A method for manufacturing a thick plate printed wiring board and a printed wiring board

Abstract

This invention discloses a method for manufacturing a thick plate printed circuit board and the printed circuit board itself, belonging to the field of printed circuit board technology. The method includes: forming a dense array of small holes with conductive circuits on a thick plate to obtain a first core board; adding layers on the mating surface of the first core board through a lamination process to obtain a first multilayer core board with a dielectric layer; forming laser blind vias on the mating surface of the first multilayer core board, and forming pre-placed slots for carrying conductive paste on the laser blind vias, and then obtaining a second multilayer core board through a patterning process; attaching a photosensitive adhesive film to the mating surface of the second multilayer core board, and creating windows on the photosensitive adhesive film to form areas for printing conductive paste corresponding to the pre-placed slots; the method for manufacturing a thick plate printed circuit board and the printed circuit board provided by this invention can realize the manufacturing of HDI PCBs with higher layer counts and higher order, improving product manufacturing efficiency, reducing process complexity, and enhancing product reliability and dependability.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a thick plate printed circuit board and the printed circuit board itself, belonging to the field of printed circuit board technology. Background Technology

[0002] In the field of high-layer thick plates (≥32 layers), especially in high-end application scenarios such as server backplanes and AI accelerator cards, traditional through-hole and blind / buried via processes face problems such as aspect ratio limitations (poor electroplating uniformity), severe signal attenuation, and thermal stress concentration in thick plates, making it difficult to meet the requirements of high-performance computing for low latency, high bandwidth, and high reliability.

[0003] It is evident that, in order to solve the problem of the difficulty in manufacturing thick plate printed circuit boards in the existing technology, there is an urgent need for a manufacturing method and a printed circuit board for thick plate printed circuit boards. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for manufacturing a thick printed circuit board and a printed circuit board, which can realize the manufacturing of HDI PCBs with higher layer count and higher order, improve product manufacturing efficiency, reduce process complexity, and improve product reliability and dependability.

[0005] To achieve the above objectives / to solve the above technical problems, the present invention is implemented using the following technical solution: In a first aspect, the present invention provides a method for manufacturing a thick printed circuit board, comprising: A dense array of small holes with conductive circuits is formed on a thick plate to obtain the first core plate; A first multilayer core board with a dielectric layer is obtained by adding layers on the mating surface of the first core board through a lamination process. Laser blind holes are formed on the mating surface of the first multilayer core board, and pre-placed slots for carrying conductive paste are formed on the laser blind holes. Then, the second multilayer core board is obtained through patterning process. A photosensitive adhesive film is attached to the mating surface of the second multilayer core board, and a window is made in the photosensitive adhesive film to create a conductive paste area to be printed corresponding to the pre-laid slot, thus obtaining the third multilayer core board. A conductive paste is applied to the pre-placed slots of the third multilayer core board to form conductive butt joints, thus obtaining a fourth multilayer core board. On the mating surface of the fourth multilayer core board with conductive mating posts, a sealing film is pre-applied using a vacuum lamination process. After pre-applied film, multiple fourth multilayer core boards are laminated together using a lamination process to obtain a multilayer core board multi-press structure.

[0006] Furthermore, the thick plate is a core board with a thickness of 3.0 mm or more, including an inner core board or multiple core boards.

[0007] Furthermore, the aperture size accuracy of the dense aperture array meets the requirements of a diameter of 125±25um and a distance between the centers of two adjacent apertures of 500±50um.

[0008] Furthermore, the minimum value of the electroplating recess in the pre-placed slot is 15µm.

[0009] Furthermore, the windowing accuracy of the photosensitive film is ±50µm, and the photosensitive film includes a polyimide colloid.

[0010] Furthermore, the height of the conductive docking post exceeds that of the photosensitive adhesive film by 10~30µm.

[0011] Furthermore, the conductive paste is a colloid containing silver-copper composite particles, wherein the particle size of the silver-copper composite particles is 5-10 μm and the conductivity ρ ≤ 1.524 × 10⁻⁶. 3 mohm·μm.

[0012] Furthermore, the encapsulating film comprises polyimide colloid, which is resistant to high temperatures >200℃ and high voltages of 30kv / mm.

[0013] In a second aspect, the present invention provides a printed circuit board, which is manufactured according to the method for manufacturing a thick plate printed circuit board described in the first aspect.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: 1. Fabricating a dense array of vias on high-layer, thick PCBs improves heat dissipation efficiency and reduces signal loss during transmission. Specifically, a dense array of vias is fabricated on high-layer PCBs through mechanical drilling, laser engraving, and electroplating. This process can create interlayer via array combinations, effectively solving the interlayer heat dissipation problem in high-layer, thick PCBs and addressing thermal failure caused by material mismatch in mixed-layer circuits.

[0015] 2. Pre-laid slots are created on the mating surfaces of high-layer, thick printed circuit boards, reducing the processing difficulty of conductive mating posts. Specifically, an electroplating process is used to create a metallized coating of a certain thickness on the mating surfaces. Then, a pattern exposed by a photosensitive emulsion film is attached to the mating surfaces using vacuum lamination and patterning processes. This design utilizes the vertical shape of the metallized coating created by pattern electroplating, effectively reducing the manufacturing difficulty of the conductive mating posts and improving their processing accuracy.

[0016] 3. The application of conductive mating posts and encapsulating films on the mating surfaces of high-layer, thick printed circuit boards reduces the processing difficulty of lamination and mating of high-layer, thick boards. Specifically, conductive mating posts are fabricated and protected using printing and vacuum lamination processes. After lamination, additional layers are added to the high-layer, thick board. This invention provides a method for manufacturing high-layer, thick boards, improving the alignment between lamination layers. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the inner core board.

[0018] Figure 2 This is a schematic diagram of the structure of a dense array of small holes on the inner core plate.

[0019] Figure 3 Is Figure 1 A schematic diagram of a multilayer core board with added structural layers.

[0020] Figure 4 This is a schematic diagram of a multilayer core board with laser-etched blind holes.

[0021] Figure 5 Is Figure 4 A schematic diagram of the structure of the electroplating conductive paste pre-placement tank.

[0022] Figure 6 This is a schematic diagram of a multilayer core board with a photosensitive adhesive film pattern (double-sided).

[0023] Figure 7 This is a schematic diagram of the structure of a multilayer core board with a photosensitive film pattern (single-sided).

[0024] Figure 8 Is Figure 6 The above is a schematic diagram of the structure for fabricating conductive docking posts (double-sided).

[0025] Figure 9 Is Figure 7 A schematic diagram of the structure for fabricating a conductive docking post (single-sided).

[0026] Figure 10 This is a schematic diagram of the conductive butt joint (double-sided) structure during the pressing and joining process.

[0027] Figure 11 This is a schematic diagram of the conductive butt joint (single-sided) structure during the pressing and joining process.

[0028] Figure 12 This is a schematic diagram of the application of conductive butt posts (double-sided) in multilayer core boards.

[0029] Figure 13 This is a schematic diagram of the application of conductive butt posts (single-sided) in multilayer core boards.

[0030] In the diagram: 101, copper layer; 102a, first dielectric layer; 102b, second dielectric layer; 103, via array; 104, laser blind via; 105, conductive paste pre-placement slot; 106, photosensitive film; 107, conductive paste; 108, encapsulation film; Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0032] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention 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 the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 will understand the specific meaning of the above terms in this invention based on the specific circumstances. Example 1

[0034] This embodiment provides a method for manufacturing a thick printed circuit board, including: A dense array of small holes with conductive circuits is formed on a thick plate to obtain the first core plate; A first multilayer core board with a dielectric layer is obtained by adding layers on the mating surface of the first core board through a lamination process. Laser blind holes are formed on the mating surface of the first multilayer core board, and pre-placed slots for carrying conductive paste are formed on the laser blind holes. Then, the second multilayer core board is obtained through patterning process. A photosensitive adhesive film is attached to the mating surface of the second multilayer core board, and a window is made in the photosensitive adhesive film to create a conductive paste area to be printed corresponding to the pre-laid slot, thus obtaining the third multilayer core board. A conductive paste is applied to the pre-placed slots of the third multilayer core board to form conductive butt joints, thus obtaining a fourth multilayer core board. On the mating surface of the fourth multilayer core board with conductive mating posts, a sealing film is pre-applied using a vacuum lamination process. After pre-applied film, multiple fourth multilayer core boards are laminated together using a lamination process to obtain a multilayer core board multi-press structure.

[0035] The following will combine Figures 1 to 13 The following is a detailed description of the embodiments provided: S1. A dense array of small holes is created on a thick plate using a drilling process. like Figure 1 As shown, the thick plate includes a first dielectric layer 102a and copper layers 101 disposed on the upper and lower sides of the first dielectric layer 102a. Specifically, on a thick plate, a dense array of small holes 103 is created using patterning and drilling processes, and a conductive circuit is created using electroplating, thus obtaining a sheet as shown in the image. Figure 2 The first core board S100 with a small hole array shown is further laminated to form a second dielectric layer 102b on the first core board S100, resulting in the following: Figure 3 The first multilayer core board S200 with lamination and layering is shown.

[0036] It should be noted that this is a special technology for dense via arrays on thick, high-layer plates. Requirements include that the 103 via array have smooth walls and no copper warping at the aperture openings; the via dimensions should be accurate to 125±25µm, and the pitch should be 500±50µm. Optionally, the thick plate is a core board with a thickness of 3.0 mm or more, including an inner core board or a multi-layer core board; Drilling processes include laser drilling and mechanical drilling. S2. On the first multilayer core board S200 of the lamination and layering, the through holes and blind holes are filled by integrated electroplating.

[0037] Specifically, such as Figure 4 As shown, on the first multilayer core board S200 of the lamination and layering process, through holes and laser-drilled blind holes 104 are fabricated using a drilling process. Then, through an integrated electroplating process, the through holes are metallized, thereby connecting the circuitry of each layer of the circuit board. Simultaneously, a conductive layer is also obtained on the inner wall of the laser-drilled blind holes 104. On the laser-drilled blind holes 104, preliminary pre-placement slots 105 for carrying conductive paste are obtained. Then, through a patterning process, the desired result is achieved. Figure 5 The second multilayer core board S300 with a graphic shown is illustrated.

[0038] It should be noted that this is a technique that electroplates through-holes and blind holes simultaneously, requiring that the plating inside the holes must not have voids or gaps.

[0039] In particular, the minimum value of the pre-filling groove 105 for carrying conductive paste is 15um, which ensures the filling of subsequent conductive paste. Optionally, the electroplating process includes VCP electroplating, pattern electroplating, etc. S3. Create a plasma pre-filling tank 105.

[0040] Specifically, on the mating surface of the second multilayer core board S300, a photosensitive adhesive film 106 is attached to the mating surface of the second multilayer core board S300 using a vacuum lamination process. After a patterning process, windows are created to form the area to be printed with conductive paste, thus obtaining the desired result. Figure 6 and Figure 7 The third multilayer core board S401 / S402 shown has plasma pre-filling slots (single and double sides).

[0041] It should be noted that the windowing accuracy of the pattern on the photosensitive film 106 is ±50um; The photosensitive film 106 is free of bubbles and wrinkles; the pattern window is free of defects such as incomplete development; and the bottom of the conductive paste pre-placement tank 105 is free of colloids and impurities. Optionally, the photosensitive film 106 may be of the type containing polyimide colloid, requiring high temperature resistance (>200°C), photosensitive properties, and high voltage resistance (30 kV / mm).

[0042] S4, conductive paste 107 is used to fabricate conductive butt joints. Specifically, on the mating surfaces of the third multilayer core board S401 / S402 with conductive paste pre-placement slots (single and double sides), conductive paste 107 is uniformly coated onto the conductive paste pre-placement slots 105 using a printing process. After baking and curing, a sheet is obtained as shown in the image. Figure 8 and Figure 9 The fourth multilayer core board S501 / S502 shown has conductive mating posts (single and double sides).

[0043] It should be noted that the printing of conductive paste 107 must not result in collapse or dripping that contaminates other areas; the external dimensions of the conductive butt joints must be 300±30um. Specifically, the conductive docking posts are required to exceed the height of the photosensitive film by 10~30um, specifically based on the thickness of the second dielectric layer 102b being >45%; Optionally, the conductive paste 107 comprises a colloid containing silver-copper composite particles, wherein the particle size of the silver-copper composite particles is 5-10 μm and the conductivity ρ ≤ 1.524 × 10⁻⁶. 3 mohm·μm; Printing processes include screen printing and electrostatic spraying; S5. By using the encapsulating film 108 and conductive mating posts, the multilayer core board is pressed together and made conductive. Specifically, on the fourth multilayer core board S501 / S502 with conductive mating posts (single and double-sided), an encapsulating film 108 is pre-attached to the mating surfaces of the fourth multilayer core board S501 / S502 with conductive mating posts (single and double-sided) using a vacuum lamination process, forming a... Figure 10 and Figure 11 The structure shown in the schematic diagram of the conductive butt posts (single and double sides) bonded to the carrier adhesive film in the multilayer core board, on S601 / S602, after the lamination process, results in the following: Figure 12 and Figure 13 The multi-layer core board multi-pressure structure S701 / S702 shown herein, wherein Figure 12 The S701 shown is a three-pressure structure. Figure 13 The S702 shown is a dual-pressure structure.

[0044] It should be noted that the 108 encapsulating film should be free of bubbles and wrinkles; after lamination, there should be no snake-like patterns and no delamination during thermal stress testing; the lamination alignment should be ±30um; and the overall board warpage should be less than 3.0mm. Optionally, the encapsulating film 108 may be of the type of polyimide colloid, which is required to be resistant to high temperature (>200°C) and high voltage (30kV / mm).

[0045] In particular, the schematic diagrams S701 / S702 of the multilayer core board double-press (triple-press) structure are only examples, representing a solution that can produce high-layer thick boards with more than 2 layers of multilayer core boards in one go. Example 2

[0046] This embodiment provides a printed circuit board, which is manufactured according to the manufacturing method of the thick plate printed circuit board provided in Embodiment 1.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for manufacturing a thick printed circuit board, characterized in that, include: A dense array of small holes with conductive circuits is formed on a thick plate to obtain the first core plate; A first multilayer core board with a dielectric layer is obtained by adding layers on the mating surface of the first core board through a lamination process. Laser blind holes are formed on the mating surface of the first multilayer core board, and pre-placed slots for carrying conductive paste are formed on the laser blind holes. Then, the second multilayer core board is obtained through patterning process. A photosensitive adhesive film is attached to the mating surface of the second multilayer core board, and a window is made in the photosensitive adhesive film to create a conductive paste area to be printed corresponding to the pre-laid slot, thus obtaining the third multilayer core board. A conductive paste is applied to the pre-placed slots of the third multilayer core board to form conductive butt joints, thus obtaining a fourth multilayer core board. On the mating surface of the fourth multilayer core board with conductive mating posts, a sealing film is pre-applied using a vacuum lamination process. After pre-applied film, multiple fourth multilayer core boards are laminated together using a lamination process to obtain a multilayer core board multi-press structure.

2. The method for manufacturing a thick plate printed circuit board according to claim 1, characterized in that, The thick plate is a core plate with a thickness of 3.0 mm or more, including an inner core plate or multiple core plates.

3. The method for manufacturing a thick plate printed circuit board according to claim 1, characterized in that, Forming a dense array of small holes with conductive circuits on a thick plate includes: A dense array of small holes is created on a thick plate through pattern transfer and drilling processes, and a conductive circuit is created through electroplating processes. The drilling processes include laser drilling and mechanical drilling. The aperture size accuracy of the dense micro-aperture array meets the requirements of a diameter of 125±25um and a distance between the centers of two adjacent apertures of 500±50um.

4. The method for manufacturing a thick plate printed circuit board according to claim 1, characterized in that, The minimum value of the electroplating recess in the pre-placed slot is 15µm.

5. The method for manufacturing a thick plate printed circuit board according to claim 1, characterized in that, The windowing accuracy of the photosensitive film is ±50µm, and the photosensitive film includes a polyimide colloid.

6. The method for manufacturing a thick plate printed circuit board according to claim 1, characterized in that, The height of the conductive docking post exceeds that of the photosensitive film by 10~30um.

7. The method for manufacturing a thick plate printed circuit board according to claim 1, characterized in that, The conductive paste is a colloid containing silver-copper composite particles, wherein the particle size of the silver-copper composite particles is 5-10 μm, the electrical conductivity ρ≤1.524×10 3 mohm·μm.

8. The method for manufacturing a thick plate printed circuit board according to claim 1, characterized in that, The encapsulating film comprises polyimide colloid, which is resistant to high temperatures >200℃ and high voltages of 30kv / mm.

9. A printed circuit board, characterized in that, The printed circuit board is manufactured according to the method for manufacturing a thick plate printed circuit board as described in any one of claims 1 to 8.

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