Drilling method and circuit board

Abstract

The application relates to the printed circuit board technical field, and provides a drilling method and a circuit board.The drilling method comprises the following steps: providing a multilayer board, the multilayer board comprising a target board and first and second boards arranged on opposite sides of the target board respectively, the multilayer board being provided with a first hole, the first hole penetrating the first board and the target board, and the hole wall and the hole bottom of the first hole being respectively provided with a first plating layer and a second plating layer; drilling a second hole on the multilayer board from the side of the second board far away from the target board, the bottom of the second hole extending to the surface of the second plating layer far away from the first board; taking the surface of the second plating layer far away from the first board as a first reference surface, drilling a third hole with a first preset depth on the bottom of the second hole, the bottom of the third hole extending to the surface of the target board far away from the first board, and the aperture of the third hole being smaller than or equal to the aperture of the second hole.The drilling method can improve the drilling precision and make the invalid section of the metallized hole smaller.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printed circuit boards, and particularly relates to a drilling method and a circuit board. BACKGROUND

[0002] In order to meet the needs of high-density wiring and realize electrical connection between lines of each layer, various types of metalized holes are applied to printed circuit boards. In some printed circuit boards, the role of the metalized holes is only to transmit electrical signals between some line layers, that is, some metalized holes are invalid, and the existence of the invalid sections forms parasitic capacitance and parasitic inductance, thereby affecting the integrity of high-speed signal transmission in the printed circuit board.

[0003] In the related art, a back drilling method is usually used to remove the invalid sections of the metalized holes, which mainly removes the excess metal plating layer (i.e. the invalid section) in the metalized hole by using a depth-controlled drilling process. In order to ensure that the excess metalized plating layer can be completely removed, it is required that the drilling hole diameter of the back drilling hole must be greater than the original hole diameter, and the control of the back drilling hole depth is also one of the difficulties. Generally, firstly, the target board (signal layer) is not allowed to be drilled through, and secondly, the smaller the residual invalid section is, the better, but in actual processing, due to the influence of factors such as drilling machine precision and uniformity of the thickness of the printed circuit board, the hole is easily drilled too deep, the signal layer is drilled through, the printed circuit board is scrapped, or the hole is drilled too shallow, and the residual invalid section is too long. SUMMARY

[0004] The present application provides a drilling method and a circuit board, which improves the drilling precision and makes the residual invalid section of the metalized hole smaller.

[0005] Embodiments of the first aspect of the present application provide a drilling method, comprising:

[0006] A multi-layer board is provided, the multi-layer board comprising a target board and first and second boards respectively arranged on opposite sides of the target board, the multi-layer board being provided with a first hole, the first hole penetrating the first board and the target board, a hole wall and a hole bottom of the first hole being respectively provided with a first plating layer and a second plating layer, the first plating layer electrically connecting a line of the first board and a line of the target board;

[0007] A second hole is drilled on the multi-layer board from a side of the second board away from the target board, a bottom of the second hole extending to a surface of the second plating layer away from the first board;

[0008] A third hole of a first preset depth is drilled at the bottom of the second hole with the surface of the second plating layer away from the first board as a first reference surface, a bottom of the third hole extending to a surface of the target board away from the first board, and a hole diameter of the third hole being less than or equal to a hole diameter of the second hole.

[0009] In some embodiments, the third hole has a hole diameter greater than or equal to a hole diameter of the first hole, and the third hole is coaxially arranged with the first hole.

[0010] In some embodiments, after providing a multi-layered board, and before drilling a second hole on the multi-layered board from a side of the second board away from the target board, the drilling method further comprises:

[0011] drilling an auxiliary through hole on the multi-layered board, the auxiliary through hole is coaxially arranged with the first hole and the auxiliary through hole penetrates through the multi-layered board, the auxiliary through hole has a hole diameter smaller than the hole diameter of the first hole, and the auxiliary through hole has a hole diameter smaller than the hole diameter of the second hole.

[0012] In some embodiments, before providing a multi-layered board, the drilling method further comprises:

[0013] drilling the first hole on the multi-layered board from a side of the first board away from the target board;

[0014] performing a metalization process on the first hole, so that a hole wall and a hole bottom of the first hole form the first plating layer and the second plating layer, respectively.

[0015] In some embodiments, the first hole comprises a first sub-hole and a second sub-hole connected in series, and the target board comprises a target copper layer; drilling the first hole on the multi-layered board from a side of the first board away from the target board specifically comprises:

[0016] drilling the first sub-hole on the multi-layered board from a side of the first board away from the target board, the first sub-hole penetrates through the first board;

[0017] drilling the second sub-hole on the first sub-hole from a side of the first board away from the target board, the second sub-hole penetrates through the target copper layer, and the second sub-hole has a second preset depth.

[0018] In some embodiments, drilling the third hole on the second hole from a surface of the second plating layer away from the first board specifically comprises:

[0019] using a depth control drill machine with a conductive detection function, and extending a drill bit of the depth control drill machine into the bottom of the second hole;

[0020] when a drill tip of the drill bit contacts the surface of the second plating layer away from the first board, start drilling the third hole with a first preset depth.

[0021] In some embodiments, the second plate includes a barrier copper layer, the second plate has a relief area; before drilling a second hole on the multi-layer plate from a side of the second plate away from the target plate, the drilling method further comprises: removing the barrier copper layer in the relief area; when drilling the second hole on the multi-layer plate from the side of the second plate away from the target plate, the second hole is located in the relief area.

[0022] In some embodiments, the barrier copper layer in the relief area is removed by etching or laser burning.

[0023] In some embodiments, the same alignment target is used when drilling the second hole on the multi-layer plate from the side of the second plate away from the target plate and when drilling the first hole on the multi-layer plate from the side of the first plate away from the target plate.

[0024] Embodiments of the second aspect of the application provide a circuit board processed by the drilling method of the first aspect.

[0025] The drilling method provided by the embodiments of the application has the beneficial effects that: since the second hole is first drilled on the multi-layer plate from a side of the second plate away from the target plate, the bottom of the second hole extends to a surface of the second plating layer away from the first plate, then the third hole of the first preset depth is drilled at the bottom of the second hole with the surface of the second plating layer away from the first plate as a first reference surface, the drilling precision of the third hole can be improved, the bottom of the third hole can be more accurately extended to a surface of the target plate away from the first plate, and thus the second plating layer can be more accurately removed, and the residual invalid section is less.

[0026] The circuit board provided by the application has the beneficial effects of the drilling method provided by the application compared with the prior art, which will not be described here. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0028] Figure 1 is a flowchart of the drilling method in one of the embodiments of the application;

[0029] Figure 2 (a) in is a structural schematic diagram of the multi-layer plate after drilling the first hole in one of the embodiments of the application;

[0030] Figure 2 (b) is a structure diagram of the first hole on the multilayer board shown in (a) after a metalization process; Figure 2

[0031] Figure 3 (a) is a structure diagram of the multilayer board shown in (b) after drilling the first hole; Figure 2

[0032] Figure 3 (b) is a structure diagram of the multilayer board shown in (a) after drilling the second hole; Figure 3

[0033] Figure 4 (b) is a structure diagram of the multilayer board shown in (a) after drilling the auxiliary through hole and the second hole. Figure 2

[0034] The meaning of the mark in the figure is:

[0035] 100, multilayer board; 10, target board; 11, target copper layer; 20, first board; 21, first copper layer; 30, second board; 31, barrier copper layer; 40, first hole; 50, first plating layer; 60, second plating layer; 70, second hole; 80, auxiliary through hole. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0037] It should be noted that when an element is referred to as being "fixed to" or "set to" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0038] In addition, the terms "first", "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0039] ​​​​Reference to“one embodiment”,“some embodiments” or“an embodiment” in the present application means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrases“in one embodiment”,“in some embodiments”,“in other embodiments”,“in additional embodiments” and so on in various places in the specification are not necessarily all referring to the same embodiment, although the application can include more than one embodiment.

[0040] To illustrate the technical solutions of the present application, the following will be described in conjunction with specific drawings and embodiments.

[0041] Please refer to Figure 1 , Figure 2 (b) and Figure 4 , the application first aspect provides a drilling method, comprising:

[0042] S100: providing a multi-layer board 100, the multi-layer board 100 includes a target board 10 and a first board 20 and a second board 30 respectively arranged on the opposite sides of the target board 10, the multi-layer board 100 is provided with a first hole 40, the first hole 40 penetrates the first board 20 and the target board 10, the hole wall of the first hole 40 and the hole bottom of the first hole 40 are respectively provided with a first plating layer 50 and a second plating layer 60, the first plating layer 50 is electrically connected with the circuit of the first board 20 and the circuit of the target board 10.

[0043] Specifically, the multi-layer board 100 can be a circuit board after completing the conventional process flow of cutting, inner layer circuit pattern, inner layer AOI detection and pressing, etc., the first hole 40 is a metallized blind hole, the hole diameter of the first hole 40 is d1, the first hole 40 penetrates the first board 20 and the target board 10 but does not penetrate the second board 30, so the second plating layer 60 and the part of the first plating layer 50 located on the side of the target board 10 away from the first board 20 are the invalid sections which will form parasitic capacitance and parasitic inductance, the height of the invalid section is h1, the invalid section will affect the integrity of high-speed signal transmission in the circuit board.

[0044] It can be understood that the first board 20 and the second board 30 can be provided with multi-layer circuits, and the first plating layer 50 and the second plating layer 60 are metal plating layers that can conduct electricity.

[0045] S200: drilling a second hole 70 on the multi-layer board 100 from the side of the second board 30 away from the target board 10, the bottom of the second hole 70 extends to the surface of the second plating layer 60 away from the first board 20.

[0046] Specifically, please refer to Figure 3In (b) of the above, the second hole 70 is a blind hole, and the diameter of the second hole 70 is d2.

[0047] It can be understood that the second hole 70 can be coaxial or non-coaxial with the first hole 40. In the embodiment, the second hole 70 is coaxial with the first hole 40.

[0048] S300: Drilling a third hole with a first preset depth at the bottom of the second hole 70, taking the surface of the second plating layer 60 away from the surface of the first plate 20 as the first reference surface, and the bottom of the third hole extending to the surface of the target plate 10 away from the surface of the first plate 20, and the diameter of the third hole being less than or equal to the diameter of the second hole 70.

[0049] Specifically, since the third hole with the first preset depth is drilled at the bottom of the second hole 70, taking the surface of the second plating layer 60 away from the surface of the first plate 20 as the first reference surface, the influence of the thickness uniformity of the multi-layer plate 100 and the influence of the drilling precision can be reduced, the drilling precision of the third hole can be improved, and the bottom of the third hole can be ensured to extend to the surface of the target plate 10 away from the surface of the first plate 20 more accurately without damaging the target plate 10. After the third hole with the first preset depth is drilled at the bottom of the second hole 70, the second plating layer 60 with a height of h2 will be removed.

[0050] It can be understood that the first preset depth can be set in advance, that is, the distance between the surface of the second plating layer 60 away from the surface of the first plate 20 and the surface of the target plate 10 away from the surface of the first plate 20 is directly calculated by a theoretical value, or the first preset depth can also be determined after sampling and measuring a plurality of multi-layer plates 100. For example, a plurality of samples of multi-layer plates 100 without the second hole 70 can be provided, the plurality of samples of multi-layer plates 100 are cut to measure the distance between the surface of the second plating layer 60 away from the surface of the first plate 20 and the surface of the target plate 10 away from the surface of the first plate 20, a plurality of first measurement values are obtained, and the average value of the plurality of first measurement values is taken as the first preset depth. In this way, the value of the first preset depth can be more accurate.

[0051] It can be understood that the third hole can be coaxial or non-coaxial with the second hole 70. The second hole 70 and the third hole can be drilled together, that is, a depth control drilling machine is used to drill the second hole 70 on the multi-layer plate 100 from the side of the second plate 30 away from the target plate 10, the bottom of the second hole 70 extending to the surface of the second plating layer 60 away from the surface of the first plate 20, and then the third hole with the first preset depth is drilled at the bottom of the second hole 70, taking the surface of the second plating layer 60 away from the surface of the first plate 20 as the first reference surface. At this time, the diameter d3 of the third hole is equal to the diameter d2 of the second hole 70, and the third hole is coaxial with the second hole 70.

[0052] It can be understood that h2 can be less than or equal to h1.

[0053] The drilling method provided by the embodiments of the present application can improve the drilling precision of the third hole, ensure that the bottom of the third hole extends to the surface of the target plate 10 away from the first plate 20 more accurately, and thus can remove the second plating layer 60 more accurately, so that the residual invalid section is less.

[0054] It can be understood that the aperture of the third hole can be smaller than, greater than or equal to the aperture of the first hole 40. In the embodiments, the aperture of the third hole is greater than or equal to the aperture of the first hole 40, and the third hole is coaxially arranged with the first hole 40. In this way, after the third hole is drilled, not only the second plating layer 60 can be removed more accurately, but also the first plating layer 50 located on the side of the target plate 10 away from the first plate 20 can be removed accurately at the same time, and at this time, the height of the second plating layer 60 and the first plating layer 50 located on the side of the target plate 10 away from the first plate 20 is equal to the first preset depth.

[0055] Optionally, the second hole 70 is coaxially arranged with the first hole 40, and the aperture d2 of the second hole 70 is smaller than or equal to the aperture d1 of the first hole 40. In this way, the occupied area of the second hole 70 can be small, so that the circuit board is suitable for the demand of high-density wiring.

[0056] Optionally, after the third hole of the first preset depth is drilled at the bottom of the second hole 70, the multilayer plate 100 can also be subjected to conventional processes such as graphic circuit, solder mask, character, surface treatment and milling forming.

[0057] As one of the modes that can be implemented, the third hole of the first preset depth is drilled at the bottom of the second hole 70 with the surface of the second plating layer 60 away from the first plate 20 as the first reference surface, and specifically includes:

[0058] First, a depth control drill machine with a conductive detection function is used, and the drill bit of the depth control drill machine is inserted into the bottom of the second hole 70.

[0059] Second, when the drill tip of the drill bit contacts the surface of the second plating layer 60 away from the first plate 20, the third hole of the first preset depth is started to be drilled.

[0060] Specifically, when the conductive detection system on the depth control drill machine detects that the drill tip of the drill contacts the surface of the second plating layer 60 away from the first plate 20, the conductive detection system feeds back a signal to the control system on the depth control drill machine, the control system reads and records the height position of the drill at this time, then the motor on the depth control drill machine continues to drive the drill to feed downward, and when the feeding distance is the first preset depth, the Z-axis motor stops feeding. In this way, the depth of the third hole can be accurately controlled, so that the second plating layer 60 can be removed more accurately, and the residual invalid section is less.

[0061] Please refer to Figure 3 (a), in some embodiments, the second plate 30 includes a barrier copper layer 31, and the second plate 30 has an avoidance area.

[0062] In order to make the conductive detection system feed back a signal to the control system on the depth control drill machine only when the drill tip of the drill on the depth control drill machine contacts the surface of the second plating layer 60 away from the first plate 20, before drilling the second hole 70 on the multi-layer plate 100 from the side of the second plate 30 away from the target plate 10, the drilling method further includes: removing the barrier copper layer 31 in the avoidance area; when drilling the second hole 70 on the multi-layer plate 100 from the side of the second plate 30 away from the target plate 10, the second hole 70 is located in the avoidance area.

[0063] In this embodiment, the barrier copper layer 31 in the avoidance area can be removed by etching or laser burning.

[0064] It can be understood that if the barrier copper layer 31 is spaced and arranged in multiple layers, all the barrier copper layers 31 located in the avoidance area are removed.

[0065] Please refer to Figure 3 (a), Figure 3 (b) and Figure 4 In some embodiments, in order to further improve the drilling accuracy of the second hole 70 and the third hole, and at the same time reduce the phenomenon of copper tearing and the second plating layer 60 peeling off when drilling the second hole 70 and the third hole, after providing a multi-layer plate 100, and before drilling the second hole 70 on the multi-layer plate 100 from the side of the second plate 30 away from the target plate 10, the drilling method further includes: drilling an auxiliary through hole 80 on the multi-layer plate 100, the auxiliary through hole 80 is coaxially arranged with the first hole 40 and the auxiliary through hole 80 penetrates the multi-layer plate 100, the diameter of the auxiliary through hole 80 is smaller than the diameter of the first hole 40, and the diameter d3 of the auxiliary through hole 80 is smaller than the diameter d2 of the second hole 70.

[0066] It can be understood that the auxiliary through hole 80 will drill through the second plating layer 60, thereby removing part of the second plating layer 60, such as removing Figure 4A second plating layer 60 with a middle height h3, h3 = (1 / 2d3) / tanα, α is half of the angle of the drill bit tip when drilling the first hole 40.

[0067] It can be understood that after the third hole is drilled, another part of the second plating layer 60 is removed, such as removing Figure 4 A second plating layer 60 with a middle height h4, h3+h4≤h1.

[0068] Please refer to Figure 2 (a) and Figure 2 (b) in which, in some embodiments, before the multilayer board 100 is provided, the hole drilling method further comprises:

[0069] First, drill the first hole 40 on the multilayer board 100 from the side of the first plate 20 away from the target plate 10.

[0070] Second, the first hole 40 is metallized to form a first plating layer 50 and a second plating layer 60 on the hole wall and the hole bottom of the first hole 40, respectively.

[0071] Specifically, the first hole 40 can be metallized by copper plating to form a first plating layer 50 and a second plating layer 60 with a predetermined thickness on the hole wall of the first hole 40, but is not limited thereto. In the present embodiment, the first plating layer 50 and the second plating layer 60 are both copper layers.

[0072] In the present embodiment, the first hole 40 includes a first sub-hole and a second sub-hole in communication, and the target plate 10 includes a target copper layer 11; the first hole 40 is drilled on the multilayer board 100 from the side of the first plate 20 away from the target plate 10, specifically comprising:

[0073] First, drill the first sub-hole on the multilayer board 100 from the side of the first plate 20 away from the target plate 10, the first sub-hole penetrating through the first plate 20.

[0074] Specifically, the bottom of the first sub-hole extends to the side of the target copper layer 11 close to the first plate 20.

[0075] Second, drill the second sub-hole with a second predetermined depth on the bottom of the first sub-hole from the side of the first plate 20 away from the target plate 10, taking the side of the target copper layer 11 close to the first plate 20 as the second reference surface, the second sub-hole penetrating through the target copper layer 11.

[0076] It can be understood that the second preset depth can be set in advance, that is, the distance between the side of the target copper layer 11 close to the first plate 20 and the surface of the target plate 10 away from the first plate 20 is directly calculated by a theoretical value, or the second preset depth can also be determined by sampling and measuring a plurality of multi-layer plates 100. For example, a plurality of samples of multi-layer plates 100 without the second hole 70 drilled can be provided, the plurality of samples of multi-layer plates 100 are cut to measure the distance between the side of the target copper layer 11 close to the first plate 20 and the surface of the target plate 10 away from the first plate 20, a plurality of second measurement values are obtained, and the average value of the plurality of second measurement values is taken as the second preset depth. In this way, the setting value of the second preset depth can be more accurate.

[0077] By adopting the above scheme, the drilling precision of the second hole 70 can be higher, so that the first hole 40 can more accurately ensure that it penetrates the first plate 20 and the target plate 10, and the influence of the thickness uniformity of the multi-layer plate 100 and the influence of the drilling machine precision are reduced.

[0078] It can be understood that the first sub-hole and the second sub-hole can be drilled together, that is, the first sub-hole is drilled from the side of the first plate 20 away from the target plate 10 on the multi-layer plate 100 using the depth control drilling machine, the first sub-hole penetrates the first plate 20, and then the second sub-hole with the second preset depth is drilled from the side of the first plate 20 away from the target plate 10 at the bottom of the first sub-hole with the side of the target copper layer 11 close to the first plate 20 as the second reference surface. At this time, the hole diameter of the first sub-hole is equal to the hole diameter of the second sub-hole, and the first sub-hole and the second sub-hole are coaxially arranged.

[0079] As one of the ways that can be implemented, the second sub-hole with the second preset depth is drilled from the side of the first plate 20 away from the target plate 10 at the bottom of the first sub-hole with the side of the target copper layer 11 close to the first plate 20 as the second reference surface, and specifically includes:

[0080] In the first step, the depth control drilling machine with the electrically conductive detection function is used, and the drill bit of the depth control drilling machine is inserted into the bottom of the first sub-hole.

[0081] In the second step, when the drill tip of the drill bit contacts the side of the target copper layer 11 close to the first plate 20, the second sub-hole with the second preset depth is started to be drilled.

[0082] Specifically, when the electrically conductive detection system on the depth control drilling machine detects that the drill tip of the drill bit contacts the side of the target copper layer 11 close to the first plate 20, the electrically conductive detection system feeds back a signal to the control system on the depth control drilling machine, and the control system reads and records the height position of the drill bit at this time. Then, the motor on the depth control drilling machine continues to drive the drill bit to feed downward, and when the feeding distance is the second preset depth, the Z-axis motor stops feeding. In this way, the depth of the first hole 40 can be accurately controlled.

[0083] Please refer to Figure 2In (a) of some embodiments, the first plate 20 includes a first copper layer 21 and has a first region.

[0084] Before drilling the first sub-hole on the multilayer board 100 from the side of the first board 20 away from the target board 10, the drilling method further includes: removing the first copper layer 21 in the first region; when drilling the first sub-hole on the multilayer board 100 from the side of the first board 20 away from the target board 10, the first sub-hole is located in the first region.

[0085] By adopting the above scheme, the conductive detection system will only send a feedback signal to the control system on the depth-controlled drilling machine when the drill tip of the drill bit on the depth-controlled drilling machine contacts the side of the target copper layer 11 close to the first plate 20.

[0086] In this embodiment, the first copper layer 21 in the first region can be removed by etching or laser ablation.

[0087] Please refer to Figure 3 In (b) of some embodiments, the same alignment target (not shown) is used when drilling the second hole 70 on the multilayer board 100 from the side of the second plate 30 away from the target plate 10 and when drilling the first hole 40 on the multilayer board 100 from the side of the first plate 20 away from the target plate 10. This ensures that the offset between the axis of the drilled second hole 70 and the axis of the first hole 40 is minimized.

[0088] In this embodiment, the alignment target is a plurality of alignment through holes, such as three or more, provided on the multilayer board 100. In this way, more precise alignment can be achieved when drilling the second hole 70 on the multilayer board 100 from the side of the second board 30 away from the target board 10 and when drilling the first hole 40 on the multilayer board 100 from the side of the first board 20 away from the target board 10.

[0089] Optionally, multiple alignment vias are disposed on the edge of the multilayer board 100 to reduce the impact on the circuitry on the multilayer board 100.

[0090] An embodiment of the second aspect of this application provides a circuit board, which is manufactured by the drilling method of the first aspect.

[0091] The circuit board provided in this application embodiment has a second hole 70 drilled on the multilayer board 100 from the side of the second board 30 away from the target board 10 during drilling. The bottom of the second hole 70 extends to the surface of the second plating layer 60 away from the first board 20. Then, taking the surface of the second plating layer 60 away from the first board 20 as the first reference surface, a third hole of a first preset depth is drilled at the bottom of the second hole 70. Therefore, the second plating layer 60 in the circuit board can be removed more accurately, resulting in smaller residual invalid segments, thereby improving the quality and performance of the circuit board.

[0092] The above examples are only used to illustrate the technical solutions of the present application, but not to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those ordinarily skilled in the art should understand: the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method of drilling a borehole, characterized by, The drilling method comprises the following steps: providing a multilayer board, the multilayer board comprising a target board and a first board and a second board arranged on opposite sides of the target board respectively, the multilayer board being provided with a first hole, the first hole being a metallized blind hole, the first hole penetrating the first board and the target board, the hole wall and the hole bottom of the first hole being provided with a first plating layer and a second plating layer respectively, the first plating layer electrically connecting a circuit of the first board and a circuit of the target board, the second board comprising a copper blocking layer, the second board having an avoidance area, the copper blocking layer in the avoidance area being removed; drilling a second hole on the multilayer board from a side of the second board away from the target board, the bottom of the second hole extending to a surface of the second plating layer away from the first board, the second hole being coaxially arranged with the first hole, the second hole being located in the avoidance area; using a depth control drilling machine with a conductive detection function, extending a drill bit of the depth control drilling machine into the bottom of the second hole, when a drill tip of the drill bit contacts the surface of the second plating layer away from the first board, starting to drill a third hole with a first preset depth, the bottom of the third hole extending to a surface of the target board away from the first board, the diameter of the third hole being equal to the diameter of the second hole, the diameter of the third hole being greater than or equal to the diameter of the first hole, the third hole being coaxially arranged with the first hole; wherein the distance between the surface of the second plating layer away from the first board and the surface of the target board away from the first board is directly calculated by a theoretical value as the first preset depth; or the first preset depth is determined by sampling and measuring a plurality of multilayer boards.

2. The drilling method according to claim 1, characterized by, After providing a multilayer board, and before drilling a second hole on the multilayer board from a side of the second board away from the target board, the drilling method further comprises: drilling an auxiliary through hole on the multilayer board, the auxiliary through hole being coaxially arranged with the first hole and penetrating the multilayer board, the diameter of the auxiliary through hole being smaller than the diameter of the first hole, the diameter of the auxiliary through hole being smaller than the diameter of the second hole.

3. The drilling method according to claim 1, characterized by, Before providing a multilayer board, the drilling method further comprises: drilling the first hole on the multilayer board from a side of the first board away from the target board; performing a metallization treatment on the first hole, so that the hole wall and the hole bottom of the first hole form the first plating layer and the second plating layer respectively.

4. The drilling method according to claim 3, characterized by, The first hole comprises a first sub-hole and a second sub-hole connected in communication, and the target board comprises a target copper layer; drilling a first hole on the multilayer board from a side of the first board away from the target board, specifically comprising: drilling a first sub-hole on the multilayer board from a side of the first board away from the target board, the first sub-hole penetrating the first board; taking a surface of the target copper layer close to the first board as a second reference surface, drilling a second sub-hole with a second preset depth on the bottom of the first sub-hole from a side of the first board away from the target board, the second sub-hole penetrating the target copper layer.

5. The method of drilling a borehole according to claim 1, wherein, Removing the copper blocking layer in the avoidance area by etching or laser burning.

6. The drilling method according to any one of claims 3 to 5, characterized in that, The same alignment target is used when drilling the second holes in the multi-layer board from the side of the second board that is further from the target board and when drilling the first holes in the multi-layer board from the side of the first board that is further from the target board.

7. A circuit board, characterized by The circuit board is processed by the hole drilling method as claimed in any one of claims 1 to 6.

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