Transformer and its manufacturing method

Abstract

This invention discloses a transformer, comprising a primary winding and a secondary winding spaced apart from each other, and an insulating substrate covering the primary and secondary windings. The transformer also includes a first opening and a plurality of second openings on the insulating substrate, with the primary and secondary windings surrounding the outside of the first opening and the plurality of second openings surrounding the primary and secondary windings. Furthermore, it includes a center post located in the first opening and side posts located in the second openings. The center post and the side posts are made of a non-metallic magnetic material and a molding compound. Compared with conventional technology, the transformer of this invention can better concentrate and guide the magnetic field, greatly improving the magnetic induction intensity, thereby improving the efficiency and stability of the transformer.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and more particularly to a method for manufacturing a transformer and the same. Prior Technology

[0002] Currently, most Bobbin transformers on the market use upper and lower cover plates as the transformer core. Since conventional transformers only have upper and lower cover plates, the magnetic induction intensity of the transformer core is low. To ensure the performance of the transformer, it is necessary to increase the thickness or area of ​​the upper and lower cover plates, which undoubtedly increases the size of the transformer. This is unacceptable for manufacturing small-sized transformers. How to reduce the size of the transformer while ensuring its performance is an urgent technical problem to be solved in this field. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a transformer and its manufacturing method, which can effectively solve the technical problem of reducing the size of the transformer while ensuring its performance in the prior art. Compared with the prior art, the addition of the center column and side column forms a closed magnetic circuit in the transformer core, which can greatly improve the magnetic induction intensity of the transformer. In addition, the transformer core is made of insulating magnetic material, which can ensure the withstand voltage of the transformer. In other words, the solution of this invention can reduce the size of the transformer while ensuring its performance.

[0004] In a first embodiment of the present invention, a transformer is provided, including a primary winding and a secondary winding spaced apart from each other, and an insulating substrate covering the primary winding and the secondary winding. The transformer also includes a first opening and a plurality of second openings on the insulating substrate, with the primary winding and the secondary winding surrounding the outside of the first opening, and the plurality of second openings surrounding the primary winding and the secondary winding. Furthermore, the transformer includes a center post located in the first opening and side posts located in the second openings. The center post and the side posts are made of non-metallic magnetic material and encapsulating material.

[0005] Preferably, the non-metallic magnetic material is an insulating magnetic material.

[0006] Preferably, the insulating magnetic material is a nickel-zinc ferrite material.

[0007] Preferably, it further includes a first cover plate disposed on the first surface of the insulating substrate, wherein the first cover plate comprises an insulating magnetic material.

[0008] Preferably, the device further includes a second cover plate disposed on the second surface of the insulating substrate, wherein the second cover plate comprises an insulating magnetic material; the first surface and the second surface are disposed opposite to each other.

[0009] Preferably, the insulating substrate is made of one or more of glass fiber, epoxy resin, and polyimide.

[0010] Preferably, the molding compound is an epoxy resin material.

[0011] Preferably, it also includes an external pin, which is electrically connected to the output of the winding.

[0012] Preferably, the organic material is plastic.

[0013] Preferably, the first cover plate and the second cover plate are made by hot pressing powdered nickel-zinc ferrite.

[0014] Preferably, the first opening and the plurality of second openings penetrate the insulating substrate.

[0015] Preferably, the first opening and the plurality of second openings are blind vias on the insulating substrate.

[0016] In the first embodiment of the present invention, a method for manufacturing a transformer is provided, comprising: providing an insulating substrate; forming a primary winding and a secondary winding spaced apart within the insulating substrate, and covering the primary winding and the secondary winding with the insulating substrate; forming a first opening and a plurality of second openings on the insulating substrate, with the primary winding and the secondary winding surrounding the outside of the first opening, and the plurality of second openings surrounding the primary winding and the secondary winding; forming a center post within the first opening, and forming side posts within the plurality of second openings; wherein the center post and the side posts comprise non-metallic magnetic materials and encapsulating materials.

[0017] Preferably, the non-metallic magnetic material is an insulating magnetic material.

[0018] Preferably, the insulating magnetic material is a nickel-zinc ferrite material.

[0019] Preferably, the method further includes forming a first cover plate on the first surface of the insulating substrate, wherein the first cover plate comprises an insulating magnetic material.

[0020] Preferably, the method further includes forming a second cover plate on the second surface of the insulating substrate, wherein the second cover plate comprises an insulating magnetic material; the first surface and the second surface are disposed opposite to each other.

[0021] Preferably, the insulating substrate is made of one or more of glass fiber, epoxy resin, and polyimide.

[0022] Preferably, the molding compound is an epoxy resin material.

[0023] Preferably, it also includes forming an external pin, which is electrically connected to the output of the primary winding and the secondary winding.

[0024] Preferably, the first opening and the plurality of second openings penetrate the insulating substrate.

[0025] Preferably, the first opening and the plurality of second openings are blind vias on the insulating substrate.

[0026] Compared with conventional technology, the technical solution of this invention adds a central column and side columns. In this invention, the central column, side columns, and cover plate form a closed magnetic circuit. Compared with conventional transformers without a central column or side columns, this better concentrates and guides the magnetic field, greatly increasing the magnetic induction intensity, thereby improving the transformer's efficiency and stability. Furthermore, the central column and side columns are made of insulating magnetic material, which increases the magnetic induction intensity without affecting the transformer's withstand voltage. In other words, while ensuring the transformer's withstand voltage, the magnetic induction intensity is increased, thus significantly reducing the transformer's size. Thirdly, the technical solution of this invention involves batch manufacturing, followed by cutting into individual transformers. During the manufacturing process, the windings of multiple transformers can be formed simultaneously, saving process steps. Therefore, the technical solution of this invention can shorten the transformer manufacturing time. Simple Explanation of the Diagram

[0027] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0028] [Figures 1a-1e] are structural diagrams corresponding to some steps of the transformer manufacturing method according to an embodiment of the present invention;

[0029] [Figure 2a] is a structural diagram of a transformer according to one embodiment of the present invention;

[0030] [Figure 2b] is a cross-sectional view of the transformer in Figure 2a;

[0031] [Figure 3] is a structural diagram of a transformer according to another embodiment of the present invention;

[0032] [Figure 4] is a structural diagram of a transformer according to another embodiment of the present invention. Implementation

[0033] The present invention is described below based on embodiments, but the invention is not limited to these embodiments. In the following detailed description of the invention, certain specific details are described in detail. The invention will be fully understood by those skilled in the art even without these details. To avoid obscuring the essence of the invention, conventional methods, processes, procedures, elements, and circuits are not described in detail.

[0034] Furthermore, those skilled in the art should understand that the accompanying drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.

[0035] Furthermore, it should be understood that in the following description, "circuit" refers to a conductive circuit consisting of at least one element or sub-circuit connected by electrical or electromagnetic connections. When an element or circuit is said to be "connected" to another element or "connected" between two nodes, it can be directly coupled or connected to another element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected" to another element, it means that there are no intermediate elements between them.

[0036] Unless the context explicitly requires it, words such as "including," "etc." throughout the application should be interpreted as having the meaning of "including but not limited to," rather than "exclusive" or "exhaustive."

[0037] In the description of this invention, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0038] This invention provides a method for manufacturing a transformer. Figures 1a-1e are structural diagrams corresponding to some steps of the transformer manufacturing method according to an embodiment of this invention. As shown in Figure 1a, an insulating substrate 1 is provided, and windings 2 are formed within the insulating substrate 1. The windings 2 include primary windings and secondary windings spaced apart, and the insulating substrate 1 covers the primary windings and secondary windings. In this embodiment, four sets of primary and secondary windings are used horizontally and four sets of primary and secondary windings are used vertically as an example. In other embodiments, the number of primary and secondary windings is not limited; it can be four sets horizontally and five sets vertically, or five sets horizontally and five sets vertically, etc., and can be set according to actual conditions. In this embodiment, the primary and secondary windings are formed by the RDL (Reduce Layer) process. In this embodiment, since the 16 sets of windings 2 in the insulating substrate are formed simultaneously, it is not necessary to manufacture the 16 sets of windings 2 one by one sequentially, which can greatly shorten the transformer manufacturing time.

[0039] Multiple openings are formed on the insulating substrate 1, including one first opening 112 and multiple second openings 113 corresponding to a transformer. The primary winding and the secondary winding are arranged around the outside of the first opening, and the multiple second openings are arranged around the perimeter of the primary winding and the secondary winding. The number of second openings 113 can be two, with two second openings 113 respectively located on both sides of the primary winding and the secondary winding; or the number of second openings 113 can be four, with four second openings 113 respectively located on the four sides of the primary winding and the secondary winding; or the second openings... The number of second openings 113 can be other than the number shown in Figure 1a. The number of second openings 113 is not limited and can be set according to actual conditions. For example, in this embodiment, there are four second openings 113, which are respectively placed on the four sides of the primary winding and the secondary winding. In this embodiment, the shapes of the first opening 112 and the second opening 113 are not limited. The shapes of the first opening 112 and the second opening 113 can be designed according to actual needs. The shape of the first opening 112 can be circular as shown in Figure 1a, and the shape of the second opening 113 can be rectangular as shown in Figure 1a. The material of the insulating substrate includes one or more of glass fiber, epoxy resin, and polyimide.

[0040] A central pillar 41 is formed within the first opening 112, and side pillars 421 are formed within the plurality of second openings 113; wherein, the central pillar 41 and the side pillars 421 comprise non-metallic magnetic materials and encapsulating materials.

[0041] As an example, as shown in Figure 1b, a magnetic material containing non-metallic materials and a molding compound is placed inside the first opening 112 and the second opening 113, serving as the central pillar 41 and the side pillar 421 of the transformer's magnetic core 4. In this embodiment, the central pillar 41 and the side pillar 421 are jointly made of the molding compound and the insulating magnetic material. Specifically, in this embodiment, a mixture of powdered molding compound and powdered insulating magnetic material is placed inside the first opening 112 and the second opening 113. Then, a hot-pressing process is used to form the central pillar 41 and the side pillar 421 from the powdered molding compound and the powdered insulating magnetic material. Further, the powdered molding compound includes one or more of epoxy resin, PVC material, PE material, and PP material, and may also be other molding compounds, which are not limited here. The powdered insulating magnetic material can be powdered nickel-zinc ferrite material, or other insulating magnetic materials, which are not limited here. In actual production, the nickel-zinc ferrite can be changed to other insulating magnetic materials as needed.

[0042] In other embodiments, the transformer further includes a first cover plate 3 formed on the first surface of the insulating substrate 1, wherein the first cover plate 3 comprises an insulating magnetic material.

[0043] As shown in Figure 1c, a first cover plate 3 is formed on the first surface of the insulating substrate 1. In this embodiment, the first cover plate 3 is made of an insulating magnetic material. Specifically, the insulating magnetic material can be nickel-zinc ferrite or other insulating magnetic materials, which are not limited here. In other embodiments, the method of forming the first cover plate 3 can be: hot pressing with nickel-zinc ferrite powder core material. In other embodiments, the method of forming the first cover plate 3 can also be: covering the outside of the insulating plate with a material containing nickel-zinc ferrite. The insulating plate can be made of epoxy material or other insulating materials.

[0044] In this embodiment, the central column 41, the side column 421, and the first cover plate 3 form a closed magnetic circuit. This closed magnetic circuit significantly increases the transformer's magnetic flux density, thereby increasing its power density and greatly reducing its size. Furthermore, the central column 41 and the side column 421 are made of insulating magnetic material, which increases the transformer's magnetic flux density without affecting its withstand voltage. In other words, while maintaining the transformer's withstand voltage, the magnetic flux density is increased, thus significantly reducing the transformer's size.

[0045] As shown in Figure 1d, the multiple transformers in the above steps are divided into a plurality of transformers. The specific division method is not limited here. After division, individual transformers are formed. Each transformer has two leads of the primary winding and two leads of the secondary winding exposed on its sidewall or bottom. In Figure 1d, only two leads are shown; the other two leads are located opposite leads 51 and 52. In other embodiments, the winding leads can be located at the bottom of the transformer, which will not be elaborated further here.

[0046] The technical solution of this invention involves mass-producing transformers and then dividing them into individual transformers. During the manufacturing process, the windings of multiple transformers can be formed simultaneously, saving process steps. Therefore, the technical solution of this invention can shorten the manufacturing time of transformers.

[0047] In other embodiments, as shown in FIG1e, the method further includes forming external pins 6 at the edges of the segmented transformer; wherein, the external pins 6 are electrically connected to the leads of the winding 2. Two external pins 6 are electrically connected to two leads of the primary winding of the transformer, and the other two external pins 6 are electrically connected to two leads of the secondary winding of the transformer. The transformer windings can exit from the bottom or the side; there is no restriction on the exit position of the transformer windings.

[0048] In other embodiments, a second cover plate 7 is formed on the second surface of the insulating substrate 1, wherein the second cover plate 7 comprises an insulating magnetic material; the first surface and the second surface are disposed opposite each other. Specifically, the insulating magnetic material can be nickel-zinc ferrite or other insulating magnetic materials, which are not limited here. In other embodiments, the method of forming the second cover plate 7 can be: hot pressing with nickel-zinc ferrite powder core material. In other embodiments, the method of forming the second cover plate 7 can also be: covering the outside of the insulating plate with a material containing nickel-zinc ferrite, the insulating plate can be made of epoxy material or other insulating materials. That is to say, the second cover plate 7 is placed on the bottom of the substrate 1. In this embodiment, the central column 41, the side column 421, the first cover plate 3 and the second cover plate 7 form a closed magnetic circuit. Since the closed magnetic circuit greatly increases the magnetic induction intensity of the transformer, the power density is improved and the volume of the transformer is greatly reduced.

[0049] In other embodiments, the second cover plate 7 is the same as the first cover plate 3; the sameness here means that the shape and size of the second cover plate 7 are the same as those of the first cover plate 3, and the material is also the same as that of the first cover plate 3. Therefore, the first cover plate 3 and the second cover plate 7 can be mass-produced without changing the size. During the assembly of the transformer, there is no situation of reversed or incorrect installation, which can greatly save the production and manufacturing time of the transformer.

[0050] In other embodiments, the first opening 112 and the plurality of second openings 113 penetrate the insulating substrate. That is, the central post 41 and the side post 421 formed in the first opening 112 and the plurality of second openings 113 can contact the first cover plate 3 and the second cover plate 7, respectively. In other words, the central post 41, the side post 421, and the first cover plate 3 and the second cover plate 7 form a closed magnetic circuit. Since the closed magnetic circuit greatly increases the magnetic induction intensity of the transformer, it improves the power density and greatly reduces the size of the transformer.

[0051] In other embodiments, the first opening 112 and the plurality of second openings 113 are blind vias on the insulating substrate. That is, the central post 41 and the side post 421 formed in the first opening 112 and the plurality of second openings 113 can contact one of the first cover plate 3 or the second cover plate 7. In other words, the central post 41, the side post 421, and the first cover plate 3 or the second cover plate 7 form a closed magnetic circuit. Compared with the conventional transformers that do not have a central post and only have the first cover plate 3 or the second cover plate 7, the closed magnetic circuit greatly increases the magnetic induction intensity of the transformer, improves the power density, and greatly reduces the size of the transformer.

[0052] In the second aspect, the present invention also provides a transformer. Specifically, Figure 2a shows a structural diagram of a transformer according to one embodiment of the present invention, and Figure 2b is a cross-sectional view of the transformer in Figure 2a. As shown in Figures 2a and 2b, the transformer of the present invention is manufactured using the manufacturing method of the transformer in the first aspect.

[0053] As shown in Figure 2a, for ease of illustration, the first cover plate 3 and the magnetic core are hidden in this figure. Only the winding 2, winding outlet 51, winding outlet 52, insulating substrate 1, and external pin 6 are shown. Specifically, the transformer includes: a primary winding and a secondary winding arranged at intervals, and an insulating substrate 1 covering the primary winding and the secondary winding. It also includes a first opening and a plurality of second openings located on the insulating substrate 1. The primary winding and the secondary winding are arranged around the outside of the first opening, and the plurality of second openings are arranged around the primary winding and the secondary winding. It also includes a central post located in the first opening and a side post located in the second opening. The central post and the side post are made of non-metallic magnetic material and encapsulation material.

[0054] In other embodiments, as shown in Figures 2a and 2b, the transformer includes a winding 2 disposed within an insulating substrate 1. The winding 2 includes a primary winding and a secondary winding spaced apart from each other, and also includes a central column of a magnetic core disposed within the winding 2 and side columns of the magnetic core disposed around the winding 2. As shown in Figure 2b, for ease of illustration, the magnetic core portion is not shown in this figure. The transformer also includes a first cover plate 3 covering a first surface of the insulating substrate 1 and a second cover plate 7 covering a second surface, and external leads 6 disposed around the transformer, wherein the external leads are electrically connected to the leads of the primary winding and the secondary winding, respectively. In this embodiment, only the primary winding 21, the secondary winding 22, the first cover plate 3, the substrate 1, the external leads 6, and the second cover plate 7 are shown. In this embodiment, the winding is manufactured using an RDL electroplating process and is made of copper. In other embodiments, the winding can also be made of gold, silver, or other metals; the material of the winding is not limited here. The insulating substrate 1 is made of one or more of glass fiber, epoxy resin, and polyimide; the central pillar and side pillars are made of a molding compound and an insulating magnetic material. In this embodiment, specifically, a mixture of powdered molding compound and powdered insulating magnetic material can be placed in the first opening 112 and the second opening 113, and then a hot-pressing process can be used to form the central pillar and side pillars. In other embodiments, other processes can be used to mix organic materials and insulating magnetic materials to form the central pillar and side pillars, which is not limited here. The first cover plate 3 is made of an insulating magnetic material; the insulating magnetic material can be nickel-zinc ferrite or other insulating magnetic materials, which is not limited here.

[0055] In this embodiment, the central column, the side column, the first cover plate 3, and the second cover plate 7 form a closed magnetic circuit. The closed magnetic circuit greatly increases the magnetic induction intensity of the transformer, improves the power density of the transformer, and greatly reduces the size of the transformer.

[0056] Figure 3 shows a structural diagram of a transformer according to another embodiment of the present invention. As shown in Figure 3, in this embodiment, the side posts can be four side posts as shown in Figure 1b, surrounding the winding 2. In other embodiments, the number of side posts can be two, respectively disposed on both sides of the transformer winding 2. In other embodiments, the first opening and the plurality of second openings are blind holes on the insulating substrate. The depth of the blind hole is greater than the height of the winding in the depth direction of the blind hole. That is, the central post and side posts formed in the first opening and the plurality of second openings can also extend to the bottom of the insulating substrate 1. In other words, the central post and side posts extend to the bottom of the insulating substrate 1 and form an integral magnetic component with the first cover plate 3. This can improve the magnetic induction intensity of the transformer. The transformer also includes external pins 6, which are disposed on the side surface and bottom surface of the transformer. The external pins 6 are electrically connected to the leads of the primary winding and the secondary winding of the transformer, respectively. In this embodiment, the coils of the primary winding and the secondary winding are stacked coils. In other embodiments, the coils of the primary winding and the secondary winding of the transformer can also be other types of coils. There is no limitation on the form of the coils here.

[0057] Figure 4 shows a structural diagram of a transformer according to another embodiment of the present invention. As shown in Figure 4, in this embodiment, the first opening and the second opening penetrate the insulating substrate. That is, the central column and the side column formed by the first opening and the second opening can be directly connected to the first cover plate 3 and the second cover plate 7. The central column, the side column, and the first cover plate 3 and the second cover plate 7 form a closed magnetic circuit. Since the closed magnetic circuit greatly increases the magnetic induction intensity of the transformer, improves the power density, and greatly reduces the volume of the transformer.

[0058] Compared with conventional technology, the addition of a central column and side columns, along with the cover plate, forms a closed magnetic circuit. Compared with conventional transformers without a central column or side columns, this invention can better concentrate and guide the magnetic field, greatly increasing the magnetic induction intensity, thereby improving the efficiency and stability of the transformer. In addition, the central column and side columns are made of insulating magnetic materials, which can increase the magnetic induction intensity without affecting the transformer's withstand voltage. That is to say, while ensuring the transformer's withstand voltage, the magnetic induction intensity of the transformer is increased, thereby greatly reducing the size of the transformer.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principle of the present invention should be within the scope of protection of the present invention.

[0060] 1: Insulating substrate 2: Winding 112: First opening 113: Second opening 41: Central Pillar 421: Side Post 3: First cover plate 51: Emerging 52: Emerging 6: External pins 7: Second cover plate 21: Primary winding 22: Secondary winding

Claims

1. A transformer, characterized in that it comprises a primary winding and a secondary winding spaced apart from each other, and an insulating substrate covering the primary winding and the secondary winding, further comprising a first opening and a plurality of second openings located on the insulating substrate, the primary winding and the secondary winding surrounding the outside of the first opening, and the plurality of second openings surrounding the primary winding and the secondary winding; and further comprising a center post located in the first opening, and side posts located in the second openings; wherein, The central column and the side columns comprise non-metallic magnetic materials and encapsulating materials.

2. The transformer according to claim 1, wherein, The non-metallic magnetic material is an insulating magnetic material.

3. The transformer according to claim 2, wherein, The insulating magnetic material is a nickel-zinc ferrite material.

4. The transformer according to claim 1, wherein, It also includes a first cover plate disposed on the first surface of the insulating substrate, wherein the first cover plate comprises an insulating magnetic material.

5. The transformer according to claim 4, wherein, It also includes a second cover plate disposed on the second surface of the insulating substrate, wherein the second cover plate comprises an insulating magnetic material; the first surface and the second surface are disposed opposite to each other.

6. The transformer according to claim 1, wherein, The insulating substrate is made of one or more of glass fiber, epoxy resin, and polyimide.

7. The transformer according to claim 1, wherein, The molding material is epoxy resin.

8. The transformer according to claim 1, wherein, It also includes an external pin, which is electrically connected to the output of the winding.

9. The transformer according to claim 6, wherein, The organic material is plastic.

10. The transformer according to claim 5, wherein, The first cover plate and the second cover plate are made by hot pressing powdered nickel-zinc ferrite.

11. The transformer according to claim 1, wherein, The first opening and a plurality of second openings penetrate the insulating substrate.

12. The transformer according to claim 1, wherein, The first opening and the plurality of second openings are blind holes on the insulating substrate.

13. A method for manufacturing a transformer, characterized in that: an insulating substrate is provided; a primary winding and a secondary winding are formed spaced apart within the insulating substrate, and the insulating substrate covers the primary winding and the secondary winding; a first opening and a plurality of second openings are formed on the insulating substrate, and the primary winding and the secondary winding surround the outside of the first opening, and the plurality of second openings surround the periphery of the primary winding and the secondary winding; a center post is formed within the first opening, and side posts are formed within the plurality of second openings; wherein, The central column and the side columns comprise non-metallic magnetic materials and encapsulating materials.

14. A method for manufacturing a transformer according to claim 13, wherein, The non-metallic magnetic material is an insulating magnetic material.

15. A method for manufacturing a transformer according to claim 14, wherein, The insulating magnetic material is a nickel-zinc ferrite material.

16. A method for manufacturing a transformer according to claim 13, wherein, It also includes forming a first cover plate on the first surface of the insulating substrate, wherein the first cover plate comprises an insulating magnetic material.

17. A method for manufacturing a transformer according to claim 16, wherein, It also includes forming a second cover plate on the second surface of the insulating substrate, wherein the second cover plate comprises an insulating magnetic material; the first surface and the second surface are disposed opposite to each other.

18. A method for manufacturing a transformer according to claim 13, wherein, The insulating substrate is made of one or more of glass fiber, epoxy resin, and polyimide.

19. A method for manufacturing a transformer according to claim 13, wherein, The molding material is epoxy resin.

20. A method for manufacturing a transformer according to claim 13, wherein, It also includes forming an external pin, which is electrically connected to the output of the primary winding and the secondary winding.

21. A method for manufacturing a transformer according to claim 13, wherein, The first opening and a plurality of second openings penetrate the insulating substrate.

22. A method for manufacturing a transformer according to claim 13, wherein, The first opening and the plurality of second openings are blind holes on the insulating substrate.

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