A drill bit and a drill bit for drilling holes in printed circuit boards.

Abstract

This application discloses a drill bit and a drill bit for drilling printed circuit boards, belonging to the field of drill bit technology. It comprises a drill shank portion, a transition portion, and a drill body portion, which are connected sequentially. A drill tip portion is provided at the end of the drill body portion away from the drill shank portion, and the apex angle of the drill tip portion is 125°~180°. The drill tip portion includes two first flank faces, a second flank face, and a chisel edge. The two first flank faces intersect to form the chisel edge, and the intersection line of the first and second flank faces is not collinear with the center line of the drill tip portion. This eliminates the correlation between the drill tip apex angle and the chisel edge length. The drill tip can adopt a large apex angle design to reduce the height of the machined stump, while maintaining a shorter chisel edge, thereby reducing chip resistance and preventing hole clogging caused by copper chips.

Description

Technical Field

[0001] This application relates to the field of drill bit technology, and in particular to a drill bit and a drill bit for drilling holes in printed circuit boards. Background Technology

[0002] With the development of artificial intelligence technology, the requirements for high-speed signal transmission in electronic devices continue to increase. The back-drilling process of printed circuit boards (PCBs) removes excess copper plating from through holes through secondary drilling to eliminate signal reflection, and is a core process to ensure the integrity of high-speed signals.

[0003] Current high-multilayer PCBs are trending towards greater thickness, deeper back-drilling, and smaller hole diameters, requiring back-drilling micro-drills to possess both small diameter and long drill body characteristics. However, existing drill bit manufacturing suffers from the following problems: to reduce the height of signal reflection studs, the drill tip angle needs to be increased, but increasing the tip angle of traditional drill bits significantly increases the length of the transverse cutting edge. An excessively long transverse cutting edge can easily damage the copper layer on the hole wall, causing difficulties in chip removal and hole clogging, leading to a sharp increase in cutting force and even drill bit breakage.

[0004] To address the aforementioned issues, existing technologies typically reduce the core thickness or re-grind the chisel edge. However, these methods have significant drawbacks in small-diameter applications: reducing the core thickness drastically decreases drill bit rigidity, leading to deformation and inaccuracy during deep hole machining; furthermore, chisel edge re-grinding is a complex process, costly, and results in poor batch-to-batch stability. Therefore, resolving the contradiction between using a large-aperture drill tip to reduce residual pile height and avoiding an excessively long chisel edge, thus balancing drill bit rigidity, has become the core challenge in back drill design. Summary of the Invention

[0005] This application aims to solve at least one of the technical problems existing in the prior art. To this end, this application proposes a drill bit and a drill bit for drilling printed circuit boards, which adopts a design that combines a large tip angle and a short cross-cutting edge. This design can reduce the height of the residual pile and reduce the squeezing of the copper in the hole by the cross-cutting edge, thereby improving the processing quality of back drilling.

[0006] A drill bit according to a first aspect embodiment of this application includes: a drill shank portion, a transition portion, and a drill body portion, the drill shank portion, the transition portion, and the drill body portion being connected sequentially. The drill body portion has two helical grooves and a central axis along its axial direction. The helical grooves extend from one end of the drill body portion along the central axis to the other end. A drill tip portion is provided at the end of the drill body portion away from the drill shank portion, and the apex angle of the drill tip portion is 125°~180°. The drill tip portion includes two first flank faces, a second flank face, and a chisel edge. The two first flank faces intersect to form the chisel edge. The drill body portion has a central axis along its axial direction. A plane perpendicular to the central axis is defined as a reference plane. The orthographic projection of the intersection line of the first flank face and the second flank face onto the reference plane is not collinear with the orthographic projection of the centerline of the drill tip portion onto the reference plane.

[0007] The drill bit according to the first aspect of this application has at least the following beneficial effects: In this invention, the two first flank faces intersect to form the chisel edge, and the orthographic projection of the intersection line of the first and second flank faces on the reference plane is not collinear with the orthographic projection of the center line of the drill tip portion on the reference plane. The chisel edge is optimized from being formed by four planes in the traditional method to being formed by only two planes. The formation of the chisel edge is no longer related to the second flank face. According to the micro-drill bit structure, with the back angle remaining unchanged, the length of the chisel edge no longer increases with the increase of the apex angle, thus eliminating the correlation between the drill tip apex angle and the length of the chisel edge. The drill tip portion adopts a large apex angle design of 125°~180° to reduce the height of the machining residual pile without increasing the length of the chisel edge. With the large apex angle design, a shorter chisel edge can also be maintained, thereby reducing chip resistance and preventing hole blockage caused by the extrusion of copper chips.

[0008] The short chisel edge and the large apex angle structure of the drill tip are achieved through geometric design, eliminating the need for chisel edge re-grinding at the drill tip. Since the drill bit does not require a complex chisel edge re-grinding process, it avoids quality fluctuations caused by unstable re-grinding accuracy, improving the consistency and reliability of the main cutting edge at the drill tip. Furthermore, the drill bit of this application eliminates the need for chisel edge re-grinding, simplifying the production process and reducing manufacturing costs.

[0009] According to some embodiments of this application, the orthographic projection of the intersection line of the first flank face and the second flank face on the reference plane and the orthographic projection of the center line of the drill tip portion on the reference plane have a certain distance W, where 0 < the distance W ≤ 25% of the diameter of the drill body portion.

[0010] According to some embodiments of this application, the spiral groove intersects with the first flank face at the drill tip portion to form the main cutting edge; 0 ≤ the distance H between the orthographic projection of the main cutting edge on the reference plane and the orthographic projection of the center line on the reference plane ≤ 13% of the diameter of the drill body portion.

[0011] According to some embodiments of this application, the length L of the orthographic projection of the main cutting edge on the reference plane is 10 to 50% of the drill body diameter.

[0012] According to some embodiments of this application, the apex angle of the drill tip is 150°~165°.

[0013] According to some embodiments of this application, the first region extends from the drill tip portion to the other end of the drill body portion until it intersects with the drill body portion at a first position. The drill body portion is provided with a drill core. The length of the first region is 0 to 30% of the length of the drill body portion. Within the first region, the diameter of the drill core is 10 to 30% of the diameter of the drill body portion.

[0014] According to some embodiments of this application, the drill body portion includes a second region extending from the drill tip portion towards the other end of the drill body portion until it intersects with a second position on the drill body portion. The length of the second region is 0% to 50% of the length of the drill body portion. Within the second region, the helix angle of the spiral groove is 25° to 48°. According to some embodiments of this application, the length L of the orthographic projection of the main cutting edge on the reference plane is 12 to 45% of the diameter of the drill body portion.

[0015] According to some embodiments of this application, the drill tip portion further includes at least one third rake face.

[0016] According to some embodiments of this application, a drill core is provided inside the drill body portion, and the diameter of the drill core extends along the axial direction of the drill body portion. The diameter of the drill core is the same or varies in a gradient; the gradient variation is a continuous variation or a segmented variation.

[0017] According to some embodiments of this application, the spiral groove and the second flank face intersect at the drill tip portion to form a flank groove edge, and the main cutting edge and the flank groove edge are connected directly, in a straight line, or in a curve.

[0018] According to some embodiments of this application, a coating is deposited on the surface of the drill body portion and / or the surface of the drill tip portion; the coating is any one of a diamond coating, a diamond-like coating, and a nitride coating, or the coating is a composite coating including a diamond coating, a diamond-like coating, and a nitride coating.

[0019] According to some embodiments of this application, the coating covers all or part of the surface of the drill body portion; and / or, the coating covers all or part of the surface of the drill tip portion.

[0020] A drill bit for drilling printed circuit boards according to a second aspect embodiment of the present application includes a drill bit according to the first aspect embodiment of the present application, wherein the diameter of the drill body portion is 0.15~0.7mm.

[0021] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0022] The present application will be further illustrated below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments illustrated in the following drawings are exemplary and are only used to explain the present application, and should not be construed as limiting the present application.

[0023] Figure 1 This is a side view of a double-edged single-groove drill bit according to an embodiment of this application; Figure 2 yes Figure 1 Schematic diagram of the cross-sectional structure along the AA direction; Figure 3 This is a side view of a double-edged, double-groove drill bit according to an embodiment of this application; Figure 4 yes Figure 3 Schematic diagram of the cross-sectional structure in the middle BB direction; Figure 5 This is a schematic diagram of drilling holes in a PCB circuit board; Figure 6 This is a schematic diagram of a back-drilled residual pile; Figure 7 yes Figure 5 Enlarged view of point C in the middle; Figure 8 This is a schematic diagram of back-drilling and plugging; Figure 9 This is a schematic diagram of standard PCB drill bits and slot types. Figure 1 ; Figure 10 This is a schematic diagram of standard PCB drill bits and slot types. Figure 2 ; Figure 11 This is a schematic diagram of the drill tip of a traditional drill bit; Figure 12 This is a schematic diagram of a drill bit according to an embodiment of this application; Figure 13 This is a schematic diagram showing the relationship between the intersection line of the first and second flank faces of a traditional drill bit and the center line. Figure 14 This is a schematic diagram showing the relationship between the intersection line of the first and second flank faces and the center line according to an embodiment of this application. Figure 15 This is a schematic diagram illustrating the relationship between the main cutting edge and the centerline according to an embodiment of this application. Figure 1 ; Figure 16 This is a schematic diagram illustrating the relationship between the main cutting edge and the centerline according to an embodiment of this application. Figure 2 ; Figure 17 This is a schematic diagram illustrating the relationship between the main cutting edge and the centerline according to an embodiment of this application. Figure 3 ; Figure 18 This is a schematic diagram of the main cutting edge length L according to an embodiment of this application; Figure 19 This is a schematic diagram of a high-center multi-flank head type according to an embodiment of this application; Figure 20 This is a schematic diagram of a flat-center multi-flank head type according to an embodiment of this application; Figure 21 This is a schematic diagram of a concave center multi-flank head type according to an embodiment of this application; Figure 22 This is a schematic diagram of a linear cutting head according to an embodiment of this application; Figure 23 This is a schematic diagram of a curved cutting head according to an embodiment of this application; Figure 24 This is a schematic diagram of a grinding head type according to an embodiment of this application; Figure 25 This is a schematic diagram of a non-grinding head type according to an embodiment of this application; Figure 26 This is a schematic diagram of the main cutting edge and the rear groove edge being connected in a straight line according to an embodiment of this application; Figure 27 This is a schematic diagram showing the straight transition between the main cutting edge and the rear groove edge according to an embodiment of this application; Figure 28 This is a schematic diagram showing the transition between the main cutting edge and the rear groove curve in one embodiment of this application.

[0024] Reference numerals: 110, Drill shank portion; 120, Transition portion; 130, Drill body portion; 140, Drill tip portion; 200, First flank face; 210, Main cutting edge; 220, Transition junction; 300, Second flank face; 310, Back groove edge; 320, Grinding back; 400, Chisel edge; 500, Spiral groove; 600, Third flank face; 710, Copper plating; 720, Electroplated copper; 810, Hole plug; 820, Copper wire; 830, Copper shavings. Detailed Implementation

[0025] The embodiments of this application are described in detail below with reference to the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0026] In the description of this application, it should be understood that the terms "center", "middle", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0027] In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0028] In the description of this application, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0029] In the description of this application, the use of terms such as "one embodiment," "some embodiments," "an example," "some instances," "some embodiments," "illustrative embodiment," "example," "specific example," and "some examples" indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0030] Reference Figures 1-4According to an embodiment of this application, the drill bit's overall structure includes a drill shank portion 110, a transition portion 120, and a drill body portion 130 connected sequentially along an axis. The drill body portion 130 has two helical grooves 500 and a central axis along its axial direction. The helical grooves 500 extend from one end of the drill body portion 130 along the central axis to the other end. A drill tip portion 140 is provided at the end of the drill body portion 130 away from the drill shank portion 110, and the apex angle θ of the drill tip portion 140 is 125°~180°. The drill shank portion 110 is used to be clamped by a chuck of a machine tool and transmits torque to drive the drill bit to rotate. The transition portion 120 connects the drill shank portion 110 and the drill body portion 130.

[0031] To reduce the size of the stub formed after back drilling, the apex angle θ of the drill tip 140 is set to a larger angle, not less than 125°, specifically ranging from 125° to 180°. Compared to traditional drill bits with apex angles less than 120°, this application, by setting a larger apex angle, leaves a shallower conical pit at the bottom of the circuit board hole when the drill bit reaches the predetermined depth, thereby forming a lower stub and improving the quality of signal transmission.

[0032] Reference Figures 5-7 This provides the relationship between the 710 copper plating, 720 electroplated copper, back drill diameter R2, and through hole diameter R1. Based on the micro-drill bit structure, to achieve a smaller residual height after drilling, a larger tip angle θ is required, typically above 130°. With the back angle remaining constant, the length of the chisel edge 400 increases with the increase of the tip angle θ. (Refer to...) Figure 8 During the drilling process, if the transverse cutting edge 400 is too long, it will easily squeeze the copper in the hole. Copper wire 820 and copper shavings 830 will cause the hole to be blocked 810. The above two are contradictory.

[0033] In traditional designs, increasing the apex angle θ leads to an increase in the length of the transverse blade 400, as shown in the reference. Figures 9-10 As shown, the transverse cutting edge E2 at a 150° apex angle θ is greater than the transverse cutting edge E1 at a 130° apex angle θ. (Refer to...) Figure 11 As shown, the traditional chisel edge 400 is formed by four flank faces, specifically by the intersection of two first flank faces 200 and two second flank faces 300. (Refer to...) Figure 12In this embodiment, the chisel edge 400 is formed by the intersection of two oppositely arranged first back facets 200. The chisel edge 400 is formed by two planes instead of four planes. According to the structure of the micro drill bit, with the back angle and the first back facets 200 unchanged, the length of the chisel edge 400 does not increase as the apex angle increases. This design can eliminate the correlation between the apex angle of the drill tip 140 and the length of the chisel edge 400. Even when a larger apex angle is used, a short chisel edge 400 design can still be used.

[0034] The drill body portion 130 has a central axis along its axial direction. A plane perpendicular to the central axis is defined as a reference plane. In the conventional drill tip portion 140 structure, the reference plane is... Figure 13 As shown, the orthographic projections of the intersection lines I and I' of the first flank face 200 and the second flank face 300 onto the reference plane coincide with the orthographic projection of the drill bit's centerline O onto the reference plane. However, in this application, the reference... Figure 14 As shown, the drill tip 140 has a first flank face 200 and a second flank face 300. The orthographic projections of the intersection lines I and I' of the first flank face 200 and the second flank face 300 on the reference plane are not collinear with the orthographic projection of the center line O of the drill tip 140 on the reference plane. This arrangement means that the intersection lines I and I' of the first flank face 200 and the second flank face 300 no longer pass through the rotation center of the drill bit. There is an offset distance W between the orthographic projections of the intersection lines I and I' of the first flank face 200 and the second flank face 300 on the reference plane and the orthographic projection of the center line O on the reference plane. This allows the center of the drill tip 140 to also have a certain cutting capability, thereby further reducing the axial force. It should be noted that the distance W between the intersection lines I and I' of the first flank face 200 and the second flank face 300 mentioned in the subsequent embodiments and the center line O is the distance between the orthographic projection of the intersection lines I and I' of the first flank face 200 and the second flank face 300 on the reference plane and the orthographic projection of the center line O on the reference plane.

[0035] Therefore, the drill bit of this application combines three methods: increasing the angle of the apex, the formation method of the chisel edge 400, and offsetting the orthographic projection of the intersection line of the first flank face 200 and the second flank face 300 on the reference plane relative to the orthographic projection of the center line of the drill tip on the reference plane. This allows the drill bit to achieve both the shallow cone pit and low residual stub effect brought by the large apex angle and the anti-clogging effect brought by the short chisel edge 400 without the need for secondary chisel edge 400 re-grinding.

[0036] Reference Figure 14In some embodiments, the distance W between the intersection lines I, I' of the first flank face 200 and the second flank face 300 and the center line O is greater than 0 and does not exceed 25% of the diameter of the drill body portion 130. An offset distance W greater than 0 is a necessary condition to ensure that the intersection lines I, I' of the first flank face 200 and the second flank face 300 are not collinear with the center line O. The offset distance W not exceeding 25% of the diameter of the drill body portion 130 is to avoid excessive offset W causing chip compression and affecting chip discharge.

[0037] In some embodiments, when the distance W between the intersection line of the first flank face 200 and the second flank face 300 and the center line O is 20-25% of the diameter of the drill body portion 130, the wider first flank face 200 supports the high-intensity impact during cutting, enhances wear resistance, and improves heat dissipation to reduce local heat concentration. However, if the distance W between the intersection line of the first flank face 200 and the second flank face 300 and the center line O is too large, it will compress the chips, affect the chip flow space, reduce the smoothness of chip removal, and even form copper chips 830 accumulation at the first flank face 200 and the second flank face 300, causing tool breakage.

[0038] In some embodiments, when the distance W between the intersection line of the first flank face 200 and the second flank face 300 and the center line O is 0-10% of the diameter of the drill body portion 130, the contact between the second flank face 300 and the machined surface can be significantly reduced, the axial cutting force can be reduced, the hole quality can be improved, the risk of sheet metal tearing can be reduced, and the smoothness of chip removal can be improved. However, if the distance W between the intersection line of the first flank face 200 and the second flank face 300 and the center line O is too small, the drilling life will be drastically reduced, and even the tool may break.

[0039] In some of these embodiments, when the distance W between the intersection line of the first flank face 200 and the second flank face 300 and the center line O is 10-20% of the diameter of the drill body portion 130, it has high comprehensive performance. It can ensure a shorter chisel edge 400, balance the sharpness and strength of the cutting edge, and better control the production quality of the drill bit, thus greatly improving the product qualification rate.

[0040] Therefore, the effect is better when the distance W between the intersection line of the first flank face 200 and the second flank face 300 and the center line O is 10~20% of the diameter of the drill body 130.

[0041] In some embodiments, the helical groove 500 intersects with the first flank face 200 at the drill tip portion 140 to form the main cutting edge 210. The distance H between the orthographic projection of the main cutting edge 210 on the reference plane and the orthographic projection of the center line O on the reference plane does not exceed 13% of the diameter of the drill body portion 130. The intersection lines I and I' of the main cutting edge 210 and the first flank face 200 and the second flank face 300 can be located on opposite sides or on the same side of the center line O. Regardless of whether they are on the same side, the distance H between the main cutting edge 210 and the center line O does not exceed 13% of the diameter of the drill body portion 130. When the distance H between the main cutting edge 210 and the center line O is 0, the main cutting edge 210 and the center line O are collinear. It should be noted that the distance H between the main cutting edge 210 and the center line O mentioned in subsequent embodiments refers to the distance between the orthographic projection of the main cutting edge 210 on the reference plane and the orthographic projection of the center line O on the reference plane.

[0042] In some of these embodiments, reference is made to Figures 15-17 The distance H between the main cutting edge 210 and the center line O is greater. The greater the distance from the center line O, the longer the chisel edge 400 is, which is not conducive to cutting. Furthermore, there is interference friction between the first flank face 200 and the second flank face 300. The smaller the distance from the center line O, the smaller the width of the cutting edge and the less wear-resistant it is.

[0043] In some embodiments, the distance H between the main cutting edge 210 and the center line O is 0 to 5% of the diameter of the drill body portion 130. This provides better overall performance, reducing axial cutting force, friction between the flank face and the chip, reducing flank face interference, and extending tool life.

[0044] In some of these embodiments, reference is made to Figure 18 The length L of the orthographic projection of the main cutting edge 210 onto the reference plane is 10-50% of the diameter of the drill body 130. It should be noted that the length L of the main cutting edge 210 mentioned in subsequent embodiments refers to the length of its orthographic projection onto the reference plane. The main cutting edge 210 is the part that undertakes the main cutting task, and its length L directly affects the stability of the cutting process. If the length L of the main cutting edge 210 is too short, only the cutting edge has cutting ability, while the rest will squeeze the material, resulting in poor cutting stability and a sharp increase in cutting force, which can easily lead to hole wall quality problems or even tool breakage. If the length L of the main cutting edge 210 is too long, it may affect the overall structural design of the drill tip 140. Limiting the length L of the main cutting edge 210 to the range of 10-50% of the diameter of the drill body 130 ensures a smooth cutting process, reasonable cutting force distribution, and effectively avoids hole wall quality problems and the risk of tool breakage. Preferably, when the length L of the main cutting edge 210 is 12-45% of the diameter of the drill body portion 130, the cutting process is more stable.

[0045] In some embodiments, the apex angle θ of the drill tip 140 is preferably 150° to 165°. Although a range of 125° to 180° can achieve the effect of reducing stub height, the effect is particularly significant within this preferred range, while simultaneously achieving an ideal balance between the strength of the drill tip 140 and the sharpness of the cutting edge. Therefore, the drill bit of this application, employing an apex angle θ of 150° to 165°, not only controls the height of the stub to an extremely low level but also achieves excellent hole wall quality and machining stability.

[0046] In some embodiments, the drill body portion 130 includes a first region extending from the drill tip portion 140 to the other end of the drill body portion 130 until it intersects with a first position on the drill body portion 130. A drill core is disposed inside the drill body portion 130. The length of the first region is 0-30% of the length of the drill body portion 130. Within the first region, the drill core diameter K of the drill body portion 130 is 10-30% of the diameter of the drill body portion. The area near the drill tip portion 140 is the weakest part of the drill bit structure and bears the greatest stress. By ensuring a relative drill core diameter of 10-30% in this area, this application can provide the necessary rigidity and strength to the drill bit, effectively resisting bending and torsional loads during drilling and preventing deformation or breakage of the drill bit during high-speed rotation and feeding.

[0047] In some embodiments, the drill body portion 130 includes a second region extending from the drill tip portion 140 to the other end of the drill body portion 130 until it intersects with a second position on the drill body portion 130. The length of the second region is 0-50% of the length of the drill body portion 130. Within this second region, the helix angle β of the helical groove 500 is 25°-48°. Within this range, a larger helix angle β facilitates the formation of curled chips and their rapid discharge along the helical groove 500, preventing hole blockage. Preferably, when the helix angle β is 30-45°, the cutting edge of the drill bit is sharper, the anti-chipping performance is stronger, the cutting is lighter, and the chip removal effect is better.

[0048] In some embodiments, the drill tip portion 140, in addition to the first flank face 200 and the second flank face 300, also includes at least one third flank face, as shown in the figure. Figures 19-21 The drill bit of this application includes a first flank face 200, a second flank face 300, and a third flank face 600. Therefore, by providing multiple flank faces (e.g., a first flank face 200, a second flank face 300, and a third flank face 600), the drill bit of this application can reduce the contact between the flank face and the hole wall, thereby reducing the impact on drilling. Depending on the drilling requirements, multiple third flank faces 600 can be provided, and the multiple third flank faces 600 are provided on the side of the second flank face 300 away from the first flank face 200.

[0049] Reference Figures 19-21 Based on the different distances H between the main cutting edge 210 and the center line, three types of multi-flank head shapes are formed: high center, flat center, and concave center.

[0050] In some embodiments, a drill core is provided inside the drill body portion 130. The diameter K of the drill core extends axially along the drill body portion 130, and the diameter of the drill core is either constant or varies gradually. The gradient variation can be continuous or segmented. If the drill core diameter is constant, the entire drill body structure is consistent in the length direction; different gradient variations will have different effects on chip removal.

[0051] In some of these embodiments, reference is made to Figures 1-4 The drill body 130 structure can be either a double-edged single-groove type or a double-edged double-groove type. The double-edged single-groove type has higher rigidity and strength, while the double-edged double-groove type has more chip removal space, and the drill bit type can be selected according to the drilling needs.

[0052] In some embodiments, the helical groove 500 intersects with the second flank face 300 at the drill tip portion 140 to form a flank groove 310, as shown in the figure. Figures 26-28 The transition joint 220 between the main cutting edge 210 and the second flank face 300 and the flank groove 310 adopts direct, straight, and curved connections to influence the stress distribution and durability of the drill tip 140 corner. Direct connection means the main cutting edge 210 and the flank groove 310 are directly connected without a transition. Because there is no transition at the joint point, stress is concentrated there, and under the same conditions, the chisel edge 400 length corresponding to direct connection is the longest of the three designs. Straight connection means the main cutting edge 210 and the flank groove 310 are connected by a straight transition. Because of the straight segment, stress is concentrated at the connection points between the straight segment and the main cutting edge 210, and between the straight segment and the flank groove 310. The chisel edge 400 length under straight connection is shorter than that under direct connection. Curved connection means the main cutting edge 210 and the flank groove 310 are connected by a curved transition. The curved design disperses stress distribution, and under the same conditions, the curved transition connection has the shortest chisel edge 400 design among the three connection methods.

[0053] At the same time, refer to Figures 22-23 The main cutting edge 210 can be designed as a straight edge or a curved edge to adapt to the cutting characteristics of different materials and the control requirements of chip shape.

[0054] In some of these embodiments, reference is made to Figures 24-25 The drill tip 140 can be either backed or unbacked. Adjusting the backing 320 reduces friction between the drill bit and the hole, thus lowering cutting resistance.

[0055] In some embodiments, coatings are deposited on the surfaces of the drill body portion 130 and the drill tip portion 140. The coatings can be deposited on the entire surface of the drill body portion 130 or localized areas, or on the entire surface of the drill tip portion 140 or localized areas, such as on the drill tip portion 140, on the peripheral cutting edge, or within the spiral groove 500, but not limited to these locations. The coating is any one of a diamond coating, a diamond-like carbon coating, or a nitride coating, or a composite coating including a diamond coating, a diamond-like carbon coating, and a nitride coating. These coatings can significantly improve the hardness and wear resistance of the drill bit surface, effectively resisting high temperatures and abrasive wear during machining, while reducing friction with the workpiece material during cutting, reducing cutting heat and cutting force, thereby significantly extending the service life of the drill bit and improving the quality of the machined surface.

[0056] A drill bit for drilling printed circuit boards according to an embodiment of this application includes the aforementioned drill bit, wherein the drill body portion 130 has a diameter of 0.15~0.7mm.

[0057] In some embodiments, in addition to back-drilling applications, the drill bit structure of the present invention is also suitable for through-hole machining of ordinary circuit boards. Its low axial force and high chip removal efficiency enable higher machining efficiency and better hole wall quality when machining multilayer boards or thick copper boards, reducing defects such as drill smudges and studs.

[0058] Furthermore, the technical concept of this invention is not limited to PCB manufacturing. Due to its excellent cutting geometry, this drill bit is also suitable for precision drilling of other materials. For example, when machining non-ferrous metals such as aluminum alloys and magnesium alloys, its sharp cutting edge and smooth chip removal can effectively prevent the formation of built-up edge, resulting in smooth hole walls. When machining engineering plastics and polymer-based composite materials, its stable cutting process and strong rigidity can effectively suppress material delamination, tearing, and burrs, achieving high-quality precision drilling.

[0059] The technical solution of this application will be described in detail below through more specific embodiments. Specific Implementation Example 1 The drill body portion 130 for back drilling has a cutting diameter of 0.4 mm and a length of 5.5 mm. The drill bit is a double-edged, single-groove type. The main cutting edge 210 is straight and transitions to the second flank face 300 with a curved transition to the groove 310. The flank faces are the first flank face 200 and the second flank face 300. The drill tip portion 140 has a grinding back 320. The drill tip portion 140 has a apex angle θ of 150°, a helix angle β of 36°, a core diameter K of 0.068 mm, a distance H of the main cutting edge 210 relative to the center line O of 0.01 mm, a distance W of 0.045 mm from the intersection line of the first flank face 200 and the second flank face 300 to the center line O, and a length of 0.132 mm for the main cutting edge 210. A lubricating coating is prepared on the surface of the drill body portion 130, and the coating covers the entire drill body portion 130.

[0061] Comparative Example 1 The drill body portion 130 for back drilling has a cutting diameter of 0.4 mm and a length of 5.5 mm. The drill bit is a double-edged, single-groove type. The main cutting edge 210 is straight and directly transitions to the rear groove 310 of the second flank face 300. The flank faces are the first flank face 200 and the second flank face 300. The drill tip portion 140 has a grinding back 320. The drill tip portion 140 has a apex angle of 130°, a helix angle β of 36°, a core diameter K of 0.052 mm, a distance H of the main cutting edge 210 relative to the center line O of 0.023 mm, a distance W of the intersection line of the first flank face 200 and the second flank face 300 to the center line O of 0.023 mm, and a length L of the main cutting edge 210 of 0.186 mm. A lubricating coating is prepared on the surface of the drill body portion 130, and the coating covers the entire drill body portion 130.

[0062] Test information: Back drilling was performed at D+8mil (D represents a through-hole φ0.20mm), with a drilled hole diameter of φ0.40mm, a copper thickness of 50μm, and a drilled depth of 4.0mm. Printed circuit board material: M6 high-speed board, 6.0mm thick, 46 layers. Test results are compared below:

[0063] The difference between Specific Embodiment 1 and Comparative Example 1 is that, in Specific Embodiment 1, the cutting edge 210 is straight and transitions to the groove 310 of the second flank face 300 with a curve; the drill tip 140 has a apex angle θ of 150°, a helix angle β of 36°, a drill core diameter K of 0.068 mm, a distance H of the main cutting edge 210 relative to the center line O of 0.01 mm, a distance W of the intersection line of the first flank face 200 and the second flank face 300 with the center line O of 0.045 mm, and a length of 0.132 mm for the main cutting edge 210. Comparative Example 1 is a traditional drill bit. In Comparative Example 1, the main cutting edge 210 is straight and directly transitions to the groove edge 310 of the second flank face 300. The drill tip 140 has a apex angle of 130°, a helix angle β of 36°, a core diameter K of 0.052 mm, a distance H of the main cutting edge 210 relative to the center line O of 0.023 mm, a distance W of the intersection line of the first flank face 200 and the second flank face 300 to the center line O of 0.023 mm, and a length L of the main cutting edge 210 of 0.186 mm.

[0064] Test results show that after machining with the comparative drill bit, the residual pile height was 186.7 μm, while after machining with the drill bit of this embodiment, the residual pile height was significantly reduced to 104.2 μm, a reduction of 44.2%. This fully demonstrates the effectiveness of the large apex angle design of this invention in reducing residual pile height. Meanwhile, regarding the hole-clogging rate, the hole-clogging rate of the drill bit of this embodiment was only 0.04%, which is lower than the 0.06% of the comparative drill bit. Furthermore, no tool breakage, wire entanglement, or dust blockage occurred during the entire test. This indicates that the novel drill tip 140 structure of this invention successfully solves the hole-clogging risk caused by the large apex angle, achieving the goals of small residual pile height and anti-clogging. It is evident that the large apex angle, i.e., the 150° apex angle in specific embodiment one, significantly optimizes the drilling effect compared to the 130° apex angle in comparative embodiment one. Specific Implementation Example 2 The drill body portion 130 for back drilling has a cutting diameter of 0.35 mm and a length of 5.5 mm. The drill bit is a double-edged, single-groove type. The main cutting edge 210 is straight and transitions to the second flank face 300 with a curved groove 310. The flank faces are the first flank face 200 and the second flank face 300. The drill tip portion 140 has a grinding back 320. The drill tip portion 140 has a apex angle of 150°, a helix angle β of 36°, a core diameter K of 0.060 mm, a distance H of the main cutting edge 210 relative to the center line O of 0 mm, a distance W of 0.039 mm from the intersection line of the first flank face 200 and the second flank face 300 to the center line O, and a length L of 0.104 mm for the main cutting edge 210. A lubricating coating is prepared on the surface of the drill body portion 130, and the coating covers the entire drill body portion 130.

[0066] Comparative Example 2 The drill body portion 130 for back drilling has a cutting diameter of 0.35 mm and a length of 5.5 mm. The drill bit is a double-edged, single-groove type. The main cutting edge 210 is straight and directly transitions to the rear groove 310 of the second flank face 300. The flank faces are the first flank face 200 and the second flank face 300. The drill tip portion 140 has a grinding back 320. The drill tip portion 140 has a apex angle of 150°, a helix angle β of 36°, a core diameter K of 0.060 mm, a distance H of the main cutting edge 210 relative to the center line O of 0.024 mm, a distance W of 0.039 mm from the intersection line of the first flank face 200 and the second flank face 300 to the center line O, and a length L of 0.104 mm for the main cutting edge 210. A lubricating coating is prepared on the surface of the drill body portion 130, and the coating covers the entire drill body portion 130.

[0067] Test information: Back drilling was performed at D+6mil (D represents a through-hole diameter of 0.20mm), with a drilled hole diameter of 0.35mm, a copper thickness of 50μm, and a drilled depth of 4.0mm. Printed circuit board material: M6 high-speed board, 6.0mm thick, 46 layers. Test results are compared below:

[0068] The difference between Specific Embodiment 2 and Comparative Example 2 is that in Specific Embodiment 2, the distance H between the main cutting edge 210 and the center line O is 0 mm, while in Comparative Example 2, the distance H between the main cutting edge 210 and the center line O is 0.024 mm.

[0069] Test results show that after machining with the drill bit of Comparative Example 2, the residual pile height was 117.8 μm, while after machining with the drill bit of Specific Example 2, the residual pile height was reduced to 96.3 μm, and the hole blockage rate also decreased from 0.13% to 0.02%. It is evident that a smaller distance H between the main cutting edge 210 and the center line O results in a shorter chisel edge 400, which is beneficial for drilling. Simultaneously, it reduces friction between the flank face and the machined surface, lowering the risk of metal copper being squeezed and removed from the worn cutting edge, thereby reducing the residual pile height and the hole blockage rate. Specific Implementation Example 3 The drill body portion 130 for back drilling has a cutting diameter of 0.4 mm and a length of 5.5 mm. The drill bit is a double-edged, single-groove type. The main cutting edge 210 is straight and transitions to the second flank face 300 with a curved groove 310. The flank faces are the first flank face 200 and the second flank face 300. The drill tip portion 140 has a grinding back 320. The drill tip portion 140 has a apex angle of 150°, a helix angle β of 36°, a core diameter K of 0.068 mm, a distance H of the main cutting edge 210 relative to the center line O of 0.012 mm, a distance W of 0.065 mm from the intersection line of the first flank face 200 and the second flank face 300 to the center line O, and a length L of 0.156 mm for the main cutting edge 210. A lubricating coating is prepared on the surface of the drill body portion 130, and the coating covers the entire drill body portion 130.

[0071] Comparative Example 3 The drill body portion 130 for back drilling has a cutting diameter of 0.4 mm and a length of 5.5 mm. The drill bit is a double-edged, single-groove type. The main cutting edge 210 is straight and directly transitions to the rear groove 310 of the second flank face 300. The flank faces are the first flank face 200 and the second flank face 300. The drill tip portion 140 has a grinding back 320. The drill tip portion 140 has a apex angle of 150°, a helix angle β of 36°, a core diameter K of 0.068 mm, a distance H of the main cutting edge 210 relative to the center line O of 0.012 mm, a distance W of 0.165 mm from the intersection line of the first flank face 200 and the second flank face 300 to the center line O, and a length L of 0.156 mm for the main cutting edge 210. A lubricating coating is prepared on the surface of the drill body portion 130, and the coating covers the entire drill body portion 130.

[0072] Test information: Back drilling was performed at D+8mil (D represents a through-hole diameter of 0.20mm), with a drilled hole diameter of 0.40mm, a copper thickness of 50μm, and a drilled depth of 4.0mm. Printed circuit board material: M6 high-speed board, 6.0mm thick, 46 layers. Test results are compared below:

[0073] The difference between Specific Embodiment 3 and Comparative Example 3 is that in Specific Embodiment 3, the distance W between the intersection line of the first flank face 200 and the second flank face 300 and the center line O is 0.065mm, while in Comparative Example 3, the distance W between the intersection line of the first flank face 200 and the second flank face 300 and the center line O is 0.165mm.

[0074] Test results show that after machining with the comparative example three drill bits, the residual pile height was 108.1 μm, while after machining with the drill bit of specific embodiment three, the residual pile height decreased to 104.2 μm, the hole blockage rate decreased from 0.07% to 0.04%, and the residual pile rate also decreased from 0.03% to 0.01%, with no tool breakage observed throughout the test. If the first flank face 200 is too large, it will compress the chips, affecting the chip flow space, reducing chip removal smoothness, and even causing copper chip accumulation on the flank face, leading to tool breakage; however, if the first flank face 200 is too small, it will cause a sharp reduction in drilling life, and even tool breakage at the bottom. Therefore, the optimal effect is achieved when the distance W between the intersection line of the first flank face 200 and the second flank face 300 and the center line O is 10-20% of the diameter. Specific Implementation Example 4 The drill body portion 130 for back drilling has a cutting diameter of 0.45 mm and a length of 5.5 mm. The drill bit is a double-edged, single-groove type. The main cutting edge 210 is straight and transitions to the second flank face 300 with a curved groove 310. The flank faces are the first flank face 200 and the second flank face 300. The drill tip portion 140 has a partially ground back 320. The drill tip portion 140 has a apex angle of 150°, a helix angle β of 36°, a core diameter K of 0.072 mm, a distance H of the main cutting edge 210 relative to the center line O of 0 mm, a distance W of 0.05 mm from the intersection line of the first flank face 200 and the second flank face 300 to the center line O, and a length L of 0.126 mm for the main cutting edge 210. A lubricating coating is prepared on the surface of the drill body portion 130, and the coating covers the entire drill body portion 130.

[0076] Comparative Example 4 The drill body portion 130 for back drilling has a cutting diameter of 0.45 mm and a length of 5.5 mm. The drill bit is a double-edged, single-groove type. The main cutting edge 210 is straight and directly transitions to the groove 310 of the second flank face 300. The flank faces are the first flank face 200 and the second flank face 300. The drill tip portion 140 has a grinding back 320. The drill tip portion 140 has a apex angle of 150°, a helix angle β of 36°, a core diameter K of 0.072 mm, a distance H of the main cutting edge 210 relative to the center line O of 0 mm, a distance W of 0.05 mm from the intersection line of the first flank face 200 and the second flank face 300 to the center line O, and a length L of 0.04 mm for the main cutting edge 210. A lubricating coating is prepared on the surface of the drill body portion 130, and the coating covers the entire drill body portion 130.

[0077] Test information: Back drilling was performed at D+10mil (D represents a through-hole φ0.20mm), with a drilled hole diameter of φ0.45mm, a copper thickness of 50μm, and a drilled depth of 4.0mm. Printed circuit board material: M6 high-speed board, 6.0mm thick, 46 layers. Test results are compared below:

[0078] The difference between Specific Embodiment 4 and Comparative Example 2 is that the length L of the main cutting edge 210 in Specific Embodiment 4 is 0.126 mm, while the length L of the main cutting edge 210 in Comparative Example 4 is 0.04 mm.

[0079] Test results show that after machining with the drill bit of Comparative Example 4, the residual pile height was 108.1 μm, while after machining with the drill bit of Comparative Example 5, the residual pile height was 104.2 μm. The hole blockage rate decreased from 0.07% to 0.04%, and the residual pile rate decreased from 0.03% to 0.01%. Furthermore, no tool breakage occurred during the entire test. This demonstrates that when the cutting edge length is too short, only the cutting edge has cutting ability, while the remaining part compresses the material, resulting in poor cutting stability, a sharp increase in cutting force, and a high risk of hole wall quality problems and tool breakage. Specific Implementation Example 5 The drill body portion 130 for back drilling has a cutting diameter of 0.4 mm and a length of 7.0 mm. The drill bit is a double-edged, single-groove type. The main cutting edge 210 is straight and transitions to the second flank face 300 with a curved groove 310. The flank faces are the first flank face 200 and the second flank face 300. The drill tip portion 140 has a grinding back 320. The drill tip portion 140 has a apex angle of 165°, a helix angle β of 36°, a core diameter K of 0.068 mm, a distance H of the main cutting edge 210 relative to the center line O of 0 mm, a distance W of 0.045 mm from the intersection line of the first flank face 200 and the second flank face 300 to the center line O, and a length L of 0.107 mm for the main cutting edge 210. A lubricating coating is prepared on the surface of the drill body portion 130, and the coating covers the entire drill body portion 130.

[0081] Test information: Back drilling was performed at D+8mil (D represents a through-hole diameter of 0.20mm), with a drilled hole diameter of 0.40mm, a copper thickness of 50μm, and a drilled depth of 6.0mm. In this example, 10,000 holes were drilled for testing. Printed circuit board material: M8 grade high-speed board, 7.2mm thick, 42 ​​layers. Test results are as follows:

[0082] Test results show that the average residual stub height after machining is 84.7 μm. In a test drilling 10,000 holes, the hole blockage rate remained at a low level of 0.04%, and zero tool breakage was achieved throughout the process. The machined hole shape value was only 12 μm, demonstrating high machining accuracy and stability. This embodiment shows that the drill bit design of the present invention has high robustness and long service life, and can maintain stable performance even under specific working conditions.

[0083] In the drill bit provided in this application, a chisel edge 400 is formed by the intersection of two first flank faces 200, and the intersection line of the first flank face 200 and the second flank face 300 is not collinear with the center line of the drill tip portion 140. The chisel edge 400 is optimized from being formed by four planes in the traditional method to being formed by only two planes, and the formation of the chisel edge 400 is no longer related to the second flank face 300. According to the micro-drill bit structure, with the clearance angle remaining unchanged, as the point angle θ increases, the length of the chisel edge 400 no longer increases accordingly, thus eliminating the correlation between the drill tip point angle θ and the length of the chisel edge 400. The drill tip portion adopts a large point angle design of 125°~180° to reduce the height of the machining residual pile without increasing the length of the chisel edge 400. With the large point angle design, a shorter chisel edge 400 can also be maintained, thereby reducing chip resistance and preventing hole blockage caused by the extrusion of copper chips.

[0084] The aforementioned short chisel edge 400 and the large apex angle structure of the drill tip 140 are obtained through geometric design, eliminating the need for chisel edge grinding of the drill tip 140. Since the drill bit does not require a complex chisel edge grinding process, it avoids drill bit quality fluctuations caused by unstable grinding accuracy, improving the consistency and reliability of the main cutting edge at the drill tip. Furthermore, the drill bit of this application eliminates the need for chisel edge grinding, simplifying the production process and reducing manufacturing costs. The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

Claims

1. A drill bit, comprising: The drill shank portion (110), the transition portion (120), and the drill body portion (130) are connected sequentially, characterized in that... The drill body (130) has two spiral grooves (500) and a central axis along its axial direction. The spiral grooves (500) extend from one end of the drill body (130) along the central axis to the other end. The drill body portion (130) is provided with a drill tip portion (140) at one end away from the drill shank (110), and the apex angle of the drill tip portion (140) is 125°~180°; The drill tip portion (140) includes two first flank faces (200), a second flank face (300), and a transverse cutting edge (400); wherein the two first flank faces (200) intersect to form the transverse cutting edge (400). A plane perpendicular to the central axis is defined as a reference plane. The orthographic projection of the intersection line of the first flank face (200) and the second flank face (300) on the reference plane is not collinear with the orthographic projection of the center line of the drill tip portion (140) on the reference plane.

2. The drill bit according to claim 1, characterized in that: The intersection line of the first back face (200) and the second back face (300) is projected onto the reference plane at a certain distance W between the orthographic projection of the center line of the drill tip portion (140) onto the reference plane and the center line of the drill body portion (130) at a certain distance W, where 0 < the distance W ≤ 25% of the diameter of the drill body portion (130).

3. The drill bit according to claim 1, characterized in that: The spiral groove (500) intersects with the first flank face (200) at the drill tip to form the main cutting edge (210), and the distance H between the orthographic projection of the main cutting edge (210) on the reference plane and the orthographic projection of the center line on the reference plane is ≤ 13% of the diameter of the drill body portion.

4. The drill bit according to claim 3, characterized in that: The drill bit satisfies at least one of the following conditions: (a) The length L of the orthographic projection of the main cutting edge (210) on the reference plane is 10-50% of the diameter of the drill body portion (130); (b) The apex angle of the drill tip portion (140) is 150°~165°; (c) The drill body portion (130) includes a first region, which extends from the drill tip portion (140) to the other end of the drill body portion (130) until it intersects with the drill body portion (130) at a first position. The drill body portion (130) is provided with a drill core. The length of the first region is 0 to 30% of the length of the drill body portion (130). Within the first region, the diameter of the drill core is 10 to 30% of the diameter of the drill body portion. (d) The drill body portion includes a second region, which extends from the drill tip portion (140) to the other end of the drill body portion (130) until it intersects with the drill body portion (140) at a second position. The length of the second region is 0 to 50% of the length of the drill body portion. Within the second region, the helix angle of the spiral groove (500) is 25° to 48°.

5. The drill bit according to claim 4, characterized in that: The length L of the orthographic projection of the main cutting edge (210) on the reference plane is 12 to 45% of the diameter of the drill body portion.

6. The drill bit according to claim 3, characterized in that: The drill bit satisfies at least one of the following conditions: (a) The drill tip portion (140) further includes at least one third flank face (600). (b) The drill body is provided with a drill core inside, the diameter of which extends along the axial direction of the drill body, and the diameter of the drill core is the same or varies in gradient; The gradient change can be continuous or segmented.

7. The drill bit according to claim 3, characterized in that: The spiral groove (500) and the second back face (300) intersect at the drill tip portion (140) to form a back groove edge (310), and the main cutting edge (210) and the back groove edge (310) are connected directly, in a straight line or by a curve.

8. The drill bit according to claim 1, characterized in that: A coating is deposited on the surface of the drill body portion (130) and / or the surface of the drill tip portion (140); The coating is any one of diamond coating, diamond-like coating, and nitride coating, or the coating is a composite coating including diamond coating, diamond-like coating, and nitride coating.

9. The drill bit according to claim 8, characterized in that, The coating covers all or part of the surface of the drill body portion; and / or, the coating covers all or part of the surface of the drill tip portion.

10. A drill bit for drilling holes in printed circuit boards, characterized in that: The drill bit is the drill bit according to any one of claims 1 to 9, and the diameter of the drill body portion (130) is 0.15 to 0.7 mm.

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