CN110972389B

CN110972389B - Circuit board

Info

Publication number: CN110972389B
Application number: CN201811152665.9A
Authority: CN
Inventors: 何明展; 沈芾云; 徐筱婷; 肖如敏
Original assignee: Hongqisheng Precision Electronics Qinhuangdao Co Ltd; Avary Holding Shenzhen Co Ltd
Current assignee: Hongqisheng Precision Electronics Qinhuangdao Co Ltd; Avary Holding Shenzhen Co Ltd
Priority date: 2018-09-29
Filing date: 2018-09-29
Publication date: 2023-07-21
Anticipated expiration: 2038-09-29
Also published as: CN110972389A

Abstract

The circuit board comprises a circuit layer, a protection layer arranged on one side of the circuit layer, a shielding layer arranged on one side of the protection layer away from the circuit layer, a plurality of electronic elements and a plurality of shielding units, wherein the electronic elements are electrically connected with the circuit layer, at least one connecting hole penetrating through the protection layer and exposing the circuit layer is formed in the periphery of each electronic element, each shielding unit covers the exposed surface of at least one electronic element, each shielding unit is electrically connected with the circuit layer through the connecting hole, and each shielding unit is electrically connected with the shielding layer.

Description

Circuit board

Technical Field

The present invention relates to a circuit board, and more particularly, to a circuit board with high electromagnetic shielding capability.

Background

In recent years, many electronic devices such as mobile phones and tablet terminals have been provided with a large number of circuit boards, and many electronic components for transmitting large-capacity data have been mounted on the circuit boards. The presence of these electronic components is not only prone to noise generation, but also has high sensitivity to noise and is prone to malfunction when exposed to noise from the outside. On the other hand, in order to achieve both downsizing and weight saving and high functionality of electronic devices, it is necessary to increase the mounting density of electronic components. However, if the mounting density is increased, not only are the number of electronic components serving as noise generation sources increased, but also the number of electronic components affected by noise is increased.

In the prior art, a metal cover is often mounted on a circuit board to shield an electronic component from the metal cover. However, the metal cover is arranged on the circuit board, so that a large space is occupied, the shielding effect is poor, under the trend that the density of electronic elements in the circuit board is gradually increased, the difficulty of arranging the metal cover is increased, and if the metal cover is thinned so that the metal cover is suitable for a high-density circuit board, the shielding effect is further weakened. How to design a circuit board with better shielding effect and small space occupation rate of the shielding unit is needed to be solved by those skilled in the art.

Disclosure of Invention

The invention provides a circuit board, which comprises a circuit layer, a protective layer arranged on one side of the circuit layer, a shielding layer arranged on one side of the protective layer far away from the circuit layer, a plurality of electronic components and a plurality of shielding units, wherein the electronic components are electrically connected with the circuit layer, at least one connecting hole penetrating through the protective layer and exposing the circuit layer is arranged around each electronic component, each shielding unit covers the exposed surface of at least one electronic component, each shielding unit is electrically connected with the circuit layer through the connecting hole, and each shielding unit is electrically connected with the shielding layer.

The invention also provides another circuit board which comprises a circuit layer, a protective layer positioned on one side of the circuit layer and a shielding layer positioned on one side of the protective layer far away from the circuit layer, and is characterized by further comprising a plurality of electronic components and a plurality of shielding units, wherein the electronic components are electrically connected with the circuit layer, each shielding unit covers the exposed surface of at least one electronic component, at least one conducting sheet is arranged around each electronic component, the conducting sheet is not contacted with the electronic component, and the shielding units are electrically connected with the shielding layer through the conducting sheets.

According to the circuit board, the shielding units are respectively arranged on the single electronic components, so that the shielding units have smaller sizes, the space occupation rate is reduced, the shielding units cover the exposed surfaces of the electronic components, the shielding units are electrically connected with the shielding layers, and the shielding effect is greatly improved.

Drawings

Fig. 1 is a top view of a circuit board according to a first embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view of a circuit board along the direction II-II according to a first embodiment of the present invention.

Fig. 3A to 3F are schematic views of a manufacturing process and a structure of a circuit board according to a first embodiment of the present invention.

Fig. 4 is a top view of a circuit board according to a second embodiment of the present invention.

Fig. 5 is a schematic cross-sectional view of a circuit board along the V-V direction according to a second embodiment of the present invention.

Fig. 6A to 6F are schematic views of a manufacturing process of a circuit board according to a second embodiment of the present invention.

Description of the main reference signs

The invention will be further described in the following detailed description in conjunction with the above-described figures.

Detailed Description

For a more complete and thorough description of the present application, reference is made to the accompanying drawings, in which like reference numerals represent the same or similar elements, and in which are shown various embodiments of the present invention. However, it will be understood by those of ordinary skill in the art that the examples provided below are not intended to limit the scope of the present invention. Furthermore, the drawings are for illustrative purposes only and are not drawn to scale in accordance with their actual dimensions.

The following describes in further detail the embodiments of the present invention with reference to the accompanying drawings.

First embodiment

As shown in fig. 1, a circuit board 10 according to a first embodiment of the present invention is shown in a top view. Fig. 2 is a schematic cross-sectional view of the circuit board along the direction II-II according to the first embodiment of the present invention. The circuit board 10 includes a base layer 180, a circuit layer 110 disposed on a surface of one side of the base layer 180, a protective layer 120 disposed on a side of the circuit layer 110 away from the base layer 180, and a shielding layer 130 disposed on a side of the protective layer 120 away from the circuit layer 110. The circuit board 10 further includes a plurality of electronic components 150, a plurality of dielectric units 140, and a plurality of shielding units 160, wherein one electronic component 150 is electrically connected to the circuit layer 110 through one dielectric unit 140. At least one connection hole 121 penetrating through the protection layer 120 and exposing the circuit layer 110 is disposed around one electronic component 150, each shielding unit 160 covers the exposed surface of at least one electronic component 150, each shielding unit 160 is electrically connected to the circuit layer 110 through the connection hole 121, and each shielding unit 160 is electrically connected to the shielding layer 130.

The circuit layer 110 is disposed on a surface of one side of the base layer 180, the circuit layer 110 includes a plurality of mounting areas 111, the circuit layer 110 is disposed in an area corresponding to the mounting areas 111, the protective layer 120 and the shielding layer 130 are not disposed on a side far away from the base layer 180, and the thickness of the area corresponding to the mounting areas 111 of the circuit layer 110 is smaller than that of other areas.

The circuit layer 110 is made of a conductive material, and the circuit layer 110 has good conductivity, and in one embodiment, the circuit layer 110 may be made of a metal simple substance, an alloy, a composite metal or other conductive materials, and in this embodiment, the material of the circuit layer 110 is copper (Cu). The circuit layer 110 is provided with a plurality of wires 112 corresponding to the mounting area 111, the electronic component 150 is provided corresponding to the mounting area 111, the electronic component 150 is electrically connected with the wires 112 through a dielectric unit 140, the wires 112 can extend to be electrically connected with other components, for example, connected with a Central Processing Unit (CPU), and the wires 112 can have other electrical functions, for example, can be used as signal transmitting antennas; other functional circuitry, such as ground circuitry (not shown), is also included in the circuitry layer 110.

The protection layer 120 is disposed on a side of the circuit layer 110 away from the base layer 180, where the protection layer 120 can protect the covered portion of the circuit layer 110 from oxidation caused by contact with air, or from water vapor erosion, or from short circuit caused by contact with other conductive materials, or from physical damage caused by rubbing and bumping. The protective layer 120 is an insulating material, and its component may include at least one of Polyimide (PI), polyethylene naphthalate (Polyethylene naphthalate two formic acid glycol ester, PEN), polyethylene terephthalate (polyethylene glycol terephthalate, PET), or ink.

The protection layer 120 is provided with a plurality of connection holes 121 and through holes 123. The connection holes 121 penetrate through the protection layer 120 and expose at least part of the surface of the circuit layer 110, the connection holes 121 are disposed adjacent to the mounting areas 111, in an embodiment, at least one connection hole 121 is disposed around each mounting area 111, in other embodiments, at least two connection holes 121 are disposed around each mounting area 111, a plurality of connection holes 121 are disposed on opposite sides of the mounting area 111 or around the mounting area 111, and the diameter of the connection holes 121 is greater than or equal to 0.2mm. The circuit board 10 may further include a plurality of connection pads 122, at least one connection pad 122 is disposed in each connection hole 121, the connection pads 122 cover at least a portion of the surface of the exposed circuit layer 110 in the connection holes 121 to protect the at least a portion of the surface of the circuit layer 110, the connection pads 122 are made of a conductive material, and may be metal, for example, gold (Au), and the connection pads 122 are electrically connected to the circuit layer 110. The through hole 123 penetrates through the protection layer 120 and exposes at least a portion of the surface of the circuit layer 110, the through hole 123 is disposed on a side of the connection hole 121 away from the mounting region 111, and one or more through holes 123 may be provided.

The shielding layer 130 covers the surface of the protection layer 120 far from the circuit layer 110 and fills the through hole 123 to extend to contact with the circuit layer 110, but the protection layer 120 between the mounting region 111 and the connection hole 121 is not covered by the shielding layer 130, the shielding layer 130 is made of conductive material, the shielding layer 130 is disposed outside the circuit layer 110 to form a continuous shielding field, and the shielding layer 130 is electrically connected with the circuit layer 110 and is connected with a ground circuit in the circuit layer 110.

The dielectric unit 140 is disposed corresponding to the mounting region 111 and fills at least a recess region surrounded by the base layer 180, the circuit layer 110 and the protection layer 120, the electronic component 150 is disposed on a side of the dielectric unit 140 away from the base layer 180, and the electronic component 150 is electrically connected to the trace 112 through the dielectric unit 140. In an embodiment, the dielectric unit 140 may be a conductor or a semiconductor, and in this embodiment, the dielectric unit 140 is an anisotropic conductive adhesive, and the anisotropic conductive adhesive has conductivity only in a wire connecting direction of the electronic element 150 and the wire 112, so as to realize directional electrical connection between the electronic element 150 and the wire 112. The electronic component 150 may be a transistor, a resistor, a capacitor, or an inductor, or other microelectronic device or component.

In an embodiment, the shielding unit 160 covers a surface of the electronic component 150 that is not contacted with the dielectric unit 140, that is, the shielding unit 160 covers an exposed surface of the electronic component 150, and the shielding unit 160 is partially disposed in the connection hole 121 and contacts with the connection pad 122 to form an electrical connection, where the shielding unit 160 is electrically connected with the shielding layer 130. In the present embodiment, the shielding unit 160 is silver paste, which is coated on the exposed surface of the electronic component 150 and further extends to contact with the shielding layer 130 and extends into the connection hole 121 to contact with the connection pad 122, and the shielding unit 160 formed by silver paste is electrically connected to the shielding layer 130 and electrically connected to the ground line of the circuit layer 110 through the connection pad 122 to form a continuous shielding structure, which has a better electromagnetic shielding effect. In an embodiment, the thickness of the shielding unit 160 on the side of the electronic component 150 away from the circuit layer 110 is greater than the thickness of the shielding unit 160 on other exposed surfaces of the electronic component 150, in this embodiment, the thickness of the silver paste on the side wall of the electronic component 150 is smaller than the thickness of the silver paste on the top surface of the electronic component 150 away from the circuit layer 110, and the ratio of the thickness of the silver paste on the side wall to the thickness of the silver paste on the top surface may be greater than or equal to 0.5.

Fig. 3A to 3F are schematic views illustrating a manufacturing process and a structure of the circuit board 10 according to the first embodiment of the present invention. The manufacturing method of the circuit board 10 according to the first embodiment of the present invention includes the following steps:

step one: a base layer 180 is provided, and a conductive material layer a is disposed on a surface of the base layer 180.

Specifically, as shown in fig. 3A, a conductive material layer a may be formed on a surface of the base layer 180 by Physical Vapor Deposition (PVD), chemical Vapor Deposition (CVD), adhesion, or crystal growth, and the conductive material layer a may uniformly cover the base layer 180.

Step two: the conductive material layer a is patterned to obtain the circuit layer 110.

Specifically, as shown in fig. 3B, a mask may be formed on the conductive material layer a by forming a photosensitive film, then exposing and etching the mask to pattern the surface of the mask, and then etching the mask and the conductive material layer a by a conventional etching method and removing the mask to obtain the circuit layer 110, where the etched circuit layer 110 includes a mounting region 111 having a thickness smaller than that of other regions and a trace 112 located in the mounting region.

Step three: a protective layer 120 is formed on the surface of the circuit layer 110 away from the base layer 180.

Specifically, as shown in fig. 3C, an insulating material layer is formed on the surface of the circuit layer 110 by wet coating, dry film pressing, etc., a mask is formed on the surface of the insulating material layer on the side away from the circuit layer 110 by forming a photosensitive film, then the mask is exposed and etched to pattern the surface of the mask, and then the mask and the insulating material layer are etched and removed by conventional etching means to obtain a protective layer 120, wherein the protective layer 120 is not disposed in the mounting region 111. The protection layer 120 obtained by etching has a plurality of connection holes 121 and through holes 123 penetrating the protection layer 120, the connection holes 121 are located around the mounting region 111, and the through holes 123 are located on a side of the connection holes 121 away from the mounting region 111.

Step four: a shielding layer 130 is formed on the surface of the protective layer 120 away from the circuit layer 110.

Specifically, as shown in fig. 3D, in this example, the shielding layer 130 may be formed on the surface of the side of the protective layer 120 away from the circuit layer 110 by sputtering, physical vapor deposition, chemical vapor deposition, or applying conductive silver paste, so that the shielding layer 130 covers at least the surface of the protective layer 120 and does not include the area between the connection hole 121 and the mounting region 111, and the shielding layer 130 extends and fills the through hole 123 and contacts the circuit layer 110. A connection pad 122 is disposed in the connection hole 121, so that the exposed circuit layer 110 in the connection hole 121 is covered.

Step five: the electronic component 150 is mounted.

Specifically, as shown in fig. 3E, a dielectric unit 140 is disposed corresponding to the mounting region 111 and fills the recessed region of the mounting region 111, the dielectric unit 140 covers the traces 112, and the electronic component 150 is mounted on one end of the dielectric unit 140 so as not to directly contact the circuit layer 110 or the protection layer 120.

Step six: the shielding unit 160 is formed.

Specifically, as shown in fig. 3F, the exposed surface of the electronic component 150 is covered with silver paste by spraying, printing, spin coating, or the like, the silver paste further extends into the connection hole 121 nearest to the electronic component 150 and contacts the connection pad 122, the silver paste further extends into contact with the shielding layer 130, and the silver paste is solidified by baking, ventilation, or standing, or the like, and finally the shielding unit 160 is formed.

Second embodiment

As shown in fig. 4, a circuit board 20 according to a second embodiment of the present invention is shown in a top view. Fig. 5 is a schematic cross-sectional view of a circuit board along the V-V direction according to a second embodiment of the present invention. The circuit board 20 includes a base layer 280, a circuit layer 210 disposed on a surface of the base layer 280, a protective layer 220 disposed on a side of the circuit layer 210 away from the base layer 280, and a shielding layer 230 disposed on a side of the protective layer 220 away from the circuit layer 210. The circuit board 20 further includes a plurality of electronic components 250, a plurality of dielectric units 240, and a plurality of shielding units 260, where each electronic component 250 is electrically connected to the circuit layer 210 through a corresponding dielectric unit 240. Each shielding unit 260 covers the exposed surface of at least one electronic component 250, at least one conductive sheet 270 is disposed around one or more electronic components 250, the conductive sheet 270 is not in contact with the electronic component 250, and the shielding unit 260 is electrically connected to the shielding layer 230 through the conductive sheet 270.

The circuit layer 210 is disposed on a side surface of the base layer 280, the circuit layer 210 includes a plurality of mounting areas 211, the protective layer 220 and the shielding layer 230 are not disposed on a side of the circuit layer 210, which is far away from the base layer 280, corresponding to the area where the mounting areas 211 are located, and the thickness of the circuit layer 210, which is corresponding to the area where the mounting areas 211 are located, is smaller than that of other areas.

The circuit layer 210 is made of a conductive material, and the circuit layer 210 has good conductivity, and in one embodiment, the circuit layer 210 may be made of a metal simple substance, an alloy, a composite metal or other conductive materials, and in this embodiment, the material of the circuit layer 210 is copper (Cu). The circuit layer 210 is provided with a plurality of wires 212 corresponding to the mounting area 211, the electronic component 250 is provided corresponding to the mounting area 211, the electronic component 250 is electrically connected with the wires 212 through a dielectric unit 240, the wires 212 can extend to be electrically connected with other components, for example, connected with a Central Processing Unit (CPU), and the wires 212 can have other electrical functions, for example, can be used as a signal transmitting antenna; other functional circuitry, such as ground circuitry (not shown), is also included in the circuitry layer 210.

The protection layer 220 is disposed on a side of the circuit layer 210 away from the base layer 280, where the protection layer 220 can protect the covered portion of the circuit layer 210 from oxidation due to contact with air, or from water vapor erosion, or from short circuit due to contact with other conductive materials, or from physical damage due to scratch and bump. The protective layer 220 is an insulating material, and its component may include at least one of Polyimide (PI), polyethylene naphthalate (Polyethylene naphthalate two formic acid glycol ester, PEN), polyethylene terephthalate (polyethylene glycol terephthalate, PET), or ink.

The protection layer 220 is provided with a plurality of through holes 223, the through holes 223 penetrate through the protection layer 220 and expose at least part of the surface of the circuit layer 210, the through holes 223 are disposed around the mounting region 211, and one or more through holes 223 may be provided.

The shielding layer 230 covers the surface of the protection layer 220 away from the circuit layer 210 and fills the through hole 223 to extend to contact with the circuit layer 210, the shielding layer 230 is not disposed in a region corresponding to the mounting region 211, the shielding layer 230 is made of a conductive material, the shielding layer 230 is disposed outside the circuit layer 210 to form a continuous shielding field, and the shielding layer 230 is electrically connected with the circuit layer 210 and is connected with a ground circuit in the circuit layer 210.

The dielectric unit 240 is disposed corresponding to the mounting region 211 and fills at least a recess region defined by the base layer 280, the circuit layer 210, the protection layer 220 and the shielding layer 230, the electronic component 250 is disposed on a side of the dielectric unit 240 away from the base layer 280, and the electronic component 250 is electrically connected to the trace 212 through the dielectric unit 240. In an embodiment, the dielectric unit 240 may be a conductor or a semiconductor, and in this embodiment, the dielectric unit 240 is an anisotropic conductive adhesive, and the anisotropic conductive adhesive has conductivity only in a wire connecting direction of the electronic component 250 and the wire 212, so as to realize directional electrical connection of the electronic component 250 and the wire 212. The electronic component 250 may be a transistor, a resistor, a capacitor, or an inductor, or other microelectronic device or component.

The conductive sheet 270 is disposed on the surface of the shielding layer 230 away from the protective layer 220, the conductive sheet 270 is disposed around the mounting region 211, and the conductive sheet 270 is not in direct contact with the electronic component 250. In one embodiment, at least one conductive sheet 270 is disposed around each mounting region 211, and in other embodiments, at least two conductive sheets 270 are disposed around each mounting region 211, and a plurality of conductive sheets 270 are disposed on opposite sides of the mounting region 211 or around the mounting region 211. The conductive sheet 270 is made of a conductive material, which may be a simple substance, a mixture, or a composite material, for example, the conductive sheet 270 may be a composite gold foil, which includes a conductive adhesive, a copper foil layer, a gold foil layer, and a protective layer that are sequentially stacked, the composite gold foil has high conductivity, and one side of the composite gold foil provided with the conductive adhesive is pressed on the surface of the shielding layer 230 to electrically connect the conductive sheet 270 and the shielding layer 230. The length of the conductive sheet 270 is greater than or equal to 2mm and the width of the conductive sheet is greater than or equal to 2mm.

In an embodiment, the shielding unit 260 covers the surface of the electronic component 250 that is not in contact with the dielectric unit 240, i.e. the shielding unit 260 covers the exposed surface of the electronic component 250, and the shielding unit 260 fills the gap between the electronic component 250 and the conductive sheet 270 and covers the side of the conductive sheet 270 away from the shielding layer 230. In this embodiment, the shielding unit 260 is made of silver paste, the silver paste is coated on the exposed surface of the electronic component 250 and further fills the gap between the electronic component 250 and the conductive sheet 270 and covers one side of the conductive sheet 270 away from the shielding layer 230, the shielding unit 260 made of silver paste is electrically connected with the conductive sheet 270 and the shielding layer 230, and the shielding layer 230 is electrically connected with the grounding circuit of the circuit layer 210, and the shielding unit 260, the conductive sheet 270 and the shielding layer 230 are conducted up and down to form a continuous shielding structure, which has a better electromagnetic shielding effect.

In an embodiment, the thickness of the shielding unit 260 on the side of the electronic component 250 away from the circuit layer 210 is greater than the thickness of the shielding unit 260 on other exposed surfaces of the electronic component 250, in this embodiment, the thickness of the silver paste on the side wall of the electronic component 250 is smaller than the thickness of the silver paste on the top surface of the electronic component 250 away from the circuit layer 210, and the ratio of the thickness of the silver paste on the side wall to the thickness of the silver paste on the top surface may be greater than or equal to 0.5.

Fig. 6A to 6F are schematic views of a manufacturing process structure of a circuit board 20 according to a second embodiment of the present invention. The manufacturing method of the circuit board 20 according to the second embodiment of the present invention includes the following steps:

step one: a base layer 280 is provided, and a conductive material layer a is disposed on a surface of the base layer 280.

Specifically, as shown in fig. 6A, a conductive material layer a may be formed on a surface of the base layer 280 by Physical Vapor Deposition (PVD), chemical Vapor Deposition (CVD), adhesion, or crystal growth, and the conductive material layer a may uniformly cover the base layer 280.

Step two: the conductive material layer a is patterned to obtain a circuit layer 210.

Specifically, as shown in fig. 6B, a mask may be formed on the conductive material layer a by forming a photosensitive film, then exposing and etching the mask to pattern the surface of the mask, and etching the mask and the conductive material layer a by conventional etching means and removing the mask to obtain a circuit layer 210, where the etched circuit layer 210 includes a mounting region 211 having a thickness smaller than that of other regions and a trace 212 located in the mounting region.

Step three: a protective layer 220 is formed on the surface of the circuit layer 210 away from the base layer 280.

Specifically, as shown in fig. 6C, an insulating material layer is formed on the surface of the circuit layer 210 by wet coating, dry film pressing, etc., a mask is formed on the surface of the insulating material layer on the side away from the circuit layer 210 by forming a photosensitive film, then the mask is exposed and etched to pattern the surface of the mask, and then the mask and the insulating material layer are etched and removed by conventional etching means to obtain a protective layer 220, wherein the protective layer 220 is not disposed in the mounting region 211. The protection layer 220 obtained by etching has a plurality of through holes 223 penetrating the protection layer 220, and the through holes 223 are located around the mounting region 211.

Step four: a shielding layer 230 is formed on the surface of the protective layer 220 away from the circuit layer 210 and a conductive sheet 270 is disposed.

Specifically, as shown in fig. 6D, in this example, the shielding layer 230 may be formed on the surface of the side of the protective layer 220 away from the circuit layer 210 by sputtering, physical vapor deposition, chemical vapor deposition, or conductive silver paste, so that the shielding layer 230 is not disposed in the mounting region 211, and the shielding layer 230 extends and fills the through hole 223 and contacts the circuit layer 210. A conductive sheet 270 is disposed on a side of the shielding layer 230 remote from the protective layer 220.

Step five: the electronic component 250 is mounted.

Specifically, as shown in fig. 6E, a dielectric unit 240 is disposed corresponding to the mounting region 211 and fills the recessed region of the mounting region 211, the dielectric unit 240 covers the traces 212, and the electronic component 250 is mounted on one end of the dielectric unit 240 so as not to directly contact the circuit layer 210 or the conductive sheet 270.

Step six: the shielding unit 260 is formed.

Specifically, as shown in fig. 6F, the exposed surface of the electronic component 250 is covered with silver paste by spraying, printing, spin coating, or the like, the silver paste further fills the gap between the electronic component 250 and the conductive sheet 270 and covers the side of the conductive sheet 270 away from the shielding layer 230, and the silver paste is solidified by baking, ventilation, or standing, or the like, and finally the shielding unit 260 is formed.

Hereinabove, the specific embodiments of the present invention are described with reference to the accompanying drawings. However, those of ordinary skill in the art will appreciate that various modifications and substitutions can be made to the specific embodiments of the invention without departing from the spirit and scope thereof. Such modifications and substitutions are intended to be within the scope of the following claims.

Claims

1. The circuit board comprises a circuit layer, a protective layer arranged on one side of the circuit layer and a shielding layer arranged on one side of the protective layer away from the circuit layer, and is characterized by further comprising a plurality of electronic components and a plurality of shielding units, wherein the electronic components are electrically connected with the circuit layer, at least one connecting hole penetrating through the protective layer and exposing the circuit layer is formed around each electronic component, one shielding unit covers at least one exposed surface of the electronic component, each shielding unit is electrically connected with the circuit layer through the connecting hole, each shielding unit is electrically connected with the shielding layer, the shielding units are made of silver paste, and the shielding units completely cover the exposed surfaces of the electronic components and extend into the connecting holes to be electrically connected with the circuit layer and extend into contact with the shielding layer to form electrical connection.

2. The circuit board of claim 1, wherein at least two of said connection holes are disposed around each electronic component, said at least two connection holes being disposed on opposite sides of said electronic component, and a shielding unit being disposed in each of said connection holes and electrically connected to said circuit layer.

3. The circuit board comprises a circuit layer, a protective layer arranged on one side of the circuit layer and a shielding layer arranged on one side of the protective layer away from the circuit layer, and is characterized by further comprising a plurality of electronic components and a plurality of shielding units, wherein the electronic components are electrically connected with the circuit layer, one shielding unit covers at least one exposed surface of the electronic components, at least one conducting strip is arranged around the electronic components, the conducting strip is not in contact with the electronic components, the shielding units are electrically connected with the shielding layer through the conducting strip, silver paste is used as a material of the shielding units, the conducting strip is arranged on one side of the shielding layer away from the protective layer, and the conducting strip is covered on one side of the shielding layer and is electrically connected with the conducting strip.

4. A circuit board according to claim 3, wherein at least two of said conductive strips are disposed around each electronic component, said at least two conductive strips being disposed on opposite sides of said electronic component.

5. The circuit board of claim 4, wherein the conductive sheet is a composite gold foil comprising a conductive adhesive, a copper foil layer, a gold foil layer, and a protective layer laminated in this order.

6. The circuit board of claim 1 or 3, wherein the circuit layer comprises a plurality of mounting areas, a portion of the circuit layer corresponding to the mounting areas is not covered by the protective layer and the shielding layer, a plurality of wires are disposed on the circuit layer corresponding to the mounting areas, and the electronic component is electrically connected with the wires through a dielectric unit.

7. The circuit board of claim 6, wherein the thickness of the circuit layer corresponding to the mounting region is smaller than the thickness of other regions, one of the dielectric units fills the region corresponding to one of the mounting regions, and the dielectric unit is anisotropic conductive adhesive.

8. A circuit board according to claim 1 or 3, wherein a plurality of through holes are provided in the protective layer, and the shielding layer extends into the through holes and is electrically connected to the circuit layer.