Circuit board

Abstract

The utility model relates to a circuit board. The circuit board comprises a substrate and a heat dissipation block, the substrate comprises a first core board, a second core board and a third core board, the first core board, the second core board and the third core board are sequentially connected in an overlapped mode, the first core board is provided with a first installation hole, the second core board is provided with a second installation hole, the first installation hole is communicated with the second installation hole, and the substrate is provided with a through hole. And the heat dissipation block is embedded into the first mounting hole and the second mounting hole. Wherein a first electroplated layer is arranged on the hole wall of the through hole, and a heat dissipation medium is arranged in the through hole. The circuit board has the advantages of being low in production difficulty, good in quality and good in reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printed circuit boards, in particular to a circuit board. BACKGROUND

[0002] With the volume of electronic products becoming smaller and smaller, the volume of circuit boards is also continuously reduced, resulting in the continuous improvement of the line density of circuit boards. Moreover, the power density of components mounted on the circuit board is also becoming higher and higher, and the heat dissipation of the circuit board is too large, which easily affects the service life of the components and causes the components to fail.

[0003] Therefore, in order to strengthen the heat dissipation capacity of the circuit board, the current solution is to directly embed a copper block on the circuit board, the specific operation method being to drill installation grooves on the etched core board, then manually install the copper block into the installation grooves, and then press the core boards, embed the copper block, and then set a blind hole on the circuit board, and perform copper plating on the hole wall of the blind hole through a copper plating process to connect different circuit layers in the circuit board into a conductive circuit. However, when the longitudinal depth ratio of the blind hole is more than 1:1, copper is easily not formed in the hole or the electroplated layer is too thin when the blind hole is plated with copper, and the bottom of the blind hole is difficult to clean and the heat dissipation capacity of the circuit board cannot be improved, which has the defects of great manufacturing difficulty, high cost, and low reliability. CONTENT OF THE INVENTION

[0004] Therefore, it is necessary to provide a circuit board to solve the problems of great manufacturing difficulty, high cost, and low reliability of the circuit board.

[0005] The present application provides a circuit board, comprising:

[0006] a substrate, the substrate comprising a first core board, a second core board, and a third core board, the first core board, the second core board, and the third core board being connected in sequence, the first core board and the second core board being provided with a first installation hole, the second core board being provided with a second installation hole, the first installation hole and the second installation hole being communicated, the substrate being provided with a through hole;

[0007] and a heat dissipation block, the heat dissipation block being embedded in the first installation hole and the second installation hole;

[0008] wherein the hole wall of the through hole is provided with a first electroplated layer, and the inside of the through hole is provided with a heat dissipation medium.

[0009] In one embodiment, the through hole comprises a plurality of through holes, the through holes penetrating through the heat dissipation block and the third core board, and / or the through holes penetrating through the first core board, the second core board, and the third core board.

[0010] In one of the embodiments, the substrate is further provided with a back-drilling hole, the back-drilling hole is arranged at the end of the through-hole, the back-drilling hole is in communication with the through-hole, and the back-drilling hole is used for removing the unused first electroplated layer.

[0011] In one of the embodiments, the axis of the back-drilling hole coincides with the axis of the through-hole, and the diameter of the back-drilling hole is greater than the diameter of the through-hole.

[0012] In one of the embodiments, the first core plate is respectively provided with a first circuit layer and a second circuit layer on the two side surfaces in the thickness direction, the second core plate is respectively provided with a third circuit layer and a fourth circuit layer on the two side surfaces in the thickness direction, the third core plate is respectively provided with a fifth circuit layer and a sixth circuit layer on the two sides in the thickness direction, and two or more of the first circuit layer, the second circuit layer, the third circuit layer, the fourth circuit layer, the fifth circuit layer, and the sixth circuit layer are electrically connected.

[0013] In one of the embodiments, the first electroplated layer connects two or more of the first circuit layer, the second circuit layer, the third circuit layer, the fourth circuit layer, the fifth circuit layer, and the sixth circuit layer to form a conductive circuit.

[0014] In one of the embodiments, the drilling depth of the back-drilling hole is less than the depth from the surface of the side of the substrate where the back-drilling hole is arranged to the conductive circuit.

[0015] In one of the embodiments, the surface of the substrate is provided with a second electroplated layer; the substrate further comprises a first prepreg and a second prepreg, the first core plate and the second core plate are connected through the first prepreg, and the second core plate and the third core plate are connected through the second prepreg.

[0016] In one of the embodiments, the long side length of the first mounting hole is 1 mil to 2 mil less than the long side length of the heat dissipation block, and the short side length of the first mounting hole is 1 mil to 2 mil less than the short side length of the heat dissipation block; the long side length of the second mounting hole is 1 mil to 2 mil less than the long side length of the heat dissipation block, and the short side length of the second mounting hole is 1 mil to 2 mil less than the short side length of the heat dissipation block.

[0017] In one of the embodiments, the flatness of the end surface of the heat dissipation block relative to the surface of the first circuit layer is less than 25 um.

[0018] The circuit board, the substrate is made of a first core plate, a second core plate and a third core plate, and the heat dissipation block is pressed into the mounting hole drilled in the first core plate and the second core plate, so that the heat of the substrate is transmitted through the heat dissipation block, thereby enhancing the heat dissipation capacity of the circuit board and improving the reliability of the circuit board. The substrate is also provided with a through hole, and the heat of the substrate is transmitted through the heat dissipation medium arranged in the through hole after the heat dissipation medium is fixed, thereby further improving the heat dissipation capacity of the circuit board and ensuring the stability of use. The through hole is formed with a first electroplated layer on the hole wall through a copper plating process in the production process. The first electroplated layer can be used to connect the circuit in the substrate, and the first electroplated layer has the advantages of low production difficulty, good quality and good reliability. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The structure schematic diagram of the circuit board described in the embodiment of the present application.

[0020] Figure 2 The structure schematic diagram of the circuit board described in another embodiment of the present application.

[0021] REFERENCE NUMERALS:

[0022] 100, substrate; 110, first core plate; 111, first circuit layer; 112, second circuit layer; 120, second core plate; 121, third circuit layer; 122, fourth circuit layer; 130, third core plate; 131, fifth circuit layer; 132, sixth circuit layer; 140, first prepreg; 150, second prepreg; 160, heat dissipation medium; 101A, first mounting hole; 102A, second mounting hole; 100B, through hole; 100C, back drilling hole;

[0023] 200, heat dissipation block;

[0024] 310, first electroplated layer; 320, second electroplated layer. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below. In the following description, a large number of specific details are set forth in order to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0026] In the description of the present application, it should be understood that, if there are terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, these terms indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0027] In addition, if the terms "first", "second" appear, these terms are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, if the term "multiple" appears, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0028] In the present application, unless otherwise explicitly specified and limited, if the terms "mounting", "connecting", "connecting", "fixing" and the like appear, these terms should be interpreted broadly. For example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0029] In the present application, unless otherwise explicitly specified and limited, if the first feature is described as "on" or "under" the second feature, etc., it can mean that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature "above", "above" and "above" of the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" of the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0030] It is to be noted that when an element is referred to as being "fixed" or "set" on another element, it can be directly on the other element or there can be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there can be an intervening element. The terms "vertical", "horizontal", "upper", "lower", "left", "right", and similar terms as used herein are for the purpose of illustration only and do not indicate the only orientation of the embodiments.

[0031] Referring to Figure 1 , a structural schematic diagram of a circuit board in an embodiment of the present application is shown, the circuit board comprising a substrate 100 and a heat dissipation block 200, the substrate 100 comprising a first core plate 110, a second core plate 120 and a third core plate 130, the first core plate 110, the second core plate 120 and the third core plate 130 being connected in turn, the first core plate 110 being provided with a first mounting hole 101A, the second core plate 120 being provided with a second mounting hole 102A, the first mounting hole 101A and the second mounting hole 102A being in communication, the substrate 100 being provided with a through hole 100B. The heat dissipation block 200 is embedded in the first mounting hole 101A and the second mounting hole 102A.

[0032] The hole wall of the through hole 100B is provided with a first electroplated layer 310, and the inside of the through hole 100B is provided with a heat dissipation medium 160.

[0033] In an embodiment, as shown in Figure 1 , the surface of the substrate 100 is provided with a second electroplated layer 320, the second electroplated layer 320 being used to connect external components. The manufacturing method of the circuit board of the present application is to first press the first core plate 110 and the second core plate 120 together, then drill a first mounting hole 101A through the first core plate 110 and a second mounting hole 102A through the second core plate 120 by drilling, then press the heat dissipation block 200 into the first mounting hole 101A and the second mounting hole 102A, so that the end face of the heat dissipation block 200 is flush with the surface of the first core plate 110. Then press the third core plate 130 to the surface of the second core plate 120, so that the first core plate 110, the second core plate 120 and the third core plate 130 are connected into the substrate 100, then drill the through hole 100B, electroplate the surface of the substrate with the second electroplated layer 320 by electroplating process, and electroplate the hole wall of the through hole 100B with the first electroplated layer 310 by copper plating process. Finally, the heat dissipation medium 160 is placed in the through hole 100B, so that the heat dissipation medium 160 is solidified in the through hole 100B. The second electroplated layer 320 and the first electroplated layer 310 are both copper plating layers.

[0034] The circuit board described in this embodiment is formed by laminating a first core board 110, a second core board 120, and a third core board 130 onto a substrate 100. A first mounting hole 101A is drilled in the first core board 110 and the second core board 120, and a through mounting hole 102A is drilled in the second core board 120. A heat sink 200 is then pressed into the first mounting hole 101A and the second mounting hole 102A, embedding the heat sink 200 into the substrate 100. This allows heat from the substrate 100 to be transferred through the heat sink 200, thereby enhancing the heat dissipation capacity of the circuit board and improving its reliability. The substrate 100 also has a through hole 100B. By placing a heat dissipation medium 160 within the through hole 100B, the heat transfer from the substrate 100 can be further accelerated after the heat dissipation medium 160 is fixed, further improving the heat dissipation capacity of the circuit board and ensuring stability during use. During the production process, the through-hole 100B will form a first electroplated layer 310 on the hole wall after a copper plating process. The first electroplated layer 310 can be used to connect the circuit in the substrate 100.

[0035] The circuit board described in this application embodiment has the advantages of low production difficulty, high quality, and high reliability. It is easier to fabricate the first electroplated layer 310 on the through hole 100B than to conventionally deposit copper in blind holes. Moreover, the thickness uniformity of the fabricated first electroplated layer 310 is good.

[0036] In an exemplary embodiment, the heat dissipation medium 160 can be an epoxy-based heat dissipation oil, a silicone rubber-based heat dissipation oil, an acrylic ester-based heat dissipation oil, or a polyurethane-based heat dissipation oil, etc., which can be selected according to different application scenarios of the circuit board. The heat dissipation medium 160 is a plugging material for the through hole 100B of the circuit board, and the main purpose is to enhance the heat dissipation performance of the circuit board. The heat dissipation medium 160 usually has good thermal conductivity, which can effectively conduct the heat of the substrate 100 away from the heat dissipation medium 160, preventing local overheating. At the same time, the heat dissipation medium 160 should also have appropriate fluidity, so as to be able to smoothly fill the through hole 100B, and after solidification, it can maintain stable physical and chemical properties such as hardness, insulation, etc. Before plugging, the substrate 100 needs to be cleaned to remove dust, oil stains and other impurities in the through hole 100B. In addition, for some high-precision circuit boards, the through hole 100B may also need to be pre-activated to enhance the bonding force of the heat dissipation medium 160 and the hole wall. After plugging, the heat dissipation medium 160 needs to be preliminarily solidified to form a stable filling structure in the through hole 100B. Preliminary solidification can be carried out by heating, so that the fluidity of the heat dissipation medium 160 decreases and begins to solidify, and is preliminarily fixed in the through hole 100B. The circuit board after preliminary solidification needs to be subjected to post-curing treatment, and the circuit board is placed in a curing oven for baking at a higher temperature for a certain period of time, so that the heat dissipation medium 160 is completely solidified. The completely solidified heat dissipation medium 160 has better mechanical properties and thermal conductivity, and can better play the role of heat dissipation. At the same time, post-curing can also enhance the bonding force of the heat dissipation medium 160 and the hole wall of the through hole 100B, preventing problems such as falling off in subsequent processing or use.

[0037] In combination Figure 2 , a structural schematic diagram of a circuit board in another embodiment of the present application is shown. In some embodiments, the through hole 100B includes a plurality of through holes 100B, which pass through the heat dissipation block 200 and the third core plate 130, and / or the through hole 100B passes through the first core plate 110, the second core plate 120 and the third core plate 130. The first electroplated layer 310 on the hole wall of the through hole 100B is used to accurately connect specific circuit layers in the substrate 100, optimizing the signal transmission path. By setting multiple through holes 100B and first electroplated layers 310 to optimize the signal transmission path of the circuit board, the position of the through hole 100B can be set at a position penetrating through the heat dissipation block 200, thereby connecting the circuit layers of the first core plate 110, or can be set at a position penetrating through the first core plate 110, the second core plate 120 and the third core plate 130, which can be arranged according to the circuit of the circuit board. The through hole 100B has the heat dissipation medium 160 inside the hole, which can enhance the heat dissipation capacity of the substrate 100 and improve the stability of the circuit board.

[0038] In an optional embodiment, as Figure 1 andFigure 2 As shown, the first core plate 110 is provided with a first circuit layer 111 and a second circuit layer 112 on the two side surfaces in the thickness direction, the second core plate 120 is provided with a third circuit layer 121 and a fourth circuit layer 122 on the two side surfaces in the thickness direction, the third core plate 130 is provided with a fifth circuit layer 131 and a sixth circuit layer 132 on the two sides in the thickness direction, and two or more of the first circuit layer 111, the second circuit layer 112, the third circuit layer 121, the fourth circuit layer 122, the fifth circuit layer 131 and the sixth circuit layer 132 are electrically connected. According to the overall design of the circuit board, the first circuit layer 111 and the second circuit layer 112 are etched on the two surfaces of the first core plate 110, the third circuit layer 121 and the fourth circuit layer 122 are etched on the two surfaces of the second core plate 120, and the fifth circuit layer 131 and the sixth circuit layer 132 are etched on the two surfaces of the third core plate 130, so that the first circuit layer 111, the second circuit layer 112, the third circuit layer 121, the fourth circuit layer 122, the fifth circuit layer 131 and the sixth circuit layer 132 can carry high-speed digital signals and analog signals, thereby realizing the complex circuit function of the circuit board.

[0039] Further, as shown in Figure 1 and Figure 2 , the first plated layer 310 connects two or more of the first circuit layer 111, the second circuit layer 112, the third circuit layer 121, the fourth circuit layer 122, the fifth circuit layer 131 and the sixth circuit layer 132 to form a conductive circuit. The first circuit layer 111, the second circuit layer 112, the third circuit layer 121, the fourth circuit layer 122, the fifth circuit layer 131 and the sixth circuit layer 132 are respectively distributed on different layers, and when the circuit layers of different layers extend to the position of the through hole 100B, the electrical connection can be realized through the first plated layer 310 in the through hole 100B. This way of connecting different circuit layers through the first plated layer 310 enables signals, power supplies and the like to be freely transmitted in the multi-layer circuit board, thereby realizing the electrical connection between different circuit layers. In an embodiment, the first plated layer 310 can also be connected to the second plated layer 320.

[0040] In an alternative embodiment, as shown in Figure 1 and Figure 2As shown, the substrate 100 is also provided with a back-drilling hole 100C, which is arranged at the end of the through-hole 100B, and which communicates with the through-hole 100B, and which is used to remove the unused first plating layer 310. When the circuit board transmits high-speed signals, if the through-hole 100B is not properly processed, signal reflection will occur, and the unused first plating layer 310 at both ends of the through-hole 100B will act like an antenna, causing interference to the signal. By back-drilling the unused part at both ends of the through-hole 100B, the back-drilling hole 100C can remove the unnecessary first plating layer 310 in the through-hole 100B, thereby reducing signal reflection, enabling smoother signal transmission, and reducing noise and bit error rate caused by signal reflection.

[0041] In an exemplary embodiment, as shown in Figure 1 and Figure 2 The through-hole 100B penetrates the first core board 110, the second core board 120 and the third core board 130, but the first plating layer 310 in the through-hole 100B only communicates with the circuit layers of the first core board 110 and the second core board 120, and the unused part of the first plating layer 310 in the third core board 130 will cause high-frequency reflection and resonance, so the back-drilling hole 100C is arranged to remove the unused part of the first plating layer 310 in the third core board 130, thereby improving the signal transmission capability of the first plating layer 310.

[0042] In an alternative embodiment, as shown in Figure 1 and Figure 2 The axis of the back-drilling hole 100C coincides with the axis of the through-hole 100B, and the diameter of the back-drilling hole 100C is greater than the diameter of the through-hole 100B. In order to remove the excess first plating layer 310, the diameter of the back-drilling hole 100C needs to be greater than the diameter of the through-hole 100B, so that the excess first plating layer 310 can be completely removed during processing, otherwise it is not possible to remove all the unnecessary first plating layer 310. In an exemplary embodiment, the difference between the diameter of the back-drilling hole 100C and the diameter of the through-hole 100B is greater than 0.2mm.

[0043] In an alternative embodiment, as shown in Figure 1 and Figure 2 The drilling depth of the back-drilling hole 100C is less than the depth from the surface of the side of the substrate 100 where the back-drilling hole 100C is arranged to the conductive circuit. Since the back-drilling hole 100C is used to remove the first plating layer 310 between the conductive circuit and the surface of the substrate 100, the drilling depth of the back-drilling hole 100C needs to be drilled close to the conductive circuit, but the back-drilling hole 100C needs to avoid damaging the connectivity of the first plating layer 310. In an exemplary embodiment, the minimum distance between the bottom of the back-drilling hole 100C and the conductive circuit is greater than 0.3mm.

[0044] In an alternative embodiment, as shown in Figure 1 and Figure 2 The substrate 100 further comprises a first prepreg 140 and a second prepreg 150, the first core plate 110 and the second core plate 120 are connected by the first prepreg 140, and the second core plate 120 and the third core plate 130 are connected by the second prepreg 150.

[0045] In this embodiment, the first prepreg 140 is placed between the first core plate 110 and the second core plate 120, and the second circuit layer 112 and the third circuit layer 121 are arranged towards the first prepreg 140, then the first core plate 110 and the second core plate 120 are connected as a whole by heating and pressing, and the quality and performance of the circuit board after pressing are checked to ensure that they meet the requirements. After the heat dissipation block 200 is pressed in, the second prepreg 150 is placed between the second core plate 120 and the third core plate 130, and the fourth circuit layer 122 and the fifth circuit layer 131 are arranged towards the second prepreg 150, then the second core plate 120 and the third core plate 130 are connected as a whole by heating and pressing, and the quality and performance of the circuit board after pressing are checked to ensure that they meet the requirements.

[0046] In an alternative embodiment, the long side length of the first mounting hole 101A is 1mil-2mil smaller than the long side length of the heat dissipation block 200, and the short side length of the first mounting hole 101A is 1mil-2mil smaller than the short side length of the heat dissipation block 200. The long side length of the second mounting hole 102A is 1mil-2mil smaller than the long side length of the heat dissipation block 200, and the short side length of the second mounting hole 102A is 1mil-2mil smaller than the short side length of the heat dissipation block 200.

[0047] In this embodiment, the long side length and the short side length of the first mounting hole 101A and the second mounting hole 102A are set to be smaller than the long side length and the short side length of the heat dissipation block 200, so that the heat dissipation block 200 is in interference fit in the first mounting hole 101A and the second mounting hole 102A, and the heat dissipation block 200 can be firmly embedded in the first mounting hole 101A and the second mounting hole 102A, so that the heat dissipation block 200 will not be displaced in the subsequent pressing process, ensuring that the heat dissipation block 200 is flush with the surface of the substrate 100, thereby ensuring that the flatness of the circuit board surface is better, and improving the processing quality and the pass rate.

[0048] In other embodiments, if the first mounting hole 101A, the second mounting hole 102A and the heat sink 200 are circular, the diameter of the first mounting hole 101A and the second mounting hole 102A is 1-2 mil smaller than the diameter of the heat sink 200. Similarly, the circular heat sink 200 can also be firmly installed in the first mounting hole 101A and the second mounting hole 102A by interference fit, thereby improving the flatness of the surface of the circuit board.

[0049] In an optional embodiment, the flatness between the end surface of the heat sink 200 and the first circuit layer 111 is less than 25 um.

[0050] In the embodiment, the heat sink 200 is embedded in the first mounting hole 101A of the first core plate 110 and the second mounting hole 102A of the second core plate 120 in a semi-buried manner. During processing, the first core plate 110 and the second core plate 120 are first solidified, then the first mounting hole 101A is drilled through the first core plate 110, the second mounting hole 102A is drilled through the second core plate 120, and then the heat sink 200 is pressed from one side of the first core plate 110, so that the heat sink 200 is flush with the first circuit layer 111 of the third core plate 130 on the side of the first core plate 110, thereby improving the flatness between the heat sink 200 and the first circuit layer 111, and the flatness between the heat sink 200 and the first circuit layer 111 is less than 25 um, which has the advantages of good processing quality and high qualification rate.

[0051] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present application.

[0052] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.

Claims

1. A circuit board, characterized by, The circuit board comprises a substrate (100), a heat dissipation block (200), and a heat dissipation medium (160). The substrate (100) comprises a first core plate (110), a second core plate (120), and a third core plate (130), which are sequentially connected in a stacked manner. The first core plate (110) is provided with a first mounting hole (101A), and the second core plate (120) is provided with a second mounting hole (102A). The first mounting hole (101A) and the second mounting hole (102A) are in communication, and the substrate (100) is provided with a through hole (100B). The heat dissipation block (200) is embedded in the first mounting hole (101A) and the second mounting hole (102A). The through hole (100B) is provided with a first electroplated layer (310), and the inside of the through hole (100B) is provided with a heat dissipation medium (160).

2. The circuit board according to claim 1, wherein the through hole (100B) comprises a plurality of through holes, and the through holes (100B) pass through the heat dissipation block (200) and the third core plate (130), and / or the through holes (100B) pass through the first core plate (110), the second core plate (120), and the third core plate (130).

3. The circuit board according to claim 1, wherein the substrate (100) is further provided with a back drilling hole (100C), the back drilling hole (100C) is arranged at the end of the through hole (100B), the back drilling hole (100C) is in communication with the through hole (100B), and the back drilling hole (100C) is used for removing unused first electroplated layer (310).

4. The circuit board according to claim 3, wherein the axis of the back drilling hole (100C) coincides with the axis of the through hole (100B), and the diameter of the back drilling hole (100C) is greater than the diameter of the through hole (100B).

5. The circuit board according to claim 3, wherein the first core plate (110) is provided with a first circuit layer (111) and a second circuit layer (112) on the two side surfaces in the thickness direction, respectively, the second core plate (120) is provided with a third circuit layer (121) and a fourth circuit layer (122) on the two side surfaces in the thickness direction, respectively, the third core plate (130) is provided with a fifth circuit layer (131) and a sixth circuit layer (132) on the two side surfaces in the thickness direction, respectively, and two or more of the first circuit layer (111), the second circuit layer (112), the third circuit layer (121), the fourth circuit layer (122), the fifth circuit layer (131), and the sixth circuit layer (132) are electrically connected.

6. The circuit board according to claim 5, wherein ​ ​ The first electroplating layer (310) connects two or more of the first circuit layer (111), the second circuit layer (112), the third circuit layer (121), the fourth circuit layer (122), the fifth circuit layer (131) and the sixth circuit layer (132) to form a conductive circuit.

7. The circuit board of claim 6, wherein: The drilling depth of the back-drilling hole (100C) is less than the depth from the surface of the substrate (100) on which the back-drilling hole (100C) is disposed to the conductive circuit.

8. The circuit board of claim 1, wherein: The surface of the substrate (100) is provided with a second electroplating layer (320); the substrate (100) further comprises a first prepreg (140) and a second prepreg (150), the first core board (110) and the second core board (120) are connected by the first prepreg (140), and the second core board (120) and the third core board (130) are connected by the second prepreg (150).

9. The circuit board of claim 1, wherein: The long side length of the first mounting hole (101A) is 1 mil-2 mil less than the long side length of the heat dissipation block (200), and the short side length of the first mounting hole (101A) is 1 mil-2 mil less than the short side length of the heat dissipation block (200); The long side length of the second mounting hole (102A) is 1 mil-2 mil less than the long side length of the heat dissipation block (200), and the short side length of the second mounting hole (102A) is 1 mil-2 mil less than the short side length of the heat dissipation block (200).

10. The circuit board of claim 5, wherein: The flatness of the end surface of the heat dissipation block (200) relative to the surface of the first circuit layer (111) is less than 25 um.

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