CN115243465A

CN115243465A - Drilling method and circuit board

Info

Publication number: CN115243465A
Application number: CN202210831487.2A
Authority: CN
Inventors: 李少强; 康国庆; 白亚旭; 王俊
Original assignee: Jingwang Electronic Technology Zhuhai Co ltd
Current assignee: Jingwang Electronic Technology Zhuhai Co ltd
Priority date: 2022-07-15
Filing date: 2022-07-15
Publication date: 2022-10-25

Abstract

The application relates to the technical field of printed circuit boards, and provides a drilling method and a circuit board, wherein the drilling method comprises the following steps: providing a multilayer board, wherein the multilayer board comprises a target board and a first board and a second board which are respectively arranged on two opposite sides of the target board, a first hole is formed in the multilayer board, the first hole penetrates through the first board and the target board, and a first plating layer and a second plating layer are respectively arranged on the hole wall and the hole bottom of the first hole; drilling a second hole on the multilayer board from one side of the second board far away from the target board, wherein the bottom of the second hole extends to the surface of the second plating layer far away from the first board; and drilling a third hole with a first preset depth at the bottom of the second hole by taking the surface of the second plating layer far away from the first plate as a first reference surface, wherein the bottom of the third hole extends to the surface of the target plate far away from the first plate, and the aperture of the third hole is smaller than or equal to that of the second hole. The drilling method can improve the drilling precision and enable the residual invalid sections of the metallized holes to be smaller.

Description

Drilling method and circuit board

Technical Field

The application relates to the technical field of printed circuit boards, in particular to a drilling method and a circuit board.

Background

To meet the requirements of high-density wiring and to realize electrical connection between the circuits of each layer, various types of metallized holes are applied to printed circuit boards. In some circuit boards, the metallized holes are only used for transmitting electrical signals between some circuit layers, that is, some metallized holes are not effective, and the existence of the ineffective sections can form parasitic capacitance and parasitic inductance, thereby affecting the integrity of high-speed signal transmission in the circuit board.

In the related art, a back drilling method is generally used to remove the invalid section of the metalized hole, which mainly uses a deep drilling method to remove the redundant metal plating (i.e. the invalid section) in the metalized hole. In order to ensure that the redundant metallization layer can be completely removed, the hole diameter of the back drilling hole needs to be larger than the original hole diameter, and the control of the depth of the back drilling hole is also one of the difficulties. Generally, it is required that a target board (signal layer) is not allowed to be drilled, and it is required that the residual invalid section is smaller and better, but in actual processing, due to the influence of factors such as the precision of a drilling machine and the thickness uniformity of a printed circuit board, a drill hole is too deep, the signal layer is drilled and broken, and the circuit board is scrapped, or the drill hole is too shallow, and the residual invalid section is too long.

Disclosure of Invention

The application provides a drilling method and a circuit board, which improve the drilling precision and enable residual invalid sections of a metallized hole to be fewer.

Embodiments of the first aspect of the present application provide a drilling method, including:

providing a multilayer board, wherein the multilayer board comprises a target board, and a first board and a second board which are respectively arranged on two opposite sides of the target board, a first hole is formed in the multilayer board, the first hole penetrates through the first board and the target board, a first plating layer and a second plating layer are respectively arranged on the hole wall and the hole bottom of the first hole, and the first plating layer is electrically connected with a circuit of the first board and a circuit of the target board;

drilling a second hole in the multilayer board from the side of the second board far away from the target board, wherein the bottom of the second hole extends to the surface of the second plating layer far away from the first board;

with the second cladding material is kept away from the surface of first board is first reference surface the third hole of first default depth is drilled out to the bottom in second hole, the bottom in third hole extends to the target board is kept away from the surface of first board, the aperture of third hole is less than or equal to the aperture in second hole.

In some of these embodiments, the third bore has a bore diameter greater than or equal to the bore diameter of the first bore, and the third bore is disposed coaxially with the first bore.

In some embodiments, after providing a multiwall sheet, and before drilling a second hole in the multiwall sheet from a side of the second sheet remote from the target sheet, the drilling method further comprises:

and drilling an auxiliary through hole on the multilayer board, wherein the auxiliary through hole is coaxially arranged with the first hole and penetrates through the multilayer board, the aperture of the auxiliary through hole is smaller than that of the first hole, and the aperture of the auxiliary through hole is smaller than that of the second hole.

In some embodiments, prior to providing a multiwall sheet, the drilling method further comprises:

drilling the first hole in the multi-layer board from the side of the first board away from the target board;

and carrying out metallization treatment on the first hole, so that the first plating layer and the second plating layer are respectively formed on the hole wall and the hole bottom of the first hole.

In some of these embodiments, the first aperture comprises a first sub-aperture and a second sub-aperture in communication, and the target plate comprises a target copper layer; drilling a first hole in the multilayer board from the side of the first board far away from the target board, and specifically comprising:

drilling a first sub-hole on the multilayer board from the side of the first board far away from the target board, wherein the first sub-hole penetrates through the first board;

and drilling a second sub-hole with a second preset depth at the bottom of the first sub-hole from one side of the first plate far away from the target plate by taking one surface, close to the first plate, of the target copper layer as a second reference surface, wherein the second sub-hole penetrates through the target copper layer.

In some embodiments, with a surface of the second plating layer away from the first plate as a first reference surface, drilling a third hole with a first preset depth at the bottom of the second hole, specifically including:

extending a drill bit of the depth control drilling machine into the bottom of the second hole by using the depth control drilling machine with a conductive detection function;

drilling the third hole at the first predetermined depth is started when a tip of the drill contacts a surface away from the first plate with the second plating layer.

In some of these embodiments, the second plate comprises a barrier copper layer, the second plate having an exclusion zone; before drilling a second hole in the multilayer board from a side of the second board remote from the target board, the drilling method further includes: removing the copper barrier layer in the dislocation avoiding area; when a second hole is drilled in the multilayer board from the side of the second board away from the target board, the second hole is located within the relief area.

In some embodiments, the barrier copper layer of the exclusion region is removed by etching or laser burning.

In some of these embodiments, the same alignment targets are used when drilling the second hole in the multiwall sheet from the side of the second sheet away from the target sheet and when drilling the first hole in the multiwall sheet from the side of the first sheet away from the target sheet.

Embodiments of a second aspect of the present application provide a circuit board processed by the drilling method according to the first aspect.

The drilling method provided by the embodiment of the application has the beneficial effects that: the second hole is drilled on the multilayer board from the side, far away from the target board, of the second board, the bottom of the second hole extends to the surface, far away from the first board, of the second plating layer, and then the surface, far away from the first board, of the second plating layer serves as a first reference surface, and the third hole with the first preset depth is drilled at the bottom of the second hole.

Compared with the beneficial effects of the prior art, the circuit board provided by the application has the beneficial effects compared with the drilling method provided by the application, and the drilling method is not repeated herein.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required to be used in the embodiments or the prior art description will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings may be obtained according to these drawings without inventive labor.

FIG. 1 is a flow chart of a method of drilling in one embodiment of the present application;

fig. 2 (a) is a schematic view of the structure of a multilayer board after the first hole is drilled in one embodiment of the present application;

fig. 2 (b) is a schematic view of the structure after metallization of the first hole on the multilayer board shown in fig. 2 (a);

fig. 3 (a) is a schematic view of the structure after the auxiliary through-hole is drilled in the multilayer board shown in fig. 2 (b);

fig. 3 (b) is a schematic view of the structure after the auxiliary second hole is drilled in the multilayer board shown in fig. 3 (a);

fig. 4 is a schematic view of drilling an auxiliary through hole and a second hole in the multilayer board shown in (b) of fig. 2.

The designations in the figures mean:

100. a multilayer board; 10. a target plate; 11. a target copper layer; 20. a first plate; 21. a first copper layer; 30. a second plate; 31. a barrier copper layer; 40. a first hole; 50. a first plating layer; 60. a second plating layer; 70. a second hole; 80. and (5) auxiliary through holes.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of and not restrictive on the broad application.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be 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 be indirectly connected to the other element.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.

Reference throughout this specification to "one embodiment," "some embodiments," or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the present application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," or the like, in various places throughout this specification are not necessarily all referring to the same embodiment, but rather "one or more but not all embodiments" unless specifically stated otherwise. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

To explain the technical solution of the present application, the following description is made with reference to the specific drawings and examples.

Referring to fig. 1, (b) of fig. 2 and fig. 4, an embodiment of the first aspect provides a drilling method, including:

s100: providing a multilayer board 100, wherein the multilayer board 100 comprises a target board 10 and a first board 20 and a second board 30 respectively arranged on two opposite sides of the target board 10, a first hole 40 is formed in the multilayer board 100, the first hole 40 penetrates through the first board 20 and the target board 10, a hole wall of the first hole 40 and a hole bottom of the first hole 40 are respectively provided with a first plating layer 50 and a second plating layer 60, and the first plating layer 50 is electrically connected with a circuit of the first board 20 and a circuit of the target board 10.

Specifically, the multilayer board 100 may be a circuit board after completing conventional process flows such as cutting, inner layer circuit pattern, inner layer AOI detection, and lamination, the first hole 40 is a metallized blind hole, the aperture of the first hole 40 is d1, and the first hole 40 penetrates through the first board 20 and the target board 10 but does not penetrate through the second board 30, so the second plating layer 60 and a portion of the first plating layer 50 located on a side of the target board 10 away from the first board 20 are invalid sections that may form parasitic capacitance and parasitic inductance, the height of the invalid sections is h1, and the invalid sections may affect the integrity of high-speed signal transmission in the circuit board.

It is understood that multiple layers of traces can be disposed on both the first board 20 and the second board 30, and that the first plating layer 50 and the second plating layer 60 are both metal plating layers that can be electrically conductive.

S200: a second hole 70 is drilled in the multilayer board 100 from the side of the second board 30 remote from the target board 10, the bottom of the second hole 70 extending to the surface of the second plating layer 60 remote from the first board 20.

Specifically, referring to fig. 3 (b), the second hole 70 is a blind hole, and the diameter of the second hole 70 is d2.

It will be appreciated that the second bore 70 may or may not be coaxially disposed with the first bore 40. In this embodiment, the second bore 70 is disposed coaxially with the first bore 40.

S300: and drilling a third hole with a first preset depth at the bottom of the second hole 70 by taking the surface of the second plating layer 60 far away from the first plate 20 as a first reference surface, wherein the bottom of the third hole extends to the surface of the target plate 10 far away from the first plate 20, and the aperture of the third hole is smaller than or equal to that of the second hole 70.

Specifically, since the third hole is drilled at the bottom of the second hole 70 to the first predetermined depth with the surface of the second plating layer 60, which is far from the first plate 20, as the first reference surface, it is possible to reduce the influence of the thickness uniformity of the multilayer board 100 and the influence of the accuracy of the drilling machine, improve the drilling accuracy of the third hole, ensure that the bottom of the third hole extends more accurately to the surface of the target board 10, which is far from the first plate 20, without damaging the target board 10, and remove the second plating layer 60 having the height h2 after the third hole is drilled at the bottom of the second hole 70 to the first predetermined depth.

It can be understood that the first preset depth may be set in advance, that is, the distance between the surface of the second plating layer 60 away from the first board 20 and the surface of the target board 10 away from the first board 20 is directly calculated by a theoretical value, or may be determined by sampling and measuring a plurality of multilayer boards 100, for example, a plurality of samples of the multilayer boards 100 without the second hole 70 being drilled may be provided, the samples of the plurality of multilayer boards 100 are cut, the distance between the surface of the second plating layer 60 away from the first board 20 and the surface of the target board 10 away from the first board 20 is measured, a plurality of first measurement values are obtained, and then an average value obtained by calculating the plurality of first measurement values is taken as the first preset depth, so that the value of the first preset depth is more accurate.

It will be appreciated that the third bore and the second bore 70 may be coaxially or non-coaxially disposed. The second hole 70 and the third hole can be drilled together, that is, the second hole 70 is drilled on the multilayer board 100 from the side of the second board 30 far from the target board 10 by using a depth control drilling machine, the bottom of the second hole 70 extends to the surface of the second plating layer 60 far from the first board 20, and then the surface of the second plating layer 60 far from the first board 20 is taken as a first reference surface, and the third hole with the first preset depth is drilled at the bottom of the second hole 70, wherein the hole diameter d3 of the third hole is equal to the hole diameter d2 of the second hole 70, and the third hole is arranged coaxially with the second hole 70.

It is understood that h2 may be less than or equal to h1.

According to the drilling method provided by the embodiment of the application, since the second hole 70 is drilled on the multilayer board 100 from the side of the second board 30 far away from the target board 10, the bottom of the second hole 70 extends to the surface of the second plating layer 60 far away from the first board 20, and then the surface of the second plating layer 60 far away from the first board 20 is taken as the first reference surface, and the third hole with the first preset depth is drilled at the bottom of the second hole 70, the drilling precision of the third hole can be improved, the bottom of the third hole is ensured to extend to the surface of the target board 10 far away from the first board 20 more accurately, so that the second plating layer 60 can be removed more accurately, and the number of residual invalid sections is less.

It is understood that the third hole may have a pore size that is smaller than, greater than, or equal to the pore size of the first hole 40. In this embodiment, the aperture of the third hole is larger than or equal to the aperture of the first hole 40, and the third hole is disposed coaxially with the first hole 40. In this way, after the third hole is drilled, not only the second plating layer 60 but also the first plating layer 50 on the side of the target board 10 away from the first board 20 can be removed more accurately at the same time, where the sum of the heights of the second plating layer 60 and the first plating layer 50 on the side of the target board 10 away from the first board 20 is equal to the first preset depth.

Alternatively, the second hole 70 is disposed coaxially 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. Thus, the occupied area of the second hole 70 can be made small, so that the circuit board is suitable for the requirement of high-density wiring.

Alternatively, after drilling a third hole with a first preset depth at the bottom of the second hole 70, the multi-layer board 100 may be subjected to conventional processes such as pattern routing, solder resist, character, surface treatment, and routing.

As an implementation manner, the drilling of the third hole with the first preset depth 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 specifically includes:

first, the drill of the depth control drill is extended into the bottom of the second hole 70 using the depth control drill having the electrical conduction detection function.

Next, when the tip of the drill contacts the surface of the second plating layer 60 away from the first plate 20, drilling of a third hole of a first predetermined depth is started.

Specifically, when the conductive detection system on the depth-control drilling machine detects that the drill tip of the drill is in contact with the surface of the second plating layer 60 far away from the first plate 20, the conductive detection system feeds back a signal to the control system on the depth-control drilling machine, the control system reads and records the height position of the drill at the moment, then the motor on the depth-control drilling machine continues to drive the drill to feed downwards, and when the feeding distance is the first preset depth, the Z-axis motor stops feeding. In this manner, the depth of the third hole can be precisely controlled, so that the second plating layer 60 can be more precisely removed, resulting in less remaining inactive segments.

Referring to fig. 3 (a), in some embodiments, the second plate 30 includes a copper barrier layer 31, and the second plate 30 has an exclusion zone.

In order that the conduction detection system will feed back a signal to the control system of the depth-controlling drilling machine only when the tip of the drill bit of the depth-controlling drilling machine contacts the surface of the second plated layer 60 away from the first plate 20, the drilling method further comprises, before the second hole 70 is drilled in the multilayer plate 100 from the side of the second plate 30 away from the target plate 10: removing the barrier copper layer 31 in the avoiding area; when the second hole 70 is drilled in the multilayer board 100 from the side of the second board 30 away from the target board 10, the second hole 70 is located in the dislocation area.

In this embodiment, the barrier copper layer 31 in the exclusion region can be removed by etching or laser ablation.

It is understood that if the barrier copper layers 31 are disposed at intervals in a plurality of layers, all the barrier copper layers 31 located in the dislocation region are removed.

Referring to fig. 3 (a), 3 (b) and 4, in some embodiments, in order to further improve the drilling accuracy of the second hole 70 and the third hole, and reduce the copper-pulling and peeling-off phenomenon of the second plating layer 60 caused by drilling the second hole 70 and the third hole, after providing a multilayer board 100 and before drilling the second hole 70 on the multilayer board 100 from the side of the second board 30 away from the target board 10, the drilling method further includes: and drilling an auxiliary through hole 80 on the multilayer board 100, wherein the auxiliary through hole 80 is coaxially arranged with the first hole 40, the auxiliary through hole 80 penetrates through the multilayer board 100, the aperture of the auxiliary through hole 80 is smaller than that of the first hole 40, and the aperture d3 of the auxiliary through hole 80 is smaller than that of the second hole 70.

It will be understood that the auxiliary via 80 will drill through the second plating layer 60 to remove a portion of the second plating layer 60, such as removing the second plating layer 60 with a height h3 in fig. 4, where h3= (1/2 d 3)/tan α, α is half of the drill tip angle of the drill bit when drilling the first hole 40.

It will be appreciated that after the third hole is drilled, another portion of the second plating layer 60 is removed, such as removing the second plating layer 60 having a height h4 in FIG. 4, h3+ h4 ≦ h1.

Referring to fig. 2 (a) and fig. 2 (b), in some embodiments, before providing a multilayer board 100, the drilling method further includes:

first, a first hole 40 is drilled in the multilayer board 100 from the side of the first board 20 remote from the target board 10.

Next, the first hole 40 is metallized so that a first plating layer 50 and a second plating layer 60 are formed on the hole wall and the hole bottom of the first hole 40, respectively.

Specifically, the first hole 40 may be metalized by copper deposition and electroplating, so that the first plating layer 50 and the second plating layer 60 with a predetermined thickness are formed on the wall of the first hole 40, but not limited thereto, in this embodiment, the first plating layer 50 and the second plating layer 60 are both copper layers.

In this embodiment, the first hole 40 includes a first sub-hole and a second sub-hole communicating with each other, and the target plate 10 includes a target copper layer 11; drilling a first hole 40 in the multilayer board 100 from the side of the first board 20 remote from the target board 10, including:

first, a first sub-hole is drilled in the multilayer board 100 from the side of the first board 20 away from the target board 10, the first sub-hole penetrating through the first board 20.

Specifically, the bottom of the first sub-hole extends to the side of the target copper layer 11 near the first board 20.

And secondly, drilling a second sub-hole with a second preset depth at the bottom of the first sub-hole from one side of the first plate 20 far away from the target plate 10 by taking one surface of the target copper layer 11 close to the first plate 20 as a second reference surface, wherein the second sub-hole penetrates through the target copper layer 11.

It is understood that the second predetermined depth may be set in advance, that is, the distance between the side of the target copper layer 11 close to the first board 20 and the surface of the target board 10 far from the first board 20 is directly calculated by a theoretical value, or may be determined by sampling and measuring a plurality of multilayer boards 100, for example, a plurality of samples of the multilayer boards 100 without the second holes 70 drilled therein may be provided, the samples of the plurality of multilayer boards 100 are cut, the distance between the side of the target copper layer 11 close to the first board 20 and the surface of the target board 10 far from the first board 20 is measured, a plurality of second measurement values are obtained, and then an average value obtained by calculating the plurality of second measurement values is used as the second predetermined depth, so that the set value of the second predetermined depth may be more accurate.

By adopting the scheme, the precision is higher when the second hole 70 is drilled, so that the first hole 40 can be more accurately ensured to penetrate through the first plate 20 and the target plate 10, and the influence of the thickness uniformity of the multilayer plate 100 and the influence of the precision of a drilling machine are reduced.

It will be appreciated that the first sub-hole and the second sub-hole can be drilled together, i.e. the first sub-hole is drilled on the multilayer board 100 by using a depth-controlled drilling machine from the side of the first board 20 away from the target board 10, the first sub-hole penetrates through the first board 20, and then the second sub-hole is drilled at a second predetermined depth from the side of the first board 20 away from the target board 10 at the bottom of the first sub-hole by using the side of the target copper layer 11 close to the first board 20 as a second reference surface, wherein the diameter of the first sub-hole is equal to the diameter of the second sub-hole, and the first sub-hole and the second sub-hole are coaxially arranged.

As a practical way, with the surface of the target copper layer 11 close to the first board 20 as a second reference surface, drilling a second sub-hole with a second preset depth at the bottom of the first sub-hole from the side of the first board 20 away from the target board 10, specifically including:

in the first step, a depth control drilling machine with a conductive detection function is used, and a drill bit of the depth control drilling machine extends into the bottom of the first sub-hole.

In the second step, when the drill tip of the drill contacts the surface of the target copper layer 11 close to the first board 20, the drilling of a second sub-hole of a second preset depth is started.

Specifically, when the conductive detection system on the depth-control drilling machine detects that the drill point of the drill bit contacts one surface of the target copper layer 11 close to the first plate 20, the conductive detection system feeds back a signal to the control system on the depth-control drilling machine, the control system reads and records the height position of the drill bit at the moment, then the motor on the depth-control drilling machine continuously drives the drill bit to feed downwards, and when the feeding distance is the second preset depth, the Z-axis motor stops feeding. In this manner, the depth of the first hole 40 can be precisely controlled.

Referring to fig. 2 (a), in some embodiments, the first board 20 includes a first copper layer 21, and the first board 20 has a first region.

Before drilling the first sub-hole in 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 the first sub-hole is drilled in 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 area.

By adopting the scheme, the conductive detection system can feed back a signal to the control system on the depth-control drilling machine only when the drill point of the drill bit on the depth-control drilling machine is contacted with the surface, close to the first plate 20, of the target copper layer 11.

In the present embodiment, the first copper layer 21 in the first region can be removed by etching or laser burning.

Referring to fig. 3 (b), in some embodiments, the same alignment targets (not shown) are used for drilling second holes 70 in multiwall sheet 100 from the side of second sheet 30 away from target sheet 10 and for drilling first holes 40 in multiwall sheet 100 from the side of first sheet 20 away from target sheet 10. In this manner, a minimum offset of the axis of the second bore 70 and the axis of the first bore 40 is ensured.

In the present embodiment, the alignment targets are a plurality of alignment through holes, such as more than 3, disposed on the multilayer board 100. In this manner, more precise alignment can be performed when drilling the second hole 70 in 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 in the multilayer board 100 from the side of the first board 20 away from the target board 10.

Optionally, a plurality of alignment vias are disposed at the edge of the multi-layer board 100 to reduce the impact on the circuitry on the multi-layer board 100.

Embodiments of the second aspect of the present application provide a circuit board, which is processed by the drilling method as in the first aspect.

According to the circuit board provided by the embodiment of the application, the second hole 70 is drilled on the multilayer board 100 from the side, far away from the target board 10, of the second board 30 at first during drilling, the bottom of the second hole 70 extends to the surface, far away from the first board 20, of the second plating layer 60, and then the surface, far away from the first board 20, of the second plating layer 60 serves as a first reference surface, and the third hole with the first preset depth is drilled at the bottom of the second hole 70, so that the second plating layer 60 in the circuit board can be removed more accurately, the residual invalid section is smaller, and the quality and the performance of the circuit board are improved.

The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.

Claims

1. A method of drilling, comprising:

providing a multilayer board, wherein the multilayer board comprises a target board and a first board and a second board which are respectively arranged on two opposite sides of the target board, a first hole is formed in the multilayer board, the first hole penetrates through the first board and the target board, a first plating layer and a second plating layer are respectively arranged on the hole wall and the hole bottom of the first hole, and the first plating layer is electrically connected with the circuit of the first board and the circuit of the target board;

and drilling a third hole with a first preset depth at the bottom of the second hole by taking the surface of the second plating layer far away from the first plate as a first datum plane, wherein the bottom of the third hole extends to the surface of the target plate far away from the first plate, and the aperture of the third hole is smaller than or equal to that of the second hole.

2. The method of drilling according to claim 1, wherein the third hole has a hole diameter larger than or equal to a hole diameter of the first hole, and the third hole is provided coaxially with the first hole.

3. The method of drilling according to claim 1, wherein after providing a multi-layer board and prior to drilling a second hole in the multi-layer board from a side of the second board remote from the target board, the method further comprises:

4. The method of drilling according to claim 1, wherein prior to providing a multi-layer board, the method further comprises:

drilling the first hole in the multiwall sheet from a side of the first sheet remote from the target sheet;

5. The method of drilling according to claim 4, wherein the first hole comprises a first sub-hole and a second sub-hole in communication, the target plate comprises a target copper layer; drilling a first hole in the multilayer board from the side of the first board far away from the target board, and specifically comprising:

drilling a first sub-hole on the multilayer board from one side of the first board far away from the target board, wherein the first sub-hole penetrates through the first board;

6. The drilling method according to claim 1, wherein a third hole with a first preset depth is drilled at the bottom of the second hole by taking the surface of the second plating layer away from the first plate as a first reference surface, and the drilling method specifically comprises the following steps:

7. The method of drilling according to claim 6, wherein the second plate comprises a barrier copper layer, the second plate having an exclusion zone; before drilling a second hole in the multiwall sheet from a side of the second sheet remote from the target sheet, the drilling method further comprises: removing the barrier copper layer in the avoiding area; when a second hole is drilled in the multilayer board from the side of the second board away from the target board, the second hole is located within the relief area.

8. The drilling method as claimed in claim 7, wherein the barrier copper layer of the dislocation area is removed by etching or laser burning.

9. The drilling method according to any one of claims 4 to 8, wherein the same alignment target is used when drilling the second hole in the multiwall sheet from the side of the second sheet remote from the target sheet and when drilling the first hole in the multiwall sheet from the side of the first sheet remote from the target sheet.

10. A circuit board, characterized in that it is manufactured by the drilling method according to any one of claims 1 to 9.