Raised island abrasive, method of use and lapping apparatus

• US 6,769,969 B1
• Filed: 11/17/2000
• Issued: 08/03/2004
• Est. Priority Date: 03/06/1997
• Status: Expired due to Term

• Current Assignee: Keltech Engineering Incorporated
• Original Assignee: Keltech Engineering Incorporated
• Inventors: Duescher, Wayne O.
• Primary Examiner(s): Hail, III, Joseph J.
• Assistant Examiner(s): Thomas, David B.
• Application Number:
  US09/715,448
• Time in Patent Office: 1,355 Days
• Field of Search: 451/9, 451/28, 451/36, 451/41, 451/59, 451/178, 451/259, 451/268-270, 451/285-290, 451/340, 451/364, 451/387, 451/388, 451/461, 451/490, 451/494, 451/526, 451/527, 451/530, 451/533, 451/534, 451/538, 451/539, 156/345.1, 156/345.12, 156/345.13, 156/345.14, 156/345.15, 156/345.51
• US Class Current: 451/59
• CPC Class Codes: B24B 1/00 Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
• CPC Class Codes: B24B 37/00 Lapping machines or devices; Accessories B24B3/00 takes precedence
• CPC Class Codes: B24B 37/14 characterised by the composition or properties of the plate materials
• CPC Class Codes: B24B 45/00 Means for securing grinding wheels on rotary arbors suppression of vibrations in systems F16F15/00; testing static or dynamic balancing of machines G01M1/00
• CPC Class Codes: B24B 5/00 Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor B24B11/00 - B24B21/00 take precedence; honing machines or devices using abrading blocks performing axial and rotary movements superimposed on one another B24B33/00
• CPC Class Codes: B24B 7/00 Machines or devices designed for grinding plane surfaces on work, including polishing plane glass surfaces; Accessories therefor B24B21/00 takes precedence; honing of plane surfaces on work B24B33/055
• CPC Class Codes: B24B 9/00 Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor B24B21/00 takes precedence; for sharpening cutting edges on tools B24B3/00; removing burrs by loose abrasive material B24B31/00
• CPC Class Codes: B24D 9/10 with suction means for securing the material

Abstract

Abrasive sheet materials, abrasive sheet materials with island distributions of abrasive particles, processes for manufacture of abrasive sheet materials with minimized abrasive content (with monolayers and as few as four layers of abrasive particles), processes for using the abrasive sheeting in high speed lapping/abrading processes, and apparatus for using the abrasive sheeting are described. The process for manufacturing the abrasive sheeting provides an economical method for providing improved quality sheeting, while also allowing for greater control over the shape and distribution of abrasive islands on the sheet than is available from present processes of manufacture.

Claims

1. A workpiece holder for supporting a workpiece during lapping or grinding of a surface of the workpiece, the workpiece holder having a recess in a rotating gimbal that has a spherical center of rotation with a diameter of rotation, the workpiece being supported in the workpiece holder so that a geometric center of a surface of the workpiece that is to be lapped lies in a plane that is within 20% of the diameter of the spherical rotation as measured from the spherical center of rotation during initiation of abrasion of that surface.

2. A process for lapping a workpiece on a circular or annular abrasive sheet, rotating the abrasive sheet at a speed of at least 500 revolutions per minute while a surface of the workpiece is in contact with the abrasive sheet, wherein the outside diameter of the abrasive sheet in contact with the workpiece is at least 25 cm, and the width of an area of abrasive on the sheet that may contact the workpiece is at least 3.5 cm, wherein abrasive action on a surface of the workpiece that is being abraded is equalized between portions of the surface of the workpiece that are more exterior with respect to the abrasive sheet and portions that are more interior with respect to the abrasive sheet, the equalization being increased by rotating the workpiece so that rotation of a radially outer edge of the workpiece rotates in the same direction of rotation as the rotation of the abrasive sheet, the rotation of the workpiece effectively bringing the relative tangential speed of movement between the abrasive sheet and the workpiece at the radially outward portion of the workpiece surface closer in relative tangential speed between the abrasive sheet radially interior portion and the sheet radially exterior portion, as compared to the relative tangential speeds when a workpiece is not rotated.

3. A process of lapping a surface on a rotating workpiece on an annular band of an raised island abrasive on a support surface of a sheet mounted on a rotating platen by rotating the sheet at a speed of at least 500 rpm to provide a moving platen abrasive surface, wherein the surface of the rotating workpiece is less wide than the width of the annular band of the abrasive mounted to a rotating platen, the workpiece is oscillated across the surface of the annular band back and forth between or slightly in excess of the inner and outer radial edges of the annular band while the workpiece is in lapping contact with said moving platen abrasive surface, using a gimbal or spherical action workpiece holder rotatable spindle to support the workpiece.

4. The process of claim 3 where the workpiece holder rigidly fixes the workpiece to the workpiece holder rotatable spindle axis.

5. An apparatus providing spherical motion to a workpiece being supported during a surface abrading procedure, the apparatus comprising:

a) a workpiece holder mechanism that rotates about a center of rotation of spherical action, the center of rotation being offset from the mechanism and a surface of the workpiece that is to be abraded lies within 20% of a diameter of the spherical rotation;

b) the workpiece attached to a rotor having a three-point construction of a set of at least three separate island legs that define a spherical support area underneath the island legs, the spherical support area having a common center with the workpiece holder mechanism spherical center;

c) a rotor housing having a three-point construction with a set of at least three separate island legs that define a second spherical support area by at least three arc segment areas under the at least three legs, with the second spherical support area having a common center with the workpiece holder mechanism spherical center;

d) leg defining edge boundaries of the island legs of both the spherical rotor and the island legs of the rotor housing being aligned, where the leg boundaries for the two sets of island legs are in alignment;

e) a fluid passageway in the center of each of the three rotor housing support island leg arc area segments to allow injection of a fluid into the arc segment area surfaces common to both the rotor and the rotor housing to create a separation of the rotor from the housing by a very thin layer of fluid that is less than 0.2 mm in thickness, when the fluid is injected by high pressure into the joint areas, through the passageway;

g) the spherical rotor is restrained from single degree of freedom motion, with respect to the rotor housing, about an axis extending through the workpiece holder spindle rotation axis anti-lineal rotation by use of a linkage arm which has a low friction pivot joint at one end of the arm attached to an outer portion of the spherical rotor and the other end of the linkage arm attached to an outboard portion of the rotor housing by a low friction low friction pivot joint.

6. The apparatus of claim 5 wherein the spherical rotor is restrained in direct contact with the spherical rotor housing at all three island leg mutual spherical arc segment contact surface areas by an extension spring, sufficiently strong to overcome the forces of gravity on both the rotor and the rotor mounted workpiece, which is attached at one spring end to the rotor at a position close to the workpiece and which is attached at the other spring end to the rotor housing on an axis located at the center of the spring length aligned coincident with the workpiece holder rotating spindle axis.

7. The apparatus of claim 5 where pressurized gas is injected into each of the three spherical area arc segments for all of at least three island legs to create a gas bearing fluid film between the rotor and the rotor housing, or where pressurized liquid is injected into each of the spherical area arc segments of the at least three island legs to create a liquid bearing fluid film between the rotor and the rotor housing.

8. The apparatus of claim 6 where the rotor retention spring is strong enough that the rotor is rigidly locked into the rotor housing by friction forces on the three island leg arc segments, when pressurized fluid is not injected into the rotor housing island fluid bearing joints, so that no movement of the rotor relative to the rotor housing occurs when a rotor mounted workpiece is polished or ground as it contacts a moving abrasive.

9. The apparatus of claim 5 where the spherical rotor is constructed of aluminum, titanium or composite material.

10. The apparatus of claim 5 where a moat style groove is created around the arc segment area center feed hole is surrounded and water or other fluid exiting the fluid bearing joint is collected with the use of a vacuum suction line.

11. The apparatus of claim 5 is employed as a workpiece holder for use in abrasive slurry grinding or lapping of a workpiece or is employed as a workpiece holder for use in chemical mechanical polishing material removal from the surface of a workpiece.

12. A method of leveling a platen on an annular lapping ring area on a rotatable platen, wherein the annular lapping ring area has an inner radius that is greater than 30 percent of an outer radius of the annular lapping ring area, wherein the platen is periodically, in between uses, machined flat after the platen has been mounted on a lapping machine platen spindle.

13. The process of claim 12 where the platen is machined flat by use of a lathe cutting tool or by use of an abrasive grinding apparatus.

14. A lapping system comprising:

a) A rotary workpiece holder which is mounted on a rotating spindle which is attached to a vertical slide;

b) a lapping machine frame;

c) an abrasive sheet mounted on a rotary platen attached to a lapping machine frame;

d) position sensors are attached between machine members to sense the deflection of members relative to other members during lapping, polishing or grinding to determine the status of the lapping or grinding procedure as it is applied to a workpiece.

15. The system of claim 14 where process variables are changed or the lapping process is terminated as a function of the movement or displacement between machine members during the lapping procedure during lapping as a function of the movement or displacement between machine members changed during the process procedure.

16. The system of claim 15 wherein the process variables are selected from the group consisting of abrasive particle material type, width of abrasive annular ring, type of abrasive sheet including island type or flat coated type, rotation speed of the platen, rotation speed of the workpiece, contact pressure between the workpiece and the abrasive sheet, the length of time of the operation of the process, type of lubricant used, amount of lubricant applied, amount of fluid flow, and rate of fluid flow.

17. The system of claim 15 where a non-contact sensor measures the deflection of a workpiece holder spindle away from a workpiece holder vertical slide, to which said holder is mounted, in a direction of the vector representing the abrasive platen speed at a location of the abrasive contact with the workpiece surface or a sensor measures the deflection of said workpiece holder mechanism vertical slide away from the machine frame during the workpiece lapping process procedure.

18. The system of claim 15 wherein displacement sensors are present and the displacement sensors used are a) capacitance gauges or b) air gauges using a constant air flow rate acting against gage components attached to two different machine component members to produce air pressures which reflect the positional relative change of displacement between two machine members, machine tool displacement sensors, laser gages, and other gages.

19. A flexible, continuous abrasive sheet disk comprising a flexible backing sheet with an annular band of raised abrasive particles where inner said band radius is greater than 30% of the outer said band radius, the abrasive particles comprising islands of a first structural material having a top surface, the top surface having at least a monolayer of abrasive particles supported in a polymeric resin, the height of all islands measured above the surface of a backing has within all 1 cm width annular bands having a standard deviation in height of less than 0.03 mm, and a total thickness of the abrasive island measured from a top surface of the abrasive to a support surface of the backing sheet within all 1 cm width annular bands has a standard deviation in thickness of less than 0.03 mm.

20. The abrasive disk of claim 19 wherein the standard deviation in said height and said thickness is less than 0.01 mm.

21. The abrasive disk of claim 19 where the annular array of islands is made up of circular island shapes.

22. The abrasive disk of claim 19 where the annular band of raised abrasive particles is made up of narrow serpentine shapes extending radially outward or chevron-bar shapes or diamond configuration shapes.

24. The disk of claim 19 wherein spacing between islands varies among at least 10% of islands on the tangential path by tangential spacing by at least 10% of average spacing between island edges on that tangential path.

25. The abrasive disk of claim 19 where a single shape configuration is used but certain of the island shapes are smaller in size than others.

27. The abrasive disk of claim 19 with islands having widths measured in a tangential direction ranging from 1 mm to 7 mm.

28. The abrasive disk of claim 21 with islands having diameters ranging from 1 mm to 7 mm.

29. The disk of claim 19 where the open gap measured in a tangential direction between adjacent islands is between 0.2 mm to 4.0 mm.

30. The disk of claim 19 where a plateau height of the islands measured from the top of exposed abrasive particles to an upper surface of the backing, on a backing side closest to an island foundation, is 0.1 mm to 1.0 mm.

31. The flexible abrasive disk of claim 19 wherein the backing sheet is made of a metal, composite or polymeric material.

35. The process of claim 19 where island base foundations are precision thickness resin coated by a web transfer coating process where a coated transfer web is pressed into conformation in uniform contact with the nominally flat top surfaces of the array band of raised islands until the resin wets a top surface on each island, after which wetting the coated web transfer sheet is removed, leaving at least 5% of the resin attached as a uniform layer on the island top surfaces.

36. The process of claim 35 wherein the coated transfer web is manufactured by knife, gravure, roll or other coating process technique.

39. The abrasive disk of claim 35 where hard abrasive particles are attached to the island base foundation top flat surfaces by drop coating onto or electrostatically coating a wet surface partially cured state make coat resin, followed by a size coat coated over and surrounding the diamonds attached to the make coat.

40. The abrasive disk of claim 39 where the size coat is applied by a transfer coat process or a spin coat process or a spray coat process.

41. The abrasive disk of claim 39 where a supersize coat is applied by spin coating or by transfer sheet coating or a spin coat process or a spray coat process.

55. The process of claim 35 wherein the coated transfer sheet is manufactured by spin coating.

23. A thin flexible abrasive disk with an annular band of raised abrasive top-surface coated particle islands which are positioned with less than 0.5 cm gap spacing between the edges of islands measured in a tangential direction islands, the islands positioned at least around the outer periphery of the disk, wherein the annular band of islands is made up of island shapes that are arranged with a tangentially non-uniform or tangentially non-repeating spacing between individual islands.

26. An abrasive disk having an array of raised, shaped islands positioned in an annular ring on a backing sheet with the disk outer peripheral gap border area free of the raised island array and with the array of islands extending to within 0.2 cm to 3.0 cm of the outer radius of the disk, leaving an outer annular border ring free of abrasive islands.

32. A process of making a disk backing having non-abrasive island foundations thereon comprising providing a flexible backing continuous over its full diameter with a layer of material thereon, chemically machining or chemically etching of islands onto the layer of material, forming a disk backing with an annular ring distribution of islands having flat top surfaces, leaving an annular array of islands raised above the backing surface in an annular array.

33. The process of claim 32 where vertical edges of island walls are tapered to provide that the top surface of the island is smaller than the base of the island at the location where the island base joins with the backing.

34. The process of claim 32 wherein uncoated island base foundations are flat and thick to within ±

0.02 mm, measured from the backside of the backing, and then applying abrasive particles to the surface of the islands.

37. An abrasive disk with an outer annular array of raised island shapes where the island disk foundation is top coated with a monolayer of diamonds or other hard abrasive particles at least 7 up to 400 micrometers in average particle diameter.

38. An abrasive disk with an outer annular array of island shapes where each island base foundation is top coated with a layer of diamond or other hard abrasive particles that are smaller than 10 micrometer, where the diamonds are stacked or partially stacked into a single coated layer that is approximately 10 micrometers thick.

42. An abrasive disk where raised island base foundation material comprises a particle filled resin or a non-particle filled resin.

45. The abrasive disk of claim 42 where the height of fluid non solidified island foundations is precisely controlled relative to the backside of the abrasive flexible backing sheet by use of two mold plates having matching surfaces precisely flat relative to each other wherein the backside of the abrasive backing sheet is attached to the precise flat surface of one matching mold plate and the precise flat surface of the other matching mold plate is brought into contact with the non solidified island foundations thereby driving the top of the island foundation down in height until the precision surface of one of the mold plates is in direct contact with precision thickness gap spacers attached to the precision surface outer periphery of the other matching mold plate to effectively establish the height of all of the island foundations such that the height of the island foundation measured above the surface of the backing sheet plus the thickness of the backing sheet together equal the thickness of said precision gap spacers.

43. An abrasive disk having a metal backing thickness of 0.05 mm to 0.5 mm thick with an outer annular array of island shapes with small enough diameters and wide enough spacing between the island shapes over a range of metal material moduli of elasticity stiffness characteristics so that the disk maintains the nominal flexibility of a thin disk backing to sucessfully conform to the flat surface of a abrasive rotatable platen where said disk has precision height, electrically conductive island foundations and a thin layer of diamond or other hard abrasive particles electroplated to the island top surfaces.

44. A flexible, continuous abrasive sheet web comprising a flexible backing web sheet with an full web width band of raised abrasive particles, the abrasive particles comprising island of a first structural material having a top surface, the top surface having at least a monolayer of abrasive particles supported in a polymeric resin, the height of all islands measured above the surface of a backing is within all 1 cm width web-length strands having a standard deviation in abrasive particle coated islands height of less than 0.01 mm and a total thickness of the abrasive island measured from the top surface of the abrasive to the bottom of the backing sheet within all 1 cm width annular bands having a standard deviation in thickness of less than 0.03 mm.

46. A process comprising:

a) a circular disk hole plastic or metal font sheet used to produce an array of island base foundation shapes in an annular ring band on an abrasive article disk backing sheet;

b) the font sheet having the nominal thickness of the desired height of the island bases;

c) with through holes in the font sheet of the diameter or island cross sectional shape;

d) where each hole is positioned at the location of each island;

e) the font sheet attached flat to a disk backing sheet;

f) the holes in the font sheet filled level to the font sheet top surface with adhesive particle filled or unfilled resin material;

g) using phenolic, polyimide, polyester, epoxy or other resins with or without the use of solvents;

h) after partial solidification of the resin by heat, light, electron beam, laser, or other curing or drying, the font sheet is separated from the backing sheet leaving raised islands in an annular band which are adhesively attached to the backing sheet;

i) the resin island foundations are fully solidified by heat, light, electron beam, laser curing or drying.

47. The process of claim 46 where the island hole font sheet is constructed of magnetic materials including steel or magnetic stainless steel and a flat magnet surface used to clamp the font sheet flat and conformally tight to a backing disk sheet for application of island foundation resin material into the font sheet holes to form an array of raised island foundations which are adhesively attached to the backing sheet to form an annular band of raised islands on said backing disk sheet.

49. The process of claim 46 where the holes in the font have tapered walls with a smaller opening at the top and a larger opening at the bottom, the bottom of which is in direct contact with the backing surface, which will form an island with tapered walls where the top flat surface is less wide than the base.

48. A process where a continuous perforated hole font belt is used to print island foundations on a continuous web backing with the holes in the belt having the desired configuration of the island surface shape and the thickness of the belt corresponding to the raised height of each island foundation, as measured from the top surface of the web backing.

50. The process of claim 48 where the font is made of a magnetic material such as steel or certain magnetic stainless steels.

51. A process where an annular band of island foundations on a disk backing is created by a pin head coater, the process comprising:

a) providing an annular array of small pins having diameters ranging from 1 mm to 10 mm which are attached rigidly to a circular pin head holder, or in a fashion which allows free but limited range of motion axial motion of the pins within the pin head holder, having the free ends of the pins extending some distance away from said holder;

b) the pin head holder is positioned to insert the free pin ends into a vat of island foundation particle filled or unfilled resin liquid material sufficient to wet the free end of the pins some distance up from the end of the pin with a consistent controlled drop volume of foundation liquid attached to each pin end;

c) the pin head is then positioned vertically over a target flexible disk backing sheet attached horizontally to a flat surface and lowered until all of the pins contact the backing sheet surface, wetting each pin site on the backing sheet with a consistent sized drop of liquid foundation adhesive resin fluid;

d) after raising the pin head, the drops of foundation material are stripped from each pin and then deposited on the backing sheet to form an array pattern of island foundations on the backing sheet.

52. The process of claim 51 where the island foundation resin material is solidified by heat, light or other curing processes or dried to form strong rigid island foundations having raised heights measured from the backing surface of from 0.1 mm to 1.0 mm and diameters ranging from 1 mm to 10 mm.

53. The process of claim 52 where the island foundations are machined or ground to a precise height as measured from the bottom surface of the backing to effect a precision thickness common to each island foundation where the thickness is measured from the flat top of each island to the bottom side of the backing in a area within 1 cm of the island foundation.

54. The process of claim 53 where island base foundations are precision thickness resin coated by a web transfer coating process where a coated transfer web is pressed conformally in uniform contact with the nominally flat top surfaces of the array band of raised islands until the resin wets each island top surface after which the coated web transfer sheet is removed, leaving at least 35% of the resin attached as a uniform layer on the island top surfaces.

56. The process of claim 53 where the disk backing having an outer annular array of raised island shapes where the island foundation tops are coated with a monolayer of diamonds or other hard abrasive particles at least 7 up to 400 micrometers in average particle diameter.

57. The process of claim 53 where the disk backing having an outer annular array of island shapes where the island foundation tops are coated with a layer of diamond or other hard abrasive particles that are smaller than 10 micrometer, where the diamonds are stacked or partially stacked into a single coated layer that is approximately 10 micrometers thick.

58. The process of claim 54 where hard abrasive particles are attached to the island base foundation top flat surfaces by drop coating onto or electrostatically coating a wet surface partially cured state make coat resin, followed by a size coat coated over and surrounding the diamonds attached to the make coat.

59. The process of claim 58 where a size coat is applied by a transfer coat process or a spin coat process or a spray coat process.

60. The process of claim 58 where a supersize coat is applied by spin coating or by transfer sheet coating or a spin coat process or a spray coat process.

61. A process where abrasive grinding or lapping is performed and water coolant is applied on the abrasive surface wherein the grinding, lapping or polishing is completed in a closed environment with reduced atmospheric pressure of 10 cm mercury or more up to 25 cm mercury.

62. The process of claim 61 where an additive is added to the water coolant to lower the vapor boiling pressure of the new water mixture.

63. An abrasive article with flexible backing and annular bands of raised island foundations, the raised island foundations having flat top surfaces that may be coated with a mono layer of abrasive particles which raised island foundations are distributed in the approximate form of a disk with petal spokes extending radially outwardly from a common backing center, where only the outer radial 70 percent of the outside disk diameter annular portion of the disk petals of the daisy-wheel is covered with abrasive islands and the corresponding inner radial 30 percent portion of the disk backing is free of abrasive islands.

64. The abrasive article of claim 63 where the height of fluid non solidified island foundations is precisely controlled relative to the backside of the abrasive flexible backing sheet by use of two mold plates having matching surfaces precisely flat relative to each other wherein the backside of the abrasive backing sheet is attached to the precise flat surface of one matching mold plate and the precise flat surface of the other matching mold plate is brought into contact with the non solidified island foundations thereby driving the top of the island foundation down in height until the precision surface of one of the mold plates is in direct contact with precision thickness gap spacers attached to the precision surface outer periphery of the other matching mold plate to effectively establish the height of all of the island foundations such that the height of the island foundation measured above the surface of the backing sheet plus the thickness of the backing sheet together equal the thickness of said precision gap spacers.