Circuit board and circuit board manufacturing method

Abstract

The invention belongs to the technical field of circuit board manufacturing, and discloses a circuit board and a circuit board manufacturing method. The circuit board comprises a first board layer, a heat absorption piece and a second board layer, the first board layer is provided with a containing groove, a communication cavity, a first liquid inlet hole and a first liquid outlet hole, the communication cavity is communicated with the containing groove, and the first liquid inlet hole and the first liquid outlet hole are both communicated with the communication cavity; the heat absorbing piece is clamped in the accommodating groove; the heat absorption piece is provided with a flow channel, and an inlet and an outlet of the flow channel communicate with the communicating cavity. The second plate layer is fixed to the first plate layer and covers the containing groove, the end, away from the first plate layer, of the second plate layer is used for fixing the heating element, and the heating element directly faces the heat absorption part. According to the circuit board, effective heat dissipation of the heating element can be achieved, the heat dissipation effect is good, in addition, user experience cannot be affected, space is saved, and the circuit board is reliable.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit board manufacturing, and in particular to a circuit board and a circuit board manufacturing method. Background Art

[0002] With the rapid development of integrated circuit technology, chip technology continues to break through, and electronic equipment is moving towards miniaturization and integration. The reliability of current electronic equipment is facing severe tests, namely, reliability problems caused by chip power consumption and heat generation. Therefore, it is necessary to design a heat dissipation device to solve the problem of overheating of heating components such as chips on circuit boards during operation.

[0003] The prior art generally uses air cooling to dissipate heat from the circuit board, thereby reducing the heat of the heating components on the circuit board. In the fields of high-performance computing, servers, gaming hardware, etc., the power density of heating components such as CPUs and GPUs is very high, and the heat generated is also very large. However, air cooling relies on air flow to carry away the heat, and the thermal conductivity of air is low, so air cooling may not be able to achieve effective heat dissipation. Secondly, the heat dissipation effect of the air cooling system is greatly affected by the ambient temperature and airflow, which may cause the operating temperature of the electronic components to fluctuate. In addition, the air cooling system usually requires a fan to drive the air flow, especially under high load conditions, the fan noise may increase significantly, affecting the user experience. In addition, efficient air-cooled radiators are usually large in size, which increases the complexity and weight of the overall design and may not be suitable for applications with limited space. Finally, the air cooling system easily inhales dust and other contaminants, which may cause the radiator to be blocked, reduce heat dissipation efficiency, and increase maintenance costs.

[0004] Therefore, there is an urgent need for a circuit board and a circuit board manufacturing method to solve the above technical problems. Summary of the invention

[0005] The purpose of the present invention is to provide a circuit board and a method for manufacturing the circuit board, which can achieve effective heat dissipation of heating elements and have a good heat dissipation effect. In addition, it will not affect the user experience, save space, and is relatively reliable.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In one aspect, a circuit board is provided, comprising:

[0008] The first plate layer is provided with a receiving groove, a connecting cavity, a first liquid inlet hole and a first liquid outlet hole, wherein the connecting cavity is connected with the receiving groove, and the first liquid inlet hole and the first liquid outlet hole are both connected with the connecting cavity;

[0009] A heat absorbing member is clamped in the containing groove; the heat absorbing member is provided with a flow channel, and the inlet and the outlet of the flow channel are both connected with the connecting cavity;

[0010] The second plate layer is fixed to the first plate layer and covers the accommodation groove. One end of the second plate layer away from the first plate layer is used to fix the heating element, and the heating element is disposed opposite to the heat absorption member.

[0011] In some possible implementation manners, there are two communication cavities. The two communication cavities are spaced around the accommodation groove. The inlet of the flow channel and the first liquid inlet hole are both communicated with one of the communication cavities, and the outlet of the flow channel and the first liquid outlet hole are both communicated with the other communication cavity.

[0012] In some possible implementation manners, the communication cavity penetrates through the end face of the first plate layer close to the second plate layer, and the communication cavity and part of the accommodation groove form a stepped groove in combination.

[0013] In some possible implementation manners, the cavity wall of the communication cavity, the hole wall of the first liquid inlet hole, and the hole wall of the first liquid outlet hole are all covered with a metal layer; and / or,

[0014] A polyimide film layer is provided on one side of the second plate layer close to the accommodation groove, and the polyimide film layer covers the accommodation groove.

[0015] In some possible implementation manners, the circuit board further includes a liquid cooling assembly. The liquid cooling assembly includes a liquid tank, an inlet pipe, an outlet pipe, a pump, and a cooling member. Two ends of the inlet pipe are respectively communicated with the liquid tank and the first liquid inlet hole. Two ends of the outlet pipe are respectively communicated with the first liquid outlet hole and the liquid tank. The pump is fixed to the liquid tank and is used for conveying the coolant; the cooling member is used for cooling the coolant flowing out of the first liquid outlet hole.

[0016] In some possible implementation manners, threaded holes are provided at the openings of the first liquid inlet hole and the first liquid outlet hole, and the inlet pipe and the outlet pipe are respectively threadedly connected to the corresponding threaded holes; or, clamping holes are provided at the openings of the first liquid inlet hole and the first liquid outlet hole, and the inlet pipe and the outlet pipe are respectively clamped and sealed with the corresponding clamping holes.

[0017] In some possible implementation manners, the heat absorption member is attached to and abutted against the second plate layer; and / or,

[0018] The material of the heat absorption member is copper.

[0019] In some possible implementation manners, the flow channel is horizontally arranged and has a "ji" - shaped cross - sectional shape.

[0020] On the other hand, a method for manufacturing a circuit board is provided, which is applied to the circuit board in any of the above - mentioned solutions, and includes:

[0021] Manufacturing a first plate layer, and processing a receiving groove, a connecting cavity, a first liquid inlet hole, and a first liquid outlet hole;

[0022] Making a heat absorbing member, processing a flow channel on the heat absorbing member, and inserting the heat absorbing member into the receiving groove;

[0023] A second board layer is manufactured, and the second board layer is fixed on the first board layer and covers the receiving groove.

[0024] In some possible embodiments, processing the receiving groove, the connecting cavity, the first liquid inlet hole and the first liquid outlet hole includes: milling the receiving groove on the first plate layer; milling two connecting cavities at intervals on the outer periphery of the receiving groove, so that the connecting cavity passes through the end surface of the first plate layer and is combined with part of the receiving groove to form a stepped groove; drilling the first liquid inlet hole and the first liquid outlet hole on the first plate layer, and making the first liquid inlet hole and the first liquid outlet hole connected to the two connecting cavities respectively.

[0025] Beneficial effects of the present invention:

[0026] The circuit board provided by the present invention comprises a first plate layer, a heat absorbing member and a second plate layer. The present invention clamps the heat absorbing member in the receiving groove, and the heating element and the heat absorbing member are arranged opposite to each other. The heat absorbing member absorbs the heat of the heating element, and the heat of the heat absorbing member is absorbed by the heat absorbing member through heat exchange of the cooling liquid, so as to realize cooling of the heat absorbing member. The present invention absorbs the heat of the heating element through the heat absorbing member. On the basis of the heat absorbing member absorbing the heat of the heating element, when the heat absorbing member absorbs the heat and the temperature rises to a temperature close to that of the heating element, the heat absorption capacity will be significantly reduced. The present invention further absorbs the heat of the heat absorbing member through the flow of the cooling liquid. Such a setting can realize effective heat dissipation of the heating element, and the heat dissipation effect is good. In addition, by combining the heat absorbing member with liquid cooling, the heat conduction efficiency is much higher than that of air, and the noise is small, which will not affect the user experience. In addition, the heat absorbing member and the flow channel are both arranged in the circuit board, which saves space, does not inhale dust and other pollutants, and makes the operation more reliable. In addition, the flow of the cooling liquid can also dissipate heat for the first plate layer and the second plate layer.

[0027] The present invention also provides a method for manufacturing a circuit board. The circuit board manufactured by the method can achieve effective heat dissipation of heating elements, and the heat dissipation effect is good. In addition, it will not affect the user experience, save space, and is relatively reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a cross-sectional view of a circuit board provided by the present invention;

[0029] Figure 2 is a cross-sectional view of a first plate layer involved in the present invention;

[0030] Figure 3 It is a schematic structural diagram of the heat absorbing element involved in the present invention;

[0031] Figure 4 It is a schematic diagram of the structure after processing the accommodating groove on the first plate layer involved in the present invention.

[0032] In the figure:

[0033] 1. first plate layer; 11. containing groove; 12. connecting cavity; 13. first liquid inlet hole; 14. first liquid outlet hole;

[0034] 2. Heat absorbing part; 21. Flow channel;

[0035] 3. The second board layer;

[0036] 100. Heating element. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0038] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0040] In the description of this embodiment, the terms "upper", "lower", "right", etc., directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0041] like Figures 1 to 4 As shown, the present invention provides a circuit board, including a first board layer 1, a heat absorbing member 2 and a second board layer 3. The first board layer 1 is provided with a receiving groove 11, a connecting cavity 12, a first liquid inlet hole 13 and a first liquid outlet hole 14. The connecting cavity 12 is connected with the receiving groove 11, and the first liquid inlet hole 13 and the first liquid outlet hole 14 are both connected with the connecting cavity 12. One or more of the first liquid inlet hole 13 and the first liquid outlet hole 14 can be provided according to product requirements. The heat absorbing member 2 is clamped in the receiving groove 11; the heat absorbing member 2 is provided with a flow channel 21, and the inlet and outlet of the flow channel 21 are both connected with the connecting cavity 12; the second board layer 3 is fixed to the first board layer 1 and covers the receiving groove 11. The end of the second board layer 3 away from the first board layer 1 is used to fix the heating element 100, and the heating element 100 is arranged opposite to the heat absorbing member 2.

[0042] The present invention clamps the heat absorbing member 2 in the receiving groove 11, and the heating element 100 is arranged opposite to the heat absorbing member 2, and the heat of the heating element 100 is absorbed by the heat absorbing member 2. In addition, the first liquid inlet hole 13 can be injected with cooling liquid, and the cooling liquid sequentially passes through the first liquid inlet hole 13, the connecting cavity 12, the flow channel 21 of the heat absorbing member 2, the connecting cavity 12 and the first liquid outlet hole 14 and then flows out. The heat of the heat absorbing member 2 is absorbed by the cooling liquid heat exchange, and the cooling of the heat absorbing member 2 can be achieved. The present invention absorbs the heat of the heating element 100 through the heat absorbing member 2. On the basis of the heat absorbing member 2 absorbing the heat of the heating element 100, when the heat absorbing member 2 absorbs the heat and the temperature rises to a temperature close to that of the heating element 100, the heat absorption capacity will be significantly reduced. The present invention further absorbs the heat of the heat absorbing member 2 through the flow of cooling liquid. Such a setting can achieve effective heat dissipation of the heating element 100, and the heat dissipation effect is good.

[0043] In addition, by combining the heat absorbing element 2 with liquid cooling, the heat conduction efficiency is much higher than that of air, and the noise is small, which will not affect the user experience. In addition, the heat absorbing element 2 and the flow channel 21 are both arranged inside the circuit board, which saves space and does not inhale dust and other pollutants, making the operation more reliable and extending the service life. In addition, the flow of the coolant can also dissipate heat from the first board layer 1 and the second board layer 3, thereby reducing the overall heat of the finished circuit board, which refers to the structure after the heating element 100 is fixed to the circuit board.

[0044] Optionally, in this embodiment, two connecting cavities 12 are provided, and the two connecting cavities 12 are arranged around the receiving tank 11 at intervals, and the inlet of the flow channel 21 and the first liquid inlet hole 13 are both connected to one of the connecting cavities 12, and the outlet of the flow channel 21 and the first liquid outlet hole 14 are both connected to the other connecting cavity 12. In this way, the flow channel 21 is connected to the first liquid inlet hole 13 and the first liquid outlet hole 14 through the two connecting cavities 12, so that the connection of the coolant flow path can be achieved, and the structure is simple. In other embodiments, there is one connecting cavity 12, and the connecting cavity 12 is arranged around the receiving tank 11, and the inlet and outlet of the flow channel 21 are both connected to the connecting cavity 12, and the first liquid inlet hole 13 and the first liquid outlet hole 14 are both connected to the connecting cavity 12.

[0045] Furthermore, in this embodiment, on the basis of not affecting the clamping and fixing of the heat absorbing member 2, in order to facilitate the processing of the connecting cavity 12 and enable the coolant to absorb the heat of the outer wall of the heat absorbing member 2 and improve the heat dissipation efficiency, the connecting cavity 12 passes through the end surface of the first plate layer 1 close to one end of the second plate layer 3, and the connecting cavity 12 is combined with part of the accommodating groove 11 to form a stepped groove. On this basis, in order to improve the heat dissipation effect, multiple connecting cavities 12 can be provided to form multiple stepped grooves. In other embodiments, there are two connecting cavities 12, and the connecting cavities 12 are holes. The two openings of one hole are respectively connected to the inlet of the flow channel 21 and the first liquid inlet hole 13, and the two openings of the other hole are respectively connected to the outlet of the flow channel 21 and the first liquid outlet hole 14.

[0046] Optionally, in this embodiment, the cavity wall of the connecting cavity 12, the hole wall of the first liquid inlet hole 13 and the hole wall of the first liquid outlet hole 14 are all covered with a metal layer, which can prevent the coolant from corroding the circuit board or affecting the performance of the circuit board and ensure the sealing of the coolant flow path.

[0047] Optionally, in this embodiment, the coolant is water or a mixture of water and antifreeze, and a polyimide film layer (PI film) is provided on one side of the second plate layer 3 close to the receiving groove 11, and the polyimide film layer covers the receiving groove 11. The polyimide film layer can prevent the coolant from flowing into the first plate layer 1 and the second plate layer 3, and the PI film has excellent insulation and waterproof properties.

[0048] Optionally, in this embodiment, the circuit board further includes a liquid cooling component, which includes a liquid tank, a liquid inlet pipe, a liquid outlet pipe, a pump and a cooling element. The two ends of the liquid inlet pipe are respectively connected to the liquid tank and the first liquid inlet hole 13, and the two ends of the liquid outlet pipe are respectively connected to the first liquid outlet hole 14 and the liquid tank. The pump is fixed to the liquid tank for conveying the coolant; the cooling element is used to cool the coolant flowing out of the first liquid outlet hole 14. When working, the liquid cooling component conveys the coolant to the flow channel 21 of the heat absorbing element 2 through the pump. The coolant absorbs the heat of the heat absorbing element 2 during the flow process, causing the temperature to rise. The coolant with the increased temperature flows out from the first liquid outlet hole 14 and flows to the cooling element. After being cooled by the cooling element, the coolant with a lower temperature is pumped back to the flow channel 21 of the heat absorbing element 2 again. In this way, a circulation system can be formed to continuously conduct and dissipate heat, which can effectively reduce the temperature of the heating element 100, improve the heat dissipation efficiency, extend the service life of the circuit board, and improve the overall performance of the circuit board, and can be recycled. The cooling element is a mature technology in the related field, and will not be described in detail in this embodiment. In other embodiments, the cooling element may not be circulated, for example, the cooling liquid may be continuously introduced into the first liquid inlet hole 13 .

[0049] Optionally, threaded holes are provided at the openings of the first liquid inlet hole 13 and the first liquid outlet hole 14, and the liquid inlet pipe and the liquid outlet pipe are respectively threadedly connected with the corresponding threaded holes. While ensuring the sealing performance, the connection is firm. Alternatively, the openings of the first liquid inlet hole 13 and the first liquid outlet hole 14 are provided with clamping holes, and the liquid inlet pipe and the liquid outlet pipe are respectively clamped and sealed with the corresponding clamping holes. Specifically, a sealant or a sealing tape is coated at the connection to seal.

[0050] Optionally, the heat absorbing member 2 is fitted and pressed against the second plate layer 3, which improves the heat absorption efficiency of the heat absorbing member 2 for the heating element 100, and can support the second plate layer 3 to make the structure stable. Optionally, the material of the heat absorbing member 2 is copper. Copper has good thermal conductivity and corrosion resistance.

[0051] Optionally, in this embodiment, the first board layer 1 includes a PP prepreg, copper foil, solder mask and multiple core boards, and the second board layer 3 includes a PP prepreg, copper foil and solder mask. The specific internal structures of the first board layer 1 and the second board layer 3 belong to mature technologies in related fields, and this embodiment will not be repeated. In this embodiment, the accommodating groove 11 can be provided through the core board closest to the second board layer 3 in the first board layer 1, or through multiple core boards in the first board layer 1.

[0052] Optionally, in this embodiment, if Figure 3 As shown, the flow channel 21 is arranged horizontally, and the cross-section is in the shape of a "J". Such an arrangement allows the coolant to fully contact the heat absorbing element 2, and obtains the best heat dissipation effect and uniform heat dissipation. In other embodiments, the flow channel 21 may be in the shape of a straight line or other irregular shapes.

[0053] The present invention also provides a circuit board manufacturing method, which is applied to a circuit board. The circuit board manufactured by the method can achieve effective heat dissipation of the heating element 100, and the heat dissipation effect is good. In addition, it will not affect the user experience, save space, and is relatively reliable. The circuit board manufacturing method includes:

[0054] S1 , manufacturing a first plate layer 1 , and processing a containing groove 11 , a connecting cavity 12 , a first liquid inlet hole 13 , and a first liquid outlet hole 14 .

[0055] Specifically, first, according to the circuit board stacking design method, the core board and the PP prepreg are made into the first board layer 1 through cutting operation, inner layer operation and pressing operation. Then, Figure 4 As shown, a receiving groove 11 is milled on the first plate layer 1. Figure 2 As shown, two connecting cavities 12 are milled at intervals on the periphery of the receiving groove 11, so that the connecting cavity 12 passes through the end surface of the first plate layer 1 and forms a stepped groove in combination with a part of the receiving groove 11. Afterwards, a first liquid inlet hole 13 and a first liquid outlet hole 14 are drilled on the first plate layer 1, and the first liquid inlet hole 13 and the first liquid outlet hole 14 are respectively connected to the two connecting cavities 12. Finally, a metal layer is electroplated on the cavity wall of the connecting cavity 12, the hole wall of the first liquid inlet hole 13, and the hole wall of the first liquid outlet hole 14.

[0056] S2, manufacturing the heat absorbing member 2, processing the flow channel 21 on the heat absorbing member 2, and inserting the heat absorbing member 2 into the receiving groove 11;

[0057] S3 , manufacturing a second board layer 3 , fixing the second board layer 3 on the first board layer 1 and covering the receiving groove 11 .

[0058] The manufacturing method of the second board layer 3 is the same as that of the first board layer 1, and the first board layer 1 and the second board layer 3 are fixed by a pressing operation.

[0059] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A circuit board, characterized in that: include: A first plate layer (1) is provided with a containing groove (11), a connecting cavity (12), a first liquid inlet hole (13) and a first liquid outlet hole (14), wherein the connecting cavity (12) is connected to the containing groove (11), and the first liquid inlet hole (13) and the first liquid outlet hole (14) are both connected to the connecting cavity (12); A heat absorbing member (2) is clamped in the containing groove (11); the heat absorbing member (2) is provided with a flow channel (21), and an inlet and an outlet of the flow channel (21) are both connected to the connecting cavity (12); The second board layer (3) is fixed to the first board layer (1) and covers the receiving groove (11); an end of the second board layer (3) away from the first board layer (1) is used to fix the heating element (100), and the heating element (100) is arranged opposite to the heat absorbing element (2).

2. The circuit board according to claim 1, characterized in that: Two communicating cavities (12) are provided, and the two communicating cavities (12) are arranged around the containing groove (11) at intervals, and the inlet of the flow channel (21) and the first liquid inlet hole (13) are both connected to one of the communicating cavities (12), and the outlet of the flow channel (21) and the first liquid outlet hole (14) are both connected to the other communicating cavity (12).

3. The circuit board according to claim 2, characterized in that: The connecting cavity (12) passes through the end surface of the first plate layer (1) close to one end of the second plate layer (3), and the connecting cavity (12) is combined with a part of the containing groove (11) to form a stepped groove.

4. The circuit board according to claim 1, characterized in that: The cavity wall of the communicating cavity (12), the hole wall of the first liquid inlet hole (13) and the hole wall of the first liquid outlet hole (14) are all covered with a metal layer; and / or, A polyimide film layer is provided on one side of the second plate layer (3) close to the containing groove (11), and the polyimide film layer covers the containing groove (11).

5. The circuit board according to claim 1, characterized in that: The circuit board also includes a liquid cooling component, which includes a liquid tank, a liquid inlet pipe, a liquid outlet pipe, a pump and a cooling element. The two ends of the liquid inlet pipe are respectively connected to the liquid tank and the first liquid inlet hole (13), and the two ends of the liquid outlet pipe are respectively connected to the first liquid outlet hole (14) and the liquid tank. The pump is fixed to the liquid tank and is used to transport cooling liquid. The cooling element is used to cool the cooling liquid flowing out of the first liquid outlet hole (14).

6. The circuit board according to claim 5, characterized in that: The openings of the first liquid inlet hole (13) and the first liquid outlet hole (14) are both provided with threaded holes, and the liquid inlet pipe and the liquid outlet pipe are respectively threadedly connected to the corresponding threaded holes; or, the openings of the first liquid inlet hole (13) and the first liquid outlet hole (14) are both provided with clamping holes, and the liquid inlet pipe and the liquid outlet pipe are respectively clamped and sealed to the corresponding clamping holes.

7. The circuit board according to claim 1, characterized in that: The heat absorbing element (2) and the second plate layer (3) are in close contact and in tight contact; and / or, The material of the heat absorbing element (2) is copper.

8. The circuit board according to claim 1, characterized in that: The flow channel (21) is arranged horizontally, and has a cross-sectional shape of a "J" shape.

9. A method for manufacturing a circuit board, applied to the circuit board according to any one of claims 1 to 8, characterized in that: include: Manufacturing a first plate layer (1), and processing a containing groove (11), a connecting cavity (12), a first liquid inlet hole (13), and a first liquid outlet hole (14); Manufacturing a heat absorbing member (2), processing a flow channel (21) on the heat absorbing member (2), and inserting the heat absorbing member (2) into the receiving groove (11); A second board layer (3) is manufactured, and the second board layer (3) is fixed to the first board layer (1) and covers the receiving groove (11).

10. The method for manufacturing a circuit board according to claim 9, characterized in that: Processing the receiving groove (11), the connecting cavity (12), the first liquid inlet hole (13) and the first liquid outlet hole (14) comprises: milling the receiving groove (11) on the first plate layer (1); milling two connecting cavities (12) at intervals on the outer periphery of the receiving groove (11), so that the connecting cavity (12) passes through the end surface of the first plate layer (1) and is combined with part of the receiving groove (11) to form a stepped groove; drilling the first liquid inlet hole (13) and the first liquid outlet hole (14) on the first plate layer (1), and making the first liquid inlet hole (13) and the first liquid outlet hole (14) communicate with the two connecting cavities (12) respectively.

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