CN115413158A

CN115413158A - Electronic equipment

Info

Publication number: CN115413158A
Application number: CN202210940317.8A
Authority: CN
Inventors: 廖建兴
Original assignee: Queclink Wireless Solutions Co Ltd
Current assignee: Queclink Wireless Solutions Co Ltd
Priority date: 2022-08-05
Filing date: 2022-08-05
Publication date: 2022-11-29

Abstract

The embodiment of the application relates to the technical field of equipment heat dissipation, and discloses electronic equipment, which comprises a shell and a PCB (printed Circuit Board), wherein the shell is provided with a cavity, and a first inner wall surface and a second inner wall surface which are separated by the cavity and are oppositely arranged; the PCB is arranged in the cavity and provided with a first surface and a second surface which are oppositely arranged; the distance between the first inner wall face and the PCB is smaller than the distance between the second inner wall face and the PCB, the first surface is opposite to the first inner wall face and is provided with a first device, the first device is a heating device, the second surface is opposite to the second inner wall face and is provided with a second device, and the height of the second device on the PCB is higher than that of the first device on the PCB. The electronic equipment provided by the embodiment of the application can be favorable for timely transmitting the heat generated by the device to the outside to realize heat dissipation.

Description

Electronic device

Technical Field

The embodiment of the application relates to the technical field of equipment heat dissipation, in particular to an electronic device.

Background

The electronic device usually includes a signal processing circuit and a signal transceiving circuit, and a device for processing a signal and a device for transceiving a signal are simultaneously designed on a PCB of the electronic device. In addition, other devices with auxiliary functions, such as a connecting device for transmitting signals, an isolating device for isolating signals, a signal lamp for indicating signals, and the like, are designed on the PCB of the electronic device, and these devices are designed to work on one PCB at the same time.

In the current electronic equipment shell, heat generated by devices during operation can be transferred to the electronic equipment shell through air, so that the heat can be continuously released to the ambient environment through the shell, and normal heat dissipation of the electronic equipment is realized. However, the existing electronic devices have poor heat dissipation effects, and cannot timely transfer heat generated by the devices to the outside to achieve heat dissipation.

Disclosure of Invention

An object of the embodiment of the application is to provide an electronic device, which can be beneficial to timely transferring heat generated by a device to the outside to realize heat dissipation.

In order to solve the above technical problem, an embodiment of the present application provides an electronic device, including a housing and a PCB, where the housing has a cavity, and a first inner wall surface and a second inner wall surface that are separated by the cavity and are oppositely disposed; the PCB is arranged in the cavity and provided with a first surface and a second surface which are oppositely arranged; the first inner wall surface and the first surface are spaced from each other; the second inner wall surface and the second surface are spaced from each other; the distance between the first inner wall face and the PCB is smaller than the distance between the second inner wall face and the PCB, the first surface is opposite to the first inner wall face and is provided with a first device, the first device is a heating device, the second surface is opposite to the second inner wall face and is provided with a second device, and the height of the second device on the PCB is higher than that of the first device on the PCB.

The electronic equipment that this application embodiment provided, first type device is arranged on the PCB board apart from the less one side of shell internal wall face, and is higher than the second type device of first type device and arranges on the great one side of PCB board apart from shell internal wall face, through arranging two types of devices respectively on the two sides of PCB board, the device that generates heat is arranged on one of them face of PCB board alone promptly. Like this, the distance between device and the shell internal face that generates heat can not receive the influence of highly great device, and the distance between device and the shell internal face that generates heat promptly compares in the distance between highly great device and the shell internal face, can set up to less scope, can reduce the heat transfer distance between device and the shell internal face that generates heat to be favorable to in time transmitting the heat that the device during operation that generates heat to the external world in order to realize the heat dissipation.

In addition, the electronic equipment further comprises a heat conduction gasket which is arranged between the first inner wall surface and the first type device and is respectively attached to the first inner wall surface and the first type device. Therefore, the heat of the heating device can be transmitted to the shell in time through the heat conducting gasket.

In addition, the compression amount of the heat conduction gasket in the thickness direction of the heat conduction gasket is greater than or equal to 5% and less than or equal to 45%. Therefore, the thermal resistance can be reduced through the compression of the heat conduction gasket, and meanwhile, excessive bad acting force cannot be caused to the warping of the PCB.

In addition, the compression amount of the heat conduction gasket in the thickness direction of the heat conduction gasket is larger than 20%, the PCB is provided with a screw hole adjacent to the first type device, the PCB is fixed with the shell through a screw penetrating through the screw hole, and the distance between the screw hole adjacent to the first type device and the first type device is 1-30 mm. Therefore, the problem that the PCB is warped due to overlarge compression amount of the heat conducting gasket can be well prevented through the fastening effect of the screw at the screw hole, and meanwhile, the problem that the screw is installed due to the overlarge distance can be avoided, and the problem that the warping of the PCB is improved due to the overlarge distance is avoided.

In addition, the breakdown voltage between the housing and the first type of device is greater than or equal to 1kV. Therefore, the heat conducting gasket cannot be broken down under 2kV static test, and the safety requirement is met.

In addition, the shell packaging material of the first device is an insulating material, and the sum of the insulating strength of the heat conducting gasket and the insulating strength of the shell packaging material of the first device is greater than or equal to 1kV; or the shell packaging material of the first device is a conductive material, and the insulating strength of the heat conducting gasket is greater than or equal to 1kV.

In addition, the first type device is welded on the PCB, the shell packaging material of the first type device is an insulating material, pins of the first type device are arranged at the bottoms of the periphery or two sides of the body of the first type device, the pins extend along the surface of the PCB in the direction far away from the body, soldering tin is covered on the pins and is welded on a bonding pad of the PCB through the soldering tin, the surface creepage distance between the first inner wall surface and the first surface of the PCB is larger than or equal to 1.0mm, wherein the surface creepage distance is the sum of the thickness of the heat conducting gasket, the distance from the edge of the heat conducting gasket to the edge of the first type device, and the height from the soldering tin to the top of the first type device; or the like, or a combination thereof,

the first type device is welded on the PCB, a shell packaging material of the first type device is an insulating material, a pin of the first type device is arranged on a side wall between the top and the bottom of the body of the first type device, the pin is bent and extends from the side wall towards the direction close to the PCB, the tail end of the pin extends to the PCB and is welded on a pad of the PCB through soldering tin, and the surface creepage distance between the first inner wall surface and the first surface of the PCB is larger than or equal to 1.0mm, wherein the surface creepage distance is the sum of the thickness of the heat conduction gasket, the distance from the edge of the heat conduction gasket to the edge of the first type device, and the height from the pad to the top of the first type device.

In addition, the shell packaging material of the first type device is a conductive material, and the surface creepage distance between the first inner wall surface and the shell of the first type device is greater than or equal to 1.0mm, wherein the surface creepage distance is the sum of the thickness of the heat conduction gasket and the distance between the edge of the heat conduction gasket and the edge of the first type device. Therefore, the phenomenon that the first-type device is broken down due to creeping discharge between the heat conducting gasket and the shell can be avoided.

In addition, the first device is welded on the PCB, the shell packaging material of the first device is an insulating material, the pins of the first device are arranged on the bottom surface of the body of the first device and are electrically connected with the bonding pads of the PCB, the pins of the first device and the bonding pads of the PCB are both covered under the body, the creepage distance between the first inner wall surface and the first surface of the PCB is larger than or equal to 1.0mm, wherein the creepage distance is the sum of the thickness of the heat conducting gasket, the distance from the edge of the heat conducting gasket to the edge of the first device and the height of the first device perpendicular to the PCB.

In addition, the first type of device comprises a radio frequency device, a digital device and a power supply device, the radio frequency device is arranged in a first area of the PCB, the digital device is arranged in a second area of the PCB, and the first area and the second area are arranged at intervals. The radio frequency device is arranged in the first area, the digital device is arranged in the second area, and the first area and the second area are arranged at intervals. Therefore, the partition design of the digital circuit and the analog circuit on the PCB can be realized.

In addition, a shielding cover for covering the first type of device is arranged on the PCB.

In addition, the shielding case comprises a first shielding case, the first shielding case is arranged on the PCB and surrounds a first shielding cavity, and the radio frequency device and the digital device are both positioned in the first shielding cavity and are separated from each other through a partition plate arranged in the first shielding case. Therefore, the signal energy can be shielded in the corresponding area through the first shielding cover, and the signal energy is prevented from being diffused to the area where other devices of the PCB are located; meanwhile, the partition board in the first shielding case plays a role in isolating and shielding the radio frequency device, the digital device and the power supply device.

In addition, the shield cover includes first shield cover and second shield cover, first shield cover is located on the first region of PCB board and enclose into first shielding chamber, the radio frequency device is located in the first shielding chamber, second shield cover is located on the second region of PCB board and enclose into second shielding chamber, digital device is located in the second shielding chamber. Therefore, the shielding cavity formed between the first shielding cover, the second shielding cover and the PCB can be used for respectively isolating and shielding the radio frequency device and the digital device, so that signal energy is effectively shielded in a corresponding area, and the signal energy is prevented from being diffused to the area where other devices of the PCB are located.

In addition, a first heat conduction gasket which is respectively attached to the first shielding cover and the first inner wall face is arranged in the shell, and a second heat conduction gasket which is respectively attached to the first shielding cover and the radio frequency device is arranged in the shielding cavity. Therefore, heat transfer from the radio frequency device to the shell can be achieved through the first heat conduction gasket, the first shielding cover and the second heat conduction gasket, and heat generated by the radio frequency device during working can be transferred to the shell through the first heat conduction gasket and the second heat conduction gasket in time to achieve heat dissipation.

In addition, a third heat conduction gasket which is respectively attached to the second shielding cover and the first inner wall surface is arranged in the shell. Therefore, heat transfer from the digital device to the shell can be realized through the second heat conduction gasket, and heat generated by the digital device during working can be transferred to the shell through the third heat conduction gasket and the second shielding case in time to realize heat dissipation.

In addition, the heat conduction gasket is a ceramic gasket, and heat conduction glue is filled between the heat conduction gasket and a part attached to the heat conduction gasket. Therefore, gaps among the heat conduction gasket, the first inner wall surface and the first device can be filled with the heat conduction glue, and the heat transfer effect is prevented from being influenced by air filled into the gaps.

In addition, a plurality of screw columns are arranged on the first inner wall face, a plurality of screw holes which correspond to the screw columns one to one are formed in the PCB, and the PCB is fixed to the shell through screws which penetrate through the screw holes and are screwed on the corresponding screw columns. Thus, the PCB board and the shell can be quickly fixed into a whole.

In addition, the first type device and the second type device are mutually staggered in the direction perpendicular to the PCB. Therefore, an air convection environment can be provided for the heat transferred to the PCB by the first device, and the heat transferred to the PCB by the first device can be timely dispersed to the second inner wall surface of the shell.

In addition, the shell comprises a first shell and a second shell, the first shell and the second shell are arranged oppositely to enclose the cavity, the first inner wall surface is located on the first shell, and the second inner wall surface is located on the second shell. Therefore, the PCB can be conveniently installed, and the top shell and the bottom shell can be conveniently detached so as to maintain and replace the PCB and various devices.

In addition, a plurality of racks which are spaced from each other are arranged on the outer wall surface of the first shell, which is far away from the first inner wall surface, and each rack protrudes from the outer wall surface of the first shell in the direction far away from the first inner wall surface. Thus, the surface area of the outer wall surface of the first casing can be increased by the heat dissipation rack, so that the heat transfer area of the first casing is increased.

In addition, the first shell is a bottom cover of the electronic device. In this way, heat can be transferred to the bottom of the electronic device while avoiding excessive temperatures at the top of the electronic device that are more easily reached by the user.

In addition, the first type device is also arranged on the second surface. Therefore, a part of the first-type devices can be dispersed to the other surface of the PCB, heat concentration is reduced, and heat dissipation pressure is reduced.

In addition, the PCB further comprises a heat conduction structure penetrating through the PCB, the first type device is arranged on the second surface, is in thermal contact with the heat conduction structure and transfers heat to the heat conduction structure so as to be transferred to the first surface side through the heat conduction structure. Therefore, the heat at the second surface of the PCB can be transferred to one side of the first surface, and the heat of the electronic device can be transferred out from the same side.

In addition, the heat conduction structure includes a heat dissipation pad disposed on the second surface, exposed copper disposed on the first surface, and heat dissipation vias penetrating the PCB and connected to the heat dissipation pad and the exposed copper, respectively.

In addition, still including setting up in PCB inboard layer, and be located inlayer ground copper foil or power copper foil between the first surface with the second surface, the heat dissipation via hole with inlayer ground copper foil or power copper foil electricity are connected. Therefore, the heat dissipation area in the horizontal direction of the inner layer of the PCB can be increased through the ground copper foil or the power copper foil of the inner layer of the PCB while the heat dissipation through hole (along the thickness direction of the PCB) plays a vertical heat conduction role.

In addition, the heat dissipation welding plate further comprises a bottom layer ground copper foil or a power supply copper foil arranged on one side of the second surface, and the heat dissipation welding plate is electrically connected with the bottom layer ground copper foil or the power supply copper foil. Therefore, the heat dissipation area in the horizontal direction of the bottom layer of the PCB can be increased through the ground copper foil or the power copper foil of the bottom layer of the PCB.

In addition, still include the top layer ground copper foil or the power copper foil of setting in first surface one side, the copper exposure with top layer ground copper foil or power copper foil electricity are connected. Therefore, the heat dissipation area in the horizontal direction of the top layer of the PCB can be increased through the ground copper foil or the power copper foil of the top layer of the PCB.

In addition, the heat conduction gasket is arranged between the first inner wall surface and the exposed copper and is respectively attached to the first inner wall surface and the exposed copper. In this way, heat conducted to the first surface side of the PCB can be transferred to the housing of the electronic device through the thermal pad as quickly as possible.

In addition, the heating power of the first device is more than 0.25W.

In addition, the PCB is provided with a shielding case, at least one first-type device is arranged in the shielding case, a first heat conduction gasket attached to the shielding case and the first inner wall face is arranged in the shell, and a second heat conduction gasket attached to the shielding case and the first-type device is arranged in the shielding case.

In addition, the surface creepage distance between the first inner wall surface and the shielding case is greater than or equal to 1.0mm, wherein the surface creepage distance between the first inner wall surface and the shielding case is the sum of the thickness of the heat conduction gasket and the distance between the edge of the heat conduction gasket and the edge of the shielding case.

In addition, the shell comprises a top shell and a bottom shell, and at least one first fastener column is arranged on the shell inner side surface of the top shell or the bottom shell; the PCB is provided with at least one first drilling hole; the electronic device further includes at least one fastener mated with the at least one fastener post; wherein,

the fastener penetrates through the first drilling hole of the PCB and is combined with the fastener column on the inner side surface of the shell of the top shell; or

The fastener penetrates through the first drilling hole of the PCB and is combined with the fastener column on the inner side surface of the bottom shell; or

The bottom shell is provided with at least one second drilling hole, at least one second fastener column is arranged between the bottom shell and the PCB, and the fastener penetrates through the second drilling hole of the bottom shell, the second fastener column and the drilling hole of the PCB to combine the second drilling hole with the first fastener column on the shell inner side surface of the top shell; or

The top shell is provided with at least one third drilled hole, and at least one third fastener column is arranged between the top shell and the PCB; the fastener passes through the third drilling hole of the top shell, the third fastener column and the drilling hole of the PCB and is combined with the first fastener column on the inner side surface of the bottom shell.

In addition, the packaging shell of the first type device is made of a conductive material, a first heat conduction gasket which is respectively attached to the first type device and the first inner wall surface is arranged in the shell, the creepage distance between the first inner wall surface and the first type device is larger than or equal to 1.0mm, and the creepage distance between the first inner wall surface and the first type device is the sum of the thickness of the heat conduction gasket and the distance between the edge of the heat conduction gasket and the edge of the first type device.

In addition, the first surface is opposite to the first inner wall surface and is provided with a third device, the third device is a heating device, the heating value of the third device is smaller than that of the first device, and the height of the third device on the PCB is lower than that of the second device on the PCB.

In addition, the top of the third type of device is made of metal, the top of the third type of device is spaced from the first inner wall surface, and the distance between the top of the third type of device and the first inner wall surface is larger than or equal to 0.6mm.

In addition, the top of the third type of device is made of an insulating material, the top of the third type of device is spaced from the first inner wall surface, and the height of the third type of device on the PCB is smaller than the distance between the first inner wall surface and the first surface.

In addition, the top of the third type of device is made of metal, an insulating sheet is arranged between the top of the third type of device and the first inner wall face, and the sum of the height of the third type of device on the PCB and the thickness of the insulating sheet in the direction perpendicular to the PCB is smaller than the distance between the first inner wall face and the first surface.

In addition, a groove facing the third device is formed in the first inner wall face, and the top of the third device is spaced from the inner wall of the groove.

In addition, the top of the third device is made of metal, the top of the third device is spaced from the inner wall of the groove, the minimum distance between the top of the third device and the inner wall of the groove is larger than or equal to 0.6mm,

and/or the top of the third device is made of an insulating material, the top of the third device is spaced from the inner wall surface of the groove, and the height of the third device on the PCB is smaller than the sum of the distance between the first inner wall surface and the first surface and the depth of the inner wall surface of the groove in the direction vertical to the PCB.

In addition, the top of the third type of device is made of metal, an insulating sheet is arranged between the top of the third type of device and the inner wall of the groove, and the height of the third type of device on the PCB and the thickness of the insulating sheet are smaller than the sum of the distance between the first inner wall face and the first surface and the depth of the inner wall face, perpendicular to the PCB direction, of the groove.

Drawings

One or more embodiments are illustrated by way of example in the accompanying drawings which correspond to and are not to be construed as limiting the embodiments, in which elements having the same reference numeral designations represent like elements throughout, and in which the drawings are not to be construed as limiting in scale unless otherwise specified.

Fig. 1 is a schematic cross-sectional structure diagram of an electronic device provided in an embodiment of the present application;

FIG. 2 is a schematic cross-sectional view of an electronic device when a first device provided in an embodiment of the present application is disposed on a top layer of a PCB;

fig. 3 is a schematic cross-sectional structure diagram of an electronic device when a first type device provided by an embodiment of the present application is arranged on a bottom layer of a PCB;

fig. 4 is a schematic view of radiation in an electronic device provided by an embodiment of the present application when a shielding cover is not provided;

FIG. 5 is a diagram of a thermal resistance model of an electronic device using an insulating soft thermal gasket according to an embodiment of the present disclosure;

FIG. 6 is a schematic view of an installation structure of an insulating hard thermal pad according to an embodiment of the present application;

FIG. 7 is a diagram of a thermal resistance model of an electronic device using an insulating hard thermal gasket according to an embodiment of the present disclosure;

FIG. 8 is an enlarged fragmentary view of the cross-sectional view of FIG. 2;

FIG. 9 is another enlarged partial view of the cross-sectional view of FIG. 2;

FIG. 10 is a current waveform diagram of electrostatic discharge under the requirement related to International Standard IEC 61000-4-2;

FIG. 11 is a view of a discharge model of the electrostatic discharge device;

fig. 12 is a schematic cross-sectional view of an electronic device provided in an embodiment of the present application when the electronic device is placed vertically;

fig. 13 is a schematic cross-sectional view of an electronic device according to an embodiment of the present disclosure;

fig. 14 is a schematic cross-sectional structure diagram of an electronic device when a first device provided by an embodiment of the present application is simultaneously disposed on a top layer and a bottom layer of a PCB board;

fig. 15 is a cross-sectional view of a heat generating device + a thermal pad + a metal housing of a BGA package according to an embodiment of the present application;

fig. 16 is a cross-sectional view of a heat generating device + a thermal pad + a metal housing of an SOP package provided in an embodiment of the present application;

fig. 17 is a cross-sectional view of a heat generating device + a thermal pad + a metal housing of a QFN package according to an embodiment of the present disclosure;

fig. 18 is a partial cross-sectional structural view of an electronic apparatus having both a high heat generating device and a low heat generating device according to an embodiment of the present application;

fig. 19 is a partial cross-sectional structural view of another electronic device provided in an embodiment of the present application and having both a high heat generating device and a low heat generating device;

fig. 20 is a partial cross-sectional structural view of still another electronic device provided in an embodiment of the present application and having both a high heat generating device and a low heat generating device;

fig. 21 is a partial cross-sectional structural view of still another electronic device having both a high heat generating device and a low heat generating device according to an embodiment of the present application;

fig. 22 is a schematic cross-sectional view of an electronic device when a first device provided in an embodiment of the present application is disposed on a top layer of a PCB.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following describes each embodiment of the present application in detail with reference to the accompanying drawings. However, it will be appreciated by those of ordinary skill in the art that numerous technical details are set forth in various embodiments of the present application in order to provide a better understanding of the present application. However, the technical solution claimed in the present application can be implemented without these technical details and various changes and modifications based on the following embodiments. The following embodiments are divided for convenience of description, and should not constitute any limitation to the specific implementation manner of the present application, and the embodiments may be mutually incorporated and referred to without contradiction.

Referring to fig. 1, fig. 1 is a cross-sectional structure diagram of an electronic device according to an embodiment of the present disclosure, the electronic device includes a housing and a PCB 13, the housing has a cavity, and a first inner wall surface A1 and a second inner wall surface B1 that are separated by the cavity and are disposed oppositely; the PCB 13 is arranged in the cavity, the PCB 13 is provided with a first surface and a second surface which are oppositely arranged, and the first inner wall surface A1 and the first surface of the PCB 13 are mutually spaced; the second inner wall surface B1 is spaced from the second surface of the PCB 13; the distance between the first inner wall surface A1 and the PCB 13 is smaller than the distance between the second inner wall surface B1 and the PCB 13, the first surface of the PCB 13 is just opposite to the first inner wall surface A1 and is provided with a first device, the first device is a heating device, the second surface of the PCB 13 is just opposite to the second inner wall surface B1 and is provided with a second device, and the height of the second device on the PCB 13 is higher than that of the first device on the PCB 13.

It should be noted that the electronic device in the embodiment of the present application may be an industrial router that adopts a scheme of WiFi6 (sixth generation wireless network technology) plus mobile 5G (fifth generation mobile communication technology) or a scheme of WiFi5 (fifth generation wireless network technology) plus mobile 4G (fourth generation mobile communication technology), or may be various electronic products, communication devices, medical apparatuses, vehicle-mounted devices, industrial devices, and mining devices that have metal shells or non-metal shells. For convenience of description, the embodiments of the present application are described by taking an industrial router as an example, but this does not represent a limitation on electronic devices.

Before describing the embodiments of the present application, a heat dissipation scenario in an industrial router related to the embodiments of the present application is first described.

As shown in fig. 1, the housing of the industrial router 17 is provided with a PCB 13, and the heights of heat generating devices such as a baseband chip 5, a DDR (dynamic memory chip) particle 6, and a FEM (Front End Module) chip 12 in the PCB 13 are not high; the network port transformer 11, the relay (not shown in fig. 1), the R232/R485 interface connector (not shown in fig. 1), the lamp panel (not shown in fig. 1), the SMA socket (radio frequency connector socket, not shown in fig. 1), the network port connector 10, and the like in the PCB 13 belong to high-sized devices. In general, the PCB stack and layout of the industrial router are formed by disposing heat generating devices such as baseband chips 5, DDR particles 6, FEM chips 12, and the like, and high-voltage devices such as a network interface transformer 11, a relay (not shown), an R232/R485 interface connector (not shown), a lamp panel (not shown), an SMA seat (not shown), a network interface connector 10, and the like on a TOP surface 8 (i.e., the first surface) of the PCB board. In addition, industrial routers basically employ a metal housing (e.g., a commonly used aluminum housing). In order to ensure that the tall components do not interfere with the metal top case 15 or the metal bottom case 16, the distance between the inner wall surface of the metal top case 15 or the inner wall surface of the metal bottom case 16 and the PCB board is usually required to be greater than the height of the tall components. The height of the heat generating device is low, and there is a problem if the metal top case 15 or the metal bottom case 16 is used for heat dissipation. This problem is that the inner wall surface of the metal top case 15 or the inner wall surface of the metal bottom case 16 is far from the heat generating device, which makes it inconvenient to add a very thick heat conductive gasket (e.g., the heat conductive gasket 2 shown in fig. 1). In addition, even if a very thick heat conduction gasket is added, the thickness of the heat conduction gasket can also affect the heat transfer effect of the heat conduction gasket (the heat conduction coefficient of the heat conduction gasket is lower than that of a metal material, so that the thinner the heat conduction gasket is, the smaller the self thermal resistance is), the heat of the heating device cannot be transferred to the metal shell in time, and the heating device is easy to burn out under the high-temperature condition. If the convex part of the metal top shell 15 is added at the position opposite to the heating device, so that the surface A1 in the metal top shell 15 is close to the surface of the heating device, the metal shell needs to be processed by high-cost CNC machining and forming (the processing efficiency is very low, the cost is very high), or the metal shell needs to be processed by die-casting (the die sinking cost is very high), although the schemes can solve the problem that the inner wall surface of the metal bottom shell 16 or the inner wall surface of the metal top shell 15 is far away from the heating device and the interference between large devices, the processing cost is very high.

The case may be made of a metal material having a high thermal conductivity (for example, aluminum has a thermal conductivity of 237W/(m · K), copper has a thermal conductivity of 401W/(m · K), silver has a thermal conductivity of 429W/(m · K), etc.), or may be made of a non-metal material having a good thermal conductivity, and the non-metal material is required to have a thermal conductivity of more than 20W/(m · K), for example, boron carbide has a thermal conductivity of 33W (m · K), aluminum oxide has a thermal conductivity of 20W/(m · K) to 30W/(m · K), cubic boron nitride has a thermal conductivity of 33W/(m · K), monocrystalline aluminum nitride has a thermal conductivity of 275W/(m · K), beryllium oxide has a thermal conductivity of about 200W/(m · K), diamond has a thermal conductivity of 2000W/(m · K), polycrystalline has a thermal conductivity of 70 to 210W/(m · K), and the monocrystalline aluminum nitride and beryllium oxide have thermal conductivities equivalent to those of pure aluminum, and even exceed the general thermal conductivity of pure aluminum, and also exceeds the thermal conductivity of far from tin/(m · K)), and all the thermal conductivity of pure aluminum. Some non-metallic materials not only have good heat-conducting property, but also have higher hardness, are not easy to deform, have good machinable manufacturing characteristics at the same time, and can be completely used for processing shells of products.

In order to solve the problem that heat dissipation is not facilitated in the electronic device, according to the electronic device provided by the embodiment of the application, the heat generating device (i.e., the first type of device) and the tall and big device (i.e., the second type of device) in the PCB 13 are placed on different surfaces of the PCB. That is, the heating device can be placed on the top surface of the PCB 13, and the tall device can be placed on the bottom surface of the PCB 13 (at this time, the first surface of the PCB 13 is the top surface, and the second surface is the bottom surface); alternatively, the heat generating device is placed on the bottom surface of the PCB 13, and the tall device is placed on the top surface of the PCB 13 (in this case, the first surface of the PCB 13 is the bottom surface, and the second surface is the top surface). Thus, the distance between the heat generating device and the inner wall surface of the housing is not affected by a device having a large height. The distance between the device that generates heat and the shell internal face compares in the distance between highly great device and the shell internal face promptly, can set up to less scope to can reduce the heat transfer distance between device and the shell internal face that generates heat, thereby be favorable to in time transmitting the heat that the device during operation that generates heat to the external world in order to realize the heat dissipation.

In the first case, the tall and big components in the PCB 13 are placed on the BOTTOM surface of the PCB 13, so that the distance between the inner wall surface of the metal BOTTOM case 16 and the BOTTOM layer 7 of the PCB 13 is greater than the height of the tall and big components. Thus, the metal bottom shell 16 will not interfere with the tall devices, and the heat generating devices in the PCB 13 are placed on the surface of the TOP (TOP) layer, and the distance between the metal TOP shell 15 and the surface of the TOP layer 8 of the PCB is slightly larger than the height of the heat generating devices in the TOP layer 8. The inner wall surface of the metal top shell 15 is close to the heating device, and favorable conditions are provided for adding a thin heat conduction gasket (low-thermal-resistance heat conduction gasket) at the position opposite to the heating device.

In the first case of the electronic device shown in fig. 1 and 2, the housing of the industrial router 17 may be composed of a metal top shell 15 and a metal bottom shell 16, and an internal cavity is formed between the metal top shell 15 and the metal bottom shell 16; a PCB 13 is arranged in the inner cavity of the shell of the industrial router 17, and a TOP layer 8 of the PCB 13 is provided with devices such as a baseband chip 5, a DDR particle 6 and an FEM chip 12. The baseband chip 5, the DDR particles 6, and the FEM chip 12 all belong to devices with large power consumption, that is, devices with large heat generation, that is, devices of the first type. The BOTTOM layer 7 of the PCB 13 is provided with high and large devices, such as a net port transformer 11, a net port connector 10, a relay (not shown), an R232/R485 interface connector (not shown), a lamp panel (not shown), and an SMA socket (not shown).

At this time, the height of the net port transformer 11 is h10 (the height of the surface of the BOTTOM layer 7 protruding from the PCB 13), and the height of the net port connector 10 is h11 (the height of the surface of the BOTTOM layer 7 protruding from the PCB 13).

The relationship between the height H2 from the BOTTOM layer 7 of the PCB 13to the inner B1 surface of the BOTTOM metal shell 16, the height H10 of the net port transformer 11, and the height H11 of the net port connector 10 is as follows:

H2≧h11。

H2≧h10。

that is, the height H2 from the BOTTOM layer 7 of the PCB 13to the inner B1 surface of the BOTTOM metal shell 16 is greater than or equal to the height H10 of the network port transformer 11 (second type device) and the height H11 of the network port connector 10 (second type device). In consideration of the tolerance of the components, the flatness tolerance of the B1 surface in the metal BOTTOM shell 16, and the tolerance between the assembly of the metal BOTTOM shell 16 and the metal top shell 15, to avoid the interference problem between the high and large devices such as the net mouth transformer 11 and the net mouth connector 10 and the B1 surface in the metal BOTTOM shell 16, it is preferable that the height H2 between the BOTTOM layer 7 of the PCB 13 and the B1 surface in the metal BOTTOM shell 16 must be greater than the height H10 of the net mouth transformer 11 (high and large device) and the height H11 of the net mouth connector 10 (high and large device) by at least 0.5mm (millimeter).

In the second case, the tall device in the PCB board is placed on the TOP layer 8 such that the distance between the inner wall surface of the metal TOP case 15 and the TOP layer 8 of the PCB board is greater than the height of the tall device. Therefore, the metal top shell 15 can not interfere with tall devices, the heat generating devices in the PCB are placed on the BOTTOM layer 7, and the distance between the metal BOTTOM shell 16 and the BOTTOM layer 7 of the PCB is slightly larger than the height of the heat generating devices on the BOTTOM layer 7. The inner wall surface of the metal bottom shell 16 is close to the heating device, and a favorable condition is provided for adding a thin heat conduction gasket (low-thermal-resistance heat conduction gasket) at the position opposite to the heating device.

The electronic device in the second situation is shown in fig. 3, and the difference between fig. 3 and fig. 2 is that the heat generating devices (such as baseband chip 5, DDR particles 6, etc.) in the industrial router 17 in fig. 3 are disposed on the BOTTOM layer 7 of the PCB 13, and the tall devices (such as network port transformer 11, network port connector 10, etc.) are disposed on the TOP layer 8 of the PCB 13. The advantage of this arrangement is that when the industrial router 17 is in operation, the natural convection mainly occurs in the cavity B, not in the cavity a, because the heat generating device is disposed on the BOTTOM layer 7 of the PCB 13. Most of heat (80% -90%) of the heating device is transferred to the metal bottom shell 16, the heat is dissipated to the outside air through convection heat dissipation and radiation heat dissipation of the metal bottom shell 16 and the outside air, and only a small amount of heat is transferred to the cavity A through the air. The tall devices hardly generate heat, and only a small amount of heat (10% -20%) is transferred to the metal top shell 15 through internal air convection, so that the metal top shell 15 is not scalded when being touched by a hand, and the body feeling of a user is not influenced. In some cases, a very low cost extruded metal housing (high production efficiency) can be used for both the bottom metal shell 16 and the top metal shell 15.

Similarly, the height H1 from the TOP layer 8 of the PCB 13to the inside B1 surface of the metal TOP case 15 is greater than or equal to the height H10 of the mesh transformer 11 (second type device) and the height H11 of the mesh connector 10 (second type device), and is preferably greater than or equal to 0.5mm or more.

Through with the device and the tall and big device layering that generate heat for the first internal face of shell is nearer apart from the device that generates heat, provides the advantage for generating heat the device and just adding the heat conduction gasket in the position. Therefore, in some embodiments of the present application, the electronic apparatus may further include a heat conducting pad, and the heat conducting pad is disposed between the first inner wall surface of the housing and the first type device and is attached to the first inner wall surface and the first type device, respectively.

Through the heat-conducting gasket, the thermal resistance between the shell and the heating device can be reduced, and therefore heat generated by the heating device during working is timely transferred to the shell to dissipate heat.

In some embodiments of the present application, the first type device includes a radio frequency device, a digital device, and a power device, the radio frequency device is disposed in a first area of the PCB, the digital device is disposed in a second area of the PCB, and the first area and the second area are spaced apart from each other. Therefore, the partition design of the digital circuit and the analog circuit on the PCB can be realized. Specifically, the radio frequency device includes at least one of an FEM chip, a Wifi chip, a 5G module, and a 4G module.

More specifically, in the embodiment of the present application, the first type device may include a baseband chip 5, DDR particles 6 and an FEM chip 12, where the baseband chip 5 is disposed adjacent to the DDR particles 6 in a first region of the first surface of the PCB 13, and the FEM chip 12 is disposed in a second region of the first surface of the PCB 13, where the first region and the second region are disposed at an interval.

The baseband chip 5 and the DDR particles 6 are located in the digital circuit of the PCB board 13, and the FEM chip 12 is located in the analog circuit of the PCB board 13. In order to implement the partition design of the digital circuit and the analog circuit on the PCB 13, the baseband chip 5 and the DDR particles 6 may be arranged in a partition manner with the FEM chip 12. That is, the base tape chip 5 and the DDR particles 6 are disposed on a first area of the first surface of the PCB 13, and the FEM chip 12 is disposed on a second area of the first surface of the PCB 13, with the first area being spaced apart from the second area.

In addition, the baseband chip 5, the DDR particles 6 and the FEM chip 12 are arranged in a partitioned mode, heat generated by the heating device during working can be dispersed, and the heat is prevented from being concentrated to influence the heat transfer to the shell. The first type of device can also comprise other heating devices such as a radio frequency power amplifier chip, a 5G chip and the like.

In some embodiments of the present application, as shown in fig. 1, the electronic device may further include a first shield cover 88 and a second shield cover 20, the first shield cover 88 is disposed on the first surface of the PCB 13 and encloses a first shield cavity with the first surface, the baseband chip 5 and the DDR particles 6 are located in the first shield cavity, the second shield cover 20 is disposed on the first surface of the PCB 13 and encloses a second shield cavity with the first surface, and the FEM chip 12 is located in the second shield cavity. First shield cover 88 contains metal shielding lid base 4, shielding lid 18, and wherein metal shielding lid base 4 welds on PCB board 13, and baseband chip 5, DDR granule 6 set up in metal shielding lid base 4, fill heat conduction gasket 2, then cover shielding lid 18 in the top of metal shielding lid base 4, after the close coupling, pack heat conduction gasket 1 again between shielding lid 18 and metal top shell 15.

The first shielding cover 88 covers the periphery of the baseband chip 5 and the DDR particles 6, so as to prevent electromagnetic radiation generated by the baseband chip 5 and the DDR particles 6 from leaking out and causing the EMI (electromagnetic interference) radiation of the product to exceed the standard. The base band chip 5 is close to the DDR particles 6, the metal shielding cover base 4 is arranged on the periphery of the base band chip 5 of the TOP layer 8 of the PCB and the DDR particles 6, and the metal shielding cover upper cover is arranged above the metal shielding cover base 4 to form a first shielding cover 18.

Meanwhile, the second shielding cover 20 is arranged on the TOP layer 8 of the PCB 13, and the second shielding cover 20 covers the periphery of the FEM chip 12, so that the problem that the FEM chip 12 generates stray to cause stray overproof can be avoided.

The effect of the shield cover in the PCB 13 is the following 6 points: 1. the shielding cover is used for shielding devices in the shielding cover, such as CPU (central processing unit), DDR (double data rate) particles 6, crystal oscillator and other strong disturbance source devices and radiation generated by wiring, and preventing the devices and the wiring in the shielding cover from radiating to cause the EMI radiation test of a product to exceed the standard; 2. the shielding cover is used for electrostatic discharge (ESD) electrostatic test, and provides an ESD electrostatic discharge channel for CPU, DDR particle 6, FEM chip 12 and other key devices (related to the bypass of the electrostatic through the metal shielding cover, for example, when a set top box of a two-layer plate of a certain model SOC scheme is used for carrying out 4kV air discharge test on a USB interface, the shielding cover is not added, so that the dead halt is easy to occur, the electrostatic test cannot be carried out, unless a complete ground plane is arranged in the 4-layer plate as the discharge channel, and a complete ground plane is not arranged in the 2-layer plate, so that the shielding cover can become the ESD electrostatic discharge channel); 3. strong space electromagnetic radiation can be generated during air discharge test, and the shielding cover can shield sensitive devices such as the FEM chip 12 and the like, so that the condition that the sensitive devices such as the FEM chip 12 and the like are interfered by the space radiation to cause abnormal product functions is avoided; 4. RS (Radiated immunity) test (anti-radiation test) to avoid RS space radiation interference on sensitive devices such as CPU, DDR particles 6, FEM chip 12, etc.; the shielding cover can provide shielding for sensitive devices such as the CPU, the DDR particles 6 and the FEM chip 12, and the problem that the sensitive devices such as the CPU, the DDR particles 6 and the FEM chip 12 are interfered by RS space radiation to cause abnormal functions of products is avoided; 5. when in EMC (electromagnetic compatibility), an RF (Radio Frequency) device is placed in a shielding cover (a filter must be placed in the shielding cover), noise waves except 2.4GHz or 5.8GHz contained in the device are filtered out before the filter, an RF trace behind the filter can be designed outside the shielding cover, and then an antenna (for stray and sideband parameters in a Radio Frequency circuit, the filter and the shielding cover are two important parts, and the RF trace which does not pass through the filter can not be exposed outside the shielding cover in principle) 6 is arranged, and the shielding cover is added to the RF circuit, so that the interference of a BUCK power supply (BUCK switching power supply), a baseband chip 5, DDR particles 6, a clock and high-speed signals to the RF circuit can be prevented.

As shown in fig. 1, the first shielding cover 88 is provided to prevent electromagnetic radiation generated by the baseband chip 5 and the DDR particles 6 from leaking out and causing an EMI (electromagnetic interference) emission of the product to exceed a standard. The base band chip 5 is close to the DDR particles 6, the metal shielding cover base 4 is arranged on the periphery of the base band chip 5 of the TOP layer 8 of the PCB and the DDR particles 6, and the metal shielding cover upper cover is arranged above the metal shielding cover base 4 to form a first shielding cover 18.

It will be appreciated that the number of shielding cases may be only one, for example, only one first shielding case may be disposed on the PCB, such that the first shielding case is disposed on the PCB and encloses a first shielding cavity, and the radio frequency device and the digital device are both located in the first shielding cavity and are separated from each other by a partition disposed in the first shielding case. Therefore, the signal energy can be shielded in the corresponding area through the first shielding cover, and the signal energy is prevented from being diffused to the area where other devices of the PCB are located; meanwhile, the partition board in the first shielding case plays a role in isolating and shielding the radio frequency device and the digital device.

In some cases, the shield cover around the heat generating device may also be removed. Fig. 2 and 3 are cross-sectional views showing the electronic apparatus without the shield cover of the heat generating device. This scheme is generally applied to the situation that when no shielding cover is added, the radio frequency spurious test, EMI radiation and the like meet the related requirements of CE of european union, 3C of china and FCC of north america, and then the shielding cover of DDR particles 6, baseband chip 5 and FEM chip 12 can be removed.

When no shielding cover is added, the radiation pattern of each device can be described with reference to fig. 4, in fig. 4, taking the example that the baseband chip 26, the BUCK power supply 24, the DDR particles 28, the DDR traces 27 (traces between the DDR particles 28 and the baseband chip 26), the EFM chip 30, and the radio frequency traces 29 are arranged on the TOP layer 8 of the PCB. When the DDR particle 28 is in operation, the DDR trace 27 will emit radiation a, radiation b, and radiation c. Radiation a generated from the DDR trace 27 reaches gaps between product interfaces, such as a gap between a USB connector (not shown) and a network connector (not shown), a gap between a 232/485 interface connector (not shown) and a network connector (not shown), and leakage caused by the gap between the product interfaces may cause the rf stray of the whole device to exceed the standard, the EMI radiation to exceed the standard, and the like. Radiation b is generated from the DDR trace 27 to the FEM chip 30, so that the FEM chip 30 is interfered, and performance indexes of the FEM chip 30 are reduced, for example, an EVM (Error Vector Magnitude) index is deteriorated, and an acceptance sensitivity index is deteriorated. Radiation c is generated from the DDR trace 27 to the rf trace 29, so that the rf trace 29 is interfered, and the rf performance index is reduced, for example, the EVM (Error Vector Magnitude) index is degraded, and the reception sensitivity index is degraded. The DDR particles 28 will emit radiation d, radiation e, radiation f. The leakage from the radiation f generated by the DDR particles 28 to the gaps of the product interface, such as the gap between the USB connector (not shown) and the network interface connector (not shown), and the gap between the 232/485 interface connector (not shown) and the network interface connector (not shown), causes the rf stray of the whole device to exceed the standard, the EMI radiation to exceed the standard, and so on. Radiation e generated from the DDR particles 28 is transmitted to the FEM chip 30, and the FEM chip 30 is disturbed, which results in a decrease in performance index of the FEM chip 30, for example, an EVM (Error Vector Magnitude) index becomes worse, and an acceptance sensitivity index becomes worse. Radiation d is generated from the DDR particle 28 to the rf trace 29, and the rf trace 29 is disturbed, which results in a decrease of rf performance indexes, such as a degradation of EVM (Error Vector Magnitude) index, a degradation of acceptance sensitivity index, and the like. In addition, there are radiation h reaching the gap between the product interfaces generated when the rf trace 29 operates, and radiation g reaching the gap between the product interfaces generated when the FEM chip 30 operates.

The elimination of the shield cover of the industrial router here requires the following conditions to be met:

when the DDR particles 28 and the DDR traces 27 emit pulse electric fields to directly radiate on the radio frequency traces 29 and the FEM chips 30, if the frequency points at which the DDR particles 28 and the DDR traces 27 emit radiation (the pulse electric fields and the pulse magnetic fields) do not fall on the radio frequency working frequency points, then each index (for example, receiving sensitivity, emission power EVM, frequency offset, and the like) of the radio frequency traces 27 and the FEM chips 30 will not be affected, at this time, no shielding cover may be added at the positions of the baseband chips 26, the DDR particles 28 and the DDR traces 27, and no shielding cover may be added at the positions of the radio frequency traces 29 and the FEM chips 30, it should be noted that this design scheme without adding a shielding cover only aims at the situation that each index of the radio frequency is not affected;

when no shielding cover is added at the position of the FEM chip 30, if the stray and sideband test of the radio frequency can meet the requirements, no shielding cover can be added at the positions of the radio frequency routing 29 and the FEM chip 30, and it should be noted that the design scheme without adding the shielding cover only aims at the situation that the stray and sideband test indexes are not influenced;

when no shielding cover is added at the positions of the baseband chip 26, the BUCK power supply 24, the DDR particles 28, the DDR routing 27 and the FEM chip 30, if an EMI radiation test satisfies a margin (preferably 5dB or more) of 3dB (decibel) or more, no shielding cover may be added; it should be noted that, this design scheme without adding a shielding cover only aims at the situation that the EMI radiation test index is not affected;

when no shielding cover is added to the baseband chip 26, the BUCK power supply 24, the DDR particles 28, the DDR routing 27, and the FEM chip 30, if the electrostatic test (air discharge, contact discharge) does not result in abnormal phenomena such as packet loss, dead halt, and device damage, the shielding cover may not be added; it should be noted that, this design scheme without adding a shielding cover only aims at the situation that the static test index is not affected;

when no shielding cover is added to the baseband chip 26, the BUCK power supply 24, the DDR particles 28, the DDR routing 27, and the FEM chip 30, if the RS test (anti-radiation disturbance) does not generate abnormal phenomena such as packet loss, dead halt, and device damage, no shielding cover may be added; it should be noted that, this design scheme without adding a shielding cover only aims at the situation that the radiation disturbance resistance test index is not influenced.

In addition, under the condition that the distance between the heating device, namely the first device, and the inner wall surface of the shell is not influenced by the second device, an insulating heat conduction gasket can be arranged between the first inner wall surface of the shell and the first device, and heat generated by the first device is transferred to the first inner wall surface of the shell in time through the insulating heat conduction gasket.

In some embodiments of the present application, the insulating heat conducting pad may include a first heat conducting pad 1 and a second heat conducting pad 2, the first heat conducting pad 1 is located between the shielding cover 18 in the first shielding cover 88 and the first inner wall surface of the housing and respectively attached to the shielding cover 18 in the first shielding cover 88 and the first inner wall surface, and the second heat conducting pad 2 is located in the first shielding cavity and respectively attached to the shielding cover 18 in the first shielding cover 88, the baseband chip 5, and the DDR particles 6.

As shown in fig. 1, a first heat conducting gasket 1 (preferably, an insulating soft heat conducting gasket material) is added between the first shielding cover 18 and the in-case A1 surface of the metal top case 15, and a gap between the first shielding cover 18 and the metal top case 15 may be filled with the first heat conducting gasket 1 to reduce a thermal resistance therebetween.

And the second heat conducting gasket 2 is added between the first shielding cover 18 and the baseband chip 5 and the DDR particles 6, and the second heat conducting gasket 2 (optional heat conducting silicone grease, preferably soft heat conducting gasket material) is used for filling the gap between the first shielding cover 18 and the baseband chip 5 (heating device) and the gap between the first shielding cover 18 and the DDR particles 6 (heating device), so as to reduce the thermal resistance between the first shielding cover 18 and the baseband chip 5 (heating device).

In some embodiments of the present application, the heat conducting gasket may further include a third heat conducting gasket 3, and the third heat conducting gasket 3 is located between the second shielding case 20 and the first inner wall surface of the housing and is respectively attached to the second shielding case 20 and the first inner wall surface.

Since the FEM chip 12 belongs to a radio frequency chip, the air filling between the second shielding cover 20 and the FEM chip 12 can avoid affecting the radio frequency electrical performance of the FEM chip 12 (avoiding affecting the impedance of the FEM chip 12). And the third heat conduction gasket 3 is added between the second shielding case 20 and the first inner wall surface of the shell to realize timely heat transfer. As shown in fig. 1, a third heat conduction gasket 3 is added between the second shielding cover 20 and the in-housing A1 surface of the metal top housing 15, and the third heat conduction gasket 3 is used for filling a gap between the metal top housing 15 and the second shielding cover 20 to reduce air thermal resistance therebetween.

At this time, the height H1 from the TOP layer 8 of the PCB 13to the in-shell A1 surface of the metal TOP shell 15 is H1, the thickness of the first heat conducting pad 1 is H3, the thickness of the shielding cover 18 in the first shielding shell 88 is H4, the compressed thickness of the first heat conducting pad 1 is H5 (the compressed thickness of the heat conducting pad is at least 5% (preferably 20%) lower than the static uncompressed thickness, that is, the compressed amount of the heat conducting pad is at least 5% or more (preferably 20% or more), and the larger the compressed amount of the heat conducting pad is, the smaller the thermal resistance of the heat conduction of the heat conducting pad is), the relationship between the height H1 from the TOP layer 8 of the PCB 13to the in-shell A1 surface of the metal TOP shell 15 and the thickness H4 of the shielding cover 18 in the first shielding shell 88, the thickness H5 of the second heat conducting pad 2, and the thickness H6 of the DDR particles is as follows:

H1＝h6+h5+h4+h3。

meanwhile, the relationship between the height H1 of the TOP layer 8 of the PCB 13to the in-case A1 surface of the metal TOP case 15, the height H7 of the second shield cover 20, and the thickness H8 of the third heat conductive pad 3 is as follows:

H1＝h7+h8。

it should be noted that the addition of the thermal gasket is advantageous for filling the gap that is originally filled with air. Taking the situation shown in fig. 2 as an example, if the surface A1 in the metal top shell 15 is directly contacted with the baseband chip 5 and the DDR particles 6, the two surfaces are usually very flat, and the actual contact area is only 20% to 40%. In this case, the gap is filled with air between the surface A1 in the metal top case 15 and the base band chip 5 and DDR particles 6, and the air is a poor heat conductor, and the heat conductivity (under a stable heat transfer condition, a material with a thickness of 1 meter, a temperature difference between the surfaces on both sides is 1 degree, and heat is transferred through an area of 1 square meter in 1 hour) is only 0.01W/(m · K) to 0.04W/(m · K), which is not favorable for heat transfer. And the addition of the insulating heat-conducting gasket 1 is beneficial to realizing the heat transfer between the heat-generating device and the shell (such as the metal top shell 15).

Therefore, in the electronic device shown in fig. 2 and 3 with the shielding cover omitted, the base band DDR particles 6 and the base band chip 5 are directly in surface contact with the inside A1 of the metal top case 15 through the first heat conductive gasket 1; meanwhile, the FEM chip 12 is directly in surface contact with the inner shell A1 of the metal top shell 15 through the third thermal conductive gasket 3.

In some cases, the thickness of the thermal pad 1 may be 0.3mm to 3.0mm.

For example, in one embodiment, the thickness of the thermal pad 1 may be 1mm. By controlling the thickness of the thermal pad 1, it is possible to avoid the thermal pad being too thick to affect the heat transfer effect between the first type device and the housing (e.g., the metal top case 15 or the metal bottom case 16). Meanwhile, the situation that the gap between the first-type device and the shell cannot be filled well due to the fact that the heat conducting gasket 1 is too thin is avoided.

It should be noted that the housing includes a top shell (e.g., a metal top shell 15) and a bottom shell (e.g., a metal bottom shell 16). The amount of compression of the heat conductive gasket (e.g., the heat conductive gasket 1) between the heat generating device (e.g., the base tape chip 5 and the DDR particles 6) and the inner side surface (e.g., the in-case A1 surface of the metal top case 15 or the metal bottom case 16) of the housing (e.g., the metal top case 15 or the metal bottom case 16) is controlled by controlling the distance between the PCB board (e.g., the PCB board 13) and the housing (e.g., the metal top case 15 or the metal bottom case 16), and the distance between them is controlled by the fastener (e.g., the screw 51, the screw 55, the screw 58 in fig. 2) and the fastener post (e.g., the screw post 57, the screw post 53, the screw post 50 in the metal top case 15 in fig. 2) fixed in the housing (e.g., the metal top case 15 or the metal bottom case 16). The main 3 assembly modes are realized:

as shown in fig. 2, a screw post 57 (one of the fastener posts), a screw post 53 (one of the fastener posts), and a screw post 50 (one of the fastener posts) are disposed on a surface A1 in the metal top case 15, a screw hole 56 (i.e., a drilled hole is disposed in the PCB 13) is disposed in the PCB 13, a screw hole 54 (i.e., a drilled hole is disposed in the PCB 13), and a screw hole 52 (i.e., a drilled hole is disposed in the PCB 13), and the projections of the screw hole 56, the screw hole 54, and the screw hole 52 in the case A1 of the metal top case 15 respectively fall on the positions corresponding to the screw post 57, the screw post 53, and the screw post 50, i.e., the positions of the screw hole 56, the screw hole 54, and the screw hole 52 respectively correspond to the positions of the screw post 57, the screw post 53, and the screw post 50. A screw 55 (a kind of fastener), a screw 58 (a kind of fastener), and a screw 51 (a kind of fastener) are rotatably injected into the screw post 57, the screw post 53, and the screw post 50 through a screw hole 56, a screw hole 54, and a screw hole 52, respectively, of the PCB 13, compressing the distance H1 between the TOP layer 8 of the PCB 13 and the in-case A1 surface of the metal TOP case 15, and at this time, a stress is generated between the PCB 13 and the metal TOP case 15, which stress compresses the heat conductive gasket 1 between the base band chip 5 and the DDR particles 6 and the in-case A1 surface of the metal TOP case 15, and compresses the heat conductive gasket 3 between the FEM chip 12 and the in-case A1 surface of the metal TOP case 15, so that the thickness H5 of the heat conductive gasket 1 mounted between the base band chip 5 and the DDR particles 6 and the in-case A1 surface of the metal TOP case 15 is smaller than the thickness of the static unassembled heat conductive gasket 1, and the thickness H8 of the heat conductive gasket 3 mounted between the FEM chip 12 and the in-case A1 surface of the metal TOP case 15 is smaller than the static unassembled gasket 3. The deeper the screw 55, the screw 58 and the screw 51 are rotationally injected into the screw post 57, the screw post 53 and the screw post 50, the smaller the distance H1 between the TOP layer 8 of the PCB 13 and the in-shell A1 surface of the metal TOP shell 15, the smaller the thickness H5 of the heat conducting gasket 1 and the thickness H8 of the heat conducting gasket 3, the larger the compression amount of the heat conducting gasket 1 and the heat conducting gasket 3, the smaller the thermal resistance between the base band chip 5 and the DDR particles 6 and the in-shell A1 surface of the metal TOP shell 15, and the smaller the thermal resistance between the FEM chip 12 and the in-shell A1 surface of the metal TOP shell 15.

From fig. 2 and the above analysis, it is concluded that the depth to which the fastener (e.g., screw 51, screw 55, screw 58) is rotated into the fastener post (e.g., screw post 57, screw post 53, screw post 50) is inversely proportional to the distance H1 from the TOP layer of the PCB 13to the in-case A1 face of the metal TOP case 15, proportional to the amount of compression of the heat generating device to the thermally conductive pad between the in-case A1 face of the metal TOP case 15, and inversely proportional to the thermal resistance between the heat generating device and the in-case A1 face of the metal TOP case 15.

Compared with fig. 2, the difference between fig. 3 and fig. 2 is that the metal bottom case 16 and the metal bottom case 16 are exchanged, and nothing else is changed. As shown in fig. 3, a screw post 57 (a kind of fastener post), a screw post 53 (a kind of fastener post), and a screw post 50 (a kind of fastener post) are provided on the B1 side in the case of the metal bottom case 16, and a screw hole 56, a screw hole 54, and a screw hole 52 are provided in the PCB 13; the screws 55 (one type of fastener), the screws 58 (one type of fastener), and the screws 51 (one type of fastener) are rotatably injected into the screw holes 56, 54, 52 of the PCB 13 through the screw holes 57, 53, 50, respectively, to compress the distance H2 between the BOTTOM layer 7 of the PCB 13 and the B1 surface of the BOTTOM metal shell 16, and at this time, stress is generated between the PCB 13 and the BOTTOM metal shell 16, which compresses the heat conductive gasket 1 between the base tape chip 5 and the DDR particles 6 and the B1 surface of the BOTTOM metal shell 16, and compresses the heat conductive gasket 3 between the FEM chip 12 and the B1 surface of the BOTTOM metal shell 16, such that the thickness H5 of the heat conductive gasket 1 mounted between the base tape chip 5 and the DDR particles 6 and the B1 surface of the BOTTOM metal shell 16 is smaller than the thickness of the static unassembled heat conductive gasket 1, and the thickness H8 of the heat conductive gasket 3 mounted between the FEM chip 12 and the B1 surface of the BOTTOM metal shell 16 is smaller than the thickness of the unassembled heat conductive gasket 3. The deeper the screw 55, the screw 58 and the screw 51 are rotationally injected into the screw post 57, the screw post 53 and the screw post 50, the smaller the distance H2 between the BOTTOM layer of the PCB 13 and the in-shell B1 surface of the metal BOTTOM case 16 is, the smaller the thickness H5 of the heat conductive gasket 1 and the thickness H8 of the heat conductive gasket 3 are, the larger the compression amount of the heat conductive gasket 1 and the heat conductive gasket 3 is, the smaller the thermal resistance between the base band chip 5 and the DDR particles 6 and the in-shell B1 surface of the metal BOTTOM case 16 is, and the smaller the thermal resistance between the FEM chip 12 and the in-shell B1 surface of the metal BOTTOM case 16 is.

From fig. 3 and the above analysis, the following conclusions are drawn: the depth to which the fasteners (e.g., screws 51, 55, 58) are rotated into the fastener posts (e.g., screw posts 57, 53, 50) is inversely proportional to the distance H2 from the TOP layer of the PCB board 13to the in-case B1 side of the metal bottom case 16, proportional to the amount of compression of the heat generating device to the thermally conductive pad between the in-case B1 side of the metal bottom case 16, and inversely proportional to the thermal resistance between the heat generating device and the in-case B1 side of the metal bottom case 16.

FIG. 22 is a schematic cross-sectional view of an electronic device with a first type of device disposed on a top layer of a PCB; fig. 22 is different from fig. 2 in that fig. 2 shows a compression amount by which screws 55, screws 58, and screws 51 are attached to screw posts 57, screw posts 53, and screw posts 50 of the PCB 13 and the metal top case 15, and by applying stress to the PCB 13 by the screws (screws 55, screws 58, and screws 51) being coupled to the screw posts (screw posts 57, screw posts 53, and screw posts 50) of the metal top case 15, the heat conductive gasket 1 and the heat conductive gasket 3 are compressed by the stress between the PCB 13 and the in-case A1 surface of the metal top case. Fig. 22 shows that the metal bottom case 16 is provided with a drilling hole 67, a drilling hole 69, and a drilling hole 66, respectively, and a screw post 70 (i.e., a fastener post, which may or may not have a thread therein), a screw post 71 (i.e., a fastener post, which may or may not have a thread therein), and a screw post 72 (i.e., a fastener post, which may or may not have a thread therein) are provided in the cavity B; and screws 55, 58, 51 are mounted outside the metal bottom shell 16: the screw 55 penetrates through the drilling hole 67 of the metal bottom shell 16, the screw column 70 and the screw hole 56 of the PCB 13, is inserted into the screw column 57 of the metal top shell 15, and is matched with the internal thread of the screw column 53 through the external thread of the screw 55, so that the effect of fixing the whole machine is achieved, and meanwhile, the compression amount of the heat conduction gasket 1 and the heat conduction gasket 3 is compressed; the screw 58 penetrates through the drilling hole 69 of the metal bottom shell 16, the screw column 71 and the screw hole 54 of the PCB 13, is inserted into the screw column 52 of the metal top shell 15, and is matched with the internal thread of the screw column 50 through the external thread of the screw 51, so that the effect of fixing the whole machine is achieved, and meanwhile, the compression amount of the heat conduction gasket 1 and the heat conduction gasket 3 is compressed; that is, stress is generated between the screws 55, 58, 51 and the screw columns 57, 53, 50, respectively, and the stresses are applied to the metal bottom case 16, the screw columns 70, 71, 72, and the PCB 13 by the screws 55, 58, 51, respectively, and finally the compression amounts of the heat-conducting gasket 1 and the heat-conducting gasket 3 are compressed by the stress between the PCB 13 and the in-case A1 surface of the metal top case. The screw post 70 can be welded and fixed at the position of the BOTTOM layer copper exposure 76 in the PCB 13 (the screw hole 56 is at the center position of the copper exposure 76), the screw post 71 can be welded and fixed at the position of the BOTTOM layer copper exposure 73 in the PCB 13 (the screw hole 56 is at the center position of the screw hole 78), and the screw post 72 can be welded and fixed at the position of the BOTTOM layer copper exposure 74 in the PCB 13 (the screw hole 56 is at the center position of the screw hole 78). The screw column 70 can also be embedded and fixed at the intersection position 77 of the drilling 67 of the metal bottom shell 16 and the inner B1 surface of the metal bottom shell 16; the screw column 71 can also be embedded and fixed at the intersection position 78 of the drilling hole 67 of the metal bottom shell 16 and the inner B1 surface of the metal bottom shell 16; the screw post 51 may also be embedded in the intersection 78 of the bore 67 of the bottom metal shell 16 and the B1 surface of the bottom metal shell 16.

From fig. 22 and the above analysis, it is concluded that the depth of rotation of the fastener (e.g., screw 55, screw 58, screw 51) into the fastener post (e.g., screw post 57, screw post 53, screw post 50) is inversely proportional to the distance H2 from the TOP layer of the PCB board 13to the in-case B1 side of the metal bottom case 16, directly proportional to the amount of compression of the heat generating device to the in-case B1 side of the metal bottom case 16, and inversely proportional to the thermal resistance from the heat generating device to the in-case B1 side of the metal bottom case 16.

It is understood that the structures of the metal top shell 15 and the metal bottom shell 16 may be interchanged. That is, a drilled hole is provided in the metal top case 15, and a screw post (which may or may not have a thread inside) as a fastener post is provided in the cavity a; correspondingly, the screw can be installed outside the metal top shell 15, and the screw penetrates through the drilling hole of the metal top shell 15, the screw column serving as the fastener column and the screw hole of the PCB 13 and then is inserted into the screw column of the metal bottom shell 16, and the external thread of the screw is matched with the internal thread of the screw column of the metal bottom shell 16, so that the effect of fixing the whole machine is achieved, and meanwhile, the compression amount of the heat conduction gasket 1 and the heat conduction gasket 3 is compressed, which is not described in detail herein.

In some embodiments of the present application, the insulating thermal pad may be an insulating soft thermal pad or an insulating hard thermal pad. When the insulating soft heat-conducting pad is selected, the thickness of the insulating soft heat-conducting pad which is not used is at least 5% and more (preferably more than 20%, preferably more than 30%) thicker than the formed thickness after assembly, that is, the formed thickness of the insulating soft heat-conducting pad after assembly is compressed by at least 5% and more (preferably more than 20%, preferably more than 30%) than the thickness when not used. Therefore, when the heating device is arranged on the top surface of the PCB, the insulating soft heat-conducting gasket can be made to fully fill the gap between the surface A1 in the metal top shell 15 and the baseband chip 5 and the DDR particles 6, and especially, the tiny gap between the surface A1 in the metal top shell 15 and the baseband chip 5 and the DDR particles 6 is reduced as much as possible, because the tiny gap contains air, the thermal resistance of the air is very high, which can cause the heat transfer capability to be greatly reduced. And the forming thickness of the insulating soft heat-conducting gasket between the surface A1 in the shell of the metal top shell 15 and the baseband chip 5 and the DDR particles 6 is reduced, so that the heat resistance of the insulating soft heat-conducting gasket assembled between the surface A1 in the shell of the metal top shell 15 and the baseband chip 5 and the DDR particles 6 can be reduced as much as possible.

Under the condition of adopting the insulating soft heat-conducting gasket, the compression amount of the thickness of the insulating soft heat-conducting gasket determines the thermal resistance between the surface A1 in the metal top shell 15 and the baseband chip 5 and DDR particles 6 to a certain extent. This amount of compression can be concluded by thermal testing as follows: the compression amount of the thickness of the insulating soft heat-conducting gasket is preferably more than 20%, preferably more than 30%, and the larger the compression amount of the thickness of the insulating soft heat-conducting gasket is, the smaller the heat resistance is.

Meanwhile, the compression amount of the insulating soft heat-conducting gasket has certain influence on the warping of the PCB 13. Normally, the PCB 13 will warp slightly downward under the gravity of itself and the components. If the compression amount of the thickness of the insulating soft thermal pad exceeds 30%, the PCB 13 may be warped further downward. When the PCB 13 is seriously warped, the PCB 13 is easily broken when the PCB is subjected to a severe drop test for 500 times; in addition, if the base band chip 5 and the DDR particles 6 soldered on the TOP layer 8 of the PCB 13 are packaged by BGA (Ball Grid Array), when the PCB 13 is seriously warped, the BGA pins are easily split from the pads, so that the base band chip 5 packaged by BGA having pin pitches of 0.5mm and 0.4mm provides a strict requirement for the warping ratio of the PCB 13, and therefore, in order to reduce the thermal resistance by the compression of the thermal pad and not to cause an excessive bad acting force to the warping of the PCB, in this embodiment, the compression amount of the thermal pad in the thickness direction thereof may be controlled within a range of 5% or more and 45% or less. Further, a conclusion is drawn according to a plurality of experimental test data: the warping rate of the PCB 13 is within 0.7%, and the influence on the splitting of the base band chip 5 and the DDR particle 6 in the PCB and the bonding pad is very small. The compression amount of the thickness of the insulating soft heat-conducting gasket is preferably 30%, the warping rate of the PCB 13 can be controlled within 0.7%, and meanwhile, the low heat resistance among the metal top shell 15, the insulating soft heat-conducting gasket, the base band chip 5 and the DDR particles 6 can be kept.

In some cases, the warpage of the PCB 13 can be improved by increasing the fixing position of the PCB 13, so as to increase the compression amount of the thermal pad as much as possible while avoiding the excessive warpage of the PCB 13, for example, when the compression amount of the thermal pad in the thickness direction thereof is greater than 20%, a screw hole adjacent to the first type device can be provided on the PCB 13, and the PCB 13 is fixed to the housing by a screw passing through the screw hole. As shown in fig. 2, the base band chip 5 and the DDR particles 6 are disposed on the TOP layer 8 of the PCB 13, the screw post 57, the screw post 53, and the screw post 50 are disposed on the inner surface A1 of the metal TOP case 15, and the screw hole 56, the screw hole 54, and the screw hole 52 are sequentially disposed on the PCB 13 in this order. If the heating device (the base band chip 5, the DDR particle 6) is arranged at the approximate center of the PCB 13, a screw hole 54 is arranged on the PCB 13 near the heating device (the base band chip 5, the DDR particle 6), and a screw column 53 is arranged at the position of the screw hole 54 corresponding to the projection of the A1 surface of the metal top case 15, that is, the screw column 53 is close to the first heat conducting gasket 1, the screw 58 is screwed into the screw column 53 through the screw hole 54 on the PCB 13, and the PCB 13, the heating device (the base band chip 5, the DDR particle 6), the first heat conducting gasket 1, and the metal top case 15 are combined into a whole by being fastened with the screw column 57, the screw 55, the screw column 50, and the screw 51 around the PCB. Wherein the screw 55 is screwed into the screw post 57 through the screw hole 56 in the PCB 13, the screw 58 is screwed into the screw post 53 through the screw hole 54 in the PCB 13, and the screw 51 is screwed into the screw post 50 through the screw hole 52 in the PCB 13. Specifically, in a practical embodiment, the heat conducting gasket has a compression amount in the thickness direction of the heat conducting gasket greater than 20%, the PCB 13 is provided with a screw hole adjacent to the first type device, the PCB 13 is fixed to the housing by a screw penetrating through the screw hole, and the distance between the screw hole adjacent to the first type device and the first type device is 1mm to 30mm.

The arrangement of the screw columns 53, the screws 58 and the screw holes 54 within the range of 1 mm-30 mm near the heating devices (the baseband chip 5 and the DDR particles 6) and the first heat-conducting gasket 1 greatly improves the warping degree of the PCB, and simultaneously, the compression amount of the insulating soft heat-conducting gasket can be controlled within the range of 30% -50%, so that the heat resistance between the heating devices (the baseband chip 5 and the DDR particles 6) and the first heat-conducting gasket 1 and the metal top shell 15 is greatly reduced. Meanwhile, the warping degree of the PCB 13 can be maintained below 0.7%, so that the phenomenon of splitting between pins and bonding pads can not be caused for the heating devices of BGA packages and high-density double-row QFN packages with the pin pitch of 0.5mm and 0.4 mm. That is to say, the screw columns 53, the screws 58 and the screw holes 54 are arranged in the range of 2mm to 30mm near the heating devices (the baseband chips 5 and the DDR particles 6) or the first heat conducting gasket 1, so that the contradiction between the thermal resistance between the heating devices (the baseband chips 5 and the DDR particles 6) and the heat conducting gasket and the metal top shell 15 and the warping degree of the PCB 13 can be solved.

It should be noted that, after the insulating soft heat-conducting gasket is compressed, the self thermal resistance and the thermal resistance between the heat-conducting gasket and the heating device and between the heat-conducting gasket and the metal top shell 15 can be greatly reduced. In order to meet the requirements of product safety, the creepage distance from the surface A1 in the shell of the metal top shell 15 to the heating device can be larger than the distance required by the safety requirements by increasing the area of the insulating soft heat-conducting gasket or the area of the surface A1 in the shell of the metal top shell 15.

The insulating soft heat-conducting gasket mainly comprises a heat-conducting silicone rubber sheet, and the heat conductivity coefficient of the heat-conducting silicone rubber sheet is in the range of 0.8W/(m.K) -6W/(m.K). Table 1 shows the relevant parameters of the insulating soft heat conducting gasket of a certain type.

TABLE 1 parameters associated with a type of thermally conductive silicone rubber sheet

Specification of	Unit of	XK-P45
			Surface viscosity adhesive Surface Tack (1-/2-sized)		2-side
Colour(s)		Grey colour
			Thickness of	mm (millimeter)	0.3～3.0
Density of	g/cm3 (g/cubic centimeter)	3.24
			Hardness of	Asker C	25～30
Thermal impedance	DEG C/W (centigrade/tile)	0.26
			Coefficient of thermal conductivity	W/(m.K) (Tile/meter. Degree)	4.5
Volume resistance	Omega cm (ohm cm)	>1013
			Breakdown voltage	KV/mm (kilovolt/millimeter)	>10
Dielectric constant	1	8
			Temperature of use	DEG C (degree centigrade)	-50～200
Tensile strength	Pa (Pa)	23
			Elongation percentage	％		50
Low molecular Siloxane content Siloxane volalites D4-D20	％	<0.005
			Flame retardant Flammability	UL94	V-0

In the process of actually adding the insulating soft heat-conducting gasket, the part of the A1 surface in the metal top shell 15, which is in contact with the insulating soft heat-conducting gasket, is required to be parallel and level with the baseband chip 5 and the DDR particle 6 in the horizontal direction, and meanwhile, the part of the A1 surface in the shell of the metal top shell 15, which is in contact with the insulating soft heat-conducting gasket, is required to be as flat as possible, so that gaps among the A1 surface in the shell of the metal top shell 15, the baseband chip 5 and the DDR particle 6 and the insulating soft heat-conducting gasket can be greatly reduced, and the thermal resistance among the parts is reduced. The surface A1 in the shell of the aluminum die-cast shell can completely achieve very good flatness to achieve the precision. In addition, the surface treatment of the in-case A1 surface of the aluminum die-cast housing also optimizes the flatness of the portion of the in-case A1 surface of the metal top case 15 in contact with the insulating soft heat conductive pad. The surface treatment of the aluminum die-cast shell mainly comprises an aluminum material phosphating process, an aluminum alkaline electrolytic polishing process, an aluminum and aluminum alloy environment-friendly chemical polishing process, an aluminum and aluminum alloy electrochemical surface strengthening treatment, an YL112 (alloy code) aluminum all-gold surface oxidation treatment process and the like.

For the thickness selection of the insulating and heat conducting pad, it can be calculated according to the fourier equation:

Q＝KA T/d，

R＝A T/Q，

wherein Q is heat, and the unit is W (watt); k is the thermal conductivity (thermal conductivity) in W/(m.K); a is the contact area; d is the heat transfer distance; t is the temperature difference; r is a thermal resistance value;

the two formulas are combined to obtain K = d/R, and the K value is unchanged, so that the thermal resistance value R is obtained and is in direct proportion to the thickness d of the material, namely the thicker the material is, the larger the thermal resistance is.

Because most of the heat conduction materials are not composed of single components, correspondingly, the thermal resistance value R of the heat conduction materials is not in a completely direct proportion relation with the thickness d and has nonlinear change. I.e. the thickness of the thermal pad increases, the thermal resistance value must increase, but not necessarily in a perfectly proportional linear relationship, possibly in a steeper curve. Therefore, the measured and calculated thermal resistance value is not completely the thermal resistance value of the material, but the thermal resistance value of the material and the thermal resistance value of the contact surface. Different contact surface thermal resistance values are generated due to the flatness, smoothness or roughness of the contact surfaces and different installation fastening pressure, so that different total thermal resistance values can be obtained. In the thermal resistance test, the contact area, the heat value and the pressure value applied to the contact surface are selected, the same method is used for testing different materials, and the obtained results have comparative significance.

Therefore, the thermal resistance value obtained by the test is not completely a true thermal resistance value. The thermal conductivity value calculated according to the thermal resistance value and the thickness is not completely a real thermal conductivity value. The fourier equation is a fully idealized formula, and can be used to understand the principle of the heat conducting material, but the practical application and the calculation of the thermal resistance are complex mathematical models, and there are many problems that may occur when the fourier equation is modified to perfect all links.

For the same material, the thermal conductivity is a constant value, and the thermal resistance value changes with the thickness. For the same material, the greater the thickness, it can be simply understood that the longer the heat is transferred out of the material, the more time is consumed, and the poorer the efficiency is.

For the heat conduction material, the heat conduction performance is greatly related to the heat dissipation performance by selecting proper heat conduction rate and thickness. For example, a material with high thermal conductivity is selected, but the material has high thickness and poor performance. The most desirable choices are: high thermal conductivity and thin thickness, and ensures proper contact pressure to ensure good interface contact.

Fig. 5 shows a thermal resistance model of a heat dissipation scheme of the metal top case 15, the insulating soft heat-conducting gasket, and the heating device, that is, a thermal resistance model from the baseband chip 5 (heating device), the DDR particles 6 (heating device) to the insulating soft heat-conducting gasket, and the metal top case 15 in fig. 2. In fig. 5, the labels are a die (heat source) of the heating device, a package thermal resistance θ a of the heating device, a thermal resistance θ c of the insulating soft heat-conducting gasket, a thermal resistance θ b (high thermal resistance) of the air between the metal top case 15 and the copper foil (not shown in fig. 2) of the PCB 13, and a thermal resistance θ b of the metal top case 15. The heat dissipation path of the heating device is divided into two paths: one path is heating device die (heat source) → heating device encapsulation → insulating soft heat conducting gasket → metal top shell 15 → ambient air; the other path is the heating device die (heat source) → heating device packaging → PCB board 13 pad, top copper foil, via hole, inner copper foil and bottom copper foil → PCB board 13 pad, top copper foil, via hole, inner and bottom copper foils to the inside of the structure between the metal top case 15 → the case inside A1 face of the metal top case 15 → the base 14 → a plurality of raised aluminum racks 19 provided above the base 14 → ambient air. The heat generating device die (heat source) pin is connected with the pad of the PCB 13, a part of heat is transferred to the top copper foil inner layer and the bottom copper foil through the pad and the via hole of the PCB 13, the heat conductivity coefficient of the air between the top copper foil inner layer and the bottom copper foil to the metal top shell 15 is very low (only 0.01W/(m · K) -0.04W/(m · K)), and the heat conductivity coefficient of the insulating soft heat conducting gasket (such as a heat conducting silicone grease film) is 0.8W/(m · K) -6W/(m · K), so the heat conducting performance of the air inside the space between the metal top shell 15 and the copper foil of the PCB 13 and the heat generating device can be ignored. The heat transfer is mainly performed by an insulating soft heat-conducting gasket.

It should be noted that die of the heat generating device is a heat source, and die is a wafer, which is known as die and becomes a particle after being packaged. Grains are small irregularly shaped crystals that make up a polycrystalline body, and each grain sometimes consists of several sub-grains with slightly different orientations. The average diameter of the grains is typically in the range of 0.015mm to 0.25mm, while the average diameter of the sub-grains is typically of the order of 0.001 mm.

The insulating hard heat-conducting gasket mainly comprises a mica sheet, a ceramic gasket (such as a ceramic oxide gasket, an aluminum nitride ceramic gasket, a beryllium oxide ceramic gasket and a single crystal aluminum nitride gasket), an inorganic non-metallic material sheet (such as cubic boron nitride) and the like. The thermal conductivity of the ceramic sesquioxide gasket is 20W/(m.K) to 30W/(m.K); the heat conductivity coefficient of the single crystal aluminum nitride ceramic gasket is 275W/(m.K), and the heat conductivity coefficient of the single crystal aluminum nitride ceramic gasket and the heat conductivity coefficient of the beryllium oxide ceramic gasket are close to that of metal aluminum. The thermal conductivity of boron carbide is 33W/(m.K), the thermal conductivity of polycrystal is 70-210W/(m.K), the thermal conductivity of cubic boron nitride is 33W/(m.K), the thermal conductivity of single crystal aluminum nitride can reach 275W/(m.K), the thermal conductivity of diamond can reach 2000W/(m.K), the thermal conductivity of single crystal aluminum nitride and beryllium oxide is equivalent to that of pure aluminum, even exceeds that of pure aluminum, and also far exceeds that of common metal materials, for example, the thermal conductivity of tin is 67W/(m.K), and the thermal conductivity of diamond far exceeds that of all metals.

In some cases, a thermally conductive adhesive scheme may be used to secure the insulating hard thermal pad.

Fig. 6 is a cross-sectional view of a heat dissipation scheme of the aluminum die-cast metal top case 15 or the extruded metal top case 15, the heat conductive glue, the ceramic gasket, the heat conductive glue, and the heat generating device. The heat dissipation scheme of the aluminum die-cast metal top case 15, the heat conducting glue 41, the ceramic gasket 40, the heat conducting glue 42, and the heat generating devices (such as the baseband chip 45 and the DDR particles 46) is described as an example, but the insulating hard heat conducting gasket is not limited to be the ceramic gasket 40, and the heat generating devices are not limited to be the baseband chip 45 and the DDR particles 46.

Because the surface A1 in the metal top shell 15, the surfaces of the base band chip 45 and the DDR particles 46 and the ceramic gasket 40 have certain roughness, if the ceramic gasket 40 is directly installed between the surface A1 in the metal top shell 15 and the base band chip 45 and the DDR particles 46, a larger gap is formed between the ceramic gasket 40 and the heating device (such as the base band chip 45 and the DDR particles 46), the larger gap is filled with air, and the air thermal resistance is higher (the thermal conductivity of the air is 0.01W/(m.K) -0.04W/(m.K)); this may result in the ceramic gasket 40 not exhibiting heat transfer properties. Therefore, it is necessary to fill the heat conductive paste 41 between the ceramic gasket 40 and the case inner A1 surface of the metal top case 15, and fill the air in the gap between them with the heat conductive paste 41; the heat conductive paste 42 is filled between the ceramic pad 40 and the heat generating device (e.g., the base tape chip 45, the DDR particles 46), and the air in the gap therebetween is filled with the heat conductive paste 42.

The heat conductive paste 41 filled between the ceramic spacer 40 and the in-case A1 surface of the metal top case 15 and between the ceramic spacer 40 and the heat generating device (e.g., the base tape chip 45, the DDR particles 46) is preferably a heat conductive paste with an adhesive function in view of mounting and fixing. In some cases, the ceramic pad 40 may be fixed on the surface A1 of the top metal shell 15 by the thermal conductive paste 41, and then the thermal conductive paste 42 may be applied between the ceramic pad 40 and the heat generating device (e.g., the base band chip 45 and the DDR particles 46), and the thermal conductive paste may be semi-solid thermal conductive paste, such as thermal conductive silicone paste, thermal conductive silicone grease, or the like. The ceramic pad 40 is first fixed on the inner A1 surface of the metal top case 15 by a heat conductive adhesive with an adhesive function, and a heat conductive adhesive 42 is applied between the B2 surface of the ceramic pad 40 and the contact surface of the heat generating device (e.g., the base band chip 45 and the DDR particles 46), or a heat conductive adhesive is applied on the contact surface of the heat generating device (e.g., the base band chip 45 and the DDR particles 46) and the B2 surface of the ceramic pad 40. When the metal top case 15 is assembled with the PCB 43, the B2 surface of the ceramic gasket 40 may contact with the surface of the heat generating device (e.g., the base band chip 45, the DDR particles 46) with low thermal resistance through the semi-solid thermal conductive adhesive 42, the A2 surface of the ceramic gasket 40 may contact with the A1 surface of the metal top case 15 with low thermal resistance through the thermal conductive adhesive 41 with adhesive function, so that the ceramic gasket 40 and the A1 surface of the metal top case 15 form heat transfer with low thermal resistance, and the B2 surface of the ceramic gasket 40 and the heat generating device (e.g., the base band chip 45, the DDR particles 46) form heat transfer with low thermal resistance. The heat that the device that generates heat (for example baseband chip 45, DDR granule 46) during operation produced can be fast transmitted for ceramic pad 40 through heat conduction glue 42, and the shell internal A1 face that the metal top shell 15 was given in the transmission of rethread area bonding function heat conduction glue 40, and the retransmission is for top shell base 49, and the retransmission is for a plurality of bellied racks 48 that top shell base 49 top set up, and the effective transmission ambient air of at last through convection current heat dissipation mode and thermal radiation heat dissipation mode is gone out with the heat is fast effectively transmitted.

In other cases, the ceramic pad 40 may be fixed on the heat generating device (e.g. the base band chip 5, DDR particles) by the heat conductive adhesive 42, and then the heat conductive adhesive 41 is applied between the A1 surface in the metal top case 15 and the A2 surface of the ceramic pad 40. The heat-conducting glue can be semi-solid heat-conducting glue, such as heat-conducting silica gel, heat-conducting silicone grease, and the like. The ceramic pad 40 is first fixed on a heating device (for example, a base band chip 45 and DDR particles 46) by a heat conductive adhesive 42 with an adhesive function, and a heat conductive adhesive 41 is applied on the surface A2 of the ceramic pad 40 and the surface A1 inside the metal top case 15, or the heat conductive adhesive 41 is applied on the surface A1 inside the metal top case 15 and the surface A2 of the ceramic pad in contact. When the metal top case 15 is assembled with the PCB 43, the A2 surface of the ceramic gasket 40 may contact the A1 surface of the metal top case 15 through the semi-solid heat-conducting glue 41; the ceramic gasket 40 can be in low-heat-resistance contact with the surface of a heating device (such as a base band chip 45 and DDR particles 46) through a heat conducting adhesive 42 with an adhesive function; thus, the ceramic pad 40 and the inner A1 surface of the metal top case 15 form heat transfer with lower thermal resistance, and the ceramic pad 40 and the heat generating device (e.g. the base band chip 5, DDR particles) form heat transfer with lower thermal resistance. The heat that the device that generates heat (for example baseband chip 5, DDR granule) during operation produced can be fast through taking bonding function heat-conducting glue 42 to transmit for ceramic pad 40, and the shell internal A1 face that the metal top shell 15 was given in the transmission of rethread bonding function heat-conducting glue 42, and the retransmission is given top shell base 49, and the retransmission is given a plurality of bellied racks 48 that top shell base 49 top set up, effectively transmits the ambient air through convection current and heat radiation mode at last, effectively transmits away the heat fast.

The corresponding schemes in the two cases are slightly different in implementation mode, but the difference of the generated thermal resistances is not large. Fig. 7 shows a thermal resistance model of a scheme of adopting a metal top shell 15, an inner surface A1 of the shell, heat-conducting glue, a ceramic gasket, heat-conducting glue and a heating device. In fig. 7, the labels are a die (heat source) of the heating device, a package thermal resistance θ a of the heating device, a thermal resistance θ c of the heat-conducting glue, a thermal resistance θ e of the insulating hard heat-conducting gasket, a thermal resistance θ f of the heat-conducting glue, a thermal resistance θ b (high thermal resistance) of the air between the metal top case 15 and the copper foil of the PCB 43 and the heating device, and a thermal resistance θ g of the metal top case 15. The heat dissipation path of the heating device is divided into two paths: one path is heating device die (heat source) → heating device encapsulation → thermal conductive adhesive → insulating soft thermal conductive pad → thermal conductive adhesive → the in-case A1 face of the metal top case 15 → base 49 → a plurality of raised aluminum racks 48 arranged above the base 49 → ambient air; the other path is air inside the structure between the heating device die (heat source) → heating device package → PCB 43 pad, top copper foil, via hole, inner copper foil and bottom copper foil → PCB 43 pad, top copper foil, via hole, inner and bottom copper foils to the metal top case 15 → ambient air. The heat generating device die (heat source) pin is connected with the PCB 43 bonding pad, a part of heat is transferred to the top copper foil inner layer and the bottom copper foil through the PCB 43 bonding pad and the through hole, the heat conductivity coefficient of air between the top copper foil inner layer and the bottom copper foil to the metal top shell 15 is very low and is only 0.01W/(m.K) -0.04W (m.K), the heat conductivity coefficient of the heat conducting glue (for example, the heat conductivity coefficient of the heat conducting silicone grease is 0.8W/(m.K) -10W/(m.K)) and the heat conductivity coefficient of the insulating hard heat conducting gasket (for example, the heat conductivity coefficient of the ceramic gasket of the silicon oxide is 20W/(m.K) -30W/(m.K), and the heat conductivity coefficient of the single crystal aluminum nitride ceramic gasket is 275W/(m.K)), so that the heat conducting performance of air between the metal top shell 15 and the PCB 43 copper foil and the heat generating device can be ignored, and the heat transfer is mainly carried out by the heat conducting glue, the insulating hard heat conducting gasket and the heat conducting glue.

In addition, a communication device such as a router or an exchange is usually provided with a TNV (communication Network Voltage) circuit, that is, the communication device such as the router or the exchange is externally connected with a Network cable, and the Network cable may be struck by high-Voltage lightning. GB4943 standard in 3C of China has a requirement for clearly providing safety certification for TNV circuits, and North America UL62368-1 has a requirement for clearly providing safety certification for TNV circuits. Taking the requirements of north america UL62368-1 as an example, the high voltage part of the net mouth metal shell and the low voltage part in the PCB plate are subjected to a 1kV alternating current isolation test, or the high voltage part of the net mouth metal shell and the low voltage part in the PCB plate are subjected to a 1.5kV direct current isolation test, and electric breakdown cannot occur. The metal top case 15 and the heat generating device (for example, the base band chip 15, the DDR particles 6, etc.) in fig. 2 are taken as an example for explanation, and the metal top case 15 and the heat generating device have the same safety requirements. Because the metal top shell 15 is connected to the metal mesh shell (not shown in fig. 2), the metal top shell 15 needs to be isolated from the heating device (e.g., the baseband chip 15, the DDR particles 6, etc.) by 2kV, and no electrical breakdown occurs (the heating device is damaged or the heating device is introduced into the PCB to damage other devices of the PCB).

In order to meet the requirements of the strict safety standard test of GB4943 in 3C of China and UL62368-1 in North America, multiple test experiments are carried out to obtain the conclusion that: the high-voltage part of the mesh opening metal shell and the low-voltage part in the PCB are designed according to the 2kV isolation requirement, so that the requirement that 1kV alternating current isolation test is carried out on the high-voltage part of the mesh opening metal shell and the low-voltage part in the PCB or electric breakdown cannot occur when 1.5kV direct current isolation test is carried out on the high-voltage part of the mesh opening metal shell and the low-voltage part in the PCB can be met. Thus, in this embodiment, the breakdown voltage between the enclosure and the first type of device is greater than 1kV (1 kV here is a specified requirement in safety certification: AC 1kV is not broken).

Taking the industrial router in fig. 2 as an example for illustration, if a 2kV dc voltage is applied between the PCB 13 and the metal top case 15 (electrically connected to the high voltage network port metal case), a strong electric field is generated in the medium of the insulating soft heat-conducting pad (or insulating hard heat-conducting pad) between the outer shell surface of the heat generating device (e.g. the baseband chip 5, the DDR particles 6, etc.) and the metal top case 15. Under the action of a strong electric field, polarization is established in an insulating soft heat-conducting gasket (or insulating hard heat-conducting gasket) medium between the outer shell surface of the heating device (such as the baseband chip 5, the DDR particles 6 and the like) and the metal top shell 15, at the moment, the insulating soft heat-conducting gasket (or insulating hard heat-conducting gasket) medium becomes a dielectric medium (namely an insulating medium), and the resistivity rho of the insulating medium is>10 ⁹ Ω · m, electric charges appear in the dielectric of the insulating soft heat-conducting pad (or the insulating hard heat-conducting pad), and the phenomenon in which electric charges appear in the dielectric under the action of an external electric field is called polarization of the dielectric, and the generated electric charges are called induced charges.

When the intensity of the dielectric electric field of the insulating soft heat-conducting pad (or insulating hard heat-conducting pad) applied between the outer shell surface of the heat generating device (such as the baseband chip 5, the DDR particles 6, etc.) and the metal top shell 15 is higher than a predetermined value, the dielectric surface of the insulating soft heat-conducting pad (or insulating hard heat-conducting pad) loses its insulating property, which is called breakdown. The electric field strength when the dielectric surface of the insulating soft heat conducting gasket (or the insulating hard heat conducting gasket) is punctured is called the puncture strength, and the unit is: kV/mm.

Under the action of high field intensity, initial electrons on the surface of an insulating soft heat conduction gasket medium between the shell surface of a heating device (such as the base band chip 5, the DDR particles 6 and the like) and the metal top shell 15 are easier to move, and more electrons are generated along with the impact of the initial electrons, so that the breakdown strength is reduced.

Specifically, the formula of the breakdown strength is calculated as EB = UB/d; where UB is the electric field strength (i.e., voltage) between two conductors and d is the thickness of the dielectric of the two conductors or the distance of the surface dielectric between the two conductors. Breakdown strength is proportional to the electric field strength and inversely proportional to the thickness or distance of the dielectric.

According to the derivation formula and the conclusion, the analysis is explained as follows:

taking a certain type of heat-conducting silicone rubber sheet (one of the soft heat-conducting gaskets) as an example shown in table 1, according to the relevant requirements obtained by the test, the vertical layer-wise insulation strength of the insulating soft heat-conducting gasket is more than 10kv/mm, the layer-wise breakdown voltage is more than 10kv, and the medium of the insulating soft heat-conducting gasket is broken down. The case of the heat generating device can be divided into two different cases for explanation according to whether it is made of an insulating material or a metal material.

In the first case, the housing of the heat generating device is made of an insulating material (e.g., epoxy resin, ceramic, glass, or engineering plastic).

Fig. 8 is a partially enlarged view of the cross-sectional view shown in fig. 2, and compared with fig. 2, the difference is that the DDR particles 6 and the baseband chip 5 in fig. 2 are replaced with a baseband chip 77 with DDR particles inside (that is, the baseband chip 77 integrates the DDR particles and belongs to a heat generating device), and the rest is the same. Since the housing of the baseband chip 77 is made of epoxy resin, ceramic, glass or engineering plastic, which are insulating materials, the substrate has a certain high voltage breakdown resistance, and the baseband chip 77 is protected from high voltage breakdown. In fig. 8, the surface A3, the left side surface A4, and the right side surface A5 of the base tape chip 77 (heat generating device) are made of an insulating material.

When a high-voltage isolation test voltage (e.g., 2kV isolation test voltage) is applied between the metal case 15 and the heat generating device (e.g., the base band chip 77) of the insulating case, their withstand voltage capability is the sum of the thermal conductive pad dielectric strength (withstand voltage capability) and the heat generating device case dielectric strength (withstand voltage capability). The ability to withstand voltage is the ability of the two to withstand high voltage without being broken down. For example, in a possible embodiment, the housing packaging material of the first device is an insulating material, and the sum of the insulating strength of the thermal pad and the insulating strength of the housing packaging material of the first device is greater than or equal to 1kV.

In the second case, the housing of the heat generating device is made of a conductive material (e.g., a metal material).

Fig. 9 is another enlarged partial view of the cross-sectional view shown in fig. 2, and is different from fig. 8 in that the case of the heat generating device 78 in fig. 8 is made of a conductive material. In fig. 9, the surfaces A8, A6, and A7 directly above the heat generating device 78 are made of a conductive material. For example, a Direct FET package MOSFET (metal-oxide semiconductor field effect transistor) is of a flip-chip type, and a heat dissipation plate of a drain (D) is directed upward and covers a metal case through which heat is dissipated. I.e., the MOSFET housing of the Direct FET package is a conductive material.

When a high voltage isolation test voltage (e.g., 2kV isolation test voltage) is applied between the metal case 15 and the heat generating device 78 (e.g., direct FET package MOSFET) of the conductive case, their ability to withstand voltage is the dielectric strength (ability to withstand voltage) of the thermal pad.

Taking table 1 as an example, a certain type of heat-conducting silicone grease sheet (one of the soft heat-conducting gaskets 1) is installed between the metal top case 15 shown in fig. 9 and the heating device 78 of the conductive housing, 2kV isolation test voltage is applied between the metal top case 15 and the heating device 78 of the conductive housing, and the certain type of heat-conducting silicone grease sheet 1 is not broken down by the 2kV isolation test voltage. The breakdown voltage of a heat-conducting silicone grease film of a certain type in table 1 is 10kV/mm, namely when the thickness of the soft heat-conducting gasket 1 after being installed between the metal top shell 15 and the heating device 78 of the electric conduction shell is 1mm, the breakdown voltage is 10kV, and the insulation test voltage is far greater than 2kV, so that the design requirement is reasonable, and the scheme is scientific and reasonable. For example, in one possible embodiment, the housing packaging material of the first device is an electrically conductive material, and the insulating strength of the thermal pad is greater than or equal to 1kV.

In addition to the isolation test, the creeping discharge capability between the heat generating device, the heat conductive pad, and the metal top case 15 needs to be considered. Taking fig. 2 as an example for illustration, a thermal pad (including an insulating soft thermal pad or an insulating hard thermal pad) is added between the inner surface of the metal casing and the heat generating device, and a breakdown between the heat generating device (e.g., the baseband chip 5, the DDR particles 6, etc.) in the PCB 13 and the metal top case 15 is mainly represented by a surface discharge of a thermal pad medium, which is called a creeping discharge (also called a surface flashover). The creeping discharge is closely related to the surface cleanliness of the solid dielectric, the air pressure, and the ambient air (e.g., air or vacuum). The creeping discharge voltage is obviously lower than the pure gap discharge voltage, the surface of the solid dielectric medium is affected with damp or pollution, and the discharge voltage is lower. Creeping discharge generally describes the capability of creeping discharge by using a creepage distance, that is, when the creepage distance reaches a certain critical value, creeping discharge does not occur between two electric conductors.

The breakdown strength of the metal top case 15 is inversely proportional to the distance between the heat generating devices (e.g., the base band chip 5, the DDR particles 6, etc.) in the PCB board 13 and the metal top case 15, and is proportional to the electric field of the breakdown strength. That is, the higher the voltage (the higher the electric field) between the outer shell surface of the heat generating device (such as the baseband chip 5, the DDR particle 6, etc.) in the PCB 13 and the metal top shell 15, the longer the distance (the creepage distance) between the heat generating device (such as the baseband chip 5, the DDR particle 6, etc.) in the PCB 13, the trace, the pad, the via hole in the PCB 13 and the heat conducting pad medium surface between the metal top shell 15 is required.

As shown in fig. 8, the surface insulating material (e.g., epoxy resin, ceramic, glass, engineering plastic, etc.) of the housing of the heat generating device (e.g., the base band chip 5, the DDR particles 6, etc.) in the PCB 13. As long as the high-voltage breakdown resistance of the insulating material on the surface of the shell of the heating device and the high-voltage breakdown resistance of the heat-conducting gasket can withstand 1kV alternating-current isolation test, or the high voltage of the net mouth metal shell and the low voltage part in the PCB do 1.5kV direct-current isolation test, no electric breakdown occurs (preferably, 2kV isolation test is satisfied). Only the creepage distance for the creeping discharge may need to be considered. The shell of the heating device is made of insulating materials and is divided into two cases, which are respectively as follows:

A. when both the pins and the pads are directly under the body of the heat generating device (e.g., the baseband chip of a BGA package).

Fig. 15 shows a cross-sectional view of the heat generating device + heat conductive pad + metal case of the BGA package (only the heat generating device of the BGA package is taken as an example for explanation). The metal housing 207 is provided with a metal rack 206 for increasing the surface area of the metal housing 207 exposed to the outside air, and increasing the radiation capability and the convection heat dissipation capability. The heat generating device 211 is packaged by BGA, the heat generating device 211 is soldered on the PCB 202, all pins (e.g., one pin 213) of the heat generating device 211 are disposed under the BGA package (i.e., on the bottom surface of the body of the heat generating device 211), the pin 213 is electrically connected to the pad 212, the PCB trace 215 is led out from the pad 212, and the pins of the heat generating device 211 and the pad of the PCB 202 are both covered under the body of the heat generating device 211 (i.e., the pins of the heat generating device 211 and the pad of the PCB 202 are both covered by the body of the heat generating device 211 without being exposed). The heat generating device 211 has a length L63 in the horizontal direction. The heat conductive pad 203 is disposed between the heat generating device 211 and the inner side of the metal case 207. The length of the thermal pad 203 in the horizontal direction is L60, and h55 is the compressed thickness of the thermal pad 203. In the horizontal direction, the length from the left edge of the heat conducting pad 203 to the left edge of the heat generating device 211 is L62, the length from the right edge of the heat conducting pad 203 to the right edge of the heat generating device 211 is L61, and the height of the heat generating device 211 is H54. The top surface A8 of the heating device 211 is made of insulating material.

The length of the heat generating device 211 in the horizontal direction is L63, and the length of the heat conductive pad 203 in the horizontal direction is L60. L60= L63+ L62+ L61 is satisfied.

The creepage distance from the metal housing 207 to the creeping discharge on the left side of the heat generating device 211 is: l7 left = h55+ L62+ h54;

the creepage distance of the creeping discharge from the metal housing 207 to the right side of the heat generating device 211 is: l8 right = h55+ L61+ h54

L7 is required to be equal to or larger than 1.0mm (preferably equal to or larger than 2.0 mm) to meet the requirements of UL62368-1 in North America and GB4943 related safety certification in 3C in China.

L8 is required to be equal to or larger than 1.0mm on the right (preferably equal to or larger than 2.0mm on the left) so as to meet the requirements of UL62368-1 in North America and GB4943 related safety certification in 3C in China.

All pins of baseband chip 213 of BGA encapsulation all set up under the BGA encapsulation, do not expose and come the pad, can float high soldering tin on the pad, and soldering tin can draw close creepage distance and the electric clearance with metal casing 207.

B. When both the pins and the pads are on both sides of a heat generating device (e.g., a heat generator of an SOP package).

Fig. 16 shows a cross-sectional view of the SOP packaged heat generating device + heat conducting pad + metal case. The difference in fig. 16 from fig. 15 is that the heat generating device 211 of the BGA package in fig. 15 is replaced with an SOP package heat generating device 210 (only the SOP package heat generating device is exemplified), and the other steps are the same. The pins 111 of the heat generating device 210 are arranged on a side wall between the top and the bottom of the body, the pins 111 are bent and extended from the side wall toward the direction 202 close to the PCB board, the tail ends of the pins 111 extend to the PCB board 202 and are welded on the pads of the PCB board 202 through soldering tin, and the surface creepage distance between the first inner wall surface and the first surface of the PCB board 202 is greater than or equal to 1.0mm, wherein the surface creepage distance is the sum of the thickness of the heat conducting gasket 203, the distance from the edge of the heat conducting gasket 203 to the edge of the heat generating device 210, and the height from the pins (that is, the intersection position of the top of the pins and the side wall) to the top of the heat generating device 210. Specifically, the top surface A6 of the heat generating device 210 is made of an insulating material. The SOP package pins 111 are led out from the left side surface and the right side surface of the horizontal side of the SOP package, the height of the SOP package pins 111 perpendicular to the PCB board 202 is h53, the distance from the SOP package pins 111 to the A6 surface of the top surface of the heating device 210 in the vertical direction is h50, and the height of the heating device 210 perpendicular to the PCB board 202 is h50+ h53;

h55 is the compression thickness of the heat conduction pad, and in the horizontal direction, the length from the left edge of the heat conduction pad 203 to the left edge of the heat generating device 210 is L62, and the length from the right edge of the heat conduction pad 203 to the right edge of the heat generating device 210 is L61.

The length of the heat generating device 210 in the horizontal direction is L63, and the length of the heat conductive pad 203 in the horizontal direction is L60. L60= L63+ L62+ L61 is satisfied.

The creepage distance from the metal housing 207 to the creeping discharge on the left side of the heat generating device 210 is: l9 left = h55+ L62+ h50;

the creepage distance of the creeping discharge from the metal housing 207 to the right side of the heat generating device 210 is: l10 right = h55+ L61+ h50 requires L9 left ≧ 1.0mm (preferably L left ≧ 2.0 mm) to satisfy the requirements for safety certification related to GB4943 in North America UL62368-1 and 3C of China.

L10 is required to be equal to or larger than 1.0mm on the right (preferably equal to or larger than 2.0mm on the left) so as to meet the requirements of UL62368-1 in North America and GB4943 related safety certification in 3C in China.

C. When the pins and the pads are both right under the body of the heat generating device (such as a heater of a QFN package), the pads are exposed at both sides of the body of the heat generating device.

Fig. 17 shows a cross-sectional view of the heat generating device + heat conducting pad + metal housing of the QFN package. The difference in fig. 17 from fig. 16 is that the SOP-packaged heat generating device 210 in fig. 16 is replaced with a QFN-packaged heat generating device 216 (only the heat generating device of the QFN package is taken as an example for explanation), and the others are the same. The top surface A7 of the heating device 216 is made of insulating material. The pins 218 of the heat generating device 216 are disposed at the bottom of the periphery or two sides of the body of the heat generating device 216, the pads of the PCB 202 extend along the surface of the PCB 202 in a direction away from the body, the pins 218 are covered with solder and are soldered to the pads 217 of the PCB 202 via the solder, and a surface creepage distance between the first inner wall surface and the first surface of the PCB 202 is greater than or equal to 1.0mm, wherein the surface creepage distance is the sum of the thickness of the heat conducting pad 203, the distance from the edge of the heat conducting pad 203 to the edge of the heat generating device 216, and the height from the solder (i.e., the position where the top of the solder meets the side wall) to the top of the heat generating device 216.

Although the pins and the pads of the PCB are located right below the body of the heat generating device 216 of the QFN package, since the pads at both ends (for example, the pads 217 in fig. 17) are distributed at both ends of the heat generating device 216 of the QFN package, the pads are exposed outside the QFN package, and solder is floated on the pads, the height from the floating solder to the heat generating device of the QFN package is calculated. A pin 218 of the heating device 216 is led out of a bonding pad 217, and the height from the bonding pad 217 (including floating solder) to the surface A7 of the top surface A7 of the heating device 216 is h50; the pad 217 (including the solder float) has a height h59 perpendicular to the PCB 202 and the heat generating device 211 has a height h59+ h50.

The length of the heat generating device 216 in the horizontal direction is L63, and the length of the heat conductive pad 203 in the horizontal direction is L60. L60= L63+ L62+ L61 is satisfied.

h55 is the compressed thickness of the thermal pad. In the horizontal direction, the length from the left edge of the heat conducting pad 203 to the left edge of the heat generating device 216 is L62, and the length from the right edge of the heat conducting pad 203 to the right edge of the heat generating device 216 is L61.

The creepage distance from the metal casing 207 to the creeping discharge on the left side of the heat generating device 216 is: l11 left = h55+ L62+ h51;

the creepage distance from the metal casing 207 to the creeping discharge on the right side of the heat generating device 216 is: l12 right = h55+ L61+ h51 requires L11 left ≧ 1.0mm (preferably L left ≧ 2.0 mm) in order to satisfy the requirements for safety certification related to GB4943 in North America UL62368-1 and China 3C.

L12 is required to be equal to or larger than 1.0mm on the right (preferably equal to or larger than 2.0mm on the left) so as to meet the requirements of UL62368-1 in North America and GB4943 related safety certification in 3C in China.

Therefore, a heat conduction gasket (a soft heat conduction gasket or a hard heat conduction gasket) is added between the metal shell and the heating device, and the surface creepage distance between the surface A1 of the metal shell (for example, the surface A1 of the metal top shell 15 in fig. 2) and the heating device (for example, the baseband chip 5 and the DDR particles 6 in fig. 2), the pad, the via hole, the trace, and the copper foil needs to be greater than or equal to 1.0mm; the surface creepage distance is the sum of the thickness of the heat conduction gasket (the thickness of the hard heat conduction gasket or the thickness of the soft heat conduction gasket after compression) and the distance from the edge of the heat conduction gasket to the edge of the heating device.

It is understood that the first type devices of the electronic apparatus provided by the embodiment of the present application may include the heat generating device 216 of the QFN package and the heat generating device 210 of the SOP package, that is, at least two types of the first type devices, where:

at least one first-type device is welded on the PCB, the shell packaging material of the first-type device is an insulating material, pins of the first-type device are arranged at the bottoms of the periphery or two sides of the body of the first-type device, a pad of the PCB extends along the surface of the PCB in a direction far away from the body, soldering tin is covered on the pins and is welded on the pad of the PCB through the soldering tin, the surface creepage distance between the first inner wall surface and the first surface of the PCB is larger than or equal to 1.0mm, wherein the surface creepage distance is the sum of the thickness of the heat-conducting gasket, the distance from the edge of the heat-conducting gasket to the edge of the first-type device, and the height from the soldering tin (namely the position where the top of the soldering tin and the side wall meet) to the top of the first-type device;

and

the at least one other first-type device is welded on the PCB, the shell packaging material of the first-type device is an insulating material, the pins of the first-type device are arranged on the side wall between the top and the bottom of the body of the first-type device, the pins are bent and extended from the side wall towards the direction close to the PCB, the tail ends of the pins extend to the PCB and are welded on the bonding pads of the PCB through soldering tin, and the surface creepage distance between the first inner wall surface and the first surface of the PCB is larger than or equal to 1.0mm, wherein the surface creepage distance is the sum of the thickness of the heat conduction gasket, the distance from the edge of the heat conduction gasket to the edge of the first-type device, and the height from the pins (namely the positions where the tops of the pins and the side wall meet) to the top of the first-type device.

Second, the heating device is arranged inside the metal shielding cover

Referring to fig. 1, in the case of including the shielding cover, it is described that the shape of the in-housing A1 surface of the metal top housing 15 is a square (a type of rectangle), and the shape of the insulating soft heat-conducting gasket is a square (a type of rectangle), the width of the in-housing A1 surface of the metal top housing 15 is L22, the length and the width of the insulating soft heat-conducting gasket are L32, and the area of the in-housing A1 surface of the metal top housing 15 is equal to or larger than the insulating soft heat-conducting gasket, that is, L22 ≧ L32.

The length of the shielding cover 18 in the first shielding case 88 is L34, the distance from the leftmost edge of the shielding cover 18 in the first shielding case 88 to the leftmost edge of the first heat-conducting pad 1 is L35, and the distance from the rightmost edge of the shielding cover 18 in the first shielding case 88 to the rightmost edge of the first heat-conducting pad is L36, then L32= L36+ L35+ L34.

When the first heat conduction gasket 1 is added between the inside A1 surface of the metal top case 15 and the shielding cover 18 in the first shielding case 88, a creepage distance from the leftmost edge of the inside A1 surface of the metal top case 15 to the leftmost edge of the shielding cover 18 in the first shielding case 88 is lvir = lvir 3, and h3 is a compression thickness of the first heat conduction gasket 1.

L left ≧ 1.0mm (L left ≧ 1.0mm is preferred) is required to satisfy the requirements for the safety certification related to UL62368-1 in North America and GB4943 in 3C in China.

And a creepage distance from a rightmost edge of the case inside A1 face of the metal top case 15 to a rightmost edge of the shield cover 18 in the first shield shell 88 is lrright = L36+ h3.

L right ≧ 1.0mm (preferably L right ≧ 1.0 mm) is required to satisfy the requirements related to the safety certification of GB4943 in North America UL62368-1 and China 3C.

Third, the shell of the heating device is made of conductive material (such as metal material)

In fig. 9, the surfaces A8, A6, and A7 directly above the heat generating device 78 are made of a conductive material. For example, a Direct FET package MOSFET (metal-oxide semiconductor field effect transistor) is of a flip-chip type, and a heat dissipation plate of a drain (D) is directed upward and covers a metal case through which heat is dissipated. I.e., the MOSFET housing of the Direct FET package is a conductive material.

Fig. 9 shows a cross-sectional view of the heat generating device + heat conducting pad + metal casing of the conductive housing. The top surface A8 of the heat generating device 78 is made of a conductive material. h5 is the compression thickness of the insulating soft heat-conducting gasket, and in the horizontal direction, the length from the left edge of the heat-conducting gasket 1 to the left edge of the heating device 78 is L25, and the length from the right edge of the heat-conducting gasket 1 to the right edge of the heating device 78 is L26. The length of the heat generating device 78 in the horizontal direction is L24, and the length of the heat conductive pad 1 in the horizontal direction is L23. L23= L24+ L25+ L26 is satisfied.

The creepage distance from the metal case 15 (the metal case 15 includes a metal top case) to the creeping discharge on the top left side of the heat generating device 78 is: l13 left = h5+ L25;

the creepage distance from the metal shell 15 (the metal shell 15 includes a metal top shell) to the creeping discharge on the right side of the top of the heat generating device 78 is: l14 right = h5+ L26

L11 is required to be equal to or greater than 1.0mm on the left (preferably equal to or greater than 2.0mm on the left) so as to meet the requirements of UL62368-1 in North America and GB4943 related safety certification in 3C of China.

In addition, when the router is actually installed, the influence of the altitude height on the safety regulation of the isolation test needs to be considered. According to the Pasteur law, the breakdown voltage of a harmonic electric field is proportional to the product of the gas pressure and the distance between the two poles, and when the distance between the two poles is constant, the smaller the gas pressure, the lower the breakdown voltage. The air pressure is inversely proportional to the altitude, and thus the altitude is one of the important factors affecting the distance between spaces. According to Bass' Law, various parameters of the industrial router such as atmospheric pressure, breakdown voltage and the like under the environment with the altitude of 2000 m, 3000 m, 4000 m, 5000 m, 6000 m, 7000 m, 8000 m, 9000 m, 10000 m, 15000 m, 20000 m and the like are tested in detail, and it can be known that a correction factor needs to be considered when the altitude exceeds 2000 m, the correction factors of different altitudes are different, and the following correction factors are obtained by testing the router:

1. when the altitude is 2000 m, the atmospheric pressure is 80kpa, and the correction factor is 1;

2. when the altitude is 3000 m, the atmospheric pressure is 70kpa, and the correction factor is 1.14;

3. when the altitude is 4000 meters, the atmospheric pressure is 62kpa, and the correction factor is 1.29;

4. when the altitude is 5000 meters, the atmospheric pressure is 54kpa, and the correction factor is 1.48;

5. when the altitude is 6000 meters, the atmospheric pressure is 47kpa, and the correction factor is 1.7;

6. when the altitude is 7000 m, the atmospheric pressure is 41kpa, and the correction factor is 1.95;

7. when the altitude is 8000 m, the atmospheric pressure is 35.5kpa, and the correction factor is 2.25;

8. when the altitude is 9000 meters, the atmospheric pressure is 30.5kpa, and the correction factor is 2.62;

9. when the altitude is 10000 m, the atmospheric pressure is 26.5kpa, and the correction factor is 3.02;

10. when the altitude is 15000 meters, the atmospheric pressure is 12kpa, and the correction factor is 6.67;

11. when the altitude is 20000 meters, the atmospheric pressure is 5.5kpa, and the correction factor is 14.5.

A heat conducting gasket (an insulating soft heat conducting gasket or an insulating hard heat conducting gasket) is added between the metal shell and the heating device, and when the surface creepage distance between the surface A1 in the shell of the metal shell (for example, the surface A1 in the shell of the metal top shell 15 in fig. 2) and the heating device (for example, the baseband chip 5 and the DDR particle 6 in fig. 2) is not less than 1.0mm, the metal shell is only suitable for the requirement that the altitude is less than 2000 meters. When the altitude of the industrial router is higher, the creepage distance and the electric clearance need to be multiplied by the correction factor so as to avoid surface discharge of the electronic device in an alternating current 1kV isolation test, a 1.5kV isolation test or a 2kV isolation test, which causes breakdown of a heating device in the industrial router and causes abnormal function.

Meanwhile, the insulation strength of the heat conduction gasket is related to the lightning-proof insulation performance, and the insulation strength of the heat conduction gasket is related to the material and the thickness of the heat conduction gasket. The heat conducting gasket can be made of rubber, plastic, laminated materials, films, resins, mica, ceramics, glass, bakelite and the like. Among them, the ceramic is most resistant to static electricity (dielectric strength). Taking alumina ceramics (aluminum oxide) as an example, the breakdown strength of the alumina ceramics needs to satisfy more than 15 kV. The breakdown strength of the heat-conducting gasket needs to meet more than 1.5kV, and the router can meet strict safety regulations such as UL62368-1 in North America, GB4943 in 3C in China and the like. For the selection of the heat-conducting gasket material, GB/T1695-2005 vulcanized rubber power frequency voltage breakdown strength and voltage-resistant strength can be adopted to simulate and verify the insulation material test. The parameters related to the heat-conducting silicone grease film of a certain model in table 1 can be obtained as follows: the soft heat-conducting gasket can bear the laminar breakdown voltage of 10kV under the condition of the thickness of 1mm. Meanwhile, the soft heat-conducting gasket meets the flame retardance of UL 94V-0 and the relevant safety standard of UL and the like.

The housing of communication equipment such as an industrial router, a switch and the like is a metal housing, and according to the related requirements of international standard IEC61000-4-2, the metal housing needs to meet the requirements of static contact discharge test (for example, the metal housing of the industrial router needs to make 8kV contact discharge).

FIG. 10 shows a waveform diagram of electrostatic discharge current under the requirements related to International Standard IEC61000-4-2, and Table 2 shows discharge current values of contact discharge tests of 2kV, 4kV, 6kV and 8kV at different periods. When under 2kV level contact discharge test conditions: the discharge current reaches 7.5A within the discharge current rise time of 0.6 ns-1 ns; the discharge current reaches 4A when being 30 ns; the discharge current reaches 2A at 60 ns. When in 4kV class contact discharge test conditions: in the discharge current rise time of 0.6 ns-1 ns, the discharge current reaches 15A; the discharge current reaches 8A when being 30 ns; when the discharge current is 60ns, the discharge current reaches 4A; when in the 6kV class contact discharge test condition: the discharge current reaches 22.5A within the discharge current rise time of 0.6 ns-1 ns; the discharge current reaches 12A when being 30 ns; the discharge current reached 6A at 60 ns. When under the contact discharge test condition of 8kV level: in the discharge current rise time of 0.6 ns-1 ns, the discharge current reaches 30A; the discharge current reaches 16A when being 30 ns; the discharge current reaches 8A when 60 ns; that is, the higher the contact discharge test level is, the larger the discharge current generated by the test is, and the ratio between the two is almost direct, which brings great challenges to the design of electrostatic protection of products or equipment. Especially industrial equipment, the contact discharge 8kV test needs to be carried out aiming at the I/O of vehicle-mounted equipment, which can greatly increase the time to market of products.

Table 2 different levels of contact discharge test discharge current values at different periods

Fig. 11 shows a discharge model of the electrostatic discharge device, and the meanings of the respective symbols in fig. 11 are as follows: UO is the DC high voltage power supply of the electrostatic discharge equipment, rc is the internal resistance (about 50-100 megaohms) of the DC high voltage power supply, the discharge capacitance Cs is 150pF, the internal resistance Rd is 330 ohms, 330 ohms represents the human body resistance of human body holding keys and other metal tools, K1 is the switch of the electrostatic discharge equipment, the discharge head of the M1 electrostatic discharge equipment, and M2 is the connection point of a discharge loop. The international standard IEC61000-4-2 considers that this discharge model (including capacitance and resistance values) is sufficiently rigorous to describe electrostatic discharge.

In order to meet the requirements of 4 kV-8 kV electrostatic discharge tests (contact discharge tests) related to international standard IEC61000-4-2, 8kV contact discharge tests need to be performed on the industrial router, that is, 8kV electrostatic contact discharge is applied to the metal casing of the industrial router, and the heat generating devices (such as the baseband chip 5 and the DDR particles 6 in fig. 2) cannot be out of function (such as a crash, a data packet loss, and the like) or damaged (such as the baseband chip 5 and the DDR particles 6 in fig. 2).

Taking the industrial router in fig. 2 as an example for illustration, if the electrostatic gun injects 4 kV-10 kV contact discharge into the metal top case 15 (electrically connected to the high voltage net mouth metal case), a strong electric field is generated in the dielectric of the insulating soft heat-conducting pad (or insulating hard heat-conducting pad) between the heat generating device (such as the baseband chip 5, DDR particles 6, etc.) and the metal top case 15. Under the action of the strong electric field, polarization is established between the insulating soft heat-conducting gasket (or insulating hard heat-conducting gasket) medium between the heating device (such as the base band chip 5, the DDR particles 6, etc.) and the metal top shell 15, and at this time, the insulating soft heat-conducting gasket (or insulating hard heat-conducting gasket) medium becomes a dielectric medium (i.e., an insulating medium). Therefore, the breakdown voltage of the heat conducting gasket can be larger than 10kV, so that the phenomenon that the heating device is broken down under a contact discharge test is avoided.

In some cases, the vertical layer insulation strength of the thermal pad may be greater than 10kV/mm. Taking a certain type of heat-conducting silicone grease film (one of the insulating soft heat-conducting gaskets) as an example shown in table 1, according to the relevant requirements obtained by the test, the vertical layer-wise insulation strength of the insulating soft heat-conducting gaskets exceeds 10kV/mm, the layer-wise breakdown voltage exceeds 10kV, and the medium of the insulating soft heat-conducting gaskets is broken down.

The case of the heat generating device can be divided into two different cases for explanation according to whether it is made of an insulating material or a metal material.

In the first case, the shell of the heating device is made of epoxy resin, ceramic, glass or engineering plastics.

Fig. 8 is a partially enlarged view of the cross-sectional view shown in fig. 2, and compared with fig. 2, the difference is that the DDR particles 6 and the baseband chip 5 in fig. 2 are replaced with the baseband chip 77 with the DDR particles built therein (that is, the baseband chip 77 integrates the DDR particles and belongs to a heat generating device), and the rest is the same. Since the housing of the baseband chip 77 is made of epoxy resin, ceramic, glass or engineering plastic, which are insulating materials, the substrate has a certain high voltage breakdown resistance, and the baseband chip 77 is protected from high voltage breakdown. In fig. 7, the surface directly above the base tape chip 77 (heat generating device) is A3 surface, the left side surface is A4 surface, and the right side surface is A5 surface, which are all made of an insulating material.

When the heat generating device (such as the baseband chip 77) is an insulating material housing, applying 4 kV-8 kV high voltage electrostatic contact discharge to the metal housing 15 will generate 4 kV-8 kV high voltage electrostatic field between the metal housing 15 and the heat generating device (such as the baseband chip 77), and their withstand voltage capability is the sum of the insulating strength of the heat conducting gasket (withstand voltage capability) and the insulating strength of the heat generating device housing (withstand voltage capability). The ability to withstand voltage is the ability of the two to withstand high voltage without being broken down.

Fig. 9 is a partially enlarged view of the cross-sectional view shown in fig. 2, and is different from fig. 8 in that the encapsulating material of the case of the heat generating device 78 in fig. 8 is a conductive material. In fig. 9, the surface directly above the heat generating device 78 is a surface A8, the left side surface is a surface A6, and the right side surface is a surface A7, which are made of a conductive material. For example, the Direct FET packaged MOSFET belongs to a reverse type, the heat dissipation plate of the drain electrode (D) faces upwards, and covers the metal shell, and the heat dissipation is carried out through the metal shell. That is, the housing of the Direct FET packaged MOSFET is a conductive material.

When the housing of the heat generating device 78 is made of a conductive material (e.g., direct FET package MOSFET), applying 4kV to 10kV high voltage electrostatic contact discharge to the metal housing 15 will generate 4kV to 10kV high voltage electrostatic field between the metal housing 15 and the heat generating device (e.g., baseband chip 77), and their ability to withstand voltage is the insulating strength (ability to withstand voltage) of the heat conductive gasket 1.

Taking table 1 as an example, a certain type of heat-conducting silicone grease film (one of the soft heat-conducting gaskets 1) is installed between the metal top case 15 shown in fig. 8 and the heating device 78 of the conductive outer case, 4kV to 8kV high-voltage electrostatic contact discharge is applied to the metal outer case 15, and the certain type of heat-conducting silicone grease film 1 cannot be punctured by the 4kV to 8kV high-voltage electrostatic contact discharge voltage. The breakdown voltage of a certain type of heat-conducting silicone grease film in table 1 is 10kV/mm, that is, when the compressed thickness of the soft heat-conducting gasket 1, which is installed between the metal top case 15 and the heating device 78 of the conductive housing, is not less than 1mm, the breakdown voltage is 10kV, which is already greater than the high-voltage electrostatic contact discharge voltage of 4 kV-8 kV, so that the scheme is a reasonable design requirement, scientific and reasonable scheme.

In some embodiments of the present application, the first type device and the second type device may be disposed to be offset from each other in a direction perpendicular to the PCB.

By mutually shifting the two types of devices with different heights in the direction perpendicular to the PCB, the positions of the network port connector 10 and the network port transformer 11 shown in fig. 1 and 2 and the position of the heat generating device are mutually shifted. The heat of the heating device can be prevented from being transferred to a higher device through the PCB, and the normal work of the second device is prevented from being influenced. And can provide the air convection environment for the heat that generates heat the device and transmit to the PCB board to be favorable to generating heat the device and transmit in time the dispersion to the second internal face of shell on the heat on the PCB board 13.

In some embodiments of the present application, the housing may include a first shell and a second shell, the first shell and the second shell being disposed opposite to each other to enclose a cavity, the first inner wall surface being located on the first shell, and the second inner wall surface being located on the second shell.

The first shell and the second shell are two parts of the shell, and it can be understood that when the first shell is a top shell, the second shell is a bottom shell; when the first shell is a bottom shell, the second shell is a top shell. The PCB board can be fixed to the drain pan through fasteners such as screws to seal the space at PCB board place through the top shell, can be convenient for realize the installation of PCB board through first casing and second casing, and, convenient to detach top shell and drain pan, in order to carry out the maintenance of PCB board and each device and change.

In the actual design process of the industrial router, as shown in fig. 1, if heat-generating devices (such as the baseband chip 5, the DDR particle 6, the FEM chip 12, etc.) are disposed on the TOP layer 8 of the PCB 13, the metal TOP case 15 of the industrial router 17 needs to be a heat sink with a larger size, that is, the metal TOP case 15 needs to have a certain thickness: firstly, the deformation rate of the metal top shell 15 is affected by the thickness of the metal top shell 15, that is, the metal top shell 15 and the metal bottom shell 16 are combined to support the whole product structure, so that the product is not deformed by external stress; secondly, heat of the heating device (such as the baseband chip 5, the DDR particles 6, the FEM chip 12 and the like) is transferred to the inner side surface A1 of the metal top shell 15 through the heat-conducting gasket (such as the baseband chip 5 and the DDR particles 6 are transferred through the second heat-conducting gasket 2, the shielding cover 18 in the first shielding cover 88 and the first heat-conducting gasket 1; heat of the FEM chip 12 is transferred through the third heat-conducting gasket 3), then is transferred to the rack 19 protruding outside the metal top shell 15 through the base 14 of the metal top shell 15, and finally is dissipated to outside air through the rack 19 protruding outside the metal top shell 15 in a convection heat dissipation and radiation heat dissipation mode, so that temperature rise of the heating device is rapidly reduced, the heating device is balanced with outside temperature, and the heating device is maintained within a certain allowable safe working temperature range. The thickness of the metal top 15 and the base 14 affects the heat transfer speed, and the thicker the metal top 15 and the base 14, the smaller the thermal resistance of the metal top 15 and the base 14, and the faster the heat transfer speed. The larger the surface area of the rack 19 protruding outside the metal top case 15 is, the smaller the thermal resistance of the convection heat dissipation and the radiation heat dissipation is, and the better the performance of the convection heat dissipation and the radiation heat dissipation is.

Since the tall devices (such as the network port transformer 11, the network port connector 10, etc.) basically do not generate heat, it is considered to make the thickness of the metal bottom shell 16 thin (save the material of the metal bottom shell 16 as much as possible), as long as the metal top shell 15 and the metal bottom shell 16 support the whole product structure, and the product is not deformed by the external stress. That is, the metal top shell 15 made of more metal materials meets the heat dissipation requirements of heating devices (such as the baseband chip 5, the DDR particles 6, the FEM chip 12, and the like), and meanwhile, the metal top shell 15 made of more metal materials greatly enhances the strength of the whole machine to support the structure of the whole product. Although the metal bottom case 16 made of a smaller amount of metal material is easily deformed, the metal top case 15 made of a larger amount of metal material and the metal bottom case 16 made of a smaller amount of metal material support the entire product structure, so that the strength of the entire machine is not affected, and the weight and material cost of the entire machine are reduced.

In some embodiments of the present application, the outer wall surface of the first housing away from the first inner wall surface may be provided with a plurality of spaced racks, each rack protruding from the outer wall surface of the first housing in a direction away from the first inner wall surface.

In practical situations, an external raised rack 19 can be arranged on the top of the metal top shell 15 of the industrial router to increase the surface area of the metal top shell 15 to the outside air, so that convection heat dissipation and radiation heat dissipation are facilitated. That is, the larger the surface area of the metal top case 15 exposed to the external space, the better the performance of the convection heat dissipation and the radiation heat dissipation.

In some embodiments of the present application, the first housing and the second housing may be made of a metal material.

Taking an industrial router as an example, the metal top case 15 is preferably made of an aluminum-type material (without limitation to which kind of metal material, such as silver, gold, iron, copper, etc.) with good thermal conductivity, and the metal top case 15 not only supports the whole product structure (so as to prevent the whole product from deforming and falling apart), but also plays a role of a heat sink, that is, the metal top case 15 is equivalent to exposing the heat sink to the outside air, so that convection heat dissipation and radiation heat dissipation with excellent performance can be realized.

Because the metal shell is exposed in the outside air, the metal shell has good convection heat dissipation and radiation heat dissipation conditions. To prove the rationality and the practicability of the heating device and the metal shell in the above embodiment of the present application, taking the industrial router shown in fig. 2 as an example, a Flotherm (3D electronic system heat dissipation simulation software) is used to perform analog thermal simulation analysis on the Wifi6 industrial router, and the following is the whole process of analog thermal simulation analysis:

fig. 12 is a simplified illustration of fig. 2, the Wifi6 industrial router is placed vertically, that is, the metal top shell 15 (including the rack 19 with the top protruding) is placed vertically together with the PCB 13, the heat generating device (only the base band chip 45 and the DDR particles 46 are taken as examples) is arranged on the PCB 13, the first heat conducting gasket 1 is added between the heat generating device and the metal top shell 15, and the high devices such as the network port connector 10 are arranged in the cavity formed by the back of the PCB 13 and the metal bottom shell 16. The metal top shell 15 is 100mm long and wide and 17mm high;

the proportion of convection heat dissipation and radiation heat dissipation of the housing of the industrial router under different heating power consumptions of the heating device is given in table 3.

When the total of the power consumption of the base band chip 45 and the power consumption of the DDR particles 46 is 6W, the convective heat dissipation amount is about 3.43W, which accounts for 57.17%, and the radiant heat amount is about 2.57W, which accounts for 42.83%;

when the power consumption of the base band chip 45 and the power consumption of the DDR particles 46 total 8W, the convective heat radiation amount is about 4.71W, which accounts for about 58.88%, and the radiant heat amount is about 3.29W, which accounts for about 41.13%;

when the total power consumption of the baseband chip 45 and the DDR particles 46 is 10W, the convective heat dissipation amount is 6.033W, which accounts for 60.33%, and the radiant heat amount is 3.967W, which accounts for 39.67%;

when the total of the power consumption of the base band chip 45 and the power consumption of the DDR particles 46 is 12W, the convective heat dissipation amount is about 7.35W, which is about 61.25%, and the radiant heat amount is about 4.65W, which is about 38.75%;

when the power consumption of the base band chip 45 and the power consumption of the DDR particles 46 add up to 14W, the convective heat radiation amount is about 8.68W, which accounts for 62.00%, and the radiant heat amount is about 5.32W, which accounts for 38.00%;

when the total of the power consumption of the base band chip 45 and the power consumption of the DDR particles 46 is 16W, the convective heat dissipation amount is about 10.2W, which accounts for 62.63%, and the radiant heat amount is about 5.98W, which accounts for 37.38%;

when the total of the power consumption of the base band chip 45 and the power consumption of the DDR particles 46 is 18W, the convective heat dissipation amount is about 11.33W, which is about 62.94%, and the radiant heat amount is about 6.67W, which is about 37.38%.

Table 3, under different heating power consumptions, the metal top case 15 is vertically placed with the respective proportions of convection and radiation heat dissipation:

table 4 shows the ratio of the convection heat dissipation and the radiation heat dissipation of the housing of the industrial router at different ambient temperatures when the power consumption of the heat generating device (baseband chip 45+ ddr particles 46) is 18W:

when the ambient temperature is 25 ℃, the convection heat dissipation is about 11.33W, which accounts for 62.94%, and the radiation heat dissipation is about 6.67W, which accounts for 37.06%;

when the ambient temperature is 30 ℃, the convection heat dissipation is about 11.12W, which accounts for 61.78%, and the radiation heat dissipation is about 6.88W, which accounts for 38.22%;

when the ambient temperature is 35 ℃, the convection heat dissipation is 10.925W, which accounts for 60.69%, and the radiation heat dissipation is 7.075W, which accounts for 39.31%;

when the ambient temperature is 40 ℃, the convection heat dissipation is 10.718W, which accounts for 59.54%, and the radiation heat dissipation is 7.282W, which accounts for 40.46%;

when the ambient temperature is 45 ℃, the convection heat dissipation is about 10.51W, which accounts for 58.39%, and the radiation heat dissipation is about 7.49W, which accounts for 41.61%.

Table 4, when the power consumption of the heating device is 18W and the temperature is different, the convection and radiation amount of the metal top case 15 are respectively placed vertically:

fig. 13 is a diagram of fig. 12 parallel to the ground, in which the Wifi6 industrial router is horizontally placed, that is, the metal top shell 15 (including the rack 19 with a raised top) and the PCB 13 are horizontally placed together, a heat generating device (only taking the baseband chip 45 and the DDR particles 46 as an example) is built in the PCB 13, a heat conducting gasket 1 is added between the heat generating device and the metal top shell 15, and a cavity formed by the back of the PCB and the metal bottom shell 16 is provided with high devices such as a network port connector 10. The metal top shell 15 is 100mm long and wide and 17mm high;

table 5 shows the proportion of convection heat dissipation and radiation heat dissipation of the housing of the industrial router under different heating power consumptions of the heating device.

When the total of the power consumption of the base band chip 45 and the power consumption of the DDR particles 46 is 6W, the convective heat dissipation amount is about 3.303W, which is about 50.55%, and the radiant heat amount is about 2.57W, which is about 42.83%;

when the total of the power consumption of the baseband chip 45 and the power consumption of the DDR particles 46 is 8W, the convective heat dissipation amount is about 4.323W and about 54.04%, and the radiant heat amount is about 3.677W and about 45.96%;

when the total power consumption of the baseband chip 45 and the DDR particles 46 is 10W, the convective heat dissipation amount is 5.432W, which accounts for 54.32%, and the radiant heat amount is 4.568W, which accounts for 45.68%;

when the total of the power consumption of the base band chip 45 and the power consumption of the DDR particles 46 is 12W, the convective heat dissipation amount is about 6.97W, which is about 58.08%, and the radiant heat amount is about 5.03, which is about 41.92%;

when the power consumption of the base band chip 45 and the power consumption of the DDR particles 46 are 14W in total, the convective heat dissipation capacity is about 8.263W, which accounts for 59.02%, and the radiant heat capacity is about 5.737, which accounts for 40.98%;

when the power consumption of the base band chip 45 and the power consumption of the DDR particles 46 are 16W in total, the convective heat dissipation capacity is about 9.412W, about 58.83%, and the radiant heat capacity is about 6.588, about 41.18%;

when the power consumption of the base tape chip 45 and the power consumption of the DDR particles 46 are 16W in total, the convective heat radiation amount is about 10.32W, about 57.33%, and the radiant heat amount is about 7.68, about 42.67%.

Table 5, when the heating device is placed horizontally on the top metal shell 15 under different heating power consumptions, the proportion of convection heat dissipation and radiation heat dissipation of the housing of the industrial router is as follows:

table 6 shows the ratio of convection heat dissipation and radiation heat dissipation of the housing of the industrial router at different ambient temperatures when the power consumption of the heat generating device (baseband chip 45, DDR particles 46) is 18W.

When the ambient temperature is 25 ℃, the convection heat dissipation is about 10.32W, which accounts for 57.33%, and the radiation heat dissipation is about 7.68W, which accounts for 42.67%;

when the ambient temperature is 30 ℃, the convection heat dissipation is 10.085W, which accounts for 56.03%, and the radiation heat dissipation is 7.915W, which accounts for 43.97%;

when the ambient temperature is 35 ℃, the convection heat dissipation is 10.176W and about 56.53%, and the radiation heat dissipation is 7.824W and about 43.47%;

when the ambient temperature is 40 ℃, the convection heat dissipation is 10.189W, which accounts for 56.61%, and the radiation heat dissipation is 7.811W, which accounts for 43.39%;

when the ambient temperature is 45 ℃, the convection heat dissipation is 9.924W, about 55.13%, and the radiation heat dissipation is 8.076W, about 44.87%.

Table 6, when the power consumption of the heating device is 18W and the metal top case 15 is horizontally placed at different environmental temperatures, the proportion of the convection heat dissipation and the radiation heat dissipation of the industrial router housing is as follows:

from the above described thermal simulation results of the flowtherm on metal housing industrial router, the following conclusions can be drawn:

1. among the natural flow heat dissipation, the radiation heat dissipation of the metal top case 15 or the metal bottom case 16 is not negligible.

2. The proportion of the radiation heat dissipation of the metal top shell 15 or the metal bottom shell 16 is increased along with the increase of the environmental temperature, and the proportion of the radiation heat dissipation is increased from 35% to 50%.

From the above conclusion, after the heat generating device (for example, the baseband chip 45+ ddr particles 46) is combined with the metal housing through the heat conducting gasket, the metal housing has excellent heat dissipation performance, and meanwhile, the size of the whole machine housing can be reduced, the metal material for heat dissipation can be saved, and the heat dissipation performance can be obviously improved.

It should be added that the first type device is not limited to be disposed on only the first surface (hereinafter referred to as "top layer") of the PCB, and in other possible modified embodiments, the first surface and the second surface of the PCB may be disposed with the first type device (i.e., heat generating device), which will be exemplified below.

Fig. 14 is a schematic cross-sectional structural diagram of an electronic apparatus when the first type device provided in the embodiment of the present application is disposed on the top layer and the bottom layer of a PCB and the tall device is disposed on the bottom layer of the PCB. Fig. 14 is compared with fig. 2, and the difference is that in fig. 14, the heat generating device (e.g. DDR particle 6, baseband chip 5) is disposed on the TOP layer 8 (i.e. TOP layer 8) of the PCB 13, the FEM chip 12 is disposed on the BOTTOM layer 7 (i.e. BOTTOM layer 7) of the PCB 13, where the FEM chip 12 is disposed on the BOTTOM layer of the PCB 13, and the heat generating device is not limited to the FEM chip only, the heat dissipation pad 99 of the FEM chip is disposed on the FEM chip projection position of the BOTTOM layer 7 of the PCB 13, the heat dissipation pad 99 in the PCB 13 is disposed with heat dissipation vias 97, the number of the heat dissipation vias 97 is at least 1, the heat dissipation vias 97 belong to a part of the PCB 13, and the heat dissipation vias 97 are perpendicular to the horizontally disposed PCB 13; if the PCB 13 is a 2-layer board, the heat dissipation through hole 97 is electrically connected with the heat dissipation pad 99 at the bottom layer of the PCB 13, and the heat dissipation through hole 97 is electrically connected with the exposed copper 98 at the top layer 8 of the PCB 13; if the PCB 13 is a 4-layer PCB or more than 4 layers PCB, the heat dissipation via 97 is electrically connected with the heat dissipation pad 99 of the bottom layer 7 of the PCB 13, the heat dissipation via 97 is electrically connected with the exposed copper 98 of the top layer 7 of the PCB 13, and the heat dissipation via 97 is electrically connected with the inner-layer ground copper foil or the power copper foil (not marked in the figure) of the PCB 13; the exposed copper 98 on the top layer of the PCB 13 is arranged on the top layer of the PCB 13 and is positioned in the projection position area of the FEM chip 12. The heat dissipation pad 99 may be electrically connected to a ground copper foil or a power copper foil (not shown) of the bottom layer 7 of the PCB 13, and the heat dissipation pad 99 may not be connected to the ground copper foil or the power copper foil (not shown) of the bottom layer 7 of the PCB 13; preferably, the heat dissipation pad 99 can be electrically connected to a ground copper foil or a power copper foil (not shown) of the bottom layer 7 of the PCB 13, so as to increase the heat dissipation area of the copper foil in the horizontal direction of the bottom layer 7 of the PCB 13; the top copper-exposed layer 98 can be electrically connected to the ground copper foil or the power copper foil (not shown) of the top layer 8 of the PCB 13, and the top copper-exposed layer 98 can be disconnected from the ground copper foil or the power copper foil (not shown) of the top layer 8 of the PCB 13; preferably, the heat dissipation pads 99 can be electrically connected to the ground copper foil or the power copper foil (not shown) of the top layer 8 of the PCB 13, so as to increase the heat dissipation area of the copper foil in the horizontal direction of the top layer 8 of the PCB 13. The thermal dissipating via 97 may be electrically connected to a ground copper foil or a power copper foil (not shown) on the inner layer of the PCB 13, and the thermal dissipating via 97 may not be connected to the ground copper foil or the power copper foil (not shown) on the inner layer of the PCB 13; preferably, the thermal dissipating via 97 is electrically connected to a ground copper foil or a power copper foil (not shown) on the inner layer of the PCB 13, so as to increase a heat dissipating area of the copper foil on the inner layer of the PCB 13 in a horizontal direction. The thermal vias 97 in the PCB 13 serve for vertical heat conduction, and the ground or power copper foils (not shown) on the top layer 8 of the PCB 13, the ground or power copper foils (not shown) on the bottom layer 7 of the PCB 13, and the ground or power copper foils (not shown) on the inner layer of the PCB 13 serve for horizontal heat conduction.

In addition, in order to transfer heat conducted to the top layer (i.e. the first surface) side of the PCB to the housing of the electronic device as soon as possible, a heat conducting pad 3 attached to the exposed copper 98 may be further disposed at the top layer exposed copper 98, where the thickness of the heat conducting pad 3 is H12, and unlike the thickness of the heat conducting pad 3 in fig. 2, the thickness of the heat conducting pad 3 is H12, and H12= H5+ H6.

The top copper exposure 98 means that a ground copper foil or a power copper foil is provided on the top layer 8 of the PCB 13, and the ink projected on the ground copper foil or the power copper foil on the top layer 8 of the PCB 13 of the FEM chip 12 is removed, and the ink-removed copper foil or the power copper foil 98 is electrically connected to the heat dissipating via 97.

In addition, because communication equipment such as an industrial router and the like is required to work at high temperature environment temperature such as 75 ℃ or 85 ℃, the junction temperature of key devices of the industrial router is more than 90 ℃ or more than 100 ℃, and devices such as a baseband, DDR particles and the like which generate heat and generate heat with larger heat require higher junction temperature, otherwise, the devices are difficult to bear the environment temperature of 75 ℃ or 85 ℃ and are damaged: the ambient temperature of 75 ℃ is higher than 90 ℃ corresponding to the junction temperature of the device; the ambient temperature of 85 ℃ corresponds to the junction temperature of the device being greater than 90 ℃. The consumer router is required to work at the ambient temperature of 40 ℃, and the junction temperature of key devices of the consumer router is only required to be higher than 55 ℃; if the industrial router needs to meet some special function requirements, devices with junction temperature higher than 90 ℃ or higher than 100 ℃ can be selected very rarely, at the moment, the junction temperature is selected to be higher than 90 ℃ or 100 ℃ (75 ℃ environmental temperature corresponds to device junction temperature higher than 90 ℃, 85 ℃ environmental temperature corresponds to device junction temperature higher than 90 ℃), temperature rise cannot exceed 5 ℃, and then the industrial router can work at 75 ℃ or 85 ℃ environmental temperature, so that the power consumption of the heating device is higher than 0.25W, namely the power consumption of the heating device exceeds 0.25W, the heating device must be considered to be radiated by a heat conduction gasket and a metal shell, and otherwise the heating device is damaged at 75 ℃ or 85 ℃ and other environmental temperatures. Therefore, the electronic device provided by the embodiment of the application is more suitable for the situation that the power consumption of the heat generating device is larger than 0.25W.

Further, the electronic device also includes devices with very low heat generation (such as ceramic capacitors, resistors, low power transistors, low power MOSFETs, ESD devices, etc.), which need not be added with a thermal pad to contact the metal housing to take into account heat dissipation, and such devices are referred to as a third class of devices 80. The third type device 80 is disposed on the TOP layer 8 of the PCB board and generates a lower amount of heat than the first type device. As long as a safe spacing between the third type of device and the metal housing (e.g., metal top shell 15) is considered.

The safe spacing of the device according to the third category from the metal housing (e.g., metal top shell 15) includes two aspects: A. during assembly, the first inner wall surface A1 of the metal TOP shell 15 does not interfere with the third device 80 on the TOP layer 8 in the PCB 13; B. the first inner wall surface A1 of the metal TOP shell 15 does not have enough electrical clearance with the third device 80 on the TOP layer 8 in the PCB 13, and the metal TOP shell 15 discharges air to the third device 80, so that the third device 80 is abnormal in function and even damaged.

In the first case, the height of the third device 80 is between the shielding cover or the heating device (first device) and the tall device (second device), and a groove is locally arranged on the surface A1 in the metal shell, so that the interference between the third device 80 and the metal shell is avoided, and the safety electrical gap requirement and the contact discharge electrical gap requirement are met.

Fig. 18 shows a cross-sectional view between the high and low heat generating devices and the metal top case. Fig. 18 is a partially enlarged view of fig. 1, with the FEM chip 12 replaced with a PMIC chip 122 (Power Management IC). The PMIC chip 122 belongs to a heat-generating device, and includes a plurality of BUCK (BUCK switching power supplies) and a plurality of LDOs (low dropout regulators), and provides a multi-path power supply for the entire PCB 13, and the PMIC chip 122 is a device generating more heat, and the PMIC chip 122 belongs to a first type of device as well as the baseband chip 5 and the DDR particles 6. The baseband chip 5 and the DDR particles 6 are arranged in the metal shielding cover base 4, the heat conduction gasket 2 is filled, then the shielding cover 18 is covered above the metal shielding cover base 4, and after tight combination, the heat conduction gasket 1 is filled between the shielding cover 18 and the metal top shell 15. The thickness of the heat conducting gasket 1 is h3, the shielding cover 18 and the metal shielding cover base 4 form a first shielding cover 88, and the height of the first shielding cover 88 is h17; the height of the PMIC chip 122 is h7, and the height of the thermal pad 130 is h18. The relationship between the height H17 of the first shielding can 88, the height H3 of the heat-conducting pad 1, the height H7 of the PMIC chip 122, the height H18 of the heat-conducting pad 130, and the distance H1 from the TOP layer 8 of the PCB board to the surface of the metal TOP case A1 is as follows:

H1＝h17+h3＝h7+h18

in fig. 18, the height h16 of the third type device 80 is higher than the height h17 of the first shield case 88 and the height h7 of the PMIC chip 122, and the height h16 of the third type device 80 is higher than that of the first shield case 88. Since the height H16 of the third type device 80 is close to the distance H1 from the TOP layer 8 of the PCB to the surface of the metal TOP shell A1, the third type device 80 cannot interfere with the metal TOP shell 15 in consideration of the PCB 13 during assembly. An electrostatic test (international standard IEC 61000-4-2) of 4kV to 10kV contact discharge is required to be carried out on the metal top shell 15, and the high voltage of alternating current 1kV or direct current 1.5kV brought by the electric contact of the metal top shell 15 and the metal mesh shell (UL 62368-1 in North America and GB4943 related safety certification requirements in 3C in China) is also considered. That is, although there is a certain electrical gap between the metal case (e.g., the top metal case 15 in fig. 18) and the third type device 80, due to the very high voltage difference between the two, if the third type device 80 contains a metal portion distributed on the top of the body (e.g., the top metal electrode on the top of the ceramic capacitor body), the metal case (e.g., the top metal case 15 in fig. 18) will discharge air (generate air electrical breakdown) to the metal portion of the third type device 80. Therefore, the requirement of a safety distance needs to be considered between the metal top shell 15 and the third type device 80 (especially the third type device 80 with metal parts distributed on the top of the body), otherwise, when 4 kV-10 kV contact discharge is performed, the distance between the metal top shell 15 and the third type device 80 is short, static electricity can break through air between the metal top shell 15 and the third type device 80, so that the third type device 80 is connected with high-voltage static electricity in series, so that the third type device 80 fails in function, and in serious cases, the third type device 80 can be broken through (such as a low-power triode). Therefore, the third type of device 80 is partially hollowed out by a CNC milling cutter at the position projected on the first inner wall surface A1 of the metal top case 15. In fig. 18, a groove G1 is cut by CNC milling at the position where the third type device 80 projects on the first inner wall surface A1 of the metal top case 15, the width of the groove G1 is L82, the width of the third type device 80 is L83, the distance from the left edge of the third type device 80 to the left edge of the groove G1 is L80, that is, the electrical gap from the left side surface of the third type device 80 to the left side surface of the groove G1 is L80; the distance from the right edge of the third device 80 to the right edge of the groove G1 is L81, that is, the electrical gap from the right side surface of the third device 80 to the right side surface of the groove G1 is L81; the relationship between the width L82 of the groove G1 and the width L83 of the third type device 80 satisfies:

L82＝L81+L80+L83

l80 ≧ 0.6mm (preferably L80 ≧ 0.8 mm) and L81 ≧ 0.6mm (preferably L81 ≧ 0.8 mm) are required to satisfy requirements for safety certification related to GB4943 in North America UL62368-1 and China 3C. Meanwhile, when the metal top shell 15 is in contact discharge of 4kV to 10kV, static electricity cannot break through air between the left side face of the third device 80 and the groove G1, normal work of the third device 80 cannot be influenced, and the third device 80 cannot be damaged.

The height of the third device 80 is h16, the depth of the groove G1 is h15, and the height from the top of the third device 80 to the top A9 of the groove G1 is h19, i.e. the electrical gap from the top of the third device 80 to the top A9 of the groove G1 is h19.

The requirement of h19 ≧ 0.6mm (preferably h19 ≧ 0.8 mm) is satisfied in order to satisfy the requirements for the safety certification related to GB4943 in North America UL62368-1 and China 3C. Meanwhile, when the metal top shell 15 is subjected to contact discharge of 4kV to 10kV, static electricity cannot break down air between the top of the third device 80 and the surface A9 of the top of the groove G1, normal work of the third device 80 cannot be influenced, and the third device 80 cannot be damaged.

The relationship between the height of the third device 80 being H16, the depth of the groove G1 being H15, the height from the TOP of the third device 80 to the TOP A9 of the groove G1 being H19, and the distance H1 from the TOP layer 8 of the PCB board to the first inner wall surface A1 of the metal TOP case 15 is as follows:

h16+h19＝H1+h15

the groove G1 formed on the A1 surface of the metal top case may be implemented by die casting, or by CNC milling, and the like, and the specific method is not limited. As such, the minimum distance between the top of the third type device 80 and any inner wall of the groove G1 is greater than or equal to 0.6mm (preferably greater than or equal to 0.8 mm), that is, the minimum distance between the top of the third type device 80 and the inner wall of the groove G1 is greater than or equal to 0.6mm (preferably greater than or equal to 0.8 mm), so as to ensure that neither the A1 surface inside the metal housing nor the inner wall surfaces of the groove G1 are too close to the top of the third type device 80 to cause electrostatic breakdown.

For the third type device 80 (such as QFN package or BGA package) with the pins and pads on the bottom and top of the body as an insulating housing, the groove G1 on the A1 surface inside the metal housing of the metal top case and the third type device 80 are considered as the main considerations, and no interference occurs during assembly.

Fig. 19 shows another cross-sectional view between the high and low heat generating devices and the metal top case. Compared with fig. 18, the difference is that an insulation sheet 81 is added between the third type device 80 in fig. 19 and the groove G1 on the metal top case 15. That is, when the electrical gap between the third type device 80 (e.g. ceramic capacitor) with the metal portion distributed on the top of the body and the groove G1 on the metal top case 15 does not satisfy the safety certification requirements related to GB4943 in 3C of china or the electrostatic test (international standard IEC 61000-4-2) with 4 kV-10 kV contact discharge or UL62368-1, the insulating sheet 81 is required to be added between the third type device 80 (e.g. ceramic capacitor) with the metal portion distributed on the top of the body and the groove G1 on the metal top case 15, thereby greatly increasing the insulating strength between the two, and satisfying the safety certification requirements related to GB 43 in 3C of china or the electrostatic test (international standard IEC 61000-4-2) with 4 kV-10 kV contact discharge or UL 62368-1. In this way, in the case that an insulation sheet is disposed between the groove G1 of the top metal shell 15 and the top of the third type device 80, the minimum distance between the groove G1 of the top metal shell 15 and the top of the third type device 80 may be smaller than 0.6mm to ensure that the insulation strength requirement of the electrostatic test is satisfied. It can be understood that the technical scheme that an insulating sheet is arranged between the groove G1 of the metal top shell 15 and the top of the third type device 80 is also suitable for a scene that the distance between the groove G1 of the metal top shell 15 and the top of the third type device 80 is greater than or equal to 0.6mm, and the metal top shell can have higher insulating strength and meet higher static test requirements.

Fig. 20 shows another cross-sectional view between the high and low heat generating devices and the metal top case. Compared with fig. 18, the difference is that the third type device 80 (low heat generating device) in fig. 20 has a low height and does not interfere with the first inner wall surface A1 of the metal top case 15 during assembly, so that it is not necessary to provide the groove G1 on the first inner wall surface A1 of the metal top case 15, and for the third type device 80 (for example, QFN package, BGA package, etc.) having the pins and pads at the bottom and the top of the body as an insulating case, the groove G1 on the first inner wall surface A1 of the metal top case 15 and the third type device 80 do not interfere with each other during assembly.

The relationship among the height H16 of the third type device 80, the electrical gap H13 between the third type device 80 and the first inner wall surface A1 of the TOP metal shell 15, and the distance H1 from the first inner wall surface A1 of the TOP metal shell 15 to the TOP layer 8 of the PCB board is as follows:

h16+h13＝H1

when the electric gap h13 ≧ 0.6mm (preferably h13 ≧ 0.8 mm) between the third device 80 (such as a ceramic capacitor) with the metal part distributed on the top of the body and the first inner wall surface A1 of the metal top shell 15, the requirements of electrostatic test (international standard IEC 61000-4-2) or UL62368-1 of contact discharge of 4 kV-10 kV, and the safety certification requirements related to GB4943 in 3C of China are met. There is no need to add an insulating sheet to the third type of device 80 (e.g., ceramic capacitor) and the first inner wall surface A1 of the metal top case 15, which are distributed on the top of the body at the metal portion, to increase the insulation strength.

Fig. 21 shows another cross-sectional view between the high and low heat generating devices and the metal top case. Compared with fig. 20, the difference is that an insulating sheet 82 is added between the third type device 80 in fig. 21 and the first inner wall surface A1 inside the metal top case 15. That is, when the electrical gap between the third type device 80 (e.g. ceramic capacitor) with the metal portion distributed on the top of the body and the first inner wall surface A1 of the metal top shell 15 does not satisfy the static test (international standard IEC 61000-4-2) of 4 kV-10 kV contact discharge or the safety certification requirements related to GB4943 in UL62368-1 and 3C in china, the insulating sheet 82 is required to be added between the third type device 80 (e.g. ceramic capacitor) with the metal portion distributed on the top of the body and the groove G1 on the metal top shell 15, thereby greatly increasing the insulating strength between the two. In this way, in the case that the insulation sheet is disposed between the first inner wall surface A1 of the top metal shell 15 and the top of the third type device 80, the distance between the first inner wall surface A1 of the top metal shell 15 and the top of the third type device 80 may be smaller than 0.6mm to ensure that the insulation strength requirement of the electrostatic test is satisfied. It can be understood that the technical scheme that an insulating sheet is arranged between the first inner wall surface A1 of the metal top shell 15 and the top of the third type device 80 is also suitable for a scene that the distance between the first inner wall surface A1 of the metal top shell 15 and the top of the third type device 80 is greater than or equal to 0.6mm, and the metal top shell can have higher insulating strength and meet higher static test requirements.

It should be noted that, in the foregoing embodiment, the first inner wall surface A1 and the second inner wall surface B1 are shown as flat surfaces in the drawings (fig. 1 to fig. 22), but designing the first inner wall surface A1 and the second inner wall surface B1 as flat surfaces is merely an example of a possible solution, and in other possible modification, the first inner wall surface A1 and/or the second inner wall surface B1 may also be other non-flat surfaces such as an arc surface, and is not limited in this respect.

It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples for carrying out the present application, and that various changes in form and details may be made therein without departing from the spirit and scope of the present application in practice.

Claims

1. An electronic device, comprising:

a housing having a cavity, and a first inner wall surface and a second inner wall surface which are partitioned by the cavity and are oppositely arranged;

the PCB is arranged in the cavity and is provided with a first surface and a second surface which are oppositely arranged; the first inner wall surface and the first surface are spaced from each other; the second inner wall surface and the second surface are spaced from each other;

the distance between the first inner wall face and the first surface is smaller than the distance between the second inner wall face and the second surface, the first surface is opposite to the first inner wall face and is provided with a first device, the first device is a heating device, the second surface is opposite to the second inner wall face and is provided with a second device, and the height of the second device on the PCB is higher than that of the first device on the PCB.

2. The electronic device of claim 1, wherein:

the heat conducting gasket is arranged between the first inner wall surface and the first type device and is respectively attached to the first inner wall surface and the first type device.

3. The electronic device of claim 2, wherein: the compression amount of the heat conduction gasket in the thickness direction of the heat conduction gasket is greater than or equal to 5% and less than or equal to 45%.

4. The electronic device of claim 2, wherein: the heat conduction gasket is compressed by more than 20% in the thickness direction, the PCB is provided with a screw hole adjacent to the first type device, the PCB is fixed with the shell through a screw penetrating through the screw hole, and the distance between the screw hole adjacent to the first type device and the first type device is 1-30 mm.

5. The electronic device of claim 2, wherein: the breakdown voltage between the housing and the first type of device is greater than or equal to 1kV.

6. The electronic device of claim 5, wherein:

the shell packaging material of the first type device is an insulating material, and the sum of the insulating strength of the heat conducting gasket and the insulating strength of the shell packaging material of the first type device is greater than or equal to 1kV; or

The shell packaging material of the first device is a conductive material, and the insulating strength of the heat conducting gasket is greater than or equal to 1kV.

7. The electronic device of claim 5, wherein:

the first type of device is welded on the PCB, a shell packaging material of the first type of device is an insulating material, pins of the first type of device are arranged at the bottoms of the periphery or two sides of the body of the first type of device, a pad of the PCB extends along the surface of the PCB in a direction far away from the body, soldering tin is covered on the pins and is welded on the pad of the PCB through the soldering tin, and the surface creepage distance between the first inner wall surface and the first surface of the PCB is larger than or equal to 1.0mm, wherein the surface creepage distance is the sum of the thickness of the heat conducting gasket, the distance from the edge of the heat conducting gasket to the edge of the first type of device, and the height from the soldering tin to the top of the first type of device;

or,

the first type device is welded on the PCB, a shell packaging material of the first type device is an insulating material, a pin of the first type device is arranged on a side wall between the top and the bottom of the body of the first type device, the pin is bent and extended from the side wall towards the direction close to the PCB, the tail end of the pin extends to the PCB and is welded on a bonding pad of the PCB through soldering tin, and the surface creepage distance between the first inner wall surface and the first surface of the PCB is larger than or equal to 1.0mm, wherein the surface creepage distance is the sum of the thickness of the heat conduction gasket, the distance from the edge of the heat conduction gasket to the edge of the first type device, and the height from the pin to the top of the first type device;

or,

the first-type device is welded on the PCB, the shell packaging material of the first-type device is insulating material, pins of the first-type device are arranged at the bottoms of the periphery or two sides of the body of the first-type device, a pad of the PCB extends along the surface of the PCB in the direction far away from the body, soldering tin is covered on the pins and is welded on the pad of the PCB through the soldering tin, and the surface creepage distance between the first inner wall surface and the first surface of the PCB is larger than or equal to 1.0mm, wherein the surface creepage distance is the sum of the thickness of the heat conduction gasket, the distance from the edge of the heat conduction gasket to the edge of the first-type device, and the height from the soldering tin to the top of the first-type device; the pin of the first device is arranged on the side wall between the top and the bottom of the body of the first device, the pin is bent and extended from the side wall towards the direction close to the PCB, the tail end of the pin extends to the PCB and is welded on a bonding pad of the PCB through soldering tin, and the surface creepage distance between the first inner wall surface and the first surface of the PCB is larger than or equal to 1.0mm, wherein the surface creepage distance is the sum of the thickness of the heat conduction gasket, the distance from the edge of the heat conduction gasket to the edge of the first device and the height from the pin to the top of the first device;

or the like, or a combination thereof,

the first-class device is welded on the PCB, a shell packaging material of the first-class device is an insulating material, pins of the first-class device are arranged on the bottom surface of the body of the first-class device and are electrically connected with bonding pads of the PCB, the pins of the first-class device and the bonding pads of the PCB are covered under the body, and the surface creepage distance between the first inner wall surface and the first surface of the PCB is larger than or equal to 1.0mm, wherein the surface creepage distance is the sum of the thickness of the heat conduction gasket, the distance from the edge of the heat conduction gasket to the edge of the first-class device, and the height of the first-class device perpendicular to the PCB.

8. The electronic device of claim 5, wherein: the shell packaging material of the first type device is a conductive material, and the surface creepage distance between the first inner wall surface and the shell of the first type device is greater than or equal to 1.0mm, wherein the surface creepage distance is the sum of the thickness of the heat conduction gasket and the distance between the edge of the heat conduction gasket and the edge of the first type device.

9. The electronic device of claim 1, wherein: the first type of device comprises a radio frequency device, a digital device and a power supply device, wherein the radio frequency device is arranged in a first area of the PCB, the digital device is arranged in a second area of the PCB, and the first area and the second area are arranged at intervals.

10. The electronic device of claim 9, wherein: the PCB board is provided with a shielding case for covering the first device, wherein,

the shielding case comprises a first shielding case, the first shielding case is arranged on the PCB and encloses a first shielding cavity, and the radio frequency device and the digital device are both positioned in the first shielding cavity and are separated from each other by a partition plate arranged in the first shielding case;

or,

the shielding case includes first shielding case and second shielding case, first shielding case cover is located on the first region of PCB board and enclose into first shielding chamber, the radio frequency device is located in the first shielding intracavity, second shielding case cover is located on the second region of PCB board and enclose into second shielding chamber, digital device is located in the second shielding intracavity.

11. The electronic device of claim 10, wherein: the shielding case comprises a first shielding case and a second shielding case, the first shielding case is arranged on a first area of the PCB and encloses a first shielding cavity, the radio frequency device is positioned in the first shielding cavity, the second shielding case is arranged on a second area of the PCB and encloses a second shielding cavity, and the digital device is positioned in the second shielding cavity; wherein,

a first heat conduction gasket which is respectively attached to the first shielding cover and the first inner wall surface is arranged in the shell, and a second heat conduction gasket which is respectively attached to the first shielding cover and the radio frequency device is arranged in the shielding cavity;

and/or the presence of a gas in the gas,

and a third heat conduction gasket which is respectively attached to the second shielding cover and the first inner wall surface is arranged in the shell.

12. The electronic device of claim 1, wherein: the shell comprises a first shell and a second shell, the first shell and the second shell are arranged oppositely to enclose a cavity, the first inner wall surface is located on the first shell, the second inner wall surface is located on the second shell, a plurality of racks are arranged on the outer wall surface of the first shell, which is far away from the first inner wall surface, at intervals, each rack protrudes from the outer wall surface of the first shell in a direction far away from the first inner wall surface, and the first shell is a bottom cover or a top cover of the electronic equipment.

13. The electronic device of claim 1, wherein: the second surface is also provided with the first-class device, the electronic equipment further comprises a heat conduction structure penetrating through the PCB, and the first-class device arranged on the second surface is in thermal contact with the heat conduction structure and transfers heat to the heat conduction structure so as to be transferred to one side of the first surface through the heat conduction structure.

14. The electronic device of claim 13, wherein: the heat conductive structure includes a heat dissipation pad disposed on the second surface, exposed copper disposed on the first surface, and heat dissipation vias penetrating the PCB and connected to the heat dissipation pad and the exposed copper, respectively,

the electronic equipment further comprises an inner-layer ground copper foil or a power copper foil which is arranged on the inner layer of the PCB and located between the first surface and the second surface, and the heat dissipation through hole is electrically connected with the inner-layer ground copper foil or the power copper foil;

and/or the presence of a gas in the gas,

the electronic equipment further comprises a bottom-layer ground copper foil or a power copper foil arranged on one side of the second surface, and the heat dissipation pad is electrically connected with the bottom-layer ground copper foil or the power copper foil;

and/or the presence of a gas in the gas,

the electronic equipment further comprises a top-layer ground copper foil or a power copper foil arranged on one side of the first surface, and the exposed copper is electrically connected with the top-layer ground copper foil or the power copper foil;

and/or the presence of a gas in the gas,

the electronic equipment further comprises a heat conduction gasket which is arranged between the first inner wall surface and the exposed copper and is respectively attached to the first inner wall surface and the exposed copper.

15. The electronic device of claim 1, wherein: the PCB board is provided with a shielding case, at least one first-type device is arranged in the shielding case, a first heat conduction gasket attached to the shielding case and the first inner wall face is arranged in the shell, and a second heat conduction gasket attached to the shielding case and the first-type device is arranged in the shielding case.

16. The electronic device of claim 15, wherein: the surface creepage distance between the first inner wall surface and the shielding case is greater than or equal to 1.0mm, wherein the surface creepage distance between the first inner wall surface and the shielding case is the sum of the thickness of the heat conduction gasket and the distance between the edge of the heat conduction gasket and the edge of the shielding case.

17. The electronic device of claim 2, wherein: the shell comprises a top shell and a bottom shell, and at least one first fastener column is arranged on the inner side surface of the top shell or the bottom shell; the PCB is provided with at least one first drilling hole; the electronic device further includes at least one fastener mated with the at least one fastener post; wherein,

the fastener penetrates through the first drilling hole of the PCB and is combined with the fastener column on the inner side surface of the top shell; or

18. The electronic device of claim 1, wherein: the first surface is opposite to the first inner wall surface and is provided with a third device, the third device is a heating device, the heating value of the third device is smaller than that of the first device, and the height of the third device on the PCB is lower than that of the second device on the PCB.

19. The electronic device of claim 18, wherein: the top of the third device is made of metal, the top of the third device is spaced from the first inner wall surface, and an electric gap between the top of the third device and the first inner wall surface is larger than or equal to 0.6mm; or

The top of the third device is made of an insulating material, the top of the third device is spaced from the first inner wall surface, and the height of the third device on the PCB is smaller than the distance between the first inner wall surface and the first surface; or

The top of the third type device is made of metal, an insulating sheet is arranged between the top of the third type device and the first inner wall face, and the sum of the height of the third type device on the PCB and the thickness of the insulating sheet in the direction perpendicular to the PCB is smaller than the distance between the first inner wall face and the first surface.

20. The electronic device of claim 18, wherein: a groove opposite to the third device is formed in the first inner wall face, the top of the third device is spaced from the inner wall of the groove, the top of the third device is made of metal, the top of the third device is spaced from the inner wall of the groove, and the minimum electric gap between the top of the third device and the inner wall of the groove is larger than or equal to 0.6mm;

or the top of the third device is made of an insulating material, the top of the third device is spaced from the inner wall surface of the groove, and the height of the third device on the PCB is smaller than the sum of the distance between the first inner wall surface and the first surface and the depth of the inner wall surface of the groove in the direction vertical to the PCB;

or, the top of the third type device is made of metal, the top of the third type device is spaced from the inner wall surface of the groove, an insulating sheet is arranged between the top of the third type device and the inner wall of the groove, and the height of the third type device on the PCB board and the thickness of the insulating sheet are smaller than the sum of the distance between the first inner wall surface and the first surface and the depth of the inner wall surface of the groove in the direction perpendicular to the PCB.