The method for manufacturing finely roughened electrolytic copper foil includes the steps of: forming a main body layer having a basically flat surface; forming a roughened plating layer containing a plurality of fine copper bumps on the basically flat surface; and forming a fixing plating layer between the roughened plating layer and the basically flat surface so as to fix the plurality of fine copper bumps. In the present invention, the plurality of fine copper bumps are uniformly distributed on the basically flat surface, the maximum particle diameter of each of the fine copper bumps is less than 100 nm, and the surface roughness Rz of the finely roughened electrolytic copper foil is less than 0.8 μm.

[0008] In an implementable or preferred embodiment of the present invention, the basically flat surface has a thickness of 1.0 μm. 2 It has an average of 135 to 203 microscopic copper nodules per unit area.

[0009] In an implementable or preferred embodiment of the present invention, the roughness Rz of the basically flat surface is less than 0.5 μm, and the 60-degree gloss of the basically flat surface is greater than 400 GU.

[0010] In an implementable or preferred embodiment of the present invention, the step of forming the roughened plating layer includes roughening the main layer using a roughening solution, wherein the copper ion concentration in the roughening solution is 5 g / L to 25 g / L, the sulfuric acid concentration is 60 g / L to 150 g / L, and the concentration of at least one non-copper metal ion is 0.1 ppm to 300 ppm, and the at least one non-copper metal ion is selected from at least one metal ion from the group consisting of tungsten, tin, iron, cobalt, nickel, and molybdenum. Furthermore, the roughening treatment is performed at 1 A / dm 2 ~60A / dm 2 The process is carried out at a current density of 0.5 to 6 seconds.

[0011] In an implementable or preferred embodiment of the present invention, in the step of forming the fixed plating layer, a fixing treatment is performed on the main layer of the roughened treatment using a fixing solution, wherein the copper ion concentration in the fixing solution is 30 g / L to 80 g / L, the sulfuric acid concentration is 60 g / L to 150 g / L, and the concentration of organic components is 0.1 ppm to 300 ppm. Furthermore, the fixing treatment is performed at 0.1 A / dm 2 ~20A / dm 2 The process is carried out at a current density of 0.1 to 3 seconds.

[0012] In an implementable or preferred embodiment of the present invention, the organic component is a nitrogen-containing compound.

[0013] In order to solve the above technical problems, another technical means adopted in the present invention is to provide a copper foil substrate including a substrate and the above-mentioned micro-roughened electrolytic copper foil installed on the surface of the substrate.

Advantages of the Invention

[0014] As one of the advantageous effects of the present invention, the micro-roughened electrolytic copper foil and its manufacturing method according to the present invention have technical features such as "the main body layer has a basically flat surface, and the plurality of the micro copper bumps are uniformly distributed on the basically flat surface, and the maximum particle diameter of each of the micro copper bumps is less than 100 nm", and "the surface roughness Rz of the micro-roughened electrolytic copper foil is less than 0.8 μm", which help to reduce the electrical resistance, improve the signal transmission efficiency, and maintain the peel strength between the copper foil and the resin base material at an industry-acceptable level. Furthermore, the micro-roughened electrolytic copper foil according to the present invention can maintain the signal integrity and reduce the signal transmission loss even in the application of 5G high-frequency and high-speed transmission.

Brief Description of the Drawings

[0015] [Figure 1] It is a flowchart of a method for manufacturing a micro-roughened electrolytic copper foil according to an embodiment of the present invention. [Figure 2] It is a schematic diagram showing the structure of a micro-roughened electrolytic copper foil according to an embodiment of the present invention. [Figure 3] It is an image obtained by observing the surface morphology of the micro-roughened electrolytic copper foil of the present invention at 5,000 times using a scanning electron microscope. [Figure 4] It is an image obtained by observing the surface morphology of the micro-roughened electrolytic copper foil of the present invention at 10,000 times using a scanning electron microscope. [Figure 5] It is an image obtained by observing the surface morphology of the micro-roughened electrolytic copper foil of the present invention at 20,000 times using a scanning electron microscope. [Figure 6] It is an image obtained by observing the surface morphology of the micro-roughened electrolytic copper foil of the present invention at 50,000 times using a scanning electron microscope. [Figure 7] It is a schematic diagram showing the structure including the copper foil substrate of the micro-roughened electrolytic copper foil according to an embodiment of the present invention. [Modes for carrying out the invention]

[0016] To further understand the features and technical details of this invention, please refer to the following detailed description of the invention and the accompanying drawings. However, the accompanying drawings provided are for reference and illustrative purposes only and do not limit the scope of the claims of this invention.

[0017] Hereinafter, the implementation of the "fine roughened electrolytic copper foil, method for manufacturing the same, and copper foil substrate containing the fine roughened electrolytic copper foil" according to the present invention will be described by predetermined specific embodiments, and those skilled in the art will be able to understand the advantages and effects of the present invention based on the contents disclosed herein. The present invention can be carried out or applied by other different specific embodiments, and various modifications and changes can be made to each detail herein, based on different viewpoints and applications, as long as they do not deviate from the concept of the present invention. It should be noted in advance that the accompanying drawings of the present invention are for simple schematic explanation and are not drawn to actual size. The technical content of the present invention will be described in more detail below based on the embodiments, but the scope of protection of the present invention is not limited by the contents disclosed.

[0018] It should be understood that while this specification may use terms such as “first,” “second,” and “third” to describe various elements or signals, these elements or signals are not limited by these terms. These terms are primarily used to distinguish one element from another, or one signal from another. Furthermore, the term “or” as used herein may, depending on the context, include any one or more of the items listed in relation to the subject.

[0019] Unless otherwise specified, terms used in this invention are synonymous with those commonly understood by those skilled in the art. The materials used in the following embodiments are commercially available materials or materials manufactured by the prior art unless otherwise specified. The methods or operations used in the following examples are common methods or operations in the art unless otherwise specified.

[0020] As shown in Figure 1, the present invention provides a method for manufacturing finely roughened electrolytic copper foil, comprising the steps of: step S1 for forming a main body layer of copper foil; step S2 for roughening the main body layer of copper foil; and step S3 for fixing the roughened main body layer of copper foil. Furthermore, as shown in Figure 2, the finely roughened electrolytic copper foil Z obtained using the manufacturing method of the present invention includes a main body layer 1 (raw foil layer), a roughened plating layer 2, and a fixing plating layer 3. The main body layer 1 has a basically flat surface 100, that is, there are no obvious peaks or valleys in the surface morphology. The roughened plating layer 2 is formed on the basically flat surface 100 and includes a plurality of fine copper bumps 21, and the fixing plating layer 3 is formed between the basically flat surface 100 of the main body layer 1 and the roughened plating layer 2 to fix the plurality of fine copper bumps 21.

[0021] Furthermore, Figures 3 to 6 are images of the surface morphology of the copper foil observed using a Hitachi scanning electron microscope SU8220 at magnifications of 5,000x, 10,000x, 20,000x, and 50,000x under an acceleration voltage of 10.0kV. As shown in Figures 3 to 6, the multiple fine copper bumps 21 are uniformly distributed on the basically flat surface 100 of the main layer 1, and the maximum particle size of each of the fine copper bumps 21 is less than 100 nm. Moreover, the surface roughness Rz of the fine roughened electrolytic copper foil Z is less than 0.8 μm. Notably, the present invention, by the above technical means, helps to smooth the surface of the copper foil, reduce the surface roughness of the copper foil, and maintain the peel strength between the copper foil and the resin substrate at an industry-acceptable level.

[0022] The following describes in detail each step of the manufacturing method of the present invention with reference to the drawings.

[0023] In step S1, the main body layer 1 (raw foil layer) may be formed by electrolytic extraction, where the action of an electric field moves copper ions in the copper sulfate electrolyte to the surface of the cathode roller and deposits them, forming a continuous and uniform copper layer. In the embodiment of the present invention, the thickness of the main body layer 1 is 9 μm to 70 μm, and the roughness Rz of the basically flat surface 100 of the main body layer 1 may be 0.5 μm or less, and preferably less than 0.5 μm. The 60-degree gloss of the basically flat surface 100 of the main body layer 1 exceeds 400 GU. Notably, by controlling the roughness Rz and gloss of the basically flat surface 100 of the main body layer 1, the roughened plating layer 2 formed in step S2 has characteristics such as a high surface area and low roughness that meet the requirements of high-frequency and high-speed transmission.

[0024] In step S2, the main layer 1 is roughened using a roughening solution, that is, the main layer 1 is electrolyzed with a copper sulfate-based roughening solution under conditions of high current density, causing scattered metallic copper to deposit on the basically flat surface 100 of the main layer 1, growing into multiple uniformly distributed fine copper nodules 21. On the said basically flat surface, 1.0 μm 2 The surface area has an average of 135 to 203 fine copper bumps 21. In the embodiment of the present invention, the basically flat surface 100 of the main body layer 1 has 1.0 μm 2 The surface area contains an average of 135 to 203 micro-copper nodules 21, preferably 120 to 180. The number of copper nodules per unit area can be calculated by analyzing the SEM image in Figure 6 using Image-Pro software.

[0025] Furthermore, a formulation with a high copper sulfate ratio is adopted as the roughening solution. The copper ion concentration in the roughening solution is 5 g / L to 25 g / L, the sulfuric acid concentration is 60 g / L to 150 g / L, and the concentration of at least one non-copper metal ion is 0.1 ppm to 300 ppm. At least one of the non-copper metal ions is selected from at least one metal ion in the group consisting of tungsten (W), tin (Sn), iron (Fe), cobalt (Co), nickel (Ni), and molybdenum (Mo). When the copper ion concentration is 5 g / L to 25 g / L, the copper crystal grains basically grow horizontally, resulting in excellent uniformity of the formed roughened plating layer 2 and excellent roughening effect. When the sulfuric acid concentration is 60 g / L to 150 g / L, it improves the uniformity of the roughened plating layer 2 and has a positive effect on increasing the peel strength and reducing the powder shedding on the copper foil surface. By adding the above non-copper metal ions, the copper precipitation mechanism or crystal form can be changed, which also has a positive effect on increasing the peel strength and reducing the powder shedding on the copper foil surface.

[0026] Also, the operating conditions of the roughening treatment are controlled such that the temperature is in the range of 25°C to 35°C, and the current density is 1 A / dm 2 ~60 A / dm 2 and preferably controlled in the range of 20 A / dm 2 ~50 A / dm 2 The roughening treatment time is in the range of 0.5 seconds to 20 seconds, preferably 0.5 seconds to 6 seconds. Using a relatively high current density can refine the copper crystal grains to form copper nodules with a small particle size. Also, when the current density is within the above range, the effect of electrolytic polishing can be obtained, and the roughness of the copper foil surface can be reduced.

[0027] In an embodiment, the temperature of the roughening treatment may be 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, or 35°C. The current density of the roughening treatment is 1 A / dm 2 、5 A / dm 2 、10 A / dm 2 、15 A / dm 2 、20 A / dm 2 、25 A / dm2 , 30A / dm 2 , 35A / dm 2 , 40A / dm 2 , 45A / dm 2 , 50A / dm 2 , 55A / dm 2 , or 60A / dm 2 The roughening treatment time may be 0.5 seconds, 1 second, 2 seconds, 3 seconds, 4 seconds, 5 seconds, or 6 seconds.

[0028] In step S3, the main layer 1, which has been roughened using a fixing solution, can be fixed. Specifically, by placing the main layer 1 in a copper sulfate-based fixing solution and performing electrolysis under relatively low current density conditions, dense metallic copper is filled between the fine copper bumps 21, firmly fixing the fine copper bumps 21 to the basically flat surface 100 of the main layer 1 and reducing powder shedding from the copper foil surface.

[0029] Furthermore, a low copper oxide ratio formulation is used as the fixing solution, where the copper ion concentration in the fixing solution is 30 g / L to 80 g / L, the sulfuric acid concentration is 60 g / L to 150 g / L, and the organic component concentration is 0.1 ppm to 300 ppm. In the electrolytic environment with a low copper oxide ratio, the roughened copper nodules are surrounded and reinforced by the formed fixed plating layer 3, and the copper nodules and the main layer 1 are firmly bonded. By adding organic components, a metallic copper-organic coordination structure is formed, which has a positive effect on increasing peel strength and reducing powder shedding from the copper foil surface. In actual application, the organic component may be a nitrogen-containing compound, for example, an azole compound containing an amino group. Suitable azole compounds containing an amino group for the present invention include benzotriazole (BTA), 3-amino-1,2,4-triazole, and 5-aminotetrazole, but the present invention is not limited thereto.

[0030] Furthermore, the operating conditions for the fixed process are a current density of 0.1 A / dm 2 ~20A / dm 2The current density is controlled within a range of 0.1 to 3 seconds for the fixing process. By using a low current density, copper crystal grains can be deposited into the gaps of the roughened copper nodules, increasing the contact area between the copper nodules and the main layer 1, while also reducing the surface roughness of the copper foil.

[0031] In one embodiment, the current density for the fixing process is 0.1 A / dm 2 , 0.5A / dm 2 , 1A / dm 2 , 5A / dm 2 , 10A / dm 2 , 15A / dm 2 , or 20A / dm 2 This is also acceptable. The time for the fixed processing may be 0.1 seconds, 0.5 seconds, 1 second, 2 seconds, or 3 seconds.

[0032] If necessary, the manufacturing method of the present invention may include multiple roughening-fixing treatments. For example, after completing the first roughening treatment (step S2) and the first fixing treatment (step S3), a second roughening treatment and a second fixing treatment may be performed, and the second roughening treatment may use the same treatment solution and operating conditions as the first roughening treatment, and the second fixing treatment may use the same treatment solution and operating conditions as the first fixing treatment.

[0033] In actual application, after performing the first roughening treatment step (step S2) and the first fixing treatment step (step S3), the manufacturing method of the present invention may include one or more surface treatment steps, such as corrosion resistance treatment, heat resistance treatment, oxidation prevention treatment, passivation treatment and / or silane coupling agent treatment steps, but is not limited to these.

[0034] The technical effects of the present invention will be demonstrated in several embodiments below, but the present invention is not limited to the embodiments listed.

[0035] [Table 1]

[0036] Table 1 shows the maximum particle size and distribution density of copper nodules in the copper foil samples of each example. These are images of the surface morphology of the copper foil observed with a scanning electron microscope at a magnification of 50,000x using Image-Pro software. The particle size distribution of the copper nodules was analyzed, and the number of copper nodules per unit area was calculated. Specifically, using an image of the surface morphology of a copper foil with a size of 2.65 μm × 2 μm observed with a scanning electron microscope at a magnification of 50,000x using Image-Pro software, the software can automatically calculate the number and particle size of copper nodules. It should be noted that the maximum particle size in this application refers to the average particle size (mean) set by default in the Image-Pro software. The surface roughness Rz of the copper foil samples of each example was measured using a Keyence VK-X1000 laser microscope at a magnification of 1,000x at three randomly selected points, and the average of these measurements was calculated.

[0037] As shown in Figure 7, the finely roughened electrolytic copper foil Z of the present invention is suitable for manufacturing copper foil substrates (copper-clad laminates), and the resulting copper foil substrate can be used to manufacture printed circuit boards with high adhesion and excellent high-frequency transmission characteristics. Furthermore, by thermocompression bonding, a predetermined number of resin substrates S (e.g., prepregs) can be laminated between two finely roughened electrolytic copper foils Z to produce a copper foil substrate with copper foil on both sides. In addition, the finely roughened electrolytic copper foil Z can be patterned by known processes to form a fine pitch.

[0038] [Advantageous effects of the embodiment] The finely roughened electrolytic copper foil and its manufacturing method according to the present invention have technical features such as "the main layer has a basically flat surface, the plurality of fine copper bumps are uniformly distributed on the basically flat surface, and the maximum particle size of each of the fine copper bumps is less than 100 nm," and "the surface roughness Rz of the finely roughened electrolytic copper foil is less than 0.8 μm," which helps to reduce electrical resistance, improve signal transmission efficiency, and maintain the peel strength between the copper foil and the resin substrate at an industry-acceptable level. Furthermore, the finely roughened electrolytic copper foil according to the present invention can maintain signal integrity and reduce signal transmission loss even in 5G high-frequency and high-speed transmission applications.

[0039] The information disclosed above represents only preferred and implementable embodiments of the present invention, and the claims of the present invention are not limited thereto. Therefore, any equivalent technical modifications made using the description and drawings of the present invention are all included within the scope of the claims of the present invention. [Explanation of symbols]

[0040] S...Resin base material Z... Finely roughened electrolytic copper foil 1...Main layer 100... Basically a flat surface 2... Roughened plating layer 21... Fine copper bumps 3... Fixed plating layer S1, S2, S3, S4...manufacturing process

Claims

1. The main body layer basically has a flat surface, The aforementioned roughened plating layer, formed on a basically flat surface and having a plurality of fine copper bumps, A finely roughened electrolytic copper foil comprising a fixing plating layer formed between the roughened plating layer and the basically flat surface so as to fix a plurality of the fine copper nodules, Multiple of the aforementioned fine copper bumps are uniformly distributed on the basically flat surface, and the maximum particle diameter of each of the fine copper bumps is less than 100 nm. The finely roughened electrolytic copper foil is characterized in that the surface roughness Rz of the finely roughened electrolytic copper foil is less than 0.8 μm.

2. The aforementioned basically flat surface has a thickness of 1.0 μm. ２ The finely roughened electrolytic copper foil according to claim 1, having an average of 135 to 203 fine copper bumps per area.

3. The finely roughened electrolytic copper foil according to claim 1, wherein the roughness Rz of the basically flat surface is less than 0.5 μm, and the 60-degree gloss of the basically flat surface exceeds 400 GU.

4. The process involves forming a main body layer that basically has a flat surface, A step of forming a roughened plating layer containing multiple fine copper bumps on the basically flat surface, A method for manufacturing finely roughened electrolytic copper foil, comprising the step of forming a fixing plating layer between the roughened plating layer and the basically flat surface so as to fix a plurality of the fine copper bumps, Multiple of the aforementioned fine copper bumps are uniformly distributed on the basically flat surface, and the maximum particle diameter of each of the fine copper bumps is less than 100 nm. A method for producing finely roughened electrolytic copper foil, characterized in that the surface roughness Rz of the finely roughened electrolytic copper foil is less than 0.8 μm.

5. The aforementioned basically flat surface has a thickness of 1.0 μm. ２ A method for producing finely roughened electrolytic copper foil according to claim 4, wherein the foil has an average of 135 to 203 fine copper bumps per area.

6. The step of forming the roughened plating layer includes performing a roughening treatment on the main body layer using a roughening solution, The copper ion concentration in the roughening solution is 5 g / L to 25 g / L, the sulfuric acid concentration is 60 g / L to 150 g / L, the concentration of at least one non-copper metal ion is 0.1 ppm to 300 ppm, and the at least one non-copper metal ion is selected from at least one metal ion from the group consisting of tungsten, tin, iron, cobalt, nickel, and molybdenum, and the roughening treatment is performed at 1 A / dm ２ ~60A / dm ２ A method for producing finely roughened electrolytic copper foil according to claim 5, wherein the process is carried out at a current density and the duration of the roughening treatment is 0.5 seconds to 6 seconds.

7. In the step of forming the fixed plating layer, a fixing solution is used to fix the main body layer that has undergone roughening treatment. The copper ion concentration in the fixative solution is 30 g / L to 80 g / L, the sulfuric acid concentration is 60 g / L to 150 g / L, the organic component concentration is 0.1 ppm to 300 ppm, and the fixative treatment is performed at 0.1 A / dm ２ ~20A / dm ２ A method for manufacturing finely roughened electrolytic copper foil according to claim 4, wherein the process is carried out at a current density and the time of the fixing process is 0.1 seconds to 3 seconds.

8. The method for producing finely roughened electrolytic copper foil according to claim 7, wherein the organic component is a nitrogen-containing compound.

9. The method for manufacturing finely roughened electrolytic copper foil according to claim 4, wherein in the step of forming the main body layer, the roughness Rz of the basically flat surface is less than 0.5 μm, and the 60-degree gloss of the basically flat surface exceeds 400 GU.

10. A copper foil substrate comprising a substrate and a finely roughened electrolytic copper foil according to claim 1, which is placed on the surface of the substrate.

Images