Solder-bumping structures produced by a solder bumping method

Abstract

A method for solder bumping provides a substrate and forms a film on the substrate. The film has openings therethrough. A stencil is aligned on the film. The stencil has openings therethrough over the openings through the film. Solder paste is printed onto the substrate and into the openings through the stencil and the openings through the film. The solder paste is reflowed to form solder balls therefrom. The stencil and the film are then removed.

1 . A solder-bumping structure, comprising:
 a substrate;   a film on the substrate, the film having openings therethrough;   a stencil on the film, the stencil having openings therethrough over the openings through the film; and   solder paste printed onto the substrate and into the openings through the stencil and the openings through the film.   
   
   
       2 . The solder-bumping structure of  claim 1  wherein the film on the substrate further comprises a photoresist layer. 
   
   
       3 . The solder-bumping structure of  claim 1  further comprising bond pads on the substrate located beneath the openings through the film. 
   
   
       4 . The solder-bumping structure of  claim 1  wherein the film has a thickness of about 75 μm, and the stencil has a thickness of about 150 μm. 
   
   
       5 . The solder-bumping structure of  claim 1  wherein the openings through the film have an equivalent diameter of about 350 μm, and the openings through the stencil have an equivalent diameter of about 400 μm. 
   
   
       6 . A solder-bumping structure, comprising:
 a flip chip having under bump metallurgy layers exposed thereon;   a laminated dry film on the flip chip having openings therethrough over respective under bump metallurgy layers, to provide access to the under bump metallurgy layers therebeneath;   an electroformed metal stencil on the laminated dry film, the metal stencil having openings therethrough substantially centered over the openings through the laminated dry film to provide access to the under bump metallurgy layers therebeneath; and   solder paste screen-printed onto the flip chip and the under bump metallurgy layers and filling the openings through the metal stencil and the openings through the laminated dry film.   
   
   
       7 . The solder-bumping structure of  claim 6  wherein the laminated dry film on the flip chip further comprises a photoresist layer. 
   
   
       8 . The solder-bumping structure of  claim 6  further comprising bond pads on the flip chip located beneath the under bump metallurgy layers. 
   
   
       9 . The solder-bumping structure of  claim 6  wherein the laminated dry film has a thickness of about 75 μm, and the metal stencil has a thickness of about 150 μm. 
   
   
       10 . The solder-bumping structure of  claim 6  wherein the openings through the laminated dry film have an equivalent diameter of about 350 μm, and the openings through the metal stencil have an equivalent diameter of about 400 μm.