Back drilling printed circuit and depth control method thereof

Abstract

The present application discloses a back-drilling printed circuit board and a depth control method thereof, wherein the depth control method of the back-drilling printed circuit board comprises: providing a printed circuit board; wherein the printed circuit board comprises a surface copper layer, a start-drilling copper layer, a target copper layer and a back-drilling copper layer in sequence; performing a window opening process on the surface copper layer to form a window; drilling a through hole at the window and detecting the position information of the start-drilling copper layer; the through hole penetrates the surface copper layer, the start-drilling copper layer, the target copper layer and the back-drilling copper layer; and controlling the depth of the secondary drilling of the through hole according to the position information of the start-drilling copper layer to form a back-drilling hole of a preset depth. By the above method, the accuracy of the preset back-drilling depth is improved.

Description

Technical Field

[0001] The present application relates to the field of back drilling processing and manufacturing, and in particular to a back drilling printed circuit board and a depth control method thereof. Background Art

[0002] With the continuous promotion of the information industry, the speed of digital signal transmission is getting faster and faster, the frequency is getting higher and higher, and it is becoming more and more critical to ensure the integrity of the signal. A section of useless copper in the metallized hole in the circuit board that is not used for signal transmission will increase the loss of signal transmission in the circuit board. And when the frequency of the circuit signal increases to a certain height, the excess copper plating in the useless copper hole is equivalent to an antenna, generating signal radiation that interferes with other surrounding signals, and in severe cases will destroy the integrity of signal transmission. Therefore, the back drilling processing method is usually used to drill out the excess copper plating as much as possible, thereby reducing its impact on the signal transmission of the metallized hole board.

[0003] At present, a preset back-drilling depth is usually set in advance, and then the metallized hole is back-drilled according to the preset back-drilling depth to remove the excess copper plating in the metallized hole. However, in actual production, due to various factors such as uneven board thickness and inner layer graphic design, the back-drilling accuracy of back-drilling to remove residual piles according to the preset back-drilling depth is insufficient, resulting in a large signal loss in the signal hole, which is difficult to meet the high-frequency and high-speed performance requirements of the product. Summary of the invention

[0004] The present application proposes a back-drilled printed circuit and a depth control method thereof to improve the accuracy of a preset back-drilling depth.

[0005] To solve the above technical problems, the present application provides a depth control method for back-drilling a printed circuit board, the back-drilling method for a printed circuit board comprising: providing a printed circuit, the printed circuit board sequentially comprising a surface copper layer, a start-drilling copper layer, a target copper layer and a back-drilling copper layer; performing a window opening process on the surface copper layer to form a window; drilling a through hole at the window, and detecting the position information of the start-drilling copper layer; the through hole passes through the surface copper layer, the start-drilling copper layer, the target copper layer and the back-drilling copper layer; and controlling the depth of the secondary drilling of the through hole according to the position information of the start-drilling copper layer to form a back-drilled hole of a preset depth.

[0006] In this embodiment, the window is circular or ring-shaped.

[0007] In this embodiment, the diameter of the window is larger than the diameter of the through hole and smaller than the diameter of the back-drilled hole.

[0008] In this embodiment, the step of performing window opening processing on the surface copper layer to form a window includes:

[0009] A portion of the surface copper layer is etched away by an etching process to form the window.

[0010] In this embodiment, the step of performing window opening processing on the surface copper layer to form a window further includes: using 3D printing technology to print part of the surface copper layer on the surface of the printed circuit board to form the window.

[0011] In this embodiment, the back-drilled hole penetrates the surface copper layer and the initial-drilling copper layer, and abuts against the copper surface of the target copper layer.

[0012] In this embodiment, the step of controlling the depth of the secondary drilling of the through hole according to the position information of the initially drilled copper layer to form a back-drilled hole of a preset depth includes: obtaining the position information of the target copper layer according to the distance between the initially drilled copper layer and the target copper layer and the position information of the initially drilled copper layer; and controlling the depth of the back-drilled hole according to the position information of the target copper layer to form the back-drilled hole of a preset depth.

[0013] In this embodiment, the step of drilling a through hole at the window and detecting the position information of the copper layer to be drilled includes: copper plating the through hole by using a copper electroplating process.

[0014] In this embodiment, the step of controlling the depth of the secondary drilling of the through hole according to the position information of the initially drilled copper layer to form a back-drilled hole of a preset depth includes: performing a secondary drilling on the through hole using a drilling process to remove the copper plating layer on the surface of the through hole to form the back-drilled hole.

[0015] In order to solve the above technical problems, the present application provides a back-drilled printed circuit board, the back-drilled printed circuit board surface copper layer, the starting copper layer, the target copper layer, the back copper layer, as well as through holes and back-drilled holes, wherein the through holes and the back-drilled holes are made using the depth control method for the back-drilled printed circuit board described in any of the above embodiments.

[0016] The beneficial effects of the present application are: by performing window processing on the surface copper layer to form a circular or annular window, the influence of the surface copper layer on the position information of the drill bit detecting the starting copper layer can be eliminated, so that the drill bit can accurately detect the position information of the starting copper layer, so as to obtain more accurate position information of the target copper layer, so as to accurately control the back drilling depth according to the position information of the target copper layer, thereby improving the accuracy of the preset back drilling depth. On the other hand, the distance between the starting copper layer and the target copper layer is closer than the distance between the surface copper layer and the target copper layer. By calculating the back drilling depth with the starting copper layer as the reference surface, the influence caused by the uneven thickness of the dielectric layer other than the starting copper layer and the target copper layer can be effectively eliminated, and the accuracy of the back drilling depth control can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0018] Figure 1 A schematic flow chart of an implementation method of a depth control method for back-drilling a printed circuit board according to the present application;

[0019] Figure 2 This is a schematic structural diagram of an embodiment of a printed circuit board of the present application;

[0020] Figure 3 This is a schematic diagram of the structure of an implementation method of the window of this application;

[0021] Figure 4 This is a schematic structural diagram of an implementation method of a back-drilled printed circuit board in the present application. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0023] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms of "a", "said", and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless otherwise clearly indicated above, and "multiple" generally includes at least two, but does not exclude the inclusion of at least one.

[0024] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0025] It should be understood that the terms "include", "comprises" or any other variations used herein are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, the elements defined by the sentence "includes..." do not exclude the presence of other identical elements in the process, method, article or device that includes the elements.

[0026] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back...), such directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0027] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The presence of the phrase at each location in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0028] This application provides a depth control method for back drilling a printed circuit. Figure 1 , Figure 1 FIG. 1 is a flow chart of an embodiment of a method for controlling the depth of back-drilling a printed circuit board according to the present application. Figure 1 As shown, including:

[0029] Step S11: providing a printed circuit board.

[0030] The printed circuit board includes a surface copper layer 21, a starting copper layer 22, a target copper layer 23 and a back copper layer 24. For details, please refer to Figure 2 , Figure 2 This is a schematic diagram of the structure of an embodiment of a printed circuit board of the present application. Figure 2 As shown, the surface copper layer 21 and the back copper layer 24 are arranged opposite to each other and are respectively located on two opposite sides of the printed circuit board. A starting copper layer 22 and a target copper layer 23 are arranged between the surface copper layer 21 and the back copper layer 24, wherein the target copper layer 23 is the target layer of the back drilling hole, that is, the depth between the target copper layer 23 and the surface copper layer 21 is the depth of the back drilling hole. Among them, the surface copper layer 21, the starting copper layer 22, the target copper layer 23 and the back copper layer 24 are filled with a dielectric layer. Among them, the target copper layer 23 is not a large-area copper layer.

[0031] In one embodiment, the distance between the target copper layer 23 and the surface copper layer 21 is calculated with the surface copper layer 21 as a reference surface, and the position information of the target copper layer 23 relative to the surface copper layer 21 is obtained, thereby obtaining the depth of the back drill hole, and drilling is performed according to the depth of the back drill hole so that the back drill depth reaches the target copper layer 23.

[0032] In this embodiment, the distance between the copper layer 22 to be drilled and the target copper layer 23 is calculated with the copper layer 22 to be drilled as the reference surface, so as to obtain the position information of the target copper layer 23. Specifically, the absolute position information of the copper layer 22 to be drilled is obtained by the drill bit, and the absolute position information of the target copper layer 23 is obtained based on the relative position information between the copper layer 22 to be drilled and the target copper layer 23 and the absolute position information of the copper layer 22 to be drilled, so as to obtain the depth of the back drilling hole, and drill according to the depth of the back drilling hole. Among them, the absolute position information of the copper layer 22 to be drilled refers to the position information of the copper layer 22 to be drilled from the reference surface. Among them, the reference surface can be the manufacturing platform surface, or the surface of the copper layer 21 of the printed circuit board, or the surface of the back copper layer 24. The reference surface should be a surface with a constant distance or thickness from the copper layer 22 to be drilled. In one embodiment, the copper layer 21 or the back copper layer 24 is used as the reference surface. If the copper surface of the copper layer 21 or the back copper layer 24 is thickened, the distance between the copper layer 22 to be drilled and the reference surface is also increased accordingly.

[0033] Step S12: performing window opening processing on the surface copper layer to form a window.

[0034] The process of performing window opening treatment on the surface copper layer includes etching away part of the surface copper layer by chemical etching process to expose the dielectric layer and form a window.

[0035] In another embodiment, when manufacturing the surface copper layer, a portion of the surface copper layer is leak-printed on the surface of the printed circuit board according to a predetermined pattern using 3D printing technology to form a surface copper layer with a window.

[0036] The shape of the window is as follows: Figure 3 As shown, Figure 3 This is a schematic diagram of the structure of an implementation method of the window of this application, such as Figure 3 As shown, a window 3 is provided on the surface of the surface copper layer 21, and the shape of the window 3 can be circular or annular.

[0037] The diameter of the window is larger than the diameter of the through hole and smaller than the diameter of the back-drilled hole.

[0038] Step S13: drilling a through hole at the window and detecting the position information of the copper layer where drilling starts.

[0039] The through hole penetrates the surface copper layer, the initial copper layer, the target copper layer and the back copper layer.

[0040] Specifically, the first drilling is performed at the window to form a through hole. During the process of drilling the through hole, the drill bit detects the position information of the copper layer to be drilled, and the position information is absolute position information. The detection method includes recording the position information of the copper layer when the detection probe contacts the capacitance signal generated by the large-area metal layer or copper layer, which is the position information of the copper layer to be drilled. In this embodiment, by performing window processing on the surface copper layer, the drill bit has no contact with the surface copper layer and will not generate obvious capacitance signals, thereby eliminating the interference of the capacitance signal generated by the surface copper layer on the electrical signal generated by the copper layer to be drilled, so as to obtain accurate position information of the copper layer to be drilled.

[0041] In this embodiment, the initial copper layer is the copper layer closest to the surface copper layer. In the printed circuit board, in addition to the initial copper layer and the target copper layer, other copper layers are also included between the surface copper layer and the back copper layer, which are not limited here.

[0042] This step also includes: copper plating the hole wall of the through hole by using a copper plating process. Before copper plating the hole wall of the through hole by using a copper plating process, the step includes: de-drilling the through hole.

[0043] Step S14: controlling the depth of secondary drilling of the through hole according to the position information of the initially drilled copper layer to form a back-drilled hole of a preset depth.

[0044] Among them, back drilling is to drill the through hole twice to remove the excess copper layer on the inner wall of the through hole, thereby forming a back drilled hole with no copper layer on the inner wall.

[0045] In this embodiment, the back-drilled hole penetrates the surface copper layer and the initial copper layer, and abuts against the copper surface of the target copper layer. Specifically, the back-drilled hole can contact the copper surface of the target copper layer, or be close to the copper surface of the target copper layer but not in contact. Ideally, the bottom of the back-drilled hole contacts the copper surface of the target copper layer, but there are errors in actual production. Therefore, in this embodiment, the back-drilled hole penetrates the target copper layer means that the bottom of the back-drilled hole contacts the copper surface of the target copper layer. In other embodiments, the back-drilled hole can also penetrate the copper surface of the target copper layer.

[0046] This step S14 specifically includes: obtaining the position information of the target copper layer according to the distance between the starting copper layer and the target copper layer and the position information of the starting copper layer; and controlling the depth of the back-drilling hole according to the position information of the target copper layer to form a back-drilling hole of a preset depth. The back-drilling hole of the preset depth includes making the back-drilling hole penetrate the surface copper layer, the starting copper layer, and abut against the target copper layer.

[0047] Among them, the distance between the starting copper layer and the target copper layer is obtained in advance, which can be obtained according to the preset distance between the copper layers in the production process, or the distance between the starting copper layer and the target copper layer can be obtained by a drill bit, which is not limited here.

[0048] The position information of the target copper layer is calculated based on the distance between the starting copper layer and the target copper layer and the position information of the starting copper layer, and then the depth required for back drilling is obtained based on the position information of the target copper layer, and a back drilling hole is drilled according to the back drilling depth, thereby obtaining a back drilling hole of a preset depth.

[0049] The beneficial effect of this embodiment is: by performing window processing on the surface copper layer to form a circular or annular window, the influence of the surface copper layer on the position information of the drill bit detecting the start-drill copper layer is eliminated, so that the drill bit can accurately detect the position information of the start-drill copper layer, so as to obtain more accurate position information of the target copper layer, so as to accurately control the back-drilling depth according to the position information of the target copper layer, thereby improving the accuracy of the preset back-drilling depth. On the other hand, the distance between the start-drilling copper layer and the target copper layer is closer than the distance between the surface copper layer and the target copper layer. By calculating the back-drilling depth with the start-drilling copper layer as the reference surface, the influence caused by the uneven thickness of the dielectric layer other than the start-drilling copper layer and the target copper layer can be effectively eliminated, and the accuracy of back-drilling hole depth control can be further improved.

[0050] This application also provides a back-drilled printed circuit board, see Figure 4 , Figure 4 This is a schematic diagram of the structure of an implementation method of back-drilling a printed circuit board in this application. Figure 4 As shown, the back-drilled printed circuit board includes a surface copper layer 41 , a start-drilling copper layer 42 , a target copper layer 43 , a back copper layer 44 , a through hole 45 and a back-drilled hole 46 .

[0051] The back-drilled hole 46 has a larger diameter than the through hole 45 . The back-drilled hole 46 penetrates the surface copper layer 41 and the initial copper layer 42 and contacts the target copper layer 43 . The through hole 45 penetrates the target copper layer 43 and the back copper layer 44 .

[0052] The hole wall of the through hole 45 is electroplated with a copper layer, while the hole wall of the back-drilled hole 46 is free of a copper layer.

[0053] There is no copper layer around the surface copper layer 41 near the through hole 45 , and a circular or annular window can be formed by a window opening process. The diameter of the window is larger than the diameter of the through hole 45 and smaller than the diameter of the back-drilled hole 46 .

[0054] In this embodiment, the through hole 45 is formed by primary drilling, and then the back-drilled hole 46 is formed by secondary drilling to cover a portion of the through hole 45 .

[0055] The beneficial effect of this embodiment is: by performing window processing on the surface copper layer to form a circular or annular window, the influence of the surface copper layer on the position information of the drill bit detecting the start-drill copper layer is eliminated, so that the drill bit can accurately detect the position information of the start-drill copper layer, so as to obtain more accurate position information of the target copper layer, so as to accurately control the back-drilling depth according to the position information of the target copper layer, thereby improving the accuracy of the preset back-drilling depth. On the other hand, the distance between the start-drilling copper layer and the target copper layer is closer than the distance between the surface copper layer and the target copper layer. By calculating the back-drilling depth with the start-drilling copper layer as the reference surface, the influence caused by the uneven thickness of the dielectric layer other than the start-drilling copper layer and the target copper layer can be effectively eliminated, and the accuracy of back-drilling hole depth control can be further improved.

[0056] The above description is only an implementation method of the present application, and does not limit the patent protection scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A depth control method for back drilling a printed circuit board, characterized in that: The depth control method for back-drilling a printed circuit board comprises: Provided is a printed circuit board; wherein the printed circuit board comprises a surface copper layer, a starting copper layer, a target copper layer and a back copper layer in sequence; Performing window opening processing on the surface copper layer to form a window; Drilling a through hole at the window and detecting the position information of the initially drilled copper layer; the through hole passes through the surface copper layer, the initially drilled copper layer, the target copper layer and the back copper layer; Obtaining the position information of the target copper layer according to the distance between the starting copper layer and the target copper layer and the position information of the starting copper layer; Controlling the depth of the back-drilled hole according to the position information of the target copper layer to form a back-drilled hole of a preset depth; Wherein, the diameter of the window is larger than the diameter of the through hole and smaller than the diameter of the back-drilled hole.

2. The depth control method for back drilling a printed circuit board according to claim 1, characterized in that: The window is circular or annular.

3. The depth control method for back drilling a printed circuit board according to claim 1, characterized in that: The step of performing window opening processing on the surface copper layer to form a window comprises: A portion of the surface copper layer is etched away by an etching process to form the window.

4. The depth control method for back drilling a printed circuit board according to claim 1, characterized in that: The step of performing window opening processing on the surface copper layer to form a window also includes: A portion of the surface copper layer is printed on the surface of the printed circuit board using 3D printing technology to form the window.

5. The depth control method for back drilling a printed circuit board according to claim 1, characterized in that: The back-drilled hole penetrates the surface copper layer and the initial-drilling copper layer, and abuts against the copper surface of the target copper layer.

6. The depth control method for back drilling a printed circuit board according to claim 1, characterized in that: The step of drilling a through hole at the window and detecting the position information of the copper layer to be drilled comprises: The through hole is plated with copper using a copper electroplating process.

7. The depth control method for back drilling a printed circuit board according to claim 6, characterized in that: The step of controlling the depth of the back drilling hole according to the position information of the target copper layer comprises: The through hole is drilled again by using a drilling process to remove the copper plating layer on the surface of the through hole to form the back-drilled hole.

8. A back-drilled printed circuit board, characterized in that: The back-drilled printed circuit board comprises a surface copper layer, a starting copper layer, a target copper layer, a back copper layer, a through hole and a back-drilled hole, wherein the through hole and the back-drilled hole are made by the depth control method for the back-drilled printed circuit board according to any one of claims 1 to 7.

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