CN220965253U - Circuit board unit and circuit board assembly - Google Patents

Abstract

The application provides a circuit board unit and a circuit board assembly, wherein the circuit board unit comprises a power device, a metal heat dissipation piece and a circuit board, the circuit board comprises two sub-circuit boards which are stacked, and the board surface of any one of the two sub-circuit boards is provided with a mounting port which penetrates through the two opposite sides of the sub-circuit board. At least part of the metal heat dissipation piece is positioned in the mounting opening, and a gap is formed between the metal heat dissipation piece and the inner wall of the mounting opening. The power device is connected to one side of the circuit board and is arranged opposite to the metal heat dissipation piece. The side of the power device facing the circuit board is provided with a heat dissipation pad, and the metal heat dissipation piece is in heat conduction contact with the heat dissipation pad and is configured to conduct heat of the power device to the side of the circuit board provided with the heat sink. The circuit board unit can meet the heat dissipation requirement of the power device with larger power consumption, has longer service life and lower processing cost.

Description

Circuit board unit and circuit board assembly

Technical Field

The present application relates to the field of circuit board heat dissipation technologies, and in particular, to a circuit board unit and a circuit board assembly.

Background

With the rapid application of the fifth generation mobile communication technology (english: 5th Generation Mobile Communication Technology, abbreviated as 5G), the demands of high-rise buildings, roads, low dense areas, ultra dense areas for wireless access network speeds and the like are becoming higher and higher, which requires a wireless outdoor base station to have a larger transmitting power to meet.

For a base station with a remote radio module or an active antenna processing module, the improvement of the transmitting Power makes the remote radio module or the active antenna processing module need to adopt a Power amplification (abbreviated as PA) chip with larger Power output, so that the Power consumption of the PA chip packaged by adopting a square Flat No-pin (abbreviated as QFN) is larger, and the PA chip packaged by the QFN needs to be timely radiated. At present, when the PA chip packaged by QFN is applied to a radio frequency remote module or an active antenna processing module, generated heat is firstly transferred to a radio frequency board through a heat dissipation pad on the bottom surface, and then transferred to a radiator through a heat dissipation via hole on the radio frequency board and the digital board, so that the PA chip is subjected to heat dissipation through the radiator.

However, the above heat dissipation method cannot meet the heat dissipation requirement of the PA chip with QFN package and larger power consumption.

Disclosure of utility model

The application provides a circuit board unit and a circuit board assembly, which not only can meet the heat dissipation requirement of a power device with larger power consumption, but also can prolong the service life of the circuit board unit and reduce the processing cost of the circuit board unit.

In a first aspect, an embodiment of the present application provides a circuit board unit, where the circuit board unit includes a power device, a metal heat dissipation member, and a circuit board, the circuit board includes two stacked sub-circuit boards, and a board surface of any one of the two sub-circuit boards has a mounting hole penetrating through two opposite sides of the sub-circuit board; at least part of the metal heat dissipation piece is positioned in the mounting opening and a gap is formed between the metal heat dissipation piece and the inner wall of the mounting opening;

The power device is connected to one side of the circuit board and is arranged opposite to the metal heat dissipation piece; the side of the power device facing the circuit board is provided with a heat dissipation pad, and the metal heat dissipation piece is in heat conduction contact with the heat dissipation pad and is configured to conduct heat of the power device to the side of the circuit board provided with the heat sink.

According to the circuit board unit provided by the embodiment of the application, the metal heat dissipation piece and the mounting opening on the board surface of any one of the two sub-circuit boards are arranged, and as at least part of the metal heat dissipation piece is positioned in the mounting opening, the metal heat dissipation piece is in heat conduction contact with the heat dissipation pad of the power device in the circuit board unit and is configured to conduct the heat of the power device to one side of the circuit board provided with the heat sink, so that the heat of the power device can be conducted to the heat sink sequentially through the heat dissipation pad and the metal heat dissipation piece, and finally the purpose of heat dissipation of the power device is achieved through the heat sink. Compared with the traditional heat dissipation mode only by means of the heat dissipation through holes, the heat resistance of the power device on the heat dissipation path can be reduced through the arrangement of the metal heat dissipation piece, so that the heat dissipation requirement of the power device with larger power consumption is met, and meanwhile the service life of the circuit board unit can be prolonged.

In addition, because the clearance is arranged between the metal heat dissipation part and the inner wall of the mounting port, the metal heat dissipation part and the inner wall of the mounting port do not need to be connected, and the mounting port can be formed after the sub-circuit board is manufactured, so that the manufacturing process and the processing difficulty of the sub-circuit board provided with the metal heat dissipation part can be simplified, the processing cost of the circuit board unit can be reduced, and the reliability of the connection of the metal heat dissipation part in the circuit board unit can be increased.

Further, the circuit board has a first side and a second side disposed opposite to each other in a board thickness direction, the power device is located on the first side, and the second side is configured to be in heat conductive contact with the heat sink, such that the power device and the heat sink are distributed on opposite sides of the circuit board, and heat of the power device can be transferred to the heat sink in the board thickness direction of the circuit board through the heat dissipation pads and the metal heat dissipation member.

Further, the metal heat dissipation piece is a metal block matched with the shape of the mounting opening, so that the heat resistance of the power device on a heat dissipation path is reduced, and the open area of the sub-circuit board can be reduced while the characteristic that metal has higher heat conductivity is utilized.

Further, a plurality of heat dissipation through holes are formed in the sub-circuit board without the mounting port, and the plurality of heat dissipation through holes are arranged opposite to the metal heat dissipation part, so that heat of the power device can be transferred to the metal heat dissipation part or the heat radiator through the heat dissipation through holes.

Further, the heat dissipation via hole is a metal via hole, and the axial direction of the metal via hole is parallel to the plate thickness direction of the sub-circuit board, so that the heat conduction function is realized, and meanwhile, the heat dissipation path of the power device can be shortened.

Further, the power device is further provided with a signal pad, and the power device is conducted with the adjacent sub-circuit board through the signal pad so as to conduct the power device with the adjacent sub-circuit board.

Further, the signal pad and the heat dissipation pad are located on the same face of the power device, and the signal pad is located outside the projection range of the mounting port on the power device, so that when the power device is stacked on an adjacent sub-circuit board, the power device can be welded with the adjacent sub-circuit board through the signal pad.

Further, the mounting port is positioned on the upper layer sub-circuit board of the two sub-circuit boards;

The metal heat dissipation piece is in heat conduction connection between the heat dissipation bonding pad and the lower-layer sub-circuit boards of the two sub-circuit boards, so that heat of the power device can be directly transferred onto the metal heat dissipation piece through the heat dissipation bonding pad and then transferred onto the heat radiator through the metal heat dissipation piece, and therefore the heat dissipation requirement of the power device with larger power consumption is met through heat dissipation of the heat radiator. In addition, the mounting port is positioned on the upper-layer sub-circuit board, so that the lower-layer sub-circuit board has higher compatibility, and the platformization of the circuit board unit can be facilitated.

Further, the thickness tolerance of the metal heat dissipation part is smaller than or equal to 0.1mm, so that the metal heat dissipation part has good flatness, and the heat dissipation thermal resistance of the power device on a heat dissipation path is reduced.

Further, the mounting port is positioned on the lower layer sub-circuit board of the two sub-circuit boards;

The metal heat dissipation piece is in heat conduction connection with the heat dissipation pad through the upper sub-circuit board of the two sub-circuit boards, so that heat of the power device can be sequentially transferred to the radiator through the heat dissipation pad, the upper sub-circuit board and the metal heat dissipation piece, and therefore the radiator is used for dissipating heat of the power device, and the heat dissipation requirement of the power device with larger power consumption is met.

Further, the metal heat sink includes a heat sink body and a lap joint portion connected to each other, at least a portion of the heat sink body is located in the mounting opening and is configured to be thermally connected between the upper sub-circuit board and the heat sink, so that the upper sub-circuit board can transfer heat of the power device 810 to the heat sink through the heat sink body;

the lap joint part is positioned on the periphery of the heat dissipation body facing one end of the power device and lap-joints the lower-layer sub-circuit board, so that the heat dissipation body can be pre-fixed in the mounting port through the lap joint part, and the heat dissipation body and the upper-layer sub-circuit board can be welded conveniently.

Further, the upper layer sub-circuit board is provided with an avoidance hole at a position corresponding to the lap joint part;

The overlap joint portion is embedded in the avoidance hole, and a gap is formed between the overlap joint portion and the hole wall of the avoidance hole.

Through the setting of dodging the hole like this for overlap joint portion can be dodged to upper sub-circuit board, so that when overlap joint portion overlap joint was on lower floor's sub-circuit board, can also avoid the setting of overlap joint portion to influence the welding of upper sub-circuit board and lower floor's sub-circuit board.

Further, the number of the lap joint parts is one, and the lap joint parts are of annular structures surrounding the periphery of the heat dissipation body;

Or the number of the lap joint parts is at least two, and the at least two lap joint parts are distributed on the periphery side of the heat dissipation body.

Therefore, the metal heat dissipation piece and the upper layer sub-circuit board can be more diversified in structure while the lap joint part is lapped on the lower layer sub-circuit board.

Further, the height difference of one surface of the lap joint part facing the lower-layer sub-circuit board is smaller than or equal to 0.1mm, so that the surface of the lap joint part facing the lower-layer sub-circuit board is guaranteed to have good flatness, and the situation that the metal heat dissipation piece inclines relative to the circuit board when the lap joint part is lapped on the lower-layer sub-circuit board is avoided.

Further, the thickness of the heat dissipation body is smaller than or equal to the thickness of the lower-layer sub-circuit board, so that the whole heat dissipation body can be located in the mounting opening, and the lower-layer sub-circuit board can be in heat conduction contact with the radiator, so that the radiator can dissipate heat of the power device and simultaneously dissipate heat of the lower-layer sub-circuit board.

Further, the power device comprises a radio frequency chip, the sub-circuit board comprises a radio frequency and/or digital board, so that the power device can be conducted with the radio frequency board, and a radio frequency remote module (called RRU module for short) or an active antenna processing module (called AAU module for short) can be formed together with the radio frequency board and the digital board, and meanwhile the heat dissipation requirement of the radio frequency chip can be met.

In a second aspect, an embodiment of the present application further provides a circuit board assembly, including a heat sink and a circuit board unit according to any one of the above, the circuit board unit including a circuit board and a power device, the heat sink being located on a side of the circuit board remote from the power device.

The circuit board assembly has the beneficial effects of the circuit board unit and is not repeated herein.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings may be obtained according to the drawings without inventive effort to a person skilled in the art.

Fig. 1 is a schematic structural diagram of a circuit board assembly in a base station provided in the related art;

FIG. 2 is a schematic diagram of another circuit board assembly in a base station provided in the related art;

fig. 3 is a schematic structural view of still another circuit board assembly in a base station provided in the related art;

FIG. 4 is a schematic diagram of a manufacturing process of the circuit board assembly of FIG. 3;

fig. 5 is a schematic structural diagram of a circuit board unit according to an embodiment of the present application;

FIG. 6 is a schematic diagram illustrating a manufacturing process of the circuit board unit in FIG. 5;

Fig. 7 is a schematic structural diagram of another circuit board unit according to an embodiment of the present application;

fig. 8 is a schematic diagram of a manufacturing process of the circuit board unit in fig. 7.

Reference numerals:

A 100-PA chip; 110-signal pads; 120-heat dissipation pads; 200-radio frequency board; 300-digital board; 310-core plate; 320-resin member; 330-windowing; 400-heat dissipation via holes; 500-a heat sink; 510-a boss; 600-a heat conducting layer; 700-copper block;

800-circuit board units; 810-power devices; 820-metal heat sink; 821—heat dissipation body; 822—lap;

830-a sub-circuit board; 831-upper sub-circuit board; 8311-dodge hole; 832-lower sub-circuit board; 833—a mounting port; 840-solder; 850—a solder layer;

z-plate thickness direction.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

For ease of understanding, related art terms related to the embodiments of the present application are explained and explained first.

The quad flat no-lead package, QFN package for short, is a surface mount package technology. The semiconductor chip has no epitaxial pins after QFN packaging, but the bottom surface is provided with a heat dissipation pad and a signal pad. For convenience of description, devices formed after the semiconductor chip is subjected to QFN package are collectively referred to as QFN devices.

Junction temperature, which refers to the highest temperature of an actual semiconductor chip (wafer, die) in an electronic device, may be denoted by Tj. It is typically higher than the case temperature and the device surface temperature. Junction temperature can measure the time required for heat dissipation from the semiconductor chip to the package housing of the device, as well as the thermal resistance. The lower the junction temperature of the device, the better.

As described in the background art, with the rapid application of 5G, a wireless outdoor base station is required to have a larger transmission power in order to meet the network speed requirement of wireless access. In order to meet the requirement of the improvement of the transmitting power, a PA chip with high power output is needed. The PA chip is used as a radio frequency chip and is mainly responsible for signal amplification of a transmitting channel in a radio frequency communication system, so that the PA chip becomes an important chip for influencing signal coverage and plays an important role in a base station.

Currently, to meet the increase in transmit power, the power consumption of PA chips has increased to a single channel of 20w, which can lead to a sharp increase in temperature within the module including such PA chips within the base station. When the temperature in the module is too high, internal devices of the module can be damaged, and even the overall function of a cabinet containing the module is affected.

Some existing base stations typically include a remote radio module or an active antenna processing module. The remote radio module may also be called an RRU module, and the RRU module is mainly used for radio frequency processing in a base station of the fourth generation mobile communication technology (english: the4th generation mobile communication technology, abbreviated as 4G). The active antenna processing module can also be called an AAU module, and the AAU module integrates the functions of the RRU module and the passive antenna and is applied to the 5G base station.

Referring to fig. 1, the RRU module and the AAU module each include a PA chip 100, a radio frequency board 200, and a digital board 300, which are sequentially stacked in a board thickness direction. The rf board 200 may also be referred to as a PA board or a power splitter. The digital board 300 may also be referred to as a TRX board, and mainly integrates functions such as a transceiver, a filter, and power management. The RRU module and the PA chip 100 within the AAU module employ QFN packaging, which can be regarded as a QFN device. The PA chip 100 is electrically connected to the rf board 200 through a communication pad on the bottom surface.

After the power consumption of the PA chip 100 is increased, the heat dissipation requirements of the RRU module and the AAU module are more and more intense, especially after the power consumption of the PA chip 100 packaged by QFN is increased to a single channel 20 w.

The heat dissipation of PA chip 100 is further described below using an AAU module as an example.

Referring to fig. 1, PA chip 100 primarily dissipates heat through heat dissipation pads 120 on the bottom surface. Fig. 1 illustrates a first heat dissipation method adopted when the PA chip 100 is applied to an AAU module, where the heat dissipation method is a conventional heat dissipation method. Referring to fig. 1, when the PA chip 100 is applied, the PA chip 100 is conducted with the radio frequency board 200 through the signal pad 110. The heat generated by the PA chip 100 is firstly transferred to the radio frequency board 200 through the heat dissipation pad 120, then transferred to the radiator 500 through the heat dissipation via holes 400 on the radio frequency board 200 and the digital board 300, and finally radiated to the air through the heat dissipation teeth of the radiator 500, thereby realizing heat dissipation and temperature reduction of the PA chip 100.

The thermal simulation result shows that when the PA chip 100 with single-channel power consumption of 20w dissipates heat by adopting the heat dissipation mode, the plate temperature of the AAU module is 145 ℃, the junction temperature is 198 ℃, and the maximum junction temperature can reach 200 ℃, which is seriously higher than the normal use temperature corresponding to the relative thermal Index (r.t. RELATIVE THERMAL Index, abbreviated as RTI) of the AAU module.

Therefore, the heat dissipation requirements of the PA chip 100 and the AAU module cannot be met, and the rf board 200 and the digital board 300 have a risk of burning out after the AAU module is used for a long time, resulting in a shorter service life of the AAU module. The board temperature of the AAU module refers to the temperatures of the radio frequency board 200 and the digital board 300.

In order to facilitate the heat of the PA chip 100 to be quickly conducted to the heat spreader 500 along the heat dissipating via 400, it is necessary to reduce the thermal resistance of the heat dissipating path of the PA chip 100, and the smaller the thermal resistance, the better.

For this reason, fig. 2 illustrates a heat dissipation manner adopted when the second PA chip 100 is applied to the AAU module in the related art.

Referring to fig. 2, the PA chip 100 is soldered on a radio frequency board 200, and the radio frequency board 200 is soldered to a digital board 300. The digital board 300 is perforated at a position corresponding to the PA chip 100. The heat sink 500 is provided with a boss 510 on one surface facing the PA chip 100, and the boss 510 is thermally connected to the bottom surface of the radio frequency board 200 through a thermally conductive layer 600 formed of a thermally conductive material. The heat dissipation pad 120 of the PA chip 100, a solder paste layer (not labeled) between the heat dissipation pad 120 and the radio frequency board 200, the heat dissipation via 400 on the radio frequency board 200, and the heat conductive layer 600 expect that the heat spreader 500 forms the entire heat dissipation path of the PA chip 100.

Compared to the first heat dissipation method, the shape and size of the boss 510, and the tolerance dimension chain between the boss 510 and the rf board 200 determine the heat dissipation thermal resistance of the entire heat dissipation path of the PA chip 100. Compared with the first heat dissipation mode, when the PA chip 100 with single-channel power consumption of 20w adopts the second heat dissipation mode, the board temperature of the AAU module is 140 ℃, the board temperature gain is 5 ℃, and the junction temperature is 195 ℃, so that the second heat dissipation mode still cannot meet the requirements of the PA chip 100 with single-channel power consumption of 20w and the AAU module, but has a certain application value on a part of chips with relatively low power consumption.

Therefore, the two heat dissipation methods cannot meet the heat dissipation requirement of the PA chip 100 with single-channel power consumption of 20w and above in the AAU module.

For this reason, fig. 3 illustrates a third heat dissipation method adopted when the PA chip 100 is applied to the AAU module in the related art.

Referring to fig. 3, unlike the first heat dissipation method described above, the digital board 300 has a copper block 700 embedded in the digital board 300, and the copper block 700 is in heat-conducting contact with the heat dissipation via 400 of the radio frequency board 200 through the heat-conducting layer 600, so that the heat conductivity of the digital board 300 at the corresponding PA chip 100 is improved through the copper block 700, thereby reducing the thermal resistance of the PA chip 100 on the heat dissipation path, and enabling the heat of the PA chip 100 to be quickly conducted.

The shape and size of the copper block 700, and the flatness of the copper block 700 and the digital board 300 determine the thermal resistance of the entire heat dissipation path. Compared with the arrangement of the boss 510 of the heat sink 500, the flatness of the copper block 700 and the digital board 300 is easier to control, and the heat dissipation resistance of the whole heat dissipation path can be reduced. Therefore, the third heat dissipation method has better heat dissipation effect on the PA chip 100 with single-channel power consumption at 20w than the first and second heat dissipation methods.

The thermal simulation result shows that when the third heat dissipation mode is adopted by the PA chip 100 with single-channel power consumption of 20w, the plate temperature of the AAU module is 129 ℃, the junction temperature is 182 ℃, and compared with the first heat dissipation mode, the heat dissipation requirements of the PA chip 100 with single-channel power consumption of 20w and the AAU module can be met.

Referring to fig. 4, since the digital board 300 is embedded with the copper block 700, the digital board 300 is manufactured by milling the windows 330 on the plurality of core plates 310 and the plurality of resin members 320 made of resin material. After wiring is performed on the core board 310, the plurality of core boards 310 and the plurality of resin members 320 are alternately stacked in the board thickness direction (Z direction) of the core board 310. Then, the copper block 700 of the corresponding size after the browning is again placed in the open window 330, and then the copper block 700 and the molten resin component 320 flowed into the open window 330 are bonded together by a high temperature bonding process. Finally, the resin material overflowed to the surface of the outermost core plate 310 is removed after the resin material is cured, so as to obtain the digital board 300 in which the copper block 700 is embedded.

Since the curing process of the resin material is irreversible, the copper block 700 needs to be embedded in advance in the manufacturing process of the digital board 300. Moreover, since the pre-burying process of the copper block 700 is complex, the manufacturing process of the digital board 300 is complex, the manufacturing cost is increased by at least 30%, the processing difficulty of the digital board 300 is high, the delivery period of the digital board 300 is long, few suppliers with mass rapid supply are provided, and the risk of supply shortage of the digital board 300 exists.

In addition, since the difference between the coefficient of thermal expansion (Z-CTE) of the copper block 700 and the resin material in the board thickness direction (Z direction) of the digital board 300 is large, the digital board 300 is easy to have a delamination risk in the reflow soldering process, and the connection between the copper block 700 and the resin member 320 is under the stress, so that the copper block 700 is less reliable in connection in the digital board 300.

In view of this, the embodiment of the present application provides a circuit board unit 800, where the circuit board unit 800 not only can meet the heat dissipation requirement of the power device 810 with larger power consumption, but also has the characteristics of longer service life, lower processing cost and higher reliability of the circuit board unit 800.

The structure of the circuit board unit 800 of the present application is further described with reference to the drawings.

Referring to fig. 5, the circuit board unit 800 includes a power device 810, a metal heat sink 820, and a circuit board (not shown). The circuit board includes two sub-circuit boards 830 arranged in a stack. Referring to fig. 5, two sub-circuit boards 830 may be stacked up and down in the Z direction. For convenience of description, the sub-circuit board 830 adjacent to the power device 810 is defined as an upper sub-circuit board 831, and the sub-circuit board 830 distant from the power device 810 is defined as a lower sub-circuit board 832.

The board surface of either one of the two sub-circuit boards 830 is provided with a mounting opening 833 penetrating through the opposite sides of the sub-circuit board 830. The structure of the mounting hole 833 on the upper sub-circuit board 831 is illustrated in fig. 5, and is not limited to the structure of the circuit board unit 800. In some embodiments, the mounting port 833 may also be located on the underlying sub-circuit board 832. At least a portion of the metal heat sink 820 is positioned within the mounting opening 833 with a gap between the inner wall of the mounting opening 833. That is, the metal heat sink 820 may be located entirely within the mounting opening 833 or may be located partially within the mounting opening 833. In the present application, it is not further limited whether the metal radiator 820 is entirely located in the mounting hole 833.

The power device 810 is connected to one side of the circuit board and disposed opposite to the metal heat sink 820. The power device 810 may be regarded as a QFN device. The side of the power device 810 facing the circuit board has heat dissipation pads 120. The metal heat sink 820 is in thermally conductive contact with the heat sink pad 120 and is configured to conduct heat from the power device 810 to the side of the circuit board on which the heat sink 500 is disposed.

The power device 810 is disposed opposite to the metal heat sink 820, which can be understood that the power device 810 is connected to a position of the circuit board where the metal heat sink 820 is disposed, and is disposed face to face with the metal heat sink 820, and the projection of the two in the Z direction has at least a partial overlapping area, so that the heat generated by the power device 810 can be transferred to the metal heat sink 820 through the heat dissipation pad 120, and meanwhile, the heat dissipation path of the power device 810 can be reduced, so that the rapid heat dissipation of the power device 810 is facilitated.

Referring to fig. 5, the metal heat sink 820 may be located in a projection range of the power device 810 on the sub-circuit board 830, so as to increase a heat dissipation area of the power device 810 by the metal heat sink 820, and to facilitate rapid heat dissipation of the power device 810, and meanwhile, to avoid an influence of the arrangement of the metal heat sink 820 on connection between the power device 810 and the circuit board.

Through the arrangement of the metal heat dissipation element 820 and the mounting hole 833 on the board surface of any one of the two sub-circuit boards 830, as at least part of the metal heat dissipation element 820 is positioned in the mounting hole 833 and is configured to conduct the heat of the power device 810 to the side of the circuit board provided with the heat sink 500, the heat of the power device 810 can be conducted to the heat sink 500 through the heat dissipation pad 120 and the metal heat dissipation element 820 in sequence, so that the heat sink 500 can radiate the heat of the power device 810 into the air, and finally the purpose of dissipating the heat of the power device 810 is achieved through the heat sink 500, so as to reduce the temperature of the power device 810.

Compared with the first heat dissipation mode and the second heat dissipation mode, the circuit board unit 800 of the embodiment of the application uses the higher heat conductivity characteristic of the metal through the arrangement of the metal heat dissipation member 820, so that the heat dissipation resistance of the power device 810 on the heat dissipation path can be reduced, the heat dissipation requirement of the power device 810 with larger power consumption can be met, and meanwhile, the temperature of the circuit board unit 800 in long-term use exceeds the normal use temperature of the circuit board unit 800, so that the risk of burning out the sub-circuit board 830 is avoided, the service life of the circuit board unit 800 is prolonged, and the circuit board unit 800 has the characteristic of longer service life.

The heat dissipation path may be understood as a transfer path of heat of the power device 810 to the heat sink 500.

It should be noted that the power device 810 may include a QFN package chip with high heat dissipation requirements, and the power device 810 may include a radio frequency chip, which may include, but is not limited to, the PA chip 100 described above. Where the power device 810 is a radio frequency chip, the daughter circuit board 830 may include the radio frequency board 200 or the digital board 300. At this time, one of the two sub-circuit boards 830 may be the rf board 200, and the other one may be the digital board 300, and the rf chip is electrically connected to the rf board 200. At this time, the circuit board unit 800 may be the RRU module or the AAU module, and the circuit board unit 800 may meet the heat dissipation requirement of the radio frequency chip such as the PA chip 100.

When the circuit board unit 800 of the present application is applied, the power device 810 at least can achieve a heat dissipation effect substantially equivalent to the third heat dissipation manner, so that the circuit board unit 800 of the present application can meet the heat dissipation requirement of the PA chip 100 with single-channel power consumption of 20w or other QFN package chips with higher heat dissipation requirement. For example, the circuit board unit 800 of the present application can also meet the heat dissipation requirements of power devices or other QFN devices with greater power consumption. When the power device 810 is a power device, one of the two sub-circuit boards 830 may be a power board that is in conduction with the power device, and the other may be the digital board 300.

It should be noted that other structures for the power device 810 and the sub-circuit board 830 are also possible. In the present application, the kinds of the power device 810 and the sub-circuit board 830 are not further limited.

The structure of the circuit board unit 800 of the present application will be further described below by taking the PA chip 100 as an example of the power device 810.

In addition, since the metal heat dissipation element 820 and the inner wall of the mounting opening 833 have a gap, the metal heat dissipation element 820 and the inner wall of the mounting opening 833 do not need to be connected, and the mounting opening 833 can be opened after the sub-circuit board 830 is manufactured, and does not need to be pre-buried in the manufacturing process of the sub-circuit board 830, thus not only simplifying the manufacturing process and the processing difficulty of the sub-circuit board 830 provided with the metal heat dissipation element 820, reducing the processing cost of the circuit board unit 800, shortening the lead time of the sub-circuit board 830, but also avoiding the risk that the sub-circuit board 830 is layered and the metal heat dissipation element 820 falls off, and increasing the reliability of the connection of the metal heat dissipation element 820 in the circuit board unit 800, thereby the circuit board unit 800 has the characteristic of higher reliability.

Referring to fig. 5, the power device 810 further has a signal pad 110, and the power device 810 is conducted with an adjacent sub-circuit board 830 through the signal pad 110 to achieve conduction of the power device 810 with the adjacent sub-circuit board 830. When the power device 810 is the PA chip 100, the adjacent sub-circuit board 830 may be the radio frequency board 200 described above. When the power device 810 is a power device, the adjacent sub-circuit board 830 may be the power board described above.

Specifically, the signal pads 110 may be soldered to pads (not shown) on the adjacent sub-circuit board 830 to enable conduction between the power device 810 and the adjacent sub-circuit board 830 for signal transfer between the power device 810 and the adjacent sub-circuit board 830. The two sub-circuit boards 830 may be connected and conducted by soldering, so as to realize signal transmission between the two sub-circuit boards 830.

Referring to fig. 5, the signal pad 110 and the heat dissipation pad 120 are located on the same side of the power device 810, and the signal pad 110 is located outside the projection range of the mounting opening 833 on the power device 810, so that when the power device 810 is stacked on the adjacent sub-circuit board 830, it can be soldered with the pad on the adjacent sub-circuit board 830 through the signal pad 110.

Referring to fig. 5, a circuit board (not shown) has a first side and a second side disposed opposite to each other in a board thickness direction. Wherein the power device 810 is located at a first side, and the second side is configured to be in heat conductive contact with the heat sink 500, such that the power device 810 and the heat sink 500 are distributed at opposite sides of the circuit board, and heat of the power device 810 can be transferred to the heat sink 500 through the heat dissipation pad 120 and the metal heat sink 820 in a plate thickness direction (Z direction) of the circuit board.

The metal heat sink 820 may be a metal block with a shape matching (same or similar) to that of the mounting hole 833, so that the heat dissipation resistance of the power device 810 on the heat dissipation path is reduced and the open area of the sub-circuit board 830 can be reduced by using the characteristic of high heat conductivity of metal.

The mounting port 833 may include, but is not limited to, a circular hole, a square hole, etc. In the present application, the shape of the mounting port 833 is not further limited.

The metal block may be made of a heat conductive material having a heat conductivity of 100W/(mK) or more. For example, the metal block may be made of copper, aluminum or an alloy material containing the metal, so that the metal block has high thermal conductivity, and the heat dissipation effect of the metal heat dissipation element 820 on the power device 810 is enhanced.

The total thickness of the metal heat sink 820 may be less than or equal to the length of the mounting opening 833 so that the metal heat sink 820 can be positioned entirely within the mounting opening 833. The total thickness of the metal radiator 820 and the length direction of the mounting opening 833 are parallel to each other, and can be referred to as the Z direction.

Referring to fig. 5, a plurality of heat dissipation vias 400 are disposed on a sub-circuit board 830 without a mounting hole 833, and the plurality of heat dissipation vias 400 are disposed opposite to the metal heat sink 820. That is, in the Z direction, the plurality of heat dissipating vias 400 and the metal heat sink 820 have an overlapping region therebetween. In this way, the heat of the power device 810 can be transferred to the metal heat sink 820 through the heat dissipation pad 120 and the heat dissipation via 400 in sequence, or the metal heat sink 820 can transfer the heat of the power device 810 to the heat sink 500 through the heat dissipation via 400, so as to dissipate the heat of the power device 810.

The metal heat sink 820 has a projection area on the sub-circuit board 830 where the mounting opening 833 is not provided in the Z direction. The plurality of heat dissipation vias 400 may be uniformly distributed in the projection area, so that each heat dissipation via 400 may be located in the projection range of the metal heat dissipation element 820 and disposed opposite to the metal heat dissipation element 820.

The heat dissipation via 400 is a metal via, and the axial direction of the metal via is parallel to the board thickness direction of the sub-circuit board 830, i.e., the axial direction of the metal via is parallel to the Z direction, so that the heat dissipation path of the power device 810 can be shortened while the heat conduction function is achieved. By way of example, the metal vias may include, but are not limited to, vias that are copper holes or are made of other thermally conductive metals.

The heat dissipation via 400 is further filled with a resin (not shown), so that the heat dissipation of the power device 810 is not affected, and the two sub-circuit boards 830 and the welding of the power device 810 and the sub-circuit boards 830 can be prevented from being affected by the solder 840 for welding entering the heat dissipation via 400 when the power device 810 and the sub-circuit boards 830 are welded.

Possible configurations of the circuit board unit 800 of the present application are further described in connection with various embodiments.

Example 1

Referring to fig. 5, the mounting port 833 may be located on the upper sub-circuit board 831. The metal heat sink 820 is thermally connected between the heat sink pad 120 and the lower sub-circuit board 832, so that the metal heat sink 820 is disposed on the bottom surface of the power device 810, so that the heat of the power device 810 can be directly transferred to the metal heat sink 820 through the heat sink pad 120, then transferred to the heat sink 500 through the metal heat sink 820, and finally the heat of the power device 810 is dissipated through the heat sink 500, thereby meeting the heat dissipation requirement of the power device 810 with larger power consumption.

In addition, compared with the third heat dissipation scheme, the circuit board unit 800 of the present embodiment not only has lower processing cost and shorter lead time, but also has higher reliability. In addition, since the mounting opening 833 is located on the upper sub-circuit board 831, the lower sub-circuit board 832 (such as a TRX board) can be shared among different circuit board units 800, so that the compatibility is high, and the platformization of the circuit board units 800 can be facilitated.

The metal heat sink 820 may be soldered to the heat sink pad 120, and a solder layer 850 is formed between the metal heat sink 820 and the heat sink pad 120. In the case of soldering, the solder layer 850 may be referred to as a solder layer. The tin solder layer may be formed of a paste or sheet solder material such as tin bismuth (SnBi) alloy, tin silver copper (SnAgCu) alloy, tin (Sn), silver (Ag), or the like.

The lower sub-circuit board 832 is provided with a fixing portion (not shown) at a position where the heat dissipation via 400 is provided, and the fixing portion may be a pad. The metal heat sink 820 may also be soldered to the anchor of the underlying sub-circuit board 832, and a solder layer 850 is also formed between the metal heat sink 820 and the anchor. The heat sink 500 is disposed on a side of the lower sub-circuit board 832 away from the upper sub-circuit board 831, and may be in heat conductive contact with the heat sink 500 through a heat conductive medium or other structure. The heat transferred from the power device 810 to the metal heat sink 820 can thus be transferred to the heat spreader 500 through the heat dissipating vias 400.

Referring to fig. 5, the metal heat sink 820 may have a block structure. The thickness of the metal heat sink 820 may be less than or equal to the thickness of the upper sub-circuit board 831, so that the metal heat sink 820 can be completely located in the mounting opening 833, and meanwhile, the connection between the components in the circuit board unit 800 can be realized by means of the fixture printing solder 840. Taking PA chip 100 as an example, when the thickness of upper sub-circuit board 831 is 1mm, the thickness of metal heat sink 820 may be less than or equal to 1mm. For example, the thickness of the metal heatsink 820 may be 0.6mm, 0.75mm, etc.

The thickness tolerance of the metal heat sink 820 may be less than or equal to 0.1mm. The 0.1mm is a positive and negative tolerance of the metal heat sink 820 in the thickness direction, that is, the thickness tolerance of the metal heat sink 820 is +/-0.1mm, so that the metal heat sink 820 has better flatness on the plane in the Z direction, which is beneficial to reducing the heat dissipation thermal resistance of the power device 810 on the heat dissipation path.

Referring to fig. 5, the heat dissipation path of the power device 810 may include a heat dissipation pad 120, a soldering layer 850 between the heat dissipation pad 120 and the metal heat sink 820, the soldering layer 850 between the metal heat sink 820 and the fixing portion, a fixing portion (not shown), a heat dissipation via 400 of the lower sub-circuit board 832, and a heat sink 500. At the same time, these structures in the heat dissipation path also form the heat dissipation structure of the power device 810.

Taking the power device 810 as an example of the PA chip 100 with single-channel power consumption of 20w, thermal simulation is performed on the heat dissipation effect of the power device 810 in this embodiment.

The thermal simulation result shows that when the circuit board unit 800 of the present embodiment is used, the board temperature is 130 ℃, and compared with the board temperature gain of 15 ℃ in the first heat dissipation mode, the junction temperature is 184 ℃, which can meet the heat dissipation requirement of the PA chip 100 with single-channel power consumption of 20w or the power device 810 with larger heat dissipation requirement, and the effect is equivalent to that of the third heat dissipation scheme.

In the manufacturing process of the circuit board unit 800 of the present embodiment, the metal heat sink 820 and the power device 810 may be assembled together, and then assembled with the upper sub-circuit board 831 and the lower sub-circuit board 832 at the same time, so as to obtain the circuit board unit 800.

The manufacturing process of the circuit board unit 800 of the present embodiment is further described below with reference to the accompanying drawings.

Referring to fig. 6, the manufacturing process of the circuit board unit 800 includes the following steps:

s1: a mounting port 833 is formed in advance on the upper layer sub-circuit board 831;

S2: a fixture or other mode is adopted to print solder 840 on the heat dissipation pad 120 of the power device 810, and the power device 810 and the metal heat dissipation element 820 are welded, so that the metal heat dissipation element 820 is back-stuck and sintered on the power device 810 and assembled with the power device 810;

S3: solder 840 is printed on the bonding pads of the upper sub-circuit board 831 and the fixing portions of the lower sub-circuit board 832, respectively, and the upper sub-circuit board 831 and the lower sub-circuit board 832 are stacked together to form a circuit board;

S4: stacking the power device 810 with the sintered metal heat sink 820 on the upper layer sub-circuit board 831, bonding the signal pad 110 of the power device 810 to the pad of the upper layer sub-circuit board 831, and bonding the metal heat sink 820 to the fixing portion and corresponding to the heat dissipation via 400; the soldering between the upper and lower sub-circuit boards 831 and 832 and the metal heat sink 820 and the upper and lower sub-circuit boards 831 and 832, respectively, is achieved by a surface mount technology (Surface Mounted Technology, SMT) to obtain the circuit board unit 800, and at the same time, the solder 840 forms a soldering layer 850 of the circuit board unit 800.

The heat of the power device 810 is ultimately conducted out of the circuit board unit 800 through the heat dissipating vias 400 on the underlying sub-circuit board 832.

Thus, when the heat spreader 500 is mounted on the side of the lower sub-circuit board 832 away from the upper sub-circuit board 831 where the heat dissipating via 400 is disposed, the heat of the power device 810 can be finally conducted to the heat spreader 500 through the heat dissipating via 400 on the lower sub-circuit board 832, so as to dissipate the heat of the power device 810 through the heat spreader 500.

Example 2

Referring to fig. 7, the mounting port 833 may be located at the lower sub-circuit board 832. The metal heat sink 820 is thermally coupled to the heat sink pad 120 through the upper sub-circuit board 831. At this time, the upper sub-circuit board 831 is provided with heat dissipation vias 400 at positions corresponding to the heat dissipation pads 120 and the metal heat sink 820. Thus, the heat of the power device 810 can be sequentially transferred to the heat sink 500 through the heat dissipation pad 120, the heat dissipation via hole 400 on the upper sub-circuit board 831 and the metal heat dissipation member 820, so as to dissipate the heat of the power device 810 through the heat sink 500, thereby meeting the heat dissipation requirement of the power device 810 with larger power consumption.

The metal heat sink 820 may include a heat sink body 821 and a lap joint 822 connected to each other. At least a portion of the heat dissipation body 821 is located in the mounting hole 833 and is configured to be thermally connected between the upper sub-circuit board 831 and the heat sink 500, so that the heat dissipation via 400 of the upper sub-circuit board 831 can transfer heat of the power device 810 to the heat sink 500 through the heat dissipation body 821. The heat sink body 821 may have a block structure.

It should be noted that, the heat dissipation body 821 may be soldered with the upper sub-circuit board 831, and a soldering layer 850 is formed between the heat dissipation body 821 and the upper sub-circuit board 831, and the heat dissipation body 821 may be in contact with the heat sink 500 through the heat conduction layer 600, so as to realize a heat conduction connection between the upper sub-circuit board 831 and the heat sink 500. The thermally conductive layer 600 may be formed using a thermally conductive interface material (THERMAL INTERFACE MATERIAL, TIM). TIMs may include, but are not limited to, silicone grease, thermally conductive gels, and the like. The kind of TIM is not further limited in the present application.

Referring to fig. 7, the heat sink body 821 has a thickness less than or equal to a thickness of the lower sub-circuit board 832. At this time, the whole heat dissipation body 821 may be located in the mounting opening 833, and the lower sub-circuit board 832 may be in heat conduction contact with the heat sink 500, so that the heat sink 500 dissipates heat to the power device 810 and also dissipates heat to the lower sub-circuit board 832. In the present application, the thickness of the heat dissipation body 821 is not further limited.

Or the thickness of the heat dissipation body 821 may be larger than the thickness of the lower sub-circuit board 832, at this time, a portion of the heat dissipation body 821 is located in the mounting hole 833 and a portion thereof protrudes from the lower sub-circuit board 832. The surface of the radiator 500 facing the lower sub-circuit board 832 may be provided with a groove, so that a portion of the radiating body 821 protruding the lower sub-circuit board 832 may be accommodated in the groove, so as to ensure that the radiator 500 has a better fit with the lower sub-circuit board 832 when mounted on the lower sub-circuit board 832, so that the radiator 500 radiates heat to the power device 810 and radiates heat to the lower sub-circuit board 832.

Referring to fig. 7, the lap joint part 822 is located at a peripheral side of the heat dissipation body 821 facing one end of the power device 810 and lap-joints to the lower sub-circuit board 832, so that the heat dissipation body 821 can be pre-fixed in the mounting hole 833 through the lap joint part 822, so as to realize welding of the heat dissipation body 821 and the upper sub-circuit board 831.

The overlap 822 and the heat sink body 821 may be integrally formed, and form the metal heat sink 820.

The upper sub-circuit board 831 has a relief hole 8311 at a position corresponding to the overlap portion 822. The overlap portion 822 is embedded in the avoidance hole 8311, and a gap is formed between the overlap portion and the wall of the avoidance hole 8311. Through the setting of dodging hole 8311 like this for overlap joint portion 822 can be dodged to upper sub-circuit board 831 to overlap joint portion 822 overlap joint in lower floor's sub-circuit board 832, can also avoid overlap joint portion 822's setting to cause the influence to the welding of upper sub-circuit board 831 and lower floor's sub-circuit board 832.

In addition, the installation of the heat dissipation metal piece in the circuit board can be facilitated by the arrangement of the gap between the lap joint part 822 and the hole wall of the avoidance hole 8311.

The relief holes 8311 may be through holes or blind holes on the sub-circuit board 830. The relief holes 8311 are shaped to match (be the same or similar to) the shape of the overlap 822. The avoidance holes 8311 may be round holes, square holes, etc. The structure and shape of the escape holes 8311 are not further limited in the present application.

The number of the overlap portions 822 may be one, and the overlap portions 822 are ring-shaped structures around the circumferential side of the heat dissipation body 821. Or the number of the overlapping portions 822 may be at least two. For example, the number of tabs 822 may be two, three, four, etc. At least two overlapping portions 822 are distributed on the peripheral side of the heat dissipation body 821. This allows the metal heat sink 820 and the upper sub-circuit board 831 to be more diversified in structure while achieving the overlap of the overlap portion 822 on the lower sub-circuit board 832.

The height difference of the surface of the lapping portion 822 facing the lower sub-circuit board 832 is less than or equal to 0.1mm, so as to ensure that the surface of the lapping portion 822 facing the lower sub-circuit board 832 has better flatness, thereby avoiding the situation that the metal heat sink 820 is inclined relative to the circuit board when the lapping portion 822 is lapped on the lower sub-circuit board 832.

Referring to fig. 7, the heat dissipation path of the power device 810 may include the heat dissipation pad 120, the soldering layer 850 between the heat dissipation pad 120 and the upper sub-circuit board 831, the heat dissipation via 400 on the upper sub-circuit board 831, the soldering layer 850 between the upper sub-circuit board 831 and the metal heat sink 820, the heat conduction layer 600 between the metal heat sink 820 and the heat sink 500, and the heat sink 500. At the same time, these structures in the heat dissipation path also form the heat dissipation structure of the power device 810.

Taking the power device 810 as an example of the PA chip 100 with single-channel power consumption of 20w, thermal simulation is performed on the heat dissipation effect of the power device 810 in this embodiment.

The thermal simulation result shows that the circuit board unit 800 of the present embodiment can meet the heat dissipation requirement of the PA chip 100 with single-channel power consumption of 20w and the circuit board unit 800, and the effect is equivalent to that of the third heat dissipation scheme.

In the manufacturing process of the circuit board unit 800 of the present embodiment, the metal heat sink 820 and the lower sub-circuit may be assembled together, and then assembled with the upper sub-circuit 831 and the power device 810 at the same time, so as to obtain the circuit board unit 800.

The manufacturing process of the circuit board unit 800 of the present embodiment is further described below with reference to the accompanying drawings.

Referring to fig. 8, the manufacturing process of the circuit board unit 800 includes the following steps:

s1: the upper layer sub-circuit board 831 is provided with an avoidance hole 8311 in advance, and the lower layer sub-circuit board 832 is provided with a mounting hole 833 in advance;

s2: solder 840 is printed on pads (not shown) of the upper sub-circuit board 831 and the lower sub-circuit board 832, respectively;

S3: firstly, placing the metal heat dissipation member 820 into the mounting hole 833, overlapping the overlapping part 822 on the lower layer sub-circuit board 832, then placing a soldering lug or other solder 840 on one surface of the heat dissipation body 821 adjacent to the overlapping part 822, and then stacking the upper layer sub-circuit board 831 on the lower layer sub-circuit board 832 to enable the overlapping part 822 to be positioned in the avoidance hole 8311;

S4: the power device 810 is stacked on the upper sub-circuit board 831 such that the heat dissipation pad 120 is attached to the heat dissipation via 400 of the upper sub-circuit board 831, the signal pad 110 is attached to the pad of the upper sub-circuit board 831, and soldering between the power device 810 and the upper sub-circuit board 831, and between the upper sub-circuit board 831 and the lower sub-circuit board 832 and the metal heat sink 820, respectively, is achieved through an SMT process, so that the solder 840 forms a soldering layer 850 of the circuit board unit 800 while the circuit board unit 800 is obtained.

Thus, when the heat sink 500 is mounted on the side of the lower sub-circuit board 832 away from the upper sub-circuit board 831, where the mounting opening 833 is provided, the heat of the power device 810 can be finally transferred to the heat sink 500 through the metal heat sink 820, so as to dissipate the heat of the power device 810 through the heat sink 500.

On the basis of the above, the embodiment of the application also provides a circuit board assembly, which comprises the heat sink 500 and the circuit board unit 800. The circuit board unit 800 includes a circuit board and a power device 810, and the heat sink 500 is located at a side of the circuit board away from the power device 810 so that heat of the power device 810 is diffused into air through the heat sink 500 to dissipate heat of the power device 810.

The connection between the heat sink 500 and the circuit board unit 800 may be referred to as the above description, and will not be repeated here.

It should be noted that, since the circuit board unit 800 is a part of the circuit board assembly, the circuit board assembly has the beneficial effects of the circuit board unit 800, which is not described herein.

In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on the drawings are merely for convenience in describing the present application and simplifying the description, and do not indicate or imply that the device or element in question must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application.

In the description of the present application, it should be understood that the terms "comprises" and "comprising," and any variations thereof, as used herein, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements that are expressly listed or inherent to such process, method, article, or apparatus.

Unless specifically stated or limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally formed; can be directly connected or indirectly connected through an intermediate medium, and can lead the interior of two elements to be communicated or lead the two elements to be in interaction relationship. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application.

Claims (17)

1. The circuit board unit is characterized by comprising a power device, a metal heat dissipation piece and a circuit board, wherein the circuit board comprises two sub-circuit boards which are stacked, and the board surface of any one of the two sub-circuit boards is provided with a mounting port which penetrates through two opposite sides of the sub-circuit board; at least part of the metal heat dissipation piece is positioned in the mounting opening, and a gap is formed between the metal heat dissipation piece and the inner wall of the mounting opening;

The power device is connected to one side of the circuit board and is arranged opposite to the metal heat dissipation piece; the side of the power device facing the circuit board is provided with a heat dissipation bonding pad, and the metal heat dissipation piece is in heat conduction contact with the heat dissipation bonding pad and is configured to conduct heat of the power device to one side of the circuit board provided with a heat radiator.

2. The circuit board unit according to claim 1, wherein the circuit board has a first side and a second side disposed opposite in a board thickness direction, the power device being located on the first side, the second side being configured to be in heat conductive contact with the heat sink.

3. The circuit board unit according to claim 1, wherein the metal heat sink is a metal block adapted to the shape of the mounting opening.

4. The circuit board unit according to claim 1, wherein a plurality of heat dissipation vias are provided on the sub-circuit board not provided with the mounting port, the plurality of heat dissipation vias being disposed opposite to the metal heat dissipation member.

5. The circuit board unit according to claim 4, wherein the heat dissipation via is a metal via, and an axial direction of the metal via is parallel to a board thickness direction of the sub-circuit board.

6. The circuit board unit of claim 1, wherein the power device further has a signal pad through which the power device is in conductive communication with the adjacent sub-circuit board.

7. The circuit board unit of claim 6, wherein the signal pad and the heat sink pad are located on a same side of the power device, and the signal pad is located outside a projection range of the mounting opening on the power device.

8. The circuit board unit according to any one of claims 1 to 7, wherein the mounting openings are located on upper sub-circuit boards of two of the sub-circuit boards;

The metal heat dissipation piece is connected between the heat dissipation pad and the lower-layer sub-circuit boards of the two sub-circuit boards in a heat conduction mode.

9. The circuit board unit of claim 8, wherein the metal heat sink has a thickness tolerance of less than or equal to 0.1mm.

10. The circuit board unit according to any one of claims 1 to 7, wherein the mounting openings are located on lower sub-circuit boards of two of the sub-circuit boards;

the metal heat dissipation piece is in heat conduction connection with the heat dissipation bonding pads through the upper layer sub-circuit boards of the two sub-circuit boards.

11. The circuit board unit of claim 10, wherein the metal heat sink comprises a heat sink body and a landing portion connected to each other, at least a portion of the heat sink body being located within the mounting opening and configured to be thermally conductively connected between the upper sub-circuit board and the heat sink;

The lap joint part is positioned on the periphery side of the heat dissipation body facing one end of the power device and is lapped on the lower layer sub-circuit board.

12. The circuit board unit according to claim 11, wherein the upper sub-circuit board has a relief hole at a position corresponding to the lap joint portion;

The overlap joint portion is embedded in the avoidance hole, and a gap is formed between the overlap joint portion and the wall of the avoidance hole.

13. The circuit board unit according to claim 11, wherein the number of the lap joint portions is one, and the lap joint portions are ring-shaped structures around the peripheral side of the heat dissipation body;

Or the number of the lap joint parts is at least two, and at least two lap joint parts are distributed on the periphery side of the heat dissipation body.

14. The circuit board unit according to claim 11, wherein a height difference of a face of the lap joint portion facing the lower sub-circuit board is less than or equal to 0.1mm.

15. The circuit board unit according to claim 11, wherein the heat dissipation body has a thickness less than or equal to a board thickness of the lower sub-circuit board.

16. The circuit board unit according to any of claims 1-7, wherein the power device comprises a radio frequency chip and the sub-circuit board comprises a radio frequency board and/or a digital board.

17. A circuit board assembly comprising a heat sink and a circuit board unit according to any one of claims 1-16, the circuit board unit comprising a circuit board and a power device, the heat sink being located on a side of the circuit board remote from the power device.