CN115209624A

CN115209624A - PCB back drilling method and PCB

Info

Publication number: CN115209624A
Application number: CN202210830568.0A
Authority: CN
Inventors: 李少强; 姚远; 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: 2022-10-18

Abstract

The application relates to the technical field of printed circuit boards, and provides a PCB back drilling method and a PCB, wherein the PCB back drilling method comprises the following steps: providing a substrate, wherein the substrate comprises a target plate, a first plate and a second plate which are respectively arranged on two opposite sides of the target plate, a first hole is formed in the substrate, the first hole comprises a first sub-hole and a second sub-hole, and a first plating layer, a second plating layer and a third plating layer are respectively arranged on the hole wall of the first sub-hole, the hole bottom of the first sub-hole and the hole wall of the second sub-hole; drilling a second hole penetrating through the second plating layer on the substrate; drilling a third hole in the substrate from the side of the second plate away from the target plate, the third hole extending to the surface of the remaining second plating layer away from the first plate; and drilling a fourth hole with a first preset depth at the bottom of the third hole by taking the surface of the residual second plating layer far away from the first plate as a first reference surface. The PCB back drilling method can remove the residual invalid section more accurately and improve the quality of the PCB.

Description

PCB back drilling method and PCB

Technical Field

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

Background

In order to realize the electrical connection of each layer of circuit on the PCB, a metallized through hole needs to be arranged on the PCB, and on part of the PCB, only the electrical signal transmission between part of the circuit layers needs to be realized through the metallized through hole, so that redundant metallized plating layers (namely, invalid sections) in the metallized through holes need to be removed, so as to avoid that the invalid sections form parasitic capacitance and parasitic inductance to influence the integrity of high-speed signal transmission.

The traditional method for removing the invalid section usually adopts a back drilling mode, when back drilling processing is carried out, the back drilling processing is influenced by factors such as precision influence of a drilling machine and thickness uniformity of a PCB, the depth of a back drilling hole is not easy to control, a signal layer is easily drilled off due to too deep drilling, or the quality of the PCB is influenced due to too long residual invalid section due to too shallow drilling.

Disclosure of Invention

The application provides a PCB back drilling method and a PCB, so that residual invalid sections can be removed more accurately, and the quality of the PCB is improved.

An embodiment of a first aspect of the present application provides a PCB backdrilling method, including:

providing a substrate, wherein the substrate comprises a target plate and a first plate and a second plate which are respectively arranged on two opposite sides of the target plate, a first hole is formed in the substrate, the first hole penetrates through the substrate, the first hole comprises a first sub-hole and a second sub-hole which are coaxial and communicated with each other, the aperture of the first sub-hole is larger than that of the second sub-hole, the first sub-hole penetrates through the first plate and the target plate, a first plating layer, a second plating layer and a third plating layer are respectively arranged on the hole wall of the first sub-hole, the hole bottom of the first sub-hole and the hole wall of the second sub-hole, and the first plating layer is electrically communicated with the circuit of the first plate and the circuit of the target plate;

drilling a second hole penetrating through the second plating layer on the substrate, and removing the third plating layer and a part of the second plating layer, wherein the second hole is coaxially arranged with the first hole, the aperture of the second hole is larger than that of the second sub-hole, and the aperture of the second hole is smaller than that of the first sub-hole;

drilling a third hole in the substrate from a side of the second plate remote from the target plate, the third hole extending to a surface of the remaining second plating layer remote from the first plate, the third hole being disposed coaxially with the first hole, the third hole having an aperture larger than an aperture of the second hole;

and drilling a fourth hole with a first preset depth at the bottom of the third hole by taking the surface, far away from the first plate, of the residual second plating layer as a first reference surface, removing the residual second plating layer, and extending the bottom of the fourth hole to the surface, far away from the first plate, of the target plate.

In some of these embodiments, the fourth hole is disposed coaxially with the first hole, and the fourth hole has an aperture that is greater than or equal to the aperture of the first sub-hole.

In some embodiments, before providing a substrate, the PCB backdrilling method further comprises:

drilling a through hole in the substrate, the through hole penetrating through the first plate, the target plate and the second plate;

drilling a first sub-hole at the through hole of the substrate from one side of the first plate far away from the target plate, wherein the aperture of the first sub-hole is larger than that of the through hole, and the rest of the through holes are second sub-holes;

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

In some embodiments, the first sub-hole includes a first via and a second via that are connected, the target board includes a target copper layer, and a first sub-hole is drilled in the substrate from a side of the first board away from the target board, the first sub-hole extending through the first board and the target board, and the method includes:

drilling a first machining hole in the substrate from one side, far away from the target plate, of the first plate, wherein the first machining hole penetrates through the first plate;

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

In some embodiments, the step of drilling a fourth hole with a first preset depth at the bottom of the third hole with the surface of the remaining second plating layer away from the first plate as a first reference surface, and removing the remaining second plating layer specifically includes:

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

and when the drill tip of the drill bit contacts the surface of the second plating layer far away from the first plate, starting to drill the fourth hole until the fourth hole forms the first preset depth.

In some of these embodiments, the second plate comprises a barrier copper layer, the second plate having keep-away areas; before drilling a third hole in the substrate from a side of the second plate away from the target plate, the PCB backdrilling method further comprises: removing the barrier copper layer in the avoiding area; when a third hole is drilled in the substrate from a side of the second plate remote from the target plate, the third hole is located within the aversion region.

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

In some of these embodiments, the same alignment targets are used when drilling the second hole through the second plated layer in the substrate from the side of the second plate away from the target plate and when drilling the third hole in the substrate from the side of the second plate away from the target plate.

In some embodiments, the alignment targets are provided as a plurality of through holes located at the edge of the substrate.

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

The PCB back drilling method provided by the embodiment of the application has the beneficial effects that: a second hole penetrating through a second plating layer is drilled on the substrate from one side, far away from the target plate, of the second plate, the third plating layer and part of the second plating layer are removed, a third hole is drilled on the substrate from one side, far away from the target plate, of the second plate, the third hole extends to the surface, far away from the first plate, of the second plating layer, the surface, far away from the first plate, of the second plating layer serves as a first reference surface, a fourth hole with a first preset depth is drilled at the bottom of the third hole, and the remaining second plating layer is removed, so that the remaining second plating layer and the remaining third plating layer can be removed more accurately, and the quality of the PCB is improved.

Compared with the beneficial effects of the prior art, the PCB back drilling method provided by the application has the beneficial effects of being compared with the PCB back drilling method provided by the application, and the PCB back 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 needed to be used in the embodiments or the prior art descriptions 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 it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

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

fig. 2 (a) is a schematic structural diagram of the substrate after the through hole is drilled in one embodiment of the present application;

fig. 2 (b) is a schematic view of the structure after the first sub-hole is drilled in the substrate shown in fig. 2 (a);

fig. 3 (a) is a schematic structural view of the substrate shown in fig. 2 (b) after the first sub-hole and the second sub-hole are subjected to metallization treatment;

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

fig. 4 is a schematic view of the structure after a fourth hole is drilled in the substrate shown in (b) of fig. 3;

fig. 5 is a schematic view of drilling a first sub-hole, a second hole, a third hole, and a fourth hole in the substrate shown in (a) of fig. 2.

The meaning of the labels in the figures is:

100. a substrate; 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; 41. a first sub-aperture; 411. a first plating layer; 412. a second plating layer; 42. a second sub-aperture; 421. a third plating layer; 50. a second hole; 60. a third aperture; 70. and a through hole.

Detailed Description

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

In order 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, fig. 3 (a) and fig. 5, an embodiment of a first aspect of the present application provides a PCB back drilling method, including:

s100: providing a substrate 100, wherein the substrate 100 comprises a target plate 10 and a first plate 20 and a second plate 30 respectively arranged on two opposite sides of the target plate 10, a first hole 40 is arranged on the substrate 100, the first hole 40 penetrates through the substrate 100, the first hole 40 comprises a first sub-hole 41 and a second sub-hole 42 which are coaxial and communicated, the aperture of the first sub-hole 41 is larger than that of the second sub-hole 42, the first sub-hole 41 penetrates through the first plate 20 and the target plate 10, a first plating layer 411, a second plating layer 412 and a third plating layer 421 are respectively arranged on the hole wall of the first sub-hole 41, the hole bottom of the first sub-hole 41 and the hole wall of the second sub-hole 42, and the first plating layer 411 electrically conducts the circuit of the first plate 20 and the circuit of the target plate 10.

Specifically, the substrate 100 may be a circuit board after completing conventional process flows such as cutting, inner layer circuit pattern, inner layer AOI detection, and pressing, the first hole 40 is a metalized through hole, the aperture of the first sub-hole 41 is d2, the aperture of the second sub-hole 42 is d1, and the first sub-hole 41 penetrates through the first board 20 and the target board 10 but does not penetrate through the second board 30, so that the second plating layer 412, the third plating layer 421, and a portion of the first plating layer 411 located on a side of the target board 10 away from the first board 20 may form an invalid section of a parasitic capacitance and a parasitic inductance, the height of the invalid section is h1, and the invalid section may affect the integrity of high-speed signal transmission of the medium-high speed circuit board.

It is understood that a plurality of layers of circuits may be disposed on the first board 20 and the second board 30, and the first plating layer 411, the second plating layer 412, and the third plating layer 421 are all metal plating layers that may be conductive.

S200: a second hole 50 penetrating through the second plating layer 412 is drilled in the substrate 100, and the third plating layer 421 and a part of the second plating layer 412 are removed, the second hole 50 is disposed coaxially with the first hole 40, the diameter of the second hole 50 is larger than that of the second sub-hole 42, and the diameter of the second hole 50 is smaller than that of the first sub-hole 41.

Specifically, referring to fig. 3 (b), a second hole 50 penetrating through the second plating layer 412 may be drilled in the substrate 100 from a side of the second plate 30 away from the target plate 10 or a side of the first plate 20 away from the target plate 10, the diameter of the second hole 50 is d3, after the second hole 50 is drilled, the third plating layer 421 and the second plating layer 412 with the height h2 are removed, as h2=1/2 (d 3-d 1)/tan α in fig. 5, α is a half of the drill tip angle of the depth control drill for drilling the second hole 50, and the inactive segment on the substrate 100 only remains the height h3 and another portion of the second plating layer 412 and a portion of the first plating layer 411 located on a side of the target plate 10 away from the first plate 20.

S300: a third hole 60 is drilled in the substrate 100 from the side of the second plate 30 remote from the target plate 10, the third hole 60 extending to the surface of the remaining second plating layer 412 remote from the first plate 20, the third hole 60 being arranged coaxially with the first hole 40, the third hole 60 having a larger aperture than the second hole 50.

Specifically, referring to fig. 4 together, the aperture of the third hole 60 is d4.

S400: and drilling a fourth hole with a first preset depth at the bottom of the third hole 60 by taking the surface of the remaining second plating layer 412 far away from the first plate 20 as a first reference surface, and removing the remaining second plating layer 412, wherein the bottom of the fourth hole extends to the surface of the target plate 10 far away from the first plate 20.

Specifically, since the fourth hole of the first predetermined depth is drilled at the bottom of the third hole 60 with the surface of the second plating layer 412 away from the first plate 20 as the first reference surface, the influence of the thickness uniformity of the substrate 100 and the influence of the accuracy of the drilling machine can be reduced, the drilling accuracy of the fourth hole can be improved, it is ensured that the bottom of the fourth hole extends more accurately to the surface of the target plate 10 away from the first plate 20, the remaining second plating layer 412 is removed, and the target plate 10 is not damaged.

It is understood that the first predetermined depth may be set in advance, that is, the distance between the surface of the second plating layer 412 away from 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 may be determined by sampling and measuring a plurality of substrates 100, for example, a plurality of samples of the substrates 100 without drilling the third hole 60 may be provided, the samples of the plurality of substrates 100 are cut, the distance between the surface of the second plating layer 412 away from the first plate 20 and the surface of the target plate 10 away from the first plate 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 used as the first predetermined depth, so that the value of the first predetermined depth may be more accurate.

It will be appreciated that the fourth bore and the third bore 60 may be coaxially or non-coaxially disposed. The fourth hole and the third hole 60 can be drilled together, that is, the third hole 60 is drilled on the substrate 100 from the side of the second plate 30 far from the target plate 10 by using a depth control drill, the bottom of the third hole 60 extends to the surface of the second plating layer 412 far from the first plate 20, then the surface of the remaining second plating layer 412 far from the first plate 20 is taken as a first reference surface, a fourth hole with a first preset depth is drilled at the bottom of the third hole 60, the hole diameter of the third hole 60 is equal to the hole diameter of the fourth hole, and the third hole 60 and the fourth hole are coaxially arranged.

According to the method for backdrilling the PCB provided by the embodiment of the application, the second hole 50 penetrating through the second plating layer 412 is drilled on the substrate 100 from the side of the second plate 30 away from the target plate 10, the third plating layer 421 and a part of the second plating layer 412 are removed, the third hole 60 is drilled on the substrate 100 from the side of the second plate 30 away from the target plate 10, so that the third hole 60 extends to the surface of the second plating layer 412 away from the first plate 20, finally, the surface of the second plating layer 412 away from the first plate 20 is used as a first reference surface, a fourth hole with a first preset depth is drilled at the bottom of the third hole 60, and the remaining second plating layer 412 is removed, so that the remaining second plating layer 412 and the remaining third plating layer 421 can be more accurately removed, and the quality of the PCB is improved.

As an implementation manner, the drilling a fourth hole with a first preset depth at the bottom of the third hole 60 with the surface of the remaining second plating layer 412 away from the first plate 20 as a first reference surface, and removing the remaining second plating layer 412 specifically includes:

in a first step, a depth control drill having a conductivity detection function is used to extend a drill bit of the depth control drill into the bottom of the third hole 60.

In the second step, when the tip of the drill contacts the surface of the second plating layer 412 away from the first plate 20, a fourth hole is drilled until the fourth hole has a first predetermined depth.

Specifically, when the conductive detection system on the depth-control drilling machine detects that the drill point of the drill bit contacts the surface of the second plating layer 412 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 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 first preset depth, the Z-axis motor stops feeding. In this manner, the depth of the fourth hole can be precisely controlled, so that the remaining second plating layer 412 can be more precisely removed, resulting in less remaining ineffective segments.

Referring to fig. 3 (b), in some embodiments, the second plate 30 includes a copper barrier layer 31, and the second plate 30 has an exclusion zone. Before drilling the third hole 60 on the substrate 100 from the side of the second plate 30 away from the target plate 10, the PCB back drilling method further includes: the barrier copper layer 31 in the exclusion region is removed.

When the third hole 60 is drilled in the substrate 100 from the side of the second plate 30 remote from the target plate 10, the third hole 60 is located within the exclusion region.

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 of the second plating layer 412 far away from the first plate 20.

In this embodiment, the barrier copper layer 31 in the avoiding region is removed by etching or laser ablation.

It is understood that if the barrier copper layers 31 are disposed at intervals in multiple layers, all the barrier copper layers 31 in the aversion regions are removed.

Referring to fig. 4, in some embodiments, in order to simultaneously remove a portion of the first plating layer 411 on a side of the target plate 10 facing away from the first plate 20, a fourth hole is disposed coaxially with the first hole 40, and the diameter of the fourth hole is greater than or equal to that of the first sub-hole 41. After the fourth hole is drilled, the remaining second plating layer 412 with the height h3 and the first plating layer 411 on the target board 10 on the side away from the first board 20 can be accurately removed together with the height h3 of the substrate 100 without damaging the target board 10.

Referring to fig. 2 (a), fig. 2 (b), fig. 3 (a) and fig. 5, in some embodiments, before providing a substrate 100, the PCB backdrilling method further includes:

first, a through hole 70 is drilled in the substrate 100, and the through hole 70 penetrates the first plate 20, the target plate 10, and the second plate 30.

Specifically, a through hole 70 that penetrates the first plate 20, the target plate 10, and the second plate 30 may be drilled in the substrate 100 from the side of the second plate 30 away from the target plate 10 or the side of the first plate 20 away from the target plate 10, the through hole 70 having a hole diameter d1.

Next, a first sub-hole 41 is drilled at the through-hole 70 of the substrate 100 from the side of the first plate 20 away from the target plate 10, the aperture of the first sub-hole 41 being larger than the aperture of the through-hole 70, the remaining through-hole 70 being a second sub-hole 42.

Finally, the first sub-via 41 and the second sub-via 42 are metallized, so that the first plating layer 411, the second plating layer 412, and the third plating layer 421 are formed on the via wall of the first sub-via 41, the via bottom of the first sub-via 41, and the via wall of the second sub-via 42, respectively.

Specifically, the first sub-hole 41 and the second sub-hole 42 may be metalized by copper deposition and electroplating, so that the hole wall of the first sub-hole 41, the hole bottom of the first sub-hole 41, and the hole wall of the second sub-hole 42 are respectively formed with a first plating layer 411, a second plating layer 412, and a third plating layer 421 with a predetermined thickness, but not limited thereto, in this embodiment, the first plating layer 411, the second plating layer 412, and the third plating layer 421 are all copper layers.

Referring to fig. 2 (a), fig. 2 (b), fig. 3 (a) and fig. 5, in some embodiments, the first sub-hole 41 includes a first machining hole and a second machining hole which are communicated with each other, the target board 10 includes a target copper layer 11, the first sub-hole 41 is drilled on the substrate 100 from a side of the first board 20 away from the target board 10, and the first sub-hole 41 penetrates through the first board 20 and the target board 10, and specifically includes:

first, a first machining hole is drilled in the substrate 100 from the side of the first plate 20 away from the target plate 10, and the first machining hole penetrates through the first plate 20.

Specifically, the first machining hole extends to a side of the target copper layer 11 adjacent to the first board 20.

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

By adopting the scheme, the precision is higher when the second machining hole is drilled, so that the first sub-hole 41 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 substrate 100 and the influence of the precision of a drilling machine are reduced.

It can be understood that the first machining hole and the second machining hole can be drilled together, that is, the first machining hole is drilled on the substrate 100 from the side of the first plate 20 far from the target plate 10 by using a depth control drilling machine, the first machining hole penetrates through the first plate 20, then the second machining hole with a second preset depth is drilled at the bottom of the first sub-hole 41 from the side of the first plate 20 far from the target plate 10 by using the side of the target copper layer 11 close to the first plate 20 as a second reference surface, and the first machining hole and the second machining hole are coaxially arranged.

It is understood that the second predetermined depth may be set in advance, that is, the distance between the surface 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 performing sampling measurement on a plurality of substrates 100, for example, a plurality of samples of the substrates 100 without first processing holes may be provided, the distance between the surface 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 after the samples of the plurality of substrates 100 are cut, 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.

As an implementation manner, with a surface of the target copper layer 11 close to the first board 20 as a second reference surface, drilling a second machining hole with a second preset depth at the bottom of the first machining hole from a 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 machining hole.

In the second step, when the drill tip of the drill contacts a surface of the target copper layer 11 adjacent to the first board 20, a second machining hole of a second predetermined depth is drilled.

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. Therefore, the depth of the second machining hole can be accurately controlled.

Referring to fig. 2 (b), 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 machining hole in the substrate 100 plate from the side of the first plate 20 remote from the target plate 10, the drilling method further comprises: removing the first copper layer 21 in the first region; when the first machining hole is drilled in the substrate 100 plate from the side of the first plate 20 away from the target plate 10, the first machining 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) and 4, in some embodiments, the same alignment target (not shown) is used for drilling the second holes 50 through the second plating layers 412 in the substrate 100 from the side of the second plate 30 away from the target plate 10 and for drilling the third holes 60 in the substrate 100 from the side of the second plate 30 away from the target plate 10. In this manner, a minimum offset of the axes of the second and

third holes

50, 60 may be ensured.

Alternatively, drilling the through-hole 70, the first machining hole, and the second machining hole in the substrate 100 also uses the above alignment targets.

In the present embodiment, the alignment targets are provided as a plurality of through holes 70 located at the edge of the substrate 100. In this way, it is possible to perform more accurate alignment when drilling the second hole 50 penetrating the second plating layer 412 in the substrate 100 from the side of the second plate 30 away from the target plate 10 and when drilling the third hole 60 in the substrate 100 from the side of the second plate 30 away from the target plate 10, and it is also possible to reduce the influence on the wiring on the substrate 100.

Alternatively, the number of the through holes 70 is set to 3 or more.

Embodiments of the second aspect of the present application provide a PCB that is machined by the PCB backdrilling method of the first aspect.

In the PCB provided in the embodiment of the present application, when the back drilling process is performed, the second hole 50 penetrating through the second plating layer 412 is drilled on the substrate 100 from the side of the second plate 30 away from the target plate 10, the third plating layer 421 and a part of the second plating layer 412 are removed, the third hole 60 is drilled on the substrate 100 from the side of the second plate 30 away from the target plate 10, so that the third hole 60 extends to the surface of the second plating layer 412 away from the first plate 20, and finally, the surface of the second plating layer 412 away from the first plate 20 is used as a first reference surface, a fourth hole with a first preset depth is drilled at the bottom of the third hole 60, and the remaining second plating layer 412 is removed, so that the remaining second plating layer 412 and the third plating layer 421 can be removed more accurately, and the quality of the PCB is higher.

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 PCB backdrilling method, comprising:

providing a substrate, wherein the substrate comprises a target plate and a first plate and a second plate which are respectively arranged on two opposite sides of the target plate, a first hole is formed in the substrate, the first hole penetrates through the substrate, the first hole comprises a first sub-hole and a second sub-hole which are coaxial and communicated with each other, the aperture of the first sub-hole is larger than that of the second sub-hole, the first sub-hole penetrates through the first plate and the target plate, a first plating layer, a second plating layer and a third plating layer are respectively arranged on the hole wall of the first sub-hole, the hole bottom of the first sub-hole and the hole wall of the second sub-hole, and the first plating layer is electrically communicated with a circuit of the first plate and a circuit of the target plate;

drilling a second hole penetrating through the second plating layer on the substrate, and removing the third plating layer and part of the second plating layer, wherein the second hole is coaxially arranged with the first hole, the aperture of the second hole is larger than that of the second sub-hole, and the aperture of the second hole is smaller than that of the first sub-hole;

and drilling a fourth hole with a first preset depth at the bottom of the third hole by taking the surface, far away from the first plate, of the residual second plating layer as a first reference surface, removing the residual second plating layer, and extending the bottom of the fourth hole to the target plate far away from the surface of the first plate.

2. The PCB backdrilling method of claim 1, wherein the fourth hole is disposed coaxially with the first hole, and the fourth hole has an aperture that is greater than or equal to the aperture of the first sub-hole.

3. The PCB backdrilling method of claim 1, wherein prior to providing a substrate, the PCB backdrilling method further comprises:

4. The PCB backdrilling method of claim 3, wherein the first sub-hole comprises a first machining hole and a second machining hole which are communicated with each other, the target board comprises a target copper layer, a first sub-hole is drilled in the substrate from a side of the first board far away from the target board, and the first sub-hole penetrates through the first board and the target board, and the method comprises the following steps:

drilling a first machining hole in the base plate from one side, far away from the target plate, of the first plate, wherein the first machining hole penetrates through the first plate;

and drilling a second machining hole with a second preset depth at the bottom of the first machining 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 machining hole penetrates through the target copper layer.

5. The PCB backdrilling method according to claim 1, wherein a surface of the remaining second plating layer away from the first board is used as a first reference surface, a fourth hole with a first preset depth is drilled at the bottom of the third hole, and the remaining second plating layer is removed, specifically comprising:

6. The PCB backdrilling method of claim 5, wherein the second plate comprises a copper barrier layer, the second plate having an exclusion area; before drilling a third hole in the substrate from a side of the second plate away from the target plate, the PCB backdrilling method further comprises: removing the barrier copper layer in the avoiding area; when a third hole is drilled in the substrate from a side of the second plate remote from the target plate, the third hole is located within the aversion region.

7. The PCB backdrilling method of claim 6, wherein the copper barrier layer of the keep-away area is removed by etching or laser burning.

8. The PCB backdrilling method of any of claims 1 to 7, wherein the same alignment target is used when drilling the second hole through the second plating layer in the substrate from the side of the second plate remote from the target plate and when drilling the third hole in the substrate from the side of the second plate remote from the target plate.

9. The PCB backdrilling method of claim 8, wherein the alignment targets are provided as a plurality of through holes at the edge of the substrate.

10. A PCB manufactured by the PCB backdrilling method of any one of claims 1 to 9.