JP2000094221A - Electric discharge wire saw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a high electric discharge voltage for each cut wire portion by forming a plurality of wire portions to be cut by using one cutting wire. SOLUTION: This electric discharge wire saw is constructed in such a manner that a plurality of cut wire portions W1, W2, ..., are formed by winding a wire W to be cut on a plurality of guide rollers 24A, 24B, 26A and 26B, a work 28 is cut and fed while applying a voltage between each cut wire portion and the work 28, and then this is cut by electric discharging. In this case, by forming coil portions 51, ..., in the wire to be cut between the cut wire portions or setting a wire length to be sufficiently large so as to secure high impedance, the cut wire portions are insulated from each other on the appearance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge wire saw for performing electric discharge cutting of a work made of a conductive material such as low-resistance silicon with a cutting wire.

[0002]

2. Description of the Related Art Conventionally, as a cutting means for cutting a wafer from a cylindrical ingot, a wire saw using abrasive grains has been known. In this wire saw, a cutting wire wound between a plurality of guide rollers is driven at a high speed in the longitudinal direction while a workpiece is cut and fed to the wire, whereby a large number of thin pieces are simultaneously cut out from the workpiece. It is.

However, in such a wire saw, it is necessary to simultaneously supply a machining liquid (slurry) in which abrasive grains for machining are mixed to a plurality of cutting wire portions formed between guide rollers. Is not easy. Also,
Since the wire directly contacts the workpiece, the wire may be disconnected during cutting, and if such a disconnection occurs, it takes a long time to recover.

[0004] Further, with regard to the processing efficiency, in the above-mentioned conventional wire saw, it takes about 8 hours to cut out a wafer from an ingot having a diameter of 8 inches, and there is an increasing need to shorten the processing time.

[0005] In recent years, as a means for efficiently cutting a conductive work, a voltage is intermittently applied between the work and the cutting wire, and the work is applied to each cut wire portion by the principle of electric discharge machining. Development of a discharge type wire saw for cutting is in progress. (For example, Japanese Patent Application Laid-Open No.
719).

[0006]

In a conventional wire saw using abrasive grains, a plurality of cutting wire portions are formed by winding a single cutting wire around a plurality of guide rollers. The cutting wire portions are in a state of mutual conduction. Therefore, even if an attempt is made to individually apply a voltage to each cutting wire portion, this voltage is dispersed to the other cutting wire portions, so that it is very difficult to generate a high discharge voltage.

As a countermeasure, Japanese Patent Laid-Open Publication No. 9-2487
In Japanese Patent No. 19, a plurality of (three in the illustrated example) cutting wires 1, 2, 3 are prepared as shown in FIG. By winding a plurality of times (three times in the illustrated example) in between, a plurality of (three in the illustrated example) cutting wire portions 1a, 2a and 3a are formed for each cutting wire, and these are respectively formed. The workpiece 6 is cut and sent to the cutting wire portions 1a, 2a, 3a (moved to the far side in the figure), and the contacts 1b, 2b,
There is disclosed one in which a voltage is applied by bringing 3b into contact. However, even in this case, the voltage applied to each cutting wire is a plurality of cutting wire portions (for example, the voltage applied to the cutting wire 1 is three cutting wire portions 1).
a), there is a problem that the cutting efficiency is reduced to one third as compared with the case where only one cutting wire portion is applied with a voltage.

[0008] As means for securing high cutting efficiency, the same number of cutting wires as the required number of wire cutting portions are stretched (that is, only one wire cutting portion is formed with one cutting wire). It is conceivable to apply a voltage to each cutting wire while insulating the cutting wires, but in this case, an extremely large number of cutting wires are required, and the structure becomes complicated.

In view of such circumstances, the present invention can generate a high discharge voltage at each cutting wire portion while forming a large number of cutting wire portions by winding a cutting wire around a guide roller. It is an object of the present invention to provide a discharge type wire saw that can be used.

[0010]

As a means for solving the above-mentioned problems, the present invention provides a method for winding a cutting wire around a plurality of guide rollers to form a plurality of cutting wire portions with one cutting wire. A discharge wire saw that discharges and cuts the work at each cutting wire portion by cutting and feeding the work to each cutting wire portion while applying a voltage between each cutting wire portion and the work, ,
A voltage applying means for intermittently applying a voltage between the cutting wire portion and the work was provided for each cutting wire portion, and the cutting wire was coiled at a portion between the cutting wire portions. Things.

According to this configuration, since the coil-shaped portion is formed between the cut wire portions, an inductance and a wire resistance are obtained at the portion, and the combined impedance is increased. Thereby, the electrical insulation between the cutting wire portions is enhanced, and when a voltage is applied to each cutting wire portion, the discharge voltage is prevented from being dispersed to the cutting wire portion adjacent thereto, Or it is suppressed. As a result, it is possible to secure a high discharge voltage at each cutting wire portion while forming a plurality of cutting wire portions with a common cutting wire.

As means for forming the coil-shaped portion,
If the cutting wire is wound a plurality of times around a single guide roller at a portion between the cutting wire portions, a coil-shaped portion can be formed using an existing guide roller.

According to the present invention, even if the coil-shaped portion is not formed, the electrical insulation between the cut wire portions can be improved by increasing the wire length between the cut wire portions and increasing the impedance. It is. In this case, as a guide, when a voltage is applied to the cutting wire portion at a frequency of 50 kHz (estimated average value of the frequency used in electric discharge cutting), the applied voltage and the voltage distributed to the cutting wire portion adjacent thereto are applied. The wire length may be set so that the ratio of the wire length becomes 20% or less (more preferably, 10% or less). Further, by using a material having a high resistance (for example, a steel material) for the cutting wire, it is possible to obtain a sufficient impedance even if the wire length is equivalent to that of a conventional wire saw.

Here, if at least five guide rollers are provided and at least three guide rollers are wound around the zigzag cutting wire, a large wire length can be obtained with a compact structure. It is possible.

In the present invention, a plurality of cutting wires may be used. However, only one cutting wire is used, and the entire cutting wire portion is constituted by a single cutting wire. Most simplified and more effective.

As a specific structure for applying a voltage to each cutting wire portion, there is provided an electrode unit in which a plurality of voltage applying conductors are integrated while being insulated from each other.
If each conductor of the electrode unit is brought into contact with each of the cutting wire portions, the handling becomes simpler and assembly efficiency is improved as compared with a case where a plurality of conductors are individually arranged corresponding to each of the cutting wire portions. Get higher.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment according to the present invention is shown in FIGS.

The wire saw shown in FIG. 3 comprises a pair of wire feeding / winding devices 10A, 10B, pulleys 12A, 12B.
B, pulleys 14A, 14B, pulleys 16A, 16B, wire tension adjusting devices 18A, 18B, pulleys 22A, 22
B, and four guide rollers 24A, 24B, 26A,
26B. The guide rollers 24A and 24B are arranged at the same height position, and the guide rollers 26A and 26
B are disposed below the guide rollers 24A and 24B, respectively.
Is driven to rotate.

Each wire feeding / winding device 10A, 10
B is a bobbin 9A, 9B around which a cutting wire W is wound.
And bobbin drive motors 11A and 11
B. One wire feeding and winding device 1
The wire W fed out from the bobbin 9A of 0A is applied to the pulleys 12A, 14A, 16A, the pulley 20A of the wire tension adjusting device 18A, and the pulley 22A in this order, and further has guide rollers 24A, 24B having a large number of guide grooves.
After being wound many times around the outside of 26B, 26A, pulley 2
2B, the pulley 20B and the pulleys 16B, 14B and 12B of the wire tension adjusting device 18B are wound in this order, and are wound around the bobbin 9B of the other wire feeding / winding device 10B. An appropriate tension is applied to the wire W. The driving direction of the guide roller 26A by the driving motor 25 and the bobbin 9 by the bobbin driving motors 11A and 11B.
The wire W is fed out from the bobbin 9A by switching the rotation driving direction of the A, 9B between forward and reverse, and the bobbin 9B
And the state in which the wire W is unwound from the bobbin 9B and wound on the bobbin 9A.

That is, in this wire saw, as shown in FIG. 1, between the guide rollers 24A and 24B,
A large number of wire cutting portions constituted by a single cutting wire W (five cutting wire portions W1, W in FIG. 1 for convenience)
2, W3, W4, and W5) are reciprocated in the longitudinal direction while being stretched in parallel with each other.

As shown in FIG. 3, the guide rollers 24A,
Above the wire W stretched between the wires 24B, a work feeding device 30 for raising and lowering the columnar work 28 in a horizontal state.
Is provided. The work feed device 30 includes a work holding unit 32 and a work feed motor 34.
The work holding unit 32 holds the work 28 in a direction in which the axial direction of the work 28 matches the wire arrangement direction.
The work feed motor 34 integrally moves the work holding unit 32 and the work 28 up and down (that is, cuts and feeds) in combination with a ball screw (not shown).

Above the wire W stretched between the guide rollers 24A and 24B, a position between the work 28 and an electrode unit 40 which will be described later, which is located on the left and right sides of the work 28,
Processing fluid supply devices 36A and 36B are provided. These processing liquid supply devices 36A and 36B simultaneously supply a processing liquid (not a slurry) to each of the wires W driven at a high speed, and attach the processing liquid to the wires W.

Therefore, in this wire saw, a large number of cutting wire portions W1, W2, W3, W4, W5,... (FIG. 1) stretched between the guide rollers 24A, 24B are simultaneously driven at high speed in the longitudinal direction. In addition, while the machining fluid supplied to the wires W from the machining fluid supply devices 36A and 36B is supplied to the discharge cutting position, the workpiece W is cut and sent downward to the wires W. .

In this wire saw, the workpiece 28 and the respective cutting wire portions W1, W2, W3, W4, W5 are cut so as to discharge-discharge the workpiece 28 by the respective cutting wire portions W1, W2, W3, W4, W5,. ,... Are provided.

Specifically, in this wire saw, the work 2
The electrode units 40 (FIGS. 1 and 2) are disposed at positions before and after the position 8 and a voltage application circuit (FIG. 4) for applying a voltage between the work and the cutting wire portion through the electrode units 40 is provided. Provided.

As shown in FIG. 2, each electrode unit 40
Are arranged in such a manner that the same number of conductor blocks 41 and insulating blocks 42 as the cutting wire portions W1, W2,... Are alternately arranged.
The nuts 44 are tightened to the ends of the bolts 43 in a state in which the blocks 41 and 4 penetrate in the lateral direction, so that
2 are integrated. At the upper end of each conductor block 41, a conductor terminal 46a of a cable 46 derived from a voltage application circuit is connected by soldering 47, and as shown in FIG. , W2,..., The electrode unit 40 is disposed at a position where the electrode unit 40 comes into contact. In addition, each block 41,
A collar 45 is provided between 42 and the bolt 43 to fill the gap.

The electrode unit 40 does not necessarily need to be provided at the front and rear positions of the work 28, but may be provided only at the front position or the rear position.

FIG. 4 shows the voltage application circuit. In this figure, three cutting wire portions W1, W2, W
Only the circuit corresponding to No. 3 is shown.

In the figure, R1, R2, and R3 indicate discharge resistances generated between the cutting wire portions W1, W2, and W3 and the work 28, and each discharge resistance (ie, each cutting wire portion). Power supply E for voltage application
1, E2, and E3, and transistors T1, T2, and T3, which are switching elements that individually turn on and off the voltage supply from the power supplies E1, E2, and E3.

The bases of the transistors T1, T2, and T3 are connected to a controller 50. The output of a control signal from the controller 50 causes each transistor T1, T2, and T3 to output a signal.
1, T2 and T3 are individually turned on and off at a predetermined frequency, so that a pulse voltage having the frequency is applied to the work 2
8 and each cutting wire portion W1, W2, W3 is applied individually (that is, voltage is applied intermittently). Then, while applying a voltage at such a predetermined frequency, each cutting wire portion W1, W
By cutting and feeding the work 28 to 2,.
A large number of wafers are cut out from the work 28.

Further, as a feature of this wire saw, a wire portion between the cutting wire portions W1, W2, W3, W4,.
6B) is wound several times (five times in FIG. 1),
Coiled section 51, 52, ... are formed, these coiled portions 51 and 52, by ... formation of each cutting wire part W1, W2, W3, ... inductance _L 12, L ₂₃ between the adjacent, Are formed, and this inductance L
_12, L _23, ... and the resistor R ₁₂ of the wire itself, R _23, composed of ... and combined impedance Z _12, L _23, ... so that the (FIG. 4) is ensured.

Here, “sufficient impedance” means
It means an impedance sufficient to prevent a voltage applied to a specific cutting wire portion from being distributed to a cutting wire portion adjacent thereto and to secure a sufficient discharge voltage. In other words, by ensuring sufficient inductance between each cutting wire portion and making the cutting wire portions substantially electrically insulated, the voltage applied to a particular cutting wire portion will Sufficient discharge voltage is ensured by suppressing dispersion to adjacent cutting wire portions. The principle will be described in detail below using the circuit of FIG.

The RL circuit shown in the figure has characteristics of a low-pass filter. For example, paying attention to the voltage application circuit for the discharge resistor R1, its input voltage (power supply E1
The ratio of the leakage voltage (a voltage generated and distributed to the resistor R2 adjacent to the resistor R1) V2 to the voltage V1), that is, the voltage ratio Hv (= V2 / V1) is expressed by the following equation.

[0034]

(Equation 1)

The amplitude characteristic | Hv | at this time is represented by the following equation.

[0036]

(Equation 2)

As the amplitude | Hv | of this voltage ratio becomes smaller,
The rate at which the discharge voltage is dispersed to the adjacent cutting wire portion is small, and a sufficient discharge voltage can be secured. Since the voltage ratio amplitude | Hv | decreases as the impedance Z ₁₂ (combined impedance including the inductance L ₁₂ and the wire resistance R ₁₂ ) shown in Equation 1 increases, the impedance Z ₁₂ is increased (specifically, In the configuration of FIG. 1, the coil-shaped portions 51, 52,
53, to increase the inductance L ₁₂ Increase ... number of turns of, also by increasing the wire length increases the wire resistance R ₁₂₎ by, it is possible to ensure a high discharge voltage. That is, with this configuration, a single wire W
, A plurality of cutting wire portions W1, W2,... Are formed to have a simple structure, while each cutting wire portion W1, W2,.
A sufficient discharge voltage can be secured between the workpiece and the work 28.

FIG. 5 shows a second embodiment. In this embodiment, instead of forming the coiled portions 51, 52,... As in the first embodiment, the guide rollers 2
6A and 26B, both guide rollers 26A and 26
The guide rollers 27 are arranged at a position higher than B, and these guide the wires W in a zigzag manner over the guide rollers 26A, 27, 26B, thereby increasing the wire length between the cut wire portions and increasing the impedance. Like that.

Also in this configuration, by making the wire W meander, it is possible to secure a sufficient impedance between the cutting wire portions and to perform a trouble-free electric discharge cutting while keeping the compact structure.

The “wire length between the cutting wire portions” here means, for example, the work 2 as shown in FIG.
In the structure in which the electrode unit 40 or a contact corresponding thereto is provided before and after the electrode unit 8, the electrode rollers 40 (or the contact) on the rear side form the guide rollers 24A and 26A.
A, 26B, and 24B via the front electrode unit 40
(Or a contact) (in other words, from the length per circumference of the cutting wire W to the two electrode units 40).
(The length obtained by subtracting the distance between the contacts or the distance between the contacts). Further, when the electrode unit 40 (or the contact) is provided only at the front position or the rear position, it means the length per circumference of the cutting wire W.

The present invention can also adopt the following embodiments.

(1) FIG. 1 shows an embodiment using an electrode unit 40 in which conductive blocks 41 and insulating blocks 42 are alternately arranged. However, the present invention is not limited to this. The conductor contacts that individually contact each other may be installed independently of each other. However, when the unit is formed as described above, there is an advantage that the handling becomes easy and the assembling workability of the entire wire saw is improved.

(2) FIG. 1 shows a configuration in which the coiled portions 51, 52,... Are formed around the guide roller 26B, but the guide roller for winding the wire in a coil shape may be appropriately set. Alternatively, a wire may be wound in a coil shape around a plurality of guide rollers.

(3) The present invention is applicable to all wire saws having two or more guide rollers regardless of the number of guide rollers. Even when the wire length is increased as in the second embodiment, the number thereof can be set as appropriate, and it is not always necessary to extend the wire W in a zigzag shape. However, as shown in FIG. 5, by winding the wire W in at least three guide rollers in a zigzag manner, an advantage that a sufficient wire length can be secured with a compact structure can be obtained.

If a wire having a higher resistance (ie, a wire having a high impedance; for example, a steel wire such as a piano wire) than a wire (a wire made of molybdenum) is used as the cutting wire W, It is possible to obtain an impedance between the cut wire portions that is sufficient to secure a sufficient discharge voltage, even if the wire length is not particularly large compared to the wire saw.

[0046]

EXAMPLE 1) First Example In the structure shown in the first embodiment, a 300 mm diameter S10C in which a molybdenum wire having a diameter of 0.18 mm was used for the cutting wire W and a nonconductor was coated on the outer peripheral surface. By winding the wire W around the guide roller 26B five times in a non-contact state, the wire length between the cut wire portions was 6 m, the resistance was 10Ω, and the inductance of the coil portion was 50 μH. FIG. 6 shows the amplitude characteristic (the characteristic of | Hv |) with respect to the discharge frequency at this time.

As shown in the figure, according to this embodiment, 1 kHz
The amplitude characteristic can be suppressed to 20% or less at a discharge frequency of z or more, and the amplitude characteristic can be suppressed to 10% at an average frequency (50 kHz) generally used in discharge wire machining. Thus, it is possible to prevent discharge from occurring at the cutting wire portion adjacent to the cutting wire portion during discharge.

2) Second Example In the structure shown in the second embodiment, a molybdenum wire having a diameter of 0.18 mm was used as the cutting wire W, and the wire length between the cutting wire portions was set to 3.5 m. FIG. 7 shows amplitude characteristics with respect to the discharge frequency at this time.

As shown in the figure, according to this embodiment, the amplitude characteristic can be suppressed to 20% or less in the entire frequency range by increasing the resistance component of the cutting wire. Can be performed without any inconvenience.

3) Third Example In the structure shown in the third embodiment, a molybdenum wire having a diameter of 0.18 mm was used as the cutting wire W, and the wire length between the cutting wire portions was set to 7.0 m. FIG. 8 shows the amplitude characteristics with respect to the discharge frequency at this time.

As shown in the figure, according to this embodiment, it is possible to suppress the amplitude characteristic to 10% or less in the entire frequency range, and it is possible to perform cutting with higher efficiency than in the second embodiment. Can be.

4) Fourth Embodiment A structure equivalent to the conventional wire saw (the structure shown in FIG. 1 without the coiled portions 51, 52,...; The wire length between the cut wire portions is 2.5 m) In Example 2, a wire made of a piano wire having a higher resistance value per unit length was used instead of the molybdenum wire, and the amplitude characteristics with respect to the discharge frequency were examined. FIG. 9 shows the result. As shown, according to this embodiment, excellent amplitude characteristics (approximately 9
%).

[0053]

As described above, according to the present invention, a plurality of cutting wire portions are formed by a single cutting wire by winding a cutting wire around a plurality of guide rollers. Each time, while applying a voltage intermittently between the cutting wire portion and the workpiece, the cutting wire in the portion between the respective cutting wire portions into a coil shape,
Alternatively, by adopting a large wire length, the impedance is gained in the portion, and high electrical insulation is secured between the cutting wire portions, so that the number of cutting wires to be used is reduced and the structure is simplified. In addition, there is an effect that a high discharge voltage can be secured for each cutting wire portion and a cutting operation with high efficiency can be performed.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of a discharge type wire saw according to a first embodiment of the present invention.

FIG. 2 is a sectional front view of an electrode unit used for the wire saw.

FIG. 3 is an overall configuration diagram of the wire saw.

FIG. 4 is a diagram showing a voltage application circuit provided in the wire saw.

FIG. 5 is a front view showing a main part of a discharge type wire saw according to a second embodiment of the present invention.

FIG. 6 is a graph showing a relationship between a discharge frequency and an amplitude characteristic of the discharge type wire saw according to the first embodiment of the present invention.

FIG. 7 is a graph showing a relationship between a discharge frequency and an amplitude characteristic of a discharge type wire saw according to a second embodiment of the present invention.

FIG. 8 is a graph showing a relationship between a discharge frequency and an amplitude characteristic of a discharge type wire saw according to a third embodiment of the present invention.

FIG. 9 is a graph showing a relationship between a discharge frequency and an amplitude characteristic of a discharge type wire saw according to a fourth embodiment of the present invention.

FIG. 10 is a plan view showing a main part of a conventional discharge wire saw.

[Explanation of symbols]

 W Cutting wire W1, W2, W3, W4, W5 Cutting wire portion E1, E2, E3 Power supply (voltage applying means) T1, T2, T3 Transistor (voltage applying means) 24A, 24B, 26A, 26B, 27 Guide roller 28 Work 40 Electrode unit 41 Conductor block 42 Insulation block 51, 52, 53 Coiled part

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Keiji Kawaguchi 5-3-38 Ujinahigashi, Minami-ku, Hiroshima-shi F-term in TOYO ATEC Corporation (reference) 3C059 AA01 AB05 BA15 BA21 FB04

Claims (8)

[Claims] 1. A cutting wire is wound around a plurality of guide rollers to form a plurality of cutting wire portions with one cutting wire, and a voltage is applied between each cutting wire portion and a work. A discharge wire saw that discharges and cuts the work at each cutting wire portion by cutting and sending the work to each cutting wire portion, and for each cutting wire portion, between the cutting wire portion and the work. A voltage applying means for intermittently applying a voltage is provided,
A discharge wire saw, wherein the cutting wire is formed in a coil shape at a portion between the cutting wire portions. 2. The discharge wire saw according to claim 1, wherein a cutting wire is wound a plurality of times around a single guide roller at a portion between the cutting wire portions to form a coil. Discharge type wire saw. 3. A cutting wire is wound around a plurality of guide rollers to form a plurality of cutting wire portions with one cutting wire, and a voltage is applied between each cutting wire portion and the work. A discharge wire saw that discharges and cuts the work at each cutting wire portion by cutting and sending the work to each cutting wire portion, and for each cutting wire portion, between the cutting wire portion and the work. A voltage applying means for intermittently applying a voltage is provided,
When the wire length between the respective cutting wire portions is set to 20% or less, the ratio between the applied voltage and the voltage distributed to the cutting wire portion adjacent thereto when a voltage is applied to the cutting wire portion at a frequency of 50 kHz. A discharge type wire saw characterized by having a length set. 4. The discharge wire saw according to claim 3, wherein the wire length between the respective cutting wire portions is set such that when a voltage is applied to the cutting wire portion at a frequency of 50 kHz, the applied voltage and the cutting adjacent thereto are applied. A discharge type wire saw characterized in that the length of the wire saw is set so that the ratio of the voltage to the wire portion is 10% or less. 5. The discharge wire saw according to claim 3, further comprising five or more guide rollers, wherein at least three of the guide rollers have a cutting wire wound in a zigzag manner. Discharge type wire saw. 6. The discharge wire saw according to claim 3, wherein said wire is made of steel wire. 7. The discharge type wire saw according to claim 1, wherein the entire cutting wire portion is constituted by a single cutting wire. 8. The discharge wire saw according to claim 1, further comprising an electrode unit in which a plurality of conductors for voltage application are integrated while being insulated from each other. A discharge type wire saw, wherein the wire saw is in contact with each of the cutting wire portions.