A buried copper foil and its preparation method and electronic product

Abstract

The present application relates to the field of copper foil technology. The present application provides a buried copper foil and a preparation method thereof and an electronic product. The preparation method comprises: obtaining copper foil; micro-roughening the copper foil; performing a first passivation on the micro-roughened copper foil; brush plating the passivated copper foil; wherein the copper foil comprises a single-sided photoelectrolytic copper foil, a double-sided photoelectrolytic copper foil or a rolled copper foil. Through the above operations, the present application obtains a buried copper foil with excellent performance and uniformity. The copper foil still has no oxidation phenomenon after high-temperature baking for 3 hours, and the resistor can be customized, thereby expanding the application scenarios.

Description

Technical Field

[0001] The present application relates to the technical field of copper foil, and in particular to a buried barrier copper foil, a preparation method thereof, and an electronic product. Background Art

[0002] In the process of rapid development of electronic technology today, with the widespread application of 5G communication technology and the continuous increase in the number of high-speed and high-performance electronic products, printed circuit boards (PCBs) are showing a development trend of miniaturization, easy packaging, high frequency and high speed. Under this trend, the traditional passive component mounting method has gradually shown many shortcomings, which leads to an increase in the number of pads on the PCB surface, a corresponding decrease in the available surface area, and an increase in the parasitic effect between pad components, which makes the high-frequency signal transmission stability worse, becoming an important factor limiting the performance improvement of electronic equipment.

[0003] Buried copper foil is an ideal material for manufacturing embedded resistor PCBs. It plays an important role in resistor power amplification, voltage conversion, signal input / output, temperature compensation, and power supply filtering. Its performance has a significant impact on the competitiveness of electronic products. However, in the field of buried copper foil preparation, the sputtering process for preparing nickel-phosphorus alloy resistor layers has its specific process characteristics, which requires a carrier layer as a preparation substrate. This requirement increases the complexity of the process and dependence on raw materials. The existing technical situation has formed a major obstacle to the development of domestic buried copper foil application products.

[0004] For example, in Chinese patent application CN118996555A, a method for improving the corrosion resistance of resistor copper foil by electroplating a nickel-phosphorus alloy layer is proposed. The method mainly includes the following steps: first, the raw foil is pickled to remove surface impurities, then a rough curing treatment is performed to increase the surface roughness, and finally a nickel-phosphorus alloy layer is deposited using an electroplating solution of a specific composition. Although this method can improve the corrosion resistance of resistor copper foil to a certain extent, in actual application, due to the influence of factors such as uneven current distribution, it may cause the problem of insufficient or excessive thickness of the resistor layer in local areas. This unevenness not only affects the electrical performance of the resistor layer, but also may reduce its reliability in long-term use. Summary of the invention

[0005] In view of the above shortcomings of the prior art, the present application proposes a buried barrier copper foil and a preparation method thereof and an electronic product by improving the process and optimizing the technology of double-sided smooth copper foil.

[0006] According to a first aspect of the present application, a method for preparing a buried copper foil is provided, comprising: obtaining a copper foil; roughening the copper foil; passivating the roughened copper foil for the first time; depositing the passivated copper foil to prepare a resistor layer; wherein the copper foil comprises a single-sided photoelectrolytic copper foil, a double-sided photoelectrolytic copper foil or a rolled copper foil.

[0007] Optionally, the micro-roughening includes: mixing the copper foil with a micro-roughening solution for roughening; the micro-roughening solution includes a copper-containing material and an acid-containing material.

[0008] Optionally, the roughening treatment conditions are: temperature of 15°C to 25°C, current density of 10 A / dm 2 ~30A / dm 2 , pH-1.0~5, time is 10s ~50s.

[0009] Optionally, a micro-roughening treatment is performed on the matte side of the double-sided smooth copper foil.

[0010] Optionally, in the micro-roughening solution, the copper-containing material is 15g / L~40g / L, and the acid-containing material is 30g / L~65g / L; the acid-containing material is composed of two or more types of acids; preferably, the acid-containing material includes: 30g / L~60g / L sulfuric acid, 1g / L~5g / L phosphoric acid.

[0011] Optionally, the first passivation includes: placing the roughened double-sided copper foil in a passivation solution to perform the first passivation.

[0012] Optionally, the passivation solution includes: 1.5g / L~3.5g / L phytic acid, 5g / L~10g / L zinc ions, and 0.3g / L~0.8g / L nickel ions; preferably, the mass ratio of phytic acid, zinc ions, and nickel ions is 1:3:0.2.

[0013] Optionally, the first electroplating conditions are: at a temperature of 20°C to 50°C and a current density of 1 A / dm 2 ~5A / dm 2 .

[0014] Optionally, the brush plating deposition includes: coating the surface of the passivated copper foil with a deposition solution containing silicon, fluorine, nickel, phosphorus and chromium.

[0015] Optionally, the brush plating deposition conditions are: temperature 15°C~60°C, current density 5A / dm 2 ~50A / dm 2 .

[0016] Optionally, the second passivation includes: placing the copper foil after brush plating deposition in a passivation solution for the second passivation.

[0017] Optionally, the conditions for the second passivation are: at a temperature of 20°C to 50°C and a current density of 1A / dm 2 ~5A / dm 2 .

[0018] Optionally, the double-sided bright copper foil is prepared from a raw foil generating solution; the raw foil generating solution comprises: 70 g / L to 100 g / L copper, 70 g / L to 100 g / L sulfuric acid, and 1 g / L to 5 g / L brightener.

[0019] Optionally, the brightener includes polypropylene glycol, gelatin, and hydroxymethyl cellulose; the mass ratio of polypropylene glycol, gelatin, and hydroxymethyl cellulose is (0.5~1.5): (1.5~2.5): 0.5.

[0020] Optionally, in the preparation method of double-sided smooth copper foil, the temperature is 48°C to 52°C, the pH is -1.0 to 5, and the current density is 10 A / dm 2 ~30 A / dm 2 .

[0021] According to a second aspect of the present application, there is provided a buried copper foil prepared by any of the above-mentioned preparation methods.

[0022] Optionally, surface roughness <5.0 microns; tensile strength >30kg / mm 2 ; Elongation>5%.

[0023] According to a third aspect of the present application, there is provided application of the buried copper foil in conductive materials, circuit boards or batteries.

[0024] The beneficial effects of this application are as follows:

[0025] The preparation method first obtains copper foil (which may be single-sided photoelectrolytic copper foil, double-sided photoelectrolytic copper foil or rolled copper foil) and performs micro-roughening treatment on it. Micro-roughening treatment can increase the roughness of the copper foil surface, provide more attachment sites for the subsequent deposition of the resistor layer, and make the bond between the resistor layer and the copper foil stronger. The copper foil after micro-roughening treatment is passivated for the first time. Passivation can form a protective film on the surface of the copper foil. This film can effectively prevent the copper foil from being over-oxidized or modified by other substances during the subsequent preparation process, thereby ensuring the uniformity and stability of the deposition of the resistor layer. The resistor layer is then prepared by brush plating deposition on the passivated copper foil. This preparation method avoids the sputtering process's reliance on a specific carrier layer as a preparation substrate, and reduces the complexity of the process and the limitation of raw materials.

[0026] Through the above steps, the problems of equipment dependence, complex process, high cost and low product yield caused by existing technology can be effectively overcome, so that PCB can better achieve the development goals of miniaturization, easy packaging, high frequency and high speed, improve the stability of high-frequency signal transmission, save circuit board surface space, improve product reliability and improve electrical performance, and play a more stable and efficient role in resistor power amplification, voltage conversion, signal input / output, temperature compensation and power supply filtering. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and other features and advantages of the present application will become more apparent by describing in detail example embodiments thereof with reference to the attached drawings.

[0028] Figure 1 It is a preparation flow chart of the method for preparing the buried barrier copper foil in the embodiment of the present application.

[0029] Figure 2 It is a further preparation flow chart of the method for preparing the buried copper foil in the embodiment of the present application.

[0030] Figure 3 It is a hierarchical structure diagram of the buried copper foil in the embodiment of the present application.

[0031] Figure 4 It is a flow chart of the buried barrier copper foil production equipment in the embodiment of the present application.

[0032] Figure 5 It is a production flow chart of buried copper foil in the embodiment of the present application.

[0033] Figure 6 It is a schematic diagram of the structure of the preparation and assembly of the resistance layer in one embodiment of the present application.

[0034] Figure 7 It is a schematic diagram of the structure of the preparation and assembly of the resistance layer in another embodiment of the present application.

[0035] Description of reference numerals:

[0036] Original foil layer 1; micro-roughened interface 2; first passivation layer 3; resistor layer 4; second passivation layer 5;

[0037] First brush plating device 10; copper foil 30; first brush plating tank 101; chemical solution A 102; titanium roller 103; conveying roller 104;

[0038] Second brush plating equipment 20; second brush plating tank 201; chemical solution B 202; electrode 204. DETAILED DESCRIPTION

[0039] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar structures, and thus their detailed description will be omitted.

[0040] The present application provides a method for preparing a buried barrier copper foil. The method for preparing a buried barrier copper foil of the present invention mainly comprises the following steps: Figure 1 As shown:

[0041] S1 Obtain copper foil

[0042] In this step, single-sided photoelectrolytic copper foil, double-sided photoelectrolytic copper foil or rolled copper foil can be used;

[0043] The present application obtains double-sided photoelectrolytic copper foil by an electrolytic process. The electrolyte contains copper, sulfuric acid and a brightener, wherein the brightener is composed of polypropylene glycol, gelatin and hydroxymethyl cellulose in a mass ratio of 1:2:0.5. During the electrolysis process, the temperature is controlled at 48°C to 52°C, and the current density is 10 A / dm² to 30 A / dm².

[0044] In the embodiment using electrolytic copper foil as the copper foil base layer, the cathode roller used for electrolytic copper foil generation can be prepared in a continuous machine with the several preparation steps described later. In this way, compared with the prior art, the copper foil is prepared by the cathode roller, rolled and packaged, and then transported to the resistance layer preparation process for preparation after unwinding. The continuous machine preparation method of this embodiment can reduce the oxidation time of the copper foil in the air, thereby ensuring that the crystalline structure of the copper foil surface remains in a better state. Of course, when the continuous machine preparation is not adopted, the micro-roughening treatment and passivation of the following embodiments of the present application can be understood as the modification and optimization of the copper foil surface that has been oxidized for a long time.

[0045] Single-sided photoelectrolytic copper foil can also be obtained by electrolysis, but the electrolyte does not contain brightener.

[0046] It can also be a rolled copper foil made by repeatedly rolling and annealing a high-precision copper strip (usually less than 150 microns thick) through the principle of plastic processing.

[0047] S2 Micro-roughening treatment

[0048] The copper foil is subjected to micro-roughening treatment to increase its surface area. The micro-roughening solution contains 15g / L to 40g / L copper, 30g / L to 65g / L sulfuric acid, and 1g / L to 5g / L phosphoric acid. The treatment conditions are a temperature of 15°C to 25°C, a current density of 10 A / dm² to 30 A / dm², a pH value of 1.0 to 5.0, and a treatment time of 10 seconds to 50 seconds.

[0049] S3 First passivation

[0050] The micro-roughened copper foil is first passivated in a passivation solution to form a first passivation layer. The passivation solution contains 1.5g / L to 3.5g / L of phytic acid, 5g / L to 10g / L of zinc ions, and 0.3g / L to 0.8g / L of nickel ions. Preferably, the mass ratio of phytic acid, zinc ions, and nickel ions is 1:3:0.2. The passivation conditions are a temperature of 20°C to 50°C and a current density of 1 A / dm² to 5 A / dm².

[0051] S4 Brush Deposition

[0052] The surface of the passivated copper foil is coated with a deposition solution containing silicon, fluorine, nickel, phosphorus, and chromium for brush plating. The brush plating conditions are: temperature 15℃~60℃, current density 5 A / dm 2 ~50A / dm 2 Brush plating will be exemplarily described below, but it is understood that brush plating is a preferred method of preparing a resistance layer by electrodeposition, but is not limited thereto.

[0053] like Figure 2 As shown, the method for preparing the buried copper foil of the present invention may further include the following steps:

[0054] S5 Second passivation

[0055] The copper foil after brush plating is placed in the passivation solution for the second passivation. The conditions for the second passivation are: temperature 20℃~50℃, current density 1 A / dm 2 ~5A / dm 2 .

[0056] S6 Finished Product Inspection

[0057] The cured buried copper foil must undergo strict finished product inspection, and the inspection items include surface roughness, tensile strength, elongation, etc. to ensure that the product performance meets the standards.

[0058] Test method: Use polyurethane adhesive to tightly bond the resistor layer to PET, with a curing temperature of 40°C and a curing time of 12 hours. Then use an etching solution (a mixed solution of copper chloride, ammonium chloride, ammonia water and pure water, with a mass ratio of 15%:15%:50%:20%) to completely etch away the copper layer; the etching temperature is 60°C and the etching time is 1 minute. Take out the PET film, rinse it with water, and bake it at 70°C for 3 minutes. Use a four-probe square resistance tester to test the resistance.

[0059] After completing all the steps, the present application obtains an embedded copper foil product with excellent performance, marking the end of the entire preparation process.

[0060] The method for preparing buried copper foil of the present application has made a significant change in the selection of the base layer for preparing the resistor layer. In contrast to the common practice of using PET as the carrier layer in the prior art, the present method directly uses copper foil as the base layer for preparing the resistor layer.

[0061] First, the removal of the PET carrier layer and its accompanying peeling layer greatly simplifies the product structure. In traditional processes, the presence of the PET carrier layer and the peeling layer increases the complexity and cost of the materials, and may introduce interface problems in the multi-layer structure, affecting the overall performance and reliability of the product. However, this application directly constructs the resistor layer based on copper foil, reducing the number and types of material layers, reducing quality risks caused by compatibility and fit between different materials, and improving the structural stability of the product.

[0062] Secondly, from the perspective of production process, the processing steps related to the PET carrier layer are omitted, such as the laying of the carrier layer, the bonding with the resistor layer, and the subsequent processing of the peeling layer. This not only reduces the investment in production equipment and the occupied space, but also shortens the entire production cycle, improves production efficiency, reduces production costs, and makes the product more price-competitive in the market.

[0063] Furthermore, using copper foil as the base layer for the resistor layer is beneficial to improving the electrical performance of the product. Copper foil itself has good conductivity. Compared with building a resistor layer on a PET carrier layer, it can better achieve electrical connection between the resistor layer and other circuit elements, reduce loss and interference during signal transmission, and improve the performance and response speed of the entire circuit system. It is especially suitable for electronic equipment and circuit application scenarios with high requirements for electrical performance.

[0064] The present application proposes a charged passivation process containing phytic acid. Conventional passivation processes often use chromium, a toxic metal. Chromium and its compounds can cause harm to the health of operators during the production process. For example, long-term exposure may cause health problems such as respiratory diseases, skin allergies, and even cancer. Moreover, during the subsequent use and disposal of the product, the chromium-containing passivation layer may release chromium ions, causing environmental pollution, especially pollution of soil and water sources, and damaging the ecological balance.

[0065] The charged passivation process containing phytic acid in the present application successfully avoids the use of chromium. Phytic acid is a natural organic compound with good biocompatibility and environmental friendliness. During the passivation process, phytic acid can undergo an effective complexation reaction with the surface of the copper foil to form a stable protective film on the surface of the copper foil, which plays an anti-corrosion and anti-oxidation role similar to that of the traditional passivation layer. At the same time, the introduction of the charged passivation process further optimizes the passivation effect. By precisely controlling parameters such as current density, the thickness, structure and performance of the passivation layer can be more accurately adjusted, and the density and uniformity of the passivation layer can be improved, thereby better protecting the copper foil surface, extending the service life of the copper foil, and ensuring that the buried copper foil can maintain stable performance in various complex environments.

[0066] In summary, the buried copper foil preparation method of the present application has innovations in the preparation base layer of the resistor layer and the passivation process, which not only improves the performance of the product itself, simplifies the structure, and reduces the cost, but also has made significant progress in production safety and environmental protection. It has broad application prospects and important industry value.

[0067] In one implementation, the production equipment for buried copper foil can be used for preparation, such as Figure 4 As shown, it mainly includes a copper foil generation tank or a rolling platform, a micro-roughening tank, a first passivation tank, a brush plating deposition tank and a second passivation tank. The copper foil generation tank contains the original foil generation solution; the rolling platform can be used to repeatedly roll and anneal the copper strip; the micro-roughening tank contains the micro-roughening solution; the first passivation tank contains the passivation solution; the brush plating deposition tank contains the deposition solution containing silicon, fluorine, nickel, phosphorus and chromium; the second passivation tank contains the passivation solution.

[0068] Wherein, the copper foil is prepared by raw foil generating solution.

[0069] The raw foil generating solution includes: 70g / L ~100g / L copper, 70g / L ~100g / L sulfuric acid, and 1g / L ~5g / L brightener; wherein, the mass of copper can be 70g / L, 75g / L, 80g / L, 85g / L, 90g / L, 95g / L, 100g / L or any other value within the range; the mass of sulfuric acid can be 70g / L, 75g / L, 80g / L, 85g / L, 90g / L, 95g / L, 100g / L or any other value within the range; the mass of brightener can be 1g / L, 2g / L, 3g / L, 4g / L, 5g / L or any other value within the range.

[0070] Brighteners include surfactants, etc., which can effectively remove dirt and oxides on the copper surface, and play a role in cleaning, brightening, and rust prevention.

[0071] The brightener includes polypropylene glycol, gelatin and hydroxymethyl cellulose. The mass ratio of polypropylene glycol, gelatin and hydroxymethyl cellulose is (0.5-1.5): (1.5-2.5): 0.5, preferably 1:2:0.5.

[0072] In the preparation method of double-sided photoelectrolytic copper foil, the temperature is 48°C to 52°C, for example, 48°C, 49°C, 50°C, 51°C, 52°C or any other value in the range; the current density is 10 A / dm 2 ~30 A / dm 2 , for example 10 A / dm 2 、15A / dm 2 , 20 A / dm 2 , 25 A / dm 2 , 30 A / dm 2 Or any other value in this range.

[0073] The micro-roughening process includes: mixing the copper foil with a micro-roughening solution for micro-roughening; preferably, the matte surface of the copper foil is subjected to micro-roughening treatment.

[0074] The micro-roughening solution includes copper-containing materials and acid-containing materials.

[0075] In the micro-roughening solution, the copper-containing material is 15 g / L to 40 g / L, for example, it can be 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L or other arbitrary values; the copper-containing material is preferably copper.

[0076] The acid-containing material is 30g / L ~ 65g / L, for example, it can be 30g / L, 35g / L, 40g / L, 45g / L, 50g / L, 55g / L, 60g / L, 65g / L or other arbitrary values; the acid-containing material can be an inorganic acid such as phosphoric acid, nitric acid, sulfuric acid, hydrochloric acid, etc.

[0077] The acid-containing material is composed of two or more types of acids; preferably, the acid-containing material includes: sulfuric acid 30g / L~60g / L, for example, it can be 30g / L, 35g / L, 40g / L, 45g / L, 50g / L, 55g / L, 60g / L or other arbitrary values; phosphoric acid 1~5g / L, can be 1g / L, 2g / L, 3g / L, 4g / L, 5g / L or other arbitrary values ​​in this range.

[0078] The use of composite acid can not only increase the amount of copper deposition, but also limit the deposition rate of copper through the mutual restraint between different types of acids, thus avoiding surface inhomogeneity caused by too fast deposition.

[0079] The roughening treatment conditions are: the temperature is 15°C to 25°C, for example, 15°C, 20°C, 25°C or any other value in the range; the current density is 10 A / dm 2 ~30A / dm 2 , for example 10 A / dm 2 、15A / dm 2 , 20 A / dm 2 , 25 A / dm 2 , 30 A / dm 2 Or any other value in this range; pH 1.0-5, for example, can be 1.0, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or any other value in this range; time is 10s-50s, for example, can be 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s or any other value in this range.

[0080] The setting of current density and the selection of temperature should not be too high; when the temperature is too high or the current density is too high, the free movement of acid will increase, which will further affect the deposition of copper; when the temperature is too low or the current density is too low, the sedimentation speed will be too low, which will take a long time and affect the deposition efficiency. At the same time, it will also cause the contact time between the deposited copper and the air to be longer, which may easily have an adverse effect on the service life.

[0081] The first passivation includes: placing the micro-roughened copper foil in a passivation solution for the first passivation.

[0082] The micro-roughened copper foil has a higher surface area, which will produce better protection when passivated.

[0083] The passivation solution includes: phytic acid 1.5g / L~3.5g / L, for example, 1.5g / L, 2g / L, 2.5g / L, 3g / L, 3.5g / L or any value within the range; zinc ion 5g / L~10g / L, for example, 5g / L, 5.5g / L, 6g / L, 6.5g / L, 7g / L, 7.5g / L, 8g / L, 8.5g / L, 9g / L, 9.5g / L, 10g / L or any value within the range; nickel ion 0.3g / L~0.8g / L, for example, 0.3 / L, 0.4g / L, 0.5g / L, 0.6g / L, 0.7g / L, 0.8g / L or any value within the range. Preferably, the mass ratio of phytic acid, zinc ion and nickel ion is 1:3:0.2.

[0084] The passivation solution also includes sulfate ions, which are used for ion balancing of zinc ions and nickel ions.

[0085] Phytic acid will first form a phosphating film on the deposited copper foil layer; then nickel and zinc will form a passivation layer on the basis of the phosphating film due to the chelation effect of phytic acid, which can better protect the copper foil. The combined use of nickel and zinc can avoid the gaps that exist when nickel is used alone, making the passivation layer more compact; at the same time, the co-deposition of zinc and nickel greatly increases the amount of nickel deposited, thereby making the protection effect of the passivation layer better.

[0086] The conditions for the first passivation are: at a temperature of 20°C to 50°C, for example, 20°C, 30°C, 40°C, 50°C or any other value within the range; a current density of 1 A / dm 2 ~5A / dm 2 , for example, 1A / dm 2 , 2A / dm 2 、3A / dm 2 , 4 A / dm 2 , 5A / dm 2 Or any other value in this range.

[0087] The temperature of the first passivation cannot be too high, otherwise the nickel-zinc deposition structure will be uneven; the current density does not need to be too large, just ensure the production of a nickel-zinc passivation layer to avoid excessive deposition and affect the thickness of the copper foil.

[0088] Brush plating deposition includes: coating the surface of the passivated copper foil with a deposition solution containing silicon, fluorine, nickel, phosphorus and chromium for brush plating deposition.

[0089] By applying a deposition solution containing silicon, fluorine, nickel, phosphorus, and chromium, brush plating deposition is performed. Due to the presence of the passivation layer, the initial deposition of nickel, phosphorus, and chromium can be made more uniform, avoiding the inhomogeneity caused by direct contact with copper; in addition, since the deposition solution also contains phytic acid and nickel, the deposition rate is increased, and at the same time, the co-deposition of nickel, phosphorus, and chromium, that is, the complexation of organic phosphorus with nickel and chromium, increases the corrosion resistance of the resistor layer. The presence of silicon and fluorine can continuously generate active nickel and active chromium, thereby promoting the deposition of nickel and chromium.

[0090] The conditions for brush plating deposition are: temperature 15°C to 60°C, for example, 15°C, 20°C, 30°C, 40°C, 50°C, 60°C or any other value in the range; current density 5 A / dm 2 ~50A / dm 2 , for example 5 A / dm 2 、10A / dm 2 、15A / dm 2 , 20 A / dm 2 、25A / dm 2 、30A / dm 2 、35A / dm 2 , 40 A / dm 2 、45A / dm 2 、50A / dm 2 Or any other value in this range.

[0091] The current density of brush plating deposition is higher than the current density of the first passivation, which can achieve rapid generation of the resistance layer, while reconstructing the structure of the passivation layer to make it more compact; and the resistance layer and the passivation layer are closely connected, which improves the anti-oxidation ability of the passivation layer. Preferably, the temperature of brush plating is higher than the temperature of the first passivation.

[0092] The deposition solution includes: phytic acid 1.5g / L~3.5g / L, for example, 1.5g / L, 2g / L, 2.5g / L, 3g / L, 3.5g / L or any value within the range; nickel ion 5g / L~10g / L, for example, 5g / L, 5.5g / L, 6g / L, 6.5g / L, 7g / L, 7.5g / L, 8g / L, 8.5g / L, 9g / L, 9.5g / L, 10g / L or any value within the range; chromium ion 0.3g / L~0.8g / L, for example, 0.3 / L, 0.4g / L, 0.5g / L, 0.6g / L, 0.7g / L, 0.8g / L or any value within the range. Preferably, the mass ratio of phytic acid, nickel ion and chromium ion is 1:3:0.2.

[0093] The sedimentation solution also includes sulfate ions for ion balancing of zinc and nickel ions.

[0094] The deposition potion also includes: 2 g / L to 5 g / L of silicate, for example, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L or any value within this range; 2 g / L to 5 g / L of sodium fluoride, for example, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L or any value within this range.

[0095] See also Figure 6 , which illustrates a first brush plating device, a schematic structural diagram of the first brush plating device 10. The copper foil 30 is conveyed to the first brush plating tank 101 by the conveying roller 104. The first brush plating tank 101 contains a liquid medicine A102. When the copper foil 30 is conveyed to the first brush plating tank 101, the titanium roller 103 brush-plates the liquid medicine A onto the surface of the copper foil 30 to form a resistance layer. The titanium roller 103 can be configured as an anode.

[0096] See also Figure 7 , which illustrates another brush plating preparation method of the resistor layer, and a schematic structural diagram of the second brush plating device 20. The copper foil 30 after the first passivation is transferred to the second brush plating tank 201. The second brush plating tank 201 contains a liquid medicine B 202. When the copper foil 30 after the first passivation is transferred to the second brush plating tank 201, the titanium roller 103 and the electrode 204 brush-plate the liquid medicine B to the surface of the resistor layer of the copper foil 30 to form a resistor layer. It can be understood that during the second brush plating, the liquid medicine B overflows from the second brush plating tank 201 and is brush-plated by the titanium roller 103 to the surface of the resistor layer of the copper foil 30 to form a phosphide layer.

[0097] In the embodiment of the present application, the resistance layer is prepared by brush plating, which can effectively overcome the disadvantages of the traditional sputtering process, such as expensive equipment and complicated process. Brush plating can accurately control the thickness, composition and uniformity of the resistance layer, and improve the resistance performance and stability.

[0098] Second passivation: Place the copper foil after brush plating in the passivation solution.

[0099] The passivation solution here can be the same as or different from the passivation solution of the first passivation; preferably, they are the same.

[0100] The conditions for the second passivation are: at a temperature of 20°C to 50°C, for example, 20°C, 30°C, 40°C, 50°C or any other value within the range; a current density of 1 A / dm 2 ~5A / dm 2 , for example, 1A / dm 2 , 2A / dm 2 、3A / dm 2 , 4 A / dm2 , 5A / dm 2 Or any other value in this range.

[0101] The second passivation can also form a passivation layer on the other side of the resistor layer, thereby improving the corrosion resistance of the resistor layer. Preferably, the temperature and current density of the second passivation are greater than the parameters of the first passivation; the density of the passivation layer can be increased, and it has better anti-oxidation ability. More preferably, the temperature and current density of the second passivation are less than the parameters of the brush plating, so as to avoid damaging the structure of the resistor layer and reducing the uniformity of the resistor.

[0102] In this embodiment, the micro-roughening can be performed by Figure 6 or Figure 7 In the brush plating process shown, during the brush plating process, the electrode 204 and the titanium roller 103 work together to evenly brush the micro-roughening solution onto the copper foil surface. This method can make the micro-roughening structure formed on the copper foil surface more regular, and the uniformity of the micro-roughening depth is improved by about 25%. This will provide more ideal surface conditions for subsequent processes, which is conducive to improving the adhesion between the resistor layer and the copper foil, making the distribution of the resistor layer on the copper foil surface more uniform, and thus improving the overall electrical performance and stability of the buried copper foil.

[0103] For the first passivation, it can also be used Figure 6 or Figure 7 In the brush plating process shown in the figure, during brush plating, the titanium roller 103 and the electrode 204 accurately brush the passivation solution onto the surface of the copper foil. The uniformity of the distribution of each component in the passivation layer can be improved by about 35%, thanks to the precise control of the supply of solution and current distribution by the brush plating process. A more uniform distribution of components helps to form a more continuous and dense passivation layer, enhances the protection of the copper foil, reduces the risk of oxidation or corrosion of the copper foil in subsequent processes, and provides a more stable substrate for the preparation of the resistor layer, thereby improving the quality and performance stability of the resistor layer.

[0104] When the second passivation is adopted Figure 6 or Figure 7 The brush plating process shown in the figure can make the interface between the passivation layer and the resistor layer more tightly bonded by optimizing the brush plating parameters, such as current density and temperature. The interface bonding strength can be increased by about 50%, because brush plating can promote the chemical bonding and physical intercalation between the passivation layer and the resistor layer while forming the passivation layer. Tighter interface bonding can effectively prevent the peeling between the passivation layer and the resistor layer during use, improve the integrity and durability of the entire buried copper foil structure, ensure the reliability of the product under various environmental conditions, extend its service life, and better meet the needs of electronic products for high-performance buried copper foil.

[0105] The present application provides a buried copper foil, which is prepared by the above method; the buried copper foil is a multi-layer hierarchical structure, which includes an original foil layer 1, a micro-roughened interface 2, a first passivation layer 3, a resistance layer 4 and a second passivation layer 5 (the buried copper foil has a square resistance of 10 to 1000 ohms after copper etching); Figure 3 As shown, after the original foil layer 1 (equivalent to the copper foil in the previous embodiment) is generated, the surface area of ​​the original foil layer 1 is increased by micro-roughening, which can facilitate a better bonding effect with the resistor layer, thereby achieving a better protection effect; through multiple interactions in the first passivation layer 3, the resistor layer 4 and the second passivation layer 5, these multiple layers are tightly bonded, thereby producing an excellent protection effect and greatly improving the corrosion resistance.

[0106] In one embodiment, a connected machine is used to prepare buried copper foil. Compared with the prior art, the three key processes of raw foil, dielectric layer preparation, and resistor layer preparation are continuous production of the machine. After the raw foil machine is discharged, it is not wound up but directly enters the post-processing machine at the same speed for roughening, passivation, and resistor layer preparation, omitting the winding and unwinding logistics links between the work sections in the traditional process. The key to this innovative technology is the process of online preparation of the resistor layer, which can bypass the key process of sputtering equipment used in the prior art process to prepare the resistor layer, and instead adopt the method of solvent coating (brush plating in the previous embodiment) to achieve online preparation of the resistor layer. This method not only improves production efficiency, but also reduces costs, and is expected to solve the technical problems in the preparation of domestic buried copper foil.

[0107] The present application provides a production device for buried copper foil. The production device comprises a copper foil generation tank or rolling platform, a micro-roughening tank, a first passivation tank, a brush plating deposition tank and a second passivation tank in sequence; the copper foil generation tank contains raw foil generation solution; the rolling platform can be used to repeatedly roll and anneal the copper strip; the micro-roughening tank contains micro-roughening solution; the passivation tank contains passivation solution; the first passivation tank contains passivation solution; the brush plating deposition tank contains deposition solution containing silicon, fluorine, nickel, phosphorus and chromium; the second passivation tank contains passivation solution; for details, please refer to Figure 3 , Figure 4 as well as Figure 5 shown.

[0108] A water washing tank is also included between the micro-roughening tank and the first passivation tank; the surface of the double-sided copper foil after micro-roughening is rinsed clean by water washing to avoid affecting the passivation layer generated subsequently.

[0109] At present, the production equipment of copper foil at home and abroad is 3 roughening tanks and 3 curing tanks on the rough surface of single-sided copper foil, and the curing tank is used to plate a dense and hard copper layer to improve corrosion resistance, etc. The production equipment provided by this application is less in number and simpler in setting; it can greatly reduce the amount of copper used, but the effect is better; in addition, cleaning is required after each roughening; there is only one roughening tank in this application, so the cleaning tank only needs to be set up once, which greatly reduces the generation of wastewater, has the effect of energy saving and environmental protection, and reduces production costs.

[0110] The above-mentioned medicine solution, medicine solution temperature, current density, treatment time, etc. have been described above and will not be repeated here.

[0111] It is understandable that the device also includes a transfer rod, through which the copper foil is transported from the copper foil generating tank or the rolling platform to the micro-roughening tank, the first passivation tank, the brush plating deposition tank and the second passivation tank in sequence.

[0112] The present application provides a production process flow of buried copper foil; the process flow comprises: firstly generating copper foil in a copper foil generating tank or a rolling platform; then transferring the generated copper foil to a micro-roughening tank for micro-roughening to obtain the micro-roughened copper foil; then transferring the generated copper foil to a first passivation tank for the first passivation to obtain the copper foil after the first passivation; then transferring the copper foil to a brush plating deposition tank for brush plating; then transferring the copper foil to a second passivation tank for the second passivation.

[0113] The process flow also includes: first generating copper foil in a copper foil generating tank or a rolling platform; then transferring the generated copper foil to a micro-roughening tank for micro-roughening to obtain a micro-roughened copper foil; then transferring to a water washing tank to wash away the residue on the surface; then transferring to a first passivation tank for a first passivation to obtain a copper foil after the first passivation; then transferring to a brush plating deposition tank for brush plating; then transferring to a second passivation tank for a second passivation.

[0114] This process is an integrated production process. Through the close coordination between various process steps, a buried barrier copper foil with better performance can be obtained.

[0115] Example 1

[0116] (1) Obtaining copper foil;

[0117] Double-sided smooth copper foil is prepared from the original foil generating solution. The temperature is 50 ℃ and the current density is 30A / dm 2 The original foil forming solution: copper 70 g / L, sulfuric acid 70 g / L, brightener 3.5 g / L; the brightener is polypropylene glycol, gelatin, hydroxymethyl cellulose (mass ratio is 1:2:0.5), and the solvent is water.

[0118] (2) Micro-roughening of copper foil

[0119] The double-sided smooth copper foil is mixed with a roughening solution for roughening.

[0120] Micro-roughening solution: copper 15 g / L, sulfuric acid 35 g / L, phosphoric acid 5 g / L, solvent is water. Micro-roughening treatment conditions: temperature 23 ° C, current density 10 A / dm 2 , pH < 1.5, time is 15 s.

[0121] (3) First passivation of the micro-roughened copper foil

[0122] The roughened double-sided copper foil is placed in the passivation solution for the first passivation.

[0123] The passivation solution includes: phytic acid 3 g / L, zinc ion 9 g / L, nickel ion 0.6 g / L, and the negative ion is sulfate ion. The conditions for the first passivation are: temperature 30℃, current density 4A / dm 2 .

[0124] (4) Brush plating the passivated copper foil

[0125] The passivated double-sided copper foil was brush-plated. The deposition solution included: 3 g / L phytic acid, 9 g / L nickel ions, 0.6 g / L chromium ions, and the negative ions were sulfate ions; 5 g / L silicate, and 4 g / L sodium fluoride. The brush plating conditions were: at a temperature of 50°C and a current density of 10 A / dm 2 .

[0126] (5) Passivate the copper foil after brush plating for the second time

[0127] The double-sided smooth copper foil after brush plating deposition is placed in the passivation solution for the second passivation.

[0128] The passivation solution includes: phytic acid 3 g / L, zinc ion 9 g / L, nickel ion 0.6 g / L, and the negative ion is sulfate ion. The conditions for the second passivation are: temperature 40℃, current density 5 A / dm 2 .

[0129] The buried copper foil prepared above was tested and the results were as follows: surface roughness was about 3.5 microns; tensile strength was 38 kg / mm 2 ; Elongation 8%; No oxidation after baking at 250℃ for 3 hours; Square resistance after copper etching is 56 ohms, with good uniformity and deviation of 2.5%.

[0130] Example 2

[0131] (1) Obtaining copper foil;

[0132] Single-sided copper foil is prepared from the original foil generating solution. The temperature is 50 ℃ and the current density is 30A / dm 2 The original foil generation solution: copper 70 g / L, sulfuric acid 70 g / L, the solvent is water.

[0133] (2) Micro-roughening of copper foil

[0134] Mix the single-sided smooth copper foil with the roughening solution for roughening.

[0135] Micro-roughening solution: 32 g / L copper, 60 g / L sulfuric acid, 2 g / L phosphoric acid, the solvent is water. The micro-roughening treatment conditions are: temperature 18°C, current density 28 A / dm 2 , pH<1.5, time is 45s.

[0136] (3) First passivation of the micro-roughened copper foil

[0137] The single-sided copper foil after roughening is placed in the passivation solution for the first passivation.

[0138] The passivation solution includes: phytic acid 2g / L, zinc ion 6g / L, nickel ion 0.4g / L, and the negative ion is sulfate ion. The conditions for the first passivation are: temperature 20℃, current density 3A / dm 2 .

[0139] (4) Brush plating the passivated copper foil

[0140] The passivated single-sided copper foil was placed in a deposition solution for brush plating deposition. The deposition solution includes: phytic acid 2 g / L, nickel ion 6 g / L, chromium ion 0.4 g / L, negative ion is sulfate ion; silicate 2 g / L, sodium fluoride 2 g / L. The brush plating deposition conditions are: temperature 30℃, current density 43 A / dm 2 .

[0141] (5) Passivate the copper foil after brush plating for the second time

[0142] Place the single-sided copper foil deposited by brush plating in the passivation solution.

[0143] The passivation solution includes: phytic acid 2 g / L, zinc ion 6 g / L, nickel ion 0.4 g / L, and the negative ion is sulfate ion. The conditions for the second passivation are: temperature 25℃, current density 4 A / dm 2 .

[0144] The buried copper foil prepared above was tested and the results were as follows: surface roughness was about 2.4 microns; tensile strength was 45 kg / mm 2; Elongation 7%; No oxidation after baking at 250℃ for 3 hours; Square resistance after copper etching is 82 ohms, with good uniformity and deviation of 2.8%.

[0145] Example 3

[0146] (1) Obtaining copper foil

[0147] Double-sided bright copper foil is prepared from the original foil generation solution. The temperature is 50℃ and the current density is 30A / dm². The original foil generation solution: copper 70g / L, sulfuric acid 70g / L, brightener 3.5g / L; the brightener is polypropylene glycol, gelatin, hydroxymethyl cellulose (mass ratio is 1:2:0.5), and the solvent is water.

[0148] (2) Micro-roughening of copper foil

[0149] The double-sided smooth copper foil is mixed with a roughening solution for roughening.

[0150] Micro-roughening solution: copper 15g / L, sulfuric acid 35g / L, phosphoric acid 5g / L, solvent is water. Micro-roughening treatment conditions are: temperature 23℃, current density 10A / dm², pH<1.5, time 15s.

[0151] (3) First passivation of the micro-roughened copper foil

[0152] The roughened double-sided copper foil is first passivated with a passivation solution in a brush plating device.

[0153] The passivation solution includes: phytic acid 3g / L, zinc ion 9g / L, nickel ion 0.6g / L, and the negative ion is sulfate ion. The conditions for the first passivation are: temperature 30℃, current density 4A / dm².

[0154] (4) Brush plating the passivated copper foil

[0155] The passivated double-sided copper foil was brush-plated. The deposition solution included: 3g / L phytic acid, 9g / L nickel ions, 0.6g / L chromium ions, negative ions were sulfate ions, 5g / L silicate, and 4g / L sodium fluoride. The brush plating conditions were: temperature 50°C, current density 10A / dm².

[0156] (5) Performance testing

[0157] The prepared buried copper foil samples were cut into the same size, immersed in a 5% sulfuric acid solution (simulating an acidic corrosion environment) and a 10% ammonia solution (simulating an alkaline corrosion environment) at a constant temperature of 25°C for 24 hours, and after the immersion, the thickness change and resistance change of the resistor layer were measured. In addition, the square resistance value of the buried copper foil of this embodiment and embodiment 1, embodiment 2, comparative example 1, and comparative example 2 was tested, and the test method was the same as described above (the resistor layer was tightly bonded to the PET using a polyurethane adhesive, the curing temperature was 40°C, and the curing time was 12h. Then, the copper layer was completely etched away using an etching solution (a mixed solution of copper chloride, ammonium chloride, ammonia water and pure water, with a mass ratio of 15%:15%:50%:20%); the etching temperature was 60°C, and the etching time was 1min. The PET film was taken out, washed with water, and baked at 70°C for 3min. The resistance was tested using a four-probe square resistance tester).

[0158] (6) Results analysis

[0159] The surface of the passivation layer prepared by the brush plating process is flat and dense, without obvious holes and cracks, and the elements are evenly distributed, indicating that the brush plating technology ensures the uniformity and stability of the passivation layer. From the corrosion test data, after being soaked in sulfuric acid solution, the thickness of the resistor layer is reduced by an average of 0.5μm (compared with before soaking), and the resistance value changes within ±3%; after being soaked in ammonia solution, the thickness of the resistor layer is reduced by an average of 0.3μm, and the resistance value changes within ±2%. Compared with similar corrosion tests in CN118996555A (the thickness of the resistor layer is reduced by 1.2μm after soaking in sulfuric acid solution of the same concentration, and the resistance value changes within ±5%; the thickness of the resistor layer is reduced by 0.8μm after soaking in ammonia solution of the same concentration, and the resistance value changes within ±4%), the resistor layer of this embodiment performs better in corrosion resistance, which fully proves that due to the effect of components such as phytic acid and nickel in the deposition solution, the deposition speed is accelerated, and the corrosion resistance of the resistor layer is enhanced.

[0160] Example 4

[0161] (1) Obtaining copper foil

[0162] Single-sided smooth copper foil is prepared from the original foil generating solution. The temperature is 50℃, and the current density is 30A / dm². The original foil generating solution: copper 70g / L, sulfuric acid 70g / L, and the solvent is water.

[0163] (2) Micro-roughening of copper foil

[0164] Mix the single-sided smooth copper foil with the roughening solution for roughening.

[0165] Micro-roughening solution: 32g / L copper, 60g / L sulfuric acid, 2g / L phosphoric acid, the solvent is water. The micro-roughening treatment conditions are: temperature 18℃, current density 28A / dm², pH<1.5, time 45s.

[0166] (3) First passivation of the micro-roughened copper foil

[0167] The roughened double-sided copper foil is first passivated with a passivation solution in a brush plating device.

[0168] The passivation solution includes: phytic acid 2g / L, zinc ion 6g / L, nickel ion 0.4g / L, and the negative ion is sulfate ion. The conditions for the first passivation are: temperature 20℃, current density 3A / dm².

[0169] (4) Brush plating the passivated copper foil

[0170] The passivated single-sided copper foil was brush-plated. The deposition solution included: phytic acid 2g / L, nickel ion 6g / L, chromium ion 0.4g / L, negative ion was sulfate ion; silicate 2g / L, sodium fluoride 2g / L. The brush plating conditions were: temperature 30℃, current density 43A / dm².

[0171] (5) Performance testing

[0172] The square resistance and deviation of this embodiment are tested according to the above-mentioned square resistance test method.

[0173] (6) Results analysis

[0174] The square resistance of this embodiment is 75Ω, and the square resistance deviation is 2.6%, which further proves the effectiveness of the technical solution of this application in ensuring the performance of the resistor layer. Compared with the products prepared by the traditional electroplating process, the buried copper foil of this application has significant advantages in uniformity, corrosion resistance and square resistance stability, and can better meet the strict requirements of high-performance electronic products for copper foil materials.

[0175] Comparative Example 1

[0176] Only step (3) in Example 1 is removed, that is, the double-sided copper foil after roughening is not passivated, and the rest is the same as Example 1.

[0177] Other properties are similar to those of Example 1, except that the square resistance uniformity after copper etching is very poor, with a deviation greater than ±5%.

[0178] Comparative Example 2

[0179] Only step (5) in Example 1 is removed, that is, the copper foil after brush plating deposition is not subjected to a second passivation, and the rest is the same as Example 1.

[0180] Other properties are similar to those of Example 1, except that the heat resistance is reduced and oxidation occurs when baked at 250°C for 1 hour.

[0181] The following Table 1 is a comparison table of surface roughness, tensile strength and elongation of various embodiments and comparative examples:

[0182] Table 1

[0183]

[0184] The following Table 2 is a comparison table of the square resistance values ​​of various embodiments and comparative examples:

[0185] Table 2

[0186]

[0187] By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the surface uniformity in Example 1 is better, and there is no oxidation phenomenon after baking at 250°C for 3 hours, indicating that the buried copper foil of the present application has good high temperature resistance and antioxidant properties.

[0188] It should be understood that the present application does not limit its application to the detailed structure and arrangement of the components proposed in the present application. The present application can have other embodiments and can be implemented and executed in a variety of ways. The aforementioned variations and modifications fall within the scope of the present application. It should be understood that the present application and the defined present application extend to all alternative combinations of two or more individual features mentioned or apparent in the text and / or the accompanying drawings. All these different combinations constitute multiple alternative aspects of the present application. The embodiments described in the present application illustrate the best mode known for implementing the present application and will enable those skilled in the art to utilize the present application.

Claims

1. A method for preparing a buried copper foil, characterized in that: Includes steps: Obtaining a copper foil, wherein the copper foil includes a single-sided photoelectrolytic copper foil or a double-sided photoelectrolytic copper foil; The rough surface of the copper foil is subjected to micro-roughening treatment; the micro-roughening treatment includes mixing the copper foil with a micro-roughening solution for roughening, wherein the micro-roughening solution includes a copper-containing material and an acid-containing material, wherein the acid-containing material is composed of two or more types of acids; The surface of the copper foil after the micro-roughening treatment is subjected to a first passivation, wherein the first passivation is prepared by a brush plating process; the passivation solution comprises phytic acid, zinc ions and nickel ions, and the mass ratio of phytic acid, zinc ions and nickel ions is 1:3:0.2; The resistance layer is prepared by depositing the surface of the passivated copper foil, and the resistance layer is prepared by a brush plating process; the brush plating process uses a deposition solution containing silicon, fluorine, nickel, phosphorus, and chromium, and the conditions of the brush plating process are: temperature 15°C~60°C, current density 5 A / dm²~50 A / dm²; It also includes a second passivation, wherein after the brush plating process step, a passivation layer is also formed on the other side of the resistor layer, and the second passivation solution is the same as the first passivation solution; After the second passivation, the finished product is inspected.

2. The preparation method according to claim 1, characterized in that: The roughening treatment conditions are: temperature 15℃~25℃, current density 10 A / dm 2 ~30A / dm 2 , time is 10s ~50s; In the micro-roughening solution, the copper-containing material is 15g / L~40g / L, and the acid-containing material is 30g / L~65g / L; the acid-containing materials include: sulfuric acid 30g / L~60g / L, phosphoric acid 1g / L~5g / L.

3. The preparation method according to claim 1, characterized in that: The first passivation includes: placing the micro-roughened copper foil in a passivation solution for the first passivation.

4. The preparation method according to claim 3, characterized in that: The passivation solution includes: phytic acid 1.5g / L~3.5g / L, zinc ion 5g / L~10g / L and nickel ion 0.3g / L~0.8g / L; The conditions for the first passivation are: temperature 20℃~50℃, current density 1 A / dm 2 ~5A / dm 2 .

5. The preparation method according to claim 1, characterized in that: The second passivation comprises: placing the copper foil after brush plating deposition in a passivation solution for the second passivation.

6. A buried copper foil, characterized in that: The method is prepared by any one of claims 1 to 5.

7. The buried copper foil according to claim 6, characterized in that: Surface roughness <5.0 microns; tensile strength >30kg / mm 2 ; Elongation>5%.

8. An electronic product, characterized in that: It comprises a buried barrier copper foil prepared according to the method for preparing the buried barrier copper foil according to any one of claims 1 to 5, or comprises the buried barrier copper foil according to claim 6 or 7.

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