WO2015086544A1 - Traitement post-synthèse du diamant et matériaux super durs associés - Google Patents

Traitement post-synthèse du diamant et matériaux super durs associés Download PDF

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Publication number
WO2015086544A1
WO2015086544A1 PCT/EP2014/076944 EP2014076944W WO2015086544A1 WO 2015086544 A1 WO2015086544 A1 WO 2015086544A1 EP 2014076944 W EP2014076944 W EP 2014076944W WO 2015086544 A1 WO2015086544 A1 WO 2015086544A1
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WIPO (PCT)
Prior art keywords
super
processing
hard material
material product
wheel
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PCT/EP2014/076944
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English (en)
Inventor
Mark MCCLYMONT
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Element Six Technologies Limited
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Publication of WO2015086544A1 publication Critical patent/WO2015086544A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/04—Lapping machines or devices; Accessories designed for working plane surfaces
    • B24B37/042—Lapping machines or devices; Accessories designed for working plane surfaces operating processes therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/04—Lapping machines or devices; Accessories designed for working plane surfaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/005—Control means for lapping machines or devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/04—Lapping machines or devices; Accessories designed for working plane surfaces
    • B24B37/07—Lapping machines or devices; Accessories designed for working plane surfaces characterised by the movement of the work or lapping tool
    • B24B37/10—Lapping machines or devices; Accessories designed for working plane surfaces characterised by the movement of the work or lapping tool for single side lapping
    • B24B37/102—Lapping machines or devices; Accessories designed for working plane surfaces characterised by the movement of the work or lapping tool for single side lapping the workpieces or work carriers being able to rotate freely due to a frictional contact with the lapping tool
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B49/00—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation
    • B24B49/16—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation taking regard of the load
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B53/00—Devices or means for dressing or conditioning abrasive surfaces
    • B24B53/017—Devices or means for dressing, cleaning or otherwise conditioning lapping tools
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B57/00—Devices for feeding, applying, grading or recovering grinding, polishing or lapping agents
    • B24B57/02—Devices for feeding, applying, grading or recovering grinding, polishing or lapping agents for feeding of fluid, sprayed, pulverised, or liquefied grinding, polishing or lapping agents

Definitions

  • the present invention relates to post-synthesis processing of diamond and related super-hard materials.
  • the present invention relates to optimized lapping processes for diamond and related super-hard materials.
  • super-hard materials are defined as those materials having a Vickers hardness of no less than 2000 kg/mm 2 .
  • These materials include a range of diamond materials, cubic boron nitride materials (cBN), sapphire, and composites comprising the aforementioned materials.
  • diamond materials include chemical vapour deposited (CVD) single crystal and polycrystalline synthetic diamond materials of a variety of grades, high pressure high temperature (HPHT) synthetic diamond materials of a variety of grades, natural diamond material, and diamond composite materials such as polycrystalline diamond which includes a metal binder phase (PCD) or silicon cemented diamond (ScD) which includes a silicon/silicon carbide binder phase.
  • CVD chemical vapour deposited
  • HPHT high pressure high temperature
  • PCD metal binder phase
  • ScD silicon cemented diamond
  • Certain processing methods have operational parameters which can be altered so as to move from a regime in which no significant processing of a super-hard material is achieved into a regime in which processing is achieved but with associated cracking and damage or failure of the super-hard material.
  • the ability to operate within a suitable window of parameter space in which processing can be achieved without cracking and damage or failure of the super-hard material will depend on the processing technique, the size of any transitional operating window for such a technique, and the level of operation parameter control which is possible to maintain processing within the window of parameter space in which processing can be achieved without cracking and damage or failure of the super-hard material.
  • Post synthesis processing may comprise one or more of the following basic processes: surface processing to remove material from the surface of the as-grown super-hard material in order to increase surface flatness, decrease surface roughness, remove surface defects, and/or attain a target thickness for the super-hard material; surface processing to achieve a fine surface finish where minimal material is removed from the super-hard product, i.e. polishing; and cutting of the super-hard material into target shapes and sizes for particular product application.
  • lapping The latter three-body approach to surface processing is known as lapping and it is this approach which is conventionally used to remove macroscopic quantities of surface material from super-hard materials.
  • Three-body lapping as opposed to a two-body surface processing technique, is preferred for removing macroscopic quantities of surface material from super- hard materials as it has been found that lapping is more efficient at removing surface material from a super-hard material without imparting a large degree of stress or thermal shock to the material which would cause macroscopic fracturing of the material due to its brittle nature and low toughness.
  • a two-body processing technique may be utilized.
  • polishing is used to remove material from the surface of an as-grown super-hard material in order to increase surface flatness, decrease surface roughness, remove surface defects, and/or attain a target thickness for the super-hard material.
  • the super-hard material is polished and this may be performed using a two-body surface processing technique in which abrasive material is fixed in a polishing wheel such as via resin bonding. Polishing may also be achieved using an iron or steel wheel which is diamond impregnated and this is known as scaife polishing.
  • scaife polishing generally utilizes free diamond abrasive particles these are of a small size relative to pores within the iron or steel wheel and are thus embedded/fixed into the wheel thus effecting a two-body processing as opposed to a true three body lapping process.
  • the present invention is primarily concerned with lapping super-hard materials using relatively coarse diamond powders or grits (or other super-hard powders or grits) to remove material from the surface of the as-grown super-hard material in order to increase surface flatness, decrease surface roughness, remove surface defects, and/or attain a target thickness for the super-hard material.
  • Lapping of super-hard materials is known in the art. The type of abrasive which should be utilized will be dependent on the type of material which is to be lapped. Obviously, when lapping super-hard materials a super-hard abrasive will be required. Accordingly, for lapping of diamond materials a diamond abrasive is utilized.
  • diamond lapping pastes and slurries are widely available comprising a diamond powder or grit disposed within a carrier fluid.
  • Diamond lapping slurries may have a variety of different concentrations of diamond powder/grit and varying particle sizes of diamond powder/grit.
  • lapping machinery for performing the lapping process is also widely commercially available (e.g. from KemetTM, LogitechTM, and Peter WoltersTM).
  • a review article summarizing various surface processing techniques for use on chemical vapour deposited (CVD) diamond films and substrates is provided in Diamond and Related Materials 8 (1999) 1198-1213.
  • This review article includes a description of mechanical lapping of diamond films using coarse diamond powders greater than 1.0 ⁇ in size (i.e. diamond grit) disposed in a binder fluid such as olive oil. It is described that this type of mechanical processing removes diamond material via a micro-chipping or micro-cleavage mechanism. It is further described that after lapping using coarse diamond abrasive particles finer diamond powers can be used for final polishing.
  • the aforementioned rolling mechanism is dominant when using larger abrasive grains in a coarse lapping technique as suggested in the Diamond and Related Materials review article.
  • a coarse lapping process can be performed to remove material from the surface of an as-grown super-hard material in order to increase surface flatness, decrease surface roughness, remove surface defects, and/or attain a target thickness for the super-hard material.
  • finer abrasive powders can be used for final polishing which are then more prone to be mechanically immobilized in pores of a processing wheel thus providing more of a microcutting processing mechanism.
  • Lapping methods for processing a super-hard material product having a Vickers hardness of no less than 2000 kg/mm 2 comprising: mounting the super-hard material product with a surface of the super-hard material product in contact with a surface of a processing wheel with an interface region disposed between the surface of the super-hard product and the surface of the processing wheel; loading the super-hard material product such that the super-hard material product is pressed against the surface of the processing wheel with a loading force; rotating the processing wheel; and feeding an abrasive slurry onto the surface of the processing wheel, the abrasive slurry comprising super-hard abrasive grit particles disposed in a carrier fluid, wherein the super-hard abrasive grit particles of the abrasive slurry have a particle size of at least 1 ⁇ and roll between the surface of the processing wheel and the surface of the super-hard material product within the interface region in order to cause surface micro- cracking of the super-hard material product and removal of
  • As-grown super-hard material products such as poly crystalline CVD diamond wafers often have variable thickness and may, for example, have a wedge shaped cross-sectional profile due to asymmetries in the growth process.
  • the loading force will generally be applied to a thicker portion of the as-grown super-hard material product, such as at a thicker side of a wedge shaped wafer of super-hard material.
  • This asymmetric loading of the super-hard material product causes preferential processing of the thicker portion of the super-hard material product thus reducing the variation in thickness and increase parallelism of front and rear surfaces of the as-grown super-hard material product.
  • one aspect of the present invention utilizes a lapping process as defined above wherein the method of processing includes at least two processing periods including a first processing period during which the loading force is applied to the super-hard material product in a non-central location of the super-hard material product and a second processing period during which the loading force applied to the super-hard material product is reduced and centralised on the super-hard material product relative to the loading force applied during the first processing period.
  • Figure 1 shows a two stage lapping process for processing a surface of a super-hard material product
  • Figure 2 shows a cross-sectional view of a standard lapping configuration
  • Figure 3 shows a plan view of a standard lapping configuration
  • Figure 4 shows a side view of a constraining ring used to mount a super-hard material product on a processing wheel as illustrated in Figures 2 and 3;
  • Figure 5 shows a cross-sectional view of a lapping configuration using an underfeed arrangement for feeding abrasive slurry onto a lapping wheel
  • Figure 6 shows a plan view of a lapping configuration using an underfeed arrangement for feeding abrasive slurry onto a lapping wheel
  • Figure 7 shows a cross-sectional view of a carrier substrate with a super-hard material product mounted thereto for processing.
  • embodiments of the present invention are directed to a lapping process for super-hard materials including a first processing period during which a loading force is applied to a super-hard material product in a non-central location of the super-hard material product and a second processing period during which the loading force applied to the super-hard material product is reduced and centralised on the super-hard material product relative to the loading force applied during the first processing period.
  • providing a loading force applied to a super-hard material product in a non-central location of the super-hard material product is useful for preferentially processing a thicker portion of the as-grown super-hard material product thus reducing thickness variations and increasing parallelism between front and rear surfaces of an as-grown super-hard material product which has non-uniform thickness. Furthermore, it has been surprisingly found that if the load force is reduced and centralised on the super-hard material product during the final stages of the lapping method this reduces edge rounding and lapping damage of the super-hard material product for a given abrasive grit size.
  • Figure 1(a) illustrates a first lapping step in which a super-hard material product 100 is lapped on a processing wheel 102 with abrasive particles 104.
  • the as-grown super-hard material product 100 has a wedge-shaped cross-section and a loading force 106 is applied at a non-central, thick portion of the super-hard material product 100. This causes preferential processing of the thick portion of the super-hard material product 100 to increase thickness uniformity and parallelism of front and rear surfaces of the super-hard material product 100.
  • a second lapping step is performed as illustrated in Figure 1(b) in which the loading force 106 is reduced in magnitude and centralized on the super-hard material product 100.
  • this has been found to reduce edge rounding and lapping damage of the super-hard material product 100 for a given abrasive grit size and by using this approach and carefully controlling the lapping process at this stage of processing it is also possible to reduce or eliminate the requirement for lapping with fine abrasive particles.
  • the loading force is reduced and moved such that it is located through the centre of mass of the super-hard material product being processed.
  • the super-hard material product is symmetrical, such as a square or round piece of super-hard material, then this may corresponding to locating the loading force through the centre of symmetry of the super-hard material product, i.e. through the geometric centre of the super-hard material.
  • perfect centralization is not a strict requirement and some benefits can still be obtained if the loading force is moved to a more central location during the second lapping period relative to the first lapping period while not necessarily being perfectly centralized in the final period of lapping. That said, a central or substantially central location for the loading force in the final period of lapping is preferred.
  • the loading force may be applied by locating weights on the super-hard material product. For example, during a first processing period a first weight is located on the super-hard material product and during the second period a second weight, which is smaller in mass than the first weight, is located on the super-hard material product. During the first processing period the first weight is positioned over the super-hard material product in a non-central location relative to the centre of mass of the super-hard material and during the second processing period the second weight is positioned in a different location to the first weight which is closer to the centre of mass of the super-hard material.
  • the first and second weights may be smaller in lateral size than the super-hard material product such that they can be readily moved around to different locations on the super-hard material product.
  • the loading force may be moved from a more peripheral location to a relatively more central location in a single step, in multiple steps in which the loading is moved sequentially towards a more central location, or otherwise moved gradually to a more central location in a continuous manner.
  • the location of the loading force during a lapping period may be calculated as the time-averaged loading location and in this case it will be the time-averaged loading location which is moved to a more central location in the second lapping period relative to the first lapping period.
  • super-hard materials are generally very rigid and the loading force is not intended to significantly bend the super-hard material product but rather provide a loading which enables the grit particle to process the surface of the super-hard material. If the loading is located in a non-central location then this will tend to cause preferential processing of the surface of the super-hard material by the abrasive grit particles at the non-central location.
  • a flatness of the processing wheel may be controlled to have a greater degree of flatness than during the first processing period, at least over a portion of the processing wheel which is utilized to process the super-hard material product. This may be achieved either by re-processing of the processing wheel between the first and second processing periods to increase the flatness of its surface profile or otherwise by re-placing the processing wheel with another processing wheel has a greater degree of flatness between the first and second processing periods.
  • the average particle size of super-hard abrasive grit particles will affect the material removal rate from a super-hard material product and the quality of surface finish.
  • the average particle size of the super-hard abrasive grit particles during the first processing period will still generally be equal to or greater than the average particle size of the super-hard abrasive grit particles during the second processing period.
  • the average particle size of the super-hard abrasive grit particles during the second processing period may still be relatively large while still achieving a good quality surface finish by using the methodology as described herein.
  • the average particle size of the super- hard abrasive grit particles during the second processing period may be at least 1 ⁇ , 5 ⁇ , 10 ⁇ , 20 ⁇ , 30 ⁇ , or 35 ⁇ and/or no more than 60 ⁇ , 50 ⁇ , or 45 ⁇ and/or in a range having end points selected from any combination of the aforementioned lower and upper values.
  • the loading force used to press the super-hard material product against the surface of the processing wheel during the lapping method may be in a range 0.05 g/mm 2 to 1.5 g/mm 2 or 0.1 g/mm 2 to 0.6 g/mm 2 , at least during at least during the second processing period. According to certain applications, during the first processing period a loading force towards an upper end of these ranges is used while during the second processing period a loading forced towards a lower end of these ranges is used.
  • the loading force may be applied directly on the super-hard material product.
  • a carrier substrate can be mounted to the super-hard material product and the loading force applied to the super-hard material product via the carrier substrate. In this case, the carrier substrate may have a surface flatness better than 20 ⁇ , 10 ⁇ , 5 ⁇ , or 1 ⁇ .
  • processing parameters which have been found to be useful include: rotating the processing wheel at a speed in a range 0.2 ms -1 to 7.5 ms -1 or 1.5 ms -1 to 5.5 ms "1 , at least during the second processing period; use of an abrasive slurry comprising a concentration of super-hard abrasive grit particles in a range 50 to 150 carats per litre (10 grams/litre to 30 grams/litre), at least during the second processing period; feeding the abrasive slurry onto the surface of the processing wheel at a feed rate in a range 0.1 litres/hour to 2 litres/hour or 0.2 litres/hour to 0.7 litres/hour, at least during the second processing period.
  • FIGS 2 to 4 illustrate a lapping apparatus on which the presently described processing method can be utilized.
  • the apparatus comprises a rotatable processing wheel 2 on which a super-hard material product to be processed is mounted.
  • the mounting configuration comprises a carrier substrate 4 to which the super-hard material 6 is adhered.
  • the carrier substrate 4 on which the super-hard material 6 is adhered is arranged such that a surface of the super-hard material is in contact with a surface of the processing wheel 2 with an interface region disposed between the surface of the super-hard material 6 and the surface of the processing wheel 2.
  • a weight 8 is provided on the carrier substrate 4 such that the super- hard material 6 is pressed against the surface of the processing wheel 2 with a suitable loading force.
  • the carrier substrate 4 and super-hard material product 6 is mounted on the processing wheel within a constraining ring 10 which constrains a location of the super-hard material product 6 over the processing wheel 2.
  • the constraining ring 10 comprises a number of slots 11 for allowing the passage of abrasive fluid therethrough as illustrated in Figure 4.
  • the constraining ring 10 has an internal diameter which is larger than the diameter of the super- hard material product 6 and carrier substrate 4. Furthermore, both the constraining ring 10 and the super-hard material product 6 are mounted so as to rotate on the surface of the processing wheel 2 driven by rotation of the processing wheel. In the illustrated configuration the constraining ring 10 is rotatable mounted on the processing wheel 2 via constraining arm 12.
  • an abrasive slurry comprising super-hard abrasive particles within a carrier fluid is dripped onto the surface of the processing wheel 2 from above.
  • the abrasive slurry 14 is housed in a slurry container 16 and a tube 18 runs from the slurry container 16 to a position above the processing wheel 2 for dripping abrasive slurry 14 onto the processing wheel 2.
  • a pump such as a peristaltic pump, may be provided to control the drip rate of abrasive slurry onto the processing wheel 2.
  • the abrasive slurry is dripped onto the processing wheel 2 near a central region thereof and the abrasive slurry moves radial outwards across the processing wheel 2 during rotation of the processing wheel in use.
  • the super-hard abrasive particles may be relatively large in size, e.g. having a particle size of greater than 1 ⁇ . These abrasive particle are larger than pores within the surface of the processing wheel 2 and thus roll between the surface of the processing wheel 2 and the surface of the super-hard material product 6 within the interface region in order to cause surface micro-cracking of the super-hard material product 6 and removal of material from the surface of the super-hard material product 6.
  • One problem the present inventors have found with the aforementioned lapping configuration is that the lapping process can be difficult to control in order to achieve high rates of material processing without causing undue damage to the surface of the super-hard material being processed. Furthermore, another problem the present inventors have found with the aforementioned lapping configuration is that the lapping process can be difficult to obtain uniform processing across large areas of super-hard material. In accordance with the presently described method, one way to alleviate these problems is to vary the location and magnitude of the loading force during the lapping process.
  • the weight 8 in the aforementioned lapping configuration can be located in a non-central location on the super- hard material to preferentially process thicker regions of the super-hard material and then the weight 8 can be reduced in magnitude and centralized on the super-hard material in the latter stages of lapping to reduce edge rounding and lapping damage of the super-hard material while still achieving good rates of material removal.
  • a pneumatic arrangement can be utilized to apply the loading force in place of the weight 8.
  • a processing wheel which has one or more feed ports disposed therein and at least a portion of the abrasive slurry is fed directly from the one or more feed ports into the interface region between the surface of the processing wheel and the super-hard material product being processed.
  • the abrasive slurry may be fed onto the surface of the processing wheel though the one or more feed ports from underneath the processing wheel rather than dripped onto the surface of the processing wheel from above. In this way, the abrasive slurry can be fed onto the surface of the processing wheel though the one or more feed ports in a continuous stream.
  • FIGs 5 to 7 illustrate a lapping apparatus re-configured according to the aforementioned arrangement.
  • the apparatus shares many common features with that illustrated in Figures 2 to 4 and like reference numerals have been used for like parts to highlight common features.
  • the apparatus comprises a rotatable processing wheel 2 on which a super-hard material product to be processed is mounted.
  • the mounting configuration may comprise a carrier substrate 4 mounted to the super-hard material 6 such that a loading force is applied to the super-hard material 6 via the carrier substrate 4.
  • the super-hard material 6 may be bonded to the carrier substrate 4.
  • the super-hard material may be retained in a free-standing configuration which is not bonded to a carrier substrate.
  • the super-hard material 6 is adhered to a carrier substrate 4 and arranged such that a surface of the super-hard material is in contact with a surface of the processing wheel 2 with an interface region disposed between the surface of the super-hard material 6 and the surface of the processing wheel 2.
  • a weight 8 is provided on the carrier substrate 4 such that the super-hard material 6 is pressed against the surface of the processing wheel 2 with a suitable loading force.
  • a pneumatic arrangement can be utilized to apply the loading force in place of the weight 8.
  • the carrier substrate 4 (if present) and the super- hard material product 6 can be mounted on the processing wheel within a constraining ring 10 which constrains a location of the super-hard material product 6 over the processing wheel 2.
  • the constraining ring 10 may comprise a number of slots for allowing the passage of abrasive fluid therethrough as previously illustrated in Figure 4 although it is possible to utilize a constraining ring which does not comprise slots.
  • the constraining ring 10 has an internal diameter which is larger than the diameter of the super-hard material product 6 and carrier substrate 4. Furthermore, both the constraining ring 10 and the super-hard material product 6 are mounted so as to rotate on the surface of the processing wheel 2 driven by rotation of the processing wheel.
  • the constraining ring 10 is rotatable mounted on the processing wheel 2 via constraining arm 12.
  • the constraining ring 10 and/or the super-hard material product 6 are rotatably driven independently of the processing wheel 2 and this can be desirable to provide a controlled rotation of the constraining ring 10 and/or the super-hard material product 6 relative to the processing wheel 2.
  • the constraining arm 12 may comprise driven wheels for rotating the constraining ring 10 and/or the super-hard material product 6.
  • a rotating force may be applied from directly above the super-hard material product 6, e.g. via an upper surface of the super-hard material product 6, the carrier substrate 4, the weight 8, and/or via a pneumatic loading configuration if present.
  • the apparatus of Figures 5 to 7 is configured to provide an under-feed arrangement for the abrasive slurry.
  • abrasive slurry is fed upwards through a rotational post 20 as illustrated by arrow 22.
  • the processing plate 2 is adapted to provide a plurality of feed ports 24 disposed in the surface thereof such that in use an abrasive slurry is fed through the feed ports 24 onto the surface of the processing wheel from underneath the processing wheel as illustrated by arrows 26.
  • the abrasive particles then move radial outwards from the feed ports 24 across the surface of the processing wheel 2 and roll through the interface region between the super-hard material product 6 and the processing wheel 2 in order to cause surface micro-cracking of the super-hard material product and removal of material from the surface of the super- hard material product.
  • the plurality of feed ports 24 can be radially distributed across the surface of the processing wheel such that at least a portion of the abrasive slurry is fed directly from the feed ports into the interface region between the surface of the processing wheel and the surface of the super- hard material product being processed.
  • the present inventors have found that higher rates of material processing can be achieved in a much more controllable manner using a lapping configuration in which the surface of the processing wheel has one or more feed ports disposed therein and the abrasive slurry is fed through the feed ports during processing of the super-hard material product onto the surface of the processing wheel from underneath the processing wheel rather than dripped onto the surface of the processing wheel from above as is done in a more standard lapping configuration.
  • a better surface finish is also achieved, especially for large poly crystalline CVD diamond wafers when compared with a top feed approach. While not being bound by theory, it is believed that the under-feed configuration is advantage over the top-feed configuration for the following reasons.
  • the modified lapping process it is also possible using the modified lapping process to achieve more uniform processing across a large surface of a super-hard material such as a polycrystalline CVD diamond wafer.
  • standard lapping techniques involve dripping a suspension of diamond grit onto the lapping wheel from above.
  • using such a technique requires grit to move into a peripheral region of the interface between the lapping wheel and a polycrystalline CVD diamond wafer and then propagate across the interface region in order to process the surface of the polycrystalline CVD diamond wafer.
  • the grit particles are broken down as they hit the peripheral region of the wafer and during propagation under the wafer. This can result in differential processing of peripheral and central regions of the wafer with central regions being processed by smaller particles of grit than peripheral regions.
  • This problem is particular to processing of super-hard materials, such as diamond wafers, as other materials do not cause the diamond grit to be broken down into smaller particles.
  • the lapping apparatus has been modified to feed the suspension of diamond grit from an underside of the lapping wheel through holes in the lapping wheel at locations which result in the grit being fed directly into the interface region between the wafer and the lapping wheel.
  • This underfeed configuration can thus be utilized in combination with a carefully controlled final stage lapping procedure as previously described in order to further reduce edge rounding, lapping damage, and differential processing of the super-hard material.
  • abrasive slurry is fed onto the surface of the processing wheel though one or more feed ports from underneath the processing wheel. Furthermore, the abrasive slurry is preferably fed onto the surface of the processing wheel though the one or more feed ports in a continuous stream.
  • the lapping apparatus may further comprise a pump configured to feed abrasive slurry though the one or more feed ports in a continuous stream and the pump may be configured to vary a rate of flow of the abrasive slurry though the one or more feed ports in the processing wheel.
  • the processing wheel may also comprise one or more grooves or slots disposed in the working surface thereof, e.g. radially disposed slots, concentrically disposed grooves, or spiral grooves.
  • Such slots and grooves can aid in controlling the movement of abrasive slurry across the processing wheel and/or removal of abrasive slurry from the surface of the processing wheel.
  • the one or more feed ports disposed in the processing wheel may be configured to inject abrasive slurry into one or more slots or grooves on the surface of the processing wheel.
  • the processing wheel may be planar without any such grooves. While slots or grooves are known to increase lapping rates in certain applications, the presence of such slots and grooves can make the re-conditioning of such processing wheels more problematic.
  • the entire apparatus could, in principle, be inverted relative to the Earth.
  • the super-hard material product would be mounted against a lower surface of the processing wheel and abrasive slurry would be fed through feed ports in the processing wheel from above the processing wheel to the lower surface with at least a portion of the abrasive slurry being fed directly from the one or more feed ports into the interface region between the surface of the processing wheel and the super-hard material product being processed.
  • the lapping process as described herein is sensitive to the rotation speed of the processing wheel and that the rotation speed of the processing wheel may be selected to optimize processing rates while retaining a good surface finish.
  • the rotation speed of the processing wheel may advantageously be selected to be in a range 0.2 ms "1 to 7.5 ms "1 with certain embodiments optionally using a rotation speed in a range 1.5 ms "1 to 5.5 ms "1 .
  • the lapping process as described herein is sensitive to the particle size of the super-hard abrasive grit and that the particle size of the abrasive may be selected to optimize processing rates while retaining a good surface finish. It has been found that the particle size of the super-hard abrasive grit may advantageously be selected to be in a range 5 ⁇ to 100 ⁇ with certain embodiments optionally using an abrasive particle size in a range 10 ⁇ to 65 ⁇ . It has been found that surprisingly good surface finishes with relatively low surface roughness can be achieved when lapping with relatively coarse grit.
  • Different grades of abrasives grit may be used either individually or sequentially to achieved particular surfaces finishes. For example, a coarse grit having an average particle size of approximately 50 ⁇ to 60 ⁇ , an intermediate grit having an average particle size of approximately 35 ⁇ to 45 ⁇ , and a fine grit having an average particle size of approximately 20 ⁇ to 30 ⁇ . Finer grits are more expensive and should only generally be used when a very high degree of flatness and smoothness are required. As previously indicated, it has been found that a low roughness finish can be achieved for diamond material using relatively coarse grits. For example, using a grit size of 20 to 25 ⁇ it is possible to achieve a surface roughness of better than 150 nm Ra.
  • the lapping process as described herein is sensitive to the concentration of super-hard abrasive grit particles within the abrasive slurry and that the concentration of super-hard abrasive grit particles within the abrasive slurry may be selected to optimize processing rates while retaining a good surface finish. It has been found that the concentration of super-hard abrasive grit particles within the abrasive slurry may advantageously be selected to be in a range 50 to 150 carats per litre (10 grams/litre to 30 grams/litre) for cost effective processing.
  • the lapping process as described herein is also sensitive to the rate at which the abrasive slurry is fed onto the surface of the processing wheel and that the feed rate may be selected to optimize processing rates while retaining a good surface finish. It has been found that the feed rate may advantageously be selected to be in a range 0.1 litres/hour to 2 litres/hour with certain embodiments optionally using a feed rate in a range 0.2 litres/hour to 0.7 litres/hour.
  • the weight on the wafer being processed may also be doubled such that the load per grit particle remains reasonably constant except for the final stages of lapping when the loading force is reduced and centralized as previously described.
  • a number of possible carrier fluids may be utilized for the abrasive grit particles.
  • the carrier fluid should have a viscosity which is sufficient to suspend the abrasive grit particles during transport through the one or more feed ports to the surface of the processing wheel.
  • the precise requirements for the carrier fluid will also depend on flow rate, grit size, suspension time, and grit concentration. Glycerine based carrier fiuids may be utilized but even water based carrier fiuids with various additives have been found to be suitable.
  • the processing parameters of rotation speed, loading force, grit size, grit concentration, and slurry feed rate are inter-related and preferably a combination of the aforementioned parameters is utilized to achieve the best lapping of super-hard products.
  • an under-feed lapping configuration In addition to the use of an under-feed lapping configuration and optimized processing parameters as described above, a simple and effective mounting configuration has also been developed for ensuring that highly flat surface finishes can be achieved.
  • an ultra-flat carrier substrate e.g. one which has a surface which deviates from a perfectly flat surface by no more than 20 ⁇ , 10 ⁇ , 5 ⁇ , or 1 ⁇ .
  • a very low viscosity adhesive to mount the super-hard material product to the carrier substrate. Use of a low viscosity adhesive avoids the adhesive drying with a non-uniform flatness which introduces non-uniformities in the reference surface to which the super-hard material product is adhered.
  • Such non-uniformities can result in non-uniformities in the flatness of the super-hard material being processed. That said, while low viscosity adhesives have been found to be useful for mounting super-hard material products for processing, another alternative is to leave the super-hard material product in an un-bonded state.
  • the mounting configuration comprises a carrier plate 30 having an ultra-flat surface.
  • the carrier plate 30 may be formed from a number of different materials including invar, silicon carbide, silicon cemented diamond, quartz, or borosilicate glass. Ideally, the carrier plate 30 should be made of a material which has a low thermal expansion coefficient and which is capable of being processed to a high degree of flatness.
  • the carrier substrate may be cylindrical in shape and may comprise an o-ring 32 disposed around a peripheral surface thereof. The o-ring 32 is advantageous to protect the carrier in use where it abuts against a constraining ring as previously described.
  • a super-hard material product plate 34 is mounted to the ultra-flat surface of the carrier plate 30, e.g. via a low viscosity adhesive 36. While in Figure 7 the super-hard material product plate 34 has a diameter substantially equal to that of the carrier plate 30, in practice the diameter of the super-hard material product plate 34 may often be smaller than that of the carrier plate 30.
  • One mounting technique involves pressing a wafer of super- hard material onto a carrier substrate (nucleation face down as this provides the smoothest, flattest reference face when compared with the growth face which is rough and comprises larger particles) and beading glue around the edge of the wafer.
  • the glue is drawn into the interface between the wafer and the carrier substrate around a peripheral region by capillary action and sets to adhere the wafer to the carrier substrate. If the wafer or the substrate is not sufficiently flat then glue may be drawn into a more central region of the interface which is not desirable as flatness is compromised. What is desired is a very small volume of glue within the interface region only around a peripheral region.
  • the glue must be a low viscosity adhesive in order to be drawn into the interface and set in the required manner.
  • the glue must also be capable of withstanding the temperatures generated during lapping and polishing in order to retain adhesion during processing.
  • the substrate-wafer composite is heated to soften the glue and release the wafer which is then turned over and re-adhered to the carrier substrate for processing the other surface of the wafer.
  • the growth face of the wafer is processed first before processing of the nucleation face. This is because the nucleation face is usually more smooth and flat than the growth face and thus it is preferably to mount the more smooth flat nucleation face to a carrier substrate and process the growth face prior to processing the nucleation face.
  • the lapping process as described herein may also be utilized for non-planar super-hard material products.
  • the working surface of the processing wheel may be curved and the carrier plate may also be curved to provide a suitable mounting configuration and processing surface for a non-planar super-hard material product such a dome or lens.
  • Embodiments of the present invention may be applied to a range of super- hard materials including a range of diamond materials, cubic boron nitride materials (cBN), sapphire, and composites comprising the aforementioned materials.
  • diamond materials include chemical vapour deposited (CVD) single crystal and polycrystalline synthetic diamond materials of a variety of grades, high pressure high temperature (HPHT) synthetic diamond materials of a variety of grades, natural diamond material, and diamond composite materials such as polycrystalline diamond which includes a metal binder phase (PCD) or silicon cemented diamond (ScD) which includes a silicon/silicon carbide binder phase.
  • CVD chemical vapour deposited
  • HPHT high pressure high temperature
  • PCD metal binder phase
  • ScD silicon cemented diamond

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
  • Polishing Bodies And Polishing Tools (AREA)

Abstract

L'invention concerne un procédé de traitement d'un produit en matériau super dur (100) possédant une dureté Vickers supérieure ou égale à 2 000 kg/mm2. Le procédé comprend les étapes consistant à : monter le produit en matériau super dur (100) de sorte qu'une surface du produit en matériau super dur (100) soit en contact avec une surface d'une roue de traitement (102) possédant une région d'interface disposée entre la surface du produit en matériau super dur (100) et la surface de la roue de traitement (102) ; mettre en charge le produit en matériau super dur (100) de sorte que le produit en matériau super dur (100) soit appuyé contre la surface de la roue de traitement (102) sous l'effet d'une force de mise en charge (106) ; faire tourner la roue de traitement (102) ; et appliquer une boue abrasive sur la surface de la roue de traitement (102), la boue abrasive comprenant des particules abrasives super dures (104) disposées dans un fluide porteur, les particules abrasives super dures (104) de la boue abrasive possédant une dimension moyenne d'au moins 1 µm et roulant entre la surface de la roue de traitement (102) et la surface du produit en matériau super dur (100) à l'intérieur de la région d'interface afin de provoquer une microfissuration de la surface du produit en matériau super dur (100) et une élimination de matière de la surface du produit en matériau super dur (100). Ledit procédé de traitement comprend au moins deux périodes de traitement, notamment une première période de traitement au cours de laquelle la force de mise en charge (106) est appliquée au produit en matériau super dur (100) en un point non central du produit en matériau super dur (100), et une seconde période de traitement au cours de laquelle la force de mise en charge (106) appliquée au produit en matériau super dur (100) est réduite et centralisée sur le produit en matériau super dur (100) par rapport à la force de mise en charge (160) appliquée au cours de la première période de traitement.
PCT/EP2014/076944 2013-12-11 2014-12-08 Traitement post-synthèse du diamant et matériaux super durs associés WO2015086544A1 (fr)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0684106A2 (fr) * 1994-05-23 1995-11-29 Sumitomo Electric Industries, Ltd. Procédé et appareil pour la production d'un semi-conducteur couvert d'une couche dure
US20020076838A1 (en) * 2000-10-26 2002-06-20 Hiroyuki Kojima Polishing method
US20030092363A1 (en) * 2001-11-15 2003-05-15 Thomas Laursen Method and apparatus for controlling slurry distribution
USRE38854E1 (en) * 1996-02-27 2005-10-25 Ebara Corporation Apparatus for and method for polishing workpiece
US20060003677A1 (en) * 2004-07-01 2006-01-05 Moo-Yong Park Polishing pad and chemical mechanical polishing apparatus comprising the same
US20090214826A1 (en) * 2008-01-04 2009-08-27 Charles West Controlling diamond film surfaces

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05154761A (ja) * 1991-12-06 1993-06-22 Ibiden Co Ltd 結晶性薄膜の研磨方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0684106A2 (fr) * 1994-05-23 1995-11-29 Sumitomo Electric Industries, Ltd. Procédé et appareil pour la production d'un semi-conducteur couvert d'une couche dure
USRE38854E1 (en) * 1996-02-27 2005-10-25 Ebara Corporation Apparatus for and method for polishing workpiece
US20020076838A1 (en) * 2000-10-26 2002-06-20 Hiroyuki Kojima Polishing method
US20030092363A1 (en) * 2001-11-15 2003-05-15 Thomas Laursen Method and apparatus for controlling slurry distribution
US20060003677A1 (en) * 2004-07-01 2006-01-05 Moo-Yong Park Polishing pad and chemical mechanical polishing apparatus comprising the same
US20090214826A1 (en) * 2008-01-04 2009-08-27 Charles West Controlling diamond film surfaces

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GB201421809D0 (en) 2015-01-21
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GB2522982B (en) 2016-11-16

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