Solder Injection - Mold plates containing cavities are first heated, filled with molten solder and then cooled to solidify the solder.

Inspection - After being scanned and filled, the mold plate solidifies and is ready to be inspected. With properly configured lighting, contrast between filled and unfilled cavities is significant and inspection can be done by various automated optical techniques.  Inspection after solder fill optimizes yield for solder transfer.

Solder Transfer - After proper alignment, the mold and wafer pass through a furnace for bump transfer. Once the solder is in liquidus state and the wafer pads are sufficiently oxide free, the wetting forces of solder to pad exceed the surface tension forces that maintain the molten solder in their cavities. Upon cooling, the solder bumps are released from the mold plate as the latter is lifted from the wafer.

Dice... Sort... Pick - Finally, the wafers are diced to produce individual IC's.