Method and apparatus for assisting laser material processing

Abstract

A laser machining apparatus includes a nozzle connected to a pressurized gas and liquid reservoir for propelling a fine spray, mist or stream of a liquid such as water at the workpiece to be machined. A laser beam, preferably as may be generated by a UV laser or other source of exposure radiation, but is not strongly absorbed by the liquid assist material, is focused to the workpiece using, e.g., a focusing or imaging lens, while the fine spray, mist or liquid stream is propelled at the workpiece creating a layer of the liquid on its surface as the beam is incident upon the workpiece for machining.

1 . A method for removing material from a workpiece using laser energy comprising the steps of: 
 directing a flow of liquid to the workpiece in a manner to form a flowing layer of liquid across a portion of the surface of the workpiece wherein the thickness of the layer is in the range of 25 to 100 microns; and    directing a laser beam to the workpiece through the liquid layer, said laser beam having a fluence sufficient to remove material from the workpiece in one of a cutting, grooving, drilling or etching procedure.    
   
   
       2 . A method as recited in  claim 1 , wherein the laser beam has a wavelength in the ultraviolet spectrum.  
   
   
       3 . A method as recited in  claim 1 , wherein the laser beam is focused onto the workpiece.  
   
   
       4 . A method as recited in  claim 1 , wherein said laser beam is pulsed.  
   
   
       5 . A method as recited in  claim 1 , wherein said laser beam is CW.  
   
   
       6 . A method as recited in  claim 1 , wherein said liquid is substantially transmissive to the wavelength of the laser beam  
   
   
       7 . A method as recited in  claim 1 , wherein said step of directing the liquid flow includes coupling a propellant with the liquid to create a spray of liquid onto the workpiece.  
   
   
       8 . A method as recited in  claim 7 , wherein the propellant includes a pressurized gas that is not substantially photoabsorbing at the wavelength of the laser beam.  
   
   
       9 . A method as recited in  claim 8 , wherein the pressure of the pressurized gas is between 5 and 100 psi.  
   
   
       10 . A method as recited in  claim 8 , wherein the pressure of the pressurized gas is around 18 psi.  
   
   
       11 . A method as recited in  claim 1 , further including the step of withdrawing excess liquid from the workpiece.  
   
   
       12 . A method as recited in  claim 11 , wherein said step of withdrawing excess liquid is performed using a vacuum.  
   
   
       13 . A method as recited in  claim 1 , wherein the flow of liquid is controlled by a computer.  
   
   
       14 . A method as recited in  claim 1 , further including the step of translating the workpiece with respect to the laser beam.  
   
   
       15 . A method as recited in  claim 1 , wherein the thickness of the layer is maintained in the range of 25 to 50 microns.  
   
   
       16 . A method as recited in  claim 1 , wherein the flow rate of the liquid layer is around one milliliter per minute.  
   
   
       17 . A method as recited in  claim 1 , further including the step of ceasing the discharge of liquid across the workpiece prior to the laser beam completing a cut-through of the workpiece.