JP6089672B2 - Multi-wire electric discharge machining apparatus and machining method thereof. - Google Patents

Description

  The present invention relates to a multi-wire electric discharge machining apparatus and a machining method thereof.

  A wire saw is known as an apparatus for slicing a silicon ingot into a large number of thin pieces. Recently, there is a multi-wire electric discharge machining apparatus that uses a multi-wire to slice a member into a thin plate by an electric discharge machining technique.

  In the technology for slicing a silicon ingot into a thin piece, for example, in the prior art document 1, in order to sufficiently supply the machining liquid to the slicing surface, the work is tilted and the silicon ingot is sliced so as to come into contact with the wire. A wire saw technique is disclosed.

JP 2011-104746 A

  In the wire electric discharge machining technique, discharge traces are randomly generated on the machining surface depending on the relative position of the traveling wire and the machining surface, and the workpiece is cut by the accumulated discharge traces.

  Especially when the work surface at the start of electric discharge machining is a uniform surface, if the area of the work surface where electric discharge from the wire is likely to occur is large, there are many places where discharge marks are generated on the work surface. Therefore, there arises a problem that a discharge location where discharge starts at a stable wire interval cannot be determined. However, the prior art does not disclose any means for solving this problem.

  An object of this invention is to provide the structure which can make each thickness of the sliced workpiece uniform by defining a discharge start location so that discharge may occur easily.

The present invention is a wire electric discharge machining apparatus for slicing a workpiece with an electric wire array arranged side by side, and traveling means for traveling the wire row in the same direction, and slicing the workpiece with the electric discharge. In such a case, an arrangement means for arranging the workpiece so that two sides of the workpiece to be square intersect the wire row direction and face the wire row, and a power consumption value for electric discharge machining Detecting means for detecting the change of the workpiece , and before slicing the workpiece, the placement means arranges the workpiece so that one of the two sides is farther from the wire row. And holding the gap between the workpiece and the wire row , detecting that the power consumption value is constant after slicing the workpiece and starting the slicing, For the surface of the Characterized by holding the machining gap of the change the arrangement of the workpiece as machined surface of the engineering product is substantially parallel to the workpiece and the wire row.

Further, the before starting a slice of the workpiece, one of said locating means is farther in front Symbol two sides, front and the side of the travel to Ruwa unpleasant column progresses before Symbol workpiece serial, characterized in that for holding the machining gap between the workpiece and the prior SL wire array.

Also, the difference in the inter-electrode distance until verge ear columns of one of the two sides of the workpiece held by said locating means prior to starting a slice of the workpiece and its other is, wire It is characterized in that either one of the diameters of 2 mm or more or 1 mm or more is satisfied.

  According to the present invention, it is possible to provide a mechanism capable of making the thickness of each sliced workpiece uniform by determining the discharge start location so that the discharge is likely to occur.

It is a figure which shows the front view of the multi-wire electric discharge machining system in this invention. It is a figure which shows the front view of the multi-wire electric discharge machining apparatus in this invention. It is a figure which shows the side view of the electric power feeding unit in this invention. It is a figure which shows the side view of the electric discharge machining part in this invention. It is a figure which shows the side view of the sub guide roller in this invention. It is a figure which shows the front view of the sub guide roller in this invention. It is a figure which shows the front view of the running direction of the wire in this invention. It is a figure showing the positional relationship of the wire and workpiece in a prior art. It is a figure showing the positional relationship of the wire and workpiece in this invention. It is a figure showing the positional relationship of the wire and workpiece in this invention. It is a figure showing the positional relationship of the wire and workpiece in this invention. It is a figure showing the positional relationship of the wire and workpiece in this invention. It is the figure which showed the processing result (photograph) of the silicon ingot processed with the multi-wire electric discharge processing system in this invention.

  Referring to FIG.

  FIG. 1 is an external view of a multi-wire electric discharge machining system according to an embodiment of the present invention as viewed from the front. The configuration of each mechanism shown in FIG. 1 is an example, and it goes without saying that there are various configuration examples depending on the purpose and application.

FIG. 1 is a diagram showing a configuration of a multi-wire electric discharge machining system according to the present invention. The multi-wire electric discharge machining system includes a multi-wire electric discharge machining device 1, a power supply device 2, and a machining fluid supply device 50.
The multi-wire electric discharge machining system can slice a workpiece (workpiece) into thin pieces at intervals of a plurality of wires (wire electrodes) arranged in parallel by electric discharge.

  Reference numeral 1 denotes a multi-wire electric discharge machining apparatus. In FIG. 1, a work feeding unit 3 driven by a servo motor is provided on the upper part of the work 105, and the work 105 can be moved in the vertical direction. In the present invention, the workpiece 105 is sent downward, and electric discharge machining is performed between the workpiece 105 and the wire 103.

  Reference numeral 2 denotes a power supply device. In FIG. 2, the discharge servo control unit that controls the servo motor keeps the discharge gap (distance between the poles) constant in order to efficiently generate discharge according to the state of discharge. By controlling, the workpiece is positioned and electric discharge machining is advanced.

The machining power supply unit 400 supplies a discharge power supply pulse for electric discharge machining to the wire 103, performs detection adapted to a state such as a short circuit generated in the electric discharge machining unit, and sends a discharge gap control signal to the discharge servo control unit. Supply.
Reference numeral 50 denotes a machining fluid supply device that circulates and supplies machining fluid necessary for removal of machining chips (machining scraps) generated by electric discharge machining and an electric discharge phenomenon to an electric discharge machining unit.

  Furthermore, the specific resistance or electric conductivity (1 μS to 250 μS) by the ion exchange resin is managed, and the liquid temperature (around 20 ° C.) is also managed for cooling. Water is mainly used as the working fluid.

  Reference numerals 8 and 9 denote main guide rollers. Grooves corresponding to a predetermined pitch (interval) and number (number of processed pieces) are formed on the surface of the main guide roller so that the wire can run at a uniform interval. The necessary number of wires from the wire supply bobbin (IN) are wound around the two main guide rollers and sent to the take-up bobbin (OUT). Electrical discharge machining is performed at a wire traveling speed of about 100 m / min to 1000 m / min.

That is, the two main guide rollers rotate in the same rotational direction and at the same rotational speed, so that one wire 103 sent from the wire feeding portion reaches the outer periphery of the main guide rollers (two) at the maximum. By winding about 2000 times, a plurality of (up to about 2000) wires 103 arranged in parallel at a predetermined wire interval (pitch) in the electric discharge machining portion travel in the same direction and at the same speed. I am letting.
Thus, the wire traveling at a high speed is a first factor for vibrating the wire 103.

  The main guide rollers 8 and 9 have a plurality of rows of grooves for attaching the wires 103 uniformly and at a constant interval, and the wires 103 are attached to the grooves. Then, the main guide rollers 8 and 9 are all rotated together to the right (or left), so that the wire 103 is juxtaposed and travels.

The wire 103 is attached to the main guide rollers 8 and 9 and forms a row of a plurality of wires arranged side by side above and below the main guide rollers 8 and 9.
A machining current flows through the wire 103 from the power supply 104 to the electric discharge machining portion, and functions as a wire electrode that generates electric discharge in the electric discharge machining portion.

The wire 103 is a single connected wire, which is fed out from a bobbin (IN) (not shown) and is wound around the outer surface of the main guide roller while being spirally wound around the outer surface of the main guide roller. It is wound around a bobbin (OUT) (not shown).
The multi-wire electric discharge machining apparatus 1 is connected to the power supply apparatus 2 via an electric wire 513 and performs electric discharge machining with electric power supplied from the power supply apparatus 2.

  The multi-wire electric discharge machine 1 includes a housing 15 that functions as a base of the multi-wire electric discharge machine 1, a block 20 that is installed in an upper portion of the housing 15, a work feeding unit 3, and an adhesive unit 4. A silicon ingot 105, a processing tank 6, a main guide roller 8, a wire 103, a main guide roller 9, a power supply unit 10, and a power supply 104.

The machining tank 6 stores ion-exchanged water managed to have a specific resistance (electrical conductivity) within a predetermined range and a machining liquid that is circulated and supplied to a position (electric discharge machining unit) where the wire 103 and the workpiece 105 are close to each other.
The block 20 is joined to the work feeding unit 3. Further, the workpiece feeding unit 3 is bonded (bonded) by the silicon ingot 105 and the bonding unit 4.
The adhesive part 4 may be anything as long as it is for adhering (joining) the workpiece feeding part 3 and the silicon ingot 105. For example, a conductive adhesive is used.

The workpiece feeding unit 3 is a mechanism for moving the silicon ingot 105 bonded (bonded) by the bonding unit 4 in the vertical direction. The workpiece feeding unit 3 moves downward to move the silicon ingot 105 to the wire 103. It becomes possible to approach.
FIG. 2 will be described.
FIG. 2 is an enlarged view within a dotted line 16 frame shown in FIG.
The main guide roller has a cylindrical structure in which a metal bar is used at the center and the outside of the metal bar is covered with resin.

An area near the center between the two main guide rollers is provided with a power supply unit 10 for supplying a discharge power pulse from the machining power supply, and is in contact with the wire 103 to supply power.
Since the material of the power supply 104 is required to be highly resistant to mechanical wear and conductive, a cemented carbide is used.
A work feeding unit 3 is provided in an upper area substantially at the center of the two main guide rollers.
A processing tank 6 is provided approximately at the center between the two main guide rollers.
FIG. 3 will be described.
FIG. 3 shows an enlarged view of the power supply unit 10 in which the power supply 104 is in contact with the wire 103.
In this embodiment, the wires 103 (10) are in contact with the power supply 104 (1).

In FIG. 3, the number of wires 103 that are in contact with ten wires 103 is shown as one, but the number of wires that come into contact with each of the number of wires 103 and the total number of the supplied electrons depends on the required number. Needless to say, increase it.
FIG. 4 will be described.
FIG. 4 shows an enlarged view of a portion where the wire 103 traveling with the workpiece 105 immersed in the machining fluid is subjected to electric discharge machining.

All the wires 103 are discharged simultaneously to the workpiece 105, and the workpiece feeding unit 3 gradually moves the workpiece 105 downward, so that the slicing process proceeds at the intervals of the wires.
Here, the interval between the wires 103 (wire pitch) is about 0.3 mm (300 μm).
In the present embodiment, a silicon ingot that is a rectangular parallelepiped will be described as an example of the processing material (work).

  The processing tank 6 is a container for storing a processing liquid. The working fluid is, for example, deionized water having a high resistance value. As shown in FIG. 4, when the workpiece 105 is immersed in the machining liquid and approaches the wire 103, the machining liquid enters the gap (between the electrodes) between the wire 103 and the silicon ingot 105, so that the wire 103 and the silicon ingot 105 When a discharge current flows through the machining liquid that has entered the gap, a normal discharge is generated in the gap between the wire 103 and the silicon ingot 105, and the silicon ingot 105 can be discharged.

In addition, the wire 103 is a conductor, and the power supply 104 of the power supply unit 10 to which power is supplied from the power supply device 2 and the wire 103 are in direct contact, so that the supplied power is supplied from the power supply 104 to the wire 103. Applied. (The power supply 104 is applying power to the wire 103.)
Then, discharge occurs between the electrodes of the wire 103 and the silicon ingot 105 to form a thin silicon wafer.
The machining fluid supplied from the machining fluid supply device circulates in the machining tank, and a water flow is generated by the circulation. A water flow is also generated by running the wire in the machining fluid.

As described above, the water flow of the machining liquid in the machining tank further amplifies the vibration of the wire 103 as well as the vibration caused by the high-speed wire travel, and causes a large cutting margin in the region where the workpiece is discharged. .
FIG. 5 will be described.
FIG. 5 shows an enlarged view of the sub guide roller 701.
The sub guide roller has a cylindrical structure in which a metal bar 801 is used at the center and the outside of the metal bar is covered with a resin 802.
A number of V-shaped grooves 803 for dispersing a plurality of wires running on the surface of the resin 802 at an equal interval of 0.3 mm (300 μm) are machined.
FIG. 6 will be described.
FIG. 6 shows an enlarged view of the sub guide roller 701.
Reference numerals 701 and 702 denote a pair of sub guide rollers which are the same.
FIG. 7 will be described.
The pair of sub guide rollers rotate in conjunction with the traveling of the plurality of wires when the plurality of wire electrodes traveling in the same direction come into contact with the grooves.
The pair of sub guide rollers are disposed on both sides of the workpiece.
The pair of sub guide rollers are arranged inside a plurality of wire electrodes wound around the outer circumferences of the plurality of main guide rollers.

  Reference numerals 703 and 704 denote mechanisms for adjusting the sub guide rollers in the vertical direction in order to adjust the contact (approach) distance between the sub guide rollers and the plurality of traveling wire electrodes (adjustment means). The contact (approach) distance by the adjusting means can be changed to an arbitrary distance, and the contact (approach) distance can be fixed.

  By moving (lifting) each sub-guide roller upward, the tension of the plurality of wire electrodes that are traveling is increased, so the tension of the plurality of wire electrodes that are wound around the outer periphery of the plurality of main guide rollers Can be adjusted collectively from the inside, and can be made less susceptible to the effects of high-speed wire travel and water flow that cause vibration.

However, if the sub guide rollers are moved excessively upward, the machining liquid does not enter the gap (between the electrodes) between the wire 103 and the silicon ingot 105 as shown in FIG. And the height at which the machining fluid enters the gap (between the electrodes) between the silicon ingot 105 becomes the upper limit (limit) of the adjusting means.
FIG. 8 will be described.
It is a schematic arrangement | positioning figure showing the positional relationship of the wire 103 and the workpiece 105 in a prior art.

Since multiple wires run almost parallel to the machined surface, the distance between the workpiece and the wire is almost uniform across the machined surface, so that discharge is likely to occur anywhere on the machined surface. Become.
FIG. 9 will be described.
1 is a schematic layout diagram (first embodiment) showing a positional relationship between a wire 103 and a workpiece 105 in the present invention.

  Since multiple wires are running at an angle to the machining surface, the distance between the workpiece and the pole due to the wire is not uniform over the entire machining surface, and discharge is likely to occur where the distance between the poles is close. Become.

In the present embodiment, the processing surface of the workpiece 105 is set at a predetermined angle θ1 so that the distance between the wire and the wire approaching side (IN) is farther with respect to the surface formed by a plurality of traveling wires. This is a case where the work piece is fixed to the fixed angle adjusting table 902 so as to be inclined only.
As a result, the workpiece 105 starts to be processed from the corner (discharge start portion) on the side (OUT) from which the wire is discharged.

  In order to slice the workpiece, the workpiece feeding unit 3 is arranged so as to intersect and face a plurality of wires on which two sides of the workpiece 105 having a rectangular shape (cuboid) travel.

  Further, by the fixed angle adjustment base 902, the workpiece 105 having a rectangular shape is arranged so that one of the two sides (IN and OUT corners) is further away from the traveling plurality of wires, Processing is proceeding in a state in which the gap between the workpiece 105 having a square shape and a plurality of traveling wires is maintained. (Placement means).

The difference in the distance between the poles from one side of the two sides held by the arrangement means to the other side of the wire and the other side of the wire must satisfy at least one of the diameter of the wire at least twice or at least 1 mm. Is preferred.
FIG. 10 will be described.

  Contrary to the case of FIG. 9, the workpiece 105 is inclined with respect to the surface of the plurality of traveling wires so that the side from which the wire is discharged (OUT) is farther from the pole. This is a fixed case.

  Even when the workpiece is tilted so that the wire discharge side (OUT) is further away from the wire as shown in FIG. 10, the machining is started from the corner (discharge start portion). Therefore, it is possible to process even in this positional relationship.

However, in the case of FIG. 10, the inclination angle (θ2) formed by the angle at which machining is started and the traveling direction of the wire is larger than θ1 in the case of FIG. 9. It is desirable to increase the distance between the wire entry side shown in 9 and the wire electrode.
FIG. 11 will be described.
FIG. 11 is another schematic layout diagram (second embodiment) showing the positional relationship between the wire 103 and the workpiece 105 in the present invention.

  Since multiple wires are running at an angle to the machining surface, the distance between the workpiece and the pole due to the wire is not uniform over the entire machining surface, and discharge is likely to occur where the distance between the poles is close. Become.

In this embodiment, the workpiece is fixed to a fixed angle adjustment unit (servo motor) 901 in order to support the workpiece. The processing surface of the workpiece can be tilted with respect to the surface of the wire by rotating the servo motor by a predetermined angle θ1.
In order to slice the workpiece, the workpiece feeding unit 3 is arranged so as to intersect and face a plurality of wires on which two sides of the workpiece 105 having a square shape travel.

  Further, the fixed angle adjusting unit 901 arranges the angular workpiece 105 so that one of the two sides is further away from the traveling wires, and the traveling angle with the angular workpiece 105 is plural. Processing is proceeding with the gap between the wire and the wire held. (Placement means).

  When the wire is further processed to a stable state against vibration and the wire enters the workpiece (after slicing is started), the servomotor rotates backward by a predetermined angle θ1 to the surface of the wire. It can return so that the processed surface of a to-be-processed object may become substantially parallel.

  That is, the servo motor 901 changes the position of the angular work piece so that it is farther away before the start of slicing, and travels with the angular work piece so that it is not far away. It is also possible to maintain the gap between the plurality of wires (the gap changing means).

  In other words, the angle between the workpiece and the wire electrode at the start of machining is to determine the discharge start location so that electric discharge is likely to occur. It is more effective to return the wire electrodes in parallel.

  Moreover, it can switch to parallel by detecting the change of the average value of the electric power consumption (discharge current value) concerning electric discharge machining as a judgment standard at the time of returning a work to be parallel to a wire.

  This is because only a part of the workpiece is electrodischarge machined at the start of machining, so the amount of power required for machining is less than the amount of power used to machine the entire surface of the workpiece and is consumed as the machining proceeds. The amount of power increases.

When the processing of the entire surface of the workpiece starts, the power consumption basically becomes constant, so that the constant state can be detected and the positional relationship between the wire electrode and the workpiece can be returned in parallel.
FIG. 12 will be described.
FIG. 12 is another schematic layout diagram (third embodiment) showing the positional relationship between the wire 103 and the workpiece 105 in the present invention.

The sub guide rollers 701 and 702 are installed at positions where the workpiece is sandwiched in order to give tension to the wire for the purpose of stabilizing the vibration of the wire, and are fixed and used so as to slightly lift the wire (upper figure). By making a difference (below) between the wire entry side and the wire discharge side in the lifting amounts of both the sub-guides, it is possible to achieve a positional relationship similar to that when the workpiece is inclined relative to the wire. it can.
In order to slice the workpiece, the workpiece feeding unit 3 is arranged so as to intersect and face a plurality of wires on which two sides of the workpiece 105 having a square shape travel.

Further, a plurality of wires that travel so that one of the two sides is further away from the plurality of wires that are traveling by the sub guide roller 701, and the plurality of wires that travel with the workpiece 105 that is square. Processing is proceeding in a state where the gap between and is maintained. (Placement means).
In this case as well, it is possible to start processing from the wire entry side and to start processing from the wire discharge side.
FIG. 13 will be described.

(A) is a processing result of the silicon ingot which is the workpiece 105 when the opposing surface of the workpiece and the traveling surface of the wire are arranged so that θ1 becomes 0 ° (parallel).
From the processing results, the variation (maximum value-minimum value) of the three processing widths was 8.18 micrometers.
(B) is a processing result of the workpiece 105 when the opposing surface of the workpiece and the traveling surface of the wire are arranged so that θ1 becomes 1 ° (inclination).

  In order to arrange the facing surface of the workpiece and the traveling surface of the wire so that θ1 is 1 ° (inclination), an angle with a side length of 156 mm is obtained by the formula of length × tan (1 °). In the case of a workpiece, it may be arranged so that the distance between one pole on two sides is more than about 2.7 mm.

  From the processing results, the variation (maximum value-minimum value) of the three processing widths was 2.04 micrometers. According to this result, since the variation in the three machining widths is smaller when the opposing surface of the workpiece and the traveling surface of the wire are arranged so that θ1 is 1 ° (inclination), θ1 is 0 ° ( The thickness of each of the sliced workpieces can be made uniform as compared to the case where the opposing surface of the workpiece and the traveling surface of the wire are arranged so as to be parallel.

  Looking further at the processing results, the average value of the three processing widths is about 7% when the opposing surface of the workpiece and the traveling surface of the wire are arranged so that θ1 is 1 ° (inclination). Since the size is reduced, the processing area of the silicon ingot, which is the portion that does not become the finally sliced substrate (the cutting margin), can also be reduced.

  In addition, the ingot such as silicon and SiC (silicon carbide) sliced by the multi-wire electric discharge machining system of the present invention can be used as a substrate for a semiconductor device or a substrate for a solar cell.

DESCRIPTION OF SYMBOLS 1 Multi-wire electric discharge machine 2 Power supply device 8, 9 Main roller 50 Processing liquid supply apparatus 103 Wire electrode 104 Electric supply 105 Work 701 Sub guide roller (arrangement means)
702 Sub guide roller (placement means)
901 Fixed angle adjustment unit (placement means)
902 Fixed angle adjustment stand (placement means)

Claims (4)

A wire electric discharge machining apparatus for slicing a workpiece by electric discharge with a parallel wire array,
Traveling means for traveling the wire rows in the same direction;
When slicing the work piece by the electric discharge, the work piece is arranged so that two sides of the work piece having a square shape intersect the wire row direction and face the wire row. Means,
Detection means for detecting a change in the power consumption value for electric discharge machining;
With
Before slicing the workpiece, the placement means arranges the workpiece so that one of the two sides is further away from the wire row, and the workpiece and the wire row Hold the gap,
Detecting that the power consumption value is constant after starting the slicing of the workpiece, the placement means is arranged so that the processing surface of the workpiece is substantially parallel to the surface of the wire row A wire electrical discharge machining apparatus characterized in that an arrangement of workpieces is changed to hold a gap between the workpiece and the wire row.   Before starting the slicing of the workpiece, the workpiece and the wire are arranged such that the arrangement means becomes farther on the two sides and the traveling wire row advances to the workpiece. The wire electrical discharge machining apparatus according to claim 1, wherein the gap between the electrodes is held.   Before starting to slice the workpiece, the difference between the distances between the poles of one of the two sides of the workpiece and the other held by the positioning means to the wire row is 2 of the diameter of the wire. The wire electric discharge machining apparatus according to claim 1, wherein the wire electric discharge machining apparatus satisfies at least one of double or 1 mm or more. A processing method in a wire electric discharge machining apparatus comprising running means for slicing a workpiece by electric discharge with wire rows arranged in parallel, and running the wire rows in the same direction,
When slicing the work piece by the electric discharge, the work piece is arranged so that two sides of the work piece having a square shape intersect the wire row direction and face the wire row. Including a process and a detection process for detecting a change in a power consumption value for electrical discharge machining ,
In the placement step before slicing the workpiece, the workpiece is placed so that one of the two sides is further away from the wire row, and the gap between the workpiece and the wire row Hold
When it is detected in the detection step that the power consumption value is constant after starting the slicing of the workpiece, in the arrangement step, the processing surface of the workpiece is substantially parallel to the surface of the wire row. A processing method comprising: changing an arrangement of the workpiece to hold a gap between the workpiece and the wire row.

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