Electrolytic copper foil as well as preparation method and application thereof

Abstract

The invention provides an electrolytic copper foil which is at least provided with a low-roughness surface, copper nodules on the low-roughness surface are rod-shaped protrusions and / or granular protrusions, the distance between every two adjacent protrusions ranges from 10 nm to 650 nm, the height of the copper nodules of the rod-shaped protrusions ranges from 300 nm to 800 nm, and the height of the copper nodules of the granular protrusions ranges from 80 nm to 250 nm. And the number of the rod-shaped bulge copper nodules and / or the granular bulges is 50-150 in every 25 mu m < 2 > of the area of the low-roughness surface. The invention further provides a preparation method and application of the electrolytic copper foil. The electrolytic copper foil provided by the invention has a low-roughness surface, so that the signal integrity of the copper foil substrate is improved, the problem of large signal transmission loss in the prior art is solved, the peeling strength between the copper foil and the substrate is improved, and the defect of insufficient peeling strength in the prior art is overcome.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic circuit copper foil, and particularly relates to an electrolytic copper foil, a preparation method thereof and application thereof. BACKGROUND

[0002] With the rapid development of electronic information industry, high-frequency high-speed signal transmission has become a link of modern circuit design and manufacturing. In order to meet the demand of electronic products for high-frequency high-speed signal transmission, the copper foil substrate needs to have good signal integrity performance under high frequency, so as to prevent excessive loss of high-frequency signals during transmission; and the signal integrity of the copper foil substrate is highly related to the surface roughness of the copper foil. Generally speaking, the flatter the surface morphology of the copper foil, that is, the lower the surface roughness, the better the signal integrity of the copper foil substrate.

[0003] However, reducing the surface roughness of the copper foil will also cause the peeling strength between the copper foil and the substrate to decrease, affecting the yield of the back-end product. Therefore, how to maintain the peeling strength of the copper foil substrate at the industry level while making the copper foil substrate have good signal integrity performance has become a problem to be solved in the field.

[0004] In order to solve the problem of simultaneously meeting the signal transmission integrity and the peeling strength, the staff has carried out a lot of research, for example: a micro-rough electrolytic copper foil is disclosed in Chinese patent CN112118671A, which comprises a micro-rough surface and a plurality of copper tumors. The micro-rough surface has a plurality of copper tumor-free areas and a plurality of arranged copper tumor areas. In the micro-rough surface with an area of 120 μm 2 , the number of copper tumor-free areas is more than 5, the area of each copper tumor-free area is greater than or equal to 62500 nm 2 , the length of each arranged copper tumor area is 300 nm to 2,500 nm, the average width of the copper tumors in each arranged copper tumor area is 10 nm to 300 nm, and the number of copper tumors in each arranged copper tumor area is 3 to 50. In order to achieve the above-mentioned simultaneous effect, the surface morphology and copper tumor distribution still need to be further optimized.

[0005] A Chinese patent with publication number CN111194134A discloses a micro-roughened electrolytic copper foil and a copper-clad substrate using the same; the electrolytic copper foil has a micro-roughened surface, and the micro-roughened surface has a plurality of mountain-shaped structures and a plurality of recessed structures relative to the mountain-shaped structures, the product (Sa x Spd) of the arithmetic average height (Sa) and the vertex density (Spd) of the plurality of mountain-shaped structures is 150000 to 400000 microns per square millimeter according to the international standard ISO25178, and the arithmetic average fluctuation (Wa) of the plurality of mountain-shaped structures is greater than 0.06 microns and less than or equal to 1.5 microns according to the Japanese Industrial Standard JIS B0601-2001. In order to achieve the above-mentioned simultaneous effects, the parameters of the micro-roughened surface still need to be further optimized to better reduce signal transmission loss.

[0006] In summary, there is no electrolytic copper foil in the prior art that can simultaneously consider low surface roughness and good peeling strength, therefore, the surface topography and copper tumor distribution need to be further optimized, the shape and size of the copper tumor are controlled, in order to improve the high-frequency signal transmission efficiency and reduce the insertion loss. SUMMARY

[0007] The technical problem solved by the present application is to provide an electrolytic copper foil, the electrolytic copper foil provided by the present application has low surface roughness, which ensures the signal integrity of the electrolytic copper foil under high-frequency transmission, and improves the peeling strength between the electrolytic copper foil and the substrate.

[0008] Therefore, the present application provides an electrolytic copper foil, the electrolytic copper foil has at least a low-roughness surface, the copper tumor of the low-roughness surface is in the form of rod-shaped protrusions and / or granular protrusions, the distance between two adjacent protrusions is 10-650 nm, the height of the copper tumor of the rod-shaped protrusion is 300-800 nm, and the height of the copper tumor of the granular protrusion is 80-250 nm; and the number of the rod-shaped protrusions and / or the granular protrusions per 25 microns 2 of the low-roughness surface is 50-150.

[0009] In some specific embodiments, the copper tumor of the low-roughness surface is in the form of rod-shaped protrusions and granular protrusions, and the proportion of the rod-shaped protrusions is 60-80% of the total number of the rod-shaped protrusions and the granular protrusions.

[0010] In some specific embodiments, the distance between two adjacent protrusions is 12-450 nm.

[0011] In some specific embodiments, the height of the copper tumor of the rod-shaped protrusion is 310-750 nm, and / or the height of the copper tumor of the granular protrusion is 85-230 nm.

[0012] In some embodiments, the number of the rod-shaped protruding copper tumors and / or the granular protrusions is 80-140 per 25μm 2 area.

[0013] The application also provides a preparation method of the electrolytic copper foil, comprising the following steps:

[0014] S1, sequentially performing acid pickling and water washing on the electrolytic green foil;

[0015] S2, performing roughening treatment and solidification treatment on the surface of the electrolytic green foil obtained in step S1;

[0016] The roughening plating solution of the roughening treatment comprises 5-10g / L of copper ions, 90-110g / L of sulfuric acid and 10-50mg / L of roughening additives, the roughening additives comprise one or more of metal salts; the current density of the roughening treatment is 15-30A / dm 2 ;

[0017] The solidification solution of the solidification treatment comprises 50-70g / L of copper ions and 80-100g / L of sulfuric acid; the current density of the solidification treatment is 15-25A / dm 2 ;

[0018] S3, sequentially performing blackening nickel plating treatment, graying zinc plating treatment and passivation chromium plating treatment on the electrolytic green foil obtained in step S2;

[0019] S4, performing silanization treatment on the surface of the electrolytic green foil obtained in step S3, and drying to obtain the electrolytic copper foil.

[0020] In some embodiments, in step S1, the acid pickling solution has a copper ion concentration of ≤5g / L, a sulfuric acid concentration of 50-100g / L, a temperature of 30-40℃ and a flow rate of 8-12m 3 / h; and / or, in step S2, the roughening plating solution has a temperature of 40-50℃; and / or, in step S2, the solidification solution has a copper ion concentration of 55-65g / L.

[0021] In some embodiments, in step S3, the nickel plating solution of the blackening nickel plating treatment comprises 15-25g / L of nickel ions and 25-35g / L of boric acid, has a temperature of 40-50℃ and a current density of 8-12A / dm 2 ; and / or, the zinc plating solution of the graying zinc plating treatment comprises 3-10g / L of zinc ions and 25-35g / L of boric acid, has a temperature of 40-50℃ and a current density of 10-20A / dm 2; and / or, the plating solution of the passivation chromium plating process comprises 1-5 g / L of chromium ions, the temperature is 25-35℃, the current density is 15-25 A / dm 2 .

[0022] The application also provides a printed circuit board comprising a substrate and a copper foil formed on the surface of the substrate, wherein the copper foil is the electrolytic copper foil described in the above solution or the electrolytic copper foil prepared by the preparation method described in the above solution.

[0023] The application also provides the application of the electrolytic copper foil described in the above solution or the electrolytic copper foil prepared by the preparation method described in the above solution in a battery.

[0024] The application provides an electrolytic copper foil, which has at least a low roughness surface, the copper tumor of the low roughness surface is rod-shaped protrusion and / or granular protrusion, the distance between adjacent two protrusions is 10-650 nm, the height of the copper tumor of the rod-shaped protrusion is 300-800 nm, and the height of the copper tumor of the granular protrusion is 80-250 nm; and the number of the rod-shaped protrusion copper tumor and / or the granular protrusion in every 25 μm 2 area of the low roughness surface is 50-150; the surface morphology of the electrolytic copper foil provided by the application is more uniform and has smaller high-low undulation, which not only effectively reduces the surface roughness, improves the signal integrity of the copper foil substrate, solves the problem of large signal transmission loss in the prior art, but also is beneficial to improve the peeling strength between the copper foil and the substrate and overcome the defect of insufficient peeling strength in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The scanning electron microscope graph of the surface of the electrolytic copper foil prepared for Example 1 observed at a magnification of 5000 times;

[0026] Figure 2 The scanning electron microscope graph of the surface of the electrolytic copper foil prepared for Example 1 observed at a magnification of 8000 times;

[0027] Figure 3 The field emission scanning electron microscope graph of the cross section of the electrolytic copper foil prepared for Example 1 observed at a magnification of 30000 times;

[0028] Figure 4 The scanning electron microscope graph of the surface of the electrolytic copper foil provided for Comparative Example 1 observed at a magnification of 8000 times. DETAILED DESCRIPTION

[0029] In order to further understand the application, the preferred embodiments of the application are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the application, and are not a limitation on the claims of the application.

[0030] In view of the problem that the signal integrity of the copper foil substrate is related to the surface roughness in the prior art, and reducing the surface roughness will reduce the peeling strength between the copper foil and the substrate, the present application provides an electrolytic copper foil having at least one low roughness surface, which effectively reduces the surface roughness of the electrolytic copper foil by optimizing the topographic features of the low roughness surface, improves the signal integrity of the copper foil substrate, solves the problem of large signal transmission loss in the prior art, and is also conducive to improving the peeling strength between the copper foil and the substrate. Specifically, the present application discloses an electrolytic copper foil, which has at least one low roughness surface, the copper tumors of the low roughness surface are rod-shaped protrusions and / or granular protrusions, the spacing between two adjacent protrusions is 10-650 nm, the height of the copper tumors of the rod-shaped protrusions is 300-800 nm, and the height of the copper tumors of the granular protrusions is 80-250 nm; and the number of the rod-shaped protrusions and / or the granular protrusions per 25 μm 2 area of the low roughness surface is 50-150.

[0031] In the present application, the electrolytic copper foil has at least one low roughness surface, i.e., one surface of the electrolytic copper foil has a low roughness, or both surfaces of the electrolytic copper foil have a low roughness; the topographic features of the low roughness surface can be clearly observed under a scanning electron microscope with a magnification of 8000 times; specifically, the surface of the electrolytic copper foil is distributed with copper tumors, the copper tumors are rod-shaped protrusions and / or granular protrusions, i.e., the copper tumors are rod-shaped protrusions, or granular protrusions, or both rod-shaped protrusions and granular protrusions exist, and in specific embodiments, the copper tumors have both rod-shaped protrusions and granular protrusions. Further, the proportion of the rod-shaped protrusions is 60-80% of the total number of the rod-shaped protrusions and the granular protrusions, specifically, the proportion of the rod-shaped protrusions is 62-75% of the total number of the rod-shaped protrusions and the granular protrusions, and more specifically, the proportion of the rod-shaped protrusions is 65-72% of the total number of the rod-shaped protrusions and the granular protrusions.

[0032] In the present application, the rod-shaped protrusion refers to an elongated protrusion with a clear length-diameter ratio, and the granular protrusion refers to a round or circular protrusion with a length-diameter ratio close to 1; those skilled in the art can clearly distinguish the above rod-shaped protrusion and the above granular protrusion by scanning electron microscopy.

[0033] The distance between two adjacent protrusions is 10-650 nm, the distance between two adjacent rod-shaped protrusions is 10-650 nm, the distance between two adjacent granular protrusions is 10-650 nm, and the distance between a rod-shaped protrusion and a granular protrusion is 10-650 nm. Specifically, the distance between two adjacent protrusions is 12-450 nm, more specifically, the distance between two adjacent protrusions is 16-420 nm, more specifically, the distance between two adjacent protrusions is 17-330 nm, more specifically, the distance between two adjacent protrusions is 20-265 nm, and more specifically, the distance between two adjacent protrusions is 50-220 nm.

[0034] Meanwhile, the height of the copper tumor on the surface of the electrolytic copper foil is also limited, wherein the height of the rod-shaped protrusion is 300-800 nm, and the height of the granular protrusion is 80-250 nm. Specifically, the height of the rod-shaped protrusion is 310-750 nm, and the height of the granular protrusion is 85-230 nm, more specifically, the height of the rod-shaped protrusion is 320-700 nm, and the height of the granular protrusion is 90-200 nm, more specifically, the height of the rod-shaped protrusion is 350-650 nm, and the height of the granular protrusion is 100-180 nm, more specifically, the height of the rod-shaped protrusion is 370-630 nm, and the height of the granular protrusion is 110-160 nm.

[0035] Further, the density of the copper tumor on the surface of the electrolytic copper foil is also limited. The number of rod-shaped protrusions and / or granular protrusions is 50-150 per 25 μm 2 area, specifically, the number of rod-shaped protrusions and / or granular protrusions is 80-140 per 25 μm 2 area, more specifically, the number of rod-shaped protrusions and / or granular protrusions is 90-135 per 25 μm 2 area, more specifically, the number of rod-shaped protrusions and / or granular protrusions is 95-125 per 25 μm 2 area, and more specifically, the number of rod-shaped protrusions and / or granular protrusions is 100-115 per 25 μm 2 area.

[0036] The low-roughness surface of the electrolytic copper foil provided by the present application has an Rz of 0.5-1.5 μm and an Sdr of 2-5% as tested by a laser confocal microscope. Further, the peel strength of the electrolytic copper foil after being pressed with PPO resin is ≥0.8 N / mm, and the electrical performance loss of the PCB board processed by pressing the electrolytic copper foil with PPO resin is between -0.6 and -0.8 dB / in at 16 GHz.

[0037] The application also provides a preparation method of the above-mentioned electrolytic copper foil, comprising the following steps:

[0038] S1, sequentially performing acid pickling and water washing on the electrolytic green foil;

[0039] S2, performing roughening treatment and solidification treatment on the surface of the electrolytic green foil obtained in step S1;

[0040] The roughening plating solution of the roughening treatment comprises 5-10 g / L of copper ions, 90-110 g / L of sulfuric acid and 10-50 mg / L of a roughening additive, the roughening additive comprises one or more of metal salts; the current density of the roughening treatment is 15-30 A / dm 2 ;

[0041] The solidification solution of the solidification treatment comprises 50-70 g / L of copper ions and 80-100 g / L of sulfuric acid; the current density of the solidification treatment is 15-25 A / dm 2 ;

[0042] S3, sequentially performing blackening nickel plating treatment, graying zinc plating treatment and passivation chromium plating treatment on the electrolytic green foil obtained in step S2;

[0043] S4, coating the surface of the electrolytic green foil obtained in step S3 with a silane coupling agent, and drying to obtain the electrolytic copper foil.

[0044] In the preparation method of the electrolytic copper foil provided by the application, the electrolytic green foil is first prepared, and the preparation method of the electrolytic green foil is performed according to a method well known to those skilled in the art, which is not particularly limited in the application, and the preparation method of the electrolytic green foil is specifically as follows:

[0045] An additive solution containing a leveling agent, a brightener and an inhibitor is prepared, wherein the leveling agent is selected from at least one of benzotriazole, 2-mercaptobenzimidazole and 2-tetrahydrothiazoline thione, the brightener is selected from at least one of polydithiopropane sulfonic acid sodium, polyethyl cellulose and sodium dodecyl sulfonate, the inhibitor is polyethylene glycol, and the mass ratio of the leveling agent, the brightener and the inhibitor is 3:2:1, and the total concentration of the additives is 30-50 mg / L;

[0046] 80-90 g / L of copper ions, 90-110 g / L of sulfuric acid and 8-15 mg / L of chloride ions are used as raw materials, a current density of 60-80 A / dm 2 is applied to the cathode roller and the insoluble anode at a temperature of 50°C, and the electrolytic green foil is continuously wound on the guide roller.

[0047] The electrolytic green foil is then subjected to acid washing and water washing in sequence, the acid washing solution of the acid washing has a copper ion concentration of ≤5 g / L, a sulfuric acid concentration of 50-100 g / L, a temperature of 30-40 °C, and a flow rate of 8-12 m 3 / h, specifically, the acid washing solution of the acid washing has a copper ion concentration of 1-4 g / L, a sulfuric acid concentration of 60-80 g / L, a temperature of 33-37 °C, and a flow rate of 10-11 m 3 / h. The acid washing is to remove the oxide layer on the surface of the green foil.

[0048] According to the present application, the electrolytic green foil after water washing is subjected to low roughening treatment, and through the low roughening treatment, a copper foil with a low-roughness surface having the topographical feature of the present application is formed. The low roughening treatment comprises roughening treatment and solidification treatment in sequence, both of which are electroplating treatments; the roughening electroplating solution of the roughening treatment comprises 5-10 g / L of copper ions, 90-110 g / L of sulfuric acid, and 10-50 mg / L of a roughening additive, the roughening additive comprises one or more of metal salts; the current density of the roughening treatment is 15-30 A / dm 2 ; specifically, the concentration of copper ions in the roughening electroplating solution is 6-8 g / L, the concentration of sulfuric acid is 95-105 g / L, and the concentration of the roughening additive is 20-40 mg / L; the temperature of the electroplating solution is 40-50 °C, and the current density of the roughening treatment is 18-25 A / dm 2 . Specifically, the roughening additive is selected from one or more of zinc sulfate, titanium sulfate, molybdenum tungstate, and sodium molybdate; more specifically, the roughening additive is selected from zinc sulfate and titanium sulfate. The solidification solution of the solidification treatment comprises 50-70 g / L of copper ions and 80-100 g / L of sulfuric acid; the current density of the solidification treatment is 15-25 A / dm 2 ; specifically, the concentration of copper ions in the solidification solution is 55-65 g / L, the concentration of sulfuric acid is 85-93 g / L, and the current density is 18-23 A / dm 2 ; more specifically, the concentration of copper ions is 58-61 g / L, the concentration of sulfuric acid is 88-91 g / L, and the current density is 19-21 A / dm 2 .

[0049] In the step of the above low roughening treatment, specific additives are introduced and combined with the parameters of the roughening treatment, and then specific solidification treatment is performed, so that copper tumors with specific topography can grow on the surface of the green foil.

[0050] In order to avoid the above-mentioned oxidation of the electrolytic raw foil surface after the low roughening treatment, the electrolytic raw foil obtained above is then subjected to blackening nickel plating treatment, graying zinc plating treatment and passivation chromium plating treatment, and the nickel plating treatment, zinc plating treatment and chromium plating treatment are all realized by using an electroplating process to realize the anti-oxidation treatment of the electrolytic raw foil; specifically, the nickel plating solution for the blackening nickel plating treatment comprises 15-25 g / L of nickel ions and 25-35 g / L of boric acid, the temperature is 40-50°C, and the current density is 8-12 A / dm 2 ; specifically, the concentration of nickel ions in the nickel plating solution is 18-22 g / L, the concentration of boric acid is 28-33 g / L, the temperature is 43-48°C, and the current density is 9-11 A / dm 2 ; more specifically, the concentration of nickel ions in the nickel plating solution is 19-20 g / L, the concentration of boric acid is 29-30 g / L, the temperature is 45-47°C, and the current density is 10 A / dm 2 .

[0051] The zinc plating solution for the graying zinc plating treatment comprises 3-10 g / L of zinc ions and 25-35 g / L of boric acid, the temperature is 40-50°C, and the current density is 10-20 A / dm 2 ; specifically, the concentration of zinc ions in the zinc plating solution is 4-8 g / L, the concentration of boric acid is 28-33 g / L, the temperature is 42-47°C, and the current density is 12-18 A / dm 2 ; more specifically, the concentration of zinc ions in the zinc plating solution is 5-7 g / L, the concentration of boric acid is 30-32 g / L, the temperature is 45-46°C, and the current density is 15-17 A / dm 2 .

[0052] The chromium plating solution for the passivation chromium plating treatment comprises 1-5 g / L of chromium ions, the temperature is 25-35°C, and the current density is 20-30 A / dm 2 ; specifically, the concentration of chromium ions in the chromium plating solution is 2-3 g / L, the temperature is 27-30°C, and the current density is 18-22 A / dm 2 .

[0053] The electrolytic raw foil obtained above is finally subjected to silanization treatment, specifically, a silane coupling agent solution is coated on the surface of the electrolytic raw foil obtained above, the silane coupling agent is well known to those skilled in the art, and an acrylic-based silane coupling agent is used in the present application; the concentration of the silane coupling agent in the silane coupling agent solution is 0.8-1.2 wt%, and the solvent is water. The above-mentioned blackening nickel plating treatment, graying zinc plating treatment, passivation chromium plating treatment and silanization treatment are preferably performed on both sides of the raw foil.

[0054] Further, the application also provides a printed circuit board, which comprises a substrate and a copper foil formed on the surface of the substrate, the copper foil being the electrolytic copper foil described in the above-mentioned solution; the printed circuit board can only comprise the substrate and the copper foil, and the low-roughness surface of the copper foil is arranged on the side of the substrate; the printed circuit board can be in a sandwich structure, and the copper foil is arranged between two substrates. In the printed circuit board, the substrate is a substrate well known to those skilled in the art, for example, the substrate can be a polyphenylene oxide resin (PPO). The printed circuit board can be used in communication, radar and electronic products.

[0055] The application also provides application of the above-mentioned electrolytic copper foil in a battery, in particular in a lithium ion battery, which can be applied in automobile power batteries, energy storage systems and consumer electronics.

[0056] The application provides an electrolytic copper foil with low roughness, which has the following beneficial effects:

[0057] 1. By optimizing the topographic features of the low-roughness surface, the copper tumors are in the form of rod-shaped or granular protrusions, and the distance between two adjacent protrusions is 10-650 nm. The copper tumors are further limited in a specific height range (the height of the rod-shaped protrusions is 300-800 nm, and the height of the granular protrusions is 80-250 nm) and a density range (the sum of the number of rod-shaped and granular protrusions per 25 μm 2 area is 50-150), so that the surface topography of the copper foil is more uniform and has smaller high-low undulations, which not only effectively reduces the surface roughness, improves the signal integrity of the copper foil substrate, solves the problem of large signal transmission loss in the prior art, but also is beneficial to improving the peeling strength between the copper foil and the substrate and overcoming the defect of insufficient peeling strength in the prior art;

[0058] 2. By controlling the surface roughness of the electrolytic copper foil (the laser confocal test Rz is 0.5-1.5 μm, and the Sdr is 2-5%), the surface flatness of the electrolytic copper foil is further optimized, and the signal integrity of the copper foil substrate under high-frequency transmission is ensured;

[0059] 3. The anti-peeling strength measured after the electrolytic copper foil is pressed with a PPO resin is ≥0.8 N / mm, which can meet the peeling strength requirement between the copper foil and the resin substrate, and solves the problem of low yield of end products caused by insufficient peeling strength in the prior art;

[0060] 4. The electrical performance loss of the PCB board processed by pressing with a PPO resin is between-0.6 and-0.8 dB / in at 16 GHz, which meets the demand of high-speed and high-frequency signal transmission and overcomes the defect of large electrical performance loss in the prior art.

[0061] In summary, by using the low-roughness electrolytic copper foil of the present application, since the electrolytic copper foil has specific surface topography and / or surface characteristics, the peel strength between the micro-roughness electrolytic copper foil and the resin substrate in the copper foil substrate can not only meet the specifications of the industry's desired peel strength, but also the degree of insertion loss of such copper foil substrate under high-frequency transmission can be as far as possible inhibited or reduced, thereby improving the high-frequency signal transmission performance of such copper foil substrate applied to high-frequency high-speed electronic products.

[0062] In order to further understand the present application, the electrolytic copper foil and the preparation method thereof provided by the present application are described in detail below in conjunction with examples, and the protection scope of the present application is not limited by the following examples.

[0063] The following examples and comparative examples were prepared, and the surface and interface topography of the electrolytic copper foil was observed, and the performance test was carried out using the following methods:

[0064] A) Surface and cross-section topography observation

[0065] A scanning electron microscope (TESCAN VEGA3) was used to observe the surface topography of each sample to be tested, with an inclination angle of 40° and magnifications of 5000x and 8000x;

[0066] A ZEISS FE-SEM Sigma 300 field emission scanning electron microscope was used to observe the cross-section sample of the copper foil at a magnification of 30000x;

[0067] B) Performance test

[0068] (1) Surface roughness Rz and Sdr test: Rz and Sdr test was carried out using an Olympus OLS5100 laser confocal microscope at an objective magnification of 50x; Rz: the sum of the average height of the five highest peaks and the average depth of the five lowest valleys within the sampling length; Sdr: interface expansion area ratio, which indicates how much the interface area (surface area) has increased relative to the surface area of the interface region;

[0069] (2) Peel strength test: the copper foil prepared in the present application was laminated with prepreg (4 pieces of glass transition temperature of 200℃ were placed between the upper and lower copper foils), and then hot-pressed, wherein the hot-pressing temperature was between 230℃, the surface pressure was 25kg / cm 2 , and the time was 120min;

[0070] The copper-clad plate after hot-pressing was cut into a sample with a width of 3.0mm using a cutting knife; then the copper foil on one side of the copper-clad plate was peeled off 1-2cm using a craft knife, and the peeled copper foil was fixed to one end of the weight; finally, the peel strength test was carried out on the peel strength tester by moving the weight to drive the copper foil;

[0071] (3) Electrical performance loss test: using the hot-pressed copper clad plate to make the sample for electrical performance loss test, and measuring the transmission loss in high frequency bandwidth; in the evaluation of electrical performance loss, using the network analyzer to measure the insertion loss of each sample to be tested at 16 GHz frequency; the sample making method and test method are based on the Delta L method proposed by INTEL.

[0072] Example 1

[0073] A method for preparing a low-roughness electrolytic copper foil, comprising the following steps:

[0074] (1) Electrolytic green foil: preparing an additive solution containing leveling agent, brightener and inhibitor, in the additive solution, the leveling agent is 2-mercaptobenzimidazole, the brightener is sodium polydithiopropanesulfonate, and the inhibitor is polyethylene glycol, the mass ratio of the leveling agent, the brightener and the inhibitor is 3:2:1, and the total concentration of the additives is 30 mg / L; using 90 g / L of copper ion concentration, 110 g / L of sulfuric acid concentration and 10 mg / L of chloride ion concentration as raw materials, applying a current density of 60 A / dm 2 on the cathode roller and insoluble anode at a temperature of 50°C to continuously wind on the guide roller to obtain a 35 μm thick green foil;

[0075] (2) Pickling: moving the prepared green foil roll to a surface treatment equipment, the winding speed of the surface treatment equipment is 15 m / min, first performing pickling to remove the oxidation layer on the surface of the green foil, and then performing water washing after pickling, the copper ion concentration of the pickling solution is ≤5 g / L, the sulfuric acid concentration is 80 g / L, the temperature is maintained at 35±2°C, and the flow rate is 10 m 3 / h;

[0076] (3) Low roughening treatment: performing two steps, first step: roughening treatment: using 10 g / L of copper ion concentration and 110 g / L of sulfuric acid concentration as raw materials, and adding 20 mg / L of roughening additive to obtain a roughening plating solution, the roughening solution temperature is maintained at 45±2°C, and the current density is 25 A / dm 2 ;

[0077] (4) Blackening and nickel plating treatment: using 20 g / L of nickel ion concentration and 30 g / L of boric acid concentration as raw materials, the temperature is controlled at 45±2°C, and the current density is 10 A / dm2;

[0078] (5) Graying and zinc plating treatment: using 5 g / L of zinc ion concentration and 30 g / L of boric acid concentration as raw materials, the temperature is controlled at 40±2°C, and the current density is 15 A / dm2;

[0079] (6) Passivation chromium plating treatment: with 1 g / L chromium ion concentration as raw material, temperature control at 30±2℃, current density is 18A / dm 2 ;

[0080] (7) Silane coupling agent coating: the silane coupling agent is acrylic-based silane coupling agent, the concentration is 1wt%, water is used as solvent for dilution;

[0081] (8) Drying and winding: the silane coupling agent treated raw foil is dried in 120℃ oven and then wound, to obtain low roughness electrolytic copper foil.

[0082] Example 1 is the low roughness electrolytic copper foil prepared by the present application, the surface copper tumor morphology contains both rod-shaped protrusions and granular protrusions, the surface morphology and cross-sectional morphology of the copper foil are shown in Figure 1 、 Figure 2 and Figure 3 ; wherein, Figure 1 is the surface morphology scanning electron micrograph observed at 5000 times magnification, which can show that the electrolytic copper foil prepared in this example has rod-shaped protrusions and granular protrusions rough surface morphology, Figure 2 is the surface morphology scanning electron micrograph observed at 8000 times magnification, the range framed by the dashed box in the figure represents an area of 25μm2, which can show that the electrolytic copper foil prepared in this example has rod-shaped protrusions and granular protrusions rough surface morphology, Figure 3 is the cross-sectional field emission scanning electron micrograph observed at 30000 times magnification, which can show that the electrolytic copper foil prepared in this example has rod-shaped protrusions and granular protrusions rough cross-sectional morphology, part of the rod-shaped protrusions height is represented by the green scale, the granular protrusions height is represented by the black scale, and the distance between adjacent two protrusions is represented by the blue scale.

[0083] As can be seen from Figure 2 , the low roughness electrolytic copper foil of Example 1 has the following morphological characteristics: (1) the surface copper tumor morphology contains both rod-shaped protrusions and granular protrusions, Figure 2 the area marked as 23 in the figure is a typical rod-shaped protrusion, and the area marked as 24 is a typical granular protrusion, the copper tumor morphology of the above two areas still includes rod-shaped protrusions and granular protrusions, the key is that the rod-shaped protrusions and granular protrusions corresponding to the above two areas are more representative and can be visually distinguished;(2) Figure 2 the proportion of rod-shaped protrusions in the figure is 65%; (3) Figure 2 the sum of the number of rod-shaped protrusions and granular protrusions in the area marked as 21 in the figure is 88, Figure 2 the sum of the number of rod-shaped protrusions and granular protrusions in the area marked as 22 in the figure is 102,Figure 2 The sum of the number of rod-shaped projections and granular projections in the region marked as 23 is 86, Figure 2 The sum of the number of rod-shaped projections and granular projections in the region marked as 24 is 108, Figure 3 The sum of the number of rod-shaped projections and granular projections in the region marked as 25 is 114.

[0084] From Figure 4 It can be seen that the low-roughness electrolytic copper foil of Example 1 has the following characteristics: (1) the rod-shaped projection height is 446.6 nm, 495.3 nm, 422.2 nm, 374.4 nm, 312.6 nm, 532.5 nm, 651.7 nm; (2) the granular projection height is 90.2 nm, 192.4 nm, 201.1 nm; (3) the distance between adjacent two projections is 72.3 nm, 216.4 nm, 17.5 nm.

[0085] Example 2

[0086] The preparation method is basically the same as that of Example 1, except that the thickness of the green foil is 18 μm.

[0087] Example 3

[0088] The preparation method is basically the same as that of Example 1, except that in the low-roughening treatment of step (3): the current density applied in the first roughening treatment is 22 A / dm2; the current density applied in the second solidification treatment is 17 A / dm 2 .

[0089] Example 4

[0090] The preparation method is basically the same as that of Example 1, except that in the low-roughening treatment of step (3): the current density applied in the first roughening treatment is 27 A / dm2; the current density applied in the second solidification treatment is 17 A / dm 2 .

[0091] Example 5

[0092] The preparation method is basically the same as that of Example 1, except that in the low-roughening treatment of step (3): the current density applied in the first roughening treatment is 27 A / dm2; the current density applied in the second solidification treatment is 20 A / dm 2 .

[0093] Comparative Example 1

[0094] Comparative Example 1 is an HVLP-specification electrolytic copper foil produced by Company A.

[0095] The surface morphology of the copper foil of this comparative example is as ​As shown, the surface morphology is obviously different from the low roughness electrolytic copper foil of the examples, not only the shape of the copper tumor cluster is aggregated growth, but also the surface protrusions are mainly needle-shaped protrusions, and the size of the copper tumor is obviously larger than that in the examples.

[0096] Comparative Example 2

[0097] The preparation method is basically the same as that of Example 1, except that no roughening additive is added in step (3).

[0098] The morphology data of the electrolytic copper foils prepared in the above examples and Comparative Example 2 are shown in Table 1:

[0099] Table 1 Morphology data of the electrolytic copper foils prepared in the examples and Comparative Example 2

[0100]

[0101]

[0102] The Rz value, Sdr value, and peel strength of the electrolytic copper foils prepared in the examples and Comparative Example are tested by laser confocal microscopy, and the electrical performance loss value of the PCB board processed by pressing the electrolytic copper foil and PPO resin at 16 GHz is shown in Table 2.

[0103] Table 2 Performance data of the PCB board obtained in the examples and Comparative Example

[0104]

[0105] According to the above experimental results, by controlling the surface morphology of the low roughness electrolytic copper foils of Examples 1-5, optimizing the morphology characteristics, the copper tumors are in the form of rod-shaped and granular protrusions, and the distance between adjacent two protrusions is 10-650 nm, and at the same time, the copper tumors are limited in a specific height range (the height of the rod-shaped protrusion is 300-800 nm, and the height of the granular protrusion is 80-250 nm) and density range (the number of rod-shaped and granular protrusions in each 25 μm 2 area is 50-150), the surface morphology of the electrolytic copper foil is more uniform and has smaller high-low undulation, which not only effectively reduces the surface roughness, so that the Rz value is in the range of 0.8-1.2 and the Sdr value is in the range of 2.8%-4.1%, but also makes the peel strength >0.8 N / mm and the 16 GHz insertion loss in the range of -0.66 to -0.74 dB / in, so as to comprehensively inhibit or reduce the degree of insertion loss at 16 GHz high frequency on the copper foil substrate under the premise of meeting the industry's expectation of peel strength, and further improve the high-frequency signal transmission efficiency of electronic products.

[0106] The comparative example 1 has not only the shape of the cluster growth of the copper tumor, but also the surface protrusions mainly in the form of needle-shaped protrusions, the surface topography has a relatively large ups and downs, and the size of the copper tumor is obviously larger than that in the examples, so the anti-peeling strength is higher than that in the examples, but the 16GHz insertion loss is-0.89dB / in, which is more difficult to meet the transmission requirements of high-frequency signals.

[0107] In the low roughening process of the comparative example 2, no additives are added, so that the proportion of rod-shaped protrusions is as high as 90%, although the anti-peeling strength is higher, but the roughness is also higher, and the 16GHz insertion loss is-0.96dB / in, which is more difficult to meet the transmission requirements of high-frequency signals.

[0108] In summary, by controlling the surface topography and surface properties of the low-roughened electrolytic copper foil, the degree of the insertion loss of the high-frequency downlink transmission caused by the copper foil on the copper foil substrate can be inhibited or reduced under the premise of meeting the industry's expected peeling strength, thereby improving the high-frequency signal transmission efficiency of electronic products.

[0109] The above description of the examples is only used to help understand the method of the present application and its core idea. It should be pointed out that for those skilled in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

[0110] The above description of the disclosed examples enables those skilled in the art to implement or use the present application. Various modifications to the examples will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other examples without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the examples shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An electrolytic copper foil having at least one low-roughness surface, characterized in that: The copper nodules on the low-roughness surface are rod-shaped protrusions and / or granular protrusions, the distance between two adjacent protrusions is 10 to 650 nm, the height of the copper nodules of the rod-shaped protrusions is 300 to 800 nm, and the height of the copper nodules of the granular protrusions is 80 to 250 nm; and every 25 μm of the low-roughness surface 2 Within the area, the number of the rod-shaped copper nodules and / or the granular protrusions is 50 to 150.

2. The electrolytic copper foil according to claim 1, wherein The copper nodules on the low-roughness surface are in the form of rod-shaped protrusions and granular protrusions, and the rod-shaped protrusions account for 60-80% of the total number of the rod-shaped protrusions and the granular protrusions.

3. The electrolytic copper foil according to claim 1 or 2, characterized in that The distance between the two adjacent protrusions is 12 to 450 nm.

4. The electrolytic copper foil according to claim 1 or 2, characterized in that The height of the rod-shaped copper nodules is 310 to 750 nm, and / or the height of the granular copper nodules is 85 to 230 nm.

5. The electrolytic copper foil according to claim 1 or 2, characterized in that Each 25 μm 2 Within the area, the number of the rod-shaped copper nodules and / or the granular protrusions is 80 to 140.

6. The method for preparing the electrolytic copper foil according to claim 1, comprising the following steps: S1, sequentially pickling and washing the electrolytic raw foil; S2, roughening the surface of the electrolytic green foil obtained in step S1, and then curing it; The roughening electroplating solution for the roughening treatment includes 5-10 g / L of copper ions, 90-110 g / L of sulfuric acid and 10-50 mg / L of a roughening additive, wherein the roughening additive includes one or more metal salts; the current density of the roughening treatment is 15-30 A / dm 2 ; The curing liquid for the curing treatment includes 50-70 g / L of copper ions and 80-100 g / L of sulfuric acid; the current density for the curing treatment is 15-25 A / dm 2 ; S3, sequentially subjecting the electrolytic raw foil obtained in step S2 to blackening nickel plating, ashing zinc plating, and passivation chromium plating; S4. Performing silanization treatment on the surface of the electrolytic raw foil obtained in step S3, and drying to obtain electrolytic copper foil.

7. The preparation method according to claim 6, characterized in that In step S1, the copper ion concentration in the pickling solution is ≤5g / L, the sulfuric acid concentration is 50-100g / L, the temperature is 30-40°C, and the flow rate is 8-12m 3 / h; and / or, in step S2, the temperature of the roughening plating solution is 40-50°C; and / or, in step S2, the copper ion concentration of the solidifying solution is 55-65g / L.

8. The preparation method according to claim 6, characterized in that In step S3, the nickel plating solution for the black nickel plating treatment includes 15-25 g / L nickel ions, 25-35 g / L boric acid, a temperature of 40-50°C, and a current density of 8-12 A / dm 2 and / or, the zinc plating solution of the ashing zinc plating treatment comprises 3 to 10 g / L of zinc ions, 25 to 35 g / L of boric acid, a temperature of 40 to 50 ° C, a current density of 10 to 20 A / dm 2 and / or, the chromium plating solution of the passivation chromium plating treatment comprises 1 to 5 g / L of chromium ions, a temperature of 25 to 35 ° C, a current density of 15 to 25 A / dm 2 .

9. A printed circuit board comprising a substrate and a copper foil formed on a surface of the substrate, wherein the copper foil is the electrolytic copper foil according to any one of claims 1 to 5 or the electrolytic copper foil prepared by the preparation method according to any one of claims 6 to 8.

10. Use of the electrolytic copper foil according to any one of claims 1 to 5 or the electrolytic copper foil prepared by the preparation method according to any one of claims 6 to 8 in batteries.

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