JPH0729262B2 - Groove roller for multi-wire saw - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a groove roller of a multi-wire saw for cutting brittle materials such as semiconductor materials, magnetic materials, and ceramics into a large number of thin wafers with a wire, and a groove during cutting. The present invention relates to a groove roller that prevents wire breakage due to thermal expansion of the roller, improves cutting accuracy, and reduces wire cost.

2. Description of the Related Art A multi-wire saw used to cut an ingot of a brittle material such as a semiconductor material into a wafer is a wire cut object (hereinafter referred to as a work) in which multiple threads are hung at a predetermined pitch.
Is a device that presses against a wire and pours a grinding liquid containing abrasive grains (hereinafter referred to as a grinding liquid), relatively moves the wire and the work, and cuts by a grinding action. The relative movement of the wire and the work is given by a method of reciprocating the wire (for example, Japanese Patent Publication No. 56-199) and a method of reciprocating the work with respect to a wire traveling in one direction (for example, Japanese Patent Publication No. 52-12954). ,
There is a method of running a wire in one direction with respect to a fixed work (for example, Japanese Patent Laid-Open No. 61-100361), but a groove roller is used in all of the multiple-thread hanging means of the wire.

For example, as shown in FIG. 3, winding one wire (4) around many grooves engraved on the outer peripheral surface of three groove rollers (1), (2) and (3) that are rotatably held. Has adopted a method of maintaining the pitch of the wire. The wire pitch is determined in consideration of the thickness of the wafer to be cut, the diameter of the wire, and the grinding loss due to the abrasive grains.

As a method of supplying the polishing liquid (6), a method of pouring it into a wire row from a nozzle (7) arranged above the work (5) or a method of immersing the work (5) in the polishing liquid is used. During the cutting, the push-up base (8) to which the work (5) is attached is gradually raised to complete the cutting.

By the way, in a multi-wire saw, it is extremely important to prevent wire breakage. That is, once the wire breakage occurs, not only the loss of expensive wire and the enormous restoration man-hour but also the work is discarded in the worst case, and the loss is extremely large. In particular, if a wire break occurs between the groove rollers (1), (2) and (3) shown in FIG. 3, the wire may get caught in the groove roller and damage the groove of the groove roller, further increasing the damage.

Needless to say, wire breakage is caused by an excessive tensile force applied to the wire, but especially the wire between the groove rollers has reduced strength due to frictional heat accompanying sliding with the work piece Damage to the wire surface due to unavoidable damage is liable to occur.

Therefore, there are two measures for preventing wire breakage: a method of slowing down the traveling speed of the wire to suppress heat generation, and a method of updating the wire before breaking.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, the above-described conventional measures for preventing disconnection have the following problems.

In the method of suppressing the heat generation by slowing down the traveling speed of the wire, the amount of grinding per unit time is reduced, so that the cutting efficiency is reduced. To compensate for this, for example, a method of reciprocally vibrating the work in the wire traveling direction and in the opposite direction (Japanese Patent Publication No. 52-12).
954), but due to the "play" of the mechanism required for reciprocating motion, the cutting accuracy decreases and saw marks (scratches that occur on the cutting surface)
Is a concern.

Pre-updating the wire has the problem that the cost of the wire is high. That is, in a wire saw that reciprocates a wire and a work, the wire is usually discarded by cutting once. Of course, even if it is cut once, it will break if the sliding distance of the same part of the wire is long.Therefore, the feeding length of the new wire should be set to a large value to repeat the sliding distance of the same part of the wire. Measures to reduce are taken. However, in this case, the total length of the wire required for cutting becomes large, and the cost of the wire becomes high.

Also, with a wire saw that fixes the work and travels the wire in one direction, the sliding distance between the wire and the work can be minimized, so it is possible to repeatedly use the used wire. It has to be discarded after a few uses to avoid.

In any case, in the multi-wire saw, it is necessary to update the wires one after another to avoid disconnection, which is uneconomical.

In view of such an actual situation, the present invention aims to reduce the wire cost of the multi-wire saw and stabilize the cutting accuracy and the cutting efficiency, and to provide a groove roller capable of significantly reducing the risk of disconnection in the multi-wire saw. Is what you are trying to do.

Means for Solving the Problems As a result of detailed investigation of the cause of disconnection between the groove rollers in the wire saw, the present inventor has found that the groove rollers have the above-described decrease in wire strength due to frictional heat and sliding damage on the wire surface. It was found that the influence of the shape of was large.

That is, a representative example of the cross-sectional structure of a conventional groove roller is shown in FIG. 4 (A is the entire cross-sectional structure, B is the dotted circle b portion (groove portion) in FIG.
(Enlarged view of Fig.), A resin sleeve of equal diameter (11)
Is press-fitted into a metal cored bar (12), positioned with one end against the cored bar flange (12-1), and the other end face is tightened with a nut (13). Grooves (11-1) having the same depth (g) are formed on the outer peripheral surface of (11) over the entire length. The sleeve is made of resin because it is necessary to easily grip the wire in the groove in order to suppress the slip between the wire and the groove.

In the case of the groove roller having such a structure, as described above, the wire being cut generates heat by sliding on the work, and the heat is transmitted to the sleeve (11) and the sleeve expands. FIG. 5 illustrates the shape of the thermally expanded sleeve.

The reason for forming such a middle bulge is that both end surfaces of the sleeve (11) are restrained by the flange (12-1) and the nut (13), and heat is taken away by the flange and the nut. Due to the small increase in the outer diameter of the sleeve and because the expansion in the longitudinal direction of the sleeve (11) is restrained at both ends, a compressive force in the longitudinal direction acts on the sleeve (11), and the central portion is bulging. This is because

As a matter of course, the tension of the wire row wound around the sleeve expanded in the middle bulge shape is affected by the tension. FIG. 6 shows the relationship between the groove contours (11a) (11b) and the wires (4a) (4b) at both ends and the center of the sleeve of the three thermally expanded groove rollers.

That is, the length of the wire that goes around the three groove rollers (1), (2), and (3) is longer in the sleeve central portion than in the sleeve both ends. Therefore, when the wire wraps around from the sleeve end toward the center, the tension of the wire increases, and then the tension decreases as it moves to the opposite sleeve end. It goes without saying that the risk of wire breakage increases during this tension increase process.

By the way, in the multi-wire saw, in order to maintain the cutting accuracy, a strong tension is applied to the wire before the start of cutting,
Since resistance generated by sliding with the work is added as tension at the start of cutting, if the tension is further increased by thermal expansion of the sleeve, the risk of disconnection increases.

The present invention focuses on the fact that the wire breakage accident is largely caused by the increase in tension due to the thermal expansion of the sleeve described above, and an invention of the groove roller which prevents the increase in tension due to the thermal expansion of the sleeve by the shape of the sleeve. I arrived.

That is, the groove roller for a multi-wire saw according to the present invention has a shape in which the wire winding radius of the groove becomes uniform in the roll axial direction when the temperature of the groove roller being cut is increased by frictional heat. The gist is that the diameter of both ends of a resin sleeve in which grooves of the same depth are engraved is larger than the diameter of the central portion of the sleeve, and the radius of curvature of the wire winding is due to the thermal expansion of the sleeve during cutting. It has a shape that is almost uniform in the direction, and the depth of the groove of a resin sleeve of equal diameter is made uniform due to the thermal expansion of the sleeve during cutting so that the wire winding radius of curvature is substantially uniform in the roll axis direction. It is characterized in that it is shallowly cut at both ends and deeply cut at the center so that

The diameter of a resin sleeve with grooves of the same depth is cut into the center of both ends of the sleeve so that the wire winding curvature radius becomes almost uniform in the roll axis direction due to the thermal expansion of the sleeve during cutting. In the case of a larger groove roller, even if the temperature of the sleeve rises due to frictional heat between the wire and the workpiece during cutting, the central portion bulges due to the compressive force in the longitudinal direction that acts on the sleeve, and the diameter is almost the same as both ends. Therefore, the tension of the wire does not increase in the central portion of the sleeve, and the tension is almost constant over the entire length.

Further, the depth of the groove of the sleeve having the same diameter over the entire length is made shallow so that both ends of the sleeve are shallow and the central portion is deeply carved so that the radius of curvature of the wire winding becomes substantially uniform in the roll axial direction by thermal expansion of the sleeve. In the case of a groove roll, even if the sleeve temperature rises during the cutting process and the longitudinal compressive force acts on the sleeve and the center of the sleeve swells, the groove winding depth does not increase the winding radius of the wire. Therefore, the tension of the wire does not increase in the central portion of the sleeve, and the tension is almost constant over the entire length.

As described above, in the case of the groove roller for a multi-wire saw of the present invention, by increasing the shape of the resin sleeve itself or the depth of the groove, it is possible to prevent an increase in wire tension due to thermal expansion of the sleeve during cutting. Therefore, even if the strength of the wire is reduced due to frictional heat with the work, the risk of wire breakage is greatly reduced, and damage to the wire surface is also reduced.

Example 1 Example 1 FIG. 1 illustrates a groove roller corresponding to claim 1 of the present invention, and FIG. 1 (A) is a vertical sectional side view showing the entire roller.
FIG. 6B is an enlarged view of a portion indicated by a dotted circle (b) in FIG.

That is, the groove roller (20) of the present invention is formed in a loop shape in which the outer diameter Da of both ends (21a) of the resin sleeve is larger than the outer diameter Db of the central portion (21b). A groove (11-1) having the same depth (g) is engraved in the groove, and both ends (21a) and the center part (21b) of the sleeve are formed in the groove ( 11-1)
It is manufactured so that the wire winding radius of is uniform in the roll axial direction.

An example in which the above-mentioned claw-shaped groove roller is applied to a one-way traveling wire saw having a three-roll structure shown in FIG. 3 (interaxial distance 400 mm) is shown below.

The groove roller used is a 300 mm long ultra high molecular weight polyethylene sleeve shown in Fig. 1 with Da = 150 mm and Db = 1.
It has a grooving shape of 49.5 mm, and a groove with a depth of 1.7 mm is engraved in the sleeve, and a piano wire with a diameter of 0.16 mm is wound around this groove roller with a tension of 2 kg and a pitch of 2 mm over the entire length of the sleeve. Run at 400 mm per minute, 100 mm while pouring the polishing liquid
Push-up speed (constant) of quartz block with square cross section at 0.5 mm / min
Was cut. As a result, disconnection did not occur even after cutting was repeated 10 times, and stable cutting was possible.

On the other hand, for comparison, when a similar cutting process was carried out using a groove roller having a constant D = 150 mm and a constant groove depth of 1.7 mm shown in FIG. 4, disconnection occurred at the sixth and seventh times.

Embodiment 2 FIG. 2 exemplifies a groove roller corresponding to claim 2 of the present invention. FIG. 2A is a vertical sectional side view of the roller as a whole, and FIG. 2B and FIG. ) Point circle (b),
It is an enlarged view of the (c) part.

That is, in the groove roller (30) shown in FIG. 2, the outer diameter D of the resin sleeve (31) is uniform in the axial direction, but the groove (11-2) of the both ends (31a) of the sleeve is the same. Depth (g _a )
Is made shallower than the depth (g _b ) of the groove (11-3) in the central part (31b), and the groove depth is gradually increased from both ends to the central part. groove in a state where the roller during processing is increased temperatures (g _a) (g _b) is fabricated such wire winding radius is equal to the roll axis direction. The groove pitch p and the groove opening angle θ are the same for all grooves.

An example of applying the groove roller to the same one-way traveling wire saw as in Example 1 will be described below.

The groove roller used was 300 mm in length and had an outer diameter D, as in Example 1.
A 150 mm ultra high molecular weight polyethylene swivel with g _a = 1.2 mm at the end and g _b = at the center as shown in FIG.
A groove whose depth is continuously changed to 1.7 mm is machined, and this groove roller has a tension of 2 k as in Example 1.
g, with a pitch of 2 mm, running at 400 mm / min, running a quartz block of 100 mm square cross section at a pushing speed of 0.5 mm / min (constant) while pouring the abrasive liquid, resulting in 10 cuts. No wire breakage occurred even after repeated use, and stable cutting was possible.

In Examples 1 and 2 above, only the outer diameter of the resin sleeve was changed and the groove depth was changed, but it goes without saying that these can be combined. Further, the above two examples show the case where the wire is wound over substantially the entire length of the resin sleeve, but when the wire is wound only in a certain area in the axial direction of the resin sleeve, after the thermal expansion in that range, Needless to say, a resin sleeve having a shape such that the wire winding radius is uniform can be used.

EFFECTS OF THE INVENTION As described above, the groove roller according to the first and second aspects of the present invention has a structure in which the winding radius of the wire after thermal expansion of the sleeve is uniform, so that the sweep during cutting is performed. The occurrence rate of wire breakage due to thermal expansion is extremely low, and not only the wire saw operating rate can be significantly improved, but also work loss due to wire breakage can be significantly reduced, and the economic effect is great. Moreover, since the cross-sectional shape of the wire is kept to be a perfect circle by reducing the damage on the wire surface, there is no concern about saw marks, and it is possible to obtain a wafer that can be cut with high accuracy and has high surface quality.

[Brief description of drawings]

FIG. 1 exemplifies a groove roller corresponding to claim 1 of the present invention, and FIG. 1 (A) is a vertical sectional side view showing the entire roller,
FIG. 2B is an enlarged view of a portion indicated by a dotted circle (a) in FIG. 2A, and FIG. 2 is an example of a groove roller corresponding to claim 2 of the present invention, and FIG. 2A shows the entire roller. A vertical side view, an enlarged view of a dot circle (b) portion of FIG. (B) FIG. (A), an enlarged view of a dotted circle (c) portion of FIG. (A), and FIG. FIG. 4 is a schematic perspective view showing a main part of a multi-wire saw, FIG. 4 shows a typical example of a sectional structure of a conventional groove roller for a multi-wire saw, and FIG. 4A is a vertical sectional side view showing the entire roller. ) Is an enlarged view showing a portion of a dotted circle (b) in FIG. (A), FIG. 5 is a side view showing an example of the shape of a thermally expanded sleeve of the groove roller, and FIG. 6 is a view of three thermally expanded groove rollers. FIG. 6 is a schematic view showing the relationship between the contour of the groove and the wire at both ends and the center of the sleeve. 11-1, 11-2, 11-3 ... Groove, 12 ... Core bar 12-1 ... Flange, 13 ... Nut 20, 30 ... Groove roller 21, 31 ... Resin sleeve 21a, 31a ... … Sleeve ends 21b, 31b …… Sleeve center

Claims (2)

[Claims] 1. A wire array formed by winding a wire a plurality of times between a plurality of groove rollers is run, and a member to be cut is pressed against the wire array while supplying a working liquid to the part to be cut. In the groove roller of a multi-wire saw that cuts a large number of wafers with the required thickness, the diameter of both ends of the resin sleeve with grooves of the same depth is larger than the diameter of the central part of the sleeve The groove roller for a multi-wire saw, wherein the sleeve has a shape in which the radius of curvature for winding the wire is made substantially uniform in the axial direction of the roll by thermal expansion of the sleeve. 2. A wire array formed by winding a wire a plurality of times between a plurality of groove rollers is run, and a member to be cut is pressed against the wire array while supplying a working liquid to the portion to be cut. In the groove roller of a multi-wire saw that cuts many objects into multiple wafers, the groove depth of the resin sleeve of equal diameter is adjusted by the thermal expansion of the sleeve during cutting so that the wire winding radius of curvature is in the roll axis direction. A grooved roller for a multi-wire saw, characterized in that it is shallowly formed at both ends and deeply formed at the center so as to be substantially uniform.