Circuit board preparation method and circuit board

Abstract

The present application discloses a method for preparing a circuit board and a circuit board, the preparation method comprising: obtaining a plate to be processed, wherein at least one first step groove is provided on the first surface of the plate to be processed; wherein the first step groove is filled with an adhesive material; obtaining a first core plate layer, and performing a pressing process on the first core plate layer and the first surface of the plate to be processed; processing a second step groove on a side surface of the first core plate layer away from the first surface to expose each first step groove, the adhesive material filled in the first step groove, and the copper layer that forms an inner layer pattern together with the first step groove; wherein the adhesive material and the copper layer have the same thickness in the lamination direction. The present application can avoid the need to open the cover of the first step groove, thereby optimizing the process flow and reducing the preparation time. It can also avoid the problem of no structure in the area surrounding the first step groove caused by opening the cover, thereby effectively preventing damage to the board during processing.

Description

Technical Field

[0001] The present application relates to the technical field of circuit board processing, and in particular to a circuit board preparation method and a circuit board. Background Art

[0002] With the development of 5G technology and electronic products, the demand for circuit boards is increasing. To improve product performance, assembly density, and reduce weight and size, a new process is currently being used in the PCB (Printed Circuit Board) production process: the step-groove process. This involves digging at least one groove in the inner core of the PCB to increase heat dissipation area or improve the safety of surface components.

[0003] In the prior art, step groove processing mainly involves laminating the core sheet where the step groove is located with the outer sheet. After lamination, the step groove is uncovered to expose the step groove. Specifically, the uncovering process involves identifying the specific area covering the step groove on the outer sheet, setting an ant line at the edge of this area, and then cutting from the ant line to peel off the sheet above the step groove.

[0004] However, since the lower cutting position cannot correspond to the step groove, a part of the area outside the specific area covering the step groove will be reserved as the lower cutting edge when opening the cover, resulting in no structure around the step groove, which can easily damage the panel during the opening process. At the same time, due to the complicated process, it will also take a long time to open the cover. Summary of the Invention

[0005] The main technical problem solved by the present application is to provide a circuit board preparation method and a circuit board, which can solve the problems of easily damaged boards and complicated processes caused by opening the step groove cover.

[0006] In order to solve the above technical problems, the first technical solution adopted in this application is to provide a circuit board preparation method, including: obtaining a board to be processed, and at least one first step groove is provided on the first surface of the board to be processed; wherein the first step groove is filled with adhesive material; obtaining a first core board layer, and pressing the first core board layer and the first surface of the board to be processed; processing a second step groove on the side surface of the first core board layer away from the first surface to expose each first step groove, the adhesive material filled in the first step groove, and the copper layer that forms an inner layer pattern together with the first step groove; wherein the thickness of the adhesive material and the copper layer in the lamination direction are equal.

[0007] Among them, the step of processing a second step groove on the side surface of the first core board layer away from the first surface to expose each first step groove, the adhesive material filled in the first step groove and the copper layer that forms the inner layer pattern together with the first step groove includes: processing a first blind hole on the side surface of the first core board layer away from the first surface, the bottom of the first blind hole is the insulating layer laminated by the first core board layer and the first surface; wherein the orthographic projection of the first blind hole overlaps with the orthographic projection of each first step groove and the copper layer that forms the inner layer pattern together with the first step groove; surface treatment is performed on the bottom of the first blind hole to remove the insulating layer at the bottom of the hole to form a second step groove; wherein the bottom of the second step groove is the adhesive material filled in each first step groove and the copper layer that forms the inner layer pattern together with the first step groove; surface treatment is performed on the bottom of the second step groove to make the thickness of the adhesive material and the copper layer equal in the lamination direction.

[0008] Among them, the step of processing a first blind hole on the side surface of the first core plate layer away from the first surface, and the bottom of the first blind hole is the insulating layer laminated between the first core plate layer and the first surface, includes: processing the first blind hole on the side surface of the first core plate layer away from the first surface by mechanically controlling the depth, and the bottom of the first blind hole is the insulating layer laminated between the first core plate layer and the first surface.

[0009] Among them, mechanical depth control methods include one-time depth control and distributed depth control.

[0010] Among them, the step of performing surface treatment on the bottom of the first blind hole to remove the insulating layer at the bottom of the hole to form a second step groove includes: performing surface treatment on the bottom of the first blind hole by one or more methods of laser ablation, laser cutting, ion cutting and water jet to remove the insulating layer at the bottom of the hole to form a second step groove.

[0011] The step of performing surface treatment on the bottom of the second step groove so that the thickness of the adhesive material and the copper layer in the lamination direction are equal includes: performing at least one surface treatment on the adhesive material having a thickness greater than that of the copper layer in the lamination direction so that the thickness of the adhesive material and the copper layer in the lamination direction are equal.

[0012] Among them, the step of obtaining a plate to be processed, wherein at least one first step groove is provided on the first surface of the plate to be processed, includes: obtaining a plate to be processed, processing at least one first preset position on the first surface of the plate to be processed to form at least one first step groove; filling each first step groove with a viscous material to obtain the plate to be processed.

[0013] Among them, the step of obtaining a plate to be processed and processing at least one first preset position on the first surface of the plate to be processed to form at least one first step groove includes: processing at least one first preset position on the first surface of the plate to be processed by mechanical processing or laser ablation to form at least one first step groove.

[0014] The adhesive material includes adhesive tape or ink.

[0015] In order to solve the above technical problems, the second technical solution adopted in this application is to provide a circuit board, which includes an exposed second step groove and at least one first step groove, and the bottom of the second step groove is a viscous material filled in each first step groove and a copper layer that forms an inner layer pattern together with the first step groove; wherein the thickness of the viscous material and the copper layer in the lamination direction is equal.

[0016] The beneficial effects of the present application are as follows: Different from the prior art, the present application provides a circuit board preparation method and a circuit board. By processing a second step groove on the side surface of the first core layer away from the first surface to expose each first step groove, it is possible to avoid the need to open the cover of the first step groove. This not only optimizes the process flow and reduces the preparation time, but also avoids the problem of the area around the first step groove being unstructured due to opening the cover, thereby effectively preventing damage to the board during processing. Furthermore, by making the thickness of the viscous material filled in the first step groove and the copper layer that forms the inner layer pattern together with the first step groove equal in the lamination direction, it is also possible to avoid the height difference between the board surface of the first step groove and the surrounding copper layer, thereby improving the flatness of the first step groove, avoiding quality defects in the circuit board, and then improving product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 This is a flow chart of an embodiment of a method for preparing a circuit board according to the present application;

[0019] Figure 2 is a flow chart of an embodiment of a method for obtaining a plate to be processed in S11;

[0020] Figure 3 is a structural schematic diagram of an embodiment of the plate to be processed obtained in S21;

[0021] Figure 4is a structural schematic diagram of an embodiment of the plate to be processed obtained in S11;

[0022] Figure 5 is a structural schematic diagram of an embodiment of the plate to be processed obtained in S12;

[0023] Figure 6 It is a flow chart of a specific implementation method of S13;

[0024] Figure 7 is a structural schematic diagram of an embodiment of the plate to be processed obtained in S131;

[0025] Figure 8 It is a structural diagram of an embodiment of the circuit board of the present application. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0027] The terms used in the examples of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms "a," "the," and "the" used in the examples of this application and the appended claims are also intended to include plural forms. Unless otherwise clearly indicated above, "a plurality" generally includes at least two, but does not exclude the inclusion of at least one.

[0028] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0029] It should be understood that the terms "comprises," "comprising," or any other variations used herein are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0030] In the prior art, the processing of step grooves mainly involves pressing the core plate layer where the step groove is located with the outer plate, and then opening the step groove to expose the step groove. Specifically, opening the cover requires determining the specific area covering the step groove on the outer plate, setting an ant line at the edge of the area, and cutting from the ant line to peel off the plate above the step groove. However, since the cutting position cannot correspond to the step groove, a part of the area outside the specific area covering the step groove will be reserved as the cutting edge when opening the cover, resulting in no structure around the step groove, which can easily damage the plate during the opening process. At the same time, due to the cumbersome process, it will also take a long time to open the cover.

[0031] Based on the above situation, the present application provides a circuit board preparation method and a circuit board, which can solve the problems of easily damaged boards and complicated processes caused by opening the step groove cover.

[0032] The present application is described in detail below with reference to the accompanying drawings and implementation methods.

[0033] See also Figure 1 , Figure 1 1 is a flow chart of an embodiment of a method for preparing a circuit board of the present application. In this embodiment, the method includes:

[0034] S11: Acquire a plate to be processed, wherein at least one first step groove is provided on a first surface of the plate to be processed; wherein the first step groove is filled with a viscous material.

[0035] Specifically, see Figure 2 , Figure 2 1 is a flow chart of an embodiment of a method for obtaining a plate to be processed in S11. In this embodiment, the method includes:

[0036] S21: A plate to be processed is obtained, and processing is performed at least one first preset position on a first surface of the plate to be processed to form at least one first step groove.

[0037] In this embodiment, at least one first step groove is formed by machining or laser ablation at at least one first predetermined position on the first surface of the plate to be processed. The specific number of the first predetermined position and the first step grooves can be determined based on the desired number of step grooves, and this application does not impose any limitation thereto.

[0038] The first step groove and a portion of the copper layer surrounding the first step groove form an inner layer pattern.

[0039] In this embodiment, the panel to be processed is a multi-layer core board obtained by lamination. Lamination refers to the process of combining two or more layers of the same or different materials into a whole by applying heat and pressure, with or without an adhesive. The core board is a copper-clad laminate, which includes a dielectric layer and a copper layer. The dielectric layer may be covered with copper on one side or both sides.

[0040] In this embodiment, the double-sided copper layer of the insulation layer of the copper clad laminate is used as an example. PP sheets (prepreg sheets) are provided between the multi-layer core boards. Both the dielectric layer and the PP layer are insulating layers.

[0041] In this embodiment, the first surface is the surface of the copper layer, and the bottom of the first step groove formed by processing is the surface of the insulating layer stacked with the copper layer.

[0042] In this embodiment, prior to processing on the plate to be processed, the plate to be processed needs to be subjected to a browning treatment. Specifically, the copper layer surface of the plate to be processed is first micro-etched with a browning liquid to form an extremely thin and uniform organic metal conversion film, which gives the copper surface a smooth microscopic uneven surface shape. At the same time, the organic additives in the browning liquid form an organic metal conversion film on the copper surface. This film can effectively embed into the copper surface, forming a brown gridded conversion layer. This treatment not only increases the bonding strength between the plates, but also browns the plates, increasing the copper surface's absorption of laser light.

[0043] In other embodiments, at least one step groove may be formed on the first surface of the plate to be processed by using a boss process, which is not limited in this application.

[0044] Specifically, see Figure 3 , Figure 3 It is a structural schematic diagram of an embodiment of the plate to be processed obtained in S21.

[0045] The sheet material 100 to be processed includes a multi-layer core sheet 10, with prepregs 20 disposed between adjacent core sheets 10. The core sheet 10 includes a dielectric layer 101 and copper layers 102 disposed on both sides of the dielectric layer 101. A plurality of first step grooves 30 are formed on a first surface 1021 of the outermost copper layer 102 of the sheet material 100 to be processed. The first step grooves 30 and the portion of the copper layer 102 surrounding the first step grooves 30 form an inner layer pattern. The bottom of the first step grooves 30 is the surface of the dielectric layer 101 stacked with the copper layer 102.

[0046] S22: Filling each first step groove with a viscous material to obtain a plate to be processed.

[0047] In this embodiment, the adhesive material includes tape or ink.

[0048] In a specific implementation scenario, the tape is attached to a designated area, where the designated area includes an orthographic projection area of ​​each first step groove and an orthographic projection area of ​​a copper layer that forms an inner layer pattern together with the first step groove.

[0049] In another specific implementation scenario, liquid ink is filled in a designated area by silk screen printing, and the designated area includes the orthographic projection area of ​​each first step groove and the orthographic projection area of ​​the copper layer that forms the inner layer pattern together with the first step groove.

[0050] Specifically, see Figure 4 , Figure 4 It is a structural schematic diagram of an implementation method of the plate to be processed obtained in S11.

[0051] The plate 200 to be processed includes a multi-layer core plate 10, with prepregs 20 disposed between adjacent core plates 10. The core plate 10 includes a dielectric layer 101 and a copper layer 102 disposed on both sides of the dielectric layer 101. A plurality of first step grooves 30 are formed on the first surface 1021 of the outermost copper layer 102 of the plate 200 to be processed. The bottom of the first step groove 30 is the surface of the dielectric layer 101 stacked with the copper layer 102. The first step groove 30 is filled with an adhesive material 40, and the surface of the copper layer 102, which forms the inner layer pattern together with the first step groove 30, is covered with the adhesive material 40.

[0052] S12: Obtain a first core plate layer, and perform a pressing process on the first core plate layer and the first surface of the plate to be processed.

[0053] In this embodiment, the first core board layer may be a copper clad board or a copper foil layer.

[0054] In a specific implementation scenario, when the first core board layer is a single-sided copper-clad board, the dielectric layer of the first core board layer is bonded to the first surface of the board to be processed by lamination.

[0055] In another specific implementation scenario, when the first core board layer is a copper foil layer, a semi-cured sheet is placed on the first surface of the board to be processed, and then pressed and filled to the entire surface at high temperature to form a semi-cured layer, and then the copper foil layer is pressed onto the semi-cured layer.

[0056] Specifically, see Figure 5 , Figure 5 It is a structural schematic diagram of an implementation method of the plate to be processed obtained in S12.

[0057] The plate 300 to be processed includes a multi-layer core plate 10, and a semi-cured sheet 20 is arranged between adjacent core plates 10. The core plate 10 includes a dielectric layer 101 and a copper layer 102 arranged on both sides of the dielectric layer 101. A plurality of first step grooves 30 are formed on the first surface 1021 of the inner copper layer 102 of the plate 300 to be processed. The bottom of the first step groove 30 is the surface of the dielectric layer 101 stacked with the copper layer 102. The first step groove 30 is filled with an adhesive material 40, and the surface of the copper layer 102 that forms the inner layer pattern together with the first step groove 30 is covered with the adhesive material 40. The first core plate layer 50 is pressed onto the first surface 1021 and the surface of the adhesive material 40 on the side away from the first step groove 30. The first core plate layer 50 includes a copper layer 102 and a semi-cured sheet 20 stacked in sequence. The first surface 1021 and the surface of the adhesive material 40 on the side away from the step groove are pressed onto the first core plate layer 50 through the semi-cured sheet 20.

[0058] S13: A second step groove is processed on the side surface of the first core layer away from the first surface to expose each first step groove, the adhesive material filled in the first step groove, and the copper layer that forms an inner layer pattern together with the first step groove; wherein the thickness of the adhesive material and the copper layer in the lamination direction are equal.

[0059] Specifically, see Figure 6 , Figure 6 This is a flow chart of a specific embodiment of S13. In this embodiment, a second step groove is machined on a surface of the first core layer away from the first surface to expose each first step groove, the viscous material filled in the first step groove, and the copper layer that forms the inner layer pattern together with the first step groove, specifically including:

[0060] S131: A first blind hole is processed on the side surface of the first core board layer away from the first surface, and the bottom of the first blind hole is the insulating layer laminated by the first core board layer and the first surface; wherein, the orthographic projection of the first blind hole overlaps with the orthographic projection of each first step groove and the copper layer that forms the inner layer pattern together with the first step groove.

[0061] In this embodiment, a first blind hole is machined on a surface of the first core plate away from the first surface by mechanical depth control, and the bottom of the first blind hole is the insulating layer laminated between the first core plate layer and the first surface.

[0062] Among them, mechanical depth control methods include one-time depth control and distributed depth control.

[0063] In this embodiment, the orthographic projection area corresponding to the first blind hole is the orthographic projection area of ​​each first step groove and the orthographic projection area of ​​the copper layer that forms the inner layer pattern together with the first step groove.

[0064] It can be understood that the bottom of the first blind hole obtained by processing is the insulating layer laminated by the first core board layer and the first surface, so as to avoid damage to the first step groove, adhesive material and the copper layer that forms the inner layer pattern together with the first step groove due to mechanical processing.

[0065] Specifically, see Figure 7 , Figure 7 It is a structural schematic diagram of an implementation method of the plate to be processed obtained in S131.

[0066] The plate material 400 to be processed includes a multi-layer core plate 10, and a prepreg 20 is arranged between adjacent core plates 10. The core plate 10 includes a dielectric layer 101 and a copper layer 102 arranged on both sides of the dielectric layer 101. A plurality of first step grooves 30 are formed on the first surface 1021 of the inner copper layer 102 of the plate material 400 to be processed. The bottom of the first step groove 30 is the surface of the dielectric layer 101 stacked with the copper layer 102. The first step groove 30 is filled with an adhesive material 40, and the surface of the copper layer 102 that forms the inner layer pattern together with the first step groove 30 is covered with the adhesive material 40. A first core plate layer 50 is pressed onto the first surface 1021 and the surface of the adhesive material 40 on the side away from the first step groove 30. The first core plate layer 50 includes a copper layer 102 and a prepreg 20 stacked in sequence. The first surface 1021 and the surface of the adhesive material 40 on the side away from the first step groove 30 are pressed onto the first core plate layer 50 via the prepreg 20. A first blind hole 60 is formed on a surface of the first core plate layer 50 away from the first surface 1021 . The bottom of the first blind hole 60 is the prepreg 20 for laminating the first core plate layer 50 and the first surface 1021 .

[0067] S132: Surface treatment is performed on the bottom of the first blind hole to remove the insulating layer at the bottom of the hole to form a second step groove; wherein the bottom of the second step groove is the viscous material filled in each first step groove and the copper layer that forms the inner layer pattern together with the first step groove.

[0068] In this embodiment, the bottom of the first blind hole is surface treated by one or more methods including laser ablation, laser cutting, ion cutting and water jet cutting to remove the insulating layer at the bottom of the hole and form a second step groove.

[0069] In order to avoid possible damage caused by a single surface treatment, the range and depth of the surface treatment can be controlled, and the insulating layer at the bottom of the first blind hole can be removed through multiple surface treatments to form a second step groove.

[0070] It can be understood that the orthographic projection area corresponding to the second step groove is the orthographic projection area of ​​each first step groove and the orthographic projection area of ​​the copper layer that forms the inner layer pattern together with the first step groove.

[0071] As can be understood, since the first step groove is directly exposed by preparing the second step groove, there is no need to open the cover of the processed plate, thus avoiding the need to set an ant line and reserve a portion of the area for the lower cutting edge. This avoids the problem of the area around the first step groove being unstructured due to opening the cover, and thus effectively prevents damage to the plate during processing. At the same time, since there is no need to open the cover, the process flow is optimized and the preparation time is reduced.

[0072] S133: performing surface treatment on the bottom of the second step groove so that the thickness of the adhesive material and the copper layer in the lamination direction are equal.

[0073] In this embodiment, the adhesive material having a thickness exceeding that of the copper layer in the lamination direction is subjected to at least one surface treatment so that the thickness of the adhesive material and the copper layer in the lamination direction are equal.

[0074] Understandably, since the bottom of the second step groove is composed of the adhesive material filled in each first step groove and the copper layer that forms the inner layer pattern together with the first step groove, and the surface of the copper layer may also be covered with adhesive material, it is necessary to perform surface treatment again to remove the adhesive material from the surface of the copper layer. Furthermore, the thickness of the adhesive material filled in the first step groove may also exceed the thickness of the copper layer in the lamination direction. Therefore, by performing surface treatment again to make the thickness of the filled adhesive material equal to that of the copper layer, it is possible to avoid the height difference between the board surface of the first step groove and the surrounding copper layer, thereby improving the flatness of the first step groove, avoiding quality defects in the circuit board, and thus improving product quality.

[0075] Specifically, see Figure 8 , Figure 8: This is a structural schematic diagram of an embodiment of a circuit board of the present application. The circuit board 500 includes a multi-layer core board 10, and a semi-cured sheet 20 is arranged between adjacent core boards 10. The core board 10 includes a dielectric layer 101 and a copper layer 102 arranged on both sides of the dielectric layer 101. A plurality of first step grooves 30 are formed on the first surface 1021 of the inner copper layer 102 of the circuit board 500. The bottom of the first step groove 30 is the surface of the dielectric layer 101 stacked with the copper layer 102. The first step groove 30 and the portion of the copper layer 102 surrounding the first step groove 30 form an inner layer pattern. The first step groove 30 is filled with an adhesive material 40, and the adhesive material 40 has the same thickness as the copper layer 102 constituting the inner layer pattern in the lamination direction. A first core board layer 50 is laminated onto the first surface 1021 and the surface of the adhesive material 40 away from the first step groove 30. The first core board layer 50 includes a copper layer 102 and a prepreg 20 stacked in sequence. The first surface 1021 and the surface of the adhesive material 40 away from the first step groove 30 are laminated to the first core board layer 50 via the prepreg 20. A second step groove 70 is formed on the surface of the first core board layer 50 away from the first surface 1021. The bottom of the second step groove 70 is formed by the adhesive material 40 filling each first step groove 30 and the copper layer 102 that forms an inner layer pattern together with the first step groove 30.

[0076] Different from the prior art, the present application processes a second step groove on the side of the first core layer away from the first surface to expose each first step groove, thereby avoiding the need to open the cover of the first step groove. This not only optimizes the process flow and reduces preparation time, but also avoids the problem of the area around the first step groove being unstructured due to opening the cover, thereby effectively preventing damage to the board during processing. Furthermore, by ensuring that the thickness of the viscous material filled in the first step groove and the copper layer that forms the inner layer pattern together with the first step groove are equal in the lamination direction, it is also possible to avoid the height difference between the board surface of the first step groove and the surrounding copper layer, thereby improving the flatness of the first step groove, avoiding quality defects in the circuit board, and thus improving product quality.

[0077] The above description is only an implementation method of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a circuit board, characterized in that: include: A plate to be processed is obtained, wherein at least one first step groove is provided on a first surface of the plate to be processed; wherein the first step groove is filled with a viscous material, and a surface of a copper layer forming an inner layer pattern together with the first step groove is covered with the viscous material; Obtaining a first core plate layer, and performing a pressing process on the first core plate layer and the first surface of the plate to be processed; A second step groove is machined on a side of the first core layer away from the first surface to expose each of the first step grooves, the adhesive material filled in the first step grooves, and the copper layer that forms an inner layer pattern together with the first step grooves; wherein the adhesive material and the copper layer have the same thickness in the lamination direction; The step of machining a second step groove on a side surface of the first core layer away from the first surface to expose each of the first step grooves, the viscous material filled in the first step grooves, and the copper layer forming an inner layer pattern together with the first step grooves includes: A first blind hole is machined on a surface of the first core layer away from the first surface, wherein the bottom of the first blind hole is the insulating layer laminated between the first core layer and the first surface; wherein the orthographic projection of the first blind hole overlaps with the orthographic projection of each of the first step grooves and the copper layer that forms an inner layer pattern together with the first step grooves; Performing surface treatment on the bottom of the first blind hole to remove the insulating layer at the bottom of the hole to form a second step groove; wherein the bottom of the second step groove is the viscous material filled in each first step groove and the copper layer that forms an inner layer pattern together with the first step groove; The bottom of the second step groove is subjected to surface treatment so that the thickness of the adhesive material and the copper layer in the lamination direction are equal.

2. The method for preparing a circuit board according to claim 1, wherein: The step of machining a first blind hole on a surface of the first core plate layer away from the first surface, wherein the bottom of the first blind hole is an insulating layer laminated between the first core plate layer and the first surface, comprises: The first blind hole is processed on the surface of the first core plate layer away from the first surface by mechanical depth control, and the bottom of the first blind hole is the insulating layer laminated by the first core plate layer and the first surface.

3. The method for preparing a circuit board according to claim 2, wherein: The mechanical depth control method includes one-time depth control and distributed depth control.

4. The method for preparing a circuit board according to claim 1 or 2, wherein: The step of performing surface treatment on the bottom of the first blind hole to remove the insulating layer at the bottom of the hole to form the second step groove includes: The bottom of the first blind hole is surface-treated by one or more methods selected from the group consisting of laser ablation, laser cutting, ion cutting, and water jet cutting to remove the insulating layer at the bottom of the hole and form the second step groove.

5. The method for preparing a circuit board according to claim 4, wherein: The step of performing surface treatment on the bottom of the second step groove so that the thickness of the adhesive material and the copper layer in the lamination direction are equal includes: The adhesive material having a thickness exceeding that of the copper layer in the lamination direction is subjected to at least one surface treatment so that the thickness of the adhesive material and the copper layer in the lamination direction are equal.

6. The method for preparing a circuit board according to claim 1, wherein: The step of obtaining a plate to be processed, wherein at least one first step groove is provided on a first surface of the plate to be processed, comprises: Acquire a plate to be processed, and process at least one first preset position on the first surface of the plate to be processed to form at least one first step groove; The viscous material is filled into each of the first step grooves to obtain the plate to be processed.

7. The method for preparing a circuit board according to claim 6, wherein: The step of obtaining a plate to be processed and processing at least one first preset position on the first surface of the plate to be processed to form at least one first step groove includes: At least one first step groove is formed by machining or laser ablation at at least one first preset position on the first surface of the plate to be machined.

8. The method for preparing a circuit board according to claim 1 or 6, wherein: The adhesive material includes tape or ink.

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