CN112238243A

CN112238243A - Back drill bit

Info

Publication number: CN112238243A
Application number: CN202010966039.4A
Authority: CN
Inventors: 杨令; 张辉; 卢成; 何先友
Original assignee: Shenzhen Jinzhou Precision Technology Corp
Current assignee: Shenzhen Jinzhou Precision Technology Corp
Priority date: 2020-09-15
Filing date: 2020-09-15
Publication date: 2021-01-19

Abstract

The invention is suitable for deep hole back drilling technology, and discloses a back drilling drill point, which comprises a drill handle and a working part, wherein the rear end of the working part is connected with the drill handle, the peripheral surface of the working part is provided with two main chip removal grooves which are symmetrical relative to the center of the working part, the two main chip removal grooves spirally extend from the front end to the rear end of the working part and are intersected at one point, the two main chip removal grooves are respectively intersected with the end surface of the front end of the working part to obtain two cutting edges, the included angle between the rear cutter surfaces of the two cutting edges is 115-125 degrees, the intersection line of the rear cutter surfaces of the two cutting edges is connected with the inner ends of the two cutting edges to form a cross edge, the length of the cross edge is 0.02-0.18mm, and the peripheral surface of the working part is also provided with at least two auxiliary. The back drilling drill point provided by the invention can solve the problems of poor hole shape and deviated holes in back drilling deep hole processing of a multilayer circuit board and meet the use requirements of customers.

Description

Back drill bit

Technical Field

The invention belongs to the technical field of deep hole back drilling, and particularly relates to a back drilling drill point.

Background

The back drilling process is to drill NPTH holes with certain depth requirement on some PTH holes by using a drill with a larger diameter by using the depth control function of a mechanical drilling machine so as to remove through hole sections which do not play any connection or transmission role, avoid causing reflection, scattering, delay and the like of signal transmission and bring distortion to signal transmission. With the development of communication PCBs, the back drilling machining depth is deeper and deeper, and back drilling holes with the depth exceeding 3 mm are common, so that the back drilling difficulty is higher and higher. The problem of the hole shape is bad can appear in current back drilling drill point when carrying out the degree of depth processing, and the S hole shape that also we often say, because the hole shape is bad too big (the height point difference exceeds 20um), the tangent risk of back drilling exists in the back drilling inner circuit that is close to mutually, brings very big hidden danger for PCB model transmission, also can bring the quality problems such as inclined to one side hole simultaneously, and high-end PCB manufacturing enterprise also attaches attention to this type of quality problem. There is a strong need for a back-drilling drill point to solve this problem.

Disclosure of Invention

The invention aims to solve at least one of the technical problems and provides a back drilling drill point, which can solve the problems of poor hole shape and deviated holes in back drilling deep hole processing of a multilayer circuit board and meet the use requirements of customers.

The technical scheme of the invention is as follows: the utility model provides a back drill point, includes drillstock and working portion, the rear end of working portion with the drillstock is connected, the outer peripheral face of working portion is provided with two about the chip removal owner groove of working portion center symmetry, two the chip removal owner groove is followed with the heliciform the working portion front end extends towards the rear end and crosses in a point, two the chip removal owner groove respectively with the front end terminal surface of working portion intersects and obtains two cutting edges, two contained angle is 115-125 between the back knife face of cutting edge, two the intersection line of cutting edge back knife face connects two the inner of cutting edge forms the chisel edge, the length of chisel edge is 0.02-0.18mm, the outer peripheral face of working portion still be provided with two at least from the intersection point to the chip removal auxiliary tank that the working portion rear end spirally extended side by side.

Optionally, the depth of the chip discharge auxiliary groove gradually decreases from the intersection point to the rear end of the working part.

Optionally, the helix angle of the primary flutes is 40 °.

Optionally, the distance from the front end of the working portion to the junction is 0.4-1.6 mm.

Optionally, the distance from the front end of the working portion to the junction is 0.8-1.2 mm.

Optionally, the helix angle of the chip ejection sub-groove is 40-60 °.

The back drilling drill needle provided by the invention optimizes the size of the top angle and the length of the cross edge, compared with the existing back drilling drill needle, the length of the cross edge and the top angle are reduced, the drilling stability of the drill needle is improved through the fusion design of the cross edge and the top angle, the length of the cross edge is shortened, the width of the edge surface is increased, the wear resistance of the drill tip is improved, meanwhile, two chip removal main grooves are converged at one point, and at least two parallel chip removal auxiliary grooves are arranged behind the convergence point.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a back drill bit according to an embodiment of the present invention;

FIG. 2 is a right side view of FIG. 1;

fig. 3 is a schematic structural view of a conventional backdrilling drill bit.

In the figure, 1-drill handle, 2-working part, 3-chip removal main groove, 4-intersection point, 5-cutting edge, 6-horizontal edge, 7-chip removal auxiliary groove, D-edge surface width, L-horizontal edge length, alpha-vertex angle, beta-chip removal auxiliary groove helix angle, gamma-chip removal main groove helix angle, 3 ' -chip removal groove of the existing back drill needle, alpha ' -vertex angle of the existing back drill needle and gamma ' -helix angle of the chip removal groove of the existing back drill needle.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

It should be noted that the terms "disposed" and "connected" should be interpreted broadly, and may be, for example, directly disposed or connected, or indirectly disposed or connected through intervening elements or intervening structures.

In addition, in the embodiments of the present invention, if there are terms of orientation or positional relationship indicated by "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., it is only for convenience of describing the present invention and simplifying the description, but not for indicating or implying that the structure, feature, device or element referred to must have a specific orientation or positional relationship, nor must be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

The various features and embodiments described in the embodiments may be combined in any suitable manner, for example, different embodiments may be formed by combining different features/embodiments, and in order to avoid unnecessary repetition, various possible combinations of features/embodiments in the present invention will not be described in detail.

As shown in fig. 1 and 2, the back drilling drill point provided by the embodiment of the invention is used for back drilling with the aperture of 0.15-0.6mm, and particularly in the field of back drilling of deep holes, can reduce the hole shape fraction defective (the probability of occurrence of S-hole shape) of back drilling and improve the hole position precision. The drill bit comprises a drill handle 1 and a working part 2, wherein the drill handle 1 is used for holding the drill bit on the main shaft of the machine tool, relative to the working part 2, the drill handle 1 is connected to the rear end of the working part 2, the outer peripheral surface of the working part 2 is provided with two main chip removal grooves 3 which are symmetrical relative to the center of the working part 2, the two main chip removal grooves 3 extend from the front end to the rear end of the working part 2 in a spiral shape and are converged at one point, the two main chip removal grooves 3 are respectively intersected with the front end surface of the working part 2 to obtain two cutting edges 5, the two cutting edges 5 are main cutting parts of the drill bit, the included angle between the rear cutter surfaces of the two cutting edges 5 is 115-125 degrees, namely the vertex angle alpha of the drill bit is 115-125 degrees, the intersection line of the rear cutter surfaces of the two cutting edges 5 is connected with the inner ends of the two cutting edges 5 to, the length L of the chisel edge 6 is 0.02-0.18mm, and the peripheral surface of the working part 2 is also provided with at least two chip removal auxiliary grooves 7 which spirally extend from the intersection point 4 to the rear end of the working part 2 side by side. Compared with the existing back drilling drill point, the back drilling drill point has the advantages that the vertex angle is reduced, the chisel edge is shortened, the sharpness of the drill point is enhanced and the drilling stability of the drill point is improved by combining the size of the vertex angle and the length of the chisel edge, the length of the chisel edge is shortened, the width D of the cutting surface can be increased, and the wear resistance of the drill point is improved. Meanwhile, the two main chip removal grooves are converged at one point, at least two side-by-side chip removal auxiliary grooves are arranged behind the convergence point, and chips generated by the cutting edge 5 during cutting are converged at the convergence point 4 and are discharged by the chip removal auxiliary grooves 7. Design like this, guarantee the chip removal ability of boring point department on the one hand, prevent that the smear metal from blockking up at the point of boring, on the other hand can ensure the rigidity intensity of working part behind the meeting point, avoids the drilling course of working, avoids drill point department to appear shake or incline effectively, solves the current drill bit and carries out the bad problem of S hole shape that deep hole back drilling processing appears, satisfies the preparation of high accuracy requirement PCB board for the signal can be quick in PCB, high efficiency, accurate transmission.

Optionally, the depth of the chip removal auxiliary groove 7 is gradually reduced from the intersection point 4 to the rear end of the working part 2, that is, the core thickness of the working part 2 is larger as the drill shank 1 is closer, the core diameter of the working part behind the intersection point is in a forward-cone structure, and the rigidity strength of the working part is further improved.

Specifically, the number of the chip removal auxiliary grooves 7 can be determined according to the actual cutting speed, for example, two, three, four, etc., and only the front end of each chip removal auxiliary groove 7 needs to be connected to the junction 4, so that the chips can be quickly discharged, and the chips are prevented from blocking the back drilling hole in the high-speed cutting process.

Optionally, the helix angle γ of the two chip removal main grooves 3 is 40 °, and the dimensional tolerance is ± 3 °.

Alternatively, the distance from the front end of the working part 2 to the junction 4 may be 0.4-1.6mm, if the distance from the front end of the working part 2 to the junction 4 is less than 0.4mm, the chips may be easily accumulated in the chip removal main groove, which is not favorable for chip removal, and if the distance from the front end of the working part 2 to the junction 4 is greater than 1.6mm, the rigidity strength of the working part may be affected, which may easily cause the drill tip to shake or deflect.

Specifically, the distance from the front end of the working part 2 to the junction 4 may be 0.8-1.2 mm.

Optionally, the helix angle beta of the chip removal auxiliary groove 7 can be 40-60 degrees, and under the condition of ensuring the rigidity of the drill body, the helix angle beta of the chip removal auxiliary groove 7 is optimized, so that chips can be favorably discharged from the hole.

In particular, the helix angle of the debris ejection sub-grooves may be 45 °.

According to the back drilling drill point provided by the embodiment of the invention, on one hand, the size of the vertex angle alpha and the length L of the chisel edge are optimized, compared with the existing back drilling drill point, the length L of the chisel edge is shortened, the vertex angle alpha is reduced, the stability of the drilling drill point is correspondingly improved through the fusion design of the length L of the chisel edge and the vertex angle alpha, the width D of the cutting surface is increased due to the shortened length L of the chisel edge, and the wear resistance of the drill point is improved; on the other hand, make two chip removal owner grooves 3 meet in a point, and be provided with two at least chip removal auxiliary flutes 7 side by side behind the meeting point 4, and the degree of depth of chip removal auxiliary flute 7 diminishes gradually towards the direction of 2 rear ends of work portion 4 at the meeting point, make the core footpath of work portion 2 be in the same direction as the awl structure, the super high chip removal ability of drill point had both been guaranteed, prevent that the smear metal from blockking up at the drill point portion, can ensure the rigidity intensity of work portion 2 behind meeting point 4 again, avoid the drilling course of working, avoid the work portion shake or incline to appear effectively, solve the current drill bit and carry out the bad problem of S hole shape that deep hole back drilling processing appears.

In order to better embody the effects of the present invention, the following description is made with reference to specific examples:

example 1

Control group: in the conventional drill point, the vertex angle alpha ' is 130 degrees, the length of a cross edge is 0.2mm, and the helical angle gamma ' of a chip groove 3 ' is 25 degrees; (two flutes extending helically, without meeting point)

Experimental group 1: the drill point has the advantages that the vertex angle alpha is 115 degrees, the length of the cross edge 6 is 0.15mm, the helix angle gamma of the chip removal main groove 3 is 40 degrees, the distance from the intersection point 4 to the front end of the working part 2 is 0.5mm, the number of the chip removal auxiliary grooves 7 is two, and the helix angle beta is 40 degrees;

experimental group 2: the drill point has the advantages that the vertex angle alpha is 120 degrees, the length of the cross edge 6 is 0.1mm, the helix angle gamma of the chip removal main groove 3 is 40 degrees, the distance from the intersection point 4 to the front end of the working part 2 is 0.65mm, the number of the chip removal auxiliary grooves 7 is two, and the helix angle beta is 40 degrees;

experimental group 3: the drill point has a vertex angle alpha of 125 degrees, a cross edge 6 with the length of 0.08mm, a helix angle gamma of a chip removal main groove 3 of 40 degrees, a distance between a junction point 4 and the front end of a working part 2 of 0.8mm, two chip removal auxiliary grooves 7 and a helix angle beta of 40 degrees;

the experimental conditions were the same: machine tool equipment: SCHMOOL (depth control function), back-drilling drill point working diameter is 0.04mm, spindle speed: 85KRPM, feed amount: 1.8m/min, tool retracting speed: 20m/min, back drilling times: 400 holes, processing materials: high-speed material multiply wood, the thick 3.8mm of board, back drilling depth of processing: shallow hole 0.20mm, deep hole 2.4 mm.

Shallow hole processing, the back drilling depth is 0.20mm, and the specific conditions are as follows in table 1:

TABLE 1

From the data in table 1, when the back drilling processing of shallow holes is performed, the back drilling needles corresponding to the control group, the experimental group 1, the experimental group 2 and the experimental group 3 have low probability of having poor hole shape, hole blockage and hole deviation, and the difference between the hole shape poor rate, the hole blockage rate and the hole deviation rate is relative.

Wherein, the hole shape defective rate refers to: in the cross section of the back drilling hole obtained by processing, two boundaries of the back drilling hole are in an S-shaped curve structure relative to the central axis of the back drilling hole, and the S hole value refers to the difference value between the highest peak and the lowest valley in the S-shaped curve, and in the field, the back drilling hole with the S hole value of less than 12 microns can meet the requirement.

By offset is meant that the axes of the backdrilled hole and the via hole do not coincide.

Deep hole processing, the back drilling depth is 2.4mm, and the specific conditions are as follows in table 2:

TABLE 2

From the data in table 2, when deep hole back drilling is performed, the back drilling drill points in the control group are processed, the S-hole value of the back drilling holes obtained by processing does not meet the requirement, and the back drilling drill points corresponding to the experimental group 1, the experimental group 2 and the experimental group 3 have poor hole shapes, and have lower probability of hole plugging and hole deviation than the back drilling drill points in the control group, that is, the back drilling drill points corresponding to the experimental group 1, the experimental group 2 and the experimental group 3 are superior to the back drilling drill points in the control group. Therefore, the back drilling drill points corresponding to the experimental group 1, the experimental group 2 and the experimental group 3 can be used for back drilling processing of shallow holes and deep holes.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents or improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. The utility model provides a back drill point, includes drillstock and work portion, the rear end of work portion with the drillstock is connected, its characterized in that, the outer peripheral face of work portion is provided with two about the symmetrical chip removal owner's groove in work portion center, two the chip removal owner's groove is followed with the heliciform the work portion front end is extended towards the rear end and is intersected in a point, two the chip removal owner's groove respectively with the front end terminal surface of work portion intersects and obtains two cutting edges, two the contained angle is 115-125 between the back knife face of cutting edge, two the intersection line of cutting edge back knife face is connected two the inner of cutting edge forms the chisel edge, the length of chisel edge is 0.02-0.18mm, the outer peripheral face of work portion still be provided with two at least from the intersection to the vice groove of chip removal that the spiral extends side by side in work portion rear end.

2. A back drill bit according to claim 1, wherein the depth of the chip ejection sub-groove gradually decreases from the intersection towards the rear end of the working portion.

3. A back drill bit as claimed in claim 1, wherein said primary flutes for chip removal have a helix angle of 40 °.

4. A back drill bit according to claim 1, wherein the distance from the front end of the working portion to the junction is 0.4-1.6 mm.

5. A back drill according to claim 4, wherein the distance from the front end of the working portion to the junction is 0.8-1.2 mm.

6. A back drill bit as claimed in claim 1, wherein the helix angle of the chip evacuation sub-flutes is between 40 ° and 60 °.