Copper (Cu) pillar bump is a next generation flip chip interconnect which offers advantages in many designs while meeting current and future ROHS requirements. It is an excellent interconnect choice for applications such as Transceivers, Embedded Processors, Application Processors, Power Management, Baseband, ASICs, and SOCs where some combination of fine pitch, ROHS / Green compliance, low cost and electromigration performance are required.

 
Copper Pillar Benefits

• Fine pitch capable down to 50 μm in-line and 40 μm / 80 μm staggered
• Cost reduction achievable in many designs by reducing substrate layer counts
• Superior electromigration performance for high current carrying capacity applications
• Electrical test at wafer level prior to copper pillar bump
• Compatible with bond pad opening / pitch and pad metallization of die designed for wire bond which enables quick time-to-market for conversion to flip chip
• Lower cost fine pitch flip chip (FPFC) interconnect versus Au stud bump for high bump density designs
• Lead free bump cap on copper pillar for green solutions
• Available with and without re-passivation
• Qualified for advanced silicon node Low-k devices
• Small fillet requirement for underfill enables more aggressive die-to-package design rule / smaller package footprint
• Extreme Fine Pitch on Silicon Package down to 40 μm for Thru Silicon Via (TSV) and Chip-On-Chip (CoC)
• Large installed capacity for turnkey fine pitch flip chip copper pillar bump, assembly and test

Copper Pillar Bump Design Rules

FEATURE DIMENSION Cu Pillar Diameter (D) 20 -50 μm Total Height (TH) 30 - 45 μm

Pad Design Guidelines

General Design Rules 60 Pitch 50 Pitch 45 / 90 Pitch 40 / 80 Pitch 30 / 60 Pitch (A) Row to Row Pitch N/A N/A 90 80 60 (B) Bond Pad Width 30 25 22 20 TBD (C) Trace Pitch 60 50 45 40 30

Cross Sections

Electromigration Reliability Comparison of Cu Pillar with SnAg Bump

The above plot shows improvement in life for Copper Cu pillar over SnAg bump for the same current / temperature condition and similar bump / UBM geometry. No failure was observed in Cu Pillar Bump even after 8000 hours of testing at the same condition.

SQB Results