Patent ID: 7833897
Filing Date: 2010-11-16
Classification: B23K

Abstract:
1. A method for forming solder bumps on an electronic substrate surface comprising the steps of: providing a solder transfer mold having a plurality of solder mold openings in an array, which mold openings are filled with solder; positioning the solder containing openings of the mold proximate the surface of an electronic substrate to which the solder is to be transferred, the array openings in the mold corresponding to an array on the electronic substrate surface; providing a seal around the mold and the electronic substrate and forming a chamber; heating the chamber to an elevated temperature preferably sufficient to liquify the solder; passing a reducing gas into the chamber contacting the mold and the electronic substrate to remove oxides from the mold solder and electronic component surfaces and removing the gas after passing through the chamber; determining the flow rate of the reducing gas into the chamber needed to provide a sufficient gas velocity to prevent any significant Sn or other solder components from depositing on the substrate surface; maintaining the determined flow rate during the transfer of the solder from the mold to the substrate; transferring the solder from the mold openings to the corresponding array on the electronic substrate surface by bringing the solder mold and electronic substrate into transfer contact or near contact; and removing the seal from the around the mold and removing the solderless mold from the electronic substrate leaving the electronic substrate with the solder from the mold openings on the surface thereof.