Copper post solder bumps on substrates

Abstract

A method comprises forming semiconductor flip chip interconnects having electrical connecting pads and electrically conductive posts terminating in distal ends operatively associated with the pads. We solder bump the distal ends by injection molding, mask the posts on the pads with a mask having a plurality of through hole reservoirs and align the reservoirs in the mask to be substantially concentric with the distal ends. Injecting liquid solder into the reservoirs and allowing it to cool provides solidified solder on the distal ends, which after mask removal produces a solder bumped substrate which we position on a wafer to leave a gap between the wafer and the substrate. The wafer has electrically conductive sites on the surface for soldering to the posts. Abutting the sites and the solder bumped posts followed by heating joins the wafer and substrate. The gap is optionally filled with a material comprising an underfill.