JPH01146655A - Frame sawing machine lap-cutting bar-shaped or block-shaped work to disk in multiple manner - Google Patents

Abstract

PURPOSE: To cut a bar-like or a block work into disks for lapping without generating a crack or breakage by connecting a work support system for housing a work in a feeding system to a real feeding block through a system such as a spring oscillatable in the feeding direction. CONSTITUTION: A power meter 6 detects the cutting force of a pair of reciprocating saw blades 15 to be vertically applied to a work 1. In response to the fluctuation of the cutting force, drive of a motor 17 is controlled by a command from a computer so as to rotate a spindle 18, and a feeding block 19 is vertically moved in a feeding frame 14 at the predetermined speed. The vertical movement of this feeding block 9 is transmitted to a work support system through a plate spring 8, and the work 1 is pushed to the saw blade 15 by the predetermined pushing force. As a result, the work 1 can be sawed without generating a crack or breakage.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial field of application The present invention relates to a tensioning machine in which a rod-shaped or block-shaped workpiece, in particular made of semiconductor material, is reciprocated using a feed system while being supplied with a lapping agent suspension. The present invention relates to a rectangular saw machine that cuts multiple laps of a workpiece into disks by pressing against a set of saw blades clamped in a frame.

Prior art, in particular rod-shaped or block-shaped machining made of semiconductor materials, such as silicon, germanium, gallium arsenide or indium phosphite, or of oxide materials, such as gallium-gadolinium-garnet, ruby, spinel, quartz or glass. In order to saw objects into discs with a thickness of typically 0.1 to 1 mm, in addition to saws with a circular hole, as is well known, rectangular saws are also used. These scissors work with multiple lap cutting principles,
That is, the workpieces to be separated are pressed by a feed system against a reciprocating grid consisting of a pair of saw blades clamped in a tension frame, with the actual material being ground at the separation points. A suspension of cutting particles from a hard material, such as silicon carbide, is provided in most cases. Such sawing methods or corresponding sawing with a reed saw are known and are described, for example, in DE-A-272-2782 or in corresponding U.S. Pat. No. 3,247,826 or the corresponding US Pat. No. 4,539,972.

IdlI on the saw blade and workpiece during the course of the sawing process.

Wear contours occur, which cause strong, almost collisional forces between the saw blade and the workpiece, especially at the point of reversal. Of course, due to these impact forces, the resulting discs constantly crack and break. In particular, when sawing a polycrystalline silicon block with a square cross section (-side length typically about 10 cm) into thin disks as substrates for solar cells, it is possible to Reducing the thickness of the disc to a value less than the standard thickness currently in use of approximately 350-550 μm, as desired for improved efficiency, is due to the fact that losses occur rapidly during the sawing process. OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide a method for cutting discs without cracks and breaks, with low losses and high sawing efficiency, by means of a multiple lap cutting method. The purpose was to describe a recoiling saw with which thin discs with a thickness of less than 350 μm can be obtained.

The object is to carry out the actual feed movement via one or several systems in which the workpiece support system accommodating the workpiece in the feed system can vibrate in the feed direction. The problem is solved by a recoiling saw machine, which is characterized in that it is combined with a feed block.

The workpieces are thus supported vertically so that they can vibrate, so that they can be subjected to impact forces caused by the saw blade profile during the sawing process. That is, ultimately these impact forces are absorbed by the deflection movements of the workpiece, so that the applied loads and at the same time also the fluctuations of the cutting forces can be clearly reduced.

Particular preference is given to using a spring system as the vibrating system, for example in the form of a spiral spring, a disk spring or, in particular, a leaf spring. It is likewise possible to use hydraulic systems, for example hydraulic, pneumatic or electromagnetic systems.

The oscillating natural frequency allows a sufficiently rapid following of the workpiece,
In order to thus ensure constant contact with the saw blades, it is advantageous to choose a frequency higher than the frequency of the reciprocating movement of the set of saw blades.

In this connection, in order to be able to adapt the device to possible changes in the operating parameters, the natural frequency can be adjusted, for example in the case of leaf springs by changing the free length. It has also been proven that it is advantageous to have a system.

In some cases, the movement of the workpiece support system that is ultimately forced by the movement of a set of saw blades is superimposed with additional vertical vibrations, for example by placing this system in oscillation with a vibrator. be able to. In this case, the amplitude of this vibration is advantageously adjusted to be approximately 1/2 to 1/1000 of the vertical movement of the workpiece support system caused by the pair of saw blades. The frequency advantageously corresponds to 2 to 10 times the reciprocating movement of a pair of saw blades.

The drawing schematically shows one possible embodiment of a feed system constructed according to the invention, in which case a complete cosaw saw has not been shown for reasons of clarity.

The exemplary drawings show a workpiece l, for example a block consisting of a solar cell substrate based on polycrystalline silicon, which block is joined, for example, on a cutting table 2, which are fastened into the workpiece table 3, for example by screws. The workpiece table 3 has an upper spring support device 4.
and a lower spring support device 5 are attached.

According to one advantageous embodiment, the workpiece table 3 includes:
A dynamometer 6, for example in the form of a power sensor, is connected, by means of which it is possible to monitor the cutting forces occurring during the sawing process. The workpiece support device ends with a support block 7 which is connected via a leaf spring 8 with a feed block 9 which carries out the actual feed movement.

In order to guide this entire workpiece support system in the feed block,
and in the feed direction (in order to ensure that it is possible to oscillate), it is connected with the lower spring mounting device 5 and the upper spring mounting device 4 of the support system on the - side, and on the other side the lower spring suspension device 12.
A lower guide spring 10 and an upper guide spring 11 are used and supported by an upper spring suspension device 13. However, instead of such spring-loaded guide systems, which have the advantage of almost wear-free operation, other guide systems are also applicable, such as, for example, sliding or roller guides or guides with pneumatic or hydraulic bearings. .

Instead of the embodiment shown in this case with individual workpieces 1, a device in which the workpieces are each sawed in pairs has also proven advantageous. However, furthermore, the example will relate to only one workpiece for reasons of simplicity, even though this example can likewise be applied to several workpieces, in particular pairs of workpieces. .

The feed block 9 can be moved up and down in the feed frame 14, so that the workpiece 1 can be pressed against a reciprocating set of saw blades 15, which in this case are only shown schematically. Moreover, in each case, the specified pressing force can be applied or the pressing can be performed at a specified feed rate. To guide this feed movement in the feed frame 14, which must have as little lateral play as possible, a v-shaped guide device 16 can be provided, for example.

According to the embodiment illustrated in this case, the feed block 9 is connected to a spindle 18 driven by a motor 17, for example a continuously controllable motor;
This spindle causes a vertical movement of the feed block within the feed frame 14. According to one advantageous embodiment of the invention, this feed movement extends vertically to the workpiece l.
controlled, for example by a computer, in response to fluctuations detected by a dynamometer 6 in the cutting force acting on the cutting force. Advantageously, in the case of deviations from the target value range confirmed in preliminary tests, a strong pressing of the workpiece 1 against a set of saw blades can increase the feed rate if a force is required, which force It can also be reduced by slowing down the feed rate if necessary.

However, in principle, embodiments are also conceivable which work with a fixedly adjusted constant feed or a preprogrammed variable feed.

In order to transmit the feed movement determined by the spindle 18 and the feed block 9 to the workpiece support system, in addition to the preferred leaf spring 8 presented by way of example in this case, other vibratory systems also apply. That is, it is conceivable to use hydraulic suspension systems, even though such systems generally have a shorter lifespan than mechanical spring systems.

A recoiling saw made in accordance with the present invention is distinguished by a series of advantages compared to a reticulating saw with a conventional feed system. Since the feed system with bearings is virtually vibration-free, the service life of the bearings is clearly increased. Since the peak power and impact forces that occur during the sawing process are compensated, the mechanical load on the workpiece resulting from these forces during the sawing process is also reduced, and the achievable disc thickness is therefore clearly can be reduced to

For example, by using a conventional scissor saw, a disk as a solar cell substrate can be produced from a silicon block with a columnar structure consisting of regions with a crystallographic orientation, according to experience.
Only up to a thickness of about 350-400 μm can be sawn with satisfactory quality, ie without cracks, grooves and breaks, and with a satisfactory yield, ie more than 90%. When using the scissor saw according to the invention, thicknesses of up to 10 mm can be reduced with excellent yields and yields of over 90%.
It was possible to reduce the thickness to within the range of 0 μm. This means that the number of silicon disks that can be obtained per block at the same time is more than doubled. Furthermore, in the case of standard disc thicknesses currently in common use, the cutting speed, i.e. the area sawn per unit time (each silicon disc ) could be increased from the previous common value of about 1.4 cm, 7 minutes to about 1.8-2.0 Cm2/min.

It follows from this that the sawing time required to cut each block into disks is clearly shorter. Furthermore, the mass of the feed system can be significantly reduced compared to conventional feed systems, and in particular the lower mass of the support system allows the workpiece to better adapt to the wear contour. This results in that the cutting forces are subject to only smaller fluctuations.

[Brief explanation of the drawing]

The drawing is a partially schematic cross-sectional view showing an embodiment of a scissor saw machine according to the invention for multiple lap cutting of a bar-shaped or block-shaped workpiece into disks. ■ Workpiece, 2 Cutting table, 3 Crop table, 4 Upper spring support device, 5 Lower spring support device, 6 Dynamometer, 8 ... Leaf spring, 9... Feed block, 10... Lower guide spring, 11... Upper guide spring, 12... Lower spring suspension device, 13... Upper spring suspension device, 14.・・Feed frame, 15・・Saw blade of drawstring,
16...V-shaped guide device, 17...motor, 18...
−Svindr

Claims (1)

[Claims] 1. A feed system is used to push a bar-shaped or block-shaped workpiece toward a set of saw blades clamped in a tension frame, which is reciprocated under the supply of a lapping agent suspension. In a rectangular saw machine that cuts the workpiece into multiple laps into a disk, the workpiece support system that accommodates the workpiece in the feed system can vibrate in one or several feed directions. A rectangular saw machine for multiple lap cutting of bar-shaped or block-shaped workpieces into disks, characterized in that it is coupled with a feed block that carries out the actual feed movement through the system. 2. The recoiling saw machine according to claim 1, wherein a system capable of vibrating is selected, the natural frequency of which is higher than the reciprocating frequency of the set of saw blades. 3. Scissor saw machine according to claim 1 or 2, characterized in that the spring system is provided as a vibrating system. 4. Scissor saw machine according to claim 1, wherein the workpieces are each fixed in pairs on a workpiece support system. 5. Scissor saw machine according to claim 1, wherein vertical vibrations are additionally superimposed on the movement of the workpiece support system. 6. Claim 5, wherein the additional vertical vibration has a frequency corresponding to 2 to 10 times the reciprocating frequency of the set of saw blades.
The described resor saw machine. 7. The machine according to claim 1, wherein the actual feed movement is controlled in dependence on the vertical force that occurs when pressing the workpiece against a set of saw blades. Sawing board. 8. Use of a recoiling saw according to any one of claims 1 to 7 for sawing a silicon block into discs. 9. The use according to claim 8, wherein the silicon block has a columnar structure consisting of regions having a crystal orientation arrangement. 10. Use according to claim 8 or 9 when sawing discs with a thickness of less than 10,350 μm.