DIRECT INJECTION MOLDED SOLDER PROCESS FOR FORMING SOLDER BUMPS ON WAFERS

摘要

Solder bumps are provided on round wafers 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 mask layer. Solder is injected over the pillars or BLM, filling the channels. Molten solder can be injected in cavities formed in round wafers without leakage using a carrier assembly that accommodates wafers that have been previously subjected to mask layer deposition and patterning. One such carrier assembly includes an elastomeric body portion having a round recess, the walls of the recess forming a tight seal with the round wafer. Other carrier assemblies employ adhesives applied around the peripheral edges of the wafers to ensure sealing between the carrier assemblies and wafers.

主权项

1. A method comprising:
obtaining a carrier comprising a recess having a circular configuration and an elastomeric body portion adjoining the recess; obtaining a round wafer structure including a wafer having a plurality of electrically conductive structures and a photoresist layer on the wafer, the photoresist layer including a plurality of channels aligned with the electrically conductive structures; placing the wafer structure in the recess such that a top surface of the photoresist layer is coplanar with a top surface of the carrier and the elastomeric body portion of the carrier engages a peripheral edge of the wafer structure, thereby forming a compliant seal between the wafer structure and the elastomeric body portion; passing a fill head containing molten, flux-free solder over the wafer structure and carrier while injecting the molten, flux-free solder into the channels such that the solder contacts the electrically conductive structures and fills the channels, and solidifying the solder in the channels, forming solder bumps on the wafer.