A multilayer structure copper foil, a preparation method and a printed circuit board

Abstract

This invention relates to the field of electrolysis technology, and in particular to a multilayer copper foil, its preparation method, and a printed circuit board. The multilayer copper foil comprises a first copper foil layer, a second copper foil layer, and a third copper foil layer; a first insulating coating layer disposed between the first and second copper foil layers; a second insulating coating layer disposed between the second and third copper foil layers; and a surface roughening layer disposed on the side of the third copper foil layer away from the second insulating coating layer. This invention provides a multilayer copper foil, unlike traditional single-layer copper foil where the thickness is fixed during production (e.g., a 12μm thickness at the production end), which downstream printed circuit board manufacturers will use to match their processing technology to the 12μm copper foil specification. The key to the multilayer copper foil designed in this invention is its multilayer insulating coating layer and copper foil layer structure, wherein the temperature resistance of the multiple insulating coating layers varies.

Description

Technical Field

[0001] This invention relates to the field of electrolysis technology, and in particular to a multilayer copper foil, its preparation method, and a printed circuit board. Background Technology

[0002] Copper foil is an ultra-thin copper material widely used in the electronics industry, printed circuit boards (PCBs), lithium batteries, electromagnetic shielding, and other fields. Its thinness and conductivity make it indispensable in microelectronics and high-precision engineering.

[0003] Electrolytic copper foil is produced through an electrolytic process, using a pure copper plate as the anode and employing an electrochemical reaction to deposit copper ions onto a rotating cathode to form the foil. Electrolytic copper foil has a rough surface and uniform thickness, making it suitable for applications requiring precise bonding and conductivity. It is primarily used in electronic circuit boards (such as printed circuit boards) and as a negative electrode current collector in lithium-ion batteries.

[0004] In the fields of printed circuit board (PCB) processing and integrated circuit (IC) manufacturing, copper foil is an important raw material widely used in various terminal electronic devices. The thickness of the copper foil is one of the key factors affecting its performance and application scenarios. Traditional copper foil manufacturing technology typically involves depositing copper ions from a solution onto a substrate via electroplating to form a uniform metallic copper layer. Based on the thickness of the copper layer, the industry classifies copper foil into thick copper foil (thickness greater than 70μm), standard thickness copper foil (between 18μm and 70μm), thin copper foil (between 12μm and 18μm), and ultra-thin copper foil (thickness less than 12μm). These copper foils of different thicknesses are widely used in multiple fields due to their unique physical and chemical properties.

[0005] Thick copper foil is primarily used in high-power, high-current, and high-heat-dissipation applications. Copper foil thicker than 70μm is commonly used in high-power, high-current, and high-heat-dissipation-requirement electronic devices due to its low resistance and high heat dissipation performance, such as inverters for new energy vehicles, charging piles, and ECUs (on-board computers). Thick copper foil effectively reduces heat load, improving equipment reliability and lifespan.

[0006] Standard thickness copper foil is primarily used in circuit board manufacturing and related electronic components. Copper foil with a thickness between 18μm and 70μm is widely used in circuit board manufacturing as a conductive layer to connect electronic components and the circuit board, ensuring stable signal transmission. It is also suitable for electronic components with high precision requirements, such as capacitors and inductors.

[0007] Thin and ultra-thin copper foils are mainly used in high-speed, high-frequency circuits and miniaturized devices. Ultra-thin copper foils with a thickness of less than 12μm are particularly suitable for high-frequency circuits and miniaturized devices, such as high-speed signal transmission lines in portable electronic products like mobile phones and tablets, due to their low resistance and high frequency response characteristics.

[0008] Traditional copper foil manufacturing technology cannot meet the requirements of different application scenarios for copper foil thickness. Different thicknesses of copper foil need to be prepared for different application scenarios, resulting in too many categories of copper foil products, complicated product design, and increased production changeover and management costs. Summary of the Invention

[0009] To solve the above-mentioned technical problems, the present invention provides a multilayer copper foil, the multilayer copper foil comprising a first copper foil layer, a second copper foil layer and a third copper foil layer; a first isolation coating disposed between the first copper foil layer and the second copper foil layer; a second isolation coating disposed between the second copper foil layer and the third copper foil layer; and a surface roughening layer disposed on the side of the third copper foil layer away from the second isolation coating.

[0010] In one embodiment of the present invention, the thickness of the first copper foil layer is selected from 9μm, 35μm, and 18μm.

[0011] In one embodiment of the present invention, the thickness of the second copper foil layer is selected from 1.5μm, 5μm, and 3μm.

[0012] In one embodiment of the present invention, the thickness of the third copper foil layer is selected from 1.5μm, 5μm, and 3μm.

[0013] A second aspect of this invention provides a method for preparing a multilayer copper foil, comprising the following steps:

[0014] (1) The first copper foil layer is prepared:

[0015] Using sulfuric acid containing 110 g / L and Cu 2+ An electrolyte solution of CuSO4·5H2O with an ion concentration of 97 g / L was used at a temperature of 54 °C with a flow rate of 36 A / dm³. 2 Electrolysis was performed at a current density for 25 seconds to obtain a first copper foil layer with a thickness of 9 μm.

[0016] (2) Pre-treatment of the first copper foil layer:

[0017] Use sulfuric acid with a concentration of 85 g / L, and immerse both sides of the first copper foil layer in the treatment solution at a temperature of 40°C for 20 seconds, then wait for use.

[0018] (3) Apply the first layer of isolation coating:

[0019] The pretreated first copper foil layer is immersed in the electrolyte of the first isolation coating layer to prepare the isolation coating layer; thus, the first copper foil layer + the first isolation coating layer is obtained.

[0020] The chromic anhydride concentration in the electrolyte for the adhesion layer was 0.5 g / L, and the electrolyte temperature was 45℃. After 12 seconds of electroplating, the surface metal was removed by immersion rinsing, and then the metal was physically adsorbed into an organic adhesion solution. This organic adhesion solution was 3 g / L Se-propylene-based selenium cysteine ​​sulfoxide, and the temperature of the adhesion solution was 35℃, with an immersion time of 20 seconds. After drying in a forced-air oven at 150℃, the first isolation coating was obtained.

[0021] (4) Prepare the first copper foil layer + the first isolation coating layer + the second copper foil layer.

[0022] The first copper foil layer + first isolation coating structure obtained in step (3) is then introduced into a solution containing sulfuric acid and Cu with a concentration of 110 g / L. 2+ In a CuSO4·5H2O electrolyte with an ion concentration of 97 g / L, at a temperature of 54 °C, at a flow rate of 20 A / dm³... 2 Electrolysis was performed at a current density for 8 seconds to obtain the structure: first copper foil layer + first insulating coating layer + second copper foil layer;

[0023] (5) Prepare a first copper foil layer + a first isolation coating layer + a second copper foil layer + a second isolation coating layer.

[0024] After the first copper foil layer, the first isolation coating layer, and the second copper foil layer are prepared, they are immersed in the second isolation coating adhesion solution to coat the second isolation copper layer. The adhesion solution contains 5 g / L of tris(2-hydroxyethyl)amine, the temperature of the adhesion solution is 35℃, and the immersion and adsorption time is 20 s. After drying in a forced-air oven at 150℃, the second isolation coating layer is obtained.

[0025] (6) Prepare a first copper foil layer + a first isolation coating layer + a second copper foil layer + a second isolation coating layer + a third copper foil layer.

[0026] The structure prepared in step (5) is then introduced into a solution containing sulfuric acid at a concentration of 110 g / L and Cu. 2+ CuSO4·5H2O with an ion concentration of 97 g / L was used in an electrolyte at 54 °C with a flow rate of 20 A / dm³. 2 Electrolysis was performed at a current density for 8 seconds to obtain a third copper layer with a thickness of 1.5 μm.

[0027] (7) Prepare multilayer copper foil

[0028] The structure obtained in step (6) can be obtained by surface roughening treatment.

[0029] In one embodiment of the present invention, the first isolation coating is an organic adhering substance containing non-copper metal; wherein the non-copper metal is selected from one or more of nickel, titanium, molybdenum, and chromium; and the organic adhering substance is one or more of selenium-containing organic matter, sodium-containing organic matter, or amino-containing organic matter.

[0030] In one embodiment of the present invention, when the thickness of the first copper foil layer is 9 μm, the thickness of the second copper foil layer is 1.5 μm, and the thickness of the third copper foil layer is 1.5 μm, the raw materials for preparing the first isolation coating layer include:

[0031] Electrolyte for the adhesion layer: chromium anhydride, sulfuric acid, RC-25K.

[0032] Organic adhering solution: a solution of Se-propylene-selenocysteine ​​sulfoxide mixed with deionized water.

[0033] In one embodiment of the present invention, the second coating layer is selected from one or more organic compounds containing glycerol, amines or triazoles.

[0034] In one embodiment of the present invention, when the thickness of the first copper foil layer is 9 μm, the thickness of the second copper foil layer is 1.5 μm, and the thickness of the third copper foil layer is 1.5 μm, the raw materials for preparing the second isolation coating layer include:

[0035] Organic adhering liquid: a solution of tri(2-hydroxyethyl)amine and deionized water.

[0036] A third aspect of the present invention provides a printed circuit board prepared from the aforementioned multilayer copper foil.

[0037] By adopting the above technical solution, the present invention has the following beneficial effects:

[0038] 1. This invention employs a multilayer electroplating process; by depositing multiple layers of isolation coating and copper layer on a substrate, different coatings at different locations can be peeled off after heating at different temperatures. Thus, by controlling the heating temperature, the thickness of the copper foil can be adjusted according to the circuit board processing requirements, improving product compatibility.

[0039] 2. This invention provides a multi-layer copper foil structure. Compared to traditional single-layer copper foil, whose thickness is fixed during production (e.g., 12μm), downstream printed circuit board manufacturers will match their processing technology to the 12μm copper foil specification. The key to the multi-layer copper foil structure designed in this invention is its multi-layer isolation coating and copper foil layers, where the isolation coatings have different temperature resistances. Some coatings fail after being heated above a certain temperature, losing their peelability, while the remaining coatings have higher temperature resistance and retain their peelability after being heated to the same temperature. By peeling off some copper layers during downstream use, the copper foil thickness can be reduced, thus meeting the different thickness requirements of various downstream applications.

[0040] 3. The multi-layered copper foil designed in this invention, due to its multi-layered insulating coating and copper foil structure, can be separated into copper foils of various thicknesses depending on the heating temperature during downstream processing. For example, the copper foil designed in this invention has a total thickness of 12μm, which is composed of stacked 1.5μm, 1.5μm, and 9μm copper foils, with an insulating coating between each layer. During downstream processing, peeling off the 1.5μm and 9μm copper foils yields a copper foil with a thickness of 1.5μm. If the temperature is too high (e.g., 280℃), all insulating coatings will fail, and the multi-layered copper foil cannot be separated, ultimately resulting in a 12μm copper foil. Therefore, the copper foil of this invention can be made into copper foil products of different thicknesses depending on the temperature, improving the compatibility of copper foil products, and allowing one product to meet different downstream thickness requirements. Attached Figure Description

[0041] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0042] Figure 1 This invention provides an interface diagram of a multilayer copper foil structure.

[0043] Wherein, 1-first copper layer; 2-first isolation coating; 3-second copper foil; 4-second isolation coating; 5-third copper layer; 6-surface roughening layer.

[0044] Figure 2 The attached images show the surface morphology of the products obtained in Examples 1 to 4. Figure 2-1 ~Attached Figure 2 -4 corresponds to Examples 1 to 4 respectively.

[0045] Appendix Figure 3This is a diagram showing the separation force performance after pressing at 250℃. Detailed Implementation

[0046] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Example 1

[0048] This embodiment provides a multilayer copper foil, which includes a first copper foil layer, a second copper foil layer, and a third copper foil layer; a first isolation coating layer disposed between the first copper foil layer and the second copper foil layer; a second isolation coating layer disposed between the second copper foil layer and the third copper foil layer; and a surface roughening layer disposed on the side of the third copper foil layer away from the second isolation coating layer.

[0049] In this embodiment, the thickness of the first copper foil layer is 9 μm, the thickness of the second copper foil layer is 1.5 μm, and the thickness of the third copper foil layer is 1.5 μm.

[0050] The second aspect of this embodiment provides a method for preparing a multilayer copper foil, the steps of which are as follows:

[0051] (1) The first copper foil layer is prepared:

[0052] Using sulfuric acid containing 110 g / L and Cu 2+ An electrolyte solution of CuSO4·5H2O with an ion concentration of 97 g / L was used at a temperature of 54 °C with a flow rate of 36 A / dm³. 2 Electrolysis was performed at a current density for 25 seconds to obtain a first copper foil layer with a thickness of 9 μm.

[0053] (2) Pre-treatment of the first copper foil layer:

[0054] Use sulfuric acid with a concentration of 85 g / L, and immerse both sides of the first copper foil layer in the treatment solution at a temperature of 40°C for 20 seconds, then wait for use.

[0055] (3) Apply the first layer of isolation coating:

[0056] The first copper foil layer after the pretreatment in step (2) is immersed in the metal electrolyte of the first isolation coating layer, with a current surface density of 1.5 A / dm. 2The electrolyte temperature is 45℃. After 12 seconds of electroplating, the surface metal liquid is removed by immersion rinsing tank, and then the metal is physically adsorbed in an organic adhesion solution at 35℃ for 20 seconds. After drying in a forced-air oven at 150℃, the first copper foil layer and the first isolation coating layer are obtained.

[0057] The electrolyte for the adhesion layer metal contains: chromium trioxide, sulfuric acid, and RC-25K, wherein the concentration of chromium trioxide is 0.5 g / L, the concentration of sulfuric acid is 5 g / L, and the concentration of RC-25K is 16 ml / L;

[0058] The organic adhering solution is a mixture of Se-propylene-selenocysteine ​​sulfoxide and deionized water with a concentration of 3 g / L.

[0059] (4) Prepare the first copper foil layer + the first isolation coating layer + the second copper foil layer.

[0060] The first copper foil layer + first isolation coating structure obtained in step (3) is then introduced into a solution containing sulfuric acid and Cu with a concentration of 110 g / L. 2+ In a CuSO4·5H2O electrolyte with an ion concentration of 97 g / L, at a temperature of 54 °C, at a flow rate of 20 A / dm³... 2 Electrolysis was performed at a current density for 8 seconds to obtain the structure: first copper foil layer + first insulating coating layer + second copper foil layer;

[0061] (5) Prepare a first copper foil layer + a first isolation coating layer + a second copper foil layer + a second isolation coating layer.

[0062] After the first copper foil layer, the first isolation coating layer, and the second copper foil layer are prepared, they are immersed in the second isolation coating adsorption solution to apply the second isolation copper layer. The second isolation coating adsorption solution is a solution of tri(2-hydroxyethyl)amine and deionized water with a concentration of 5 g / L, an adsorption solution temperature of 35℃, and an immersion adsorption time of 20 s. After drying in a forced-air oven at 150℃, the second isolation coating layer is obtained.

[0063] (6) Prepare a first copper foil layer + a first isolation coating layer + a second copper foil layer + a second isolation coating layer + a third copper foil layer.

[0064] The structure prepared in step (5) is then introduced into a solution containing sulfuric acid at a concentration of 110 g / L and Cu. 2+ CuSO4·5H2O with an ion concentration of 97 g / L was used in an electrolyte at 54 °C with a flow rate of 20 A / dm³. 2 Electrolysis was performed at a current density for 8 seconds to obtain a third copper layer with a thickness of 1.5 μm.

[0065] (7) Prepare multilayer copper foil

[0066] The structure obtained in step (6) was introduced into a sulfuric acid solution with a concentration of 90 g / L and Cu. 2+ In a copper sulfate electrolyte with an ion concentration of 25 g / L, the third copper foil layer is opposite to the anode plate, while the first copper foil layer is far from the anode plate, at a current of 14 A / dm. 2 An initial surface roughening layer was obtained by electroplating at an average current density for 12 seconds. Then, sulfuric acid with a concentration of 95 g / L and Cu were further introduced. 2+ The curing electroplating was carried out in a copper sulfate solution with an ion concentration of 55 g / L and an electroplating current density of 15 A / dm³. 2 The electroplating time is 15 seconds. Then, the electrolyte is added with a sulfuric acid concentration of 75 g / L and a cobalt concentration of 10 g / L. The electrolysis temperature is 40℃, and the current density is 12 A / dm³. 2 The electroplating time was 10 seconds; finally, the electrolysis was carried out at a sulfuric acid concentration of 85 g / L, a zinc concentration of 18 g / L, an electrolysis temperature of 45℃, and a current density of 10 A / dm³. 2 The electroplating time is 10 seconds. Finally, the surface electrolyte or water stains are removed by spraying water washing and drying in an oven, and the multilayer copper foil can be prepared.

[0067] The multilayer copper foil structure prepared in this embodiment can produce copper foils of different thicknesses under different temperature pressing conditions.

[0068] For example: when the bonding temperature with the prepreg is higher than 280°C, the first and second isolation coatings in the multilayer copper foil structure ( Figure 1 Both steps 2 and 4) failed, and the copper layer could not be peeled off from the interlayer after the pressing was completed, resulting in a copper-clad laminate with an attached copper foil thickness of 12 μm (Example 1-1).

[0069] For example: when the bonding temperature with the prepreg is between 230-280℃, the second isolation coating ( Figure 1 (4) Failure, first layer of isolation coating ( Figure 1 (2) It still retains the peelable properties. After the lamination is completed, a 9μm thick copper foil can be peeled off from the surface of the prepreg, leaving a 3μm thick copper foil on the surface of the copper-clad laminate. (Examples 1-2)

[0070] For example, when the lamination temperature with the prepreg is below 210°C, both the first and second isolation coatings in the multilayer copper foil structure remain effective, maintaining peelability after lamination. After peeling off a 9μm copper layer and a 1.5μm copper layer along the first and second isolation coatings respectively, a copper foil with a final thickness of 1.5μm remains on the copper-clad laminate surface. (Examples 1-3)

[0071] The copper-clad laminate prepared by the multilayer copper foil in this embodiment can be processed by coating a photosensitive film, exposure, development, copper plating, film removal, etching, surface treatment, and cutting to obtain a printed circuit board made of the multilayer copper foil.

[0072] Example 2

[0073] The difference between this embodiment and Embodiment 1 is that:

[0074] The first insulating coating layer's electrolyte comprises: 6.5 g / L nickel chloride hexahydrate, 8 g / L titanium oxysulfate, and 20 g / L boric acid, with a pH of 5 (current density 0.3 A / dm³). 2 Electroplating time 7s);

[0075] The organic adhesive liquid of the first isolation coating layer is sodium benzenesulfinate (a mixture of sodium benzenesulfinate and deionized water) with a concentration of 3 g / L.

[0076] The second isolation coating is a 0.5 wt% triacetyl ester (a mixture of triacetyl ester and deionized water).

[0077] In this embodiment, after lamination with a prepreg at 280°C, both the first and second isolation coating layers fail, resulting in a copper-clad laminate with an attached copper foil thickness of 12 μm. After lamination with a prepreg at 230-280°C, the second isolation coating layer fails, resulting in a copper-clad laminate with an attached copper foil thickness of 10.5 μm. After lamination with a prepreg at a temperature below 210°C, both the first and second copper layers can be effectively separated, resulting in a copper-clad laminate with an attached copper foil thickness of 1.5 μm.

[0078] Example 3

[0079] The difference from Example 2 is that the thickness of the first copper foil layer is adjusted to 35 μm; the thickness of the second copper foil layer is adjusted to 5 μm; and the thickness of the third copper foil layer is adjusted to 5 μm.

[0080] After lamination with a prepreg at 300℃, both the first and second isolation coating layers failed, resulting in a copper-clad laminate with an attached copper foil thickness of 40μm. After lamination with a prepreg at 250℃, the second isolation coating layer failed, resulting in a copper-clad laminate with an attached copper foil thickness of 10μm. After lamination with a prepreg at 210℃, both the first and second copper layers could be effectively separated, resulting in a copper-clad laminate with an attached copper foil thickness of 5μm.

[0081] Example 4

[0082] The difference from Example 1 is that the thickness of the first copper layer was adjusted to 18 μm; the thickness of the second copper layer was adjusted to 3 μm; and the thickness of the third copper layer was adjusted to 3 μm.

[0083] The type of the first isolation coating was adjusted. The electrolyte for the first isolation coating layer consisted of sodium molybdate at a concentration of 8 g / L and potassium pyrophosphate at a concentration of 10 g / L. The electroplating pH was 9.5 (current density 0.5 A / dm³). 2 Electroplating time: 7 seconds.

[0084] The organic adhesive liquid of the first isolation coating layer is N-methyldiethanolamine (a mixture of N-methyldiethanolamine and deionized water) with a concentration of 3 g / L.

[0085] The second isolation coating is a 2 g / L solution of 1-hydroxybenzotriazole (a mixture of 1-hydroxybenzotriazole and deionized water).

[0086] After lamination with a prepreg at 300℃, both the first and second isolation coating layers failed, resulting in a copper-clad laminate with an attached copper foil thickness of 24μm. After lamination with a prepreg at 250℃, the second isolation coating layer failed, resulting in a copper-clad laminate with an attached copper foil thickness of 6μm. After lamination with a prepreg at 210℃, both the first and second copper layers could be effectively separated, resulting in a copper-clad laminate with an attached copper foil thickness of 3μm.

[0087] Comparative Example 1:

[0088] The difference between this comparative example and Example 1 is that the isolation coating was omitted, and the second and third copper layers were deposited directly after the first copper layer electrodeposition.

[0089] Comparative Example 1, after being pressed with a prepreg at temperatures of 300℃, 250℃, and 210℃, could only produce copper-clad laminates with an attached copper foil thickness of 12μm.

[0090] Performance testing:

[0091] Test 1: See attachment Figure 2 , attached Figure 2-1 ~Attached Figure 2 -4 shows the surface morphology of the products obtained in Examples 1 to 4, which can effectively obtain thinner copper foils with excellent performance and are not affected by the isolation layer.

[0092] Test 2: See attachment Figure 3 The diagram shows the separation force performance after pressing at 250℃.

[0093] Test 3: See Table 1, which is the performance data table for Examples 1-4.

[0094] Table 1 Performance data for Examples 1-4

[0095]

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multilayer copper foil, characterized in that, The multilayer copper foil includes a first copper foil layer, a second copper foil layer, and a third copper foil layer; a first insulating coating layer disposed between the first copper foil layer and the second copper foil layer; and a second insulating coating layer disposed between the second copper foil layer and the third copper foil layer. and a surface roughening layer disposed on the side of the third copper foil layer away from the second isolation coating layer; Wherein: the thickness of the first copper foil layer is selected from one of 9μm, 35μm, and 18μm; The thickness of the second copper foil layer is selected from one of 1.5μm, 5μm, and 3μm; The thickness of the third copper foil layer is selected from one of 1.5μm, 5μm, and 3μm.

2. The method for preparing a multilayer copper foil according to claim 1, characterized in that, The steps are as follows: (1) The first copper foil layer is prepared: Using sulfuric acid containing 110 g / L and Cu 2+ Electrolysis was performed using a CuSO4·5H2O electrolyte with an ion concentration of 97 g / L to obtain a first copper foil layer with a thickness of 1. (2) Pretreatment of the first copper foil layer: Use sulfuric acid with a concentration of 85 g / L, and immerse both sides of the first copper foil layer in the treatment solution at a temperature of 40°C for 20 seconds, then wait for use. (3) Apply the first layer of isolation coating: The pretreated first copper foil layer is immersed in the electrolyte of the first isolation coating to prepare the isolation coating; The first copper foil layer + the first isolation coating layer are obtained; (4) A first copper foil layer + a first isolation coating layer + a second copper foil layer are prepared. The first copper foil layer + first isolation coating structure obtained in step (3) is then introduced into a solution containing sulfuric acid and Cu with a concentration of 110 g / L. 2+ Electrolysis was performed in a CuSO4·5H2O electrolyte with an ion concentration of 97 g / L to obtain a structure of: first copper foil layer + first isolation coating layer + second copper foil layer; (5) A first copper foil layer + a first isolation coating layer + a second copper foil layer + a second isolation coating layer are prepared. After the first copper foil layer, the first isolation coating layer, and the second copper foil layer are prepared, they are immersed in the second isolation coating coating solution to coat the second isolation copper layer. (6) A first copper foil layer + a first isolation coating layer + a second copper foil layer + a second isolation coating layer + a third copper foil layer is prepared. The structure prepared in step (5) is then introduced into a solution containing sulfuric acid at a concentration of 110 g / L and Cu. 2+ Electrolysis of CuSO4·5H2O with an ion concentration of 97 g / L yielded a third copper foil layer. (7) A multilayer copper foil was prepared. The structure obtained in step (6) can be obtained by surface roughening treatment.

3. The method for preparing a multilayer copper foil according to claim 2, characterized in that, The first isolation coating is an organic adhering substance containing non-copper metal; wherein the non-copper metal is selected from one or more of nickel, titanium, molybdenum, and chromium; and the organic adhering substance is one or more of selenium-containing organic matter, sodium-containing organic matter, or amino-containing organic matter.

4. The method for preparing a multilayer copper foil according to claim 3, characterized in that, When the thickness of the first copper foil layer is 9 μm, the thickness of the second copper foil layer is 1.5 μm, and the thickness of the third copper foil layer is 1.5 μm, the raw materials for preparing the first isolation coating layer include: Adhesive layer metal electrolyte: chromic anhydride, sulfuric acid, RC-25K Organic adhering solution: a solution of Se-propylene-selenocysteine ​​sulfoxide mixed with deionized water.

5. The method for preparing a multilayer copper foil according to claim 2, characterized in that, The second coating layer is selected from one or more organic compounds containing glycerol, amines, or triazoles.

6. The method for preparing a multilayer copper foil according to claim 5, characterized in that, When the thickness of the first copper foil layer is 9 μm, the thickness of the second copper foil layer is 1.5 μm, and the thickness of the third copper foil layer is 1.5 μm, the raw materials for preparing the second isolation coating layer include: Organic adhering liquid: a solution of tris(2-hydroxyethyl)amine mixed with deionized water.

7. A printed circuit board, characterized in that, It is prepared from the multilayer copper foil described in claim 1.

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