PCB structure, PCB preparation method and PCB

Abstract

The invention discloses a PCB structure, a PCB preparation method and a PCB, the PCB structure comprises a first blind hole plate and a second blind hole plate, the first blind hole plate and the second blind hole plate are formed by pressing a plurality of core plates, and the first blind hole plate and the second blind hole plate are pressed together to form a final pressing PCB; the blind hole plate is provided with a blind hole, a cavity and a protective layer, and the blind hole is located in the corresponding blind hole plate and connected with the inner layer circuit; the cavity is located in the corresponding blind hole plate, and one side is connected with the blind hole; the protective layer is located on the surface of one side of the blind hole plate and connected with the cavity; according to the method, the protective layer is manufactured on the back drilling hole of the blind hole plate, air is sealed in the back drilling hole to form the back drilling cavity, signals make contact with the air after walking to the back drilling position at the tail end of the hole, the signals are kept consistent with the back drilling hole of the final pressing plate, the influence of different media in the back drilling hole is avoided, and signal integrity is improved.

Description

Technical Field

[0001] The present invention relates to a PCB structure, a PCB board preparation method and a PCB board, and belongs to the technical field of circuit boards. Background Art

[0002] Driven by new technologies and application scenarios such as 5G and AI, PCBs are developing towards higher layers, denser circuits, and stricter signal integrity. The N+M double-pressing structure (for example, a 32-layer board is first made into two blind-via boards, a 20-layer board and a 12-layer board, and then the two blind-via boards are pressed together to form a 32-layer final pressed PCB board) is an important trend in the current industry to cope with complex designs and high-performance requirements.

[0003] Backdrilled copper residue can degrade signal integrity at high speeds due to parasitic effects, reflections, scattering, and electromagnetic interference (EMI). The industry primarily addresses this by reducing the length of the backdrilled copper residue. However, for N+M structures, backdrilled holes in blind vias are often plugged with resin to prevent pressure loss and voids caused by the polypropylene (PP) being squeezed into the backdrilled holes during secondary lamination. Consequently, the resin can affect the parasitic effects, reflections, scattering, and EMI of the backdrilled copper residue. Furthermore, the backdrilled holes in the final press-fit PCB, formed by laminating two blind vias together, are processed last, leaving air on one side of the backdrilled copper residue. Therefore, the backdrilled copper residue is affected by the air. The dielectric constant of resin is above 4, while that of air is 1. Therefore, the signals are affected differently by resin and air, resulting in inconsistent signal performance on the blind via and final press-fit boards, which in turn degrades signal integrity.

[0004] The current industry often considers reducing the length of backdrilled copper residue when improving signal integrity, ignoring the impact of different media in the backdrilled hole. Summary of the Invention

[0005] The present invention aims to provide a PCB structure, a PCB board preparation method, and a PCB board. By forming a protective layer on the back-drilled cavity of a blind via board, air is enclosed in the back-drilled hole to form a cavity, thereby solving the influence of different media in the back-drilled hole and improving signal integrity.

[0006] In order to achieve the above objectives / solve the above technical problems, the present invention is implemented by adopting the following technical solutions.

[0007] In one aspect, the present invention provides a PCB structure, comprising: a first blind hole plate and a second blind hole plate formed by laminating a plurality of core plates, wherein the first blind hole plate and the second blind hole plate are laminarly connected by a semi-cured material, wherein the semi-cured material is PP material;

[0008] A first blind hole and a second blind hole are respectively provided on one side of the first blind hole plate and the second blind hole plate, and the first blind hole and the second blind hole are respectively connected to the inner layer circuits of the corresponding blind hole plate.

[0009] A first cavity and a second cavity are respectively formed on the other side of the first blind hole plate and the second blind hole plate; the first blind hole is connected to the first cavity, and the second blind hole is connected to the second cavity;

[0010] A protective layer is provided at the openings of the first cavity and the second cavity respectively. The protective layer is located between the corresponding blind hole plate and the semi-cured material to prevent the semi-cured material from entering the first cavity and the second cavity during lamination.

[0011] Furthermore, the hole walls of the first blind hole and the second blind hole are metallized, and the holes are filled with resin, while the hole walls of the first cavity and the second cavity are non-metallized, and the holes are filled with air.

[0012] Furthermore, the aperture of the first cavity is larger than that of the first blind hole, and the aperture of the second cavity is larger than that of the second blind hole plate.

[0013] Furthermore, the protective layer includes: an ink layer and a polyimide cover film; the protective layer has the characteristics of selective retention and removal, can withstand a pressure greater than 300psi and a temperature greater than 150°C, and the peeling force between the protective layer and the PCB substrate and the copper surface is greater than 100g / inch.

[0014] In a second aspect, the present invention provides a method for preparing a PCB board based on the above-mentioned PCB structure, comprising the following steps:

[0015] Processing several core boards according to pre-designed patterns and circuits;

[0016] Laminating the processed core plates according to a pre-designed method to obtain a first blind hole plate and a second blind hole plate;

[0017] Drilling is performed on one side of the first blind hole plate and the second blind hole plate, and the first blind hole and the second blind hole formed by the drilling are metallized and filled with resin.

[0018] Drilling is performed on the other side of the plurality of first blind hole plates and the second blind hole plates, the drilled first cavities and the second cavities are respectively connected to the first blind holes and the second blind holes, and the surfaces of the first cavities and the second cavities are sealed with a protective layer;

[0019] The sides of the first blind hole plate and the second blind hole plate with the protective layer are laminated to obtain finished plates.

[0020] Furthermore, the method of sealing the first cavity and the second cavity by a protective layer specifically includes:

[0021] Cleaning and roughening the surfaces of the first blind hole plate and the second blind hole plate;

[0022] Covering the surfaces of the first blind hole plate and the second blind hole plate with a protective layer;

[0023] The protective layer on the surface of the first cavity and the second cavity is retained by developing, exposing or laser method, and the protective layer in the remaining area is removed.

[0024] Furthermore, when the protective layer is an ink layer, an exposure and development method is used, specifically:

[0025] Expose the ink covering the surfaces of the first cavity and the second cavity to ultraviolet light using an exposure device;

[0026] The ink in the remaining area is washed away by chemical reaction through the developing equipment;

[0027] The retained ink area is baked and cured in an oven;

[0028] Furthermore, when the protective layer is a polyimide cover film, a laser method is used, specifically: the polyimide cover film covering the surfaces of the first cavity and the second cavity is retained by a laser device, and the polyimide cover film in the remaining area is ablated.

[0029] In a third aspect, the present invention provides a PCB board produced by the above-mentioned PCB board production method.

[0030] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the present application seals the air in the cavity formed by the back-drilled hole by making a protective layer on the back-drilled hole of the blind hole plate, so that the signal contacts the air after reaching the back-drilled hole at the end of the hole, which is consistent with the back-drilled hole of the final pressure plate, solves the influence of different media in the back-drilled hole, and improves the signal integrity. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the PCB structure in Example 1 of this application;

[0032] Figure 2 This is a schematic diagram of the structure of the first blind hole plate in Example 1 of the present application;

[0033] Figure 3 This is a schematic diagram of the structure of the second blind hole plate in Example 1 of the present application;

[0034] Figure 4 Schematic diagram of the preparation method in Example 2 of the present application;

[0035] Wherein: 1: first blind hole plate, 101: first blind hole, 102: first cavity, 103: first protective layer, 2: second blind hole plate, 201: second blind hole, 202: second cavity, 203: second protective layer. DETAILED DESCRIPTION

[0036] It should be noted that:

[0037] The technical solution of the present invention is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0038] The term "and / or" simply describes a relationship between related objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. Additionally, the character " / " generally indicates an "or" relationship between the related objects.

[0039] Example 1

[0040] like Figures 1-3 In one embodiment, a PCB structure is provided, comprising: a first blind hole plate 1 and a second blind hole plate 2 formed by laminating a plurality of core plates, wherein the first blind hole plate 1 and the second blind hole plate 2 are laminarly connected by a semi-cured material, wherein the semi-cured material is PP (epoxy resin) material;

[0041] A first blind hole 101 and a second blind hole 201 are respectively provided on one side of the first blind hole plate 1 and the second blind hole plate 2, and the first blind hole 101 and the second blind hole 201 are respectively connected to the inner layer circuits of the corresponding blind hole plates.

[0042] A first cavity 102 and a second cavity 202 are respectively formed on the other side of the first blind hole plate 1 and the second blind hole plate 2; the first blind hole 101 is connected to the first cavity 102, and the second blind hole 201 is connected to the second cavity 202;

[0043] Protective layers are respectively disposed at the openings of the first cavity 102 and the second cavity 202 .

[0044] The hole walls of the first blind hole 101 and the second blind hole 201 are metallized, and the holes are filled with resin. The hole walls of the first cavity 102 and the second cavity 202 are non-metallized, and the holes are filled with air.

[0045] The aperture of the first cavity 102 is larger than that of the first blind hole 101 , and the aperture of the second cavity 202 is larger than that of the second blind hole plate 2 .

[0046] The first cavity 102 and the second cavity 202 are formed on the first blind hole plate and the second blind hole plate, and then a protective layer sealing treatment is performed to prevent the semi-cured material from entering the first cavity 102 and the second cavity 202 during lamination.

[0047] Example 2:

[0048] like Figure 4 As shown, this embodiment provides a method for preparing a PCB board based on the above-mentioned PCB structure, comprising the following steps:

[0049] Processing several core boards according to pre-designed patterns and circuits;

[0050] The processed core plates are laminated according to a pre-designed method to obtain a first blind hole plate 1 and a second blind hole plate 2;

[0051] The first blind hole plate 1 and the second blind hole plate 2 are drilled on one side, and the first blind hole 101 and the second blind hole 201 formed by the drilling are metallized and filled with resin.

[0052] Drilling is performed on the other side of the plurality of first blind hole plates 1 and the second blind hole plates 2. The drilled first cavities 102 and the second cavities 202 are connected to the first blind holes 101 and the second blind holes 201, respectively. The surfaces of the first cavities 102 and the second cavities 202 are sealed with a protective layer.

[0053] The sides of the first blind hole plate 1 and the second blind hole plate 2 with the protective layer are laminated to obtain finished plates.

[0054] The method for sealing the first cavity 102 and the second cavity 202 by a protective layer specifically includes:

[0055] Cleaning and roughening the surfaces of the first blind hole plate 1 and the second blind hole plate 2;

[0056] The surfaces of the first blind hole plate 1 and the second blind hole plate 2 are covered with protective layers, which are respectively the first ink layer 103 and the second ink layer 203 between the corresponding blind hole plates and the semi-cured material;

[0057] The ink layer (protective layer) on the surface of the first cavity 102 and the second cavity 202 is retained by the development and exposure method, and the ink layer (protective layer) in the remaining area is removed.

[0058] Development and exposure method, specifically:

[0059] The ink area to be retained is irradiated with ultraviolet light through the exposure equipment, and the ultraviolet light energy is 200-2000mj / cm2;

[0060] The ink in the remaining area is washed away by chemical reaction through the developing equipment. The developing solution is a sodium carbonate aqueous solution with a concentration of 1-3%, a temperature of 25-35°C, a reaction time of 20-50 seconds, and a spray pressure of 0.1-0.2Mpa. After the reaction, it is washed with pure water and then dried;

[0061] The retained ink is baked and cured in an oven at a temperature of 120-160°C for 60-120 minutes.

[0062] Example 3:

[0063] In addition to the technical solution in Example 2, this embodiment replaces the protective layer with a polyimide covering film, specifically:

[0064] Retain the polyimide covering film (protective layer) on the surface of the first cavity 102 and the second cavity 202 by a laser method, and remove the polyimide covering film (protective layer) in the remaining area;

[0065] The laser method is as follows: the area that does not need to be retained is ablated by laser equipment, the laser energy is 1-10mj, and the laser time is 1-10us.

[0066] Example 4

[0067] This embodiment provides a PCB board, which is manufactured by the above-mentioned PCB board manufacturing method.

[0068] The present invention forms a back-drilled cavity by making ink on the back-drilled hole of the blind hole plate, thereby enclosing air in the back-drilled hole. After the signal reaches the back-drilled part at the end of the hole, it contacts the air, which is consistent with the back-drilled hole of the final pressure plate. This solves the influence of different media in the back-drilled hole and improves signal integrity.

[0069] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which are all protected by the present invention.

Claims

1. A PCB structure, characterized in that: include: A first blind hole plate (1) and a second blind hole plate (2) formed by pressing a plurality of core plates together, wherein the first blind hole plate (1) and the second blind hole plate (2) are pressed and connected by a semi-cured material; A first blind hole (101) and a second blind hole (201) are respectively provided on one side of the first blind hole plate (1) and the second blind hole plate (2), and the first blind hole (101) and the second blind hole (201) are respectively connected to the inner layer circuits of the corresponding blind hole plates. A first cavity (102) and a second cavity (202) are respectively formed on the other side of the first blind hole plate (1) and the second blind hole plate (2); the first blind hole (101) and the first cavity (102) are connected, and the second blind hole (201) and the second cavity (202) are connected; Protective layers are respectively provided at the openings of the first cavity (102) and the second cavity (202), and the protective layers are located between the corresponding blind hole plates and the semi-cured material to prevent the semi-cured material from entering the first cavity (102) and the second cavity (202) when pressed.

2. The PCB structure according to claim 1, wherein: The hole walls of the first blind hole (101) and the second blind hole (201) are metallized, and the holes are filled with resin; the hole walls of the first cavity (102) and the second cavity (202) are non-metallized, and the holes are filled with air.

3. The PCB structure according to claim 1, wherein: The aperture of the first cavity (102) is larger than that of the first blind hole (101), and the aperture of the second cavity (202) is larger than that of the second blind hole plate (2).

4. The PCB structure according to claim 1, wherein: The protective layer includes an ink layer and a polyimide covering film.

5. A method for preparing a PCB board based on the PCB structure according to any one of claims 1 to 4, characterized in that: The following steps are involved: Processing several core boards according to pre-designed patterns and circuits; Laminating the processed core plates according to a pre-designed method to obtain a first blind hole plate (1) and a second blind hole plate (2); Drilling is performed on one side of the first blind hole plate (1) and the second blind hole plate (2), and the first blind hole (101) and the second blind hole (201) formed by the drilling are subjected to a hole wall metallization process and a hole resin filling process; Drilling is performed on the other side of the plurality of first blind hole plates (1) and the second blind hole plates (2), the drilled first cavities (102) and the second cavities (202) being communicated with the first blind holes (101) and the second blind holes (201) respectively, and the surfaces of the first cavities (102) and the second cavities (202) are sealed by a protective layer; The first blind hole plate (1) and the second blind hole plate (2) are laminated on the side with the protective layer to obtain a finished plate.

6. The method for preparing a PCB according to claim 5, wherein: The method for sealing the first cavity (102) and the second cavity (202) by means of a protective layer specifically comprises: Cleaning and roughening the surfaces of the first blind hole plate (1) and the second blind hole plate (2); Covering the surfaces of the first blind hole plate (1) and the second blind hole plate (2) with a protective layer; The protective layers on the surfaces of the first cavity (102) and the second cavity (202) are retained by developing, exposing or laser methods, and the protective layers in the remaining areas are removed.

7. The method for preparing a PCB according to claim 6, wherein: When the protective layer is an ink layer, an exposure and development method is used, specifically: Exposure equipment is used to irradiate the ink on the surface of the first cavity (102) and the second cavity (202) with ultraviolet light; The ink in the remaining area is washed away by chemical reaction through the developing equipment; The remaining ink areas are baked and cured in an oven.

8. The method for preparing a PCB according to claim 6, wherein: When the protective layer is a polyimide covering film, a laser method is used, specifically: the polyimide covering film on the surface of the first cavity (102) and the second cavity (202) is retained by a laser device, and the polyimide covering film in the remaining area is ablated.

9. A PCB board, characterized in that: The PCB board is prepared by the PCB board preparation method according to any one of claims 5 to 8.

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