JPS6229177B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for cutting hard and brittle members, such as semiconductor members, with a wire.

Conventionally, a wire cutting method has been widely adopted as a method for obtaining flaky wafers from columnar semiconductor members.

In this method, multiple wires are stretched in parallel and pressed against a semiconductor member (hereinafter referred to as the workpiece) while reciprocating, and a slurry containing a mixture of abrasive grains and oil is supplied to the pressed area to perform wrapping. This is a method of cutting. This method is superior to other methods such as those using a cutting grindstone in that the precision of the wafer obtained is high, but it has the drawback that the cutting speed is very slow and efficiency is poor. In other words, in this cutting method, the contact length between the wire and the workpiece is short at the beginning of the cut, and the depth of cut is shallow, so sufficient slurry is supplied and the cutting speed is high, but as the depth of cut increases, the contact length increases. On the other hand, since the processing area also becomes deep, slurry cannot be sufficiently supplied to the processing area. In addition, since the contact length differs greatly between the beginning and the middle (large diameter part of the workpiece), the wrapping pressure also changes greatly, making it difficult to maintain an appropriate wrapping pressure at all times, and the cutting speed is slow.

In order to solve the above-mentioned problems, cutting the workpiece while swinging it has also been practiced. By swinging, the cutting line is in an arc shape, and the almost straight wire is brought into contact with a slight arc, so the wrapping pressure changes much less than in the past, and the sriller can be fed smoothly. Therefore, the disadvantages of the conventional method are greatly improved.

However, in this oscillating cutting method, since the oscillating angle is constant throughout, there is a disadvantage that there is a long period of time during which wrapping is not performed at both ends of the oscillation until the center (maximum diameter portion) of the workpiece is reached, resulting in poor efficiency. In addition, the wire separates from the workpiece even at the beginning of cutting, resulting in poor precision at the beginning of cutting, and even at the end of cutting, the swinging causes cracks in the workpiece.

The present invention was made in order to eliminate the above-mentioned disadvantages, and the cutting is made without swinging at the beginning and end of cutting, and the swinging angle is gradually increased up to the vicinity of the center of the workpiece, and is kept constant near the center. This is a wire cutting method for a hard and brittle member that cuts the hard and brittle member with high precision and efficiency by sequentially decreasing the swing angle after passing near the center.

The details of the present invention will be explained below using one example.
First, the apparatus implementing the present invention will be briefly described. A processing section 2 constituted by a plurality of wires 1, ... stretched in parallel so as to be able to reciprocate, a main body section 4 provided below opposite to this and supporting a workpiece 3, and a main body section 4 for controlling the processing section 2. It is composed of a control section 5. In the main body 4, a processing table 8 is attached to a piston rod 7 of a hydraulic device 6 that can freely adjust pressure, and a swing drive mechanism 9 consisting of a motor, a reduction gear, a gear train, etc. is mounted on the top surface of the processing table 8.
A swing table 11 supported by a bracket 10 is mounted on the swing table 11, and a cylindrical workpiece 3 is fixed on the swing table 11 via an auxiliary member 13 made of ceramics or the like. ing. The control unit 5 includes a motor control circuit 20 that controls the swing drive mechanism 9, a hydraulic control circuit 21 that controls the hydraulic device 6, and two sets of detection bodies 22, 22 that detect the height of the processing table 8. It is growing. The detection object 22 is a light receiving object that includes a light emitter 23 with a built-in light source installed at one end of the processing table 8, and a plurality of photoelectric conversion elements (in this example, every 5 mm) arranged vertically in a row at equal intervals. The body 24 is the projector 2
3 and are arranged opposite to each other. As the processing table 8 moves up and down, each light projecting body 23 also moves up and down, and each photoelectric conversion element facing the detection light that is projected from this receives an electric signal corresponding to the height of the processing table 8. Each detection object 22, 2
Send from 2. One of these electric signals enters the motor control circuit 20, and the rotation speed of the motor is switched to a preset motor rotation speed according to the height of the processing table 8, and the swing angles are determined accordingly. The other electric signal enters the hydraulic control circuit 21, and the hydraulic pressure of the hydraulic device 6 is switched to a preset pressure according to the height of the processing table 8, and the wire 1
The load of the workpiece 3 on each is determined.

Next, an embodiment of the method of the present invention will be described along with the operation of the above-described apparatus.

The relationship between the depth of cut t and the swing angle θ and the relationship between the depth of cut t and the load in this example are as follows.
The settings are as shown in the figure, and processing is performed based on these settings.

In FIG. 2, the horizontal axis represents the depth of cut t from the cutting start point, the vertical axis for curve A represents the swing angle, and the curve B represents the wrapping pressure (load W). The swing angle θ is the angle at which the workpiece 3 swings, as shown in FIG. This is the angle θ formed at the swing center C (actually, it is slightly larger than this). Further, the wrapping pressure (load W) is the force with which the workpiece 3 presses the wire 1 by the hydraulic device 6. The processing mode will be explained with reference to these diagrams A and B. First, as for the swing angle θ, as shown by curve A, the cut is made without swinging at first, and swinging is started for the first time at the cutting depth t ₁ . As the cutting depth t increases, the cutting line R increases, and the swing angle increases accordingly. Although this increase is shown linearly in curve A for convenience, since the detection body 22 detects the height of the processing table 8 discontinuously, it increases stepwise. When the depth of cut reaches t ₂ near the center O of the workpiece 3, that is, approximately 1/3 of the diameter of the workpiece, it stops increasing and continues cutting at a constant swing angle θ ₂ until the center O
The oscillation angle is gradually decreased until the depth of cut reaches t ₃ , which is approximately 2/3, and the depth of cut is reached near the cutting completion position.
At t ₄ , the rocking is stopped and the cutting is completed in the same manner as the beginning.

In addition, the pressing force (load W) is as shown in curve B.
After cutting several mm (t' ₁ ), it increases sequentially according to the depth of cut t, stops increasing at the depth of cut t' ₂ , which is before the depth of cut _t2 , and continues cutting until the depth of cut t' ₄ , which is near the cutting completion position. , the pressing force is gradually decreased from here, and reaches almost the initial pressing force at _t5 when cutting is completed.

Note that the above-mentioned schedule is implemented by an electric signal from the detection body 22, and when the height of the processing table 8 corresponding to the depth of cut t is detected, the corresponding swing angle and pressing force are adjusted. Appropriate values are set in advance in each of the control circuits 20 and 21 so that the control circuits 20 and 21 can be used.

As detailed above, in the wire cutting method for hard and brittle members of the present invention, the cut is made without rocking at first, so the wire is not detached from the workpiece or chipped, and the cut is made accurately. progresses,
After the wire stabilizes, the workpiece is cut while swinging, so the cutting line becomes arcuate due to the swinging, and the contact area between the wire and workpiece is much larger than with conventional straight cutting methods. Since it is small and kept almost constant, it is easy to manage the lap pressure, and the slurry flows in and out smoothly, resulting in good cutting efficiency.Furthermore, since the swing angle changes according to the cutting depth, There is no waste at both ends of the swing, further improving efficiency. In addition, since the swinging is stopped near the cutting completion point, undesired breakage is prevented at the end of cutting, processing in subsequent steps is significantly reduced, and the yield is improved.

In addition, as in this example, when the pressing force is initially cut,
The method of cutting by keeping it small and keeping it large during rocking is as follows.
The first cut is made accurately and accurately, and the contact area of the wire increases during swinging, further improving cutting efficiency.

[Brief explanation of the drawing]

FIG. 1 is a front view showing the main parts of an apparatus for implementing an embodiment of the present invention, and FIG. 2 is a diagram for explaining the schedule of the embodiment. 1: wire, 3: workpiece, θ: swing angle,
O: Center of the workpiece.

Claims (1)

[Claims] 1 In a wire cutting method in which a wire is pressed against a workpiece made of a columnar hard brittle member while reciprocating, and abrasive grains are supplied to the pressed area to cut the workpiece, the above-mentioned cutting process is performed until a predetermined depth of cut is reached. After reaching the predetermined depth of cut without oscillating the workpiece, the oscillation is started, and the oscillation angle of the oscillation is sequentially increased according to the depth of cut. A wire of a hard brittle member, characterized in that the swinging angle is set at a maximum, and the swinging angle is decreased in accordance with the cutting depth of the object passing through the vicinity, and when the swinging angle reaches the vicinity of the cutting completion part, the swinging is stopped and the wire is cut and separated. Cutting method.