Processes and tools for forming lead-free alloy solder precursors

摘要

Precursors for lead free alloy solder bumps are formed through selective deposition of at least two conductive layers. The conductive layers may include tin, silver, copper, gold, or bismuth. The conductive layers can also include alloys of the foregoing components. The precursor of the alloy solder bumps is re-flowed to form alloyed solder bumps.