Preparation method of printed circuit board and printed circuit board

Abstract

The invention discloses a preparation method of a printed circuit board and the printed circuit board. The preparation method comprises the following steps: filling a via hole of the printed circuit board to form a first organic insulating layer; the inner wall of a via hole of the printed circuit board and the first surface and the second surface of the printed circuit board are provided with first conductive layers, and the via hole comprises a first sub-hole and a second sub-hole which are connected. Removing the first conductive layer on the inner wall of the second sub-hole to form an etching ring; filling and forming a second organic insulating layer in the etching ring, wherein the second organic insulating layer is flush with the first conductive layer on the second surface and is connected with the first conductive layer on the second surface; forming a second conductive layer on one side, away from the second surface, of the first conductive layer; the second conductive layer covers the first conductive layer, the first organic insulating layer and the second organic insulating layer; and performing line pattern etching on the second conductive layer and the first conductive layer to obtain a bonding pad. According to the invention, the problem that the bonding pad is eroded by etching liquid medicine and is lost can be effectively avoided.

Description

Technical Field

[0001] Embodiments of the present invention relate to the technical field of printed circuit boards, and in particular, to a method for manufacturing a printed circuit board and a printed circuit board. Background Art

[0002] With the development of the printed circuit board industry (Printed Circuit Board, abbreviated as PCB), the requirement for the signal rate in the PCB board is getting higher and higher, resulting in denser wiring in the PCB board.

[0003] With the application of the back drilling technology, the unnecessary hole wall part at the end of the plated through hole is drilled off by means of mechanical drilling machine depth control drilling, so as to eliminate the problem of signal distortion. However, with the application of the back drilling technology, there may be pads at the back drilling positions in the board, and the pads do not completely cover or avoid the back drilling holes, but instead there are overlapping parts. There may be pads at the back drilling positions in the PCB board, and the pads do not completely cover or avoid the back drilling holes. Moreover, according to the existing back drilling manufacturing process, when resin plugging the back drilling holes, there will be a certain depression in the resin plugging holes, and the outer dry film cannot fit perfectly, resulting in a gap between the resin plugging holes and the outer dry film. As a result, when performing line etching, the etching solution will flow into the unfitted gap, and the etching solution will etch part of the pads that need to be retained, resulting in the loss of part of the pads. Summary of the Invention

[0004] The present invention provides a method for manufacturing a printed circuit board and a printed circuit board, so as to improve the fullness of the first organic insulating layer on the printed circuit board, avoid forming a gap between the second conductive layer and the dry film, and effectively avoid the problem that the pads are eroded by the etching solution and missing.

[0005] In a first aspect, an embodiment of the present invention provides a method for manufacturing a printed circuit board, and the manufacturing method includes:

[0006] Filling and forming a first organic insulating layer in the via holes of the printed circuit board; wherein, a first conductive layer is provided on the inner wall of the via holes of the printed circuit board, as well as on the first surface and the second surface of the printed circuit board, and the first surface and the second surface are oppositely arranged; the via holes include a connected first sub-hole and a second sub-hole, and the first sub-hole is located between the first surface and the second sub-hole;

[0007] Removing the first conductive layer on the inner wall of the second sub-hole to form an etching ring, the etching ring is flush with the first conductive layer located on the second surface, the center of the etching ring is the first organic insulating layer, and the etching ring is connected to the first conductive layer located on the second surface;

[0008] A second organic insulating layer is filled and formed within the etching ring. The second organic insulating layer is flush with the first conductive layer located on the second surface and is connected to the first conductive layer located on the second surface.

[0009] A second conductive layer is formed on a side of the first conductive layer away from the second surface. The second conductive layer covers the first conductive layer, the first organic insulating layer, and the second organic insulating layer.

[0010] Line pattern etching is performed on the second conductive layer and the first conductive layer to obtain pads.

[0011] In a second aspect, an embodiment of the present invention further provides a printed circuit board. The printed circuit board is formed by the preparation method of the printed circuit board according to any embodiment of the present invention. The printed circuit board is provided with a via hole, and the via hole includes a connected first sub-hole and a second sub-hole.

[0012] The printed circuit board includes a first surface and a second surface, and the first surface and the second surface are disposed opposite to each other.

[0013] The first sub-hole is located between the first surface and the second sub-hole.

[0014] A first organic insulating layer is filled within the first sub-hole and the second sub-hole.

[0015] A first conductive layer is located between the inner wall of the first sub-hole and the first organic insulating layer, and the first conductive layer is also located on the first surface and the second surface.

[0016] A second organic insulating layer is located between the inner wall of the second sub-hole and the first organic insulating layer. The second organic insulating layer is flush with the first conductive layer located on the second surface and is connected to the first conductive layer located on the second surface.

[0017] A second conductive layer is located on a side of the first conductive layer away from the second surface, and the second conductive layer and the first conductive layer form pads.

[0018] The present invention provides a method for preparing a printed circuit board and a printed circuit board. By filling a first organic insulating layer in the via holes of the printed circuit board, a first conductive layer is provided on the inner wall of the via holes of the printed circuit board, as well as on the first surface and the second surface of the printed circuit board, and the first surface and the second surface are oppositely arranged; the via hole includes a connected first sub-hole and a second sub-hole, and the first sub-hole is located between the first surface and the second sub-hole; the first conductive layer on the inner wall of the second sub-hole is removed to form an etching ring, and the etching ring is flush with the first conductive layer on the second surface. The center of the etching ring is the first organic insulating layer, and the etching ring is connected to the first conductive layer on the second surface. By using the etching ring instead of back drilling, because the filling area of the etching ring is small, the secondary filling can be more saturated, and the surface depression of the first organic insulating layer can be further filled; a second organic insulating layer is filled in the etching ring, and the second organic insulating layer is flush with the first conductive layer on the second surface and is connected to the first conductive layer on the second surface, avoiding the depression on the exposed surface of the second organic insulating layer and preventing the formation of a gap between the dry film attached above the second conductive layer and the pad during the etching of the pad, resulting in the etching solution entering the gap and attacking the pad, thereby effectively avoiding the problem that the pad is eroded by the etching solution and missing. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a flowchart of the production of the existing PCB provided by the embodiment of the present invention;

[0020] Figure 2 It is a flowchart of a method for preparing a printed circuit board in an embodiment of the present invention;

[0021] Figure 3 It is a schematic structural diagram of the printed circuit board when filling the first organic insulating layer in an embodiment of the present invention;

[0022] Figure 4 It is a schematic structural diagram of the printed circuit board when removing the inner wall of the second sub-hole in an embodiment of the present invention;

[0023] Figure 5 It is a schematic structural diagram of the printed circuit board after removing the inner wall of the second sub-hole in an embodiment of the present invention;

[0024] Figure 6 It is a schematic structural diagram of the printed circuit board after filling the second organic insulating layer in an embodiment of the present invention;

[0025] Figure 7 It is a schematic structural diagram of the printed circuit board after forming the second conductive layer in an embodiment of the present invention;

[0026] Figure 8 It is a schematic structural diagram of the printed circuit board during the etching of the circuit pattern in an embodiment of the present invention;

[0027] Figure 9 Another structural schematic diagram when performing line pattern etching on a printed circuit board provided by an embodiment of the present invention;

[0028] Figure 10 A structural schematic diagram of a printed circuit board completed by an embodiment of the present invention;

[0029] Figure 11 A structural schematic diagram of a printed circuit board provided by an embodiment of the present invention. Specific embodiments

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the convenience of description, only parts related to the present invention rather than all structures are shown in the drawings.

[0031] In the prior art, when performing resin plugging on back drills, due to the large area of the back drills, in actual production, there will more or less be a certain depression in the resin in the back drills, and there will also be a certain depression in the metal layer above the resin in the back drills. The outer dry film above the metal layer cannot perfectly fit the metal layer, resulting in a gap between the metal layer and the dry film, and thus the etching solution flows into the gap, causing damage to the integrity of the pads.

[0032] Figure 1 The manufacturing flowchart of the existing PCB provided by an embodiment of the present invention is as Figure 1 shown. In step A, through holes are provided on the PCB board 101. The wider side of the through hole is the back drill formed by a mechanical drilling machine. Since the volume increases a lot after resin plugging is required for the through hole after back drilling, and the area of the back drill is large, after resin plugging in the back drill, the formed resin through hole 102 will have a certain depression, and the middle part of the resin through hole 102 also has a depression compared with the metal layers 103 on both sides; in step B, after electroless copper plating on the surfaces of the resin through hole 102 and the metal layer 103, an electroplated metal layer 104 will be formed on the surfaces of the resin through hole 102 and the metal layer 103. Since there is a certain depression in the resin through hole 102, the electroplated metal layer 104 will also have a certain depression; in step C, a dry film 105 is attached above the electroplated metal layer 104. The surface of the electroplated metal layer 104 can be etched with a chemical solution through the dry film 105 as a mask to form a circuit pattern on the surface of the electroplated metal layer 104. The dry film 105 has a certain leveling ability, but if the gap is too large, such as Figure 1As shown, a gap will be formed between the electroplated metal layer 104 and the dry film 105. In the design of a general PCB board, there is a complete pad above the back drill hole, or it is entirely a substrate. However, there is also a design where there is half a pad and half a substrate above the back drill hole. Therefore, when conducting circuit etching, the etching solution will flow into the incompletely adhered gap, and the etching solution will etch part of the pad that needs to be retained, resulting in partial loss of the pad and damage to the integrity of the pad.

[0033] An embodiment of the present invention also provides a method for manufacturing a printed circuit board. Figure 2 It is a flowchart of a method for manufacturing a printed circuit board in an embodiment of the present invention. The method for manufacturing a printed circuit board in an embodiment of the present invention is used to form the printed circuit board of any embodiment of the present invention. As Figure 2 shown, it includes:

[0034] S110. Fill and form a first organic insulating layer in the via hole of the printed circuit board; wherein, a first conductive layer is provided on the inner wall of the via hole of the printed circuit board, as well as on the first surface and the second surface of the printed circuit board, and the first surface and the second surface are oppositely arranged; the via hole includes a connected first sub-hole and a second sub-hole, and the first sub-hole is located between the first surface and the second sub-hole.

[0035] Wherein, Figure 3 It is a schematic structural diagram of the printed circuit board when filling the first organic insulating layer in an embodiment of the present invention. As Figure 3 shown, a first conductive layer 230 is provided on the inner wall of the via hole 210 of the printed circuit board, as well as on the first surface A1 and the second surface A2 of the printed circuit board, and the first surface A1 and the second surface A2 are oppositely arranged; the via hole 210 includes a connected first sub-hole 211 and a second sub-hole 212, and the first sub-hole 211 is located between the first surface A1 and the second sub-hole 212.

[0036] Specifically, by filling resin into the via hole 210 of the printed circuit board, a first organic insulating layer 221 can be formed. Due to the influence of the resin plugging process control and the resin curing shrinkage during the subsequent baking process, there is an easy problem of depression on the surface of the resin in the via hole 210. Then, there is also a certain degree of depression on the surface of the formed first organic insulating layer 221. The depression is as Figure 3 shown. The larger the aperture of the via hole 210, the more serious the depression problem. In addition, a first conductive layer 230 with a preset thickness is provided on the inner wall of the via hole 210.

[0037] S120. Remove the first conductive layer on the inner wall of the second sub-hole to form an etching ring. The etching ring is flush with the first conductive layer located on the second surface. The center of the etching ring is the first organic insulating layer, and the etching ring is connected to the first conductive layer located on the second surface.

[0038] Specifically, Figure 4Schematic diagram of the structure when removing the inner wall of the second sub-hole in the printed circuit board according to an embodiment of the present invention Figure 5 Schematic diagram of the structure of the printed circuit board after removing the inner wall of the second sub-hole according to an embodiment of the present invention, as Figure 4 and Figure 5 shown, a dry film 260 is attached to the first conductive layer 230 on the second surface A2, so that the first conductive layer 230 on the inner wall of the second sub-hole 212 can be removed by etching solution, and thus an etching ring 201 for filling the second insulating layer 222 can be formed. Part of the etching ring 201 is located in the second sub-hole 212, and the etching ring 201 is the Figure 5 blank area in the second sub-hole 212 in

[0039] Compared with the method of forming a back drill hole by mechanical drilling in the prior art, the etching ring 201 formed by removing the first conductive layer 230 on the inner wall of the second sub-hole 212 in the embodiment of the present invention has a much smaller orifice area compared with the orifice area of the traditional back drill hole, and the volume of the etching ring 201 is also much smaller compared with the volume of the traditional back drill hole. When filling the resin into the etching ring 201 to form the second organic insulating layer 222, the fullness of the second organic insulating layer 222 and the filling process can be ensured, and it is ensured that the second organic insulating layer 222 is located between the inner wall of the second sub-hole 212 and the first organic insulating layer 221. The second organic insulating layer 222 is flush with the first conductive layer 230 on the second surface A2 and is connected to the first conductive layer 230 on the second surface A2, avoiding depressions on the exposed surface of the second organic insulating layer 222.

[0040] S130. Fill the etching ring to form a second organic insulating layer, and the second organic insulating layer is flush with the first conductive layer on the second surface and is connected to the first conductive layer on the second surface.

[0041] Specifically Figure 6 Schematic diagram of the structure of the printed circuit board after filling the second organic insulating layer according to an embodiment of the present invention, as Figure 6 shown, when filling into Figure 5After the etching ring 201 is filled with resin, a second organic insulating layer 222 can be formed. The second organic insulating layer 222 is located between the inner wall of the second sub-hole 212 and the first organic insulating layer 221. The second organic insulating layer 222 is flush with the first conductive layer 230 located on the second surface A2 and is connected to the first conductive layer 230 located on the second surface A2. When filling the etching ring 201 with resin to form the second organic insulating layer 222, since the volume and area of the etching ring 201 are smaller than those of the back drill hole in the prior art, the fullness of the second organic insulating layer 222 and the filling process can be ensured, so that the second organic insulating layer 222 is flush with the first conductive layer 230 located on the second surface A2 and is connected to the first conductive layer 230 located on the second surface A2, avoiding depressions on the exposed surface of the second organic insulating layer 222.

[0042] S140. Form a second conductive layer on the side of the first conductive layer away from the second surface; the second conductive layer covers the first conductive layer, the first organic insulating layer, and the second organic insulating layer.

[0043] Specifically, Figure 7 is a schematic structural diagram of the printed circuit board in the embodiment of the present invention after the second conductive layer is formed, as Figure 7 shown. Since there are no depressions on the exposed surface of the second organic insulating layer 222, there are also no depressions on the second conductive layer 240 formed above the second organic insulating layer 222. The second conductive layer 240 covers the first conductive layer 230, the first organic insulating layer 221, and the second organic insulating layer 222. Optionally, before forming the second conductive layer 240, the surfaces where the first conductive layer 230, the first organic insulating layer 221, and the second organic insulating layer 222 are located can be thinned and the board can be polished, etc., to further remove the resin remaining on the first conductive layer 230.

[0044] S150. Perform circuit pattern etching on the second conductive layer and the first conductive layer to obtain pads.

[0045] Specifically, Figure 8 is a schematic structural diagram of the printed circuit board in the embodiment of the present invention during circuit pattern etching, as Figure 8 shown. Since there are also no depressions on the second conductive layer 240, there are no depressions on the dry film attached above the second conductive layer 240. The dry film is the Figure 8 second dry film 250 shown in. Then, there will be no gap between the second conductive layer 240 and the second dry film 250. When etching the pads formed by the first conductive layer 230 and the second conductive layer 240, since there is no gap between the second organic insulating layer 222, the second conductive layer 240, and the second dry film 250, the etching solution will not enter the gap to attack the first conductive layer 230 and the second conductive layer 240, thus effectively avoiding the problem that the pads are eroded by the etching solution and missing.

[0046] On the one hand, when there is an interleaved design between the back drill holes and the pads in the method for manufacturing a printed circuit board provided by the embodiment of the present invention, it can solve the problem of partial loss of the pads after etching caused by such an interleaved design between the back drill holes and the pads; on the other hand, it can also make the positions where there is partial back drill interleaving originally become completely inside or outside the pads, directly without the risk of etching. For example, since only the first conductive layer on the inner wall of the second sub-hole is etched away, the vertical projection area of the first conductive layer exposed by the etching pattern on the printed circuit board is equal to the vertical projection area of the via hole on the printed circuit board, then the via hole originally located outside the pad can still have the second organic insulating layer obtained after etching completely outside the pad, and the via hole originally located inside the pad can still have the second organic insulating layer obtained after etching completely inside the pad. Therefore, by using the method for manufacturing a printed circuit board in the embodiment of the present invention to replace the production of back drill holes, there is directly no risk of pad loss.

[0047] The embodiment of the present invention provides a method for manufacturing a printed circuit board. A first organic insulating layer is filled in the via hole of the printed circuit board. A first conductive layer is provided on the inner wall of the via hole of the printed circuit board, as well as on the first surface and the second surface of the printed circuit board, and the first surface and the second surface are oppositely arranged; the via hole includes a connected first sub-hole and a second sub-hole, and the first sub-hole is located between the first surface and the second sub-hole; the first conductive layer on the inner wall of the second sub-hole is removed to form an etching ring, and the etching ring is flush with the first conductive layer on the second surface. The center of the etching ring is the first organic insulating layer, and the etching ring is connected to the first conductive layer on the second surface. By using the etching ring to replace the back drill, because the filling area of the etching ring is small, the secondary filling can be more plump, and the depression on the surface of the first organic insulating layer can be further filled; a second organic insulating layer is filled in the etching ring, and the second organic insulating layer is flush with the first conductive layer on the second surface and is connected to the first conductive layer on the second surface, avoiding the existence of depressions on the exposed surface of the second organic insulating layer and preventing the formation of a gap between the dry film attached above the second conductive layer and the pad when etching the pad, resulting in the etching solution entering the gap to attack the pad, thereby effectively avoiding the problem of the pad being eroded by the etching solution and missing.

[0048] The embodiment of the present invention also provides a method for removing the first conductive layer on the inner wall of the second sub-hole, including: laminating a dry film on the second surface, after exposure and development, etching the first conductive layer exposed without being covered by the dry film with an etching solution to remove the first conductive layer on the inner wall of the second sub-hole and form an etching ring.

[0049] Specifically, Figure 4 and Figure 5As shown, compared with the existing method of forming back-drilled holes through mechanical drilling, by etching the exposed first conductive layer 230 of the dry film 260 with an etching solution, since the etching solution does not etch non-metallic materials, the substrate material of the printed circuit board will not be damaged during the etching process. The exposed area of the etching ring 201 formed by removing the first conductive layer 230 on the inner wall of the second sub-hole 212 on the second surface A2 is smaller, that is, the filling area and volume of the etching ring 201 are smaller, so that it can ensure that the filling of the etching ring 201 is more plump and there is no depression in the filled resin.

[0050] Optionally, after laminating a dry film on the second surface, exposing and developing it, and etching the first conductive layer exposed without being covered by the dry film with an etching solution to remove the first conductive layer on the inner wall of the second sub-hole to form an etching ring, including:

[0051] S210. Laminate a dry film on the second surface, expose and develop it, and then etch the first organic insulating layer and the first conductive layer exposed without being covered by the dry film with an etching solution; the vertical projection area of the exposed first conductive layer in the printed circuit board is equal to the vertical projection area of the via hole in the printed circuit board.

[0052] Specifically, referring to Figure 4 and Figure 5 , a dry film 260 is laminated on the first conductive layer 230 on the second surface A2, and an etching pattern is provided on the dry film. The etching pattern exposes the first organic insulating layer 221 and the first conductive layer 230. The vertical projection area of the exposed first conductive layer 230 in the printed circuit board is equal to the vertical projection area of the via hole 210 in the printed circuit board, so that the first conductive layer 230 on the inner wall of the second sub-hole 212 can be removed by the etching solution.

[0053] Figure 9 FIG. is a schematic structural diagram of another printed circuit board provided by an embodiment of the present invention during line pattern etching. Figure 4 and Figure 5 only show the case where the vertical projection area of the exposed first conductive layer 230 in the printed circuit board is larger than the vertical projection area of the via hole 210 in the printed circuit board, but in this step, actually the vertical projection area of the exposed first conductive layer 230 in the printed circuit board is equal to the vertical projection area of the via hole 210 in the printed circuit board. The finally formed printed circuit board can be referred to Figure 9 .

[0054] It should be noted that since only the first conductive layer 230 on the inner wall of the second sub-hole 212 is etched away, the vertically projected area of the first conductive layer 230 exposed by the etching pattern on the printed circuit board is equal to the vertically projected area of the via hole 210 on the printed circuit board. Then, the via hole 210 originally located outside the pad can still have all of the second organic insulating layer 222 obtained after etching remain outside the pad, and the via hole 210 originally located inside the pad can still have all of the second organic insulating layer 222 obtained after etching remain inside the pad. Such a design directly eliminates the risk of pad loss.

[0055] S220. Remove the first conductive layer exposed by the etching pattern to form an etching ring.

[0056] Specifically, referring to Figure 4 and Figure 5 , the first conductive layer 230 exposed by the etching pattern is removed by the etching solution, so that the etching ring 201 for filling the second insulating layer 222 can be formed. The etching ring 201 is located inside the second sub-hole 212, and the vertically projected area of the etching ring 201 on the printed circuit board is larger than the vertically projected area of the via hole 210 on the printed circuit board. Thus, the first conductive layer 230 exposed by the etching pattern can be etched away by the etching solution.

[0057] The orifice area of the etching ring 201 is greatly reduced compared with the orifice area of the traditional back drill hole, and the volume of the etching ring 201 is also greatly reduced compared with the volume of the traditional back drill hole. When the resin is filled into the etching ring 201 to form the second organic insulating layer 222, the fullness of the second organic insulating layer 222 and the filling process can be ensured, and it is ensured that the second organic insulating layer 222 is located between the inner wall of the second sub-hole 212 and the first organic insulating layer 221. The second organic insulating layer 222 is flush with the first conductive layer 230 located on the second surface A2 and is connected to the first conductive layer 230 located on the second surface A2, which can further fill the depression on the surface of the first organic insulating layer 221 and avoid the depression on the exposed surface of the second organic insulating layer 222. When the pad pattern circuit of the printed circuit board according to the embodiment of the present invention is etched, since the exposed surface area of the second organic insulating layer 222 is small and there is no depression on the exposed surface of the second organic insulating layer 222, there is no depression on the second conductive layer 240 formed above the second organic insulating layer 222, and there is no depression on the second dry film 250 attached above the second conductive layer 240. When the pad formed by the first conductive layer 230 and the second conductive layer 240 is etched, there is no gap between the second organic insulating layer 222, the second conductive layer 240 and the second dry film 250, and the etching solution will not enter the gap to attack the pad, so that the problem of pad loss due to the erosion of the etching solution can be further effectively avoided.

[0058] S230. Remove the dry film.

[0059] Specifically, after removing the dry film 260, operations such as copper reduction → panel grinding → electroless copper plating → resin plug hole electroplating filling process (plate over filled via, abbreviated as POFV) can be carried out.

[0060] Optionally, an embodiment of the present invention further provides another method for removing the first conductive layer on the inner wall of the second sub-hole. After pasting a dry film on the second surface, exposing and developing it, and etching the exposed first conductive layer that is not covered by the dry film with etching solution to remove the first conductive layer on the inner wall of the second sub-hole and form an etching ring, including:

[0061] S310. Paste a dry film on the second surface. After exposing and developing it, etch the exposed first organic insulating layer and first conductive layer with etching solution; the vertical projected area of the exposed first conductive layer in the printed circuit board is larger than the vertical projected area of the via hole in the printed circuit board.

[0062] Specifically, referring to Figure 4 and Figure 5 , a dry film 260 is pasted on the first conductive layer 230 of the second surface A2. An etching pattern is provided on the dry film 260. The etching pattern exposes the first organic insulating layer 221 and the first conductive layer 230. The vertical projected area of the exposed first conductive layer 230 in the printed circuit board is larger than the vertical projected area of the via hole 210 in the printed circuit board. Thus, the first conductive layer 230 on the inner wall of the second sub-hole 212 can be removed by the etching solution.

[0063] S320. Remove the first conductive layer exposed by the first etching pattern to form an etching ring.

[0064] Specifically, referring to Figure 4 and Figure 5 , during the formation of the second organic insulating layer 222, when removing the first conductive layer 230 exposed by the first etching pattern, a part of the first conductive layer 230 located on the second surface A2 can also be selectively etched, ensuring that the first conductive layer 230 on the inner wall of the second sub-hole 212 is completely etched off, and then a ring-shaped etching ring 201 will be formed. The vertical projected area of the etching ring 201 in the printed circuit board is larger than the vertical projected area of the via hole 210 in the printed circuit board.

[0065] The center of the etching ring 201 is the first organic insulating layer 221. The orifice area of the etching ring 201 is greatly reduced compared with that of the traditional back drill hole, and the volume of the etching ring 201 is also greatly reduced compared with that of the traditional back drill hole. When filling the resin into the etching ring 201 to form the second organic insulating layer 222, the fullness of the second organic insulating layer 222 and the filling process can be ensured, and it is ensured that the second organic insulating layer 222 is located between the inner wall of the second sub-hole 212 and the first organic insulating layer 221. The second organic insulating layer 222 is flush with the first conductive layer 230 located on the second surface A2 and is connected to the first conductive layer 230 located on the second surface A2, which can further fill the depression on the surface of the first organic insulating layer 221 and avoid the depression on the exposed surface of the second organic insulating layer 222. When etching the pad pattern circuit of the printed circuit board formed by the embodiment of the present invention, since the exposed surface area of the second organic insulating layer 222 is small and there is no depression on the exposed surface of the second organic insulating layer 222, there is no depression on the second conductive layer 240 formed above the second organic insulating layer 222, and there is no depression on the second dry film 250 attached above the second conductive layer 240. When etching the pads formed by the first conductive layer 230 and the second conductive layer 240, there is no gap between the second organic insulating layer 222, the second conductive layer 240 and the second dry film 250, and the etching solution will not enter the gap to attack the pads, so that the problem of the pads being eroded by the etching solution and missing can be further effectively avoided.

[0066] In addition, by controlling the etching time of the etching solution, the etching depth can be controlled, and further the depth of the etching ring 201 can be controlled.

[0067] S330. Remove the dry film.

[0068] Specifically, after removing the dry film 260, operations such as copper reduction → board grinding → copper deposition → POFV electroplating can be carried out.

[0069] In the embodiment of the present invention, before forming the second conductive layer on the side of the first conductive layer away from the second surface, it further includes:

[0070] S410. Thinning the first conductive layer.

[0071] Specifically, referring to Figure 6 , the first conductive layer 230 on the second surface A2 can be thinned by etching or grinding operations, and the first conductive layer 230 with a preset copper reduction thickness can be removed.

[0072] S420. Grinding the first conductive layer and the second organic insulating layer.

[0073] Specifically, referring to Figure 6, by grinding the first conductive layer 230 on the second surface A2, the first conductive layer 230, the second organic insulating layer 222, and the first organic insulating layer 221 with a preset copper reduction thickness can be removed, so as to realize the thinning process of the first conductive layer 230, the second organic insulating layer 222, and the first organic insulating layer 221, and further ensure that there are no depressions on the surface of the first organic insulating layer 221. Through the plate grinding process, the resin remaining on the first conductive layer 230 is further removed, so as to continue to deposit copper electroplating above the first conductive layer 230 on the second surface A2, keep the first conductive layer 230 on the second surface A2 at its original thickness, and a new conductive layer can be formed on the second organic insulating layer 222 and the first organic insulating layer 221.

[0074] Optionally, referring to Figure 7 , after the plate grinding process on the first conductive layer and the second organic insulating layer, it further includes:

[0075] Deposit metal above the first conductive layer 230 on the second surface A2, and form a second conductive layer 240 above the first conductive layer 230 on the second surface A2 through the POFV electroplating process.

[0076] It should be noted that the second conductive layer 240 can also be formed on the first surface A1 by the above steps.

[0077] In the embodiment of the present invention, etching the circuit patterns of the second conductive layer and the first conductive layer to obtain pads includes:

[0078] S510. Attach a second dry film on the side of the second conductive layer away from the first conductive layer; after exposure and development, a second etching pattern is formed on the surface of the second conductive layer; the second etching pattern exposes part of the second conductive layer.

[0079] Specifically, referring to Figure 8 and Figure 9 , a second dry film 250 is formed on the side of the second conductive layer 240 away from the first conductive layer 230. The second dry film 250 is provided with a second etching pattern, and the second etching pattern exposes part of the second conductive layer 240. By etching with etching solution, the second conductive layer 240 and the first conductive layer 230 can be etched.

[0080] In addition, since the exposed surface area of the second organic insulating layer 222 is small, there are no depressions on the exposed surface of the second organic insulating layer 222, there are no depressions on the second conductive layer 240 formed above the second organic insulating layer 222, and there are no depressions on the second dry film 250 disposed above the second conductive layer 240. When etching the pads formed by the first conductive layer 230 and the second conductive layer 240, there are no gaps between the second organic insulating layer 222, the second conductive layer 240, and the second dry film 250, and the etching solution will not enter the gaps to attack the pads, thereby effectively avoiding the problem that the pads are missing due to erosion by the etching solution.

[0081] S520. Remove the second conductive layer exposed by the second etching pattern to etch the circuit patterns of the second conductive layer and the first conductive layer to obtain pads.

[0082] Specifically, referring to Figure 8 and Figure 9 , the second conductive layer 240 exposed by the second etching pattern is removed by the etching solution to etch the circuit patterns of the second conductive layer 240 and the first conductive layer 230 to obtain pads. There will be a stepped effect after etching, and normally ink is used to cover it, which does not affect the product performance. The pads are composed of the first conductive layer 230 and the second conductive layer 240 on the second surface A2.

[0083] In addition, since the exposed surface area of the second organic insulating layer 222 is small, there are no depressions on the exposed surface of the second organic insulating layer 222, there are no depressions on the second conductive layer 240 formed above the second organic insulating layer 222, and there are no depressions on the second dry film 250 disposed above the second conductive layer 240. When etching the pads formed by the first conductive layer 230 and the second conductive layer 240, there are no gaps between the second organic insulating layer 222, the second conductive layer 240, and the second dry film 250, and the etching solution will not enter the gaps to attack the pads, thereby effectively avoiding the problem that the pads are missing due to erosion by the etching solution.

[0084] S530. Remove the second dry film.

[0085] Specifically, after removing the second dry film 250, since there are no gaps between the second organic insulating layer 222, the second conductive layer 240, and the second dry film 250, the area below the second dry film 250 in the obtained printed circuit board will not be eroded by the etching solution, and the integrity of the pads can be ensured.

[0086] Optionally, the length of the first sub-hole is greater than the length of the second sub-hole.

[0087] Specifically, Figure 10 is a schematic structural diagram of a printed circuit board after being manufactured according to an embodiment of the present invention. As Figure 10As shown, the second sub-hole 212 is equivalent to a back drill hole in a conventional printed circuit board, but the second sub-hole 212 is formed by etching. By setting the length a2 of the first sub-hole 211 to be greater than the length a1 of the second sub-hole 212, a shallower second sub-hole 212 can be obtained in the printed circuit board, ensuring the accuracy of the second sub-hole 212.

[0088] Optionally, both the first organic insulating layer 221 and the second organic insulating layer 222 are resins.

[0089] According to the method for manufacturing a printed circuit board in an embodiment of the present invention, with reference to Figure 2 - 10 , the manufacturing process of the printed circuit board in the embodiment of the present invention can be summarized into the following steps: pre-process → panel electroplating → resin plugging hole 1 → resin grinding 1 → outer layer dry film pattern transfer 1 → outer layer etching 1 → resin plugging hole 2 → resin grinding 2 → copper reduction → board grinding → copper deposition → POFV electroplating → outer layer dry film pattern transfer 2 → outer layer etching 2 → outer layer AOI → post-process. Resin plugging hole 1 is equivalent to step S110; resin grinding 1 can grind the second surface A2 after step S110 to remove the resin remaining on the second surface A2; outer layer dry film pattern transfer 1 and outer layer etching 1 are the processes of removing the first conductive layer 230 on the inner wall of the second sub-hole 212 in step S120; resin plugging hole 2 and resin grinding 2 refer to the process of step S130; outer layer dry film pattern transfer 2 and outer layer etching 2 refer to the process of step S150. The manufacturing process of a printed circuit board in the prior art includes: pre-process → panel electroplating → back drilling → resin plugging hole → copper reduction → board grinding → copper deposition → POFV electroplating → outer layer dry film pattern transfer → outer layer etching → outer layer AOI → post-process. Compared with the method in the prior art, the method for manufacturing a printed circuit board in the embodiment of the present invention changes the back drilling manufacturing process and the outer layer etching process, that is, uses the method of etching insulation instead of back drilling, so that the volume and area of the resin plugging hole can be significantly reduced, ensuring the fullness of the resin plugging hole, thereby avoiding the problem of the dry film bonding gap.

[0090] In the preparation method of the printed circuit board according to the embodiments of the present invention, on the one hand, when there is an interleaved design between the back drill holes and the pads, the problem of partial missing of the pads after etching caused by such an interleaved design between the back drill holes and the pads can be solved; on the other hand, the positions where there are originally some back drill interleave will become completely inside or outside the pads, directly without the risk of etching. For example, since only the first conductive layer on the inner wall of the second sub-hole is etched away, the vertical projection area of the first conductive layer exposed by the etching pattern on the printed circuit board is equal to the vertical projection area of the via hole on the printed circuit board, then the second organic insulating layer obtained after etching the via hole originally located outside the pad is still completely outside the pad, and the second organic insulating layer obtained after etching the via hole originally located inside the pad is still completely inside the pad. Therefore, by using the preparation method of the printed circuit board according to the embodiments of the present invention instead of the production of the back drill holes, there is directly no risk of pad missing.

[0091] The embodiments of the present invention provide a preparation method of a printed circuit board. When forming the second organic insulating layer, the space between the inner wall of the second sub-hole and the first organic insulating layer can be etched and insulated to replace the back drill, so that the volume of the formed second organic insulating layer is smaller, and the exposed area of the surface of the second organic insulating layer is smaller, thereby ensuring the fullness of the filling process of the second organic insulating layer, ensuring that the second organic insulating layer is flush with the first conductive layer located on the second surface and is connected to the first conductive layer located on the second surface, avoiding depressions on the exposed surface of the second organic insulating layer, and preventing a gap from being formed between the dry film disposed above the second conductive layer and the pad during etching of the pad, resulting in the etching solution entering the gap to attack the pad. Thus, the problem of the pad being eroded and missing by the etching solution can be effectively avoided.

[0092] The embodiments of the present invention further provide a printed circuit board, which is formed by the preparation method of the printed circuit board according to any one of the embodiments of the present invention. Figure 11 It is a schematic structural diagram of a printed circuit board provided by the embodiments of the present invention, as Figure 11As shown, the printed circuit board is provided with a via hole 210, and the via hole 210 includes a connected first sub-hole 211 and a second sub-hole 212; the printed circuit board includes a first surface A1 and a second surface A2, and the first surface A1 and the second surface A2 are oppositely arranged; the first sub-hole 211 is located between the first surface A1 and the second sub-hole 212; a first organic insulating layer 221 is filled in the first sub-hole 211 and the second sub-hole 212; a first conductive layer 230 is located between the inner wall of the first sub-hole 211 and the first organic insulating layer 221, and the first conductive layer 230 is also located on the first surface A1 and the second surface A2; a second organic insulating layer 222 is located between the inner wall of the second sub-hole 212 and the first organic insulating layer 221, and the second organic insulating layer 222 is flush with the first conductive layer 230 located on the second surface A2 and is connected to the first conductive layer 230 located on the second surface A2; a second conductive layer 240 is located on the side of the first conductive layer 230 away from the second surface A2, and the second conductive layer 240 and the first conductive layer 230 form a pad.

[0093] Among them, the via hole 210 is provided on the printed circuit board and penetrates the printed circuit board, and the first sub-hole 211 and the second sub-hole 212 included in the via hole 210 can be formed by drilling and etching. The first surface A1 and the second surface A2 are respectively two opposite surfaces of the printed circuit board, the first sub-hole 211 is located between the first surface A1 and the second sub-hole 212, and the second sub-hole 212 is located between the first sub-hole 211 and the second surface A2, that is, the via hole 210 penetrates the first surface A1 and the second surface A2. The first organic insulating layer 221 and the second organic insulating layer 222 are both formed by filling the first sub-hole 211 and the second sub-hole 212 with the same material, and the first conductive layer 230 and the second conductive layer 240 are both formed by a copper deposition electroplating process. Optionally, the first organic insulating layer 221 and the second organic insulating layer 222 are both resins, and the first conductive layer 230 and the second conductive layer 240 are copper metal layers.

[0094] Specifically, the first organic insulating layer 221 is filled in the first sub-hole 211 and the second sub-hole 212. The first organic insulating layer 221 can be formed by filling resin when the via hole 210 is a through hole. Due to the influence of the resin plug hole process control and the resin curing shrinkage during the subsequent baking process, there is an easy problem of depression on the resin surface in the via hole 210, so there is also a certain degree of depression on the surface of the formed first organic insulating layer 221. The depression is as Figure 3As shown, the larger the aperture of the via hole 210, the more serious the depression problem. During the formation of the first conductive layer 230, a conductive layer is also provided on the inner wall of the second sub-hole 212. However, through chemical etching, the conductive layer on the inner wall of the second sub-hole 212 is etched away, so that the conductive layer is only located on the inner wall of the first sub-hole 211, serving as the first conductive layer 230. The first conductive layer 230 is also located on the first surface A1 and the second surface A2 to form pads in subsequent steps. During the formation of the second organic insulating layer 222, etching can be used instead of back drilling to etch the conductive layer on the inner wall of the second sub-hole 212. Since the conductive layer on the inner wall of the second sub-hole 212 is etched away, and a part of the conductive layer located on the second surface A2 can also be selectively etched away during the etching process, ensuring that the conductive layer on the inner wall of the second sub-hole 212 is completely etched away, an annular etching hole will be formed. The center of the etching hole is the first organic insulating layer 221. The orifice area of the etching hole is much smaller than that of the traditional back drilling hole, and the volume of the etching hole is also much smaller than that of the traditional back drilling hole. When filling the etching hole with resin to form the second organic insulating layer 222, the fullness of the second organic insulating layer 222 and the filling process can be ensured, and it is ensured that the second organic insulating layer 222 is located between the inner wall of the second sub-hole 212 and the first organic insulating layer 221. The second organic insulating layer 222 is flush with the first conductive layer 230 located on the second surface A2 and is connected to the first conductive layer 230 located on the second surface A2, thereby filling the depression on the resin surface in the via hole 210 and avoiding the depression on the exposed surface of the second organic insulating layer 222.

[0095] Furthermore, referring to Figure 2 - 10 , when etching the pad pattern circuit of the printed circuit board according to the embodiment of the present invention, since the exposed surface area of the second organic insulating layer 222 is small, there is no depression on the exposed surface of the second organic insulating layer 222, there is no depression on the second conductive layer 240 formed above the second organic insulating layer 222, and there is no depression on the second dry film 250 attached above the second conductive layer 240. When etching the pads formed by the first conductive layer 230 and the second conductive layer 240, there is no gap between the second organic insulating layer 222, the second conductive layer 240 and the second dry film 250, and the etching solution will not enter the gap to attack the pads, thereby effectively avoiding the problem that the pads are missing due to being eroded by the etching solution.

[0096] An embodiment of the present invention provides a printed circuit board. The printed circuit board is provided with a via hole, and the via hole includes a connected first sub-hole and a second sub-hole; the printed circuit board includes a first surface and a second surface, and the first surface and the second surface are oppositely arranged and serve as two opposite sides of the printed circuit board; the first sub-hole is located between the first surface and the second sub-hole; a first organic insulating layer is filled in the first sub-hole and the second sub-hole; a first conductive layer is located between the inner wall of the first sub-hole and the first organic insulating layer, and the first conductive layer is also located on the first surface and the second surface. A second conductive layer is located on the side of the first conductive layer away from the second surface, and the second conductive layer and the first conductive layer form a pad. A second organic insulating layer is located between the inner wall of the second sub-hole and the first organic insulating layer. Thus, when the second organic insulating layer is formed, the space between the inner wall of the second sub-hole and the first organic insulating layer can be etched and insulated instead of back drilling, so that the volume of the formed second organic insulating layer is smaller, and the exposed area of the surface of the second organic insulating layer is smaller. Thus, the fullness of the filling process of the second organic insulating layer can be ensured, the second organic insulating layer is flush with the first conductive layer located on the second surface and is connected to the first conductive layer located on the second surface, avoiding depressions on the exposed surface of the second organic insulating layer, and preventing a gap from being formed between the dry film attached above the second conductive layer and the pad during the etching of the pad, resulting in the etching solution entering the gap to attack the pad. Thus, the problem of the pad being eroded and missing by the etching solution can be effectively avoided.

[0097] In the embodiment of the present invention, to further avoid depressions on the exposed surface of the second organic insulating layer 222, optionally, the vertical projection area of the second organic insulating layer 222 on the printed circuit board is greater than or equal to the vertical projection area of the via hole on the printed circuit board.

[0098] Specifically, refer to Figure 2 - 11, in the step of forming the second organic insulating layer 222, when etching the conductive layer on the inner wall of the second sub-hole 212, the conductive layer on the inner wall of the second sub-hole 212 can be accurately etched off. Since the conductive layer on the inner wall of the second sub-hole 212 is etched off, an annular etching ring 201 will be formed. The vertical projection area of the etching ring 201 on the printed circuit board is equal to the vertical projection area of the via hole 210 on the printed circuit board. The center of the etching ring 201 is the first organic insulating layer 221. The orifice area of the etching ring 201 is greatly reduced compared with the orifice area of the traditional back drill hole, and the volume of the etching ring 201 is also greatly reduced compared with the volume of the traditional back drill hole. When filling the resin into the etching ring 201 to form the second organic insulating layer 222, the fullness of the second organic insulating layer 222 and the filling process can be ensured, and it is ensured that the second organic insulating layer 222 is located between the inner wall of the second sub-hole 212 and the first organic insulating layer 221. The second organic insulating layer 222 is flush with the first conductive layer 230 located on the second surface A2 and is connected to the first conductive layer 230 located on the second surface A2, avoiding the existence of depressions on the exposed surface of the second organic insulating layer 222, so that the problem of the pad being eroded by the etching solution and missing can be further effectively avoided.

[0099] In an embodiment of the present invention, to further ensure that the conductive layer on the inner wall of the second sub-hole 212 is completely etched away and to avoid depressions on the exposed surface of the second organic insulating layer 222, during the formation of the second organic insulating layer 222, when etching the conductive layer on the inner wall of the second sub-hole 212, a part of the conductive layer located on the second surface A2 can also be selectively etched away to ensure that the conductive layer on the inner wall of the second sub-hole 212 is completely etched away. The vertically projected area of the formed etching ring 201 on the printed circuit board is larger than the vertically projected area of the via hole 210 on the printed circuit board. The center of the etching ring 201 is the first organic insulating layer 221. The orifice area of the etching ring 201 is greatly reduced compared with the orifice area of a traditional back drill hole, and the volume of the etching ring 201 is also greatly reduced compared with the volume of a traditional back drill hole. When filling the etching ring 201 with resin to form the second organic insulating layer 222, the fullness of the second organic insulating layer 222 and the filling process can be ensured, and it is ensured that the second organic insulating layer 222 is located between the inner wall of the second sub-hole 212 and the first organic insulating layer 221. The second organic insulating layer 222 is flush with the first conductive layer 230 located on the second surface A2 and is connected to the first conductive layer 230 located on the second surface A2, avoiding depressions on the exposed surface of the second organic insulating layer 222. When etching the pad pattern circuit of the printed circuit board according to the embodiment of the present invention, since the exposed surface area of the second organic insulating layer 222 is small and there are no depressions on the exposed surface of the second organic insulating layer 222, there are no depressions on the second conductive layer 240 formed above the second organic insulating layer 222, and there are no depressions on the second dry film 250 attached above the second conductive layer 240. When etching the pads formed by the first conductive layer 230 and the second conductive layer 240, there are no gaps between the second organic insulating layer 222, the second conductive layer 240, and the second dry film 250, and the etching solution will not enter the gaps to attack the pads, thereby further effectively avoiding the problem that the pads are eroded by the etching solution and missing.

[0100] An embodiment of the present invention provides a printed circuit board. The second organic insulating layer in the printed circuit board is located between the inner wall of the second sub-hole and the first organic insulating layer. Thus, when forming the second organic insulating layer, the space between the inner wall of the second sub-hole and the first organic insulating layer can use the etching insulation method instead of back drilling, so that the volume of the formed second organic insulating layer is small, and the exposed surface area of the second organic insulating layer is small. Thus, the fullness of the filling process of the second organic insulating layer can be ensured, ensuring that the second organic insulating layer is flush with the first conductive layer located on the second surface and is connected to the first conductive layer located on the second surface, avoiding depressions on the exposed surface of the second organic insulating layer, and preventing gaps from being formed between the dry film attached above the second conductive layer and the pads when etching the pads, resulting in the etching solution entering the gaps to attack the pads, thereby effectively avoiding the problem that the pads are eroded by the etching solution and missing.

[0101] Note that the above are only the preferred embodiments of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments here, and various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments only. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for preparing a printed circuit board, characterized in that, The preparation method includes: Filling and forming a first organic insulating layer in the via holes of the printed circuit board; wherein, a first conductive layer is provided on the inner wall of the via holes of the printed circuit board, and the first surface and the second surface of the printed circuit board, and the first surface and the second surface are oppositely arranged; the via hole includes a connected first sub-hole and a second sub-hole, and the first sub-hole is located between the first surface and the second sub-hole; Removing the first conductive layer on the inner wall of the second sub-hole to form an etching ring, the etching ring is flush with the first conductive layer located on the second surface, the center of the etching ring is the first organic insulating layer, and the etching ring is connected to the first conductive layer located on the second surface; Filling and forming a second organic insulating layer in the etching ring, the second organic insulating layer is flush with the first conductive layer located on the second surface and is connected to the first conductive layer located on the second surface; Forming a second conductive layer on the side of the first conductive layer away from the second surface; the second conductive layer covers the first conductive layer, the first organic insulating layer and the second organic insulating layer; Performing line pattern etching on the second conductive layer and the first conductive layer to obtain pads.

2. The preparation method of the printed circuit board according to claim 1, wherein Removing the first conductive layer on the inner wall of the second sub-hole to form an etching ring, including: Laminating a dry film on the second surface, after exposure and development, etching the first conductive layer exposed without being covered by the dry film through etching solution to remove the first conductive layer on the inner wall of the second sub-hole and form the etching ring.

3. The method for preparing a printed circuit board according to claim 2, wherein Laminating a dry film on the second surface, after exposure and development, etching the first conductive layer exposed without being covered by the dry film through etching solution to remove the first conductive layer on the inner wall of the second sub-hole and form the etching ring, including: Laminating a dry film on the second surface; after exposure and development, an etching pattern is formed on the second surface, and the etching pattern exposes the first organic insulating layer and the first conductive layer; the vertical projection area of the first conductive layer exposed by the etching pattern on the printed circuit board is equal to the vertical projection area of the via hole on the printed circuit board; Removing the first conductive layer exposed by the etching pattern to form the etching ring; Removing the dry film.

4. The method for preparing a printed circuit board according to claim 2, wherein Laminating a dry film on the second surface, after exposure and development, etching the first conductive layer exposed without being covered by the dry film through etching solution to remove the first conductive layer on the inner wall of the second sub-hole and form the etching ring, including: Laminating a dry film on the second surface; after exposure and development, an etching pattern is formed on the second surface, and the etching pattern exposes the first organic insulating layer and the first conductive layer; the vertical projection area of the first conductive layer exposed by the etching pattern on the printed circuit board is greater than the vertical projection area of the via hole on the printed circuit board; Removing the first conductive layer exposed by the etching pattern to form the etching ring; Removing the dry film.

5. The method for preparing a printed circuit board according to claim 2, characterized in that, Before forming the second conductive layer on the side of the first conductive layer away from the second surface, it further includes: Performing a thinning treatment on the first conductive layer; Perform a panel grinding process on the first conductive layer and the second organic insulating layer.

6. The preparation method of the printed circuit board according to claim 1, characterized in that Perform a circuit pattern etching on the second conductive layer and the first conductive layer to obtain pads, including: Laminating a second dry film on the side of the second conductive layer away from the first conductive layer; after exposure and development, a second etching pattern is formed on the surface of the second conductive layer; the second etching pattern exposes a part of the second conductive layer; Remove the second conductive layer exposed by the second etching pattern to perform a circuit pattern etching on the second conductive layer and the first conductive layer to obtain pads; Remove the second dry film.

7. The method for preparing a printed circuit board according to claim 1, wherein The length of the first sub-hole is greater than the length of the second sub-hole.

8. The method for preparing a printed circuit board according to claim 1, wherein, Both the first organic insulating layer and the second organic insulating layer are resins.

9. A printed circuit board, characterized in that, The printed circuit board is formed by the preparation method of the printed circuit board according to any one of claims 1-8; the printed circuit board is provided with a via hole, and the via hole includes a connected first sub-hole and a second sub-hole; The printed circuit board includes a first surface and a second surface, and the first surface and the second surface are oppositely arranged; The first sub-hole is located between the first surface and the second sub-hole; A first organic insulating layer is filled in the first sub-hole and the second sub-hole; A first conductive layer is located between the inner wall of the first sub-hole and the first organic insulating layer, and the first conductive layer is also located on the first surface and the second surface; A second organic insulating layer is located between the inner wall of the second sub-hole and the first organic insulating layer, and the second organic insulating layer is flush with the first conductive layer on the second surface and is connected to the first conductive layer on the second surface; A second conductive layer is located on the side of the first conductive layer away from the second surface, and the second conductive layer and the first conductive layer form a pad.

10. The printed circuit board according to claim 9, characterized in that, The vertical projection area of the second organic insulating layer on the printed circuit board is greater than or equal to the vertical projection area of the via hole on the printed circuit board.

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