Solder bumps of uniform height are provided on a substrate through the use of injection molded solder. Copper pillars or ball limiting metallurgy are formed over I/O pads within the channels of a patterned layer of photoresist. Solder is injected over the pillars or BLM, filling the channels. The solder, which does not contain flux, is allowed to solidify. It forms a plurality of solder structures (bumps) of equal heights. Solder injection and solidification are preferably carried out in a nitrogen environment or a forming gas environment. Molten solder can be injected in channels formed in round wafers without spillage using a carrier assembly that accommodates such wafers and a fill head.