JP3540250B2 - Drill with single crystal diamond at its tip - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a drill having a single-crystal diamond at its tip, and relates to a drill suitable for drilling holes in a hard and brittle material such as quartz glass, silicon, machinable ceramics, or an IC substrate. Furthermore, the invention relates to the field of so-called microdrill technology, which is useful not only for drilling holes of normal size but also for small diameter drills or finer pores.
[0002]
[Prior art]
In a multilayer board on which an IC package is mounted, via holes are frequently used for connection between layers. It is desired that the diameter of the via hole be as small as the manufacturing technology allows.
[0003]
Conventionally, for the drilling of via holes and other holes, the surface of the cemented carbide microdrill with a string-shaped blade groove or the surface of the cemented carbide blade of this microdrill is coated with a number of fine diamonds by plating. A microdrill provided with a wear-resistant layer, or a microdrill having a cemented carbide shaft having a string-shaped blade groove and a polycrystalline diamond brazed to the end thereof is used.
[0004]
Since these micro drills have a helical groove (twist groove), when the diameter is small, not only the manufacturing becomes difficult but also the cross-sectional area of the drill is reduced by the provision of the twist groove. As a result, the strength has decreased and the use limit has been reached.
[0005]
The twist groove is provided from the tip cutting edge to just before the shank in order to discharge chips generated at the tip of the drill. Such a twist groove is conventionally considered to be indispensable, and has been almost provided except for a drill which does not have a special chip discharge structure such as a gun drill and a core leaving drill.
[0006]
Further, a chisel edge is formed at the tip of the drill, and since the chisel edge has little or no distance from the center, the peripheral speed at this point is little or zero. On the one hand, the axial advance speed of the drill is equal everywhere, regardless of the distance from the center of rotation, so that the rake angle is theoretically negative and little or no cutting action occurs at the chisel edge.
[0007]
Further, conventionally, the chisel edge has two ridges that gradually become higher toward the center of the drill (chisel point). When the point ()) bites into the workpiece, the position may slightly deviate from the center due to unpredictable conditions such as slight distortion of the surface of the workpiece, local variation in the material of the workpiece, and axial deviation of the drill. Such a slight shift of the biting position greatly affects the final position of the drilled hole.
[0008]
Further, even if the drill bites into the workpiece at the intended position, a phenomenon in which the direction of travel of the tip of the drill changes during the drilling and the hole is bent may occur.
[0009]
For this reason, in a weak drill such as a microfine drill, a lateral force is applied to the drill, so that the drill is broken or, even if not broken, the center of a drilled hole (a front opening circle or a back opening circle) is intended. A phenomenon such as deviation from the specified position occurs.
[0010]
Also, in the case of drilling a hard brittle material such as quartz glass, a silicon plate or a machinable ceramic with a polycrystalline diamond drill, the life of the drill is short-lived, or the bite at the intended position is poor. There is also the problem of axis breakage.
[0011]
In order to avoid such a bad effect of a non-sharp drill tip and to avoid a reduction in strength due to a twist groove, a drill having a pyramid tip and no twist groove has been considered.
[0012]
Under such circumstances, in order to increase the strength of the tip, the idea of forming the tip (cutting edge and guide) of the drill with single crystal diamond has been proposed in Japanese Utility Model Laid-Open No. 5-9814 (Japanese Utility Model Application No. 3-83585). No.) gazette and its CD-ROM specification. It is described that a quadrangular prism guide portion and a continuous end thereof are formed of a single-crystal diamond with a square angle of 60 ° to 90 °.
[0013]
As widely known, diamond is the hardest material in the world, and has a very wide range of uses, including jewelry and industrial use. In recent years, relatively inexpensive industrial diamonds have been supplied due to the development of diamond synthesis technology, but it is undeniably expensive.
[0014]
In the drill disclosed in the above publication, since the portion from the tip to the guide portion is made of single-crystal diamond, large single-crystal diamond is required, which is very expensive and impractical. Furthermore, this publication does not consider or disclose the direction of the crystal axis when processing a single crystal diamond and the crystal plane when attaching to a drill shaft.
[0015]
[Problems to be solved by the invention]
The shape (outside shape) and size of diamonds supplied irrespective of nature or synthesis are varied by chance during synthesis. For this reason, in processing the diamond, individual measures must be taken for each of the supplied diamonds.
[0016]
That is, diamond is difficult to process because its hardness is high. Usually, diamond powder is applied to a rotating cast iron disk and pressed against the disk. Since diamond has a crystal structure, its physical and chemical properties show anisotropy depending on the crystal direction, and its workability is no exception.
[0017]
Since there is no material that is harder than diamond, there is no material that can be selected as a material to be processed beyond diamond, and therefore, it is practically or substantially impossible to freely process a diamond single crystal in any direction. It is possible.
[0018]
FIG. 1 shows a crystal plane of a diamond crystal. Diamond has a crystal structure belonging to a cubic system, and three types of crystal planes appear in the crystal as shown in this figure.
[0019]
In FIG. 1, (a) shows a {100} plane, and a crystal composed only of this plane. A {100} plane appears for each of the crystal axes x, y, and z (the {100} plane, the {101} plane, and the {001} plane are equivalent to each other), and the flesh side (inside) and the space side of the crystal. There are apparently a total of six faces, depending on whether the face that separates is on the front or the back, respectively. A case composed of only these six planes is a hexahedral crystal shown in FIG.
[0020]
(B) shows a {110} plane and a crystal composed only of this plane. Considering the same as (a), there are a total of 12 faces in appearance. The case composed of only these 12 planes is a dodecahedral crystal shown in FIG. Further, (c) shows a {111} plane, and a crystal composed only of this plane. Similarly, there are a total of eight faces in appearance. An octahedral crystal shown in FIG. 1 is composed of only these eight planes.
[0021]
These three aspects usually appear compounded. FIG. 2 is a diagram showing an example of a diamond single crystal in which all three types of crystal planes appear. However, as shown in this diagram, it is rare that the shape becomes a nearly spherical and uniform.
[0022]
As described above, the workability greatly differs depending on the crystal plane. FIG. 3 is a graph showing the relationship between the crystal orientation and wear (workability), and showing that the workability differs depending on the orientation. The experiment was conducted by placing a diamond set at a predetermined polishing angle on a cast iron plate held horizontally and polishing the same for a certain load and for a certain time. The polishing angle in the direction parallel to the crystal axis was set to 0 degree, and only the octahedral plane {111} plane was experimentally selected in an arbitrary direction.
[0023]
As can be seen from the graph of FIG. 3, the dodecahedral {110} plane has the highest workability, followed by the hexahedral {100} plane. On the other hand, the octahedral surface {111} surface was hardly polished with almost no wear.
[0024]
Now, in this graph, although the octahedral surface {111} cannot be substantially machined, the machined surface is inclined to the dodecahedral surface {110} or the hexahedral surface {100}. And shows that this is possible.
[0025]
One object of the present invention is to provide a technique for processing the top of a drill in consideration of such workability, and furthermore, a single crystal diamond as small as possible is used to obtain a diamond drill of the same size. It is an object of the present invention to provide a shape that can be formed (a shape in consideration of the crystal axis direction).
[0026]
As described above, since diamond single crystals have anisotropy, the single crystal diamond fixed to the tip of the drill must not only be aware of its axial direction, but also have any effect on the surface fixed to the drill axis. It is important to take it widely. The bonding of diamond is usually performed by brazing. At this time, if the brazing surface (bonding surface) is narrow, the bonding strength cannot be increased, and the difference in thermal expansion between diamond and the material of the drill shaft is added. The problem of unexpected dropouts occurs.
[0027]
The present invention further provides a shape of the drill tip of the single crystal diamond having such a wide brazing surface so that a strong fixing performance can be obtained, and further, an effect of a reaming effect and a dimensioning operation. The goal is to obtain
[0028]
[Means for Solving the Problems]
The above problem is solved by the following means. That is,
"Solution of the First Invention"
A first solution of the present invention is a drill having a single crystal diamond having a hexahedral diamond as a rough ore at the tip thereof, and the tip of the single crystal diamond has a diagonal angle of 90 ± 10 degrees. And the center line of the pyramid coincides with one crystal axis and the drill axis of the single crystal diamond, and when projected onto a plane perpendicular to the axis of the drill axis, The projected image of the ridge line of the quadrangular pyramid makes an angle of 2 degrees or more and 15 degrees or less with respect to the remaining two crystal axes.
[0029]
"Second Solution of the Second Invention"
According to a second aspect of the present invention, there is provided a drill having the single crystal diamond according to the first aspect at the tip thereof, wherein the single crystal diamond is brazed to a drill axis by a {100} plane.
[0030]
"Solution means according to the third aspect of the invention"
Solution of the third invention, in the drill having a single-crystal diamond at the tip of the first or fifth invention, to 85 degrees from 65 degrees relative to the plane including the central axis and the ridge line of the drill The clearance angle dropped by the surface forming the angle in the range is formed.
[0031]
"Solving means of the fourth invention"
Solution of the fourth invention, in the drill having a single crystal diamond of the invention from the first to third in the tip, at the bottom corners of the quadrangular pyramid of the single crystal diamond, a drill shaft A parallel rake plane is formed by a plane that forms an angle in the range of 65 to 85 degrees with respect to the plane including the central axis of the drill and the ridge line, thereby forming a negative rake angle.
[0032]
"Solving means of the fifth aspect of the invention"
Solution of the fifth invention, in the drill having a single crystal diamond from the first to fourth in the tip, in which the drill was drill comprising small diameter drills and micro drills.
[0033]
Furthermore, herein, in the drill having a single crystal diamond from the first to fifth in the tip, to the material of the drill axis and the cemented carbide, that the material of the drill shaft and steel It is disclosed that the cylindrical surface of the drill shaft has a wear resistant layer of fine diamond and that the brazing of the single crystal diamond to the drill shaft is performed in an inert gas.
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
Earlier, FIGS. 1 and 2 show examples of the shape of a diamond to be produced or synthesized, and explained that it is rare that such a uniform shape is obtained. The single crystal diamond synthesized by the diamond synthesis method includes a relatively large amount of single crystal diamond having a relatively flat {100} face and a relatively flat shape as shown in FIG. The plane of this crystal has a wide {100} plane in the upper and lower directions and a {111} plane (hexahedral plane) connecting this plane and a narrow {100} plane between adjacent {111} planes (octahedral plane). It consists of faces. In this shape, the {110} plane shown in FIG. 2 does not appear.
[0035]
In this specification, since the outer surface is composed of the hexahedral surface and the octahedral surface as described above, for convenience, a single crystal diamond having this shape is referred to as a hexaoctahedral diamond. -Octahedral diamond 1 is used as a rough diamond at the tip of the drill.
[0036]
In FIG. 4, a part of the drill shaft 2 to which the hexa-octahedral diamond 1 is attached is shown by a dotted line. Further, for easy understanding, FIG. 4 shows a balanced one of the hexa-octahedral diamonds 1, but the actually used one is slightly distorted (upper and lower $ 100). ｝ The size of the surface is different). However, even in this case, the direction of each crystal plane is constant due to the nature of the crystal.
[0037]
FIGS. 5A and 5B show a top view and a side view from three directions of the hexa-octahedral diamond 1, respectively. FIG. 5A is a top view seen from the z-axis direction, and FIG. (C) is a view as seen from a direction in which one of the faces of the quadrangular pyramid formed by processing is seen straight, and (d) is two opposite ridges of the four ridges of the quadrangular pyramid. It is the figure which looked at from the front.
[0038]
In the embodiment of the present invention, the hexahedral diamond at the tip of the drill is brazed to the drill shaft 2 by the {100} plane below it. This hexaoctahedral diamond is polished to form a quadrangular pyramid that is the tip of a drill having the same axis as the drill axis, the four ridges of which are the octahedral ridges of the rough (the four {111} faces of the rough). A quadrangular pyramid is formed which is inclined by an angle α degrees (when projected onto the z-plane) with respect to each of the ridges a, b, c, d of the quadrangular pyramid to be formed.
[0039]
The angle α is more than 0 degree and 15 degrees or less, preferably 2 degrees or more and 15 degrees or less. The reason for setting this range is that when α is 0 degree, it becomes substantially impossible to machine since it coincides with the {111} plane especially when the opposite ridge angle described later is 90 degrees, and when 15 degrees or more, the same size is obtained. This is because the size of the drill tip polished and formed from the rough diamond becomes too small.
[0040]
FIG. 5D shows an example in which the diagonal angle of the formed quadrangular pyramid is 90 degrees, which is equal to the diagonal angle of the octahedral crystal. Therefore, at this time, the facing angle is 70 degrees 32 minutes, and (c) shows the half angle of 35 degrees 16 minutes.
[0041]
The drill angle with respect to the ridge can be selected in a range of 90 degrees ± 10 degrees. The reason for selecting the conical angle in this range is that if the conical angle exceeds 100 degrees, the biting of the drill becomes worse, and the accuracy of the center position of the drilled hole deteriorates. This is because the parts are easily chipped and the life is shortened. That is, the range is determined in consideration of the balance between the life and the accuracy.
[0042]
FIG. 6 shows the hexagonal octahedral diamond 1 thus formed into a quadrangular pyramid and the drill shaft 2 to which it is fixed.
[0043]
In other words, the quadrangular pyramid has a centerline of the quadrangular pyramid that coincides with one crystal axis and the drill axis of the single crystal diamond, and further, when projected onto a plane perpendicular to the axis of the drill axis, The projected image of the ridge line of the quadrangular pyramid makes an angle of 5 to 15 degrees with respect to the remaining two crystal axes. The facing angle of this quadrangular pyramid is about 70 degrees 32 minutes ± 10 degrees.
[0044]
The drill shaft 2 has a normal shank 15 (see FIG. 11) for gripping the drill, and in the embodiment of the present invention, it can be used as a drill in this state. However, since the ridge defining the diameter of the drilled hole forms a sharp corner, the inner surface of the drilled hole is roughened. Then, in order to adjust the diameter of the hole to be drilled, the corner 8 (corner of the bottom of the pyramid) of the enclosing part 5 in FIG. 6 is dropped by one or two planes.
[0045]
FIG. 7 shows this polished surface (the processed surface processed by the dotted line 6 indicated by the clearance angle γ to reduce the angle 8). This polished surface is a surface 6 parallel to the drill axis. FIG. 8 is an enlarged view of a main part of a corner portion. As a result of dropping this corner, a surface indicated by hatching 9 appears. In this state, it can be used as a drill, but the ridges 10, 11 appearing there still form the corners 13, 14, so that the corners 13, 14 are further dropped. That is, the surface at this time is shown in FIG. 9, and this corner is further dropped by the surface parallel to the drill axis, which is hatched.
[0046]
The ridge line 12 appears as a cutting edge, and is a ridge line formed by the intersection of two surfaces parallel to the drill axis. Not only the diameter of the hole is determined, but also the cutting edge reams the inner surface of the hole to improve the surface roughness of the hole.
[0047]
FIG. 10 is an enlarged view of a main part of a corner as viewed from the drill axis direction at this time, and the two surfaces with the corners dropped form a clearance angle and a rake angle (negative), respectively. . The clearance angle and the rake angle are each in a range of 5 ° to 25 ° (a range of 65 ° to 85 ° with respect to the plane including the center axis and the ridge line of the drill).
[0048]
In other words, the base corner of the four-sided pyramid of the single crystal diamond is a plane parallel to the drill axis and at an angle in the range of 65 to 85 degrees with respect to the plane including the ridge and the central axis of the drill. And a negative rake angle dropped by a plane that forms an angle in the range of 65 to 85 degrees with respect to the plane including the center axis and the ridge line of the drill.
[0049]
FIG. 11 is an overall view of a drill having a completed single crystal diamond according to the embodiment of the present invention at the tip. Except for the tip portion, it is preferable to have the same size and configuration as a normal micro drill. The drill shaft 2 uses carbide as its material, and can prevent the drill shaft 2 from being thinned by cutting chips and becoming thin. On the other hand, carbide is fragile and easily breaks.Therefore, the drill shaft is made of high toughness steel. Can be provided. This wear-resistant layer can be provided even when the drill shaft is made of a super hard material.
[0050]
After the rough of the hexa-octahedral diamond 1 is fixed (brazed) to the drill shaft 2 in advance, it can be processed into a quadrangular pyramid as described above, or the rough of the hexa-octahedral diamond 1 can be converted to another After being attached to the shaft and processed into a quadrangular pyramid, it is also possible to remove it and fix it to the drill shaft. In the former case, it is not necessary to strictly align the tip of the drill with the shank as in the latter case, so that productivity is improved. It is better to perform brazing in an inert gas.
[0051]
Although the octahedral surface, that is, the {111} surface is a surface that can hardly be machined as described above, in the embodiment of the present invention, each of the conical surfaces (tip surfaces) of the drill is close to the {111} surface, although it is close to the {111} surface. Since they are angularly shifted, they can be worked, and have the effect of having appropriate wear resistance.
[0052]
It is also conceivable that each of the conical surfaces is constituted by a surface close to the {110} surface. However, in comparison with this case, in the embodiment of the present invention, a large drill tip can be obtained for a rough having the same size. There is an advantage that a relatively small and relatively inexpensive rough hexahedral diamond can be used.
[0053]
And, in the rough of hexa-octahedral diamond 1, the {100} plane, where the widest surface is apt to appear, can secure a wide brazing surface when brazing to the drill shaft 2 and can firmly adhere, so that the tip of the drill falls off. It becomes difficult.
[0054]
Further, the drill according to the embodiment of the present invention has a sharp pointed tip, so that it does not deviate from the center when biting into the workpiece, thereby enabling hole drilling with high positional accuracy.
[0055]
【The invention's effect】
According to the present invention, since the single-crystal diamond pyramid face at the tip of the drill has a face which is close to the {111} face but deviated from the {111} face, the highest abrasion resistance can be imparted within a workable range. This has the effect of extending the life. Furthermore, since the drilling radius and the reaming effect can be obtained by dropping the corner of the cone bottom, the drill according to the present invention has high diameter accuracy and good inner surface roughness. Holes can be drilled.
[0056]
The present invention considers the shape (shape in consideration of the crystal axis direction) so that a small single crystal diamond can be used to obtain a diamond drill of the same size. Is provided. Further, the surface to be brazed (fixed surface) to the drill shaft can be widened, and the single crystal diamond is less likely to fall off even when subjected to a cutting force.
[0057]
Since the drill of the present invention has a four-sided pyramid, it has a good bite and can form a hole with high positional accuracy. Further, since the drill shaft has a fine diamond layer having high wear resistance, the drill can be used during use. This has the effect that the problem of the shaft becoming thinner is less likely to occur. One of the present inventions has the effect that the toughness is high and the breakage is small because the drill shaft is made of steel.
[0058]
In the present invention, the brazing between the single crystal diamond and the drill shaft is performed in an inert gas. Therefore, there is an effect that the brazing strength does not decrease due to the influence of the air.
[0059]
In the present invention, since an edge parallel to the drilling axis for reaming is formed at the corner of the bottom of the quadrangular pyramid, the diameter of the hole can be adjusted, and the inner surface of the drilled hole can be favorably machined. it can.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a crystal plane of a diamond crystal and a crystal outline formed by the plane.
FIG. 2 is a bird's-eye view showing an example of a diamond single crystal in which all three crystal planes appear.
FIG. 3 is a graph showing the relationship between crystal orientation and wear (workability), and showing that workability differs depending on the orientation.
FIG. 4 is a bird's-eye view showing a hexa-octahedral diamond and a part of a drill shaft to which the diamond is attached.
FIGS. 5A and 5B are a top view and a side view from three directions of the hexa-octahedral diamond 1, respectively. FIG. 5A is a top view as viewed from the z-axis direction, and FIG. 5B is a side view as viewed from the y-axis direction. FIG. 2C is a view of one of the surfaces of the quadrangular pyramid formed by the processing viewed from a direction in which it is seen as a straight line. FIG. FIG.
FIG. 6 is a bird's-eye view showing a hexahedral diamond in which a tetragonal pyramid surface is created and a drill axis to which the diamond is fixed.
FIG. 7 is an explanatory diagram showing a processing surface to be processed by a dotted line indicated by a clearance angle γ for reducing a corner, and a processing radius of a drill to be obtained;
FIG. 8 is an enlarged view of a main part of a corner portion in FIG. 7;
9 is a diagram showing a surface (hatching) that appears when a corner shown in FIG. 8 is dropped.
FIG. 10 is an enlarged view of a main part of a corner portion viewed from a drill axis direction.
FIG. 11 is an overall view of a drill having a tip of a completed single crystal diamond according to an embodiment of the present invention.
[Explanation of symbols]
1 Hexahedral diamond 2 Drill axis 3 Faces 8, 13, 14 Angles 10, 11, 12 Edges (ridges)
12 shank

Claims (5)

A drill having, at its tip, a single-crystal diamond made of a hexa-octahedral diamond as a raw material , wherein the tip of the single-crystal diamond has a quadrangular pyramid surface having a diagonal angle of 90 ° ± 10 °. The center line of the quadrangular pyramid coincides with one crystal axis and the drill axis of the single crystal diamond, and when projected on a plane perpendicular to the axis of the drill axis, the projected image of the ridge line of the quadrangular pyramid remains. A drill having a single-crystal diamond at its tip, which is at an angle of 2 degrees or more and 15 degrees or less with respect to two crystal axes . A drill having a single-crystal diamond at its tip according to claim 1,
A drill having a single crystal diamond at its tip, wherein the single crystal diamond is brazed to a drill axis by a {100} plane. A drill having a single-crystal diamond at its tip according to claim 1 or claim 2 ,
At the bottom corner of the quadrangular pyramid of the single crystal diamond, a plane parallel to the drill axis and at an angle in the range of 65 to 85 degrees with respect to the plane including the center axis of the drill and the ridge line is formed. A drill having a single-crystal diamond at its tip, wherein a dropped relief angle is formed. A drill having a single-crystal diamond at its tip according to any one of claims 1 to 3 ,
The bottom corner of the quadrangular pyramid of the single crystal diamond is dropped by a plane parallel to the drill axis and at an angle in the range of 65 to 85 degrees with respect to a plane including the ridge and the central axis of the drill. A drill having a single-crystal diamond at its tip, characterized in that a formed negative rake angle is formed. A drill according to any one of claims 1 to 4 , having a single crystal diamond at its tip, wherein the drill is a drill including a small diameter drill and a micro drill. A drill at the tip.

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