Drilling tools and blind hole processing methods

Abstract

The present invention discloses a drilling tool and a blind hole processing method. The drilling tip of the drilling tool can perform pre-drilling, and the tapered portion can ensure that the hole shape of the drilled hole is tapered. The drilling tool can directly form the tapered hole without repeatedly changing the tool to process the tapered hole, which can reduce the workload and improve the processing accuracy of the tapered hole, thereby improving the processing efficiency of the tapered hole. The blind hole processing method first uses the above-mentioned drilling tool to mechanically drill a PCB board to form a preliminary mechanical tapered hole, and then uses a laser to remove the medium between the bottom of the preliminary mechanical blind hole and the target circuit layer to form a blind hole. The blind hole processing method combines the advantages of high mechanical drilling efficiency and precise hole depth control of the laser, can simplify the blind hole processing process and improve processing efficiency. The above-mentioned drilling tool can be used for mechanical drilling to pre-drill the PCB board by the drilling tip, and the hole shape of the blind hole can be ensured by the tapered portion.

Description

Technical Field

[0001] The present invention relates to the technical field of machining tools, and in particular to a drilling tool and a blind hole machining method. Background Art

[0002] Tapered holes are a common hole type in mechanical processing. In order to process tapered holes, a round hole is generally drilled out with a drill bit first, and then the round hole is expanded, and then a tapered hole is cut out with a reducing boring tool or a tapered hole is cut out with a reamer. The boring tool or reamer is easy to wear and easy to be scrapped, and the utilization rate of the boring tool or reamer is low and the processing volume is small. The drilling process of the tapered hole is cumbersome, and the tool needs to be replaced frequently during the processing, which increases the workload and lows the processing efficiency. Replacing the tool during the drilling process is likely to increase the clamping error and cause a large processing error of the tapered hole. Summary of the Invention

[0003] The object of the present invention is to provide a drilling tool which does not require multiple tool changes, can ensure the taper of the machined hole, reduce the workload and improve the machining efficiency.

[0004] Another object of the present invention is to provide a blind hole processing method, which uses the above-mentioned drilling tool to ensure that the blind hole is a tapered hole and improve processing efficiency.

[0005] To achieve the above-mentioned object, the present invention provides a drilling tool comprising a coaxially arranged straight shank and a drilling portion, the straight shank being connected to the drilling portion, the outer wall of the drilling portion being recessed with a chip groove, the chip groove spirally surrounding the central axis of the drilling portion, the outer wall of the drilling portion also being formed with a land connected to the outer edge of the chip groove, the land spirally surrounding the central axis of the drilling portion;

[0006] The drilling portion includes a drilling tip and a tapered portion that are coaxially connected and away from the straight shank portion. The drilling tip is away from the straight shank portion relative to the tapered portion. The outer surface of the tapered portion is located on a rotating curved surface with the central axis as the rotation axis. The outer surface of the tapered portion has a first end and a second end distributed axially along the central axis. The first end of the outer surface of the tapered portion is connected to the cutting edge, and the second end of the outer surface of the tapered portion is connected to the drilling tip. The generatrix of the rotating curved surface is a straight line segment inclined toward the central axis, and the distance from the generatrix to the central axis gradually increases from the second end to the first end.

[0007] Optionally, the drilling tip has a first cutting surface and a second cutting surface connected to each other, and a chisel edge, the first cutting surface and the second cutting surface are centrally symmetrical along the central axis, the angle between the first cutting surface and the second cutting surface is a drill point angle β of the drilling tip, and the chisel edge is formed at the connection position between the first cutting surface and the second cutting surface;

[0008] The first cutting surface has a first cutting edge connected to the chisel edge and a first side opposite to the chisel edge, the second cutting surface has a second cutting edge connected to the chisel edge and a second side opposite to the chisel edge, and the first cutting edge and the second cutting edge are centrally symmetrical along the central axis;

[0009] The drilling portion is provided with two chip grooves which are symmetrical along the central axis, and two cutting bands which are symmetrical along the central axis are formed between the two chip grooves; the first cutting edge and the second cutting edge are respectively formed in the two chip grooves; the tapered portion forms a first part and a second part which are symmetrical about the central axis, the first end of the outer surface of the first part and the first end of the outer surface of the second part are respectively connected to the two cutting bands, and the second end of the first part and the second end of the second part are respectively connected to the first side and the second side.

[0010] Optionally, the blade lengths of the first cutting surface and the second cutting surface are first blade lengths l1, where the first blade length l1 is the distance from the center point of the chisel edge to the intersection of the first cutting edge and the first side edge; the blade length of the tapered portion is second blade length l2, where the second blade length l2 is the generatrix length of the rotational curved surface. The relationship between the first blade length l1 and the second blade length l2 is:

[0011] l 1< l2.

[0012] Optionally, the cone portion has a cone angle α, and the relationship among the cone angle α, the drill point angle β, the first edge length l1 and the second edge length l2 is:

[0013]

[0014] Wherein, R is the distance from the end of the generatrix away from the drilling tip to the central axis.

[0015] Optionally, a distance R from one end of the busbar away from the drilling tip to the central axis is greater than or equal to 0.05 mm and less than or equal to 0.35 mm.

[0016] Optionally, the drilling tip has a circumferential tooth clearance angle δ, which is the angle between a perpendicular line connecting a line of the intersection of the first cutting edge and the first side and a center point of the transverse edge and a tangent line passing through the intersection of the first cutting edge and the first side, and the circumferential tooth clearance angle δ is greater than or equal to 25° and less than or equal to 35°.

[0017] Optionally, the drilling tip has a first clearance angle γ, a perpendicular plane to the center axis, and the first clearance angle γ is the angle between the first cutting surface, the second cutting surface and the perpendicular plane; the helix angle θ of the chip groove is greater than or equal to 25° and less than or equal to 30°, and the relationship between the helix angle θ and the first clearance angle γ is: γ = 40° - θ.

[0018] Optionally, the first cutting surface further comprises a third side opposite to the first cutting edge and connected to the first side and the chisel edge, and the second cutting surface further comprises a fourth side opposite to the second cutting edge and connected to the second side and the chisel edge, wherein the third side and the fourth side are centrally symmetrical along the central axis.

[0019] The projections of the first side and the second side on the end face of the drilling tip are circular arcs, and the arc projected on the end face by the first side extends from the end connected to the first cutting edge to the end connected to the third side close to the center point of the chisel edge; the arc projected on the end face by the second side extends from the end connected to the second cutting edge to the end connected to the fourth side close to the center point of the chisel edge.

[0020] In order to achieve the above-mentioned further object, the present invention further provides a blind hole processing method for processing a blind hole on a PCB board, comprising:

[0021] Determining the opening position of the blind via of the PCB board and the target circuit layer to be reached;

[0022] Using the drilling tool as described above to mechanically drill at the opening position, drilling through the upper circuit layer adjacent to the target circuit layer to form a preliminary mechanical tapered hole;

[0023] Using laser to remove the medium between the bottom of the preliminary mechanical tapered hole and the target circuit layer to form the blind hole;

[0024] The blind hole is electroplated to connect the target circuit layer and the surface circuit layer of the PCB board.

[0025] Optionally, multiple pulse lasers are used to remove the medium between the bottom of the preliminary mechanical tapered hole and the target circuit layer in a gradient annular processing manner.

[0026] In the drilling tool of the present invention, the drilling tip can perform pre-drilling, and the tapered portion can ensure that the hole shape of the drilled hole is tapered. The drilling tool can directly form a tapered hole without the need to repeatedly change the tool to process the tapered hole, which can reduce the workload and improve the processing accuracy of the tapered hole, thereby improving the processing efficiency of the tapered hole. The blind hole processing method of the present invention first uses the above-mentioned drilling tool to mechanically drill a PCB board to form a preliminary mechanical tapered hole, and then uses a laser to remove the medium between the bottom of the preliminary mechanical blind hole and the target circuit layer to form a blind hole. It combines the advantages of high mechanical drilling efficiency and precise control of hole depth by laser, can simplify the blind hole processing process and improve processing efficiency. The use of the above-mentioned drilling tool for mechanical drilling can pre-drill the PCB board by the drilling tip, and the tapered portion can ensure the hole shape of the blind hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of a drilling tool according to an embodiment of the present invention.

[0028] Figure 2 yes Figure 1 Enlarged view of part A in the middle.

[0029] Figure 3 It is a structural schematic diagram of the drilling tool according to another perspective of an embodiment of the present invention.

[0030] Figure 4 yes Figure 3 Enlarged view of part B in the middle.

[0031] Figure 5 It is a schematic end view of the drilling tip of the drilling tool according to an embodiment of the present invention.

[0032] Figure 6 yes Figure 5 Enlarged view of part C in the middle.

[0033] Figure 7 It is a flow chart of a blind hole processing method according to an embodiment of the present invention.

[0034] Figures 8a-8c The figure is a schematic diagram of the changing process of processing a blind hole of a PCB board in the blind hole processing method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to explain the technical content, structural features and achieved effects of the present invention in detail, the following is a detailed description in conjunction with the embodiments and the accompanying drawings.

[0036] like Figure 7 and Figures 8a-8c As shown, for a PCB board with a large aperture and thick dielectric, an embodiment of the present invention provides a blind hole processing method for processing a blind hole 100 on a PCB board, comprising the following steps:

[0037] S110 , determining the opening position of the blind via 100 of the PCB board and the target circuit layer 102 to be reached.

[0038] According to the design requirements of the PCB board, the opening position of the blind via 100 of the PCB board and the target circuit layer 102 to be reached are determined.

[0039] S120, using the drilling tool 1 to perform mechanical drilling at the opening position, drilling through the upper circuit layer 103 adjacent to the target circuit layer 102 to form a preliminary mechanical tapered hole 101 (such as Figure 8a As shown), that is, the bottom of the preliminary mechanical tapered hole 101 is located in the dielectric layer between the target circuit layer 102 and the upper circuit layer 103 adjacent to the target circuit layer 102.

[0040] S130, using laser to remove the medium between the bottom of the preliminary mechanical tapered hole 101 and the target circuit layer 102 to form a blind hole 100 (such as Figure 8b In the embodiment of the present invention, multiple pulsed lasers can be used to remove the dielectric between the bottom of the preliminary mechanical tapered hole 101 and the target circuit layer 102 in a gradient annular processing manner, thereby improving the flatness of the bottom of the blind hole 100, ensuring that the blind hole 100 can be uniformly electroplated, improving the electroplating yield, and thus improving the reliability of the blind hole 100 and the conductivity between the plating layers.

[0041] S140, electroplating the blind hole 100 to connect the target circuit layer 102 and the surface circuit layer 104 of the PCB board. Figure 8c shown.

[0042] The target circuit layer 102 , the upper circuit layer 103 adjacent to the target circuit layer 102 , and the surface circuit layer 104 are copper layers, and may also be conductive layers formed of other materials.

[0043] The drilling tool 1 used in step S120 of the embodiment of the present invention is as follows: Figures 1 to 6 As shown, it includes a coaxially arranged straight shank portion 10 and a drilling portion 20, the straight shank portion 10 is connected to the drilling portion 20, and the outer wall of the drilling portion 20 is concavely provided with a chip removal groove 21, and the chip removal groove 21 spirally surrounds the central axis of the drilling portion 20 (as shown in FIG. Figure 1The outer wall of the drilling portion 20 is further formed with a cutting edge 22 connected to the outer edge of the chip groove 21, and the cutting edge 22 spirally surrounds the central axis of the drilling portion 20; the drilling portion 20 includes a drilling tip 23 and a tapered portion 24 that are coaxially connected and away from the straight shank portion 10, the drilling tip 23 is away from the straight shank portion 10 relative to the tapered portion 24, the outer surface of the tapered portion 24 is located on a rotating curved surface with the central axis as the rotation axis (that is, the outer surface of the tapered portion 24 is part of the rotating curved surface), the outer surface of the tapered portion 24 has a first end and a second end distributed axially along the central axis, the first end of the outer surface of the tapered portion 24 is connected to the cutting edge 22, and the second end of the outer surface of the tapered portion 24 is connected to the drilling tip 23, the generatrix of the rotating curved surface is a straight line segment inclined toward the central axis, and the distance from the generatrix to the central axis gradually increases from the second end of the rotating curved surface to the first end of the rotating curved surface. The drilling tip 23 of the drilling tool 1 pre-drills the opening position on the PCB board, and the tapered portion 24 ensures that the hole shape of the blind hole 100 is tapered. The improved drilling tool 1 of the embodiment of the present invention can quickly drill a hole in a PCB board and form a tapered hole.

[0044] It is understood that the straight shank portion 10 and the drilling portion 20 may be connected by at least one transition portion to enhance the overall strength of the drilling tool 1. Figure 1 and Figure 3 As shown, one end of the straight shank portion 10 close to the drilling portion 20 is connected to one end of the first transition portion 25, the other end of the first transition portion 25 is connected to one end of the reinforcing support portion 26, the other end of the reinforcing support portion 26 is connected to one end of the second transition portion 27, and the other end of the second transition portion 27 is connected to the drilling portion 20. The first transition portion 25 and the second transition portion 27 are truncated cone-shaped, and the reinforcing support portion 26 is cylindrical. The diameter of the first transition portion 25 decreases from the straight shank portion 10 to the reinforcing support portion 26. The diameter of the end of the first transition portion 25 connected to the straight shank portion 10 is the same as the diameter of the straight shank portion 10, and the diameter of the other end of the first transition portion 25 is the same as the diameter of the reinforcing support portion 26; the diameter of the second transition portion 27 decreases from the reinforcing support portion 26 to the drilling portion 20, the diameter of the end of the second transition portion 27 connected to the reinforcing support portion 26 is the same as the diameter of the reinforcing support portion 26, and the diameter of the other end of the second transition portion 27 is the same as the diameter of the drilling portion 20.

[0045] like Figure 2 and Figure 6As shown, the drilling tip 23 has a first cutting surface 230, a second cutting surface 231, and a chisel edge 232. The first cutting surface 230 and the second cutting surface 231 are symmetrical along the central axis. The angle between the first cutting surface 230 and the second cutting surface 231 is the drill point angle β of the drilling tip 23. The chisel edge 232 is formed at the connection position of the first cutting surface 230 and the second cutting surface 231. The first cutting surface 230 has a first cutting edge 2302 connected to the chisel edge 232 and a first side 2301 opposite to the chisel edge 232. The second cutting surface 231 has a second cutting edge 2312 connected to the chisel edge 232 and a second side 2311 opposite to the chisel edge 232. The first cutting edge 2302 The drilling portion 20 is formed with two chip flutes 21 symmetrically about the central axis, and two lands 22 symmetrically about the central axis are formed between the two chip flutes 21. The first cutting edge 2302 and the second cutting edge 2312 are respectively formed in the two chip flutes 21. The tapered portion 24 is formed with a first portion 241 and a second portion 242 symmetrically about the central axis. The first end of the outer surface of the first portion 241 and the first end of the outer surface of the second portion 242 are respectively connected to the two lands 22, and the second end of the outer surface of the first portion 241 and the second end of the outer surface of the second portion 242 are respectively connected to the first side 2301 and the second side 2311. The drilling tool 1 in this embodiment has two chip flutes 21 and two lands 22, the drilling tip 23 has a first cutting surface 230 and a second cutting surface 231, and the tapered portion 24 forms the first portion 241 and the second portion 242, forming a double-edged drilling tool 1, which can improve the drilling speed and drilling stability of the drilling tool 1.

[0046] Furthermore, if Figure 4 As shown, the tapered portion 24 has a taper angle α, which is greater than or equal to 25° and less than or equal to 35°. The drill point angle β is greater than the taper angle α and less than 180°. Setting the taper angle α to be greater than or equal to 25° and less than or equal to 35° ensures that the hole shape and hole wall roughness of the preliminary mechanical tapered hole 101 remain within the designed range after multiple grinding and drilling operations. Setting the drill point angle β to be greater than the taper angle α and less than 180° not only serves the purpose of pre-drilling, but also prevents the formation of a countersink at the bottom of the preliminary mechanical tapered hole 101 due to an excessively small drill point angle β. It is understood that the closer the drill point angle β is to 180°, the less likely it is to form a countersink, which helps improve the flatness of the bottom of the blind hole 100. However, to ensure the drilling capability of the drilling tip 23, the drill point angle β is set to less than 180°.

[0047] Preferably, the cone angle α can be set to 30°, and the drill point angle β can be set to 165°.

[0048] Of course, in the drilling tool 1 of the embodiment of the present invention, the drilling portion 20 is not limited to being provided with two chip flutes 21 and two cutting edges 22 , and may also be provided with only one chip flute 21 and one cutting edge 22 .

[0049] like Figure 2 As shown, the blade length of the first cutting surface 230 and the second cutting surface 231 is a first blade length l1, which is the distance from the center point of the chisel edge 232 to the intersection of the first cutting edge 2302 and the first side 2301 (the first blade length l1 is also the distance from the center point of the chisel edge 232 to the intersection of the second cutting edge 2312 and the second side 2311); the blade length of the tapered portion 24 is a second blade length l2, which is the generatrix length of the rotational curved surface. The relationship between the first blade length l1 and the second blade length l2 is:

[0050] l 1< l2

[0051] This minimizes the depth of the countersunk hole, reduces the amount of dielectric material removed by the laser between the bottom of the initial mechanical tapered hole 101 and the target circuit layer 102, and improves laser processing efficiency while ensuring the hole shape and depth. It will be appreciated that the first portion 241 and the second portion 242 of the tapered portion 24 are symmetrical about the central axis, and therefore, the busbars on the first portion 241 and the second portion 242 are the same length.

[0052] It can be understood that the hole depth of the preliminary mechanical tapered hole 101 is h, and the hole depth h satisfies Therefore, when the hole depth and taper of the blind hole 100 machined by the drilling tool 1 are known, the second blade length l2 and the taper angle α of the drilling tool 1 can be set according to the hole depth and taper.

[0053] Furthermore, the relationship between the taper angle α, the drill point angle β, the first edge length l1 and the second edge length l2 is:

[0054]

[0055] Where R is the distance from the end of the generatrix away from the drill tip 23 to the center axis. When the angle α, the drill tip angle β, the first edge length l1, and the second edge length l2 satisfy the aforementioned relationship, the shape of the tapered portion 24 of the drilling tool 1 can be maintained. Depending on the machining requirements for R and hole depth h, the taper of the hole produced by the drilling tool 1 according to the embodiment of the present invention can meet the machining requirements.

[0056] Furthermore, a distance R from the end of the generatrix of the rotational curved surface away from the drilling tip 23 to the central axis is greater than or equal to 0.05 mm and less than or equal to 0.35 mm.

[0057] like Figure 6As shown, the drilling tip 23 has a circumferential tooth clearance angle δ, which is the angle between a perpendicular line connecting a line of the intersection of the first cutting edge 2302 and the first side 2301 on the end face of the drilling tip 23 and the center point of the chisel edge 232 and a tangent line passing through the intersection of the first cutting edge 2302 and the first side 2301. The circumferential tooth clearance angle δ is greater than or equal to 25° and less than or equal to 35°. The larger the angle of the circumferential tooth clearance angle δ is, the smaller the contact area between the first side 2301 and the second side 2311 of the drilling tip 23 and the hole wall of the preliminary mechanical tapered hole 101 will be, which can reduce the friction of the first side 2301 and the second side 2311 on the hole wall and improve the quality of the hole wall. However, if the angle of the circumferential tooth clearance angle δ is too large, the rigidity of the drilling tip 23 and the cone 24 will be reduced, thereby reducing the wear resistance of the drilling tip 23 and the cone 24. Therefore, the angle of the circumferential tooth clearance angle δ can be set to greater than or equal to 25° and less than or equal to 35°, which can not only reduce the friction of the first side 2301 and the second side 2311 on the hole wall and improve the quality of the hole wall, but also ensure the rigidity of the drilling tip 23 and the cone 24.

[0058] It should be noted that the end face of the drilling tip 23 refers to a plane passing through the center point of the chisel edge 232 and perpendicular to the center axis of the drilling tool. The first cutting edge 2302, the first side 2301 and the chisel edge 232 on the end face of the drilling tip 23 refer to the first cutting edge 2302, the first side 2301 and the chisel edge 232 of the drilling tip 23 projected on the end face of the drilling tip 23, that is, the circumferential tooth clearance angle δ is: the angle between the perpendicular line of the connecting line of the intersection of the first cutting edge 2302 and the first side 2301 projected on the end face and the center point of the chisel edge 232 and the tangent line passing through the intersection of the first cutting edge 2302 and the first side 2301 projected on the end face, that is, the circumferential tooth clearance angle δ is formed on the end face of the drilling tip 23.

[0059] Similarly, the circumferential tooth clearance angle δ can also be the angle between the perpendicular line of the connecting line of the intersection of the second cutting edge 2312 and the second side 2311 of the end face of the drilling tip 23 and the center point of the chisel edge 232 and the tangent line passing through the intersection of the second cutting edge 2312 and the second side 2311.

[0060] like Figure 4As shown, the drilling tip 23 has a first clearance angle γ, which is a perpendicular plane to the central axis. The first clearance angle γ is the angle between the first cutting surface 230 and the second cutting surface 231 and the perpendicular plane. The helix angle θ of the chip flute 21 is greater than or equal to 25° and less than or equal to 30°. The relationship between the helix angle θ and the first clearance angle γ is: γ = 40° - θ, so as to ensure the strength and sharpness of the drilling tool 1. According to the relationship between the helix angle θ being greater than or equal to 25° and less than or equal to 30° and the helix angle θ and the first clearance angle γ, it can be concluded that the first clearance angle γ must be greater than or equal to 10° and less than or equal to 15°. Since the first clearance angle γ is the angle between the first cutting surface 230 or the second cutting surface 231 and the vertical plane, the relationship between the first clearance angle γ and the drill point angle β is: β = 180° - 2γ. It can be concluded that the drill point angle β is greater than or equal to 150° and less than or equal to 160°. Therefore, the first clearance angle γ and the drill point angle β can be solved in sequence according to the helix angle θ.

[0061] like Figure 6 As shown, the first cutting surface 230 is further formed with a third side 2303 opposite to the first cutting edge 2302 and connected to the first side 2301 and the chisel edge 232, and the second cutting surface 231 is further formed with a fourth side 2313 opposite to the second cutting edge 2312 and connected to the second side 2311 and the chisel edge 232, and the third side 2303 and the fourth side 2313 are centrally symmetrical along the central axis; the projections of the first side 2301 and the second side 2311 on the end face of the drilling tip are circular arcs, and the first side 2313 is opposite to the second cutting edge 2312 and connected to the second side 2311 and the chisel edge 232. The arc 01 projected on the end surface extends from the end connected to the first cutting edge 2302 to the end connected to the third side 2303 close to the center point of the transverse edge 232; the arc 01 projected on the end surface extends from the end connected to the second cutting edge 2312 to the end connected to the fourth side 2313 close to the center point of the transverse edge 232, thereby reducing the contact between the first side 2301 and the second side 2311 and the hole wall, reducing the friction between the first side 2301 and the second side 2311 and the hole wall, and improving the quality of the hole wall.

[0062] The blind hole processing method of the embodiment of the present invention first uses the above-mentioned drilling tool 1 to mechanically drill the PCB board to form a preliminary mechanical tapered hole 101, and then uses a laser to remove the medium between the bottom of the preliminary mechanical blind hole and the target circuit layer 102 to form the blind hole 100. This method combines the advantages of high mechanical drilling efficiency and precise hole depth control by laser, can simplify the processing steps of the blind hole 100 and improve processing efficiency. The above-mentioned drilling tool 1 can be used for mechanical drilling to pre-drill the PCB board by the drilling tip 23, and the tapered portion 24 can ensure the hole shape of the blind hole 100.

[0063] In the drilling tool 1 of the embodiment of the present invention, the drilling tip 23 can perform pre-drilling, and the tapered portion 24 can ensure that the drilled hole is tapered. Therefore, the drilling tool 1 can directly form a tapered hole without having to repeatedly change tools to produce the tapered hole. This can reduce the workload and improve the machining accuracy of the tapered hole, thereby improving the machining efficiency of the tapered hole. Of course, the drilling tool 1 of the embodiment of the present invention is not limited to use in the above-mentioned blind hole machining method. The drilling tool 1 of the embodiment of the present invention can also be used directly to perform mechanical drilling to form a tapered hole.

[0064] The above disclosure is merely a preferred embodiment of the present invention and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention still fall within the scope covered by the present invention.

Claims

1. A drilling tool, characterized in that: The invention comprises a coaxially arranged straight shank portion and a drilling portion, wherein the straight shank portion is connected to the drilling portion, the outer wall of the drilling portion is recessed with a chip removal groove, the chip removal groove spirally surrounds the central axis of the drilling portion, and the outer wall of the drilling portion is further formed with a land connected to the outer edge of the chip removal groove, the land spirally surrounds the central axis of the drilling portion; The drilling portion includes a drilling tip and a tapered portion that are coaxially connected and are separated from the straight shank portion. The drilling tip is separated from the straight shank portion relative to the tapered portion. The outer surface of the tapered portion is located on a rotational curved surface with the central axis as the rotation axis. The outer surface of the tapered portion has a first end and a second end distributed axially along the central axis. The first end of the outer surface of the tapered portion is connected to the cutting edge, and the second end of the outer surface of the tapered portion is connected to the drilling tip. The generatrix of the rotational curved surface is a straight line segment inclined toward the central axis, and the distance from the generatrix to the central axis gradually increases from the second end to the first end. The drilling tip has a first cutting surface and a second cutting surface connected to each other, and a chisel edge, the first cutting surface and the second cutting surface being centrally symmetrical along the central axis, the angle between the first cutting surface and the second cutting surface being a drill point angle β of the drilling tip, and the chisel edge being formed at the connection position between the first cutting surface and the second cutting surface; The first cutting surface has a first cutting edge connected to the chisel edge and a first side opposite to the chisel edge, the second cutting surface has a second cutting edge connected to the chisel edge and a second side opposite to the chisel edge, and the first cutting edge and the second cutting edge are centrally symmetrical along the central axis; The drilling portion is provided with two chip removal grooves symmetrically along the central axis, and two cutting edges symmetrically along the central axis are formed between the two chip removal grooves; the first cutting edge and the second cutting edge are respectively formed on the two chip removal grooves; the tapered portion is formed into a first part and a second part symmetrically about the central axis, a first end of an outer surface of the first part and a first end of an outer surface of the second part are respectively connected to the two cutting edges, and a second end of the first part and a second end of the second part are respectively connected to the first side edge and the second side edge; The drilling tip has a circumferential tooth clearance angle δ, which is the angle between a perpendicular line connecting a line at the intersection of the first cutting edge and the first side edge on the end face of the drilling tip and a center point of the chisel edge and a tangent line passing through the intersection of the first cutting edge and the first side edge, and the circumferential tooth clearance angle δ is greater than or equal to 25° and less than or equal to 35°; The first cutting surface further comprises a third side opposite to the first cutting edge and connected to the first side and the chisel edge, and the second cutting surface further comprises a fourth side opposite to the second cutting edge and connected to the second side and the chisel edge, wherein the third side and the fourth side are centrally symmetrical along the central axis; The projections of the first side and the second side on the end face of the drilling tip are circular arcs, and the arc projected on the end face by the first side extends from the end connected to the first cutting edge to the end connected to the third side close to the center point of the chisel edge; the arc projected on the end face by the second side extends from the end connected to the second cutting edge to the end connected to the fourth side close to the center point of the chisel edge.

2. The drilling tool according to claim 1, characterized in that The edge length of the first cutting surface and the second cutting surface is the first edge length l 1. First blade length l 1 is the distance from the center point of the chisel edge to the intersection of the first cutting edge and the first side edge; the blade length of the tapered portion is the second blade length l 2. The second blade length l 2 is the generatrix length of the rotational surface, the first blade length l 1 and the second blade length l The relationship between 2 is: 。 3. The drilling tool according to claim 2, characterized in that The cone portion has a cone angle α, the cone angle α, the drill point angle β, and the first edge length l 1 and the second blade length l The relationship between 2 is: Wherein, R is the distance from the end of the generatrix away from the drilling tip to the central axis.

4. The drilling tool according to claim 3, characterized in that A distance R between an end of the generatrix away from the drilling tip and the central axis is greater than or equal to 0.05 mm and less than or equal to 0.35 mm.

5. The drilling tool according to claim 1, characterized in that The drilling tip has a first clearance angle γ, which is a perpendicular plane to the central axis. The first clearance angle γ is the angle between the first cutting surface, the second cutting surface and the perpendicular plane. The helix angle θ of the chip groove is greater than or equal to 25° and less than or equal to 30°. The relationship between the helix angle θ and the first clearance angle γ is: γ=40°-θ.

6. A blind hole processing method for processing blind holes on PCB boards, characterized in that: include: Determining the opening position of the blind via of the PCB board and the target circuit layer to be reached; Using the drilling tool according to any one of claims 1 to 5 to perform mechanical drilling at the opening position, drilling through the upper circuit layer adjacent to the target circuit layer to form a preliminary mechanical tapered hole; Using laser to remove the medium between the bottom of the preliminary mechanical tapered hole and the target circuit layer to form the blind hole; The blind hole is electroplated to connect the target circuit layer and the surface circuit layer of the PCB board.

7. The blind hole processing method according to claim 6, characterized in that: The dielectric between the bottom of the preliminary mechanical tapered hole and the target circuit layer is removed in a gradient annular processing manner by using multiple pulse lasers.

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