JPH0860348A - Formation of coating layer on tool - Google Patents

Abstract

PURPOSE: To provide a method for uniformly coating the blade edge of a tool having the sharp blade edge with a hard film of the nitride, carbide or carbonitride of metal in order to improve the wear resistance, etc., of this blade edge. CONSTITUTION: The intensity of the electric fields around the base material of the tool generated when bias potential is impressed on the base material of the tool at the time of coating the tool T having the sharp blade edge with the hard film by an ion plating method are made uniform by enclosing the required range of the tool by a conductive perforated bias control jig 5. As a result, the coating layer having a smooth surface and uniform film thickness is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to a sharp tool such as a microdrill for which a hard film such as a metal nitride is used to improve the wear resistance of the cutting edge. The present invention relates to a method for uniformly coating the same.

[0002]

2. Description of the Related Art As a method for coating a hard film on a tool-shaped substrate, a thermal CVD method utilizing a thermochemical reaction and an ion plating method, which is a kind of PVD method, are widely adopted. There is. Among them, an ion plating method having a low coating temperature is generally used for a tool base material such as a drill having a sharp tip end to suppress thermal influence on the tool base material. The feature of the ion plating method is that in order to increase the adhesion of the coating layer to the extent that there is no practical problem, a bias potential is applied to the tool substrate to accelerate the ionized vapor deposition particles and form a film. It is to form a film. Therefore, even with a tool base material having a complicated shape, the vapor deposition particles are likely to wrap around due to the application of this bias potential, so that the so-called wraparound property is improved.

However, for example, when such a tool base material is used for coating a tool (microdrill) having a very sharp cutting edge having a diameter of 0.1 to 2.0 mm, the sharp cutting edge is generated by the bias potential. The electric field tends to concentrate on the part.
Therefore, there arises a problem that the vapor-deposited particles having an electric charge are more concentrated in a portion where the electric field is concentrated. As a result, vapor deposition particles excessively accumulate on the sharp edge,
Since the electric charges are concentrated, the cutting edge portion is heated at a higher temperature and extremely higher than the other portions due to the energy, and abnormal growth of crystals occurs. That is, so-called nodules occur. As a result, the thickness of the film coated on the cutting edge portion becomes extremely thick, and the sharpness of the tool deteriorates. Furthermore, in the ion plating method, particles (referred to as droplets) in which a large number of vapor-deposited particles collectively grow may occur in rare cases. In some cases, the droplets may fly to the tool base material and adhere to the cutting edge portion and its vicinity to cause the above-mentioned problem. As a result, when the coated microdrill is used to make a hole in, for example, a printed circuit board, a smooth hole cannot be formed. In addition, smear phenomenon (the insulating substrate constituting the printed circuit board is melted by frictional heat and adheres to the underlying copper foil or the like) is likely to occur. The above-mentioned problems similarly occur with tools other than micro drills, which have sharp cutting edges.

The present invention was devised in order to solve the above-mentioned problems. The purpose of the present invention is to deposit vapor deposition particles on the sharp edge of the tool in the ion plating method, and to make the deposition thick on the edge of the tool. It is an object of the present invention to provide a method for forming a coating layer capable of preventing deposition.

[0005]

In order to achieve the above object, the present invention provides a metal nitride, a carbide or a carbonitride of a hard film on the surface of a tool substrate by an ion plating method in which a negative bias voltage is applied. In the method of coating a hard film, in order to prevent the metal nitride, carbide or carbonitride coated particles from concentrating on a sharp tool tip and thickly depositing on the tip, an electric field around the tool is applied to the tool. It is configured to cover while making the strength uniform. As a method to equalize the electric field strength around the tool generated when a negative bias voltage is applied to the tool, a method of surrounding the required range of the tool with a conductive porous bias control jig at the time of hard film coating is effective. Target. In addition, as the metal forming the nitride, carbide or carbonitride coated particles, generally, a group IVa metal (Ti, Zr, Hf), Va
Group metals (V, Nb, Ta) and VIa group metals (Cr, M)
o, W) is any one metal selected from the group consisting of metals.

The present invention will be described below in detail with reference to the accompanying drawings. The hard film of metal nitride, carbide or carbonitride is formed by an ion plating method, but this ion plating method is not particularly limited and various methods can be adopted. For example, those having an electron beam evaporation source, those having a hollow cathode discharge plasma beam evaporation source, those having an arc discharge evaporation source, etc., all of which apply a negative bias potential to the substrate (tool substrate) on which the film is formed. It is applied. Specifically, for example, a method of ionizing vaporized particles from the vaporization source by introducing a gas above the vaporization source and arranging an ionization electrode in the vicinity of the vaporization source to apply a positive voltage to cause arc discharge. Is simple. Instead of this, an arc discharge type ion plating method, that is, a method of arranging an ionization electrode in the vicinity of an evaporation source and further disposing a thermionic emission filament between the evaporation source and the ionization electrode to emit thermoelectrons , Reactive ion plating method using an activation nozzle, that is, a thermoelectron emission filament is arranged near the evaporation source to emit thermoelectrons, and an activation nozzle to which a positive voltage is applied is arranged at the opposite position. A method of introducing an ionized gas, such as an arc-like plasma ion plating method, that is, a method of arranging a thermionic emission filament and an ionization electrode opposite to each other above the evaporation source and introducing the gas from a different position. It can also be used. Also,
A magnetic field excitation type ion plating method can also be used. This method does not require special consideration for the exhaust system or evaporation source, can easily form high-density plasma in a high vacuum, and easily forms a metal nitride, carbide, or carbonitride hard film. There is an advantage that it can be obtained at a relatively high speed. In any of the ion plating methods, the film forming conditions are
Generally, the following conditions may be appropriately selected according to the film quality to be formed. That is, when forming a nitride or a carbide, gas pressure: 5 × 1/10 ² to 1 × 1/10 ⁴ Torr, anode voltage: 30 to 80 V, anode current: 10 to 80
A, cathode heating current: 30 to 60 A, bias power output: 500 W or less, electron gun power: 1.5 to 4.0 KW.

FIG. 1 shows an outline of the magnetic field excitation type ion plating method. Reference numeral 1 is a vacuum chamber, 2 is an evaporation source provided below the vacuum chamber 1, and a crucible for containing a metal B, A means for heating and evaporating this, for example, an electron gun and a resistance heater 21 are provided. The evaporation source may be a multi-source evaporation mechanism. As the metal B, a group IVa metal (T
i, Zr, Hf), a group Va metal (V, Nb, Ta), and a group VIa metal (Cr, Mo, W), selected from the group consisting of metals. Reference numeral 3 denotes a holder to which the tool T to be coated is detachably attached, and is arranged at a position facing the evaporation source 2 in the vacuum chamber 1. Holder 3 is an external bias power supply 30
Connected to a negative DC voltage or high frequency voltage,
Further, it is heated by the heater 35 for heating if necessary.
Reference numeral 4 denotes a gas nozzle, and a reaction gas such as nitrogen gas is supplied by a flow rate adjusting valve 41 provided in an introduction pipe extending outside the vacuum chamber 1.
A hydrocarbon gas or a mixed gas thereof is introduced into the vacuum chamber 1. 6 is a cathode for thermionic emission, 7 is an anode facing it, 8a and 8b are in the same horizontal plane as the cathode 6 and the anode 7, and in the same direction as the direction of the electric field formed by the cathode 6 and the anode 7. A pair of magnets arranged so that a parallel magnetic field is formed, and 9 are auxiliary anodes arranged on the anode side, which constitute a plasma generation mechanism, and the entire plasma generation mechanism is provided in the vacuum chamber 1. It is provided at an intermediate position between the evaporation source 2 and the holder 3, for example, at a position separated from the evaporation source 2 by 150 mm or more. The distance between the cathode 6 and the anode 7 is preferably widened to widen the plasma space, and an example thereof is 200 to 500 mm. The cathode 6 is composed of a filament made of a hot cathode material such as W, Ta, W / Th, and emits thermoelectrons by being electrically heated by a power source 60. The anode 7 may be connected to the magnet 8b on the side facing the cathode 6 to use the magnet itself as an electrode, or may be configured by separately installing an electrode on the front surface side of the magnet 8b. 7, a positive DC or AC voltage with respect to the ground potential, for example, 40 to 70
A DC voltage of V is applied by the power supply 71. Magnet 8
a and 8b face each other, and the strength of the magnetic field is 20 to 20 at the midpoint between the two magnets in order to form high-density plasma.
It is preferably 40 Oe.

When a hard film is formed by this ion plating apparatus, a tool T as a work is attached to the holder 3, and the work is heated to a required temperature by the heater 35 as needed, and at the same time, the inside of the vacuum chamber 1 is heated. Evacuate. Thereafter, the heater 35 is stopped, a gas such as argon is introduced from the gas nozzle 4 into the vacuum chamber 1, ion bombardment is performed for a required time, and then film formation is performed. In this film forming process, a gas of a predetermined component is introduced into the vacuum chamber 1 by the gas nozzle 4, a high positive voltage is applied to the auxiliary anode 9, the cathode 6 is energized, and a positive voltage is applied to the anode 7. As a result, plasma is formed together with the parallel magnetic fields of the magnets 8a and 8b. In this state, the heating means 21 of the evaporation source 2 is operated to evaporate the metal B as an evaporation material.
The vaporized particles ascend and pass through the plasma to be attached to the work, while the negative ions applied to the work via the holder 3 or the self-bias voltage generated by the high frequency attracts the gas ions generated in the plasma.
It collides with a base material or a work. As a result, a hard film of metal nitride, carbide or carbonitride as a reaction product film is deposited on the substrate or the work T.

Since the cathode 6 and the anode 7 are arranged in a parallel magnetic field, the magnetic field and the electric field cause the thermoelectrons emitted from the cathode 6 to make an electric field while performing cyclotron motion due to a velocity component in a direction different from the direction of the magnetic field. Direction, that is, toward the anode 7. Gas is introduced into the vacuum chamber 1 in advance, and ionization occurs when the molecules of the gas collide with the accelerated electrons as described above, and the gas molecules are ionized to form plasma. This plasma is densified by the parallel magnetic field, thereby canceling the negative space charge near the cathode due to thermionic emission, and a current having a saturation current value of about the hot cathode (filament) flows from the cathode to the anode. Since the heat radiation current is proportional to the temperature of the cathode, it can easily flow about 20 A. At this time, since the initial velocity of thermions is sufficiently smaller than the magnetic field and the electric field, the electron flow is almost in the form of a sheet beam. Thus, a high-density plasma space can be stably formed between the magnets 8a and 8b. In the case of the arc discharge method, an ionization electrode may be arranged in the vicinity of the evaporation source 2 in FIG. 1, and the pair of magnets 8a and 8b and the auxiliary anode 9 on the anode side may be removed.

In any of the ion plating methods, the tool base material is generally attached to a holder 3 having a revolving jig so as to form a uniform coating layer around the tool. An example of this holder 3 is shown in FIG. The structure of this auto-revolution jig is arbitrary, but in this example, a gear 31 that can be fitted and fixed around the holder 3, a actuator 33 that drives this, and an annular rail 32 with a gear that meshes with the gear.
It has. This figure also shows a power supply 30 for applying a bias potential. The holder 3 has a bias control jig 5 surrounding the tool T. The bias control jig 5 equalizes the electric field strength around the tool generated when a bias is applied to the tool T from the bias power source 30, so that the film can be appropriately formed even on the sharp edge of the tool T. Is a means to do.

That is, in the ion plating method, it is essential to form a film by applying a negative bias potential to the tool T as described above. Therefore, the electric charge is concentrated on the cutting edge portion of the tool T. This results in a thicker coating of the film on the cutting edge for the reasons mentioned above. Therefore, in the present invention, by controlling the electric field strength around the tool T generated when a bias is applied to be uniform, it is possible to prevent the concentration of electric charges and form a coating layer having a uniform film thickness. It is what makes me.

From this, the bias control jig 5 is made of a conductive material, is porous, and has a shape corresponding to the shape of the target tool T, and a part thereof is in contact with the holder 1. is necessary. As a concrete example,
Examples thereof include a wire mesh made of stainless steel or copper or the like, or a wire mesh having a shape similar to this, or the like. In this case, if the pore size is too small, the penetration of vapor-deposited particles or gas ions is hindered, the absolute amount required for film formation is insufficient, and the film formation rate decreases, while if the pore size is too large, the equipotential effect is poor. Therefore, it is easy for electric charges to concentrate. Therefore, the preferable conditions are the hole diameter (opening of the eye) of 1 to 5 mm, the hole interval (mesh wire diameter).
Is 0.2 to 1.0 mm. When the distance 1 between the bias control jig 5 and the tool surface is too large, the same potential effect is lost, and the vapor deposition particles passing through the holes are concentrated. The throwing power to the tool becomes poor and the film becomes a mesh pattern. Therefore, the distance 1 is usually 1.0 to 6.0 mm, preferably 3 to 4 mm.

If the appropriate bias control jig 2 as described above is used, the gas ions A and the vapor deposition particles B that react during the formation of the hard film are influenced by the bias control jig 5 and accelerated as shown in FIG. It is released and enters the internal space from the hole 50 by inertial force. For this reason, the density of the vapor deposition particles flying to the tool substrate is made uniform, and a coating layer having a uniform film thickness is formed.

[0014]

EXAMPLES Examples of the present invention will be described below. The present invention was applied to coat a microdrill with a titanium nitride (TiN) film. The target drill has a total length of 3 made of WC-Co cemented carbide.
7 mm, blade length 5 mm, drill diameter 0.4 mmφ. For this drill, while introducing a reactive gas above the electron beam evaporation source, an ionization electrode was placed near the evaporation source to apply a positive voltage to cause arc discharge, and to evaporate particles from the evaporation source. A high vacuum arc discharge type ion plating device for ionization was used to coat the periphery with a TiN film. At this time, Ti was used as the evaporation source and nitrogen gas was used as the reaction gas. The drill was attached to a holder having a revolving jig similar to the one schematically shown in FIG. 2, and was surrounded by a stainless mesh cylinder having a diameter of 4 mmφ as a bias control jig. The mesh opening was 2 mm and the wire diameter was 0.5 mm, and the stainless mesh cylinder had a length reaching 20 mm ahead from the drill tip. The film formation was performed by bombarding a tool fixed to a holder and then evaporating Ti having a purity of 99.9% from an electron beam evaporation source. The film forming conditions at this time were as follows: electron beam output: -8.5 kV, 250 mA, ionization electrode voltage: 3
0 V, ionization current: 50 A, nitrogen gas pressure: 1 × 1 /
It was 10 ³ Torr, bias voltage: −300 V, and tool temperature: 350 ° C. The thickness of the obtained TiN coating layer was about 1.5 μm, and the film was uniformly formed on the main cutting edge of the drill, the corner and the margin. It is clear that this is because a uniform film could be formed by the effect of the bias control jig. Then, the cutting characteristics of the obtained coated drill were examined. C for the drilling device in this test
An NC drilling machine was used. The work material is a glass epoxy four-layer board (NEMA grade, FR-4).
The cutting conditions were a drill rotation speed: 75000 rpm, a Z-axis feed rate: 2.4 m / min, and a drilling pitch: 2.5 mm, and a test was performed in which two glass epoxy substrates were stacked to form a through hole. No cutting fluid was used during drilling. A drill with a TiN coating layer was also obtained under the same conditions except that the bias control jig was not used, and the cutting characteristics of the drill were also examined under the above conditions. As a result, the micro drill coated with the TiN film by the conventional method (a method that does not use the bias control jig and covers under the same conditions) has an average life of the uncoated drill (smear phenomenon occurs and becomes unusable). Although it was somewhat improved from a certain 3000 hits (times), the average life reached about 4000 hits (times). However, in some cases, the life was shorter than 3000 hits was also observed. On the other hand, in the case of the microdrill coated by the method of the present invention, about 10,000 hits (times)
It was confirmed that the life was improved by about 2 to 3 times. This is because the TiN film C is formed on the outermost part D of the tool edge portion with a uniform film thickness without causing the nodule phenomenon, as shown schematically in FIG. It is clear that it depends. On the other hand, in the conventional method, as shown in an enlarged schematic view of the cutting edge portion in FIG. 5, a TiN nodule C ′ is generated at the cutting edge, which results in poor sharpness and falling off, which is satisfactory. It seems that the life was not improved.

In the above method, in addition to the above-mentioned TiN formed by the ion plating method, a group IVa metal (Zr, Hf) and a group Va metal (V, Nb, Ta) are used.
Or VIa group metal (Cr, Mo, W) nitrides, carbides or carbonitrides such as HfN, CrN, ZrN, TiC,
Of course, it can be applied to the coating of a thin film such as TiCN. Further, the above method can of course be applied to thin film coating on a tool having a sharp cutting edge other than the micro drill as described above.

[0016]

According to claim 1 of the present invention described above, evaporation is performed in order to equalize the electric field strength around the tool generated when a bias potential is applied to the tool base material when forming the coating layer. The vaporized particles with a charge generated from the source concentrate on the cutting edge of a sharp tool, and large size droplets adhere to the cutting edge of the tool and its vicinity to improve the sharpness of the tool. It is possible to obtain the excellent effect that it is possible to obtain a tool with good sharpness which is prevented from being lowered and has a coating layer having a smooth surface and excellent in film thickness uniformity. According to the second aspect, since the required range of the tool is surrounded by the conductive porous bias control jig, the excellent effect that the electric field strength around the tool can be easily realized at low cost can be obtained. .

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of an ion plating device used in a coating layer forming method of the present invention.

FIG. 2 is a side view showing a bias control jig used for ion plating in a used state.

FIG. 3 is an explanatory diagram showing an operation of a bias control jig.

FIG. 4 is an enlarged sectional view of a blade portion of a coated microdrill to which the present invention is applied.

FIG. 5 is an enlarged cross-sectional view of a cutting edge portion of a coated microdrill when a bias control jig is not used.

[Explanation of symbols]

 3 Holder 5 Bias control jig 30 Bias power supply 50 Hole T Tool to be coated A Reactive gas ions B Evaporated particles C Hard film coating layer D Tool edge outermost

Claims (3)

[Claims] 1. A method for coating a hard film of a metal nitride, a carbide or a carbonitride on the surface of a tool substrate by an ion plating method in which a negative bias voltage is applied, wherein the metal nitride is A tool characterized in that carbide or carbonitride coated particles are coated on the tool while making the electric field strength around the tool uniform in order to prevent the particles from being concentrated and sharply deposited on the sharp edge of the tool. Of forming a coating layer on the surface. 2. A method for equalizing the electric field strength around a tool generated when a negative bias voltage is applied to the tool,
The method for forming a coating layer according to claim 1, which is a method of surrounding a required range of the tool with a conductive porous bias control jig when coating a hard film. 3. The metal forming the nitride, carbide or carbonitride coated particles is a group IVa metal (Ti, Zr, Hf), Va.
Group metals (V, Nb, Ta) and VIa group metals (Cr, M)
The method for forming a coating layer on a tool according to any one of claims 1 to 2, wherein the coating layer is a metal selected from the group consisting of metals (o, W).