Solder bump structure and method for forming a solder bump

Abstract

A solder bump structure includes a contact pad, an intermediate layer located over the contact pad, a solder bump located over the intermediate layer, and at least one metal projection extending upwardly from a surface of the intermediate layer and embedded within the solder bump. Any crack in the solder bump will tend to propagate horizontally through the bump material, and in this case, the metal projections act as obstacles to crack propagation. These obstacles have the effect of increasing the crack resistance, and further lengthen the propagation path of any crack as it travels through the solder bump material, thus decreasing the likelihood device failure.

1 - 29 . (canceled)  
     
     
         30 . A solder bump structure, comprising: 
 a contact pad;    an intermediate layer located over the contact pad;    a solder bump located over the intermediate layer; and    at least one metal protrusion extending upwardly from a surface of the intermediate layer and embedded within the solder bump.    
     
     
         31 . The solder bump structure of  claim 30 , comprising a plurality of metal protrusions extending upwardly from the surface of the intermediate layer and embedded within the solder bump.  
     
     
         32 . The solder bump structure of  claim 31 , wherein a cross-section of the plurality of protrusions define a mesh pattern in a plane parallel to the contact pad.  
     
     
         33 . The solder bump structure of  claim 31 , wherein the plurality of metal protrusions are dendrites grown on the surface of the intermediate layer.  
     
     
         34 . The solder bump structure as claimed in  claim 31 , wherein a material of the metal is selected from the group consisting of Ni, Cu, Pd, Pt or alloys thereof.  
     
     
         35 . The solder bump structure as claimed in  claim 31 , wherein a material of the solder bump is selected from the group consisting of Sn, Pb, Ni, Au, Ag, Cu, Bi or alloys thereof.  
     
     
         36 . The solder bump structure as claimed in  claim 31 , wherein a melting point of a material of the solder bump is less than a melting point of the metal.  
     
     
         37 . The solder bump structure as claimed in  claim 31 , wherein the contact pad is located on a semiconductor chip contained a flip chip package or a wafer level package.