CN218042315U

CN218042315U - Circuit board assembly and electronic equipment

Info

Publication number: CN218042315U
Application number: CN202221238911.4U
Authority: CN
Inventors: 熊振兴; 赵才军; 熊建波; 庄宝山; 赵亚涛
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2022-05-20
Filing date: 2022-05-20
Publication date: 2022-12-13
Anticipated expiration: 2032-05-20
Also published as: WO2023222045A1

Abstract

The present application relates to a circuit board assembly and an electronic device. The circuit board assembly includes a circuit board, a chip-on-board, a heat sink, a shield frame, and a shield. The on-board chip is carried on a first plane of the circuit board, the radiator comprises a binding surface facing the on-board chip, and a heat conduction layer is arranged between the binding surface and the on-board chip; the radiator is fixed on the circuit board through a fastener so that the binding surface is bound with the heat conducting layer. On the shielding frame was fixed in the first plane, the shielding frame encircled the setting of board chip carrier, formed annular gap between shielding frame and the board chip carrier. The shielding piece is of a hollow structure, the inner edge of the shielding piece is fixed on the on-board chip, the outer edge of the shielding piece is in contact with the shielding frame, or the outer edge of the shielding piece is positioned on one side of the shielding frame, which is far away from the on-board chip, and is arranged at an interval with the shielding frame; the shield is used for shielding the annular gap. The circuit board assembly has a compact structure and a better shielding effect.

Description

Circuit board assembly and electronic equipment

Technical Field

The present application relates to the field of electronic devices, and more particularly, to a circuit board assembly and an electronic device.

Background

The electronic equipment is internally provided with a circuit board assembly for realizing the preset function of the electronic equipment. Along with the function expansion of electronic equipment, the number of chips required to be accommodated in the circuit board assembly is correspondingly increased, and the distance between the chips is gradually reduced; meanwhile, the transmission rate of the chip per se is also gradually increased, which puts higher requirements on the electromagnetic shielding of the chip in the circuit board assembly.

SUMMERY OF THE UTILITY MODEL

The application aims to provide a circuit board assembly which is small in size and reliable in shielding. Meanwhile, the application also relates to electronic equipment for assembling the circuit board assembly.

In a first aspect, the present application is directed to a circuit board assembly comprising a circuit board, a chip on board, a heat sink, a shield frame, and a shield; the on-board chip is carried on a first plane of the circuit board, the radiator comprises a binding surface facing the on-board chip, and a heat conduction layer is arranged between the binding surface and the on-board chip; the radiator is fixed on the circuit board through a fastener so as to enable the binding surface to be bound with the heat conduction layer; the shielding frame is fixed on the first plane, the shielding frame is arranged around the on-board chip, and an annular gap is formed between the shielding frame and the on-board chip; the shielding piece is of a hollow structure, the inner edge of the shielding piece is fixed on the on-board chip, the outer edge of the shielding piece is in contact with the shielding frame, or the outer edge of the shielding piece is positioned on one side of the shielding frame, which is far away from the on-board chip, and is arranged at an interval with the shielding frame; the shield is used for shielding the annular gap.

This application circuit board assembly carries on board through the circuit board and carries on the chip, then carries out the heat dissipation to the board through the radiator and carries out the chip. And between the on-board chip and the heat sink, the circuit board assembly is provided with a structure of a shield frame and a shield member. The shielding frame surrounds the periphery of the on-board chip and forms an annular gap with the on-board chip at intervals. The shield may then be used to shield the annular gap. Therefore, in the side direction between the board-mounted chip and the circuit board and the radiator, the shielding effect in the direction can be realized by the combination of the shielding frame and the shielding piece, and the electromagnetic interference phenomenon possibly formed by too close distance between two adjacent board-mounted chips or between the board-mounted chip and other surrounding devices is avoided. The circuit board assembly is compact in structure and reliable in shielding effect, and high-density arrangement design of all devices in the circuit board can be achieved.

In a possible implementation manner, the onboard chip comprises a substrate base plate, a chip bare crystal and a fence, wherein the substrate base plate is fixed on the first plane, the chip bare crystal is fixed on one side of the substrate base plate, which is deviated from the first plane, the fence is arranged around the periphery of the chip bare crystal, the heat conduction layer is arranged on the outer surface of the chip bare crystal, and the inner edge of the shielding piece is fixed on the fence.

In this implementation, the chip bare chip in the on-board chip is exposed above the rail, the heat-conducting layer is directly arranged on the chip bare chip, and the binding surface of the radiator can form a better radiating effect on the chip bare chip.

In a possible implementation manner, the circuit board assembly further includes a flexible shielding ring, the flexible shielding ring is disposed around the periphery of the attachment surface and located between the rail and the heat sink, and two opposite surfaces of the flexible shielding ring are respectively abutted against the heat sink and the rail, so as to form a shielding effect on the die of the chip.

In one possible implementation, the fence is made of a conductive material.

In this implementation, the flexible shielding ring abuts against the space between the heat sink and the rail, so that shielding can be formed on the side of the bare chip, and interference signals can be prevented from passing through the gap between the rail and the heat sink to form an electromagnetic interference phenomenon. The flexible shielding ring is made of flexible materials, and when the flexible shielding ring is abutted between the radiator and the rail, the flexible shielding ring can adapt to the manufacturing tolerance between the radiator and the rail through compression deformation, so that the reliability of the shielding structure is ensured.

In a possible implementation manner, the flexible shielding ring may be made of conductive foam, conductive sponge, conductive adhesive, or metal.

In one possible implementation, the inner edge of the shield is sandwiched between the flexible shield ring and the rail.

In this implementation, the inward flange clamp that sets up the shielding part is located between flexible shield ring and the rail, is convenient for be fixed in flexible shield ring or rail with the shielding part on to through support between flexible shield ring and the rail hold, guarantee that the relative position between shielding part and the board chip of carrying is stable, thereby promote this application circuit board assembly's shielding effect.

In a possible implementation mode, the on-board chip comprises a substrate base plate, a bare chip and a shell, wherein the substrate base plate is fixed on a first plane, the shell is fixed on one side, away from the first plane, of the substrate base plate, the shell and the substrate base plate surround to form an accommodating space, the bare chip is accommodated in the accommodating space, the inner edge of the shielding piece is arranged on the outer surface of the shell, and the shell is further used for forming a heat conduction layer.

In the implementation mode, the bare chip in the on-board chip is accommodated in the accommodating space formed by the enclosure of the shell and the substrate, the shell can shield and protect the bare chip, and the working reliability of the bare chip is ensured by matching with the structures of the shielding frame and the shielding piece. The outer surface of the shell close to the binding surface can be in contact with the radiator for heat conduction, so that heat generated by the bare chip is discharged through the radiator.

In a possible implementation manner, a heat-conducting interface material is further filled between the bare chip and the shell, so that the heat conduction efficiency from the bare chip to the shell is improved.

In a possible implementation manner, the outer edge of the shielding element is in contact with the shielding frame, and the material of the shielding element is flexible.

In this implementation, the shield realizes shielding of the annular gap by direct contact with the on-board chip and the shield frame, respectively. And the shielding part is made of flexible materials, and can be used for adapting to the manufacturing tolerance between the on-board chip and the shielding frame.

In a possible implementation manner, the shielding member may be made of conductive foam, conductive sponge, conductive adhesive, conductive plastic, conductive film, or metal.

In one possible implementation, the shield includes a connecting portion and a shielding portion, an inner edge of the shield is located on the connecting portion, an outer edge of the shield is located on the shielding portion, and an extending direction of the shielding portion is perpendicular to the first plane.

In this implementation, the shielding member extends out of the shielding frame through the connecting portion, and forms clearance fit with the shielding frame through the shielding portion extending in the direction perpendicular to the first plane, and can achieve the effect of realizing electromagnetic shielding on the board-mounted chip by controlling the size of the clearance.

In one possible implementation, the material of the shield may be conductive plastic, conductive film, or metal.

In a possible implementation manner, the projection of the shielding piece on the heat sink is contained in the outer contour of the heat sink.

In a possible implementation manner, the circuit board includes a transmission line, the transmission line is located on the first plane, one end of the transmission line is fixedly connected and conducted with the on-board chip, the other end of the transmission line is located on a side, away from the on-board chip, of the shielding frame, and the shielding frame is provided with a hollowed-out area used for allowing the transmission line to pass through.

In this implementation, a transmission line may be disposed on the first plane of the circuit board, so as to electrically connect the on-board chip and other devices on the circuit board. The hollow-out area arranged on the shielding frame is used for the transmission line to pass through.

In a possible implementation manner, the shielding frame comprises a main body, protruding portions and conductive adhesive, the protruding portions are arranged on one side, close to the first plane, of the main body at intervals and protrude towards the first plane, a hollow-out area is formed between every two adjacent protruding portions, and the conductive adhesive is arranged between the protruding portions and the first plane.

In this implementation, through set up the bellying that the interval was arranged on the main part of shielding frame, can be used to form the fretwork district. The conductive adhesive is used for ensuring the conductive connection between each protruding part and the first plane so as to improve the shielding effect of the protruding part.

In a possible implementation manner, the shielding frame comprises a main body, pads and conductive adhesive, the pads are arranged on the first plane at intervals, the main body is located on one side, away from the first plane, of the pads, the conductive adhesive is located between the pads and the main body, and a hollow-out area is formed between every two adjacent pads.

In this implementation, through set up the pad of interval arrangement on first plane, also can form the structure of fretwork district. And the conductive adhesive is positioned between the bonding pad and the main body, so that the conductive connection between the bonding pad and the main body can be ensured, and the shielding effect of the bonding pad position can be ensured.

In one possible implementation, the shielding frame is further fixed to the circuit board by a connector.

In a possible implementation manner, in any cross section perpendicular to the first plane, the shielding frame comprises a first side close to the first plane and a second side far away from the first plane, and the wall thickness of the first side is larger than that of the second side.

In this implementation, the first side wall of the shielding frame is thicker, so that reliable connection between the shielding frame and the circuit board is ensured. And the second lateral wall thickness of shield frame is thinner, then the cooperation of shield frame and shielding piece of being convenient for, the whole size of constricting this application circuit board subassembly.

In one possible implementation, the wall thickness of the first side is 1mm and the wall thickness of the second side is 0.75mm.

In one possible implementation, the shield includes a shielding portion having a wall thickness of 0.2mm, and a gap between the shielding portion and the shield frame is 0.1mm.

In a possible implementation mode, the onboard chips in the circuit board assembly are multiple, the onboard chips are arranged at intervals, and a shielding frame and a shielding piece are arranged on the periphery of each onboard chip and used for achieving shielding and protecting effects on each onboard chip.

In a second aspect, the present application provides an electronic device, comprising a housing and the circuit board assembly provided in the first aspect of the present application, the circuit board assembly being mounted to the housing for implementing a function of the electronic device.

It can be understood that, in the electronic device provided in the second aspect of the present application, because the circuit board assembly provided in the first aspect of the present application is provided, the electronic device also has the beneficial effects of small size and reliable shielding.

Drawings

Fig. 1 is a schematic structural diagram of an electronic device according to an embodiment of the present application;

fig. 2 is a schematic structural diagram of a circuit board assembly in an electronic device according to an embodiment of the present application;

fig. 3 is an exploded schematic view of a circuit board assembly in an electronic device according to an embodiment of the present disclosure;

fig. 4 is a schematic structural diagram of a circuit board assembly in an electronic device according to another embodiment of the present application;

fig. 5 is an exploded schematic view of a circuit board assembly in an electronic device according to another embodiment of the present disclosure;

fig. 6 is a schematic cross-sectional structure diagram of a circuit board assembly in an electronic device according to an embodiment of the present application;

fig. 7 is a schematic cross-sectional structure diagram of a circuit board assembly in an electronic device according to another embodiment of the present application;

FIG. 8 is a prior art schematic diagram of the specification of chip rate and electromagnetic shielding in a circuit board assembly;

fig. 9 is a schematic diagram illustrating a structure of a heat sink and a circuit board of a circuit board assembly according to an embodiment of the present application;

FIG. 10 is a cross-sectional schematic view of a chip on board of a circuit board assembly provided in accordance with an embodiment of the present application;

fig. 11 is a schematic diagram illustrating a matching structure between a chip on board and a shielding frame in a circuit board assembly according to an embodiment of the present disclosure;

fig. 12 is a schematic diagram illustrating a matching structure of a chip on board, a shielding frame and a shielding member in a circuit board assembly according to an embodiment of the present disclosure;

fig. 13 is a schematic view illustrating a matching structure of a chip on board, a shielding frame and a shielding member in a circuit board assembly according to another embodiment of the present disclosure;

FIG. 14 is a cross-sectional schematic view of a chip on board assembly of a circuit board assembly provided in accordance with another embodiment of the present application;

fig. 15 is a schematic diagram of a shield in a circuit board assembly according to another embodiment of the present application;

FIG. 16 is a cross-sectional schematic view of a prior art circuit board assembly;

fig. 17 is a schematic cross-sectional view of another prior art circuit board assembly;

FIG. 18 is a schematic diagram of the shielding performance of a wave-absorbing material of a circuit board assembly in comparison with the width of the wave-absorbing material;

FIG. 19 is a graphical illustration of a prior art statistical result of saw tooth coplanarity of a shield for a circuit board assembly;

FIG. 20 is a schematic diagram illustrating a plan view of a circuit board, a chip on board, and a shielding frame in a circuit board assembly according to an embodiment of the present application;

fig. 21 is a schematic side view of a shielding frame in a circuit board assembly according to an embodiment of the present application;

fig. 22 is a schematic side view of a shield frame in a circuit board assembly according to another embodiment of the present application;

FIG. 23 is a cross-sectional structural view of a circuit board assembly of the present application;

FIG. 24 is a schematic plan view of a chip on board assembly of the present application.

Detailed Description

Technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making creative efforts shall fall within the protection scope of the present application.

The numbering of the components as such, e.g., "first", "second", etc., is used herein only to distinguish the objects as described, and does not have any sequential or technical meaning. The term "coupled", as used herein, includes both direct and indirect coupling, unless otherwise indicated. In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "back", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are used only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present application.

In this application, unless expressly stated or limited otherwise, a first feature is "on" or "under" a second feature such that the first and second features are in direct contact, or the first and second features are in indirect contact via an intermediary. Also, a first feature "on" or "over" a second feature may be directly or diagonally over the first feature or may simply indicate that the first feature is at a higher level than the second feature. A first feature "under" or "beneath" a second feature may be directly or obliquely under the first feature or may simply mean that the first feature is at a lesser elevation than the second feature.

Please refer to fig. 1 for an electronic device 200 provided in the present application. In the illustration of fig. 1, the electronic device 200 is a mobile phone. The electronic device 200 includes a housing 210 and the circuit board assembly 100 provided herein. The circuit board assembly 100 is disposed on the housing 210 for implementing a predetermined function of the electronic device 200. The preset functions of the electronic device 200 may include data processing, data storage, signal transceiving, data acquisition, data output, and implementing specific mechanism actions.

Correspondingly, the circuit board assembly 100 is loaded with a chip and other electronic devices, and the circuit board assembly 100 may implement the preset function of the electronic device 200 through the interaction between the chip and the electronic devices. At this time, the chip in the circuit board assembly 100 of the present application may be a central processing chip, a memory chip, a network chip, a baseband chip, an image processing chip, a display chip, an audio processing chip, and the like. Further, the chip in the circuit board assembly 100 may also be an integrated chip of the at least two chips, or a plurality of chips may be simultaneously mounted in the circuit board assembly 100 to cooperate to implement one or more functions described above.

In the schematic illustration of fig. 1, the electronic device 200 is a mobile phone, in other embodiments, the electronic device 200 may also be a tablet, a computer, an intelligent appliance, a Customer Premises Equipment (CPE) such as a router and a base station, or any other electronic device 200, and the application does not specifically limit the type of the electronic device 200.

For convenience of description, in the following embodiments of the present application, the electronic device 200 is taken as a mobile phone, and the chip in the circuit board assembly 100 includes a network chip as an example, so as to introduce the solution of the present application.

Please refer to fig. 2 for a structural schematic diagram of a circuit board assembly 100 provided in the present application, and fig. 3 for an exploded structural schematic diagram of the circuit board assembly 100.

In the circuit board assembly 100 of the present application shown in fig. 2 and 3, a circuit board 10, a chip on board 20, a heat sink 30, a shield frame 40, and a shield 50 are included. In the circuit board assembly 100 shown in fig. 2, the circuit board 10 has a first plane 11, one on-board chip 20 is mounted on the first plane 11, and the heat sink 30, the shielding frame 40, and the shielding member 50 are disposed corresponding to the on-board chip 20, so as to achieve the heat dissipation and electromagnetic shielding functions of the on-board chip 20. The circuit board assembly 100 is also provided with other devices 110, the other devices 110 also being carried on the first plane 11 and being arranged adjacent to the on-board chip 20. The other devices 110 may be capacitors, inductors, resistors, etc., and the on-board chip 20 is electrically connected to the other devices 110 through the circuit board 10 to cooperate with the predetermined functions of the circuit board assembly 100 in the electronic device 200.

Please refer to fig. 4 for a schematic structure of another circuit board assembly 100 provided by the present application, and fig. 5 for an exploded schematic structure of the circuit board assembly 100.

In another structure of a circuit board assembly 100 shown in fig. 4, a plurality of board-mounted chips 20 are mounted on a first plane 11 of a circuit board 10, and a heat sink 30 for assisting heat dissipation thereof, and a shield frame 40 and a shield 50 for implementing electromagnetic shielding thereof are provided corresponding to each board-mounted chip 20. A plurality of on-board chips 20 are arranged at intervals on the first plane 11, and in the illustration of fig. 4, the number of on-board chips 20 is 8, and 8 on-board chips are arranged in a matrix on the first plane 11 in a "2 × 4" manner, and the corresponding heat sink 30 is also fixed relative to the circuit board 10 in this arrangement.

It will be appreciated that in other embodiments, the number of on-board chips 20 in the circuit board assembly 100 may have other values, and the arrangement of the on-board chips 20 may be in a linear arrangement, a matrix arrangement, or any other arrangement. The plurality of on-board chips 20 may each implement a preset function of the circuit board assembly 100 in the electronic device 200; the plurality of on-board chips 20 can also electrically communicate with each other and cooperate with each other to realize the predetermined functions of the circuit board assembly 100 in the electronic device 200. In some embodiments, multiple on-board chips 20 and other devices 110 may be simultaneously mounted in the circuit board assembly 100, and the multiple on-board chips 20 and other devices 110 are arranged side by side and act individually or together to achieve the intended function of the circuit board assembly 100 in the electronic device 200.

With the stacking of the preset functions of the electronic apparatus 200, the number of the on-board chips 20 and/or other devices 110 that may be mounted on the circuit board 10 increases accordingly, and the size of the on-board chips 20 increases accordingly (the external size of the existing on-board chips 20 may reach 50-110 mm). The circuit board 10 is designed to be densely populated, with the spacing between the on-board chip 20 and the adjacent other devices 110 or on-board chip 20 being gradually reduced. In the cross-sectional schematic view of the circuit board assembly 100 shown in FIG. 6, the distance between the on-board chip 20 and the adjacent other devices 110 on the first plane 11 of the circuit board 10 may be less than 4mm; in the cross-sectional view of the circuit board assembly 100 shown in fig. 7, the distance between the heat sinks 30 of two adjacent chip-on-board assemblies 20 may be less than 4mm.

On the other hand, the increase of the chip speed also causes a larger electromagnetic shielding interference phenomenon. As shown in FIG. 8, when the chip rate is increased from 10Gb/s to 56Gb/s, the 56Gb/s high speed chip EMI exceeds the standard by about 5dB, based on the limits required by the Federal Communications Commission (FCC). The above phenomena all put higher demands on the performance of the electromagnetic shielding of the on-board chip 20 in the circuit board assembly 100.

In the cross-sectional illustration of the circuit board assembly 100 of the present application shown in fig. 6 and 7, the on-board chip 20 is secured to the first planar surface 11 of the circuit board 10 and the heat sink 30 is located on a side of the on-board chip 20 facing away from the first planar surface 11. Referring to fig. 9 in particular, the heat sink 30 includes an attachment surface 31 and a heat dissipation surface 32 opposite to each other, and a fixing hole 33 penetrating between the attachment surface 31 and the heat dissipation surface 32. The circuit board assembly 100 is provided with a fastener 120, the fastener 120 passes through the fixing hole 33 to fix the heat sink 30 outside the first plane 11 of the circuit board 10, the attaching surface 31 of the heat sink 30 faces the chip-on-board 20, and the heat dissipating surface 32 faces away from the first plane 11. The heat dissipating surface 32 is provided with heat dissipating teeth 321 for increasing the heat dissipating area of the heat dissipating surface 32. The attaching surface 31 is connected to the on-board chip 20 through the heat conducting layer 130 in a heat conducting manner, so as to conduct the heat of the on-board chip 20 to the heat dissipating surface 32, thereby achieving the heat dissipating effect on the on-board chip 20.

For the sake of clarity, the shielding frame 40 and the shield 50, and the on-board chip 20, etc. are omitted from the illustration of fig. 9. In the remaining drawings of the embodiment of the present application, the fixing holes 33 of the heat sink 30 and the fastening members 120 of the circuit board assembly 100 are omitted.

Please refer to the structural schematic of the on-board chip 20 shown in fig. 10. In one embodiment of the circuit board assembly 100 of the present application, the on-board chip 20 includes a substrate base 21, a chip die 22, and a housing 23. The substrate base plate 21 includes a first surface 211 and a second surface 212 opposite to each other, wherein the first surface 211 is attached to and fixed on the first plane 11 of the circuit board 10, and the die 22 and the housing 23 are located on the second surface 212 of the substrate base plate 21. The housing 23 covers the second surface 212 and forms an accommodating space with the second surface 212. The bare chip 22 is located in the accommodating space and attached to the second surface 212. The shell 23 may be made of a conductive material, and covers the periphery of the die 22 to shield the die 22.

The bare chip 22 is a main heat source of the on-board chip 20, the case 23 is disposed at an interval relative to the bare chip 22, and a Thermal Interface Material (TIM), such as Thermal grease, thermal glue or graphite sheet, may be filled between the bare chip 22 and the case 23, and the Thermal Interface Material is used to conduct heat generated during the operation of the bare chip 22 to the case 23. The bonding surface 31 of the heat sink 30 is bonded to the case 23. In this case, in the illustration of fig. 6, the structure of the portion of the case 23 located between the bare chip 22 and the bonding surface 31 is also used to form the heat conductive layer 130. Or as described, the thermal interface material filled between the die 22 and the housing 23 and a part of the structure of the housing 23 are used together to form the thermal conductive layer 130 in this embodiment. One surface of the heat conduction layer 130 is directly attached to the bare chip 22, and the other surface is attached to the attachment surface 31 of the heat sink 30, so that heat generated by the bare chip 22 during operation can be transferred to the heat dissipation surface 32 of the heat sink 30 through the heat conduction layer 130, and heat dissipation is realized through the heat dissipation teeth 321.

The shield frame 40 and the shield 50 are both located between the circuit board 10 and the heat sink 30. Please refer to fig. 11 for a schematic diagram of the matching structure of the chip-on-board 20 and the shielding frame 40. In the present embodiment, the planar projection of the on-board chip 20 is rectangular as shown in fig. 11, and the shield frame 40 is also configured as a rectangular frame body. The shield frame 40 is also fixed to the circuit board 10, and the shield frame 40 is disposed around the periphery of the board chip 20 and spaced apart from the board chip 20, that is, the shield frame 40 is disposed around the board chip 20. An annular gap 140 is formed between the shield frame 40 and the board chip 20, and the shield 50 is used to shield the annular gap 140 (as shown in fig. 12).

Specifically, in the circuit board assembly 100 of the present application, the shielding member 50 has a hollow structure. The shield 50 includes an inner edge 51 and an outer edge 52, and the inner edge 51 and the outer edge 52 are each rectangular in shape to fit the outer configuration of the board-mounted chip 20 and the shield frame 40, respectively. The inner edge 51 of the shield 50 is fixed to the chip-on-board 20, in this embodiment in particular to the housing 23. The outer edge 52 of the shield 50 is in contact with the shield frame 40, thereby achieving a shielding effect of the shield 50 against the annular gap 140.

The material of the main body of the shielding frame 40 may be a conductive material, such as metal. Which is fixed to the circuit board 10 and forms a rigid shielding structure at the side of the on-board chip 20. Electromagnetic signals generated during the operation of the die bare chip 22 are shielded by the housing 23 and the shielding frame 40, and electromagnetic interference with other adjacent devices 110 and/or the on-board die 20 can be avoided. Electromagnetic signals of other external devices 110 and/or the on-board chip 20 may be shielded by the shielding frame 40 and the housing 23, and may not enter the housing space formed by the housing 23 and the substrate 21, thereby ensuring reliable operation of the bare chip 22.

The electromagnetic signal may also propagate through the annular gap 140, and at this time, the shielding member 50 in the circuit board assembly 100 of the present application shields the annular gap 140, so as to form a shielding effect, and prevent the bare chip 22 from transmitting or receiving an external electromagnetic interference signal. In some embodiments, the shielding member 50 may be made of conductive foam, conductive sponge, conductive adhesive, conductive plastic, conductive film or metal. When the material of the shielding element 50 is a conductive foam, a conductive sponge, a conductive adhesive, a conductive plastic or a conductive film, the shielding element 50 is a non-newtonian body, and the shielding element 50 can deform by itself to accommodate the tolerance of the fitting dimension between the on-board chip 20 and the shielding frame 40, and ensure a reliable contact between the inner edge 51 and the housing 23 and a reliable contact between the outer edge 52 and the shielding frame 40.

In the illustration of fig. 6, the shielding member 50 is made of a conductive film. The inner edge 51 of the shield 50 is fixed to the top surface of the housing 23, and the outer edge 52 is fixed to the top surface of the shield frame 40. In the embodiment illustrated in fig. 13, the shielding element 50 may be made of conductive foam, conductive sponge, conductive adhesive or conductive plastic, the shielding element 50 is integrally embedded in the annular gap 140, and the inner edge 51 thereof is attached to the outer side surface of the housing 23, and the outer edge 52 thereof is attached to the inner side surface of the shielding frame 40. The above-mentioned structure can ensure the shielding effect formed by the shielding frame 40 and the shielding member 50 together.

Fig. 14 illustrates a structural schematic of another chip-on-board 20 of the circuit board assembly 100 of the present application. In the present embodiment, the on-board chip 20 includes a substrate base 21, a chip die 22, and a fence 24. The first surface 211 of the substrate base 21 is used for being attached and fixed to the first plane 11 of the circuit board 10, and the die 22 and the rail 24 are located on the second surface 212 of the substrate base 21. The die 22 is located at the central region of the second surface 212, and the rail 24 surrounds the die 22 and is spaced apart from the die 22. The material of the rail 24 can be a conductive material, and the rail 24 can be used to improve the structural stability of the substrate base plate 21.

In the embodiment of the present application, the chip die 22 is exposed on a side of the on-board chip 20 facing away from the first plane 11, that is, the chip die 22 is exposed in a direction toward the heat sink 30. In this case, the heat conductive layer 130 disposed between the die bare chip 22 and the bonding surface 31 may include a heat conductive interface material. One surface of the thermal interface material is bonded to the die 22, and the other surface is directly bonded to the bonding surface 31 of the heat spreader 30. Thus, heat generated by the die 22 during operation can be directly transferred to the heat sink 30 through the thermal interface material, and the heat can be dissipated through the heat dissipation teeth 321 at the heat dissipation surface 32.

The shield frame 40 and the shield 50 are both located between the circuit board 10 and the heat sink 30. The shield frame 40 is fixed to the circuit board 10, and the shield frame 40 surrounds the periphery of the on-board chip 20 and is spaced apart from the on-board chip 20. An annular gap 140 is formed between the shield frame 40 and the chip on board 20, and the shield 50 is used to shield the annular gap 140.

In the circuit board assembly 100 of the present embodiment, the shielding element 50 is also a hollow structure. Referring to fig. 15, the shielding member 50 includes a connecting portion 53 and a shielding portion 54, wherein the inner edge 51 of the shielding member 50 is located at the connecting portion 53, and the outer edge 52 is located at the shielding portion 54. Thus, the connecting portion 53 is used to be fixedly connected to the rail 24, and the shielding portion 54 is used to achieve an electromagnetic shielding effect in cooperation with the shield frame 40.

In this embodiment, the connecting portion 53 may extend in a direction parallel to the first plane 11, and extend over the top of the shielding frame 40 to a side of the shielding frame 40 facing away from the chip on board 20, so as to shield the annular gap 140. Meanwhile, the shielding portion 54 may be located on a side of the shield frame 40 facing away from the chip-on-board 20 and spaced apart from the shield frame 40. The shielding portion 54 extends from the top of the shield frame 40 toward the first plane 11 of the circuit board 10. In a direction perpendicular to the first plane 11, the shielding portion 54 at least partially overlaps the shielding frame 40, i.e. a projection of the outer edge 52 of the shielding member 50 on the shielding frame 40 is located at an outer side wall of the shielding frame 40. The gap between the shielding part 54 and the shield frame 40 is small, and is used for realizing the electromagnetic shielding function of the shield 50 on the shield frame 40 side.

Defining that the electromagnetic wave generated by the on-board chip 20 in the present embodiment has a wavelength λ, the gap between the shielding portion 54 and the shielding frame 40 can be controlled to be less than or equal to 1/4 λ, so as to achieve the electromagnetic shielding function of the shielding element 50 on the side of the shielding frame 40. In this embodiment, the shielding element 50 may be made of conductive plastic, conductive film or metal material, so as to ensure the structural stability of the shielding element 50, ensure the size interval of the shielding element 50 relative to the shielding frame 40, and ensure the shielding effect formed by the shielding element 50 and the shielding frame 40 together.

It will be appreciated that the structure of the shield 50 of the present application is also applicable to the embodiment of the circuit board assembly 100 shown in fig. 6. The connecting portion 53 of the shielding member 50 can be fixed to the top surface of the housing 23, and the shielding portion 54 is used to form a fitting with the shielding frame 40. The structure of the shielding element 50 shown in fig. 6, which uses conductive foam, conductive sponge, conductive adhesive, conductive plastic, and conductive film, can also be applied to the embodiment of the circuit board assembly 100 shown in fig. 7. The inner edge 51 of the shielding element 50 is fixedly connected to the rail 24, and the outer edge 52 is fixedly connected to the shielding frame 40, so that a better shielding effect can be achieved.

In the illustration of fig. 7, the present circuit board assembly 100 may also be provided with the structure of a flexible shield ring 60. The flexible shielding ring 60 is disposed around the periphery of the abutting surface 31, and the flexible shielding ring 60 is further disposed between the rail 24 and the heat sink 30. Opposite sides of the flexible shielding ring 60 respectively abut against the heat spreader 30 and the rail 24 to shield the die 22.

Specifically, the heat sink 30 is further provided with a step surface 34 on the side close to the bonding surface 31. The step surface 34 surrounds the periphery of the attaching surface 31 and is away from the first plane 11 of the circuit board 10 relative to the attaching surface 31. Since the die 22 is exposed toward the heat sink 30, a transmission channel for electromagnetic signals is also formed between the rail 24 and the step surface 34, which may cause the electromagnetic signals formed by the die 22 to be transmitted outwards, causing electromagnetic interference; or cause external electromagnetic interference signals to enter the die 22, which may affect the normal operation of the die 22.

The flexible shielding ring 60 is disposed such that opposite sides thereof respectively abut against the heat sink 30 and the rail 24, thereby cutting off the transmission channel of the electromagnetic signal and further enhancing the shielding effect between the die 22 and the outside. The flexible shielding ring 60 may be made of conductive foam, conductive sponge, conductive adhesive, or metal (e.g., reed). The two opposite sides of the heat spreader are respectively abutted against and matched with the step surface 34 of the heat spreader 30 and the top surface of the rail 24, so as to ensure the sealing effect on the die 22. Meanwhile, the flexible shielding ring 60 is made of elastic material, so as to accommodate the tolerance of the fit size between the heat sink 30 and the rail 24 by self-deformation and ensure reliable contact between the two sides thereof in the abutting process.

In the embodiment shown in fig. 7, on the side where the flexible shielding ring 60 is engaged with the rail 24, the inner edge 51 of the shielding member 50 is further sandwiched between the flexible shielding ring 60 and the rail 24, and the flexible shielding ring 60 indirectly abuts against the rail 24 by abutting against the shielding member 50. Such an arrangement may secure the flexible shield ring 60 directly to the step surface 34 and the shield 50 to the side of the flexible shield ring 60 facing away from the heat sink 30.

In assembling the circuit board assembly 100 of the present application, the chip-on-board 20 and the shielding frame 40 may be fixed to the circuit board 10, and then the heat sink 30 may be fixed by the fastening member 120. Because the flexible shielding ring 60 and the shielding element 50 are fixed relative to the heat sink 30, the process of assembling the heat sink 30 simultaneously completes the installation operation of the flexible shielding ring 60 and the shielding element 50, which simplifies the assembly process of the circuit board assembly 100 and ensures the position accuracy of the flexible shielding ring 60 and the shielding element 50 relative to the heat sink 30.

In the embodiment illustrated in fig. 6 and 7, the overall outside dimension width of the shield 50 and the shield frame 40 is also smaller than the outside dimension width of the heat sink 30. That is, the projections of the shield 50 and the shield frame 40 on the heat sink 30 are contained within the outer contour of the heat sink 30. Because the heat sink 30 achieves a predetermined heat dissipation effect, the area of the heat dissipation surface 32 is generally larger than that of the attachment surface 31. The widths of the shielding frame 40 and the shielding element 50 are both contained in the outer contour of the heat sink 30, so that the shielding frame 40 and the shielding element 50 do not exceed the outer contour size of the heat sink 30, the overall area of the circuit board assembly 100 is ensured to be small, and the high-density layout design of the circuit board assembly 100 is facilitated.

Fig. 16 and 17 illustrate the structures of a circuit board assembly 100a and a circuit board assembly 100b, respectively, in the related art. In the illustration of FIG. 16, prior art circuit board 100a also includes circuit board 10a, on-board chip 20a, and heat sink 30a. Further, the prior art circuit board assembly 100a also provides a shield ring 60a on the outside of the on-board chip 20 a. The shield ring 60a is fixed to the heat sink 30a and surrounds the periphery of the chip-on-board 20 a. The shielding ring 60a may be made of a wave-absorbing material to absorb electromagnetic signals to form a shielding effect; or the shielding ring 60a may be configured as a Frequency Selective Surface (FSS) to form an electromagnetic shielding effect of the on-board chip 20 based on the slot waveguide theory.

However, the shielding performance of the wave-absorbing material is in direct proportion to the width of the wave-absorbing material (as shown in fig. 18), which results in that the circuit board assembly 100a in the prior art needs to realize a preset shielding effect, the cross-sectional width of the wave-absorbing material needs to exceed at least 10mm, and the overall area of the circuit board assembly 100a in the prior art is greatly increased; the shielding performance of the frequency selective surface is then correlated with the wavelength λ of the electromagnetic wave, and also limits the overall area miniaturization of the circuit board assembly 100 a.

In the prior art circuit board assembly 100b shown in fig. 17, a circuit board 10b, a chip-on-board 20b, and a heat sink 30b are also included. Further, the prior art circuit board assembly 100b also provides a shield cover 40b on the outside of the on-board chip 20 b. The shield case 40b is fixed to the circuit board 10b and surrounds the periphery of the on-board chip 20 b. The structure of the shield can 40b needs to partially extend between the heat sink 30b and the chip-on-board 20b and form a clearance fit with the heat sink 30b and the chip-on-board 20b, respectively, and the height of the clearance is not less than 0.5mm. The gap between the heat sink 30b and the chip-on-board 20b at this time needs to be at least more than 1mm, which increases the height of the prior art circuit assembly 100b and also is not advantageous for its miniaturized design.

Meanwhile, the shield case 40b is fixed to the circuit board 10b, and a transmission line passing through the shield case 40b may be provided at a surface of the circuit board 10 b. The position where the shield case 40b is combined with the circuit board 10b needs to be provided with a spaced saw-tooth structure to avoid the structure of the transmission line. The bonding precision between the spaced saw-tooth structures and the circuit board 10b cannot be guaranteed due to process limitations. As shown in fig. 19, when the external dimension of the shielding case 40b reaches 98 × 89mm, the total coplanarity of the saw-tooth structures in 6 samples reaches 0.12-0.23mm, which exceeds the requirement of 0.1mm for coplanarity, and thus a good shielding effect cannot be achieved.

And this application circuit board assembly 100, through the structure that sets up shield frame 40 to cooperation shield 50 and onboard chip 20 direct contact, and shield 50 and shield frame 40 direct contact or the less structure setting in clearance can be on the basis of guaranteeing onboard chip 20 shielding effect, reduce shielding structure's overall size, be favorable to circuit board assembly 100's miniaturization, the design of highly densely arranging, further also reduced this application electronic equipment 200's whole volume.

The circuit board assembly 100 can be applied to a scene that the size of the on-board chip 20 is large (such as 50-110 mm), and by using the scheme of the circuit board assembly 100, the high-density arrangement design of the circuit board assembly 100 in the scene can be realized.

Referring to fig. 20, a transmission line 12 is further disposed on the first plane 11 of the circuit board 10. One end of the transmission line 12 is connected and conducted with the on-board chip 20, and the other end is connected and conducted with the other device 110, for realizing the data transmission function of the on-board chip 20. In one embodiment, the transmission line 12 may be a power line used to provide the electrical power needed for operation to the on-board chip 20. The other devices 110 are located outside the shielding frame 40, i.e. the end of the transmission line 12 remote from the chip-on-board 20 is located at the side of the shielding frame 40 remote from the chip-on-board 20. The number of the transmission lines 12 can be multiple, and the multiple transmission lines 12 can penetrate through one side of the shielding frame 40 to realize connection and conduction with external devices. In the illustration of fig. 20, the plurality of transmission lines 12 pass through the shield frame 40 from opposite sides thereof, respectively. It is understood that in other embodiments, the transmission line 12 may also pass through more sides of the shielding frame 40, which is not particularly limited in this application.

The shield frame 40 may also be fixed to the circuit board 10 by a connector 150. For clarity, the structure of the connector 150 at the shield frame 40 is omitted from the remaining drawings of the embodiments of the present application.

Please refer to the structural schematic of the shielding frame 40 shown in fig. 21. In the present embodiment, the shield frame 40 includes a main body 41, a boss 42, and a conductive paste 43. Wherein the body 41 includes a first side 411 and a second side 412. The first side 411 is located close to the circuit board 10 and the second side 412 is located far from the circuit board 10. The protruding portions 42 are arranged at intervals on the first side 411 of the main body 41 and protrude toward the first plane 11 of the circuit board 10. A hollow area 44 is formed between two adjacent protrusions 42, and the hollow area 44 is used for allowing the transmission line 12 to pass through.

It will be appreciated that each hollowed-out region 44 may be adapted to allow a single transmission line 12 to pass through. In some embodiments, the hollow-out region 44 may also allow multiple transmission lines 12 to pass through simultaneously. The structure of the shielding frame 40 can be based on the number, width and position of the transmission lines 12, and the number, spacing distance and position of the protruding portions 42 are correspondingly arranged, so that a better shielding effect is achieved on the basis that the transmission lines 12 penetrate.

The conductive paste 43 is at least disposed between the protrusion 42 and the first plane 11, i.e. the conductive paste 43 can be used to fill the gap between the protrusion 42 and the first plane 11. As mentioned above, in the circuit board 100b of the prior art shown in fig. 17, the coplanarity of the saw-tooth structures is difficult to ensure, so that the individual saw-tooth structures cannot be reliably attached to the circuit board 10b, which affects the shielding effect. In the embodiment of the present invention, the conductive paste 43 is applied to fill the gap between the protrusion 42 and the first plane 11, so that the poor shielding caused by the gap can be eliminated. Further, the conductive adhesive 43 may be coated on the sidewall of the protruding portion 42, so as to increase the contact area between the conductive adhesive 43 and the protruding portion 42, and improve the structural stability of the conductive adhesive 43.

In the structural schematic of the shielding frame 40 shown in fig. 22, the shielding frame 40 includes a main body 41, a pad 45, and a conductive paste 43. The pads 45 are arranged on the first plane 11 of the circuit board 10 at intervals, the main body 41 is located on a side of the pads 45 away from the first plane 11, and the conductive adhesive 43 is located between the pads 45 and the main body 41. The conductive adhesive 43 is used for realizing electrical communication between the pads 45 and the main body 41 so as to ensure a shielding effect at the positions of the pads 45, and a hollow area 44 is formed between two adjacent pads 45.

In the present embodiment, the pad 45 has a structure similar to the protruding portion 42 in fig. 21, and is used to form a hollow 44 on the first plane 11 of the circuit board 10 to allow the transmission line 12 to pass through. The bonding pad 45 can also be synchronously manufactured along with the circuit board 10, so that the position precision of the bonding pad 45 is improved, and the overall shielding effect of the shielding frame 40 is ensured.

Fig. 23 illustrates a cross-sectional structure of a circuit board assembly 100 of the present application in one embodiment. The direction of the cross section is a direction perpendicular to the first plane 11. Fig. 24 illustrates a planar structure of the chip on board 20 of this embodiment.

In designing the circuit board assembly 100 of the present application, it is first necessary to determine the frequency band in which the on-board chip 20 is likely to generate electromagnetic signals based on the operating characteristics of the chip. In the illustration of FIG. 23, the lower limit of the transmission rate of the on-board chip 20 is 20.625Gb/s and the upper limit of the transmission rate is 28Gb/s, thereby determining that the rejection band to the shielding structure is in the range of 20-30 GHz.

Then, the external dimensions of the on-board chip 20 were determined to be 61 × 61mm, and the on-board chip 20 was configured in the rail 24. The outer contour of the rail 24 is substantially aligned with the outer contour of the substrate base 21, the rail 24 having a width of about 6mm and a thickness of about 2mm. The peak power consumption of die 22 is about 393W.

Further, the gap between the heat sink 30 and the rail 24 is 1.2mm, and the thickness of the connection portion 53 of the shield 50 is about 0.2mm. The mounting height of the flexible shield ring 60 is about 1mm at this time. The flexible shielding ring 60 can be made of conductive adhesive, the tolerance band of the conductive adhesive is about 0.316mm, the range of the resilience force of the conductive adhesive is 5% -32%, the height of the flexible shielding ring 60 is 1.1mm, the width of the flexible shielding ring is about 1mm, the flexible shielding ring 60 is compressed after assembly, and the compression elasticity of the flexible shielding ring can ensure reliable support with the fence 24 and the radiator 30.

On the shielding portion 54 side of the shield 50, the gap between the shielding portion 54 and the shield frame 40 is set to 0.1mm. In order to ensure that the shielding element 50 and the shielding frame 40 are both accommodated within the outer contour of the heat sink 30, the width of the first side 411 of the shielding frame 40 is set to be wider than the width of the second side 412, i.e. the shielding frame 40 is set to be stepped as shown in fig. 23. The width of the first side 411 may be set to 1mm for ensuring a reliable connection between the shield frame 40 and the circuit board 10; the width of the second side 412 may be set to 0.75mm, so that the shielding portion 54 of the shielding element 50 is contracted toward the chip-on-board 20 to avoid the shielding portion 54 protruding beyond the outer contour of the heat sink 30 and causing interference with the adjacent device.

The above description is only for the specific embodiment of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions, such as the reduction or addition of structural elements, the change of shape of structural elements, etc., within the technical scope of the present application, and shall be covered by the scope of the present application; the embodiments and features of the embodiments of the present application may be combined with each other without conflict. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A circuit board assembly includes a circuit board, an on-board chip, a heat sink, a shield frame, and a shield;

the on-board chip is carried on a first plane of the circuit board, the radiator comprises a binding surface facing the on-board chip, and a heat conduction layer is arranged between the binding surface and the on-board chip; the radiator is fixed on the circuit board through a fastener, so that the binding surface is bound with the heat conduction layer;

the shielding frame is fixed on the first plane, the shielding frame is arranged around the on-board chip, and an annular gap is formed between the shielding frame and the on-board chip;

the shielding piece is of a hollow structure, the inner edge of the shielding piece is fixed on the on-board chip, the outer edge of the shielding piece is in contact with the shielding frame, or the outer edge of the shielding piece is positioned on one side of the shielding frame, which is far away from the on-board chip, and is arranged at an interval with the shielding frame; the shield is used for shielding the annular gap.

2. The circuit board assembly of claim 1, wherein the on-board chip comprises a substrate, a die, and a fence, the substrate is fixed on the first plane, the die is fixed on a side of the substrate facing away from the first plane, the fence is disposed around the die, the heat-conducting layer is disposed on an outer surface of the die, and an inner edge of the shield is fixed on the fence.

3. The circuit board assembly of claim 2, further comprising a flexible shielding ring surrounding the bonding surface and located between the rail and the heat sink, wherein two opposite surfaces of the flexible shielding ring respectively abut against the heat sink and the rail to shield the die.

4. The circuit board assembly of claim 3, wherein an inner edge of the shield is sandwiched between the flexible shield ring and the fence.

5. The circuit board assembly according to claim 1, wherein the on-board chip includes a substrate, a bare chip, and a housing, the substrate is fixed on the first plane, the housing is fixed on a side of the substrate facing away from the first plane, the housing and the substrate surround to form a receiving space, the bare chip is received in the receiving space, an inner edge of the shield is disposed on an outer surface of the housing, and the housing is further configured to form the heat conducting layer.

6. The circuit board assembly of any one of claims 1-5, wherein an outer edge of the shield contacts the shield frame, and the shield is flexible.

7. A circuit board assembly according to any of claims 1-5, wherein the shield comprises a connection portion and a shielding portion, wherein an inner edge of the shield is located on the connection portion, an outer edge of the shield is located on the shielding portion, and the shielding portion extends in a direction perpendicular to the first plane.

8. The circuit board assembly according to any one of claims 1 to 7, wherein the circuit board comprises a transmission line, the transmission line is located on the first plane, one end of the transmission line is fixedly connected and conducted with the on-board chip, the other end of the transmission line is located on a side, away from the on-board chip, of the shielding frame, and the shielding frame is provided with a hollowed-out area for allowing the transmission line to pass through.

9. The circuit board assembly according to claim 8, wherein the shielding frame includes a main body, protruding portions and a conductive adhesive, the protruding portions are spaced apart from each other on a side of the main body close to the first plane and protrude toward the first plane, a hollow area is formed between two adjacent protruding portions, and the conductive adhesive is disposed between the protruding portions and the first plane.

10. The circuit board assembly according to claim 8, wherein the shielding frame includes a main body, pads and a conductive adhesive, the pads are arranged on the first plane at intervals, the main body is located on a side of the pads, which faces away from the first plane, the conductive adhesive is located between the pads and the main body, and one of the hollow-out areas is formed between two adjacent pads.

11. The circuit board assembly of any of claims 1-10, wherein the shielding frame includes a first side proximate to the first plane and a second side distal from the first plane in any cross-section perpendicular to the first plane, the first side having a greater wall thickness than a wall thickness of the second side.

12. An electronic device comprising a housing and a circuit board assembly as claimed in any one of claims 1-11 mounted to the housing for performing the functions of the electronic device.