A method for manufacturing a planar transformer and the planar transformer itself.

Abstract

This invention discloses a method for manufacturing a planar transformer, comprising the following steps: manufacturing a first circuit board containing a first circuit and a second circuit board containing a second circuit; stacking a first magnetic component and a second magnetic component using a prepreg, a magnetic sheet, a pressure plate, and copper foil; bonding the first circuit board to the first magnetic component via a third pressure plate to form a third circuit board; setting a third circuit and a first through-hole on the third circuit board to form a fourth circuit board; bonding the second circuit board to the fourth circuit board via a fourth pressure plate to form a fifth circuit board; setting magnetic pillars in the fifth circuit board to form a sixth circuit board; bonding the second magnetic component to the sixth circuit board via a fifth pressure plate to form a seventh circuit board; and setting outer layer circuits and a second through-hole on the seventh circuit board to obtain the planar transformer. This invention can improve the coupling coefficient of the planar transformer in the embedded magnetic PCB and reduce board warping defects in the lamination process.

Description

Technical Field

[0001] This invention belongs to the field of inductive devices, and specifically relates to a method for manufacturing a planar transformer and a planar transformer. Background Technology

[0002] Currently, with the development of switching power supply PCB technology, a solution using embedded magnetic technology to replace traditional surface mount technology for manufacturing planar transformers has emerged. This solution has the advantages of small size and no need for transformer surface mount technology. However, the process of embedding magnetic blocks in the industry is not yet fully mature, and the shape of the embedded magnetic blocks is relatively simple, such as single embedded magnetic sheets or magnetic pillars. Among them, single embedded magnetic sheets are placed on the upper and lower layers of the conductive coil winding. Due to the lack of a magnetic pillar that runs through the coil, the magnetic circuit is in a semi-closed state, the magnetic field between the magnetic sheets is disordered, the coupling coefficient between the primary and secondary coils is low, and the transmission efficiency of the transformer is poor. On the other hand, because metal oxide magnetic blocks (magnetic sheets or magnetic pillars) with a large difference in expansion coefficient from the PCB material are embedded in the circuit board, it is easy to cause serious board warping defects during the manufacturing process due to asymmetrical pressing. Summary of the Invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a method for manufacturing a planar transformer and a planar transformer, which aims to overcome at least one of the defects in the prior art, improve the coupling coefficient of the planar transformer in the embedded magnetic PCB, and reduce board warping defects in the lamination process.

[0004] As a first aspect of the present invention, an embodiment of the planar transformer manufacturing method is provided as follows:

[0005] A method for manufacturing a planar transformer includes the following steps:

[0006] A first circuit board 11 and a second circuit board 12 are fabricated. The first circuit board 11 is a copper-clad board with a first line 1111 on one surface, and the second circuit board 12 is a copper-clad board with a second line 1211 on one surface.

[0007] A first magnetic component 21 and a second magnetic component 22 are fabricated. The first magnetic component 21 includes a first prepreg 211, a first magnetic sheet 212, a first pressure plate 213, and a first copper foil 214. The first magnetic sheet 212 is filled into the through-groove recess of the first prepreg 211. The first pressure plate 213 and the first copper foil 214 are stacked sequentially on one surface of the first prepreg 211 after the first magnetic sheet 212 is filled. The second magnetic component 22 includes a second prepreg 221, a second magnetic sheet 222, a second pressure plate 223, and a second copper foil 224. The second magnetic sheet 222 is filled into the through-groove recess of the second prepreg 221. The second pressure plate 223 and the second copper foil 224 are stacked sequentially on one surface of the second prepreg 221 after the second magnetic sheet 222 is filled.

[0008] A third circuit board 13 is fabricated. The third circuit board 13 is a stacked structure in which the first circuit board 11 is pressed together with the first magnetic component 21 through a third pressure plate 1301, wherein the first circuit 1111 and the first magnetic sheet 212 are respectively located on both sides of the third pressure plate 1301.

[0009] A fourth circuit board 14 is fabricated, wherein the fourth circuit board 14 is based on the third circuit board 13, and a third circuit 1401 is provided on another surface of the first circuit board 11, and a first through hole 1402 is provided between the top and bottom layers of the third circuit board 13.

[0010] A fifth circuit board 15 is fabricated. The fifth circuit board 15 is a stacked structure in which the second circuit board 12 is pressed together with the fourth circuit board 14 through a fourth pressure plate 1501, wherein the second circuit 1211 and the third circuit 1401 are respectively located on both sides of the fourth pressure plate 1501.

[0011] A sixth circuit board 16 is fabricated based on the fifth circuit board 15. A magnetic pillar 1603 is provided therein, and a fourth line 1604 is provided on another surface of the second circuit board 12. The magnetic pillar 1603 is disposed in the fifth circuit board 15 and penetrates the second circuit board 12, the fourth pressure plate 1501, the first circuit board 11, and the third pressure plate 131, so that the first line 1111, the second line 1211, the third line 1401, and the fourth line 1604 can form a concentrated magnetic circuit with the magnetic pillar 1603, the first magnetic sheet 212, and the second magnetic sheet 222.

[0012] A seventh circuit board 17 is fabricated. The seventh circuit board 17 is a stacked structure in which the second magnetic component 22 is pressed together with the sixth circuit board 16 through the fifth pressure plate 1701, wherein the second magnetic sheet 222 and the fourth circuit 1604 are respectively located on both sides of the fifth pressure plate 1701.

[0013] The planar transformer is obtained by fabricating an eighth circuit board 18, wherein the eighth circuit board 18 is based on the seventh circuit board 17 with an outer layer circuit 1801 and a second through hole 1802 is provided between the top and bottom layers of the seventh circuit board 17.

[0014] Furthermore, the fabrication of the first magnetic component 21 and / or the second magnetic component 22 includes the following steps:

[0015] Apply the adhesive film onto the prepreg;

[0016] With the recessed opening of the semi-cured sheet through groove facing upwards, fill the magnetic sheet into the recessed opening of the semi-cured sheet through groove;

[0017] The pressure plate and copper foil are stacked sequentially on one surface of the prepreg after the magnetic sheet is filled, and then pressed together;

[0018] Remove the adhesive film.

[0019] Furthermore, the fabrication of the sixth circuit board 16 includes the following steps:

[0020] A receiving hole 1601 is provided on the fifth circuit board 15, and the receiving hole 1601 passes through the second circuit board 12, the fourth pressure plate 1501, the first circuit board 11 and the third pressure plate 1301.

[0021] Magnetic powder resin 1602 is filled into the receiving hole 1601 in one go, and the volume occupied by the magnetic powder resin 1602 in the receiving hole 1601 is smaller than the volume of the receiving hole 1601.

[0022] The magnetic post 1603 is filled into the receiving hole 1601;

[0023] The fourth line 1604 is disposed on another surface of the second circuit board 12 to obtain the sixth circuit board 16.

[0024] As a second aspect of the present invention, an embodiment of the planar transformer is provided as follows:

[0025] A planar transformer, manufactured by the planar transformer manufacturing method described in any one of the first aspects above.

[0026] Furthermore, the number of the magnetic columns 1603 is 1. The first magnetic sheet 212, the second magnetic sheet 222 and the magnetic column 1603 form a "work" - shaped magnetic core structure. The first circuit 1111, the second circuit 1211, the third circuit 1401 and the fourth circuit 1604 surround the magnetic column 1603.

[0027] Furthermore, the number of the magnetic columns 1603 is 3, one of which is the middle column and two are side columns. The side columns are arranged parallel to the left and right sides of the middle column, such that the first magnetic sheet 212, the second magnetic sheet 222 and the magnetic column 1603 form an inverted "day" - shaped magnetic core structure. The first circuit 1111, the second circuit 1211, the third circuit 1401 and the fourth circuit 1604 surround the middle column and are arranged in the area between the two side columns.

[0028] Furthermore, there is an air gap left between the magnetic column 1603 and the second magnetic sheet 222.

[0029] Term Explanation:

[0030] Circuit: The carrier of the flowing current. The manufacturing method is to use photoresist on the copper - clad laminate to determine the local etching area, then expose and develop, and pickling to remove the photoresist and the excess copper foil to form a coil pattern.

[0031] Prepreg: Also known as "PP sheet", it is one of the main materials in the production of multi - layer boards, mainly composed of resin and reinforcing materials.

[0032] Carrier board: Also called "PP sheet", it is also one of the main materials in the production of multi - layer boards, mainly composed of resin and reinforcing materials.

[0033] Concentrated magnetic circuit: Usually, magnetic flux is generated due to the charging of the coil winding and circulates around the conductive coil. The magnetic permeability of air is 1. Therefore, after the winding coil in the air is conductive, the magnetic flux will disperse around the winding, so the magnetic circuit is not concentrated. When a high - magnetic - permeability magnetic column is added between two magnetic sheets, because the magnetic permeability of the magnetic column is much greater than 1, it provides a high - speed conduction magnetic path, so that the magnetic flux is concentrated in the magnetic column for circulation, which is called a concentrated magnetic circuit.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) A magnetic column is added between the upper and lower magnetic sheets in the buried - magnet planar transformer, so that the magnetic circuit of the planar transformer is closed, the coupling coefficient between the primary - side winding and the secondary - side winding is increased, the eddy - current loss of the coil is reduced, and the transmission efficiency of the PCB buried - magnet planar transformer is improved.

[0036] (2) The circuit board is laminated in three stages, which can effectively reduce board warping defects caused by the introduction of metal magnetic blocks with large differences in expansion coefficients and asymmetrical lamination during the lamination process. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the lamination sequence for embedded magnets on the PCB according to the present invention;

[0038] Figure 2 This is a schematic diagram illustrating the fabrication of the first and second circuit boards in an embodiment of the planar transformer manufacturing method of the present invention.

[0039] Figure 3 This is a schematic diagram of the structure of the first semi-cured sheet and the second semi-cured flat sheet;

[0040] Figure 4 This is a schematic diagram of the lamination of the first semi-cured sheet with the first adhesive film and the lamination of the second semi-cured sheet with the second adhesive film in an embodiment of the planar transformer manufacturing method of the present invention;

[0041] Figure 5 This is a schematic diagram of the first magnetic component and the second magnetic component in an embodiment of the planar transformer manufacturing method of the present invention;

[0042] Figure 6 This is a schematic diagram of the first pressing process for manufacturing the third circuit board in an embodiment of the planar transformer manufacturing method of the present invention;

[0043] Figure 7 This is a schematic diagram illustrating the fabrication of the fourth circuit board in an embodiment of the planar transformer manufacturing method of the present invention;

[0044] Figure 8 This is a schematic diagram of the second lamination process for fabricating the fifth circuit board in an embodiment of the planar transformer manufacturing method of the present invention;

[0045] Figure 9 This is a schematic diagram showing the opening of a receiving hole on the fifth circuit board during the fabrication of the sixth circuit board in an embodiment of the planar transformer manufacturing method of the present invention;

[0046] Figure 10 This is a schematic diagram illustrating the filling of a receiving hole with resin containing magnetic powder and a magnetic column during the fabrication of the sixth circuit board in an embodiment of the planar transformer manufacturing method of the present invention.

[0047] Figure 11 This is a schematic diagram illustrating the setting of a fourth circuit on another surface of the second circuit board during the fabrication of the sixth circuit board in an embodiment of the planar transformer manufacturing method of the present invention.

[0048] Figure 12 This is a schematic diagram of the third lamination process for fabricating the seventh circuit board in an embodiment of the planar transformer manufacturing method of the present invention;

[0049] Figure 13This is a schematic diagram illustrating the fabrication of the eighth circuit board in an embodiment of the planar transformer manufacturing method of the present invention;

[0050] Figure 14 This is a cross-sectional view along the thickness direction of the planar transformer in an embodiment of the present invention, when the "I"-shaped magnetic core structure is adopted.

[0051] Figure 15 This is a cross-sectional view along the thickness direction of the planar transformer in an embodiment of the present invention, when the transformer adopts a side-shaped magnetic core structure.

[0052] Main component description:

[0053] 11. First circuit board; 111. First copper-clad laminate; 1111. First circuit line;

[0054] 12. Second circuit board; 121. Second copper-clad laminate; 1211. Second circuit;

[0055] 13. Third circuit board, 1301. Third pressure plate

[0056] 14. Fourth circuit board, 1401. Third line, 1402. First through hole

[0057] 15. Fifth circuit board; 1501. Fourth pressure plate;

[0058] 16. Sixth circuit board, 1601. Receiving hole, 1602. Magnetic powder-containing resin, 1603. Magnetic pillar, 1604. Fourth circuit;

[0059] 17. Seventh circuit board; 1701. Fifth pressure plate;

[0060] 18. Eighth circuit board; 1801. Fifth circuit; 1802. Second through hole;

[0061] 21. First magnetic component; 211. First prepreg; 212. First magnetic sheet; 213. First pressure plate; 214. First copper foil;

[0062] 22. Second magnetic component; 221. Second prepreg; 222. Second magnetic sheet; 223. Second pressure plate; 224. Second copper foil;

[0063] 301. First adhesive film; 302. Second adhesive film. Detailed Implementation

[0064] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0065] Unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0066] In this invention, unless otherwise stated, directional terms such as "up," "down," "left," and "right" are generally used in relation to the directions shown in the accompanying drawings, or to the vertical, perpendicular, or gravitational orientation of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0067] The terms "first," "second," "step S1," "step S2," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate for the purposes of describing embodiments of this application herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or structures is not necessarily limited to those explicitly listed, but may include other steps or structures not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0068] It should be understood that in the specification, claims, and drawings, when a step is described as continuing into another step, the step may directly continue into that other step, or may continue into that other step through a third step; when a plate / component is described as being "stacked" onto another plate / component, the plate / component may be "directly stacked" onto that other plate / component, or may be "stacked" onto that other plate / component through a third plate / component.

[0069] Figure 1 This is a schematic diagram of the PCB embedded magnet lamination sequence of the present invention, including the first lamination Y1, the second lamination Y2, and the third lamination Y3. The following is in conjunction with... Figures 2 to 13 The embodiments of the planar transformer manufacturing method of the present invention will be described in detail below. The planar transformer manufacturing method of the present invention includes the following steps:

[0070] Step S1: Fabricate a first circuit board 11 and a second circuit board 12. The first circuit board 11 is a copper-clad board with a first line 1111 on one surface, and the second circuit board 12 is a copper-clad board with a second line 1211 on one surface.

[0071] Please refer to Figure 2A first copper-clad laminate 111 and a second copper-clad laminate 121 are provided. A first circuit 1111 is fabricated on the first copper-clad laminate 111 as a primary winding circuit of a planar transformer to obtain a first circuit board 11. A second circuit 1211 is fabricated on the second copper-clad laminate 121 as a secondary winding circuit of a planar transformer to obtain a second circuit board 12.

[0072] Step S2: Fabricate a first magnetic component 21 and a second magnetic component 22. The first magnetic component 21 includes a first prepreg 211, a first magnetic sheet 212, a first pressure plate 213, and a first copper foil 214. The first magnetic sheet 212 is filled in the through-groove recess of the first prepreg 211. The first pressure plate 213 and the first copper foil 214 are stacked sequentially on one surface of the first prepreg 211 after the first magnetic sheet 212 is filled. The second magnetic component 22 includes a second prepreg 221, a second magnetic sheet 222, a second pressure plate 223, and a second copper foil 224. The second magnetic sheet 222 is filled in the through-groove recess of the second prepreg 221. The second pressure plate 223 and the second copper foil 224 are stacked sequentially on one surface of the second prepreg 221 after the second magnetic sheet 222 is filled.

[0073] Please refer to Figures 3 to 5 The process involves preparing a first semi-cured sheet 211 and a second semi-cured sheet 221, both with through-holes; a first adhesive film 301 and a second adhesive film 302, both being high-temperature adhesive films with adhesive properties; a first copper foil 214 and a second copper foil 224; a first pressure plate 213 and a second pressure plate 223; a first magnetic sheet 212 and a second magnetic sheet 222. First, the first adhesive film 301 is applied to the first semi-cured sheet 211. Then, with the through-hole recess of the first semi-cured sheet 211 facing upwards, the first magnetic sheet 212 is inserted into the through-hole recess of the first semi-cured sheet 211. Next, the first pressure plate 213 and the first copper foil 214 are stacked sequentially, and a first magnetic component 21 is formed by pressing. Finally, the first adhesive film 301 is removed. The second magnetic component 22 is then manufactured using the same method.

[0074] Please refer to Figure 6 The system provides a first circuit board 11, a third pressure plate 1301, and a first magnetic component 21. The first line 1111 in the first circuit board 11 is placed facing upwards, and the first magnetic sheet 212 in the first magnetic component 21 is placed facing downwards. Then, the third pressure plate 1301 and the first magnetic component 21 are stacked on the first circuit board 11 in sequence. The third circuit board 13 is formed by the first pressing Y1.

[0075] Step S4: Fabricate the fourth circuit board 14. The fourth circuit board 14 is based on the third circuit board 13, with a third line 1401 provided on another surface of the first circuit board 11 and a first through hole 1402 provided between the top and bottom layers of the third circuit board 13. The third line 1401 is the number of turns of the second half of the primary winding of the planar transformer, and the first through hole 1402 is used for the electrical connection between the primary winding and the top pad of the transformer.

[0076] Please refer to Figure 7 , for in Figure 6 Based on the third circuit board 13, the third circuit 1401 is fabricated, and the cross-sectional view after the first through hole 1402 is set is completed.

[0077] Step S5: Fabricate the fifth circuit board 15. The fifth circuit board 15 is a stacked structure in which the second circuit board 12 is pressed together with the fourth circuit board 14 through the fourth pressure plate 1501, wherein the second circuit 1211 and the third circuit 1401 are located on both sides of the fourth pressure plate 1501 respectively.

[0078] Please refer to Figure 8 The system provides a second circuit board 12, a fourth pressure plate 1501 and a fourth circuit board 14. The second line 1211 on the second circuit board is placed facing upwards, and the third line 1401 on the fourth circuit board 14 is placed facing downwards. Then, the fourth pressure plate 1501 and the fourth circuit board 14 are stacked on the second circuit board 12 in sequence, and the fifth circuit board 15 is formed by the second pressing Y2.

[0079] Step S6: Fabricate a sixth circuit board 16. The sixth circuit board 16 is based on the fifth circuit board 15. A magnetic post 1603 is provided in it, and a fourth line 1604 is provided on another surface of the second circuit board 12. The fourth line 1604 is used for the second half of the turns of the secondary coil winding. The magnetic post 1603 is set in the fifth circuit board 15 and passes through the second circuit board 12, the fourth pressure plate 1501, the first circuit board 11 and the third pressure plate 131, so that the first line 1111, the second line 1211, the third line 1401 and the fourth line 1604 can form a concentrated magnetic circuit with the magnetic post 1603, the first magnetic sheet 212 and the second magnetic sheet 222.

[0080] Please refer to Figure 9 A receiving hole 1601 is provided on the fifth circuit board 15, and the receiving hole 1601 passes through the second circuit board 12, the fourth pressure plate 1501, the first circuit board 11 and the third pressure plate 1301.

[0081] Please refer to Figure 10Magnetic powder resin 1602 is filled into the receiving hole 1601, and the volume occupied by magnetic powder resin 1602 in the receiving hole 1601 is smaller than the volume of the receiving hole 1601; then magnetic pillar 1603 is filled into the receiving hole 1601.

[0082] Please refer to Figure 11 A fourth line 1604 is provided on another surface of the second circuit board 12 to obtain a sixth circuit board 16.

[0083] Step S7: Fabricate the seventh circuit board 17. The seventh circuit board 17 is a stacked structure in which the second magnetic component 22 is pressed together with the sixth circuit board 16 through the fifth pressure plate 1701, wherein the second magnetic sheet 222 and the fourth circuit 1604 are located on both sides of the fifth pressure plate 1701 respectively.

[0084] Please refer to Figure 12 The system provides a second magnetic component 22, a fifth pressure plate 1701 and a sixth circuit board 16. The second magnetic sheet 222 in the second magnetic component 22 is placed facing upwards, and the fourth line 1604 in the sixth circuit board 16 is placed facing downwards. The fifth pressure plate 1701 and the sixth circuit board 16 are stacked on the second magnetic component 22 in sequence, and a seventh circuit board 17 is formed by a third pressing Y3.

[0085] Step S8: Fabricate an eighth circuit board 18 to obtain the planar transformer of the present invention. The eighth circuit board 18 is formed by setting an outer layer circuit 1801 on the basis of the seventh circuit board 17, and setting a second through hole 1802 between the top and bottom layers of the seventh circuit board 17.

[0086] Please refer to Figure 13 The outer layer circuit 1801 is used for electrical connection with external circuits and is generally set as a pad. It can also be used for other circuit traces of devices used in planar transformers (such as switching power supplies). The second through hole 1802 is used for electrical connection between the secondary coil winding and the external circuit or the top pad. Then, operations such as solder resist (ink) and electroplating (nickel / nickel target gold) can be performed to facilitate soldering or improve reliability.

[0087] This invention also provides a planar transformer manufactured using the above-described planar transformer manufacturing method. The structure of the resulting transformer is shown in the reference document. Figure 13 .

[0088] Figure 13 The number of magnetic pillars is 1, thus the magnetic core is an I-shaped magnetic core consisting of a first magnetic sheet 212, a second magnetic sheet 222, and a magnetic pillar 1603. The first line 1111, the second line 1211, the third line 1401, and the fourth line 1604 surround the magnetic pillar 1603. For a cross-sectional view along the thickness direction of a planar transformer using this magnetic core structure, please refer to... Figure 14 .

[0089] By setting the number and position of the magnetic posts 1603, other magnetic core structures can also be formed in the planar transformer according to embodiments of the present invention. For example, the number of magnetic posts 1603 is 3, one of which is a middle post and two are side posts. The side posts are arranged in parallel on the left and right sides of the middle post, so that the first magnetic sheet 212, the second magnetic sheet 222 and the magnetic posts 1603 form an inverted "day" - shaped magnetic core structure. The first circuit 1111, the second circuit 1211, the third circuit 1401 and the fourth circuit 1604 are arranged around the middle post in the area between the two side posts. For the cross - sectional view of the planar transformer with this magnetic core structure along the thickness direction, please refer to Figure 15 .

[0090] Furthermore, an air gap is left between the magnetic post 1603 and the second magnetic sheet 222, which can improve the anti - saturation ability of the planar transformer, enabling the transformer to withstand a larger working current and reducing the influence of the mechanical stress caused by PCB pressing on the magnetic sheet, which may lead to a decrease in inductance.

[0091] The above are only the preferred and feasible embodiments of the present invention, and the protection scope of the present invention is not limited thereby. Therefore, equivalent technical changes made by using the content of the specification and drawings of the present invention are all included in the protection scope of the present invention.

Claims

1. A method for manufacturing a planar transformer, characterized in that, Includes the following steps: Fabricate a first circuit board (11) and a second circuit board (12), wherein the first circuit board (11) is a copper-clad board with a first line (1111) on one surface, and the second circuit board (12) is a copper-clad board with a second line (1211) on one surface. A first magnetic component (21) and a second magnetic component (22) are fabricated. The first magnetic component (21) includes a first prepreg (211), a first magnetic sheet (212), a first pressure plate (213), and a first copper foil (214). The first magnetic sheet (212) is filled in the through-groove recess of the first prepreg (211). The first pressure plate (213) and the first copper foil (214) are stacked sequentially on one surface of the first prepreg (211) after the first magnetic sheet (212) is filled. The second magnetic component (22) includes a second prepreg (221), a second magnetic sheet (222), a second pressure plate (223), and a second copper foil (224). The second magnetic sheet (222) is filled in the through-groove recess of the second prepreg (221). The second pressure plate (223) and the second copper foil (224) are stacked sequentially on one surface of the second prepreg (221) after the second magnetic sheet (222) is filled. Fabricate a third circuit board (13), wherein the third circuit board (13) is a stacked structure in which the first circuit board (11) is pressed together with the first magnetic component (21) through a third pressure plate (1301), wherein the first circuit (1111) and the first magnetic sheet (212) are located on both sides of the third pressure plate (1301); A fourth circuit board (14) is fabricated, wherein the fourth circuit board (14) is based on the third circuit board (13), and a third circuit (1401) is provided on another surface of the first circuit board (11), and a first through hole (1402) is provided between the top and bottom layers of the third circuit board (13). A fifth circuit board (15) is fabricated. The fifth circuit board (15) is a stacked structure in which the second circuit board (12) is pressed together with the fourth circuit board (14) through the fourth pressure plate (1501). The second circuit (1211) and the third circuit (1401) are located on both sides of the fourth pressure plate (1501). A sixth circuit board (16) is fabricated based on the fifth circuit board (15), in which a magnetic pillar (1603) is provided, and a fourth line (1604) is provided on another surface of the second circuit board (12). The magnetic pillar (1603) is located in the fifth circuit board (15) and penetrates the second circuit board (12), the fourth pressure plate (1501), the first circuit board (11) and the third pressure plate (131), so that the first line (1111), the second line (1211), the third line (1401) and the fourth line (1604) can form a concentrated magnetic circuit with the magnetic pillar (1603), the first magnetic sheet (212) and the second magnetic sheet (222); A seventh circuit board (17) is fabricated. The seventh circuit board (17) is a stacked structure in which the second magnetic component (22) is pressed together with the sixth circuit board (16) through the fifth pressure plate (1701). The second magnetic sheet (222) and the fourth circuit (1604) are located on both sides of the fifth pressure plate (1701). The planar transformer is obtained by fabricating an eighth circuit board (18), wherein the eighth circuit board (18) is based on the seventh circuit board (17) with an outer layer circuit (1801) and a second through hole (1802) is provided between the top and bottom layers of the seventh circuit board (17).

2. The method for manufacturing a planar transformer according to claim 1, characterized in that, The fabrication of the first magnetic component (21) and / or the second magnetic component (22) includes the following steps: Apply the adhesive film onto the prepreg; With the recessed opening of the semi-cured sheet through groove facing upwards, fill the magnetic sheet into the recessed opening of the semi-cured sheet through groove; The pressure plate and copper foil are stacked sequentially on one surface of the prepreg after the magnetic sheet is filled, and then pressed together; Remove the adhesive film.

3. The method for manufacturing a planar transformer according to claim 1, characterized in that, The fabrication of the sixth circuit board (16) includes the following steps: A receiving hole (1601) is provided on the fifth circuit board (15), and the receiving hole (1601) passes through the second circuit board (12), the fourth pressure plate (1501), the first circuit board (11) and the third pressure plate (1301); The receiving hole (1601) is filled with magnetic powder resin (1602) in one go, and the volume occupied by the magnetic powder resin (1602) in the receiving hole (1601) is smaller than the volume of the receiving hole (1601). The magnetic column (1603) is filled into the receiving hole (1601); The fourth line (1604) is disposed on another surface of the second circuit board (12) to obtain the sixth circuit board (16).

4. A planar transformer, characterized in that: It is manufactured by the planar transformer manufacturing method according to any one of claims 1 to 3.

5. The planar transformer according to claim 4, characterized in that: The number of the magnetic columns (1603) is 1. The first magnetic sheet (212), the second magnetic sheet (222) and the magnetic columns (1603) form a "work" - shaped magnetic core structure. The first circuit (1111), the second circuit (1211), the third circuit (1401) and the fourth circuit (1604) surround the magnetic columns (1603).

6. The planar transformer according to claim 4, characterized in that: The number of the magnetic columns (1603) is 3, one of which is the middle column and two are side columns. The side columns are arranged parallel to the left and right sides of the middle column, so that the first magnetic sheet (212), the second magnetic sheet (222) and the magnetic columns (1603) form an inverted "day" - shaped magnetic core structure. The first circuit (1111), the second circuit (1211), the third circuit (1401) and the fourth circuit (1604) surround the middle column and are arranged in the area between the two side columns.

7. A planar transformer according to claim 5, wherein: An air gap is left between the magnetic column (1603) and the second magnetic sheet (222).

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