Unusual Morphological Evolution of the Cu Pillar/Solder Micro-joints During High-Temperature Annealing
Abstract
The morphological evolution of Cu pillars capped with Sn-1.8 wt pct Ag solder during high-temperature annealing was investigated. Two intermetallic compounds (Cu6Sn5 + Cu3Sn) formed at the Cu/solder interface which changed the pillar's morphology. Surface diffusion enhanced the growth of Cu6Sn5 + Cu3Sn around the pillar brim and transformed the pillar top from a plane into a truncated cone. Bulk diffusion dominated after long-term annealing and the pillar top became hemispherical shaped. A mechanism was proposed to explain the unusual morphological evolution.
- Publication:
-
Metallurgical and Materials Transactions A
- Pub Date:
- May 2015
- DOI:
- 10.1007/s11661-015-2825-4
- Bibcode:
- 2015MMTA...46.1834C