A drill bit and a drill bit for drilling processing of printed circuit boards

Abstract

The application discloses a drill bit, comprising a drill body part, a transition part and a drill shank part, which are sequentially connected, one end of the drill body part is provided with two spiral cutting edges, the two spiral cutting edges are provided with two spiral grooves which extend from one end of the drill body part to the other end along the axial direction, the two spiral grooves extend along the drill body part until intersecting at a first position of the drill body part, and after the intersection, the two spiral grooves are combined into one spiral groove which extends to a second position of the drill body part. The key structural parameters of the drill body part of the drill bit, such as the length, core diameter and spiral angle, are integrated and optimized, so that the drill bit has higher strength and stronger chip removal capacity, and the machining quality of back drilling is improved.

Description

Technical Field

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

[0002] Drilling is a critical process in the production of printed circuit boards (PCBs), as its quality directly affects the transmission speed, frequency, and quality of signals. To reduce signal loss during transmission, back-drilling is increasingly common in PCB manufacturing, with ever-higher quality requirements. Since back-drilling is performed after copper plating on the inner walls of the through-holes, it involves not only cutting through the copper foil and resin in the PCB as with regular drilling, but also continuously cutting through the copper plating on the inner walls of the drilled holes, and the quality requirements for back-drilling are extremely stringent. Therefore, back-drilling is one of the most challenging processes in PCB manufacturing.

[0003] With the upgrading of printed circuit board structures and materials for AI and next-generation mobile communications, the back-drilling depth has increased from 2mm to 9mm, the stub precision requirement has tightened from 6-10mil to 2-4mil, the hole diameter has decreased from approximately 0.45mm to below 0.30mm, and the copper plating thickness inside the hole has increased from approximately 30μm to approximately 50μm. These changes have significantly increased the difficulty of back-drilling, often causing hole blockage, off-center holes, tool breakage, and residual stubs, leading to tool wire entanglement and poor chip removal. In addition, tool wire entanglement can cause inconsistent conductivity detection, resulting in poor consistency in machining depth (abnormal copper wire entry into the hole can cause the drilling machine's current detection machining depth function to malfunction), and frequent stub quality abnormalities, as shown in Figure 1. Therefore, current back-drilling processes require drill bits with strong chip removal capabilities (e.g., small core diameter and large helix angle). However, reducing the core diameter and increasing the helix angle significantly reduces drill bit rigidity, increasing the likelihood of drill bit deviation and even causing tool breakage. Furthermore, increasing the helix angle increases the risk of wire entanglement, leading to a decrease in the depth control capability of conductive hole depth detection machines and poorer consistency in hole machining depth. Therefore, resolving the contradiction between strong chip removal drill bit structural design, wire entanglement structural design, and drill bit rigidity has become the core challenge in back-drill design. Utility Model Content

[0004] This application aims to at least solve one of the aforementioned problems existing in the prior art. To this end, one objective of this application is to provide a drill bit that, through integrated optimization of key structural parameters such as the length, core diameter, and helix angle of the drill body, achieves higher strength and stronger chip removal capability, thereby improving the processing quality of back drilling. A second objective of this application is to provide a drill bit for drilling holes in printed circuit boards, capable of adapting to the processing requirements of small-diameter, deep-hole back drilling, thick copper printed circuit boards, and high-precision machining, while still achieving excellent back drilling processing quality under these conditions.

[0005] To achieve the above objectives, the technical solution adopted in this application is as follows: It includes a drill body portion, a transition portion, and a drill shank portion, which are connected sequentially. Two helical cutting edges are provided at one end of the drill body. The two helical cutting edges extend from one end of the drill body along its axial direction to the other end and are provided with two helical grooves. The two helical grooves extend along the drill body until they intersect at a first position of the drill body. After intersecting, the two helical grooves merge into one helical groove and extend to a second position of the drill body. The drill body includes a first region, a second region, and a third region. The first region extends from one end of the drill body with the helical cutting edge to the first position where the two helical grooves intersect. The second region extends from one end of the drill body with the helical cutting edge to the second position of the drill body. The third region extends from the first position of the drill body to the second position of the drill body. Wherein, the length of the first region is 2 to 10 times the drill diameter, the core diameter of the first region is 10% to 30% of the drill diameter, and the helix angle of the spiral groove in the first region is 25° to 45°. The length of the second region is less than or equal to 95% of the length of the drill body portion, the core diameter of the third region is 65% to 90% of the drill diameter, and the helix angle of the spiral groove in the third region is 25° to 48°.

[0006] Therefore, the drill bit of this application has at least the following beneficial effects: This application integrates and optimizes key structural parameters such as the length, core diameter, and helix angle of the drill bit's body, resulting in a drill bit with high strength and strong chip removal capability. This enables low cutting force, smooth chip removal, and no wire tangling during back drilling. Furthermore, the drill bit of this application is suitable for back drilling of small diameters and large depths, thick copper printing plates, and high-precision machining requirements, and can still achieve excellent back drilling quality under such machining requirements.

[0007] According to some embodiments of this application, along the axial direction of the drill body portion, the helix angle changes continuously or segmentally from the first region to the third region; and / or, along the axial direction of the drill body portion, the core diameter increases continuously or segmentally from the first region to the third region.

[0008] According to some embodiments of this application, the first region of the drill body portion satisfies at least one of the following conditions: (a) The length of the first region is 4 to 6 times the drill diameter; (b) The core diameter of the first region is 12% to 22% of the drill diameter; (c) The helix angle of the spiral groove in the first region is 30°~45°.

[0009] When the drill bit portion meets condition (a), the drill bit can improve its resistance to chip breakage while maintaining its rigidity; when the drill bit portion meets condition (b), it can better balance the chip removal capacity and rigidity of the drill bit in the first region, further improving the working stability of the drill bit; when the drill bit portion meets condition (c), it can increase the sharpness of the drill bit, which is more conducive to the cutting of copper and has a better processing effect.

[0010] According to some embodiments of this application, the second region of the drill body portion satisfies at least one of the following conditions: (a) The core diameter of the third region is 70% to 85% of the drill diameter; (b) The helix angle of the spiral groove in the third region is 30°~40°; (c) The trench width of the second region is 0.8 to 3.0 times the drill diameter.

[0011] When the drill bit portion meets condition (a), it can better balance the chip removal capacity and rigidity of the drill bit, resulting in better machining effect; when the drill bit portion meets condition (b), the drill bit's ability to resist copper chip entanglement is significantly improved, and the drill bit at this time is particularly suitable for machining scenarios with a diameter ≤0.5mm and a hole depth of 3mm~10mm; when the drill bit portion meets condition (c), it can better meet the chip holding and chip removal needs of the drill bit in the second region.

[0012] According to some embodiments of this application, the first region of the drill body portion satisfies at least one of the following conditions: (a) The groove width of the first region is 0.8 to 2.5 times the drill diameter; this better meets the requirements of the drill bit of this application for chip containment and chip removal in the first region; (b) The first region includes a drill tip position, wherein the drill tip angle at the drill tip position is 80° to 180°.

[0013] According to some embodiments of this application, the drill tip angle at the drill tip position is 130°~165°. In this case, the main cutting edge of the drill bit has excellent resistance to chipping.

[0014] According to some embodiments of this application, the drill bit has an ST-type or UC-type structure. The ST-type drill bit has a straight drill body, while the UC-type drill bit has an Undercut structure on its drill diameter. This structure reduces friction between the drill bit and the hole wall, lowers the drilling temperature, and improves the hole wall quality.

[0015] According to some embodiments of this application, the first region includes a drill tip position, wherein a helical sub-groove is provided at the drill tip position, wherein the core diameter of the helical sub-groove is 5% to 27% of the drill diameter of the drill body portion; when the length of the sub-groove is 0.1 to 2 mm extending axially from the center point of the drill tip position along the drill body portion, the helical sub-groove extends axially from the drill tip position with a taper of 1-50 μm along the drill body portion, and the taper of the helical sub-groove is continuously varied or segmented.

[0016] According to some embodiments of this application, the core diameter of the spiral sub-groove is 5% to 18% of the drill diameter of the drill body portion. When the length of the sub-groove is 0.3 to 1.6 mm extending axially from the center point of the drill tip position along the drill body portion, the spiral sub-groove extends axially from the drill tip position with a taper of 1 to 40 μm along the drill body portion.

[0017] According to some embodiments of this application, the surface of the drill bit is either uncoated or coated, and the coating is a diamond coating, a nitride coating, or a diamond-like coating.

[0018] According to some embodiments of this application, when the surface of the drill bit is coated with a diamond-like carbon coating, the thickness of the coating is ≤2μm and the coefficient of friction of the coating is <0.2.

[0019] According to some embodiments of this application, the diamond-like coating is a ta-C coating, the thickness of the coating is 0.1μm≤0.5μm, and the coefficient of friction of the coating is <0.1.

[0020] According to some embodiments of this application, the coating covers all or part of the drill body.

[0021] According to some embodiments of this application, 3mm ≤ the cutting length of the drill bit ≤ 12mm, and 0.13mm ≤ the drill diameter of the drill bit ≤ 0.6mm.

[0022] The second aspect of this application provides a drill bit for drilling holes in printed circuit boards. The drill bit is the same as the drill bit described in the first aspect of this application. The diameter of the hole is ≤0.6mm and the depth of the hole is 3mm~6mm.

[0023] The third aspect of this application provides a drill bit for drilling printed circuit boards, wherein the drill bit is the drill bit described in the first aspect of this application, and the diameter of the drill hole is ≤0.6mm and the depth of the drill hole is 3mm~10mm.

[0024] Therefore, the drill bit for printed circuit board processing of this application has high strength and strong chip removal capability, which can achieve small cutting force, smooth chip removal and no wire tangling in the back drilling process, especially in the working conditions of small diameter, large depth back drilling, thick copper printed circuit board and high precision processing requirements, and can still obtain excellent back drilling quality under such processing requirements. Attached Figure Description

[0025] Figure 1 is a schematic diagram of machining defects during the back drilling process in the prior art; Among them, Figure 1(a) shows a stub exceeding tolerance; Figure 1(b) shows a plugged hole; Figure 1(c) shows a residual pile; Figure 1(d) shows a hole with poor wall roughness; Figure 1(e) shows a deviated hole; Figure 1(f) shows wire entanglement; Figure 1(g) shows an abnormal hole depth; and Figure 1(h) shows a deviated hole.

[0026] Figure 2 This is a schematic diagram of the drill bit structure of this application; Figure 3 The figures are cross-sectional views of the drill bit of this application at B-B, C-C, MM and E-E. Figure 4 This is a schematic diagram showing the measurement of the helix angle of the first region of the drill body portion of the drill bit in this application; Figure 5 This is a schematic diagram showing the measurement of the helix angle in the second region of the drill body portion of the drill bit in this application; Figure 6 This is an enlarged view of section A-A of the ST-type drill bit structure of this application; Figure 7 This is an enlarged view of the A-A section of the drill bit structure of this application, which is of the UC type; Figure 8 An enlarged view of section A-A of the drill bit of this application with helical sub-grooves; Figure 9 A schematic diagram showing the length of the sub-groove with spiral sub-grooves for the drill bit of this application; Figure 10 This is a schematic diagram of the structure of the drill bit of this application with coating only inside the groove; Figure 11 This is a schematic diagram of the drill bit of this application with coating only on the peripheral cutting edge; Figure 12 This is a schematic diagram of the structure of the drill bit coating (without coating except for the drill tip) of this application; Figure 13 This is a schematic diagram of the structure of all coatings on the drill bit in this application.

[0027] Reference numerals: 100-Drill body section, 200-Transition section, 300-Drill shank section, 1001-First region, 1002-Second region, 1003-Third region, 1004-Sub-groove length, 400-Helical sub-groove, 500-Coating, 600-Uncoated drill tip, β-Helix angle, GW-Groove width, K B - Core diameter of the BB section of the drill bit, K C - Core diameter of the CC section of the drill bit, K M - Core diameter (mm) of the drill bit section, K E - Core diameter of the EE section of the drill bit. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] In the description of the embodiments of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of 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. Therefore, they should not be construed as limitations on the embodiments of this application. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a replaceable 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 the embodiments of this application based on the specific circumstances.

[0031] Figure 2 A schematic diagram of the drill bit of this application is shown. The drill bit of this application includes a drill body portion 100, a transition portion 200, and a drill shank portion 300, which are connected in sequence.

[0032] The drill body portion 100 of this application is provided with two helical cutting edges at one end. The two helical cutting edges extend from one end of the drill body portion 100 along its axial direction to the other end and are provided with two helical grooves. The two helical grooves extend along the drill body portion 100 until they intersect at a first position of the drill body portion 100. After intersecting, the two helical grooves merge into one helical groove and extend to a second position of the drill body portion 100. The drill body portion 100 of this application includes a first region 1001, a second region 1002, and a third region 1003. The first region 1001 is from one end of the drill body portion 100 with the helical cutting edge to the first position where the two helical grooves intersect. The second region 1002 is from one end of the drill body portion 100 with the helical cutting edge to the second position of the helical groove drill body portion 100. The third region 1003 is from the first position of the drill body portion 100 to the second position of the drill body portion 100, that is, the third region 1003 is the second region 1002 excluding the first region 1001.

[0033] Figure 3 The diagram shows cross-sectional views of the drill bit of this application along lines B-B, C-C, M-M, and E-E. The cross-sectional view of the drill bit along line B-B shows two helical grooves, while the cross-sectional views of lines C-C, M-M, and E-E show only one helical groove. This is because the two helical grooves intersect at a first position in the drill body portion 100 and then merge into a single helical groove extending to a second position in the drill body portion 100. Furthermore... Figure 3 The diagram shows the core diameters of drill body section 100 at points B-B, C-C, M-M, and E-E, which are K... B K C K M K E .

[0034] Wherein, the length of the first region 1001 is 2 to 10 times the drill diameter, the core diameter of the first region 1001 is 10% to 30% of the drill diameter, and the helix angle of the spiral groove of the first region 1001 is 25° to 45°. The length of the second region 1002 is less than or equal to 95% of the length of the drill body 100, the core diameter of the third region 1003 is 65% to 90% of the drill diameter, and the helix angle of the spiral groove of the third region 1003 is 25° to 48°.

[0035] In another embodiment, along the axial direction of the drill body portion 100, the spiral groove β changes continuously or segmentally from the first region 1001 to the second region 1003 of the drill body portion 100; and / or, along the axial direction of the drill body portion 100, the core diameter of the drill body portion 100 increases continuously or segmentally from the first region 1001 to the third region 1003 of the drill body portion 100.

[0036] If the change is continuous, the change can be linear or non-linear; if the change is continuously increasing, the change can increase linearly or non-linearly, without specific limitations.

[0037] Figure 4-5 A schematic diagram showing the measurement of the helix angle β of the first region 1001 and the second region 1002 of the drill body portion 100 of the drill bit of this application is illustrated. In another embodiment, the first region 1001 of the drill body portion 100 of this application satisfies at least one of the following conditions: (a) The length of the first region 1001 is 4 to 6 times the drill diameter; (b) The core diameter of Zone 1001 is 12% to 22% of the drill diameter; (c) The helix angle β of the spiral groove in the first region 1001 is 30°~45°.

[0038] When the drill bit portion 100 of the drill bit of this application meets condition (a), the drill bit can improve its anti-breakage ability while maintaining rigidity; when the drill bit portion 100 of the drill bit of this application meets condition (b), it can better balance the chip removal ability and rigidity of the drill bit in the first region, further improving the working stability of the drill bit; when the drill bit portion 100 of the drill bit of this application meets condition (c), it can increase the sharpness of the drill bit, which is more conducive to the cutting of copper and has a better processing effect.

[0039] In another embodiment, the second region 1002 of the drill body portion of this application satisfies at least one of the following conditions: (a) The core diameter of the third region 1003 is 70% to 85% of the drill diameter; (b) The helix angle of the spiral groove in the third region 1003 is 30°~40°; (c) The trench width GW of the second region 1002 is 0.8 to 3.0 times the drill diameter.

[0040] When the drill bit portion 100 of the drill bit of this application meets condition (a), it can better balance the chip removal capacity and rigidity of the drill bit, and has a better processing effect; when the drill bit portion 100 meets condition (b), the drill bit's ability to resist copper chip entanglement is significantly improved, and the drill bit is particularly suitable for processing scenarios with a diameter ≤0.5mm and a hole depth of 3mm~10mm; when the drill bit portion meets condition (c), it can better meet the chip holding and chip removal needs of the drill bit in the second region.

[0041] In another embodiment, the first region 1001 of the drill body portion 100 of the drill bit of this application satisfies at least one of the following conditions: (a) The groove width GW of the first region 1001 is 0.8 to 2.5 times the drill diameter; wherein, when the drill bit portion 100 of the drill bit of this application meets condition (a), it can better meet the chip holding and chip removal requirements of the first region 1001.

[0042] (b) The first region 1001 includes a drill tip position, wherein the drill tip angle at the drill tip position is 80° to 180°.

[0043] In another embodiment, the drill tip angle is 130°~165°. In this case, the main cutting edge of the drill bit has excellent resistance to chipping.

[0044] In this application, when the drill body portion 100 of the drill bit has the same core diameter, helix angle β, and groove width GW within a length region of 1.5 times the drill diameter from the drill tip to the end of the groove, the drill bit can better adapt to the application scenario of drill tip reverse wear. When two helical grooves are parallel in the third region 1001 (it should be noted that after the two helical grooves intersect, they become one helical groove, but they can still be distinguished; therefore, it is described as parallel here), the groove lengths of the two helical grooves can be equal or unequal, with equal groove lengths being more advantageous.

[0045] In another embodiment, such as Figure 6-7 As shown, the drill bit structure of this application can be ST type or UC type. Among them, the drill body of the ST type drill bit is straight, and the drill diameter of the UC type drill bit is provided with an Undercut structure, which can reduce the friction between the drill bit and the hole wall, lower the drilling temperature, and improve the hole wall quality.

[0046] In another embodiment, such as Figure 8-9 As shown, the first region 1001 of the drill body portion 100 of the drill bit of this application includes a drill tip position, and a helical sub-groove 400 is provided at the drill tip position. By providing the helical sub-groove 400, the cutting force during the cutting process can be reduced.

[0047] The core diameter of the helical sub-groove 400 is 5% to 27% of the drill diameter of the drill body 100. When the sub-groove length 1004 extends 0.1 to 2 mm axially from the center of the drill tip along the drill body, the sub-groove length 1003 extends 0.1 to 2 mm from the center of the drill tip towards the drill shank in the first region. The helical sub-groove 400 extends axially from the drill tip with a taper of 1-50 μm along the drill body 100. The helical sub-groove 400 extends along the end away from the helical cutting edge according to this taper. The taper of the helical sub-groove can be continuously varied or segmented. If it is continuously varied, the amount of variation can be linear or non-linear.

[0048] In another embodiment, the core diameter of the spiral groove 400 is 5% to 18% of the drill diameter of the drill body portion 100. When the spiral groove length 1003 extends 0.3 to 1.6 mm from the center point of the tip position along the axial direction of the drill body portion, the spiral groove 400 extends along the axial direction of the drill body portion 100 with a taper of 1-40 μm from the drill tip position. At this time, the chip removal effect of the drill bit is better.

[0049] In another embodiment, the drill bit surface of this application may be uncoated or coated, wherein the coating 500 is a diamond coating, a nitride coating, or a diamond-like coating.

[0050] In another embodiment, when the drill bit surface is a diamond-like carbon coating, the thickness of the coating 500 is ≤2μm and the coefficient of friction of the coating 500 is <0.2. At this time, the drill bit has good lubrication performance and is more suitable for application scenarios where the hole depth is 3mm~6mm and the hole diameter is ≤0.6mm.

[0051] In another embodiment, the diamond-like coating is a ta-C coating, with a thickness of 0.1μm ≤ 0.5μm and a coefficient of friction of <0.1. In this case, the lubrication performance of the drill bit is further improved, making it more suitable for applications where the hole depth is 3mm~10mm and the hole diameter is ≤0.6mm.

[0052] like Figure 10-13 As shown, coating 500 can be a coating only inside the spiral groove, a coating only on the peripheral edge, a coating on both the spiral groove and the peripheral edge, or the entire drill bit of this application can be covered by coating 500.

[0053] In another embodiment, the drill bit of this application satisfies the following conditions: 3mm ≤ the cutting length of the drill bit ≤ 12mm, and 0.13mm ≤ the drill diameter of the drill bit ≤ 0.6mm.

[0054] This application discloses a drill bit for drilling holes in printed circuit boards. The primary processing method is back drilling, but it can also be used for through-hole drilling, and for drilling through-holes and blind holes in metals such as stainless steel, titanium alloys, and hardened steel. This drill bit is particularly suitable for the following processing environments: hole diameter ≤ 0.6 mm and hole depth 3 mm to 6 mm; or, hole diameter ≤ 0.6 mm and hole depth 3 mm to 10 mm. Therefore, the drill bit for printed circuit board processing of this application has high strength and strong chip removal capability, which can achieve small cutting force, smooth chip removal and no wire tangling in the back drilling process. Especially in the working conditions of small diameter, large depth back drilling, thick copper printed circuit board and high precision processing requirements, excellent back drilling quality can still be obtained under such processing conditions.

[0055] The drill bit of this application is described in detail below through specific embodiments, and the drill bit of this application is compared and analyzed with drill bits in the prior art according to standard test methods.

[0056] Example 1 The drill bit selected for back drilling has a diameter of 0.4 mm and a length of 5.0 mm for the drill body portion 100. The drill body portion 100 of this application has two helical cutting edges in its tip region (it should be noted that the first region 1001 includes the tip region). The two helical cutting edges extend axially from one end of the drill body portion 100 to the other end, forming two helical grooves. These two helical grooves extend along the drill body portion 100 until they intersect at a first position. After intersecting, the two helical grooves merge into one helical groove extending to a second position on the drill body portion 100. The first region 1001 has a length of 1.6 mm, a core diameter of 0.08 mm, a helix angle of 36°, and a apex angle of 140°. The second region 1002 has a length of 4.7 mm, and the third region 1003 has a core diameter of 0.32 mm and a helix angle of 30°. In addition, along the axial direction of the drill body portion 100, the helix angle β changes linearly from the first region 1001 to the third region 1003; along the axial direction of the drill body portion 100, the core diameter increases in segments from the first region 1001 to the third region 1003.

[0057] Comparative Example 1 A drill bit with a diameter of 0.4 mm and a drill body 100 length of 5.0 mm is selected for back drilling. The drill tip region of the selected drill bit's drill body 100 is provided with two helical cutting edges (it should be noted that the first region 1001 includes the drill tip region). These two helical cutting edges extend axially from one end of the drill body 100 to the other end, forming two helical grooves. These two helical grooves extend along the drill body 100 until they intersect at a first position on the drill body 100, after which they merge into one helical groove extending to a second position on the drill body 100. Specifically, the first region 1001 has a length of 4.1 mm, a core diameter of 0.16 mm, a helix angle of 46°, and a apex angle of 78°. The second region 1002 has a length of 5.0 mm, and the third region 1003 has a core diameter of 0.38 mm and a helix angle of 50°. In addition, along the axial direction of the drill body portion 100, the helix angle β changes linearly from the first region 1001 to the third region 1003; along the axial direction of the drill body portion 100, the core diameter increases in segments from the first region 1001 to the third region 1003.

[0058] Test Information: Back drilling is D+8mil (D represents a through hole φ0.20mm), with a back drill hole diameter of φ0.40mm, a through hole copper thickness of 65μm, and a back drill depth of 4.0mm. Printed Circuit Board Material: High-speed board (M6 grade), board thickness 5.0mm, 40 layers. Back drill test results show that the hole blockage rate at the bottom of the back drilled hole is reduced from 30% to 0.02% compared to the conventional design; there is no residual copper (residual studs) at the bottom of the back drilled hole, which is reduced from 17% to 0.01% compared to the conventional design. Example 1 achieves zero tool breakage and reduces the leakage rate to 0. There is no wire entanglement or dust blockage after back drilling. This example solves the industry pain points of deep hole back drilling by integrating the key structural parameters of the first region 1001, the second region 1002, and the third region 1003.

[0059]

[0060] Example 2: The drill bit selected for back drilling has a diameter of 0.4 mm and a length of 5.5 mm for the drill body portion 100. The drill tip region of the drill body portion 100 of this application is provided with two helical cutting edges (it should be noted that the first region 1001 includes the drill tip region). The two helical cutting edges extend axially from one end of the drill body portion 100 to the other end, forming two helical grooves. These two helical grooves extend along the drill body portion 100 until they intersect at a first position on the drill body portion 100. After intersecting, the two helical grooves merge into one helical groove extending to a second position on the drill body portion 100. The first region 1001 has a length of 2.2 mm, a core diameter of 0.084 mm, a helix angle β of 40°, and a apex angle of 140°. The second region 1002 has a length of 5.0 mm, and the third region 1003 has a core diameter of 0.31 mm and a helix angle β of 35°. Furthermore, along the axial direction of the drill body portion 100, the helix angle β changes linearly from the first region 1001 to the third region 1003; along the axial direction of the drill body portion 100, the core diameter increases segmentally from the first region 1001 to the third region 1003. In addition, a ta-C coating is prepared on the surface of the drill bit of this application, and the coating 500 covers the entire drill body portion 100 of the drill bit.

[0061] Comparative Example 2: A drill bit with a diameter of 0.4 mm and a drill body 100 length of 5.5 mm is selected for back drilling. The drill tip region of the selected drill bit's drill body 100 is provided with two helical cutting edges (it should be noted that the first region 1001 includes the drill tip region). These two helical cutting edges extend axially from one end of the drill body 100 to the other end, forming two helical grooves. These two helical grooves extend along the drill body 100 until they intersect at a first position on the drill body 100, after which they merge into one helical groove extending to a second position on the drill body 100. Specifically, the first region 1001 has a length of 4.4 mm, a core diameter of 0.084 mm, a helix angle of 40°, and a apex angle of 140°. The second region 1002 has a length of 5.5 mm, and the third region 1003 has a core diameter of 0.35 mm and a helix angle of 50°. Furthermore, along the axial direction of the drill body portion 100, the helix angle β changes linearly from the first region 1001 to the third region 1003; along the axial direction of the drill body portion 100, the core diameter increases segmentally from the first region 1001 to the third region 1003. In addition, a ta-C coating is prepared on the selected drill bit surface, and the coating covers the entire drill body portion 100 of the drill bit.

[0062] The test information is as follows: Back drilling was performed at D+8mil (D being a through hole φ0.20mm), with a back drill hole diameter of φ0.40mm. 10,000 holes were drilled using both designs, and the quality results were statistically analyzed. The printed circuit board material was a high-speed board (M6 grade), 5.9mm thick, with 46 layers. Due to the sharp helix angle design at the front end, back drilling effectively and quickly removes copper from the hole and a portion of the printed circuit board substrate. Simultaneously, the small core diameter of the drill bit and the groove width of the helical grooves (GW1 and GW2) of 0.9 times the diameter ensure that copper chips at the bottom of the drilled hole are completely discharged through the drill's chip removal grooves. The test results are compared below:

[0063] Example 3: The drill bit selected for back drilling has a diameter of 0.35 mm and a length of 5.0 mm for the drill body portion 100. The drill body portion 100 of this application has two helical cutting edges in its tip region (it should be noted that the first region 1001 includes the tip region). The two helical cutting edges extend axially from one end of the drill body portion 100 to the other end, forming two helical grooves. These two helical grooves extend along the drill body portion 100 until they intersect at a first position. After intersecting, the two helical grooves merge into one helical groove extending to a second position on the drill body portion 100. The first region 1001 has a length of 1.4 mm, a core diameter of 0.07 mm, a helix angle β of 40°, and a apex angle of 140°. The second region 1002 has a length of 4.7 mm, and the third region 1003 has a core diameter of 0.31 mm and a helix angle β of 32°. Furthermore, along the axial direction of the drill body portion 100, the helix angle β changes linearly from the first region 1001 to the third region 1003; along the axial direction of the drill body portion 100, the core diameter increases segmentally from the first region 1001 to the third region 1003. In addition, a ta-C coating is prepared on the surface of the drill bit of this application, and the coating covers the entire drill body portion of the drill bit.

[0064] Comparative Example 3: A micro drill with a diameter of 0.35 mm and a body length of 5.0 mm was selected for back drilling. The drill body portion 100 of the selected drill bit has two helical cutting edges at its tip (it should be noted that the first region 1001 includes the tip region). These two helical cutting edges extend axially from one end of the drill body portion 100 to the other end, forming two helical grooves. These two helical grooves extend along the drill body portion 100 until they intersect at a first position. After intersecting, the two helical grooves merge into one helical groove extending to a second position on the drill body portion 100. The first region 1001 has a length of 1.4 mm, a core diameter of 0.07 mm, a helix angle of 40°, and a apex angle of 140°. The second region 1002 has a length of 5.0 mm, and the third region 1003 has a core diameter of 0.21 mm and a helix angle of 48°. In addition, along the axial direction of the drill body portion 100, the helix angle β changes linearly from the first region 1001 to the third region 1003; along the axial direction of the drill body portion 100, the core diameter increases in segments from the first region 1001 to the third region 1003.

[0065] The test information is as follows: Back drilling was performed at D+6mil (D being a through-hole φ0.20mm), with a drilled hole diameter of φ0.35mm, a copper thickness of 50μm, and a drilling depth of 4.0mm. The printed circuit board material was a high-speed board (M6 grade), 5.5mm thick, with 38 layers. Results showed that the copper wire cut during back drilling was long and thin. This design significantly improved issues such as wire entanglement in the drill bit groove, tool breakage rate, deviation errors, and large hole diameter values ​​(>15μm). The test results are as follows:

[0066] Example 4: The drill bit selected for back drilling has a diameter of 0.45 mm and a length of 7.0 mm for the drill body portion 100. The drill body portion 100 of this application has two helical cutting edges in its tip region (it should be noted that the first region 1001 includes the tip region). The two helical cutting edges extend axially from one end of the drill body portion 100 to the other end, forming two helical grooves. These two helical grooves extend along the drill body portion 100 until they intersect at a first position. After intersecting, the two helical grooves merge into one helical groove extending to a second position on the drill body portion 100. The first region 1001 has a length of 1.8 mm, a core diameter of 0.09 mm, a helix angle β of 39°, and a apex angle of 150°. The second region 1002 has a length of 6.6 mm, the third region 1003 has a core diameter of 0.36 mm, and the helix angle of the third region 1003 is 36°. Furthermore, along the axial direction of the drill body portion 100, the helix angle β changes linearly from the first region 1001 to the third region 1003; along the axial direction of the drill body portion 100, the core diameter increases segmentally from the first region 1001 to the third region 1003. In addition, the surface of the drill bit of this application is coated with a ta-C coating, and the coating covers the helical grooves of the drill body portion 100 of the drill bit.

[0067] Back drill test information: Back drilling was performed at D+8mil (D being the through-hole diameter of 0.25mm), with a hole diameter of 0.45mm, a copper thickness of 50μm, and a drilling depth of 6.0mm. Example 4 and the original design product were compared by drilling 10,000 holes each. Printed circuit board material: high-speed board (M7 grade), board thickness 7.2mm, 45 layers. Results: The integrated design of the drill bit structure and coating resulted in excellent processing results. The experimental results of this example are as follows:

[0068] Therefore, the drill bit of this application, especially a drill bit for a printed circuit board, integrates and optimizes key structural parameters such as the length of the drill body, the core diameter, and the helix angle, so that the drill bit has high strength and strong chip removal capability, achieving low cutting force, smooth chip removal, and no wire tangling in the back drilling process. Especially in working conditions with small diameter, large depth back drilling, thick copper printed circuit boards, and high precision processing requirements, it can still obtain excellent back drilling quality.

[0069] The above embodiments are preferred embodiments of this application, but the implementation of this application is not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of this application shall be considered equivalent substitutions and shall be included within the protection scope of this application.

Claims

1. A drill bit, comprising a drill body portion, a transition portion, and a drill shank portion, wherein the drill body portion, the transition portion, and the drill shank portion are connected sequentially, characterized in that, Two helical cutting edges are provided at one end of the drill body. The two helical cutting edges extend from one end of the drill body along its axial direction to the other end and are provided with two helical grooves. The two helical grooves extend along the drill body until they intersect at a first position of the drill body. After intersecting, the two helical grooves merge into one helical groove and extend to a second position of the drill body. The drill body includes a first region, a second region, and a third region. The first region extends from one end of the drill body with the helical cutting edge to the first position where the two helical grooves intersect. The second region extends from one end of the drill body with the helical cutting edge to the second position of the drill body. The third region extends from the first position of the drill body to the second position of the drill body. Wherein, the length of the first region is 2 to 10 times the drill diameter, the core diameter of the first region is 10% to 30% of the drill diameter, and the helix angle of the spiral groove in the first region is 25° to 45°. The length of the second region is less than or equal to 95% of the length of the drill body portion, the core diameter of the third region is 65% to 90% of the drill diameter, and the helix angle of the spiral groove in the third region is 25° to 48°.

2. A drill bit according to claim 1, characterized in that, Along the axial direction of the drill body portion, the helix angle varies continuously or segmentally from the first region to the third region; and / or, along the axial direction of the drill body portion, the core diameter increases continuously or segmentally from the first region to the third region.

3. The drill bit according to any one of claims 1 to 2, characterized in that, The first region of the drill body portion satisfies at least one of the following conditions: (a) The length of the first region is 4 to 6 times the drill diameter; (b) The core diameter of the first region is 12% to 22% of the drill diameter; (c) The helix angle of the spiral groove in the first region is 30°~45°.

4. The drill bit according to any one of claims 1 to 2, characterized in that, The second region of the drill body portion satisfies at least one of the following conditions: (a) The core diameter of the third region is 70% to 85% of the drill diameter; (b) The helix angle of the spiral groove in the third region is 30°~40°; (c) The trench width of the second region is 0.8 to 3.0 times the drill diameter.

5. The drill bit according to claim 3, characterized in that, The first region of the drill body portion satisfies at least one of the following conditions: (a) The trench width in the first region is 0.8 to 2.5 times the drill diameter; (b) The first region includes a drill tip position, wherein the drill tip angle at the drill tip position is 80° to 180°.

6. The drill bit according to claim 5, characterized in that, The drill tip angle at the drill tip position is 130°~165°.

7. The drill bit according to any one of claims 1 to 2, characterized in that, The drill bit has an ST or UC type structure.

8. The drill bit according to any one of claims 1 to 2, characterized in that, The first region includes a drill tip position, wherein a helical sub-groove is provided at the drill tip position, wherein the core diameter of the helical sub-groove is 5% to 27% of the drill diameter of the drill body portion; when the length of the sub-groove is 0.1 to 2 mm extending axially from the center point of the drill tip position along the drill body portion, the helical sub-groove extends axially from the drill tip position with a taper of 1-50 μm along the drill body portion, and the taper of the helical sub-groove is continuously varied or segmented.

9. The drill bit according to claim 8, characterized in that, The core diameter of the spiral sub-groove is 5% to 18% of the drill diameter of the drill body. When the length of the sub-groove is 0.3 to 1.6 mm extending axially from the center point of the drill tip along the drill body, the spiral sub-groove extends axially from the drill tip with a taper of 1 to 40 μm along the drill body.

10. The drill bit according to any one of claims 1 to 2, characterized in that, The surface of the drill bit is either uncoated or coated, and the coating is a diamond coating, a nitride coating, or a diamond-like coating.

11. The drill bit according to claim 10, characterized in that, When the surface of the drill bit is coated with a diamond-like carbon coating, the thickness of the coating is ≤2μm and the coefficient of friction of the coating is <0.

2.

12. The drill bit according to claim 11, characterized in that, The diamond-like carbon coating is a ta-C coating, with a thickness of 0.1 μm ≤ 0.5 μm and a coefficient of friction of < 0.

1.

13. The drill bit according to claim 10, characterized in that, The coating covers all or part of the drill body.

14. The drill bit according to any one of claims 1 to 2, characterized in that, 3mm ≤ the cutting length of the drill bit ≤ 12mm, 0.13mm ≤ the drill diameter of the drill bit ≤ 0.6mm.

15. A drill bit for drilling holes in printed circuit boards, wherein the drill bit is the drill bit according to any one of claims 1 to 14, characterized in that, The diameter of the drilled hole is ≤0.6mm, and the depth of the drilled hole is 3mm~6mm.

16. A drill bit for drilling holes in printed circuit boards, said drill bit being the drill bit of claim 12, characterized in that, The diameter of the drilled hole is ≤0.6mm, and the depth of the drilled hole is 3mm~10mm.

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