JP2014166674A - Wire electric discharge machining device and wire electric discharge machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid that the time during which electric discharge machining is generated stably among electrodes varies depending on the number of actually-discharging wires even in a case that plural wires are electrified collectively.SOLUTION: A wire electric discharge machining device, in which a work-piece is made into slices with spacings of wires arranged in parallel by electric discharge machining, comprises plural main rollers which make the wires circle so as to travel in the same direction, a power-supply terminal which supplies machining electric power for electric discharge machining to the plural circling wires collectively, a work-piece feed part which feeds the work-piece to the direction approaching the circling wires, and a power source line which supplies machining electric power for electric discharge machining through electrifying the power-supply terminal and the work-piece. The power-supply terminal and the work-piece feed part are arranged inside of the wires circling around the plural main rollers, and a power source circuit for machining electric power using the power source line is connected to the power-supply terminal and the work-piece feed part respectively.

Description

  The present invention relates to a technique of a wire electric discharge machining apparatus and a wire electric discharge machining method.

Conventionally, a wire saw is known as an apparatus for slicing a silicon ingot into a large number of thin pieces. Recently, there is a technique for slicing a workpiece into a thin plate using a wire electric discharge machining technique.
For example, Patent Document 1 discloses a technique in which a workpiece feeding device is arranged among a plurality of guide rollers that run on a wire.

JP 2010-260151 A

  In multi-wire electric discharge machining, even if a machining power supply with the same pulse value and the same voltage value is fed to multiple wires at once, the occurrence of discharge between the poles differs for each wire, so the discharge current is always stable for each wire at the same time. It does not necessarily flow into the state.

  In Patent Document 1, if the rise time of the discharge current varies for each wire between the electrodes as described above, the machining energy after the discharge current rises changes, so the machining shape for each wire also varies. There is no disclosure regarding the problem of becoming.

  In the present invention, even when power is supplied to a plurality of wires at once, the machining energy is dependent on the number of wires that are actually discharged between the electrodes depending on the number of wires that are actually discharged. It aims at providing the mechanism which can prevent that it falls apart.

  The present invention is a wire electric discharge machining apparatus for slicing a workpiece by electric discharge machining at an interval between wires arranged side by side, and a plurality of main rollers for rotating the wire so as to run in the same direction, and the plurality of rotating To the wire of the electric power supply that collectively feeds the machining power source for the electric discharge machining, the work feeding unit that feeds the work in a direction approaching the wire to go around, and the electric supply and the work A power supply wiring for supplying a machining power for the electric discharge machining, and the power supply and the work feeding portion are arranged inside wires that circulate around the plurality of main rollers, and the power supply wiring is used. A power supply circuit of the machining power supply is connected to the power supply and the work feeding unit, respectively.

  In addition, it further includes a processing tank that is disposed outside the wire that circulates around the plurality of main rollers and stores a processing liquid, and the work feeding unit is disposed at a position lower than the power supply and the work to be held is The workpiece feeding section feeds the workpiece in a direction approaching the wire that circulates so as to be immersed in the machining fluid.

  In addition, the power supply wiring includes a coaxial wiring portion that includes an upstream cable and a downstream cable, and the included upstream or downstream cable branches from the coaxial wiring portion to supply the power or A single wire connected to one of the workpiece feed parts;

  And the length of the branched single wire portion is shorter than the length due to the interval between two wire running surfaces running in different directions formed on the outer periphery of the plurality of main rollers. To do.

  In addition, the power supply wiring includes a coaxial wiring portion that includes an upstream cable and a downstream cable, and the included upstream or downstream cable branches from the coaxial wiring portion to supply the power or A single wire portion connected to one of the workpiece feeding portions, and the length of the branched single wire portion is substantially equal to a distance that the workpiece feeding portion feeds in a direction approaching a wire that goes around the workpiece. It is characterized by being.

A discharge unit that discharges the machining power supplied to the wire in a batch to the workpiece; a power supply that supplies a machining power for the electric discharge to the power supply; and from the power supply to the power supply The power supply wiring has a resistance smaller than that of the wire from the power supply to the discharge portion.
In addition, the resistance of the power supply wiring from the power supply unit to the power supply is smaller than 0.1Ω.

  According to the present invention, even when power is supplied to a plurality of wires at once, electric discharge machining is stable between the electrodes, and machining energy can be prevented from varying depending on the number of wires. Can be provided.

The figure which looked at the wire electric discharge machining system of the present invention from the front. The figure which looked at the wire electric discharge machining apparatus of the present invention from the front. The figure which looked at the arrangement | positioning relationship between the electric power feeder and a wire in this invention from the side. The figure which showed arrangement | positioning of the electric circuit and various components in a prior art (single wire electric discharge machining system). The figure which showed arrangement | positioning of the electric circuit and various components in a prior art (multi-wire electric discharge machining system). The inter-electrode state (voltage and current) and the machining power supply pulse (ON / OFF) cycle in the present invention. The figure which showed arrangement | positioning of the electric circuit and various components in this invention. The figure which showed arrangement | positioning of the electric circuit and various components in this invention. The figure which showed arrangement | positioning of the electric circuit and various components in this invention. The figure which looked at the cable wiring at the time of arrange | positioning a power supply and a workpiece | work ideally from the front. The figure which showed the cable wiring at the time of arrange | positioning the electric power supply and the workpiece | work so far that wiring resistance mainly consisting of inductance was large. The figure which showed the cable wiring at the time of arrange | positioning an electric supply and a workpiece | work ideally so that the wiring resistance mainly consisting of inductance may become small. It is the result of having compared the rise time (tau) of discharge between several wires in this invention. It is the graph which compared the theoretical calculation value of the total processing current which changes with the increase in the number of the wires in this invention. It is the figure which divided the way of rising of the discharge current in the multi-wire electric discharge machining system of the present invention. The figure which looked at the modification of the arrangement | positioning relationship between the electric power feeding unit and work feeding part in this invention from the front. The figure which looked at the modification of the arrangement | positioning relationship between the electric power feeding unit and work feeding part in this invention from the front. The figure which looked at the modification of the arrangement | positioning relationship between the electric power feeding unit and work feeding part in this invention from the front.

  Referring to FIG.

  FIG. 1 is an external view of a multi-wire electric discharge machine 1 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 the configuration of a multi-wire electric discharge machining system (semiconductor substrate or solar cell substrate manufacturing 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 into thin pieces at intervals of a plurality of wires arranged in parallel by electric discharge.

  Reference numeral 1 denotes a multi-wire electric discharge machining apparatus. In FIG. 1, a workpiece feeding device 3 driven by a servo motor is provided on the upper portion of the wire 103 and can move the workpiece 105 in the vertical direction. In the present invention, the workpiece 105 is sent in the downward (gravity) direction, 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, a discharge servo control circuit that controls the servo motor controls the discharge gap to be a constant gap in order to efficiently generate discharge according to the state of discharge. Positioning is performed and electric discharge machining proceeds.

  The machining power supply circuit (FIG. 7) supplies a discharge pulse for electric discharge machining to the wire 103, performs control adapted to a state such as a short circuit occurring in the discharge gap, and outputs a discharge gap signal to the discharge servo control circuit. Supply.

  Reference numeral 50 denotes a machining liquid supply device. Reference numeral 50 denotes a machining chip necessary for cooling the electric discharge machining portion and removing machining chips (debris) to the workpiece 105 and the wire 103 by a pump and machining chips in the machining liquid. , Management of conductivity (1 μS to 250 μS) by ion exchange, and management of liquid temperature (around 20 ° C.). Although water is mainly used, electric discharge machining oil can also be used.

Reference numerals 8 and 9 denote main rollers. Grooves are formed on the main rollers at a predetermined pitch and number so as to be processed at a desired thickness, and two wires whose tension is controlled from the wire supply bobbin are provided. The necessary number of rolls are wound around one main roller and sent to a take-up bobbin. A wire speed of about 100 m / min to 900 m / min is used.
When the two main rollers rotate in the same direction and at the same speed,

One wire 103 sent from the Y feeding section can go around the outer circumference of the main roller (two), and a plurality of wires 103 arranged side by side can run in the same direction (running means).

As shown in FIG. 8, the wire 103 is a single connected wire. The wire 103 is fed from a bobbin (not shown) and fitted into a guide groove (not shown) on the outer peripheral surface of the main roller. After being wound spirally (approximately 2000 times at the maximum), it is wound around a bobbin (not shown).
The multi-wire electric discharge machine 1 is connected to the power supply unit 2 via the electric wire 513 and is operated by electric power supplied from the power supply unit 2.

As shown in FIG. 1, the multi-wire electric discharge machine 1 includes a block 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 block 15, and a work feeding device 3. And a bonding portion 4, a silicon ingot 105, a working liquid tank 6, a main roller 8, a wire 103, a main roller 9, a power supply unit 10, and a power supply 104.
FIG. 2 will be described.
FIG. 2 is an enlarged view within a dotted line 16 frame shown in FIG.

Reference numerals 8 and 9 denote main rollers. A wire 103 is wound around the main roller a plurality of times, and the wires 103 are aligned at a predetermined pitch according to a groove formed in the main roller.
The main roller has a structure in which metal is used in the center and the outside is covered with resin.

A power supply 104 attached to the power supply unit is disposed between the two main rollers and substantially above the center of the main rollers 8 and 9, and the power supply 104 is exposed upward. A machining power supply is collectively fed to a plurality of wires 103 traveling by bringing the surface into contact with the wires.
As shown in FIG. 3, the power supply 104 is in contact with 10 of the wires 103 to supply the discharge pulses (504 in FIG. 6) from the machining power source to the 10 wires.
The position where the power supply 104 is arranged is provided at a position (511L1 = 511L2) where the lengths of the wires are substantially equal from both ends of the silicon ingot 105.
The power supply 104 is required to be resistant to mechanical wear and have electrical conductivity, and a cemented carbide is used.

  A silicon ingot 105 attached to the work feeding device 3 is disposed between the two main rollers and substantially below the center of the main rollers 8 and 9. Slicing progresses by sending it downward.

  A processing tank 6 is provided below the main roller, and the wire 103 and the silicon ingot 105 are immersed to cool the electric discharge machining portion and remove the machining chip. The processing tank 6 is for storing the processing liquid and immersing the fed workpiece.

  As shown in FIG. 3, the number of wires 104 that contact 10 wires is shown as one, but the number of wires per the number of electrons and the total number of electrons are increased according to the required number. Needless to say.

The block 20 is joined to the work feeding device 3. Further, the workpiece feeding unit 3 is bonded (bonded) to the silicon ingot 105 (work) and the bonding unit 4.
In this embodiment, a silicon ingot 105 will be described as an example of a processing material (workpiece).

  The bonding part 4 may be anything as long as it is for bonding (joining) the work feeding device 3 and the silicon ingot 105 (work). For example, a conductive adhesive is used.

The workpiece feeding unit 3 is a device having a mechanism for moving the silicon ingot 105 bonded (bonded) by the bonding unit 4 in the vertical direction, and the workpiece feeding unit 3 is moved downward (gravity) while holding the workpiece 105. It is possible to bring the silicon ingot 105 closer to the direction of the wire 103 by moving in the direction).
The work feeding unit 3 is disposed at a position lower than the power supply 104.
The workpiece feeding unit 3 feeds the workpiece 105 in a direction approaching the wire that goes around the workpiece 105 so that the workpiece 105 to be held is immersed in the machining liquid.
The processing liquid tank 6 is a container for storing the processing liquid, and is disposed outside the wire that goes around the plurality of main rollers (8, 9).

The working fluid is, for example, deionized water having a high resistance value. By providing the machining liquid between the wire 103 and the silicon ingot 105, a discharge occurs between the wire 103 and the silicon ingot 105, and the silicon ingot 105 can be shaved.

The main rollers 8 and 9 are formed with a plurality of rows of grooves for attaching the wires 103, and the wires 103 are attached to the grooves. Then, the main roller 8, 9 rotates to the right or left, so that the wire 103 travels.
As shown in FIG. 2, the wire 103 is attached to the main rollers 8 and 9, and forms a wire row on the upper side and the lower side of the main rollers 8 and 9.

  In addition, the wire 103 is a conductor, and the supplied voltage is supplied from the power supply 104 to the wire 103 by contacting the wire 103 with the power supply 104 of the power supply unit 10 supplied with the voltage from the power supply unit 2. To be applied. (The power supply 104 applies a voltage to the wire 103.)

Then, electric discharge occurs between the wire 103 and the silicon ingot 105, and the silicon ingot 105 is shaved (electric discharge machining is performed), so that a thin plate silicon (silicon wafer) can be formed.
FIG. 3 will be described.
FIG. 3 shows an enlarged view of the power supply 104.
The power supply 104 (1 piece) is in contact with the wire 103 (10 pieces).
The distance between the wires 103 (wire pitch) is about 0.3 mm.
FIG. 4 will be described.
FIG. 4 is a diagram showing an electric circuit 400 with individual power feeding that feeds a machining current individually for each wire, which is a conventional method.

  Reference numeral 401 denotes a machining power source (Vm). This is a machining voltage set to supply a current necessary for electric discharge machining. Vm can be set to an arbitrary machining voltage in the range of 60V to 150V.

Reference numeral 402 denotes a machining power source (Vs). It is an induced voltage set to induce discharge. Furthermore, it is also used for the purpose of monitoring the state of the interelectrode voltage (interelectrode current) between the wire and the workpiece. Vs can be set to any induced voltage between 60V and 300V.
Reference numeral 403 denotes a transistor (Tr2). The processing power source Vm is switched between ON (conductive) state and OFF (non-conductive) state by switching.
Reference numeral 404 denotes a transistor (Tr1). The processing power supply Vs is switched between ON (conductive) state and OFF (non-conductive) state by switching.

  Reference numeral 405 denotes a resistance (Rm) of the machining current limiting resistor. By setting a fixed resistance value, each wire current (Iw) and inter-electrode discharge current (Ig) are limited. Rm can be set to an arbitrary resistance value of 1Ω to 100Ω. That is, when Vm = 60V (volt), Vg = 30V, and Rm = 10Ω, Iw (Ig) = (60V−30V) / 10Ω = 3A (ampere).

  In the above calculation formula, the voltage drop from the machining power source (Vm) to the feeding point (power supply) is 30 V, but the voltage drop from the feeding point to the discharge point due to the wire resistance (Rw) is not considered. .

  That is, in the case of the conventional individual power feeding method, the value of the machining current Iw is determined by the resistance Rm of the machining current limiting resistor, so that a desired wire current or discharge current (Ig) can be obtained for each wire. Is set so that the wire resistance Rw has a relationship of Rm> Rw.

Reference numeral 406 denotes an induced current limiting resistor (Rs). By setting a fixed resistance value, the induced current that induces discharge is limited. Rs can be set to an arbitrary resistance value of 1Ω to 100Ω.
Reference numeral 407 denotes an interelectrode voltage (Vg). This is an inter-electrode discharge voltage applied between the wire 103 and the workpiece 105 (between the electrodes) during discharge.
Reference numeral 408 denotes an interelectrode current (Ig). This is an inter-electrode discharge current that flows between the wire 103 and the workpiece 105 during discharge.
Reference numeral 410 denotes a machining current (Iw) supplied individually for each wire.
FIG. 5 will be described.
FIG. 5 is a diagram in which an electric circuit 400 with individual power feeding that feeds a machining current individually for each wire according to the conventional method feeds a plurality of wires.
Reference numeral 409 denotes a wire resistance (Rw) indicating the resistance of each wire.
Reference numeral 204 denotes an individual power supply. Electric discharge machining is performed by applying a machining voltage pulse from two individual supply electrons provided in the vicinity of both ends of the silicon ingot 105.
The same number of power supply circuits 400 as the number of wires 103 to be wound are connected.

  FIG. 6 shows changes in the interelectrode discharge voltage (Vgn) and interelectrode discharge current (Ign) and ON / OFF operations (timing charts) of Tr1 and Tr2 according to the present invention. The horizontal axis of the graph is time.

First, the transistor Tr1503 is turned on and an induced voltage is applied. At this time, since the wire 103 and the workpiece 105 (between the electrodes) are insulated, the discharge current between the electrodes hardly flows. After that, when the discharge current starts to flow and the discharge is started, the voltage Vgn drops, and when the discharge start is detected and Tr2 is turned on, a large discharge current is obtained. Tr2 is turned off after a predetermined time has elapsed. A series of operations is repeated again after a predetermined time has elapsed after turning off Tr2.
FIG. 7 will be described.

FIG. 7 is a diagram showing a relationship between the electric circuit 2 and the wire electric discharge machining apparatus 1 in batch feeding that feeds a machining current to a plurality of wires (10) in the present invention. The state where the machining current, the wire current, and the inter-electrode discharge current are flowing is shown.
FIG. 7 shows an equivalent circuit of the electric circuit 2 shown in FIG.

If the conventional electric circuit 400 shown in FIG. 4 is introduced as it is into an electric circuit for batch feeding that feeds machining current to a plurality of wires (10 wires) as a whole, between the machining power source and the feeding point. In order to control the machining current, instead of the current limiting resistor Rm405, Rm is set to 10 so that the machining current of the total (10 times) of the wire current supplied to the plurality of wires (10 wires) is supplied. What is necessary is just to install the current limiting resistor of the resistance value divided by the book (the number of times of winding the main rollers 8 and 9) between the machining power source and the feeding point.
First, a case where Rm / 10 having such a fixed resistance value is installed between the machining power supply and the power supply will be described.

  When the discharge state occurs uniformly and simultaneously between all 10 wires and the workpiece, the discharge current is evenly distributed over the 10 wires, so that the fixed resistance value (Rm / 10) Since a discharge current according to the above is supplied between each wire and the workpiece, supply of an excessive discharge current does not cause a problem.

  However, when the discharge state is not uniform between all ten wires and the workpiece, the wire current corresponding to the fixed resistance value (Rm / 10) is in the discharge state. Therefore, supply of excessive wire current becomes a problem. That is, when only one of the ten wires is in a discharge state, one wire and a wire current that is 10 times the wire current to be supplied to the workpiece are The wire is broken by being supplied to the workpiece.

Reference numeral 505 denotes an impedance (resistance) of the wiring 513. This is an upstream cable connected to the negative side of the machining power supply (Vmn). Processing power is supplied from the processing power supply unit (Vmn) to the power supply 104.
Reference numeral 520 denotes an impedance (resistance) of the wiring 514. This is a downstream cable connected to the processing power supply (Vmn) plus side.

  The resistance value Rmn 505 of the wiring 513 of the present invention does not fix the resistance value to a predetermined value as in the conventional processing current limiting resistor, but only when one of the 10 wires is in a discharge state. Even if it exists, the mechanism which can be controlled so that resistance value fluctuates according to the number which became the discharge state is provided.

  Furthermore, by changing the resistance value Rmn505 of the present invention in a range of resistance values sufficiently smaller than the wire resistance Rwn509, the Rwn509 becomes dominant in limiting the machining current, and the influence of the resistance value Rmn505 is almost the same. Can be ignored.

That is, it is not necessary to provide a machining current limiting resistor that limits the lower limit of the machining current that flows between the machining power supply unit 501 and the power supply 104 and becomes an inter-electrode discharge current that discharges to the workpiece 105 between the electrodes. It is.
That is, the resistance value may be smaller than the resistance value obtained by simply dividing Rmn by 10 (the number of turns around which the main rollers 8 and 9 are wound).

That is, by using the impedance which is the resistance Rwn 509 of each wire, the wire current Iwn of each wire is stably supplied, so that the concentration of the wire current does not occur.
Reference numeral 509 denotes a resistance (Rwn) for each wire.

Here, the wire resistance value from the power supply 104 to the discharge part is a resistance due to the length of the wire to the discharge part due to the traveling wire (one piece) after being in contact with the power supply 104.
For example, let Rw1, Rw2, and Rw10 be the wire resistances when supplying power to 10 wires (the main rollers 8 and 9 are wound 10 turns) in a lump.

  As in the conventional method, instead of Rmn, Rwn is a resistor that limits the wire current (Iw) or discharge current (Ig) for each wire, so that the wire current (Iwn) or discharge current (Ign) for each wire is reduced. Can be limited. That is, an arbitrary resistance value can be set by changing the distance (length L) between the power feeding point (power supply) and the discharge point (discharge part). That is, when Vmn = 60V, Vgn = 30V, and Rwn = 10Ω, Iwn (Ign) = (60V−30V) / 10Ω = 3A.

  In the above calculation formula, the voltage drop from the feed point to the discharge point due to the wire resistance (Rwn) is 30 V, but the feed point to the discharge point due to the resistor (Rmn) causing the voltage drop from the machining power source to the feed point. The voltage drop up to is not considered.

  That is, in the case of the collective power supply method according to the present invention, Iwn is determined by Rmn. Therefore, in order to obtain a desired wire current (Iwn) and discharge current (Ign) for each line, the power supply point from the machining power supply. The resistance Rmn that causes a voltage drop up to is set so that Rmn <Rwn.

  The wire resistance Rwn for each wire is calculated from the following three parameters: (1) electrical resistance value ρ depending on the wire material, (2) wire cross-sectional area B, and (3) wire length L. Rwn = (ρ × B ) / L.

Reference numeral 501 denotes a machining power supply unit (Vmn). This is a machining voltage set to supply a machining current necessary for electric discharge machining. Vmn can be set to an arbitrary machining voltage. Furthermore, since the supply amount of machining current is larger than that in the conventional method, a larger electric power (product of machining voltage and machining current) is supplied than 401.
The machining power supply unit 501 supplies machining power (Vmn) to the power supply 104.

Reference numeral 502 denotes a machining power supply unit (Vsn). It is an induced voltage set to induce discharge. Furthermore, it is also used for the purpose of monitoring the state of the interelectrode voltage (interelectrode current) between the wire and the workpiece and using it for controlling the workpiece feeder. Vsn can be set to any induced voltage. Furthermore, since the supply amount of the induced current is larger than that in the conventional method, a larger amount of electric power is supplied compared to 402.
The machining power supply unit 502 supplies a machining power supply (Vsn) to the power supply 104.
Reference numeral 503 denotes a transistor (Tr2). The processing power supply Vmn is switched between ON (conductive) state and OFF (non-conductive) state by switching.
Reference numeral 504 denotes a transistor (Tr1). The processing power source Vsn is switched between ON (conductive) state and OFF (non-conductive) state by switching.
Reference numeral 507 denotes a discharge electrode voltage (Vgn). This is an interelectrode discharge voltage applied between the wire 103 and the workpiece 105 during discharge.
For example, the voltage between the discharge electrodes when supplying power to 10 wires at once is set to Vg1, Vg2, and to Vg10, respectively.

A portion where the discharge electrode voltage is applied between the wire 103 and the workpiece 105 by discharge is a discharge portion. In the discharge part, the machining power supplied in a batch to the plurality of wires traveling by contact between the plurality of traveling wires and the power supply is discharged to the workpiece.
Reference numeral 508 denotes an interelectrode discharge current (Ign). This is an interelectrode discharge current that flows between the wire 103 and the workpiece 105 during discharge.
For example, the discharge-electrode currents when power is supplied to 10 wires at once are Ig1, Ig2, and Ig10, respectively.

A portion where a discharge-electrode current flows between the wire 103 and the workpiece 105 due to the discharge is a discharge portion. In the discharge part, the machining power supplied in a batch to the plurality of wires traveling by contact between the plurality of traveling wires and the power supply is discharged to the workpiece.
Reference numeral 510 denotes a wire current (Iwn) supplied individually for each wire.
For example, each wire current when power is supplied to 10 wires at once is assumed to be Iw1, Iw2, and .about.Iw10, respectively.
Reference numeral 511 denotes a distance L from the power supply point to the discharge point, that is, the length of the wire from the power supply point (power supply) to the discharge point (work).
FIG. 8 will be described.
FIG. 8 is a diagram in which a plurality of wires are collectively fed by a batch feeding electric circuit 2 that feeds a machining current to a plurality of wires (10) in the present invention.

Reference numeral 104 denotes a power supply. The power supply 104 contacts a plurality of traveling wires at once. An electric discharge pulse is applied from one power supply 104 provided at a position facing the silicon ingot 105 to perform electric discharge machining.
One power supply circuit 2 is connected to the number (10) of wires 103 around which the main roller is wound.
Hereinafter, the machining current (total of each wire current) flowing in the wire will be described with reference to the arrangement of FIG.

As shown in FIG. 8, since the wire current flowing from the power supply point (position where the power supply 104 and the wire 103 contact) to the discharge point (between the wire 103 and the workpiece 105) flows in two directions of the left and right main rollers, There is wire resistance in each direction.
511L1 is the length (distance) between the power supply point and the discharge point when the current flows in the direction of the left main roller, and the wire resistance determined in the case of L1 is Rw1a.
511L2 is the length (distance) between the discharge point and the feed point when the current flows in the direction of the right main roller. The wire resistance determined in the case of L2 is Rw1b.
The length that the wire 103 winds the main rollers 8 and 9 once is set to 2 m.
Since the power supply 104 is arranged at a distance approximately half the length of one turn, the distance between the discharge point and the power supply point (the length L of the wire) is 1 m.
Therefore, the distance of the wire that travels from the power supply to the discharge unit is longer than 0.5 m.

The main component of the material of the wire 103 is iron, and the diameter of the wire is 0.12 mm (cross-sectional area 0.06 × 0.06 × πmm ² ). Since the resistance values Rw1a and Rw1b of the wires are the same length (L1 = L2 = 1 m), if each wire resistance value is about the same 20Ω, one of Rw1a and Rw1b (one main roller 8, 9 is 1). The combined wire resistance value is about 10Ω.

Further, as shown in FIG. 8, in order to make the wire resistance value according to the lengths of L1 and L2 the same resistance value, it is preferable to arrange the power supply 104 so that the lengths of L1 and L2 are the same. There is no particular problem even if the power supply 104 is arranged so that the difference in length between L2 and L2 is about 10% (for example, L1 is 1 m and L2 is 1.1 m).
When the discharge voltages Vg1 to Vg10 are substantially equal, since Vmn is applied to each of Rw1 to Rw10, Iw1 to Iw10 are all the same wire current.
Here, Vmn is obtained from the voltage drop value (Rw1 × Iw1) due to the wire resistance and the discharge voltage (Vgn).
The voltage drop from the power supply 104 to the discharge part is a voltage drop due to the resistance of the traveling wire.
Rw1 = 10Ω (resistance value from the power supply 104 to the discharge part).
Iw1 = 3A
If Vgn = 30V, Vmn is as follows.
Vmn = 10 (Ω) × 3 (A) + 30V = 60V
Therefore, the voltage drop from the power supply to the discharge part is larger than 10V.
Therefore, the resistance value from the power supply to the discharge part is larger than 1Ω.
Note that the voltage drop value due to the wire resistance may be set by the wire parameter according to the relational expression of Rwn = (ρ × B) / L.

Therefore, when Rmn is calculated when the discharge state occurs uniformly and simultaneously between all the 10 wires and the workpiece, the discharge state occurs in all the wires, and Iw1 = 3A flows through the 10 wires. A total machining current of 10 × 3A = 30A is required between the machining power source and the feed point, and the voltage drop between this machining power source and the feed point is 1 / 100th of Vmn (0.6V). Then, Rmn in this case is as follows.
Therefore, the voltage drop from the machining power supply unit to the power supply 104 is smaller than 1V.
Therefore, the voltage drop from the machining power supply unit to the supply unit is smaller than the voltage drop from the supply unit to the discharge unit.
Rmn = 0.6V / 30A = 0.02Ω (resistance value from the processing power supply unit 501 to the power supply 104).
Therefore, the resistance value from the machining power source to the power supply is less than 0.1Ω.
Therefore, the resistance value from the machining power supply unit to the supply unit is smaller than the resistance value from the supply unit to the discharge unit.
Therefore, the ratio of the voltage drop from the machining power supply unit to the supply unit 104 and the voltage drop from the supply unit 104 to the discharge unit is 10 times or more.
Therefore, the ratio of the resistance value from the machining power supply unit to the power supply 104 and the resistance value from the power supply unit to the discharge unit is 10 times or more.
Therefore, when 10 machining currents are calculated in consideration of Rmn, (60V-30V) / ((10Ω / 10 pieces) + 0.02Ω) = 29.41A, and the machining current after dividing per wire is 2. 941A.

  Moreover, even if one wire current flows when the discharge state does not occur between all 10 wires and the workpiece uniformly and simultaneously, the machining current after dividing the wire per wire is (60V). −30V) / (10Ω + 0.02Ω) = 2.994 A, and there is no significant difference compared to the case where the discharge state occurs uniformly and simultaneously between all 10 wires and the workpiece.

As a further effect, when power is supplied to a plurality of N wires (the main rollers 8 and 9 are wound N times) at one location (in a lump), power is supplied individually for each wire. The machining speed is 1 / N compared to the machining speed at the time, but according to the present invention, even when power is supplied to N wires at one place (collective), The same processing speed can be maintained.
9 and 10 will be described.

Reference numeral 600 denotes a coaxial cable (coaxial wiring portion), which supplies power to the wire electric discharge machine 1 for electric discharge machining. In order to suppress the wiring resistance L _L , the coaxial wiring section includes an upstream wiring 513 that supplies a current to be processed at point A and a downstream wiring 514 to which the current after processing into the processing power supply section (Vmn) returns. Yes.
Reference numeral 601L denotes the physical length of the cable of the wiring 513.
Reference numeral 602L denotes the physical length of the cable of the wiring 514.
Point A is the end point of the cable of the wiring 513 and is electrically connected to the power supply 104.

Point B is the end point of the cable 514 in the coaxial cable, and the point from here is further connected to the line 515. The point B to the point C are branched as a single line (wiring 515).
Point C is the end point of the single-wire cable of the wiring 515 and is electrically connected to the workpieces 105 and 3 via the workpiece feeding unit 3.
Reference numeral 515 denotes a single wire cable (single wire portion), which is a portion where an up or down cable contained in the coaxial wiring portion 600 branches off from the coaxial wiring portion 600.

Further, the branched single wire portion is electrically connected to either one side (or both sides) of the power supply or the workpiece feeding portion 3. In the case of FIG. 10, the case where it connects with the workpiece | work feeding part 3 is shown.
FIG. 11 will be described.

  Wiring is performed from the power supply device to the relay terminals (points A and B) by the coaxial cable 600. Since it is a coaxial cable to the relay terminal, the impedance is low and the influence of the length is not great.

  In order to apply a voltage to the workpiece and the wire for electric discharge machining, the workpiece is separated (branched) into the workpiece side (+) and the electric supply (wire) side (−) at the relay terminal, and wired to each by a single wire.

  The branching single wire portion is electrically connected to either one side (or both sides) of the electric supply or work feeding portion 3. In the case of FIG. 11, the case where it connects with the workpiece | work feeding part 3 is shown.

  As shown in FIG. 11, when the work feeding unit 3 and the power supply 104 are arranged outside the loop of the wire that circulates, the single wire part to the work and the power supply is connected to the wire loop to avoid interference with the wire that circulates. It is necessary to route the wire outside.

The length of each single-wire part to a workpiece | work and an electric power supply needs about 50 cm-1 m. The total of the two wires is 1 m to 2 m, and therefore has a relatively large impedance, and the individual discharge energy is not constant depending on the number of wires to be discharged.
FIG. 12 will be described.

  A case where the work and the power supply are arranged in the loop of the wire will be described. For wiring to the work and the power supply, attach one side (minus pole) of the coaxial cable from the power supply directly to the power supply or to the power supply mounting base. The positive pole of the coaxial cable is connected to a single wire and wired to the work mounting base.

If the distance between the power supply mounting base and the work mounting base can be arranged at the shortest distance, the length of the single wire section is enough for the work movement amount, and the work movement amount is that of a standard silicon ingot. Since the size is 156 mm, only the cable portion that follows the workpiece as the workpiece moves needs to be branched from the coaxial wiring portion, and the length of the single wire portion 515 is about 20 cm at the shortest (the wire around which the workpiece feeding portion 3 circulates). The distance is approximately equal to the distance at which the workpiece 105 is sent out in the direction approaching 103.
Therefore, when compared with FIG. 11, the length of the single wire portion can be shortened from 1/5 to 1/10.

  That is, as shown in FIG. 12, when the power supply 104 and the work feeding unit 3 are arranged on the inner side, two wires that are formed on the outer periphery of the plurality of main rollers 8 and 9 at the longest and run in different directions. The length of the single wire portion 515 branched from the coaxial cable portion is shorter than the length (distance) due to the distance between the running surfaces (upper surface and lower surface).

Note that the single wire portion 511 branched from the coaxial cable portion may be one downstream device connected only to the work 105 as shown in FIG. 12, or one upstream device connected only to the power supply 104. Good. In addition, two downstreams may be branched, one downstream for connection to the workpiece and one upstream for connection to the power supply 104. In this case, the total extension of the single wire portion 515 including the two wires is formed on the outer periphery of the plurality of main rollers 8 and 9, and the distance between two wire running surfaces (upper surface and lower surface) that travel in different directions, respectively. It is sufficient if it is shorter than the length (distance).
FIG. 13 will be described.
FIG. 13 summarizes the results of theoretical calculations described later in a table.
A pulse voltage is generated by Tr1, and the discharge current between the wire and the workpiece is controlled.

The discharge current I can be simply calculated from the power supply voltage (Vmn), the wiring resistance L _L mainly composed of inductance, and the wire resistance (pure resistance Rwn, inductance Lw) by the following formula. (Strictly speaking, there is a discharge electrode voltage, but it is omitted here.)
The wiring resistance L _L means the same as the total resistance component of the wiring 513, the wiring 514, and the wiring 515.
When only one wire is discharged, the discharge current (ampere) can be calculated by the following equation.
I = (Vmn / Rw) * (1-e− ^{t / τ} )
τ is the rise time of the discharge current.
τ = (L _L + Lw) / Rw
When there are a large number of wires (10 wires), the discharge current can be calculated by the following equation.
I10 = (Vmn / (Rw / n) * (1-e- ^{t / τ} )
τ10 = (L _L + (Lw / n)) / (Rw / n)
Here, n is the number of wires to be collectively fed (the number of wires being discharged).
It becomes.
Since the wiring resistance L _L is mainly an inductance, it greatly affects the rise time of the discharge current (Ign) between the electrodes.
Thus, the rise time τ (shown in FIG. 15) relates to the magnitude of the resistance value of the power supply wiring, which is the wiring resistance L _L (inductance).

  Since the impedance (resistance) component due to the power supply power supply cable originally used in the wire electric discharge machining apparatus can cause a voltage drop of the machining power supply, it is generally desirable to be as small as possible.

Therefore, even in a general single-wire wire electric discharge machine, wiring is performed using a coaxial cable that can reduce the impedance (resistance) component from the power supply device to the vicinity of the wire electric discharge machine.
As shown in FIG. 11, in the multi-wire electric discharge machining apparatus of the present invention, the positions where the workpiece and the power supply are respectively arranged are as described above.

(1) By making the wire length from the discharge point to the power supply unit (the length that the wire travels) as long as possible, the impedance (resistance component) due to the wire length increases, and as a result, the impedance (resistance) for each wire Component) becomes dominant in the power supply circuit, and the current value flowing for each wire can be determined by the impedance (resistance component) for each wire.

(2) By making the wire lengths (L1 and L2) on both the left and right sides from the power supply unit to the discharge point as equal as possible, the impedance (resistance component) due to the wire length is also almost equal, and as a result, the current value flowing for each wire Can be made equal on both the left and right sides, and the workpiece can be processed with high precision on both the left and right sides (traveling direction of the traveling wire).

  The power supply unit and the discharge point are separated from each other for two reasons, and the workpiece moves as the electric discharge machining proceeds. Therefore, the machining power is supplied from the power supply device to the power supply and flows through the wire. A single wire branched from a coaxial cable routed to the vicinity of the multi-wire electrical discharge machine to construct a power supply circuit that generates electrical discharge between the poles and returns the gap current flowing through the workpiece to the machining power supply. The cable wired in is always necessary.

When the length of a cable wired with a single wire becomes longer, the impedance (resistance) component due to the cable length becomes larger, which becomes a factor of increasing the wiring resistance L _L (inductance).

In the multi-wire electric discharge machining apparatus of the present invention, it is a general reason for a general single-wire wire electric discharge machining apparatus that shortening the cable length wired as a single line as much as possible causes a voltage drop of the machining power supply. In contrast, the object is to make the processing energy of each wire uniform regardless of the discharge state.

Thus, in the multi-wire electric discharge machining apparatus of the present invention, the cable length is preferably as short as possible in order to reduce the impedance of the single-wire portion cable as much as possible. The cable length of the single-wire portion is the most satisfying the above two conditions. In order to shorten the length, it is most preferable to dispose both the workpiece feeding unit and the power supply unit inside the plurality of main rollers.
The results of theoretical calculation using the above equation are as follows.
This theoretical calculation can show the influence of the variation in τ as the rise time and the length of the power supply wiring.
When performing batch power supply to 10 wires per wiring,
It is assumed that the wire resistance Rwn is 10Ω and the wire inductance Lw is 50 μH.
The length of the wiring is a 2μH wiring resistance _{L L} when the 2m, wiring resistance _L L when the 0.2m: 0.2μH and was the τ when calculated respectively.
1301 is the number of wires discharged between the electrodes.
Reference numeral 1302 denotes a total of wiring resistance and wire inductance. The unit is [microhenry]
1303 is the resistance of the wire.
1304 is τ. The unit is time [microseconds].
1305 is a variation of τ.
The influence by the state of occurrence of discharge is shown.

  From the table, when the result 1300 and the result 1400 are compared, the variation in τ is smaller in the case where the length of the single wire portion is 0 and 2 m than in the case of 2 m, that is, the time when the discharge rises between the wires to be discharged [micro It can be said that [second] is almost uniform.

  FIG. 14 shows the above-mentioned (Vmn−Vgn) / ((Rwn / number of wires) + Rmn) = theoretical calculation value of the total machining current that changes as the number of wires increases, using the formula for machining current. Is a graph comparing only Rmn. In the equation, the value (ampere) of the machining current was obtained with Vmn = 60V, Vgn = 30V, and Rwn = 10Ω.

The vertical axis of the graph is the ampere indicating the total machining current, and the vertical axis of the graph is the number of wires that are in contact with the feeder and fed at one place (collective). The number of wires (1, 2, 10,..., 100) to be fed at one place (collective) can be changed by feeding the different size feeders 104 in contact with the wires. .
In the graph, parameters other than Rmn are fixed, and only the resistance value (Ω) of Rmn is replaced with three different resistance values.

  From the graph, it can be seen that as Rmn becomes smaller, the total machining current, which can be said to be directly related to the machining speed, increases as the number of wires increases, so as to be almost proportional to the number of wires.

In the present invention, the resistance value of the machining fluid between the wire 103 and the workpiece 105 (between the electrodes) varies depending on the distance between the electrodes. Therefore, by setting Rsn 506, which is the induced current limiting resistance, to a value that is approximately the same as the resistance value of the machining fluid between the electrodes, it is possible to detect a variation in the voltage (Vgn) between the electrodes.
FIG. 15 will be described.

FIG. 15 shows the relationship between the application of the pulse power supply and the discharge current rising with the application of the pulse power supply. In the wire electric discharge machining of the present invention, even when a machining power supply having the same voltage value is fed to a plurality of wires with the same pulse,
1. Machining for a wire that rises quickly (above)
2. Machining for slow-starting wire (below)

As shown in Fig. 5, the machining energy is determined in proportion to the current and time product, that is, the amount of electricity. Since the occurrence of electric discharge between the electrodes is different for each wire, the processing energy is different if the rise time of the current is different. That is, when the rise time (τ) in the above figure is short, the amount of electricity, that is, the machining energy increases, and the workpiece is machined much.

Conversely, when the rise time (τ) in the figure below is long, the amount of electricity, that is, the machining energy is reduced, and the workpiece is machined less. In this way, if the rise time (τ) until the discharge current flows stably for each wire between the electrodes varies, the processing energy after the discharge current rises also changes. The shape will also fall apart.
FIG. 16 will be described.

FIG. 16 is a modification of the arrangement of FIG. In this case, both the work feeding unit and the power supply unit are arranged inside the plurality of main rollers, and L1 (the length of traveling on the left main roller) and L2 (the length of traveling on the right main roller) are substantially equal. Although the distances are equal to each other, the arrangement of the work feeding unit and the arrangement of the power supply units are not necessarily aligned in the vertical direction, but an arrangement example in which the object of the present invention is achieved is shown.
FIG. 17 will be described.

FIG. 17 is a modification of the arrangement of FIG. In this case, both the workpiece feeding unit and the power supply unit are arranged inside the plurality of main rollers, but L1 (the length of traveling on the left main roller) and L2 (the length of traveling on the right main roller). ) Is different. In this case, since the value of the current flowing for each wire is different on both the left and right sides, the accuracy of the workpiece on both the left and right sides (the direction of travel of the traveling wire) is also affected by machining, but if the difference is about 10%, The objective is achieved.
FIG. 18 will be described.

  FIG. 18 is a modification of the arrangement of FIG. In this case, both the work feeding unit and the power supply unit are arranged inside the plurality of main rollers, and L1 (the length of traveling on the left main roller) and L2 (the length of traveling on the right main roller) are substantially equal. Although the distance is equal, a plurality of main rollers are not located at two places as shown in FIG. 2, but an arrangement example is shown in which the object of the present invention can be achieved even if they are arranged at four places as shown in FIG. Is. FIG. 2 shows an arrangement example in which the object of the present invention can be achieved even if the number of the power supply units is not one as shown in FIG. 2 but two places as shown in FIG.

  The semiconductor ingot sliced by the multi-wire electric discharge machining system of the present invention is manufactured as a semiconductor substrate or a solar cell substrate, and can be used as a semiconductor device or a solar cell.

DESCRIPTION OF SYMBOLS 1 Multi wire electric discharge machine 2 Power supply device 3 Work feed part 103 Wire electrode 104 Electric supply 105 Work (silicon ingot)
505 Impedance by cable from machining power supply (minus side) to power supply (feeding part) 520 Impedance by cable from work feeding part (workpiece) to machining power supply (plus side) 509 Between electrodes (feeding part) to discharge (discharge) Impedance 513 by one wire up to a part) Power supply wiring cable 514 connected to the machining power supply (minus side) Power supply wiring cable 515 connected to the machining power supply (plus side) Single line cable (single line part)
600 Coaxial cable (coaxial wiring part)

Claims (7)

A wire electric discharge machining apparatus for slicing a workpiece by electric discharge machining at an interval between wires arranged in parallel,
A plurality of main rollers for rotating the wire so as to run in the same direction;
A plurality of wires that circulate, and a power supply that collectively feeds a machining power source for electric discharge machining,
A workpiece feeding section for feeding the workpiece in a direction approaching the wire that circulates;
Power supply wiring for supplying a machining power for conducting the electric discharge machining in conduction with the electric supply and the workpiece,
The power supply and the work feed unit are arranged inside wires that circulate around the plurality of main rollers, and a power supply circuit of the machining power source using the power supply wiring is connected to the power supply and the work feed unit. A wire electrical discharge machining apparatus characterized by being connected to each other. A processing tank that is disposed outside a wire that circulates around the plurality of main rollers, and stores a processing liquid;
The work feeding unit is disposed at a position lower than the power supply,
The wire electric discharge machining apparatus according to claim 1, wherein the workpiece feeding unit feeds the workpiece in a direction approaching the wire that circulates so that the workpiece to be held is immersed in the machining liquid. The power supply wiring is
A coaxial wiring section that encloses cables for upstream and downstream;
A single wire portion in which the enclosing or descending cable is branched from the coaxial wiring portion and connected to one of the electric supply or the work feeding portion;
Have
The length of the branched single wire portion is shorter than the length due to the distance between two wire running surfaces formed on the outer periphery of the plurality of main rollers and running in different directions. Or the wire electric discharge machining apparatus of Claim 2. The power supply wiring is
A coaxial wiring section that encloses cables for upstream and downstream;
A single wire portion in which the enclosing or descending cable is branched from the coaxial wiring portion and connected to one of the electric supply or the work feeding portion;
Have
4. The length of the branched single wire portion is substantially equal to a distance that the workpiece feeding portion feeds in a direction approaching a wire that circulates the workpiece. The wire electric discharge machining apparatus according to Item. A discharge unit for discharging the machining power source fed to the wire in a batch to the workpiece;
A power supply unit for supplying a machining power for the electric discharge machining to the electric supply;
The resistance of the power supply wiring from the said power supply part to the said power supply is smaller than the resistance of the wire from the said power supply to the said discharge part, The any one of Claim 1 thru | or 4 characterized by the above-mentioned. Wire electrical discharge machining equipment.   The wire electric discharge machining apparatus according to claim 5, wherein a resistance of a power supply wiring from the power supply unit to the power supply is smaller than 0.1Ω. A plurality of main rollers for slicing the workpiece by electrical discharge machining at intervals between the wires arranged in parallel and traveling in the same direction, and machining for performing electrical discharge machining on the plurality of wires that circulate Supplying power to a power source collectively, supplying a workpiece feeding unit for sending the workpiece in a direction approaching the wire that circulates, and supplying machining power for conducting the electric discharge machining with the supply and the workpiece. A wire electric discharge machining method in a wire electric discharge machining apparatus comprising a power supply wiring,
The power supply and the work feed unit are arranged inside wires that circulate around the plurality of main rollers, and a power supply circuit of the machining power source using the power supply wiring is connected to the power supply and the work feed unit. A wire electric discharge machining method characterized by being connected to each other.

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