CN112584600A

CN112584600A - Printed circuit board and manufacturing method thereof

Info

Publication number: CN112584600A
Application number: CN201910926187.0A
Authority: CN
Inventors: 王蓓蕾; 陆平; 谢占昊; 缪桦
Original assignee: Shennan Circuit Co Ltd
Current assignee: Shennan Circuit Co Ltd
Priority date: 2019-09-27
Filing date: 2019-09-27
Publication date: 2021-03-30

Abstract

The application discloses printed circuit board and manufacturing method thereof, the printed circuit board includes: the circuit board comprises a plurality of layers of core boards, a second insulating layer, connecting holes and back drilling holes, wherein each core board comprises a first insulating layer and a circuit layer arranged on at least one of two opposite surfaces of the first insulating layer; the second insulating layer is arranged between the adjacent core plates and used for connecting the adjacent core plates; the connecting hole penetrates through the multilayer core board and the second insulating layer, and a conductive layer is arranged on the inner wall of the connecting hole so that the circuit layers with the connecting holes are mutually and electrically connected; the back drilling hole is formed by increasing the aperture of the connecting hole on the basis of the connecting hole so as to remove the conducting layer to ensure that the plurality of circuit layers provided with the back drilling hole are electrically disconnected; a magnetic core is embedded in the first insulating layer of at least one of the core boards. Through setting up the back drilling hole that the aperture is greater than the aperture of connecting hole, the conducting layer on the circuit layer that will not need the electricity to connect is got rid of to shorten signal transmission's route, reduce signal transmission loss and return loss.

Description

Printed circuit board and manufacturing method thereof

Technical Field

The present disclosure relates to circuit board technologies, and particularly to a printed circuit board and a method for manufacturing the same.

Background

In network transformer products or other printed circuit board products designed with embedded inductors, such as power transformers, power switches, converters, filters, oscillators, etc., the printed circuit board usually includes multiple layers of core boards, and each layer of core board is provided with a circuit layer for transmitting signals. At present, in order to realize the transmission of signals on different circuit layers, a printed circuit board is usually provided with a conductive hole penetrating through the printed circuit board to realize the electrical connection between different circuit layers. The arrangement of the conductive holes not only communicates with the circuit layers which need to be electrically connected, but also penetrates through the circuit layers which do not need to be electrically connected, so that the signal transmission path is lengthened, the loss of signal transmission is large, and the return loss is easily caused.

Disclosure of Invention

The application provides a printed circuit board and a manufacturing method thereof, which aim to solve the technical problems of large signal transmission loss and return loss of the printed circuit board in the prior art.

In order to solve the technical problem, the application adopts a technical scheme that: providing a printed circuit board, the circuit board comprising: the circuit board comprises a plurality of core boards which are arranged in a stacked mode, wherein each core board comprises a first insulating layer and a circuit layer arranged on at least one of two opposite surfaces of the first insulating layer; the second insulating layer is arranged between the adjacent core plates and used for connecting the adjacent core plates; a connection hole penetrating through the multilayer core board and the second insulating layer, wherein a conductive layer is disposed on an inner wall of the connection hole, so that the plurality of circuit layers formed with the connection hole are electrically connected to each other; a back-drilled hole formed by increasing the aperture of the connection hole on the basis of the connection hole to remove the conductive layer so that the plurality of line layers provided with the back-drilled hole are electrically disconnected; wherein, a magnetic core is embedded in the first insulating layer of at least one core plate.

In order to solve the above technical problem, another technical solution adopted by the present application is: provided is a method for manufacturing a printed circuit board, including: providing a plurality of first insulating layers and a toroidal magnetic core, embedding the toroidal magnetic core in at least one of the first insulating layers; arranging a metal layer on at least one side of the first insulating layer, and carrying out patterning treatment on the metal layer to form a circuit layer, wherein each first insulating layer and the circuit layer arranged on the surface of the first insulating layer form a core board; arranging a second insulating layer between the adjacent core plates along the axial direction of the annular magnetic core, and laminating to form the printed circuit board; forming a connecting hole penetrating through the printed circuit board on the printed circuit board along the axial direction of the annular magnetic core, and forming a conductive layer in the connecting hole so as to electrically connect the plurality of circuit layers formed with the connecting hole with each other; and carrying out back drilling treatment on the printed circuit board on the basis of the connecting hole to form a back drilling hole so as to electrically disconnect the plurality of circuit layers provided with the back drilling hole.

The beneficial effect of this application is: being different from the situation of the prior art, the application provides a printed circuit board and a manufacturing method thereof, and the back drilling hole with the aperture larger than that of the connecting hole is arranged on the basis of the connecting hole, so that the conducting layer on the circuit layer which does not need to be electrically connected is removed, the electric connection between the circuit layer which needs to be electrically connected and the circuit layer which does not need to be electrically connected is cut off, the signal transmission path can be shortened, and the signal transmission loss and the return loss are reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of a process for manufacturing a printed circuit board according to an embodiment of the present disclosure;

FIG. 2 is a schematic view of a manufacturing process of step S10 in FIG. 1;

FIGS. 3 to 4 are schematic process flows corresponding to FIG. 2;

FIG. 5 is a schematic view of a manufacturing process of step S20 of the application example;

FIGS. 6-7 are schematic process flow diagrams corresponding to FIG. 5;

fig. 8 is a schematic sectional view of the core board after a coil loop is formed on the core board in which the magnetic core is embedded;

fig. 9 is a schematic cross-sectional view of a printed circuit board formed after laminating a plurality of core boards;

fig. 10 to 11 are schematic views of a process flow corresponding to step S40 in fig. 1;

FIG. 12 is a schematic flow chart illustrating a process of forming a conductive layer in step S40 in FIG. 1;

FIG. 13 is a schematic cross-sectional view of a printed circuit board obtained according to the manufacturing process shown in FIG. 1;

FIG. 14 is a schematic view of a manufacturing process of step S50 in FIG. 1;

FIG. 15 is a schematic view of a manufacturing process of step S40 of another embodiment of the printed circuit board of the present application;

fig. 16 is a schematic manufacturing flow chart of step S50 of another embodiment of the printed circuit board of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be described clearly and completely below, and it should be understood that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

Referring to fig. 1, fig. 1 is a schematic view illustrating a manufacturing process of a printed circuit board according to an embodiment of the present disclosure.

The manufacturing method specifically comprises the following steps:

s10: a plurality of first insulating layers and a toroidal core are provided, the toroidal core being embedded in at least one of the first insulating layers.

Wherein the first insulating layer may be made of a material that allows a radio frequency signal of a certain frequency to pass through. For example, the material may be a hydrocarbon system material or a polytetrafluoroethylene system mixed material. Common materials for hydrocarbon systems include: glass fiber ceramic-based high frequency materials (if any) having a dielectric constant of 3.48 to 3.66, polyphenylene ether resin-based materials, and the like.

The choice of material for the first insulating layer may be selected according to the role of each core board. It is also possible that the dielectric ceramic material is a material with a low loss factor (DF) suitable for radio frequency circuits, such as ceramic-based high frequency materials or teflon. Or may be of a material having a high dissipation factor, such as FR-4 (including epoxy), suitable for use in conventional circuits.

In this embodiment, the first insulating layer may be a thermosetting material, and the first insulating layer is cured by heat treatment in advance, so that the shape of the first insulating layer is fixed, and the first insulating layer is not deformed again in the subsequent heating process; meanwhile, the material can also be thermoplastic material which is softened after being heated.

Wherein, the thermosetting material is: the material can soften and flow when heated for the first time, and is heated to a certain temperature to generate chemical reaction, so that the cross-linking is solidified and hardened; this change is irreversible, after which, on reheating, the material can no longer flow softly.

Common thermoset materials include, but are not limited to, allyl resins, epoxy resins, thermoset polyurethanes, silicones or polysiloxanes, and the like. These resins may be formed from the reaction product of a polymerizable composition comprising at least one urethane (meth) acrylate. Typically, the polyurethane (meth) acrylate is a poly (meth) acrylate. The term "(meth) acrylate" is used to refer to esters of acrylic acid and methacrylic acid, and "poly (meth) acrylate" refers to molecules comprising more than one (meth) acrylate group, as opposed to "poly (meth) acrylates" which typically refer to (meth) acrylate polymers. Most commonly, the poly (meth) acrylate is a di (meth) acrylate, but tri (meth) acrylates, tetra (meth) acrylates, and the like are also contemplated.

The cross section of the annular magnetic core can be in the shape of a circular ring, a square ring, an ellipse and the like, and the application is not limited specifically. In the present embodiment, a circular ring-shaped magnetic core is employed.

The magnetic core can be an iron core, and can also be composed of various magnetic metal tea oxides, such as manganese-zinc ferrite, nickel-zinc ferrite and the like. The manganese-zinc ferrite has the characteristics of high magnetic permeability, high magnetic flux density and low loss, and the nickel-zinc ferrite has the characteristics of extremely high impedance rate, low magnetic permeability and the like. The magnetic core in this embodiment is made of manganese-zinc ferrite by high-temperature sintering. May be made of ferrite material.

As shown in fig. 2 to 4, fig. 2 is a schematic view of a manufacturing flow of step S10 in fig. 1, and fig. 3 to 4 are schematic views of a process flow corresponding to fig. 2.

The step of embedding the toroidal core in the first insulating layer includes:

s110: first insulating layers 10 are provided, and one side of at least one first insulating layer 10 is provided with an annular accommodating groove 12 matched with the shape of an annular magnetic core 20.

Specifically, as shown in fig. 3, an annular receiving groove 12 matching the shape of the annular magnetic core 20 is formed in the first insulating layer 10 in which the annular magnetic core 20 is to be embedded. The depth of the annular accommodating groove 12 may be greater than or equal to the height of the annular magnetic core 20, so that the annular magnetic core 20 can be completely accommodated in the annular accommodating groove 12. Generally, the depth of the annular accommodation groove 12 is set to be 0 to 0.5mm greater than the height of the annular magnetic core 20.

The number of the first insulating layers 10 required to embed the toroidal core 20 may be flexibly set according to the design requirement of the printed circuit board, and is not particularly limited in the present application.

S120: the ring-shaped magnetic core 20 is placed in the ring-shaped receiving groove 12.

S130: the side of the first insulating layer 10 where the annular receiving groove 12 is formed and the annular receiving groove 12 are filled with insulating materials, and then the first insulating layer 10 with the annular magnetic core 20 embedded therein is formed by pressing.

Specifically, the insulating material may be the same as the material used to form the first insulating layer 10, being a thermosetting material. The insulating material is different from the first insulating layer 10 in that the first insulating layer 10 is an insulating material that is subjected to a thermosetting process and is not deformed when heated. The insulating material is heated to be in a molten state, and is further filled between the annular magnetic core 20 and the annular receiving groove 12, and the surface of the annular receiving groove 12 is opened, so that the annular magnetic core 20 is completely embedded in the first insulating layer 10. Fig. 4 is a schematic sectional view showing a structure after the toroidal core 20 is embedded in the first insulating layer 10.

S20: and arranging a metal layer on at least one side of the first insulating layer, and patterning the metal layer to form a circuit layer, wherein each first insulating layer and the circuit layer arranged on the surface of the first insulating layer form a core board.

As shown in fig. 5 to 7, fig. 5 is a schematic view of a manufacturing flow of step S20 in the application embodiment, and fig. 6 to 7 are schematic views of a process flow corresponding to fig. 5.

S210: an adhesive layer 30 and a metal layer 40 are provided.

The adhesive layer 30 may be an insulating material with certain adhesive ability, and the metal layer 40 is a conductive material. In this embodiment, the adhesive layer 30 is made of a thermosetting material, which is the same as the insulating material, and is heated to be in a molten state, thereby adhering the metal layer 40 to the first insulating layer 10. The metal layer 40 is made of copper.

S220: the adhesive layer 30 is placed between the surface of the first insulating layer 10 and the metal layer 40.

The adhesive layer 30 and the metal layer 40 are provided on the side of the first insulating layer 10 where the metal layer 40 is required to be provided. When the annular magnetic core 20 is provided in the first insulating layer 10, the adhesive layer 30 and the metal layer 40 are provided on a surface perpendicular to the axis of the annular magnetic core 20.

In the present embodiment, as shown in fig. 6, the adhesive layer 30 and the metal layer 40 are disposed on opposite sides of the first insulating layer 10.

S230: the first insulating layer 10, the adhesive layer 30 and the metal layer 40 are laminated.

Wherein, when the adhesive layer 30 and the metal layer 40 are disposed on one side of the first insulating layer 10, a single panel is formed by press-fitting. When the adhesive layer 30 and the metal layer 40 are disposed on both sides of the first insulating layer 10, a double-sided board is formed by press-fitting.

In the present embodiment, the first insulating layer 10, the adhesive layer 30 and the metal layer 40 shown in fig. 6 are pressed, and after the adhesive layer 30 is cooled, the adhesive layer and the first insulating layer 10 form an integral structure, thereby forming the printed circuit board embedded with the toroidal core 20 as shown in fig. 7.

After forming the double-sided board or the single-sided board, the metal layer 40 on each first insulating layer 10 is further patterned to form a circuit layer.

The circuit layer comprises a plurality of loops for transmitting signals or processing the signals. The wiring layer may be divided into a signal layer and a ground layer according to the function. Generally, a signal layer is a layer on which a plurality of metal lines for forming electrical connections between electronic devices are located; the ground plane is typically a layer of large contiguous metal area.

As shown in fig. 8, for the core board 100 embedded with the toroidal core 20, it is further necessary to form conductive holes 14 in the region of the first insulating layer 10 inside or outside the toroidal core 20, and the conductive holes 14 electrically connect the circuit patterns on the circuit layers 42 on two opposite sides of the first insulating layer 10, so as to form a coil loop wound around the toroidal core 20, and further form an embedded transformer or an embedded inductor.

The above is a method of manufacturing a core board in which a magnetic core is embedded, and a method of forming a core board in which a magnetic core is not embedded is similar to that of forming a core board in which a magnetic core is embedded. The two core board forming methods are different in that the core board in which the core is not embedded is formed without the step of embedding the core. For other steps of disposing a circuit layer on the surface of the first insulating layer, please refer to the method for forming the core board for embedding the magnetic core, which is not described herein again.

As shown in fig. 1 and 9, after forming a plurality of core boards, the following steps are performed:

s30: the second insulating layer 50 is provided between the adjacent core boards 100 in the axial direction of the toroidal core 20, and press-fitted to form a printed circuit board.

In the present embodiment, the material of the second insulating layer 50 may be the same as the material used to form the first insulating layer 10, and is a thermosetting material. The second insulating layer 50 is different from the first insulating layer 10 in that the first insulating layer 10 is an insulating material that is heat cured and does not deform when heated. The second insulating layer 50 is heated to be in a molten state, and the molten second insulating layer 50 has an adhesive property, and after cooling, the adjacent core boards 100 are adhered to form the printed circuit board. Fig. 9 is a schematic cross-sectional structure view of a printed circuit board formed after laminating a plurality of core boards 100.

The wiring layers 42 in the printed circuit board formed above are independent of each other, and are not electrically connected to each other, so that signal transmission between the wiring layers 42 of different layers cannot be realized. Therefore, in order to improve the performance of the printed circuit board, it is also necessary to electrically connect the circuit layers 42 located at different layers for signal transmission.

Referring to fig. 1 and fig. 10 to 11, fig. 10 to 11 are schematic processing flows corresponding to step S40 in fig. 1.

Specifically, the method of forming the electrical connection between the circuit layers 42 of different layers is:

s40: a connection hole 60 penetrating the printed circuit board is opened in the printed circuit board along the axial direction of the ring-shaped magnetic core 20, and a conductive layer 70 is formed in the connection hole 60 so that the plurality of wiring layers 42 formed with the connection hole 60 are electrically connected to each other.

Specifically, as shown in fig. 10, a connection hole 60 is opened at a predetermined position of the printed circuit board, and the connection hole 60 penetrates the printed circuit board. As shown in fig. 11, a conductive layer 70 is formed on the inner wall of the connection hole 60 so that the conductive layer 70 is electrically connected to each wiring layer 42, so that the wiring layers 42 located at different layers are electrically connected through the conductive layer 70.

The conductive layer 70 includes a first conductive layer and a second conductive layer.

Referring to fig. 12, fig. 12 is a schematic view illustrating a manufacturing process of forming a conductive layer in step S40 in fig. 1.

S410: the connection hole 60 is subjected to a metallization process to form a first conductive layer on the inner wall of the connection hole 60.

Specifically, a layer of metal may be deposited on the inner wall of the connection hole 60 by a chemical reaction, such as a deposition reaction, to form the first conductive layer.

S420: the connection hole 60 is subjected to an electroplating process to form a second conductive layer on the first conductive layer.

Specifically, the connection hole 60 may be plated by an electroplating method, so that the second conductive layer is formed on the side of the first conductive layer facing away from the inner wall of the connection hole 60.

In the above, the first conductive layer may enhance the bonding force between the second conductive layer and the inner wall of the connection hole 60; the second conductive layer can increase the thickness of the first conductive layer, thereby enhancing the electrical connection strength and enhancing the conductivity.

The material of the first conductive layer and the material of the second conductive layer may be the same or different. In this embodiment, since copper has excellent conductivity and low cost, the first conductive layer and the second conductive layer are formed using copper.

The printed circuit board formed by the above method can make all the circuit layers 42 penetrated by the connection holes 60 electrically connected through the conductive layers 70 in the connection holes 60, so that a back drilling process is also required to form back drilling holes, so that the conductive layers 70 which do not need to be electrically connected are removed, the signal transmission path is shortened, and the transmission loss and the return loss are reduced.

As shown in fig. 1, after forming the conductive layer 70, the following steps are further included:

s50: the printed circuit board is back-drilled on the basis of the connection holes 60 to form back-drilled holes 80 to electrically disconnect the plurality of wiring layers 42 provided with the back-drilled holes 80.

For clarity of description, the wiring layer 42 in the printed circuit board may be divided into a first wiring layer and a second wiring layer as shown in fig. 13. The first circuit layer is the circuit layer 42 that does not need to be electrically connected in the printed circuit board, and when the back drilling process is performed, the conductive layer 70 on the first circuit layer needs to be removed to disconnect the electrical connection between the first circuit layer and the conductive layer 70. The second circuit layer is the circuit layer 42 of the printed circuit board that needs to be electrically connected, and the conductive layer 70 on the second circuit layer does not need to be removed during the back drilling process.

Specifically, as shown in fig. 14, when step S50 is executed, the following steps are included:

s510: the first circuit layer to be electrically disconnected from the backdrilled hole is selected.

Specifically, the wiring layers of the printed circuit board that do not require electrical connection are selected according to design requirements.

S520: and a back drilling hole is formed in the surface of the printed circuit board, extends from the surface of the printed circuit board, sequentially penetrates through the first circuit layer, and extends to a position with a preset distance away from the first circuit layer to a second circuit layer closest to the first circuit layer.

Specifically, as shown in fig. 13, the back-drilled hole 80 is disposed coaxially with the connection hole 60, and the aperture of the back-drilled hole 80 is larger than that of the connection hole 60 to remove the conductive layer 70 attached on the inner wall of the connection hole 60. Typically, the diameter of the back-drilled hole 80 is set to be 0.1mm larger than that of the connection hole 60 to completely remove the conductive layer 70 on the inner wall of the connection hole 60. The back-drilled holes 80 sequentially penetrate the wiring layers 42 that do not need to be electrically connected and do not interfere with the wiring layers 42 that need to be electrically connected.

Wherein the predetermined distance may be set to 2-14 mils. For example, it may be set to 2mil, 5mil, 8mil, 11mil, 14mil, or the like. The distance between the end of the back drilled hole 80 and the second circuit layer closest to the end is greater than or equal to 2-14mil, so that the electric connection between the second circuit layers can be prevented from being damaged, and the connection is more stable.

For example, as shown in fig. 13, the printed circuit board includes 4 wiring layers 42. Two connection holes 60 penetrating the printed circuit board are formed on the printed circuit board, and a conductive layer 70 is formed in the two connection holes 60 for electrically connecting the 4-layer wiring layers 42 of the printed circuit board.

The connection holes 60 at the printed circuit board a are designed to electrically connect the 1 st to 3 rd layer wiring layers 42 and to electrically disconnect the 4 th layer wiring layers 42. Then at a, the layer 4 wiring layer 42 is the first wiring layer and the layer 1-3 wiring layers 42 are the second wiring layers. During backdrilling, the backdrilled hole 80 is opened at the side of the printed circuit board where the fourth layer of circuit layer 42 is disposed, and after penetrating through the fourth layer of circuit layer 42, extends to a predetermined distance from the third layer of circuit layer 42. That is, the end of the conductive layer 70 in the connection hole 60 protrudes from the surface of the third circuit layer 42 nearest to the end by 2-14 mil.

The connection holes 60 at the printed circuit board B are designed to electrically connect the 2 nd to 4 th layer wiring layers 42 and to electrically disconnect the 1 st layer wiring layers 42. Then at B, the layer 1 wiring layer 42 is the first wiring layer and the layer 2-4 wiring layers 42 are the second wiring layers. During backdrilling, the backdrilled hole 80 is drilled at the side of the pcb where the first layer of circuit layer 42 is disposed, and extends to a distance of 2-14mil from the second layer of circuit layer 42 after penetrating the first layer of circuit layer 42. That is, the end of the conductive layer 70 in the connection hole 60 protrudes from the surface of the second circuit layer 42 nearest to the end by 2-14 mils.

Through the manufacturing process, the printed circuit board provided with the back drilling hole 80 can be manufactured, and the printed circuit board is provided with the back drilling hole 80, and the electric connection between the circuit layer 42 without the back drilling hole 80 and the circuit layer 42 without the back drilling hole 80 is disconnected, so that the signal transmission path can be shortened, the return loss is reduced, and the performance of the printed circuit board is improved.

Referring to fig. 15 and 16, fig. 15 is a schematic view of a manufacturing process of step S40 of another embodiment of the printed circuit board of the present application, and fig. 16 is a schematic view of a manufacturing process of step S50 of another embodiment of the printed circuit board of the present application.

The present embodiment is different from the previous embodiment in that, in step S40, after the second conductive layer is formed in step S420, the present embodiment further includes step S430. In step S50, after the back-drilled hole is formed in step S520, step S530 is further included. The method comprises the following specific steps:

s430: and electroplating the connecting hole to form a covering layer on the second conductive layer.

Wherein, a covering layer can be electroplated on the side of the second conducting layer, which is far away from the first conducting layer, through electroplating treatment. In this embodiment, the metal may be tin, i.e., a tin layer is formed on the second conductive layer by electroplating.

S530: and etching the connecting hole to remove the covering layer.

The connecting hole can be etched by adopting a method such as alkaline etching, and burrs generated by back drilling can be removed firstly along with the etching; the cover layer attached to the second conductive layer is then removed.

The alkaline etchant should be selected to etch away only the coating layer adhered to the inner wall of the second conductive layer without affecting the second conductive layer.

This embodiment, before the back drilling, cover one deck overburden outside the second conducting layer to get rid of the overburden through alkaline etching solution after the back drilling, can get rid of the burr that the back drilling in-process produced, thereby avoid appearing burr hole blocking phenomenon.

Referring to fig. 13, fig. 13 is a schematic cross-sectional structure diagram of an embodiment of a printed circuit board according to the present application.

The printed circuit board may include a multilayer core board 100 and a second insulation layer 50. In which the plurality of core boards 100 are stacked, and the second insulating layer 50 is disposed between adjacent core boards 100, for bonding the adjacent core boards 100 to form a printed circuit board.

Wherein, the number of the core plates 100 may be two, three or four, etc. The number of core plates 100 is not limited in the present application.

Further, each core board 100 includes a first insulating layer 10 and a circuit layer 42 disposed on at least one of two opposite surfaces of the first insulating layer 10. The forming method of the circuit layer 42 may refer to the description in the above embodiments, and the detailed description is omitted here.

In the present embodiment, as shown in fig. 13, the printed circuit board includes two core boards 100, and the circuit layers 42 are formed on two opposite surfaces of each core board 100. The second insulating layer 50 is disposed between the two core boards 100, bonding the two core boards 100.

Further, the toroidal core 20 is embedded in the first insulating layer 10 of at least one core board 100. Specifically, a toroidal core 20 is embedded in a portion of the first insulating layer 10 of the core board 100, via holes are formed inside and outside the toroidal core 20, and coil loops wound around the core are formed on the wiring layers 42 on opposite sides of the core board 100 to form an embedded inductor or an embedded transformer.

As shown in fig. 1, in the present embodiment, the printed circuit board includes two core boards 100, and one ring-shaped magnetic core 20 is disposed in each core board 100.

Further, in the present embodiment, the toroidal core 20 buried in the first insulating layer 10 is a toroidal core, and the axial direction of the toroidal core is the same as the lamination direction of the core boards 100.

In the axial direction perpendicular to the annular magnetic core, the cross section of the annular magnetic core can be a concentric circular ring shape, a concentric rectangle, a concentric elliptical ring shape and the like. The present application is not specifically limited herein.

Further, the height of the annular magnetic core 20 in the axial direction is smaller than the height of the first insulating layer 10. That is, two opposite surfaces of the annular magnetic core 20 perpendicular to the axis do not contact with two opposite surfaces of the first insulating layer 10. The insulating material disposed between the surface of the toroidal core 20 and the surface of the first insulating layer 10 may insulate the toroidal core 20 from the line layer 42 located on the surface of the first insulating layer 10.

The circuit layers 42 on different layers in the printed circuit board formed by lamination are not electrically connected, so that a complete functional circuit cannot be formed, and therefore, a connection hole 60 is also needed to electrically connect the circuit layers 42 on different layers, so that all the circuit layers 42 on the printed circuit board can be electrically connected to form the functional circuit of the printed circuit board.

As shown in fig. 12, a connection hole 60 penetrating the core board 100 and the second insulating layer 50 is opened on the printed circuit board, and a conductive layer 70 is provided on an inner wall of the connection hole 60 so that the plurality of wiring layers 42 formed with the connection hole 60 are electrically connected to each other.

Specifically, the conductive layer 70 includes a first conductive layer and a second conductive layer. The first conductive layer is disposed on an inner wall of the connection hole 60, and the second conductive layer is disposed on a side of the first conductive layer that is away from the inner wall of the connection hole 60. The first conductive layer and the second conductive layer are formed on the inner wall of the connection hole 60 by different methods, respectively, and specific reference may be made to the description in the above embodiment.

The first conductive layer may increase a coupling force of the second conductive layer with the connection hole 60, and the second conductive layer may increase a thickness of the first conductive layer to make an electrical connection between the line layers 42 more stable.

Further, the printed circuit board also includes a back-drilled hole 80. Wherein the back-drilled hole 80 is formed on the basis of the connection hole 60. As shown in fig. 13, the axis of the back-drilled hole 80 coincides with the axis of the connection hole 60, and the diameter of the back-drilled hole 80 is larger than that of the connection hole 60 to remove the conductive layer 70 on the inner wall of the connection hole 60.

In the present embodiment, the difference between the diameter of the back-drilled hole 80 and the diameter of the connection hole 60 is equal to or greater than 0.1mm, that is, the diameter of the back-drilled hole 80 is at least 0.1mm greater than the diameter of the connection hole 60. For example, the diameter of the back drilled hole 80 may be 0.1mm, 0.15mm, 0.2mm, or the like larger than the diameter of the connection hole 60.

Specifically, in the present embodiment, the back-drilled hole 80 extends from one side of the printed circuit board, and penetrates through the circuit layer 42 that does not need to be electrically connected, and then is cut off between the circuit layer 42 that does not need to be electrically connected and the circuit layer 42 that needs to be electrically connected.

For example, the wiring layer 42 is divided into a first wiring layer and a second wiring layer. The first circuit layer is a circuit layer 42 that does not need to be electrically connected, and the second circuit layer is a circuit layer 42 that needs to be electrically connected. The back-drilled holes 80 extend through the first circuit layer and not through the second circuit layer.

As shown in fig. 13, the back-drilled hole 80 is located at the end of the printed circuit board between the adjacent first and second circuit layers, i.e., in the first insulating layer 10 or the second insulating layer 50. The conductive layer 70 disposed in the connection hole 60 protrudes a distance from the second circuit layer, which can prevent the back drilling from causing the electrical connection between the second circuit layers to fail.

Further, the distance from the end of the back-drilled hole 80 to the nearest second circuit layer is set to be greater than or equal to a preset distance. Wherein the predetermined distance may be selected according to the conductivity of the conductive layer 70. In this embodiment, the predetermined distance may be 2-14 mils.

The present application also provides an electronic device comprising the printed circuit board as described above. The electronic device can be a power transformer, a power switch, a converter, a filter, an oscillator and the like.

In summary, the present application provides an electronic device, a printed circuit board and a manufacturing method, by providing a back-drilled hole 80 with an aperture larger than that of the connection hole 60 on the basis of the connection hole 60, the conductive layer 70 on the circuit layer 42 not required to be electrically connected is removed to cut off the electrical connection between the circuit layer 42 required to be electrically connected and the circuit layer 42 not required to be electrically connected, thereby shortening the signal transmission path and reducing the signal transmission loss and the return loss.

The above description is only an example of the present application and is not intended to limit the scope of the present application, and all modifications of equivalent structures and equivalent processes, which are made by the contents of the specification and the drawings, or which are directly or indirectly applied to other related technical fields, are intended to be included within the scope of the present application.

Claims

1. A printed circuit board, comprising:

the circuit board comprises a plurality of core boards which are arranged in a stacked mode, wherein each core board comprises a first insulating layer and a circuit layer arranged on at least one of two opposite surfaces of the first insulating layer;

the second insulating layer is arranged between the adjacent core plates and used for connecting the adjacent core plates;

a connection hole penetrating through the multilayer core board and the second insulating layer, wherein a conductive layer is disposed on an inner wall of the connection hole, so that the plurality of circuit layers formed with the connection hole are electrically connected to each other;

a back-drilled hole formed by increasing the aperture of the connection hole on the basis of the connection hole to remove the conductive layer so that the plurality of line layers provided with the back-drilled hole are electrically disconnected;

wherein, a magnetic core is embedded in the first insulating layer of at least one core plate.

2. The printed circuit board of claim 1, wherein a difference between a diameter of the back-drilled hole and a diameter of the connection hole is 0.1mm or more.

3. The printed circuit board of claim 1, wherein the circuit layers comprise a first circuit layer and a second circuit layer, wherein the back-drilled hole extends from a surface of the printed circuit board and through the first circuit layer and not through the second circuit layer.

4. The printed circuit board of claim 3, wherein the back-drilled hole is located within the printed circuit board at an end located between adjacent first and second circuit layers.

5. The printed circuit board of claim 4, wherein a distance between the end and the second circuit layer closest to the end is greater than or equal to a preset distance.

6. The printed circuit board of claim 5, wherein the predetermined distance is 2-14 mils.

7. The printed circuit board according to claim 1, wherein the core is a toroidal core, and an axial direction of the toroidal core is the same as a lamination direction of the core boards.

8. The printed circuit board of claim 7, wherein a height of the magnetic core in the axis direction is less than a height of the first insulating layer.

9. The printed circuit board according to claim 1, wherein the conductive layer includes a first conductive layer and a second conductive layer, the first conductive layer is disposed on the inner wall of the via hole, and the second conductive layer is disposed on a side of the first conductive layer facing away from the inner wall of the via hole.

10. A method of fabricating a printed circuit board, comprising:

providing a plurality of first insulating layers and a toroidal magnetic core, embedding the toroidal magnetic core in at least one of the first insulating layers;

arranging a metal layer on at least one side of the first insulating layer, and carrying out patterning treatment on the metal layer to form a circuit layer, wherein each first insulating layer and the circuit layer arranged on the surface of the first insulating layer form a core board;

arranging a second insulating layer between the adjacent core plates along the axial direction of the annular magnetic core, and laminating to form the printed circuit board;

forming a connecting hole penetrating through the printed circuit board on the printed circuit board along the axial direction of the annular magnetic core, and forming a conductive layer in the connecting hole so as to electrically connect the plurality of circuit layers formed with the connecting hole with each other; and

and carrying out back drilling treatment on the printed circuit board on the basis of the connecting hole to form a back drilling hole so as to electrically disconnect the plurality of circuit layers provided with the back drilling hole.

11. The method of claim 10, wherein a plurality of first insulating layers and a toroidal core are provided, and the step of embedding the toroidal core in at least one of the first insulating layers comprises:

providing first insulating layers, and arranging an annular accommodating groove matched with the annular magnetic core in shape on one side of at least one first insulating layer;

placing the annular magnetic core in the annular accommodating groove; and

and filling an insulating material in one side of the first insulating layer, which is provided with the annular accommodating groove, and pressing to form the first insulating layer in which the annular magnetic core is embedded.

12. The method of claim 11, wherein the step of providing the metal layer on at least one side of the first insulating layer comprises:

providing an adhesive layer and the metal layer;

placing the adhesive layer between the surface of the first insulating layer and the metal layer;

and laminating the first insulating layer, the bonding layer and the metal layer.

13. The method of claim 11, wherein the depth of the annular receiving groove is greater than or equal to the height of the annular magnetic core.

14. The method of manufacturing according to claim 10, wherein the circuit layer includes a first circuit layer and a second circuit layer; the step of back-drilling the printed circuit board on the basis of the connection hole to form a back-drilled hole includes:

selecting the first circuit layer to which the backdrilled hole is to be electrically disconnected;

and arranging a back drilling hole on the surface of the printed circuit board, wherein the back drilling hole extends from the surface of the printed circuit board, sequentially penetrates through the first circuit layer and then extends to a position with a preset distance from the second circuit layer closest to the first circuit layer.

15. The method of claim 14, wherein the predetermined distance is greater than or equal to 2-14 mil.

16. The method according to claim 10, wherein the conductive layer includes a first conductive layer and a second conductive layer, and the step of forming a conductive layer in the connection hole includes:

carrying out metallization processing on the connecting hole to form the first conducting layer on the inner wall of the connecting hole;

and electroplating the connecting hole to form the second conductive layer on the first conductive layer.

17. The method of manufacturing according to claim 16, further comprising, after forming the second conductive layer, before performing a back-drilling process: and electroplating the connecting hole to form a covering layer on the second conductive layer.

18. The method of manufacturing of claim 17, further comprising, after forming the back-drilled hole: and etching the connecting hole to remove the covering layer.