Embedded-magnet printed circuit board and preparation method therefor

Abstract

The present application provides an embedded-magnet printed circuit board and a preparation method therefor. The embedded-magnet printed circuit board comprises a magnetic plate, a first substrate, two second substrates respectively arranged on two sides of the first substrate, and a dielectric layer arranged between the first substrate and each second substrate, wherein a buried via that fits the magnetic plate in terms of shape is formed in the first substrate; the first substrate is stacked on one second substrate and has a buried slot formed therein at the buried via, in which buried slot the magnetic plate is arranged; the magnetic plate and the buried via are polygonal shaped; and an accommodating recess is formed in an inner side wall of the buried via at a position corresponding to a chamfer of the magnetic plate, the accommodating recess being in communication with the buried slot and being configured to accommodate the chamfer of the magnetic plate. In the embedded-magnet printed circuit board and the preparation method therefor provided in the present application, the chamfer of the magnetic plate is accommodated by additionally providing the accommodating recess, so that the magnetic plate is prevented from entering a gap between the first substrate and the dielectric layer, thus ensuring that the chamfer of the magnetic plate does not come into direct contact with a wall of the recess, thereby effectively solving the problem of the magnetic plate, especially, the chamfer of the magnetic plate, being easily damaged under stress during lamination.

Description

Embedded magnetic printed circuit board and preparation method thereof

[0001] This application claims priority to Chinese patent application No. 202311701312.0 filed on December 11, 2023, entitled “EMBEDDED MAGNETIC PRINTED CIRCUIT BOARD AND METHOD FOR PREPARING THE SAME,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the technical field of printed circuit boards, and in particular to an embedded magnetic printed circuit board and a preparation method thereof. Background Art

[0003] PCBs (Printed Circuit Boards) are important electronic components that support and connect electronic components. With the rapid development of the PCB industry, their applications are becoming increasingly widespread. Embedded PCBs are one such type. As the name suggests, these incorporate specific components within the PCB to achieve their intended function. For example, embedded copper block PCBs, for example, achieve localized, efficient heat dissipation by embedding copper blocks within the PCB. With the development of power module PCBs, the use of embedded magnetics in power converters has emerged, replacing traditional surface-mounted inductors. Embedding the magnetic core within the PCB significantly reduces the surface area occupied by the inductor during mounting, providing an effective solution for the high-density and miniaturization of electronic products.

[0004] However, currently, embedded magnetic PCB processing presents challenges. The embedded magnetic discs are relatively small and thin, typically ≤0.2mm thick. These thin discs are inherently brittle and prone to breakage and misalignment during lamination. These misaligned discs can slip into the gap between the core board and the dielectric layer, creating uneven forces during lamination and leading to disc breakage. These damages negatively impact the inductance, withstand voltage, and reliability of the embedded magnetic PCB, rendering it unsuitable for use. If a disc is found to be damaged in a laminated embedded magnetic PCB, the product must be scrapped, increasing production costs.

[0005] In summary, the current embedded magnetic PCB process is difficult. When preparing the embedded magnetic PCB, the magnetic sheet is easily damaged, causing the entire embedded magnetic PCB to be scrapped. Technical issues

[0006] The purpose of the embodiments of the present application is to provide a magnetic embedded printed circuit board and a preparation method thereof, so as to solve the technical problems that the existing magnetic embedded PCB process is difficult and the magnetic sheet is easily damaged during the preparation process. Technical Solutions

[0007] The technical solution adopted in the embodiment of this application is:

[0008] In a first aspect, the present application provides a magnetic embedded printed circuit board, comprising a magnetic sheet, a first substrate, two second substrates respectively provided on both sides of the first substrate, and a dielectric layer provided between the first substrate and the second substrate, wherein the dielectric layer is used to connect the first substrate and the second substrate;

[0009] The first substrate is provided with an embedding hole adapted to the shape of the magnetic piece, the first substrate is stacked on the second substrate, and an embedding groove is formed at the embedding hole, and the magnetic piece is placed in the embedding groove;

[0010] The magnetic sheet and the embedding hole are polygonal in shape, and an accommodating groove is provided on the inner side wall of the embedding hole corresponding to the convex corner of the magnetic sheet. The accommodating groove is connected to the embedding groove and is used to accommodate the convex corner of the magnetic sheet.

[0011] In a second aspect, the present application provides a method for preparing a magnetic embedded printed circuit board, comprising the following steps:

[0012] Provide the magnetic sheet, the first substrate, the second substrate, and the dielectric layer described in the first aspect;

[0013] The dielectric layer and the first substrate are sequentially stacked on one of the second substrates to form a first stacked structure, wherein the first stacked structure forms the buried groove at the buried hole;

[0014] Placing the magnetic sheet in the embedding groove, with the convex corner of the magnetic sheet located in the receiving groove;

[0015] The dielectric layer and another second substrate are further stacked on the first stacked structure to obtain a second stacked structure, which is then pressed to obtain the embedded magnetic printed circuit board.

[0016] According to the technical solution of the embodiment of the present application, in application, the edge or convex corner of the magnetic sheet can easily enter the gap between the dielectric layer and the first substrate, resulting in damage to the magnetic sheet, especially the convex corner, during the pressing process, causing the entire embedded magnetic PCB to be scrapped; the embedded magnetic printed circuit board provided by the present application, by adding a receiving groove to accommodate the convex corner of the magnetic sheet, so as to avoid the convex corner of the magnetic sheet directly contacting the groove wall, especially even if the magnetic sheet is completely biased to one side of the embedded groove, the convex corner of the magnetic sheet will not directly contact the groove wall, effectively solving the problem that the magnetic sheet, especially the convex corner of the magnetic sheet, is easily broken when pressed. The above preparation method is simple and easy to operate as a whole, and by adding a receiving groove to accommodate the convex corner of the magnetic sheet, the magnetic sheet, especially the convex corner of the magnetic sheet, is prevented from being broken during pressing, and the convex corner of the magnetic sheet is prevented from colliding with the groove wall of the embedded groove and being damaged.

[0017] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present application, nor is it intended to limit the scope of the present application. Other features of the present application will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] FIG1 is a schematic cross-sectional view of a magnetic embedded printed circuit board according to an embodiment of the present application;

[0020] FIG2 is a schematic diagram of a partial structure of an embedded magnetic printed circuit board provided in an embodiment of the present application;

[0021] FIG3 is a schematic diagram of a partial structure of an embedded magnetic printed circuit board provided in another embodiment of the present application;

[0022] FIG4 is a schematic diagram of the pre-laminated structure in FIG1 ;

[0023] FIG5 is a schematic diagram of the arrangement of bonding points of an embedded magnetic printed circuit board provided in an embodiment of the present application;

[0024] FIG6 is a schematic flow chart of a method for preparing an embedded magnetic printed circuit board according to an embodiment of the present application. Modes for Carrying Out the Invention

[0025] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obscuring the description of the present application with unnecessary detail.

[0026] It will also be understood that the term "and / or" used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0027] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0028] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0029] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0030] References to "one embodiment" or "some embodiments" in the present specification mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the phrases "in some embodiments", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized. "Multiple" means two or more.

[0031] In a first aspect, as shown in Figures 1 and 2 , the present application provides a magnetic embedded printed circuit board, comprising a magnetic sheet 10, a first substrate 20, two second substrates 30, and a dielectric layer 40;

[0032] The two second substrates 30 are respectively disposed on both sides of the first substrate 20;

[0033] The dielectric layer 40 is provided between the first substrate 20 and the second substrate 30 and is used to connect the second substrate 30 and the first substrate 20;

[0034] The first substrate 20 is provided with an embedding hole, the shape of which matches the shape of the magnetic sheet 10, and the shapes of the magnetic sheet 10 and the embedding hole are both polygonal. The first substrate 20 is stacked on a second substrate 30, and an embedding groove 200 is formed at the embedding hole, and the magnetic sheet 10 is placed in the embedding groove 200;

[0035] The inner side wall of the embedding hole is provided with a receiving groove 201 corresponding to the convex corner of the magnetic piece 10 . The receiving groove 201 is connected to the embedding groove 200 and is used to receive the convex corner of the magnetic piece 10 .

[0036] In application, the magnetic sheet 10 is arranged in a polygonal shape. Generally speaking, a rectangular magnetic sheet 10 is more common, so the magnetic sheet 10 will have multiple convex corners. However, in the process of embedding the polygonal magnetic sheet 10, since the magnetic sheet 10 itself is relatively thin, usually less than 0.2 mm thick, and brittle and fragile; in particular, the convex corners of the magnetic sheet 10 are very easy to break when they hit the groove wall of the embedding groove 200. Therefore, the embedded magnetic printed circuit board provided by the present application provides a receiving groove 201 on the inner side wall of the embedding hole to accommodate the convex corners of the magnetic sheet 10, providing sufficient accommodation space for the magnetic sheet 10, especially the convex corners, thereby effectively avoiding direct contact between the convex corners of the magnetic sheet 10 and the groove wall of the embedding groove 200. In particular, even if the magnetic sheet 10 is completely biased to one side of the embedding groove 200, the convex corners of the magnetic sheet 10 will not directly contact the groove wall, effectively solving the problem that the magnetic sheet 10, especially the convex corners of the magnetic sheet 10, are easily broken when pressed.

[0037] In some embodiments, the shape of the magnetic sheet 10 can also be other polygons, such as a triangle, a rectangle, a square, a trapezoid, etc. It should be noted that the convex corners of the magnetic sheet 10 are only a feature that is present when the magnetic sheet 10 is arranged in a polygonal shape. For example, when the magnetic sheet 10 is a triangle, the positions corresponding to the three corners of the triangle are the convex corners of the magnetic sheet 10. When the magnetic sheet 10 is a rectangle, the four corners of the rectangle are the convex corners of the magnetic sheet 10. The concept of convex corner in this application is similar to the definition of "convex corner" and "concave corner" in mathematics, but it should be noted that the convex corner in this application is a physical concept and is a part of the magnetic sheet 10.

[0038] The magnetic sheet 10 is primarily composed of a magnetic material, which can be either hard or soft. Hard magnetic materials (also known as permanent magnets) have high coercivity and remanence, meaning that once magnetized, they retain strong magnetism for a long time. Common materials include neodymium iron boron, samarium cobalt, alnico, and ferrite. Soft magnetic materials include, but are not limited to, silicon steel, permalloy, amorphous metals, and nanocrystalline soft magnetic materials.

[0039] In some embodiments, the size of the embedding groove 200 is greater than or equal to the size of the magnetic disc 10. Setting the size of the embedding groove 200 equal to the size of the magnetic disc 10 ensures that the magnetic disc 10 can be accommodated in the embedding groove 200; setting the size of the embedding groove 200 larger than the size of the magnetic disc 10 provides sufficient space for the magnetic disc 10, making it easier to place the magnetic disc 10 without damaging the magnetic disc 10 due to the embedding groove 200 being too small.

[0040] It should be noted that the size of the embedding groove 200 is greater than or equal to the size of the magnetic piece 10. That is, the magnetic piece 10 can at least be placed in the embedding groove 200, or after the magnetic piece 10 is placed in the embedding groove 200, there is still extra space in the embedding groove 200.

[0041] In some specific embodiments, the magnetic sheet 10 and the embedded hole are both rectangular in shape, the embedded slot 200 has a width a1 and a length b1, and the magnetic sheet 10 has a width a2 and a length b2, wherein a1, a2, b1, and b2 satisfy the following relationship:

[0042] a1≥a2; and / or b1≥b2.

[0043] In application, the width of the embedded groove 200 is greater than or equal to the width of the magnetic sheet 10, or the length of the embedded groove 200 is greater than or equal to the length of the magnetic sheet 10, or the width of the embedded groove 200 is greater than or equal to the width of the magnetic sheet 10, and the length of the embedded groove 200 is greater than or equal to the length of the magnetic sheet 10. In one specific embodiment, a1-a2=0.15mm, in another specific embodiment, b1-b2=0.15mm, and in yet another specific embodiment, a1-a2=0.15mm and b1-b2=0.15mm. With such a configuration, the magnetic sheet 10 is easy to place, and the magnetic sheet 10 will not be damaged due to the embedded groove 200 being too small, nor will it be difficult to accurately position it during pressing due to the embedded groove 200 being too large.

[0044] In some embodiments, the thickness of the first substrate 20 is equal to the thickness of the magnetic sheet 10 . In this way, the thickness of the embedded groove 200 is equal to that of the magnetic sheet 10 , so that the embedded groove 200 can just accommodate the magnetic sheet 10 .

[0045] In some embodiments, as shown in Figures 2 and 3, the cross section of the receiving groove 201 is at least one of circular, elliptical, and rectangular. The above shapes are easy to form by mechanical milling, die cutting, laser cutting, drilling, etc.

[0046] In some embodiments, both sides of the first substrate 20 are not covered with metal foil or at least one side of the first substrate 20 is covered with metal foil;

[0047] The second substrate 30 is a metal foil, or at least one side of the second substrate 30 is covered with a metal foil.

[0048] In practice, the first substrate 20 may be uncoated with metal foil on both sides, coated with metal foil on one side, or coated with metal foil on both sides; the second substrate 30 may be coated with metal foil on one side or coated with metal foil on both sides. In a preferred embodiment of this application, the first substrate 20 may be uncoated with metal foil on both sides, while the second substrate 30 may be coated with metal foil on both sides. This ensures the insulation of the first substrate 20, while the corresponding functions can be achieved by routing circuits on the metal foil on the second substrate 30. In some embodiments, the metal foil is copper foil or aluminum foil.

[0049] In some embodiments, the first substrate 20 and dielectric layer 40 are made of at least one of epoxy resin, polyimide resin, polyester resin, polyphenylene oxide resin, and polytetrafluoroethylene resin. In addition to the aforementioned resin materials, the first substrate 20 and dielectric layer 40 may also include fiberglass cloth, meaning the first substrate 20 and dielectric layer 40 are a composite of at least one of the aforementioned resin materials and fiberglass cloth. All of these materials are inexpensive and readily available insulating dielectrics. Epoxy resin is one of the most commonly used base materials in PCBs, offering excellent electrical insulation, mechanical strength, and heat resistance. It also provides excellent dimensional stability and processability. Polyimide resin is a high-performance engineering plastic with excellent high-temperature resistance, chemical stability, and mechanical strength. Polyester resin is relatively low-cost and offers excellent electrical insulation and a reasonable degree of mechanical strength. Polyphenylene oxide resin has high heat resistance, low moisture absorption, and excellent electrical properties. It is suitable for high-frequency applications and electronic products requiring high reliability. Polytetrafluoroethylene resin is known for its excellent electrical insulation, low dielectric constant, and low loss tangent, making it well-suited for high-frequency and microwave applications. It also has excellent chemical inertness and temperature resistance and is commonly used in high-end communication equipment and military applications. Fiberglass cloth is often used in combination with the above resins as a reinforcement to improve the mechanical strength and dimensional stability of the composite material.

[0050] In one specific embodiment, the first substrate 20 is primarily made of epoxy resin and reinforced fiberglass cloth. One second substrate 30 is copper foil, and the other second substrate 30 is selected from a single-sided copper-clad substrate, a double-sided copper-clad substrate, a double-sided copper-free substrate, or a multilayer board. The dielectric layer 40 is an epoxy resin prepreg. The dielectric layer 40 primarily serves as an adhesive within the entire embedded magnetic printed circuit board. Under high temperature and high pressure, the dielectric layer 40 melts and flows, and solidifies after cooling. Therefore, during lamination, the molten dielectric layer 40 fills the gap between the magnetic sheet 10 and the embedding groove 200 and the receiving groove 201, bonding the first and second substrates 20 and 30 together to form a single unit.

[0051] In a second aspect, as shown in Figures 1 and 6, the present application provides a method for preparing a magnetic embedded printed circuit board, comprising the following steps:

[0052] S1. Provide the magnetic sheet 10, the first substrate 20, the second substrate 30 and the dielectric layer 40 described in the first aspect;

[0053] S2, stacking the dielectric layer 40 and the first substrate 20 on a second substrate 30 in sequence to form a first stacked structure, wherein the first stacked structure forms a buried trench 200 at the buried hole;

[0054] S3, placing the magnetic piece 10 in the embedding groove 200, and making the convex corner of the magnetic piece 10 be located in the receiving groove 201;

[0055] S4. Continue to stack the dielectric layer 40 and another second substrate 30 on the first stacked structure to obtain a second stacked structure, and then press together to obtain an embedded magnetic printed circuit board.

[0056] By adopting the above steps to prepare an embedded magnetic printed circuit board, on the one hand, the steps are simple and the operation is convenient, which is conducive to large-scale production. The embedded magnetic printed circuit board prepared by the above method has a high yield and low cost. On the other hand, by setting an accommodating groove 201 at the convex corner position of the magnetic piece 10 corresponding to the embedded groove 200, it is used to accommodate the convex corner part of the magnetic piece 10, so that even if the magnetic piece 10 is completely biased to one side of the embedded groove 200, the convex corner will not directly contact the groove wall of the embedded groove 200, effectively solving the problem that the magnetic piece 10, especially the convex corner of the magnetic piece 10, is easily broken by the force during pressing.

[0057] In some embodiments, as shown in FIG4 , the step of sequentially stacking the dielectric layer 40 and the first substrate 20 on a second substrate 30 to form a first stacked structure includes:

[0058] Pre-fixing the dielectric layer 40 to one side of the first substrate 20 to obtain a pre-laminated structure;

[0059] The pre-laminated structure is laminated onto a second substrate 30 .

[0060] By pre-fixing the dielectric layer 40 to one side of the first substrate 20, a part or all of the dielectric layer 40 is connected to the first substrate 20 to obtain an integral pre-laminated structure, thereby blocking the gap between the dielectric layer 40 and the first substrate 20. When the magnetic sheet 10 is placed, the edges or convex corners of the magnetic sheet 10 will not slide into the gap between the dielectric layer 40 and the first substrate 20, thereby avoiding the problem of uneven force on different parts of the magnetic sheet 10 during pressing and causing damage.

[0061] In some embodiments, as shown in Figures 4 and 5, the pre-fixation includes the following steps: setting a plurality of bonding points 400 on the dielectric layer 40 along the edge of the buried groove 200, and the plurality of bonding points 400 are evenly distributed along the edge of the buried groove 200, and heating the dielectric layer 40 located at the bonding points 400 to melt the dielectric layer 40 and bond it to the buried groove 200, thereby sealing the gap between the dielectric layer 40 and the first substrate 20.

[0062] By setting a plurality of bonding points 400, the dielectric layer 40 on the bonding points 400 is heated and melted in a targeted manner, so that the dielectric layer 40 on the bonding points 400 is bonded to the first substrate 20, thereby making the dielectric layer 40 and the first substrate 20 become a whole, preventing the magnetic sheet 10 from entering the gap between the two.

[0063] In some embodiments, pre-fixation includes the following steps: heating the dielectric layer 40 located at the edge of the embedded groove 200 to melt the dielectric layer 40 and thus adhere to one side of the first substrate 20, thereby blocking the gap between the dielectric layer 40 and the first substrate 20, fundamentally avoiding the problem of the magnetic sheet 10 sliding into the gap between the first substrate 20 and the dielectric layer 40 during pressing, and being damaged by uneven force during pressing.

[0064] It should be pointed out that the serial numbers before the above steps do not represent the order of precedence. In steps S2 and S3, the dielectric layer 40 is first pre-fixed to one side of the first substrate 20 to obtain a pre-laminated structure. At this time, the embedded groove 200 has been formed, so the magnetic sheet 10 can be placed in the embedded groove 200 first, and then the pre-laminated structure with the built-in magnetic sheet 10 is continued to be stacked on a second substrate 30 to form a first laminated structure.

[0065] In other embodiments, the pre-laminated structure may be first laminated onto a second substrate 30 to obtain a first laminated structure, and then the magnetic sheet 10 may be placed. In this way, the pre-laminated structure does not need to be moved, and the magnetic sheet 10 located in the embedded groove 200 can be ensured not to move, thereby preventing the magnetic sheet 10 from shifting.

[0066] In a preferred embodiment, the dielectric layer 40 may include multiple epoxy resin prepregs. A prepreg adjacent to the first substrate 20 may be bonded first, and then laminated with other prepregs and the second substrate 30 and pressed together. This operation is more convenient.

[0067] In some embodiments, the second stacked structure is riveted and / or fused before the lamination step to reduce the occurrence of sliding or offset during lamination, thereby improving the alignment between the first substrate 20 and the second substrate 30 .

[0068] In some embodiments, before the lamination step, lamination auxiliary materials, such as steel plates, kraft paper, etc., may be added to the upper and lower sides of the second stacked structure (from top to bottom: second substrate 30, dielectric layer 40, first substrate 20, dielectric layer 40, and second substrate 30) to achieve better lamination quality.

[0069] In some embodiments, the lamination parameters are specifically set as follows: a heating rate controlled at (2.2±0.5)°C / min; eight temperature settings: 70 / 140 / 170 / 225 / 210 / 170 / 90 / 70°C; six vacuum settings: 1000 / ≤30 / ≤30 / 1000 / 1000 / 1000 mbar; and five pressure settings: 60 / 95 / 320 / 180 / 60 N / cm. Under these parameters, the laminated embedded magnetic printed circuit board can be ensured to have tight connections between the layers, to protect the magnetic sheet 10 from damage, and to achieve a high yield.

[0070] In some embodiments, after the lamination step, the embedded magnetic printed circuit board is cold-pressed at 40° C.±5° C. for 70 min±10 min. The lamination time and pressure are controlled, and the cold-pressing time is prolonged to prevent the magnetic sheet 10 from being squeezed and thus breaking.

[0071] In some embodiments, after lamination, at least one of the following post-processing steps can be performed, such as drilling, hole metallization, resin plugging, outer layer circuitry, solder masking, surface treatment, and molding. Furthermore, the laminated embedded magnetic PCB can be used as a daughterboard for lamination of multiple PCB layers. The post-lamination steps are implemented based on the product design and are not limited.

[0072] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0073] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A magnetic embedded printed circuit board, characterized in that: It comprises a magnetic sheet, a first substrate, two second substrates respectively arranged on both sides of the first substrate, and a dielectric layer arranged between the first substrate and the second substrate, wherein the dielectric layer is used to connect the first substrate and the second substrate; The first substrate is provided with an embedding hole matching the shape of the magnetic sheet, the first substrate is stacked on the second substrate, and an embedding groove is formed at the embedding hole, and the magnetic sheet is placed in the embedding groove; The magnetic sheet and the embedding hole are polygonal in shape, and an accommodating groove is provided on the inner side wall of the embedding hole corresponding to the convex corner of the magnetic sheet. The accommodating groove is connected to the embedding groove, and is used to accommodate the convex corner of the magnetic sheet.

2. The embedded magnetic printed circuit board according to claim 1, characterized in that: The size of the embedded groove is greater than or equal to the size of the magnetic sheet.

3. The embedded magnetic printed circuit board according to claim 2, characterized in that: The magnetic sheet and the embedded hole are rectangular in shape, the embedded groove has a width of a1 and a length of b1, the magnetic sheet has a width of a2 and a length of b2, wherein a1, a2, b1 and b2 satisfy the following relationship: a1≥a2; and / or b1≥b2.

4. The embedded magnetic printed circuit board according to claim 1, characterized in that: The cross section of the receiving groove is at least one of circular, elliptical and rectangular.

5. The embedded magnetic printed circuit board according to claim 1, characterized in that: Both sides of the first substrate are not covered with metal foil, and the second substrate is covered with metal foil.

6. The embedded magnetic printed circuit board according to claim 1, characterized in that: Both sides of the first substrate are not covered with metal foil, and at least one side of the second substrate is covered with metal foil.

7. The embedded magnetic printed circuit board according to claim 1, characterized in that: At least one side of the first substrate is covered with metal foil, and the second substrate is metal foil.

8. The embedded magnetic printed circuit board according to claim 1, characterized in that: At least one side of the first substrate is covered with a metal foil, and at least one side of the second substrate is covered with a metal foil.

9. The embedded magnetic printed circuit board according to any one of claims 5 to 8, characterized in that: The material of the first substrate and the dielectric layer includes at least one of epoxy resin, polyimide resin, polyester resin, polyphenylene ether resin, and polytetrafluoroethylene resin.

10. A method for preparing a magnetic embedded printed circuit board, characterized in that: The following steps are involved: Providing a magnetic sheet, a first substrate, a second substrate and a dielectric layer as described in any one of claims 1 to 9; The dielectric layer and the first substrate are sequentially stacked on one of the second substrates to form a first stacked structure, wherein the first stacked structure forms the buried groove at the buried hole; Placing the magnetic sheet in the embedding groove, and making the convex corner of the magnetic sheet located in the receiving groove; The dielectric layer and another second substrate are continuously stacked on the first stacked structure to obtain a second stacked structure, which is then pressed to obtain the embedded magnetic printed circuit board.

11. The preparation method according to claim 10, characterized in that: The step of sequentially stacking the dielectric layer and the first substrate on one of the second substrates to form a first stacked structure includes: Pre-fixing the dielectric layer to one side of the first substrate to obtain a pre-laminated structure; The pre-laminated structure is laminated onto one of the second substrates.

12. The preparation method according to claim 11, characterized in that: The pre-fixation comprises the following steps: The dielectric layer located at the edge of the buried trench is heated.

13. The preparation method according to claim 11, characterized in that: The pre-fixation comprises the following steps: A plurality of bonding points are arranged on the dielectric layer along the edge of the buried groove, and the plurality of bonding points are evenly distributed along the edge of the buried groove. The dielectric layer located at the bonding points is heated to melt the dielectric layer and bond it to the buried groove, thereby sealing the gap between the dielectric layer and the first substrate.

14. The preparation method according to any one of claims 10 to 13, characterized in that: Before the pressing step, the second stacked structure is fixed by riveting and / or fusing.

15. The preparation method according to any one of claims 10 to 13, characterized in that: After the pressing step, the embedded magnetic printed circuit board is cold pressed at a temperature of 40° C.±5° C. for 70 min±10 min.

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