Low-roughness copper foil having high distribution density of copper tumors, method of making same, and copper foil substrate including same

Abstract

Disclosed are a low-roughness copper foil with high distribution density of copper nodules, a manufacturing method thereof, and a copper foil substrate including the same. The copper foil includes a main body layer, a roughened plating layer, and at least one surface treatment layer. The main body layer has a substantially flat surface, the roughened plating layer is formed on the substantially flat surface and includes a plurality of fine copper nodules, and at least one of the surface treatment layers is formed on the roughened plating layer. The plurality of fine copper nodules are uniformly distributed on the substantially flat surface, and there are 135 to 203 fine copper nodules per square micron of the substantially flat surface on average. The copper foil has a surface roughness Rz of less than 0.8 microns. Thus, the copper foil can meet the requirements of high frequency and high speed transmission.

Description

Technical Field

[0001] This invention relates to an electrolytic copper foil, and more particularly to a low-roughness copper foil with a high copper nodule distribution density that can meet the requirements of high-frequency and high-speed transmission. Background Technology

[0002] With the booming development of the electronics and information industries, high-frequency, high-speed signal transmission has become a major consideration in the design and manufacturing of copper foil. It is well known that the roughness (smoothness) of copper foil is a crucial factor affecting high-frequency, high-speed signal transmission. Higher roughness results in slower signal transmission speeds and lower accuracy. Furthermore, excessive roughness can lead to signal transmission loss, affecting the stability of high-frequency signal transmission. Therefore, copper foil manufacturers typically focus on and control the roughness of copper foil to ensure the expected performance levels 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 clad laminate (CCL) during subsequent processing or use. Generally, reducing the surface roughness of the copper foil will also weaken the peel strength between the copper foil and the resin substrate, indicating that surface roughness and peel strength are conflicting indicators.

[0004] Therefore, how to improve the structural design to achieve an extremely low roughness with a near-smooth surface on the copper foil while also ensuring the peel strength between the copper foil and the resin substrate, thus overcoming the aforementioned defects, has become one of the important issues that copper foil manufacturers want to address. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a low-roughness copper foil with high copper nodule distribution density, a method for manufacturing the same, and a copper foil substrate including the same, addressing the shortcomings of the prior art. The low-roughness copper foil with high copper nodule distribution density of the present invention can achieve low roughness while maintaining a certain peel strength. Furthermore, the low-roughness copper foil with high copper nodule distribution density of the present invention is suitable for manufacturing copper foil substrates, and the obtained copper foil substrates can be used to manufacture printed circuit boards with high bonding density and excellent high-frequency transmission characteristics.

[0006] To address the aforementioned technical problems, one technical solution adopted by the present invention is to provide a low-roughness copper foil with a high copper nodule distribution density, comprising a main layer, a roughening plating layer, and at least one surface treatment layer. The main layer has a substantially flat surface, the roughening plating layer is formed on the substantially flat surface and includes a plurality of small copper nodules, and at least one surface treatment layer is formed on the roughening plating layer. In the present invention, the plurality of small copper nodules are uniformly distributed on the substantially flat surface, and there are 135 to 203 small copper nodules per square micrometer on average on the substantially flat surface. Furthermore, the low-roughness copper foil with a high copper nodule distribution density has a surface roughness Rz of less than 0.8 micrometers.

[0007] To address the aforementioned technical problems, another technical solution adopted by the present invention is to provide a method for manufacturing a low-roughness copper foil with a high copper nodule distribution density, comprising: forming a main layer having a substantially flat surface; forming a roughening coating on the substantially flat surface, the roughening coating comprising a plurality of small copper nodules; and forming at least one surface treatment layer on the roughening coating. In the present invention, the plurality of small copper nodules are uniformly distributed on the substantially flat surface, and there are 135 to 203 small copper nodules per square micrometer on average on the substantially flat surface. Furthermore, the low-roughness copper foil with a high copper nodule distribution density has a surface roughness Rz of less than 0.8 micrometers.

[0008] In a feasible or optional embodiment of the present invention, the maximum particle size of each of the tiny copper nodules is less than 100 nanometers.

[0009] In a feasible or optional embodiment of the present invention, the roughness Rz of the substantially flat surface is less than 0.5 micrometers, and the 60-degree gloss of the substantially flat surface is greater than 400 GU.

[0010] In feasible or optional embodiments of the present invention, at least one of the surface treatment layers includes a heat-resistant treatment layer formed on the roughened coating and a silane coupling agent layer formed on the heat-resistant treatment layer.

[0011] In a feasible or optional embodiment of the present invention, the low-roughness copper foil with high copper nodule distribution density has a peel strength greater than 3.5 lb / in as measured according to IPC-TM-650 2.4.8 standard.

[0012] In a feasible or optional embodiment of the present invention, the step of forming the roughened coating includes roughening the base layer using a roughening solution, wherein the concentration of copper ions in the roughening solution is 3-25 g / L, the concentration of sulfuric acid is 60-150 g / L, and the concentration of at least one non-copper metal ion is 0.1-300 ppm. The at least one non-copper metal ion is selected from at least one of the following metal ions: tungsten, tin, iron, cobalt, nickel, and molybdenum. Furthermore, the roughening treatment is performed at a rate of 1-60 A / dm. 2 The roughening process is performed at a current density of 0.5-6 seconds.

[0013] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is to provide a copper foil substrate, which includes a substrate and a low-roughness copper foil with a high copper nodule distribution density as described above, and the electrolytic copper foil is disposed on the surface of the substrate.

[0014] One of the beneficial effects of this invention is that the low-roughness copper foil with high copper nodule distribution density and its manufacturing method provided by this invention can achieve an extremely low roughness with a near-smooth surface by means of technical features including "the main layer has a substantially flat surface, a plurality of small copper nodules are uniformly distributed on the substantially flat surface, and there are 135 to 203 small copper nodules per square micrometer on average" and "the low-roughness copper foil with high copper nodule distribution density has a surface roughness Rz of less than 0.8 micrometers". This also ensures the peel strength between the copper foil and the resin substrate. Furthermore, the low-roughness copper foil with high copper nodule distribution density provided by this invention can maintain signal integrity and reduce signal transmission loss in 5G high-frequency, high-speed transmission applications.

[0015] To further understand the features and technical content of the present invention, please refer to the following detailed description and accompanying drawings. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention. Attached Figure Description

[0016] Figure 1 This is a flowchart of the method for manufacturing a low-roughness copper foil with high copper nodule distribution density according to the present invention.

[0017] Figure 2 This is a schematic diagram of the structure of the low-roughness copper foil with high copper nodule distribution density of the present invention.

[0018] Figure 3 for Figure 2 A magnified view of a section III.

[0019] Figure 4The image is an image obtained by observing the surface morphology of a low-roughness copper foil with high copper nodule distribution density using a scanning electron microscope at a magnification of 5,000x.

[0020] Figure 5 The image is an image obtained by observing the surface morphology of a low-roughness copper foil with high copper nodule distribution density using a scanning electron microscope at a magnification of 10,000x.

[0021] Figure 6 The image is an image obtained by observing the surface morphology of a low-roughness copper foil with high copper nodule distribution density using a scanning electron microscope at a magnification of 20,000.

[0022] Figure 7 The image is an image obtained by observing the surface morphology of a low-roughness copper foil with high copper nodule distribution density using a scanning electron microscope at a magnification of 50,000.

[0023] Figure 8 This is a schematic diagram of a copper foil substrate including the low-roughness copper foil with high copper nodule distribution density of the present invention. Detailed Implementation

[0024] The following specific embodiments illustrate the implementation of the invention regarding "a low-roughness copper foil with high copper nodule distribution density, its manufacturing method, and a copper foil substrate including the same". Those skilled in the art can understand the advantages and effects of the invention from the content disclosed in this specification. The invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the invention. Furthermore, the accompanying drawings are for simple illustrative purposes only and are not depictions of actual dimensions; this is stated beforehand. The following embodiments will further describe the relevant technical content of the invention in detail, but the disclosed content is not intended to limit the scope of protection of the invention.

[0025] It should be understood that while terms such as "first," "second," and "third" may be used in this document to describe various components or signals, these components or signals should not be limited by these terms. These terms are primarily used to distinguish one component from another, or one signal from another. Furthermore, the term "or" as used in this document should, depending on the context, include any combination of one or more related listed items.

[0026] Unless otherwise defined, the terms used herein have the same meaning as commonly understood by those skilled in the art. Materials involved in the embodiments are commercially available or made according to prior art, unless otherwise specified. Methods or operations involved in the embodiments are conventional methods or operations in the art, unless otherwise specified.

[0027] See Figure 1 As shown, this invention provides a method for manufacturing a low-roughness copper foil with a high copper nodule distribution density, comprising: step S1, forming a copper foil main layer; step S2, roughening the copper foil main layer; and step S3, performing surface treatment on the roughened copper foil main layer. (And in conjunction with...) Figure 2 As shown, the low-roughness copper foil Z with high copper nodule distribution density obtained by the manufacturing method of the present invention includes a main layer 1 (green foil layer), a roughening plating layer 2, and at least one surface treatment layer 3. The main layer 1 has a substantially flat surface 100, that is, the surface morphology of the main layer 1 does not have obvious peaks and valleys. The roughening plating layer 2 is formed on the substantially flat surface 100 and includes a plurality of small copper nodules 21, and at least one surface treatment layer 3 is formed on the roughening plating layer 2.

[0028] Further reading Figures 4 to 7 Images of the surface morphology of copper foil were observed using a Hitachi SU8220 scanning electron microscope at an accelerating voltage of 10.0 kV, at magnifications of 5,000x, 10,000x, 20,000x, and 50,000x. Figures 3 to 6 As shown, multiple tiny copper nodules 21 are uniformly distributed on the substantially flat surface 100 of the main body layer 1, and the maximum particle size of each tiny copper nodule 21 is less than 100 nanometers. Based on this, the low-roughness copper foil Z with high copper nodule distribution density of the present invention has a surface roughness Rz of less than 0.8 micrometers. It is worth noting that the present invention, through the above-mentioned technical means, can smooth the surface of the copper foil, reduce the surface roughness of the copper foil, and is beneficial to maintaining the peel strength between the copper foil and the resin substrate at an industry-acceptable standard.

[0029] The following will describe in detail the various steps of the manufacturing method of the present invention with reference to the accompanying drawings.

[0030] In step S1, the main body layer 1 can be formed by electrolytic deposition, wherein copper ions in the copper sulfate electrolyte migrate to the surface of the cathode roller and deposit under the action of an electric field, forming a continuous and uniformly thick green foil layer. In embodiments of the present invention, the thickness of the main body layer 1 can be in the range of 9 micrometers to 70 micrometers; the roughness Rz of the substantially flat surface 100 of the main body layer 1 is less than 0.5 micrometers, and can be selected to be less than or equal to 0.3 micrometers; the 60-degree gloss of the substantially flat surface 100 of the main body layer 1 is greater than 400 GU. It is worth noting that by controlling the roughness Rz and gloss of the substantially flat surface 100 of the main body layer 1, the roughened coating 2 formed in step S2 can have characteristics such as high surface area and low roughness to meet the requirements of high frequency and high speed transmission.

[0031] In step S2, the host layer 1 can be roughened using a roughening solution. This involves placing the host layer 1 in a copper sulfate system and electrolyzing it under high current density conditions to deposit loose metallic copper on the substantially flat surface 100 of the host layer 1, resulting in the growth of multiple uniformly distributed fine copper nodules 21. In embodiments of the invention, there are an average of 135 to 203 fine copper nodules 21 per square micrometer on the substantially flat surface 100 of the host layer 1, and optionally 120 to 180 nodules. Image-Pro software can be used to... Figure 6 The number of copper nodules per unit area was calculated from the SEM images.

[0032] Furthermore, the roughening solution employs a high acid-to-copper ratio formulation, wherein the copper ion concentration in the roughening solution is 3-25 g / L, the sulfuric acid concentration is 60-150 g / L, and the concentration of at least one non-copper metal ion is 0.1-300 ppm; the at least one non-copper metal ion is selected from at least one of the following metal ions: tungsten (W), tin (Sn), iron (Fe), cobalt (Co), nickel (Ni), and molybdenum (Mo). When the copper ion concentration is 3-25 g / L, the copper grains grow primarily laterally, resulting in better uniformity and roughening effect of the formed roughened coating 2. When the sulfuric acid concentration is 60-150 g / L, it can improve the uniformity of the roughened coating 2 and has a positive impact on increasing peel strength and reducing powder shedding from the copper foil surface. The addition of the aforementioned non-copper metal ions can alter the deposition mechanism or crystal morphology, which also has a positive impact on increasing peel strength and reducing powder shedding from the copper foil surface.

[0033] In addition, the operating conditions for the roughening process include: current density controlled at 1 A / dm. 2 (ASD, Amperes per square decimeter) to 60 A / dm 2 Within the range, and can be selected as 20A / dm 2 Up to 50A / dm 2The roughening process takes between 0.5 and 6 seconds. Using a higher current density can refine the copper grains to form small-diameter copper nodules; and when the current density is within the above range, an electropolishing effect can be achieved, reducing the surface roughness of the copper foil.

[0034] In some embodiments, the current density for the roughening process is 1 A / dm. 2 5A / dm 2 10A / dm 2 15A / dm 2 20A / dm 2 25A / dm 2 30A / dm 2 35A / dm 2 40A / dm 2 45A / dm 2 50A / dm 2 55A / dm 2 or 60A / dm 2 The coarsening time is 0.5 seconds, 1 second, 2 seconds, 3 seconds, 4 seconds, 5 seconds, or 6 seconds.

[0035] Depending on the requirements, the manufacturing method of the present invention may include multiple roughening processes. For example, after completing the first roughening process step (step S2), a second roughening process step may be performed; the second roughening process may use the same processing solution and operating conditions as the first roughening process.

[0036] See again Figure 1 and cooperate Figure 2 and Figure 3 As shown, in step S3, the surface treatment of the roughened main layer 1 includes heat resistance treatment and silane coupling agent treatment. In embodiments of the present invention, a treatment solution containing nickel and / or zinc can be used to perform heat resistance treatment on the roughened main layer 1 to form a heat-resistant treatment layer 31 on the roughened plating layer 2, enabling the copper foil to withstand the high temperatures of processes (e.g., hot pressing). After completing the heat resistance treatment, a treatment solution containing silane coupling agent can be used to perform silane coupling agent treatment on the heat-resistant main layer 1 to form a silane coupling agent layer 32 on the heat-resistant treatment layer 31, resulting in stronger adhesion between the copper foil and the resin substrate. After silane coupling agent treatment, the peel strength of the copper foil, measured according to IPC-TM-650 2.4.8 standard, is greater than 3.5 lb / in.

[0037] Furthermore, in the heat-resistant treatment, the roughened main layer 1 can be placed in a treatment solution containing nickel and / or zinc and electrolyzed under low current density conditions to form a heat-resistant treatment layer 31, which acts as a thermal barrier layer to protect the roughened copper nodules. The roughened copper nodules are surrounded and reinforced by the formed heat-resistant treatment layer 31. It is worth noting that the maximum particle size of the copper nodules formed in step S2 is less than 100 nanometers, so the heat-resistant treatment layer 31 alone can maintain a strong bond between the copper nodules and the main layer 1. Therefore, even without the curing process, the copper nodules can be firmly fixed on the basically flat surface 100 of the main layer 1, preventing powder from falling off the copper foil surface. Depending on actual needs, the roughened surface of the copper foil can be washed with water before the heat-resistant treatment.

[0038] In addition, during the silane coupling agent treatment, the roughened surface of the copper foil can be uniformly contacted with the treatment solution containing the silane coupling agent by coating or impregnation, followed by air drying or heat drying. Silane coupling agents suitable for this invention include epoxy silanes, amino silanes, vinyl silanes, methacrylic silanes, acrylic silanes, styryl silanes, urea silanes, mercapto silanes, thioether silanes, and isocyanate silanes, and can be optionally amino silanes and vinyl silanes. Depending on actual needs, the roughened surface of the copper foil can be washed with water before the silane coupling agent treatment.

[0039] In practical applications, in step S3, different surface treatments can be applied to the copper foil before the heat treatment or between the heat treatment and the silane coupling agent treatment, such as, but not limited to, corrosion resistance treatment, oxidation resistance treatment and / or passivation treatment.

[0040] The following examples will demonstrate the effectiveness of the present invention. However, the present invention is not limited to the examples given.

[0041] Table 1

[0042]

[0043]

[0044] Table 1 shows the maximum particle size and distribution density of copper nodules in the copper foil samples of each example. These values ​​were obtained by using Image-Pro software to analyze images of the copper foil surface morphology observed under a scanning electron microscope at 50,000x magnification. The particle size distribution of the copper nodules was analyzed, and the number of nodules per unit area was calculated. The surface roughness Rz of the copper foil samples in each example was measured using a Keyence VK-X1000 laser microscope at 1,000x magnification, and the obtained values ​​are three-point averages. The peel strength between the copper foil samples and the resin substrate in each example was also tested.

[0045] See Figure 8As shown, the finely roughened electrolytic copper foil Z of the present invention is suitable for fabricating copper foil substrates (copper clad laminates), and the obtained copper foil substrate can be used to fabricate printed circuit boards with high bonding density and excellent high-frequency transmission characteristics. Furthermore, a predetermined number of resin substrate layers S (e.g., prepreg sheets) can be laminated between two finely roughened electrolytic copper foils Z by thermoforming to form a copper foil substrate with copper foil on both sides. Moreover, the finely roughened electrolytic copper foil Z can be patterned using existing processes to form micro-circuits.

[0046] Beneficial effects of the embodiments

[0047] One of the beneficial effects of this invention is that the low-roughness copper foil with high copper nodule distribution density and its manufacturing method provided by this invention can achieve an extremely low roughness with an almost smooth surface by means of technical features including "the main layer has a substantially flat surface, a plurality of small copper nodules are uniformly distributed on the substantially flat surface, and there are 135 to 203 small copper nodules per square micrometer on average" and "the low-roughness copper foil with high copper nodule distribution density has a surface roughness Rz of less than 0.8 micrometers". At the same time, it can also maintain the peel strength between the copper foil and the resin substrate. Furthermore, the low-roughness copper foil with high copper nodule distribution density provided by this invention can maintain signal integrity and reduce signal transmission loss in 5G high-frequency, high-speed transmission applications.

[0048] Furthermore, in the low-roughness copper foil with high copper nodule distribution density provided by this invention, the maximum particle size of each tiny copper nodule is less than 100 nanometers. Therefore, even without the curing process, the copper nodules can be consolidated, ensuring a strong bond between the nodules and the main copper foil layer and preventing powder from falling off the copper foil surface.

[0049] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of protection of the claims of the present invention. Therefore, all equivalent technical changes made based on the content of the present invention specification and drawings are included within the scope of protection of the claims of the present invention.

Claims

1. A low-roughness copper foil with high copper nodule distribution density, characterized in that, The low-roughness copper foil with high copper nodule distribution density includes: The main body layer has a generally flat surface; A roughened coating, formed on the substantially flat surface and comprising a plurality of small copper nodules; and At least one surface treatment layer, wherein at least one of the surface treatment layers is formed on the roughened coating; Among them, multiple small copper nodules are evenly distributed on the substantially flat surface, and there are 135 to 203 small copper nodules per square micrometer on average on the substantially flat surface. Among them, the low-roughness copper foil with high copper nodule distribution density has a surface roughness Rz of less than 0.8 micrometers.

2. The low-roughness copper foil with high copper nodule distribution density according to claim 1, characterized in that, Each of these tiny copper nodules has a maximum particle size of less than 100 nanometers.

3. The low-roughness copper foil with high copper nodule distribution density according to claim 1, characterized in that, The roughness Rz of the substantially flat surface is less than 0.5 micrometers, and the 60-degree gloss of the substantially flat surface is greater than 400 GU.

4. The low-roughness copper foil with high copper nodule distribution density according to claim 1, characterized in that, At least one of the surface treatment layers includes a heat-resistant treatment layer formed on the roughened coating and a silane coupling agent layer formed on the heat-resistant treatment layer.

5. The low-roughness copper foil with high copper nodule distribution density according to claim 4, characterized in that, The low-roughness copper foil with high copper nodule distribution density has a peel strength greater than 3.5 lb / in as measured by IPC-TM-650 2.4.8 standard.

6. A method for manufacturing a low-roughness copper foil with high copper nodule distribution density, characterized in that, The method for manufacturing low-roughness copper foil with high copper nodule distribution density includes: A main layer is formed, which has a substantially flat surface; A roughened coating is formed on the substantially flat surface, the roughened coating comprising a plurality of small copper nodules; and At least one surface treatment layer is formed on the roughened coating; Among them, multiple small copper nodules are evenly distributed on the substantially flat surface, and there are 135 to 203 small copper nodules per square micrometer on average on the substantially flat surface. Among them, the low-roughness copper foil with high copper nodule distribution density has a surface roughness Rz of less than 0.8 micrometers.

7. The method for manufacturing a low-roughness copper foil with high copper nodule distribution density according to claim 6, characterized in that, In the step of forming the roughened coating, the maximum particle size of each of the tiny copper nodules is less than 100 nanometers.

8. The method for manufacturing a low-roughness copper foil with high copper nodule distribution density according to claim 7, characterized in that, The step of forming the roughened coating includes roughening the base layer using a roughening solution, wherein the concentration of copper ions in the roughening solution is 3-25 g / L, the concentration of sulfuric acid is 60-150 g / L, and the concentration of at least one non-copper metal ion is 0.1-300 ppm; the at least one non-copper metal ion is selected from at least one of the following metal ions: tungsten, tin, iron, cobalt, nickel, and molybdenum; wherein the roughening treatment is performed at a concentration of 1-60 A / dm. 2 The roughening process is performed at a current density of 0.5-6 seconds.

9. The method for manufacturing a low-roughness copper foil with high copper nodule distribution density according to claim 6, characterized in that, The step of forming at least one of the surface treatment layers includes: forming a heat-resistant treatment layer on the roughened coating; and forming a silane coupling agent layer on the heat-resistant treatment layer.

10. The method for manufacturing a low-roughness copper foil with high copper nodule distribution density according to claim 6, characterized in that, In the step of forming the main layer, the roughness Rz of the substantially flat surface is less than 0.5 micrometers, and the 60-degree gloss of the substantially flat surface is greater than 400 GU.

11. A copper foil substrate, characterized in that, The copper foil substrate includes a substrate and a low-roughness copper foil with a high copper nodule distribution density as described in claim 1 disposed on the surface of the substrate.

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