Surface treatment method of rolled copper foil for adhesive-free copper-clad laminate, copper foil for adhesive-free flexible copper-clad laminate and application thereof

Abstract

The present invention belongs to the technical field of rolled copper foil surfaces, and specifically relates to a rolled copper foil surface treatment method, copper foil for adhesive-free flexible copper-clad laminates, and their applications. The rolled copper foil surface treatment method comprises the following steps: using the rolled copper foil as a cathode, performing a micro-roughening treatment in an electrolyte, thereby obtaining a micro-roughened layer on the copper foil; the electrolyte being an acidic solution of copper and nickel ions; immersing the copper foil with the micro-roughened layer in an alloy solution containing nickel ions for alloying treatment to obtain an alloyed layer; immersing the copper foil with the alloyed layer in an anti-oxidation solution containing chromium ions, zinc ions, and sodium sulfate for anti-oxidation treatment to obtain an anti-oxidation layer; and spraying a coupling agent solution on the surface of the anti-oxidation layer. A two-layer flexible copper-clad laminate prepared from the surface-treated rolled copper foil has a high oxidation resistance temperature and peel strength, and the polyimide film has high transparency after etching.

Description

Technical Field

[0001] The invention belongs to the technical field of surface treatment of rolled copper foil, and in particular relates to a surface treatment method of rolled copper foil, copper foil for adhesive-free flexible copper-clad laminates and applications thereof. Background Art

[0002] Flexible Copper Clad Laminate (FCCL) refers to a thin sheet-like composite material that can be repeatedly bent by covering an insulating substrate (polyimide film, polyester film or polynaphthyl ester film, etc.) with copper foil. Flexible printed circuit boards (FPCBs) made of it are mainly used in computer peripherals and displays, aircraft instruments, navigation and positioning devices, oil exploration equipment, missile tracking instruments, artificial satellites, space shuttles and spacecraft, police radios, portable cameras and digital cameras, medical electronic products, and circuit board busbars. Traditional flexible copper clad laminates can be divided into three-layer flexible copper clad laminates (3-Layer FCCL, also known as adhesive flexible copper clad laminates) and two-layer flexible copper clad laminates (2-Layer FCCL, also known as adhesive-free flexible copper clad laminates) according to the manufacturing process and product structure. The two-layer flexible copper clad laminate consists of a copper foil layer and a polyimide insulating dielectric layer. Compared with the three-layer flexible copper clad laminate, the two-layer flexible copper clad laminate has higher heat resistance, higher dimensional stability and better flexibility, and has a wider range of applications.

[0003] Adhesive-free copper-clad laminates (CCCLs) are laminates with no adhesive layer between the copper foil layer and the insulating substrate. The manufacturing process involves directly pressing the copper foil and thermoplastic polyimide together. After high-temperature pressing, baking, and curing, the CCL is obtained. CCLs have extremely high requirements for copper foil, with the following key characteristics: (1) high transparency of the etched polyimide film; (2) resistance to high-temperature oxidation; and (3) high peel strength.

[0004] As electronic products evolve toward lighter, thinner, shorter, smaller, and more highly integrated designs, higher demands are being placed on the high-temperature resistance of two-layer flexible copper-clad laminates (FCCLs), the substrates used in these products. The polyimide in these laminates has a high glass transition temperature (GTT), with a melting point higher than its decomposition temperature, resulting in excellent high-temperature resistance. This high-temperature resistance is primarily dependent on rolled copper foil. Producing high-temperature-resistant rolled copper foil is a pressing technical challenge. Summary of the Invention

[0005] In view of this, the present invention provides a copper foil surface treatment method, a copper foil for a glue-free copper clad laminate, and applications thereof. Treating the surface of the copper foil according to the surface treatment method provided by the present invention can significantly improve the high temperature resistance of the copper foil; the surface-treated copper foil is used to prepare a two-layer flexible copper clad laminate, which has a high oxidation resistance temperature and peel strength, and the polyimide film has high transparency after etching.

[0006] In order to solve the above technical problems, the present invention provides a surface treatment method for rolled copper foil, comprising the following steps:

[0007] The rolled copper foil is used as the cathode and subjected to micro-roughening treatment in an electrolyte to obtain a micro-roughening layer, wherein the electrolyte is an acidic solution of copper ions and nickel ions;

[0008] Immersing the copper foil with the micro-roughened layer in an alloy liquid for alloying to obtain an alloyed layer; the alloy liquid includes metal ions, and the metal ions include nickel ions;

[0009] Immersing the copper foil with the alloyed layer in an anti-oxidation solution for anti-oxidation treatment to obtain an anti-oxidation layer; the anti-oxidation solution comprises chromium ions, zinc ions and sodium sulfate;

[0010] A coupling agent solution is sprayed on the surface of the anti-oxidation layer.

[0011] Preferably, the current density of the micro-roughening treatment is 40 to 50 A / dm 2 The time of the micro-roughening treatment is 3 to 5 seconds; the temperature of the micro-roughening treatment is 30 to 40°C.

[0012] Preferably, the mass concentration of copper ions in the electrolyte is 8-15 g / L, the mass concentration of nickel ions in the electrolyte is 1-3 g / L; and the mass concentration of acid in the electrolyte is 100-120 g / L.

[0013] Preferably, the mass concentration of metal ions in the alloy liquid is 1 to 15 g / L;

[0014] The temperature of the alloying treatment is 25-35°C, and the current density of the alloying treatment is 30-50A / dm 2 The alloying treatment time is 10 to 20 seconds.

[0015] Preferably, the alloy liquid further comprises alloy ions and a complexing agent; the alloy ions are provided by alloy metal salts, and the alloy metal salts include one or two of nickel salts, cobalt salts, copper salts, tungsten salts and molybdenum salts; the mass concentration of the alloy ions in the alloy liquid is 1 to 15 g / L;

[0016] The complexing agent is an organic acid, and the mass concentration of the complexing agent in the alloy liquid is 30-50 g / L.

[0017] Preferably, the mass concentration of chromium ions in the anti-oxidation solution is 0.5-1 g / L, the mass concentration of zinc ions is 2-4 g / L, and the mass concentration of sodium sulfate is 15-20 g / L; the pH value of the anti-oxidation solution is 3-4;

[0018] The temperature of the anti-oxidation treatment is 20-30°C, and the current density of the anti-oxidation treatment is 2-5A / dm 2 The anti-oxidation treatment time is 5 to 10 seconds.

[0019] Preferably, the volume concentration of the coupling agent solution is 1-2%; the coupling agent solution is a silane coupling agent solution;

[0020] The spraying temperature is 25-35°C.

[0021] Preferably, before the micro-roughening treatment, the method further comprises: sequentially subjecting the copper foil to electrolytic degreasing treatment and pickling;

[0022] The current density of the electrolytic degreasing treatment is 20 to 50 A / dm 2 The electrolytic degreasing treatment time is 10 to 15 seconds;

[0023] The electrolyte for electrolytic degreasing treatment is an alkaline solution, and the volume concentration of the alkaline solution is 10-50%.

[0024] The present invention also provides a copper foil for a non-glue flexible copper-clad laminate obtained by treating the surface of the rolled copper foil according to the above technical solution. The copper foil for the non-glue flexible copper-clad laminate comprises a copper foil, a micro-roughening layer, an alloying layer, an anti-oxidation layer and a coupling agent film layer stacked in sequence; the alloying layer contains nickel, and the anti-oxidation layer contains chromium and zinc.

[0025] The present invention also provides the use of the rolled copper foil for the adhesive-free flexible copper-clad laminate described in the above technical solution in a two-layer flexible copper-clad laminate.

[0026] The present invention provides a surface treatment method for rolled copper foil, comprising the following steps: using the rolled copper foil as a cathode, performing a micro-roughening treatment in an electrolyte comprising an acidic solution of copper ions and nickel ions to obtain a micro-roughened layer; immersing the copper foil with the micro-roughened layer in an alloying solution to perform an alloying treatment to obtain an alloyed layer; the alloying solution comprises metal ions, including nickel ions; immersing the copper foil with the alloyed layer in an anti-oxidation solution to perform an anti-oxidation treatment to obtain an anti-oxidation layer; the anti-oxidation solution comprises chromium ions, zinc ions, and sodium sulfate; and spraying a coupling agent solution on the surface of the anti-oxidation layer. In the present invention, an alloy layer containing nickel is formed on the surface of the micro-roughened copper foil layer through the alloying treatment, thereby improving the corrosion resistance and high temperature resistance of the copper foil; and an anti-oxidation layer containing chromium and zinc is formed on the surface of the alloyed layer after the alloying treatment, thereby further improving the oxidation resistance, corrosion resistance, and high temperature resistance of the copper foil. Using rolled copper foil treated with the surface treatment method provided by the present invention to produce a two-layer flexible copper-clad laminate significantly improves the high-temperature resistance of the laminate. The two-layer flexible copper-clad laminate produced using the copper foil treated with the surface treatment method of the present invention exhibits high peel strength, and the polyimide film exhibits high transparency after etching. DETAILED DESCRIPTION

[0027] The present invention provides a surface treatment method for rolled copper foil, comprising the following steps:

[0028] The rolled copper foil is used as the cathode and subjected to micro-roughening treatment in an electrolyte to obtain a micro-roughening layer, wherein the electrolyte is an acidic solution of copper ions and nickel ions;

[0029] Immersing the copper foil with the micro-roughened layer in an alloy liquid for alloying to obtain an alloyed layer; the alloy liquid includes metal ions, and the metal ions include nickel ions;

[0030] Immersing the copper foil with the alloyed layer in an anti-oxidation solution for anti-oxidation treatment to obtain an anti-oxidation layer; the anti-oxidation solution comprises chromium ions, zinc ions and sodium sulfate;

[0031] A coupling agent solution is sprayed on the surface of the anti-oxidation layer.

[0032] The present invention uses a rolled copper foil as a cathode and performs a micro-roughening treatment in an electrolyte to obtain a micro-roughening layer, wherein the electrolyte is an acidic solution of copper ions and nickel ions. In the present invention, the micro-roughening treatment preferably also includes sequentially subjecting the rolled copper foil to an electrolytic degreasing treatment and pickling. In the present invention, the electrolyte for the electrolytic degreasing treatment is preferably an alkaline solution, and the alkaline solution preferably includes a potassium hydroxide solution, a sodium hydroxide solution or a sodium carbonate solution. In the present invention, the volume concentration of the alkaline solution is preferably 10 to 50%, more preferably 20 to 40%, and most preferably 30 to 35%. In the present invention, the temperature of the degreasing treatment is preferably 50 to 60°C, more preferably 55 to 58°C. In the present invention, the current density of the electrolytic degreasing treatment is preferably 20 to 50A / dm 2 , more preferably 30 to 40 A / dm 2 The electrolytic degreasing treatment time is preferably 10 to 15 seconds, more preferably 12 to 15 seconds.

[0033] The present invention has no special limitation on the anode used for electrolytic degreasing, and conventional electrodes in the art can be used.

[0034] The present invention can remove oil stains on the surface of the copper foil through electrolytic degreasing treatment, which is beneficial to the subsequent micro-roughening treatment.

[0035] In the present invention, the pickling step preferably involves immersing the electrolytically degreased rolled copper foil in an acid solution. The acid solution is preferably an aqueous sulfuric acid solution. The mass concentration of the acid solution is preferably 100-160 g / L, more preferably 120-150 g / L. The immersion temperature is preferably 20-40°C, more preferably 25-35°C, and most preferably 30-32°C. The immersion time is preferably 5-10 seconds, more preferably 7-9 seconds.

[0036] The present invention can remove impurities on the surface of the copper foil through pickling, and the impurities are preferably copper oxide.

[0037] In the present invention, the acidic solution of copper ions and nickel ions is preferably obtained by mixing a copper salt, a nickel salt, and an acid; the copper salt preferably includes copper sulfate or copper chloride, more preferably copper sulfate; the nickel salt preferably includes nickel sulfate or nickel chloride, more preferably nickel sulfate; and the acid is preferably sulfuric acid. The present invention has no particular limitation on the mixing method, as long as it can be mixed uniformly. In the present invention, the mass concentration of copper ions in the electrolyte is preferably 8 to 15 g / L, more preferably 10 to 12 g / L; the mass concentration of nickel ions in the electrolyte is preferably 1 to 3 g / L, more preferably 1.5 to 2 g / L; the mass concentration of acid in the electrolyte is preferably 100 to 120 g / L, more preferably 105 to 110 g / L.

[0038] In the present invention, the temperature of the micro-roughening treatment is preferably 30-40°C, more preferably 33-35°C; the current density of the micro-roughening treatment is preferably 40-50A / dm 2 , more preferably 45 to 48 A / dm 2 The time of the micro-roughening treatment is preferably 3 to 5 seconds, more preferably 3.5 to 4 seconds.

[0039] The present invention has no particular limitation on the anode used for the micro-roughening treatment, and any conventional electrode in the art may be used.

[0040] The present invention forms copper buds on the surface of the rolled copper foil through a micro-roughening treatment, increasing the surface roughness of the rolled copper foil and thereby improving the peel strength of the two-layer flexible copper-clad laminate. Furthermore, the copper buds formed by the present invention have a relatively low height, which helps improve the transparency of the two-layer flexible copper-clad laminate after etching.

[0041] After obtaining the micro-roughened layer, the present invention immerses the copper foil with the micro-roughened layer in an alloying solution for alloying to obtain the alloyed layer. In the present invention, the alloying solution includes metal ions, including nickel ions. The nickel ions are preferably provided by a nickel salt, preferably nickel sulfate or nickel chloride, more preferably nickel chloride. In the present invention, the mass concentration of the nickel ions in the alloying solution is preferably 2 to 15 g / L, more preferably 5 to 10 g / L. In the present invention, the alloying solution also preferably includes alloying ions and a complexing agent. The alloying ions are preferably provided by an alloying metal salt, preferably including one or two of cobalt salts, copper salts, tungsten salts, and molybdenum salts, more preferably two of the following: the cobalt salt preferably includes cobalt sulfate or cobalt chloride, more preferably cobalt sulfate; the copper salt preferably includes copper sulfate or copper chloride, more preferably copper sulfate; the tungsten salt is preferably sodium tungstate; and the molybdenum salt preferably includes sodium molybdate or ammonium molybdate, more preferably sodium molybdate. In the present invention, the mass concentration of the metal ions in the alloy solution is preferably 1 to 15 g / L, more preferably 5 to 10 g / L, and most preferably 6 to 8 g / L. In an embodiment of the present invention, the alloy metal salt is cobalt sulfate and sodium molybdate, or copper sulfate and sodium tungstate, or copper sulfate and cobalt sulfate, or copper sulfate and sodium molybdate.

[0042] In the present invention, the complexing agent is preferably an organic acid, preferably including ethylenediaminetetraacetic acid, glycine, or citric acid, more preferably glycine or citric acid. In the present invention, the mass concentration of the complexing agent in the alloy solution is preferably 30-50 g / L, more preferably 35-40 g / L. In the present invention, the complexing agent can promote the co-deposition of nickel ions and alloy ions at the cathode, making their metal deposition potentials close, thereby achieving co-deposition and forming a multi-element alloy layer after micro-roughening during electroplating.

[0043] In the present invention, the temperature of the alloying treatment is preferably 25 to 35° C., more preferably 25 to 30° C. In the present invention, the current density of the alloying treatment is preferably 30 to 50 A / dm 2 , more preferably 35 to 40 A / dm 2 ; The alloying treatment time is preferably 10 to 20 seconds, more preferably 15 to 18 seconds.

[0044] The present invention has no special limitation on the anode for alloying treatment, and conventional electrodes in the art can be used.

[0045] The present invention electroplates a nickel-containing alloy layer on the surface of the copper bud after alloying treatment, which can improve the corrosion resistance and high temperature resistance of the copper foil and meet the high temperature resistance requirements of the continuous high temperature roller pressing or lamination pressing method of the glue-free flexible copper clad laminate.

[0046] After obtaining the alloyed layer, the present invention immerses the copper foil with the alloyed layer in an anti-oxidation solution for anti-oxidation treatment to obtain an anti-oxidation layer. In the present invention, the anti-oxidation solution includes chromium ions, zinc ions and sodium sulfate. In the present invention, the chromium ions are preferably provided by chromium trioxide; the zinc ions are preferably provided by zinc salts, and the zinc salts preferably include zinc sulfate or zinc chloride, more preferably zinc sulfate. In the present invention, the mass concentration of chromium ions in the anti-oxidation solution is preferably 0.5-1 g / L, more preferably 0.6-0.8 g / L; the mass concentration of zinc ions in the anti-oxidation solution is preferably 2-4 g / L, more preferably 2-3 g / L; the mass concentration of sodium sulfate in the anti-oxidation solution is preferably 15-20 g / L, more preferably 16-18 g / L; the pH value of the anti-oxidation solution is preferably 3-4.

[0047] In the present invention, the temperature of the anti-oxidation treatment is preferably 20-30°C, more preferably 23-25°C; the current density of the anti-oxidation treatment is preferably 2-5A / dm 2 , more preferably 3 to 4 A / dm 2 The anti-oxidation treatment time is preferably 5 to 10 seconds, more preferably 6 to 8 seconds.

[0048] The present invention has no particular limitation on the anode used for the anti-oxidation treatment, and conventional electrodes in the art may be used.

[0049] In the present invention, an anti-oxidation layer is electroplated on the surface of the alloying layer after anti-oxidation treatment, and the zinc and chromium in the anti-oxidation layer can provide the copper foil with high temperature resistance, oxidation resistance and corrosion resistance.

[0050] After obtaining the anti-oxidation layer, the present invention sprays a coupling agent solution on the surface of the anti-oxidation layer. In the present invention, the coupling agent solution is preferably a silane coupling agent solution, and the silane coupling agent in the silane coupling agent solution preferably includes a urea-based silane coupling agent, an amino-based silane coupling agent, or a methacrylic coupling agent, more preferably a urea-based silane coupling agent or an amino-based silane coupling agent. In the present invention, the urea-based silane coupling agent preferably includes a 3-ureapropyltriethoxysilane coupling agent; the amino-based silane coupling agent preferably includes a 3-aminopropyltrimethoxysilane coupling agent or a 3-aminopropyltriethoxysilane coupling agent, more preferably a 3-aminopropyltrimethoxysilane coupling agent. In the present invention, the volume concentration of the coupling agent solution is preferably 1 to 2%, more preferably 1.3 to 1.5%.

[0051] In the present invention, the spraying temperature is preferably 25 to 35°C, more preferably 28 to 30°C.

[0052] In the present invention, the spraying step preferably includes drying. In the present invention, the drying temperature is preferably 110-150°C, more preferably 120-130°C; the drying time is preferably 2-6 seconds, more preferably 3-5 seconds.

[0053] Through micro-roughening, alloying, and anti-oxidation treatments, the rolled copper foil of the present invention exhibits low copper bud height, high oxidation temperature resistance, high peel strength, and high transparency after etching of the polyimide film. The surface roughness, bendability, and high corrosion resistance of the surface-treated rolled copper foil of the present invention meet the requirements of flexible printed circuit boards.

[0054] The surface treatment method provided by the invention has simple operation steps, strong continuity and low operating cost.

[0055] The present invention also provides a non-adhesive copper foil for flexible copper-clad laminates, obtained by treating the copper foil surface according to the above-described technical solution. The non-adhesive copper foil for flexible copper-clad laminates comprises a copper foil, a micro-roughened layer, an alloyed layer, an anti-oxidation layer, and a coupling agent film layer laminated in sequence; the alloyed layer contains nickel, and the anti-oxidation layer contains chromium and zinc. In the present invention, the height of the copper buds in the micro-roughened layer is preferably less than or equal to 500 nm.

[0056] The present invention also provides the use of the rolled copper foil for adhesive-free flexible copper-clad laminates described in the above technical solution in two-layer flexible copper-clad laminates. In the present invention, the two-layer flexible copper-clad laminates produced using the copper foil for adhesive-free flexible copper-clad laminates described in the above technical solution preferably have a high-temperature oxidation resistance greater than 350°C per minute. In the present invention, the two-layer flexible copper-clad laminates exhibit high optical positioning accuracy and are less susceptible to scattering when etching circuits, making them suitable for producing fine patterns.

[0057] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0058] Example 1

[0059] (1) Electrolytic degreasing treatment: The rolled copper foil is immersed in a treatment tank filled with a sodium hydroxide solution with a volume concentration of 30%, with the rolled copper foil as the cathode, at a temperature of 55°C and a current density of 30A / dm 2 Electrolytic degreasing was performed for 15s under the conditions of

[0060] (2) Pickling: Immerse the rolled copper foil treated in step (1) in a treatment tank containing a sulfuric acid solution with a temperature of 30° C. and a mass concentration of 120 g / L for 7 seconds;

[0061] (3) Micro-roughening treatment: The rolled copper foil treated in step (2) is immersed in a micro-roughening tank filled with an electrolyte for micro-roughening treatment; the electrolyte is a mixed solution of copper sulfate, nickel sulfate and sulfuric acid, wherein the copper ion mass concentration is 8 g / L, the nickel ion mass concentration is 2 g / L, and the sulfuric acid mass concentration is 110 g / L; the rolled copper foil treated in step (2) is used as the cathode, and the temperature is 35°C and the current density is 50 A / dm 2 , and the micro-roughening treatment was carried out for 4s under the conditions of , to obtain a micro-roughening layer;

[0062] (4) Alloying treatment: The copper foil with the micro-roughened layer is immersed in an alloy liquid tank for alloying treatment; the alloy liquid is a mixture of cobalt sulfate, sodium molybdate, nickel sulfate and glycine, wherein the mass concentration of cobalt ions is 5g / L, the mass concentration of molybdenum ions is 1g / L, the mass concentration of nickel ions is 10g / L, and the mass concentration of glycine is 30g / L; the temperature is 25°C and the current density is 30A / dm 2 Electroplating was carried out under the following conditions for 15 s to obtain alloyed copper foil;

[0063] (5) Anti-oxidation treatment: The copper foil containing the alloyed layer is immersed in an anti-oxidation tank filled with an anti-oxidation solution for anti-oxidation treatment; the anti-oxidation solution is a mixed solution of chromium trioxide, zinc sulfate and sodium sulfate, wherein the mass concentration of chromium ions is 1g / L, the mass concentration of zinc ions is 3g / L, the mass concentration of sodium sulfate is 15g / L, and the pH value of the anti-oxidation solution is 3; the temperature is 30°C, the current density is 5A / dm 2 Anti-oxidation treatment was performed for 9 seconds under the conditions of , to obtain an anti-oxidation layer;

[0064] (6) Spraying 3-aminopropyltrimethoxysilane coupling agent at a temperature of 30° C. and a volume concentration of 1% on the surface of the anti-oxidation copper layer, and then drying at 120° C. for 4 seconds to obtain a copper foil for a non-adhesive flexible copper clad laminate.

[0065] Example 2

[0066] The rolled copper foil was surface treated according to the method of Example 1, except that the mass concentration of copper ions in the electrolyte of the micro-roughening treatment was 10 g / L and the mass concentration of nickel ions was 3 g / L; the current density of the micro-roughening treatment was 40 A / dm 2 , time is 5s;

[0067] The alloy solution is a mixture of copper sulfate, sodium tungstate, nickel sulfate and ethylenediaminetetraacetic acid, in which the copper ion mass concentration is 4g / L, the tungsten ion mass concentration is 1g / L, the nickel ion mass concentration is 10g / L, and the ethylenediaminetetraacetic acid mass concentration is 30g / L; the current density of the alloying treatment is 35A / dm 2 , time is 15s;

[0068] The mass concentration of chromium ions in the anti-oxidation solution is 0.5 g / L, the mass concentration of zinc ions is 4 g / L, the mass concentration of sodium sulfate is 20 g / L, and the pH value of the anti-oxidation solution is 3. The current density of the anti-oxidation treatment is 4 A / dm 2 , time is 6s.

[0069] Example 3

[0070] The rolled copper foil was surface treated according to the method of Example 1, except that the mass concentration of copper ions in the electrolyte of the micro-roughening treatment was 15 g / L and the mass concentration of nickel ions was 2 g / L; the current density of the micro-roughening treatment was 45 A / dm 2 , time is 3s;

[0071] The alloy solution is a mixture of copper sulfate, cobalt sulfate, nickel sulfate and citric acid, in which the copper ion mass concentration is 4g / L, the cobalt ion mass concentration is 2g / L, the nickel ion mass concentration is 15g / L, and the citric acid mass concentration is 30g / L; the current density of the alloying treatment is 30A / dm 2 , time is 20s;

[0072] The mass concentration of chromium ions in the anti-oxidation solution is 0.8 g / L, the mass concentration of zinc ions is 3 g / L, the mass concentration of sodium sulfate is 18 g / L, and the pH value of the anti-oxidation solution is 4. The current density of the anti-oxidation treatment is 3 A / dm 2 , time is 7s.

[0073] Comparative Example 1

[0074] The rolled copper foil was surface treated according to the method of Example 1, except that the mass concentration of copper ions in the electrolyte of the micro-roughening treatment was 10 g / L and the mass concentration of nickel ions was 0.5 g / L; the current density of the micro-roughening treatment was 50 A / dm 2, time is 5s;

[0075] The alloy solution is a mixture of copper sulfate, sodium molybdate, nickel sulfate and citric acid, in which the copper ion mass concentration is 4g / L, the molybdenum ion mass concentration is 2g / L, the nickel ion mass concentration is 10g / L, and the citric acid mass concentration is 40g / L; the current density of the alloying treatment is 40A / dm 2 , time is 20s;

[0076] The mass concentration of chromium ions in the anti-oxidation solution is 1g / L, the mass concentration of zinc ions is 4g / L, the mass concentration of sodium sulfate is 15g / L, and the pH value of the anti-oxidation solution is 3; the current density of the anti-oxidation treatment is 4A / dm 2 , time is 6s.

[0077] Comparative Example 2

[0078] The rolled copper foil was surface treated according to the method of Example 1, except that the mass concentration of copper ions in the electrolyte of the micro-roughening treatment was 10 g / L and the mass concentration of nickel ions was 2 g / L; the current density of the micro-roughening treatment was 45 A / dm 2 , time is 5s;

[0079] The alloy solution is a mixture of copper sulfate, cobalt sulfate, nickel sulfate and ethylenediaminetetraacetic acid, in which the copper ion mass concentration is 4g / L, the cobalt ion mass concentration is 2g / L, the nickel ion mass concentration is 2g / L, and the ethylenediaminetetraacetic acid mass concentration is 35g / L; the current density of the alloying treatment is 35A / dm 2 , time is 20s;

[0080] The mass concentration of chromium ions in the anti-oxidation solution is 1 g / L, the mass concentration of zinc ions is 0.5 g / L, the mass concentration of sodium sulfate is 15 g / L, and the pH value of the anti-oxidation solution is 3. The current density of the anti-oxidation treatment is 4 A / dm 2 , time is 8s.

[0081] Comparative Example 3

[0082] The rolled copper foil was subjected to electrolytic degreasing and pickling according to the method of Example 1;

[0083] The pickled copper foil was subjected to a roughening treatment, wherein the copper ion concentration was 10 g / L, the sulfuric acid concentration was 115 g / L, the temperature was 35 ° C, and the current density was 40 A / dm 2 , the coarsening treatment time is 5s, and a coarsening layer is obtained;

[0084] The copper foil with the roughened layer was cured, wherein the copper ion concentration was 40 g / L, the sulfuric acid concentration was 120 g / L, the temperature was 40 ° C, and the current density was 15 A / dm2 , the curing treatment time is 5s to obtain a cured layer;

[0085] The copper foil containing the solidified layer is alloyed to obtain an alloyed layer; the alloy liquid is a mixture of cobalt sulfate, nickel sulfate and citric acid, wherein the mass concentration of cobalt ions is 4g / L, the mass concentration of nickel ions is 4g / L, and the mass concentration of citric acid is 20g / L; the current density of the alloying treatment is 18A / dm 2 , time is 15s;

[0086] The copper foil containing the alloy layer was treated with a barrier layer to obtain a barrier layer; the mass concentration of zinc ions was 3 g / L, the mass concentration of potassium pyrophosphate was 20 g / L, the pH value of the solution was 11; the current density was 3 A / dm 2 , time is 8s;

[0087] The copper foil with the barrier layer was subjected to an anti-oxidation treatment. The mass concentration of chromium ions in the anti-oxidation solution was 1 g / L, and the pH value of the solution was 11. The current density of the anti-oxidation treatment was 2 A / dm 2 , time is 8s.

[0088] Comparative Example 4

[0089] The rolled copper foil was surface treated according to the method of Control Example 3, except that the alloy solution was a mixture of copper sulfate, nickel sulfate and citric acid, wherein the copper ion mass concentration was 6 g / L, the nickel ion mass concentration was 4 g / L, and the citric acid mass concentration was 30 g / L; the current density of the alloying treatment was 18 A / dm 2 , time is 15s.

[0090] The roughness, peel strength, and high-temperature oxidation resistance of the rolled copper foils prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were tested according to the IPC-TM-650 metal foil test method for printed circuit boards. The height of copper buds on the surfaces of the rolled copper foils prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were measured using a scanning electron microscope. The results are listed in Table 1.

[0091] The rolled copper foils prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were used to prepare two-layer flexible copper clad laminates, and the light transmittance of the polyimide in the two-layer flexible copper clad laminates after etching was tested. The results are listed in Table 1.

[0092] Table 1 Performance parameters of copper foils of Examples 1 to 3 and Comparative Examples 1 to 4

[0093]

[0094] According to Table 1, after copper-nickel micro-roughening, alloying treatment and zinc-chromium anti-oxidation treatment, the rolled copper foil obtained has a lower copper bud height, a higher oxidation resistance temperature, high peel strength and higher transparency after polyimide film etching. Other properties such as surface roughness, bendability and high corrosion resistance can meet the requirements of flexible printed circuit boards.

[0095] The results of Comparative Example 1 show that the concentration of nickel ions in the roughened electrolyte affects the light transmittance of the etched polyimide film. Only when the nickel ion concentration in the electrolyte is limited to 1-3 g / L can the etched polyimide film have a higher light transmittance.

[0096] From the results of Comparative Example 2, it can be seen that the zinc ion concentration in the anti-oxidation solution used for anti-oxidation treatment will affect the high temperature resistance of the copper foil. Only when the mass concentration of zinc ions is limited to 2-4 g / L can the copper foil have a higher high temperature resistance.

[0097] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for surface treatment of rolled copper foil, comprising the following steps: The rolled copper foil is used as the cathode and subjected to a micro-roughening treatment in an electrolyte to obtain a micro-roughening layer, wherein the height of the copper buds in the micro-roughening layer is less than or equal to 500 nm; the electrolyte is an acidic solution of copper ions and nickel ions; the mass concentration of the copper ions in the electrolyte is 8-15 g / L, and the mass concentration of the nickel ions in the electrolyte is 1-3 g / L; the current density of the micro-roughening treatment is 40-50 A / dm 2 ; The copper foil with the micro-roughened layer is immersed in an alloy liquid for alloying treatment to obtain an alloyed layer; the alloy liquid includes metal ions, the metal ions include nickel ions, and the mass concentration of the nickel ions in the alloy liquid is 5-10 g / L; the alloy liquid also includes alloy ions and a complexing agent, the alloy ions are provided by alloy metal salts, the alloy metal salts include two of cobalt salts, copper salts, tungsten salts and molybdenum salts, and the complexing agent is an organic acid, the organic acid includes ethylenediaminetetraacetic acid, glycine or citric acid; the current density of the alloying treatment is 30-50 A / dm 2 The alloying treatment time is 10 to 20 seconds; Immersing the copper foil with the alloyed layer in an anti-oxidation solution for anti-oxidation treatment to obtain an anti-oxidation layer; the anti-oxidation solution comprises chromium ions, zinc ions, and sodium sulfate; the mass concentration of zinc ions is 3-4 g / L; A coupling agent solution is sprayed on the surface of the anti-oxidation layer.

2. The surface treatment method of rolled copper foil according to claim 1, characterized in that: The time of the micro-roughening treatment is 3-5 seconds; the temperature of the micro-roughening treatment is 30-40°C.

3. The surface treatment method of rolled copper foil according to claim 1 or 2, characterized in that: The mass concentration of the acid in the electrolyte is 100-120 g / L.

4. The surface treatment method of rolled copper foil according to claim 1, characterized in that: The temperature of the alloying treatment is 25-35°C.

5. The surface treatment method of rolled copper foil according to claim 1 or 4, characterized in that: The mass concentration of the alloy ions in the alloy solution is 1-15 g / L; The mass concentration of the complexing agent in the alloy liquid is 30-50 g / L.

6. The method for surface treatment of rolled copper foil according to claim 1, wherein: The mass concentration of chromium ions in the anti-oxidation solution is 0.5-1 g / L, and the mass concentration of sodium sulfate is 15-20 g / L; the pH value of the anti-oxidation solution is 3-4; The temperature of the anti-oxidation treatment is 20-30°C, and the current density of the anti-oxidation treatment is 2-5A / dm 2 The anti-oxidation treatment time is 5 to 10 seconds.

7. The method for surface treatment of rolled copper foil according to claim 1, wherein: The volume concentration of the coupling agent solution is 1-2%; the coupling agent solution is a silane coupling agent solution; The spraying temperature is 25-35°C.

8. The method for surface treatment of rolled copper foil according to claim 1, wherein: Before the micro-roughening treatment, the copper foil is subjected to electrolytic degreasing and pickling in sequence; The current density of the electrolytic degreasing treatment is 20~50A / dm 2 The electrolytic degreasing treatment time is 10 to 15 seconds; The electrolyte for electrolytic degreasing treatment is an alkaline solution, and the volume concentration of the alkaline solution is 10-50%.

9. The copper foil for adhesive-free flexible copper-clad laminate obtained by the surface treatment method of rolled copper foil according to any one of claims 1 to 8, characterized in that: The copper foil for the adhesive-free flexible copper clad laminate comprises a copper foil, a micro-roughening layer, an alloying layer, an anti-oxidation layer and a coupling agent film layer stacked in sequence; the alloying layer contains nickel, and the anti-oxidation layer contains chromium and zinc.

10. Use of the copper foil for adhesive-free flexible copper-clad laminate according to claim 9 in a two-layer flexible copper-clad laminate.

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