JPH106114A - Drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve torsional rigidity by forming a web taper to change a web thickness of at least a tip part as a curve. SOLUTION: A plurality of strip spiral grooves 36 are arranged on a peripheral surface of a body 34 in a drill 30. A web 40 is formed between the groove 36 and the groove 36. This web 40 is made thick toward the rear end side from the tip side of the body 34. A web taper 42 to change a web thickness B is formed as a curve, and a tip side shape of the web 40 is formed in an almost warhead shape. Therefore, since the web width B in the tip vicinity of the body 34 rapidly becomes thick, rigidity and torsional rigidity of the drill 30 increase, and breaking resistance is improved, and breaking in boring work of a printed circuit board of a thin plate, a high multilayer and the large number of superposed sheets can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill for drilling holes in a workpiece, and more particularly to a drill having a diameter suitable for drilling holes in a printed wiring board on which integrated circuits and various electronic components are mounted.
It relates to a twist drill of 175 mm or less.

[0002]

2. Description of the Related Art A printed wiring board (printed circuit board) on which electronic components and the like are mounted is generally formed by laminating woven glass fiber and copper foil serving as a conductor and integrating them with a resin such as epoxy. . When an electronic component or the like is mounted on the printed circuit board to form a printed circuit board, the printed circuit board is used to electrically connect the electronic component with a circuit (printed circuit) printed on the surface of the laminated copper foil or the substrate. A large number of small-diameter through-holes are formed, and electronic components are soldered through the holes to achieve electrical continuity between the copper foil or printed circuit and the electronic components.

FIG. 6 is an explanatory view of a conventional drill used for boring a printed circuit board. The drill 10 shown in FIG. 6A is called an undercut type, which has been widely spread in recent years. A margin portion 14 having a larger diameter than the rear end side is formed at the front end of the body 12. FIG.
The drill 15 shown in (2) is a so-called straight type conventionally used, and the body 16 is formed to have the same thickness. And these drills 10, 1
In 5, the web taper 18 is formed in a straight line so that the thickness B of the web 20 increases linearly from the front end to the rear end shank 22.

[0004]

By the way, in recent years, with the increase in the packing density accompanying the high performance and miniaturization of electronic devices,
As the printed circuit board is becoming thinner and multi-layered, the diameter of a hole drilled in the printed circuit board is being accelerated. Therefore, the diameter of a drill used is increasing and the load on the drill is increasing. In addition, in the drilling of the printed circuit board, the number of stacked substrates at the time of the drilling is increasing in order to improve the working efficiency and reduce the manufacturing cost. For this reason, the substantial aspect ratio (the ratio of the thickness to the diameter of the hole) of drilling has been increasing, and the aspect ratio may be as high as 20 in recent years. As a result, the drill is broken due to an increase in the load on the drill, and a failure of the printed circuit board occurs. In particular, a drill for a printed circuit board is required to have a small diameter and a high hole position accuracy. Therefore, as shown in FIG. The precision is increased, and the torsional rigidity is reduced, so that breakage is likely to occur.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and has as its object to provide a drill capable of improving rigidity. Another object of the present invention is to make it possible to improve chip dischargeability and hole quality during drilling.

[0006]

Means for Solving the Problems The inventors have conducted various experiments to improve the breakage resistance of a drill in the drilling of a thin plate, a high multilayer and a high number of printed circuit boards by a small diameter drill. It has been found that making the web taper of the drill into a curved line not only significantly improves breakage resistance, but also improves chip dischargeability and hole quality. The present invention is based on the above findings, and the drill according to the present invention has a configuration in which, in a drill having a groove formed on the peripheral surface, a web taper that changes the thickness of the web at least at the tip portion is formed in a curved line. It is.

The curve may be such that the thickness of the web increases from the leading end side to the trailing end side, and may be a quadratic curve such as a parabola, an elliptic curve, a logarithmic curve, a trigonometric curve, or a curve. It may be a curve obtained by connecting arbitrary points so that the web thickness changes smoothly, or a curve obtained by simulation using a computer or the like.

[0008]

According to the present invention constructed as described above, it is possible to rapidly increase the thickness of the web in the vicinity of the front end from the front end to the rear end by forming the taper of the web at least at the front end portion into a curved line. . For this reason, the torsional rigidity of the drill is increased, the breakage resistance of the drill is improved, the breakage of the drill is reduced, and the occurrence of defective printed circuit boards can be reduced. Also, because the rigidity of the drill can be increased, the thickness of the web at the tip of the drill can be reduced,
The biting property of the drill is improved, and the hole position accuracy can be improved. In addition, since the thickness of the web changes in a curved shape, the chips are easily pushed out of the holes by the web, so that the chips can be easily discharged and the surface of the drilled hole becomes smoother. Quality is improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a drill according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an explanatory view of a drill according to an embodiment of the present invention, and shows an undercut type drill for drilling a printed circuit board having a luma shank. In FIG. 1, a drill 30 is a normal twist drill, in which a body 34 is integrally formed on the tip side of a shank 32, and a plurality of spiral grooves 36 are provided on a peripheral surface of the body 34. A large-diameter margin portion 38 having a predetermined length in the axial direction of the body 34 is formed at the tip of the body 34. And groove 36 and groove 3
6, a web 40 is formed. The web 40 is made thicker from the front end to the rear end of the body 34. The web taper 42 for changing the web thickness B is formed in a curved line, and the shape of the front end side of the web 40 has a substantially warhead shape.

The curve forming the web taper 42 is:
It is sufficient that the web thickness B increases from the front end side to the rear end side of the body 34. For example, a quadratic curve such as a parabola or an elliptic curve, a logarithmic curve, a trigonometric function curve, or an axial direction of the body 34 Can be plotted arbitrarily, and a curve obtained by interpolating these points smoothly so as to be connected or a curve obtained by simulation by a computer can be obtained.

In the drill 30 according to the embodiment configured as described above, since the web width B near the tip of the body 34 is rapidly increased, the rigidity and torsional rigidity of the drill 30 are increased, and the breakage resistance is improved. In addition, it is possible to eliminate breakage in drilling of a thin board, a multi-layered board, and a high number of stacked printed boards, thereby reducing the occurrence of defective printed boards. In addition, since the rigidity can be increased by increasing the thickness of the web in the vicinity of the tip, the thickness B of the web at the tip can be reduced, the biting property of the drill 30 is improved, and the hole position accuracy can be improved. Burrs around the hole can be reduced. The web 40 has a thickness B
Is changed so as to be convex outward, so that the cut chips move along the surface of the web 40 and are easily discharged from the holes, thereby improving the dischargeability of the chips and improving the drilled holes. The inner surface is smooth and the hole quality can be improved.

[0013]

As shown in FIG. 2, the space between the front end portion a of the undercut type web 40 and the rear end of the margin portion 38 is divided into three equal parts. At points corresponding to the ends, points b, c, and d that are appropriately separated from the center line 44 are plotted, and an appropriate point e near the end of the groove 36 is plotted, and these points a to e are smoothly connected. The diameter of the margin portion 38 having the web taper 42 having a curve as shown in FIG.
A drill having a length of 7 mm was prepared, and the hole position accuracy of the conventional undercut type drill 10 shown in FIG.

The shape characteristics of both drills are as shown in FIG. That is, the groove area at the tip a shown in FIG. 2 was 0.0866 mm ² in the case of the embodiment, and the groove area ratio to the radial area (hereinafter simply referred to as groove area ratio) was 65.59%. On the other hand, the conventional drill has a groove area of 0.0828 mm ² and a groove area ratio of 62.73.
%Met. In addition, 2.0 mm on the rear end side 2 mm from the front end a
In the mm part, in the case of the embodiment, the groove area is 0.046.
The groove area was 0.0608 mm ² and the groove area ratio was 46.01% in the conventional example, while the groove area ratio was 0. mm ² and the groove area ratio was 34.83%. Further, from the tip a, 5.3
In the 5.35 mm portion on the 5 mm rear end side, the groove area of the example is 0.0296 mm ² , the groove area ratio is 22.44%, and the groove area of the conventional example is 0.0286 mm ² , and the groove area ratio is 21.17. %Met.

Further, the second moment of principal area of both is obtained.
However, in the case of the embodiment at the tip a,
Surface second moment I_CUIs 4.60 × 10^-Fivemm^Four ,maximum
Second moment of principal area I_CVIs 46.07 × 10^-Fivemm^Four 
And the secondary moment of area I_P Is 50.67 × 1
0^-Fivemm^Four Met. And the conventional example at the tip
Minimum principal area second moment I_CUIs 5.52 × 10^-Fivemm
^Four , Maximum moment of inertia of principal area I_CVIs 55.02 × 10
^-Fivemm^Four And the secondary moment of area I_P Is 60.5
4 × 10^-Fivemm^Four Met. Also, in the 5.35mm section
I of the embodiment C_UIs 49.71 × 10^-Fivemm^Four , I_CVIs
96.58 × 10^-Fivemm^Four , I_P Is 146.29 × 10
^-Five mm^Four , The conventional I_CUIs 52.30 × 10^-Fivemm
^Four , I_CVIs 110.50 × 10^-Fivemm^Four , I_P Is 16
2.80 × 10^-Fivemm^Four Met.

FIG. 4 shows the measurement results of the hole position accuracy in the drilling of these drills. The conditions for drilling are as follows: Printed circuit board (PWB) is used in the United States National Electrical Manufacturers Association (National Electric).
(ManufacturersAssociation)
4 layers equivalent to FR4 standard, and 1.6m thick
m are stacked three times, and an aluminum plate having a thickness of 0.15 mm is laid under the base plate (EB). The number of rotations (rotational speed) of the drill was 70,000 rpm, and the step was performed twice, and re-grinding was performed every 2500 hits to perform a total of 7,500 hits.
Further, the hole position was obtained by the center of gravity method.

4 shows a drill according to the embodiment, in which the drill feed speed (F) is 1.5 m / d.
It is the measurement result of min, and the solid line connecting the circles indicates the average value of three drills + 3σ (σ is the standard deviation). And, ● indicates the maximum value of the three drills. In addition, △ is the drill according to the example, and is a measurement result when the feed rate is 2.1 m / min, and the broken line connecting the △ marks is the average value of three drills + 3σ, and ▲ is the maximum value. is there. Further, □ indicates the measurement result of the drill according to the conventional example, which indicates the average value of three drills + 3σ, and the □ marks are connected by a one-dot chain line. (2) indicates the maximum value of the conventional example. The feed rate of the drill according to the conventional example is 1.5 m /
min.

As is apparent from FIG. 4, the drill according to the embodiment has a higher hole position accuracy than the conventional drill. This is because, as shown in FIG. 3, the drill according to the embodiment can increase the groove area at the tip end and reduce the web thickness as compared with the conventional example, so that the drill has good biting properties. It seems to be due to becoming. In particular, in the conventional drill, the hole position accuracy decreases each time re-polishing is performed, whereas in the drill of the embodiment, the hole position accuracy does not decrease even after re-polishing, and Drilling can be performed with high precision, the life of the drill can be extended, and the cost of drilling can be reduced. In addition, in the drill according to the embodiment, since the web taper is curved, the chips move to the outside of the hole along the web taper, so that the chip dischargeability is improved and the inner wall surface of the hole is improved. And the hole quality improved.

FIG. 5 shows the measurement results of the thrust load acting on the drill of the embodiment and the conventional example. The measurement conditions are
FR4 standard, 4 layers, 3 layers of 1.6 mm thick printed circuit boards are stacked, and the number of rotations of the drill is 70000 rpm.
perforation at a feed rate of 2.1 m / min.
As shown in the drawing, the thrust load can be reduced by about 0.02 kgf in the example with the average value of five pieces compared to the conventional example, and the load on the drill can be reduced. Moreover, as shown in FIG. 3, in the drill according to the embodiment, since the web thickness rapidly increases near the tip, the web thickness at the tip can be reduced, the torsional rigidity increases, and the thrust load is reduced. In combination with the reduction, the breakage resistance is improved, and the occurrence of defects in the printed circuit board due to the breakage of the drill is reduced, so that the cost can be reduced.

Although the undercut type drill has been described in the above embodiment, the present invention can be applied to a straight type drill. In the above embodiment, the case where the web taper 42 is curved over substantially the entire length of the groove 36 has been described.
mm or the web taper up to the rear end of the margin portion 38 is curved, and the web taper at the rear end side is formed as a straight line so that the web 40 becomes gradually thicker, or as a straight line that does not change the thickness of the web 40. May be.

[0021]

As described above, according to the present invention, since the web taper at least at the front end portion is formed in a curved line, the thickness of the web near the front end can be rapidly increased, and the drill can be formed. The torsional rigidity is increased, the breakage resistance is improved, and the breakage of drills is reduced, thereby reducing the occurrence of defective printed circuit boards. In addition, since the rigidity can be increased by increasing the thickness of the web near the tip, the web thickness at the tip of the drill can be reduced, and the biting of the drill can be improved and the hole position accuracy can be improved. it can. In addition, since the thickness of the web changes in a curved shape, the chips are easily pushed out of the holes by the web, so that the chips can be easily discharged and the surface of the drilled hole becomes smoother. Quality is improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a drill according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a drill according to an embodiment.

FIG. 3 is a comparison diagram of shape characteristics between the drill according to the embodiment and the drill according to the conventional example.

FIG. 4 is a diagram showing measurement results of hole position accuracy in drilling of a drill according to an example and a drill according to a conventional example.

FIG. 5 is a diagram showing a measurement result of a thrust load at the time of drilling between the drill according to the embodiment and the drill according to the conventional example.

FIG. 6 is an explanatory view of a conventional undercut drill and a straight drill.

[Explanation of symbols]

 30 drill 34 body 36 groove 40 web 42 web taper

Claims (1)

[Claims] 1. A drill having a groove formed on a peripheral surface thereof, wherein a web taper for changing a thickness of a web at least at a tip portion is formed in a curved line.