X-Ray Alignment System For Fabricating Electronic Chips

Abstract

A system of using x-rays to align screen printing of flip chip using x-ray sub-assembly in a chip fabricating assembly. X-rays are directed onto a substrate having receptor pads and a printing screen having fine apertures. The substrate is aligned with the printing screen based on the detection and analysis of the real-time image generated from the x-rays passing through the substrate and printing screen. The x-ray alignment system is capable of aligning gold plated receptor pads of five microns or less and disposed upon a low light contrast ceramic (e.g., 9011 alumina) substrate with a screen printing stencil having very small apertures of less than 125 microns.

1 . A system for aligning a screen having apertures for printing of solder bumps onto the receptor pads of a substrate, comprising: 
 a stage assembly including means for moving said screen relative to said substrate;    an x-ray generator for beaming x-rays through said screen and said substrate;    a detector for collecting x-rays passing through said screen and said substrate; and    a camera interconnected to said detector for generating a real-time image of said screen and said substrate based on x-rays passing through said screen and said substrate.    
   
   
       2 . The system of  claim 1 , wherein said printing screen is a fine pitch printing screen having apertures of less than approximately 125 microns.  
   
   
       3 . The system of  claim 1 , wherein said receptor pads comprise flip chip pads.  
   
   
       4 . The system of  claim 1 , wherein said receptor pads are gold plated.  
   
   
       5 . The system of  claim 1 , wherein said substrate is low contrast.  
   
   
       6 . The system of  claim 1 , wherein said receptor pads are spaced no more than approximately 5 microns from one another and said screen has a fine pitch of less than approximately 125 microns.  
   
   
       7 . The system of  claim 6 , wherein said receptor pads comprise flip chip pads.  
   
   
       8 . The system of  claim 6 , wherein said receptor pads are gold plated.  
   
   
       9 . The system of  claim 6 , wherein said substrate is low contrast.  
   
   
       10 . A system for aligning a screen having apertures for printing of solder bumps onto the receptor pads of a substrate, comprising: 
 a motorized stage assembly including a carriage having a side clamping mechanism for retaining said screen and said substrate and for moving said screen relative to said substrate;    an x-ray generator for beaming x-rays through said screen and said substrate; a steering element for directing x-rays beamed by said x-ray generator at said screen and said substrate;    a detector for collecting x-rays passing through said screen and said substrate;    a x-ray sensitive camera interconnected to said detector for generating a real-time image of said screen and said substrate based on x-rays passing through said screen and said substrate; and    a display for displaying said images of said screen and said substrate in real-time, wherein said images are displayed at sufficient magnification to enable receptor pads spaced apart by a distance of no more than 5 microns to be distinguishable from apertures of a diameter of no greater than 125 microns formed in said screen.