PCB heat dissipation structure, manufacturing method thereof and PCB board comprising the same

Abstract

The application relates to a PCB heat dissipation structure, a manufacturing method thereof and a PCB board comprising the same. The PCB heat dissipation structure comprises a heat conduction layer (1) and a copper foil layer (2) covering two opposite surfaces of the heat conduction layer (1). The heat conduction layer (1) comprises a base (11) and a plurality of ceramic sheets (12) distributed in the base (11) at intervals. The base (11) is formed by an injection molding process. The PCB heat dissipation structure of the application distributes a plurality of ceramic sheets at intervals in the heat conduction layer base formed by the injection molding process, which improves the heat conduction efficiency and reduces the risk of delamination and cracks at the connection between the ceramic sheets and the copper foil layer due to the difference in the thermal expansion coefficient.

Description

Technical Field

[0001] This invention relates to the field of PCB (Printed Circuit Board) technology, and more specifically, to a PCB heat dissipation structure, a PCB board including the PCB heat dissipation structure, and a method for manufacturing the PCB heat dissipation structure. Background Technology

[0002] Applications involving high voltage, high current, and high power, such as electric vehicles and industrial equipment, place high demands on the heat dissipation performance of embedded / embedded PCB products. To quickly transfer heat from the heat source to heat dissipation devices outside the PCB, several methods have been developed based on the stacked structure of the PCB itself, such as embedding copper blocks within the substrate, using polymer-based high thermal conductivity materials or embedding ceramic materials in the insulating layer.

[0003] For embedding copper blocks within a substrate, the size of the copper blocks and their arrangement within the board are subject to significant limitations in terms of conventional HDI (High Density Interconnector) board layout and processing technology, which affects the heat flow path and increases the risk of cracks between the copper blocks and the substrate.

[0004] For common polymer-based high thermal conductivity materials suitable for PCB stacking, in order to ensure good peel strength and processability with copper foil, the content and ratio of inorganic thermally conductive fillers need to be balanced, resulting in a thermal conductivity that is generally between 6 and 15 W / mK. Moreover, the higher the thermal conductivity, the worse the processability and reliability.

[0005] In comparison, ceramic materials such as aluminum nitride ceramics and alumina ceramics have excellent thermal conductivity and insulation properties, and are widely used in power semiconductor product packaging. However, due to the significant difference in the coefficient of thermal expansion between ceramic materials and copper, cracks are prone to occur with long-term use. Furthermore, based on current processes, the bonding of large-sized ceramic sheets to PCB substrates presents reliability issues, such as a tendency for warping. Summary of the Invention

[0006] In view of the above background, the purpose of this invention is to provide a new PCB heat dissipation structure to optimize the heat dissipation and insulation of PCB boards.

[0007] To achieve the above objectives, according to one aspect of the present invention, a PCB heat dissipation structure is provided, comprising a thermally conductive layer and copper foil layers covering two opposing surfaces of the thermally conductive layer. The thermally conductive layer includes a base and a plurality of ceramic sheets spaced apart from each other within the base, the base being formed by an injection molding process.

[0008] According to one embodiment of the present invention, the ceramic sheet has a smooth outer peripheral surface.

[0009] According to one embodiment of the present invention, the ceramic sheet is a circular ceramic sheet.

[0010] According to one embodiment of the present invention, the ceramic sheet is coated with copper on both sides.

[0011] According to one embodiment of the present invention, the size of the ceramic sheet is no greater than 30*30mm.

[0012] According to one embodiment of the present invention, the ceramic sheet has an opening in the center, and the opening is filled with the material forming the base.

[0013] According to one embodiment of the present invention, the base is formed of a resin adhesive or a polymer-based thermally conductive material.

[0014] According to one embodiment of the present invention, the ceramic sheet is formed of aluminum nitride ceramic or aluminum oxide ceramic.

[0015] According to another aspect of the present invention, a PCB board is provided, the PCB board including the PCB heat dissipation structure as described above, and an insulating layer bonded to the side of at least one copper foil layer opposite to the heat-conducting layer.

[0016] According to one embodiment of the present invention, the insulating layer is formed of a prepreg and has mounting holes for mounting power devices.

[0017] According to another aspect of the present invention, a method for manufacturing a PCB heat dissipation structure is provided, the method comprising: placing a plurality of double-sided copper-clad ceramic sheets into a mold at intervals; injecting resin adhesive into the mold, the resin adhesive being cured to form a base of a thermally conductive layer; and forming copper foil layers on two opposite surfaces of the thermally conductive layer.

[0018] The PCB heat dissipation structure of this invention features multiple ceramic sheets spaced apart within a heat-conducting layer base formed by injection molding. Copper foil layers are then deposited on two opposing surfaces of the heat-conducting layer, effectively creating a CCL (Copper Clad Laminate) filled with multiple small ceramic sheets. These ceramic sheets form a three-dimensional, continuous, parallel heat flow network, improving thermal conductivity. Furthermore, the spacing between the ceramic sheets disperses thermal stress, reducing the risk of delamination and cracking at the junction of the ceramic sheets and copper foil layers due to differences in thermal expansion coefficients. Attached Figure Description

[0019] The features and advantages of the present invention will become clear from the following detailed description provided with reference to the accompanying drawings. It should be understood that the following drawings are merely schematic and not necessarily drawn to scale, and therefore should not be considered as limitations on the invention, wherein:

[0020] Figure 1 A perspective view of a PCB board according to an embodiment of the present invention is shown.

[0021] Figure 2 Show Figure 1 The diagram shown is an exploded view of the PCB board.

[0022] Figure 3 Show Figure 1 The PCB board shown is a partial cross-sectional view.

[0023] Explanation of reference numerals in the attached figures:

[0024] 1. Thermal conductive layer; 11. Base; 12. Ceramic sheet; 13. Gap; 14. Opening; 2. Copper foil layer; 3. Insulating layer; 31. Mounting hole; 4. Power device; 41. Thermal conductive pillar. Detailed Implementation

[0025] Embodiments of the present invention are described below with reference to the accompanying drawings. In the following description, numerous specific details are set forth to enable those skilled in the art to more fully understand and implement the invention. However, it will be apparent to those skilled in the art that implementation of the invention may not include some of these specific details. Furthermore, it should be understood that the invention is not limited to the specific embodiments described. Rather, the invention can be conceived to be practiced with any combination of the features and elements described below, regardless of whether they relate to different embodiments. Therefore, the following aspects, features, embodiments, and advantages are for illustrative purposes only and should not be construed as elements or limitations of the claims unless expressly set forth in the claims.

[0026] The terms “include” and “have” are used below to indicate an open-ended inclusion, meaning that there may be other elements / components besides those listed.

[0027] Figures 1 to 3 A PCB board according to an embodiment of the present invention is shown. In particular, as shown... Figure 2 As shown, the PCB board according to this embodiment includes a thermally conductive layer 1, a copper foil layer 2, an insulating layer 3, and a power device 4.

[0028] The thermally conductive layer 1 may include a base 11 and a plurality of ceramic sheets 12. The base 11 may be formed by an injection molding process. For example, resin may be injected into a mold in which the ceramic sheets 12 are placed, and the base 11 may be formed after the resin cures. The plurality of ceramic sheets 12 are distributed substantially uniformly in the base 11 thus formed. In this embodiment, the base 11 is substantially rectangular, and the plurality of ceramic sheets 12 are arranged in a matrix in the base 11. The base 11 may also be made of other conventional polymer-based thermally conductive materials that meet dielectric properties and have good flowability.

[0029] The dimensions of each ceramic tile 12 can be appropriately selected according to actual process requirements, usually not exceeding 30*30mm. "Dimensions not exceeding 30*30mm" means that the ceramic tile can be completely placed within a square area with sides of 30mm. (Continue to refer to...) Figure 2 As shown, there is a gap 13 between two adjacent ceramic sheets 12. By distributing multiple small ceramic sheets 12 at intervals within the base 11, thermal stress can be dispersed, thereby reducing the risk of delamination and cracking at the connection between the ceramic sheet 12 and the copper foil layer 2 due to the difference in thermal expansion coefficients between the ceramic material and copper.

[0030] To further balance the thermal stress difference, the ceramic sheet 12 in this embodiment has an opening 14 in its center, thus forming a ring shape. The inner diameter of the opening 14 should not be too small. During injection molding of the base 11, the opening 14 is filled with the material forming the base 11.

[0031] The ceramic sheet 12 can be made of materials such as aluminum nitride ceramics and alumina ceramics. Furthermore, the ceramic sheet 12 can be double-sided copper-plated using processes such as DPC (Direct Plated Copper), DBC (Direct Bonded Copper), and AMB (Active Metal Brazing). Such ceramic sheets are already commercially available and readily available on the market.

[0032] The ceramic sheet 12 may have a smooth outer peripheral surface, preferably circular, but it can also be elliptical or other curved. The smooth outer peripheral surface can prevent tip discharge of the ceramic sheet 12 after the copper foil layer 2 is etched.

[0033] Copper foil layer 2 can be formed on two opposing surfaces of thermally conductive layer 1 and cover these two opposing surfaces. The thickness of copper foil layer 2 can reach 18μm or more, typically 35μm, depending on product design requirements, to facilitate the etching of circuit patterns on copper foil layer 2.

[0034] The insulating layer 3 can be bonded to the side of at least one copper foil layer 2 facing away from the thermally conductive layer 1. The insulating layer 3 can be formed from a prepreg, i.e., PP (prepreg). The prepreg mainly consists of resin and reinforcing materials. The reinforcing materials are further divided into several types, such as fiberglass cloth, paper-based materials, and composite materials. For example, the prepreg can be made into a thin sheet material by impregnating treated fiberglass cloth with resin and then heat-treating (pre-baking). It will soften under heating and pressure and solidify after cooling, thereby forming the insulating layer 3. The insulating layer 3 can be bonded to the side of a copper foil layer 2 facing away from the thermally conductive layer 1 by compression bonding.

[0035] The insulating layer 3 may have multiple mounting holes 31 for mounting power devices 4. The shape of the mounting holes 31 matches the corresponding power device 4. For example, Figure 1 and Figure 2 The four power devices 4 shown have almost identical shapes and sizes and are arranged at equal intervals. Therefore, the four mounting holes 31 on the insulating layer 3 also have almost identical shapes and are arranged at equal intervals. In other embodiments, the power devices 4 may have different shapes and sizes, and may also be arranged irregularly on the insulating layer 3. Accordingly, mounting holes 31 of different shapes and sizes can be provided at any appropriate location on the insulating layer 3 according to actual needs to support and fix different power devices 4. The power devices 4 are heat sources in the PCB board, and they can be connected to the copper foil layer 2 through multiple heat-conducting pillars 41 to conduct the heat generated during their operation to the heat-conducting layer 1.

[0036] In the above embodiments, the thermally conductive layer 1 and the copper foil layers 2 on both sides constitute an example of the PCB heat dissipation structure of the present invention. The present invention also provides a method for manufacturing the above-described PCB heat dissipation structure. The method for manufacturing the PCB heat dissipation structure may include: placing a plurality of double-sided copper-clad ceramic sheets 12 spaced apart from each other in a mold; injecting resin adhesive into the mold, wherein the resin adhesive cures to form the base 11 of the thermally conductive layer 1; and forming copper foil layers 2 on the two opposite surfaces of the thermally conductive layer 1.

[0037] As is known to those skilled in the art, the mold may include a moving mold and a fixed mold, which are respectively mounted on a fixed template and a moving template of an injection molding machine. During injection molding, the moving mold moves toward the fixed mold to define a closed injection cavity between them. In this embodiment, the injection cavity is generally cuboid in shape, and its height corresponds to the thickness of the base 11 of the thermally conductive layer 1. A plurality of double-sided copper-clad ceramic sheets 12 are pre-arranged in the fixed mold. Liquid resin is injected into the injection cavity, filling the outer periphery of the plurality of ceramic sheets 12 and filling the opening 14 in the center of the ceramic sheets 12. After the resin cures to form a sheet, the moving mold is removed from the fixed mold, and the sheet containing the ceramic sheets 12 is removed from the mold.

[0038] After removing residual adhesive from the copper-clad area of ​​ceramic sheet 12, a copper layer is deposited on each of the two surfaces of the substrate. The copper plating layer needs to cover the entire surface area of ​​the substrate, including the original copper-clad area on ceramic sheet 12. Depending on the PCB product design requirements, electroplating can be further performed on the copper plating layer to meet the copper thickness requirements. Then, circuit patterns are etched onto the copper layer.

[0039] The resulting PCB heat dissipation structure is equivalent to creating a CCL filled with multiple discrete small ceramic sheets 12, which is very suitable for lamination with conventional PCB substrates. For example, the copper foil layer on one side of the thermally conductive layer 1 can be laminated together with the insulating layer 3, which is formed from a prepreg and has embedded power devices 4, to form a structure like... Figure 1 The PCB board shown.

[0040] Compared to drilling or slotting holes in a conventional PCB substrate and then embedding large-sized (e.g., larger than 50*50mm) ceramic sheets, in the PCB heat dissipation structure according to the present invention, multiple ceramic sheets 12 inside the heat-conducting layer 1 form a three-dimensional, continuous parallel heat flow network, which improves heat conduction efficiency. Furthermore, the multiple small-sized ceramic sheets 12 spaced apart from each other can disperse thermal stress, thereby reducing the risk of delamination and cracking at the connection between the ceramic sheet 12 and the copper foil layer 2 due to the difference in thermal expansion coefficients between the ceramic material and copper.

[0041] Various modifications and variations can be made to the embodiments disclosed above without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art based on the practice of the invention disclosed in this specification. This specification and the examples disclosed herein should be considered illustrative only, and the true scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A PCB heat dissipation structure, comprising: Thermal conductive layer (1); and Copper foil layers (2) covering the two opposite surfaces of the thermally conductive layer (1), The heat-conducting layer (1) includes a base (11) and a plurality of ceramic sheets (12) spaced apart from each other in the base (11), wherein the base (11) is formed by injection molding.

2. The PCB heat dissipation structure according to claim 1, characterized in that, The ceramic sheet (12) has a smooth outer peripheral surface.

3. The PCB heat dissipation structure according to claim 2, characterized in that, The ceramic sheet (12) is a circular ceramic sheet.

4. The PCB heat dissipation structure according to any one of claims 1 to 3, characterized in that, The ceramic sheet (12) is copper-clad on both sides.

5. The PCB heat dissipation structure according to any one of claims 1 to 3, characterized in that, The ceramic sheet (12) has a size of no more than 30*30mm.

6. The PCB heat dissipation structure according to any one of claims 1 to 3, characterized in that, The ceramic sheet (12) has an opening (14) in the center, and the opening (14) is filled with the material forming the base (11).

7. The PCB heat dissipation structure according to any one of claims 1 to 3, characterized in that, The base (11) is formed of resin glue or polymer-based thermally conductive material.

8. The PCB heat dissipation structure according to any one of claims 1 to 3, characterized in that, The ceramic sheet (12) is formed of aluminum nitride ceramic or aluminum oxide ceramic.

9. A PCB board, characterized in that, The PCB board includes a PCB heat dissipation structure according to any one of claims 1 to 7, and an insulating layer (3) bonded to the side of at least one copper foil layer (2) facing away from the heat-conducting layer (1).

10. The PCB board according to claim 9, characterized in that, The insulating layer (3) is formed of a prepreg and has a plurality of mounting holes (31) for mounting power devices (4).

11. A method for manufacturing a PCB heat dissipation structure according to any one of claims 1 to 8, characterized in that, The manufacturing method includes: Multiple double-sided copper-clad ceramic sheets (12) are placed in the mold at intervals; Resin glue is injected into the mold, and the resin glue is cured to form the base (11) of the thermally conductive layer (1); and Copper foil layers (2) are formed on the two opposite surfaces of the thermally conductive layer (1).

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