JP2003311522A - One-flute drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress disalignment and deterioration of positional accuracy of a hole due to poor cutting-in ability and poor rigidity of a one-flute drill, which is used to machine a printed board, etc., by improving the cutting-in ability of the one-flute drill to a workpiece without reducing its rigidity. <P>SOLUTION: A flute 4 is composed of a basic flute portion 4a, the depth of which is set within the range from 0.20 to 0.45D, and a deep flute portion 4b provided in a limited region of a tip end side of the drill so as to shift toward a heel side. The center height H is maintained over the whole range of the cutting edge length. In addition, the flute surface of the deep flute portion 4b is disposed in the neighborhood of the rotational axis of the drill so as to reduce the length of a chisel edge 3a. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-edged drill for a printed circuit board or for drilling a component hole, which has both good biting property and strength (rigidity).

[0002]

2. Description of the Related Art As a single-edged microdrill used for drilling holes in printed circuit boards, etc.
4 and Japanese Patent Laid-Open No. 2001-227189.

The former publication has a blade groove depth of 1/4.
It is set to D to 1 / 2D (D is the diameter of the drill), and a chisel blade is generated between the auxiliary tip blade and the main tip blade that remain in the center of rotation.

Further, in the drill of the latter publication, the cutting edge at the tip is provided so as to extend radially outward from the substantial center in order to improve the positional accuracy of the processed hole.

[0005]

The drill disclosed in Japanese Utility Model Laid-Open No. 7-33514, which has a chisel blade which is an incomplete cutting edge at the center of the tip, has a poor biting property on the work material and a bent machining hole. , Misalignment occurs.

On the other hand, the drill disclosed in Japanese Unexamined Patent Publication No. 2001-227189 has excellent biteability because it eliminates the chisel blade, but has a deep groove groove and a core height of zero, and therefore has a diameter of 3 mm. A micro drill with a diameter of 0.0 mm or less, especially an ultra-fine drill with a diameter of only 0.3 mm to 0.6 mm, is particularly liable to have insufficient rigidity even with a single-blade structure, resulting in bending of the machined hole due to bending and misalignment. easy.

In order to suppress the bending and positional deviation of the processed hole, it is necessary to achieve both good biting property and high rigidity. Thinning is one of the methods to meet the demand, but it is difficult to thin a microdrill and it is difficult to reproduce the function by re-polishing on the user side. A drill for a printed circuit board is also required to be easily re-polished on the user side because it is re-polished every prescribed number of HITs.

Therefore, an object of the present invention is to make it possible to secure good biteability and rigidity without making re-polishing difficult.

[0009]

In order to solve the above problems, in the present invention, a single-edged drill is constructed as follows. That is, having a single cutting edge and one blade groove consisting of a basic blade groove portion and a deep blade groove portion, the basic blade groove portion has a gradient that the groove depth becomes shallower toward the rear of the drill, and The groove depth of the basic blade groove portion is 0.
It is set to 20D to 0.45D so that the outer peripheral blade has a core height in the entire region between the blade lengths, and the deep blade groove portion is arranged at a position deviated to the heel side of the drill tip portion and the blade groove depth near the tip end. Is made larger than the groove depth of the basic blade groove portion, the groove surface of the deep blade groove portion is near the rotation center of the drill, and the length of the chisel blade is shortened.

The deep blade groove portion may be either a groove having a constant depth from the tip to the vicinity of the end or a groove having a slope in which the groove depth gradually decreases toward the rear of the drill.

The single-edged drill is particularly suitable for printed circuit boards, but is not limited to printed circuit boards.

[0012]

According to the present invention, the groove depth of the basic blade groove is made shallow so that the outer peripheral blade has a core height over the entire area between the blade lengths, and further, the basic blade groove has a gradient to reinforce.
As a result, the microdrill is also secured with sufficient rigidity, and the bending of the drill during machining, which causes bending of the hole, is suppressed.

Further, a deep blade groove portion is formed on the tip side and the groove surface of the deep blade groove portion is arranged near the center of rotation of the drill to shorten the length of the chisel blade, which improves the biting property. To do. This deep blade groove portion is formed only in a limited region of the tip, and since it is biased toward the heel side and the core height state of the outer peripheral blade is maintained even at the tip portion, the deep blade groove portion is formed. However, the rigidity of the drill is not significantly reduced.

[0014]

1 to 4 show an embodiment of a drill according to the present invention.

FIG. 1 shows the entire drill, and a shank 2 is connected to the rear of a main body 1. The main body 1 is provided with one cutting edge 3 and one blade groove 4 twisted at a predetermined helix angle α. Reference numeral 5 denotes an outer peripheral blade along the blade groove 4.

The blade groove 4 includes a basic blade groove portion 4a and a deep blade groove portion 4b.
It consists of and. Basic blade groove 4a is, the depth d ₁ shown in FIG. 2 is set in a range of 0.20D～0.45D. Further, as shown in FIG. 5, the basic blade groove portion 4a is provided with a gradient that gradually reduces the groove depth d ₁ toward the rear of the drill.

The single-flute drill has only one flute,
Since the groove width ratio (= groove width W ₂ / land width W ₁ ) is also small, there is originally less decrease in rigidity compared to a _two -flute drill. In addition to this, the basic blade groove portion 4a has a shallow groove depth so that the outer peripheral blade has a core height, and the groove has a slope corresponding to the web taper of a two-blade drill, so the rigidity of the main body portion 1 is insufficient. Can be secured without.

The deep blade groove portion 4b is provided only in a limited range of the tip of the main body, for example, a region of about 0.3D to 3.5D from the cutting edge. Further, since the deep blade groove portion 4b is provided so as to be biased toward the heel side, the outer peripheral blade 5 has a core height in the range of 0.05D to 0.30D in the entire region between the blade lengths (L _{1 in} FIG. ₁ ). Become. H in FIG. 2 represents the height of the core. If the depth d ₂ (FIG. 2) of the deep blade groove portion 4b is 0.5D at the maximum, the length of the chisel blade 3a can be made sufficiently short as shown in the drawing (it can be zero). It is not preferable to make it deeper than that in terms of ensuring rigidity. The minimum value of the depth d ₂ naturally becomes larger than the basic blade groove depth.

The deep blade groove portion 4b has a shape without a gradient, that is,
From the cutting edge to a certain range, the shape twists at an angle α without any change in depth, and then gently rises toward the basic blade groove 4a (this is because the groove bottom up to the cut-up portion is the drill axis in the developed cross-sectional view). Parallel to each other), the groove depth may gradually decrease from the cutting edge toward the rear of the drill. The former groove shape does not change the blade shape after re-polishing if it is re-polished within the installation range of the deep groove, and the flanks (first flank 6a and second flank 6b in the figure) The initial blade shape can be regenerated only by polishing. On the other hand, in the latter groove shape, when the re-polishing is performed, the chisel blade is gradually lengthened due to the influence of the gradient and the biting property is deteriorated, but the decrease in strength on the tip side is suppressed to a smaller extent.

The test results for confirming the effects of the present invention are shown below. The test was performed using the drill (material AFO) shown in Table 1. Conventional drills A and B shown in the table are both double-edged drills.

[0021]

[Table 1]

Using each of the three drills shown in Table 1, holes were drilled in a multi-layered printed circuit board under the following processing conditions.

[0023]     Processing conditions     Printed circuit board: BT resin board, thickness 0.2mm x 16 sheets     Patch: LE300     Drill rotation speed: 120,000 rpm     Feed rate: 2.4 m / min (0.020 mm / rev)     HIT number: 3000

Regarding the processed hole, HIT number 1000,
The positional accuracy at 2000 and 3000 hours was measured for all holes, and the amount of positional deviation from the design value (the average value of 3 drills for each drill) was plotted. It is shown in FIG. The position of the hole was measured on the surface of the substrate on the drill cutout side of the lowermost substrate where the displacement amount was the largest.

Next, the inner wall roughness of the hole formed by each drill was examined by cutting the substrate. The inner wall roughness was examined for the holes in the uppermost substrate which are most roughened by drilling. The results are shown in Fig. 7. The data of FIG. 7 is 3000H.
Minimum and maximum of 10 holes near IT
The average value of the roughness of the holes is shown. In addition, A-1, B-
1, Invention-1 is the first test result, A-2, B-
2, Invention-2 is the second test result.

The invented product has a shorter chisel blade and higher rigidity than the two-blade drill for comparison. The effect of this is often shown in the experimental results.

Japanese Utility Model Laid-Open No. 7-33514, Japanese Patent Laid-Open No. 2001-2001
Although the performance comparison with each single-edged drill of No. 227189 has not been performed, the drill of this invention has a shorter chisel blade than the drill of the former publication, and is even more advanced than the drill of the latter publication. Since the core height is high and the rigidity is high, the effect of improving hole position accuracy and inner wall roughness superior to these drills can be expected.

[0028]

As described above, in the single-blade drill of the present invention, the chisel blade is shortened by providing the deep groove portion that deepens the groove depth only in the limited region of the tip, and further, the deep blade By locating the groove part on the heel side, the core height of the outer peripheral blade is maintained over the entire length of the blade, so it is possible to increase the biteability with respect to the work piece without lowering the rigidity. It is possible to simultaneously meet the requirements for prevention of bending and ensuring high hole position accuracy.

Further, since the rigidity is improved, it becomes possible to perform deep hole drilling more than ever before, and it is also possible to increase the number of layers to be overlapped at the time of drilling holes in a printed circuit board or the like to improve the machining efficiency.

Further, in the case of shortening the chisel blade by thinning, it is necessary to re-thinning each time re-grinding.
Since the cutting edge can be regenerated only by re-polishing the flank in the case of the deep groove portion, the user can re-polish the micro drill as well.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of a drill of the present invention.

FIG. 2 is an enlarged front view of the above drill.

[Figure 3] Enlarged side view of the tip of the drill

FIG. 4 is an enlarged side view of a position rotated by 90 °.

FIG. 5 is a developed sectional view showing the inclination of the blade groove.

FIG. 6 is a chart showing measurement results of hole position accuracy.

FIG. 7 is a chart showing measurement results of inner wall roughness of processed holes.

[Explanation of symbols]

1 body 2 shank 3 cutting edges 3a Chisel blade 4 blade grooves 4a Basic flute groove 4b Deep flute groove 5 outer peripheral blade 6a Most flank 6b Second flank

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshiro Eguchi             2374 Fukumo, Omachi-machi, Kishima-gun, Saga Prefecture Kyushu Residence             Denseiki Co., Ltd. F-term (reference) 3C037 AA09 BB00 DD01

Claims (5)

[Claims] 1. A single cutting edge and a single flute consisting of a basic flute and a deep flute, wherein the basic flute has a gradient in which the groove depth becomes shallower toward the rear of the drill. And, the groove depth of the basic blade groove portion is 0.
It is set to 20D to 0.45D so that the outer peripheral blade has a core height in the entire region between the blade lengths, and the deep blade groove portion is arranged at a position deviated to the heel side of the drill tip portion and the blade groove depth near the tip end. A single-flute drill in which the length of the chisel blade is shortened because the groove surface of the deep blade groove portion is near the rotation center of the drill. 2. The single-edged drill according to claim 1, wherein the maximum groove depth of the deep blade groove portion is set to 0.5D. 3. The single-blade drill according to claim 1, wherein the deep blade groove portion is a groove having a constant depth from the tip to the end. 4. The single-edged drill according to claim 1 or 2, wherein the deep blade groove portion is a groove with a gradient in which the groove depth becomes shallower toward the rear of the drill. 5. The single-edged drill according to claim 1, which is configured as a microdrill having a drill diameter D of 3.0 mm or less.