Laser separation of encapsulated submount

Abstract

In a light emitting package fabrication process, a plurality of light emitting chips ( 10 ) are attached on a sub-mount wafer ( 14 ). The attached light emitting chips ( 10 ) are encapsulated. Fracture-initiating trenches ( 30, 32 ) are laser cut into the sub-mount wafer ( 14 ) between the attached light emitting chips ( 10 ) using a laser. The sub-mount wafer ( 14 ) is fractured along the fracture initiating trenches ( 30, 32 ).

1 . A method comprising: 
 attaching a plurality of light emitting chips on a sub-mount wafer;    disposing an encapsulant over the attached light emitting chips and over at least a portion of a surface of the sub-mount wafer,    laser-cutting fracture-initiating trenches into the sub-mount wafer between the attached light emitting chips, the fracture-initiating trenches passing through the encapsulant disposed on the surface of the sub-mount wafer, the laser-cutting employing operating conditions selected such that the laser-cutting causes the encapsulant to melt and re-shape to produce a desired sidewall characteristic; and    fracturing the sub-mount wafer along the fracture-initiating trenches.    
   
   
       2 . The method as set forth in  claim 1 , wherein the laser-cutting comprises: 
 employing operating conditions selected such that the laser-cutting causes the encapsulant to ball up to produce the desired sidewall characteristic.    
   
   
       3 . The method as set forth in  claim 1 , wherein the laser-cutting comprises: 
 employing operating conditions selected such that the laser-cutting causes the encapsulant to melt and re-shape by surface tension to produce the desired sidewall characteristic.    
   
   
       4 . The method as set forth in  claim 1 , wherein the laser-cutting of fracture-initiating trenches comprises: 
 performing one or more first passes of laser-cutting that cut the encapsulant disposed between the light emitting chips, the one or more first passes employing the operating conditions selected such that the laser-cutting causes the encapsulant to melt and re-shape to produce a desired sidewall characteristic; and    performing one or more subsequent passes of laser-cutting that cut into the sub-mount wafer to form a trench in the sub-mount wafer, the one or more subsequent passes employing different operating conditions from the operating conditions of the one or more first passes.    
   
   
       5 . The method as set forth in  claim 4 , wherein the one or more subsequent passes employ at least one of a higher laser-cutting power, a higher laser-cutting fluence, a higher laser-cutting energy, a slower laser-cutting scan speed, and a higher laser-cutting pulse frequency respective to the one or more first passes.  
   
   
       6 . A method comprising: 
 attaching a plurality of light emitting chips on a sub-mount wafer;    encapsulating the attached light emitting chips;    laser-cutting fracture-initiating trenches having kerfs of less than about 75 microns into the sub-mount wafer between the attached light emitting chips using a laser; and    fracturing the sub-mount wafer along the fracture-initiating trenches.    
   
   
       7 . The method as set forth in  claim 6 , wherein the encapsulating includes disposing encapsulant material on the sub-mount in areas between light emitting chips, and the laser-cutting of fracture-initiating trenches comprises: 
 removing the encapsulant disposed between the light emitting chips; and    removing a portion of the sub-mount wafer.    
   
   
       8 . The method as set forth in  claim 7 , wherein the laser-cutting of fracture-initiating trenches further comprises: 
 performing one or more first laser-cutting passes that cut the encapsulant disposed between the light emitting chips, the one or more first laser-cutting passes employing first operating parameters; and    performing one or more subsequent laser-cutting passes that cut into the sub-mount wafer to form a trench in the sub-mount wafer, the one or more subsequent laser-cutting passes employing second operating parameters different from the first operating parameters.    
   
   
       9 . The method as set forth in  claim 8 , wherein the encapsulant is disposed on a frontside of the sub-mount wafer, and the one or more subsequent laser-cutting passes are performed on a backside of the sub-mount wafer opposite the frontside.  
   
   
       10 . The method as set forth in  claim 8 , wherein the first operating parameters provide a relatively lower laser-cutting rate, and the second operating parameters provide a relatively higher laser-cutting rate.  
   
   
       11 . The method as set forth in  claim 8 , wherein the first operating parameters cause the encapsulant to melt and re-shape to produce a desired sidewall characteristic.  
   
   
       12 . The method as set forth in  claim 6 , wherein the laser-cutting fracture-initiating trenches pass about half-way through a thickness of the sub-mount.  
   
   
       13 . The method as set forth in  claim 6 , wherein the laser-cutting fracture-initiating trenches pass less than 40% through a thickness of the sub-mount.  
   
   
       14 . The method as set forth in  claim 6 , wherein the laser-cutting comprises: 
 employing feedback control of the laser-cutting based on a measurement of a depth produced by the laser-cutting.    
   
   
       15 . A method comprising: 
 attaching a plurality of light emitting chips on a sub-mount wafer;    laser-cutting fracture-initiating trenches into the sub-mount wafer between the attached light emitting chips using a laser; and    fracturing the sub-mount wafer along the fracture-initiating trenches.    
   
   
       16 . The method as set forth in  claim 15 , wherein the laser-cutting of fracture-initiating trenches comprises: 
 removing an encapsulant material encapsulating the plurality of light emitting chips in the areas of the fracture-initiating trenches.    
   
   
       17 . The method as set forth in  claim 16 , wherein the laser-cutting of fracture-initiating trenches comprises: 
 employing operating conditions for the laser-cutting selected such that the laser-cutting causes the encapsulant to melt and re-shape to produce a desired sidewall characteristic.    
   
   
       18 . The method as set forth in  claim 15 , wherein the fracture-initiating trenches have kerfs of less than about 75 microns.  
   
   
       19 . The method as set forth in  claim 15 , wherein the fracture-initiating trenches have kerfs of less than about 25 microns.  
   
   
       20 . The method as set forth in  claim 15 , wherein the sub-mount wafer includes a material, or a fusion or bonding of a plurality of materials, selected from a group of materials consisting of gallium nitride, aluminum nitride, silicon carbide, sapphire, a ceramic material, an oxide material, silicon, or a semiconductor.