HK1071869B - Porous abrasive tool and method for making the same - Google Patents

Description

Porous abrasive article and method of making the same

(1) Field of the invention

The present invention relates generally to abrasives and abrasive articles suitable for surface grinding and polishing of hard and/or brittle materials. More particularly, the present invention relates to porous bonded abrasive articles having an interconnected pore structure, and methods of making the same. The abrasive of the present invention can be used in high performance lapping operations such as back-lapping silicon wafers, aluminum titanium carbide and silicon carbide wafers commonly used in electronic component manufacturing.

(2) Background information

It is generally known that the use of porous abrasives can improve the mechanical grinding process. The pores generally provide flow channels for abrasive fluids, such as coolants and lubricants, which promote more efficient cutting, reduce metallurgical damage (e.g., surface sintering), and maximize the life of the tool. Porosity can also remove material gaps (e.g., debris or fines) from the article being abraded, which can be particularly important when the article being abraded is relatively soft or requires surface polishing to meet certain conditions (e.g., back grinding of silicon wafers).

Previous attempts to make abrasive articles and/or appliances having porous structures can generally be categorized into one of two methods. In the first method, the porous structure is made by adding a pore-forming organic medium (e.g., ground walnut shells) to the abrasive article. These media thermally decompose during sintering, leaving cavities or pores in the hardened abrasive article. Examples of such methods include Carmen et al, U.S. Pat. No. 5,221,294, Wu, U.S. Pat. No. 5,429,648, Grotoh et al, Japanese patent No. A-91-161273, and Satoh et al, Japanese patent No. A-91-281174. In a second method, the porous structure may be fabricated by adding a closed cell material, such as hollow alumina, to the abrasive article. An example of this can be seen in U.S. patent No. 5,203,886 to Sheldon et al.

In an alternative method, Wu et al, U.S. Pat. Nos. 5,738,696 and 5,738,697, the contents of which are incorporated herein by reference, disclose abrasive articles and methods for making such articles using fibrous abrasive particles having an aspect ratio of at least 5: 1. Due to the poor packing characteristics of the elongated abrasive particles, the porosity and permeability of the abrasive article are increased, which is suitable for relatively high performance abrading.

As market demand for precision components in products such as engines, refractory equipment and electronics (e.g., silicon and silicon carbide wafers, magnetic heads, display windows) has increased, so has the demand for improved abrasive articles for use in the extremely precise grinding and polishing of ceramics and other relatively hard and/or brittle materials. These abrasive articles known in the art have not proven to fully satisfy the requirements set forth above. Accordingly, there is a need for improved abrasive articles and tools, particularly those comprising relatively high porosity.

One aspect of the invention includes a method of making an abrasive article. The method includes blending a mixture of abrasive particles, binder material, and dispersoid particles, the mixture comprising about 0.5 to 25 volume percent abrasive particles, about 19.5 to 49.5 volume percent binder material, and about 50 to 80 volume percent dispersoid particles. The method further includes pressing the mixture into a milled compacted composite, thermally processing the composite, and immersing the composite in a solvent for a period of time to dissolve substantially all of the dispersion and dissolve the dispersion in the solvent. In one variation of this aspect, the bond material comprises about 35 to 85 weight percent copper, about 15 to 65 weight percent tin, and about 0.2 to 1.0 weight percent phosphorus, wherein the sum of the weight percent of each component equals 100 weight percent. Another variation of this aspect is that the dispersion comprises granular sodium chloride and the solvent comprises boiling water.

In another aspect, the invention includes a grinding segment for a segmented grinding wheel. The abrasive segment comprises a composite material comprising a plurality of superabrasive particles and a metal bond matrix sintered together at a temperature in a range of about 370-795 ℃. The composite material has a plurality of interconnected pores distributed therein. The composite material includes about 0.5 to 25 volume percent abrasive particles, about 19.5 to 49.5 volume percent metal binder, and about 50 to 80 volume percent interconnected porosity. The metal bond matrix comprises about 35 to 70 weight percent copper, about 30 to 65 weight percent tin, and about 0.2 to 1.0 weight percent phosphorus, wherein the sum of the weight percent of each component equals 100 weight percent. The plurality of superabrasive particles are selected from the group consisting of diamond and cubic boron nitride, the superabrasive particles having an average particle size of less than about 300 microns.

In another aspect, the invention includes a segmented grinding wheel. The grinding wheel comprises a core and a circular periphery, wherein the core has a minimum specific strength of 2.4MPa-cm³The density of the core is 0.5-8.0 g/cm³. The wheel further includes an abrasive rim comprised of a plurality of segments, each segment comprising a composite material having a plurality of abrasive particles and a metal bond matrix sintered together at a temperature in the range of about 370-795 ℃, and the composite material having a plurality of interconnected pores distributed therein, the composite material comprising about 50-80 vol% of each otherAnd connecting pores. The wheel still further comprises a thermally stable binder for joining said core and said segments.

In another aspect, the invention includes a method of making an abrasive article comprising about 40 to about 80 volume percent interconnected porosity. The method includes blending a mixture of abrasive particles, organic or other non-metallic binder material, and dispersoid particles, the mixture comprising about 0.5 to 25 volume percent abrasive particles, about 19.5 to 65 volume percent organic binder material, and about 40 to 80 volume percent dispersoid particles. The method further includes pressing the mixture into a ground compacted composite, thermally processing the composite, and immersing it in a solvent for a period of time to dissolve substantially all of the dispersion, dissolving the dispersion in the solvent. In one variation of this aspect, the dispersion comprises granulated sugar and the solvent comprises boiling water.

In another aspect, the invention includes a grinding segment for a segmented grinding wheel. The abrasive segment comprises a composite material comprising a plurality of superabrasive particles and a non-metallic bond matrix solidified together. The composite material has a plurality of interconnected pores distributed therein and comprises about 0.5 to about 25 volume percent abrasive particles, about 19.5 to about 65 volume percent non-metallic binder, and about 40 to about 80 volume percent interconnected pores. The plurality of superabrasive particles is selected from the group consisting of diamond and cubic boron nitride, and the plurality of superabrasive particles has an average particle size of less than about 300 microns.

In another aspect, the invention includes a segmented grinding wheel. The grinding wheel comprises a core and a circular periphery, wherein the core has a minimum specific strength of 2.4MPa-cm³The density of the core is 0.5-8.0 g/cm³. The wheel also includes an abrasive rim comprised of a plurality of segments, each segment comprising a composite material including abrasive particles and a non-metallic bond matrix cured together. The composite material has a plurality of interconnected pores distributed therein and comprises about 40-80 vol% interconnected porosity. The wheel further comprises a thermally stable bond connecting the core and each of the plurality of segments.

FIG. 1 is a schematic view of an embodiment of a grinding section according to the present invention; and is

FIG. 2A is a partial schematic view of an embodiment of a grinding wheel including 16 grinding segments of FIG. 1;

FIG. 2B is a cross-sectional view taken along the line "A" - "A" in FIG. 2A; and

fig. 2C is a partial enlarged view showing a portion 110 of fig. 2B.

The present invention includes a porous abrasive article useful in lapping, polishing or cutting operations. One example of a grinding wheel according to the present invention is a grinding segment 10 for a segmented grinding wheel 100 (shown, for example, in figures 1 and 2, which will be described in more detail in example 1 below). One embodiment of the abrasive article of the present disclosure comprises about 50 to about 80 volume percent interconnected porosity. Another embodiment of an abrasive article according to the present disclosure comprises a non-metallic binder, such as an organic binder material (e.g., a phenolic resin), and comprises about 40 to about 80 volume percent interconnected porosity. The present invention also includes methods of making porous abrasive articles. Grinding wheels (e.g., wheel 100) comprising one or more abrasive articles (e.g., segment 10) according to the present disclosure may be potentially advantageous for mirror polishing hard and/or brittle materials such as silicon wafers, silicon carbide, titanium aluminum carbide, and the like. These wheels provide further advantages in that they do not require grinding (or dressing) of the grinding surface of the wheel during mirror finish grinding of the above materials. Other potential advantages of the present invention will appear from the discussion and examples that follow.

In contrast to conventional wisdom (e.g., japanese patent No. 60-118,469 to Ishihara), one aspect of the present invention produces an abrasive article having an interconnected porosity greater than 50 volume percent, and particularly a porosity of about 50 to 80 volume percent, that provides superior abrasive performance without sacrificing all of the mechanical integrity of the abrasive article when abrading hard and/or brittle materials. Accordingly, embodiments of the abrasive articles described herein comprise at least 50 vol% interconnected porosity and an effective amount of at least one abrasive particle and a bond material. The abrasive article may also optionally include fillers, lubricants, and other ingredients known to those familiar with the art. The abrasive articles preferably comprise about 50 to about 80 volume percent interconnected porosity, and more preferably about 50 to about 70 volume percent interconnected porosity.

Essentially any type of abrasive particle may be used in the abrasive articles of the present disclosure. Conventional abrasives include, but are not limited to, alumina, silica, silicon carbide, zirconia-alumina, garnet, and silicon carbide having an abrasive grain size in the range of about 0.5 to 5000 microns, preferably about 2 to 300 microns. Superabrasive particles having a particle size very similar to conventional abrasive particles may also be used, including, but not limited to, diamond and Cubic Boron Nitride (CBN), with or without a coated metal layer. The selection of the size and type of abrasive particles generally varies depending on the characteristics of the workpiece and the type of abrading process. For super-finishing (i.e., "mirror finishing") grinding, smaller particle sizes of superabrasive particles, such as in the range of about 0.5-120 microns, to in the range of about 0.5-75 microns, are required. In general, smaller (i.e., finer) grit sizes are suitable for fine grinding and surface polishing operations, while larger (i.e., coarser) grit sizes are suitable for planing, coping, and other operations requiring the removal of relatively more material.

Essentially any bond material commonly used in the manufacture of bonded abrasive articles may be used as a substrate in the abrasive articles of the present invention. For example, metallic, organic, resinous or vitrified binders (with the addition of suitable curing agents if necessary) may be used, with metallic binders generally being selected. Generally, a fracture toughness of about 1.0 to 6.0 MPa-m is selected^1/2A metallic binder having a fracture toughness in the range of about 1.0 to 3.0 MPa-m^1/2More preferable is the range. Further details regarding fracture toughness are available in U.S. patent nos. 6,093,092 and 6,102,789 to ramamath et al, the contents of which are incorporated herein by reference, and hereinafter referred to as ramamath patents.

Materials used in the metal bond matrix include, but are not limited to, bronze, copper zinc alloy (i.e., brass), cobalt, iron, nickel, silver, aluminum, indium, antimony, titanium, zirconium, and alloys and mixtures thereof. It has been found that the metal bond matrix composition is typically a mixture of copper and tin. Compositions suitable for use in the abrasive articles of the present invention should include about 35 to 85 weight percent copper and about 15 to 65 weight percent tin. The composition preferably comprises about 35 to 70 wt.% copper, about 30 to 65 wt.% tin, and optionally about 0.2 to 1.0 wt.% phosphorus (e.g., a copper-phosphorus alloy), wherein the sum of the wt.% of each component is equal to 100 wt.%. A bond material having titanium or titanium hydride, chromium, or other well-known superabrasive active materials capable of forming carbide or nitride chemical bonds between the particles and the binder at selected sintering conditions may optionally be used to strengthen the particle/binder bond. A stronger interaction between the particles/binder generally reduces the tendency of the particles to fall off during grinding,

which can damage the workpiece and shorten the life of the abrasive article.

An example of a suitable organic binder is a thermosetting resin, but other types of resins may be used. The resin is preferably an epoxy resin or a phenol resin, and may be used in a liquid state or a powder state. Specific examples of suitable thermosetting resins include phenolic resins (e.g., novolaks and resoles), epoxy resins, unsaturated polyesters, bismaleimides, polyimides, cyanate esters, melamines, and the like.

Embodiments of the abrasive article of the present disclosure comprise about 50 to about 80 volume percent interconnected pores having an average pore size in the range of about 25 to about 500 microns. Interconnected porosity is formed during the manufacturing process by adding a sufficient amount of dispersion particles to the mixture of abrasive particles and binder to ensure that a relatively high percentage of the dispersion particles are in contact with other dispersion particles in the molded abrasive article (before and after sintering).

One embodiment of a desired porous material comprises about 0.5 to about 25 volume percent superabrasive particles and about 30.5 to about 49.5 volume percent metal bond matrix sintered together at a temperature of about 370 to about 795 ℃ and a pressure of about 20 to about 33 MPa. The metal bond matrix comprises about 35 to 70 weight percent copper, about 30 to 65 weight percent tin, and about 0.2 to 1.0 weight percent phosphorus, wherein the sum of the weight percent of each component equals 100 weight percent. The superabrasive particles comprise diamond having a particle size of between about 0.5 and 300 microns (in embodiments, between about 0.5 and 75 microns).

Other desirable embodiments of the porous material comprise about 40 to about 80 volume percent interconnected pores having an average pore size between about 150 and about 500 microns. These embodiments further comprise about 0.5 to 25 volume percent superabrasive particles and about 19.5 to 65 volume percent organic binder, and the two components are cured together at a temperature of about 100 to 200 ℃ (temperature range of about 400 to 450 ℃ for polyimide resins) and a pressure of about 20 to 33 Mpa. (preferably, acicular dispersions are used, i.e., dispersions having an aspect ratio of greater than or equal to 2:1, resulting in interconnected porosity of about 40 to 50 volume percent). Conventional powder metallurgy/polymer manufacturing processes may be used to manufacture the abrasive articles of the present disclosure. Abrasive particles, binder and dispersion powders of suitable size and composition are uniformly mixed, molded into a suitable shape, and sintered/cured at elevated temperature and pressure to produce a relatively dense composite material having a density of preferably at least 95% of theoretical density (typically about 98-99% of theoretical density). For abrasive articles comprising a metal bond matrix, these powders are typically sintered at a temperature of about 370 to 795 ℃ and a pressure of about 20 to 33 MPa. For example, in one embodiment, the powder mixture is first heated at 401 ℃ for 20 minutes. The powder was then sintered at a temperature of 401 ℃ and a pressure of 22.1MPa for 10 minutes. After cooling, the abrasive compacted composite material comprising the dispersions in sufficient contact with each other is immersed in a solvent to selectively remove (i.e., dissolve) the dispersion. The resulting abrasive article is in a foam-like structure and comprises a mixture of abrasive and bond matrix and has a network of interconnected pores that are distributed throughout the irregularities (i.e., cavities formed by dissolution of the dispersion).

Basically any dispersion which dissolves rapidly in a solvent such as water, alcohol, acetone or the like can be used. Generally, one will select a readily water soluble dispersion such as sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium silicate, sodium carbonate, sodium sulfate, potassium sulfate, magnesium sulfate, and the like, and mixtures thereof. For applications in some grinding, such as silicon wafers and other electronic components, non-ionic (i.e., non-salt) dispersions, such as sugars, dextrins, polysaccharide oligomers, may be selected. It is preferred to select those dispersions which have a higher solubility in water and faster dissolution kinetics, such as sodium chloride or sugars. The dispersions which are preferably used may also have a relatively high melting point (mp) in order to withstand the sintering process. For example, sodium chloride has a melting point of about 800 ℃. For abrasive articles requiring very high sintering temperatures, sodium aluminum silicate (mp 1650 ℃), magnesium sulfate (mp1124 ℃), potassium phosphate (mp1340 ℃), potassium silicate (mp976 ℃), sodium metasilicate (mp1088 ℃) and mixtures thereof may be used as the dispersion.

The particle size of the dispersion is typically in the range of about 25 to 500 microns. In a satisfactory embodiment, the dispersion has a particle size distribution of between about 74 and 210 microns (i.e., contains dispersion particles finer than U.S. mesh (standard sieve) 70, but coarser than U.S. mesh 200). In another satisfactory embodiment, the dispersion has a particle size distribution of between about 210 and 300 microns (i.e., comprises dispersion particles finer than U.S. mesh 50 and coarser than U.S. mesh 70). In yet another satisfactory embodiment, a sugar is used as the dispersion having a particle size distribution in the range of about 150 to 500 microns (i.e., comprising dispersion particles finer than U.S. mesh 35, but coarser than U.S. mesh 100).

The abrasive articles described above may be used to make substantially any type of abrasive article. Common tools include face wheels (e.g., ANSI 2A2T or 2A2TS type wheels and 1A1 type wheels) and cup wheels (e.g., ANSI 2 or 6 type wheels, or 119V type conical cup wheels). The grinding wheel may include a core (e.g., core 20 of fig. 2A-2C) having a central bore for securing the grinding wheel to a grinding machine and designed to support a perforated grinding rim arranged along its circumference (e.g., see grinding wheel 100 of fig. 2A, discussed in more detail below with reference to example 1). The two parts of the wheel are typically bonded together using a bond that is thermally stable under abrasive conditions. The wheel and its components are also capable of withstanding the stresses that occur when the peripheral velocity of the wheel rises to at least 80 m/s, and more preferably to 160 m/s or more.

In one embodiment, the core has a substantially circular outer shape. The core comprises a core body having a minimum specific strength of 2.4MPa-cm³A pressure of 40 to 185MPa-cm³Any material per gram. The density of the core material is 0.5-8.0 g/cm³Preferably about 2.0 to 8.0g/cm³. Examples of suitable materials for the above are steel, aluminum, titanium, bronze, composites and alloys thereof, and mixtures thereof. The core may also be made of reinforced plastic having a specified minimum specific strength. Composite and reinforcing core materials typically comprise a continuous phase of a metal or plastic matrix, often in powder form, and a relatively stiff, more resilient, and/or less dense fibrous or particulate material is added to the powder as a discontinuous phase. Examples of reinforcing materials suitable for use in the core of the appliance of the present invention are glass fibres, carbon fibres, aramid fibres, ceramic particles, and hollow filler materials such as glass, mullite, alumina and Z-Light ceramic microspheres. Typical suitable metal core materials include the steel aluminum alloys of ANSI4140, 2024, 6065, and 7178. Further details regarding suitable core materials, properties, etc. are provided in the ramatath patent.

The grinding wheel (e.g., grinding wheel 100 shown in FIG. 2A) may be manufactured by first manufacturing a single segment having a preselected size, composition, and porosity as described above (e.g., see segment 10 shown in FIG. 1, discussed in more detail below with reference to example 1). The wheel may be compression molded and sintered, fired, or cured by various techniques commonly used in the art. Among these processes are hot pressing (at pressures of about 14 to 28MPa), cold pressing (at pressures of about 400 to 500MPa or higher), and hot stamping in steel dies (at pressures of about 90 to 110 MPa). The skilled artisan will readily appreciate that cold pressing (and less intense hot embossing) is used only for dispersion particles of high compressive strength (i.e., crush resistance). For metal bonded abrasive articles, hot pressing (at about 350-500 ℃ C. and 22 MPa) is preferred. For organic bonded abrasive articles in which the saccharide-containing dispersion is used, it is preferred to perform a cold or "warm" press (temperature less than about 160 ℃). Further details regarding the pressing and heat treatment techniques are detailed in U.S. patent No. 5,827,337, the contents of which are incorporated herein by reference.

After bonding, heat treatment and immersion in a solvent, the segments are typically polished using conventional techniques. This conventional technique involves grinding or cutting using vitrified or carbide cutting wheels to produce ground rim segments of the required dimensions and tolerances. The segments may then be bonded to the circumferential edge of the core using a suitable adhesive (see, e.g., fig. 2A-2C, also discussed below). Suitable binders include 353-NDT epoxy (EPO-TEK, Billerica, MA), with a resin to hardener weight ratio of 10:1, andHT-18 epoxy resins (available from Taoka Chemicals, JP) and modified amine hardeners for the latter are mixed in proportions of about 100 parts by weight of resin and about 19 parts by weight of hardener. Further details regarding the binders, their characteristics, and their use in metal bond wheels are provided in the ramatath patent.

An alternative method of wheel manufacture involves forming a segment precursor of a powdered mixture of abrasive, binder and dispersion, compression moulding the segment precursor over the circumference of the core and applying heat and pressure to form and bond the segments in situ (i.e. co-sintering the core and rim). After co-sintering, the wheel is immersed in a solvent selected to dissolve the dispersion from the wheel rim, resulting in a porous ground wheel rim (as described above). For this optional process, it is preferred to use a chloride ion-free dispersion (e.g., sodium chloride) because once the core material contains aluminum or an aluminum alloy (e.g., alloy 7075), the aluminum alloy will exhibit craters in the presence of chloride ions.

The abrasive articles and implements of the present invention (such as the wheel 100 shown in FIG. 2A and discussed in more detail below) are suitable for use in abrading ceramic materials, including various oxides, carbides, nitrides and silicides, such as silicon nitride, silicon dioxide and silicon oxynitride, stabilized zirconia, alumina (e.g., sapphire), boron carbide, boron nitride, titanium diboride and titanium nitride, and composites of these ceramics; it may also be used in composites where certain metal matrices are ground, such as cemented carbide, polycrystalline diamond and polycrystalline cubic boron nitride. Using these abrasive tools, single crystal or polycrystalline ceramics can be ground. Moreover, the abrasive articles and tools of the present invention are particularly suitable for abrading materials used in the electronics industry, such as silicon wafers (for semiconductor fabrication), aluminum titanium carbide (for magnetic head fabrication), and other substrates.

Modifications to the above-described aspects of the invention are by way of example only. Obviously, other modifications to the above illustrative embodiments will be readily apparent to those skilled in the art. All such modifications and variations are considered to be within the scope and spirit of the invention as set forth in the appended claims.

The following examples are intended only to illustrate various embodiments of the articles and methods of the present invention. It is intended that the scope of the invention be limited not by the embodiments described herein, but rather by the claims below. All parts and percentages in the examples are by weight unless otherwise indicated.

Example 1

In accordance with the principles of the present invention, a grinding wheel 100 in the form of a metal bonded diamond grinding wheel of type 2A2TS is manufactured using the materials and methods described below.

A powdered metal alloy (described below) and non-iodinated table salt (available from Shaw's, inc., Worcester, MA) were mixed, wherein the weight ratio of metal alloy to table salt was 65:35, corresponding to a volume ratio of metal alloy to table salt of 31.56: 68.44. In Spex^TMIn a mill (manufactured by SPEX Company, Metuchen NJ), the salt (mainly sodium chloride) is crushed and the salt particles having a particle size distribution in the range of about 74 to 210 μm (i.e., coarser than mesh 200 of America but finer than mesh 70 of America) are separated by a sieve.

The powdered metal alloy described above comprises a mixture of 43.74% by weight copper powder (dendritic FS grade, particle size 325 mesh, available from sinntertech International marking corp., Ghent, NY), 6.24% by weight phosphorus/copper powder (1501 grade, particle size 325 mesh, available from New Jersey zinc company, Palmerton, PA) and 50.02% by weight tin powder (MD115 grade, particle size-100/+ 325 mesh, max 0.5%, available from alcaneal powders inc., Elizabeth, NJ).

Adding a fine diamond abrasive having a particle size distribution of about 3 to 6 μm to the above metal alloy/salt mixture (2.67 grams of diamond was added to 61.29 grams of metal alloy/salt mixture), and using Turbula^TMThe resulting mixture was thoroughly stirred by a stirrer (manufactured by Glen Mills, inc. clifton NJ) until the mixture was uniformly mixed. The resulting mixture at this point contained about 5 volume percent diamond, about 30 volume percent metal bond matrix, and about 65 volume percent common salt. Three drops of DL 42 were added to the mixture before stirring the mixture^TMMineral spirits (available from Worcester Chemical, Worcester, MA) help prevent separation of the components. The mixture is then divided into 16 equal portions (each corresponding to one of the 16 grinding segments 10 used on the grinding wheel 100). Each aliquot was placed in a graphite mold and pressed at 22.1MPa (3200 psi)Force, hot pressing at 407 ℃ for 10 minutes until a matrix with a final density of more than 95% of the theoretical value is formed. After cooling, the segments 10 are immersed in a relatively large volume (e.g., 0.5 liters) of boiling water for 45 minutes to remove salt therefrom. The segment 10 is then rinsed thoroughly with Deionized (DI) water. The washing process was repeated to ensure complete removal of the salt. Subsequent weight loss and energy dispersive X-ray (EDX) tests confirmed that almost all of the common salt in the segments had been removed.

Fig. 1 shows a schematic illustration of a segment 10. Each segment 10 is ground to the required dimensions and tolerances to fit the circumferential edge of the machined aluminum core 20 (a model 2A2TS grinding wheel shown in fig. 2A-2C). The segments 10 are arcuate in shape on their sides, with the outer diameter of the curved portion 11 being 127 mm (5 inches) and the inner diameter of the curved portion 12 being 124 mm (4.9 inches). When viewed from the front (or back), the segment 10 has a length 13 of 47 millimeters (1.8 inches) and a width 14 of 6.3 millimeters (0.25 inches).

As shown in fig. 2A, segment 10 is used to construct A2TS profile grinding wheel 100. The grinding wheel 100 comprises 16 symmetrical segments 10 bonded to an aluminum core 20, forming a grinding wheel 100 having a grooved rim 104 with an outer diameter 102 of about 282 millimeters (11.1 inches). The segmented rim protrudes from the surface of the aluminum core 20 by a distance 112 of about 3.9 millimeters (0.16 inches), as shown at 110. The grinding segments 10 and aluminum core 20 were assembled together using an epoxy/amine hardener cementitious system (Technodyne HT-18 adhesive available from Taoka Chemicals, JP) to provide a grinding wheel having a grooved rim 104 consisting of 16 grinding segments 10. The contact surfaces between the core and the segments 10 are degreased and grit blasted to ensure sufficient adhesion.

Example 2

Evaluation of polishing Properties

The metal bond segmented grinding wheel (grinding wheel 2-a) manufactured according to the method described in example 1 above was subjected to a test of fine back grinding performance of silicon wafers. It is proposed to use a commercially available grinding wheel (wheel size D3/6MIC-IN.656-BX623, available from Saint Gobain abrasives, Inc. Worcester, Mass.) containing the same grit size and concentration in a resin binder as a control wheel to perform a fine backgrind on a silicon wafer and test with the grinding wheel described herein. This comparative wheel contains about 5 volume percent diamond abrasive, about 62 volume percent hollow glass microspheres, about 12 volume percent resin, and about 21 volume percent porosity. The glass microspheres described above comprise about 15 volume percent glass shells. Thus, the comparative grinding wheel can be considered to comprise about 9.3 volume percent glass shell and about 73.7 volume percent non-interconnected porosity (i.e., about 21 volume percent porosity plus about 52.7 volume percent hollow interior of hollow glass microspheres).

The grinding test conditions were:

grinding test conditions:

mechanically: strasbaugh 7AF type

The specification of the grinding wheel is as follows: rough shaft: norton #3-R1B69

Fine shaft: d3/6MIC-IN.656-BX623 (for comparison) grinding wheel 2-A

The size of the grinding wheel is as follows: 2A2TSSA type

280X 29X 229 mm (11X 9/8X 9 inch)

Grinding mode: double grinding: coarse grinding is carried out firstly, and then fine grinding is carried out

And (3) fine grinding process:

the rotating speed of the grinding wheel is as follows: 4,350 rpm

Cooling agent: deionized water

The flow rate of the coolant: 3 gallons per minute (11 liters per minute)

Working materials: silicon wafers, N-type 100 orientation, 150 mm (6 inches) in diameter and 0.66 mm (0.026 inches) initial thickness (available from Silicon Quest, CA)

Ground-off material: the first step is as follows: 10 mu m; the second step is that: 5 μm; the third step: 5 μm; primary grinding amount: 2 μm

Feeding speed: the first step is as follows: 1 μm/s; the second step is that: 0.7 μm/s; the third step: 0.5 μm/s; primary grinding amount: 0.5 μm/s

The operation speed is as follows: 699 rpm/min, constant

When the device is stopped: 100 turns

Coarse grinding process

The rotating speed of the grinding wheel is as follows: 3,400 rpm

Cooling agent: deionized water

The flow rate of the coolant: 3 gallons per minute (11 liters per minute)

Working materials: silicon wafers, N-type 100 orientation, 150 mm (6 inches) in diameter and 0.66 mm (0.026 inches) initial thickness (available from Silicon Quest, CA)

Ground-off material: the first step is as follows: 10 mu m; the second step is that: 5 μm; the third step: 5 μm; primary grinding amount: 10 μm

Feeding speed: the first step is as follows: 3 μm/s; the second step is that: 2 μm/s; the third step: 1 μm/s; primary grinding amount: 5 μm/s

The working speed is as follows: 590 rpm/min, constant

When the device is stopped: 50 turn

When the abrasive article requires dressing and application, the test sets up the following conditions:

dressing and dressing operations:

rough grinding wheel: is free of

Fine grinding wheel: strasbaugh rough dressing liner with a diameter of 150 mm (6 inches) was used

The rotating speed of the grinding wheel is as follows: 1200 revolutions per minute

When the device is stopped: 25 turns

Ground-off material: the first step is as follows: 150 μm; the second step is that: 10 mu m; primary grinding amount: 20 μm

Feeding speed: the first step is as follows: 5 μm/s; the second step is that: 0.2 μm/s; primary grinding amount: 2 μm/s

The operation speed is as follows: 50 rpm, constant

The results of the grinding test for example 2 are shown in table 1 below. 50 silicon wafers were finely ground using a resin-bonded comparative grinding wheel and a porous grinding wheel according to the present invention (grinding wheel 2-A). As shown in table 1, the control wheel and the inventive wheel exhibited relatively stable peak normal forces for at least 50 wafers. Each wheel also requires approximately the same peak normal force. This type of polishing performance is well suited for back-side polishing of silicon wafers because these lower force and steady state conditions minimize thermal and mechanical damage to the workpiece.

Furthermore, the porous grinding wheel of the present invention provides the above-described highly suitable grinding operation for at least 50 silicon wafers without dressing the porous grinding wheel.

In summary, example 2 shows that the wheels of the invention have very suitable back-grinding performance for silicon wafers, and unexpectedly (for metal bonded wheels) use less power than the resin bonded comparative wheels.

TABLE 1

Example 3

Evaluation of polishing Properties

Performance testing of super finish back side ground etched silicon wafers was performed on a metal bonded segmented grinding wheel (wheel 3-a) made according to the method described in example 1 above. It was proposed to finish back grind silicon wafers using a commercially available grinding wheel as detailed in example 2 above as a comparison wheel and tested in conjunction with the grinding wheel of the present invention.

The grinding test conditions were:

grinding test conditions:

mechanically: strasbaugh 7AF type

The specification of the grinding wheel is as follows: rough shaft: is free of

Fine shaft: d3/6mic-20BX623C (for comparison) grinding wheel 3-A

The size of the grinding wheel is as follows: 2A2TSSA type

280X 29X 229 mm (11X 9/8X 9 inch)

Grinding mode: single grinding: using only fine shafts

And (3) fine grinding process:

the rotating speed of the grinding wheel is as follows: 4,350 revolutions per minute

Cooling agent: deionized water

The flow rate of the coolant: 3 gallons per minute (11 liters per minute)

Working materials: silicon wafers, N-type 100 orientation, 150 mm (6 inches) in diameter and 0.66 mm (0.026 inches) initial thickness (available from Silicon Quest, CA)

Ground-off material: the first step is as follows: 10 mu m; the second step is that: 5 μm; the third step: 5 μm; primary grinding amount: 2 μm

Feeding speed: the first step is as follows: 1 μm/s; the second step is that: 0.7 μm/s; the third step: 0.5 μm/s; primary grinding amount: 0.5 μm/s

The operation speed is as follows: 699 rpm, constant

When the device is stopped: 100 turns

When the abrasive article requires dressing and application, the test sets up the following conditions:

dressing and dressing operations:

fine grinding wheel: strasbaugh rough dressing liner with a diameter of 150 mm (6 inches) was used

The rotating speed of the grinding wheel is as follows: 1200 revolutions per minute

When the device is stopped: 25 turns

Ground-off material: the first step is as follows: 150 μm; the second step is that: 10 mu m; primary grinding amount: 20 μm

Feeding speed: the first step is as follows: 5 μm/s; the second step is that: 0.2 μm/s; primary grinding amount: 2 μm/s

The operation speed is as follows: 50 rpm, constant

The results of the grinding test for example 3 are shown in table 2 below. A resin bonded control wheel was used to finish back grind 55 etched silicon wafers. Because the surface of the etched silicon wafer is relatively smooth, a rough grinding step is not used in the back grinding operation of the etched silicon wafer. As shown in table 2, the peak normal force increases relatively continuously as more and more portions are ground, eventually to a value where the grinder is shut down. 75 etched silicon wafers were ground using a porous grinding wheel according to the invention. Table 2 also shows that the peak normal force remains at a low and stable value throughout the course of the experiment. These results clearly demonstrate that the wheels of the invention have self-dressing properties.

This type of polishing performance is well suited for back-side polishing of silicon wafers because these lower force and steady state environments minimize thermal and mechanical damage to the workpiece. Moreover, the self-dressing nature of the wheel provides a backgrinding operation that does not require dressing (or dressing) of the wheel. As a result, the grinding wheel of the present invention can increase the discharge amount, reduce the working cost, and have a stable grinding effect, compared to the results obtained using the conventional grinding wheel.

In summary, example 3 shows that the wheel of the invention has very suitable back-grinding properties for etched silicon wafers without the need for dressing the wheel at all. In this application, the performance of the wheel of the present invention is completely superior to that of conventional resin bonded wheels.

TABLE 2

^*Stopping the mill due to the normal force exceeding the mechanical limit

Example 4

Evaluation of polishing Properties

Two metal bonded segmented grinding wheels made in a similar manner to the method described in example 1 above were tested for grinding performance. Both wheels contain about 14 volume percent diamond abrasive having a particle size distribution of between about 63 and 74 microns (i.e., the particles are finer than mesh 200 and coarser than mesh 230). The two wheels also contained about 21 volume percent metal bond (composition as described in example 1) and about 65 volume percent interconnected porosity. The first grinding wheel (grinding wheel 4-a) was made using a salt dispersion having a particle size of-70/+ 200 U.S. mesh as described in example 1, and produced a pore size in the range of about 74-210 microns (pore size is considered to be approximately equal to the size of the salt dispersion removed). A second wheel (wheel 4-B) was made using common salt having a particle size of-50/+ 70 U.S. mesh, and produced a pore size in the range of about 210-300 microns. Although not measurable, the wheel is expected to have a larger pore size and contain larger filament sizes of the metal bond. The term "filament" is used herein consistent with its normal usage as is well known to the skilled artisan and refers to a matrix material (i.e., a framework of porous structure) that is connected between interconnected pores.

The 4.5 square inch pieces of AlTiC were coarse ground using two grinding wheels as described above. The grinding test conditions were:

grinding test conditions:

mechanically: strasbaugh 7AF type

The specification of the grinding wheel is as follows: rough shaft: grinding wheel 4-A

Grinding wheel 4-B

Fine shaft: is free of

The size of the grinding wheel is as follows: 2A2TSSA type

280.16X 28.90X 228.65 mm (11X 9/8X 9 inch)

Grinding mode: single grinding: using only a rough shaft

The rough grinding process comprises the following steps:

the rotating speed of the grinding wheel is as follows: 2,506 rpm

Cooling agent: deionized water

The flow rate of the coolant: 3 gallons per minute (11 liters per minute)

Working materials: 3M-310 titanium aluminum carbide sheet, 114.3 square millimeters (4.5 square inches) with an initial thickness of 2.0 millimeters (0.8 inches) (available from Minnesota Mining and Manufacturing Corporation, Minneapolis, MN)

Ground-off material: the first step is as follows: 100 μm; the second step is that: 100 μm; the third step: 100 μm; primary grinding amount: 20 μm

Feeding speed: the first step is as follows: 0.7 μm/s; the second step is that: 0.7 μm/s; the third step: 0.7 μm/s; primary grinding amount: 0.5 μm/s

The operation speed is as follows: 350 rpm, constant

When the device is stopped: 0 turn

When the abrasive article requires dressing and application, the test sets up the following conditions:

dressing and dressing operations:

rough grinding wheel: strasbaugh rough dressing liner with a diameter of 150 mm (6 inches) was used

The rotating speed of the grinding wheel is as follows: 1200 revolutions per minute

When the device is stopped: 25 turns

Ground-off material: the first step is as follows: 150 μm; the second step is that: 10 mu m; primary grinding amount: 20 μm

Feeding speed: the first step is as follows: 5 μm/s; the second step is that: 0.2 μm/s; primary grinding amount: 2 μm/s

The operation speed is as follows: 50 rpm, constant

The results of the grinding test for example 4 are shown in table 3 below. Both wheels were observed to be successful in grinding AlTiC wafers and showed relatively stable peak normal forces and sufficient grinding capacity over time. The AlTiC sheets were ground for 25 minutes (1500 seconds) using a first grinding wheel containing a relatively fine pore size (and likely a relatively fine wire size of the metal bond). A relatively steady peak normal force of about 35 newtons was observed with about 1150 microns of AlTiC being ground off the wafer (material at a grinding rate of about 46 microns/min). The wheel was observed to have a wear of about 488 microns (the ratio of the amount of material ground/the amount of wheel wear was about 2.4). The AlTiC sheet was ground using a second grinding wheel containing a relatively coarse pore size (and likely a relatively coarse wire size of metal bond) for approximately 7 minutes (420 seconds). A relatively steady peak normal force of about 94 newtons was observed with about 2900 microns of AlTiC abraded from the wafer (the material had an abrasion rate of about 414 microns/min). The wheel was observed to have a wear of about 18 microns (the ratio of the amount of material ground/the amount of wheel wear was about 160).

In summary, example 4 shows that the porous grinding wheel according to the invention is very suitable for grinding AlTiC flakes. Furthermore, this example shows that the abrasion resistance and self-dressing properties of the wheels of the invention can be varied by adjusting the relative pore size of the abrasive article. While not intending to be bound by any particular theory, it is believed that the increased wear of the wheel comprising smaller pores is related to the reduced strength of the metal bond due to the reduced filament size of the metal bond. However, this example shows that the performance of the wheel can be varied by adjusting the relative pore sizes therein to suit a particular application.

TABLE 3

Grinding wheel specification (salt grain size)	Peak normal force, newton	Abrasion of grinding wheel, micron
			Grinding wheel 4-B (-50/+70)	93.6	17.8
Grinding wheel 4-A (-70/+200)	35.7	487.6

Example 5

Evaluation of polishing Properties

A metal bond segmented grinding wheel (wheel 5-a) made according to the method described in example 1 above was subjected to a performance test for finish back grinding of 50 millimeter (2 inch) single crystal silicon carbide wafers. It is recommended that the silicon wafers be finish ground back using a commercially available grinding wheel as described in detail in example 2 above as a comparison wheel and tested in conjunction with the grinding wheel of the present invention.

The grinding test conditions were:

grinding test conditions:

mechanically: strasbaugh 7AF type

The specification of the grinding wheel is as follows: rough shaft: ASDC320-7.5MXL2040(S.P.)

Fine shaft: d3/6MIC-20BX623C (for comparison)

Grinding wheel 5-A

The size of the grinding wheel is as follows: 2A2TSSA type

280.16X 28.90X 228.65 mm (11X 9/8X 9 inch)

Grinding mode: double grinding: coarse grinding is carried out firstly, and then fine grinding is carried out

And (3) fine grinding process:

the rotating speed of the grinding wheel is as follows: 4,350 revolutions per minute

Cooling agent: deionized water

The flow rate of the coolant: 3 gallons per minute (11 liters per minute)

Working materials: silicon carbide wafer, single crystal, 50 mm (2 inch) in diameter and 300 microns (0.0075 inch) initial thickness (available from CREE Research, inc.)

Ground-off material: the first step is as follows: 15 μm; the second step is that: 15 μm; primary grinding amount: 5 μm

Feeding speed: the first step is as follows: 0.5 μm/s; the second step is that: 0.2 μm/s; primary grinding amount: 1.0 μm/s

The operation speed is as follows: 350 rpm, constant

When the device is stopped: 150 turn

The rough grinding process comprises the following steps:

the rotating speed of the grinding wheel is as follows: 3,400 rpm

Cooling agent: deionized water

The flow rate of the coolant: 3 gallons per minute (11 liters per minute)

Working materials: silicon carbide wafer, single crystal, 50 mm (2 inch) in diameter and 300 microns (0.0075 inch) initial thickness (available from CREE Research inc.)

Ground-off material: the first step is as follows: 10 mu m; the second step is that: 10 mu m; primary grinding amount: 5 μm

Feeding speed: the first step is as follows: 0.7 μm/s; the second step is that: 0.3 μm/s; primary grinding amount: 1.0 μm/s

The operation speed is as follows: 350 rpm, constant

When the device is stopped: 0 turn

And (3) finishing operation:

rough grinding wheel: is free of

Fine grinding wheel: strasbaugh rough dressing liner with a diameter of 150 mm (6 inches) was used

The rotating speed of the grinding wheel is as follows: 1200 revolutions per minute

When the device is stopped: 25 turns

Ground-off material: the first step is as follows: 150 μm; the second step is that: 10 mu m; primary grinding amount: 20 μm

Feeding speed: the first step is as follows: 5 μm/s; the second step is that: 0.2 μm/s; primary grinding amount: 2 μm/s

The operation speed is as follows: 50 rpm, constant

The results of the grinding test for example 5 are shown in table 4 below. As indicated by the very low grinding rates, commercially available resin bonded grinding wheels are not practically useful for grinding silicon carbide wafers. On the other hand, the porous grinding wheel of the present invention can successfully grind very hard and brittle silicon carbide wafers. Approximately 15 microns of silicon carbide was ground off at each 48 minute run time, with an average grinding rate of 0.31 microns/minute. Moreover, the porous grinding wheel disclosed by the invention can obviously reduce the roughness of the surface of the material (use of the porous grinding wheel)White light interferometer measurement, Zygo Corporation, Middlefield, CT). As shown in table 4, the use of the wheel of the present invention for grinding reduced the average surface roughness (Ra) from an initial value of greater than 100 angstroms up to less than about 40 angstroms (with one exception).

In summary, example 5 demonstrates that the wheel of the present invention provides the desired abrasive properties to a hard, brittle silicon carbide wafer. In this application, the performance of the wheels of the invention is significantly better than that of conventional resin bonded wheels.

TABLE 4

Run # test 8.299	Grinding wheel specification	Grinding quantity micron	Surface roughness
				6	Contrast grinding wheel	3
7	“	0	98
				19	Grinding wheel 5-A	17	34
20	Grinding wheel 5-A	13	32
				21	Grinding wheel 5-A	15	54.5
22	Grinding wheel 5-A	15	37.5

Example 6

The porosity of the porous medium was quantitatively determined by a permeation experiment based on the D 'Arcy's law controlling the relationship between the flow rate and the pressure applied to the porous medium, and used for evaluation of the grinding wheel according to the present invention. The apparatus and method used to determine permeability is exactly the same as that described in Wu et al, U.S. patent No. 5,738,697, in that high pressure air is applied to the flat surface of a porous test specimen.

The porous sample was prepared in essentially the same manner as described in example 1, containing 5 volume percent of 3/6 micron diamond abrasive. The relative amounts of salt and metal binder were varied so that the resulting sample contained about 0 to about 80 volume percent interconnected porosity. Samples measuring 1.5 inches in diameter and 0.5 inches thick were hot pressed at a temperature of 405 c and a pressure of 3200 psi. After cooling, the sample was hand ground with a silicon carbide abrasive slurry (grit size 180) to expose the surface of the pores in the sample. The sample was then immersed in boiling water as described in example 1. For each porosity value 4 samples were prepared. The average measurement results of permeability are shown in table 5 below.

Permeability values are reported in air volume per unit time (Q, cubic centimeters per second) per unit pressure (P, inches of water) and are measured through the thickness of a sample having a diameter of 1.5 inches (37.5 millimeters) and a thickness of 0.5 inches (12.7 millimeters). As one would expect, the permeability values were lower for samples that did not effectively contain interconnected porosity. A significant increase in permeability with increasing porosity can be observed. In particular, samples having more than about 50% interconnected porosity are characterized by a sample permeability value in excess of about 0.2 cc/sec/inch water when the content of pores is increased above about 50% by volume.

TABLE 5

Weight% of the metal binder	Weight percent of salt	Theoretical pore volume%	Permeability, Q/P (cm 3/sec/in H2O/0.5 in)
				100	0	0	0.030
91.85	8.15	25	0.034
				84.7	15.3	40	0.085
74.55	25.45	55	0.287
				65.0	35.0	65	0.338
58.99	41.01	70	0.562
				43.02	56.98	80	Invalidation

Example 7

Segmented grinding wheels each comprising 16 segments were assembled in substantially the same manner as described in example 1 (see above). However, these segments contained an organic binder (different from the metallic binder described in example 1) and were made as follows:

granulated sugar (available from Shaw's inc., Worcester, MA) was placed in a1 gallon capacity paint can using a paint shaker (available from Shaw's inc., Worcester, MA)Manufactured by Union, NJ) for about 2 hours to remove sharp corners and edges on the granulated sugar, thereby effectively "rounding" the granulated sugar. The granulated sugar is then screened to obtain a granulated sugar having a particle size distribution of between about 250 and 500 microns (i.e., -35/+60 U.S. mesh).

The powdered resin binder was previously screened through a U.S. mesh 200 sieve to remove lumps. Distribution of particle sizeFine diamond abrasive powder (of between about 3 and 6 microns)Corporation (Olyphant, Pennsylvania) was added as RB3/6 to the above powdered resin and mixed until the two components were thoroughly mixed. The mixture comprising about 80% by volume resin and about 20% by volume abrasive was sieved 3 times through a U.S. mesh 165 sieve, and then granulated sugar (prepared as described above) was added. The resin/abrasive/sugar mixture was then stirred until the three were completely mixed and sieved twice through a U.S. mesh 24 sieve.

Three complex mixtures were prepared. The first mixture (used to make wheel 7-A) contained about 4 volume percent diamond abrasive, about 20 volume percent 33-344 resin binder (bisphenol-A modified resole phenolic resin, made fromCorporation of Dallas, TX), and about 76% by volume of granulated sugar. The second mixture (used to make wheel 7-B) contained about 6 volume percent diamond abrasive, about 30 volume percent 29-346 resin binder (a long chain flow novolac resin made fromCorporation of Dallas, TX), and about 64% by volume of granulated sugar. The third mixture (used to make wheel 7-C) contained about 6 volume percent diamond abrasive, about 30 volume percent 29-108 resin binder (ultra-long chain flow bisphenol-A modified resole resin, made fromCorporation of Dallas, TX), and about 64% by volume of granulated sugar.

The resin/abrasive/sugar mixture described above was placed on a disk-shaped iron mold, laid flat, and pressed at a temperature of about 135 c and a pressure of about 4100psi (28MPa) for about 30 minutes until the matrix reached about 99% of theoretical density. After cooling, the disc was lightly sanded with 180 grit sandpaper to remove the mold shell and the sugar dispersion was removed by immersion in boiling water for about 2 hours. After removal of the sugar, the disc is dried and baked to complete the curing of the resin. The drying and baking process is as follows. First, the disc was heated to 60 ℃ over 5 minutes and maintained at this temperature for approximately 25 minutes. The disc was then heated to 90 ℃ over 30 minutes and maintained at this temperature for approximately 5 hours. Finally, the disk was heated to 160 ℃ over about 4 hours and maintained at that temperature for about 5 hours. After baking, the disks are cooled to room temperature and ground to produce segments for use in assembling the wheel.

And (5) carrying out performance test on the finish-machining back-grinding silicon wafer of the three organically bonded grinding wheels. The grinding test conditions were:

grinding test conditions:

mechanically: strasbaugh 7AF type

The specification of the grinding wheel is as follows: rough shaft: norton #3-R7B69

Fine shaft: grinding wheel 7-A

Grinding wheel 7-B

Grinding wheel 7-C

The size of the grinding wheel is as follows: 2A2TSSA type

280X 29X 229 mm (11X 9/8X 9 inch)

Grinding mode: double grinding: coarse grinding is carried out firstly, and then fine grinding is carried out

And (3) fine grinding process:

the rotating speed of the grinding wheel is as follows: 4,350 revolutions per minute

Cooling agent: deionized water

The flow rate of the coolant: 3 gallons per minute (11 liters per minute)

Working materials: silicon wafers, N-type 100 orientation, 150 mm (6 inches) in diameter and 0.66 mm (0.026 inches) initial thickness (available from Silicon Quest, CA)

Ground-off material: the first step is as follows: 10 mu m; the second step is that: 5 μm; the third step: 5 μm; primary grinding amount: 2 μm

Feeding speed: the first step is as follows: 1 μm/s; the second step is that: 0.7 μm/s; the third step: 0.5 μm/s; primary grinding amount: 0.5 μm/s

The operation speed is as follows: 590 rpm, constant

When the device is stopped: 100 turns

The rough grinding process comprises the following steps:

the rotating speed of the grinding wheel is as follows: 3,400 rpm

Cooling agent: deionized water

The flow rate of the coolant: 3 gallons per minute (11 liters per minute)

Working materials: silicon wafers, N-type 100 orientation, 150 mm (6 inches) in diameter and 0.66 mm (0.026 inches) initial thickness (available from Silicon Quest, CA)

Ground-off material: the first step is as follows: 10 mu m; the second step is that: 5 μm; the third step: 5 μm; primary grinding amount: 10 μm

Feeding speed: the first step is as follows: 3 μm/s; the second step is that: 2 μm/s; the third step: 1 μm/s; primary grinding amount: 5 μm/s

The operation speed is as follows: 590 rpm, constant

When the device is stopped: 50 turn

When the abrasive article requires dressing and application, the test sets up the following conditions:

dressing and dressing operations:

rough grinding wheel: strasbaugh rough dressing liner with a diameter of 150 mm (6 inches) was used

The rotating speed of the grinding wheel is as follows: 1200 revolutions per minute

When the device is stopped: 25 turns

Ground-off material: the first step is as follows: 190 μm; the second step is that: 10 mu m; primary grinding amount: 20 μm

Feeding speed: the first step is as follows: 5 μm/s; the second step is that: 0.2 μm/s; primary grinding amount: 2 μm/s

The operation speed is as follows: 50 rpm, constant

Fine grinding wheel: ultra-fine dressing pads using Strasbaugh with a diameter of 150 mm (6 inches)

The rotating speed of the grinding wheel is as follows: 1200 revolutions per minute

When the device is stopped: 25 turns

Ground-off material: the first step is as follows: 150 μm; the second step is that: 10 mu m; primary grinding amount: 20 μm

Feeding speed: the first step is as follows: 5 μm/s; the second step is that: 0.2 μm/s; primary grinding amount: 2 μm/s

The operation speed is as follows: 50 rpm, constant

The results of the grinding test for example 7 are shown in table 6 below. 200 silicon wafers were finely ground using the porous resin bonded grinding wheels (grinding wheels 7-A, 7-B and 7-C) according to the present invention. Each wheel of the present invention exhibits a relatively stable peak normal force of about 90 newtons (i.e., about 20 pounds) for at least 200 wafers. This type of polishing performance is well suited for back-side polishing of silicon wafers because these lower force and steady state conditions minimize thermal and mechanical damage to the workpiece. Moreover, the porous grinding wheel of the invention can provide at least 200 silicon wafers with the above-mentioned very suitable grinding operation without dressing the porous grinding wheel.

In addition, resin type grinding wheels have been found to affect the wear rate of the wheel. Wheels 7-a and 7-C showed higher wear rates with values of 2.2 and 1.7 microns/piece, respectively, while wheel 7-B (containing long chain flow novolac epoxy) showed lower (and desirable) wear rate with a value of 0.5 microns/piece.

In summary, example 7 shows that the grinding wheels of the present invention comprising organic binders provide very suitable properties for back grinding silicon wafers.

TABLE 6

Grinding wheel specification	Peak normal force (Newton)	Wear rate (micron/piece)
			Grinding wheel 7-A (DZ33-344)	90	2.2
Grinding wheel 7-B (IZ 29-346)	90	0.5
			Grinding wheel 7-C (IZ 19-108)	90	1.7

Claims (75)

1. A method of making an abrasive article having an interconnected porosity of at least 50 vol%, the method comprising:

a) blending a mixture of abrasive particles, binder material, and dispersoid particles, the mixture comprising about 0.5 to 25 volume percent abrasive particles, about 19.5 to 49.5 volume percent binder material, and about 50 to 80 volume percent dispersoid particles;

b) pressing the mixture into a ground compacted composite;

c) hot working the composite material; and

d) immersing the composite material in a solvent for a period of time to dissolve substantially all of the dispersion, the dispersion being dissolved in the solvent;

the abrasive particles and the binder material are substantially insoluble in the solvent.

2. The method of claim 1, wherein said pressing (b) and said heat treating (c) are performed substantially simultaneously.

3. The method of claim 2, wherein the mixture is pressed at a temperature of about 370 to 795 ℃ and a pressure of about 20 to 33 megapascals for at least 5 minutes.

4. The method of claim 1, wherein the volume% of the dispersion particles in the mixture is:

greater than or equal to about 50 volume%; and is

Less than or equal to about 70 volume percent.

5. The method of claim 1, wherein the binder material is a metal binder.

6. The method of claim 5, wherein the metallic binder comprises about 35-85% by weight copper and about 15-65% by weight tin.

7. The method of claim 5, wherein the metal bond comprises about 0.2 to about 1.0 wt% phosphorous.

8. The method of claim 1, wherein the binder material is an organic binder.

9. The method of claim 8, wherein the organic binder comprises a phenolic resin.

10. The method of claim 1, wherein the abrasive particles comprise superabrasive particles selected from the group consisting of diamond and cubic boron nitride.

11. The method of claim 1, wherein the abrasive particles are diamond.

12. The method of claim 1, wherein the abrasive particles have an average particle size of:

greater than or equal to about 0.5 microns; and

less than or equal to about 300 microns.

13. The method of claim 1, wherein the abrasive particles have an average particle size of:

about or equal to about 0.5 microns; and

less than or equal to about 75 microns.

14. The method of claim 1, wherein the dispersion is a water-soluble salt.

15. The method of claim 1, wherein the dispersion is selected from the group consisting of sugars, dextrins, polysaccharide oligomers, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium silicate, sodium metasilicate, potassium phosphate, potassium silicate, sodium carbonate, sodium sulfate, potassium sulfate, magnesium sulfate, and mixtures thereof.

16. The method of claim 1, wherein the dispersion comprises sodium chloride.

17. The method of claim 1, wherein the dispersion comprises a sugar.

18. The method of claim 1, wherein the dispersion has a particle size:

greater than or equal to about 25 micrometers; and

less than or equal to about 500 microns.

19. The method of claim 1, wherein the dispersion has a particle size distribution ranging from:

greater than or equal to about 74 micrometers; and

less than or equal to about 210 microns.

20. The method of claim 1, wherein the dispersion has a particle size distribution ranging from:

greater than or equal to about 210 micrometers; and

less than or equal to about 300 microns.

21. The method of claim 1, wherein the dispersion comprises a sugar and the dispersion has a particle size distribution ranging from:

greater than or equal to about 150 micrometers; and

less than or equal to about 500 microns.

22. The method of claim 1, wherein the solvent is water.

23. The method of claim 1, wherein the solvent is boiling water.

24. The method of claim 1, wherein at least one surface of the composite material is abraded after said heat treating (c) and before said immersing (d).

25. The method of claim 1, making an abrasive tool having a permeability of greater than or equal to about 0.2 cubic centimeters per second per inch of water.

26. An abrasive article made according to the method of claim 1.

27. An abrasive segment for a segmented grinding wheel, the abrasive segment comprising:

a composite comprising a plurality of superabrasive particles and a sintered metal bond matrix having a plurality of interconnected porosity distributed throughout said composite, said composite comprising from about 0.5 to about 25 volume percent abrasive particles, from about 19.5 to about 49.5 volume percent metal binder, and from about 50 to about 80 volume percent interconnected porosity;

the metal bond matrix comprises about 35 to 70 weight percent copper, about 30 to 65 weight percent tin, and about 0.2 to 1.0 weight percent phosphorus, wherein the sum of the weight percent of each component equals 100 weight percent;

wherein the plurality of superabrasive particles are selected from the group consisting of diamond and cubic boron nitride, the superabrasive particles having an average particle size of less than about 300 microns.

28. The abrasive segment of claim 27 wherein said composite material is sintered at a temperature of about 370-795 ℃.

29. The abrasive segment of claim 27 wherein said composite material comprises:

greater than or equal to about 50 volume percent interconnected porosity; and

less than or equal to about 70 volume percent interconnected porosity.

30. The abrasive segment of claim 27 wherein said plurality of interconnected pores have an average pore size of:

greater than or equal to about 25 micrometers; and

less than or equal to about 500 microns.

31. The abrasive segment of claim 27 wherein said plurality of interconnected pores have an average pore size of:

greater than or equal to about 74 micrometers; and

less than or equal to about 210 microns.

32. The abrasive segment of claim 27 wherein said plurality of interconnected pores have an average pore size of:

greater than or equal to about 210 micrometers; and

less than or equal to about 300 microns.

33. The abrasive segment of claim 27, wherein the plurality of superabrasive particles have an average particle size of:

greater than or equal to about 0.5 microns; and

less than or equal to about 75 microns.

34. The abrasive segment of claim 27 wherein said interconnected porosity is formed by:

a) adding the dispersion to the abrasive particles and the metal binder prior to sintering the composite;

b) immersing the sintered composite material in a solvent, dissolving the dispersion;

the grinding section is substantially free of dispersion particles.

35. The grinding section of claim 27, wherein the grinding section has a permeability of greater than or equal to about 0.2 cc/sec/in water.

36. A segmented grinding wheel comprising:

a core body;

a grinding rim comprising a plurality of segments of claim 27; and

a thermally stable adhesive between the core and the plurality of segments.

37. A segmented grinding wheel comprising:

a core having a minimum specific strength of 2.4MPa-cm³A density of 0.5 to 8.0g/cm³Having a circumferential edge;

an abrasive rim comprising a plurality of segments, each segment comprising a composite of a plurality of abrasive particles and a sintered-together metal bond matrix, a plurality of interconnected pores distributed in the composite, the composite comprising about 50-80 vol% of the interconnected pores;

a thermally stable adhesive between the core and the plurality of segments.

38. The segmented grinding wheel of claim 37, wherein said composite material is sintered at a temperature of about 370 to 795 ℃.

39. The segmented grinding wheel of claim 37, wherein the metal bond comprises about 35 to 85 weight percent copper and about 15 to 65 weight percent tin.

40. The segmented grinding wheel of claim 37, wherein the metal bond comprises about 0.2 to about 1.0 weight percent phosphorus.

41. The segmented grinding wheel of claim 37, wherein said abrasive particles comprise superabrasive particles selected from the group consisting of diamond and cubic boron nitride.

42. The segmented grinding wheel of claim 37, wherein the abrasive particles comprise diamond.

43. The segmented grinding wheel of claim 37, wherein said abrasive particles have an average particle size:

greater than or equal to about 0.5 microns; and

less than or equal to about 300 microns.

44. The segmented grinding wheel of claim 37, wherein said plurality of interconnected pores have an average pore size:

greater than or equal to about 25 micrometers; and

less than or equal to about 500 microns.

45. The segmented grinding wheel of claim 37, wherein the pore size distribution of said plurality of interconnected pores is:

greater than or equal to about 74 micrometers; and

less than or equal to about 210 microns.

46. The segmented grinding wheel of claim 37, wherein the pore size distribution of said plurality of interconnected pores is:

greater than or equal to about 210 micrometers; and

less than or equal to about 300 microns.

47. The segmented grinding wheel of claim 37, wherein said interconnected porosity is formed by:

a) adding the dispersion to the plurality of segments of abrasive particles and metallic binder prior to sintering;

b) immersing the plurality of segments in a solvent and dissolving the dispersion;

wherein each of the plurality of segments is substantially free of dispersoid particles.

48. The segmented grinding wheel of claim 37, wherein each segment has a permeability of greater than or equal to about 0.2 cubic centimeters per second per inch of water.

49. The segmented grinding wheel of claim 37, wherein said thermally stable bond is selected from the group consisting of epoxy bond, metallurgical bond, mechanical bond, diffusion bond, and combinations thereof.

50. The segmented grinding wheel of claim 37, wherein said thermally stable bond is an epoxy bond.

51. The segmented grinding wheel of claim 37, wherein:

the metal binder comprises about 35 to 85 weight percent copper, about 15 to 65 weight percent tin, and about 0.2 to 1.0 weight percent phosphorus, wherein the sum of the weight percent of each component equals 100 weight percent;

the abrasive particles comprise diamond having a particle size of about 0.5 to 300 microns; and

the plurality of interconnected pores has an average pore size of about 25 to about 500 microns.

52. A method of making an abrasive article having interconnected porosity of about 40 to about 80 volume percent, the method comprising:

a) blending a mixture of abrasive particles, non-metallic binder material, and dispersoid particles, the mixture comprising about 0.5 to 25 volume percent abrasive particles, about 19.5 to 65 volume percent non-metallic binder material, and about 40 to 80 volume percent dispersoid particles;

b) pressing the mixture into a ground compacted composite;

c) heat treating the composite material; and

d) immersing the composite material in a solvent for a period of time to dissolve substantially all of the dispersion, the dispersion being dissolved in the solvent;

the abrasive particles and non-metallic binder material are substantially insoluble in the solvent.

53. The method of claim 52, wherein the non-metallic binder material is an organic binder material.

54. The method of claim 53, wherein the organic binder material comprises a material selected from the group consisting of phenolic resins, epoxy resins, unsaturated polyester resins, bismaleimide resins, polyimide resins, cyanate ester resins, melamine polymers, and mixtures thereof.

55. The method of claim 53, wherein the organic binder material is a phenolic resin.

56. The method of claim 53 wherein the organic binder material is a novolac resin.

57. The method of claim 53, wherein the organic binder material is a resole.

58. The method of claim 53, wherein the abrasive particles comprise diamond having an average particle size of:

greater than or equal to about 0.5 microns; and

less than or equal to about 300 microns.

59. The method of claim 53, wherein the dispersion particles are substantially non-ionic.

60. The method of claim 53, wherein said dispersoid particles comprise sugar.

61. The method of claim 53, wherein said pressing step (b) comprises pressing at a temperature of about 100 to 200 ℃ and a pressure of about 20 to 33 megapascals for at least 5 minutes.

62. The method of claim 53, wherein said heat treating step (c) is performed after said immersing step (d), said heat treating step (c) comprising baking at a temperature of about 100 to 200 ℃ for at least 1 hour.

63. The method of claim 53, wherein at least one surface of the composite material is abraded prior to said immersing step (d).

64. A grinding section of a segmented grinding wheel, the grinding section comprising:

a composite material comprising a plurality of superabrasive particles and a consolidated non-metallic bond matrix, the composite material having a plurality of interconnected porosity distributed therein, the composite material comprising from about 0.5 to about 25 volume percent abrasive particles, from about 19.5 to about 65 volume percent non-metallic binder, and from about 40 to about 80 volume percent interconnected porosity; and

wherein the plurality of superabrasive particles are selected from the group consisting of diamond and cubic boron nitride, the superabrasive particles having an average particle size of less than about 300 microns.

65. The abrasive segment of claim 64, wherein the composite material is cured at a temperature of about 100 ℃ to about 200 ℃.

66. The abrasive segment of claim 64, wherein the plurality of superabrasive particles are diamonds having an average particle size:

greater than or equal to about 0.5 microns; and

less than or equal to about 75 microns.

67. The abrasive segment of claim 64 wherein said interconnected porosity is formed by the steps of:

a) adding the dispersion to the abrasive particles and the non-metallic binder prior to curing the composite; and

b) immersing the cured composite in a solvent and dissolving the dispersion;

the grinding section contains substantially no dispersion particles.

68. The grinding segment of claim 67 wherein the dispersion is a sugar, the solvent is water, and the non-metallic binder is a phenolic resin.

69. A segmented grinding wheel comprising:

a core body having a minimum specific strength of 2.4MPa-cm³A density of 0.5 to 8.0g/cm³Having a circumferential edge;

an abrasive rim comprising a plurality of segments, each segment comprising a composite of abrasive particles and a non-metallic bond matrix cured together, the composite having a plurality of interconnected porosity distributed therein, the composite comprising between about 40 and 80 volume percent of the interconnected porosity; and

a thermally stable adhesive between the core and the plurality of segments.

70. The segmented grinding wheel of claim 69, wherein said composite material is cured at a temperature of about 100 ℃ to about 200 ℃.

71. The segmented grinding wheel of claim 69, wherein said non-metallic bond matrix is an organic bond matrix.

72. The segmented grinding wheel of claim 71, wherein the organic bond matrix is a phenolic resin matrix.

73. The segmented grinding wheel of claim 71, wherein said interconnected porosity is formed by the steps of:

a) adding the dispersion to the abrasive particles and organic binder prior to curing the composite; and

b) immersing the cured composite in a solvent and dissolving the dispersion;

the grinding section contains substantially no dispersion particles.

74. The segmented grinding wheel of claim 73, wherein said dispersion is a sugar, said solvent is water, and said organic bond matrix is a phenolic resin.

75. The segmented grinding wheel of claim 71, wherein,

the organic binding matrix is a phenolic resin;

the abrasive particles are diamonds with an average particle size of about 0.5-300 microns;

the thermally stable adhesive is an epoxy adhesive; and

the interconnected porosity is formed by: prior to curing the composite, a particulate sugar dispersion is added to the abrasive particles and organic binder, and the cured composite is immersed in an aqueous solvent to dissolve the dispersion.