Improved interconnects are produced by injection molded solder which fills mold arrays with molten solder so that columns that have much greater height to width aspect ratios greater than one are formed, rather than conventional flip chip bumps. The columns may have filler particles or reinforcing conductors therein. In the interconnect structures produced, the cost and time of a subsequent underfill step is reduced or avoided. The problem of incompatibility with optical interconnects between chips because underfills require high loading of silica fillers which scatter light, is solved, thus allowing flip chips to incorporate optical interconnects.