Composite foil, method for producing the same, copper clad laminate, and printed circuit board

Abstract

The application provides a composite foil, a preparation method of the composite foil, a copper-clad plate and a printed circuit board. The composite foil comprises a first metal layer, an intermediate layer and a second metal layer which are stacked, and the intermediate layer is arranged between the first metal layer and the second metal layer. The intermediate layer comprises a first resistance layer, a dielectric layer and a second resistance layer which are stacked, the dielectric layer is arranged between the first resistance layer and the second resistance layer, a surface of the first resistance layer away from the dielectric layer is connected with the first metal layer, and a surface of the second resistance layer away from the dielectric layer is connected with the second metal layer. The composite foil provided by the application can realize the integration of the buried capacitor function and the buried resistance function on one device, and is beneficial to cost saving.

Description

Technical Field

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

[0002] Currently, passive components on printed circuit boards (PCBs) are primarily surface-mount, occupying a significant amount of board space. To save surface space and improve electrical reliability, a common method is to embed capacitors or resistors into the PCB in a planar embedded manner. However, this method requires separate embedded capacitor and resistor copper foils to implement the embedded capacitor and resistor functions, respectively, and cannot integrate these functions onto a single device, which is not cost-effective. Summary of the Invention

[0003] Based on this, this application provides a composite foil and its preparation method, a copper-clad laminate and a printed circuit board, which aims to integrate buried capacitor and buried resistor functions into one device, which is beneficial to saving costs.

[0004] A first aspect of this application provides a composite foil comprising a first metal layer, an intermediate layer, and a second metal layer stacked together, wherein the intermediate layer is disposed between the first metal layer and the second metal layer; the intermediate layer comprises a first resistive layer, a dielectric layer, and a second resistive layer stacked together, wherein the dielectric layer is disposed between the first resistive layer and the second resistive layer, wherein the surface of the first resistive layer away from the dielectric layer is connected to the first metal layer, and the surface of the second resistive layer away from the dielectric layer is connected to the second metal layer.

[0005] In some embodiments, the first resistive layer and the second resistive layer each independently comprise one or more oxides of aluminum, nickel, tantalum, chromium, niobium, silicon, tungsten, phosphorus, and the above elements;

[0006] Optionally, the content of the oxide in the first resistive layer is 10 at% to 30 at% of oxygen.

[0007] In some embodiments, the first resistive layer and the second resistive layer each independently include a plurality of stacked sublayers, each sublayer independently containing one or more oxides of aluminum, nickel, tantalum, chromium, niobium, silicon, tungsten, phosphorus and the above elements;

[0008] Optionally, the first resistive layer includes two sub-layers stacked together, and / or the second resistive layer includes two sub-layers stacked together;

[0009] Alternatively, the first resistive layer includes two sub-layers stacked adjacent to each other, namely a first sub-layer and a second sub-layer; wherein the first sub-layer contains one or more of nickel, phosphorus, tungsten, chromium, aluminum and silicon, and optionally contains nickel and / or phosphorus; the second sub-layer contains one or more of tantalum and its oxide, niobium and its oxide, and optionally contains one or more of tantalum, niobium, tantalum pentoxide and niobium pentoxide.

[0010] In some embodiments, the dielectric layer comprises a resin composition including an organic resin and a ceramic filler;

[0011] Optionally, the organic resin includes one or more of fluorinated resins, epoxy resins, cyanate ester resins, polyphenylene ether resins, styrene-butadiene resins, bismaleimide triazine resins, polyimide resins, phenolic resins, and acrylic resins.

[0012] Optionally, in the dielectric layer, the organic resin accounts for 20% to 30% by mass, and the ceramic filler accounts for 70% to 80% by mass.

[0013] Optionally, the ceramic filler contains a modifying group, which includes one or more of epoxy, hydroxyl, carboxyl, acyloxy, amino, alkoxy, alkyl, mercapto, and aromatic groups.

[0014] In some embodiments, the ceramic filler includes one or more of barium titanate and titanium dioxide;

[0015] Optionally, the barium titanate satisfies the chemical formula: Sr m Ca n Ba 1-m-n TiO3, m is 0.05~0.15, n is 0.005~0.03;

[0016] Optionally, the barium titanate D 50 Particle size is 0.3~0.8μm, D 90 The particle size is 0.7~1.5μm;

[0017] Optionally, the D of the titanium dioxide 50 Particle size is 0.1μm~0.5μm, D 90 The particle size is 0.5μm~0.9μm;

[0018] Optionally, the ceramic filler includes the barium titanate and the titanium oxide;

[0019] Further optionally, in the dielectric layer, the mass ratio of barium titanate to titanium dioxide is (3~4):1.

[0020] In some implementations, one or more of the following conditions are met:

[0021] (1) The thickness of the first resistive layer and the second resistive layer are each independently 0.05μm~2μm, and can be selected as 0.1μm~0.3μm;

[0022] (2) The thickness of the dielectric layer is 10μm~30μm;

[0023] (3) The first metal layer and the second metal layer each independently include one or more of gold, silver, copper, aluminum, platinum and titanium;

[0024] (4) The surface roughness Ra1 of the surface in contact with the first metal layer and the first resistive layer is 0.1 μm to 1 μm;

[0025] (5) The surface roughness Ra2 of the surface in contact with the second metal layer and the second resistive layer is 0.1 μm to 1 μm;

[0026] (6) The thickness of the first metal layer is 18μm~70μm;

[0027] (7) The thickness of the second metal layer is 9μm~70μm.

[0028] A second aspect of this application provides a method for preparing a composite foil, comprising:

[0029] A first metal layer and a second metal layer are provided, a first resistive layer is formed on one side surface of the first metal layer, and a dielectric layer is formed on the surface of the first resistive layer opposite to the first metal layer.

[0030] A second resistive layer is formed on one side surface of the second metal layer;

[0031] The surface of the second resistive layer facing away from the second metal layer is pressed together with the surface of the dielectric layer facing away from the first resistive layer to obtain a composite foil.

[0032] In some embodiments, the methods for preparing the first resistive layer and the second resistive layer each independently include electrodeposition and / or vacuum sputtering deposition;

[0033] Optionally, the vacuum sputtering deposition includes a first vacuum sputtering deposition and / or a second vacuum sputtering deposition, wherein the target material for the first vacuum sputtering deposition includes at least two of nickel, chromium, aluminum, and silicon, and the target material for the second vacuum sputtering deposition includes at least one of niobium, tantalum, and tungsten.

[0034] Optionally, the sum of the thickness of the electrodeposited layer and the thickness of the first vacuum sputtered layer is d1, the thickness of the second vacuum sputtered layer is d2, and the ratio of d1 to d2 is (0.5~2):(1~3).

[0035] Optionally, the electrodeposition plating solution contains one or more of nickel, tungsten, and phosphorus;

[0036] Optionally, the process may further include electrochemical oxidation of the deposited layer obtained by electrodeposition and / or vacuum sputtering after electrodeposition and / or vacuum sputtering.

[0037] In some embodiments, the method for fabricating the dielectric layer includes:

[0038] The resin composition is applied to the surface of the first resistive layer away from the first metal layer and dried to form the dielectric layer.

[0039] Optionally, the resin composition liquid includes an organic resin and a ceramic filler;

[0040] Further optionally, the ceramic filler contains one or more of the following groups: epoxy, hydroxyl, carboxyl, acyloxy, amino, alkoxy, alkyl, mercapto, and aromatic groups.

[0041] The third aspect of this application provides a copper-clad laminate, which is made using the composite foil of the first aspect of this application or the composite foil prepared by the preparation method of the second aspect of this application.

[0042] A fourth aspect of this application provides a printed circuit board, including the copper-clad laminate of the third aspect of this application.

[0043] The technical solution provided in this application integrates a first resistive layer, a second resistive layer, and a dielectric layer onto the same composite foil. The resistive layer, combined with the metal layer connected to it, can act as a buried resistive material; for example, the first resistive layer combined with the first metal layer connected to it can act as a buried resistive material, or the second resistive layer combined with the second metal layer connected to it can also act as a buried resistive material. Simultaneously, the intermediate layer, including the dielectric layer, can be combined with the first and second metal layers to act as a buried capacitor material. Therefore, by integrating the resistive and dielectric layers, this composite foil can simultaneously realize buried capacitor and buried resistor functions on a single device, achieving high capacitance density and high resistivity while saving costs. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of a composite foil according to one embodiment of this application.

[0045] Figure 2 This is a schematic diagram illustrating the process of preparing a copper-clad laminate using a composite foil according to one embodiment of this application.

[0046] Figure 3 This is a schematic diagram illustrating the process of preparing a copper-clad laminate using a composite foil according to one embodiment of this application.

[0047] Reference numerals: 1 First metal layer; 2 Intermediate layer; 3 Second metal layer; 4 Etched groove; 5 Resin substrate; 21 First resistive layer; 22 Dielectric layer; 23 Second resistive layer. Detailed Implementation

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] Currently, passive components on printed circuit boards (PCBs) are mainly surface-mounted, occupying a significant amount of board space. To save board space and improve electrical reliability, encapsulating capacitors or resistors in a planar embedded form within the PCB is a growing trend. Embedded capacitors are typically implemented using embedded copper foil, which has a "sandwich" structure at its core. It usually consists of two layers of copper foil sandwiching a layer of high-dielectric-constant dielectric material. This dielectric material needs to possess high permittivity, high withstand voltage (low leakage current), high peel strength between the dielectric material and the metal electrodes, and good heat resistance and processing performance. Embedded resistors are typically implemented using embedded copper foil, which has a "coating" structure. A layer of alloy or material with precise resistive characteristics is usually formed on the surface of a single layer of copper foil using a special process. It aims for accurate and stable sheet resistance (e.g., 50Ω / sq) while requiring a small temperature coefficient of resistance (TCR) to ensure stable resistance with temperature changes. However, this method of implementing buried capacitor and buried resistor functions separately using buried capacitor copper foil and buried resistor copper foil cannot simultaneously implement buried capacitor and buried resistor functions on a single device, which is not conducive to cost savings. In view of this, this application proposes the following technical solution.

[0055] Firstly, this application provides a composite foil, which can be seen in [reference 1]. Figure 1It includes a first metal layer 1, an intermediate layer 2 and a second metal layer 3 stacked together. The intermediate layer 2 is disposed between the first metal layer 1 and the second metal layer 3. The intermediate layer 2 includes a first resistive layer 21, a dielectric layer 22 and a second resistive layer 23 stacked together. The dielectric layer 22 is disposed between the first resistive layer 21 and the second resistive layer 23. The surface of the first resistive layer 21 away from the dielectric layer 22 is connected to the first metal layer 1, and the surface of the second resistive layer 23 away from the dielectric layer 22 is connected to the second metal layer 3.

[0056] The technical solution provided in this application integrates the first resistive layer 21, the second resistive layer 23, and the dielectric layer 22 onto the same composite foil. The resistive layer, combined with the metal layer connected to it, can act as a buried resistive material. For example, the first resistive layer 21 combined with the first metal layer 1 connected to it can act as a buried resistive material, or the second resistive layer 23 combined with the second metal layer 3 connected to it can also act as a buried resistive material. Simultaneously, the intermediate layer 2, including the dielectric layer 22, can be combined with the first metal layer 1 and the second metal layer 3 to act as a buried capacitor material. Therefore, by integrating the resistive layer and the dielectric layer 22, this composite foil can simultaneously realize buried capacitor and buried resistor functions on a single device, achieving both high capacitance and high resistivity while saving costs.

[0057] In some embodiments, the first resistive layer 21 and the second resistive layer 23 each independently comprise one or more oxides of aluminum, nickel, tantalum, chromium, niobium, silicon, tungsten, phosphorus, and the above elements. This facilitates the implementation of the buried resistor function; furthermore, when the first resistive layer 21 and / or the second resistive layer 23 comprise oxides of the above metals, a higher resistivity can be provided.

[0058] In some embodiments, the oxide content in the first resistive layer is 10 at% to 30 at% of oxygen. For example, the atomic percentage of oxygen can be 10 at%, 13 at%, 15 at%, 18 at%, 20 at%, 23 at%, 25 at%, 28 at%, 30 at%, or any range thereof. This configuration allows for a higher resistivity in the first resistive layer.

[0059] In some embodiments, the first resistive layer 21 and the second resistive layer 23 each independently include multiple sublayers stacked together, each sublayer independently containing one or more oxides of aluminum, nickel, tantalum, chromium, niobium, silicon, tungsten, phosphorus, and the above elements; further, the first resistive layer 21 includes two sublayers stacked together, and / or the second resistive layer 23 includes two sublayers stacked together. The multiple sublayers stacked together can better realize the buried resistor function.

[0060] Furthermore, in the first resistive layer 21 or the second resistive layer 23, the materials of two adjacent sublayers may be partially or completely different.

[0061] In some embodiments, the first resistive layer 21 includes two sublayers stacked adjacent to each other, namely a first sublayer and a second sublayer; wherein the first sublayer contains one or more of nickel, phosphorus, tungsten, chromium, aluminum, and silicon, and optionally contains nickel and / or phosphorus; the second sublayer contains one or more of tantalum and its oxide, niobium and its oxide, and optionally contains one or more of tantalum, niobium, tantalum pentoxide, and niobium pentoxide. Further, the first sublayer is adjacent to the first metal layer, and the second sublayer is adjacent to the dielectric layer.

[0062] The first resistive layer has two sublayers. The first sublayer contains nickel (such as nickel-phosphorus, nickel-phosphorus-tungsten, nickel-chromium-aluminum-silicon, etc.), which has a low resistivity. The second sublayer contains oxides with extremely high resistivity, such as tantalum pentoxide or niobium pentoxide. These oxides are almost insulating and can just compensate for the negative impact of the first resistive layer on the capacitance density.

[0063] Furthermore, the oxides in the second sublayer (such as tantalum pentoxide and / or niobium pentoxide) can synergistically work with nickel-phosphorus compounds in the first sublayer to increase the resistivity of the first resistive layer. Meanwhile, although the resistivity of the nickel-containing first sublayer is two orders of magnitude higher than that of copper, it remains conductive. This conductivity reduces the dielectric constant of the intermediate layer, negatively impacting capacitance density. In response, the oxide-containing second sublayer (such as tantalum pentoxide and / or niobium pentoxide) can act as a buffer layer, mitigating the negative impact of the nickel-containing first sublayer on the dielectric constant, thereby further stabilizing Dk.

[0064] In some embodiments, the second resistive layer 23 includes two adjacent sublayers stacked together, namely a first sublayer and a second sublayer; wherein the first sublayer contains one or more oxides of chromium, silicon, tungsten and above, and optionally contains chromium and / or silicon; the second sublayer contains one or more of tantalum and its oxide, niobium and its oxide; optionally it contains one or more of tantalum, niobium, tantalum pentoxide and niobium pentoxide.

[0065] In some embodiments, the dielectric layer 22 comprises a resin composition including an organic resin and a ceramic filler. This imparts good capacitance density to the dielectric layer 22, enabling it to achieve excellent buried capacitor functionality when combined with the first metal layer 1 and the second metal layer 3.

[0066] In some embodiments, the organic resin includes one or more of fluorinated resins, epoxy resins, cyanate ester resins, polyphenylene ether resins, styrene-butadiene resins, bismaleimide triazine (BT) resins, polyimide resins, phenolic resins, and acrylic resins.

[0067] In some embodiments, the organic resin accounts for 20% to 30% of the mass of the dielectric layer, and the ceramic filler accounts for 70% to 80% of the mass. This arrangement helps to ensure the dielectric constant of the dielectric layer. For example, the mass percentage of the organic resin in the dielectric layer can be 20%, 22%, 24%, 26%, 28%, 30%, or any range thereof; the mass percentage of the ceramic filler can be 70%, 72%, 74%, 76%, 78%, 80%, or any range thereof.

[0068] In some embodiments, the ceramic filler contains one or more modifying groups such as epoxy, hydroxyl, carboxyl, acyloxy, amino, alkoxy, alkyl, mercapto, and aromatic groups. This is beneficial for improving the dispersion of the ceramic filler in the dielectric layer 22, enabling the ceramic filler to be uniformly distributed in the dielectric layer 22, and reducing leakage caused by insufficient ceramic filler distribution at a certain location.

[0069] In some embodiments, the ceramic filler comprises one or more of barium titanate and titanium dioxide (TiO2). Further, the ceramic filler may also comprise one or more of strontium titanate, calcium titanate, lead titanate, lead zirconate titanate, barium zirconate titanate, manganese oxide, and silicon dioxide. In some embodiments, barium titanate satisfies the chemical formula: Sr m Ca n Ba 1-m-n TiO3, with m ranging from 0.05 to 0.15 and n ranging from 0.005 to 0.03. By employing barium titanate and controlling its chemical composition within the above ranges, it is beneficial to achieve the high dielectric and high capacitance requirements of embedded capacitor materials.

[0070] For example, m can be 0.05, 0.07, 0.09, 0.11, 0.13, 0.15 or any of the above values; n can be 0.005, 0.008, 0.01, 0.015, 0.02, 0.025, 0.03 or any of the above values.

[0071] In some embodiments, barium titanate D 50 Particle size ranges from 0.3 μm to 0.8 μm, D 90 The particle size is 0.7 μm to 1.5 μm. Barium titanate D 50 Particle size and D 90 The particle size is within a reasonable range, which on the one hand helps to reduce the agglomeration of barium titanate in organic resin and improve its distribution uniformity; on the other hand, it can effectively suppress the 90° domain, promote phase transition dispersion, and significantly suppress and broaden the Curie peak, thereby helping to improve the stability of the dielectric constant.

[0072] For example, barium titanate D50 The particle size can be 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, or within any range of these values; D 90 The particle size can be 0.7μm, 0.9μm, 1.1μm, 1.3μm, 1.5μm or within any of the above values.

[0073] In some embodiments, the D of titanium dioxide 50 Particle size is 0.1μm~0.5μm, D 90 The particle size is 0.5μm~0.9μm. The D of titanium dioxide... 50 Particle size and D 90 Having a particle size within a reasonable range is beneficial in two ways: firstly, it helps reduce the agglomeration of titanium dioxide in organic resins and improves its distribution uniformity; secondly, it can form a differentiated match with the particle size of barium titanate, which can better fill the missing areas of barium titanate.

[0074] For example, the D of titanium oxide 50 The particle size can be 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, or within any range of these values; D 90 The particle size can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm or within any of the above values.

[0075] In some embodiments, the ceramic filler includes barium titanate. Further, the ceramic filler includes barium titanate and titanium dioxide. Matching barium titanate with titanium dioxide helps to further improve the dispersion performance of the ceramic filler, achieving better embedded capacitor function.

[0076] In some embodiments, the mass ratio of barium titanate to titanium dioxide in dielectric layer 22 is (3~4):1. For example, this mass ratio can be 3:1, 3.5:1, 4:1, or within any of the above values. This mass ratio is within a reasonable range, which is beneficial for dielectric layer 22 to provide a high dielectric constant.

[0077] In some embodiments, the thicknesses of the first resistive layer 21 and the third resistive layer are each independently 0.05 μm to 2 μm, and can be selected as 0.1 μm to 0.3 μm. For example, the thicknesses of the first resistive layer 21 and the third resistive layer can each be independently 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, or within any range of the above values.

[0078] In some embodiments, the thickness of the dielectric layer 22 is 10 μm to 30 μm. For example, the thickness of the dielectric layer 22 can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, or within any of the above values.

[0079] In some embodiments, the first metal layer 1 and the second metal layer 3 each independently include one or more of gold, silver, copper, aluminum, platinum, and titanium, and copper may be selected. This configuration allows it to function as a buried resistor material in combination with the resistive layers (including the first resistive layer 21 and the second resistive layer 23) and as a buried capacitor material in combination with the dielectric layer 22, thereby enabling the simultaneous implementation of buried capacitor and buried resistor functions on a single device.

[0080] In some embodiments, the surface roughness Ra1 of the surface where the first metal layer 1 contacts the first resistive layer 21 is 0.1 μm to 1 μm. For example, the surface roughness Ra1 can be 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 1 μm, or within any range of the above values. This setting makes the first resistive layer 21 less likely to fall off during processing.

[0081] In some embodiments, the surface roughness Ra2 of the surface where the second metal layer 3 contacts the second resistive layer 23 is 0.1 μm to 1 μm. For example, the surface roughness Ra2 can be 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 1 μm, or within any range of the above values. This setting makes the second resistive layer 23 less likely to detach during processing.

[0082] It is understood that in this application, surface roughness "Ra" refers to the arithmetic mean of the absolute values ​​of the deviations of all points from their mean line within a sampling length, and the test standard can be found in JIS B 0601.

[0083] In some embodiments, the thickness of the first metal layer 1 is 18 μm to 70 μm. For example, the thickness of the first metal layer 1 can be 18 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm or within any of the above values.

[0084] In some embodiments, the thickness of the second metal layer 3 is 9 μm to 70 μm. For example, the thickness of the second metal layer 3 can be 9 μm, 18 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm or within any of the above values.

[0085] Secondly, this application provides a method for preparing a composite foil, which can be used to prepare the composite foil of the first aspect of this application, and may include the following steps S1 to S3:

[0086] S1. Provide a first metal layer 1 and a second metal layer 3, form a first resistive layer 21 on one side surface of the first metal layer 1, and form a dielectric layer 22 on the surface of the first resistive layer 21 opposite to the first metal layer 1.

[0087] S2. A second resistive layer 23 is formed on one side surface of the second metal layer 3;

[0088] S3. Press the surface of the second resistive layer 23 away from the second metal layer 3 and the surface of the dielectric layer 22 away from the first resistive layer 21 together to obtain a composite foil.

[0089] In some embodiments, the first metal layer 1 or the second metal layer 3 can be prepared using conventional techniques in the art, such as electrochemical deposition, the details of which are not elaborated here.

[0090] In some embodiments, before forming the first resistive layer 21 on one side surface of the first metal layer 1, or before forming the second resistive layer 23 on one side surface of the second metal layer 3, the following steps may be included: pickling the first metal layer 1 or the second metal layer 3 to obtain a fresh surface; optionally, the pickling solution contains 100 g / L to 200 g / L of concentrated sulfuric acid.

[0091] In some embodiments, the methods for preparing the first resistive layer 21 and the second resistive layer 23 each independently include electrodeposition and / or vacuum sputtering deposition.

[0092] In some embodiments, the electroplating solution for electrodeposition comprises one or more of nickel, tungsten, and phosphorus; optionally, the electroplating solution comprises one or more of nickel ions, tungstate ions, sodium hypophosphite, and phosphorous acid. Further, the concentration of nickel ions is 10-30 g / L, the concentration of tungstate ions is 7.5-30 g / L, the concentration of sodium hypophosphite is 6-18 g / L, and the concentration of phosphorous acid is 10-20 g / L.

[0093] In some embodiments, the above electroplating solution also includes at least one of a complexing agent, a buffer, and an additive.

[0094] In some embodiments, the complexing agent includes, but is not limited to, one or more of pyrophosphate, citric acid, tartaric acid, ethylenediaminetetraacetic acid, potassium pyrophosphate, sodium citrate, potassium citrate, potassium sodium tartrate, and disodium ethylenediaminetetraacetic acid.

[0095] In some embodiments, the buffer includes one or more of boric acid, sodium acetate, acetic acid, phosphoric acid, and citric acid.

[0096] In some embodiments, the additives include one or more of saccharin, sodium lauryl sulfate, sodium 2-ethylhexyl sulfate, sodium lauryl sulfonate, glucose, ascorbic acid, and hydroxylamine hydrochloride.

[0097] In some embodiments, the total concentration of the buffer is 20-40 g / L, the total concentration of the complexing agent is 30-150 g / L, the total concentration of the additive is 0.05-1 g / L, the temperature of the electroplating solution is 50-70°C, the pH value of the electroplating solution is 1-6.5, and the current density is 0.5-7 A / dm³. 2 .

[0098] In some embodiments, vacuum sputtering deposition includes a first vacuum sputtering deposition and / or a second vacuum sputtering deposition, wherein the target material for the first vacuum sputtering deposition (hereinafter referred to as the first target material) includes at least two of nickel, chromium, aluminum, and silicon, and the target material for the second vacuum sputtering deposition (hereinafter referred to as the second target material) includes at least one of niobium, tantalum, and tungsten.

[0099] In some embodiments, the process of first vacuum sputtering deposition using a first target is as follows: sputtering power of 200~500W, argon flow rate of 35~75sccm, oxygen flow rate of 0~10sccm, and working pressure of 2~6mTorr.

[0100] In some embodiments, the process of using a second target for second vacuum sputtering deposition is as follows: sputtering power of 150~400W, argon flow rate of 20~50sccm, and working pressure of 2~8mTorr. Optionally, after sputtering with the first and / or second target, vacuum annealing is performed at 150℃~200℃ for 30min~60min.

[0101] In some embodiments, the sum of the thickness of the electrodeposited layer and the thickness of the first vacuum sputtered layer is d1, and the thickness of the second vacuum sputtered layer is d2, with the ratio of d1 to d2 being (0.5~2):(1~3). This arrangement facilitates the control of the resistivity of the first resistive layer 21 and / or the second resistive layer 23, thereby achieving better insulation properties.

[0102] In some embodiments, the process further includes electrochemical oxidation of the deposited layer obtained by electrodeposition and / or vacuum sputtering after electrodeposition and / or vacuum sputtering. Electrochemical oxidation can form oxides in the first resistive layer 21 and / or the second resistive layer 23, and can significantly improve the resistivity of the first resistive layer 21 and / or the second resistive layer 23 and the capacitance density of the dielectric layer.

[0103] In some embodiments, the electrochemical oxidation treatment may include: using a first resistive layer 21 and / or a second resistive layer 23 as the anode and a titanium plate as the cathode, performing electrochemical oxidation treatment on the second sublayer of the first resistive layer 21 and / or the second sublayer of the second resistive layer 23 in a solution to form oxides in the second sublayer of the first resistive layer 21 and / or the second sublayer of the second resistive layer 23. Optionally, the solution is a mixture of ethylene glycol and water, wherein the volume ratio of ethylene glycol to water is 1:(3~6); further, the solution also includes: 0.1wt%~0.4wt% nitric acid and 1wt%~3wt% citric acid.

[0104] In some embodiments, the electrochemical oxidation treatment temperature is 50°C to 70°C, and the electrochemical oxidation treatment process includes: at 40 mA / dm 2 ~90mA / dm 2 The current density causes the voltage to rise to 30V~60V, and then the voltage is maintained constant until the current decays to zero.

[0105] In some embodiments, the method for preparing the dielectric layer 22 may include the following steps: applying a resin composition liquid onto the surface of the first resistive layer 21 opposite to the first metal layer 1, and drying it to form the dielectric layer 22.

[0106] In some embodiments, the resin composition liquid includes an organic resin and a ceramic filler. The characteristics of the organic resin and the ceramic filler are as described above.

[0107] In some embodiments, the resin composition solution can be prepared by the following steps ①~②:

[0108] ① Add the organic resin to the organic solvent and stir until completely dissolved. Adjust the viscosity to 800 mPa·s to 2000 mPa·s to form a resin solution. The mass ratio of organic resin to organic solvent is (1~2):1. While stirring, slowly add the ceramic filler, where the mass ratio of ceramic filler to resin solution is (6~8):(2~3).

[0109] ② After the ceramic filler is evenly dispersed, add defoamer to remove air from the resin solution. The amount of defoamer added is 0.01wt%~0.1wt% of the total mass of the resin solution. Then add curing agent to promote the pre-crosslinking reaction of the resin solution. The amount of curing agent added is 0.01wt%~0.5wt% of the total mass of the resin solution. After stirring, the ceramic filler is completely wetted and completely dispersed to obtain the resin composition solution.

[0110] In some embodiments, the method for preparing the dielectric layer 22 further includes: uniformly coating the prepared resin composition solution onto the surface of the first resistive layer 21 opposite to the first metal layer 1 through a slit extrusion coating head; placing the coated sample into an oven and heating it at a temperature of 100°C to 150°C to remove the solvent and convert the organic resin into a semi-cured state. The above coating process is repeated multiple times to achieve the target thickness.

[0111] In some embodiments, the step of pressing the surface of the second resistive layer 23 facing away from the second metal layer 3 and the surface of the dielectric layer 22 facing away from the first resistive layer 21 may include: bringing the surface of the second resistive layer 23 facing away from the second metal layer 3 and the surface of the dielectric layer 22 facing away from the first resistive layer 21 into contact, and pressing them under vacuum conditions at 150°C to 250°C until the resin composition is completely cured, ultimately obtaining a composite foil. Further, the pressing pressure can be 2 MPa to 5 MPa.

[0112] In some embodiments, the organic solvent includes one or more of ethyl acetate, ethylene glycol, butyl acetate, acetone, cyclohexanone, propylene glycol methyl ether acetate, toluene, n-butanol, xylene, and methyl ethyl ketone.

[0113] In some embodiments, the defoamer includes one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, sodium dodecylbenzene sulfonate, polydimethylsiloxane, polyoxypropylene glycerol ether, tributyl phosphate, polyacrylate, and silane coupling agents.

[0114] In some embodiments, the curing agent includes one or more of 2-phenylimidazole, diethylenetriamine, phthalic anhydride, m-phenylenediamine, dicyandiamide, benzoyl peroxide, and isocyanate.

[0115] In some embodiments, the ceramic filler contains modifying groups, including one or more of epoxy, hydroxyl, carboxyl, acyloxy, amino, alkoxy, alkyl, mercapto, and aromatic groups. The ceramic filler containing the modified groups can be prepared by the following method:

[0116] The coupling agent is activated by hydrolysis, with the mass ratio of coupling agent, ethanol, and water being 1:(6~9):(1~2). During preparation, ethanol and water are first mixed, and then the pH of the solution is adjusted to 3.0~6.0 using an acidic reagent (such as acetic acid). The coupling agent is added while the mixture is slowly stirred for 0.5~1.5 hours at a temperature of 25~50℃. After the coupling agent has hydrolyzed, it is diluted with ethanol to obtain a coupling agent solution with a concentration of 3%~5% by mass.

[0117] Add the ceramic filler dispersion phase to the above coupling agent solution and stir for 0.5~1h to make it uniformly dispersed. The amount of ceramic filler dispersion phase is 1~4 times the actual content of coupling agent in the coupling agent solution. After filtration and drying, ceramic filler containing the above modified groups is obtained.

[0118] In some embodiments, the coupling agent includes, but is not limited to, one or more of silane coupling agents, zirconate coupling agents, and titanate coupling agents.

[0119] In some embodiments, the ceramic filler comprises materials satisfying the chemical formula: Sr m Ca n Ba 1-m-n Barium titanate of TiO3, with m ranging from 0.05 to 0.15 and n ranging from 0.005 to 0.03, is prepared by the following non-limiting example method:

[0120] (1) Weigh out electronic-grade titanium dioxide, barium carbonate, strontium carbonate, and calcium carbonate according to the stoichiometric ratio. Based on the chemical formula of the ceramic filler, record the molar fraction of titanium dioxide as 1, then the molar fractions of strontium carbonate, calcium carbonate, and barium carbonate are m, n, and 1-mn, respectively.

[0121] (2) Add the above materials to the ball mill jar, and add deionized water. The total mass of the materials to the mass of the water is 1:(0.8~1.2). Then add the ball milling media (such as alumina balls). The ball-to-material ratio is controlled at (3~5):1. The ball milling time is 4~8 hours and the rotation speed is 300~500 rpm.

[0122] (3) Pour the ball-milled slurry into a tray and dry it at a constant temperature of 110~120℃ for 9~12h. After drying and crushing, a loose precursor powder is obtained.

[0123] (4) The above precursor powder is dry-pressed into blocks at a pressure of 10~20MPa to make the blanks dense.

[0124] (5) Calcination at normal pressure in air atmosphere: keep warm at 1100~1200℃ for 2~4h.

[0125] (6) After the above calcination, block clinker is obtained; after crushing, it is ball-milled again according to the method in step (2). In this step, the rotation speed and time can be adjusted to control the particle size of the ceramic filler.

[0126] (7) Final sintering: The sintering temperature is 1250~1350℃, and the temperature is maintained in air atmosphere for 2~3 hours. The temperature is then slowly reduced in the furnace to allow grain growth and compaction of the green body. This solidifies the Curie temperature shift and dielectric constant wide-temperature stability brought about by Sr / Ca doping, and reduces dielectric loss.

[0127] Following the above preparation process, Sr can finally be obtained.m Ca n Ba 1-m-n TiO3 ceramic filler.

[0128] In the above preparation methods, by adjusting the time and speed of the secondary ball milling, as well as the ball-to-material ratio, the D of barium titanate can be increased. 50 Particle size ranges from 0.3 μm to 0.8 μm, D 90 The particle size is 0.7μm~1.5μm.

[0129] In some embodiments, the method for preparing the composite foil may also employ the following steps S1'~S3':

[0130] S1', A first metal layer 1 is provided, a first resistive layer 21 is formed on one side surface of the first metal layer 1, and a dielectric layer 22 is formed on the surface of the first resistive layer 21 opposite to the first metal layer 1.

[0131] S2' A second resistive layer 23 is formed on the surface of the dielectric layer 22 that is away from the first resistive layer 21;

[0132] S3', A second metal layer 3 is formed on the surface of the second resistive layer 23 on the side opposite to the dielectric layer 22.

[0133] Furthermore, the method for preparing the first metal layer 1, the first resistive layer 21, and the dielectric layer 22 in step S1' can be found in the previous description; the method for preparing the second resistive layer 23 and the second metal layer 3 in steps S2' and S3' can be vacuum sputtering deposition or electroless plating, wherein the process of vacuum sputtering deposition can be found in the previous description; electroless plating can be performed using conventional electroless plating steps in the art, and specific details will not be elaborated here.

[0134] Thirdly, this application provides the application of a composite foil as described in the first aspect of this application or a composite foil prepared by the preparation method of the second aspect of this application in copper-clad laminates.

[0135] Fourthly, this application provides a copper-clad laminate made using a composite foil comprising the first aspect of this application or a composite foil prepared by the preparation method of the second aspect of this application.

[0136] In some embodiments, the process of preparing copper-clad laminates using the composite foil of this application may include the following steps: See Figure 2 A portion of the first metal layer 1 and / or a portion of the second metal layer 3 in the composite foil are etched away to form an etched groove 4; see also Figure 3 The resin substrate is pressed together with the etched first metal layer 1 and / or the etched second metal layer 3 respectively, so that the resin substrate 5 is embedded in the etched groove 4 to obtain a copper-clad laminate.

[0137] Fifthly, this application provides a printed circuit board, including the copper-clad laminate of the fourth aspect of this application.

[0138] In some embodiments, the printed circuit board can be made from copper-clad laminate (CCL), and conductive circuit patterns are formed by processing the laminated copper foil and / or composite copper foil therein through etching, pattern transfer, and other processes. The resin substrate of the CCL can constitute the insulating support portion of the printed circuit board, and the laminated copper foil and / or composite copper foil on the surface of the CCL can constitute the conductive circuit layer of the printed circuit board after processing.

[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] Step (1): Form a first resistive layer on the surface of the first metal layer:

[0142] ① A copper foil with a thickness of 18 μm was pickled. The copper foil was prepared using a conventional technique, which will not be described in detail here. The pickling solution contained 100 g / L concentrated sulfuric acid and 10 g / L hydrogen peroxide, and the pickling time was 35 s. The surface roughness Ra of one side of the copper foil was 0.5 μm. This copper foil is the first metal layer.

[0143] ② A nickel-phosphorus (Ni-P) alloy layer was electrodeposited on the side of the copper foil with a surface roughness Ra of 0.5 μm. The electroplating solution contained 18 g / L nickel ions, 12 g / L phosphorous acid, 15 g / L citric acid, 20 g / L tartaric acid, 22 g / L boric acid, 0.4 g / L saccharin, and water. The pH of the electroplating solution was 1.8, the temperature was 60℃, and the current density was 1.5 A / dm³. 2 The thickness of the nickel-phosphorus alloy layer is 0.05 μm.

[0144] ③ A tantalum (Ta) metal layer is further sputtered onto the surface of the above-mentioned deposited layer. A tantalum target with a purity greater than or equal to 99.9% is used as the sputtering target. The average grain size of the target material is 60 μm, and the base vacuum level of the cavity is controlled at 6.5 × 10⁻⁶. -6 Argon gas was continuously introduced during the deposition process at a flow rate of 35 sccm, a working pressure of 4 mTorr, and a sputtering power of 300 W. The thickness of the tantalum metal layer was 0.1 μm. The mixture was then annealed in a vacuum at 180 °C for 30 min.

[0145] ④ The first resistive layer is subjected to electrochemical oxidation treatment, with the first resistive layer as the anode and the titanium plate as the cathode. The volume ratio of ethylene glycol to water in the oxidation solution is 1:4. The oxidation solution also includes 0.3 wt% nitric acid and 2 wt% citric acid. The electrochemical oxidation treatment temperature is 60℃, and the speed is 50 mA / dm². 2 The current density causes the voltage to rise to 30V, and then the voltage is maintained constant until the current decays to zero.

[0146] Step (2): Form a dielectric layer on the surface of the first resistive layer:

[0147] ① First, vinyltriethoxysilane was hydrolyzed and activated. Ethanol and water were mixed, and the pH of the solution was adjusted to 4.0 using acetic acid. The coupling agent was added while the mixture was slowly stirred for 1 hour, maintaining the solution temperature at 30°C during stirring. The mass ratio of coupling agent, ethanol, and water was 1:8:2. After hydrolysis, the solution was diluted with ethanol to obtain a 5% (w / w) coupling agent solution.

[0148] ② Add the ceramic filler dispersion phase, i.e., Sr, to the above coupling agent solution. 0.1 Ca 0.01 Ba 0.89 A mixture of TiO3 and TiO2, with a total mass 1.5 times the actual content of the silane coupling agent, wherein Sr 0.1 Ca 0.01 Ba 0.89 The mass ratio of TiO3 to TiO2 is 3:1, and Sr 0.1 Ca 0.01 Ba 0.89 TiO3 was prepared by ball milling and calcination. After adding the ceramic filler dispersion phase, the mixture was stirred at high speed for 45 min to ensure full dispersion of the filler. The mixture was then filtered and dried at 110℃ to obtain the ceramic filler containing modified groups.

[0149] The preparation process of barium titanate ceramic filler is as follows:

[0150] (1) Weigh out electronic-grade titanium dioxide, barium carbonate, strontium carbonate and calcium carbonate according to the stoichiometric ratio. According to the chemical formula of the ceramic filler, the molar ratio of titanium dioxide, strontium carbonate, calcium carbonate and barium carbonate is 1:0.1:0.01:0.89.

[0151] (2) Add the above materials to the ball mill jar, and add deionized water. The total mass ratio of materials to water is 1:1. Then add alumina balls, and control the ball-to-material ratio at 4:1. The ball milling time is 6 hours and the rotation speed is 400 rpm.

[0152] (3) Pour the ball-milled slurry into a tray and dry it at a constant temperature of 110℃ for 10 hours. After drying and crushing, a loose precursor powder is obtained.

[0153] (4) The above precursor powder is dry-pressed into blocks at a pressure of 12 MPa to make the blanks dense.

[0154] (5) Calcination at normal pressure in air atmosphere: keep warm at 1100℃ for 3 hours.

[0155] (6) After the above calcination, block clinker is obtained; after crushing, it is ball-milled again according to the method in step (2).

[0156] (7) Final sintering: Hold at 1250℃ in air atmosphere for 2 hours, then slowly cool down with the furnace.

[0157] Following the above preparation process, Sr can finally be obtained. 0.1 Ca 0.01 Ba 0.89 TiO3 ceramic filler.

[0158] ③ Add o-cresyl phenolic epoxy resin to a solvent to obtain a resin solution; the solvent includes acetone, propylene glycol methyl ether acetate, and cyclohexanone in a mass ratio of 4:2:1, and the mass ratio of resin to organic solvent is 1:1. After the resin is completely dissolved in the solvent, slowly add the above-mentioned ceramic filler containing modified groups while stirring; the mass ratio of ceramic filler to resin solution is 5:3. After the ceramic filler is evenly dispersed, add defoamer polyoxypropylene glycerol ether at a mass of 0.06% of the total mass of the resin solution, and stir thoroughly to remove air from the resin solution. Add curing agent 2-phenylimidazole at a mass of 0.1% of the total mass of the resin solution, and stir at high speed to ensure that the ceramic filler is completely wetted and completely dispersed, thus obtaining the resin composition solution.

[0159] ④ The prepared resin composition solution is uniformly coated onto the surface of the first resistive layer through a slit extrusion coating head. The coated copper foil is placed in an oven and heated at 120°C to remove the solvent and convert the resin to a semi-cured state. The above coating process is repeated multiple times to achieve the target thickness, ultimately obtaining the dielectric layer.

[0160] Step (3): Form a second resistive layer on the surface of the second metal layer:

[0161] A copper foil with the same properties as that used in step (1) is selected as the second metal layer, and a chromium-silicon-oxygen (Cr-Si-O) alloy layer is sputtered and deposited on one side of the copper foil. The chromium-silicon-oxygen (Cr-Si-O) alloy layer contains Cr 65 Si 35(wt%), chromium oxide, silicon oxide; the total content of chromium and silicon is 93 at, and the total content of oxygen is 7 at. The sputtering process is as follows: Select Cr with a purity greater than or equal to 99.9%. 50 Si 50 (at%) was used as the sputtering target, and the base vacuum of the cavity was controlled to be 4.0 × 10⁻⁶. -4 During the deposition process, argon and oxygen were continuously introduced, with the argon flow rate controlled at 45 sccm and the oxygen flow rate at 3 sccm. The working pressure was 4 mTorr, and the sputtering power was 300 W. The thickness of the alloy layer was 0.1 μm. After sputtering, the layer was annealed in a vacuum at 170 °C for 45 min.

[0162] Step (4): Pressing to obtain composite foil:

[0163] The dielectric layer obtained in step (2) (attached to the first metal layer) is bonded to the second resistive layer obtained in step (3) (attached to the second metal layer), and then pressed under vacuum at 200°C / 2.2MPa until the resin composition is completely cured to obtain a composite foil.

[0164] Example 2

[0165] Step (1): Form a first resistive layer on the surface of the first metal layer:

[0166] ① A 35μm thick copper foil was pickled using conventional techniques, which will not be detailed here. The pickling solution contained 100g / L concentrated sulfuric acid and 10g / L hydrogen peroxide, and the pickling time was 35s. The surface roughness Ra of one side of the copper foil was 0.7μm. This copper foil constitutes the first metal layer.

[0167] ② A nickel-phosphorus-tungsten (Ni-PW) alloy layer was electrodeposited on the side of the copper foil with a surface roughness Ra of 0.7 μm. The electroplating solution contained 20 g / L nickel ions, 16 g / L tungstate ions, 15 g / L sodium hypophosphite, 40 g / L sodium citrate, 20 g / L ethylenediaminetetraacetic acid, 25 g / L boric acid, 0.08 g / L sodium 2-ethylhexyl sulfate, and water. The pH of the electroplating solution was 4.5, the temperature was 55℃, and the current density was 3.5 A / dm³. 2 The nickel-phosphorus-tungsten alloy layer has a thickness of 0.05 μm and is then annealed in a vacuum environment at 80°C for 30 min.

[0168] ③ Continue sputtering to deposit a tantalum-niobium (Ta-Nb) alloy layer on the surface of the above-mentioned deposited layer, using Ta with a purity greater than or equal to 99.9%. 90 Nb 10 (wt%) was used as the sputtering target, with an average grain size of 50 μm, and the base vacuum of the cavity was controlled at 6.7 × 10⁻⁶. -6Argon gas was continuously introduced during the deposition process at a flow rate of 40 sccm, a working pressure of 4 mTorr, and a sputtering power of 350 W. The thickness of the tantalum-niobium alloy layer was 0.2 μm. The mixture was then annealed in a vacuum at 180 °C for 30 min.

[0169] ④ The first resistive layer is subjected to electrochemical oxidation treatment, with the first resistive layer as the anode and the titanium plate as the cathode. The volume ratio of ethylene glycol to water in the oxidation solution is 1:4. The oxidation solution also includes 0.4 wt% nitric acid and 3 wt% citric acid. The electrochemical oxidation treatment temperature is 60℃, and the speed is 50 mA / dm². 2 The current density causes the voltage to rise to 45V, and then the voltage is maintained constant until the current decays to zero.

[0170] Step (2): Form a dielectric layer on the surface of the first resistive layer:

[0171] ① First, tetrabutylzirconate was hydrolyzed and activated. Ethanol and water were mixed, and the pH of the solution was adjusted to 5.0 using acetic acid. The coupling agent was added while the mixture was slowly stirred for 45 minutes, maintaining the solution temperature at 40°C during stirring. The mass ratio of coupling agent, ethanol, and water was 1:7:2. After hydrolysis, the solution was diluted with ethanol to obtain a 3% (w / w) coupling agent solution.

[0172] ② Add the ceramic filler dispersion phase, i.e., Sr, to the above coupling agent solution. 0.1 Ca 0.01 Ba 0.89 A mixture of TiO3 and TiO2, with a total mass 1.5 times the actual content of the silane coupling agent, wherein Sr 0.1 Ca 0.01 Ba 0.89 The mass ratio of TiO3 to TiO2 was 3:1. After adding the ceramic filler dispersion, the mixture was stirred at high speed for 45 min to ensure thorough dispersion. The mixture was then filtered and dried at 110℃ to obtain the ceramic filler containing modified groups. Among these, Sr... 0.1 Ca 0.01 Ba 0.89 The preparation process of TiO3 was basically the same as in Example 1, except that the rotation speed and time of the secondary ball milling were changed to 500 rpm and 6 h, respectively, so that Sr 0.1 Ca 0.01 Ba 0.89 TiO3 D 50 It is 0.60μm.

[0173] ③ Add polyphenylene ether resin SE1000F to a solvent to obtain a resin solution; the solvent includes xylene and methyl ethyl ketone in a mass ratio of 4:2, and the mass ratio of resin to organic solvent is 1.5:1. After the resin is completely dissolved in the solvent, slowly add the above-mentioned ceramic filler containing modified groups while stirring; the mass ratio of the ceramic filler to the resin solution is 6:3. After the filler is evenly dispersed, add the defoamer alkylphenol polyoxyethylene ether at 0.05% of the total mass of the resin solution, and stir thoroughly to remove air from the resin solution. Add the curing agent benzoyl peroxide at 0.1% of the total mass of the resin solution, and stir at high speed to ensure that the filler is completely wetted and completely dispersed, thus obtaining the resin composition solution.

[0174] ④ Apply the prepared resin solution evenly to the surface of the first resistive layer using a slit extrusion coating head. Place the coated copper foil in an oven and heat it at 110°C to remove the solvent and convert the resin to a semi-cured state. Repeat the above coating process multiple times to achieve the target thickness, ultimately obtaining the dielectric layer.

[0175] Step (3): Form a second resistive layer on the surface of the second metal layer:

[0176] Select a copper foil with the same physical properties as in step (1) as the second metal layer, and sputter-deposit a chromium-silicon-oxygen (Cr-Si-O) alloy layer on one side of the copper foil. The sputtering process is as follows: Select Cr with a purity greater than or equal to 99.9%. 50 Si 50 (at%) was used as the sputtering target, and the base vacuum of the cavity was controlled to be 4.0 × 10⁻⁶. -4 During the deposition process, argon and oxygen were continuously introduced, with the argon flow rate controlled at 45 sccm and the oxygen flow rate at 3 sccm. The working pressure was 4 mTorr, and the sputtering power was 300 W. The thickness of the alloy layer was 0.1 μm. After sputtering, the layer was annealed in a vacuum at 170 °C for 45 min.

[0177] Step (4): Pressing to obtain composite foil:

[0178] The dielectric layer obtained in step (2) (attached to the first metal layer) is bonded to the second resistive layer obtained in step (3) (attached to the second metal layer), and then pressed under vacuum at 200°C / 2.2MPa until the resin composition is completely cured to obtain a composite foil.

[0179] Example 3

[0180] The differences from Example 1 are as follows:

[0181] Step (1)-①: Acid pickling is performed on a copper foil with a thickness of 35 μm. The copper foil is prepared using conventional techniques, which will not be described in detail here. The pickling solution contains 130 g / L concentrated sulfuric acid and 20 g / L hydrogen peroxide, and the pickling time is 35 s. The surface roughness Ra of one side of the copper foil is 0.9 μm. This copper foil is the first metal layer.

[0182] Steps (1)-② involve vacuum sputtering a nickel-chromium-aluminum-silicon (Ni-Cr-Al-Si) alloy layer on the side of the copper foil with a surface roughness Ra of 0.9 μm. The sputtering process is as follows: using Ni... 56 Cr 34 Al6Si4 (wt%) was used as the sputtering target, and the cavity background vacuum was controlled to be 5.0 × 10⁻⁶. -4 Argon gas was continuously introduced during the deposition process, with a flow rate of 35 sccm, a working pressure of 3 mTorr, and a sputtering power of 350 W. The thickness of the nickel-chromium-aluminum-silicon alloy layer was 0.1 μm. After sputtering, the layer was annealed in a vacuum at 160 °C for 30 min.

[0183] Example 4

[0184] The differences from Example 1 are as follows:

[0185] In step (2)-②, the dispersed phase of the ceramic filler is Sr 0.13 Ca 0.03 Ba 0.84 A mixture of TiO3 and TiO2, Sr 0.13 Ca 0.03 Ba 0.84 The mass ratio of TiO3 to TiO2 is 4:1, and the particle size is different from that in Example 1. Apart from this, the process used in the remaining steps is the same as that in Example 1.

[0186] The preparation method of barium titanate ceramic filler is as follows:

[0187] (1) Weigh out electronic-grade titanium dioxide, barium carbonate, strontium carbonate and calcium carbonate according to the stoichiometric ratio. According to the chemical formula of the ceramic filler, the molar ratio of titanium dioxide, strontium carbonate, calcium carbonate and barium carbonate is 1:0.13:0.03:0.84.

[0188] (2) Add the above materials to the ball mill jar, and add deionized water. The total mass ratio of materials to water is 1:1.2. Then add alumina balls, and control the ball-to-material ratio at 5:1. The ball milling time is 4 hours and the rotation speed is 400 rpm.

[0189] (3) Pour the ball-milled slurry into a tray and dry it at a constant temperature of 110℃ for 11 hours. After drying and crushing, a loose precursor powder is obtained.

[0190] (4) The above precursor powder is dry-pressed into blocks at a pressure of 13 MPa to make the blanks dense.

[0191] (5) Calcination at normal pressure in air atmosphere: keep warm at 1200℃ for 2.5h.

[0192] (6) After the above calcination, block clinker is obtained; after crushing, it is ball-milled again according to the method in step (2).

[0193] (7) Final sintering: Hold at 1300℃ in air atmosphere for 2.5h, then slowly cool down with the furnace.

[0194] Following the above preparation process, Sr can finally be obtained. 0.13 Ca 0.03 Ba 0.84 TiO3 ceramic filler.

[0195] Example 5

[0196] The differences from Example 1 are as follows:

[0197] In steps (2)-③, the mass ratio of ceramic filler to resin solution is 7:3. Apart from this, the processes used in the remaining steps are the same as in Example 1.

[0198] Example 6

[0199] The differences from Example 1 are as follows:

[0200] Steps (1)-④ involve electrochemical oxidation of the first resistive layer, using the first resistive layer as the anode and the titanium plate as the cathode. The volume ratio of ethylene glycol to water in the oxidation solution is 1:4. The oxidation solution also includes 0.3 wt% nitric acid and 2 wt% citric acid. The electrochemical oxidation treatment is performed at 60°C, with an efficiency of 60 mA / dm². 2 The current density is increased to raise the voltage to 50V, and then the voltage is maintained constant until the current decays to zero. Apart from this, the remaining steps are performed using the same process as in Example 1.

[0201] Example 7

[0202] The differences from Example 1 are as follows:

[0203] In step (3), after obtaining the chromium-silicon-oxygen (Cr-Si-O) alloy layer, a tantalum (Ta) metal layer is further sputtered onto the chromium-silicon-oxygen alloy layer. The process used for tantalum deposition is the same as steps (1)-③ in Example 1. After obtaining the tantalum (Ta) metal layer, the second resistive layer is subjected to electrochemical oxidation treatment, which is the same as steps (1)-④ in Example 1.

[0204] Example 8

[0205] Unlike Example 1, in steps (1)-④, the first resistive layer is not subjected to electrochemical oxidation treatment, so that the first resistive layer is free of oxides.

[0206] Example 9

[0207] Unlike Example 1, in step (2), the ceramic filler dispersion phase is not subjected to silane coupling agent surface modification treatment to modify the groups; Sr 0.1 Ca 0.01 Ba 0.89 The preparation process of TiO3 is basically the same as that in Example 1, except that: Sr 0.1 Ca 0.01 Ba 0.89 The preparation process of TiO3 is basically the same as in Example 1, except that the rotation speed and time of the secondary ball milling are changed to 300 rpm and 3 h, respectively, so that Sr 0.1 Ca 0.01 Ba 0.89 TiO3 D 50 It is 1.10 μm.

[0208] Comparative Example 1

[0209] Unlike Example 1, step (1) is omitted, so that the prepared composite foil does not contain the first resistive layer. That is, the dielectric layer is formed directly on the surface of the first metal layer. The method for preparing the dielectric layer is the same as in Example (1). The second resistive layer and the subsequent lamination steps are also the same.

[0210] Comparative Example 2

[0211] Unlike Example 1, step (3) is omitted, so that the prepared composite foil does not contain the second resistive layer. That is, after the first resistive layer is prepared on the surface of the first metal layer and the dielectric layer is prepared on the surface of the first resistive layer, the second metal layer is directly pressed onto the dielectric layer, thereby eliminating the second resistive layer.

[0212] The composite foils prepared in the above embodiments and comparative examples were subjected to relevant performance tests, and the test results are shown in Tables 1-3 below; " / " indicates that they do not exist or are not applicable. In Table 2, "dielectric layer" refers to the first resistive layer + dielectric layer + second resistive layer.

[0213] The test conditions or standards for each performance test item are as follows:

[0214] 1. Thickness of each functional layer: The sample was sliced ​​and fixed with epoxy resin. The cross-section of the sample was then polished with sandpaper of 1000, 3000, and 5000 grit in sequence, and then the cross-section of the sample was polished with argon ion. The polished sample was placed under a scanning electron microscope (SEM) to measure the polished cross-section. Five points were tested for each dielectric layer, and the average value of the results was taken.

[0215] 2. Oxides contained in the first or second resistive layer: The surface of the first or second resistive layer after electrochemical oxidation was scanned using X-ray photoelectron spectroscopy (XPS). Five points were tested for each sample, and the average of the results was taken.

[0216] 3. Sr m Ca n Ba 1-m-n The composition of TiO3: First, the powder is pressed into a cake shape under a special mold, and the sample is scanned with X-ray fluorescence spectrometry (XRF). Each sample is tested 3 times.

[0217] 4. Particle size of ceramic filler: The particle size of the ceramic filler was tested using a laser particle size analyzer. Before testing, a certain amount of ceramic filler was added to ultrapure water and ultrasonically dispersed for 1 hour to ensure complete dispersion of the powder. Note: The ceramic filler was tested before and after surface modification with the silane coupling agent. Each sample was tested three times, and the average value was taken.

[0218] 5. Mass ratio of ceramic filler: The mass ratio of the resin composition cured by the dielectric layer before and after combustion is tested using the combustion method. Assuming that the mass before combustion is m1 and the remaining mass after combustion is m2, the mass ratio of the dispersed phase is m2 / m1.

[0219] 6. Dielectric layer Dk: The low-frequency bridge method was used for testing. The testing equipment was an Agilent E4980A precision digital bridge with a frequency of 1KHz.

[0220] 7. Capacitance density: The composite foils prepared in the examples and comparative examples were left unetched on one side and etched with a 15mm×15mm copper sample on the other side. There was no conductivity between the upper and lower copper parts. The capacitance value between the copper foils was tested using an Agilent E4980A precision digital bridge. The capacitance value was divided by the area of ​​the copper foil to obtain the capacitance density.

[0221] 8. Leakage current: The composite foils prepared in the examples and comparative examples were left unetched on one side and etched with a circular copper sample with a diameter of 12.7 mm on the other side. A withstand voltage tester was used to increase the voltage to DC90V at a rate of 10V / s and hold the voltage for 60s to observe the leakage current data.

[0222] 9. Resistivity of the first or second resistive layer: Using an alkaline copper ammonia etching solution, one side of the composite foils prepared in the examples and comparative examples was fully etched. The sheet resistance of the exposed first or second resistive layer was tested using the four-probe method. Nine points were tested for each dielectric layer of each sample, and the average value was taken. The product of the sheet resistance of the first or second resistive layer and the corresponding thickness is the resistivity.

[0223] Table 1

[0224]

[0225] Table 2

[0226]

[0227] Table 3

[0228]

[0229] As shown in Tables 1-3 above, by comparing Examples 1-9 with Comparative Examples 1-2, it can be seen that in Example 1 (omitting the first resistive layer) or Example 2 (omitting the second resistive layer), the dielectric layer's Dk and capacitance density are significantly lower than in Examples 1-9, and the leakage current is significantly higher than in Examples 1-9, which illustrates the necessity of simultaneously setting the first and second resistive layers in this application.

[0230] Furthermore, a comparison between Examples 1-7 and Example 8 shows that, compared to Example 8, the first or second resistive layer of Examples 1-7 undergoes electrochemical oxidation treatment to obtain Ta2O5 and / or Nb2O5 with extremely high resistivity. This not only synergizes with the dielectric layer to increase the dielectric density (Dk) of the composite foil, thereby increasing the capacitance density, but also, Ta2O5 and / or Nb2O5 themselves synergize with the nickel-containing sublayer in the first resistive layer (e.g., Example 1) or the silicon-containing sublayer in the second resistive layer (e.g., Example 7) to provide even higher resistivity. A comparison between Examples 1-8 and Example 9 shows that the ceramic filler in Example 9 does not contain modified groups, therefore it is less dispersed than in Examples 1-8, resulting in larger particle size, uneven distribution, smaller Dk and capacitance density of the dielectric layer compared to Examples 1-8, and a larger leakage current compared to Example 1.

[0231] 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.

[0232] The above embodiments merely illustrate various implementation methods of this application, and their descriptions are relatively specific and detailed, but 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 composite foil, characterized in that, The device includes a first metal layer, an intermediate layer, and a second metal layer stacked together, wherein the intermediate layer is disposed between the first metal layer and the second metal layer; the intermediate layer includes a first resistive layer, a dielectric layer, and a second resistive layer stacked together, wherein the dielectric layer is disposed between the first resistive layer and the second resistive layer, wherein the surface of the first resistive layer away from the dielectric layer is connected to the first metal layer, and the surface of the second resistive layer away from the dielectric layer is connected to the second metal layer.

2. The composite foil according to claim 1, characterized in that, The first resistive layer and the second resistive layer each independently contain one or more oxides of aluminum, nickel, tantalum, chromium, niobium, silicon, tungsten, phosphorus, and the above elements; Optionally, the content of the oxide in the first resistive layer is 10 at% to 30 at% of oxygen.

3. The composite foil according to claim 2, characterized in that, The first resistive layer and the second resistive layer each independently include multiple sub-layers stacked together, and each sub-layer independently includes one or more oxides of aluminum, nickel, tantalum, chromium, niobium, silicon, tungsten, phosphorus and the above elements; Optionally, the first resistive layer includes two sub-layers stacked together, and / or the second resistive layer includes two sub-layers stacked together; Alternatively, the first resistive layer includes two sub-layers stacked adjacent to each other, namely a first sub-layer and a second sub-layer; wherein the first sub-layer contains one or more of nickel, phosphorus, tungsten, chromium, aluminum and silicon, and optionally contains nickel and / or phosphorus; the second sub-layer contains one or more of tantalum and its oxide, niobium and its oxide, and optionally contains one or more of tantalum, niobium, tantalum pentoxide and niobium pentoxide.

4. The composite foil according to any one of claims 1 to 3, characterized in that, The dielectric layer comprises a resin composition, the resin composition including an organic resin and a ceramic filler; Optionally, the organic resin includes one or more of fluorinated resins, epoxy resins, cyanate ester resins, polyphenylene ether resins, styrene-butadiene resins, bismaleimide triazine resins, polyimide resins, phenolic resins, and acrylic resins. Optionally, in the dielectric layer, the organic resin accounts for 20% to 30% by mass, and the ceramic filler accounts for 70% to 80% by mass. Optionally, the ceramic filler contains a modifying group, which includes one or more of epoxy, hydroxyl, carboxyl, acyloxy, amino, alkoxy, alkyl, mercapto, and aromatic groups.

5. The composite foil according to claim 4, characterized in that, The ceramic filler includes one or more of barium titanate and titanium dioxide; Optionally, the barium titanate satisfies the chemical formula: Sr m Ca n Ba 1-m-n TiO3, m is 0.05~0.15, n is 0.005~0.03; Optionally, the barium titanate D 50 Particle size ranges from 0.3 μm to 0.8 μm, D 90 The particle size is 0.7μm~1.5μm; Optionally, the D of the titanium dioxide 50 Particle size is 0.1μm~0.5μm, D 90 The particle size is 0.5μm~0.9μm; Optionally, the ceramic filler includes the barium titanate and the titanium oxide; Further optionally, in the dielectric layer, the mass ratio of barium titanate to titanium dioxide is (3~4):

1.

6. The composite 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 thickness of the first resistive layer and the second resistive layer are each independently 0.05μm~2μm, and can be selected as 0.1μm~0.3μm; (2) The thickness of the dielectric layer is 10μm~30μm; (3) The first metal layer and the second metal layer each independently include one or more of gold, silver, copper, aluminum, platinum and titanium; (4) The surface roughness Ra1 of the surface in contact with the first metal layer and the first resistive layer is 0.1 μm to 1 μm; (5) The surface roughness Ra2 of the surface in contact with the second metal layer and the second resistive layer is 0.1 μm to 1 μm; (6) The thickness of the first metal layer is 18μm~70μm; (7) The thickness of the second metal layer is 9μm~70μm.

7. A method for preparing a composite foil, characterized in that, include: A first metal layer and a second metal layer are provided, a first resistive layer is formed on one side surface of the first metal layer, and a dielectric layer is formed on the surface of the first resistive layer opposite to the first metal layer. A second resistive layer is formed on one side surface of the second metal layer; The surface of the second resistive layer facing away from the second metal layer is pressed together with the surface of the dielectric layer facing away from the first resistive layer to obtain a composite foil.

8. The preparation method according to claim 7, characterized in that, The fabrication methods of the first resistive layer and the second resistive layer each independently include electrodeposition and / or vacuum sputtering deposition; Optionally, the vacuum sputtering deposition includes a first vacuum sputtering deposition and / or a second vacuum sputtering deposition, wherein the target material for the first vacuum sputtering deposition includes at least two of nickel, chromium, aluminum, and silicon, and the target material for the second vacuum sputtering deposition includes at least one of niobium, tantalum, and tungsten. Optionally, the sum of the thickness of the electrodeposited layer and the thickness of the first vacuum sputtered layer is d1, the thickness of the second vacuum sputtered layer is d2, and the ratio of d1 to d2 is (0.5~2):(1~3). Optionally, the electrodeposition plating solution contains one or more of nickel, tungsten, and phosphorus; Optionally, the process may further include electrochemical oxidation of the deposited layer obtained by electrodeposition and / or vacuum sputtering after electrodeposition and / or vacuum sputtering.

9. The preparation method according to claim 7 or 8, characterized in that, The method for preparing the dielectric layer includes: The resin composition is applied to the surface of the first resistive layer away from the first metal layer and dried to form the dielectric layer. Optionally, the resin composition liquid includes an organic resin and a ceramic filler; Further optionally, the ceramic filler contains one or more of the following groups: epoxy, hydroxyl, carboxyl, acyloxy, amino, alkoxy, alkyl, mercapto, and aromatic groups.

10. A copper-clad laminate, characterized in that, It is made using composite foil as described in any one of claims 1 to 6 or composite foil prepared by any one of claims 7 to 9.

11. A printed circuit board, characterized in that, Including the copper-clad laminate as described in claim 10.

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