Electronic packages with fine particle wetting and non-wetting zones

Abstract

Spreading or keep out zones may be formed in integrated circuit packages by altering the roughness of package surfaces. The surface roughness can be altered by applying or growing particles having a dimension less than 500 nanometers. Hydrophilic surfaces may be made hemi-wicking and hydrophobic surfaces may be made hemi-wicking by particles of the same general characteristics.

1 . A method comprising:
 forming a semiconductor integrated circuit package surface;   forming particles on said surface having a dimension less than 500 nanometers; and   applying a liquid to said package surface.   
   
   
       2 . The method of  claim 1  including forming said particles on said surface in two different regions such that one region is hydrophobic and the other region is hydrophilic. 
   
   
       3 . The method of  claim 2  including forming a semiconductor integrated package surface in the form of a package substrate. 
   
   
       4 . The method of  claim 3  including forming said particles of substantially similar dimensions. 
   
   
       5 . The method of  claim 4  including forming said particles by growing particles on said substrate. 
   
   
       6 . The method of  claim 1  including forming particles by depositing the particles on the surface. 
   
   
       7 . The method of  claim 4  wherein applying a liquid includes providing a die over said substrate, and injecting underfill material between said die and said substrate. 
   
   
       8 . The method of  claim 7  including defining a keep out zone on said substrate using hydrophobic particles around said die and providing a region of hydrophilic particles between said die and said substrate. 
   
   
       9 . The method of  claim 1  including growing rods on said substrate to form said particles. 
   
   
       10 . The method of  claim 9  including using glancing angle deposition techniques to grow said rods. 
   
   
       11 . The method of  claim 1  including forming said surface of an integrated circuit die and treating said particles so that said particles are hydrophobic in one area and hydrophilic in another. 
   
   
       12 . The method of  claim 11  including providing a die attach to said surface such that said hydrophobic particles reduce bleeding out of the die attach material. 
   
   
       13 . An integrated circuit package comprising:
 a package surface;   particles formed on said surface having a dimension less than 500 nanometers; and   a liquid applied over said particles.   
   
   
       14 . The package of  claim 13  wherein said particles are hydrophobic. 
   
   
       15 . The package of  claim 13  wherein said particles are hydrophilic. 
   
   
       16 . The package of  claim 13  wherein some of those particles are hydrophilic and some of said particles are hydrophobic. 
   
   
       17 . The package of  claim 13  wherein said liquid is underfill. 
   
   
       18 . The package of  claim 13  wherein said liquid is die attach. 
   
   
       19 . The package of  claim 13  wherein said surface is a die surface. 
   
   
       20 . The package of  claim 13  wherein said surface is a package substrate surface. 
   
   
       21 . The package of  claim 20  wherein hydrophilic particles are formed on said substrate, a die positioned over said substrate, said hydrophobic particles being formed on said substrate around said die, the surface of said substrate under said die having particles formed thereon that are hydrophilic and solder balls being provided between said die and said substrate. 
   
   
       22 . The package of  claim 13  wherein said surface is a die surface and a die attach is attached to said die surface, the region contacting said die attach being hydrophilic and a region around said die attach being hydrophobic. 
   
   
       23 . An integrated circuit package comprising:
 a package surface having particles on said surface having a dimension less than 500 nanometers; and   said surface having a surface energy of greater than or equal to 70 mN/m or less than or equal to 20 mN/m.   
   
   
       24 . The package of  claim 23  wherein said surface includes both hydrophilic and hydrophobic regions. 
   
   
       25 . The package of  claim 23  wherein said surface is a die surface. 
   
   
       26 . The package of  claim 23  wherein said surface is a substrate surface. 
   
   
       27 . The package of  claim 23  wherein said surface is partially covered with underfill, a die being positioned to sandwich the underfill between said die and said surface. 
   
   
       28 . The package of  claim 23  wherein said particles are upstanding rods. 
   
   
       29 . The package of  claim 28  wherein said rods are hydrofluoric acid treated. 
   
   
       30 . The package of  claim 23  including a substrate and a die stacked on said substrate, die attach being positioned between said substrate and said die, said die attach being surrounded by a region of said surface that is hydrophobic and said die contacting a hydrophilic region of said surface.