Injection molded solder ball method

Abstract

Methods for making solder balls, which can be used to bump semiconductor wafers are disclosed. Methods for bumping semiconductor wafers with the solder balls are also disclosed. The solder balls can be made using an injection molded soldering (IMS) process.

1 . A method for making a solder ball comprising:
 providing a mold comprising at least one cavity;   filling said at least one cavity with a molten solder;   cooling the molten solder; and   reflowing the solder to form at least one solder ball.   
     
     
         2 . The method of  claim 1 , wherein the molten solder comprises at least one material selected from the group consisting of Sn, Pb, SnPb, SnCu, SnAg, SnBi, SnAgCu, and SnAgCuBi. 
     
     
         3 . The method of  claim 1 , wherein the mold comprises at least one material selected from the group consisting of glass, silicon, metal, graphite, and polyimide. 
     
     
         4 . The method of  claim 1 , wherein the shape of the cavities are selected from hemispherical and pyramidal. 
     
     
         5 . The method of  claim 1 , wherein the diameter of the cavity ranges from about 25 microns to about 500 microns. 
     
     
         6 . The method of  claim 1 , wherein the diameter of the solder ball ranges from about 25 microns to about 500 microns. 
     
     
         7 . The method of  claim 1 , further comprising the steps of:
 cooling the at least one solder ball; and   removing the at least one solder ball from the at least one cavity.   
     
     
         8 . A method for forming a solder bump on a semiconductor wafer comprising:
 providing a mold comprising at least one cavity;   filling said at least one cavity with a molten solder;   cooling the molten solder;   reflowing the solder to form at least one solder ball;   aligning the at least one cavity with at least one receiving pad;   heating to cause the at least one solder ball to flow from the at least one cavity to the at least one receiving pad in order to form at least one solder bump; and   removing the mold.   
     
     
         9 . The method of  claim 8 , wherein the molten solder comprises at least one material selected from the group consisting of Sn, Pb, SnPb, SnCu, SnAg, SnBi, SnAgCu, and SnAgCuBi. 
     
     
         10 . The method of  claim 8 , wherein the mold comprises at least one material selected from the group consisting of the group consisting of glass, silicon, metal, graphite, and polyimide. 
     
     
         11 . The method of  claim 8 , wherein the shape of the cavities are selected from hemispherical and pyramidal. 
     
     
         12 . The method of  claim 8 , wherein the diameter of the cavity ranges from about 25 microns to about 500 microns. 
     
     
         13 . The method of  claim 8 , wherein the diameter of the solder ball ranges from about 25 microns to about 500 microns. 
     
     
         14 . The method of  claim 8 , wherein the semiconductor wafer comprises <100> silicon. 
     
     
         15 . The method of  claim 8 , wherein the at least one receiving pad comprises at least one material selected from the group consisting of Cr, Cu, CrCu, Ti, TiW, N, and Au. 
     
     
         16 . The method of  claim 8 , wherein the step of heating to cause the at least one solder ball to flow from the at least one cavity to the at least one receiving pad in order to form at least one solder bump is conducted in an oxide reducing atmosphere. 
     
     
         17 . The method of  claim 15 , wherein the oxide reducing atmosphere comprises formic acid. 
     
     
         18 . A solder ball made by a method comprising:
 providing a mold comprising at least one cavity;   filling said at least one cavity with a molten solder;   cooling the molten solder; and   reflowing the solder to form at least one solder ball.   
     
     
         19 . The solder ball of  claim 18 , wherein the solder ball comprises at least one material selected from the group consisting of Sn, Pb, SnPb, SnCu, SnAg, SnBi, SnAgCu, and SnAgCuBi. 
     
     
         20 . A semiconductor wafer comprising a solder bump made by a method comprising:
 providing a mold comprising at least one cavity;   filling said at least one cavity with a molten solder;   cooling the molten solder;   reflowing the solder to form at least one solder ball;   aligning the at least one cavity with at least one receiving pad;   heating to cause the at least one solder ball to flow from the at least one cavity to the at least one receiving pad in order to form at least one solder bump; and   removing the mold.