CN112738978A

CN112738978A - Printed circuit board with micro-channel and manufacturing method thereof

Info

Publication number: CN112738978A
Application number: CN202011334328.9A
Authority: CN
Inventors: 陈博谦; 陈锦标; 任远; 许毅钦; 刘宁炀
Original assignee: Heshan Shituo Electronic Technology Co Ltd
Current assignee: Heshan Shituo Electronic Technology Co Ltd
Priority date: 2020-11-24
Filing date: 2020-11-24
Publication date: 2021-04-30
Anticipated expiration: 2040-11-24
Also published as: CN112738978B

Abstract

The invention provides a printed circuit board with a micro-channel, which comprises a first substrate, a second substrate, an upper photoetching sheet and a lower photoetching sheet; exposing and etching the upper layer of photoetching sheet to form an upper layer channel, exposing and etching the lower layer of photoetching sheet to form a lower layer channel, wherein the upper layer channel corresponds to the lower layer channel in position, and when the upper layer of photoetching sheet is attached to the lower layer of photoetching sheet, the upper layer channel and the lower layer channel form a micro-channel; the upper layer channel, the lower layer channel, the surface of the upper layer photoetching sheet facing to the lower layer photoetching sheet, the surface of the lower layer photoetching sheet facing to the upper layer photoetching sheet are provided with coatings, and the micro-channel is filled with liquid working medium. The invention further provides a manufacturing method of the printed circuit board with the micro-channel. The scheme of the invention achieves the technical effects that the inner wall surface of the micro-channel is smoother and has higher consistency, the complex micro-channel structure is easy to align, and the reliability problems of micro short circuit, dirt blockage and the like are effectively reduced.

Description

Printed circuit board with micro-channel and manufacturing method thereof

Technical Field

The invention relates to the field of printed circuit boards, in particular to a printed circuit board with micro-channels and a manufacturing method thereof.

Background

Along with the smaller and more handy, more powerful, the performance of electronic system volume is more high-efficient, for satisfying the electric property ground of electronic product and constantly promoting, the PCB bears more and more passive and active electronic component. Large scale integration of components results in large power consumption, resulting in increased power density of electronic systems. If the heat cannot be dissipated smoothly, the junction temperature of the component will rise sharply, which seriously affects the reliability of the electronic device.

Despite the widespread use of air cooling in electronic packaging, the air cooling capacity will certainly reach its limit due to the trend toward miniaturization and integration of packaging technologies, while liquid cooling can accommodate higher heat fluxes due to the higher specific heat capacity and thermal conductivity of the liquid working medium. Therefore, the micro-channel technology of the circuit board has been developed in recent years. At present, set up top PCB layer, middle part PCB layer and bottom PCB layer among the printed circuit board, middle part PCB layer cloth is equipped with the runner, and the runner forms embedded runner through top PCB layer and bottom PCB layer after sealing, is equipped with a plurality of metal via holes on the top PCB layer of installation heating device or bottom PCB layer in addition. The heat generated by the power device is conducted to the working medium in the micro-channel through the metal through hole of the top PCB layer and then transported to the downstream, and is conducted to the bottom surface of the printed circuit board through the metal through hole of the bottom PCB layer. The cooling of circuit board is realized to the embedded runner liquid cooling heat transfer device of above printed circuit board, but still has following problem:

1. the micro-channel is realized by mechanical milling, so that on one hand, the inner wall surface of the micro-channel is likely to have non-flattening such as burrs, pits and the like, and then higher pressure drop is caused, and therefore higher pump power is required; on the other hand, the processing technology of the micro-channel may cause that the alignment precision of each channel structure is not high;

2. the inner wall surface of the micro-channel is directly contacted with the liquid working medium, which may cause potential reliability problems such as CAF (micro short circuit) and dirt blockage.

Disclosure of Invention

In order to solve at least one of the above technical problems, the present invention provides a printed circuit board with micro channels and a method for manufacturing the same, so as to achieve the purposes of improving the processing precision of the circuit board and solving the problem of circuit board blockage. The purpose of the invention is realized by the following scheme:

a printed circuit board with micro-channels comprises a first substrate, a second substrate, an upper layer photoetching sheet and a lower layer photoetching sheet; the side of the first base material facing the second base material is fixed with the upper photoetching sheet; the lower photoetching sheet is fixed on the side surface, facing the first base material, of the second base material; the upper layer photoetching sheet is exposed and etched to form an upper layer channel, the lower layer photoetching sheet is exposed and etched to form a lower layer channel, the upper layer channel corresponds to the lower layer channel in position, and when the upper layer photoetching sheet is attached to the lower layer photoetching sheet, the upper layer channel and the lower layer channel form a micro channel; the upper layer channel, the lower layer channel, the surface of the upper layer photoetching sheet facing the lower layer photoetching sheet, and the surface of the lower layer photoetching sheet facing the upper layer photoetching sheet are provided with coatings, and the micro-channel is filled with liquid working medium.

Further, a first circuit layer is arranged on the surface, away from the second base material, of the first base material, and a pad layer for welding the component is arranged on the surface of the circuit layer.

Further, the first substrate is bonded to a second substrate.

Furthermore, the packaging structure further comprises a plurality of third base materials arranged on the side face, away from the first base material, of the second base material, wherein a second circuit layer is arranged on the side face, away from the first base material, of the second base material, and a plurality of third circuit layers are arranged on the side face of the third base material.

Further, a plurality of the third substrates are insulating core layers and/or pre-prepared prepregs.

Further, the third substrate is provided with a stacked hole group, metal is filled in the stacked hole group, and the stacked hole group is communicated with the second circuit layer and the third circuit layers.

The heat conduction metal structure further comprises a lower heat conduction metal hole and an upper heat conduction metal hole, wherein the lower heat conduction metal hole is abutted against the wall surface at the bottom of the micro-channel, and the upper heat conduction metal hole is abutted against the wall surface at the top of the micro-channel; the lower heat conducting metal hole penetrates through the second base material and the plurality of third base materials; the upper heat conducting metal hole penetrates through the first substrate; the lower heat conduction metal hole and the upper heat conduction metal hole are filled with metal, and the metal in the lower heat conduction metal hole and the metal in the upper heat conduction metal hole are not conducted with the first circuit layer, the second circuit layer and the third circuit layer.

The invention also discloses a manufacturing method of the printed circuit board with the micro-channel, which comprises the following steps:

a substrate preparation step, wherein a first substrate and a second substrate are prepared, an upper layer photoetching sheet is fixed on the first substrate through a vacuum film pressing, and a lower layer photoetching sheet is fixed on the second substrate through the vacuum film pressing;

etching, namely exposing and etching the upper layer photoetching sheet and the lower layer photoetching sheet to form an upper layer channel and a lower layer channel, and heating and curing;

plating, namely plating the surfaces of the etched upper layer photoetching sheet and the etched lower layer photoetching sheet and drying the surfaces;

and a splicing step, wherein when the upper layer photoetching sheet and the lower layer photoetching sheet are spliced, the upper layer channel and the lower layer channel are combined to form a micro-channel, and liquid working media are filled in the micro-channel.

Further, etching a first circuit layer on the surface of the first substrate, which faces away from the upper photoetching sheet; etching a second circuit layer on the surface of the second substrate, which is far away from the lower photoetching sheet; the circuit board further comprises a plurality of third base materials etched with third circuit layers, and the third base materials are sequentially spliced to the second circuit layers.

Further, drilling heat-conducting metal holes on a plurality of spliced third base materials and second base materials, so that the heat-conducting metal holes penetrate through the third base materials and the second base materials and are communicated with the micro-channel; and a metal block is filled in the heat-conducting metal hole.

Compared with the prior art, the invention has the advantages that: the invention provides a printed circuit board with micro-channels and a manufacturing method of the printed circuit board. The circuit board comprises an upper layer photoetching sheet and a lower layer photoetching sheet, wherein the upper layer photoetching sheet and the lower layer photoetching sheet are etched and spliced to form the micro-channel. The micro-channel is manufactured by adopting the photoetching technology, so that compared with the micro-channel inner wall surface formed by adopting mechanical milling in the prior art, the inner wall surface is smoother and has higher consistency, and the alignment of a complex micro-channel structure is facilitated due to high process precision. Meanwhile, the upper layer channel, the lower layer channel, the surface of the upper layer photoetching sheet facing the lower layer photoetching sheet, and the surface of the lower layer photoetching sheet facing the upper layer photoetching sheet are provided with the coating, so that the reliability problems of CAF (micro short circuit), dirt blockage and the like can be effectively reduced. Further, by adopting photoetching processing, batch processing can be realized, and the time efficiency is improved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the principles of the invention.

FIG. 1 is a drawing of a first and second substrate with a photolithographic sheet applied thereto in accordance with the present invention;

FIG. 2 is a first and second substrate with a photolithographic sheet applied thereto after etching;

FIG. 3 is a first and a second base material which are spliced after being plated;

fig. 4 is a circuit board having a four-layer structure formed according to the present invention.

Wherein: 1. a first substrate; 2. a second substrate; 3. an upper layer photo-etching sheet; 4. a lower layer photo-etching sheet; 5. a microchannel; 6. a liquid working medium; 7. plating; 8. a first circuit layer; 9. a pad layer; 10. a power device; 11. an intermediate layer; 12. an outer substrate layer; 13. a second circuit layer; 14. an intermediate circuit layer; 15. an outer circuit layer; 16. a lower thermally conductive metal via; 17. a group of stacked holes; 18. a second metal tray; 19. and an upper heat conducting metal hole.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are for purposes of illustration only and are not to be construed as limitations of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.

In addition, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

Referring to fig. 1, in order to implement the scheme of the present invention, a preparation step is performed. Preparing a first substrate 1 and a second substrate 2, wherein the first substrate 1 and the second substrate 2 are pre-prepared prepregs and mainly comprise resin and reinforcing materials, and the reinforcing materials include but are not limited to glass fiber cloth, paper base, composite materials and the like. It can be softened under heating and pressurizing, and can be reacted and solidified after cooling, so that the aim of manufacturing the multilayer circuit board can be fulfilled. An upper layer of photo-resist 3 and a lower layer of photo-resist 4 are prepared, including but not limited to a sheet of PET film, photoresist, etc. The photolithographic flakes are also capable of curing during exposure to heat. The upper layer photoetching sheet 3 is fixed on the side of the first substrate 1 facing the second substrate 2 through a vacuum lamination process. The vacuum film pressing comprises a film carrying module, a vacuum film pressing module, a hot pressing system and the like, the film pressing in a vacuum environment is adopted to improve the production efficiency, various film materials can form high-filling lamination on the surface of a carrier plate with a thin line and a conducting hole in a vacuum film pressing mode, the surface after lamination keeps uniform thickness, and the vacuum film pressing has better surface smoothness. The lower layer of the photolithographic sheet 4 is fixed on the side of the second substrate 2 facing the first substrate 1.

Fig. 2 shows the etching step, and then the upper layer photo-etching sheet 3 and the lower layer photo-etching sheet 4 are exposed and etched to obtain the basic pattern of the micro-channel 5, specifically, the photo-etching sheets are firstly subjected to photo-etching exposure treatment, and then the parts to be removed are etched through a physical or chemical mode to form the upper layer channel and the lower layer channel. And then the upper layer channel and the lower layer channel are heated, so that the upper layer channel and the lower layer channel have stable structures to contain the liquid working medium 6.

Referring to fig. 3, the structure is shown after the plating step and the splicing step. And removing glue residues on the surfaces of the etched upper layer photoetching film 3 and the etched lower layer photoetching film 4, and avoiding the situation that the upper layer photoetching film 4 and the lower layer photoetching film 4 cannot be accurately attached due to the residues of the photoetching glue and the like. The surfaces of the upper photoetching sheet 3 and the lower photoetching sheet 4 are covered with the plating layers 7, and the plating layers 7 are distributed on the unetched surfaces and the wall surfaces of the upper-layer channel and the lower-layer channel, so that the inner wall surface of the micro-channel 5 is smooth and has high consistency, and the possibility of micro-short circuit and the possibility of dirt blocking the micro-channel 5 can be effectively reduced. Further, the photo-etching sheet coated with the plating layer 7 is dried so that the plating layer 7 is sufficiently cured on the upper photo-etching sheet 3 and the lower photo-etching sheet 4.

A splicing step is further performed. The upper layer photoetching plate 3 and the lower layer photoetching plate 4 are used for etching the upper layer photoetching plate 3 and the lower layer photoetching plate 4 in a mirror image mode substantially, so when the upper layer photoetching plate 3 and the lower layer photoetching plate 4 are spliced, an upper layer channel and a lower layer channel can correspond in position to form a micro-channel 5 shown in the attached drawing 3. The upper layer photoetching sheet 3 and the lower layer photoetching sheet 4 are connected in a bonding mode. Two homogeneous or heterogeneous semiconductor materials with clean surfaces and flat atomic levels are directly combined after surface cleaning and activating treatment. The bonding method mainly bonds the wafers into a whole through van der waals force, molecular force and even atomic force. The photoetching and the arrangement of the coating 7 can better ensure that the upper photoetching sheet 3 and the lower photoetching sheet 4 have atomic-level flatness.

And the microchannel 5 is filled with a liquid working medium 6. The liquid inside the microchannel 5 is able to absorb heat and transfer the heat by means of convection. The liquid working medium 6 is generally insulating liquid, and the invention preferably uses fluorine-containing liquid as the liquid working medium 6, which can effectively play the roles of insulation and cooling and ensure the safety of the circuit.

Referring to fig. 4, after the upper and lower photo-

etching sheets

3 and 4 are bonded, a multi-layer circuit board manufacturing process is applied to manufacture other layers and a carved circuit board.

Specifically, a first circuit layer 8 is disposed on a surface of the first substrate 1 facing away from the second substrate 2, and a pad layer 9 for soldering components is disposed on a surface of the circuit layer. The upper surface of the pad layer 9 is bonded to the power device 10 or the load through the pad. The power device 10 handles high voltage, high current capability or switched semiconductor devices. In essence, the structure provided by the present invention can be applied to any element that generates a large amount of heat or requires heat dissipation on an integrated circuit. The lower surface of the pad layer 9 is electrically connected to the first circuit layer 8 through a pad.

It is noted that there is a metal tray in the middle of the first circuit layer 8, which is not conductive to the first circuit. Specifically, an isolated area is scribed on the first circuit layer 8 for mounting the metal tray, thereby preventing the metal tray from shorting out the circuit. The first substrate 1 includes an upper thermally conductive metal via 19 therein, which extends through the first substrate 1 and contacts the upper photolithographic sheet 3. Specifically, the upper heat conductive metal hole 19 abuts the upper wall surface of the microchannel 5 but does not contact the liquid working medium 6 in the microchannel 5. The liquid working medium 6 is separated from the upper heat conducting metal hole 19 by a thin wall. The interior of the upper heat conducting metal hole 19 is filled with metal by pouring, the metal is connected with a metal tray on the upper part, and the metal tray is contacted with the bottom wall of the welding pad layer 9. The portion of the pad layer 9 in contact with the metal tray is not conductive. It may be arranged that the part of the pad layer 9 that is in contact with the metal tray does not have conductive devices such as pads or lines, thereby avoiding short circuits. The heat generated by the power device 10 or the load can be absorbed by the metal with good heat conductivity in the metal tray and the upper heat conducting metal hole 19 and transferred to the liquid working medium 6 in the micro-channel 5.

In a preferred embodiment, a second circuit layer 13 is also included. The second circuit layer 13 is etched on the side of the second substrate 2 facing away from the first substrate 1, thereby forming a multilayer circuit board. The second circuit layer 13 can be an independent circuit or can be connected by a metal via (not shown) penetrating the first substrate 1, the second substrate 2, the upper resist and the lower resist. Of course, the metal via is provided at a portion having the first circuit layer 8 and the second circuit layer 13, and is prevented from contacting the microchannel 5. Preferably, the micro-channel 5 is arranged below the power device 10 or the load.

Further, a plurality of third substrates are also included. The third substrate has at least one layer. And a circuit layer is etched on one side surface of the third base material, and the surfaces of the third circuit layer, which are not etched, are sequentially spliced to the second circuit layer. Referring to fig. 4, a multilayer circuit having 4 circuit layers, i.e., two circuit layers having a third substrate, is specifically shown. For clarity, the outermost third substrate is referred to as an outer substrate layer 12, and the third substrate sandwiched between the outer substrate layer 12 and the second substrate 2 is referred to as an intermediate layer 11. The intermediate layer 11 can be plural.

The outer substrate layer 12 abuts the side of the intermediate layer 11 facing away from the second substrate 2. The side of the intermediate layer 11 facing away from the second substrate 2 is provided with an intermediate circuit layer 14, the side of the outer substrate layer 12 facing away from the intermediate layer 11 is provided with an outer circuit layer 15, and the outer circuit layer 15 and the intermediate circuit layer 14 are actually third circuit layers. The multilayer circuit board is placed in a hydraulic press or laminated in an overpressure chamber (autoclave) to form a multilayer circuit board. More lines can be arranged in a limited space and the weight of the circuit board can be reduced.

In a preferred embodiment, the intermediate layer 11 is an insulating core layer and the outer substrate layer 12 is a pre-preg. The intermediate layer 11 can be made using a substrate that is more thermally stable, thereby forming a more stable base. The outer substrate layer 12 is formed by using a pre-prepared prepreg, can be attached to the intermediate layer 11 after being heated, and is solidified into a unified whole after being cooled.

Referring to fig. 4, the intermediate layer 11 and the outer substrate layer 12 are provided with stacked hole groups 17, the stacked hole groups 17 are filled with metal, and the stacked hole groups 17 communicate with the second circuit layer 13, the intermediate circuit layer 14 and the outer circuit layer 15. The positions of the stacked holes in the intermediate layer 11 and the outer substrate layer 12 may be opposite or may be offset by a certain distance. The stack of holes exhibits a tapered character, in particular in the intermediate layer 11, the interface of the stack of holes connecting the intermediate circuit layer 14 is directly smaller than the diameter of the interface connecting the second circuit layer 13. In the outer substrate layer 12, the diameter of the interface of the stack of holes connecting to the outer circuit layer 15 is directly smaller than the diameter of the interface connecting to the intermediate circuit layer 14. The tapered hole stack is formed by laser drilling, as shown in fig. 4, the laser drilling direction is from 13 planes to 14 planes, and the laser energy is attenuated with the drilling depth, so that the hole section is tapered.

And a lower heat-conducting metal hole 16, wherein the lower heat-conducting metal hole 16 penetrates through the second substrate 2, the intermediate layer 11 and the outer substrate layer 12. The lower heat conducting metal hole 16 is abutted against the bottom wall of the micro-channel 5, the lower heat conducting metal hole 16 and the liquid working medium 6 have thin walls, and the lower heat conducting metal hole 16 and the liquid working medium 6 are not in direct contact. And a metal block is filled in the heat-conducting metal hole. A second metal tray 18 is arranged on the surface of the outer substrate layer 12 facing away from the intermediate layer 11, the second metal tray 18 communicating with the filled metal blocks. The outer circuit layer 15 is not in conduction with the second metal tray 18.

The heat generated by the power device 10 or the load is conducted into the microchannel 5 from the upper surface of the first circuit layer 8 through the metal tray and the upper heat conducting metal hole 19, the heat is absorbed by the liquid working medium 6 in the microchannel 5, the liquid working medium 6 carries out heat convection in the microchannel 5, the contact part of the microchannel 5 and the lower heat conducting metal hole 16 forms a cold end, and the liquid working medium 6 carries out heat dissipation on the absorbed heat from the lower heat conducting metal hole 16 and the second metal tray 18. The metal tray and the second metal tray 18 are made of heat-dissipating copper foils, so that the heat-dissipating area can be increased, and the heat dissipation is more effective. Heat, on the one hand, is transferred in a direction perpendicular to the plate surface, as described above; on the other hand, the heat is transferred along the direction of the board surface, namely the liquid working medium 6 transports the heat from the power device to other cold ends of the board surface.

In the description herein, reference to the description of the terms "one embodiment/mode," "some embodiments/modes," "example," "specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment/mode or example is included in at least one embodiment/mode or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to be the same embodiment/mode or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments/modes or examples. Furthermore, the various embodiments/aspects or examples and features of the various embodiments/aspects or examples described in this specification can be combined and combined by one skilled in the art without conflicting therewith.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

It will be understood by those skilled in the art that the foregoing embodiments are merely for clarity of description and are not intended to limit the scope of the invention. Other variations or modifications will occur to those skilled in the art based on the foregoing disclosure and are within the scope of the invention.

Claims

1. A printed circuit board having micro-channels, comprising: comprises a first substrate, a second substrate, an upper layer photoetching sheet and a lower layer photoetching sheet;

the side of the first base material facing the second base material is fixed with the upper photoetching sheet; the lower photoetching sheet is fixed on the side surface, facing the first base material, of the second base material;

the upper layer photoetching sheet is exposed and etched to form an upper layer channel, the lower layer photoetching sheet is exposed and etched to form a lower layer channel, the upper layer channel corresponds to the lower layer channel in position, and when the upper layer photoetching sheet is attached to the lower layer photoetching sheet, the upper layer channel and the lower layer channel form a micro channel; the upper layer channel, the lower layer channel, the surface of the upper layer photoetching sheet facing the lower layer photoetching sheet, and the surface of the lower layer photoetching sheet facing the upper layer photoetching sheet are provided with coatings, and the micro-channel is filled with liquid working medium.

2. A printed circuit board having microchannels as claimed in claim 1, wherein: and a first circuit layer is arranged on the surface of the first base material, which is far away from the second base material, and a pad layer for welding elements is arranged on the surface of the first circuit layer.

3. A printed circuit board having microchannels as claimed in claim 1, wherein: the first substrate is bonded to the second substrate.

4. A printed circuit board having microchannels as claimed in claim 2, wherein: the packaging structure is characterized by further comprising a plurality of third base materials arranged on the side face, deviating from the first base material, of the second base material, wherein a second circuit layer is arranged on the side face, deviating from the first base material, of the second base material, and a plurality of third circuit layers are arranged on the side face of the third base material.

5. A printed circuit board having microchannels as claimed in claim 4, wherein: and a plurality of third base materials are insulating core layers and/or prefabricated prepregs.

6. A printed circuit board having microchannels as claimed in claim 4, wherein: the third substrate is provided with a stacked hole group, metal is filled in the stacked hole group, and the stacked hole group is communicated with the second circuit layer and the third circuit layers.

7. A printed circuit board having microchannels as claimed in claim 4, wherein: the heat conduction metal plate is characterized by also comprising a lower heat conduction metal hole and an upper heat conduction metal hole, wherein the lower heat conduction metal hole is abutted against the bottom wall surface of the micro-channel, and the upper heat conduction metal hole is abutted against the top wall surface of the micro-channel; the lower heat conducting metal hole penetrates through the second base material and the plurality of third base materials; the upper heat conducting metal hole penetrates through the first substrate; the lower heat conduction metal hole and the upper heat conduction metal hole are filled with metal, and the metal in the lower heat conduction metal hole and the metal in the upper heat conduction metal hole are not conducted with the first circuit layer, the second circuit layer and the third circuit layer.

8. A method of manufacturing a printed circuit board having micro-channels, comprising the steps of:

9. A method of manufacturing a printed circuit board having micro-channels according to claim 8, further comprising the steps of: etching a first circuit layer on the surface of the first substrate, which is far away from the upper photoetching sheet; etching a second circuit layer on the surface of the second substrate, which is far away from the lower photoetching sheet; the circuit board further comprises a plurality of third base materials etched with third circuit layers, and the third base materials are sequentially spliced to the second circuit layers.

10. A method of manufacturing a printed circuit board having a microchannel according to claim 9, wherein: drilling heat-conducting metal holes on a plurality of spliced third base materials and second base materials, so that the heat-conducting metal holes penetrate through the third base materials and the second base materials and are communicated with the micro-channel; and a metal block is filled in the heat-conducting metal hole.