Dressing bar for embedding abrasive particles into substrates

Abstract

One or more individually gimballed dressing bars for embedding abrasive particles into a substrate at a substantially uniform height. A hydrostatic and/or hydrodynamic fluid bearing (air is the typical fluid) is maintained between the dressing bar and the substrate. The fluid bearing permits the dressing bar to follow micrometer-scale and/or millimeter-scale wavelengths of waviness on the substrate, while maintaining a constant clearance, to uniformly embed the abrasive particle into the substrate.

1 . A dressing bar assembly for embedding abrasive particles into a surface of a substrate, the dressing bar assembly comprising:
 a support structure;   at least one gimbal assembly connecting at least one dressing bar to the support structure, the gimbal assembly permitting displacement of the dressing bar in at least pitch and roll;   a preload mechanism adapted to bias an active surface on the dressing bar toward the substrate; and   at least one gas conduit adapted to deliver pressurized gas to one or more pressure ports positioned opposite the substrate, the pressurized gas maintaining a hydrostatic bearing between the active surface of the dressing bar and the substrate while the active surface applies a compressive forces sufficient to embed the abrasive particles into the surface.   
     
     
         2 . The dressing bar assembly of  claim 1  comprising:
 a plurality of gimbal assemblies arranged in an array; and 
 a plurality of dressing bars each engaged with one of the gimbal assemblies, the gimbal assemblies permitting independent displacement of each dressing bar in at least pitch and roll. 
 
     
     
         3 . The dressing bar assembly of  claim 1  wherein the hydrostatic bearing generates moments on the dressing bar that are greater than moments generated by interaction of the active surface with the abrasive particles. 
     
     
         4 . The dressing bar assembly of  claim 1  wherein clearance between the active surface and the substrate of the substrate is maintained between about 25 nanometers to about 100 nanometers. 
     
     
         5 . The dressing bar assembly of  claim 1  wherein the hydrostatic bearing permits the active surface to maintain a constant clearance with the surface of the substrate. 
     
     
         6 . The dressing bar assembly of  claim 1  wherein the dressing bar includes one or more fluid bearing features. 
     
     
         7 . The dressing bar assembly of  claim 6  wherein motion of the dressing bar relative to the surface of the substrate generates a hydrodynamic fluid bearing. 
     
     
         8 . The dressing bar assembly of  claim 1  wherein the active surface comprises a plurality of spacer pads, the spacer pads have a height generally corresponding to a target height of the abrasive particles above the substrate. 
     
     
         9 . The dressing bar assembly of  claim 1  comprising three actuators configured to alter the pitch and roll of the dressing bar relative to the support structure. 
     
     
         10 . The dressing bar assembly of  claim 1  comprising one or more of a rotary table, an X-Y stage, an orbital motion generator, or an ultrasonic vibrator adapted to move the substrate relative to the dressing bar. 
     
     
         11 . An abrasive article comprising abrasive particles embedded into a substrate at a substantially uniform height made with the dressing bar of  claim 1 . 
     
     
         12 . A dressing bar assembly for embedding abrasive particles into a surface of a substrate, the dressing bar assembly comprising:
 a support structure;   at least one gimbal assembly connecting at least one dressing bar to the support structure, the gimbal assembly permitting displacement of the dressing bar in at least pitch and roll;   a preload mechanism adapted to bias an active surface on the dressing bar toward the substrate; and   one or more fluid bearing features on the dressing bar configured to generate a hydrodynamic bearing between the dressing bar and the substrate during motion of the dressing bar relative to the substrate while the active surface applies a compressive forces sufficient to embed the abrasive particles into the surface.   
     
     
         13 . The dressing bar assembly of  claim 12  comprising:
 a plurality of gimbal assemblies arranged in an array; and 
 a plurality of dressing bars each engaged with one of the gimbal assemblies, the gimbal assemblies permitting independent displacement of each dressing bar in at least pitch and roll. 
 
     
     
         14 . The dressing bar assembly of  claim 12  wherein the hydrodynamic bearing generates moments on the dressing bar that are greater than moments generated by interaction of the active surface with the abrasive particles. 
     
     
         15 . The dressing bar assembly of  claim 12  wherein the active surface comprises a plurality of spacer pads, the spacer pads have a height generally corresponding to a target height of the abrasive particles above the substrate. 
     
     
         16 . A method of making an abrasive article comprising the steps of:
 distributing a slurry including abrasive particles on a surface of a substrate;   connecting at least one dressing bar to the support structure with a gimbal assembly, the gimbal assembly permitting displacement of the dressing bar in at least pitch and roll;   biasing the dressing bar toward the substrate to engage an active surface on the dressing bar with the slurry;   creating a fluid bearing between the dressing bar assembly and the substrate, wherein the fluid bearing is one or more of a hydrostatic fluid bearing or a hydrodynamic fluid bearing;   adjusting the fluid bearing to control spacing between the dressing bar assembly and the substrate; and   applying a compressive force sufficient for the active surface to embed the abrasive particles into the surface at a generally uniform height.   
     
     
         17 . The method of  claim 16  comprising the steps of:
 arranging a plurality of gimbal assemblies in an array; and 
 engaging a plurality of dressing bars with each of the gimbal assemblies, the gimbal assemblies permitting independent displacement of each dressing bar in at least pitch and roll. 
 
     
     
         18 . The method of  claim 16  comprising generating moments on the dressing bar with the fluid bearing that are greater than moments generated by interaction of the active surface with the abrasive particles. 
     
     
         19 . The method of  claim 16  comprising maintaining a constant clearance between the active surface of the dressing bar and the surface of the substrate. 
     
     
         20 . The method of  claim 16  comprising the steps of:
 delivering a pressurized gas to one or more pressure ports positioned opposite the substrate to create a hydrostatic fluid bearing during a start-up phase; 
 moving the dressing bar relative to the substrate to create a hydrodynamic fluid bearings; and 
 subsequently reducing or terminating the flow of pressurized gas after the hydrodynamic fluid bearing is formed. 
 
     
     
         21 . The method of  claim 16  comprising the steps of:
 preparing a first abrasive article with abrasive particles at a first height relative to the substrate for use with a first lubricant having a first viscosity; and 
 preparing a second abrasive article with abrasive particles at a second height relative to the substrate for use with a second lubricant having a second viscosity different from the first viscosity. 
 
     
     
         22 . A method of lapping a surface of a work piece comprising the steps of:
 positioning an abrasive article made according to the method of  claim 16  opposite the surface of the work piece;   engaging the surface of the work piece with the abrasive particles; and   moving the work piece relative to the abrasive article.