CN211656510U

CN211656510U - Circuit board and electronic equipment

Info

Publication number: CN211656510U
Application number: CN202020013580.9U
Authority: CN
Inventors: 史洪宾; 陈曦; 马春军
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2019-12-30
Filing date: 2020-01-02
Publication date: 2020-10-09
Anticipated expiration: 2030-01-02
Also published as: CN113133180A

Abstract

The application relates to the technical field of electronic products, in particular to a circuit board, electronic equipment and a forming method of the circuit board, wherein the circuit board comprises a first board, a middle board and a second board, the middle board is positioned between the first board and the second board and connected with the first board and the second board along the thickness direction, the middle board is a hollow circuit board, and the first board, the middle board and the second board are surrounded to form a cavity; the circuit board further comprises a chip, at least part of the chip is positioned in the cavity, and the chip is welded on the first board and/or the second board; the circuit board further comprises air holes, and the air holes are used for communicating the inside of the cavity with the outside of the circuit board. By utilizing the circuit board, the electronic equipment and the forming method of the circuit board, the cooling rate of a welding spot of a chip is increased, the air permeability is improved, and the problems of welding, environmental reliability, heat dissipation and the like are avoided.

Description

Circuit board and electronic equipment

Technical Field

The present disclosure relates to electronic products, and particularly to a circuit board, an electronic device, and a method for forming the circuit board.

Background

With the development of the electronic industry, the demand of electronic products tends to be more light, thin and miniaturized, and in order to meet the demand, the circuit board arranged in the electronic products is correspondingly miniaturized. At present, due to the need of ensuring that functions which can be realized on the basis of miniaturization are unchanged or even more, after necessary electronic components are arranged on a circuit board, the transverse space of the circuit board cannot be further reduced, and the higher miniaturization requirement cannot be met. The stacking combination of the multilayer boards of the circuit board is generated, but in the stacked combination structure, a closed cavity is formed by combination, and compared with an external chip, a chip arranged in the cavity has higher welding defective rate and poorer environmental reliability, heat dissipation and the like.

SUMMERY OF THE UTILITY MODEL

The application aims to provide a circuit board, electronic equipment and a forming method of the circuit board, so that the cooling rate of a welding spot of a chip is increased, the air permeability is improved, and the problems of welding, environmental reliability, heat dissipation and the like are avoided.

In a first aspect, a circuit board is provided, where the circuit board includes a first board, an intermediate board and a second board, and the intermediate board is located between and connected to the first board and the second board along a thickness direction, the intermediate board is a hollow circuit board, and the first board, the intermediate board and the second board enclose to form a cavity;

the circuit board further comprises a chip, at least part of the chip is positioned in the cavity, and the chip is welded on the first board and/or the second board;

the circuit board further comprises air holes, and the air holes are used for communicating the inside of the cavity with the outside of the circuit board.

Through the design of bleeder vent, can make the gas and the outside circulation in the cavity, through the mode of inside and outside circulation, strengthened the flow of the air in the cavity, avoid the moist environment of high temperature high oxygen that forms in the cavity to solder joint dendritic crystal leads to badness such as electric leakage, short circuit under rosin joint, the high temperature high humidity environment that produces when avoiding inside chip welding, improves the performance and the life of heat dissipation in order to improve the intracavity chip of height.

In one possible design, the air hole is arranged at least one of the following positions: the first plate, the second plate, or the intermediate plate.

The ventilation holes are formed in any one or more of the first plate, the second plate and the middle plate, so that the communication between the cavity and the outside can be better realized while the processing is facilitated.

In one possible design, the intermediate plate has a break gap, the intermediate plate including a first end and a second end, the break gap being formed between the first end and the second end;

the vent is defined by at least the first end portion, the second end portion, the first plate, and the second plate.

Through the form that directly sets up the disconnection breach of disconnection, the deuterogamy is with first board and second board to form required bleeder vent, realization that can make things convenient for fast is to the processing of bleeder vent, practices thrift machining efficiency and processing cost, reduces the processing degree of difficulty.

In one possible embodiment, the disconnection notch includes at least a first disconnection notch and a second disconnection notch, and the first disconnection notch and the second disconnection notch are disposed opposite to each other.

Through being located relative first disconnection breach that sets up with second disconnection breach makes the intercommunication between the breach of disconnection, has improved the area of cavity and the outside intercommunication of circuit board, improves the inside air flow rate of cavity.

In one possible design, the intermediate plate is provided with a recess;

the air holes are at least formed by the surrounding of the grooves and the first plate, or the air holes are at least formed by the surrounding of the grooves and the second plate.

Compared with the design of a breaking notch, the groove is arranged, so that the middle plate can be prevented from being split into a plurality of units, and the assembly is facilitated.

In one possible design, the grooves include at least a first groove and a second groove, and the first groove and the second groove are oppositely arranged.

Through the relative first recess and the second recess that sets up, make direct intercommunication between the recess, improved the area of cavity and the outside intercommunication of circuit board, improve the inside air flow rate of cavity.

In one possible design, the intermediate plate is provided with a through hole that communicates the inside of the cavity with the outside of the circuit board enclosing the cavity portion;

the through hole is the air hole.

The arrangement of the through holes can not lead to the reduction of the welding area of the middle plate, the first plate and the second plate, so that the overall stability and the firmness of the circuit board are reduced.

In one possible design, the through holes include at least a first through hole and a second through hole, and the first through hole is opposite to the second through hole.

Through the first through-hole and the second through-hole that set up relatively, make direct intercommunication between the through-hole, improved the area of cavity and the outside intercommunication of circuit board, improve the inside air flow rate of cavity.

In one possible design, the vent further comprises a third through hole and/or a fourth through hole;

the third through hole is located the first board, the fourth through hole is located the second board, just the third through hole with the fourth through hole respectively with the inside of cavity with the outside intercommunication of circuit board.

Through corresponding third passageway and fourth passageway in first board and the second board setting to set up according to the demand, simple structure, the processing of being convenient for improves the flow rate of the interior air of cavity.

In one possible design, the circuit board is provided with the third through hole and the fourth through hole, and along the thickness direction, the projection of the third through hole is at least partially overlapped with the projection of the fourth through hole.

So as to ensure that better ventilation effect can be achieved when the first plate and the second plate are provided with corresponding through holes.

In one possible design, the first plate, the middle plate and the second plate are connected through welding spots along the thickness direction, and a welding spot layer is formed;

the air holes are formed in the welding spot layer.

Through setting up the bleeder vent in the form on solder joint layer to avoid the destruction to first board, second board and intermediate plate structure, can realize communicateing cavity and outside.

In a second aspect, an electronic device is provided, which includes a housing and a circuit board, wherein the circuit board is the circuit board described in any one of the above.

Through setting up the circuit board in the casing, can make full use of the space of circuit board thickness direction, accomplish equipment miniaturization basis on, guarantee the service function and the effect of circuit board, avoid producing welding, environmental reliability and heat dissipation scheduling problem.

In a third aspect, there is provided a molding method of a circuit board including a first plate, an intermediate plate, and a second plate in a thickness direction, the circuit board having a cavity, the molding method including:

welding a chip on the first plate and/or the second plate, and enabling at least part of the chip to be located in the cavity;

processing the air holes at least one of the following positions: the first plate, the second plate or the middle plate are communicated with the inside of the cavity and the outside of the circuit board through the air holes.

Before the multilayer board with the cavity is formed, in order to realize that the cavity can be communicated with the outside through the air holes, at least the air holes are processed in the first board, the second board and the middle board which form the cavity, and then the multilayer board with the chip is formed by welding. After the welding, because be in airtight state in the cavity, cause the inside chip of cavity to produce welding, environmental reliability and heat dissipation scheduling problem easily, through the bleeder vent that sets up in advance to make the cavity be in the intercommunication state in the outside, guarantee inside ventilation effect.

In one possible design, when the vent is processed in at least one of the first plate, the second plate, and the intermediate plate to communicate the inside of the cavity with the outside of the circuit board through the vent, the molding method includes:

and processing a disconnection notch on the middle plate, and enclosing the disconnection notch, the middle plate, the first plate and the second plate into the air holes.

Through directly seting up the form of breaking away the breach at the intermediate lamella to form the bleeder vent with first board and second board combination, the processing of intermediate lamella has been reduced to this kind of mode, improves machining efficiency.

processing a groove on the middle plate, wherein the groove is used for communicating the inside of the cavity with the outside of the circuit board;

along the thickness direction, the air holes are formed by the grooves and the first plate in a surrounding mode, or the air holes are formed by the grooves and the second plate in a surrounding mode.

This kind of processing mode is comparatively simple, improves the efficiency that the intermediate lamella set up the bleeder vent, and the recess of seting up can avoid being a plurality of units with the intermediate lamella split, and the cooperation of the intermediate lamella of being convenient for and first board and second board improves the packaging efficiency.

In one possible design, the intermediate plate includes a third plate and a fourth plate in the thickness direction, and when the intermediate plate is provided with the groove, the forming method includes:

processing a third breaking notch on the third plate, wherein the third breaking notch, the third plate and the fourth plate enclose the groove; alternatively, the first and second electrodes may be,

and processing the third breaking notch on the fourth plate, wherein the groove is defined by the third breaking notch, the third plate and the fourth plate.

Through this kind of form of setting up the disconnection breach earlier, then make up the concatenation and form the recess again, guarantee the better processing effect of recess, improve machining efficiency, avoid the overcut problem that takes place when directly processing the recess. And a disconnection notch is arranged on one of the third plate and the fourth plate, and the third plate, the fourth plate and the disconnection notch are combined to form a groove processing mode, so that a better groove processing effect is ensured, and the processing efficiency is improved. The condition that the middle plate is scrapped due to the fact that the machined groove is large in error due to error operation when the groove is formed in the integrated middle plate is avoided. The mode of connecting after seting up the second opening on the board now can reduce the requirement to operator and machining precision, practices thrift the processing cost.

the middle plate is processed with a through hole which communicates the inside of the cavity with the outside of the circuit board, and the through hole is the air hole.

Through the through-hole that sets up at the intermediate lamella, can make on the basis of cavity and outside intercommunication, can not lead to the welding area reduction of intermediate lamella and first board and second board, and can not destroy the stability of intermediate lamella and first board and second board coupling part, improve the mechanical properties of circuit board.

In one possible design, the intermediate plate includes a fifth plate, a third plate, and a fourth plate in the thickness direction, and when the through hole is machined in the intermediate plate, the molding method includes:

and processing a fourth breaking notch on the third plate, and enclosing the fourth breaking notch, the third plate, the fourth plate and the fifth plate into the through hole.

Through this kind of form of setting up the disconnection breach earlier, then make up the concatenation and form the through-hole again, guarantee the better processing effect of through-hole, improve machining efficiency.

In one possible design, the molding method further includes:

and processing the third through hole on the first plate and/or processing the fourth through hole on the second plate so as to enable the third through hole and the fourth through hole to respectively communicate the inside of the cavity with the outside of the circuit board.

Through setting up corresponding third through-hole and fourth through-hole at corresponding first board and second board to set up according to the demand, simple structure, the processing of being convenient for improves the flow rate of air in the cavity.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.

Drawings

Fig. 1 is a schematic structural diagram of a circuit board according to an embodiment of the present disclosure;

FIG. 2 is an enlarged view of a portion A of FIG. 1;

FIG. 3 is a schematic view of a first plate and an intermediate mating structure provided in an embodiment of the present application;

FIG. 4 is a partial enlarged view of the portion B in FIG. 3, wherein the dotted line portion is a schematic view of the inner structure of the ventilation hole;

FIG. 5 is a schematic diagram of a first plate structure provided in the present application;

FIG. 6 is a schematic diagram of a second plate structure according to an embodiment of the present disclosure;

fig. 7 is a schematic diagram of a middle plate structure according to an embodiment of the present application, in which a direction indicated by an arrow L is a length direction of the middle plate, and a direction indicated by an arrow W is a width direction of the middle plate;

FIG. 8 is a schematic diagram of another structure of a middle plate according to an embodiment of the present disclosure;

FIG. 9 is a schematic diagram of another structure of a middle plate according to an embodiment of the present disclosure;

FIG. 10 is a schematic diagram of another structure of a middle plate according to an embodiment of the present disclosure;

FIG. 11 is a schematic diagram of a structure of a middle plate with grooves according to an embodiment of the present disclosure;

fig. 12 is a top view of a circuit board according to an embodiment of the present disclosure;

FIG. 13 is a sectional view of portion C of FIG. 12;

FIG. 14 is an enlarged view of a portion D of FIG. 13;

fig. 15 is a schematic diagram of a simple structure of a portion in a circuit board cavity according to an embodiment of the present application, wherein a direction indicated by an arrow is a thickness direction;

fig. 16 is a schematic view of a middle plate provided with grooves according to an embodiment of the present application, wherein a direction indicated by an arrow is a length direction L of the middle plate;

FIG. 17 is a schematic view of another embodiment of the present disclosure illustrating a middle plate with a groove;

FIG. 18 is a schematic view of another embodiment of the present disclosure illustrating a middle plate with a groove;

FIG. 19 is a schematic view of a solder joint layer with air holes according to an embodiment of the present disclosure;

FIG. 20 is an exploded view of an embodiment of the present application showing a cavity in a middle plate;

FIG. 21 is an exploded view of the partial section of FIG. 20;

FIG. 22 is a flow diagram A of an alternative process configuration of FIG. 20;

FIG. 23 is a flow diagram B of an alternative process of FIG. 20;

FIG. 24 is a flow diagram C of an alternative process of FIG. 20;

FIG. 25 is a schematic view of a partial structure of a through hole formed in a middle plate according to an embodiment of the present disclosure;

FIG. 26 is an exploded view of a mid-plane of FIG. 25;

FIG. 27 is a partial exploded view of the tooling assembly of FIG. 26;

FIG. 28 is a flow diagram A of one of the processing steps of FIG. 26;

FIG. 29 is a flow diagram B of a process engagement of FIG. 26;

FIG. 30 is a flow diagram C of one of the processing steps of FIG. 26;

FIG. 31 is a flow chart D of a process set-up in FIG. 26.

Reference numerals:

1-a first plate; 2-a second plate; 3-a middle plate; 31-a third plate; 311-third break notch; 311 a-third end; 311 b-fourth end; 312-a barrier layer; 313-a fourth break notch; 313 a-a fifth end; 313 b-a sixth end; 32-a fourth plate; 33-a fifth plate; 4-electronic components; 41-chip; 5-a communicating part; 51-air holes; 511-a via; 512-break notch; 512 a-first end portion; 512 b-second end; 512 c-first break notch; 512 d-second break notch; 513-grooves; 52-fourth via; 53-third via; 6-screw holes; 7-a cavity; 8-welding spot layer; 9-adhesive layer.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and together with the description, serve to explain the principles of the application.

Detailed Description

The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

An embodiment of the present application provides an electronic device, as shown in fig. 1, the electronic device includes a housing and a circuit board, the circuit board is installed in the housing, and the electronic device may be a mobile phone, a tablet computer, and other miniaturized electronic products, which is not limited herein.

With the development of the electronic industry, the demand for electronic products tends to be more light, thin and compact, and in order to meet the demand, the circuit board disposed therein is correspondingly miniaturized. At present, due to the need to ensure that the functions which can be realized on the basis of miniaturization are unchanged or even more, the circuit board further comprises a chip 41 and other electronic components 4, and after the necessary electronic components 4 are arranged on the circuit board, the transverse space (i.e. the length and width directions of the circuit board) cannot be further reduced, and the higher miniaturization requirement cannot be met.

In this case, in order to meet the requirement when the lateral space is required to be more miniaturized, the space in the thickness direction of the circuit board may be used, and the requirement for the connection position of the sufficient electronic component 4 can be ensured to be met on the basis of the miniaturization of the circuit board. Specifically, as shown in fig. 1 and 2, the circuit board includes a first board 1, an intermediate board 3 and a second board 2 along the thickness direction, the intermediate board 3 is located between the first board 1 and the second board 2 and connected to the first board 1 and the second board 2, the intermediate board 3 is a hollow circuit board, the first board 1, the intermediate board 3 and the second board 2 enclose a cavity 7, and the first board, the second board 2 and the intermediate board 3 are all board-shaped circuit board structures and need to be used for connecting the electronic component 4, so the enclosed cavity 7 is in a closed state, and the air inside the cavity 7 is not circulated with the air outside the circuit board. Through this kind along thickness direction, with the combination of piling up of multiply wood and the form of vacuole 7, required electronic components 4 can all be arranged on first board 1 and second board 2, adopt the increase in thickness direction space to compensate with the reduction of horizontal size, make chip 41 isoelectron components 4 arrange in corresponding first board 1 and second board 2 in order, when satisfying the better overall arrangement requirement of electronic components 4, the further miniaturization of circuit board has been realized, so that satisfy the demand of electronic product frivolousization, miniaturization.

Optionally, the layout of the circuit board disposed therein can be adaptively adjusted according to the requirements of the thickness space and the size of the lateral space of different electronic products, for example, when the layout requirements of the electronic components 4 arranged thereon cannot be met when a double-layer circuit board having a cavity 7 is formed by connecting the first board 1, the second board 2 and the middle board 3, if the electronic product has a certain space along the thickness direction of the circuit board, the laminated board can be added along the thickness direction, namely, the first plate 1, the second plate 2, and the like are repeatedly connected in the thickness direction continuously through the intermediate plate 3 on the basis of the first plate 1, the second plate 2, and the intermediate plate 3, in the form of a multilayer board having a plurality of cavities 7 in the thickness direction, to miniaturize the circuit board while satisfying the demand for the layout of the electronic components 4 on the circuit board. The number and the positions of the layers of the multilayer board and the number and the positions of the cavities 7 formed by matching the layers of the multilayer board are not limited, and can be adjusted adaptively according to actual conditions.

Specifically, as shown in fig. 12, 13 and 14, in the multilayer circuit board composed by stacking, in order to ensure the reasonableness of the layout of the electronic components 4 connected thereto and to improve the lateral space utilization of the circuit board, at least a part of the chip 41 is located in the cavity 7, and the chip 41 is soldered to the first board 1 and/or the second board 2. When the electronic component 4 such as the chip 41 is soldered to a circuit board to form a plurality of pads and finally the pad layer 8 is formed, the chip 41 is connected to the circuit board by the pins in the form of pads at positions corresponding to the pins.

When the chip 41 is soldered to a circuit board, in order to improve the soldering performance, the added flux is used to remove surface oxides during soldering, and simultaneously, the surface reoxidation can be prevented, the surface tension of the solder is reduced, and the quality of electronic products is improved.

In addition, the chip 41 has different Packaging forms according to different functions, such as Ball Grid Array (BGA), Land Grid Array (LGA), Quad Flat No-lead (QFN), Wafer Level Chip Scale Package (WLCSP), and the like.

In general, when any kind of chip is soldered to a circuit board, the main components of the material used for soldering include silver, tin, and copper, and the ratio of the main components of the soldering material is different depending on the chip 41 package, so that the effect of connecting the chip 41 to the circuit board is improved.

In the structural design of the multilayer board provided for miniaturization, when the chip 41 is soldered to the first board 1 or the second board 2 in the cavity 7, on the one hand, after the chip 41 is soldered to the cavity 7, the cavity 7 has a closed structure, so that each solder joint in the cavity 7 is slowly cooled, and a longer growth time is provided for a silver dendrite component in a material used for soldering. And the structure of the closed cavity 7 is that the soldering flux used in welding can not be diffused in time, and the acidic soldering flux residue provides an environment for the rapid growth of silver dendrites. When the chip 41 is soldered to a circuit board using solder having a silver content of more than three percent, silver dendrites such as WLCSP are liable to be precipitated. On the other hand, for some chips 41, such as LGA, QFN \ BGA \ WLCSP, etc., after the chip 41 and the circuit board are connected by solder joints in the cavity 7, in order to improve the mechanical reliability of the connection, the solder joints between the chip 41 and the circuit board are underfilled with underfill adhesive or the passive component dots are encapsulated with adhesive. When the chip 41 is filled with underfill or the passive component is encapsulated, local humidity in the dispensed bubbles is higher in the closed cavity 7 in a high-temperature and high-humidity environment, so that an environment is provided for rapid growth of tin dendrites, and finally, electric leakage or poor short circuit occurs between welding points. In the sealed cavity 7, the deposition of silver dendrites, tin dendrites, or dendrites of other components of the solder causes a leak or a short circuit failure in the lead portion when the chip 41 is connected to the circuit board.

In a third aspect, when the chip 41 is connected to the circuit board, and when the density of the leads is high, for example, when the pitch of the solder joints is less than 0.4mm, the chip 41 in the cavity 7 is soldered, because the cavity 7 is in a sealed state after the first plate 1, the second plate 2 and the middle plate 3 are soldered, the circuit boards are combined to form the cavity 7 by soldering while part of the chip 41 is soldered to the first plate 1 and/or the second plate 2 or in a short time, so as to facilitate assembly of other electronic components 4, in this process, because the interval between formation of the cavity 7 and soldering of the chip 41 in the cavity 7 is short, even the chip is soldered at the same time. When the solder is placed in a welding furnace for high-temperature heating so that the welding part fully achieves the welding effect, the welding hot air is too late to fully heat the chip 41 in the cavity, and the nitrogen in the welding furnace for preventing the oxidation of the solder cannot fully flow into the cavity 7, so that the oxygen concentration in the cavity 7 is too high, the oxidation of the solder is caused, and finally the chip 41 in the cavity 7 is more sensitive to high-temperature warping and poor cold joint easily occurs.

In the fourth aspect, when the high-heat-generation Chip 41 such as a PMU (Power Management Unit), an SOC (System on Chip) is connected to the cavity 7, the structure of the closed cavity 7 may cause a problem of untimely heat dissipation, which affects the performance and the service life of the Chip 41.

Therefore, in order to solve the above four problems simultaneously in the design of the multilayer board having the cavity 7, and to avoid the occurrence of defects in the chip 41 provided in the cavity 7 formed in the multilayer board, the cavity 7 is communicated with the outside by providing the communication portion 5. That is, the communicating portion 5 is the air hole 51, the air hole 51 communicates the inside of the cavity 7 with the outside of the circuit board, the air hole 51 can be disposed in any part of the circuit board enclosed into the cavity 7 or a gap formed by connection between the circuit boards, as long as the cavity 7 can communicate with the outside air, the flow of air in the cavity 7 is enhanced by means of internal and external circulation, the high-temperature, high-oxygen and humid environment formed in the cavity 7 is avoided, the cooling rate of the welding point of the chip 41 is increased, the air permeability is improved, thereby avoiding the defects of insufficient solder, electric leakage, short circuit and the like generated when the chip 41 is welded inside, improving the performance of the chip 41 in the cavity 7 and prolonging the service life.

More specifically, in order to ensure that the air holes 51 are formed to better solve the problems of soldering, environmental reliability, heat dissipation and the like generated when the chip 41 is connected to the circuit board in the cavity 7, the arrangement positions of the air holes 51 are illustrated as follows:

A. when the chip 41 in the cavity 7 is soldered to the first board 1 or the second board 2, the solder ball used in the WLCSP, for example, has a composition of the main component in which tin is 95.5% of silver and copper is 4% of copper and 0.5% of silver, is more than three% by mass. Because the cavity 7 is internally sealed, the welding spot of the chip 41 in the cavity is cooled slowly to provide longer growth time for the silver dendrite, the soldering flux in the cavity has no diffusion channel, and the acid soldering flux residue provides an environment for the rapid growth of the silver dendrite.

B. When the chip 41 soldered in the cavity 7 needs to be glued to the gap to improve the connection reliability, the humidity of the glue provides an environment for the rapid growth of tin dendrites. In this case, it is necessary for the position of the vent hole 51 to be as close to the dispensing position as possible so that moisture can be more promptly volatilized.

C. When the chip 41 in the cavity 7 is welded with the first board 1 or the second board 2, and the distance between the welding points on the chip is smaller than 0.4mm, the internal air permeability is poor due to the sealing of the cavity 7, the chip 41 in the cavity cannot be sufficiently heated by the welding hot air, in addition, nitrogen for preventing the oxidation of the solder in the welding furnace cannot sufficiently flow into the cavity 7, so that the internal oxygen concentration is too high, the solder is oxidized, and finally, poor cold welding occurs on a fine-pitch device of which the chip 41 in the cavity 7 is more sensitive to high-temperature warping. In this case, as for the position where the ventilation holes 51 are provided, it is necessary to be as close as possible to the fine pitch position where cold joint is liable to occur, in order to be heated and reduce the oxygen concentration more efficiently.

D. When the chip 41 in the cavity 7 is of a high heat generating type, such as PMU or SOC, the sealing of the cavity 7 causes the chip 41 to dissipate heat poorly, which affects the performance and lifetime of the chip 41. In this case, as for the position where the ventilation holes 51 are provided, it is necessary to be as close as possible to the chip 41 that generates heat highly, in order to more efficiently dissipate the heat.

In summary, for the positions of the air holes 51, the positions and the number of the air holes 51 can be adaptively adjusted according to the types and the positions of the chips 41 arranged in the cavity 7, so that the arranged air holes 51 can effectively avoid the problems of welding, environmental reliability, heat dissipation and the like of the chips 41 in the cavity 7.

For the specific matching between the structure of the air hole 51 and the circuit board, the following detailed description will be given by taking the structural matching of a double-layer board formed by connecting the first board 1, the middle board 3 and the second board 2 as an example, optionally, the first board 1 is a main board, the second board 2 is a sub-board, and the middle board 3 is a frame board:

as shown in fig. 8, in the thickness direction, the two sides of the middle plate 3 are covered with solder joints, and the first plate 1 and the second plate 2 are connected by the solder joints to form a solder joint layer 8, which is respectively welded to the first plate 1 and the second plate 2, so as to ensure the connection stability and firmness of the first plate 1, the second plate 2 and the middle plate 3.

Optionally, as shown in fig. 3, in the thickness direction, screw holes 6 are uniformly distributed around the first plate 1, the second plate 2, and the middle plate 3, and bolts pass through the screw holes 6 to fixedly connect the first plate 1, the middle plate 3, and the second plate 2, so that the stability and the firmness of the connection fit are further improved by this form of fixed connection.

As shown in fig. 1, 18 and 19, the vent hole 51 may be provided at least one of: the first plate 1, the second plate 2 or the middle plate 3, and/or the vent 51 is arranged on any welding point layer 8 between the first plate 1, the second plate 2 and the middle plate 3. The gas flow is generated by providing at least one of the first plate 1, the second plate 2, the middle plate 3, and the solder joint layer 8 with a vent hole 51 so as to communicate the cavity 7 with the outside. And, adopt in the form that sets up bleeder vent 51 in at least one in first board 1, second board 2 and intermediate lamella 3 to can better realize cavity 7 and outside intercommunication when processing. And through setting up bleeder vent 51 in the form of solder joint layer 8 to avoid the destruction to first board 1, second board 2 and intermediate lamella 3 structure, can realize communicating cavity 7 with the outside, make cavity 7 and outside production gas flow.

Alternatively, as shown in fig. 19, when the air holes 51 are disposed in the solder joint layer 8, for the air holes 51 disposed in the solder joint layer 8, after the first plate 1, the second plate 2 and the middle plate 3 are connected by solder joints, the air holes 51 may be opened in the corresponding solder joint layer 8, or after the positions of the air holes 51 are pre-disposed, in the process of connecting the first plate 1, the second plate 2 and the middle plate 3 by solder joints, except for the preset position portion, the air holes 51 may be formed in the gap where the preset position is located by solder joints, or the air holes 51 of the solder joint layer 8 may be processed in other forms, which are not specifically limited herein. And, the distance between two adjacent solder joints is between 0.5mm and 0.7mm, and for the airing hole 51 provided in the solder joint layer 8, the length of the airing hole 51 in the corresponding length direction L is within the range of 2 solder joints to 1/3 in the length direction L of the middle plate 3 (as indicated by an arrow in fig. 7), and/or the length of the airing hole 51 in the corresponding width direction W is within the range of 2 solder joints to 1/3 in the width direction W of the middle plate 3 (as indicated by an arrow in fig. 7). So as to avoid that the welding spot removing area of the corresponding part is larger due to the overlong arranged air holes 51, and further increase the welding spot stress at the two sides of the thickness direction of the middle plate 3 in the peripheral area, thereby influencing the reliability of removing the welding spots at the upper side and the lower side of the thickness direction of the middle plate 3 in the welding spot peripheral area. And too small a solder joint removal area may result in poor air permeability for the purpose of improving solder quality, environmental reliability, and heat dissipation of the chip 41 in the cavity 7.

As a specific embodiment of the present application, as shown in fig. 7 and 8, when the vent hole 51 is located at least in the middle plate 3, the vent hole 51 communicates the inside of the cavity 7 with the outside of the circuit board, so as to avoid damaging the structures of the first plate 1 and the second plate 2 for connecting the chip 41, and improve the structural stability of the circuit board. The specific arrangement position thereof and the size of the area of the vent hole 51 communicating the cavity 7 with the outside are not particularly limited.

It should be emphasized here that, when the middle plate 3 is provided with the ventilation holes 51, since the middle plate 3 is a member connecting the first plate 1 and the second plate 2, full-welded points are uniformly distributed at the connection positions of the middle plate 3 and the first plate 1 and the second plate 2 in the thickness direction, and further fixedly connected by bolts, in order to ensure the reliability of the connection of the first plate 1 and the second plate 2, the ventilation holes 51 are preferably located in areas with lower stress away from the bolts or the welding points such as corners of the middle plate 3, so as to avoid reducing the reliability of the connection of the middle plate 3 and the first plate 1 and the second plate 2 while providing the ventilation holes 51.

Specifically, as shown in fig. 8, 14 and 15, the air holes 51 formed in the middle plate 3 may be square holes or polygonal holes, or may be round holes, and along the thickness direction, in order to save the space, the thickness of the middle plate 3 is limited, and if the air holes are formed as round holes, the size of the passage is limited, so that the air holes can be adjusted in the direction perpendicular to the thickness direction according to the actually required ventilation and heat dissipation area by the arrangement of the square holes, and thus different requirements can be met. The following description will be made by taking an example of providing a non-circular hole in the middle plate 3, and the specific structure thereof may have various forms:

wherein, as shown in fig. 8, the middle plate 3 has a breaking notch 512; the middle plate 3 comprises a first end 512a and a second end 512b, and a disconnection gap 512 is formed between the first end 512a and the second end 512 b; the ventilation hole 51 is defined by at least the first end 512a, the second end 512b, the first plate 1 and the second plate 2. That is, by providing the form of the disconnection gap 512 on the middle plate 3, when the middle plate 3 is connected with the first plate 1 and the second plate 2, the first plate 1 and the second plate 2 can cover both sides of the disconnection gap 512 in the thickness direction to form the airing hole 51 communicating the cavity 7 with the outside in combination. By adopting the form of arranging the breaking notches 512, according to the requirements of the positions and the number of the arranged middle air holes 51, the breaking notches 512 can be directly processed in the material preparation work before the middle plate 3 is connected with the first plate 1 and the second plate 2, when the number of the breaking notches 512 is more than 1, as shown in fig. 9 and 10, the middle plate 3 is divided into a plurality of units, and the plurality of units can be the same or different according to the different positions of the breaking notches 512. By adopting the mode, the air holes 51 can be processed conveniently and quickly, the processing efficiency and the processing cost are saved, and the processing difficulty is reduced.

The breaking gap 512 is formed by cutting the hollow middle plate 3, which has a generally square frame structure, at a position where the middle plate 3 needs to be provided with the vent holes 51, and forming a first end 512a and a second end 512b at a fracture part, and forming a gap between the first end 512a and the second end 512b, so as to form the breaking gap 512. The form of disconnection breach 512 through directly setting up this kind of disconnection, the deuterogamy is with first board 1 and second board 2 to form required bleeder vent 51, can make things convenient for quick realization to bleeder vent 51's processing, practice thrift machining efficiency and processing cost, reduce the processing degree of difficulty.

Optionally, as shown in fig. 9 and 10, when there are a plurality of the breaking notches 512, the breaking notches 512 at least include a first breaking notch 512c and a second breaking notch 512d, and the first breaking notch 512c and the second breaking notch 512d are disposed opposite to each other. Through being located relative first disconnection breach 512c that sets up with second disconnection breach 512d makes the intercommunication between the breach of disconnection, has improved the area of cavity 7 with the outside intercommunication of circuit board, improves the inside air flow rate of cavity 7, has guaranteed the better ventilation effect of bleeder vent 51.

In order to further improve the ventilation effect of the first breaking notch 512c and the second breaking notch 512d as the ventilation hole 51, the projection of the first breaking notch 512c on the vertical surface of the middle plate 3 at least partially coincides with the projection of the second breaking notch 512d on the vertical surface of the middle plate 3.

As for the vertical surface of the middle plate 3, as shown in fig. 1, since the first plate 1, the second plate 2, and the middle plate 3 are all planar plates, the three are arranged in the thickness direction (the direction indicated by the arrow in fig. 13), so that the plane of the middle plate 3 is perpendicular to the thickness direction, that is, the vertical surface of the middle plate 3 is parallel to the thickness direction.

In the above, the first breaking notch 512c and the second breaking notch 512d are oppositely arranged, and it can be understood that, as shown in fig. 9 and 10, the middle plate 3 is a frame plate structure having two sets of oppositely arranged side plates to be connected to form a closed frame structure. One of the two opposite side plates is provided with a first breaking notch 512c, and the other is provided with a first breaking notch 512 c.

More specifically, as shown in fig. 15, 16, 17 and 18, the ventilation holes 51 provided in the middle plate 3 may also take the following form: the intermediate plate 3 is provided with a groove 513, the groove 513 communicating the inside of the cavity 7 with the outside of the circuit board; along the thickness direction, at least the groove 513 and the first plate 1 enclose the vent hole 51, or at least the groove 513 and the second plate 2 enclose the vent hole 51. That is, through the positions and the number of the air holes 51, corresponding grooves 513 are processed in the material preparation work before the middle plate 3 is connected with the first plate 1 and the second plate 2, the grooves 513 are arranged to be compared with the design of the breaking notches 512, and the grooves 513 formed in the process can avoid the middle plate 3 from being split into a plurality of units, so that the assembly is facilitated. When the shapes of the plurality of cells of the same middle plate 3 are different, the assembling time is increased when the middle plate 3 is matched with the first plate 1 and the second plate 2, and the arrangement of the groove 513 can save the assembling time and facilitate the assembling.

When a plurality of grooves 513 are provided, the grooves 513 at least include a first groove and a second groove, and the first groove and the second groove are oppositely provided. Through the first groove and the second groove which are oppositely arranged, the grooves 513 are directly communicated, the area of the cavity 7 communicated with the outside of the circuit board is increased, and the air flow rate in the cavity 7 is increased.

And in order to further improve the ventilation effect of the provided first and second grooves as the ventilation holes 51, the projection of the first groove on the vertical surface of the middle plate 3 at least partially coincides with the projection of the second groove on the vertical surface of the middle plate 3.

In one possible design, for the grooves 513 to be provided, the depth of the grooves 513 in the thickness direction is between 1/3-2/3 of the thickness of the intermediate plate 3. And the distance between the bottom wall of the groove 513 and the side wall of the intermediate plate 3 in the thickness direction is 0.3mm or more, the length of the groove 513 in the corresponding length direction L (the direction indicated by an arrow in fig. 7) of the groove 513 provided in the length direction L of the intermediate plate 3 is in the range of 0.5mm to 1/3 in the length of the intermediate plate 3, and/or the length of the groove 513 in the corresponding width direction W (the direction indicated by an arrow in fig. 7) of the groove 513 provided in the width direction W of the intermediate plate 3 is in the range of 0.5mm to 1/3 in the width of the intermediate plate 3. So as to avoid that the too long recess 513 will reduce the flatness and strength of the middle plate 3 in the peripheral area of the slot, and affect the welding quality and reliability of the welding spots on both sides of the middle plate 3 in the thickness direction of the peripheral area of the slot. Also, too small a recess 513 causes a problem of poor air permeability, failing to achieve the purpose of improving the bonding quality of the chip 41 inside the cavity 7, environmental reliability, and heat dissipation.

It should be emphasized that the groove 513 may be a square groove or an arc groove with a curvature, and the specific structure is not limited in this respect. And no matter the form that the breaking notch 5112 is arranged on the middle plate 3 or the groove 13 is arranged to realize the structural matching of the air holes 51, the processing mode is simple, and the required processing precision of the air holes 51 is convenient to guarantee. However, when the airing holes 51 are formed by using the above-mentioned two structures, since the breaking notches 512 and the grooves 513 are at least partially formed to require the first plate 1 and/or the second plate 2 to be fitted to form the airing holes 51, the intermediate plate 3 has no welding point to connect the first plate 1 or the second plate 2 corresponding to the positions of the airing holes 51, as compared to when the airing holes 51 are directly formed. Resulting in a reduction in the soldering area with the first board 1 and the second board 2, and a reduction in the stability and reliability of the circuit board as a whole. In order to prevent the stability of connection from being reduced on the basis of the provision of the ventilation holes 51 in the intermediate plate 3, optionally, as shown in fig. 25, the intermediate plate 3 is provided with through holes 511, and the through holes 511 communicate the inside of the cavity 7 with the outside of the circuit board surrounding the cavity 7; the through hole 511 is an air hole 51, and the through hole 511 is preferably a non-circular hole.

For the arrangement of the through holes 511, when there are a plurality of through holes, similarly, the through holes 511 at least include a first through hole and a second through hole, the first through hole and the second through hole are oppositely arranged, and the through holes 511 are communicated through the oppositely arranged first through hole and second through hole, so that the area of the cavity 7 communicated with the outside of the circuit board is increased, and the air flow rate inside the cavity 7 is increased.

Optionally, in order to further improve the ventilation effect of the first through hole and the second through hole as the ventilation hole 51, along the vertical plane of the middle plate 3, the projection of the first through hole and the projection of the second through hole at least partially coincide.

Wherein, the diameter of the through hole 511 can be between 1/3-2/3 of the thickness of the middle plate 3, and along the thickness direction, the distance from the inner side wall of the through hole 511 to the edge of the middle plate 3 is at least more than or equal to 0.3 mm. For example, when the thickness of the middle plate 3 is 1.2mm, the through holes 511 are between 0.4mm and 0.6 mm. Therefore, the flatness and the strength of the middle plate 3 in the peripheral area of the through hole 511 are prevented from being reduced by the overlarge through hole 511, and the quality and the reliability of welding spots on two sides of the middle plate 3 in the thickness direction in the peripheral area of the through hole 511 are further influenced. Also, too small a through hole 511 causes a problem of poor air permeability, failing to achieve the purpose of improving the bonding quality of the chip 41 inside the cavity 7, environmental reliability, and heat dissipation.

It should be emphasized that, in the structure of providing the through hole 511 on the middle plate 3, the through hole 511 may be circular, elliptical or square, the number of the through holes 511 is not limited, and the axis of the through hole 511 is located at the symmetrical center of the middle plate 3 along the thickness direction, so as to ensure the flatness and strength of the middle plate 3.

In addition, in the thickness direction, when the welding points are arranged on the part of the middle plate 3 at the position of the through hole 511 to connect the first plate 1 and the second plate 2, the welding points of the part are non-functional welding points and are only used for fixing and connecting, so that the problem of assembly function failure caused by the reduction of the reliability of the welding points at the periphery of the through hole 511 when the strength of the middle plate 3 is reduced due to the through hole 511 is avoided.

The present application also provides a specific embodiment, as shown in fig. 3, 4, 5 and 6, the vent 51 may be further located on the first plate 1 and/or the second plate 2, and the vent 51 further includes a third through hole 53 and/or a fourth through hole 52; the third through hole 53 is located on the first plate 1, the fourth through hole 52 is located on the second plate 2, and the third through hole 53 and the fourth through hole 52 communicate the inside of the cavity 7 with the outside of the circuit board, respectively. Through set up corresponding third through-hole 53 and fourth through-hole 52 at corresponding first board 1 and second board 2 to set up according to the demand, this third through-hole 53 and fourth through-hole 52 can be the drilling at first board 1 and second board 2 directly, and to the diameter of drilling, to the board of drilling surrounding area can produce the problem of roughness and intensity when drilling too big, and then influences the welding quality and the reliability of peripheral zone chip 41. When the drilling is too small, the air permeability is poor, and the purposes of improving the welding quality, the environmental reliability and the heat dissipation of devices in the cavity cannot be achieved. Alternatively, the drilling position may be such that the diameter of the drill hole is between 0.5mm and 2mm, which reduces the above-mentioned risks.

It should be emphasized here that the positions of the drill holes and the number of the drill holes are not limited, and may be adaptively adjusted according to the layout of the actual circuit board.

In particular, in order to ensure that the first plate 1 and the second plate 2 are provided with the corresponding ventilation holes 51, a better ventilation effect can be achieved. The circuit board is provided with a third through hole 53 and a fourth through hole 52, and along the thickness direction, the projection of the third through hole 53 is at least partially overlapped with the projection of the fourth through hole 52. In order to adopt the form that sets up of relative arrangement, guarantee better air flow effect, improve heat exchange efficiency.

As a specific embodiment of the present application, as shown in fig. 20 and 26, with respect to the above-mentioned circuit board, there is also provided a method for molding a circuit board:

welding the chip 41 on the first plate 1 and/or the second plate 2, and enabling at least part of the chip 41 to be located in the cavity 7;

the air holes 51 are processed at least one of the following positions: a first plate 1, a second plate 2 or an intermediate plate 3 to communicate the inside of the cavity 7 with the outside of the circuit board through the airing hole 51.

Before the multi-layer board having the cavity 7 is formed, in order to communicate the cavity 7 with the outside through the vent holes 51, at least the vent holes 51 are formed in the first board 1, the second board 2 and the middle board 3 constituting the cavity 7, and then the multi-layer board having the chip 41 is formed by soldering. After welding, because the cavity 7 is in a closed state, the short circuit of the internal welding chip 41 is easily caused, and the cavity 7 is in a communicated state outside through the preset air holes 51, so that the internal ventilation effect is ensured. Wherein, for the processed air holes 51, according to the actual use requirement and according to the chip 41 arranged in the cavity 7, the arrangement position of the air holes 51 is determined after different conditions are integrated, and the processing is correspondingly performed.

When the ventilation holes 51 are required to be formed in one or more of the corresponding middle plate 3, the first plate 1 and the second plate 2, the corresponding through holes 511 may be directly drilled in the corresponding plates, or may be formed by laser cutting or by dividing the middle plate 3 into a plurality of unit combinations, which is not particularly limited herein.

Wherein, for the bleeder vent 51 of processing at intermediate lamella 3, can select more reasonable processing mode according to the designing requirement of different bleeder vents 51 to when improving machining efficiency, reduce the processing cost.

When the ventilation holes 51 are formed in the middle plate 3, the middle plate 3 may be processed with a breaking notch 512, and the breaking notch 512, the middle plate 3, the first plate 1, and the second plate 2 may surround the ventilation holes 51. By directly processing the break-away notch 512 on the intermediate plate 3, the processing precision of the intermediate plate 3 can be reduced, and the processing cost can be saved.

In addition, when the middle plate 3 is provided with the air holes 51, a groove 513 can be processed on the middle plate 3, and the groove 513 connects the inside of the cavity 7 with the outside of the circuit board; along the thickness direction, the groove 513 and the first plate 1 enclose an air hole 51, or the groove 513 and the second plate 2 enclose an air hole 51. In order to ensure a better processing effect of the groove 513, the processing efficiency is improved. As shown in fig. 20, the intermediate plate 3 includes a third plate 31 and a fourth plate 32 in the thickness direction, when the groove 513 is machined in the intermediate plate 3, a third breaking notch 311 is machined in the third plate 31, and the third breaking notch 311, the third plate 31 and the fourth plate 32 enclose the groove 513; alternatively, a third breaking notch 311 is machined in the fourth plate 32, and the third breaking notch 311, the third plate 31 and the fourth plate 32 enclose a groove 513.

Alternatively, the groove 513 is formed by combining the third breaking notches 311, and the processing manner may be, as shown in fig. 21, that the third plate 31 and the fourth plate 32 are taken, the breaking notches 512 are processed on the third plate 31 and/or the fourth plate 32 along the thickness direction, the third plate 31 and the fourth plate 32 are connected, and the groove 513 is surrounded by the third breaking notches 311, the third plate 31 and the fourth plate 32. As shown in fig. 22, 23, and 24, a barrier layer 312 may be provided on the third plate 31 or the fourth plate 32 in the thickness direction, and after the third plate 31 and the fourth plate 32 are connected, the barrier layer 312 may be located at the connection position of the third plate 31 and the fourth plate 32; corresponding to the position of the barrier layer 312, a third breaking notch 311 is cut into the third plate 31 and/or the fourth plate 32, and the third breaking notch 311, the third plate 31 and the fourth plate 32 enclose a groove 513. Through dividing the form of middle plate 3 into third board 31 and fourth board 32 along thickness direction, process the form of connecting again behind third disconnection breach 311 on corresponding board, avoid appearing when offering recess 513 on integrative middle plate 3, make the recess 513 error of processing out great because of the fault operation, cause the condemned condition of middle plate 3. The third breaking notch 311 is formed in the plate and then the connection is performed, so that the requirements on operators and machining precision can be reduced, and the machining cost is saved.

Here, as for the third breaking notch 311 provided, similarly, on the plate provided with the corresponding third breaking notch 311, it is made to have a third end 311a and a fourth end 311b by cutting or the like, and there is a gap between the third end 311a and the fourth end 311b, when it is mated with the corresponding plate, to form the groove 513.

It should be emphasized that, for the connection between the third plate 31 and the fourth plate 32, a connection layer is provided therebetween, and the connection layer may be in the form of bonding with an adhesive to form the adhesive layer 9, or may also be in the form of forming a welding point layer 8 by welding, as long as the connection between the two can be ensured to be firm, and is not particularly limited herein.

More specifically, when the ventilation holes 51 are formed in the middle plate 3, in the form of providing the through holes 511 in the middle plate 3, as shown in fig. 25 and 26, the through holes 511 are formed in the middle plate 3, the through holes 511 communicate the inside of the cavity 7 with the outside of the circuit board, and when the through holes 511 are the ventilation holes 51, the good processing effect of the through holes 511 is ensured, and the processing efficiency is improved. The intermediate plate 3 includes a fifth plate 33, a third plate 31, and a fourth plate 32 in the thickness direction, and when the through hole 511 is formed in the intermediate plate 3, a fourth breaking notch 313 is formed in the third plate 31 to surround the fourth breaking notch 313, the third plate 31, the fourth plate 32, and the fifth plate 33 as the through hole 511. Because the air holes 51 formed in the middle plate 3 are 55-shaped, the air holes 51 are formed in a combined manner of three plates and the fourth breaking notch 313 which are separated along the thickness direction, so that the processing is facilitated.

Optionally, for the through hole 511 formed by combining the fourth breaking notches 313, as shown in fig. 27, the third plate 31, the fourth plate 32 and the fifth plate 33 are taken, the fourth breaking notch 313 is machined in the third plate 31 along the thickness direction, the third plate 31, the fourth plate 32 and the fifth plate 33 are connected, and the through hole 511 is surrounded by the fourth breaking notch 313, the third plate 31, the fourth plate 32 and the fifth plate 33; alternatively, as shown in fig. 28, 29, 30 and 31, after the barrier layer 312 is disposed on the third plate 31 along the thickness direction and the third plate 31 and the fourth plate 32 are connected, the barrier layer 312 is located at the connection position of the third plate 31 and the fourth plate 32, and the fourth breaking notch 313 is cut on the third plate 31 corresponding to the position of the barrier layer 312; the third plate 31 is connected with the fourth plate 32, the third plate 31 is connected with the fifth plate 33, and the through hole 511 is surrounded by the fourth breaking notch 313, the third plate 31, the fourth plate 32 and the fifth plate 33. Through dividing the form of fifth board 33, third board 31 and fourth board 32 into with intermediate plate 3 along thickness direction, the form of carrying out the connection after processing fourth disconnection breach 313 on the board that is located corresponding in the middle, when avoiding appearing offering through-hole 511 on integrative intermediate plate 3, the through-hole 511 error that makes processing because the fault operation is great, makes intermediate plate 3 produce weak deformation region, causes the condemned condition of intermediate plate 3. The requirements on operators and machining precision can be reduced by the mode of firstly forming the fourth breaking notch 313 on the plate and then connecting, and the machining cost is saved.

Wherein, as for the fourth breaking notch 313 provided, likewise, on the plate provided with the corresponding fourth breaking notch 313, it is made to have the fifth end 313a and the sixth end 313b by cutting or the like, with a gap between the fifth end 313a and the sixth end 313b, to form the recess 513 when it is mated with the corresponding plate.

It should be emphasized that, for the connection of the fifth plate 33, the third plate 31 and the fourth plate 32 in the thickness direction, the connection position is provided with a connection layer, and the connection layer may be in the form of bonding by an adhesive to form the adhesive layer 9, or may also be in the form of welding spots to form the welding spot layer 8, as long as the connection between the plates can be ensured to be firm, and the connection is not particularly limited herein.

In conclusion, along the thickness direction, through the structure cooperation form that piles up formation cavity 7 between the circuit board to make the circuit board further reach the miniaturization, make full use of longitudinal space, simultaneously, through the setting of bleeder vent 51, with cavity 7 and outside intercommunication, avoid producing welding, environmental reliability and heat dissipation scheduling problem at this kind of miniaturized circuit board.

It should be noted that a portion of this patent document contains material which is subject to copyright protection. The copyright owner reserves the copyright rights whatsoever, except for making copies of the patent files or recorded patent document contents of the patent office.

Claims

1. A circuit board, characterized in that the circuit board comprises a first board (1), an intermediate board (3) and a second board (2), the intermediate board (3) is located between the first board (1) and the second board (2) along the thickness direction and is connected with the first board and the second board, the intermediate board (3) is a hollow circuit board, and the first board (1), the intermediate board (3) and the second board (2) enclose to form a cavity (7);

the circuit board further comprises a chip (41), at least part of the chip (41) is located in the cavity (7), and the chip (41) is soldered to the first board (1) and/or the second board (2);

the circuit board further comprises an air hole (51), and the inside of the cavity (7) is communicated with the outside of the circuit board through the air hole (51).

2. The circuit board of claim 1, wherein the vent (51) is disposed at least one of: the first plate (1), the second plate (2) or the intermediate plate (3).

3. The circuit board according to claim 2, characterized in that the intermediate plate (3) has a disconnection gap (512), the intermediate plate (3) comprising a first end portion (512a) and a second end portion (512b), the disconnection gap (512) being formed between the first end portion (512a) and the second end portion (512 b);

the vent (51) is enclosed by at least the first end portion (512a), the second end portion (512b), the first plate (1) and the second plate (2).

4. The circuit board according to claim 3, wherein the disconnection notch (512) comprises at least a first disconnection notch (512c) and a second disconnection notch (512d), the first disconnection notch (512c) and the second disconnection notch (512d) being arranged opposite to each other.

5. A circuit board according to claim 2, characterized in that the intermediate plate (3) is provided with a recess (513);

the vent hole (51) is formed by at least the groove (513) and the first plate (1) in a surrounding mode, or the vent hole (51) is formed by at least the groove (513) and the second plate (2) in a surrounding mode.

6. The circuit board according to claim 5, characterized in that the recess (513) comprises at least a first recess and a second recess, the first recess and the second recess being oppositely arranged.

7. A circuit board according to claim 2, characterized in that the intermediate plate (3) is provided with a through hole (511), the through hole (511) communicating the inside of the cavity (7) with the outside of the circuit board enclosing the part of the cavity (7);

the through hole (511) is the air hole (51).

8. The circuit board according to claim 7, characterized in that the through holes (511) comprise at least a first and a second through hole, the first through hole being arranged opposite to the second through hole.

9. The circuit board according to any of claims 1-8, wherein the vent (51) further comprises a third via (53) and/or a fourth via (52);

the third through hole (53) is located in the first board (1), the fourth through hole (52) is located in the second board (2), and the third through hole (53) and the fourth through hole (52) communicate the inside of the cavity (7) with the outside of the circuit board, respectively.

10. A circuit board according to claim 9, characterized in that the circuit board is provided with the third through hole (53) and the fourth through hole (52), the projection of the third through hole (53) at least partially coinciding with the projection of the fourth through hole (52) in the thickness direction.

11. A circuit board according to any one of claims 1-8, characterized in that the first board (1), the intermediate board (3) and the second board (2) are connected by solder joints in the thickness direction and form a solder joint layer (8);

the air holes (51) are formed in the welding spot layer (8).

12. An electronic device comprising a housing and a circuit board, characterized in that the circuit board is a circuit board according to any of claims 1-11.