Apparatus for improving stencil/screen print quality

Abstract

A method and apparatus for improved stencil/screen print quality is disclosed. The stencil or screen assists in application of a printable material onto a substrate, such as an adhesive to a semiconductor die of a semiconductor wafer during a lead-on-chip (LOC) packaging process. In one embodiment, the stencil includes a coating applied to at least one surface of a pattern of the stencil or screen to retard running of the printable material onto the surface. In another embodiment, the stencil or screen includes a second coating applied to at least one other surface of the pattern to promote spreading of the printable material onto the substrate.

1 - 8 . (canceled)  
   
   
       9 . A semiconductor die stencil having a top surface, a bottom surface, and one or more side surfaces, the bottom surface having a surface tension less than a surface tension of the top surface and less than a surface tension of the side surfaces.  
   
   
       10 . A semiconductor die stencil having at least a first surface and a second surface, the first surface having a surface tension less than a surface tension of the second surface to retard adhesive running from the second surface onto the first surface.  
   
   
       11 . The semiconductor die stencil of  claim 10 , wherein the first surface is a bottom surface.  
   
   
       12 . The semiconductor die stencil of  claim 10 , wherein the second surface is a top surface.  
   
   
       13 . The semiconductor die stencil of  claim 10 , wherein the second surface is a side surface.  
   
   
       14 . A semiconductor die stencil having at least a first surface and a second surface, the first surface having a surface tension greater than a surface tension of the second surface to promote adhesive running onto a semiconductor die  
   
   
       15 - 39 . (canceled)  
   
   
       40 . The semiconductor die stencil of  claim 9  wherein the top surface is a coating selected from the group consisting of any one or more of tungsten, tungsten carbide, tungsten nitride, nickel, and nickel alloy in any combination  
   
   
       41 . The semiconductor die stencil of  claim 9  wherein the bottom surface is a polymeric material.  
   
   
       42 . The semiconductor die stencil of  claim 12  wherein the top surface is a coating selected from the group consisting of any one or more of tungsten, tungsten carbide, tungsten nitride, nickel, and nickel alloy in any combination  
   
   
       43 . The semiconductor die stencil of  claim 11  wherein the bottom surface is a polymeric material.  
   
   
       44 . The semiconductor die stencil of  claim 14  wherein the second surface is a polymeric material.  
   
   
       45 . The semiconductor die stencil of  claim 14  wherein the first surface is a coating selected from the group consisting of any one or more of tungsten, tungsten carbide, tungsten nitride, nickel, and nickel alloy in any combination.  
   
   
       46 . A semiconductor die stencil to assist in application of a printable adhesive in a desired pattern onto a semiconductor die comprising: 
 a stainless steel sheet which is impervious to a printable adhesive applied thereto;    a plurality of apertures in the sheet of material defining a desired pattern for application of the printable adhesive; and    a coating applied to at least one top or one bottom surface of the sheet to retard spreading of the printable adhesive onto the at least one top or one bottom surface of the sheet without obstruction of the flow of printable adhesive through the apertures.    
   
   
       47 . The semiconductor die stencil of  claim 46 , wherein both the coating and the material have a surface tension, the surface tension of the coating being less than the surface tension of the material.  
   
   
       48 . The semiconductor die stencil of  claim 47 , wherein the surface tension of the coating is at least an order of magnitude less than the surface tension of the material.  
   
   
       49 . The semiconductor die stencil of  claim 48 , wherein the coating is a polymeric material.  
   
   
       50 . A semiconductor die stencil to assist in application of a printable adhesive material onto a substrate comprising: 
 a sheet of material which is impervious to a printable adhesive material applied thereto;    a plurality of apertures in the sheet material defining a desired pattern; and    a coating applied to at least one surface of the sheet to promote spreading of the printable adhesive material.    
   
   
       51 . The semiconductor die stencil of  claim 50 , wherein both the coating and the sheet have a surface tension, the surface tension of the coating greater than the surface tension of the sheet.  
   
   
       52 . The semiconductor die stencil of  claim 50 , wherein the coating is selected from the group consisting of tungsten, tungsten carbide, tungsten nitride, nickel, and nickel alloy.