Bending fatigue characteristic of Sn-3.5Ag solder bump on Ni-UBM

K. I. Kang, J. P. Jung, W. H. Bang, J. H. Park, K. H. Oh

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Scopus citations

Abstract

Bending fatigue behavior of eutectic Sn-3.5Ag solder bump bonded on FR4-PCB was characterized by experimental and finite element method (FEM). To investigate an effect of stress state on bump failure, which had not been weighed in conventional Coffin-Manson model of Nf= K·Δεp-1-2, 'fatigue frequency variable' and 'bump viscoplasticity' were included in analysis procedure. As experimental results, with increasing fatigue cycles from 3,000 to 10,000, bond strength decreased from 98.9% to 76.5%, and from 97.5% to 67.1% at the fatigue frequencies of 2.5Hz and 5.0Hz, respectively. Stress state could be critical components to determine fatigue life, which should be combined in Coffin-Manson criteria. FEM calculation showed that higher bending frequency led to higher normal stress development at the solder and IMC interface, but smaller plastic strain in bump. However, bending fatigue experiment revealed discrepant results from that of Coffin-Manson criteria. Higher bending frequency, which was predicted to give rise to smaller Δεp at solder, showed dramatic bond deterioration of solder bump on UBM (under bump metallurgy). This was confirmed experimentally through SEM (scanning electron microscopy) observation as cracks were found at the solder bump and UBM interfacial IMC, Ni3Sn4, in case of the higher bending frequency.

Original languageEnglish
Title of host publicationMaterials Science Forum - Advanced Welding and Micro Joining/Packaging for the 21st Century - Selected peer reviewed papers from the International Welding/Joining Conference-Korea 2007, IWJC 2007
EditorsChang Hee Lee, Jong-Bong Lee, Jong-Bong Lee, Dong-Hwan Park, Suck-Joo Na
PublisherTrans Tech Publications Ltd.
Pages177-182
Number of pages6
ISBN (Electronic)9780878493609
DOIs
StatePublished - 2008
EventInternational Welding/Joining Conference-Korea 2007, IWJC 2007 - Seoul, Korea, Republic of
Duration: 10 May 200712 May 2007

Publication series

NameMaterials Science Forum
Volume580-582
ISSN (Print)0255-5476
ISSN (Electronic)1662-9752

Conference

ConferenceInternational Welding/Joining Conference-Korea 2007, IWJC 2007
Country/TerritoryKorea, Republic of
CitySeoul
Period10/05/0712/05/07

Keywords

  • Bending fatigue
  • Coffin-Manson model
  • Microstructure
  • Sn-3.5Ag solder
  • Stress state

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