Additive manufacturing of polishing pads

Abstract

A method of forming a polishing pad that has a polishing region and a window region, wherein both regions are made of an interpenetrating polymer network formed from a free-radically polymerized material and a cationically polymerized material.

What is claimed is: 
     
         1 . A method of generating a formulation for forming a polishing pad comprising an interpenetrating polymer network, comprising:
 blending a cationically polymerized material with a free-radically polymerized material to form a precursor blend, wherein a ratio of the cationically polymerized material to the free-radically polymerized material in the oligomer blend is selected to control properties of the polishing pad;   blending a first amount of a mixture of a free radical photoinitiator and a cationic photoinitiator with the precursor blend to form a polishing pad blend;   blending a second amount of a mixture of a free radical photoinitiator and a cationic photoinitiator with the precursor blend to form a window blend; and   providing the polishing pad blend and the window blend to a manufacturer to generate a polishing pad having a window using a three dimensional printer.   
     
     
         2 . The method of  claim 1 , wherein the properties comprise elongation at break, ultimate tensile strength (UTS), storage modulus, or glass transition temperature, or any combinations thereof. 
     
     
         3 . The method of  claim 1 , wherein a maximum value of a viscosity of the polishing pad blend, the window blend, or both is 20 centipoise (cP). 
     
     
         4 . A method of manufacturing a polishing pad comprising an interpenetrating polymer network, comprising:
 obtaining a polishing pad blend comprising
 a free radical photoinitiator, 
 a free-radically polymerized material; 
 a cationic photoinitiator, and 
 a cationically polymerized material, wherein a ratio of the free radically polymerized material to the cationically polymerized material in a precursor blend is selected to control properties of a polishing pad; 
   obtaining a window blend comprising
 the free radical photoinitiator, wherein a concentration of the free radical photoinitiator is lower than the free radical photoinitiator in the polishing pad blend, 
 the free-radically polymerized material, 
 the cationic photoinitiator, wherein the concentration of the cationic photoinitiator is lower than the concentration of the cationic photoinitiator in the polishing pad blend, and 
 the cationically polymerized material, wherein a second ratio of the free-radically polymerized material to the cationically polymerized material in the window blend is selected to control the properties of a window in the polishing pad; 
   forming a raw polishing pad in a polishing pad region from the polishing pad blend by printing droplets of the polishing pad blend in the polishing pad region;   forming a window in a window region from the window blend by printing droplets of the window blend in the window region; and   irradiating the raw polishing pad to initiate free radical photopolymerization of the free radically polymerized material and cationic photopolymerization of the cationically polymerized material.   
     
     
         5 . The method of  claim 4 , wherein the free-radically polymerized material and the cationically polymerized material are oligomers. 
     
     
         6 . The method of  claim 5 , wherein the free-radically polymerized material is a urethane acrylate oligomer. 
     
     
         7 . The method of  claim 5 , wherein the cationically polymerized material is an epoxy oligomer. 
     
     
         8 . The method of  claim 4 , comprising annealing the polishing pad by irradiating the polishing pad, heating the polishing pad in an oven, or both. 
     
     
         9 . The method of  claim 4 , wherein a maximum viscosity of the polishing pad blend, or the window blend, or both is 20 centipoise (cP). 
     
     
         10 . The method of  claim 4 , wherein a ratio of the free-radically polymerized material and the cationically polymerized material are the same in the polishing pad blend and the window blend. 
     
     
         11 . The method of  claim 4 , wherein irradiating the raw polishing pad generates an interpenetrating polymer network formed from the free-radically polymerized material and the cationically polymerized material for both the polishing region and the window region. 
     
     
         12 . The method of  claim 11 , wherein the window region comprises a lower amount of the free radical photoinitiator, the cationic photoinitiator, or both than the polishing region. 
     
     
         13 . The method of  claim 11 , wherein the ratio of the cationically polymerized material to the free-radically polymerized material is between 10 wt. % and 65 wt. % for a polishing region. 
     
     
         14 . The method of  claim 13 , wherein the ratio of the cationically polymerized material to the free-radically polymerized material is about 25 wt. %. 
     
     
         15 . The method of  claim 4 , wherein irradiating the raw polishing pad generates a polishing pad having an E′30 modulus between 5 megapascals (MPa) and 100 MPa. 
     
     
         16 . The method of  claim 4 , wherein irradiating the raw polishing pad generates a polishing pad having an E′30 modulus between 101 megapascals (MPa) and 500 MPa. 
     
     
         17 . The method of  claim 16 , wherein irradiating the raw polishing pad generates a polishing pad having an E′30 modulus between 501 megapascals (MPa) and 3000 MPa.