Microstructure evolution during 300 degrees ºC storage of sintered Ag nanoparticles on Ag and Au substrates

S. A. Paknejad, G. Dumas, G. West, G. Lewis, S. H. Mannan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

107 Citations (Scopus)

Abstract

A silver nanoparticle based die attach material was used in a pressure free process to bond 2.5 mm square Ag plated Si die to Ag and Au plated substrates. The assemblies were stored at 300 degrees C for up to 500 h and the morphology of the sintered Ag and the shear strength were monitored as a function of time. On Ag substrate it was found that die shear strength increased and that the Ag grains grew in size and porosity decreased over time. There was also a clear difference in morphology between sintered Ag at the die edge and centre. On Au substrate, it was observed that the initially high die shear strength decreased with storage time and that voids migrated away from the Ag/Au interface and into the Ag joint. This has led to the formation of a void free layer at the interface followed by a high porosity region, which weakened the joint. The microstructure reveals a high density of grain and twin boundaries which facilitate the Ag and Au atomic diffusion responsible. The grain structure of the plated Au led to diffusion of Au into the Ag via high-angle tilt grain boundaries, and grain boundary migration further dispersed the Au into the Ag layer. 

Original languageEnglish
Pages (from-to)994-1001
Number of pages8
JournalJOURNAL OF ALLOYS AND COMPOUNDS
Volume617
Early online date13 Aug 2014
DOIs
Publication statusPublished - 25 Dec 2014

Keywords

  • Nanostructured materials
  • Sintering
  • Grain boundaries
  • Microstructure
  • SEM
  • TEM
  • DIE-ATTACH
  • METALLOORGANIC NANOPARTICLES
  • SILVER NANOPARTICLES
  • TEMPERATURE
  • ELECTRONICS
  • DIFFUSION
  • BEHAVIOR
  • JOINTS
  • PASTE
  • NANOSILVER

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