CN112140229A

CN112140229A - Back drilling tool and preparation method thereof

Info

Publication number: CN112140229A
Application number: CN202011045343.1A
Authority: CN
Inventors: 郑鑫; 陈汉泉
Original assignee: Guangdong Dingtai Hi Tech Co Ltd
Current assignee: Guangdong Dingtai Hi Tech Co Ltd
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2020-12-29
Anticipated expiration: 2040-09-28
Also published as: TWI765827B; CN112140229B; WO2022062041A1; TW202212084A; JP2023539950A

Abstract

The invention relates to the technical field of circuit board processing, in particular to a back drilling cutter and a preparation method thereof. The invention provides a back drilling cutter, which comprises a cutter handle and a cutting edge, wherein the cutting edge comprises a cutter body, a boss and a cutter point which are sequentially connected, and the cutter body is connected with the cutter handle; the maximum diameter of the tool nose and the diameter of the tool body are both smaller than the diameter of the boss; the outer surfaces of the tool tip and the tool body are not conductive, and the outer surface of the lug boss is conductive. When the processing is carried out, the boss and the inner layer of the workpiece form an electric path to play a role in signal transmission, so that the depth of the hole can be accurately controlled. By innovating the structural design of the cutter, the dependence of the hole depth precision on the thickness of a workpiece and the flow control is eliminated, and the processing efficiency and the processing precision are greatly improved. The back drilling cutter preparation method provided by the invention is used for processing the back drilling cutter, so that the back drilling cutter can accurately control the hole depth during back drilling processing, the dependence of the hole depth precision on the thickness of a workpiece and flow control is eliminated, and the processing efficiency and the processing precision are greatly improved.

Description

Back drilling tool and preparation method thereof

Technical Field

The invention relates to the technical field of circuit board processing, in particular to a back drilling cutter and a preparation method thereof.

Background

The Plated-through-hole (PTH) in a multi-layer Printed Circuit Board (PCB) has the function of interconnecting an inner power layer and a ground layer, when a system enters high-speed signal transmission, the PTH becomes a bottleneck and obstacle of signal integrity, just like more than one tail (Stubs) in a transmission line, and plays the function of a notch-type filter, and when the Stubs appear at two positions in the signal transmission line, a section of oscillation section is formed, no matter whether filtering or oscillation occurs, damage is caused to high-speed signal transmission, and signal distortion is caused. The back drilling is to remove the copper (Stubs) part of the plated PTH hole which is not beneficial to signal transmission by means of secondary drilling, and the stub length remained after the back drilling is shorter, so that the integrity of the signal transmission is more beneficial. At present, electronic products have entered the era of high-speed signal transmission, and the requirement for the length of Stubs remaining in PTH holes is becoming shorter and shorter.

At present, the method of PCB backdrilling mainly includes: the first method is that as shown in fig. 1, the outer layer is used as a signal feedback layer during back drilling by utilizing the blind hole drilling function of the drilling machine, and when a drill point contacts a plate surface, a signal is fed back to a server, and the drill point is drilled down to a preset depth. The diameter of a drill point of the back drill is generally 0.2-0.25 mm larger than that of the first drill hole, the plate is subjected to an alkaline etching process, the back drilling step is carried out after pattern electroplating and before alkaline etching, copper wires generated by drilling can be avoided, and partial hole copper can be removed during etching when the drilling depth is preset. The first method has the following disadvantages: the back drilling depth of the holes processed by the back drilling method is consistent, the thickness of the plate is uneven, the periphery of the plate is generally thin, the middle of the plate is generally thick, the uniformity of the length of the residual hole copper after back drilling is poor, the improvement of the back drilling capability is limited, and the thicker the plate is, the worse the uniformity of the thickness is, the larger the length of the residual hole copper is. And secondly, as shown in fig. 2, the signal feedback layer is arranged on an inner layer (such as a reference layer) by utilizing the blind hole drilling function of the drilling machine, the signal feedback layer is connected to the plate surface through a tool hole, the preset drilling depth is only one medium layer thick, and the back drilling precision is greatly improved. Typically, the reference layer of the backdrill is a ground layer. The second method has the following disadvantages: the inner layer is used as a signal feedback layer for back drilling, the back drilling performance is excellent in the aspect of controlling the length of the copper in the hole, the plate thickness uniformity is not the influence factor of the back drilling any more, but the requirements on the capacity of other steps in the production flow are high, the flow control difficulty is high, and the aperture of the back drilling is larger than that of the first drilling by more than 0.3 mm.

Therefore, a back-drilling tool is needed to solve the above problems.

Disclosure of Invention

The invention aims to provide a back drilling tool, which can accurately control the hole depth during back drilling processing, and can get rid of the dependence of the hole depth precision on the thickness of a workpiece and the flow control through innovative tool structure design, thereby greatly improving the processing efficiency and the processing precision.

The invention also aims to provide a back drilling cutter preparation method, which is used for preparing the back drilling cutter, so that the back drilling cutter can accurately control the hole depth during back drilling processing, the dependence of the hole depth precision on the thickness of a workpiece and flow control is eliminated, and the processing efficiency and the processing precision are greatly improved.

In order to realize the purpose, the following technical scheme is provided:

on one hand, the back drilling tool is used for machining a workpiece with conductive interior, and comprises a tool handle and a cutting edge, wherein the cutting edge comprises a tool body, a boss and a tool tip which are sequentially connected; the knife body is connected with the knife handle; the maximum diameter D1 of the tool tip and the diameter D3 of the tool body are both smaller than the diameter D2 of the boss; the outer surfaces of the tool nose and the tool body are not conductive, and the outer surface of the boss is conductive.

As an alternative to the back drilling tool, the shank and the blade are made of an electrically conductive material.

As an alternative of the back drilling tool, the outer surface of the tool body and the outer surface of the tool tip are both provided with non-conductive film layers, and whether the non-conductive film layers are coated or not is selected on the outer surface of the connecting part of the tool handle and the tool body according to the actual production condition.

As an alternative to the back-drilling tool, the conductive material may be stainless steel, die steel, high speed steel, cemented carbide, or the like.

As an alternative to the back-drilling tool, the non-conductive film layer may be a film layer prepared by a CVD or PVD process.

As an alternative of the back drilling tool, the tool nose comprises a sharp neck part and a sharp end part, and the value range of the length L1 of the sharp neck part is more than or equal to 0.1mm and less than or equal to L1 and less than or equal to 0.5 mm.

As an alternative of the back drilling tool, the length L2 of the boss ranges from 0.1mm to L2 mm to 0.5 mm.

As an alternative of the back drilling tool, the diameter D2 of the boss is the same as the hole diameter required to be processed, and is not less than 0.02mm and not more than D2-D1 and not more than 0.2 mm.

As an alternative to the back drill tool, the maximum diameter D1 of the tip is equal to the diameter of the blade.

On the other hand, the preparation method of the back drilling cutter is provided, and comprises the following steps:

s1, preprocessing a conductive raw material bar to obtain a semi-finished bar, wherein the semi-finished bar comprises a knife handle and a knife edge, the knife edge comprises a knife body, a boss and a knife tip which are sequentially connected, and the diameter D1 of the knife tip and the diameter D3 of the knife body are both smaller than the diameter D2 of the boss;

s2, forming spiral grooves on the knife body, the boss and the knife tip;

s3, sharpening the tip part of the tool nose;

s4, coating a non-conductive film layer on the blade, and selecting whether to coat the non-conductive film layer on the outer surface of the connecting part of the tool handle and the tool body according to the actual production condition;

and S5, polishing off the non-conductive film layer on the boss.

As an alternative to the back-drilling tool preparation method, in step S1, the semi-finished bar is obtained by performing outer circle step processing on a conductive raw material bar.

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a back drilling cutter which comprises a cutter handle, a cutting edge, a transition table and a non-conductive film layer, wherein the cutting edge comprises a cutter body, a boss and a cutter point which are sequentially connected; the maximum diameter of the tool nose and the diameter of the tool body are both smaller than the diameter of the boss; the outer surfaces of the tool tip and the tool body are not conductive, and the outer surface of the lug boss is conductive. When the processing is carried out, the boss and the inner layer of the workpiece form an electric path to play a role in signal transmission, so that the depth of the hole can be accurately controlled. By innovating the structural design of the cutter, the dependence of the hole depth precision on the thickness of a workpiece and the flow control is eliminated, and the processing efficiency and the processing precision are greatly improved.

The back drilling cutter preparation method provided by the invention is used for processing the back drilling cutter, so that the back drilling cutter can accurately control the hole depth during back drilling processing, the dependence of the hole depth precision on the thickness of a workpiece and flow control is eliminated, and the processing efficiency and the processing precision are greatly improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention 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 for those skilled in the art, other drawings can be obtained according to the contents of the embodiments of the present invention and the drawings without creative efforts.

FIG. 1 is a schematic diagram of a first backdrilling method provided in the prior art;

FIG. 2 is a schematic diagram of a second backdrilling method provided in the prior art;

FIG. 3 is a schematic structural diagram of a back drilling tool according to an embodiment of the present invention;

fig. 4 is a schematic view of a back-drilling tool manufacturing method according to an embodiment of the present invention.

Reference numerals:

1-a knife handle;

2-a blade; 21-a blade body; 22-a boss; 23-a knife tip; 231-sharp neck; 232-a tip portion;

3-a transition table;

4-non-conductive film layer.

Detailed Description

In order to make the technical solutions of the present invention better understood by those skilled in the art, the technical solutions of the present invention are further described below by way of specific embodiments with reference to the accompanying drawings.

In the description of the present invention, unless expressly stated or limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, removably connected, or integral to one another; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

In the description of the present embodiment, the terms "upper", "lower", "left", "right", and the like are used based on the orientations and positional relationships shown in the drawings only for convenience of description and simplification of operation, and do not indicate or imply that the referred device or element must have a specific orientation, be configured and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used only for descriptive purposes and are not intended to have a special meaning.

As shown in fig. 3, the present embodiment provides a back drilling tool, which includes a tool shank 1, a cutting edge 2, a transition table 3, and a non-conductive film layer 4, where the tool shank 1 is used to be connected to a power device, the cutting edge 2 is used to perform back drilling processing on an internal conductive workpiece, and the transition table 3 is used to connect the tool shank 1 and the cutting edge 2.

The internal conductive workpiece can be a circuit board and is used for back drilling the circuit board, so that the hole depth can be accurately controlled during back drilling, the dependence of the hole depth precision on the thickness and the flow control of the circuit board is eliminated, and the processing efficiency and the processing precision are improved.

Preferably, the cutting edge 2 comprises a cutter body 21, a boss 22 and a cutter tip 23 which are sequentially connected, one end of the transition table 3 is connected with the cutter body 21, and the other end of the transition table is connected with the cutter handle 1; the diameter D1 of the tool tip 23 and the diameter D3 of the tool body 21 are both smaller than the diameter D2 of the boss 22; the knife tip 23 and the outer surface of the knife body 21 are not conductive, and the outer surface of the boss 22 is conductive. Through using above-mentioned cutting edge 2, the back drilling cutter that this embodiment provided, the processing ability is strong, and can accurate control stub length to satisfy the higher demand of customer.

In short, by utilizing the conductivity of the boss 22, the boss 22 on the back-drilling tool contacts with the copper layer of the inner layer of the circuit board to form a via for signal transmission. Compared with the drill cutter in the prior art, the drill cutter can realize accurate control of drilling depth and is high in machining efficiency.

Optionally, the cutting edge 2 is made of a conductive material, and the outer surfaces of the cutting tip 23 and the cutting body 21 are coated with a non-conductive film layer 4. The outer surface of the boss 22 is conductive, and when the back drilling tool drills to a target depth, the boss 22 is electrified with a copper layer in the circuit board, so that timely feedback of signals is achieved, and hole depth accuracy is guaranteed. The outer surface of the connecting part of the knife handle 1 and the knife body 21 can be coated with the non-conductive film layer 4 according to the actual production condition. Alternatively, when the back-drilling tool is made of a non-conductive material, the outer surface of the boss 22 may be coated with a conductive film layer, which also achieves the above-mentioned effects.

Preferably, the back-drilling tool is made of hard alloy (tungsten steel), the material itself has conductivity, and the outer surface of the blade 2 is coated with a non-conductive layer, so that the boss 22 partially has a conductive function. Illustratively, the back-drilling tool may also be stainless steel, die steel, high speed steel, or the like.

Preferably, the non-conductive film layer 4 is a diamond-like carbon coating (DLC). The DLC film has high hardness and high elastic modulus, low friction factor, wear resistance and good vacuum tribological characteristics,

in view of facilitating the processing and preventing the needle from being broken, the tool tip 23 comprises a tip neck portion 231 and a tip portion 232, and the length L1 of the tip neck portion 231 is in a range of 0.1mm to L1 mm to 0.5 mm.

Considering that the length L2 of the boss 22 is greater than the inner copper thickness of the circuit board, and meanwhile, for convenience of processing, the length L2 of the boss 22 is in a range of 0.1mm to L2 to 0.5 mm.

Preferably, the diameter D2 of the boss 22 is the same as the hole diameter required to be processed, and is more than or equal to 0.02mm and less than or equal to D2-D1 and less than or equal to 0.2mm, so as to ensure the rigidity and the non-conductivity of the tool nose 23.

In this embodiment, the diameter D1 of the blade tip 23 is equal to the diameter of the blade body 21, so as to improve the structural strength of the blade 2 and avoid needle breakage.

Further, the tool holder 1 and the tool body 21 are connected through the transition table 3. Preferably, the transition table 3 is in a trapezoidal truncated cone shape, so that stress concentration at a connecting part is reduced, and the connecting strength of the tool holder 1 and the tool body 21 is improved.

In order to prepare the back drilling tool, as shown in fig. 4 and fig. 3, this embodiment further provides a back drilling tool preparation method, including the following steps:

s1, conducting pretreatment on a conductive raw material bar to obtain a semi-finished bar, wherein the semi-finished bar comprises a knife handle 1, a knife edge 2 and a transition table 3, the knife edge 2 comprises a knife body 21, a boss 22 and a knife tip 23 which are sequentially connected, and the diameter D1 of the knife tip 23 and the diameter D3 of the knife body 21 are both smaller than the diameter D2 of the boss 22;

s2, forming spiral grooves on the knife body 21, the boss 22 and the knife tip 23;

s3, sharpening the tip 232 of the cutting edge 23;

s4, coating a non-conductive film layer 4 on the blade 2, and selecting whether to coat the non-conductive film layer 4 on the outer surface of the connecting part of the tool handle 1 and the tool body 21 according to the actual production condition;

and S5, polishing off the non-conductive film layer 4 on the boss 22.

Illustratively, in step S1, the semi-finished bar stock is obtained by performing outer circle step machining on the conductive raw bar stock. In other embodiments, the raw bar stock may be processed into the semi-finished bar stock in other ways.

Preferably, step S1 further includes coarse finish grinding the outer circumference of the raw bar stock before the outer circumference step difference processing.

In step S4, the "whether to coat the non-conductive film layer 4 on the outer surface of the connection portion of the tool shank 1 and the tool body 21 according to the actual production situation" means that when the drilling depth is greater than the length of the blade 2, in order to avoid the influence on the system control caused by the electric communication between the tool shank 1 and the circuit board, the non-conductive film layer 4 needs to be coated on the connection portion of the blade 2 and the tool shank 1 (in this embodiment, the transition table 3 and a part of the tool shank 1); when the drilling depth is far less than the length of the blade 2, the non-conductive film layer 4 does not need to be coated on the connecting part of the tool shank 1 and the blade 2.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A back drilling tool is used for machining an internal conductive workpiece and comprises a tool shank (1) and a cutting edge (2), and is characterized in that the cutting edge (2) comprises a tool body (21), a boss (22) and a tool tip (23) which are sequentially connected, and one end of the tool body (21) is connected with the tool shank (1); the maximum diameter D1 of the tool tip (23) and the diameter D3 of the tool body (21) are both smaller than the diameter D2 of the boss (22); the outer surfaces of the tool nose (23) and the tool body (21) are not conductive, and the outer surface of the boss (22) is conductive.

2. The back drilling tool according to claim 1, characterized in that the shank (1) and the cutting edge (2) are made of an electrically conductive material.

3. The back drilling tool of claim 2, wherein the electrically conductive material is stainless steel, die steel, high speed steel, or cemented carbide.

4. The back drilling tool according to claim 2, characterized in that a non-conductive film layer (4) is provided on both the outer surface of the blade body (21) and the outer surface of the tip (23).

5. The back drilling tool according to claim 4, wherein the non-conductive film layer (4) is a film layer prepared by a CVD or PVD process.

6. The backdrill tool according to claim 1, wherein the tip (23) comprises a tip portion (231) and a tip portion (232), the length L1 of the tip portion (231) being in the range of 0.1mm ≤ L1 ≤ 0.5 mm.

7. The back drilling tool according to claim 1, wherein the length L2 of the boss (22) ranges from 0.1mm to L2 to 0.5 mm.

8. The back drilling tool according to claim 1, characterized in that the diameter D2 of the boss (22) is the same as the bore diameter to be machined, and 0.02mm ≦ D2-D1 ≦ 0.2 mm.

9. The backdrilling tool according to claim 1, wherein the maximum diameter D1 of the tip (23) is equal to the diameter of the blade body (21).

10. A back drilling cutter preparation method is characterized by comprising the following steps:

s1, conducting pretreatment on a conductive raw material bar to obtain a semi-finished bar, wherein the semi-finished bar comprises a knife handle (1) and a cutting edge (2), the cutting edge (2) comprises a knife body (21), a boss (22) and a knife tip (23) which are sequentially connected, and the diameter D1 of the knife tip (23) and the diameter D3 of the knife body (21) are both smaller than the diameter D2 of the boss (22);

s2, forming spiral grooves on the knife body (21), the boss (22) and the knife point (23);

s3, sharpening the tip part (232) of the knife edge (23);

s4, coating a non-conductive film layer (4) on the blade (2), and selecting whether to coat the non-conductive film layer (4) on the outer surface of the connecting part of the cutter handle (1) and the cutter body (21) according to the actual production condition;

and S5, polishing off the non-conductive film layer (4) on the outer surface of the boss (22).