Drill bit for processing printed circuit board and processing method

Abstract

The invention discloses a drill bit for processing a printed circuit board, which comprises a drill bit main body, and the periphery of the drill bit main body is provided with a chip groove rotating from the tail end to the base end; peripheral cutting edges are arranged between the chip grooves, and chip breaker grooves are formed in the peripheral cutting edges in a segmented mode in the rotating direction; the groove depth of the chip breaker groove is in three-order self-adaptive gradient change from the groove tail end to the groove base end in the rotation line direction, and the chip breaker groove sequentially comprises a breaking section, a flow guide section and a supporting section. The depth of the chip groove is gradually increased in the rotating direction, a spiral chip removal channel with the chip volume gradually increased is formed, chips are actively guided to be smoothly discharged from the chip groove under the action of centrifugal force generated by rotation when the drill bit works, and chip retention and blockage are effectively reduced; and meanwhile, the cutting resistance and temperature are reduced through sectional chip breaking, and the chip discharging rate is improved in cooperation with a chip discharging groove.

Description

Technical Field

[0001] This invention relates to the field of drill bit technology, and in particular to a drill bit and processing method for printed circuit board processing. Background Technology

[0002] In the processing of printed circuit boards (PCBs), small or micro drills are typically used for grooving or contouring. To improve efficiency, high-speed cutting is often performed on multiple layers of overlapping PCBs. Currently, to enhance the chip removal capability and breakage resistance of these micro-rotary cutting tools, a common technique is to incorporate chip breaker grooves on the outer cutting edge. This technique involves making the depth of the groove base shallower than the depth of the groove tip, thereby suppressing increased cutting resistance while improving the rigidity of the tool body.

[0003] However, existing chip breaker depth variation patterns (such as constant gradual decrease, segmented constant followed by gradual decrease, etc.) are fixed and static geometric designs. The actual cutting process is dynamic; the shape, stress, and chip clearance requirements differ at different stages from chip formation at the cutting edge to chip breakage and removal. A single, fixed depth variation pattern cannot achieve optimal chip breaking and removal throughout the entire cutting path, leading to chip clogging or excessive fluctuations in cutting resistance when machining certain materials or under certain conditions. Summary of the Invention

[0004] This invention provides a drill bit and processing method for printed circuit board processing, in order to solve the technical problems of chip clogging or large fluctuations in cutting resistance in current drill bit processing.

[0005] To address the aforementioned technical problems, in a first aspect, the present invention provides a drill bit for processing printed circuit boards, comprising a drill bit body, wherein the outer periphery of the drill bit body is provided with chip removal grooves that rotate from the end to the base end, and the groove depth of the chip removal grooves gradually increases along the rotation direction of the drill bit body at a first gradient rate; an outer peripheral cutting edge is provided between the chip removal grooves, and the outer peripheral cutting edge is provided with chip breaking grooves in segments along the rotation direction; the groove depth of the chip breaking grooves varies with a three-order adaptive gradient from the end of the groove to the base end along the rotation line direction, and sequentially includes a breaking section, a guiding section, and a supporting section; The length of the crushing section extending from the end of the groove accounts for 20% to 35% of the total length of the chip breaking groove, and the groove depth of the crushing section remains constant. The guide section connects to the crushing section and extends to a position accounting for 75% to 85% of the total length of the chip breaking groove. The groove depth of the guide section gradually decreases in a concave curve with a second gradient rate. The support section connects to the guide section and extends to the groove base end. The groove depth of the support section rapidly decreases in a convex curve with a third gradient rate to a preset depth. The absolute value of the third gradient rate is greater than the absolute value of the second gradient rate, and the absolute value of the first gradient rate is less than the sum of the absolute values ​​of the second gradient rate and the third gradient rate.

[0006] In some embodiments, the depth change index corresponding to the first gradient rate is 1, the depth change index corresponding to the second gradient rate is 0.5 to 0.8, and the depth change index corresponding to the third gradient rate is 1.5 to 2.5.

[0007] In some embodiments, the groove depth of the crushing section is 0.08mm~0.12mm, the groove base depth of the support section is 0.04mm~0.07mm, and the groove depth difference between the crushing section and the support section is 0.03mm~0.055mm.

[0008] In some embodiments, the surface of the drill bit body is coated with a composite coating, which includes a transition layer, a thermally conductive layer and a wear-resistant layer from the inside out. The transition layer is made of Cr or TiCrN, the thermally conductive layer is made of oriented boron nitride nanotubes or graphene, and the wear-resistant layer is made of diamond-like carbon or silicon-doped diamond-like carbon.

[0009] In some embodiments, the thermally conductive layer has a columnar crystal structure, wherein the columnar crystal orientation is at an angle of 10° to 30° to the surface normal of the drill bit body, and nanoscale longitudinal gaps are provided between the columnar crystals.

[0010] In some embodiments, the bottom surface of the support section is provided with a plurality of guide ribs extending along the rotation direction of the chip breaker groove. The top contour line of the guide ribs is lower than the cutting edge line of the outer peripheral cutting edge, and the height of the guide ribs is 0.1 to 0.2 times the depth of the chip breaker groove of the support section.

[0011] In some embodiments, the guide ribs are non-uniformly distributed on the bottom surface of the support section, and the distribution density of the guide ribs near the guide section is higher than that near the bottom of the tank.

[0012] Secondly, the present invention also provides a method for processing microgrooves in printed circuit boards, using the aforementioned drill bit for processing printed circuit boards, the method comprising: The drill bit for printed circuit board processing is mounted on the processing spindle in a rotational direction synchronized with the spindle speed. The machining spindle is controlled to rotate, and the drill bit for machining printed circuit boards is driven to process the printed circuit board in a cycle at the first feed speed, the second feed speed and the third feed speed.

[0013] In some embodiments, the drill bit for printed circuit board processing performs an axial micro-retraction action every 10 to 30 rotations, with a retraction amount of 0.5 μm to 2 μm.

[0014] In some of these embodiments, when performing small radius of curvature corner machining, the printed circuit board machining drill is controlled to perform an axial micro-feed action at the corner apex, with a feed amount of 0.5μm~2μm.

[0015] Thirdly, the present invention also provides a printed circuit board processing apparatus, including a processor and a memory, wherein the memory is used to store a computer program, and the computer program, when executed by the processor, implements the above-described microgroove processing method for printed circuit boards.

[0016] Compared with the prior art, the present invention has the following beneficial effects: By gradually increasing the depth of the chip removal groove along the direction of rotation, a spiral chip removal channel with gradually increasing chip volume is formed. Under the centrifugal force generated by the rotation of the drill bit during operation, the chips are actively guided to be discharged smoothly from the chip removal groove, effectively reducing chip retention and blockage. At the same time, segmented chip breaking reduces cutting resistance and temperature, and works with the chip removal groove to improve the chip removal rate. Setting various gradient rates can meet the requirements of both increasing chip capacity and chip removal rate, while ensuring drill bit rigidity, thereby reducing chip blockage and improving cutting stability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a drill bit for printing circuit board processing, as shown in an embodiment of the present invention; Figure 2 This is a schematic diagram of the composite coating stack structure shown in an embodiment of the present invention; Figure 3 This is a schematic flowchart illustrating a method for fabricating microgrooves on a printed circuit board according to an embodiment of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] See Figure 1 This invention illustrates a schematic diagram of a drill bit for printed circuit board (PCB) processing. The drill bit of this embodiment includes a drill body. The outer periphery of the drill body has chip removal grooves that rotate from one end to the other, with the groove depth increasing gradually along the rotation direction of the drill body at a first gradient rate. An outer peripheral cutting edge is provided between the chip removal grooves, and the outer peripheral cutting edge is segmented with chip breaking grooves along the rotation direction. The groove depth of the chip breaking grooves varies with a three-order adaptive gradient from the end to the base along the rotation direction, sequentially including a breaking section, a guiding section, and a supporting section. The length of the crushing section extending from the end of the groove accounts for 20% to 35% of the total length of the chip breaking groove, and the groove depth of the crushing section remains constant. The guide section connects to the crushing section and extends to a position accounting for 75% to 85% of the total length of the chip breaking groove. The groove depth of the guide section gradually decreases in a concave curve with a second gradient rate. The support section connects to the guide section and extends to the groove base end. The groove depth of the support section rapidly decreases in a convex curve with a third gradient rate to a preset depth. The absolute value of the third gradient rate is greater than the absolute value of the second gradient rate, and the absolute value of the first gradient rate is less than the sum of the absolute values ​​of the second gradient rate and the third gradient rate.

[0020] In this embodiment, when the drill bit tip comes into contact with the workpiece surface to begin machining, the outer peripheral cutting edge of the drill bit tip begins to cut the workpiece. The resulting chips enter the breaking section of the chip breaker groove, and under the rotation of the drill bit, the chips move along the rotation direction of the chip removal groove, forcing the continuous long chips to undergo effective transverse fracture at this point and be divided into smaller fragments. Since the chip removal groove is lower than the chip breaker groove, some fragments fall into the chip removal groove when the drill bit rotates and are smoothly discharged from the chip removal groove under the action of centrifugal force, effectively reducing chip retention. The remaining fragments continue to move towards the guide section along the rotation direction of the chip breaker groove, and gradually fall into the chip removal groove and are discharged after passing through it, improving the degree of chip breaking and chip removal efficiency.

[0021] The chip breaking section initially maintains a constant depth to provide ample space for initial chip breaking, reducing early wear at the drill bit tip. The guide section gradually decreases its depth with a gentle concave curve to maintain stable chip flow. Since chip breaking is largely complete in the guide section, the support section rapidly shallows its depth with a steeper convex curve, increasing the rigidity of the drill bit base. Simultaneously, the chip removal groove is lower than the chip breaking groove, and its depth variation is less than that of the overall chip breaking groove. This minimizes the material retention difference between the drill bit base and tip, preventing a head-heavy appearance that could cause the drill bit tip to wobble during operation, thus ensuring the overall rigidity and machining accuracy of the drill bit.

[0022] In some embodiments, the depth change index corresponding to the first gradient rate is 1, the depth change index corresponding to the second gradient rate is 0.5~0.8, and the depth change index corresponding to the third gradient rate is 1.5~2.5.

[0023] In this embodiment, the first gradient rate corresponds to an index of 1, causing the chip removal groove depth to increase linearly and uniformly, forming a stable and expanding main chip removal channel. The second gradient rate corresponds to an index of 0.5~0.8, causing the chip breaking groove guide section to have a concave curve, with a rapid decrease in depth in the early stage, providing smooth acceleration guidance for the chips. The third gradient rate corresponds to an index of 1.5~2.5, causing the support section to have a convex curve, with a sharp decrease in depth in the later stage, rapidly strengthening the rigidity of the drill body. This embodiment achieves smooth chip removal, stable transition, and rigid support, significantly improving chip removal efficiency, drilling accuracy, and drill bit breakage resistance.

[0024] In some embodiments, the groove depth of the crushing section is 0.08mm~0.12mm, the groove base depth of the support section is 0.04mm~0.07mm, and the groove depth difference between the crushing section and the support section is 0.03mm~0.055mm.

[0025] In this embodiment, the depth of the crushing section groove is set to 0.08mm~0.12mm to provide sufficient chip-bearing space for initial chip crushing and ensure effective chip breaking. The depth of the support section groove base is controlled to 0.04mm~0.07mm to retain the maximum amount of drill material to construct a high-rigidity zone. The depth difference between the two is limited to 0.03mm~0.055mm to ensure that the depth change from crushing to support is sufficient to achieve functional zoning without being excessively drastic to avoid stress concentration. This embodiment enables the drill bit to simultaneously possess excellent chip-bearing and chip-breaking capabilities and bending strength, effectively resolving the contradiction between chip removal and rigidity in micro-drill bits, and significantly improving machining stability and tool life.

[0026] In some embodiments, such as Figure 2 As shown, the surface of the drill bit body is coated with a composite coating, which includes a transition layer, a thermally conductive layer and a wear-resistant layer from the inside out. The material of the transition layer is Cr or TiCrN, the material of the thermally conductive layer is oriented boron nitride nanotubes or graphene, and the material of the wear-resistant layer is diamond-like carbon or silicon-doped diamond-like carbon.

[0027] In this embodiment, Cr or TiCrN exhibits good chemical affinity and similar coefficients of thermal expansion with the cemented carbide matrix. Using Cr or TiCrN as an inner buffer transition layer ensures extremely high bonding strength between the coating and the drill bit substrate, preventing peeling. Furthermore, Cr or TiCrN possesses a certain degree of toughness, capable of absorbing and buffering interfacial stresses generated during cutting impacts and thermal cycling. Boron nitride nanotubes or graphene exhibit extremely high thermal conductivity in specific directions. Oriented alignment of these nanomaterials along the drill bit axis creates an axial heat transfer path, rapidly dissipating heat concentrated in the cutting zone longitudinally to the entire drill bit and tool holder, thereby significantly reducing cutting temperature and suppressing thermal softening of the tool material and thermal deterioration of the workpiece. Diamond-like carbon (DLC) possesses near-diamond hardness and self-lubricating properties, reducing cutting friction and adhesion tendency. Silicon doping further enhances the coating's thermal stability and adhesion to the intermediate layer.

[0028] In some embodiments, the thermally conductive layer has a columnar crystal structure, wherein the columnar crystal orientation is at an angle of 10° to 30° to the surface normal of the drill bit body, and nanoscale longitudinal gaps are provided between the columnar crystals.

[0029] In this embodiment, the thermally conductive layer adopts a columnar crystal structure, with its grain orientation at a 10°~30° directional angle to the surface normal, rather than being completely perpendicular. This makes the growth direction of the columnar crystals more consistent with the main heat transfer path from the cutting edge to the tool holder in the drill bit body, significantly reducing the scattering of heat carrier at the grain boundaries. This forms an efficient, low-resistance heat conduction channel along the axial direction, rapidly dissipating the heat accumulated in the cutting area longitudinally. At the same time, the pre-set nanoscale longitudinal gaps between the columnar crystals act as microscopic stress buffer areas, effectively absorbing and releasing stress caused by differences in thermal expansion or mechanical impact, preventing the coating from cracking or peeling due to internal stress concentration.

[0030] In some embodiments, the bottom surface of the support section is provided with a plurality of guide ribs extending along the rotation direction of the chip breaker groove. The top contour line of the guide ribs is lower than the cutting edge line of the outer peripheral cutting edge, and the height of the guide ribs is 0.1 to 0.2 times the depth of the chip breaker groove of the support section.

[0031] In this embodiment, wave-shaped, sawtooth-shaped, or rectangular guide ribs are arranged along the rotation direction at the bottom of the support section groove. These microscopic protrusions reconstruct the contact interface between the chip and the groove bottom, transforming the original large-area planar friction into multi-point, linear guiding contact, significantly reducing frictional resistance and chip adhesion tendency. Furthermore, their specific cross-sectional shape can generate controllable micro-vortices and lifting effects when the chips flow through, pushing the chips to maintain a flow tendency towards the outside of the groove, effectively preventing them from lingering in the shallower support section. The top of the guide rib is always lower than the cutting edge line, ensuring that it only interferes with chip removal and not with cutting; its height is strictly controlled to be 0.1 to 0.2 times the groove depth, exchanging the maximum flow channel guiding effect for the minimum material removal cost, thus hardly affecting the core rigidity of this section.

[0032] In some embodiments, the guide ribs are non-uniformly distributed on the bottom surface of the support section, and the distribution density of the guide ribs near the guide section is higher than that near the bottom of the tank.

[0033] In this embodiment, the guide ribs adopt a non-uniform layout with denser ribs at the front and sparser ribs at the back. In the area near the guide section, where the chips have just transitioned from the smooth guide channel, the flow velocity is relatively high, but the flow direction still needs to be stabilized. A higher density of guide ribs can form a denser guide grid, strengthening the constraint and guidance of the chips and ensuring their smooth entry into the support section. As the chips move towards the base, the flow momentum decreases, and the chip removal space shrinks due to the sharp decrease in groove depth. At this point, reducing the density of guide ribs maintains the basic guide function while minimizing the weakening of the limited matrix material, ensuring the structural integrity of this critical area.

[0034] See Figure 3 This invention illustrates a flowchart of a method for fabricating microgrooves on a printed circuit board. The method utilizes the aforementioned drill bit for printed circuit board fabrication and specifically includes steps S101 to S102, detailed below: Step S101: Install the drill bit for printed circuit board processing onto the processing spindle in a rotational direction synchronized with the spindle speed; Step S102: Control the machining spindle to rotate, and sequentially drive the drill bit for printing circuit board processing to process the printed circuit board at the first feed speed, the second feed speed and the third feed speed.

[0035] In this embodiment, during the drill bit's rotary cutting process, the spindle feed rate is controlled to sequentially switch and cycle between three set values. This speed variation corresponds to the functional cycles of the chip-breaking section, guide section, and support section of the chip-breaking groove on the drill bit. For example, when the drill bit tip (the dominant functional area of ​​the chip-breaking section) contacts the material, a relatively low first feed rate is used to provide sufficient time and stable conditions for the initial generation of chips and effective chip breaking within the constant depth groove, ensuring chip breaking quality. Subsequently, in the middle of the drill bit (the dominant functional area of ​​the guide section), a higher second feed rate is switched to utilize the smooth, gradually decreasing concave groove shape of this section to accelerate chip transport and discharge, improving material removal rate. When the base of the drill bit (the dominant functional area of ​​the support section) participates in cutting, a relatively low third feed rate is used to match the characteristics of this section: rapidly decreasing groove depth, extremely high rigidity, but minimal chip space. This ensures machining accuracy while fully leveraging its high rigidity advantage to resist greater cutting forces and protect the drill bit.

[0036] In some embodiments, the drill bit for printed circuit board processing performs an axial micro-retraction action once every 10 to 30 rotations, with a retraction amount of 0.5 μm to 2 μm.

[0037] In this embodiment, a micro-retraction operation is used to instantly release the pressure between the cutting edge and the material at the bottom of the hole, allowing the accumulated fine chips in front of the cutting edge to loosen and detach. This embodiment effectively breaks the continuous adhesion tendency of chips through periodic micro-disturbance, significantly reducing the frictional heat and peak cutting force in the cutting zone, and avoiding a surge in instantaneous high temperature and load due to poor chip removal, thereby significantly extending the service life of the micro-drill bit when machining high-viscosity copper-clad laminate materials. Optionally, a cooling medium is added during cutting so that the cooling medium can penetrate into the cutting front edge through the tiny gap created by the retraction, achieving instantaneous cooling and lubrication.

[0038] In some embodiments, when performing small radius of curvature corner processing, the printed circuit board processing drill bit is controlled to perform an axial micro-feed action at the corner apex, with a feed amount of 0.5μm~2μm.

[0039] In this embodiment, the micro-feed operation can offset the "tool deflection" displacement caused by the elastic deformation of the tool, so that the actual position of the cutting edge coincides with the theoretical machining trajectory, thereby achieving active precision compensation for the corner size with small curvature radius; at the same time, it avoids secondary cutting and vibration caused by tool deflection, improves the hole wall quality and the stability of the machining process, and extends the service life of the tool in precision contour machining.

[0040] The following tests were conducted on several drill bit structures: The drill bit of this invention has the following characteristics: the first gradient rate corresponds to an index of 1, the second gradient rate corresponds to an index of 0.65, and the third gradient rate corresponds to an index of 2; the length of the breaking section accounts for 30%, the length of the guiding section accounts for 50%, and the length of the support section accounts for 20%; the depth of the breaking section is 0.1 mm, and the depth of the support section near the base is 0.05 mm; the height of the guiding ribs is 15% of the groove depth, and they are densely distributed at the front and sparsely distributed at the back. Machining method: A three-stage cyclic feed rate (V1=1.2 m / min, V2=1.8 m / min, V3=1 m / min) is adopted, with a 0.8 μm micro-retraction every 20 revolutions and a 1 μm micro-feed compensation at corners; Test conditions: Machining 8 layers of 1.6 mm thick FR-4 sheet, spindle speed 120,000 rpm, total machining length 20 m; Test results: No chip clogging occurred during the machining process, and the chips were discharged smoothly in small fragments. The cutting force fluctuation was <10%, the hole wall roughness Ra was <1.6μm, and the flank wear VB was <0.04mm after machining for 20m.

[0041] Drill bit two of the present invention: the second gradient rate corresponds to an index of 0.8, the third gradient rate corresponds to an index of 2.5, the breaking section depth is 0.12mm, and the support section depth near the base is 0.045mm; it adopts a three-stage cyclic feed speed, without periodic micro-retraction and corner compensation, and is otherwise the same as drill bit one of the present invention. Test results: There was basically no chip retention during the machining process, the cutting force fluctuation range was 10%~15%, the hole wall roughness Ra<2μm, and the back face wear VB≈0.055mm after machining 20m.

[0042] Compared with drill bit one: the chip breaking groove depth is constant at 0.08mm, the chip removal groove depth is constant, and other aspects are the same as drill bit one of the present invention; Test results: slight stagnation during machining, cutting force fluctuation >30%, hole wall roughness Ra >3.2μm, and flank wear VB >0.1mm after machining 20m (early chipping).

[0043] Comparison drill bit two: The conventional TiAlN wear-resistant coating replaces the composite coating, otherwise it is the same as drill bit one of the present invention; Test results: There was basically no chip clogging during the machining process, but the chips adhered slightly. The cutting force fluctuated by 10%~20%. The hole wall roughness Ra<2μm. After machining 20m, the back face wear VB≈0.08mm.

[0044] Compared to drill bit three: the guide ribs are sparse in the front and dense in the back, otherwise the same as drill bit one of this invention; Test results: During the machining process, chips occasionally remained in the support section, the cutting force fluctuated by 15%~25%, the hole wall roughness Ra≈3.2μm, and the flank wear VB≈0.075mm after machining for 20m.

[0045] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A drill bit for processing a printed wiring board, characterized by, The drill bit comprises a drill bit body, an outer periphery of the drill bit body is provided with a chip flute rotating from a tip end to a base end, a flute depth of the chip flute gradually increases at a first gradient along a rotation direction of the drill bit body; an outer peripheral cutting edge is provided between the chip flutes, the outer peripheral cutting edge is segmented to provide a chip breaking groove along the rotation direction; a groove depth of the chip breaking groove changes at a three-stage adaptive gradient from a groove tip end to a groove base end along the rotation direction, and sequentially comprises a crushing section, a flow guiding section and a supporting section; an extension length of the crushing section from the groove tip end is 20% to 35% of a total length of the chip breaking groove, and the groove depth of the crushing section remains constant; the flow guiding section is connected to the crushing section and extends to a position of 75% to 85% of the total length of the chip breaking groove, the groove depth of the flow guiding section gradually decreases at a second gradient in a concave curve; the supporting section is connected to the flow guiding section and extends to the groove base end, the groove depth of the supporting section rapidly decreases at a third gradient in a convex curve to a preset depth; an absolute value of the third gradient is greater than an absolute value of the second gradient, and an absolute value of the first gradient is less than a sum of absolute values of the second gradient and the third gradient.

2. The drill bit for processing a printed wiring board according to claim 1, wherein a depth change index corresponding to the first gradient is 1, a depth change index corresponding to the second gradient is 0.5 to 0.8, and a depth change index corresponding to the third gradient is 1.5 to 2.

5.

3. The drill bit for processing a printed wiring board as claimed in claim 1, wherein a surface of the drill bit body is coated with a composite coating, the composite coating comprises a transition layer, a heat conducting layer and a wear resistant layer from inside to outside, a material of the transition layer is Cr or TiCrN, a material of the heat conducting layer is a nitrogen boride nanotube or graphene arranged in a direction, and a material of the wear resistant layer is diamond-like or silicon-doped diamond-like.

4. The drill bit for processing a printed wiring board according to claim 3, wherein the heat conducting layer is a columnar crystal structure, a columnar crystal orientation of the columnar crystal structure has an angle of 10° to 30° with a surface normal of the drill bit body, and a longitudinal gap of a nanometer scale is provided between the columnar crystals.

5. The drill bit for processing a printed wiring board as claimed in claim 1, wherein a groove bottom surface of the supporting section is provided with a plurality of flow guiding ribs extending along the rotation direction of the chip breaking groove, a top profile line of the flow guiding rib is lower than a blade line of the outer peripheral cutting edge, and a height of the flow guiding rib is 0.1 to 0.2 times of the chip breaking groove depth of the supporting section.

6. The drill bit for processing a printed wiring board as claimed in claim 5, wherein the flow guiding ribs are unevenly distributed on the groove bottom surface of the supporting section, and a distribution density of the flow guiding ribs close to the flow guiding section is higher than a distribution density of the flow guiding ribs close to the groove base end.

7. A method for processing fine grooves of a printed wiring board, characterized by, a method for processing a printed circuit board using the drill bit according to any one of claims 1 to 6, the method comprising: installing the drill bit for processing a printed circuit board in a rotating direction synchronous with a rotation speed of a main shaft; controlling the main shaft to rotate and driving the drill bit for processing a printed circuit board to process the printed circuit board at a first feed speed, a second feed speed and a third feed speed in a cycle.

8. The fine groove processing method of a printed wiring board according to Claim 7, wherein the drill bit for processing a printed circuit board performs an axial micro-retreating action once every 10 to 30 rotations, and a retreating amount is 0.5 to 2 microns.

9. The fine groove processing method of a printed wiring board according to Claim 7, wherein when performing a small radius corner processing, the drill bit for processing a printed circuit board performs an axial micro-feeding action once at a corner vertex, and a feeding amount is 0.5 to 2 microns.

10. A printed wiring board processing apparatus characterized by comprising: A printed wiring board micro slot processing method as claimed in any one of claims 7 to 9, comprising a processor and a memory for storing a computer program which, when executed by the processor, implements the printed wiring board micro slot processing method.

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