Strippable carrier ultrathin copper foil and preparation method thereof

Abstract

The invention belongs to the technical field of electrolytic copper foils, and relates to a strippable carrier ultrathin copper foil and a preparation method thereof.The strippable carrier ultrathin copper foil comprises a carrier layer, a stripping layer and an ultrathin copper foil layer, the stripping layer comprises an inorganic stripping layer and an organic stripping layer, and the thickness of the ultrathin copper foil layer is 3-5 microns; and the ultrathin copper foil layer is prepared by adopting an alkaline copper plating process and an acidic copper plating process in sequence. According to the method, the compact and smooth copper plating layer is obtained through alkaline copper plating firstly, then acid copper plating is conducted, and the ultrathin copper layer which is few in pinhole and can be stably peeled off is prepared through the process that the two modes are combined.

Description

Technical Field

[0001] The invention belongs to the technical field of electrolytic copper foil and relates to an ultra-thin copper foil with a peelable carrier and a preparation method thereof. Background Art

[0002] With the recent miniaturization of electronic devices, ultra-thin copper foil with a thickness of approximately 5μm or less has been adopted as an electronic raw material for printed circuit boards. This ultra-thin copper foil is extremely thin and easily wrinkles during processing, making it inconvenient to use. To address this issue, a composite copper foil is currently used, in which the ultra-thin copper foil is attached to a carrier (support). Ultra-thin copper foil laminates can be formed by laminating a resin substrate to the ultra-thin copper layer of this composite copper foil through heating and pressing, and then peeling the carrier layer off. In this case, a release layer exists between the carrier layer and the ultra-thin copper layer, allowing the ultra-thin copper layer to be separated. Organic release layers coated with organic materials (such as benzotriazole) are commonly used as release layers. However, due to the low heat resistance of organic materials, the organic material in the release layer decomposes at temperatures of approximately 300°C during subsequent processing, such as prepreg pressing and precision casting. This can cause the carrier layer and ultra-thin copper layer to come into close contact, resulting in poor release performance or, in worse cases, inability to peel the ultra-thin copper layer from the carrier layer. Recently, there have been studies on the use of metal oxides in the peeling layer. These can inhibit the interdiffusion that may occur between the carrier and the ultra-thin copper layer during high-temperature or long-term hot pressing, thereby ensuring the stability of the carrier's peel strength. However, this peeling layer has grain boundaries unique to metals, and these grain boundaries grow along a specific direction, forming small bumps on the surface, which may cause defects such as pinholes in the ultra-thin copper layer. Summary of the Invention

[0003] In view of the shortcomings of the above-mentioned prior art, the present invention provides a peelable carrier ultra-thin copper foil and a preparation method thereof, which is an ultra-thin copper foil with a thickness of less than 5 μm and relatively appropriate, uniform and stable peel strength. The specific technical solution is as follows: The first object of the present invention is to provide a peelable carrier ultra-thin copper foil, comprising a carrier layer, a peeling layer and an ultra-thin copper foil layer, wherein the peeling layer comprises an inorganic peeling layer and an organic peeling layer, and the thickness of the ultra-thin copper foil layer is 3-5 μm; the ultra-thin copper foil layer is prepared by alkaline copper plating and acid copper plating processes in sequence.

[0004] The invention adopts a process combining alkaline copper plating to obtain a dense and smooth copper plating layer and then acid copper plating to prepare an ultra-thin copper layer with few pinholes and stable peeling.

[0005] Furthermore, the carrier layer is an electrolytic copper foil with a thickness of 18-70 μm, and the roughness of the smooth surface is Rz≤2.5 μm.

[0006] A second object of the present invention is to provide a method for preparing the above-mentioned peelable carrier ultra-thin copper foil, comprising the following steps: (1) Pretreatment of the carrier layer; (2) electroplating nickel on the surface of the carrier layer as an inorganic stripping layer; (3) forming an organic peeling layer on the inorganic peeling layer; (4) Electroplating an ultra-thin copper foil layer on the organic peeling layer using alkaline copper plating and acid copper plating processes in sequence.

[0007] Furthermore, in step (1), the carrier layer is pretreated by pickling the carrier layer with a sulfuric acid solution having a mass fraction of 5-15 wt%.

[0008] Furthermore, in step (2), the nickel sulfate concentration in the nickel electroplating electrolyte is 10-20 g / L, the temperature is 40-50°C, and the current density is 2-6 A / dm 2 , electroplating time 6-10S.

[0009] Furthermore, in step (3), the organic stripping layer is prepared by immersing in a solution having a carboxybenzotriazole (CBTA) concentration of 0.4-1 g / L, a sulfuric acid concentration of 50-150 g / L, and a copper concentration of 10-30 g / L, the solution temperature being 25-35° C., and the immersion time being 10-30 seconds.

[0010] Furthermore, in step (4), the concentration of copper pyrophosphate in the electrolyte of the alkaline copper plating process is 10-50 g / L, the concentration of potassium pyrophosphate is 80-240 g / L, the concentration of diammonium hydrogen citrate is 0.1-1.5 g / L, the concentration of 2-mercaptobenzimidazole is 0.5-15 ppm, the electrolyte temperature is 25-55 ° C, the pH is 8-12, and the current density is 1-10 / dm 2 , the electroplating time is 12-120S.

[0011] Furthermore, in step (4), the electrolyte of the acid copper plating process has a copper sulfate concentration of 200-400 g / L, a sulfuric acid concentration of 100-200 g / L, a sodium polydisulfide dipropane sulfonate concentration of 30-50 ppm, a hydroxyethyl cellulose concentration of 10-20 ppm, a chloride ion concentration of 30-50 ppm, an electrolyte temperature of 35-55°C, and a current density of 30-100 A / dm 2 , the electroplating time is 10-35S.

[0012] Furthermore, in step (4), the concentration of copper pyrophosphate in the electrolyte of the alkaline copper plating process is 15-45 g / L, the concentration of potassium pyrophosphate is 100-220 g / L, the concentration of diammonium hydrogen citrate is 0.3-1.2 g / L, the concentration of 2-mercaptobenzimidazole is 1-12 ppm, the electrolyte temperature is 30-50 ° C, the pH is 8.5-11.5, and the current density is 2-8 A / dm 2 , the electroplating time is 15-60S.

[0013] Furthermore, in step (4), the concentration of copper pyrophosphate in the electrolyte of the alkaline copper plating process is 20-40 g / L, the concentration of potassium pyrophosphate is 120-200 g / L, the concentration of diammonium hydrogen citrate is 0.5-1.0 g / L, the concentration of 2-mercaptobenzimidazole is 3-10 ppm, the electrolyte temperature is 35-45 ° C, the pH is 9-11, and the current density is 3-6 A / dm 2 , the electroplating time is 20-40S.

[0014] The beneficial effects of the present invention are: The present invention adopts a process combining alkaline copper plating to obtain a dense and smooth copper coating, followed by acidic copper plating, to prepare an ultra-thin copper layer with few pinholes and stable peelability. The alkaline copper plating uses copper pyrophosphate as a main component, potassium pyrophosphate as a complexing agent, and diammonium hydrogen citrate as a brightener. The addition of 2-mercaptobenzimidazole can increase the current density of the plating solution, making the coating bright and having a good leveling effect, which is conducive to forming a dense copper coating. After laminating a resin substrate onto the ultra-thin copper layer through heating and pressing, the carrier layer can be stably peeled off, while the occurrence of pinholes can be reduced, and the mechanical properties are good. The acidic copper plating process is simple, easy to operate, has low equipment cost, and has a high copper plating speed, so a thicker copper layer can be obtained in a shorter time. DETAILED DESCRIPTION

[0015] The principles and features of the present invention are described below in conjunction with embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0016] Example 1 A peelable carrier ultra-thin copper foil, the preparation method comprising the following steps: (1) Carrier layer pretreatment: The electrolytic copper foil carrier layer with a thickness of 18 μm and a smooth surface roughness Rz ≤ 2.5 μm was pickled with a sulfuric acid solution with a mass fraction of 10 wt%; (2) Formation of inorganic stripping layer: The polished surface of the pickled carrier copper foil was electroplated in a nickel plating electrolyte with a nickel sulfate concentration of 15 g / L, a temperature of 45 °C, and a current density of 4 A / dm 2 , electroplating time 8S, the smooth surface of the carrier copper foil forms an inorganic release layer; (3) Formation of organic release layer: After the smooth surface of the carrier copper foil on which the inorganic release layer was formed was washed with water, it was immersed in a solution containing carboxybenzotriazole (CBTA), wherein the concentration of carboxybenzotriazole (CBTA) was 0.8 g / L, the concentration of sulfuric acid was 100 g / L, and the concentration of copper was 20 g / L. The solution temperature was 30°C and the immersion time was 20 seconds. An organic release layer was further formed on the inorganic release layer on the smooth surface of the carrier copper foil. (4) Alkaline copper plating: The smooth surface of the carrier copper foil forming the organic release layer is washed with water and then electroplated in an alkaline copper plating electrolyte, wherein the concentration of copper pyrophosphate is 20 g / L, the concentration of potassium pyrophosphate is 120 g / L, the concentration of diammonium hydrogen citrate is 0.5 g / L, the concentration of 2-mercaptobenzimidazole is 3 ppm, the temperature is 35 ° C, the pH is 9, and the current density is 3 A / dm 2 , electroplating time is 20S; (5) Acid copper plating: After washing the smooth surface of the carrier copper foil after alkaline copper plating, electroplating is carried out in an acid copper plating electrolyte, wherein the copper sulfate concentration is 300g / L, the sulfuric acid concentration is 150g / L, the sodium polydisulfide dipropylene sulfonate concentration is 40ppm, the hydroxyethyl cellulose concentration is 15ppm, the chloride ion concentration is 40ppm, the temperature is 45℃, and the current density is 40A / dm 2 , the electroplating time is 25S, and an ultra-thin copper foil with a thickness of 5μm is obtained.

[0017] Example 2 A peelable carrier ultra-thin copper foil, the preparation method comprising the following steps: (1) Carrier layer pretreatment: The electrolytic copper foil carrier layer with a thickness of 35 μm and a smooth surface roughness Rz ≤ 2.5 μm was pickled with a sulfuric acid solution with a mass fraction of 10 wt%; (2) Formation of inorganic stripping layer: The polished surface of the pickled carrier copper foil was electroplated in a nickel plating electrolyte with a nickel sulfate concentration of 18 g / L, a temperature of 47 °C, and a current density of 5 A / dm 2 , electroplating time 7S, the smooth surface of the carrier copper foil forms an inorganic release layer; (3) Formation of organic release layer: After the smooth surface of the carrier copper foil on which the inorganic release layer was formed was washed with water, it was immersed in a solution containing carboxybenzotriazole (CBTA), wherein the concentration of carboxybenzotriazole (CBTA) was 0.8 g / L, the concentration of sulfuric acid was 130 g / L, and the concentration of copper was 25 g / L. The solution temperature was 25°C and the immersion time was 18 seconds. An organic release layer was further formed on the inorganic release layer on the smooth surface of the carrier copper foil. (4) Alkaline copper plating: The smooth surface of the carrier copper foil forming the organic release layer is washed with water and then electroplated in an alkaline copper plating electrolyte, wherein the concentration of copper pyrophosphate is 40 g / L, the concentration of potassium pyrophosphate is 200 g / L, the concentration of diammonium hydrogen citrate is 1.0 g / L, the concentration of 2-mercaptobenzimidazole is 10 ppm, the temperature is 45 ° C, the pH is 11, and the current density is 6 A / dm 2 , electroplating time is 40S; (5) Acid copper plating: After washing the smooth surface of the carrier copper foil after alkaline copper plating, electroplating is carried out in an acid copper plating electrolyte, wherein the copper sulfate concentration is 320g / L, the sulfuric acid concentration is 160g / L, the sodium polydisulfide dipropylene sulfonate concentration is 35ppm, the hydroxyethyl cellulose concentration is 13ppm, the chloride ion concentration is 30ppm, the temperature is 50℃, and the current density is 50A / dm 2 , the electroplating time is 15S, and an ultra-thin copper foil with a thickness of 3μm is obtained.

[0018] Example 3 A peelable carrier ultra-thin copper foil, the preparation method comprising the following steps: (1) Carrier layer pretreatment: The electrolytic copper foil carrier layer with a thickness of 18 μm and a smooth surface roughness Rz ≤ 2.5 μm was pickled with a sulfuric acid solution with a mass fraction of 10 wt%; (2) Formation of inorganic stripping layer: The polished surface of the pickled carrier copper foil was electroplated in a nickel plating electrolyte with a nickel sulfate concentration of 12 g / L, a temperature of 43 °C, and a current density of 3 A / dm 2 , electroplating time 7S, the smooth surface of the carrier copper foil forms an inorganic release layer; (3) Formation of organic release layer: After the smooth surface of the carrier copper foil on which the inorganic release layer was formed was washed with water, it was immersed in a solution containing carboxybenzotriazole (CBTA), wherein the concentration of carboxybenzotriazole (CBTA) was 0.5 g / L, the concentration of sulfuric acid was 75 g / L, and the concentration of copper was 15 g / L. The solution temperature was 23°C and the immersion time was 12 seconds. An organic release layer was further formed on the inorganic release layer on the smooth surface of the carrier copper foil. (4) Alkaline copper plating: The smooth surface of the carrier copper foil forming the organic release layer is washed with water and then electroplated in an alkaline copper plating electrolyte, wherein the concentration of copper pyrophosphate is 30 g / L, the concentration of potassium pyrophosphate is 165 g / L, the concentration of diammonium hydrogen citrate is 0.8 g / L, the concentration of 2-mercaptobenzimidazole is 6 ppm, the temperature is 40 ° C, the pH is 10, and the current density is 4 A / dm 2 , electroplating time is 30S; (5) Acid copper plating: After washing the smooth surface of the carrier copper foil after alkaline copper plating, electroplating is carried out in an acid copper plating electrolyte, wherein the concentration of copper sulfate is 200g / L, the concentration of sulfuric acid is 110g / L, the concentration of sodium polydisulfide propane sulfonate is 30ppm, the concentration of hydroxyethyl cellulose is 10ppm, the concentration of chloride ions is 50ppm, the temperature is 38℃, and the current density is 60A / dm 2 , the electroplating time is 20S, and an ultra-thin copper foil with a thickness of 5μm is obtained.

[0019] Example 4 A peelable carrier ultra-thin copper foil, the preparation method comprising the following steps: (1) Carrier layer pretreatment: The electrolytic copper foil carrier layer with a thickness of 18 μm and a smooth surface roughness Rz ≤ 2.5 μm was pickled with a sulfuric acid solution with a mass fraction of 10 wt%; (2) Formation of inorganic stripping layer: The polished surface of the pickled carrier copper foil was electroplated in a nickel plating electrolyte with a nickel sulfate concentration of 20 g / L, a temperature of 50 °C, and a current density of 6 A / dm 2 , electroplating time 6S, the smooth surface of the carrier copper foil forms an inorganic release layer; (3) Formation of organic release layer: After the smooth surface of the carrier copper foil on which the inorganic release layer was formed was washed with water, it was immersed in a solution containing carboxybenzotriazole (CBTA), wherein the concentration of carboxybenzotriazole (CBTA) was 1 g / L, the concentration of sulfuric acid was 150 g / L, and the concentration of copper was 30 g / L. The solution temperature was 35°C and the immersion time was 30 seconds. An organic release layer was further formed on the inorganic release layer on the smooth surface of the carrier copper foil. (4) Alkaline copper plating: The smooth surface of the carrier copper foil forming the organic release layer is washed with water and then electroplated in an alkaline copper plating electrolyte, wherein the concentration of copper pyrophosphate is 25g / L, the concentration of potassium pyrophosphate is 140g / L, the concentration of diammonium hydrogen citrate is 0.6g / L, the concentration of 2-mercaptobenzimidazole is 5ppm, the temperature is 38℃, the pH is 10, and the current density is 5A / dm 2 , electroplating time is 35S; (5) Acid copper plating: After washing the smooth surface of the carrier copper foil after alkaline copper plating, electroplating is carried out in an acid copper plating electrolyte, wherein the concentration of copper sulfate is 400g / L, the concentration of sulfuric acid is 200g / L, the concentration of sodium polydisulfide propane sulfonate is 50ppm, the concentration of hydroxyethyl cellulose is 20ppm, the concentration of chloride ions is 50ppm, the temperature is 55℃, and the current density is 80A / dm 2 , the electroplating time is 11S, and an ultra-thin copper foil with a thickness of 4μm is obtained.

[0020] Example 5 A peelable carrier ultra-thin copper foil, the preparation method comprising the following steps: (1) Carrier layer pretreatment: The electrolytic copper foil carrier layer with a thickness of 18 μm and a smooth surface roughness Rz ≤ 2.5 μm was pickled with a sulfuric acid solution with a mass fraction of 10 wt%; (2) Formation of inorganic stripping layer: The polished surface of the pickled carrier copper foil was electroplated in a nickel plating electrolyte with a nickel sulfate concentration of 10 g / L, a temperature of 40 °C, and a current density of 2 A / dm 2 , electroplating time 10S, the smooth surface of the carrier copper foil forms an inorganic release layer; (3) Formation of organic release layer: After the smooth surface of the carrier copper foil on which the inorganic release layer was formed was washed with water, it was immersed in a solution containing carboxybenzotriazole (CBTA), wherein the concentration of carboxybenzotriazole (CBTA) was 0.4 g / L, the concentration of sulfuric acid was 50 g / L, and the concentration of copper was 10 g / L. The solution temperature was 25°C and the immersion time was 10 seconds. An organic release layer was further formed on the inorganic release layer on the smooth surface of the carrier copper foil. (4) Alkaline copper plating: The smooth surface of the carrier copper foil forming the organic release layer is washed with water and then electroplated in an alkaline copper plating electrolyte, wherein the concentration of copper pyrophosphate is 38 g / L, the concentration of potassium pyrophosphate is 170 g / L, the concentration of diammonium hydrogen citrate is 0.9 g / L, the concentration of 2-mercaptobenzimidazole is 8 ppm, the temperature is 42 ° C, the pH is 11, and the current density is 4 A / dm 2 , electroplating time is 28S; (5) Acid copper plating: After washing the smooth surface of the carrier copper foil after alkaline copper plating, electroplating is carried out in an acid copper plating electrolyte, wherein the copper sulfate concentration is 200g / L, the sulfuric acid concentration is 100g / L, the sodium polydisulfide dipropylene sulfonate concentration is 30ppm, the hydroxyethyl cellulose concentration is 10ppm, the chloride ion concentration is 30ppm, the temperature is 35℃, and the current density is 55A / dm 2 , the electroplating time is 13S, and an ultra-thin copper foil with a thickness of 3μm is obtained.

[0021] Comparative Example 1 A carrier ultra-thin copper foil, the preparation method comprising the following steps: (1) Carrier layer pretreatment: The electrolytic copper foil carrier layer with a thickness of 18 μm and a smooth surface roughness Rz ≤ 2.5 μm was pickled with a sulfuric acid solution with a mass fraction of 10 wt%; (2) Formation of inorganic stripping layer: The polished surface of the pickled carrier copper foil was electroplated in a nickel plating electrolyte with a nickel sulfate concentration of 15 g / L, a temperature of 45 °C, and a current density of 4 A / dm 2 , electroplating time 8S, the smooth surface of the carrier copper foil forms an inorganic release layer; (3) Formation of organic release layer: After the smooth surface of the carrier copper foil on which the inorganic release layer was formed was washed with water, it was immersed in a solution containing carboxybenzotriazole (CBTA), wherein the concentration of carboxybenzotriazole (CBTA) was 0.8 g / L, the concentration of sulfuric acid was 100 g / L, and the concentration of copper was 20 g / L. The solution temperature was 30°C and the immersion time was 20 seconds. An organic release layer was further formed on the inorganic release layer on the smooth surface of the carrier copper foil. (4) Acid copper plating: The smooth surface of the carrier copper foil forming the organic peeling layer is washed with water and then electroplated in an acid copper plating electrolyte, wherein the concentration of copper sulfate is 300g / L, the concentration of sulfuric acid is 150g / L, the concentration of sodium polydisulfide dipropane sulfonate is 40ppm, the concentration of hydroxyethyl cellulose is 15ppm, the concentration of chloride ions is 40ppm, the temperature is 45℃, and the current density is 40A / dm 2 , the electroplating time is 25S, and an ultra-thin copper foil with a thickness of 5μm is obtained.

[0022] Comparative Example 2 A carrier ultra-thin copper foil, the preparation method comprising the following steps: (1) Carrier layer pretreatment: The electrolytic copper foil carrier layer with a thickness of 18 μm and a smooth surface roughness Rz ≤ 2.5 μm was pickled with a sulfuric acid solution with a mass fraction of 10 wt%; (2) Formation of inorganic stripping layer: The polished surface of the pickled carrier copper foil was electroplated in a nickel plating electrolyte with a nickel sulfate concentration of 15 g / L, a temperature of 45 °C, and a current density of 4 A / dm 2 , electroplating time 8S, the smooth surface of the carrier copper foil forms an inorganic release layer; (3) Formation of organic release layer: After the smooth surface of the carrier copper foil on which the inorganic release layer was formed was washed with water, it was immersed in a solution containing carboxybenzotriazole (CBTA), wherein the concentration of carboxybenzotriazole (CBTA) was 0.8 g / L, the concentration of sulfuric acid was 100 g / L, and the concentration of copper was 20 g / L. The solution temperature was 30°C and the immersion time was 20 seconds. An organic release layer was further formed on the inorganic release layer on the smooth surface of the carrier copper foil. (4) Alkaline copper plating: The smooth surface of the carrier copper foil forming the organic release layer is washed with water and then electroplated in an alkaline copper plating electrolyte with a copper pyrophosphate concentration of 20 g / L, a potassium pyrophosphate concentration of 120 g / L, and a diammonium hydrogen citrate concentration of 0.5 g / L. The temperature is 35°C, the pH is 9, and the current density is 3 A / dm 2 , electroplating time is 20S; (5) Acid copper plating: After washing the smooth surface of the carrier copper foil after alkaline copper plating, electroplating is carried out in an acid copper plating electrolyte, wherein the copper sulfate concentration is 300g / L, the sulfuric acid concentration is 150g / L, the sodium polydisulfide dipropylene sulfonate concentration is 40ppm, the hydroxyethyl cellulose concentration is 15ppm, the chloride ion concentration is 40ppm, the temperature is 45℃, and the current density is 40A / dm 2 , the electroplating time is 25S, and an ultra-thin copper foil with a thickness of 5μm is obtained.

[0023] Comparative Example 3 A carrier ultra-thin copper foil, the preparation method comprising the following steps: (1) Carrier layer pretreatment: The electrolytic copper foil carrier layer with a thickness of 18 μm and a smooth surface roughness Rz ≤ 2.5 μm was pickled with a sulfuric acid solution with a mass fraction of 10 wt%; (2) Formation of inorganic stripping layer: The polished surface of the pickled carrier copper foil was electroplated in a nickel plating electrolyte with a nickel sulfate concentration of 15 g / L, a temperature of 45 °C, and a current density of 4 A / dm 2 , electroplating time 8S, the smooth surface of the carrier copper foil forms an inorganic release layer; (3) Formation of organic release layer: After the smooth surface of the carrier copper foil on which the inorganic release layer was formed was washed with water, it was immersed in a solution containing carboxybenzotriazole (CBTA), wherein the concentration of carboxybenzotriazole (CBTA) was 0.8 g / L, the concentration of sulfuric acid was 100 g / L, and the concentration of copper was 20 g / L. The solution temperature was 30°C and the immersion time was 20 seconds. An organic release layer was further formed on the smooth surface of the carrier copper foil on the inorganic release layer. (4) Alkaline copper plating: The smooth surface of the carrier copper foil forming the organic release layer is washed with water and then electroplated in an alkaline copper plating electrolyte, wherein the concentration of copper pyrophosphate is 20 g / L, the concentration of potassium pyrophosphate is 120 g / L, the concentration of 2-mercaptobenzimidazole is 3 ppm, the temperature is 35 ° C, the pH is 9, and the current density is 3 A / dm 2 , electroplating time is 20S; (5) Acid copper plating: After washing the smooth surface of the carrier copper foil after alkaline copper plating, electroplating is carried out in an acid copper plating electrolyte, wherein the copper sulfate concentration is 300g / L, the sulfuric acid concentration is 150g / L, the sodium polydisulfide dipropylene sulfonate concentration is 40ppm, the hydroxyethyl cellulose concentration is 15ppm, the chloride ion concentration is 40ppm, the temperature is 45℃, and the current density is 40A / dm 2 , the electroplating time is 25S, and an ultra-thin copper foil with a thickness of 5μm is obtained.

[0024] test 1. Peel Strength Test: The ultra-thin copper foil carriers obtained in Examples 1-5 and Comparative Examples 1-3 were laminated onto an FR4 prepreg at a pressure of 11.5 MPa and a lamination temperature of 185°C to form a laminate. The laminated samples were cut into 25 mm × 100 mm strips and peeled using a 90-degree universal peel strength tester to measure the peel strength of the peel layer.

[0025] 2. Pinhole test: The ultra-thin copper layer of the carrier ultra-thin copper foil obtained in Examples 1-5 and Comparative Examples 1-3 was sealed together with a plastic film, and a 250 mm × 200 mm piece was cut. The carrier was peeled off and the copper foil was placed face up on a light box to record the number of pinholes.

[0026] Table 1. Peeling force and pinhole count of ultra-thin copper foil obtained from examples 1-5 and comparative examples 1-3

[0027] Note: In Table 1, MAX is the maximum peel force, MIN is the minimum peel force, and AVG is the average value of all peel force data within the sampling range of the test sample.

[0028] As can be seen from Table 1, the peeling force of the ultra-thin copper foil carriers obtained in Examples 1-5 is uniform and moderate, and the number of pinholes is also very small. However, compared with Example 1, Comparative Example 1 does not undergo alkaline copper plating, but only acid copper plating, and the peeling force of the ultra-thin copper foil carrier obtained is very large and uneven, and the number of pinholes is also relatively large; in Comparative Example 2, no 2-mercaptobenzimidazole is added to the alkaline copper plating electrolyte, and in Comparative Example 3, no diammonium hydrogen citrate is added to the alkaline copper plating electrolyte, the peeling force of the ultra-thin copper foil carrier obtained is relatively large and uneven, and the number of pinholes is also relatively large, indicating that the present invention adopts a process combining the two methods of first obtaining a dense and smooth copper plating layer through the synergistic effect of diammonium hydrogen citrate and 2-mercaptobenzimidazole in alkaline copper plating, and then acid copper plating to prepare an ultra-thin copper layer, which is conducive to forming a dense copper plating layer. After the resin substrate is laminated onto the ultra-thin copper layer by heating and pressing, the carrier layer can be stably peeled off while reducing the occurrence of pinholes.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A peelable carrier ultra-thin copper foil, characterized in that: It includes a carrier layer, a peeling layer and an ultra-thin copper foil layer. The peeling layer includes an inorganic peeling layer and an organic peeling layer. The thickness of the ultra-thin copper foil layer is 3-5μm. The ultra-thin copper foil layer is prepared by alkaline copper plating and acid copper plating processes in sequence.

2. The peelable carrier ultra-thin copper foil according to claim 1, characterized in that: The carrier layer is an electrolytic copper foil with a thickness of 18-70 μm, and the roughness Rz of the smooth surface is ≤ 2.5 μm.

3. A method for preparing a peelable carrier ultra-thin copper foil according to claim 1 or 2, characterized in that: The steps include: (1) Pretreatment of the carrier layer; (2) electroplating nickel on the surface of the carrier layer as an inorganic stripping layer; (3) forming an organic peeling layer on the inorganic peeling layer; (4) Electroplating an ultra-thin copper foil layer on the organic peeling layer using alkaline copper plating and acid copper plating processes in sequence.

4. The method for preparing a peelable carrier ultra-thin copper foil according to claim 3, characterized in that: In step (1), the carrier layer is pretreated by pickling the carrier layer with a sulfuric acid solution having a mass fraction of 5-15wt%.

5. The method for preparing a peelable carrier ultra-thin copper foil according to claim 3, characterized in that: In step (2), the nickel sulfate concentration in the nickel electroplating electrolyte is 10-20 g / L, the temperature is 40-50 ° C, and the current density is 2-6 A / dm 2 , electroplating time 6-10S.

6. The method for preparing a peelable carrier ultra-thin copper foil according to claim 3, characterized in that: In step (3), the organic stripping layer is prepared by immersing in a solution having a carboxybenzotriazole concentration of 0.4-1 g / L, a sulfuric acid concentration of 50-150 g / L, and a copper concentration of 10-30 g / L. The temperature of the solution is 25-35° C., and the immersion time is 10-30 seconds.

7. The method for preparing a peelable carrier ultra-thin copper foil according to claim 3, characterized in that: In step (4), the concentration of copper pyrophosphate in the electrolyte of the alkaline copper plating process is 10-50 g / L, the concentration of potassium pyrophosphate is 80-240 g / L, the concentration of diammonium hydrogen citrate is 0.1-1.5 g / L, the concentration of 2-mercaptobenzimidazole is 0.5-15 ppm, the electrolyte temperature is 25-55 ° C, the pH is 8-12, and the current density is 1-10 / dm 2 , the electroplating time is 12-120S.

8. The method for preparing a peelable carrier ultra-thin copper foil according to claim 3, characterized in that: In step (4), the electrolyte of the acid copper plating process has a copper sulfate concentration of 200-400 g / L, a sulfuric acid concentration of 100-200 g / L, a sodium polydisulfide dipropane sulfonate concentration of 30-50 ppm, a hydroxyethyl cellulose concentration of 10-20 ppm, a chloride ion concentration of 30-50 ppm, an electrolyte temperature of 35-55 ° C, and a current density of 30-100 A / dm 2 , the electroplating time is 10-35S.

9. The method for preparing a peelable carrier ultra-thin copper foil according to claim 7, characterized in that: In step (4), the concentration of copper pyrophosphate in the electrolyte of the alkaline copper plating process is 15-45 g / L, the concentration of potassium pyrophosphate is 100-220 g / L, the concentration of diammonium hydrogen citrate is 0.3-1.2 g / L, the concentration of 2-mercaptobenzimidazole is 1-12 ppm, the electrolyte temperature is 30-50 ° C, the pH is 8.5-11.5, and the current density is 2-8 A / dm 2 , the electroplating time is 15-60S.

10. The method for preparing a peelable carrier ultra-thin copper foil according to claim 9, characterized in that: In step (4), the concentration of copper pyrophosphate in the electrolyte of the alkaline copper plating process is 20-40 g / L, the concentration of potassium pyrophosphate is 120-200 g / L, the concentration of diammonium hydrogen citrate is 0.5-1.0 g / L, the concentration of 2-mercaptobenzimidazole is 3-10 ppm, the electrolyte temperature is 35-45 ° C, the pH is 9-11, and the current density is 3-6 A / dm 2 , the electroplating time is 20-40S.

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