Thick copper wiring board

Abstract

The application relates to the technical field of circuit boards, in particular to a thick copper circuit board. The thick copper circuit board comprises a first outer copper foil layer, a second outer copper foil layer, an outer dielectric layer and an inner layer structure; the inner layer structure is stacked between the first outer copper foil layer and the second outer copper foil layer; any one of the first outer copper foil layer and the second outer copper foil layer is laminated with the outer dielectric layer between the inner layer structure, and the outer dielectric layer comprises two laminated semi-cured sheets, and the semi-cured sheet has a high RC value. The thick copper circuit board not only does not have any negative influence on the performance of the dielectric layer, the structural strength and the glue filling performance, but also significantly reduces the thickness of the outer dielectric layer, reduces the thermal resistance value of the outer dielectric layer, thereby significantly improves the heat dissipation performance and avoids the problem of board burning caused by poor heat dissipation.

Description

Technical Field

[0001] This application relates to the field of circuit board technology, and in particular to a thick copper circuit board. Background Technology

[0002] In related technologies, circuit boards that include a copper foil layer with a thickness of not less than 2 oz are generally referred to as thick copper circuit boards. Thick copper circuit boards can withstand larger currents, have better heat dissipation performance, and also have greater mechanical strength, making them widely used in high-power applications such as power supply systems and power electronic equipment.

[0003] Thick copper coil circuit boards are a typical type of thick copper circuit board, consisting of relatively thick copper coils. The coil design has inductance requirements, thus imposing strict requirements on the thickness of both the outer and inner copper foil layers. There are also strict requirements on the thickness of the dielectric layer between the copper foil layers. Currently, the frequent product defects in these thick copper circuit boards are mainly due to the dielectric layer thickness far exceeding the theoretical thickness, and poor heat dissipation leading to board burn-out during thermal shock aging tests.

[0004] Therefore, there is an urgent need to develop a new type of thick copper circuit board to solve the problems of excessive dielectric layer thickness and poor heat dissipation leading to board burnout. Utility Model Content

[0005] The purpose of this application is to provide a thick copper circuit board, which can solve to some extent the technical problems of excessive dielectric layer thickness and poor heat dissipation causing the board to burn out in the prior art.

[0006] This application provides a thick copper circuit board, including a first outer copper foil layer, a second outer copper foil layer, an outer dielectric layer, and an inner layer structure; The inner layer structure is stacked between the first outer copper foil layer and the second outer copper foil layer; Either the first outer copper foil layer or the second outer copper foil layer is laminated with the outer dielectric layer between itself and the inner layer structure. The outer dielectric layer comprises two laminated prepreg layers, and the prepregs have a high RC value.

[0007] In the above technical solution, the inner layer structure further includes no less than four layers of inner copper foil stacked sequentially, and an inner dielectric layer and a core board laminated between adjacent inner copper foil layers. The number of layers in the inner dielectric layer is not less than the number of layers in the core plate.

[0008] In any of the above technical solutions, the inner layer structure further includes a first inner copper foil layer, a first inner dielectric layer, a second inner copper foil layer, a core board, a third inner copper foil layer, a second inner dielectric layer, and a fourth inner copper foil layer laminated sequentially. The outer dielectric layer is laminated between the first inner copper foil layer and the first outer copper foil layer, and the outer dielectric layer is laminated between the fourth inner copper foil layer and the second outer copper foil layer; Each of the first inner dielectric layer and the second inner dielectric layer comprises two laminated layers of the prepreg.

[0009] In any of the above technical solutions, the inner layer structure is further provided with blind holes, which sequentially penetrate the first inner copper foil layer, the first inner dielectric layer, the second inner copper foil layer, the core board, the third inner copper foil layer, and the second inner dielectric layer.

[0010] In any of the above technical solutions, the core board further comprises three laminated sub-core boards.

[0011] In any of the above technical solutions, the thickness of each sub-core board is further 0.127 mm.

[0012] In any of the above technical solutions, the thickness of the first inner copper foil layer, the second inner copper foil layer, the third inner copper foil layer, and the fourth inner copper foil layer is 3 oz.

[0013] In any of the above technical solutions, the thickness of both the first outer copper foil layer and the second outer copper foil layer is 1 oz.

[0014] In any of the above technical solutions, the RC value of the prepreg is further 71%.

[0015] In any of the above technical solutions, the prepreg is further described as PP of type 1080.

[0016] Compared with the prior art, the beneficial effects of this application are as follows: The thick copper circuit board provided in this application includes a first outer copper foil layer, a second outer copper foil layer, an outer dielectric layer, and an inner layer structure. The outer dielectric layer is laminated between either the first or second outer copper foil layer and the inner layer structure. The outer dielectric layer comprises two laminated prepreg layers with a high RC value, meaning the RC value of the prepreg is not less than 70%. This thick copper circuit board not only does not negatively affect the dielectric layer performance, structural strength, or filler performance, but also significantly reduces the thickness of the outer dielectric layer, resulting in a lower thermal resistance and significantly improved heat dissipation performance, thus preventing board burn-out due to poor heat dissipation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 Metallographic micrograph of a cross section of a thick copper circuit board in related technologies; Figure 2 This is a schematic diagram of the structure of a thick copper circuit board provided in an embodiment of this application; Figure 3 Metallographic micrograph of a cross section of a thick copper circuit board provided in an embodiment of this application; Figure 4 Metallographic micrograph of a thick copper circuit board at a blind via provided in an embodiment of this application; Figure 5 The first metallographic micrograph of a thick copper circuit board provided in this embodiment of the application after a thermal shock test; Figure 6 The second metallographic micrograph of the thick copper circuit board provided in the embodiment of this application after thermal shock testing.

[0019] Figure label: 1-Thick copper circuit board; 10-First outer copper foil layer; 11-First outer dielectric layer; 12-First inner copper foil layer; 13-First inner dielectric layer; 14-Second inner copper foil layer; 15-Core board; 16-Third inner copper foil layer; 17-Second inner dielectric layer; 18-Fourth inner copper foil layer; 19-Second outer dielectric layer; 20-Second outer copper foil layer; 21-Blind via; 22-Through via. Detailed Implementation

[0020] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0021] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0023] In related technologies, the dielectric layer thickness between the outer and inner copper foil layers of thick copper circuit boards is significantly excessive, and poor heat dissipation easily leads to board burn-out. To analyze the causes of the aforementioned problems, a traditional thick copper circuit board was sliced, and the resulting slices were subjected to metallographic microscopy analysis.

[0024] Metallographic micrographs as follows Figure 1 As shown in the image, the dark areas represent non-metallic dielectric layers or other structures, while the light areas represent the conductive structure of metallic copper foil. In the image, the uppermost and lowermost dielectric layers of a traditional thick copper circuit board represent the excessively thick dielectric layer between the outer and inner copper foil layers, reaching a thickness of 0.18 mm, significantly exceeding the 0.1-0.15 mm thickness requirement. Since the same dielectric material has the same thermal conductivity, increasing the dielectric layer thickness leads to an increase in thermal resistance. Consequently, under the same thermal shock test conditions or actual heat dissipation, the surface temperature of this excessively thick copper circuit board is significantly higher, leading to poor heat dissipation and board burn-out problems.

[0025] To address the issues of excessive dielectric layer thickness and poor heat dissipation leading to board burnout in thick copper circuit boards, embodiments of this application provide a thick copper circuit board.

[0026] See Figure 2 As shown, the thick copper circuit board 1 provided in this embodiment includes a first outer copper foil layer 10, a second outer copper foil layer 20, and an inner layer structure.

[0027] The inner layer structure is stacked between the first outer copper foil layer 10 and the second outer copper foil layer 20. Each of the two outer copper foil layers, 10 and 20, has an outer dielectric layer laminated between it and the inner layer structure. Specifically, the outer dielectric layer laminated between the first outer copper foil layer 10 and the inner layer structure can be designated as the first outer dielectric layer 11, and the outer dielectric layer laminated between the second outer copper foil layer 20 and the inner layer structure can be designated as the second outer dielectric layer 19.

[0028] The outer dielectric layer comprises two laminated semi-cured sheets, that is, both the first outer dielectric layer 11 and the second outer dielectric layer 19 comprise two laminated semi-cured sheets, and the semi-cured sheets have a high RC value.

[0029] The RC value represents the weight percentage of resin in the prepreg; a higher RC value indicates a higher resin content. A prepreg with an RC value less than 60% is generally considered to have a low RC value; a prepreg with an RC value between 60% and 70% is generally considered to have a medium RC value; and a prepreg with an RC value of 70% or more is generally considered to have a high RC value.

[0030] In other words, the thick copper circuit board 1 provided in this embodiment includes two laminated prepregs with an RC value of not less than 70% as the outer dielectric layer. Compared with the technology that uses three or more prepregs with medium or low RC values, the laminated structure of the thick copper circuit board 1 not only does not have any negative impact on the dielectric layer performance, structural strength, and filler performance, but also significantly reduces the thickness of the outer dielectric layer, thereby reducing the thermal resistance of the outer dielectric layer and significantly improving heat dissipation performance, thus avoiding board burn-out problems caused by poor heat dissipation.

[0031] It is understandable that the selection of prepreg materials from existing known materials can be made and applied to the laminated structure of the outer dielectric layer, without involving any improvement to the prepreg material itself.

[0032] Optionally, the prepreg can be PP of type 1080.

[0033] Optionally, the RC value of the prepreg is not less than 71%, for example, the RC value of the prepreg can be 71%. It is understood that there are already 1080 type PP materials in the existing materials that can meet the RC value of 71%, and they can be selected directly.

[0034] In an optional embodiment, the thickness of both the first outer copper foil layer 10 and the second outer copper foil layer 20 is 1 oz to meet the electrical performance requirements of the thick copper circuit board 1. It is worth noting that oz (ounce) is a unit of weight. In the PCB industry, 1 oz is typically used to represent the thickness achieved by uniformly spreading 1 oz of copper across an area of ​​1 square foot. The thickness of 1 oz copper foil is approximately 35 micrometers.

[0035] In an optional embodiment, the inner layer structure includes at least four layers of inner copper foil stacked sequentially, an inner dielectric layer laminated between adjacent inner copper foil layers, and a core board 15.

[0036] The number of inner dielectric layers is not less than the number of core board 15 layers. Typically, the thickness of core board 15 is much greater than the thickness of the inner or outer dielectric layers. While ensuring that the number of core board 15 layers is sufficient to provide the required support, minimizing the number of core board 15 layers helps reduce the total thermal resistance of core board 15, thereby reducing the overall total thermal resistance of the thick copper circuit board 1. This improves the heat dissipation performance of the inner layer structure, preventing poor heat dissipation and ultimately enhancing the heat dissipation performance of the thick copper circuit board 1. Furthermore, reducing the amount of core board 15 used also helps control and optimize production costs.

[0037] In the optional solutions of this embodiment, such as Figure 2 As shown, the inner layer structure includes a first inner copper foil layer 12, a first inner dielectric layer 13, a second inner copper foil layer 14, a core board 15, a third inner copper foil layer 16, a second inner dielectric layer 17, and a fourth inner copper foil layer 18, which are laminated sequentially.

[0038] A first outer dielectric layer 11 is laminated between the first inner copper foil layer 12 and the first outer copper foil layer 10, and a second outer dielectric layer 19 is laminated between the fourth inner copper foil layer 18 and the second outer copper foil layer 20. That is, the first inner copper foil layer 12 faces the first outer copper foil layer 10, and the fourth inner copper foil layer 18 faces the second outer copper foil layer 20.

[0039] As can be seen, the inner layer structure includes two inner dielectric layers, namely the first inner dielectric layer 13 and the second inner dielectric layer 17, and a core plate 15. Thus, the number of inner dielectric layers is two, which is greater than the number of core plate 15 layers. This satisfies the principle of configuring the number of core plate 15 layers as small as possible, which is beneficial to improving heat dissipation performance.

[0040] Each of the first inner dielectric layer 13 and the second inner dielectric layer 17 comprises two laminated prepreg layers, similar to the structure of the outer dielectric layer. By configuring the inner dielectric layer to include two laminated prepreg layers with an RC value of not less than 70%, not only is there no negative impact on the dielectric layer performance, structural strength, and filler performance of the thick copper circuit board 1, but the thickness of the inner dielectric layer is also significantly reduced, resulting in a smaller thermal resistance value of the inner layer structure. This significantly improves the heat dissipation performance of the thick copper circuit board 1 and avoids board burn-out problems caused by poor heat dissipation.

[0041] In this optional embodiment, the thicknesses of the first inner copper foil layer 12, the second inner copper foil layer 14, the third inner copper foil layer 16, and the fourth inner copper foil layer 18 are all 3 oz. To meet the requirements for inductance and other electrical performance, the thicknesses of the inner copper foil layers in the inner structure are configured, and the thicknesses of the first outer copper foil layer 10 and the second outer copper foil layer 20 are configured accordingly. As mentioned above, correspondingly, the thicknesses of the first outer copper foil layer 10 and the second outer copper foil layer 20 can both be 1 oz.

[0042] In an optional embodiment, the inner layer structure is provided with a blind via 21. The blind via 21 sequentially penetrates the first inner copper foil layer 12, the first inner dielectric layer 13, the second inner copper foil layer 14, the core board 15, the third inner copper foil layer 16, and the second inner dielectric layer 17. That is, the blind via 21 penetrates all the stacked layers of the inner layer structure except for the fourth inner copper foil layer 18, in order to meet the relevant inductance and other performance requirements.

[0043] Optionally, the thick copper circuit board 1 is provided with a through hole 22, which extends from the first outer copper foil layer 10 to the second outer copper foil layer 20. That is, the through hole 22 penetrates all the stacked structures of the thick copper circuit board 1.

[0044] In an optional embodiment, the core board 15 includes three laminated sub-core boards 15, thereby ensuring that the thickness of the core board 15 is sufficient to provide the required support through the stacking of the sub-core boards 15. Further, the thickness of each sub-core board 15 is 0.127 mm.

[0045] To verify the structural improvement effect of the thick copper circuit board 1 provided in this application, the thick copper circuit board 1 was sliced, and the slices were subjected to metallographic microscopy analysis. The thick copper circuit board 1 includes a first outer copper foil layer 10, a first outer dielectric layer 11, a first inner copper foil layer 12, a first inner dielectric layer 13, a second inner copper foil layer 14, a core board 15, a third inner copper foil layer 16, a second inner dielectric layer 17, a fourth inner copper foil layer 18, a second outer dielectric layer 19, and a second outer dielectric layer 10. The copper foil layer 20 has a copper thickness of 1 oz for both the first outer copper foil layer 10 and the second outer copper foil layer 20. The copper thickness of the first inner copper foil layer 12, the second inner copper foil layer 14, the third inner copper foil layer 16, and the fourth inner copper foil layer 18 is 3 oz. The core board 15 comprises three laminated sub-core boards 15 with a thickness of 0.127 mm. The first outer dielectric layer 11, the second outer dielectric layer 19, the first inner dielectric layer 13, and the second inner dielectric layer 17 each comprise two laminated layers of RC71% prepreg. The ideal dimensional requirements for the thick copper circuit board 1 are that the thickness of the dielectric layers (outer dielectric layer and inner dielectric layer) is 0.1-0.15 mm, and the copper foil thickness at the blind via 21 is not less than 25 micrometers.

[0046] Metallographic microscopy analysis results are as follows Figure 3 and Figure 4 As shown, where: like Figure 3 As shown, the thickness of the first outer dielectric layer 11 (the dark shadow structure adjacent to the light-colored bright area structure at the top of the figure) is 0.117 mm, the actual thickness of the first inner dielectric layer 13 (the dark shadow structure below the first outer dielectric layer 11) is 0.119 mm, the actual thickness of the second inner dielectric layer 17 (the dark shadow structure above the second outer dielectric layer 19) is 0.117 mm, and the actual thickness of the second outer dielectric layer 19 (the dark shadow structure adjacent to the light-colored bright area structure at the bottom of the figure) is 0.119 mm. Clearly, the actual thickness of all dielectric layers meets the requirement of 0.1-0.15 mm.

[0047] like Figure 4 As shown, the actual thickness of the first inner copper foil layer 12 (the second light-colored bright part structure from top to bottom in the figure), the second inner copper foil layer 14 (the third light-colored bright part structure from top to bottom in the figure), and the third inner copper foil layer 16 (the fourth light-colored bright part structure from top to bottom in the figure) is 0.0308mm, which meets the requirement that the copper foil layer thickness at the blind hole 21 is not less than 25 micrometers.

[0048] The thick copper circuit board 1 was subjected to eight repeated thermal shocks at 288℃ for 10 seconds. Then, the thick copper circuit board 1 was sliced ​​at different locations to obtain the following results: Figure 5 and Figure 6 The metallographic microscope image shown shows that the laminated structure has no thin plates, voids, missing adhesive, or cracks. The thermal shock test was passed, which proves that the heat dissipation performance of the thick copper circuit board 1 is significantly improved compared to the traditional thick copper circuit board 1. It has good heat dissipation and will not cause the board to burn out.

[0049] Furthermore, metallographic microscopy analysis was performed on 24 of the thick copper circuit boards 1. The total thickness of the thick copper circuit boards 1 at the first to fourth test points for serial numbers 1 to 24 is statistically analyzed as shown in Table 1 below. It can be seen that the total thickness of the thick copper circuit boards 1 meets the requirement of not exceeding 1.2 mm. Therefore, the stacked structure configuration of the thick copper circuit board 1 is also beneficial for optimizing the overall board thickness.

[0050] Table 1

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model. In addition, those skilled in the art can understand that although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments means that they are within the scope of this utility model and form different embodiments. For example, any one of the claimed embodiments can be used in any combination. The information disclosed in this background section is only intended to deepen the understanding of the overall background technology of this utility model, and should not be regarded as an admission or in any form implying that the information constitutes prior art known to those skilled in the art.

Claims

1. A thick copper circuit board, characterized in that, It includes a first outer copper foil layer, a second outer copper foil layer, an outer dielectric layer, and an inner layer structure; The inner layer structure is stacked between the first outer copper foil layer and the second outer copper foil layer; Either the first outer copper foil layer or the second outer copper foil layer is laminated with the outer dielectric layer between itself and the inner layer structure. The outer dielectric layer comprises two laminated prepreg layers, and the prepregs have a high RC value.

2. The thick copper circuit board according to claim 1, characterized in that, The inner layer structure includes at least four layers of inner copper foil stacked sequentially, an inner dielectric layer and a core board laminated between adjacent inner copper foil layers; The number of layers in the inner dielectric layer is not less than the number of layers in the core plate.

3. The thick copper circuit board according to claim 1, characterized in that, The inner layer structure includes a first inner copper foil layer, a first inner dielectric layer, a second inner copper foil layer, a core board, a third inner copper foil layer, a second inner dielectric layer, and a fourth inner copper foil layer, laminated sequentially. The outer dielectric layer is laminated between the first inner copper foil layer and the first outer copper foil layer, and the outer dielectric layer is laminated between the fourth inner copper foil layer and the second outer copper foil layer; Each of the first inner dielectric layer and the second inner dielectric layer comprises two laminated layers of the prepreg.

4. The thick copper circuit board according to claim 3, characterized in that, The inner layer structure is provided with blind vias, which sequentially penetrate the first inner copper foil layer, the first inner dielectric layer, the second inner copper foil layer, the core board, the third inner copper foil layer, and the second inner dielectric layer.

5. The thick copper circuit board according to claim 3, characterized in that, The core board comprises three laminated sub-core boards.

6. The thick copper circuit board according to claim 5, characterized in that, The thickness of each sub-core board is 0.127 mm.

7. The thick copper circuit board according to claim 3, characterized in that, The thickness of the first inner copper foil layer, the second inner copper foil layer, the third inner copper foil layer, and the fourth inner copper foil layer is 3 oz.

8. The thick copper circuit board according to claim 1, characterized in that, The thickness of both the first outer copper foil layer and the second outer copper foil layer is 1 oz.

9. The thick copper circuit board according to claim 1, characterized in that, The RC value of the prepreg is 71%.

10. The thick copper circuit board according to claim 1, characterized in that, The prepreg is PP of type 1080.

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