Hybrid low metal loading flux

Abstract

Flux formulations and solder attachment during the fabrication of electronic device assemblies are described. One flux formation includes a flux component and a metal particle component, the metal particle component being present in an amount of from 5 to 35 volume percent of the flux formulation. In one feature of certain embodiments, the metal particle component includes solder particles. Other embodiments are described and claimed.

1 .- 17 . (canceled) 
     
     
         18 . A method for coupling solder balls to a substrate, comprising:
 providing a substrate including a plurality of bonding pads;   positioning a flux formulation on the bonding pads, the flux formulation comprising a flux component and a metal particle component, the metal particle component being present in an amount of from 5 to 35 weight percent of the flux formulation;   positioning solder balls on the flux formulation; and   applying heat and bonding the solder balls to the bonding pads.   
     
     
         19 . The method of  claim 18 , wherein the flux component comprises an acid and a solvent. 
     
     
         20 . The method of  claim 19 , wherein the metal particle component includes solder particles and pure metal particles. 
     
     
         21 . The method of  claim 20 , wherein the pure metal particles are selected from the group consisting of noble metals and rare earth metals. 
     
     
         22 . The method of  claim 20 , wherein a plurality of the pure metal particles have a particle size in the range of 1 to 100 nm. 
     
     
         23 . The method of  claim 19 , wherein the metal particle component comprises solder particles having a particle size in the range of up to 15 μm. 
     
     
         24 . The method of  claim 18 , wherein the metal particle component comprises solder particles. 
     
     
         25 . The method of  claim 24 , wherein the solder particles comprise at least one metal and the solder particles have a melting point of less than 250° C. 
     
     
         26 . The method of  claim 19 , wherein the metal particle component comprises solder particles having a melting point less than the solder balls. 
     
     
         27 . An apparatus comprising:
 a bonding pad;   a flux formulation on the bonding pad, the flux formulation comprising a flux component and metal particle component, the metal particle component being present in an amount of from 5 to 35 weight percent of the flux formulation; and   a solder ball on the flux formulation;   wherein the metal particle component comprises solder particles, and wherein the solder particles have a melting point that is less than that of the solder ball.   
     
     
         28 . The apparatus of  claim 27 , wherein the metal particle component comprises solder particles and non-solder particles. 
     
     
         29 . The apparatus of  claim 28 , wherein the non-solder particles comprise pure metal particles having a particle size in the range of 1 to 100 nm. 
     
     
         30 . The apparatus of  claim 28 , wherein the non-solder particles comprise Ge. 
     
     
         31 . The apparatus of  claim 28 , wherein the non-solder particles comprise rare earth metals. 
     
     
         32 . The apparatus of  claim 28 , wherein the non-solder particles comprise noble metals. 
     
     
         33 . The apparatus of  claim 27 , wherein the metal particle component is present in an amount of from 10 to 30 weight percent of the flux formulation. 
     
     
         34 . A method for coupling a solder ball to a substrate, comprising:
 providing a substrate including a bonding pad;   positioning a flux formulation on the bonding pad, the flux formulation comprising a flux component and a metal particle component, the metal particle component comprising solder particles; and   positioning a solder ball on the flux formulation, the solder ball having a higher melting point than the solder particles.   
     
     
         35 . The method of  claim 34 , further comprising a first operation comprising melting the solder particles on the bonding pad and coalescing the solder particles on the bonding pad while the solder ball remains unmelted, and, after the first operation, a second operation comprising reflowing the solder ball. 
     
     
         36 . The method of  claim 34 , wherein the metal particle component comprises solder particles and non-solder particles. 
     
     
         37 . The method of  claim 34 , wherein the flux formulation includes 5 to 35 weight percent metal particles.