Printed circuit board and manufacturing process thereof

Abstract

This invention relates to the field of integrated circuit manufacturing technology, specifically to a printed circuit board and its manufacturing process. The board includes a base layer comprising a first substrate and a second substrate. The first substrate has an internal cavity, and the second substrate is fixedly disposed within the cavity. The lower surface of the second substrate has several channels, the inner surface of each channel being covered by a first copper layer. The upper surface of the second substrate has a circuit layer and multiple through-holes. Each through-hole extends downwards from the upper surface of the second substrate, with its bottom end located at the connection between two adjacent channels. Solid copper pillars are electroplated and filled within the through-holes. The two ends of the solid copper pillars are electrically and thermally connected to the circuit layer and the connection, respectively, to simultaneously conduct heat to the channels on both sides. The uniformly distributed solid copper pillars create an ultra-low thermal resistance vertical heat conduction path, efficiently conducting heat accumulated in the middle layer of the printed circuit board to the lower heat dissipation structure.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit manufacturing technology, and more specifically, to a printed circuit board and its manufacturing process. Background Technology

[0002] In packaging, the stacked structure of printed circuit boards is an effective way to achieve high-density electrical integration. However, the resulting thermal management issues, especially the heat dissipation of the printed circuit boards located in the middle layer of the stack, have become a core bottleneck restricting system performance and reliability.

[0003] First, from a materials perspective, widely used substrates, such as glass fiber reinforced epoxy resin FR-4, are inherently poor conductors of heat. Their extremely low thermal conductivity makes the substrate itself act as a heat insulation layer, unable to quickly diffuse the heat generated by the chip laterally, leading to a sharp rise in local temperature and the formation of dangerous overheated areas. Second, existing heat dissipation technologies heavily rely on passive heat conduction by filling the PCB board with interface materials such as thermal pads or gels. This method is not only inefficient due to the limited thermal conductivity of the materials themselves, but also introduces a large amount of contact thermal resistance because heat must pass through multiple interfaces of different materials. Ultimately, the heat accumulated in the intermediate layer cannot be efficiently conducted to the system's main heat sink. Therefore, existing technical solutions are limited by the inherent thermal insulation properties of the substrate and the inherent high resistance of the heat dissipation path, making it difficult to meet the stringent heat dissipation requirements of high-power-density 3D packaging. Thus, the root of the dilemma of existing technologies lies in their attempt to compensate for insufficient heat dissipation by adding external materials to a substrate that is essentially a heat insulation body—an improvement approach with inherent limitations.

[0004] Therefore, there is an urgent need for a printed circuit board and its manufacturing process to improve the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a printed circuit board and its manufacturing process, which constructs an ultra-low thermal resistance vertical heat conduction path by uniformly distributed solid copper pillars inside, efficiently conducting heat accumulated in the middle layer of the printed circuit board to the lower heat dissipation structure, thereby solving the problems mentioned in the background art, namely: In packaging, the stacked structure of printed circuit boards is an effective way to achieve high-density electrical integration. However, the resulting thermal management problems, especially the heat dissipation of the printed circuit boards located in the middle layer of the stack, are problematic. Because heat needs to pass through multiple interfaces of different materials, a large amount of contact thermal resistance is introduced, which ultimately makes it impossible for the heat accumulated in the middle layer to be efficiently dissipated to the system's main heat sink.

[0006] To achieve the above objectives, the present invention provides a printed circuit board, including a base layer, wherein the base layer includes a first substrate and a second substrate, the first substrate having a receiving cavity inside, and the second substrate being fixedly disposed within the receiving cavity; The lower surface of the second substrate is provided with a plurality of channels, and the inner surface of each channel is covered with a first copper layer; The upper surface of the second substrate is provided with a circuit layer and multiple through holes; the through holes penetrate downward from the upper surface of the second substrate, and their bottom ends are located at the connection between two adjacent channels; The through hole is filled with a solid copper pillar through electroplating. The two ends of the solid copper pillar are electrically and thermally connected to the circuit layer and the connection part, respectively, so as to conduct heat to the channels on both sides at the same time.

[0007] As a further improvement to this technical solution, the sidewall of the first substrate is provided with convection holes corresponding to the end of the channel, for forming a cooling airflow through the channel.

[0008] As a further improvement to this technical solution, the second substrate is provided with fixing holes at its four corners, and bolts pass through the fixing holes to lock the second substrate into the receiving cavity of the first substrate; the head of the bolt is recessed into the circuit layer, and its top is not higher than the upper surface of the circuit layer.

[0009] As a further improvement to this technical solution, the cross-section of the channel is semi-circular and arranged parallel to the width direction of the second substrate; the thickness of the circuit layer is greater than the thickness of the first substrate, so that the upper surface of the circuit layer protrudes from the upper surface of the first substrate; the solid copper pillars are evenly distributed on the upper surface of the second substrate.

[0010] As a further improvement to this technical solution, a solder resist layer is provided on the upper surface of the circuit layer.

[0011] The second objective of this invention is to provide a manufacturing process for a printed circuit board, comprising the following steps: S1. The insulation layer on the surface of the second substrate of the aluminum-based composite insulation board is cleaned and roughened to enhance adhesion. S2. Using CNC milling, multiple semi-circular channels are precisely machined on the lower surface of the second substrate. This process removes the insulating layer in some areas and exposes the aluminum base. Subsequently, using drilling, through holes are uniformly machined at the top of the connection between two adjacent channels, extending to the connection. S3. A continuous metal seed layer is deposited on the entire surface of the second substrate using a chemical copper plating process. S4. Patterning and Electroplating Filling: Electroplating copper is performed on the upper surface of the second substrate to thicken the exposed seed layer to form a circuit layer, and the vias are simultaneously filled with copper to form a solid copper pillar. S5. Remove the photoresist, perform surface anti-oxidation treatment on the circuit layer, and process mounting holes; S6. Place the processed second substrate into the receiving cavity of the first substrate, and use bolts to lock and fix the two together through the fixing holes to complete the preparation of the composite substrate. Compared with the prior art, the beneficial effects of the present invention are as follows: This printed circuit board and its manufacturing process utilize an aluminum-based composite insulating board as the core substrate. A vertical heat conduction path with ultra-low thermal resistance is constructed through uniformly distributed solid copper pillars, efficiently transferring heat accumulated in the middle layer of the printed circuit board to the lower heat dissipation structure. Simultaneously, heat exchange occurs between the copper-covered inner walls of the flow channels and forced convection air, achieving rapid heat transfer through optimized air cooling. This overcomes the limitations of traditional passive heat dissipation relying on thermal pads, significantly reducing chip junction temperature and middle layer operating temperature, greatly improving system performance and operational stability. Furthermore, the integrated structure effectively avoids the thermomechanical mismatch risks associated with assembling heterogeneous materials. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the overall structure of the embodiment; Figure 2 This is a schematic diagram of the overall side structure of the embodiment; Figure 3 This is a schematic diagram of the second substrate structure in the embodiment; Figure 4 This is a schematic diagram of the first substrate structure in an embodiment.

[0013] The meanings of the various markings in the diagram are as follows: 100. Base layer; 110. First substrate; 111. Convection hole; 120. Second substrate; 121. Channel; 122. First copper layer; 123. Through hole; 124. Connecting part; 200, Circuit layer; 210, Copper pillar; 220, Mounting hole; 300. Solder resist layer. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] Example 1: Currently, in packaging, the stacked structure of printed circuit boards is an effective way to achieve high-density electrical integration. However, the accompanying thermal management problem, especially the heat dissipation of the printed circuit board located in the middle layer of the stack, is a challenge. Because heat needs to pass through multiple interfaces of different materials, a large amount of contact thermal resistance is introduced, which ultimately makes it impossible for the heat accumulated in the middle layer to be efficiently dissipated to the main heat sink of the system.

[0016] Please see Figures 1-4 As shown, this embodiment provides a printed circuit board, including a base layer 100. The base layer 100 includes a first substrate 110 and a second substrate 120. The first substrate 110 has a receiving cavity inside, and the second substrate 120 is fixedly disposed in the receiving cavity. The lower surface of the second substrate 120 is provided with a plurality of channels 121, and the inner surface of each channel 121 is covered with a first copper layer 122. The upper surface of the second substrate 120 is provided with a circuit layer 200 and a plurality of through holes 123; the through holes 123 penetrate downward from the upper surface of the second substrate 120, and their bottom ends are located at the connection portion 124 between two adjacent channels 121. The through hole 123 is filled with a solid copper pillar 210 by electroplating. The two ends of the solid copper pillar 210 are electrically and thermally connected to the circuit layer 200 and the connection part 124, respectively, so as to conduct heat to the channels 121 on both sides at the same time.

[0017] When high-power components operate on the upper surface of circuit layer 200, the generated heat is first transferred to circuit layer 200. Subsequently, the heat is conducted vertically downwards through uniformly distributed solid copper pillars 210 with extremely low thermal resistance. Since the bottom of the copper pillars 210 is precisely located at the connection portion 124 between two adjacent channels 121, the heat is efficiently diverted and simultaneously introduced into the inner copper layer of the two side channels 121. The inherent high thermal conductivity of the aluminum-based composite insulating board allows heat to diffuse rapidly along the axial direction of the channel 121, avoiding the formation of local hot spots. At the same time, cooling airflow flows in from the convection hole 111 at the front end of the first substrate 110 under external power. When flowing through the inner cavity of the channel 121, it undergoes forced convection heat exchange with the heated inner wall of the copper channel 121, continuously carrying away the heat, and finally discharged from the rear convection hole 111, thereby achieving active and efficient heat dissipation of the intermediate layer printed circuit board.

[0018] See Figure 1-2As shown, when the system fan starts, the cooling airflow is forcibly introduced through the convection holes 111 on the side wall of the first substrate 110, forming a continuous airflow path that runs through all channels 121. This airflow directly contacts the copper layer covering the inner surface of the channel 121, continuously removing heat from the copper layer through convection heat transfer. Simultaneously, the second substrate 120 is securely bolted into the receiving cavity of the first substrate 110 through the fixing holes 220 at its four corners. This rigid connection not only ensures structural stability but, more importantly, guarantees precise alignment between the channel 121 and the convection holes 111, thus maintaining the integrity and sealing of the airflow path. The preload generated by the bolt locking also ensures a tight fit between the first substrate 110 and the second substrate 120, effectively preventing airflow leakage and poor thermal interface contact. Throughout the heat dissipation process, the synergistic effect of forced convection and mechanical fixing constructs a stable and reliable heat removal system, achieving efficient heat transfer from the circuit layer 200 to the cooling airflow.

[0019] During assembly, when the bolt passes through the fixing hole 220 of the second substrate 120 and is screwed into the first substrate 110, its head is completely accommodated within the pre-machined countersunk hole of the circuit layer 200. This countersunk mounting ensures that the top surface of the bolt is flush with or slightly lower than the upper surface of the circuit layer 200, thus providing a completely flat assembly base for subsequent surface mount processes. Specifically, this is reflected in the following ways: First, the flat surface allows the mounting equipment to accurately position and mount components on the circuit layer 200, avoiding component positioning deviations or cold solder joints caused by bolt protrusions; second, this design allows heat sinks or other package housings to achieve full-plane tight contact with the circuit layer 200, effectively improving auxiliary heat dissipation efficiency; at the same time, the countersunk bolt head maintains the continuity of wiring on the circuit layer 200, avoiding wiring detours caused by avoiding bolt protrusions, ensuring the integrity of high-frequency signal transmission. This structure, through precise mechanical fit, ensures the structural fixation reliability while maximizing the functional integrity of the circuit layer 200 and the convenience of subsequent assembly.

[0020] Additionally, see Figure 3-4 As shown, the printed circuit board in this embodiment achieves optimized heat dissipation and operating performance through a special structural design. Its channel 121 adopts a semi-circular cross-section and is arranged parallel to the width direction of the second substrate 120. The semi-circular cross-section provides the maximum perimeter-to-area ratio, significantly increasing the heat dissipation surface area, while simultaneously forming a smooth flow channel profile. This effectively reduces the flow resistance of the cooling airflow, allowing air to pass smoothly and fully contact the copper layer on the surface of the channel 121, maximizing convective heat transfer efficiency. The parallel arrangement ensures uniform heat dissipation and avoids the formation of localized hot spots.

[0021] Meanwhile, the circuit layer 200 is thicker than the first substrate 110, and its upper surface protrudes from the upper surface of the first substrate 110. This protruding circuit layer 200 provides surface-mounted electronic components with greater heat capacity and better lateral heat dissipation capabilities, enabling it to quickly guide the heat generated by the components to the solid copper pillar 210 below. More importantly, this protruding structure allows the circuit layer 200 to directly contact other heat dissipation components or adjacent circuit boards, establishing additional effective heat dissipation paths and further enhancing the overall heat dissipation effect. The synergistic effect of these two features constructs a highly efficient multi-path heat dissipation system that ensures basic structural functions while significantly improving heat dissipation performance.

[0022] When the electronic components on circuit layer 200 are operating, the generated heat is first conducted to the surface of circuit layer 200. Because the solid copper pillars 210 are evenly distributed in an array on the upper surface, regardless of the location of the heat source on circuit layer 200, there are sufficient copper pillars 210 below to receive and conduct heat in a timely manner. This uniform layout establishes a high-density heat conduction channel 121 covering the entire circuit area, effectively avoiding the local heat accumulation phenomenon caused by uneven distribution of heat conduction paths in traditional heat dissipation structures. Each copper pillar 210 serves as an independent, high-efficiency heat conduction channel 121, synchronously conducting the received heat downwards in parallel to the cooling channel 121 at the bottom, significantly increasing the total heat conduction cross-sectional area and greatly reducing the overall thermal resistance of the system. This ensures that the heat generated by the point heat source can be quickly dispersed into multiple heat conduction paths, and then continuously removed through forced convection heat transfer on the inner wall of the channel 121, thereby achieving comprehensive, rapid, and balanced temperature control of circuit layer 200 and providing reliable heat dissipation for high-power-density electronic components.

[0023] Both the first substrate 110 and the second substrate 120 are made of aluminum-based composite insulation board. The core advantage of the aluminum-based composite insulation board lies in its unique three-layer structure: the middle aluminum substrate provides an excellent heat conduction channel 121, and its high thermal conductivity ensures that heat can be rapidly diffused in the planar direction; the insulating layers on the upper and lower surfaces provide the necessary electrical isolation performance, allowing the circuit to be safely fabricated on the substrate surface. This material combination makes the entire base layer 100 not only a structural support but also a highly efficient heat carrier.

[0024] During operation, the solder mask layer 300 on the upper surface of circuit layer 200 precisely covers the non-soldered areas, effectively preventing short circuits between circuit traces and providing excellent insulation. More importantly, the solder mask layer 300 blocks moisture and contaminants in the air, significantly improving the long-term reliability of the circuit board. Meanwhile, the aluminum substrate, with its excellent thermal conductivity, quickly conducts any potential localized heat to the surrounding area, preventing heat concentration zones; and the insulating layer ensures that even under high-power operation, there will be no current leakage or breakdown. This perfect combination of materials and structure ensures both stable electrical performance and effective thermal management, providing an ideal working environment for electronic components.

[0025] Example 2: This example, based on the content provided in Example 1, aims to provide a manufacturing process for a printed circuit board, including the following steps: S1. The insulation layer on the surface of the second substrate 120 of the aluminum-based composite insulation board is cleaned and roughened to enhance adhesion. S2. Multiple semi-circular channels 121 are precisely machined on the lower surface of the second substrate 120 using CNC milling. This process removes the insulating layer in a local area and exposes the aluminum base. Subsequently, through holes 123 are uniformly machined on the top of the connection 124 between two adjacent channels 121 using drilling. S3. A continuous metal seed layer is deposited on the entire surface of the second substrate 120 by a chemical copper plating process. S4. Patterning and electroplating: Electroplating copper is performed on the upper surface of the second substrate 120 to thicken the exposed seed layer to form a circuit layer 200, and the through hole 123 is completely filled with copper to form a solid copper pillar 210. S5. Remove the photoresist, perform surface anti-oxidation treatment on the circuit layer 200, and process the fixing hole 220; S6. Place the processed second substrate 120 into the receiving cavity of the first substrate 110, and use bolts to pass through the fixing hole 220 to lock and fix the two together, thus completing the preparation of the composite substrate. The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A printed circuit board, comprising a substrate (100), characterized in that: The base layer (100) includes a first substrate (110) and a second substrate (120). The first substrate (110) has a cavity inside, and the second substrate (120) is fixedly disposed in the cavity. The lower surface of the second substrate (120) is provided with a plurality of channels (121), and the inner surface of each channel (121) is covered with a first copper layer (122). The upper surface of the second substrate (120) is provided with a circuit layer (200) and a plurality of through holes (123); the through holes (123) penetrate downward from the upper surface of the second substrate (120), and their bottom ends are located at the connection part (124) between two adjacent channels (121). The through hole (123) is filled with a solid copper pillar (210) by electroplating. The two ends of the solid copper pillar (210) are electrically and thermally connected to the circuit layer (200) and the connection part (124) respectively, so as to conduct heat to the channels (121) on both sides at the same time.

2. The printed circuit board according to claim 1, characterized in that: The sidewall of the first substrate (110) is provided with convection holes (111) at the end of the channel (121) to form a cooling airflow through the channel (121).

3. The printed circuit board according to claim 1, characterized in that: The second substrate (120) has fixing holes (220) at its four corners. Bolts pass through the fixing holes (220) to lock the second substrate (120) into the receiving cavity of the first substrate (110).

4. The printed circuit board according to claim 3, characterized in that: The head of the bolt is recessed into the circuit layer (200), and its top is not higher than the upper surface of the circuit layer (200).

5. The printed circuit board according to claim 1, characterized in that: The channel (121) has a semi-circular cross-section and is arranged parallel to the width direction of the second substrate (120).

6. The printed circuit board according to claim 1, characterized in that: The thickness of the circuit layer (200) is greater than the thickness of the first substrate (110), such that the upper surface of the circuit layer (200) protrudes from the upper surface of the first substrate (110).

7. The printed circuit board according to claim 1, characterized in that: The solid copper pillars (210) are uniformly distributed on the upper surface of the second substrate (120).

8. The printed circuit board according to claim 1, characterized in that: Both the first substrate (110) and the second substrate (120) are aluminum-based composite insulation boards.

9. The printed circuit board according to claim 1, characterized in that: The upper surface of the circuit layer (200) is provided with a solder resist layer (300).

10. A manufacturing process for a printed circuit board according to any one of claims 1-9, characterized in that, Includes the following steps: S1. The insulation layer on the surface of the second substrate (120) of the aluminum-based composite insulation board is cleaned and roughened to enhance adhesion; S2. Multiple semi-circular channels (121) are precisely machined on the lower surface of the second substrate (120) by CNC milling process. This process will remove the insulating layer in a local area and expose the aluminum base. Subsequently, through holes (123) are uniformly machined on the top of the connection (124) between two adjacent channels (121) by drilling process. S3. A continuous metal seed layer is deposited on the entire surface of the second substrate (120) by a chemical copper plating process. S4. Patterning and electroplating filling: Electroplating copper is performed on the upper surface of the second substrate (120) to thicken the exposed seed layer to form a circuit layer (200), and the through hole (123) is completely filled with copper to form a solid copper pillar (210). S5. Remove the photoresist, perform surface anti-oxidation treatment on the circuit layer (200), and process the fixing holes (220). S6. Place the processed second substrate (120) into the receiving cavity of the first substrate (110), and use bolts to pass through the fixing hole (220) to lock and fix the two together, thus completing the preparation of the composite substrate.

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