Microstructural Evolution of Cu/Solder/Cu Pillar-Type Structures with Different Diffusion Barriers

Hsi-Kuei Cheng, Yu-Jie Lin, Chih Ming Chen, Kuo-Chio Liu, Ying-Lang Wang, Tzeng-Feng Liu

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Microstructural evolution of the Cu/solder/Cu pillar-type bonding structures with a reduced solder volume subjected to thermal aging at 423 K to 473 K(150 A degrees C to 200 A degrees C) was investigated. In a bonding structure employing a Ni single layer as the diffusion barrier, solder was consumed with formation of the Ni3Sn4 phase at the bonding interfaces due to an usual Sn/Ni interfacial reaction. However, an unusual Sn/Cu reaction occurred with formation of the Cu6Sn5 (and Cu3Sn) phase on the periphery of the Cu pillar due to out-diffusion of Sn toward the pillar periphery. Consumption of solder was accelerated by the above two reactions which led to the formation of a continuous gap in the bonding structure. Employment of a thicker Ni layer plus a Cu cap layer as the diffusion barrier in the bonding structure effectively blocked out-diffusion of Sn toward the periphery of the Cu pillar and therefore retarded the gap formation. The retardation effect was attributed to an increment of diffusion distance on the pillar periphery due to an effective diffusion barrier composed by Ni and thicker Cu-Sn (Cu6Sn5 + Cu3Sn) phase layers. Detailed phase identification and microstructural evolution in the bonding structures were also investigated using scanning electron microscopy and transmission electron microscopy.
Original languageEnglish
Pages (from-to)3971-3980
Number of pages10
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume47A
Issue number8
DOIs
StatePublished - Aug 2016

Keywords

  • INTERMETALLIC COMPOUND FORMATION; LEAD-FREE SOLDER; INTERFACIAL REACTIONS; SN; CU; JOINTS; ELECTROMIGRATION; METALLIZATION; RELIABILITY; SYSTEMS

Fingerprint Dive into the research topics of 'Microstructural Evolution of Cu/Solder/Cu Pillar-Type Structures with Different Diffusion Barriers'. Together they form a unique fingerprint.

  • Cite this