CN113993283A

CN113993283A - Back drilling method applied to PCB

Info

Publication number: CN113993283A
Application number: CN202111247826.4A
Authority: CN
Inventors: 钟根带; 任文波; 彭镜辉; 向参军; 黎钦源
Original assignee: Guangzhou Guanghe Technology Co Ltd
Current assignee: Guangzhou Guanghe Technology Co Ltd
Priority date: 2021-10-26
Filing date: 2021-10-26
Publication date: 2022-01-28

Abstract

The invention discloses a back drilling method applied to a PCB (printed circuit board), and belongs to the technical field of circuit board manufacturing. The drilling direction of the first drill cutter starts from the lower surface of the PCB to the upper surface of the PCB, so that the position precision of the first hole close to the lower surface of the PCB is higher than the position precision of the first hole far away from the lower surface of the PCB. The drilling direction of the second drill cutter is consistent with that of the first drill cutter, so that the second drill cutter is prevented from deviating during drilling, and the accuracy of the second hole is improved. And finally, the drilling direction of the BD-B drill is consistent with that of the second drill, and the BD-B drill drills by taking the axial direction of the second hole as a guide, so that the BD-B drill is prevented from deviating during drilling, and the accuracy of back drilling is improved. And moreover, after the BD-B drill bit is used for drilling, the second drill bit can be used for discharging sundries generated in the drilling process out of the back drilling hole, so that the back drilling hole is prevented from being blocked, and the working performance of the PCB is ensured.

Description

Back drilling method applied to PCB

Technical Field

The invention relates to the technical field of circuit board manufacturing, in particular to a back drilling method applied to a PCB.

Background

In the manufacturing process of the PCB, a via section that does not perform any connection or transmission function needs to be drilled away to avoid adverse phenomena such as reflection, scattering, delay and the like during high-speed signal transmission.

The common back drilling method of the PCB comprises the following steps: drilling downwards from the upper surface of the PCB along the vertical direction according to the position of the positioning hole to form a first hole; a back-drilled hole is formed by drilling upward from the lower surface of the PCB board while using the first hole for guiding.

However, during the formation of the first hole, the drill is further into the PCB, which causes the drill to deflect, resulting in a lower accuracy of the position of the first hole closer to the lower surface of the PCB. The accuracy of the back drilling is undoubtedly reduced by guiding the back drilling with the first hole having a low positional accuracy. In addition, impurities formed in the back drilling process easily block the back drilling hole to influence the working performance of the PCB, in order to solve the problem, a BD-B drill with good dust removal performance is generally selected for back drilling, but the BD-B drill has poor rigidity and can deflect in the back drilling process to further reduce the accuracy of the back drilling hole.

Therefore, it is desirable to provide a back drilling method for PCB to solve the above problems.

Disclosure of Invention

The invention aims to provide a back drilling method applied to a PCB (printed circuit board), which solves the problem of back drilling hole blockage while ensuring the accuracy of back drilling holes, so that the accuracy of the back drilling holes is improved, and the working performance of the PCB is ensured.

In order to realize the purpose, the following technical scheme is provided:

a back drilling method applied to a PCB comprises the following steps:

s1: turning a PCB up and down, and drilling a hole on the upper surface of the PCB along the vertical direction by using the lower surface of the PCB as a starting point by using a first drill to form a first hole, wherein the first hole penetrates through the PCB;

s2: a second drill cutter drills a hole in the upper surface of the PCB along the axial direction of the first hole by taking the lower surface of the PCB as a start so as to form a second hole;

s3: and the BD-B drill cutter drills holes on the upper surface of the PCB along the axial direction of the second hole by taking the lower surface of the PCB as the start so as to form a back drilling hole of the PCB.

In an alternative of the above-described back drilling method for a PCB, the preset aperture of the back drilling hole is larger than the preset aperture of the first hole, the tool diameter of the first drill tool is the same as the preset aperture of the first hole, and the tool diameters of the second drill tool and the BD-B drill tool are the same as the preset aperture of the back drilling hole.

In an alternative of the above-mentioned back drilling method for PCB board, the difference between the preset aperture of the back drilling hole and the preset aperture of the first hole is 0.20 mm.

In an alternative of the above back drilling method for the PCB, the rotation speed of the first drill is 145 kilorevolutions per minute, the drop speed is 1.2 meters per minute, and the return speed is 12 meters per minute.

In an alternative of the above back drilling method for the PCB, the rotation speed of the second drill is 80 krpm/min, the falling speed is 2.0 m/min, and the returning speed is 12 m/min.

In an alternative of the above back drilling method for the PCB, the BD-B drill has a rotation speed of 80 krpm/min, a drop speed of 2.5 m/min, and a return speed of 12 m/min.

In an alternative of the above back drilling method for PCB board, the first drill bit has a tip angle of 150 °.

In an alternative of the above back drilling method for PCB board, the hole depth of the second hole is smaller than the preset hole depth of the back drilling hole.

In an alternative of the above back drilling method for PCB board, the preset hole depth of the back drilling hole minus the hole depth of the second hole is 0.50 mm.

In an alternative of the above back drilling method for the PCB, the lower surface of the PCB is provided with a coating aluminum sheet.

Compared with the prior art, the invention has the beneficial effects that:

according to the back drilling method applied to the PCB, the drilling direction of the first drill cutter starts from the lower surface of the PCB to the upper surface of the PCB, so that the position precision of the first hole close to the lower surface of the PCB is higher than the position precision of the first hole far away from the lower surface of the PCB. The drilling direction of the second drill cutter is consistent with that of the first drill cutter, namely the second drill cutter drills by taking the axial direction of the lower surface of the PCB close to the first hole as the guide, so that the second drill cutter is prevented from deviating during drilling, and the accuracy of the second hole is improved. The drilling direction of the BD-B drill is consistent with that of the second drill, and the BD-B drill drills by taking the axial direction of the second hole as a guide, so that the BD-B drill is prevented from deviating during drilling, and the accuracy of back drilling is improved. And moreover, the BD-B drill bit is used for drilling in the second drill bit after the BD-B drill bit, so that sundries generated in the previous two drilling processes can be discharged out of the back drilling hole, the back drilling hole is prevented from being blocked, and the working performance of the PCB is ensured.

Drawings

Fig. 1 is a flowchart of a back drilling method applied to a PCB board in an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or orientations or positional relationships that are conventionally placed when the products of the present invention are used, and are used only for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the devices or elements to be referred to must have specific orientations, be constructed in specific orientations, and operate, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "disposed" and "connected" are to be interpreted broadly, e.g., as being either fixedly connected, detachably connected, or integrally connected; either mechanically or electrically. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

The process of back drilling the PCB at present is as follows: drilling a hole downwards from the upper surface of the PCB along the vertical direction according to the position of the positioning hole to form a first hole; a back-drilled hole is formed by drilling upward from the lower surface of the PCB board while using the first hole for guiding. In the forming process of the first hole, the drill cutter is continuously deep into the PCB, so that the drill cutter is deflected, and the position accuracy of the first hole is lower as the first hole is closer to the lower surface of the PCB. The accuracy of the back drilling is undoubtedly reduced by guiding the back drilling with the first hole having a low positional accuracy. In addition, impurities formed in the back drilling process easily block the back drilling hole to influence the working performance of the PCB, in order to solve the problem, a BD-B drill with good dust removal performance is generally selected for back drilling, but the BD-B drill has poor rigidity and can deflect in the back drilling process to further reduce the accuracy of the back drilling hole. Therefore, how to avoid the blockage of the back drilling hole while ensuring the accuracy of the back drilling hole is a big problem in the manufacturing process of the PCB board nowadays. The embodiment thus provides a back drilling method applied to a PCB board.

As shown in fig. 1, the back drilling method applied to the PCB board includes the following steps:

s1: the PCB is turned over up and down, the first drill cutter drills holes on the upper surface of the PCB along the vertical direction by taking the lower surface of the PCB as a starting point so as to form a first hole, and the first hole penetrates through the PCB;

s2: the second drill cutter takes the lower surface of the PCB as a starting point to drill a hole on the upper surface of the PCB along the axial direction of the first hole so as to form a second hole;

s3: and the BD-B drill takes the lower surface of the PCB as the starting point and drills a hole to the upper surface of the PCB along the axial direction of the second hole so as to form a back drilling hole of the PCB.

The drilling direction of the first drill takes the lower surface of the PCB as the starting point to the upper surface of the PCB, so that the position precision of the first hole close to the lower surface of the PCB is higher than that far away from the lower surface of the PCB. The drilling direction of the second drill cutter is consistent with that of the first drill cutter, namely the second drill cutter drills by taking the axial direction of the lower surface of the PCB close to the first hole as the guide, so that the second drill cutter is prevented from deviating during drilling, and the accuracy of the second hole is improved. And finally, the drilling direction of the BD-B drill is consistent with that of the second drill, and the BD-B drill drills by taking the axial direction of the second hole as a guide, so that the BD-B drill is prevented from deviating during drilling, and the accuracy of back drilling is improved. And moreover, after the BD-B drill bit is used for drilling, the second drill bit can be used for discharging sundries generated in the drilling process out of the back drilling hole, so that the back drilling hole is prevented from being blocked, and the working performance of the PCB is ensured.

Since the back-drilled hole is formed by secondary drilling on the basis of the first hole, optionally, the preset aperture of the back-drilled hole is larger than the preset aperture of the first hole. And the tool diameter of the first drill is the same as the preset aperture of the first hole, and the tool diameters of the second drill and the BD-B drill are the same as the preset aperture of the back drilling hole. Further optionally, the difference between the pre-set aperture of the backdrilled hole and the pre-set aperture of the first hole is 0.20 mm. Since the preset aperture of the first hole is 0.20mm in this embodiment, the preset aperture of the second hole is 0.40 mm. Therefore, the first drill had a diameter of 0.20mm, and the second and BD-B drills had diameters of 0.40 mm. In other embodiments, the preset aperture of the first hole may be 0.15mm, and the preset aperture of the second hole and the BD-B drill may be 0.35mm, as long as the difference of 0.20mm is satisfied.

Further optionally, the first drill has a rotation speed of 145 krpm/min, a drop speed of 1.2 m/min, and a return speed of 12 m/min. The drilling speed of the first drill cutter is improved, the drilling efficiency is improved, the first drill cutter generates a large acting force in the drilling process, the possibility that the first drill cutter is blocked by the PCB and deflects is reduced, and the accuracy of the first hole is further improved. The greater drilling speed sacrifices the life of the first drill bit, which in this embodiment is only 500 hole limits.

Further optionally, the rotation speed of the second drill is 80 kilorevolutions per minute, the falling speed is 2.0 meters per minute, and the return speed is 12 meters per minute. The drilling speed of the second drill is improved by the arrangement, the drilling efficiency is improved, the second drill generates a large acting force in the drilling process, the possibility that the second drill is blocked by the PCB and deflects is reduced, and the accuracy of the second hole is further improved. The greater drilling speed sacrifices the life of the second drill, which in this embodiment is only 200 holes. Furthermore, the tool nose angle of the first drill is 150 degrees, the rigidity of the first drill is improved, the possibility of deflection of the second drill in the drilling process is reduced, and the accuracy of the second hole is further improved.

Further optionally, the rotation speed of the BD-B drill is 80 kilorevolutions per minute, the falling speed is 2.5 meters per minute, and the return speed is 12 meters per minute. The arrangement improves the drilling speed of the BD-B drill, not only improves the drilling efficiency, but also enables the BD-B drill to generate larger acting force in the drilling process, reduces the possibility that the BD-B drill is obstructed by the PCB and deflects, and further improves the accuracy of back drilling. The life of the BD-B drill is sacrificed by the greater drilling speed, which in this embodiment is only 200 holes limited.

In order to ensure the accuracy of back drilling and avoid excessive drilling, a certain margin is required to be left when the second drill bit drills. Further optionally, the second hole has a hole depth less than the pre-set hole depth of the back-drilled hole. When the BD-B drill performs back drilling, the drilling process is started from the lower surface of the PCB board, but the second hole is formed at this time, so the BD-B drill drills the second hole only to discharge impurities in the second hole, i.e., the difference between the preset hole depth of the back drilling hole and the hole depth of the second hole is the actual drilling depth of the BD-B drill. Due to the poor rigidity of the BD-B drill, the actual drilling depth cannot be too long, otherwise the hole is easy to deviate. Thus, further optionally, the pre-set hole depth of the back-drilled hole minus the hole depth of the second hole is 0.50 mm.

Further optionally, a coating aluminum sheet is arranged outside the lower surface of the PCB, so that the buffering effect is achieved on each drill cutter, and the abrasion of each drill cutter is reduced; on the other hand, when the drill cutter drills, due to the fact that high temperature is generated due to the fact that the rotating speed is too high, the coating is dissolved when heated, the temperature of the drill cutter during working can be reduced, friction between the drill cutter and the hole wall can be reduced, roughness of the hole wall is reduced, and the drill cutter is guaranteed not to break.

It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A back drilling method applied to a PCB is characterized by comprising the following steps:

2. The back-drilling method for PCB board as recited in claim 1, wherein the back-drilling hole has a predetermined diameter larger than that of the first hole, the first drill has the same diameter as that of the first hole, and the second drill and the BD-B drill have the same diameter as that of the back-drilling hole.

3. The backdrilling method for PCB according to claim 2, wherein the difference between the preset hole diameter of the backdrilling hole and the preset hole diameter of the first hole is 0.20 mm.

4. The back drilling method for PCB board as recited in claim 1, wherein the first drill has a rotation speed of 145 kilo revolutions per minute, a drop speed of 1.2 meters per minute, and a return speed of 12 meters per minute.

5. The back drilling method for PCB board as recited in claim 1, wherein the second drill has a rotation speed of 80 kilo revolutions per minute, a drop speed of 2.0 m/min, and a return speed of 12 m/min.

6. The back drilling method for PCB board as recited in claim 1, wherein the BD-B drill has a rotation speed of 80 kRoots/min, a drop speed of 2.5 m/min, and a backdrilling speed of 12 m/min.

7. The backdrilling method for PCB board according to claim 1, wherein the nose angle of the first drill is 150 °.

8. The backdrilling method for PCB of claim 1, wherein the second hole has a hole depth smaller than the preset hole depth of the backdrilling hole.

9. The backdrilling method for PCB of claim 8, wherein the preset hole depth of the backdrilling hole minus the hole depth of the second hole is 0.50 mm.

10. The backdrilling method for PCB according to claim 1, wherein the lower surface of the PCB is coated with aluminum sheet.