Copper foil and preparation method thereof, copper-clad plate and printed circuit board

Abstract

The invention provides a copper foil and a preparation method thereof, a copper-clad plate and a printed circuit board. The copper foil comprises a copper foil body, a plurality of island-shaped metal base layers arranged on at least one side of the copper foil body, and coarsening layers arranged on the surfaces of the island-shaped metal base layers, wherein a gap is formed between at least two adjacent island-shaped metal base layers. The copper foil provided by the invention can inhibit the skin effect and improve the signal transmission performance.

Description

Technical Field

[0001] This application relates to the field of copper foil, and in particular to copper foil and its preparation methods, copper-clad laminates and printed circuit boards. Background Technology

[0002] Electrolytic copper foil is a crucial material in the manufacture of copper-clad laminates (CCLs) and printed circuit boards (PCBs), primarily used in electronic products and electrical signal transmission, and is often referred to as the "neural network" of electronic products. With the trend towards thinner and lighter electronic products and higher-frequency, higher-speed signal transmission, the requirements for PCBs in end products are becoming increasingly stringent. PCB performance largely depends on the quality and performance of the copper foil, thus the demands on copper foil quality and performance are constantly rising. However, current copper foil used in printed circuit boards struggles to effectively suppress the skin effect, resulting in poor signal transmission performance. Summary of the Invention

[0003] Based on this, this application provides a copper foil and its preparation method, a copper-clad laminate, and a printed circuit board, which can suppress the skin effect and improve signal transmission performance.

[0004] The first aspect of this application provides a copper foil, comprising: a copper foil body and a plurality of island-shaped metal substrates disposed on at least one side of the copper foil body, and a roughening layer disposed on the surface of the island-shaped metal substrates;

[0005] There is a gap between at least two adjacent island-shaped metal substrates.

[0006] In some embodiments of this application, a gap is present between any two adjacent island-shaped metal substrates.

[0007] In some embodiments of this application, the spacing between the gaps is 20 μm to 100 μm.

[0008] In some embodiments of this application, the roughening layer comprises a plurality of metal clusters;

[0009] Optionally, the metal in the metal cluster includes copper;

[0010] Optionally, the distribution density of the metal clusters is 580 clusters / mm². 2 ~25,000 pieces / mm 2 Optional: 5000 pieces / mm 2 ~25,000 pieces / mm 2 ;

[0011] Optionally, the height of the metal cluster is 0.7 μm to 5.6 μm, and optionally 2 μm to 5 μm.

[0012] In some embodiments of this application, the island-shaped metal substrate includes a stacked metal alloy layer and a metal oxide layer, wherein the metal alloy layer is adjacent to the copper foil body, and the metal oxide layer is disposed between the metal alloy layer and the roughening layer;

[0013] Optionally, the metal alloy layer comprises an alloy composed of three or more elements selected from nickel, tungsten, phosphorus, and molybdenum;

[0014] Optionally, the thickness of the metal alloy layer is 0.03 μm to 0.5 μm, and optionally 0.05 μm to 0.5 μm;

[0015] Optionally, the resistivity of the metal alloy layer is 500 times or more than that of the copper foil body; more preferably, the resistivity of the metal alloy layer is 500 to 3000 times that of the copper foil body.

[0016] Optionally, the metal oxide layer includes one or more of nickel metal oxide, chromium metal oxide, zinc metal oxide, and cobalt metal oxide;

[0017] Optionally, the areal density of the metal element in the metal oxide layer is 0.37 mg / dm³. 2 ~5mg / dm 2 1 mg / dm 2 ~5mg / dm 2 .

[0018] In some embodiments of this application, one or more of the following conditions are met:

[0019] (1) The surface roughness Rz of the copper foil body on the side near the island-shaped metal substrate is 1μm~6μm, and can be selected as 1.5μm~5μm;

[0020] (2) The interface expansion area ratio Sdr' of the copper foil body is 0.6%~23%, and can be selected as 2%~15%;

[0021] (3) The thickness of the copper foil body is 3μm~70μm.

[0022] In some embodiments of this application, the copper foil further includes a protective layer disposed on the surface of the roughened layer; and / or

[0023] The protective layer is disposed on the surface of the copper foil body and located in the gap between two adjacent island-shaped metal substrates; and / or

[0024] The protective layer is disposed on the surface of the copper foil body on the side where the island-shaped metal base layer is not located.

[0025] In some embodiments of this application, the protective layer includes a first protective layer and / or a second protective layer;

[0026] Optionally, the protective layer includes a first protective layer and a second protective layer stacked together, wherein the second protective layer is disposed on the surface of the first protective layer;

[0027] Optionally, the first protective layer includes zinc, and optionally one or more of tin, chromium, and cobalt;

[0028] Optionally, the second protective layer includes a silane coupling agent, which includes one or more of γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, 3-triethoxysilyl-1-propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0029] In some embodiments of this application, one or more of the following conditions are met:

[0030] (1) The interface expansion area ratio Sdr of the copper foil is 1.9%~67%, and can be selected as 10%~45%;

[0031] (2) The horizontal difference Sk at the center of the copper foil is 0.46μm~4.33μm, and can be selected as 1.5μm~3.8μm;

[0032] (3) The aspect ratio Str of the surface properties of the copper foil is 0.3~0.9, and can be selected as 0.3~0.8.

[0033] A second aspect of this application provides a method for preparing copper foil, comprising:

[0034] A metal substrate is prepared on at least one side of the copper foil body;

[0035] A roughening layer is prepared on the metal substrate;

[0036] The metal substrate is etched to prepare multiple island-shaped metal substrates, wherein at least two adjacent island-shaped metal substrates contain a gap.

[0037] A third aspect of this application provides a copper-clad laminate, including the copper foil described in the first aspect of this application or the copper foil prepared by the preparation method of the second aspect of this application.

[0038] A fourth aspect of this application provides a printed circuit board, including the copper-clad laminate described in the third aspect of this application.

[0039] The copper foil provided in this application includes multiple island-shaped metal substrates, with gaps between at least two adjacent island-shaped metal substrates. This prevents complete interconnection between the island-shaped metal substrates, thereby hindering electron transport between them in the horizontal direction. Electron transport is confined within the copper foil body, shortening the transport path and effectively suppressing the skin effect, reducing signal transmission loss, and giving the copper foil better signal transmission performance. Furthermore, the roughening layer provides sufficient adhesion between the copper foil and the insulating resin substrate, resulting in relatively high bonding strength between them. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of a copper foil according to one embodiment of this application.

[0041] Figure 2 This is a schematic diagram of a copper foil according to another embodiment of this application.

[0042] Figure 3 This is a schematic diagram of the etching process according to one embodiment of this application.

[0043] Figure 4 A diagram illustrating the load curve and load area ratio determined according to ISO 25178-2:2021.

[0044] Figure 5 A diagram illustrating the load area ratio Smr1 that separates the prominent peaks and the center, the load area ratio Smr2 that separates the prominent valleys and the center, and the horizontal difference Sk of the center, as determined according to ISO 25178-2:2021.

[0045] Reference numerals: 1 Copper foil body; 2 Island-shaped metal base layer; 3 Roughening layer; 4 Protective layer; 21 Metal alloy layer; 22 Metal oxide layer; 30 Metal cluster; 31 Etching channel; 41 First protective layer; 42 Second protective layer. Detailed Implementation

[0046] To facilitate understanding of this application, a more complete description will be provided below. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0047] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. It should be noted that, unless otherwise stated, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items, "above," "below," includes the stated number, and "one or more" with "multiple" means two or more.

[0049] In this document, when referring to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of selectable values ​​within a numerical interval is considered continuous, and includes the two endpoints (i.e., the minimum and maximum values) of the numerical interval, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all subranges included therein. The "numerical value" in this numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, and other numerical interval types.

[0050] In this document, for methods involving multiple steps, unless otherwise explicitly stated herein, there is no strict order constraint on the execution of these steps; they may be executed in any order other than those described. Moreover, any step may include multiple sub-steps or multiple stages, which are not necessarily completed at the same time, but may be executed at different times, and their execution order is not necessarily sequential, but may be executed in turn, alternately, or simultaneously with other steps or parts of the sub-steps or stages of other steps.

[0051] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0052] Currently, to reduce the insertion loss of electrolytic copper foil or improve the interfacial adhesion of insulating resin substrates, specific additive combinations are typically used during the preparation of electrolytic copper foil, and the ratio of different components is optimized to obtain coarsened particles within a certain particle size range; or the morphology of the coarsened particles is further adjusted according to the type of insulating resin substrate; for example, copper foil with slender needle-like particles is preferred for high-frequency PCBs. However, it is undeniable that the presence of coarsened particles still prolongs the signal transmission path and reduces signal transmittance; and reducing the particle size of the coarsened particles will inevitably lead to a decrease in the adhesion between the copper foil and the insulating resin substrate. Therefore, the electrolytic copper foil currently prepared has not effectively suppressed the skin effect, but has only achieved a balance between signal transmission and adhesion strength. In view of this, the inventors have proposed the following technical solution in this application.

[0053] Firstly, this application provides a copper foil, see [link to relevant documentation]. Figure 1 It includes a copper foil body 1 and a plurality of island-shaped metal base layers 2 disposed on at least one side of the copper foil body, and a roughening layer 3 disposed on the surface of the island-shaped metal base layers 2;

[0054] Among them, at least two adjacent island-shaped metal base layers 20 contain a gap.

[0055] The copper foil provided in this application includes multiple island-shaped metal substrates, with gaps between at least two adjacent island-shaped metal substrates. This prevents complete interconnection between the island-shaped metal substrates, thereby hindering electron transport between them in the horizontal direction. Electron transport is confined within the copper foil body, shortening the transport path and effectively suppressing the skin effect, reducing signal transmission loss, and giving the copper foil better signal transmission performance. Furthermore, the roughening layer provides sufficient adhesion between the copper foil and the insulating resin substrate, resulting in relatively high bonding strength between them.

[0056] It is understood that "multiple island-shaped metal substrates" in this application refers to two or more island-shaped metal substrates.

[0057] It should be noted that the "metal substrate" mentioned in this application refers to a layered structure containing metal elements, such as a metal alloy layer, a metal oxide layer, or a metal layer.

[0058] In some implementations, a gap exists between any two adjacent island-shaped metal substrates. This prevents any two adjacent island-shaped metal substrates from connecting, further hindering electron transport between the substrates and suppressing the skin effect, thus giving the copper foil better signal transmission performance.

[0059] In some embodiments, the gap spacing is 20 μm to 100 μm. For example, the gap spacing can be 20 μm, 31 μm, 42 μm, 53 μm, 64 μm, 75 μm, 86 μm, 97 μm, 100 μm, or within any range of these values. This helps to further suppress the skin effect, giving the copper foil better signal transmission performance.

[0060] It is understood that the "gap distance" in this application refers to the distance between the edges of two adjacent island-shaped metal base layers 2, as can be seen in [reference needed]. Figure 2 The interval distance is mainly related to the surface roughness Rz of the copper foil body. By controlling the surface roughness Rz of the copper foil body within the range of this application, the interval distance can be adjusted within the above range.

[0061] In some implementations, see Figure 1 or Figure 3 The roughening layer 3 includes multiple metal clusters 30. The metal clusters help to enhance the adhesion between the copper foil and the insulating resin substrate, and improve the structural stability of the copper-clad laminate during processing.

[0062] In some embodiments, at least two adjacent metal clusters contain gaps. This provides a channel for etching, allowing the etchant to pass through the gaps between the metal clusters into the metal substrate, thereby etching away the metal alloy layer and metal oxide layer in specific areas.

[0063] In some implementations, the metal in the metal cluster includes copper.

[0064] In some embodiments, the distribution density of metal clusters is 580 clusters / mm². 2 ~25,000 pieces / mm 2 Optional: 5000 pieces / mm 2 ~25,000 pieces / mm 2 For example, the distribution density of metal clusters can be 580 clusters / mm². 2 2500 pieces / mm 2 5000 pieces / mm 2 8000 pieces / mm 2 12,000 pieces / mm 2 16,000 pieces / mm 2 18,000 pieces / mm2 23,000 pieces / mm 2 25,000 pieces / mm 2 Or it may fall within any of the above value ranges. This is beneficial for further improving the adhesion between the copper foil and the insulating resin board, resulting in higher bonding strength between the copper foil and the insulating resin board.

[0065] It is understood that the "distribution density of metal clusters" in this application refers to the number of metal clusters on the roughened layer per square millimeter.

[0066] In some embodiments, the height of the metal clusters is 0.7 μm to 5.6 μm, optionally 2 μm to 5 μm. For example, the height of the metal clusters can be 0.7 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, or within any range of these values. This is beneficial for providing sufficient adhesion to the insulating resin substrate and for reducing the risk of residual copper after etching, thus reducing the potential short circuit problems caused by residual copper.

[0067] It is understood that the "height of the metal cluster" in this application refers to the height of the metal cluster in the direction perpendicular to the surface of the copper foil body, that is, in the thickness direction of the copper foil body.

[0068] In some embodiments, the metal cluster comprises a plurality of aggregated metal particles.

[0069] In some implementations, see Figure 1 The island-shaped metal substrate 2 includes a stacked metal alloy layer 21 and a metal oxide layer 22. The metal alloy layer 21 is adjacent to the copper foil body 1, and the metal oxide layer 22 is disposed between the metal alloy layer 21 and the roughening layer 3. The metal alloy layer can act as a barrier layer, hindering the transfer of electrons from the copper foil body to the metal clusters in the vertical direction. The metal oxide layer can protect the metal alloy layer from corrosion by the electroplating solution during the electroplating process, and can also provide a conductive substrate for the subsequent roughening treatment to prepare the roughening layer.

[0070] In some embodiments, the metal alloy layer is conformally covered by a metal oxide layer. Thus, the metal oxide layer is distributed in an island-like structure on the surface of the metal alloy layer, which further hinders electron transport in the horizontal direction parallel to the surface of the copper foil, further suppressing the skin effect.

[0071] It should be noted that the above-mentioned "conformal coverage" means that the metal oxide layer grows closely in contact with the metal alloy layer, thereby enabling both the metal oxide layer and the metal alloy layer to have an island-like structure.

[0072] In some embodiments, the metal alloy layer comprises an alloy of three or more elements selected from nickel, tungsten, phosphorus, and molybdenum. This not only gives the metal alloy layer better insulation properties, hindering electron transport and reducing the skin effect, but also facilitates subsequent etching processes.

[0073] In some embodiments, the thickness of the metal alloy layer is 0.03 μm to 0.5 μm, optionally 0.05 μm to 0.5 μm. For example, the thickness of the metal alloy layer can be 0.03 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.3 μm, 0.5 μm, or within any range of these values. Therefore, if the thickness of the metal alloy layer is relatively small, it can still conduct electricity due to the quantum tunneling effect, thus electrons can still potentially enter the roughening layer from the copper foil body; if the thickness of the metal alloy layer is relatively large, there is a risk of cracking due to the internal stress of electrodeposition.

[0074] In some embodiments, the resistivity of the metal alloy layer is 500 times or more that of the copper foil body; alternatively, the resistivity of the metal alloy layer is 500 to 3000 times that of the copper foil body. Thus, the metal alloy layer can act as a barrier layer, hindering the transport of electrons.

[0075] In some embodiments, the resistivity of the metal alloy layer is 10.5 × 10⁻⁶. -4 Ω·cm ~15.5×10 -4 Ω·cm. For example, the resistivity of a metal alloy layer can be 10.5 × 10⁻⁶ Ω·cm. -4 Ω·cm, 11×10 -4 Ω·cm, 12×10 -4 Ω·cm, 13×10 -4 Ω·cm, 14×10 -4 Ω·cm, 15.5×10 -4 The value is Ω·cm or falls within any of the above ranges. Therefore, the metal alloy layer can effectively impede electron transport.

[0076] In some embodiments, the metal oxide layer includes one or more of nickel metal oxide, chromium metal oxide, zinc metal oxide, and cobalt metal oxide.

[0077] In some embodiments, the areal density of the metal element in the metal oxide layer is 0.37 mg / dm³. 2 ~5mg / dm 2 1 mg / dm 2 ~5mg / dm 2 For example, the areal density can be 0.37 mg / dm³. 2 1mg / dm 22mg / dm 2 3mg / dm 2 4mg / dm 2 5mg / dm 2 Or it may fall within any of the above value ranges. This is beneficial for providing a better conductive substrate for the subsequent roughening process of preparing the roughening layer, and is more conducive to the formation of the roughening layer.

[0078] In some embodiments, the surface roughness Rz of the copper foil body near the island-shaped metal substrate is 1 μm to 6 μm, optionally 1.5 μm to 5 μm; and the interface expansion area ratio Sdr' of the copper foil body is 0.6% to 23%, optionally 2% to 15%. For example, the surface roughness Rz can be 1 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm or within any of the above values; the interface expansion area ratio Sdr' of the copper foil body can be 0.6%, 2%, 4%, 6%, 8%, 10%, 14%, 18%, 23% or within any of the above values.

[0079] If the surface roughness Rz and interface expansion area of ​​the copper foil body are relatively small compared to Sdr', then during the subsequent roughening process of preparing the roughening layer, due to the relatively flat surface of the copper foil body and the lack of sufficient tip discharge sites, the roughening particles tend to cover the entire copper foil body, making it difficult to form metal clusters. This will affect the adhesion strength between the copper foil and the insulating resin substrate. Furthermore, if the roughening particles cover the entire copper foil body, it is not conducive to constructing island-like metal alloy layers and metal oxide layers. If the surface roughness Rz and interface expansion area of ​​the copper foil body are relatively large compared to Sdr', then due to the relatively strong tip discharge effect, the size of the metal clusters formed by the agglomeration of roughening particles will be relatively large, affecting the etching effect.

[0080] It is understood that the surface roughness "Rz" of the insulating roughening layer in this application refers to the average peak-valley height, which is the average vertical distance between multiple highest peaks and lowest valleys within a sampling length. Its test standard can be found in GB / T29847-2013.

[0081] It should be noted that in this application, "interface expansion area ratio" refers to a parameter measured according to ISO 25178-2:2021, indicating how much the expanded area (surface area) of a defined region increases relative to the area of ​​the defined region. In this application, the interface expansion area ratio is expressed as the increase in surface area (%). The smaller the value, the closer the surface shape is to a flat surface; the interface expansion area ratio for a completely flat surface is 0%. On the other hand, the larger the value, the closer the surface shape is to a surface with more irregularities. For example, an interface expansion area ratio of 20% indicates that the surface area has increased by 20% from a completely flat surface.

[0082] In some embodiments, the thickness of the copper foil body is 3 μm to 70 μm. For example, the thickness of the copper foil body can be 3 μm, 7 μm, 11 μm, 23 μm, 46 μm, 48 μm, 70 μm, or within any range of the above values.

[0083] In some embodiments, the copper foil body includes electrolytic copper foil or rolled copper foil.

[0084] In some implementations, see Figure 1 The copper foil also includes a protective layer 4, which is disposed on the surface of the roughened layer 3; and / or

[0085] The protective layer 4 is disposed on the surface of the copper foil body 1 and located in the gap between two adjacent island-shaped metal substrates 2; and / or

[0086] The protective layer 4 is provided on the surface of the copper foil body 1 on the side where the island-shaped metal base layer 2 is not provided.

[0087] In some implementations, see Figure 1 The protection layer 4 includes a first protective layer 41 and / or a second protective layer 42. The protective layers can be used to reduce or even prevent functional failures caused by oxidation of the copper foil during downstream processing and end applications.

[0088] In some embodiments, the protective layer includes a first protective layer and a second protective layer stacked together, with the second protective layer disposed on the surface of the first protective layer.

[0089] In some embodiments, the first protective layer includes zinc, and optionally one or more of tin, chromium, and cobalt. Thus, the first protective layer helps to reduce or even prevent functional failure caused by oxidation of the copper foil at high temperatures.

[0090] In some embodiments, the second protective layer comprises a silane coupling agent, including one or more of γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, 3-triethoxysilyl-1-propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane. Therefore, the second protective layer helps to reduce or even prevent functional failure caused by oxidation of the copper foil at room temperature.

[0091] It should be noted that in this application, "high temperature" refers to a temperature of 180℃~220℃; "normal temperature" refers to a temperature of 20℃~30℃.

[0092] In some embodiments, the interfacial extension area ratio (Sdr) of the copper foil is 1.9% to 67%, optionally 10% to 45%. For example, Sdr can be 1.9%, 5.8%, 10%, 21%, 34%, 40%, 45%, or within any range of the above values. This indicates that the surface of the copper foil has relatively more unevenness, reflecting a relatively larger number of island structures, which is beneficial for obtaining a better suppression effect on the skin effect and a higher adhesion strength between the copper foil and the insulating resin substrate.

[0093] In some embodiments, the horizontal difference Sk at the center of the copper foil is 0.46 μm to 4.33 μm, optionally 1.5 μm to 3.8 μm. For example, Sk can be 0.46 μm, 1.5 μm, 2.6 μm, 3.8 μm, 4.33 μm, or within any range of the above values. This facilitates a high degree of adhesion between the copper foil and the insulating resin substrate.

[0094] It should be noted that the "level difference Sk at the center" in this application refers to the value obtained by subtracting the minimum height from the maximum height at the center, as measured according to ISO 25178-2:2021; see [link to relevant documentation]. Figure 5 , is the parameter calculated from the height difference between the load area ratio of 0% and 100% through the equivalent straight line.

[0095] Here, "load area ratio" refers to the area parameter of the region above a certain height c in the load curve; the "load curve" (also called the "surface load curve") is a curve representing the load area ratio from 0% to 100% height, measured according to ISO 25178-2:2021. See also Figure 4 The load-bearing area ratio corresponding to height c is equivalent to Smr(c) in the figure. For example... Figure 5 As shown, starting from a load area ratio of 0%, a secant line is drawn along the load curve, with the difference in load area ratios set to 40%. Moving this secant line from a load area ratio of 0%, the point where the slope of the secant line is gentlest is called the central portion of the load curve. The straight line with the smallest sum of squares of deviations from the vertical axis relative to this central portion is called the equivalent straight line. The portion encompassed by the equivalent straight line within the height range of 0% to 100% load area ratio is called the central portion. The portion higher than the central portion is called the prominent peak, and the portion lower than the central portion is called the prominent valley.

[0096] In some embodiments, the aspect ratio Str of the copper foil surface morphology is 0.3 to 0.9, and can be selected as 0.3 to 0.8. For example, Str can be 0.3, 0.5, 0.7, 0.8, 0.9, or within any range of the above values. This indicates that the surface morphology of the copper foil exhibits relatively high randomness, which is beneficial for achieving a high degree of adhesion between the copper foil and the insulating resin substrate.

[0097] It should be noted that the "aspect ratio of surface properties" in this application refers to a parameter measuring the isotropic and / or anisotropic properties of a surface, as determined according to ISO 25178-2:2021. The value of Str falls between 0 and 1. When Str is 0 or close to 0, it indicates that the surface texture exhibits significant anisotropy, resulting in a highly regular surface morphology. For example, when Str is 0, adjacent peaks and troughs may all appear as stripes and be arranged parallel to each other. In contrast, when Str is 1 or close to 1, it indicates that the surface texture exhibits strong isotropy, resulting in a highly random surface morphology.

[0098] By controlling the surface morphology parameters Sdr, Sk, and Str of the copper foil within a certain range, the requirements of downstream PCB processing for the adhesion between the insulating resin substrate and the copper foil can be met.

[0099] Non-limiting, the interface expansion area ratio Sdr or Sdr', the horizontal difference Sk at the center, and the aspect ratio Str of the surface properties can be determined by using a commercially available laser confocal microscope on a specified area of ​​the surface to be tested (e.g., 18364 μm). 2 The surface profile of the two-dimensional region was measured to calculate the values ​​of the interface expansion area ratio Sdr or Sdr', the horizontal difference Sk at the center, and the aspect ratio Str of the surface features. In this application, the values ​​of these parameters were measured under conditions of a cutoff wavelength of 0.55 μm based on an S-filter and a cutoff wavelength of 10 μm based on an L-filter.

[0100] Secondly, this application provides a method for preparing copper foil, which can be used to prepare the copper foil of the first aspect of this application, and may include the following steps:

[0101] A metal substrate is prepared on at least one side of the copper foil body;

[0102] A roughening layer is prepared on a metal substrate;

[0103] The metal substrate is etched to prepare multiple island-shaped metal substrates, wherein at least two adjacent island-shaped metal substrates contain a gap.

[0104] See Figure 3The roughened layer 3 formed above includes metal clusters 30. The gaps between the metal clusters 30 can serve as etching channels 31, which allows the etching solution to selectively etch away the metal substrate (i.e., the metal alloy layer 21 and the metal oxide layer 22) in specific locations, thereby forming an island structure.

[0105] In some embodiments, the etching process includes a first etching and a second etching, wherein the second etching is performed after the first etching. Further, the first etching includes etching a metal oxide layer using etchant A; further, the second etching includes etching a metal alloy layer using etchant B. Optionally, the surface is rinsed with water after each etching.

[0106] In some embodiments, etching solution A comprises: 4 g / L to 12 g / L aminosulfonic acid, 5 g / L to 14 g / L ethylenediaminetetraacetic acid, 3 g / L to 10 g / L concentrated sulfuric acid, and 0.3 g / L to 0.6 g / L benzotriazole. Therefore, etching solution A has a very fine etching effect on copper, thus selectively etching to obtain an island-like structure in the metal oxide layer while minimizing damage to metal clusters in the roughened layer.

[0107] In some embodiments, etching solution B comprises: 200 g / L to 300 g / L copper sulfate pentahydrate and 3 g / L to 10 g / L concentrated sulfuric acid. Therefore, etching solution B has a very subtle etching effect on copper, thus selectively etching to obtain an island-like structure in the metal alloy layer while minimizing damage to metal clusters in the roughened layer.

[0108] In some embodiments, the first etching time is 25s to 55s; in other embodiments, the second etching time is 1min to 15min. For example, the first etching time can be 25s, 36s, 48s, 55s, or any value within the range above; the second etching time can be 1min, 3min, 8min, 12min, 15min, or any value within the range above. Controlling the first and / or second etching times within appropriate ranges allows for selective etching to achieve an island-like structure in the metal oxide layer and / or metal alloy layer while reducing damage to metal clusters in the roughened layer.

[0109] In some embodiments, the pH of etching solution A is 3-6; in other embodiments, the temperature of etching solution A is 20°C-25°C. In still other embodiments, the temperature of etching solution B is 80°C-95°C.

[0110] In some embodiments, the step of preparing a metal substrate on at least one side of the copper foil body may include:

[0111] Electroplating is performed on the copper foil body to prepare a metal alloy layer;

[0112] A metal oxide layer is deposited on the surface of a metal alloy layer using a vacuum sputtering method.

[0113] In some embodiments, the step of electroplating the copper foil body includes: introducing the copper foil body into an electrolytic cell, circulating an electrolyte in the electrolytic cell, using the copper foil body as the cathode and an insoluble titanium material as the anode, and electrodepositing a metal alloy layer on it.

[0114] In some embodiments, the electrolyte includes three or more ions or anions selected from nickel, tungsten, phosphorus, and molybdenum. Further, the nickel ions are derived from nickel sulfate and / or nickel chloride, the tungstate ions are derived from sodium tungstate and / or ammonium tungstate, the hypophosphite ions are derived from sodium hypophosphite and / or potassium hypophosphite, and the molybdate ions are derived from sodium molybdate. In addition to the above ions or anions, the electrolyte also includes a complexing agent and a buffer; the complexing agent may be sodium citrate, and the buffer may be boric acid.

[0115] In some embodiments, the concentrations of nickel ions in the electrolyte are 8.3 g / L to 22.3 g / L, tungstate ions are 17.2 g / L to 51.6 g / L, hypophosphite ions are 15.6 g / L to 31.5 g / L, molybdate ions are 16.2 g / L to 48.6 g / L, sodium citrate is 60 g / L to 120 g / L, and boric acid is 20 to 50 g / L.

[0116] In some embodiments, the temperature of the electrolyte is 40°C to 70°C, the pH value of the electrolyte is 4 to 8, and the electroplating current density is 0.5 A / dm³. 2 ~5A / dm 2 .

[0117] In some embodiments, before applying the metal oxide layer, the surface of the metal alloy layer can be cleaned with a cleaning solution; optionally, the pH value of the cleaning solution is 7-8, and the cleaning time is 5-10 seconds. After cleaning with the cleaning solution, it can be rinsed with anhydrous ethanol and dried with nitrogen at room temperature. Cleaning with the cleaning solution helps to remove residual electrolyte on the surface of the metal alloy layer; on the other hand, the cleaning solution is weakly alkaline, which helps to promote the passivation of the metal alloy layer, making the surface of the metal alloy layer non-conductive. The purpose of using ethanol for cleaning is that ethanol will not cause the dissolution of the passivation layer.

[0118] In some embodiments, the cleaning solution includes boric acid and / or sodium tetraborate. Further, the concentration of boric acid is 1.0 g / L to 3.0 g / L, and the concentration of sodium tetraborate is 4.0 g / L to 6.0 g / L.

[0119] In some embodiments, the step of depositing a metal oxide layer on the surface of a metal alloy layer using a vacuum sputtering method includes: depositing a metal material in the form of an oxide on the surface of the metal alloy layer by vacuum reactive sputtering.

[0120] It is understandable that the composition and thickness of the metal oxide layer can be controlled by adjusting the metal target, deposition power, deposition time, and gas volume in vacuum sputtering.

[0121] In some embodiments, the ion source for vacuum sputtering can be a Hall ion source, a Kaufman ion source, a pulsed bias ion source, etc.

[0122] In some embodiments, the metal target for vacuum sputtering can be one or more of a nickel target, a nickel-chromium alloy target, a nickel-zinc alloy target, and a nickel-cobalt alloy target; further, the mass ratio of nickel in the alloy target is greater than or equal to 60%.

[0123] In some embodiments, the working gases for vacuum sputtering are argon and oxygen, and the filling volume of each working gas is independently 50 sccm to 300 sccm for argon with a purity of 99.99%; and 20 sccm to 100 sccm for oxygen with a purity of 99.99%.

[0124] In some embodiments, the deposition power of vacuum sputtering is 5kW to 15kW, calculated as 1mg / dm³ for the deposition amount of metal elements. 2 ~5mg / dm 2 If the amount of metal elements deposited is relatively small, the conductivity of the metal oxide layer will be insufficient, and its surface will not be able to provide sufficient nucleation sites for the roughening of the roughening layer, making it difficult to form metal clusters. If the amount of metal elements deposited is relatively large, it will easily lead to an increase in the thickness of the metal oxide layer, which may result in the risk of interruption of the etching process.

[0125] In some embodiments, the step of preparing a roughened layer on a metal substrate includes: roughening a metal oxide layer to grow metal clusters on the surface of the metal oxide layer. The gaps between the metal clusters can serve as etching channels, facilitating the selective etching away of specific areas of the metal alloy layer and metal oxide layer, thereby forming an island-like structure.

[0126] In some embodiments, the roughening treatment is performed in a roughening electroplating solution, with copper foil as the cathode and the metal oxide layer on the copper foil facing the anode. Further, the roughening treatment time is 8s~15s, and the roughening current density is 6A / dm². 2 ~25A / dm 2 After roughening, it can be rinsed clean with pure water.

[0127] In some implementations, the roughening electroplating solution includes 5 g / L to 25 g / L of copper ions, 80 g / L to 150 g / L of concentrated sulfuric acid, and 10 mg / L to 30 mg / L of roughening additives. Further, the roughening additives include one or more of sodium tungstate, α-naphthylquinoline, ascorbic acid, dextrin, gelatin, thiourea, and carboxybenzotriazole.

[0128] It should be noted that the growth of metal clusters in the roughened layer can be regulated by controlling at least one of the following conditions: the current density of the roughening treatment, the concentration of each component of the roughening electroplating solution, and the type of additives.

[0129] In some implementations, the above preparation method also includes the step of preparing a protective layer;

[0130] The copper foil body containing multiple island-shaped metal substrates is subjected to rust prevention treatment to form the first protective layer;

[0131] A silane coupling agent is applied to the surface of the first protective layer to form a second protective layer.

[0132] In some embodiments, the electrolyte used for rust prevention treatment includes one or more of the following components: zinc ions 0.8 g / L to 1.2 g / L, hexavalent chromium ions 0.8 g / L to 1.2 g / L, and tin ions 0.5 g / L to 1.0 g / L; in addition to the above metal ions, the electrolyte also includes potassium pyrophosphate 50 g / L to 100 g / L. The pH of the electrolyte is 10 to 12, the temperature of the electrolyte is 35°C to 45°C, and the current density for rust prevention treatment is 1.0 A / dm³. 2 ~4.0A / dm 2 .

[0133] In some embodiments, the silane coupling agent can be applied using conventional methods in the art, with a preferred method being spraying followed by roller coating.

[0134] In some embodiments, before preparing a metal substrate on at least one side of the copper foil body, the above preparation method further includes: performing a surface pretreatment on the copper foil body.

[0135] In some embodiments, the step of surface pretreatment of the copper foil body includes: pickling the copper foil body with an acid pickling solution before applying the metal alloy layer to remove oxides and impurities on its surface. Further, the copper foil body can be rinsed thoroughly with pure water after pickling. Further, the acid pickling solution includes 3% to 10% concentrated sulfuric acid by mass; the pickling method includes immersion or spraying.

[0136] Thirdly, this application provides a copper-clad laminate, including the copper foil of the first aspect of this application or the copper foil prepared by the preparation method of the second aspect of this application.

[0137] In some embodiments, the copper-clad laminate further includes a resin substrate disposed on the roughening layer. The resin substrate provides electrical isolation between different copper foil traces on the printed circuit board, preventing short circuits. Further, the copper foil and the resin substrate can be laminated together, thereby disposing the resin substrate on the roughening layer of the copper foil.

[0138] Fourthly, this application provides a printed circuit board, including the copper-clad laminate of the third aspect of this application.

[0139] The following are specific embodiments, which describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations within the scope of the disclosure of this application will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0140] Example 1

[0141] S1) Select a copper foil body with one side having an Rz of 2.5 μm and an Sdr of 3%. Clean the copper foil body by spraying with a 5% (w / w) concentrated sulfuric acid aqueous solution, and then rinse it with pure water.

[0142] S2) A metal alloy layer is electroplated on the surface of the copper foil body with a radius (Rz) of 2.5 μm. The electrolyte composition is as follows: nickel ions 15 g / L, hypophosphite ions 19.5 g / L, molybdate ions 19 g / L, sodium citrate 80 g / L, boric acid 35 g / L. The electrolyte temperature is 60℃, the electrolyte pH is 7.6, and the current density is 2 A / dm³. 2 The thickness of the metal alloy layer is 0.08 μm.

[0143] S3)① Clean the surface of the metal alloy layer with a cleaning solution containing 1.5 g / L boric acid and 5 g / L sodium tetraborate for 10 seconds. After cleaning with the cleaning solution, rinse with anhydrous ethanol and dry with nitrogen at room temperature.

[0144] ② A metal oxide layer is vacuum sputtered onto the surface of the aforementioned metal alloy layer. The process is as follows: a nickel-zinc alloy target is selected, with a nickel mass fraction of 70%; the flow rates of argon and oxygen are 200 sccm and 40 sccm, respectively; the vacuum sputtering power is 8 kW, and the deposition time is 5 min. The deposition amount of metal elements in the metal oxide layer is 1 mg / dm³. 2 .

[0145] S4) ① The copper foil is subjected to a roughening treatment to generate metal clusters on the surface of the metal oxide. The roughening electrolyte includes 15 g / L of copper ions, 110 g / L of concentrated sulfuric acid, and 15 mg / L of carboxybenzotriazole. The roughening current density of the electrolyte is 15 A / dm³. 2 The roughening process takes 10 seconds. After roughening, rinse thoroughly with pure water.

[0146] ② After roughening treatment, etching treatment is performed. The first step is to etch the metal oxide layer using etching solution A. The formula of etching solution A is as follows: 6 g / L aminosulfonic acid, 8 g / L ethylenediaminetetraacetic acid, 5 g / L concentrated sulfuric acid, 0.3 g / L benzotriazole, pH of etching solution A is 3.5, temperature of etching solution A is 25℃, and etching time is 30s.

[0147] The second step involves etching the metal alloy layer using etching solution B. The formulation of etching solution B is as follows: 250 g / L copper sulfate pentahydrate, 8 g / L concentrated sulfuric acid. The temperature of etching solution B is 90℃, and the etching time is 3 minutes. After each etching step, rinse thoroughly with pure water.

[0148] The first step involves etching an island-shaped metal oxide layer using etching solution A, and the second step involves etching an island-shaped metal alloy layer using etching solution B. Thus, the island-shaped metal oxide layer and the island-shaped metal alloy layer together form an island-shaped metal base layer.

[0149] S5)① Apply rust prevention treatment to both surfaces of the copper foil treated in S4). The electrolyte used for rust prevention treatment includes the following components: 1 g / L zinc ions, 1 g / L hexavalent chromium ions, 70 g / L potassium pyrophosphate, pH 11, temperature 40℃, and current density 2 A / dm³. 2 Electroplating for 8 seconds. This forms the first protective layer.

[0150] ② γ-aminopropyltriethoxysilane is sprayed onto the surface of the copper foil after the above treatment to form a coupling agent layer, thereby forming a second protective layer.

[0151] Example 2

[0152] S1) Select a copper foil body with one side having an Rz of 3.5 μm and an Sdr of 5%. Clean the copper foil body by spraying with a 5% (w / w) concentrated sulfuric acid aqueous solution, and then rinse it with pure water.

[0153] S2) A metal alloy layer is electroplated on the surface of the copper foil body with a radius (Rz) of 3.5 μm. The electrolyte composition is as follows: nickel ions 15 g / L, hypophosphite ions 19.5 g / L, tungstate ions 22 g / L, sodium citrate 80 g / L, boric acid 40 g / L. The electrolyte temperature is 60℃, the electrolyte pH is 5.5, and the current density is 4 A / dm³. 2The thickness of the metal alloy layer is 0.2 μm.

[0154] S3)① Clean the surface of the metal alloy layer with a cleaning solution containing 1.5 g / L boric acid and 5 g / L sodium tetraborate for 10 seconds. After cleaning with the cleaning solution, rinse with anhydrous ethanol and dry with nitrogen at room temperature.

[0155] ② A metal oxide layer is vacuum sputtered onto the surface of the aforementioned metal alloy layer. The process is as follows: a nickel-chromium alloy is selected as the target material, with a nickel mass fraction of 70%; the flow rates of argon and oxygen are 200 sccm and 45 sccm, respectively; the vacuum sputtering power is 10 kW, and the deposition time is 10 min. The deposition amount of metal elements in the metal oxide layer is 3 mg / dm³. 2 .

[0156] S4) ① The copper foil is subjected to a roughening treatment to generate metal clusters on the surface of the metal oxide. The roughening electrolyte includes 15 g / L of copper ions, 110 g / L of concentrated sulfuric acid, and 15 mg / L of carboxybenzotriazole. The roughening current density of the electrolyte is 15 A / dm³. 2 The roughening process takes 10 seconds. After roughening, rinse thoroughly with pure water.

[0157] ② The first step is to etch the metal oxide layer using etching solution A. The formula of etching solution A is as follows: 6 g / L aminosulfonic acid, 8 g / L ethylenediaminetetraacetic acid, 5 g / L concentrated sulfuric acid, 0.3 g / L benzotriazole, pH of etching solution A is 3.5, temperature of etching solution A is 25℃, and etching time is 50 s.

[0158] The second step involves etching the metal alloy layer using etching solution B. The formulation of etching solution B is as follows: 250 g / L copper sulfate pentahydrate, 8 g / L concentrated sulfuric acid. The temperature of etching solution B is 90℃, and the etching time is 7 minutes. After each etching step, rinse thoroughly with pure water.

[0159] The first step involves etching an island-shaped metal oxide layer using etching solution A, and the second step involves etching an island-shaped metal alloy layer using etching solution B. Thus, the island-shaped metal oxide layer and the island-shaped metal alloy layer together form an island-shaped metal base layer.

[0160] S5)① Apply rust prevention treatment to both surfaces of the copper foil treated in S4). The electrolyte used for rust prevention treatment includes the following components: 1 g / L zinc ions, 1 g / L hexavalent chromium ions, 70 g / L potassium pyrophosphate, pH 11, temperature 40℃, and current density 2 A / dm³. 2 Electroplating for 8 seconds. This forms the first protective layer.

[0161] ② A γ-glycidyl etheroxypropyltrimethoxysilane is sprayed onto the copper foil surface after the above treatment to form a coupling agent layer, thereby forming a second protective layer.

[0162] Example 3

[0163] S1) Select a copper foil body with one side having an Rz of 5μm and an Sdr of 15%. Clean the copper foil body by spraying with a 5% (w / w) concentrated sulfuric acid aqueous solution, and then rinse it with pure water.

[0164] S2) A metal alloy layer is electroplated on the surface of the copper foil with a radius (Rz) of 5 μm. The electrolyte composition is as follows: nickel ions 21 g / L, hypophosphite ions 29.5 g / L, molybdate ions 30 g / L, sodium citrate 110 g / L, boric acid 45 g / L. The electrolyte temperature is 60℃, the pH value is 7.6, and the current density is 2 A / dm³. 2 The thickness of the metal alloy layer is 0.5 μm.

[0165] S3)① Clean the surface of the metal alloy layer with a cleaning solution containing 3 g / L boric acid and 6 g / L sodium tetraborate for 5 seconds. After cleaning with the cleaning solution, rinse with anhydrous ethanol and dry with nitrogen at room temperature.

[0166] ② A metal oxide layer was vacuum sputtered onto the surface of the aforementioned metal alloy layer. The process was as follows: nickel was selected as the target material, and the flow rates of argon and oxygen were 200 sccm and 50 sccm, respectively; the vacuum sputtering power was 13 kW, and the deposition time was 8 min. The deposition amount of metal elements in the metal oxide layer was 5 mg / dm³. 2 .

[0167] S4) ① The copper foil is subjected to a roughening treatment to generate metal clusters on the surface of the metal oxide. The roughening electrolyte includes 15 g / L copper ions, 110 g / L concentrated sulfuric acid, and 20 mg / L thiourea. The roughening current density of the electrolyte is 15 A / dm³. 2 The roughening process takes 15 seconds, and after roughening, rinse thoroughly with pure water.

[0168] ② The first step is to etch the metal oxide layer using etching solution A. The formula of etching solution A is as follows: 6 g / L aminosulfonic acid, 8 g / L ethylenediaminetetraacetic acid, 5 g / L concentrated sulfuric acid, 0.3 g / L benzotriazole, pH of etching solution A is 3.5, temperature of etching solution A is 25℃, and etching time is 50 s.

[0169] The second step involves etching the metal alloy layer using etching solution B. The formulation of etching solution B is as follows: 250 g / L copper sulfate pentahydrate, 8 g / L concentrated sulfuric acid. The temperature of etching solution B is 90℃, and the etching time is 14 minutes. After each etching step, rinse thoroughly with pure water.

[0170] The first step involves etching an island-shaped metal oxide layer using etching solution A, and the second step involves etching an island-shaped metal alloy layer using etching solution B. Thus, the island-shaped metal oxide layer and the island-shaped metal alloy layer together form an island-shaped metal base layer.

[0171] S5)① Apply rust prevention treatment to both surfaces of the copper foil treated in S4). The electrolyte used for rust prevention treatment includes the following components: 1 g / L zinc ions, 1 g / L hexavalent chromium ions, 70 g / L potassium pyrophosphate, pH 11, temperature 40℃, and current density 2 A / dm³. 2 Electroplating for 8 seconds. This forms the first protective layer.

[0172] ② γ-aminopropyltriethoxysilane is sprayed onto the surface of the copper foil after the above treatment to form a coupling agent layer, thereby forming a second protective layer.

[0173] Example 4

[0174] Unlike Example 1, the Rz of the copper foil body is 1.0 μm and the Sdr is 0.6%, while other conditions are the same as in Example 1.

[0175] Example 5

[0176] Unlike Example 1, the thickness of the metal alloy layer is 0.03 μm, the etching time of etchant B in step S4) is 1 min, and other conditions are the same as in Example 1.

[0177] Example 6

[0178] Unlike Example 1, the deposition amount of metal elements in the metal oxide layer is 0.37 mg / dm³. 2 In step S4), the etching time of etching solution A is 12s, and other conditions are the same as in Example 1.

[0179] Example 7

[0180] Unlike Example 1, the copper foil body has an Rz of 6.0 μm and an Sdr of 23%, while other conditions are the same as in Example 1.

[0181] Example 8

[0182] Unlike Example 1, in step S3), oxygen is not introduced during the sputtering deposition of the metal oxide layer, and a metal layer is formed instead of a metal oxide layer. Other conditions are the same as in Example 1.

[0183] Example 9

[0184] Unlike Example 1, in step S4), the roughening process takes 20 seconds, while other conditions are the same as in Example 1.

[0185] Comparative Example 1

[0186] Unlike Example 1, step S4) omits step ②, that is, selective etching is not performed on the metal alloy layer and the metal oxide layer so that the metal alloy layer and the metal oxide layer do not form island structures. Other conditions are the same as in Example 1.

[0187] The copper foils or further copper-clad laminates prepared in Examples 1-9 and Comparative Example 1 were subjected to relevant performance tests, and the test results are shown in Table 1 below. In Table 1, " / " indicates that the data is outside the measurement range or cannot be tested; the insertion loss is negative, and the more negative it is, the worse the performance.

[0188] The test conditions or standards for each performance test item are as follows:

[0189] (1) Thickness of the copper foil body: based on the mass of copper foil per unit area, for example, 1 dm 2 The thickness of the copper foil is obtained by dividing the mass of the copper foil by the density of copper, where the density of the copper foil is 8.93 g / cm³. 3 calculate.

[0190] (2) Surface roughness Rz: The surface roughness Rz was tested using a contact tester in accordance with GB / T 29847-2013.

[0191] (3) Thickness of the metal alloy layer: Three 1dm sections are cut from the copper foil processed in step S2). 2 For each sample, three 5mm × 2mm test samples were cut from each sample. The cross-section of the test sample was polished using an ion polisher. The test sample was then placed under a scanning electron microscope and the cross-section was observed at 15kx magnification. Three points were randomly tested on each sample, and the average of the results of all test points was taken.

[0192] (4) Thickness of the metal oxide layer: The elemental content of the metal oxide layer is independent of the substrate and directly related to the sputtering process; therefore, the metal oxide layer is sputtered onto a clean copper foil using the same process, and three 1dm thicknesses are taken. 2 Samples of various sizes were then digested with dilute acid, and the metal element content in the solution was determined using inductively coupled plasma spectroscopy (ICP). The results were then averaged.

[0193] (5) Distribution density of metal clusters: 1 dm of surface-treated copper foil was cut. 2 Samples of this size were tested using a laser confocal microscope in accordance with ISO 25178-3:2012 to obtain peak density values, which can be equivalent to the number of metal clusters.

[0194] (6) Height of metal clusters: 1 dm of surface-treated copper foil was cut. 2 For each sample, three 5mm × 2mm test samples were cut out. The cross-section of the test sample was polished using an ion polisher. The test sample was then placed under a scanning electron microscope and the cross-section of the copper foil was observed at 10kx magnification. Ten points were randomly tested on each test sample, and the average value of all test point results was taken.

[0195] (7) Spacing between island structures: 1 dm of surface-treated copper foil is cut. 2 Three 5mm × 5mm samples were cut from each sample and placed under a scanning electron microscope at 2.5kx magnification to observe the cross-section of the copper foil. Fifteen points were randomly tested on each sample.

[0196] (8) Surface morphology parameters Sdr', Sdr, Sk, Str: The specified measurement area of ​​the surface to be measured using a commercially available laser confocal microscope (e.g., 18364 μm). 2 The surface profile of the two-dimensional region was measured to calculate the values ​​of the interface expansion area ratio Sdr or Sdr', the horizontal difference Sk at the center, and the aspect ratio Str of the surface features. These values ​​were determined under conditions of a cutoff wavelength of 0.55 μm based on an S-filter and a cutoff wavelength of 10 μm based on an L-filter.

[0197] (9) Peel strength: The test was conducted according to Section 7.1 of GB / T 29847-2013, as follows: The prepared copper foil and prepreg were stacked, and four PPO resin prepregs with a glass transition temperature of 200℃ were placed between the two copper foils. Then, they were hot-pressed together. The hot-pressing temperature was 220℃~250℃, the surface pressure was 400~450psi, and the hot-pressing time was 100min~150min. The hot-pressed copper-clad laminate was cut into strips with a width of 3.0mm using a cutter. Then, the copper foil on one side of the copper-clad laminate was peeled off by 1~2cm using a utility knife. The peeled copper foil was fixed to one end of a weight. Finally, the copper foil was tested on the peel strength tester by moving the weight.

[0198] (10) Insertion Loss: Insertion loss was measured using the hot-pressed copper-clad laminates described above. The transmission loss in the high-frequency bandwidth was measured. In the evaluation of insertion loss, the transmission loss in the frequency range of 0-16 GHz was measured using the stripline resonator method with a bandwidth of 0-16 GHz. The microstrip line structure had the following characteristics: electrolyte thickness 50 μm, transmission line length 5 inch, conductor thickness 18 μm, conductor circuit width 120 μm, characteristic impedance 50 Ω, and impedance tolerance ±10%.

[0199] (11) Etching residual copper: The prepared copper foil and the prepreg are stacked together. Four PPO resin prepregs with a glass transition temperature of 200℃ are placed between the two copper foils. Then, they are hot-pressed together. The hot-pressing temperature is 220℃~250℃, the surface pressure is 400~450psi, and the hot-pressing time is 100min~150min. The copper foil on both sides of the copper-clad laminate is etched away using acidic copper chloride etching solution. The cross section of the copper-clad laminate is sanded and argon ion polished. The presence of residual copper is observed under a scanning electron microscope.

[0200] (12) Resistivity of the metal alloy layer: After the metal alloy layer is electroplated on the surface of the copper foil, the metal alloy layer of the copper foil is hot-pressed with the PPO resin prepreg, and the pressing process is the same as above; the copper foil body is etched away with alkaline copper ammonia etching solution, washed with water and dried, and the sheet resistance of the metal alloy layer is tested with a four-probe tester. Nine points are tested for each sample and the average value is taken. Resistivity = average sheet resistance × thickness. The thickness of the metal alloy layer is as described above.

[0201] Table 1

[0202]

[0203] Table 1 shows that by comparing Examples 1-9 with Comparative Example 1, it can be seen that in Comparative Example 1, island structures cannot be formed without selective etching. In this case, the metal alloy layer and oxide layer can still transmit electrons in the horizontal direction. The resistivity of the metal alloy layer and metal oxide layer is much greater than that of the copper foil body, resulting in a significant increase in insertion loss, reaching -0.791 dB / inch.

[0204] Furthermore, comparing Examples 1, 2, and 3, although the roughness Rz of the copper foil body is inconsistent, the presence of the metal alloy layer hinders the vertical transmission of electrons from the copper foil body to the metal clusters. Moreover, through two etching processes, the metal alloy layer and the metal oxide layer are divided into island-like structures, which further hinder electron transmission in the horizontal direction. Electrons are confined within the copper foil body, shortening the transmission path and thus significantly suppressing the skin effect. The metal clusters here only serve to enhance the physical bonding between the copper foil and the insulating resin substrate, and have virtually no impact on signal transmission.

[0205] Furthermore, comparing Examples 1, 2, and 3, by controlling the thickness of the metal oxide layer within a certain range, the greater the amount of metal deposited, that is, the greater the areal density of the metal elements in the metal oxide layer, the better the conductivity, which is conducive to the formation of more metal clusters. The more metal clusters there are, the smaller the distance between the island structures.

[0206] Furthermore, compared to Example 1, the copper foil body of Example 4 has a relatively small roughness Rz, which makes it difficult to provide sufficient tip discharge sites. The number and height of the metal clusters are also relatively small. Therefore, the peel strength of Example 4 is relatively small compared to Example 1. Moreover, the smaller peel strength makes it easier for air bubbles to form between the copper foil and the insulating resin substrate, affecting the insertion loss. Thus, the insertion loss increases compared to Example 1. On the other hand, the relatively small number of metal clusters in Example 4 makes the distance between the island structures relatively large, making it impossible to measure. In contrast, the copper foil body of Example 7 has a relatively large roughness Rz, and the height of the metal clusters is significantly increased compared to Example 1. Therefore, although its peel strength is greatly increased, there is a risk of residual copper, resulting in an increase in insertion loss compared to Example 1.

[0207] Furthermore, compared to Example 1, the thickness of the metal alloy layer in Example 5 is relatively small (less than 0.05 μm). Due to the quantum tunneling effect, it cannot completely block the transmission of electrons. Electrons in the copper foil body can still enter the metal clusters, resulting in a longer transmission path. Therefore, compared to Example 1, the insertion loss of Example 5 is increased.

[0208] Furthermore, compared to Example 1, the areal density of the metal elements in the metal oxide layer in Example 6 is relatively small (less than 1 mg / dm³). 2 This makes the conductivity of the metal oxide layer relatively insufficient, making it difficult to provide sufficient nucleation sites. As a result, the number of metal clusters is relatively small, and the height of the metal clusters is also relatively low, which reduces the peel strength compared to Example 1, and the distance between the island structures exceeds the measurement range.

[0209] Furthermore, compared to Example 1, the metal oxide layer in Example 8 is oxygen-free, and its etching resistance is enhanced compared to Example 1. However, this makes it easier for the island structures to stick together, affecting the insulation and increasing the insertion loss compared to Example 1.

[0210] Furthermore, compared to Example 1, in Example 9, the roughening time is increased, thus increasing the height of the metal clusters and posing a risk of residual copper after etching.

[0211] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0212] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A copper foil, characterized in that, include: A copper foil body and a plurality of island-shaped metal substrates disposed on at least one side of the copper foil body, and a roughening layer disposed on the surface of the island-shaped metal substrates; There is a gap between at least two adjacent island-shaped metal substrates.

2. The copper foil according to claim 1, characterized in that, One or more of the following conditions must be met: (1) There is a gap between any two adjacent island-shaped metal substrates; (2) The gap is 20μm~100μm.

3. The copper foil according to claim 1 or 2, characterized in that, The roughened layer comprises multiple metal clusters; Optionally, the metal in the metal cluster includes copper.

4. The copper foil according to claim 3, characterized in that, One or more of the following conditions must be met: (1) The distribution density of the metal clusters is 580 clusters / mm². 2 ~25,000 pieces / mm 2 Optional capacity: 5000 pieces / mm 2 ~25,000 pieces / mm 2 ; (2) The height of the metal cluster is 0.7μm~5.6μm, and can be selected as 2μm~5μm.

5. The copper foil according to any one of claims 1 to 3, characterized in that, The island-shaped metal base layer includes a stacked metal alloy layer and a metal oxide layer, wherein the metal alloy layer is adjacent to the copper foil body, and the metal oxide layer is disposed between the metal alloy layer and the roughening layer; Optionally, the metal oxide layer includes one or more of nickel metal oxide, chromium metal oxide, zinc metal oxide, and cobalt metal oxide; Optionally, the areal density of the metal element in the metal oxide layer is 0.37 mg / dm³. 2 ~5mg / dm 2 1 mg / dm 2 ~5mg / dm 2 .

6. The copper foil according to claim 5, characterized in that, One or more of the following conditions must be met: (1) The metal alloy layer comprises an alloy composed of three or more elements selected from nickel, tungsten, phosphorus, and molybdenum; (2) The thickness of the metal alloy layer is 0.03μm~0.5μm, and can be selected as 0.05μm~0.5μm; (3) The resistivity of the metal alloy layer is 500 times or more the resistivity of the copper foil body; optionally, the resistivity of the metal alloy layer is 500 to 3000 times the resistivity of the copper foil body.

7. The copper foil according to any one of claims 1 to 3, characterized in that, One or more of the following conditions must be met: (1) The surface roughness Rz of the copper foil body on the side near the island-shaped metal substrate is 1μm~6μm, and can be selected as 1.5μm~5μm; (2) The interface expansion area ratio Sdr' of the copper foil body is 0.6%~23%, and can be selected as 2%~15%; (3) The thickness of the copper foil body is 3μm~70μm.

8. The copper foil according to any one of claims 1 to 3, characterized in that, The copper foil further includes a protective layer disposed on the surface of the roughened layer; and / or The protective layer is disposed on the surface of the copper foil body and located in the gap between two adjacent island-shaped metal substrates; and / or The protective layer is disposed on the surface of the copper foil body on the side where the island-shaped metal base layer is not located; and / or The protective layer includes a first protective layer and / or a second protective layer; Optionally, the protective layer includes a first protective layer and a second protective layer stacked together, wherein the second protective layer is disposed on the surface of the first protective layer; Optionally, the first protective layer includes zinc, and optionally one or more of tin, chromium, and cobalt; Optionally, the second protective layer includes a silane coupling agent, which includes one or more of γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, 3-triethoxysilyl-1-propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

9. The copper foil according to any one of claims 1 to 3, characterized in that, One or more of the following conditions must be met: (1) The interface expansion area ratio Sdr of the copper foil is 1.9%~67%, and can be selected as 10%~45%; (2) The horizontal difference Sk at the center of the copper foil is 0.46μm~4.33μm, and can be selected as 1.5μm~3.8μm; (3) The aspect ratio Str of the surface properties of the copper foil is 0.3~0.9, and can be selected as 0.3~0.

8.

10. A method for preparing copper foil, characterized in that, include: A metal substrate is prepared on at least one side of the copper foil body; A roughening layer is prepared on the metal substrate; The metal substrate is etched to prepare multiple island-shaped metal substrates, wherein at least two adjacent island-shaped metal substrates contain a gap.

11. A copper-clad laminate, characterized in that, This includes the copper foil as described in any one of claims 1 to 9 or the copper foil prepared by the method described in claim 10.

12. A printed circuit board, characterized in that, Including the copper-clad laminate as described in claim 11.

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