阅读说明：本技术 印制电路预制板及背钻方法、印制电路板 (Printed circuit prefabricated board, back drilling method and printed circuit board ) 是由 刘定昱 于 2020-05-26 设计创作，主要内容包括：本发明涉及一种印制电路预制板及背钻方法、印制电路板。该印制电路预制板,包括第一目标信号层和第二目标信号层,以及夹设于第一目标信号层和第二目标信号层之间的终钻位导电层。该印制电路预制板,还包括贯穿第一目标信号层、终钻位导电层和第二目标信号层的过孔。过孔内设有导电连接层。终钻位导电层与导电连接层之间设有空隙,从而与导电连接层绝缘。对该印制电路板进行背钻时,可以向终钻位导电层内输入电信号。由于该终钻位导电层与导电连接层之间绝缘,因此可以避免钻头碰到导电连接层时即形成导电回路,从而可以使钻头深入至终钻位导电层所在位置。以此,即可充分去除印制电路预制板中多余的导电连接层,提升背钻精度。(The invention relates to a printed circuit board, a back drilling method and a printed circuit board. The printed circuit prefabricated board comprises a first target signal layer, a second target signal layer and a final drilling position conducting layer clamped between the first target signal layer and the second target signal layer. The printed circuit prefabricated board further comprises a through hole penetrating through the first target signal layer, the final drill bit conductive layer and the second target signal layer. And a conductive connecting layer is arranged in the through hole. And a gap is arranged between the final drilling position conducting layer and the conducting connecting layer, so that the final drilling position conducting layer is insulated from the conducting connecting layer. When the printed circuit board is back drilled, an electric signal can be input into the conductive layer of the final drilling position. Because the conducting layer and the conducting connecting layer are insulated, a conducting loop can be prevented from being formed when the drill bit touches the conducting connecting layer, and the drill bit can be made to penetrate into the position of the conducting layer at the final drilling position. Therefore, redundant conductive connecting layers in the printed circuit prefabricated board can be removed fully, and the back drilling precision is improved.)

1. A printed circuit board, comprising:

a first target signal layer and a second target signal layer which are arranged in a stacked manner;

the final drilling position conducting layer is clamped between the first target signal layer and the second target signal layer;

a via hole penetrating through the first target signal layer, the final drill bit conductive layer and the second target signal layer;

the conductive connecting layer is positioned in the through hole and covers the inner walls of the first target signal layer and the second target signal layer; and a gap is arranged between the final drilling position conducting layer and the conducting connecting layer so as to insulate the final drilling position conducting layer from the conducting connecting layer.

2. The printed circuit prefabricated panel according to claim 1, wherein the second target signal layer includes a first conductive layer, a first insulating layer, and a second conductive layer which are disposed in a stacked manner;

the final drill bit conductive layer is connected to at least one of the first conductive layer and the second conductive layer.

3. The printed circuit prefabricated panel of claim 2, wherein a minimum distance of the first and second conductive layers from the center of the via hole is greater than a first preset distance.

4. The printed circuit board of claim 1, wherein the minimum distance of the final drill bit conductive layer from the center of the via is less than or equal to a first predetermined distance.

5. A backdrilling method for backdrilling a printed circuit board to obtain a printed circuit board, the printed circuit board comprising:

a first target signal layer and a second target signal layer which are arranged in a stacked manner;

the final drilling position conducting layer is clamped between the first target signal layer and the second target signal layer;

a via hole penetrating through the first target signal layer, the final drill bit conductive layer and the second target signal layer;

the conductive connecting layer is positioned in the through hole and covers the inner walls of the first target signal layer and the second target signal layer; a gap is arranged between the final drilling position conducting layer and the conducting connecting layer so as to insulate the final drilling position conducting layer from the conducting connecting layer;

the back drilling method comprises the following steps:

inputting an electrical signal to the final drilling position conducting layer, and performing back drilling on the via hole from the back drilling side, wherein the radius of a drill bit is larger than that of the via hole;

and stopping the back drilling when the drill bit contacts the final drilling position conducting layer.

6. The back-drilling method according to claim 5, wherein the second target signal layer comprises a first conductive layer, a first insulating layer, and a second conductive layer which are stacked; the final drilling position conducting layer is connected with at least one of the first conducting layer and the second conducting layer;

when the drill bit contacts the final drilling position conducting layer and after the back drilling is stopped, the method further comprises the following steps:

and drilling to remove the connection between the final drilling position conducting layer and the first conducting layer and the second conducting layer.

7. The back-drilling method according to claim 5 or 6, wherein when the drill bit contacts the final-drill-site conductive layer, the method comprises the following steps:

and when the drill bit and the final drilling position conductive layer form a conductive loop, judging that the drill bit is in contact with the final drilling position conductive layer.

8. The backdrilling method of claim 5, wherein the first and second conductive layers have a minimum distance from the via center that is greater than a radius of the drill bit.

9. The backdrilling method of claim 5, wherein the minimum distance of the final drill bit conductive layer from the via center is less than or equal to the radius of the drill bit.

10. A printed circuit board obtained by back drilling the printed circuit board of any one of claims 1 to 4, comprising:

a first target signal layer and a second target signal layer which are arranged in a stacked manner;

the final drilling position conducting layer is clamped between the first target signal layer and the second target signal layer;

a via hole penetrating the first target signal layer;

the conductive connecting layer is positioned in the through hole and covers the inner wall of the first target signal layer;

and the through hole penetrates through the second target signal layer and exposes the final drilling position conducting layer.

Technical Field

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

Background

Printed Circuit Boards (PCB), also known as PCB boards, are important components of physical support and signal transmission of electronic products. The portion of the printed circuit board where the Plated Through Hole (PTH) is not used for signal transmission increases the loss of signal transmission of the PCB.

In the conventional art, a back drill is generally used to remove redundant portions of metallized holes in a printed circuit board.

The inventor finds out in the process of realizing the conventional technology that: the traditional back drilling method has lower precision.

Disclosure of Invention

Therefore, it is necessary to provide a printed circuit board, a backdrilling method and a printed circuit board, which solve the problem of low precision of the backdrilling method in the conventional technology.

A printed circuit pre-fabricated panel comprising:

a first target signal layer and a second target signal layer which are arranged in a stacked manner;

the final drilling position conducting layer is clamped between the first target signal layer and the second target signal layer;

a via hole penetrating through the first target signal layer, the final drill bit conductive layer and the second target signal layer;

the conductive connecting layer is positioned in the through hole and covers the inner walls of the first target signal layer and the second target signal layer; and a gap is arranged between the final drilling position conducting layer and the conducting connecting layer so as to insulate the final drilling position conducting layer from the conducting connecting layer.

In one embodiment, the second target signal layer includes a first conductive layer, a first insulating layer, and a second conductive layer that are stacked;

the final drill bit conductive layer is connected to at least one of the first conductive layer and the second conductive layer.

In one embodiment, the minimum distance between the first conductive layer and the second conductive layer and the center of the via hole is greater than a first preset distance.

In one embodiment, the minimum distance from the final drilling position conducting layer to the center of the via hole is less than or equal to a first preset distance.

A backdrilling method for backdrilling a printed circuit board to obtain a printed circuit board, the printed circuit board comprising:

a first target signal layer and a second target signal layer which are arranged in a stacked manner;

the final drilling position conducting layer is clamped between the first target signal layer and the second target signal layer;

a via hole penetrating through the first target signal layer, the final drill bit conductive layer and the second target signal layer;

the conductive connecting layer is positioned in the through hole and covers the inner walls of the first target signal layer and the second target signal layer; a gap is arranged between the final drilling position conducting layer and the conducting connecting layer so as to insulate the final drilling position conducting layer from the conducting connecting layer;

the back drilling method comprises the following steps:

inputting an electrical signal to the final drilling position conducting layer, and performing back drilling on the via hole from the back drilling side, wherein the radius of a drill bit is larger than that of the via hole;

and stopping the back drilling when the drill bit contacts the final drilling position conducting layer.

In one embodiment, the second target signal layer includes a first conductive layer, a first insulating layer, and a second conductive layer that are stacked; the final drilling position conducting layer is connected with at least one of the first conducting layer and the second conducting layer;

when the drill bit contacts the final drilling position conducting layer and after the back drilling is stopped, the method further comprises the following steps:

and drilling to remove the connection between the final drilling position conducting layer and the first conducting layer and the second conducting layer.

In one embodiment, when the drill bit contacts the final drilling position conductive layer, the method specifically comprises:

and when the drill bit and the final drilling position conductive layer form a conductive loop, judging that the drill bit is in contact with the final drilling position conductive layer.

In one embodiment, the minimum distance of the first and second conductive layers from the center of the via is greater than the radius of the drill bit.

In one embodiment, the minimum distance from the center of the via hole to the final drill position conducting layer is less than or equal to the radius of the drill bit.

A printed circuit board obtained by backdrilling a printed circuit board according to any one of the above embodiments, comprising:

a first target signal layer and a second target signal layer which are arranged in a stacked manner;

the final drilling position conducting layer is clamped between the first target signal layer and the second target signal layer;

a via hole penetrating the first target signal layer;

the conductive connecting layer is positioned in the through hole and covers the inner wall of the first target signal layer;

and the through hole penetrates through the second target signal layer and exposes the final drilling position conducting layer.

The printed circuit prefabricated board comprises a first target signal layer, a second target signal layer and a final drilling position conducting layer clamped between the first target signal layer and the second target signal layer. The printed circuit prefabricated board further comprises a through hole penetrating through the first target signal layer, the final drill bit conductive layer and the second target signal layer. And a conductive connecting layer is arranged in the through hole. And a gap is arranged between the final drilling position conducting layer and the conducting connecting layer, so that the final drilling position conducting layer is insulated from the conducting connecting layer. When the printed circuit board is back drilled, an electric signal can be input into the conductive layer of the final drilling position. Because the conducting layer and the conducting connecting layer are insulated, a conducting loop can be prevented from being formed when the drill bit touches the conducting connecting layer, and the drill bit can be made to penetrate into the position of the conducting layer at the final drilling position. Therefore, redundant conductive connecting layers in the printed circuit prefabricated board can be removed fully, and the back drilling precision is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of a conventional printed circuit board stack;

FIG. 2 is a schematic cross-sectional view of a printed circuit board prior to backdrilling in the prior art;

FIG. 3 is a schematic cross-sectional view of a printed circuit board according to an embodiment of the present application;

FIG. 4 is a schematic flow chart of a back drilling method according to an embodiment of the present application;

FIG. 5 is a cross-sectional structural view of a back drilling process in one embodiment of the present application;

FIG. 6 is a schematic cross-sectional view of a printed circuit board according to another embodiment of the present application;

FIG. 7 is a schematic cross-sectional view of a printed circuit board according to another embodiment of the present application;

FIG. 8 is a schematic flow chart of a back drilling method according to another embodiment of the present application;

fig. 9 is a schematic cross-sectional view of a printed circuit board according to another embodiment of the present application.

Wherein, the meanings represented by the reference numerals of the figures are respectively as follows:

01. a printed circuit board (in conventional technology);

10. printing a circuit prefabricated plate;

12. back drilling the side;

110. a first target signal layer;

112. a first signal layer;

114. a second signal layer;

116. a third signal layer;

118. a fourth signal layer;

120. a second target signal layer;

122. a first conductive layer;

124. a second conductive layer;

130. finally drilling a position conducting layer;

142. a first insulating layer;

144. a second insulating layer;

146. a third insulating layer;

150. a via hole;

152. a conductive connection layer;

160. a through hole;

170. a transition layer;

172. blind holes;

20. a drill bit;

30. a printed circuit board.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

The numbering of the components as such, e.g., "first", "second", etc., is used herein only to distinguish the objects as described, and does not have any sequential or technical meaning. The term "connected" and "coupled" when used in this application, unless otherwise indicated, includes both direct and indirect connections (couplings). In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present application and for simplicity in description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be considered as limiting the present application.

In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through intervening media. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

As shown in fig. 1, in the conventional art, the printed circuit board 01 may generally include a plurality of stacked signal layers, and an insulating layer is disposed between two adjacent signal layers to insulate the two adjacent signal layers. Several here refers to two or more integers. The signal layer refers to a film layer formed of a conductive wire or sheet that can transmit an electrical signal. Fig. 1 is a schematic diagram of a laminated structure of a printed circuit board 01, and for convenience of description, the signal layers shown in fig. 1 are respectively named as a first signal layer 112, a second signal layer 114, a third signal layer 116, a fourth signal layer 118, a first conductive layer 122 and a second conductive layer 124 in order from top to bottom.

In general, in the laminated structure shown in fig. 1, insulation is not required between any two signal layers, and conduction is required between some signal layers. For convenience of description, we will designate several signal layers that need to be turned on as the first target signal layer 110, and designate several signal layers that do not need to be turned on as the second target signal layer 120. In the illustration of FIG. 1, the first target signal layer 110 includes a first signal layer 112, a second signal layer 114, a third signal layer 116, and a fourth signal layer 118. The insulating layer disposed between each of the first signal layer 112, the second layer 114, the third layer 116, and the fourth layer 118 is referred to as a second insulating layer 144. The second target signal layer 120 includes a first conductive layer 122 and a second conductive layer 124. The insulating layer disposed between the first conductive layer 122 and the second conductive layer 124 is named a first insulating layer 142.

To make several of the first target signal layers 110 conductive, the printed circuit board 01 may further include a via 150 penetrating the first target signal layers 110 and the second target signal layers 120, as shown in fig. 2. Generally, the via 150 avoids the first conductive layer 122 and the second conductive layer 124 of the second target signal layer 120. At this time, the inner wall of the via hole 150 is plated with copper to obtain the conductive connection layer 152, so that the signal layers in the first target signal layer 110 can be conducted through the conductive connection layer 152.

As can be seen from fig. 2, the excess portion of the conductive connection layer 152 also extends through to the level of the second target signal layer 120. Since the portion of the conductive connection layer 152 penetrating to the level of the second target signal layer 120 affects the signal transmission, a back drilling process is required to remove the excessive portion of the conductive connection layer 152. The back drilling here refers to drilling the printed circuit board 01 from the back drilling side 12 of the printed circuit board 01, and the back drilling side 12 refers to the side of the second target signal layer 120 away from the first target signal layer 110.

The present application provides a printed circuit board (10), a back drilling method and a printed circuit board (30). The printed circuit board 30 is obtained after the printed circuit board 10 is back-drilled. The printed circuit prefabricated panel 10 can improve the accuracy of back drilling.

In one embodiment, as shown in FIG. 3, the present application provides a printed circuit pre-slab 10 that includes a first target signal layer 110, a second target signal layer 120, a final drill bit conductive layer 130, vias 150, and a conductive connection layer 152.

The printed circuit prefabricated panel 10 is used to prepare a printed circuit board 30. The printed circuit prefabricated panel 10 includes a plurality of signal layers arranged in a stack. Similarly, several herein refers to two or more integers. Following the above description, we will name the number of signal layers that need to be conducted through the conductive connection layer 152 as the first targeted signal layer 110, and the number of signal layers that need not be conducted through the conductive connection layer 152 as the second targeted signal layer 120. In the embodiment shown in FIG. 3, the first target signal layer 110 includes a first signal layer 112, a second signal layer 114, a third signal layer 116, and a fourth signal layer 118. The insulating layer disposed between each of the first signal layer 112, the second layer 114, the third layer 116, and the fourth layer 118 is referred to as a second insulating layer 144. The second target signal layer 120 includes a first conductive layer 122 and a second conductive layer 124. The insulating layer disposed between the first conductive layer 122 and the second conductive layer 124 is named a first insulating layer 142. The back-drilled side 12 refers to a side where the drill 20 enters the printed circuit prefabricated panel 10 when the printed circuit prefabricated panel 10 is back-drilled. In other words, the backdrilled side 12 refers to the side of the second target signal layer 120 that is distal from the first target signal layer 110. Thus, we can also say that the first target signal layer 110 is remote from the back drilling side 12 and the second target signal layer 120 is close to the back drilling side 12.

The final drill bit conductive layer 130 is disposed between the first target signal layer 110 and the second target signal layer 120 for positioning a final drill bit of the drill bit 20. In other words, the final drill position conductive layer 130 is used to provide positioning information to stop the back drilling if the drill 20 contacts the final drill position conductive layer 130 when the drill 20 back drills the printed circuit prefabricated panel 10 from the back drilling side 12. Thus, the printed circuit board 30 obtained by backdrilling can have the conductive connection layer 152 only penetrate through the level of the first target signal layer 110 by using the backdrilling process.

In this embodiment, a third insulating layer 146 may be disposed between the final drill bit conductive layer 130 and the first and second target signal layers 110 and 120 to insulate the final drill bit conductive layer 130 from the first and second target signal layers 110 and 120.

As described above, the printed circuit board 30 also has the via 150 extending through the entire printed circuit board 30, i.e., the via 150 extending through the first target signal layer 110, the final drill bit conductive layer 130, and the second target signal layer 120. The via 150 is used to prepare a conductive connection layer 152. The conductive connection layer 152 may be located within the via 150 and cover the inner walls of the first and second target signal layers 110 and 120. Generally, the vias 150 also extend through the signal layers of the first target signal layer 110, since the signal layers of the first target signal layer 110 need to be electrically connected through the conductive connection layer 152. The plurality of signal layers in the second target signal layer 120 need not be electrically connected through the conductive connection layer 152, and therefore, the first conductive layer 122 and the second conductive layer 124 in the second target signal layer 120 can avoid the via 150. In this embodiment, the position relationship between the final bit conductive layer 130 and the conductive connection layer 152 is as follows: a gap is formed between the final drill site conductive layer 130 and the conductive connection layer 152, so that the final drill site conductive layer 130 and the conductive connection layer 152 are insulated.

More specifically, when the printed circuit board 10 is back-drilled, an electrical signal may be applied to the conductive layer 130 at the final drilling position in the printed circuit board 10. At this time, since the final drill bit conductive layer 130 is insulated from the conductive connection layer 152, no electric signal is present in the conductive connection layer 152. When the drill 20 backdrills the printed circuit prefabricated panel 10 from the backdrilling side 12, the drill 20 first contacts the conductive connection layer 152. At this time, no electrical signal is detected by the drill bit 20. When the drill 20 contacts the final drill position conducting layer 130, a conducting loop is formed between the final drill position conducting layer 130 and the drill 20, and the drill 20 detects an electric signal, so that the back drilling of the printed circuit prefabricated board 10 can be stopped. The printed circuit board has the advantages that the conductive layer 130 at the final drilling position is insulated from the conductive connecting layer 152, so that a conductive loop can be prevented from being formed when the drill bit 20 touches the conductive connecting layer 152, and the drill bit 20 can be driven to penetrate into the position of the conductive layer 130 at the final drilling position. Therefore, the redundant conductive connecting layer 152 in the printed circuit prefabricated board 10 can be fully removed, and the back drilling precision is improved.

In one embodiment, the second target signal layer 120 includes a first conductive layer 122, a first insulating layer 142, and a second conductive layer 124, which are stacked. The final drill bit conductive layer 130 is connected to at least one of the first conductive layer 122 and the second conductive layer 124.

Specifically, as can be seen in FIG. 3, in the embodiment shown in FIG. 3, the second target signal layer 120 includes a first conductive layer 122 and a second conductive layer 124. The printed circuit board 30 requires power planes and ground planes to form vias to enable operation of the printed circuit board 30. The power plane and the ground plane are also one of the signal planes. Here, the first conductive layer 122 may be one of a power supply layer and a ground layer, and the second conductive layer 124 may be the other of the power supply layer and the ground layer. As shown in fig. 4, the final drill site conductive layer 130 may be connected to at least one of the first conductive layer 122 and the second conductive layer 124, i.e., the final drill site conductive layer 130 may be in electrical communication with the ground layer and/or the power layer via the transition layer 170. "and/or" in "ground layer and/or power layer" refers to at least one of the power layer and the ground layer.

More specifically, when the printed circuit prefabricated panel 10 is back-drilled, the printed circuit prefabricated panel 10 may be placed on a horizontal table. The workbench is equivalent to the ground, and at this time, the final drill bit conductive layer 130 and the workbench form equivalent capacitance. When the conductive layer 130 at the final drilling position of the printed circuit prefabricated board 10 is electrified, high-frequency alternating current can be introduced into the conductive layer 130 at the final drilling position, so that a passage is formed between the conductive layer 130 at the final drilling position and the workbench. It is easy to obtain: when other conditions are not changed, the smaller the surface area of the final drill bit conducting layer 130 is, the weaker the electrical signal of a channel formed between the final drill bit conducting layer 130 and the workbench is; conversely, the larger the area of the final drill bit conductive layer 130 is, the stronger the electrical signal of the path formed between the final drill bit conductive layer 130 and the worktable is.

In this embodiment, in order to increase the strength of the electrical signal when the via is formed between the final drill position conducting layer 130 and the working table, the final drill position conducting layer may be communicated with the first conducting layer 122 and the second conducting layer 124, so as to change the area of the final drill position conducting layer 130. The first conductive layer 122 and the second conductive layer 124 in the second target signal layer 120 include ground layers and/or power layers. Generally, in the printed circuit board 30, the ground and/or power layers are large area conductive layers, which may be large area copper foils. Therefore, the final drill position conducting layer 130 can be electrically connected with the first conducting layer 122 and the second conducting layer 124, so that the area of the final drill position conducting layer 130 is increased. By increasing the intensity of the electrical signal when the passage is formed between the final drill position conductive layer 130 and the table, the intensity of the electrical signal detected by the drill 20 when the drill 20 is in contact with the final drill position conductive layer 130 can be increased, thereby increasing the positioning accuracy of the final drill position conductive layer 130.

It should be understood that, in the above-mentioned embodiment, the printed circuit prefabricated plate 10 of the present application is described by taking only the example that the second target signal layer 120 includes the first conductive layer 122, the first insulating layer 142 and the second conductive layer 124 which are arranged in a stacked manner. In other embodiments, the second target signal layer 120 may also include more signal layers. And will not be described in detail.

Further, as shown in fig. 4, a through hole may be formed in the third insulating layer 146 between the final-drill-bit conductive layer 130 and the first conductive layer 122. The through-hole may be filled with a transition layer 170. The transition layer 170 may be a metal conductive material, so as to make the final bit conductive layer 130 conductive with the first conductive layer 122. Similarly, a through hole penetrating through the first insulating layer 142 may be formed in the first insulating layer 142 between the first conductive layer 122 and the second conductive layer 124. The through-hole may be filled with a transition layer 170. The transition layer 170 may be a metal conductive material, thereby making the first conductive layer 122 conductive with the second conductive layer 124.

It should be understood that in this embodiment, only one way of communicating the final drill bit conductive layer 130 with the first conductive layer 122 and the second conductive layer 124 is provided. In other embodiments, the through hole may also penetrate through the printed circuit board 10, and the inner wall of the through hole may be provided with a metal conductive material. The metallic conductive material is coupled to the final drill site conductive layer 130, the first conductive layer 122, and the second conductive layer 124, and is insulated from the first target signal layer 110, thereby allowing communication between the final drill site conductive layer 130 and the first conductive layer 122 and the second conductive layer 124. The present embodiment is directed to improving the strength of an electrical signal when a via is formed between the final drill position conductive layer 130 and the stage by communicating the final drill position conductive layer 130 with the first conductive layer 122 and the second conductive layer 124. Accordingly, any embodiment that places the final drill bit conductive layer 130 in communication with the first conductive layer 122 and the second conductive layer 124 should be understood to be within the scope of the present application.

Further, the printed circuit board 10 may have a plurality of vias 150 at different positions and a conductive connection layer 152 disposed within the vias 150. The number of signal layers to be connected through the conductive connection layer 152, that is, the number of signal layers included in the first target signal layer 110, may be different at different positions of the printed circuit board 10. Therefore, the level position of the final bit conductive layer 130 is also different. In this embodiment, the final drill bit conductive layers 130 of different levels may be connected to increase the area of the final drill bit conductive layers 130, thereby increasing the strength of the electrical signal when a via is formed between the final drill bit conductive layers 130 and the stage.

Further, as shown in fig. 4, the minimum distance between the first conductive layer 122 and the second conductive layer 124 from the center of the via 150 is greater than the first preset distance.

Specifically, in the above-described embodiment, the first conductive layer 122 and the second conductive layer 124 are located on the side of the final-drill-bit conductive layer 130 close to the back-drill side 12. In this embodiment, in order to prevent the drill bit 20 from acquiring an electrical signal when contacting the first conductive layer 122 and the second conductive layer 124 communicating with the final drilling position conductive layer 130 during the back drilling process, the positions of the first conductive layer 122 and the second conductive layer 124 need to be defined. The positions of the first conductive layer 122 and the second conductive layer 124 are: the minimum distance of the first and second conductive layers 122 and 124 from the center of the via 150 is greater than a first preset distance. The first predetermined distance may be a radius of the back drill bit 20. When the minimum distance between the first conductive layer 122 and the second conductive layer 124 and the center of the via hole 150 is greater than the first predetermined distance, i.e., greater than the radius of the back-drilling drill bit 20, the drill bit 20 does not contact the first conductive layer 122 and the second conductive layer 124 connected to the final-drilling-position conductive layer 130 during the back-drilling process, thereby improving the positioning accuracy of the final-drilling-position conductive layer 130.

In one embodiment, as shown in fig. 3 or 4, the minimum distance of the final drill bit conductive layer 130 from the center of the via 150 is less than or equal to a first preset distance.

Specifically, in the above embodiment, a gap is provided between the final drill site conductive layer 130 and the conductive connection layer 152, so as to insulate the final drill site conductive layer 130 from the conductive connection layer 152. In this embodiment, to ensure that the drill bit 20 can contact the final-drill-site conductive layer 130 during the back drilling process, the relative position between the final-drill-site conductive layer 130 and the via 150 needs to be defined. The position of the final drilling position conductive layer 130 relative to the via hole 150 is: the minimum distance from the final drilling position conductive layer 130 to the center of the via hole 150 is less than or equal to a first preset distance and greater than the radius of the via hole 150. The first predetermined distance here may also be the radius of the back drill bit 20. When the minimum distance between the final drilling position conductive layer 130 and the center of the via hole 150 is less than or equal to the first preset distance, that is, less than the radius of the back-drilling drill bit 20, the drill bit 20 can contact the final drilling position conductive layer 130 during the back-drilling process, so that the final drilling position conductive layer 130 can play a role in positioning.

The minimum distance from the final drill position conducting layer 130 to the center of the via hole 150 is greater than the radius of the via hole 150, that is, the minimum distance from the final drill position conducting layer 130 to the center of the via hole 150 is greater than the radius of the conductive connecting layer 152, so that a gap is formed between the final drill position conducting layer 130 and the conductive connecting layer 152. And will not be described in detail.

In one embodiment, the present application further provides a back drilling method for back drilling the printed circuit board 10 of any of the above embodiments to obtain the printed circuit board 30.

Specifically, as shown in fig. 3, the printed circuit prefabricated panel 10 includes: a first target signal layer 110 and a second target signal layer 120 are disposed in a stack. The final drill bit conductive layer 130 is sandwiched between the first target signal layer 110 and the second target signal layer 120. And a via 150 passing through the first target signal layer 110, the final bit conductive layer 130, and the second target signal layer 120. And a conductive connection layer 152 positioned in the via hole 150 and covering inner walls of the first target signal layer 110 and the second target signal layer 110. A gap is formed between the final drill position conductive layer 130 and the conductive connecting layer 152 to insulate the final drill position conductive layer 130 from the conductive connecting layer 152

As shown in fig. 5, the back drilling method includes the following steps:

s100, inputting an electrical signal to the final drilling position conductive layer 130, and back-drilling the via hole 150 from the back-drilling side 12, wherein the radius of the drill bit 20 is greater than the radius of the via hole 150.

The printed circuit prefabricated board 10 is back-drilled from the back-drilled side 12 to remove an excess portion of the conductive connection layer 152 located within the second target signal layer 120. In this embodiment, the radius of the drill bit 20 may be greater than the radius of the via 150, thereby substantially removing the excess portion of the conductive connection layer 152 located within the non-target signal. Fig. 6 is a schematic view illustrating backdrilling of the printed circuit prefabricated panel 10 using the drill 20.

When backdrilling is started, an electrical signal can be input into the final drill bit conductive layer 130, so that the final drill bit conductive layer 130 can play a positioning role.

And S200, stopping back drilling when the drill bit 20 contacts the final drilling position conducting layer 130.

As is known from the above description, the final bit conductive layer 130 is located between the first target signal layer 110 and the second target signal layer 120. Therefore, when the drill bit 20 contacts the final-bit conductive layer 130, the back drilling can be stopped to prevent the back drilling from excessively damaging the portion of the conductive connection layer 152 located in the first target signal layer 110.

In this embodiment, the resulting printed circuit board 30 after completion of the back drilling may be as shown in fig. 7. The printed circuit board 30 includes: a first target signal layer 110 and a second target signal layer 120 are disposed in a stack. The final drill bit conductive layer 130 is sandwiched between the first target signal layer 110 and the second target signal layer 120. And a via 150 penetrating the first target signal layer 110. And a conductive connection layer 152 located in the via hole 150 and covering an inner wall of the first target signal layer 110. And a via 160 penetrating the second target signal layer 120 and exposing the final drill bit conductive layer 130.

In the printed circuit board 30, the conductive connection layer 152 only penetrates through the first target signal layer 110, so that several signal layers in the first target signal layer 110 are electrically connected through the conductive connection layer 152. The conductive connection layer 152 does not extend to the second target signal layer 120, thereby preventing unwanted portions of the conductive connection layer 152 that are not functional from affecting signal transmission of the printed circuit board 30.

In one embodiment, as shown in fig. 8, the second target signal layer 120 includes a first conductive layer 122, a first insulating layer 142, and a second conductive layer 124 disposed in a stack, and the final bit conductive layer 130 is connected to at least one of the first conductive layer 122 and the second conductive layer 124. In this case, after step S200, the back drilling method of the present application further includes:

and S300, drilling to remove the connection of the final drilling position conducting layer 130 and the first conducting layer 122 and the second conducting layer 124.

Specifically, as can be seen from the above description, electrically connecting the final drill position conducting layer 130 with the first conducting layer 122 and the second conducting layer 124 can change the area of the final drill position conducting layer 130, so as to increase the strength of the electrical signal detected by the drill bit 20 when the drill bit 20 contacts the final drill position conducting layer 130. Therefore, after the back drilling is completed, in order to prevent the electrical communication between the final drill position conductive layer 130 and the first and second conductive layers 122 and 124 from affecting the operation of the printed circuit board 30, it is necessary to drill holes to remove the connection between the final drill position conductive layer 130 and the first and second conductive layers 122 and 124.

As with the embodiments described above and shown in fig. 4, the final drill bit conductive layer 130 may be connected to the first conductive layer 122 and the second conductive layer 124 by a transition layer 170. Thus, the connection of the final-drill-bit conductive layer 130 to the first conductive layer 122 and the second conductive layer 124 is removed by drilling, i.e., the transition layer 170 is removed by drilling. The printed circuit board 30 after removing the transition layer 170 may be as shown in fig. 9. The printed circuit board 30 includes: a first target signal layer 110 and a second target signal layer 120 are disposed in a stack. The final drill bit conductive layer 130 is sandwiched between the first target signal layer 110 and the second target signal layer 120. And a via 150 penetrating the first target signal layer 110. And a conductive connection layer 152 located in the via hole 150 and covering an inner wall of the first target signal layer 110. And a via 160 penetrating the second target signal layer 120 and exposing the final drill bit conductive layer 130.

In this embodiment, the printed circuit board 30 further includes: blind vias 172 extend through the first conductive layer 122 and the second conductive layer 124 to isolate the final drill bit conductive layer 130 from the first conductive layer 122 and the second conductive layer 124.

In an embodiment, the step S200 specifically includes:

when the drill bit 20 and the final drill position conductive layer 130 form a conductive loop, it is determined that the drill bit 20 contacts the final drill position conductive layer 130.

Specifically, before step S100, the back drilling method of the present application may further include:

and S001, placing the printed circuit prefabricated plate 10 on a workbench.

The workbench is equivalent to the ground, and after the printed circuit prefabricated board 10 is placed on the workbench, an equivalent capacitor is formed between the final drilling position conductive layer 130 and the workbench. In this case, the "input of the electric signal to the final drill bit conductive layer 130" in step S100 may be input of a high-frequency ac electric signal into the final drill bit conductive layer 130. When an equivalent capacitor is formed between the final drill position conducting layer 130 and the workbench, and a high-frequency alternating current is introduced into the final drill position conducting layer 130, a path can be formed between the final drill position conducting layer 130 and the workbench.

After a via is formed between the final drill site conductive layer 130 and a stage, which is equivalent to a ground line, the printed circuit prefabricated panel 10 is back-drilled. At this time, if the drill 20 contacts the final-drill-position conductive layer 130, a loop is formed between the drill 20 and the final-drill-position conductive layer 130. The drill bit 20 may be electrically connected to a control board for detecting electrical signals. Thus, when the control board detects an electrical signal, that is, when the control board detects that the drill bit 20 and the final drill position conductive layer 130 form a conductive loop, it is determined that the drill bit 20 contacts the final drill position conductive layer 130.

In one embodiment, the first conductive layer 122 and the second conductive layer 124 are disposed on a side of the final drill bit conductive layer 130 away from the first target signal layer 110, and the minimum distance between the first conductive layer 122 and the second conductive layer 124 and the center of the via 150 is greater than the radius of the drill bit 20.

Specifically, in the above embodiment, the first conductive layer 122 and the second conductive layer 124 are part of the second target signal layer 120, and are located on the side of the final bit conductive layer 130 close to the back drilling side 12. In this embodiment, in order to prevent the drill bit 20 from acquiring an electrical signal when contacting the first conductive layer 122 and the second conductive layer 124 communicating with the final drilling position conductive layer 130 during the back drilling process, the positions of the first conductive layer 122 and the second conductive layer 124 need to be defined. The positions of the first conductive layer 122 and the second conductive layer 124 are: the minimum distance of the first and second conductive layers 122 and 124 from the center of the via 150 is greater than a first preset distance. The first predetermined distance may be a radius of the back drill bit 20. When the minimum distance between the first conductive layer 122 and the second conductive layer 124 and the center of the via hole 150 is greater than the first predetermined distance, i.e., greater than the radius of the back-drilling drill bit 20, the drill bit 20 does not contact the first conductive layer 122 and the second conductive layer 124 connected to the final-drilling-position conductive layer 130 during the back-drilling process, thereby improving the positioning accuracy of the final-drilling-position conductive layer 130.

In one embodiment, the minimum distance of the final drill bit conductive layer 130 from the center of the via 150 is less than or equal to the radius of the drill bit 20.

Specifically, in the above embodiment, a gap is provided between the final drill site conductive layer 130 and the conductive connection layer 152, so as to insulate the final drill site conductive layer 130 from the conductive connection layer 152. In this embodiment, to ensure that the drill bit 20 can contact the final-drill-site conductive layer 130 during the back drilling process, the relative position between the final-drill-site conductive layer 130 and the via 150 needs to be defined. The position of the final drilling position conductive layer 130 relative to the via hole 150 is: the minimum distance from the final drilling position conductive layer 130 to the center of the via hole 150 is less than or equal to a first preset distance and greater than the radius of the via hole 150. The first predetermined distance here may also be the radius of the back drill bit 20. When the minimum distance between the final drilling position conductive layer 130 and the center of the via hole 150 is less than or equal to the first preset distance, that is, less than the radius of the back-drilling drill bit 20, the drill bit 20 can contact the final drilling position conductive layer 130 during the back-drilling process, so that the final drilling position conductive layer 130 can play a role in positioning.

The minimum distance from the final drill position conducting layer 130 to the center of the via hole 150 is greater than the radius of the via hole 150, that is, the minimum distance from the final drill position conducting layer 130 to the center of the via hole 150 is greater than the radius of the conductive connecting layer 152, so that a gap is formed between the final drill position conducting layer 130 and the conductive connecting layer 152. And will not be described in detail.

The present application also provides a printed circuit board 30 obtained by back-drilling the printed circuit board 10 of any of the above embodiments. The printed circuit board 30 includes a first target signal layer 110, a second target signal layer, a final drill bit conductive layer 130, a via 150 penetrating the first target signal layer 110, a conductive connection layer 152, and a via 160.

Specifically, the first target signal layer 110 and the second target signal layer 120 are stacked.

The final drill bit conductive layer 130 is sandwiched between the first target signal layer 110 and the second target signal layer 120.

And a via 150 penetrating the first target signal layer 110.

The conductive connection layer 152 is located in the via hole 150 and covers the inner wall of the first target signal layer 110, so that the first signal layer 112, the second signal layer 114, the third signal layer 116 and the fourth signal layer 118 in the first target signal layer 110 are conducted through the conductive connection layer 152.

The via 160 penetrates the second target signal layer 120 and exposes the final drill bit conductive layer 130.

Further, the printed circuit board 30 includes blind holes 172 that extend through the first conductive layer 122 and the second conductive layer 124 to isolate the final drill bit conductive layer 130 from the first conductive layer 122 and the second conductive layer 124.

Further, the first target signal layer 110 includes a first signal layer 112, a second signal layer 114, a third signal layer 116, and a fourth signal layer 118. A second insulating layer 144 is provided between each of the first signal layer 112, the second signal layer 114, the third signal layer 116, and the fourth signal layer 118. The second target signal layer 120 includes a first conductive layer 122 and a second conductive layer 124. A first insulating layer 142 is disposed between the first conductive layer 122 and the second conductive layer 124.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.