Substrate with terminal pads having respective single solder bumps formed thereon

Abstract

Methods and apparatus for forming solder bumps on terminal pads of a semiconductor substrate for an integrated circuit device employ a solder bump transfer plate and a mask to form solder deposits on the plate. One embodiment of the invention employs a metal mask having a plurality of through holes for forming solder deposits on the solder bump transfer plate by vapor phase deposition through the through holes each area of which increases in step wise from the first surface of the mask to the second surface opposite to the first surface, thereby preventing solder deposits in the through holes from being removed when the mask is separated from the plate. Another embodiment of the invention is a solder bump transfer plate having a plurality of solder deposits on the surface non-wettable to molten solder both diameter and spacing of which are both smaller than diameter and spacing of the terminal pads on the semiconductor substrate, whereby a single solder bump is accurately formed on each of the terminal pads without a fine alignment technique.

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       16 . A mask having a first surface and a second surface, opposite to the first surface, for forming solder deposits onto a surface of a substrate against which the second surface of the mask is pressed, comprising: 
 a mask sheet; and    a plurality of through holes extending through the mask sheet, a cross-sectional area of each throughole increasing in steps from the first surface of the mask to the second surface while maintaining a similar cross-sectional shape and centered about a common axis.    
   
   
       17 . The mask according to  claim 16 , wherein the mask sheet comprises: 
 plural laminated layers having circular through-holes extending therethrough, each of which through-holes consists of concentric holes having successively increasing diameters, layer by layer, for respective, successive layers from the first surface of the mask to the second surface of the mask.    
   
   
       18 . The mask according to  claim 16 , wherein the substrate is a semiconductor substrate having a plurality of metalized terminal pads.  
   
   
       19 . The mask according to  claim 16 , wherein the substrate is a substrate for a solder bump transfer plate for transferring bumps onto terminal pads on an integrated circuit device.  
   
   
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       28 . The mask according to  claim 16 , further comprising a mask-holder for pressing the second surface of the mask against the substrate.  
   
   
       29 . The mask according to  claim 16 , wherein the mask sheet is a laminated mask of nickel alloy sheets.  
   
   
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