Preparation method and application of deep micropores of PCB (Printed Circuit Board)

Abstract

The invention provides a preparation method and application of a PCB deep micropore, and relates to the technical field of PCB manufacturing. Specifically, dry film attachment, exposure, development and etching are sequentially carried out on the surface of a substrate to obtain a circuit pattern on the surface of a dry film, and the dry film and a copper layer at preset positions of deep micropores are removed; laser drilling is carried out on the preset position of the deep micropore through a hole stacking method, and the deep micropore is obtained; and carrying out first copper plating treatment on the deep micropores, then filling resin in the pores, and then carrying out second copper plating treatment to obtain the filled deep micropores. According to the invention, through a specific hole stacking method and an electroplating process, laser drilling and filling of the deep micro-hole with a high aperture and a high depth can be satisfied, no extra requirement for equipment and process parameters is needed, the operation difficulty of the deep micro-hole technology is greatly simplified, and the requirements for electrical performance and reliability of a high-quality PCB product can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of PCB manufacturing, and more particularly, to a method for preparing deep micro-holes on a PCB and its application. Background Art

[0002] A printed circuit board (PCB) is an important electronic component in the electronics industry. In any electronic component containing integrated circuits, a printed circuit board is used to achieve electrical interconnection between various components. In a multi-layer PCB, there is a blind via structure, which refers to a via hole that only connects the outer layer and the inner layer of the circuit board without penetrating the entire board thickness, used to achieve high-density interconnect (HDI) design, reduce the signal transmission path, improve signal integrity, and save circuit board space at the same time. There are two traditional methods for making blind vias: one is the mechanical blind via process, where the PCB is disassembled into sub-boards, drilled separately, electroplated and etched, and then the sub-boards are pressed into a mother board to form the final PCB, and the drilled holes in the sub-boards become the blind vias of the mother board; the other is the HDI blind via process, where after the sub-boards are laminated, layer by layer lamination is carried out, and each lamination involves one pressing, and laser drilling and electroplating to fill the holes are also required separately to form the blind vias required for the mother board. Both of these two blind via preparation technologies have defects such as long manufacturing processes, long production cycles, and high manufacturing costs.

[0003] The deep micro-hole technology is a new method for making blind vias on a PCB. The emergence of the deep micro-hole technology can significantly reduce the manufacturing process and production cycle, thereby reducing the manufacturing cost. Specifically, the deep micro-hole technology mainly relies on laser drilling. Micro-holes are directly ablated on the PCB material through a high-energy laser beam, and the drilling, electroplating, and etching of the blind vias are completed in one pressing, without the need to disassemble the PCB material into sub-boards and press, drill, electroplate, and etch them separately and then press again. Further, after laminating PCB material layers such as the core board, adhesive material, and copper foil after circuit etching to obtain a PCB semi-finished product, laser drilling technology is used to achieve through connection between the top layer or the bottom layer and the inner layer respectively, and then electrical connection is achieved through electroplating and other technologies after the deep micro-holes are formed.

[0004] Compared with the conventional HDI process where only the conduction with the sub - outer layer circuit (i.e., the conduction between L1 - L2 layers) can be achieved through one - time laser drilling, the deep micro - via technology can achieve the conduction between the outer layer and multiple - order inner - layer circuit layers (such as the conduction between L1 - L2, L1 - L3, L1 - L4 layers, etc.). However, this also means an increase in the depth of the holes to be fabricated by laser drilling in the deep micro - via technology, thus bringing about the manufacturing difficulties of laser drilling and electroplating. Specifically, in the conventional laser drilling technology, the depth - to - aperture ratio (AR) ability is 0.8:1. Due to the increase in the depth of blind holes, in order to meet the AR ability requirements, usually the laser aperture also needs to be increased, resulting in the laser aperture increasing from the conventional 0.1 mm - 0.15 mm to 0.2 mm - 0.35 mm. Therefore, the increase in the laser aperture and the increase in the depth of laser blind holes lead to an increase in the manufacturing difficulty of laser drilling and blind - hole electroplating.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The first object of the present invention is to provide a method for preparing PCB deep micro - vias, which is used to solve the defect of high manufacturing difficulty in drilling and electroplating when making large - aperture blind holes by laser in the deep micro - via process.

[0007] The second object of the present invention is to provide a method for preparing a PCB.

[0008] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0009] A method for preparing PCB deep micro - vias includes the following steps:

[0010] Perform dry - film lamination, exposure, development, and etching on the surface of the substrate in sequence to obtain the circuit pattern on the dry - film surface, and remove the dry - film and copper layer at the preset position of the deep micro - via;

[0011] Perform laser drilling at the preset position of the deep micro - via by the stacked - hole method to obtain deep micro - vias; the stacked - hole method includes: setting a first round hole at the center of the preset position of the deep micro - via; selecting N points on the circumference of the first round hole as the centers of circles, where 4 ≤ N ≤ 20, and the centers of circles are evenly distributed on the circumference of the first round hole; setting N second round holes with the centers of circles;

[0012] Perform the first copper plating treatment on the deep micro - via, then fill the hole with resin, and then perform the second copper plating treatment to obtain the filled - in deep micro - via.

[0013] A method for preparing a PCB includes the above - mentioned method for preparing PCB deep micro - vias.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a method for preparing deep micro-holes on a PCB. By using a specific stacked-hole method for laser drilling, the production of deep micro-holes with relatively large diameters and depths becomes simpler, and it can be carried out by conventional laser drilling equipment. At the same time, conventional laser drilling parameters (or fine-tuning parameters) can meet the requirements for manufacturing deep micro-holes, and complex and time-consuming DOE experiments on laser drilling parameters are not required to obtain the laser drilling parameters. In addition, the present invention also provides an electroplating treatment process for deep micro-holes to achieve hole filling, which can solve the problem that conventional deep micro-holes are difficult to be electroplated and filled, and can meet the electrical performance and reliability requirements of high-quality PCB products. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0016] Figure 1 A schematic diagram of the stacked-hole method of the present invention is provided; wherein, Figure 1 (a) is a schematic diagram of a first round hole, Figure 1 (b) is a schematic diagram of a second round hole, Figure 1 (c) is a schematic diagram of a third round hole, Figure 1 (d) is a schematic diagram of a full stacked hole;

[0017] Figure 2 A schematic diagram of the profile of a deep micro-hole of the present invention is provided;

[0018] Figure 3 A schematic diagram of the electroplating process of a deep micro-hole of the present invention is provided;

[0019] Figure 4 A schematic diagram of the PCB layer structure in Embodiment 1 of the present invention is provided. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some, but not all, of the embodiments of the present invention, and are only used to illustrate the present invention, and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0021] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0022] The first aspect of the present invention is to provide a method for preparing deep micro-holes in a PCB. Specifically, it includes the following steps (1) to (3). It should be noted that only the preparation process and method steps related to the deep micro-holes are designed and defined in this aspect. However, in actual production, the preparation of deep micro-holes usually intersects with the conventional preparation process of the PCB, and no restrictions are imposed on the conventional preparation process of the PCB involved in the present invention.

[0023] (1) Perform dry film lamination, exposure, development, and etching on the surface of the substrate in sequence to obtain the circuit pattern on the dry film surface, and remove the dry film and copper layer at the preset position of the deep micro-holes.

[0024] Specifically, first perform dry film lamination and exposure on the copper surface outside the substrate. By exposing the dry film outside the "preset position of the deep micro-holes" and obtaining the circuit pattern on its surface, then perform development and etching to remove the dry film and copper layer at the preset position of the deep micro-holes, so that the substrate material at the preset position of the deep micro-holes is exposed on the surface.

[0025] As a preferred implementation manner, the substrate includes several etched core boards, copper foils, and prepregs, and the substrate is obtained after design, assembly, and lamination.

[0026] As a preferred implementation manner, the substrate can select a suitable substrate material according to application requirements, including but not limited to conventional commercially available or unconventional substrate types such as FR-4 (glass fiber reinforced epoxy resin), high-speed materials, high-frequency materials, etc. The dry film lamination refers to thermally laminating a layer of anti-etch dry film on the substrate through a laminating machine; the exposure refers to transferring the circuit pattern to the surface of the dry film by directly imaging with a laser and exposing the circuit area to be exposed with an LDI exposure machine; the development refers to chemically treating with a developer to develop and remove the unnecessary dry film on the substrate to retain the dry film with the circuit pattern; the etching refers to using the chemical solution of an etching machine to corrode the exposed copper layer of the substrate after development to form the copper layer circuit pattern on the inner layer board surface for inner layer board circuit and signal conduction.

[0027] It is understandable that in the conventional PCB manufacturing process, the inner layer dry film process includes processing steps such as dry film lamination, exposure, development, and etching. When the present invention performs deep micro-hole preparation, the same above-mentioned process is also carried out. However, different from the conventional PCB manufacturing process, the present invention additionally stipulates that the development and the etching are also carried out at the "preset position of the deep micro-hole", so that the "preset position of the deep micro-hole" is exposed on the surface.

[0028] In the present invention, the outer copper layer at the preset position of the deep micro-hole is etched and removed. The purpose of this step is that since copper is more difficult to be laser ablated than the substrate (mainly composed of resin, glass cloth, silica filler, etc.), when making laser large holes, the surface copper layer at the deep micro-hole position is selectively etched and removed first to form a circular copper-free area at the deep micro-hole position. Thus, the material that needs to be laser ablated is the pure substrate, the laser ablation process parameter window is larger, and it is easier to obtain and control the parameters of laser drilling.

[0029] As a preferred embodiment, the consistency between the copper-free area formed by the etching and the preset shape of the deep micro-hole should be good. Usually, the consistency between the circular copper-free area and the required aperture size of the deep micro-hole should be good, and the deviation between the two is controlled within 50 μm.

[0030] (2) Laser drilling is carried out at the preset position of the deep micro-hole by the stacked hole method to obtain deep micro-holes. Specifically, the stacked hole method is processed through the drilling program of the laser drilling. The laser drilling equipment will make deep micro-holes according to the drilling program instructions after stacking holes.

[0031] The stacked hole method includes: setting a first round hole at the center of the preset position of the deep micro-hole; selecting N points on the circumference of the first round hole as the centers of circles, 4 ≤ N ≤ 20, and the centers of circles are evenly distributed on the circumference of the first round hole; setting N second round holes with the centers of circles; in some more preferred embodiments, the second round holes and the first round hole have a certain degree of overlap, and the overlap degree is 10% - 90%.

[0032] Firstly, for the laser drilling technology in the PCB field, the drilling size range of the laser drilling equipment with conventional configuration is usually from 10 μm to 200 μm, and the specific size depends on equipment type, laser power, focusing ability, and the characteristics of PCB materials, etc. For the multi-layer board situation involved in the deep micro-hole technology of the present invention, the aperture of the laser drilling equipment (usually a CO laser) is usually from 50 μm to 200 μm; also therefore, when the blind hole diameter is from 200 μm to 350 μm, the conventional laser drilling equipment is difficult to meet the one-time drilling requirement for large apertures, which leads to an increase in the manufacturing difficulty of laser drilling, and this is also the technical problem to be solved by the stacked hole method in the present invention.

[0033] As a preferred embodiment, the diameter of the deep micro-holes is 200 μm to 350 μm.

[0034] As a preferred embodiment, the diameter of the first round hole is 50 μm to 200 μm, that is, in the present invention, the drilling diameter that can be selected by a conventional laser drilling device is used as the diameter selection for the first drilling.

[0035] As a preferred embodiment, the value of N includes but is not limited to any one of 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or a numerical range formed by any two of them; it can be understood that when the value of N is higher, the shape of the obtained deep micro-holes is closer to a circle. However, when the value of N is lower, the process cost is also lower, and its shape can usually meet the process requirements for deep micro-holes.

[0036] As a preferred embodiment, the diameter of the second round hole is the same as that of the first round hole; the advantage of this is that multiple round holes can be drilled with the same laser drilling process parameters, and only the position of the laser drilling needs to be adjusted, so that the preparation method of the PCB deep micro-holes of the present invention can be realized more simply and quickly.

[0037] As a preferred embodiment, the stacked hole method further includes: arranging third round holes at a position externally tangent to the first round hole and / or at an outer position with an overlap of 10% to 90% with the second round hole, the number of the third round holes being 6 to 24, and the third round holes being evenly distributed outside the first round hole. By designing the third round holes, a deeper micro-hole with a larger diameter can be obtained by a small-diameter laser drilling device.

[0038] As a more preferred embodiment, the number of the third round holes includes but is not limited to any one of 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or a numerical range formed by any two of them.

[0039] As a more preferred embodiment, the diameters of the third round hole, the first round hole and the second round hole are all the same.

[0040] As shown by Figure 1 As an optional embodiment of the present invention: first, a small hole with a diameter of x is drilled by laser as shown in Figure 1 (a) as a pre-hole; then Figure 1(b) shows that another 4 small holes with the same diameter of x are drilled by laser. The centers of these 4 holes are located on the circumference of the pre-drilled small hole, and the center distances of these 4 holes are exactly the same. Then, Figure 1 (c) shows that another 12 small holes with the same diameter of x are drilled by laser. These 12 holes are all externally tangent to the pre-drilled small hole and are evenly distributed outside the pre-drilled small hole. Thus, as Figure 1 (d) shows, a top view distribution diagram of a total of 17 small holes is provided, and the laser drilling is completed. In this embodiment, a schematic diagram of the deep micro-hole shape as Figure 2 shown is obtained.

[0041] It should be noted that in actual implementation, the diameters of the first round hole and the second round hole (and optionally the third round hole) are not exactly the same. Those skilled in the art can adjust the diameter of the round hole to obtain deep micro-holes with any diameter; similarly, the laser drilling parameters and the number of round holes of the round hole can be flexibly adjusted according to the overlap degree between 10% and 90%. Thus, it is possible to obtain a deep micro-hole with a large aperture under the drilling aperture allowed by conventional drilling equipment; the overlapping hole method of the present invention makes the production of deep micro-holes simpler, and can be carried out with a conventional laser drilling equipment. The laser drilling parameters of the original small hole (or fine-tuned parameters) can meet the production of deep micro-holes, and complex and time-consuming DOE experiments on laser drilling parameters are not required to obtain the laser drilling parameters.

[0042] As a preferred embodiment, the laser drilling parameters include: the reticle size is 0.5 mm to 3.0 mm, the laser energy is 0.01 mJ to 50 mJ, the number of pulses is 1 to 50, and the pulse time is 1 μs to 50 μs. It can be understood that for the first round hole, the second round hole, and optionally the third round hole, those skilled in the art can adaptively adjust the parameters of the laser drilling according to the preset aperture parameters.

[0043] (3) Perform a first copper plating treatment on the deep micro-hole, then fill the hole with resin, and then perform a second copper plating treatment to obtain the filled deep micro-hole.

[0044] In the present invention, the deep micro-holes have increased aperture and depth compared with the micro-blind holes of the conventional HDI process, which have exceeded the process capabilities of filling conventional electroplated blind holes; in some alternative embodiments, the depth range of the deep micro-holes is 0.05 mm to 0.4 mm. The laser blind holes of the conventional HDI process are usually set at 0.05 mm to 0.2 mm, the laser hole depth is 0.05 mm to 0.16 mm, and the required hole metallization process is electroplating to fill the holes, that is, copper plating is used to fill the laser blind holes, and at the same time, the surface flatness after electroplating to fill the holes (the depression value is usually ≤15 μm) is required. However, the increase in the depth of the deep micro-holes cannot meet the capacity requirements of electroplating to fill the holes, resulting in insufficient filling depth and the depression value of filling the laser blind holes exceeding the requirements. Therefore, it is necessary to adopt the process route of electroplating-filling-electroplating in this step to solve the problem that electroplating in the conventional technology is difficult to meet the filling requirements of large-depth holes; at the same time, the filling process of the present invention can effectively meet the electrical performance and reliability requirements of PCB users for products. Figure 3 As shown, a schematic diagram of the electroplating process of deep micro-holes of the present invention is provided.

[0045] As a preferred embodiment, the copper plating thickness of the first copper plating treatment is 5 μm to 30 μm, and the copper plating thickness of the second copper plating treatment is 5 μm to 30 μm.

[0046] As a preferred embodiment, the process parameters of the first copper plating treatment and / or the second copper plating treatment are independently selected from: the current density is 5 ASF to 20 ASF, and the electroplating time is 10 min to 180 min; the composition and ratio of the copper plating solution involved, the temperature parameters of the copper plating solution, etc. can all be adaptively adjusted by using the conventional parameters of copper plating treatment in the art.

[0047] As a preferred embodiment, the filling resin uses a special resin for PCB plugging holes, and the reference viscosity is 400 Pa·s to 600 Pa·s.

[0048] As a preferred embodiment, the filling resin includes the following steps: using a vacuum resin hole plugging machine to plug the holes with the filling resin. In some more preferred embodiments, to ensure that the resin enters the holes, the plugging pressure needs to reach a certain range and be appropriately adjusted according to the board thickness and hole diameter, and the pressure is required to be ≥3.0 bar; to ensure that no bubbles are introduced during the hole plugging process, the hole plugging vacuum degree needs to be set within a certain range, and the absolute value is required to be ≥900 mbar; when scraping and cleaning the glue, to ensure that the remaining resin thickness reaches the standard, the pressure of the scraper needs to reach a certain range, generally ≥0.8 bar.

[0049] The second aspect of the present invention lies in providing a method for manufacturing a PCB, including the method for manufacturing deep micro-holes of the PCB as described in the first aspect. It should be noted that the PCB manufacturing process generally includes processes such as blanking, photoimaging, inner AOI, lamination, drilling, hole metallization, outer photoimaging, outer AOI, solder mask, and surface treatment. Among them, some processes overlap with the method for manufacturing deep micro-holes of the PCB and should include the complete defined steps of the method for manufacturing deep micro-holes of the PCB, but other non-overlapping processes are not limited in this aspect. That is, under the premise of being able to achieve PCB manufacturing, any process that includes the method for manufacturing deep micro-holes of the PCB can be used as an implementation manner of this aspect.

[0050] Example

[0051] This example discloses a method for manufacturing deep micro-holes of an 8-layer circuit board. Among them, two deep micro-holes respectively penetrate through layers L1 - L3 and L8 - L6.

[0052] S1. Press multiple etched core boards, copper foils, and prepregs to form an 8-layer substrate. As Figure 4 shown, the 8-layer composite board obtained after processing this step is provided. Among them, the dielectric layer thicknesses of L1 - L3 and L8 - L6 are both 0.2 mm. On the outer copper surface of this substrate, dry film is attached and exposed in sequence to obtain the circuit pattern on the dry film surface, and then development and etching are carried out to remove the dry film and copper layer at the preset positions of the two deep micro-holes.

[0053] S2. Perform laser drilling at the preset positions of the deep micro-holes by the method of stacked holes to obtain deep micro-holes. As Figure 1 (a) - (c) shown, perform the stacked hole manufacturing of the first, second, and third round holes according to its process, which is executed by a PCB numerical control laser drilling machine, and the deep micro-holes are manufactured by presetting drilling program instructions.

[0054] As Figure 1 (a) shown, at the center of the preset position of the deep micro-hole, a first round hole is drilled by laser, and the diameter of the first round hole is 100 μm.

[0055] As Figure 1 (b) shown, select 4 points with the same spacing on the circumference of the first round hole as the centers, and respectively drill 4 second round holes by laser with the 4 centers as the centers. The diameter of the second round hole is 100 μm.

[0056] As Figure 1 (c) shown, select 12 points with the same spacing at a position 100 μm away from the center of the first round hole as the centers, and respectively drill 12 third round holes by laser with the 12 centers as the centers. The diameter of the third round hole is 100 μm. It can be seen that any third round hole is externally tangent to the first round hole.

[0057] For any of the above-mentioned round holes, the laser drilling parameters are as follows: the mask size is 2.0 mm, the laser energy is 30 mJ, the number of pulses is 25, and the pulse time is 25 μs.

[0058] As Figure 2 shown, the schematic diagram of the deep micro-hole profile configuration finally obtained in this step S2 is obtained. In this embodiment, the aperture of the deep micro-hole can be regarded as 300 μm; actually, the upper aperture of the deep micro-hole blind hole is 0.296 mm, the lower aperture is 0.254 mm, and the lower aperture / upper aperture is 86%, meeting the industry requirement that the laser hole aperture ratio ≥ 75%.

[0059] S3. Inspect the deep micro-holes made by the laser drilling machine's multi-hole method. After passing the inspection, perform the next step of mechanical drilling to make through-holes. After removing the burrs at the hole openings, perform plasma degumming treatment on the deep micro-holes to remove the drilling contaminants in the deep micro-holes. The main component of the drilling contaminants is resin colloid.

[0060] S4. Perform copper deposition treatment on the deep micro-holes and other through-holes to deposit copper in the deep micro-holes and through-holes for further electroplating copper treatment.

[0061] S5. Perform the first copper plating treatment on the deep micro-holes. Electroplate copper at a current density of 10 ASF until a copper plating layer with a thickness of 20 μm is obtained. Then, fill the deep micro-holes with the special resin for PCB plugging holes by a vacuum resin plugging hole machine. The plugging hole pressure is 4.0 bar, and the absolute pressure of the equipment vacuum degree is 1 bar; then perform the second copper plating treatment to obtain a 20-μm second copper plating layer with the same copper plating process, thereby obtaining the filled deep micro-holes.

[0062] S6. After completing the electroplating production of the deep micro-holes, the deep micro-hole interlayer conduction is completed. Then, perform the conventional PCB production, including processes such as drilling, copper deposition, electroplating, outer layer exposure, development, etching, solder resist, characters, surface treatment, and shaping, and finally obtain the PCB product.

[0063] Although the present invention has been illustrated and described with specific embodiments, it should be realized that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; those of ordinary skill in the art should understand that: without departing from the spirit and scope of the present invention, the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing deep micro-holes in a PCB, characterized in that, It includes the following steps: Dry film is attached, exposed, developed, and etched on the surface of the substrate in sequence to obtain a circuit pattern on the dry film surface, and the dry film and copper layer at the preset position of the deep micro-holes are removed; Laser drilling is performed at the preset position of the deep micro-holes by the stacked hole method to obtain deep micro-holes; The stacked hole method includes: a first round hole is set at the center of the preset position of the deep micro-holes; N points are selected on the circumference of the first round hole as the centers of circles, 4 ≤ N ≤ 20, and the centers of circles are evenly distributed on the circumference of the first round hole; N second round holes are set with the centers of circles; The deep micro-holes are subjected to the first copper plating treatment, then resin is filled in the holes, and then the second copper plating treatment is performed to obtain the filled deep micro-holes.

2. The method for preparing the PCB deep micro-holes according to claim 1, characterized in that, The diameter of the deep micro-holes is 200 μm to 350 μm.

3. The method for preparing the PCB deep micro-holes according to claim 1, wherein The diameter of the first round hole is 50 μm to 200 μm; Preferably, the overlap degree of the second round hole and the first round hole is 10% to 90%.

4. The method for preparing a PCB deep microvia according to claim 1, wherein The stacked hole method further includes: A third round hole is set at a position tangent to the outside of the first round hole and / or at an outside position with an overlap degree of 10% to 90% with the second round hole, and the third round holes are evenly distributed outside the first round hole.

5. The method for preparing a PCB deep microvia according to claim 4, characterized in that, The number of the third round holes is 6 to 24.

6. The method for preparing the PCB deep micro-holes according to claim 4, wherein The diameter of the second round hole is the same as that of the first round hole; Preferably, the diameters of the third round hole, the second round hole, and the first round hole are the same.

7. The method for preparing a PCB deep micro-hole according to claim 1, characterized in that, The laser drilling parameters include: The reticle size is 0.5 mm to 3.0 mm, the laser energy is 0.01 mJ to 50 mJ, the number of pulses is 1 to 50, and the pulse time is 1 μs to 50 μs.

8. The method for preparing a PCB deep micro-hole according to claim 1, characterized in that, The copper plating thickness of the first copper plating treatment and / or the second copper plating treatment is independently 5 μm to 30 μm; Preferably, the depth range of the deep micro-holes is 0.05 mm to 0.4 mm.

9. The method for preparing the PCB deep micro-holes according to claim 1, wherein The first copper plating treatment and / or the second copper plating treatment independently adopt: the current density is 5 ASF to 20 ASF, and the electroplating time is 10 min to 180 min.

10. A method for preparing a PCB, characterized in that, It includes the preparation method of the PCB deep micro-holes as described in any one of claims 1 to 9.

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