Robinson, Gary
| 1. | A saw blade comprising: A continuous annular ring shape for cutting hard objects, the annular ring including a pair of opposite side surfaces, the annular ring having a cutting surface, a coating of diamondlike carbon material formed on one or more of the surfaces of the annular ring. |
| 2. | The saw blade of claim 1, wherein the saw blade is selected from the group consisting of : (a) diamond impregnated resinoid saw blades, (b) diamond impregnated metal sintered saw blades, and (c) diamond impregnated nickel saw blades. |
| 3. | The saw blade of claim 1, wherein the cutting edge is formed on an outer diameter of the saw blade. |
| 4. | The saw blade of claim 1, wherein the cutting edge is formed on an inner diameter of the saw blade. |
| 5. | The saw blade of claim 1, wherein the coating of diamondlike carbon material is preferably continuous over at least one selected surface of the saw blade. |
| 6. | The saw blade of claim 1, wherein the coating of diamondlike carbon material is preferably not continuous over at least one selected surface of the saw blade. |
| 7. | The saw blade of claim 6, wherein the coating of diamondlike carbon material is deposited in a series of ridges on at least one selected surface of the saw blade. |
| 8. | The saw blade of claim 1, wherein the coating of diamondlike carbon material is doped with one or more selected elements. |
| 9. | The saw blade of claim 1, wherein the average hardness of the DLC is between 40 GPa. and 60 GPa. |
| 10. | The saw blade of claim 1, wherein the width of the saw blade is less than . 0006 mils wide. |
| 11. | The saw blade of claim 1, wherein the thermal conductivity of the saw blade is less than. 0001 mils wide. |
| 12. | A method of making a saw blade, the method steps comprising: (A) obtaining a completed or near completed saw blade, the saw blade including a pair of opposing side surfaces and a cutting surface, (B) placing the saw blade into a chamber configured to coat items placed therein with a layer of diamondlike carbon, and (C) depositing a layer of diamondlike carbon on at least one surface of the saw blade. |
| 13. | The method of claim 12, further including the step (D) repositioning the saw blade over within the chamber, and depositing a layer of diamondlike carbon material on at least one other surface of the saw blade. |
| 14. | The method of claim 12, wherein step (C) comprises the following substeps: (C1) treating or cleaning the surfaces of the saw blade on which the diamondlike carbon material will be deposited prior to depositing the diamondlike carbon material, (C2) depositing a layer of diamondlike carbon material on at least one surface of the saw blade. |
| 15. | The method of claim 12, wherein the method step (C) comprises the following substeps: (C1) masking selected portions of at least one surface of the saw blade to prevent the formation of diamondlike carbon material on the saw blade in the areas of the saw blade that have been masked, (C2) depositing a layer of diamondlike carbon material on at least one surface of the saw blade. |
| 16. | The method of claim 12, wherein the method step (C) comprises the following substeps: (C1) treating or cleaning the surfaces of the saw blade on which the diamondlike carbon material will be deposited prior to depositing the diamondlike carbon material, (C2) masking selected portions of at least one surface of the saw blade to prevent the formation of diamondlike carbon material on the saw blade in the areas of the saw blade that have been masked, (C3) depositing a layer of diamondlike carbon material on at least one surface of the saw blade. |
| 17. | The method of claim 12, wherein the diamondlike carbon material layer resulting from the method is discontinuous over a surface of the saw blade. |
| 18. | The method of claim 12, wherein the saw blade of step A is selected from the group consisting of : (a) diamond impregnated resinoid saw blades, (b) diamond impregnated metal sintered saw blades, and (c) diamond impregnated nickel saw blades. |
| 19. | The saw blade of claim 17, wherein the coating of diamondlike carbon material is deposited in a series of ridges on at least one selected surface of the blade. |
| 20. | The saw blade of claim 12, wherein the coating of diamondlike carbon material formed in step (C) is doped with one or more selected elements. |
DESCRIPTION OF PRIOR ART Generally, small high speed saw blades using synthetic diamond grit are used for very precise cutting in many manufacturing applications including use in the manufacture of microelectronic devices, biomedical devices, superconductors, opto- electronics, magnetic memory devices, solar cells, printed circuit boards, and others.
Particularly heavy use of such saw blades is made in the semiconductor industry. For example, in a typical semiconductor fabrication process, numerous semiconductor devices are constructed simultaneously on a single large wafer. When the devices are completed, the devices must be separated or singulated. A variety of saw blades have been developed for dicing wafers, generally comprising some kind of matrix holding abrasive grains such as diamond crystals. Currently, diamond
impregnated nickel saw blades, sintered metal saw blades, and resin saw blades are commonly used.
The industry has seen a trend toward reducing the spacing between individual devices formed on the wafers. As much as 60% or more of the cost of the finished wafer has been invested by the time the wafer reaches the dicing saw step. Thus, damage caused to the wafers during the dicing process is extremely expensive. It is therefore very important that the saw blades remain in the street between the devices.
The street is generally defined as the distance between functional portions of adjacent semiconductor devices on a wafer. The cut made by the saw blade is called the kerf, and the width of the kerf must be less than the width of the street. One of problem encountered when using prior art saw blades to cut semiconductor wafers is chipping and cracking of the wafer. Both chipping and cracking may result in the cracking of or the removal of material from the functional areas of the device outside of the street boundary. In both cases the proper functioning of the device may be adversely affected.
Prior art saw blades have a number of other disadvantages as well. For example, the distribution of the diamond grains in most diamond impregnated saw blades is random, which results in some clumping, and also the formation of relatively open areas. The open areas are subject to loading which means that loose material sticks or loads to the surface of the saw blade in between the diamonds. Loading can negatively affect the performance of the saw blade. Also, heat buildup is a significant problem when saw blades are run at high rpm's. As the blade temperature rises, the
matrix holding the diamonds, such as nickel or resin, expands, causing the blade to expand, which changes the kerf geometry. Furthermore, the thermal expansion of the diamond particles and the nickel matrix, in nickel diamond saw blades, are different.
The difference in thermal expansion can lead to cracking and weakening of the saw blade. Additionally, prior art nickel diamond saw blades typically include deep grooves on the sides of the blade created during the etching process used to expose the blade during manufacture. The grooves may weaken the blade and may cause weaving. Finally, nickel diamond blades generally last about 30,000 linear inches of cutting on typical substrates, and resin blades typically last between 10,000 and 25,000 linear inches depending on the hardness and thickness of the material being cut. Changing worn saw blades is costly in terms of lost run time.
What is needed is a diamond impregnated saw blade, and a method of making such blades, that avoids the disadvantages of the prior art and that includes advantages and objects such as providing a saw blade that: is stronger than prior art saw blades, that has an increased ability to dissipate heat over prior art saw blades, that is less subject to loading than prior art saw blades, that may be used at higher rpm's than prior art saw blades, that is less subject to weaving than prior art saw blades, that will generate fewer and smaller chipping and cracking incidents than prior art saw blades, that will provide a cleaner more predictable kerf than prior art saw blade, and that will provide a longer cutting life than prior art saw blades.
SUMMARY OF THE INVENTION Accordingly, the present invention comprises an improved saw blade, and a method for improving saw blades. In it's broadest sense, the invention may be used to coat pre-fabricated saw blades with a layer of diamond or diamond like crystals (DLC) to improve the performance of the saw blades. DLC refers to a know family of amorphous and polycrystalline carbon materials, that may contain hydrogen, and possibly selected dopents such as nitrogen, fluorine, silicon and others, and whose properties resemble but do not exactly duplicate those of diamonds. The dopents may be used to provide or enhance desired material properties of the DLC. The coating may be formed only on the sides of the saw blade, or on both the cutting edge and sides of the saw blade. Furthermore, the layer of DLC may be continuous, or non- continuous forming a variety of possible useful patterns including but not limited to ridges.
While the invention as described is well suited for use in dicing wafers in the semiconductor industry, the invention may also be used for many other tasks including but not limited to cutting or shaping silicon ingots, microelectronic devices, biomedical devices, superconductors, opto-electronics, optical lenses, magnetic memory devices, solar cells, printed circuit boards, magnetic heads, ink jet print heads, SAW devices, integrated circuits, multilayer capacitors, piezoelectric elements, and others.
Any known method of depositing the DLC coating may be used including chemical vapor deposition (CVD) methods such as thermal-filament CVD, microwave-plasma CVD, RF-plasma CVD, ECR-Plasma CVD, DC thermo-plasma CVD, and DC arc-jet CVD. Other known and possibly useable methods include sputtering or physical vapor deposition methods, ion beam deposition, laser deposition techniques, and thermal evaporation. The particular method chosen will depend partly on the nature of the saw blade to be treated, and on the desired characteristics of the DLC layer to be formed.
A first example embodiment of the saw blade of the invention is a diamond impregnated nickel dicing saw blade comprising a base with a nickel diamond saw blade electroplated thereon. The base may, in some embodiments, include a hub. The saw blade includes two side surfaces and a continuous cutting edge or surface at its outside diameter. The saw blade further includes a coating of diamond-like carbon material formed on one and or more of the side surfaces and/or the cutting edge or surface of the saw blade.
A second example embodiment of the saw blade of the invention is a diamond impregnated resinoid dicing saw blade comprising continuous annular ring shape for cutting hard objects comprising a cured mass of resin impregnated with diamond particles, typically coated with nickel. The annular ring has a pair of opposite side surfaces, and a continuous cutting edge at its outside diameter. A coating of diamond- like carbon crystals or material formed on one or more of the side surfaces and the cutting edge of the annular ring.
The method of the invention generally comprises the following steps: (1) obtaining a completed or near completed saw blade, (2) placing the saw blade into a chamber configured to coat items placed therein with a layer of DLC, and (3) depositing a layer of DLC onto the selected surfaces of the saw blade of the blade.
The method may alternately include the step of depositing a layer of DLC on the sides and front of the saw blade. Step (3) of the method preferably also includes the process of treating and/or cleaning the surface of the saw blade prior to depositing the layer of DLC. Step (3) of the method may also include the method of masking selected portions of at least one surface of the saw blade to prevent the formation of DLC on the saw blade in the areas of the saw blade that have been masked. Also, the coating of DLC material formed in step (3) may be doped with one or more selected elements to provide or enhance selected characteristics of the DLC.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a single generic prior art dicing saw cutting a wafer.
FIG. 2 is a scanning electron microscope image of a side surface of a prior art nickel-diamond saw blade.
FIG. 3 is a schematic of a generic chemical vapor deposition reaction chamber.
FIG. 4 is a schematic of a generic ion beam chemical vapor deposition reaction chamber.
FIG. 5 is a scanning electron microscope image of a side surface of the nickel- diamond saw blade of FIG. 2 after application of a DLC coating using the method of the invention.
FIG. 6 is a side view of an embodiment of a resin blade with DLC ridges formed on the side surfaces of the saw blade.
FIG. 7 is a cross section of a portion of a nickel diamond saw blade after a coating of DLC has been applied.
DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a method for fabricating improved saw blades, and also the improved saw blades resulting from the application of the method. In its broadest sense, the invention is a method for coating saw blades with a layer of diamond-like carbon, hereafter"DLC", to improve the performance and desired characteristics of the saw blades. The coating may be formed only on the sides of the saw blade, or on both the cutting edge and sides of the saw blade. The layer may be continuous, or non-continuous forming a variety of possible useful patterns including but not limited to protruding ridges, ribs, mesas of various shapes, or other structures.
The method of the invention may be used in the manufacture of a variety of kinds of saw blades useable for a variety of purposes, including but not limited to cutting or shaping silicon ingots, microelectronic devices, biomedical devices, superconductors, opto-electronics, optical lenses, magnetic memory devices, solar cells, printed circuit boards, magnetic heads, ink jet print heads, SAW devices, integrated circuits, multilayer capacitors, piezoelectric elements, and others.
However, the method of the invention is particularly suited for use in the manufacture of diamond impregnated saw blades, such as nickel diamond saw blades, metal sintered saw blades, and resin based saw blades, used for dicing or singulating integrated circuit devices from the sheets or wafers on which they are typically manufactured. The method of the invention may be used in the fabrication both serrated and non-serrated saw blades, and in the fabrication of shaped edge blades.
FIG. 1 shows a generic dicing saw assembly including a saw blade A mounted on a hub B positioned over and making cuts in a wafer C. The particular characteristics of the selected saw blade A depend on a number of factors including the nature of the material of wafer C being cut. FIG. 2, is a scanning electron microscope image of the surface of a prior art nickel-diamond saw blade. As is typical, the distribution of the diamond grains D is random, which results in some clumping (an example of which is designated by the letter E), and also results in open areas (an example of which is designated by the letter F) where loose material may stick or load to the surface of the nickel in between the diamonds. Loading can negatively affect the performance of the saw blade, and may be of particular concern
when cutting wafers including copper, as copper has a high propensity to stick to the surface of such saw blades.
Prior art saw blades have a number of other disadvantages. One problem encountered when using prior art saw blades to cut semiconductor wafers is chipping and cracking of the wafer, which may result in the cracking of or the removal of material from the functional areas of the device outside of the street boundary. In both cases the proper functioning of the device may be adversely affected. In addition, heat buildup is a significant problem when saw blades are run at high rpm's.
As the blade temperature rises, the matrix, such as nickel or resin, holding the diamonds expands causing the blade to expand, which changes the kerf geometry.
Furthermore, the thermal expansion of the diamond particles and the matrix material are different. The difference in thermal expansion can lead to cracking and weakening of the saw blade. Additionally, prior art nickel diamond saw blades typically include deep grooves on the sides of the blade created during the etching process used to expose the blade during manufacture. The grooves may weaken the blade and may cause weaving. Finally, nickel diamond blades generally last only about 30,000 linear inches of cutting on typical substrates, and resin blades typically last between 10,000 and 25,000 linear inches, depending on the material being cut.
Changing worn saw blades is costly in terms of lost run time.
The method of the invention is preferably performed on an otherwise completed or nearly completed diamond impregnated saw blade. The disadvantages with the prior art previously discussed above have been observed to be significantly
reduced by coating otherwise completed or nearly completed diamond impregnated saw blades with a layer of diamond-like carbon (DLC). In particular, the saw blades of the invention exhibit longer useful cutting life than prior art saw blades, and produce a better quality cut, meaning less cracking and chipping, than prior art saw blades. DLC refers to a known family of amorphous carbon and polycrystalline materials, that may contain hydrogen, and possibly selected dopents such as nitrogen, fluorine, silicon and others, and whose properties resemble but do not exactly duplicate those of diamonds. The dopents may be used to provide or enhance desired material properties of the DLC.
Any known method of depositing the DLC coating may be used including chemical vapor deposition (CVD) methods such as thermal-filament CVD, microwave-plasma CVD, RF-plasma CVD, ECR-Plasma CVD, DC thermo-plasma CVD, and DC arc-jet CVD. Other known and possibly useable methods include sputtering or physical vapor deposition methods, ion beam deposition, laser deposition techniques, and thermal evaporation, and sputtering. The particular method chosen will depend partly on the nature of the saw blade to be treated. For example, microwave plasma CVD deposition of the DLC layer is currently preferred for nickel diamond and metal sintered saw blades. However, ion beam DLC deposition is currently preferred for use on diamond impregnated resin saw blades, because the heat used in the typical microwave plasma CVD process may damage the resin saw blades.
FIG. 3 shows a schematic of a generic microwave CVD reaction chamber for depositing DLC onto the surfaces of items placed therein. The assembly of such CVD systems is well known, and many such systems exist in a variety of configurations.
The exact configuration of the system may be varied as required, and the details of the particular system used will depend on the parameters of the process that must be controlled, and the specific application of the system.
A typical CVD system 90 comprises a number of interconnected components including a CVD chamber 100 that can be evacuated to reduce the gas pressures therein, a vacuum pumping system 102 for establishing and maintaining the desired pressure, various pressure gauges 104 to monitor the pressure in the CVD chamber 102, a power supply 106, gas handling apparatus 108 for metering and controlling the flow of reactant gasses, and one or more plasma generating means for creating and maintaining the plasma 118. In use, a saw blade 112 is placed within the CVD chamber 100. Methane and hydrogen (preferably in an inert carrier gas) are introduced into the CVD chamber 100 through the gas handling apparatus 108. The addition of other gasses may be preferred under some circumstances. The gasses pass through openings in a top electrode 114 mounted above the lower electrode 116, where RF energy is applied to generate a plasma 118. The dissociated gas phase species of hydrogen and methane created in the plasma 118 diffuse to the exposed surfaces of the saw blade 112 placed on lower electrode 116, and some carbon molecules condense onto the surface of the saw blade forming DLC crystals. The vacuum pumping system 102 draws the remaining gasses away through an exhaust tube, and also maintains the pressure in the CVD chamber 100 within a desired range.
A single saw blade 112 is shown in FIG 3, but in preferred embodiments a number of saw blades 112 would be treated simultaneously.
In the CVD system 90 configuration shown, the DLC layer will be deposited primarily on the exposed side surfaces of the saw blade 112. Thus in order to coat the other side of the saw blade 112, the saw blade 112 would preferably be turned over, and the method repeated. However, if desired, it may be possible to configure the CVD chamber 100 differently, or orient the saw blade 112 differently, so that the DCL is also deposited on the outer circumference or edge of the saw blade 112. In another configuration is may be possible to configure the CVD chamber 100 so that both side surfaces of the saw blade 112 are coated with DLC simultaneously.
A schematic of a typical or generic ion beam DLC deposition apparatus is seen in FIG. 4. The assembly of ion beam DLC deposition apparatus and the methods of using them are well known, and many such assemblies exist in a variety of configurations. The exact configuration of the system may be varied as required, and the details of the particular system used will depend on the parameters of the process that must be controlled, and the specific application of the system.
In general, a substrate such as a resinoid blade 150 is placed in an ion beam chamber 152 under vacuum. Two separate ion beams projectors 154 and 156 are used to project ions toward the surface of the substrate 150. The beams 154 and 156 are arranged so that the beams cross over the substrate 150. One ion source 154 also feeds the methane and hydrogen gas into the ion chamber 152. Energy of the
collision of particles in the ion beams dissociates the gas phase species of hydrogen and methane. The dissociated gas phase species impact the substrate 150 where some will condense into the DLC layer. Sputtering may be another acceptable low temperature method for depositing the DLC layer.
FIG. 5 is a scanning electron microscope image of a surface of the saw blade seen in FIG. 2 after treatment by the method of the invention. As can be seen, the saw blade surface is now covered by a layer of DLC. The layer of DLC is preferably relatively uniform, with a variation of plus or minus 5%. No significant surface areas are available for loading, and the diamond crystals are held more firmly than by the nickel matrix alone. The hardness of the DLC may be as high as 80 GPa under optimal conditions. Furthermore, the DLC is an excellent thermal conductor, so heat at the cutting edge of the blade is more rapidly dissipated. This improved thermal dissipation helps reduce the temperature of the saw blade, thus reducing changes in the geometry of the saw blade resulting from thermal expansion, and allows the saw blade to be run at higher revolutions per minute. The DCL layer presents a more even surface to the wafer being cut, which reduces the chipping and cracking experienced by the wafer. The DLC coating strengthens the saw blade, and may allow the use of significantly thinner saw blades than currently available prior art saw blades, with a width less 0.0006 and possibly with a width less than. 0001 mils wide. Furthermore, the DLC coating has been observed to significantly increase the useful cutting life of the saw blades. FIG. 6 is a schematic cross section of an outer edge of a saw blade 158 comprising a diamond impregnated matrix material 160 coated on each side surface of the saw blade 158 by a layer of DLC 162.
The layer of DLC formed on the saw blades need not be uniform, and with the use of stencils, masks or other known methods, may be deposited in various desired or useful patterns or configurations. For example, in one preferred embodiment seen in FIG. 7, ridges 166 of DLC are formed on the side surface of a resinoid saw blade 164, thereby defining grooves 168 between the ridges 166. The ridges 166 may have the effect of stiffening the saw blade 164. The grooves 168 defined by the ridges 166 may assist in bringing cooling fluids, such as deionized water, to the surface of the kerf more quickly, where the fluid acts as a lubricant, and carries away heat as the fluid leaves the active cutting site. Furthermore, the grooves 168 may act as channels through which the cooling fluid and particles cut from the kerf can easily leave the active cutting region. The number and geometry of the ridges 166 may be varied as desired, and the ridges 166 may be oriented at any practical angle from a radial line drawn from a center of the saw blade 164.
In general the method of the invention comprises the following steps: (1) obtaining a completed or near completed saw blade, (2) placing the saw blade into a chamber configured to coat items placed therein with a layer of DLC, and (3) depositing a layer of DLC on one or more surfaces of the saw blade. Step (3) of the method preferably includes the process of treating and/or cleaning the surface of the saw blade prior to depositing the layer of DLC in order to achieve good adhesion of the DLC to the saw blade. Step (3) of the method may also include the process of masking selected portions of at least one surface of the saw blade to prevent the formation of DLC on the saw blade in the areas of the saw blade that have been
masked. Also, the coating of DLC material formed in step (3) may be doped with one or more selected elements to provide or enhance selected characteristics of the DLC.
Several examples showing currently preferred implementations of the principles of the method of the invention will be explained.
EXAMPLE 1.
An example of the method of the invention will be described in the manufacture of a DLC coated nickel diamond saw blade. Nickel diamond saw blades are available commercially from a variety of sources including Disco Corporation, Kulicke & Soffa Industries, Inc., and many others, and the method of the invention may be performed on saw blades purchased from these sources. A standard nickel diamond saw blade typically comprises an aluminum base on which is formed a layer of nickel matrix holding diamond crystals. Generally, a mask is placed on the base permitting selective plating only of the perimeter or annular area where the dicing blade is to be formed. One or more such bases are coupled to a mandrel and rotated in a known nickel plating solution generally including nickel, diamonds of selected grain, and other various components selected to provide desired characteristics to the finished blade. Acceptable diamond crystals include General Electric micronized synthetic diamonds. A variety of known nickel plating solutions are currently commercially available. To convert the deposited nickel diamond layer into a saw blade, aluminum is removed, usually on a lathe, leaving a thin aluminum film. The thin aluminum film is typically etched away leaving a freestanding nickel diamond
layer. The edge of this nickel diamond layer may be further treated to create a preferred geometry. The width of such blades typically ranges between 0.6 mils and 6 mils. The configuration of the starting hub, the nickel diamond tank, the plating solutions, and the conditions under which the nickel diamond plating takes place are well known in the industry, and can be varied to obtain specific desired results.
At this point, a prior art saw blade has been completed. Once the basic saw blade is formed, the method of the invention can be used to coat the blade with DCL material, resulting in the improved blade of the invention. The saw blade is preferably cleaned to improve adhesion of the DLC to the surface of the saw blade.
Any practical method for cleaning the surface of the saw blade maybe used. Many known etching or plasma wetting methods may be useable. Such processes generally use gasses including one or more of oxygen, argon and nitrogen, and maybe performed in the same chamber in which the DLC will be applied, or in a separate chamber.
As previously mentioned, any known method of depositing the DLC coating may be used. However, the currently preferred method for depositing the DCL material on nickel diamond saw blades is a chemical vapor deposition method, as seen in FIG. 3, performed in a vacuum chamber that results in the growth of DCL crystals on the exposed surfaces of the saw blades placed therein.
The embodiment of the method used in this example is preferably performed as follows:
1) The aluminum hubs and attached blades are preferably heated to between 350 and 400 degrees C.
2) The reaction chamber gas pressure is preferably between 10 and 100 mtorr.
3) The RF power level is preferably from 50 to 200 watts, and is generated at preferably between 10 to 20 MHz, and more preferably approximately 13.56 MHz.
4) The chuck temperature is preferably between 250 and 405 degrees C, and more preferably between 300 and 355 degrees C.
5) The flow of methane will preferably be between 30 and 50 sccm percent of the total flow.
6) The flow of hydrogen in an inert carrier gas, preferably argon, will preferably be between 2020 and 4040 sccm, in which the H2 component will preferably be between 4 and 40 percent of the gas by volume.
7) The reaction will be allowed to continue under these conditions for a time between 20 and 50 minutes depending on a number of factors including the desired thickness of the DLC layer.
Use of the method of the invention results in a layer of DLC of a desired thickness deposited on the selected exposed surfaces of the saw blade. The hardness of the DLC layer created may be between 40GPa and 60 GPa. The uniformity of the DLC layer is preferably plus or minus 2% to 5%.
EXAMPLE 2.
An example of the method of the invention will be described in the manufacture of a DLC coated diamond-impregnated resinoid saw blade. Resinoid saw blades are available commercially from a variety of sources including Disco Corporation, Kulicke & Soffa Industries, Inc., and many others, and the method of the invention may be performed on saw blades purchased from these sources.
Resinoid saw blades are typically formed by placing a resin mixture including a diamond grit, typically nickel coated synthetic diamonds, into a mold. The mold and mixture are then typically placed in a chamber where the resin is treated to cure the resin material. Frequently the cutting edge of the saw blade is then shaped and dressed.
At this point, a prior art resinoid saw blade has been completed. Once the basic saw blade is formed, the method of the invention can be used to coat the blade with DCL material, resulting in the improved blade of the invention. The saw blade is preferably cleaned to improve adhesion of the DLC to the surface of the saw blade.
Any practical method for cleaning the surface of the saw blade maybe used. Many known etching or plasma wetting methods may be useable. Such processes generally use gasses including one or more of oxygen, argon and nitrogen, and maybe performed in the same chamber in which the DLC will be applied, or in a separate chamber.
As previously mentioned, any known method of depositing the DLC coating may be used. However, the currently preferred method for depositing the DCL material on resin saw blades is an ion CVD method performed in a vacuum chamber that results in the growth of DCL crystals on the exposed surfaces of the saw blades placed therein.
Ion beam DLC deposition apparatus and methods are well known. In general, a substrate such as a resinoid blade is placed in a chamber under vacuum, as seen in FIG. 4. In this example, the ion beam sources are a well known Kaufman design operating at approximately 1.8 Hz. The temperature of the substrate or target saw blades is approximately 50 degrees C. The bean energy is preferably between 800 and 1, 000 electron volts, and more preferably approximately 900 electron volts. The current density is preferably between 1 and 1.4 A/cm2, and more preferably approximately 1.2 mA/cm2. The flow of methane will preferably be approximately 2000 sccm, and the flow of hydrogen in an inert carrier gas, preferably argon, will preferably be approximately 2000 sccm, in which the H2 component will preferably be between 4% to 40% percent of the gas by volume.
Use of the method of the invention results in a layer of DLC of a desired thickness deposited on the selected exposed surfaces of the saw blade. The uniformity of the DLC layer is preferably plus or minus 2% to 5%. The hardness may be between 40-50 GPa.
The preferred embodiments described herein are illustrative only, and although the examples given include many specificities, they are intended as illustrative of only a few possible embodiments of the invention. Other embodiments and modifications will, no doubt, occur to those skilled in the art. The examples given should only be interpreted as illustrations of some of the preferred embodiments of the invention, and the full scope of the invention should be determined by the appended claims and their legal equivalents.