Flip chip with integrated flux and underfill

Abstract

A flip chip having solder bumps and an integrated flux and underfill, as well as methods for making such a device, is described. The resulting device is well suited for a simple one-step application to a printed circuit board, thereby simplifying flip chip manufacturing processes which heretofore have required separate fluxing and underfilling steps.

What is claimed is:  
     
         1 . An integrated circuit assembly which comprises: 
 a) a substrate having a plurality of solderable contact sites on a surface thereof;    b) a plurality of solder bumps positioned on the substrate such that each of the solderable contact sites has one solder bump associated therewith, the solder bumps being affixed to the solderable contact sites; and    c) an underfill material applied to the surface of the substrate, the underfill material at least occupying a space defined between each of the solder bumps and characterized in that, upon heating to a solder reflow temperature, at least a portion of the underfill material acts as a solder flux.    
     
     
         2 . The integrated circuit assembly of    claim 1    wherein the substrate comprises a semiconductor wafer.  
     
     
         3 . The integrated circuit assembly of    claim 2    wherein the substrate comprises a semiconductor chip.  
     
     
         4 . The integrated circuit assembly of    claim 3    wherein the substrate comprises a flip chip.  
     
     
         5 . The integrated circuit assembly of    claim 1    wherein the underfill material covers substantially all of each solder bump.  
     
     
         6 . The integrated circuit assembly of    claim 1    wherein the underfill material comprises an epoxy resin and a material selected from the group consisting of carboxylic acids, anhydrides and combinations thereof.  
     
     
         7 . The integrated circuit assembly of    claim 6    wherein the underfill material comprises an epoxy resin and a material selected from the group consisting of adipic acids and cyclohexane dicarboxylic acids.  
     
     
         8 . The integrated circuit assembly of    claim 1    wherein the underfill material is reworkable.  
     
     
         9 . The integrated circuit assembly of    claim 8    wherein the underfill material comprises a thermoplastic material.  
     
     
         10 . The integrated circuit assembly of    claim 9    wherein the thermoplastic material is selected from the group consisting of phenoxy resins, acrylic resins, methacrylic resins, polycarbonate resins, polyamide resins, polybutene resins, polyester resins, polyolefin resins and mixtures thereof.  
     
     
         11 . A method for making an integrated circuit assembly which comprises: 
 a) providing a substrate having a plurality of solderable contact sites on a surface thereof;    b) positioning a plurality of solder bumps on the substrate such that each of the solderable contact sites has one solder bump associated therewith;    c) affixing each solder bump to its associated contact site; and    d) applying an underfill material to the surface of the substrate in a manner such that it at least occupies a space defined between each of the solder bumps and is characterized in that, upon heating to a solder reflow temperature, at least a portion of the underfill material acts as a solder flux.    
     
     
         12 . The method for making an integrated circuit assembly of    claim 11    wherein the substrate comprises a semiconductor wafer.  
     
     
         13 . The method for making an integrated circuit assembly of    claim 12    wherein the substrate comprises a semiconductor chip.  
     
     
         14 . The method for making an integrated circuit assembly of    claim 13    wherein the substrate comprises a flip chip.  
     
     
         15 . The method for making an integrated circuit assembly of    claim 11    wherein the underfill material covers substantially all of each solder bump.  
     
     
         16 . The method for making an integrated circuit assembly of    claim 11    wherein the underfill material comprises an epoxy resin and a material selected from the group consisting of carboxylic acids, anhydrides and combinations thereof.  
     
     
         17 . The method for making an integrated circuit assembly of    claim 16    wherein the underfill material comprises an epoxy resin and a material selected from the group consisting of adipic acids and cyclohexane dicarboxylic acids.  
     
     
         18 . The method for making an integrated circuit assembly of    claim 11    wherein the underfill material is reworkable.  
     
     
         19 . The method for making an integrated circuit assembly of    claim 18    wherein the underfill material comprises a thermoplastic material.  
     
     
         20 . The method for making an integrated circuit assembly of    claim 19    wherein the thermoplastic material is selected from the group consisting of phenoxy resins, acrylic resins, methacrylic resins, polycarbonate resins, polyamide resins, polybutene resins, polyester resins, polyolefin resins and mixtures thereof.  
     
     
         21 . A method for affixing a flip chip to a circuit board which comprises the steps of: 
 a) providing a printed circuit board having a plurality of solderable contact sites on a surface thereof;    b) providing an integrated circuit chip having a plurality of solderable contact sites on a surface thereof, each solderable contact site on the integrated circuit chip having a corresponding solderable contact site on the surface of the printed circuit board, the integrated circuit chip further characterized in that it includes: 
 1) a plurality of solder bumps positioned on the integrated circuit chip such that each of the solderable contact sites located on the surface of the integrated circuit chip has one solder bump associated therewith, the solder bumps being affixed to the solderable contact sites; and  
 2) an underfill material applied to the surface of the substrate, the underfill material at least occupying a space defined between each of the solder bumps and characterized in that, upon heating to a solder reflow temperature, at least a portion of the underfill material acts as a solder flux;  
   c) positioning the integrated circuit chip relative to the printed circuit board such that each solder bump is in contact with a solderable contact site on the printed circuit board;    d) heating the integrated circuit chip to a temperature sufficiently high to melt the solder and the underfill material; and    e) allowing the solder and underfill material to solidify.    
     
     
         22 . An integrated circuit assembly which comprises: 
 a) a substrate having a plurality of solderable contact sites on a surface thereof;    b) a plurality of solder bumps positioned on the substrate such that each of the solderable contact sites has one solder bump associated therewith, the solder bumps being affixed to the solderable contact sites; and    c) an underfill material applied to the surface of the substrate, the underfill material occupying a space defined between each of the solder bumps and characterized in that, upon heating to a solder reflow temperature, at least a portion of the underfill material acts as a solder flux.