WO2024021897A1

WO2024021897A1 - Prepreg, substrate, printed circuit board and related preparation method

Info

Publication number: WO2024021897A1
Application number: PCT/CN2023/099046
Authority: WO
Inventors: 陈浩; 丁利斌
Original assignee: 华为技术有限公司
Priority date: 2022-07-27
Filing date: 2023-06-08
Publication date: 2024-02-01
Also published as: CN117510938A

Abstract

The present application provides a prepreg, a substrate, a printed circuit board and a related preparation method. The prepreg comprises a semi-cured resin and a reinforcing material. The reinforcing material comprises a fiber cloth. The fiber cloth comprises LCP fiber filament. The LCP fiber filament has a dielectric constant of 2.5-4.5 and a dielectric loss factor of less than 0.005@10GHz. In the present application, since the LCP fiber filament has a dielectric constant of 2.5-4.5, which is close to the dielectric constant of a resin material, the problem of delay skew can be minimized. Furthermore, the LCP fiber filament has a dielectric loss factor of less than 0.005@10GHz, which is lower than the dielectric loss factor of a conventional inorganic glass fiber cloth, such that the cost thereof is lower than that of the inorganic glass fiber cloth having the low dielectric loss factor. Accordingly, the prepreg of the present application may have excellent dielectric properties on the basis of ensuring low costs, and can fully meet the application requirements of high-frequency and high-speed electronic products.

Description

A kind of prepreg, substrate, printed circuit board and related preparation method

Cross-references to related applications

This application requires the priority of a Chinese patent application submitted to the China Patent Office on July 27, 2022, with the application number 202210892432.2 and the application title "A prepreg, substrate, printed circuit board and related preparation method", and its entire content has been approved This reference is incorporated into this application.

Technical field

The present application relates to the technical field of electronic materials, and in particular to a prepreg, a substrate, a printed circuit board and related preparation methods.

Background technique

With the technological development of the fifth generation mobile communication technology (5th Generation Mobile Communication Technology, 5G) industry, especially in recent years, the demand for mobile communication data and the Internet of Things has increased significantly, and the market demand for 5G-related products has increased rapidly. In order to meet the high frequency, high speed, low loss, big data carrying and other needs of the 5G industry, the sheet metal industry has gradually increased its research and development efforts and investment in sheet materials for high-frequency and high-speed substrates required for 5G products, and new sheets and new raw materials are constantly coming out.

High-frequency and high-speed substrates are one of the most important basic materials in 5G industry products. To a certain extent, the technological evolution direction and marketing results of the 5G industry heavily depend on the performance of high-frequency and high-speed substrates. The improvement of the performance of high-frequency and high-speed substrates and improvement are of great significance to the high-frequency and high-speed development of electronic products.

Existing high-frequency and high-speed substrates are first impregnated or coated with a resin mixture on inorganic glass fiber cloth, and then dried and baked until the resin mixture reaches a semi-cured state to form a prepreg, and then copper foil is stacked on the upper and lower surfaces of the prepreg. , which can be formed after high-temperature pressing. Among them, the currently commonly used inorganic glass fiber cloth is alkali-free glass (E-glass) fiber cloth, the first generation of low dielectric loss factor glass (Low Df glass) fiber cloth, the second generation of low dielectric loss factor glass (New Low Dk glass) ) fiber cloth and quartz glass (Quartz glass) fiber cloth, the dielectric constant Dk is between 6.5 and 3.7. Moreover, since inorganic glass fiber cloth is an inorganic material, the reduction of the dielectric loss factor Df is limited. It is currently extremely difficult to obtain inorganic glass fiber cloth with Df<0.001@10GHz.

However, with the rapid development of communication technology, the dielectric properties of existing inorganic glass fiber cloths can no longer meet the needs of high-frequency and high-speed substrates. Therefore, providing a high-frequency and high-speed substrate with excellent dielectric properties is an urgent technical problem that those skilled in the art need to solve.

Contents of the invention

The present application provides a prepreg, a substrate, a printed circuit board and related preparation methods, which are used to provide a substrate with excellent dielectric properties.

In a first aspect, embodiments of the present application provide a prepreg, which includes a prepreg resin and a reinforcing material. The reinforcing material includes fiber cloth; the fiber cloth includes liquid crystal polymer (LCP) fiber filaments. The dielectric constant Dk of the LCP fiber filaments is 2.5 to 4.5, and the dielectric loss factor Df is less than 0.005@10GHz.

Since the dielectric constant of the LCP fiber filaments in the fiber cloth is 2.5 to 4.5, the prepreg provided by this application is different from the resin. The dielectric constants of the materials are close, so the Delay Skew problem can be reduced. Moreover, the dielectric loss factor Df of LCP fiber filaments is less than 0.005@10GHz, which is lower than the dielectric loss factor Df of commonly used inorganic glass fiber cloth, and the cost is lower than that of inorganic glass fiber cloth with low dielectric loss factor. Therefore, the prepreg provided by this application can have excellent dielectric properties while ensuring low cost, and can fully meet the application requirements of high-frequency and high-speed electronic products.

For example, in order to effectively improve the dielectric properties of the prepreg, in the prepreg provided in the embodiments of the present application, the area ratio of LCP fiber filaments in the fiber cloth is greater than or equal to 50% of the total area of the fiber cloth. For example, the LCP fiber in the fiber cloth The ratio of the area of the filaments to the total area of the fiber cloth is 50%, 60%, 70%, 80%, 80%, 100%, etc., which is not limited here. Specifically, the area ratio of LCP fiber filaments can be flexibly designed according to the structural strength, dielectric properties and other requirements of the fiber cloth.

In specific implementation, in the prepreg provided in the embodiment of the present application, the fiber cloth is formed by braiding multiple fiber bundles. The single fiber bundle here can also be called a single yarn (warp yarn or weft yarn), and each fiber bundle includes multiple fiber filaments.

This application does not limit the weaving method of the fiber cloth, and it can be any method of weaving fiber cloth that is familiar to those skilled in the art. For example, the fiber cloth of the present application is woven using an orthogonal weaving method or an oblique weaving method.

For example, in order to make the area ratio of LCP fiber filaments in the fiber cloth greater than or equal to 50% of the total area of the fiber cloth, it can be achieved in the following ways:

The first way: at least 50% of the fiber bundles in the plurality of fiber bundles are formed by LCP fiber filaments, for example, 50%, 60%, 70%, 80%, 90% or 100% of the fiber bundles in the plurality of fiber bundles Formed from LCP fiber filaments.

The second way: at least part of the plurality of fiber bundles includes at least 50% LCP fiber filaments, for example, in part or all of the fiber bundles, each fiber bundle includes 50%, 60%, 70%, 80% , 90% or 100% LCP fiber filaments.

In specific implementation, the first method is easier to implement in terms of technology.

For example, taking the first method as an example, when the ratio of the area of the LCP fiber filaments to the total area of the fiber cloth is greater than or equal to 50% and less than 100%, the LCP fiber filaments are evenly distributed in the fiber cloth. For example, there are N fiber bundles in the warp direction and M fiber bundles in the weft direction in the fiber cloth. The fiber bundles formed by LCP fiber filaments can be evenly distributed among the N+M fiber bundles. In specific implementation, generally N=M, for example, the ratio of the area of LCP fiber filaments to the total area of fiber cloth is equal to 60%, then there are (N+M)×60% fiber bundles formed by LCP fiber filaments. , (N+M)×60% fiber bundles formed by LCP fiber filaments can be evenly distributed among the N+M fiber bundles.

For example, when the area ratio of LCP fiber filaments is less than 100% of the total area of fiber cloth, the fiber cloth can be woven from at least one fiber filament of inorganic fiber filaments and non-liquid crystal polymer type organic fiber filaments and LCP fiber filaments. form. For example, among the plurality of fiber bundles forming the fiber cloth, part of the fiber bundles is formed of LCP fiber filaments, and another part of the fiber bundles is formed of non-liquid crystal polymer type organic fiber filaments; or, among the plurality of fiber bundles forming the fiber cloth, part of the fiber bundles is formed of LCP fiber filaments. The fiber bundles are formed of LCP fiber filaments, and the other part of the fiber bundles are formed of inorganic fiber filaments; or, among the multiple fiber bundles forming the fiber cloth, the first part of the fiber bundle is formed of LCP fiber filaments, and the second part of the fiber bundle is formed of inorganic fiber filaments. , The third part of the fiber bundle is formed of non-liquid crystal polymer type organic fiber filaments. Or, among the plurality of fiber bundles forming the fiber cloth, each fiber bundle is formed of LCP fiber filaments and non-liquid crystal polymer type organic fiber filaments; or, among the plurality of fiber bundles forming the fiber cloth, each fiber bundle is made of LCP Fiber filaments and inorganic fiber filaments are formed; or, among the plurality of fiber bundles forming the fiber cloth, each fiber bundle is formed of LCP fiber filaments, inorganic fiber filaments and non-liquid crystal polymer type organic fiber filaments. Alternatively, among the plurality of fiber bundles forming the fiber cloth, some of the fiber bundles are formed of LCP fiber filaments, and the other part of the fiber bundles include a certain proportion of LCP fiber filaments in each fiber bundle.

For example, the inorganic fiber threads in this application can be inorganic glass fiber threads, and of course can also be other inorganic materials. The fiber filaments formed are not limited here.

In specific implementation, when the area ratio of LCP fiber filaments is equal to 100% of the total area of the fiber cloth, the fiber cloth can be completely woven from LCP fiber filaments, that is, each fiber bundle forming the fiber cloth only includes LCP fiber filaments.

For example, the cross-section of the LCP fiber in this application can be circular or elliptical, which is not limited here. The diameter width of the LCP fiber filaments can be designed to be 4 μm-40 μm, such as 4 μm, 10 μm, 20 μm, 30 μm, 40 μm, etc. This application does not exhaustively list specific values included in the range.

For example, the thickness of the fiber cloth in this application can reach 15 μm-200 μm. For example, 15 μm, 30 μm, 70 μm, 100 μm, 130 μm, 170 μm, 200 μm, etc. This application does not exhaustively list the specific point values included in the range.

Optionally, the semi-cured resin in this application can be formed by semi-curing thermoplastic resin and/or thermosetting resin.

Exemplarily, the thermoplastic resin may include fluorine-based resin, such as at least one of polytetrafluoroethylene (PTFE) or a copolymer of a small amount of perfluoropropyl perfluorovinyl ether and polytetrafluoroethylene (PFA).

Exemplary thermosetting resins include bismaleimide resin (BMI), cycloolefin resin (Cyclo Olefin Polymers, COP), polydivinylbenzene resin (Poly Divinylbenzene, PDVB), diethylene At least one of Oligo Divinylbenzene (ODV)), polyphenylene ether, hydrocarbon resin, phenolic resin or epoxy resin.

For example, in this application, the thickness of the prepreg can be set to 25 μm-300 μm, such as 25 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, etc. This application does not exhaustively list specific point values included in the range. The thickness of the specific prepreg can be set according to actual needs.

In a second aspect, embodiments of the present application also provide a substrate, which includes a dielectric plate, wherein the dielectric plate can be formed by hot pressing one prepreg sheet or multiple stacked prepreg sheets. When the dielectric plate is formed by hot pressing a piece of prepreg, the prepreg is the prepreg described in the first aspect or various embodiments of the first aspect. When the dielectric plate is formed by hot pressing of a plurality of stacked prepreg sheets, at least one prepreg sheet among the plurality of prepreg sheets is the prepreg sheet described in the first aspect or various embodiments of the first aspect. In order to distinguish the prepreg provided by the implementation of the application from other prepregs, the prepreg provided by the implementation of the application is called the first prepreg, and the other prepregs are called the second prepreg, where the first prepreg refers to the reinforcing material including LCP fiber filaments. The second prepreg refers to any prepreg that does not include LCP fiber filaments in the reinforcement material.

It can be understood that in the substrate provided by the present application, the number of the first prepreg and the second prepreg can be designed according to the thickness, structural strength, dielectric properties and other requirements of the substrate, and is not limited here.

This application does not limit the stacking sequence of the first prepreg and the second prepreg of the substrate, and the specific design can be based on actual needs.

Exemplarily, the substrate may also include a conductive layer disposed on at least one side of the dielectric plate. For example, the conductive layer is disposed on only one side of the dielectric plate, that is, a single-sided conductive substrate, or the conductive layer is disposed on both sides of the dielectric plate. There is a conductive layer, a substrate that conducts electricity on both sides.

The material of the conductive layer is not limited in this application. For example, it can be a metallic conductive material or a non-metal conductive material. Of course, it can also be a stack of multiple layers of conductive materials.

In specific implementation, when conductive layers are provided on both sides of the dielectric plate, this application does not limit the thickness and material of the conductive layers on both sides of the dielectric plate. The thickness of the conductive layers on both sides of the dielectric plate may be the same or different. , similarly, the materials of the conductive layers on both sides of the dielectric board may be the same or different.

For example, in this application, the thickness of the conductive layer is set uniformly, and the thickness of the conductive layer on both sides of the dielectric plate is the same.

For example, the thickness of the conductive layer can be set to 0.1 μm to 70 μm, such as 9 μm (1/4 oz), 12 μm (1/3 oz), 18 μm (1/2 oz), 35 μm (1 oz), or 70 μm (2 oz), etc., This application is not exhaustive of the specific points included in the stated ranges.

For example, the conductive layer may include a metal conductive layer, which is not limited here. Optionally, the metal conductive layer includes at least one of aluminum, copper or silver.

For example, the metal conductive layer can be a metal foil of a single metal material such as copper foil (electrolysis or calendering), aluminum foil, silver foil, etc., or a metal foil of mixed materials, and of course it can also be at least two of the above metal foils. Superposition of slices.

For example, the metal conductive layer may also be a metal conductive layer generated by metal sputtering, such as a copper layer, an alloy layer, etc.

In a third aspect, embodiments of the present application further provide a printed circuit board, including the substrate described in the second aspect or various embodiments of the second aspect. Since the problem-solving principle of the printed circuit board is similar to that of the aforementioned substrate, the implementation of the printed circuit board can be referred to the implementation of the aforementioned substrate, and repeated details will not be repeated.

In a fourth aspect, embodiments of the present application also provide a method for preparing a prepreg. The preparation method may include the following steps: forming a fiber cloth; wherein the fiber cloth includes LCP fiber filaments, and the dielectric constant of the LCP fiber filaments is 2.5. ~4.5, the dielectric loss factor is less than 0.005@10GHz; the surface of the fiber cloth is coated or impregnated with resin material; the surface of the fiber cloth coated or impregnated with the resin material is semi-cured to form a semi-cured sheet.

In specific implementation, the fiber cloth can be formed by weaving multiple fiber bundles. The single fiber bundle here can also be called a single yarn (warp yarn or weft yarn), and each fiber bundle includes multiple fiber filaments.

This application does not limit the weaving method of the fiber cloth, and it can be any method of weaving fiber cloth that is familiar to those skilled in the art. For example, this application can use orthogonal weaving or oblique weaving to form fiber cloth.

When weaving the fiber cloth, at least some of the fiber bundles include LCP fiber filaments. It can be understood here that at least part of the fiber bundles among the plurality of fiber bundles are completely formed of LCP fiber filaments; or, at least part of the fiber bundles among the plurality of fiber bundles are made of LCP fiber filaments and other fiber filaments (other than LCP fiber filaments). fiber bundles); or, part of the plurality of fiber bundles is completely formed of LCP fiber bundles, and part of the fiber bundles is formed of LCP fiber threads and other fiber threads (other fiber threads except LCP fiber threads). During specific implementation, the weaving method can be flexibly designed according to the mechanical strength, dielectric properties and other requirements of the fiber cloth in the application scenario.

In this application, LCP fiber filaments can be made from LCP resin by melt spinning. The dielectric constant Dk of LCP resin is 2.5~4.5, and the dielectric loss factor Df is less than 0.005@10GHz.

For example, the LCP resin can use a resin with a softening point greater than 250°C, which is more conducive to improving the heat resistance of the substrate.

For example, in this application, in order to effectively improve the dielectric properties of the fiber cloth, the area ratio of the LCP fiber filaments in the fiber cloth is greater than or equal to 50% of the total area of the fiber cloth. For example, the area of the LCP fiber filaments in the fiber cloth is equal to The ratio of the total area of fiber cloth is 50%, 60%, 70%, 80%, 80%, 100%, etc., which is not limited here. Specifically, the area ratio of LCP fiber filaments can be flexibly designed according to the structural strength, dielectric properties and other requirements of the fiber cloth.

In one embodiment, the fiber cloth can be woven from LCP fiber filaments, that is, each fiber bundle forming the fiber cloth only includes LCP fiber filaments.

In another embodiment, the fiber cloth may be formed by mixing and weaving at least one of inorganic fiber filaments and non-LCP type organic fiber filaments and LCP fiber filaments. For example, among the multiple fiber bundles forming the fiber cloth, part of the fiber bundles are formed of LCP fiber filaments, and the other part of the fiber bundles are formed of non-LCP type organic fiber filaments; or, among the multiple fiber bundles forming the fiber cloth, part of the fiber bundles It is formed of LCP fiber filaments, and another part of the fiber bundles is formed of inorganic fiber filaments; or, among the plurality of fiber bundles forming the fiber cloth, the first part of the fiber bundle is formed of LCP fiber filaments, the second part of the fiber bundle is formed of inorganic fiber filaments, and the third part of the fiber bundle is formed of LCP fiber filaments. Three-part fiber bundles are formed from non-LCP type organic fiber filaments. Alternatively, among the plurality of fiber bundles forming the fiber cloth, each fiber bundle is formed of LCP fiber filaments and non-LCP type organic fiber filaments; or, among the plurality of fiber bundles forming the fiber cloth, each fiber bundle is composed of LCP fiber filaments. and inorganic fiber filaments; or, among the plurality of fiber bundles forming the fiber cloth, each fiber bundle is formed of LCP fiber filaments, inorganic fiber filaments and non-LCP type organic fiber filaments. Alternatively, among the plurality of fiber bundles forming the fiber cloth, some of the fiber bundles are formed of LCP fiber filaments, and the other part of the fiber bundles include a certain proportion of LCP fiber filaments in each fiber bundle.

For example, the resin material may include only thermoplastic resin, may include only thermosetting resin, or may include both thermoplastic resin and thermosetting resin.

Optionally, the resin material in this application includes a mixture of thermoplastic resin and thermosetting resin.

Exemplary thermosetting resins include bismaleimide resin, cycloolefin resin (COP), polydivinylbenzene resin (PDVB), divinylbenzene (ODV)), polyphenylene ether, hydrocarbon At least one of resin, phenolic resin or epoxy resin.

In specific implementation, the fiber cloth whose surface is coated or impregnated with the resin material can be placed in a semi-cured processing equipment for drying and baking until the resin material reaches a semi-cured state, thereby forming a semi-cured sheet.

For example, the temperature of the semi-curing treatment can be controlled between 100°C and 160°C, such as 100°C, 120°C, 140°C, 160°C, etc. This application does not exhaustively list the specific point values included in the range. Specifically, it can be set according to the thickness of the resin material and the characteristics of the material itself.

For example, the time of the semi-curing treatment can be controlled between 4 min and 12 min, such as 4 min, 6 min, 8 min, 10 min, 12 min, etc. This application does not exhaustively list specific values included in the range. Specifically, it can be set according to the thickness of the resin material and the characteristics of the material itself.

Optionally, in this application, according to the required thickness and performance requirements of the prepreg, after forming the above-mentioned prepreg, the following steps can be performed at least once: re-coating or impregnating the resin material on the surface of the formed prepreg, and coating the surface with The cloth or the prepreg impregnated with the resin material is then semi-cured to form a new prepreg, thereby increasing the thickness of the prepreg.

In a fifth aspect, embodiments of the present application also provide a method for preparing a substrate. The preparation method may include the following steps: stacking protective layers on both sides of a prepreg sheet or a plurality of stacked prepreg sheets to form a laminated structure. The laminated structure is subjected to a hot pressing process using a hot pressing process to form a dielectric board and protective layers located on both sides of the dielectric board. Wherein, there is at least one prepreg in the laminated structure, such as the prepreg described in the first aspect or various embodiments of the first aspect, and the protective layer on one side of the protective layers on both sides is a release material, and the protective layer on the other side is a release material. The protective layer on both sides is a conductive layer; or the protective layers on both sides are both release materials; or the protective layers on both sides are conductive layers.

It should be noted that the release material is used to protect the prepreg during the hot pressing process and needs to be removed after the hot pressing process. In specific implementation, the release material can be any material familiar to those skilled in the art, and is not limited here.

During specific implementation, this application does not limit the material of the conductive layer. For example, it may be a metal conductive material or a non-metal conductive material.

It should be noted that the dielectric plate here is formed by performing a hot pressing process on the prepreg in the above-mentioned laminated structure.

For example, when a hot pressing process is used to perform a hot pressing process on a laminated structure, the pressing temperature can be controlled between 180°C and 240°C, such as 180°C, 200°C, 220°C, 240°C, etc., which are not exhaustive in this application. List specific point values included in the stated range.

For example, when a hot pressing process is used to perform a hot pressing process on a laminated structure, the pressing pressure can be controlled between 350 psi and 1000 psi, such as 350 psi, 500 psi, 700 psi, 1000 psi, etc. This application does not exhaustively list the ranges included. Specific point value.

For example, when a hot pressing process is used to perform a hot pressing process on a laminated structure, the pressing time can be controlled between 60min and 180min, such as 60mil, 90min, 120min, 150min, 180min, etc. This application does not list the ranges exhaustively. Specific point values included.

When at least one of the two protective layers is a release material, the preparation method further includes the following steps: removing the protective layer formed of the release material.

In this application, when it is necessary to form a substrate including only a dielectric plate, the protective layers on both sides of the dielectric plate need to be removed after using a hot pressing process to perform a hot pressing process on the stacked structure. That is, when one of the two protective layers is a release material and the other protective layer is a conductive layer, or when both protective layers are conductive layers, the laminated structure is hot-pressed using a hot-pressing process. After processing, all conductive layers need to be removed. This situation generally refers to the situation where using a conductive layer as a protective layer has more advantages in terms of cost and process than using a release material as a protective layer.

For example, in this application, after all protective layers are removed, a metal growth process can also be used to form a metal conductive layer on at least one side of the dielectric plate. The substrate thus formed includes a dielectric plate and a metal conductive layer located on one side or both sides of the dielectric plate. This situation generally occurs when the conductive layer cannot meet the target requirements, such as thickness requirements, material requirements, etc.

For example, in this application, when one of the two protective layers is a release material and the other protective layer is a conductive layer, after removing the release material, a metal growth process can also be used to grow a layer away from the dielectric plate. A metal conductive layer is formed on one side of the conductive layer. That is, in the formed substrate, one side of the dielectric plate is a conductive layer pressed by a hot pressing process, and the other side is a metal conductive layer formed by a metal growth process.

For example, in this application, when both protective layers are conductive layers, the stacked structure is processed using a hot pressing process. After the hot pressing process, one of the conductive layers may also be removed. That is, the formed substrate includes a dielectric plate and a conductive layer located on one side of the dielectric plate. This situation generally refers to the situation where using a conductive layer as a protective layer has more advantages in terms of cost and process than using a release material as a protective layer.

Furthermore, in this application, when both protective layers are conductive layers, after removing one of the conductive layers, a metal growth process can also be used to form a metal conductive layer on the side of the dielectric plate away from the conductive layer. That is, in the formed substrate, one side of the dielectric plate is a conductive layer pressed by a hot pressing process, and the other side is a metal conductive layer formed by a metal growth process.

Illustratively, the metal growth process provided by the embodiment of the present application can be a chemical vapor deposition (Chemical Vapor Deposition, CVD) process, a physical vapor deposition (Physical Vapor Deposition, PVD) process, an electrochemical deposition (Electrochemical Deposition) process, etc., in This is not a limitation.

In specific implementation, physical vapor deposition processes mainly include vacuum evaporation, sputtering coating, arc plasma plating, ion plating, molecular beam epitaxy, etc., which are not limited here.

In specific implementation, the material of the metal conductive layer can be a first metal material, or a mixed material of two or more metals, which is not limited here.

In this application, a metal growth process is used to form a metal conductive layer on one or both sides of the dielectric plate. By selecting the material of the metal conductive layer, a metal conductive layer with higher conductivity and lower conductor loss can be achieved.

The technical effects that can be achieved by the above-mentioned second aspect to the fifth aspect can be referred to the description of the technical effects that can be achieved by any possible design in the above-mentioned first aspect, and will not be repeated here.

Description of drawings

Figure 1 is a schematic structural diagram of a prepreg provided by an embodiment of the present application;

Figure 2 is a schematic flow chart of a method for preparing a prepreg according to an embodiment of the present application;

Figure 3 is a schematic flow chart of a method for preparing a prepreg according to another embodiment of the present application;

Figure 4 is a schematic structural diagram of a substrate provided by an embodiment of the present application;

Figure 5 is a schematic structural diagram of a substrate provided by another embodiment of the present application;

Figure 6 is a schematic structural diagram of a substrate provided by another embodiment of the present application;

Figure 7 is a schematic structural diagram of a substrate provided by another embodiment of the present application;

Figure 8 is a schematic structural diagram of a substrate provided by another embodiment of the present application;

Figure 9 is a schematic structural diagram of a substrate provided by another embodiment of the present application;

Figure 10 is a schematic structural diagram of a substrate provided by another embodiment of the present application;

Figure 11 is a schematic structural diagram of a substrate provided by another embodiment of the present application;

Figure 12 is a schematic flow chart of a method for preparing a substrate according to an embodiment of the present application;

Figure 13 is a schematic flow chart of a method for preparing a substrate according to another embodiment of the present application;

Figure 14 is a schematic structural diagram of a printed circuit board provided by an embodiment of the present application;

FIG. 15 is a schematic top structural view of one of the conductive layers in a printed circuit board according to an embodiment of the present application.

Explanation of reference symbols:

10-preg; 02-preg resin; 01-reinforcement material; 100-substrate; 110-dielectric board; 10a-first prepreg; 10b-second prepreg; 120-conductive layer; 1000-printed circuit board.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be described in further detail below in conjunction with the accompanying drawings. Example embodiments may, however, be embodied in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concepts of the example embodiments. To those skilled in the art. The same reference numerals in the drawings represent the same or similar structures, and thus their repeated description will be omitted. The words expressing position and direction described in this application are all explained by taking the accompanying drawings as examples, but they can be changed as needed, and all changes are included in the protection scope of this application. The drawings in this application are only used to illustrate relative positional relationships and do not represent true proportions.

It should be noted that specific details are set forth in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described here, and those skilled in the art can make similar extensions without violating the connotation of the present application. The present application is therefore not limited to the specific embodiments disclosed below. The following descriptions of the specification are preferred implementation modes for implementing the present application. However, the descriptions are for the purpose of illustrating the general principles of the present application and are not intended to limit the scope of the present application. The scope of protection of this application shall be determined by the appended claims.

In the following, some terms used in the embodiments of the present application are explained to facilitate understanding by those skilled in the art.

The dielectric constant (Dk) represents the degree of polarization of the dielectric, that is, its ability to bind charges. The greater the dielectric constant, the stronger its ability to bind charges.

Dielectric loss factor (Df), also called dielectric loss tangent, can generally be defined as: the current phasor and voltage flowing in the dielectric due to the hysteresis effect of dielectric conductivity and dielectric polarization in an insulating material or dielectric in an alternating electric field. A certain phase difference is produced between the phasors, that is, a certain phase angle is formed. The tangent value of this phase angle is the dielectric loss factor. The energy loss caused by the dielectric conductivity and dielectric polarization hysteresis effect is called dielectric loss. That is to say, the higher the Df, the more obvious the dielectric conductivity and dielectric polarization hysteresis effect are, and the more electrical energy loss or signal loss is.

In order to facilitate understanding of the technical solutions provided by the embodiments of this application, its specific application scenarios are first described below.

Pre-cured sheet is one of the main materials in substrate production. It is mainly composed of resin materials and reinforcing materials. The commonly used reinforcing materials are inorganic glass fiber cloth. During production, the inorganic glass fiber cloth is impregnated or coated with resin material, and then dried and baked until the resin material reaches a semi-cured state to generate a prepreg sheet. The substrate is a plate-shaped material made by laminating one or more layers of prepreg, then covering one or both sides with copper foil and hot pressing. Substrates can be widely used in Printed Circuit Boards (PCBs), integrated circuits, etc. for signal transmission and electrical interconnection.

Currently commonly used inorganic glass fiber cloths are E-glass fiber cloth, Low Df glass fiber cloth, New Low Dk glass fiber cloth and Quartz glass fiber cloth. The dielectric constant Dk is between 6.5 and 3.7. The dielectric of the resin material in the prepreg The constant Dk is generally less than 3.0, and the difference in Dk between inorganic glass fiber cloth and resin materials is large. When prepreg is applied to a substrate, for high-speed differential wiring on the substrate, the greater the difference in Dk between the inorganic glass fiber cloth and the resin material, the more serious the signal delay skew (Delay Skew) problem will be. Among them, the larger the Delay Skew value, the greater the time difference in signal transmission and the more inconsistent the transmission characteristics of the wire. When the differential wiring pairs are unbalanced, common mode noise will be introduced.

In addition, the reduction of the dielectric loss factor Df of the currently commonly used inorganic glass fiber cloth is limited: (1) The inorganic component has reached extremely high purity, and further improvement of its purity is extremely difficult and costly; (2) For extremely high purity The purity of the inorganic components limits the spinning and weaving capabilities. Therefore, it is currently extremely difficult to obtain inorganic glass fiber cloth with a dielectric loss factor Df<0.001@10GHz.

Obviously, with the rapid development of communication technology, the dielectric properties of existing inorganic glass fiber cloth can no longer meet the needs of high-frequency and high-speed substrates.

Based on this, this application provides a prepreg, a substrate, a printed circuit board and related preparation methods. In order to facilitate understanding of the technical solution of the present application, the technical solution provided by the present application will be described in detail below with reference to the accompanying drawings and specific implementation modes.

Referring to Figure 1, Figure 1 shows a prepreg 10 provided by an embodiment of the present application. The prepreg 10 may include a reinforcing material 01 and a prepreg resin 02. The reinforcing material 01 includes fiber cloth; the fiber cloth includes liquid crystal polymer (LCP) fiber filaments. The dielectric constant Dk of the LCP fiber filaments is 2.5 to 4.5, and the dielectric loss factor Df is less than 0.005@10GHz.

The prepreg provided by this application can reduce the Delay Skew problem because the dielectric constant of the LCP fiber filaments in the fiber cloth is 2.5 to 4.5, which is close to the dielectric constant of the resin material. Moreover, the dielectric loss factor Df of LCP fiber filaments is less than 0.005@10GHz, which is lower than the dielectric loss factor Df of commonly used inorganic glass fiber cloth, and the cost is lower than that of inorganic glass fiber cloth with low dielectric loss factor. Therefore, the prepreg provided in this application can have excellent dielectric properties while ensuring low cost, and can fully meet the application requirements of high-frequency and high-speed electronic products.

The second way: each fiber bundle in at least part of the plurality of fiber bundles includes at least 50% LCP fiber filaments, for example, in part or all of the fiber bundles, each fiber bundle includes 50%, 60% , 70%, 80%, 90% or 100% LCP fiber filaments.

For example, when the area ratio of LCP fiber filaments is less than 100% of the total area of the fiber cloth, the fiber cloth can be formed by mixing and weaving at least one type of inorganic fiber filaments and non-LCP type organic fiber filaments and LCP fiber filaments. For example, among the multiple fiber bundles forming the fiber cloth, some of the fiber bundles are made of LCP fiber filaments, and the other part of the fiber bundles are made of non- LCP-type organic fiber filaments are formed; or, among the plurality of fiber bundles forming the fiber cloth, part of the fiber bundles is formed of LCP fiber filaments, and the other part of the fiber bundles is formed of inorganic fiber filaments; or, among the plurality of fiber bundles forming the fiber cloth, , the first part of the fiber bundle is formed of LCP fiber filaments, the second part of the fiber bundle is formed of inorganic fiber filaments, and the third part of the fiber bundle is formed of non-LCP type organic fiber filaments. Alternatively, among the plurality of fiber bundles forming the fiber cloth, each fiber bundle is formed of LCP fiber filaments and non-LCP type organic fiber filaments; or, among the plurality of fiber bundles forming the fiber cloth, each fiber bundle is composed of LCP fiber filaments. and inorganic fiber filaments; or, among the plurality of fiber bundles forming the fiber cloth, each fiber bundle is formed of LCP fiber filaments, inorganic fiber filaments and non-LCP type organic fiber filaments. Alternatively, among the plurality of fiber bundles forming the fiber cloth, some of the fiber bundles are formed of LCP fiber filaments, and the other part of the fiber bundles include a certain proportion of LCP fiber filaments in each fiber bundle.

For example, the inorganic fiber threads in this application can be inorganic glass fiber threads, and of course they can also be fiber threads made of other inorganic materials, which are not limited here.

For example, in this application, the thickness of the prepreg 10 can be set to 25 μm-300 μm, such as 25 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, etc. This application does not exhaustively list specific point values included in the range. The specific thickness of the prepreg 10 can be set according to actual requirements.

Referring to Figure 2, Figure 2 is a schematic flow chart of a method for preparing the above-mentioned prepreg provided by an embodiment of the present application. The preparation method may include the following steps:

Step S101: Form a fiber cloth; the fiber cloth includes LCP fiber filaments, and the dielectric constant Dk of the LCP fiber filaments is 2.5-4.5, and the dielectric loss factor Df is less than 0.005@10GHz.

When weaving the fiber cloth, at least some of the fiber bundles include LCP fiber filaments. It can be understood here that at least part of the fiber bundles among the plurality of fiber bundles are completely formed of LCP fiber filaments; or, at least part of the fiber bundles among the plurality of fiber bundles are made of LCP fiber filaments and other fiber filaments (other than LCP fiber filaments). fiber bundles); or, part of the plurality of fiber bundles is completely formed of LCP fiber bundles, and part of the fiber bundles is formed of LCP fiber threads and other fiber threads (other fiber threads except LCP fiber threads). In specific implementation, the fiber cloth can be modified according to the application scenario. The weaving method can be flexibly designed according to mechanical strength, dielectric properties and other requirements.

The second way: at least part of the plurality of fiber bundles includes at least 50% LCP fiber filaments, for example, in part or all of the fiber bundles, each fiber bundle includes 50%, 60%, 70%, 80% %, 90% or 100% LCP fiber filaments.

Step S102: Coating or impregnating the resin material on the surface of the fiber cloth.

Exemplarily, the thermoplastic resin may include fluorine-based resins, such as polytetrafluoroethylene (PTFE) or a small amount of perfluoropropyl At least one copolymer of perfluorovinyl ether and polytetrafluoroethylene (PFA).

Step S103: Semi-curing the fiber cloth whose surface is coated or impregnated with the resin material to form a prepreg.

Optionally, see Figure 3. In this application, according to the required thickness and performance requirements of the prepreg, the following steps can be performed at least once after forming the above-mentioned prepreg: S104. Re-coating or impregnating the surface of the formed prepreg. Resin material, the prepreg whose surface is coated or impregnated with the resin material is then semi-cured to form a new prepreg, thereby increasing the thickness of the prepreg. It can be understood that in this application, the more times step S104 is repeated, the thicker the thickness of the prepreg formed. Of course, according to actual needs, if the thickness of the prepreg has reached the requirement after executing steps S101 to S103, there is no need to execute step S104.

The preparation method provided by the embodiments of this application can design the resin material and the content of LCP fiber filaments in the fiber cloth according to the actual needs of the product, so that the formed prepreg has excellent dielectric properties and good heat resistance. Moreover, the LCP fiber cloth in the prepreg has a lower dielectric loss factor Df than the commonly used inorganic glass fiber cloth, which can break through the limitations of low-loss inorganic glass fiber cloth, and is easy to achieve mass production, which can fully meet the requirements of high frequency and high speed. Application requirements of electronic products.

Referring to Figures 4 to 7, embodiments of the present application also provide a substrate 100. The substrate 100 includes a dielectric plate 110, wherein the dielectric plate 110 can be composed of one prepreg sheet (first prepreg sheet 10a) or multiple stacked prepreg sheets ( The first prepreg 10a and/or the second prepreg 10b) are formed after hot pressing. When the dielectric plate 110 is formed by hot pressing a piece of prepreg, the prepreg is the prepreg provided in any of the above embodiments of the present application. When the dielectric plate 110 is formed by hot pressing of a plurality of stacked prepreg sheets, at least one prepreg sheet among the plurality of prepreg sheets is a prepreg sheet provided in any of the above embodiments of the present application. In order to distinguish the prepreg provided by the implementation of the application from other prepregs, the prepreg provided by the implementation of the application is called the first prepreg 10a, and the other prepregs are called the second prepreg 10b, where the first prepreg 10a refers to the reinforcing material including LCP fiber. Silk, the second prepreg 10b refers to any prepreg that does not include LCP fiber threads in the reinforcing material.

It can be understood that in the substrate 100 provided by the present application, the number of the first prepreg 10a and the second prepreg 10b can be designed according to the thickness, structural strength, dielectric properties and other requirements of the substrate 100, and is not limited here. For example, the substrate 100 shown in FIG. 4 includes only one first prepreg sheet 10a, the substrate 100 shown in FIG. 5 includes two first prepreg sheets 10a, and the substrate 100 shown in FIG. 6 includes one first prepreg sheet 10a. and two second halves Cured sheet 10b. The substrate 100 shown in FIG. 7 includes two first prepreg sheets 10a and one second prepreg sheet 10b.

This application does not limit the stacking sequence of the first prepreg 10a and the second prepreg 10b in the substrate 100, and the specific design can be based on actual needs.

Exemplarily, referring to FIGS. 8 to 11 , the substrate 100 may further include a conductive layer 120 disposed on at least one side of the dielectric plate 110 . For example, as shown in FIGS. 8 and 9 , the conductive layer 120 is only disposed on one side of the dielectric plate 110 . One side, that is, the single-sided conductive substrate 100 , or, as shown in FIGS. 10 and 11 , conductive layers 120 are provided on both sides of the dielectric plate 110 , that is, the double-sided conductive substrate 100 .

The material of the conductive layer 120 is not limited in this application. For example, it can be a metallic conductive material or a non-metal conductive material. Of course, it can also be a stack of multiple layers of conductive materials.

In specific implementation, when the conductive layer 120 is provided on both sides of the dielectric plate 110, the thickness and material of the conductive layer 120 on both sides of the dielectric plate 110 are not limited in this application. The thickness of the conductive layer 120 on both sides of the dielectric plate 110 can be They may be the same or different. Similarly, the materials of the conductive layers 120 on both sides of the dielectric plate 110 may be the same or different.

For example, in this application, the thickness of the conductive layer 120 is set uniformly, and the thickness of the conductive layer 120 on both sides of the dielectric plate 110 is the same.

Exemplarily, the thickness of the conductive layer 120 can be set to 0.1 μm to 70 μm, such as 9 μm (1/4 oz), 12 μm (1/3 oz), 18 μm (1/2 oz), 35 μm (1 oz), or 70 μm (2 oz), etc. , this application does not exhaustively list the specific point values included in the stated range.

Correspondingly, referring to Figures 12 and 13, embodiments of the present application also provide a method for preparing a substrate. The preparation method may include the following steps:

Step S201: Stack protective layers on both sides of one prepreg sheet or a plurality of stacked prepreg sheets to form a laminated structure.

Wherein, at least one prepreg in the laminated structure is any one of the prepregs provided in the above-mentioned embodiments of the present application, and the protective layer on one side of the protective layers on both sides is a release material, and the protective layer on the other side is conductive. layer; or, the protective layers on both sides are both release materials; or, the protective layers on both sides are conductive layers.

Step S202: Use a hot pressing process to perform a hot pressing process on the stacked structure to form a dielectric plate and protective layers located on both sides of the dielectric plate.

For example, when a hot pressing process is used to perform a hot pressing process on a laminated structure, the pressing temperature can be controlled between 180°C and 240°C, such as 180°C, 200°C, 220°C, 240°C, etc., which are not exhaustive in this application. List specific points included in the stated range value.

When at least one of the two protective layers is a release material, see Figure 13, the preparation method further includes the following steps: step S203, removing the protective layer formed of the release material.

Specifically, when both protective layers are conductive layers, the substrate can be formed through steps S201-S202. The formed substrate includes a dielectric plate and conductive layers located on both sides of the dielectric plate, that is, the substrate is a double-sided conductive substrate. When one of the two protective layers is a release material and the other protective layer is a conductive layer, the substrate can be formed through steps S201-S203. The formed substrate includes a dielectric plate and a conductive layer located on one side of the dielectric plate, that is, The substrate is a single-sided conductive substrate. When both protective layers are made of release materials, the substrate can be formed through steps S201-S203, and the formed substrate only includes a dielectric plate.

For example, in this application, when both protective layers are conductive layers, after using a hot pressing process to perform a hot pressing process on the stacked structure, one of the conductive layers may also be removed. That is, the formed substrate includes a dielectric plate and a conductive layer located on one side of the dielectric plate. This situation generally refers to the situation where using a conductive layer as a protective layer has more advantages in terms of cost and process than using a release material as a protective layer.

In specific implementation, the material of the metal conductive layer can be a first metal material, or it can be two or more metals. Mixed materials are not limited here.

Correspondingly, referring to FIG. 14 , an embodiment of the present application also provides a printed circuit board 1000 , which includes any of the above-mentioned substrates 100 provided by the embodiment of the present application. Since the problem-solving principle of the printed circuit board 1000 is similar to that of the aforementioned substrate 100, the implementation of the printed circuit board 1000 can be referred to the implementation of the aforementioned substrate 100, and repeated details will not be described again.

In specific implementation, referring to FIG. 15 , when the substrate 100 in the printed circuit board 1000 includes a conductive layer 120 , the conductive layer 120 is generally also etched with lines and pads for signal transmission or interaction with other conductors. even.

In the above technical solution, since the fiber cloth of the prepreg includes LCP fiber filaments, and the dielectric constant of LCP fiber filaments is 2.5 to 4.5, which is close to the dielectric constant of the resin material, the Delay Skew problem can be reduced. Moreover, the dielectric loss factor Df of LCP fiber filaments is less than 0.005@10GHz, which is lower than the dielectric loss factor Df of commonly used inorganic glass fiber cloth, and the cost is lower than that of inorganic glass fiber cloth with low dielectric loss factor. Therefore, the technical solution provided by this application has excellent dielectric properties, low raw material cost, good dimensional stability, and good flame retardancy, and can fully meet the application needs of high-frequency and high-speed electronic products.

Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. In this way, if these modifications and variations of the present application fall within the scope of the claims of the present application and equivalent technologies, the present application is also intended to include these modifications and variations.

Claims

A semi-cured sheet, characterized by including: semi-cured resin and reinforcing material;

The reinforcing material includes fiber cloth; wherein the fiber cloth includes liquid crystal polymer fiber filaments, the dielectric constant of the liquid crystal polymer fiber filaments is 2.5-4.5, and the dielectric loss factor is less than 0.005@10GHz.
The prepreg according to claim 1, wherein the area ratio of the liquid crystal polymer fiber filaments in the fiber cloth is greater than or equal to 50% of the total area of the fiber cloth.
The prepreg of claim 2, wherein the fiber cloth is woven from a plurality of fiber bundles, and at least 50% of the plurality of fiber bundles are formed from the liquid crystal polymer fiber filaments.
The prepreg of claim 2, wherein the fiber cloth is formed by weaving a plurality of fiber bundles, and at least part of the fiber bundles among the plurality of fiber bundles includes at least 50% of the liquid crystal polymer. fiber filament.
The prepreg according to claim 3 or 4, wherein the fiber cloth is formed by weaving the liquid crystal polymer fiber filaments;

Alternatively, the fiber cloth is formed by mixing and weaving at least one of inorganic fiber filaments and non-liquid crystal polymer type organic fiber filaments with the liquid crystal polymer fiber filaments.
The prepreg according to claim 3 or 4, wherein the fiber cloth is formed from the fiber bundles by an orthogonal weaving method or an oblique weaving method.
The prepreg according to any one of claims 1 to 6, wherein the liquid crystal polymer fiber filaments have a diameter and width of 4 μm to 40 μm.
The prepreg according to any one of claims 1 to 7, characterized in that the thickness of the fiber cloth is 15 μm-200 μm.
The prepreg according to any one of claims 1 to 8, characterized in that the prepreg resin includes thermoplastic resin and/or thermosetting resin.
The prepreg according to claim 9, wherein the thermoplastic resin includes a fluorine-based resin.
The prepreg of claim 9, wherein the thermosetting resin includes bismaleimide resin, cycloolefin resin, polydivinylbenzene resin, divinylbenzene, polyphenylene ether, carbon At least one of hydrogen resin, phenolic resin or epoxy resin.
The prepreg according to any one of claims 1 to 11, characterized in that the thickness of the prepreg is 25 μm-300 μm.
A substrate, characterized in that it includes a dielectric plate, wherein the dielectric plate is formed by hot pressing a piece of prepreg according to any one of claims 1-12;

Alternatively, the dielectric board is formed by hot-pressing a plurality of stacked prepreg sheets, and at least one prepreg sheet among the plurality of prepreg sheets is the prepreg sheet according to any one of claims 1-12.
The substrate of claim 13, further comprising a conductive layer disposed on at least one side of the dielectric plate.
The substrate of claim 14, wherein the conductive layer has a thickness of 0.1 μm-70 μm.
The substrate of claim 14 or 15, wherein the conductive layer includes a metal conductive layer.
The substrate of claim 16, wherein the metal conductive layer includes at least one of aluminum foil, copper foil or silver foil.
A printed circuit board, characterized by comprising the substrate according to any one of claims 13-17.
A method for preparing prepreg, which is characterized by including:

Forming a fiber cloth; wherein the fiber cloth includes liquid crystal polymer fiber filaments, and the dielectric constant of the liquid crystal polymer fiber filaments is 2.5 to 4.5, and the dielectric loss factor is less than 0.005@10GHz;

Coating or impregnating resin material on the surface of the fiber cloth;

The fiber cloth whose surface is coated or impregnated with the resin material is subjected to semi-curing treatment to form a semi-cured sheet.
The preparation method according to claim 19, characterized in that, after forming the prepreg, it further includes: performing the following steps at least once:

The surface of the formed prepreg is then coated or impregnated with a resin material, and the surface of the prepreg coated or impregnated with the resin material is subjected to a semi-curing process.
The preparation method according to claim 20, characterized in that the temperature of the semi-curing treatment is 100°C-160°C.
The preparation method according to claim 20, characterized in that the time of the semi-curing treatment is 4 min-12 min.
The preparation method according to any one of claims 19 to 22, characterized in that said forming fiber cloth includes:

The fiber cloth is formed by weaving multiple fiber bundles, and at least part of the fiber bundles include the liquid crystal polymer fiber filaments.
The preparation method according to claim 23, characterized in that the area ratio of liquid crystal polymer fiber filaments in the fiber cloth is greater than or equal to 50% of the total area of the fiber cloth.
The preparation method of claim 24, wherein at least 50% of the plurality of fiber bundles are formed of the liquid crystal polymer fiber filaments.
The preparation method of claim 24, wherein at least some of the fiber bundles among the plurality of fiber bundles include at least 50% of the liquid crystal polymer fiber filaments.
The preparation method according to claim 25 or 26, wherein the fiber cloth is formed by weaving the liquid crystal polymer fiber filaments;

The fiber cloth is formed by mixing and weaving at least one of inorganic fiber filaments and non-liquid crystal polymer type organic fiber filaments and the liquid crystal polymer fiber filaments.
The preparation method according to any one of claims 23 to 27, wherein the fiber cloth is formed by weaving multiple fiber bundles, including:

The plurality of fiber bundles are used to form the fiber cloth through orthogonal weaving or oblique weaving.
A method for preparing a substrate, characterized by including:

Protective layers are stacked on both sides of a prepreg sheet or a plurality of stacked prepreg sheets to form a laminated structure; wherein at least one prepreg sheet in the laminated structure is the prepreg sheet according to any one of claims 1 to 12, And one of the two protective layers is a release material, and the other protective layer is a conductive layer; or both of the two protective layers are release materials; or both of the protective layers The layers are all conductive layers;

Using a hot pressing process to perform a hot pressing process on the laminated structure, a dielectric plate and protective layers located on both sides of the dielectric plate are formed;

When at least one of the protective layers is a release material, after using a hot pressing process to process the stacked structure, the step further includes: removing the release material.
The preparation method according to claim 29, characterized in that when one of the two protective layers is a release material and the other protective layer is a conductive layer, or when the two protective layers When the protective layers are all conductive layers, after the hot pressing process is used to perform the hot pressing process on the laminated structure, it also includes:

Remove all of the conductive layers.
The preparation method according to claim 29 or 30, characterized in that, after removing all the protective layers, it further includes:

A metal growth process is used to form a metal conductive layer on at least one side of the dielectric plate.
The preparation method according to claim 29, characterized in that when one of the two protective layers is a release material and the other protective layer is a conductive layer, the release material is After the materials, it also includes:

A metal growth process is used to form a metal conductive layer on the side of the dielectric plate away from the conductive layer.
The preparation method according to claim 29, characterized in that when both of the protective layers are conductive layers, after using a hot pressing process to perform a hot pressing process on the stacked structure, it further includes:

Remove one of the conductive layers.
The preparation method according to claim 33, characterized in that, after removing one of the conductive layers, it further includes:

A metal growth process is used to form a metal conductive layer on the side of the dielectric plate away from the conductive layer.
The preparation method according to any one of claims 29 to 34, characterized in that when the laminated structure is subjected to a hot pressing process, the pressing temperature is 180°C-240°C.
The preparation method according to any one of claims 29 to 34, characterized in that when the laminated structure is subjected to a hot pressing process, the pressing pressure is 350 psi to 1000 psi.
The preparation method according to any one of claims 29 to 34, characterized in that when the laminated structure is subjected to a hot pressing process, the pressing time is 60 minutes to 180 minutes.