JP2012056012A - Cutting grinding wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting grinding wheel capable of cutting even a hard brittle material like a sapphire wafer without generating chipping.SOLUTION: This cutting grinding wheel is composed by adding a boron compound to diamond abrasive grain. The boron compound is selected from a group consisting of BC, HBN and CBN.

Description

  The present invention relates to a cutting grindstone suitable for cutting hard brittle materials.

  A light emitting device such as a laser diode (LD) or a light emitting diode (LED) that emits blue or ultraviolet light having a short wavelength is manufactured by, for example, growing an epitaxial layer of gallium nitride (GaN) on a sapphire wafer.

  Since sapphire wafers have a relatively high Mohs hardness and are difficult to divide with a cutting blade, the sapphire wafer is divided into individual light-emitting devices by laser beam irradiation. The divided light-emitting devices are widely used in electric devices such as mobile phones and personal computers. It's being used.

  As a method of dividing a sapphire wafer into individual light emitting devices using a laser beam, first and second processing methods described below are known. In the first processing method, a laser beam having a wavelength (for example, 355 nm) at which ablation processing is performed on a sapphire wafer is irradiated to a region corresponding to a planned division line to form a division groove by ablation processing, and then an external force is applied. In this method, the sapphire wafer is divided into individual light emitting devices (see, for example, JP-A-10-305420).

  In the second processing method, a condensing point of a laser beam having a wavelength (for example, 1064 nm) having transparency to a sapphire wafer is positioned inside the wafer corresponding to the division line, and the laser beam is aligned along the division line. Irradiation to form a deteriorated layer inside the wafer, and then apply an external force to divide the sapphire wafer into individual light emitting devices (see, for example, Japanese Patent No. 3408805).

JP-A-10-305420 Japanese Patent No. 3408805

  However, the laser processing apparatus that performs the first and second processing methods described above is very expensive as compared with the cutting apparatus, and there is a problem that the cost is reduced.

  The present invention has been made in view of these points, and an object of the present invention is to provide a cutting grindstone capable of cutting without causing chipping even in a hard brittle material such as a sapphire wafer. It is.

  According to the present invention, there is provided a cutting grindstone for cutting a workpiece, which is constituted by adding a boron compound to diamond abrasive grains.

Preferably, the boron compound is composed of any of B ₄ C, HBN, and CBN. Preferably, the cutting grindstone is composed of an electroformed grindstone in which diamond abrasive grains and a boron compound are fixed by nickel plating. Alternatively, the cutting grindstone is composed of a sintered grindstone obtained by kneading diamond abrasive grains and a boron compound into any one of a resin bond, a vitrified bond, and a metal bond and sintering them.

  The present invention focuses on the fact that the boron compound has lubricity and is used as a release agent and has good thermal conductivity, and because the boron compound is added to the diamond abrasive grains to constitute a cutting grindstone, When a hard brittle material such as a sapphire wafer, a silicon carbide wafer, or a glass plate is cut, the impact force is alleviated by lubricity and heat dissipation, and the cutting can be performed satisfactorily without causing chipping on the front and back surfaces of the cutting groove.

It is an external appearance perspective view of the cutting device which can employ | adopt the cutting grindstone of this invention. It is a disassembled perspective view which shows the relationship between the front-end | tip part of a spindle, and the blade mount which should be fixed to a spindle. It is a disassembled perspective view which shows the relationship between the blade mount fixed to the front-end | tip of a spindle, and the hub blade which should be mounted | worn with a blade mount. It is a perspective view of the state where the hub blade is mounted on the spindle. It is a disassembled perspective view which shows the relationship between the blade mount fixed to the spindle, and the ring-shaped cutting blade which should be mounted | worn with a blade mount. It is a perspective view of a cutting unit. FIG. 7A is a photomicrograph of a sapphire wafer cut with the electroformed whetstone of the first embodiment of the present invention, and FIG. 7B is a photomicrograph of a sapphire wafer cut with a conventional electroformed whetstone. FIG. 8A is a micrograph of a sapphire wafer cut with a resin bond grindstone according to the second embodiment of the present invention, and FIG. 8B is a micrograph of a sapphire wafer cut with a conventional resin bond grindstone.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an appearance of a cutting apparatus 2 that can be divided into individual chips (light emitting devices) by mounting a cutting grindstone of the present invention and dicing a sapphire wafer.

  On the front side of the cutting device 2, there is provided operating means 4 for an operator to input instructions to the device such as machining conditions. In the upper part of the apparatus, there is provided a display means 6 such as a CRT for displaying a guidance screen for an operator and an image taken by an imaging means described later.

  On the surface of the sapphire wafer to be diced, as is well known, a plurality of division lines are formed in a lattice shape, and light-emitting devices such as LEDs and LDs are formed in areas partitioned by the division lines. ing.

  The wafer W is attached to a dicing tape T that is an adhesive tape, and the outer peripheral edge of the dicing tape T is attached to an annular frame F. As a result, the wafer W is supported by the frame F via the dicing tape T, and a plurality of wafers (for example, 25 sheets) are accommodated in the wafer cassette 8 shown in FIG. The wafer cassette 8 is placed on a cassette elevator 9 that can move up and down.

  Behind the wafer cassette 8, a loading / unloading means 10 for unloading the wafer W before cutting from the wafer cassette 8 and loading the wafer after cutting into the wafer cassette 8 is disposed. Between the wafer cassette 8 and the loading / unloading means 10, a temporary placement area 12, which is an area on which a wafer to be carried in / out, is temporarily placed, is provided. Positioning means 14 for positioning at a certain position is provided.

  In the vicinity of the temporary placement area 12, transport means 16 having a turning arm that sucks and transports the frame F integrated with the wafer W is disposed, and the wafer W carried to the temporary placement area 12 is It is sucked by the transport means 16 and transported onto the chuck table 18 and is sucked by the chuck table 18, and is held on the chuck table 18 by clamping the frame F by a plurality of clamps 19.

  The chuck table 18 is configured to be rotatable and reciprocally movable in the X-axis direction, and an alignment unit that detects a division line to be cut of the wafer W above the movement path of the chuck table 18 in the X-axis direction. 20 is arranged.

  The alignment unit 20 includes an imaging unit 22 that captures an image of the surface of the wafer W, and can detect a division line to be cut by processing such as pattern matching based on an image acquired by imaging. The image acquired by the imaging unit 22 is displayed on the display unit 6.

  On the left side of the alignment means 20, a cutting unit 24 for cutting the wafer W held on the chuck table 18 is disposed. The cutting unit 24 is configured integrally with the alignment means 20, and both move in conjunction with each other in the Y-axis direction and the Z-axis direction.

  The cutting unit 24 is configured by attaching a cutting blade 28 to the tip of a rotatable spindle 26 and is movable in the Y-axis direction and the Z-axis direction. The cutting blade 28 is located on the extended line of the imaging means 22 in the X-axis direction.

  Referring to FIG. 2, an exploded perspective view showing the relationship between the spindle and the blade mount attached to the spindle is shown. A spindle 26 that is rotationally driven by a servo motor (not shown) is rotatably accommodated in a spindle housing 32 of the spindle unit 30. The spindle 26 has a tapered portion 26a and a small distal end portion 26b, and a male screw 34 is formed on the small distal end portion 26b.

  A blade mount 36 includes a boss part (convex part) 38 and a fixed flange 40 formed integrally with the boss part 38, and a male screw 42 is formed on the boss part 38. Further, the blade mount 36 has a mounting hole 43.

  In the blade mount 36, the mounting hole 43 is inserted into the tip small diameter portion 26b and the tapered portion 26a of the spindle 26, and the nut 44 is screwed into the male screw 34 and tightened, so that the tip portion of the spindle 26 as shown in FIG. Attached to.

FIG. 3 is an exploded perspective view showing a mounting relationship between the spindle 26 to which the blade mount 36 is fixed and the cutting blade 28. The cutting blade 28 is called a hub blade, and a cutting grindstone (cutting blade) 50 in which diamond abrasive grains and a boron compound such as B ₄ C are dispersed in a nickel base material is provided on the outer periphery of a circular base 46 having a circular hub 48. It is configured by electrodeposition. As the boron compound, HBN (Hexagonal Boron Nitride) or CBN (Cubic Boron Nitride) can also be employed.

  By inserting the mounting hole 52 of the cutting blade 28 into the boss portion 38 of the blade mount 36 and screwing the fixing nut 54 into the male screw 42 of the boss portion 38 and tightening, the cutting blade 28 is moved to the spindle 26 as shown in FIG. Attached to.

Referring to FIG. 5, there is shown an exploded perspective view showing how a ring-shaped or washer-shaped cutting blade 56 is mounted on the spindle 26. The cutting blade 56 is composed of a sintered grindstone obtained by kneading diamond abrasive grains and a boron compound such as B ₄ C into a resin bond and sintering.

The resin bond is made of a phenol resin, an epoxy resin, a polyimide resin, or the like. In this embodiment, phenol resin is used as a resin bond, diamond abrasive grains and B ₄ C are kneaded with phenol resin and formed into a washer blade shape, and sintered at a sintering temperature of 180 ° C. to 200 ° C. for 7 to 8 hours. As a result, a cutting blade 56 made entirely of a sintered grindstone was produced.

The sintered grindstone is not limited to the resin bond sintered grindstone, and a metal bond sintered grindstone or a vitrified bond sintered grindstone can also be adopted. The metal bond sintered whetstone is formed by kneading diamond abrasive grains and B ₄ C into metal bond to form a washer blade shape, and sintering at a sintering temperature of 600 ° C. to 700 ° C. for about 1 hour. Here, as the metal bond, it is preferable to employ a copper and tin alloy bronze as a main component and a small amount of cobalt, nickel or the like mixed therein.

The vitrified bond sintered grindstone is formed by kneading diamond abrasive grains and B ₄ C into a vitrified bond to form a washer blade shape, and sintering at a sintering temperature of 700 ° C. to 800 ° C. for about 1 hour. Here, as the vitrified bond, it is preferable to employ a material mainly composed of silicon dioxide (SiO ₂ ) and slightly mixed with feldspar.

  The cutting blade 56 is inserted into the boss portion 38 of the blade mount 36, the detachable flange 58 is further inserted into the boss portion 38, and the fixing nut 54 is screwed into the male screw 42 and tightened, whereby the cutting blade 56 is fixed to the fixing flange 40. And is attached to the spindle 26 by being sandwiched from both sides by the detachable flange 58.

  Referring to FIG. 6, an enlarged perspective view of the cutting unit 24 that employs the hub blade 28 of the first embodiment as a cutting blade is shown. A blade cover 60 covers the cutting blade 28, and a cutting water nozzle (not shown) that extends along the side surface of the cutting blade 28 is attached to the blade cover 60. Cutting water is supplied to a cutting water nozzle (not shown) via the pipe 72.

  Reference numeral 62 denotes a detachable cover, which is attached to the blade cover 60 with screws 64. The detachable cover 62 has a cutting water nozzle 70 that extends along the side surface of the cutting blade 28 when attached to the blade cover 60. The cutting water is supplied to the cutting water nozzle 70 via the pipe 74.

  A blade detection block 66 is attached to the blade cover 60 with screws 68. A blade sensor (not shown) composed of a light emitting portion and a light receiving portion is attached to the blade detection block 66, and the state of the cutting grindstone 50 of the cutting blade 28 is detected by this blade sensor.

  When the blade sensor detects chipping or the like of the cutting grindstone 50, the cutting blade 28 is replaced with a new cutting blade. Reference numeral 76 denotes an adjusting screw for adjusting the position of the blade sensor.

A nickel plating solution in which diamond abrasive grains having a particle diameter of 5 μm and B ₄ C particles having a particle diameter of 1 μm were mixed at an appropriate ratio was prepared. The outer periphery of the hub blade as shown in FIG. 3 is electrocast in this nickel plating solution, and contains 12 to 18% by volume of diamond abrasive grains having a particle size of 5 μm, and B ₄ C particles having a particle size of 1 μm in volume. An electroformed grinding wheel having a thickness of 30 μm and containing 15 to 10% in a ratio was formed.

  The hub blade 28 having the electroformed grinding wheel was mounted on the spindle 26, and a sapphire wafer having a thickness of 100 μm was cut at a spindle rotation speed of 10000 rpm, a cutting depth of 30 μm, and a feed rate of 10 mm / second. FIG. 7A shows a micrograph of the sapphire wafer formed with two cut grooves after cutting as viewed from the surface side. The magnification is 200 times. As is apparent from this figure, almost no chipping occurred on both sides of the cutting groove.

  A nickel plating solution was prepared by mixing diamond abrasive grains having a particle diameter of 5 μm and HBN particles having a particle diameter of 1 μm at an appropriate ratio. The outer periphery of the hub blade is electrocast in this nickel plating solution, containing 12 to 18% by volume of diamond abrasive grains having a particle size of 5 μm, and HBN (hexagonal boron nitride) particles having a particle size of 15 μm by volume. An electroformed grindstone having a thickness of 30 μm and containing 10% was formed.

  When a hub blade having this electroformed grinding wheel on the outer periphery was mounted on a spindle and a sapphire wafer was cut under the same conditions as in Example 1, it was confirmed that almost no chipping occurred on both sides of the cutting groove.

  A nickel plating solution in which diamond abrasive grains having a particle diameter of 5 μm and CBN particles having a particle diameter of 1 μm were mixed at an appropriate ratio was prepared. The outer periphery of the hub blade is electrocast in this nickel plating solution, containing 12 to 18% by volume of diamond abrasive grains having a particle size of 5 μm and 15 μm CBN (cubic boron nitride) particles having a particle size of 1 μm. An electroformed grindstone having a thickness of 30 μm and containing 10% was formed.

  The hub blade 28 having this electroformed grinding wheel was mounted on the spindle 26, and the sapphire wafer was cut under the same conditions as in Example 1. As a result, it was confirmed that almost no chipping occurred on both sides of the cutting groove.

(Comparative Example 1)
A nickel plating solution was prepared by mixing diamond abrasive grains having a particle size of 5 μm. The outer periphery of the hub blade was electrocast in this nickel plating solution to produce a hub blade 28 having a 30 μm-thick electroformed grindstone 50 containing 15 to 20% by volume of diamond abrasive grains having a particle size of 5 μm.

  The hub blade was attached to the tip of the spindle 26, and the sapphire wafer was cut under the same conditions as in Example 1. FIG. 7B shows a micrograph of the sapphire wafer formed with two cut grooves after cutting as viewed from the surface side. The magnification is 200 times.

  As is apparent from this figure, many relatively large chips are generated on both sides of the cutting groove, and it has been found that a cutting blade having this cutting wheel on the outer periphery is not suitable for cutting a sapphire wafer.

Diamond abrasive grains having a particle size of 5 μm and B ₄ C particles having a particle size of 1 μm in a volume ratio of 45 to 20% were mixed in a resin bond made of phenol resin into a washer shape. This was sintered at a sintering temperature of 180 ° C. for about 8 hours to form a washer-like resin bond grindstone having a thickness of 200 μm.

  The resin bond grindstone was mounted on a spindle, and a quartz substrate having a thickness of 1000 μm was cut at a spindle rotation speed of 20000 rpm, a cutting depth of 1080 μm, and a feed rate of 15 mm / second. FIG. 8 (A) shows a photomicrograph of the cut quartz substrate taken from the back side. The magnification is 200 times. It was confirmed that almost no chipping occurred not only on the back surface side shown in FIG.

  A washer-shaped cutting grindstone was formed by mixing 10-20% by volume of diamond abrasive grains having a particle size of 5 μm and 45-20% by volume of HBN particles having a particle diameter of 1 μm in a metal bond containing bronze as a main component. This was sintered at a sintering temperature of 700 ° C. for about 1 hour to produce a 200 μm thick washer-shaped metal bond grindstone. When this metal bond grindstone was mounted on a spindle and the quartz substrate was cut under the same conditions as in Example 4, it was confirmed that almost no chipping occurred on the front surface side and the back surface side of the quartz substrate.

  A diamond abrasive grain having a particle size of 5 μm and CBN particles having a particle diameter of 1 μm in a volume ratio of 45 to 20% are mixed in a vitrified bond mainly composed of silicon dioxide to form a washer shape. The body was sintered at a sintering temperature of 700 ° C. for about 1 hour to produce a 200 μm thick washer-shaped vitrified bond grindstone. The vitrified bond grindstone was mounted on a spindle, and the quartz substrate was cut under the same conditions as in Example 4. As a result, it was confirmed that almost no chipping occurred on the front surface side and the back surface side of the quartz substrate.

(Comparative Example 2)
Molded into a washer shape by mixing diamond abrasive grains with a particle size of 5 μm in a resin bond formed from a phenolic resin with volume ratios of 10 to 20% and SiC particles with a particle diameter of 1 μm in a volume ratio of 35 to 25%. The body was sintered at a sintering temperature of 180 ° C. for about 8 hours to produce a resin bond grindstone having a thickness of 200 μm.

  This resin bond grindstone was mounted on a spindle, and a quartz substrate was cut under the same conditions as in Example 4. A micrograph of the back side of the quartz substrate after cutting is shown in FIG. The magnification is 100 times. As is clear from this figure, many relatively large chips were generated on the back side of the quartz substrate, and it was found that the conventional resin bond grindstone is not suitable for cutting the quartz substrate.

2 Cutting device 18 Chuck table 24 Cutting unit 26 Spindle 28 Cutting blade 50 Electroforming wheel 56 Washer-shaped resin bond wheel

Claims (4)

A cutting wheel for cutting a workpiece,
A cutting grindstone characterized by comprising a boron compound added to diamond abrasive grains. The cutting grindstone according to claim 1, wherein the boron compound is selected from the group consisting of B ₄ C, HBN, and CBN.   The cutting grindstone according to claim 1 or 2, wherein the cutting grindstone is composed of an electroformed grindstone in which diamond abrasive grains and a boron compound are fixed by nickel plating.   The cutting grindstone according to claim 1 or 2, wherein the cutting grindstone is composed of a sintered grindstone obtained by kneading diamond abrasive grains and a boron compound into any one of a resin bond, a vitrified bond, and a metal bond and sintering.

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