ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Bending fatigue behavior of eutectic Sn-3.5Ag solder bump bonded on FR4-PCB wascharacterized by experimental and finite element method (FEM). To investigate an effect of stressstate on bump failure, which had not been weighed in conventional Coffin-Manson model ofNf=K ⋅[removed info]εp-1~-2, ‘fatigue frequency variable’ and ‘bump viscoplasticity’ were included in analysisprocedure. As experimental results, with increasing fatigue cycles from 3,000 to 10,000, bondstrength decreased from 98.9% to 76.5%, and from 97.5% to 67.1% at the fatigue frequencies of2.5Hz 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 bendingfrequency led to higher normal stress development at the solder and IMC interface, but smaller plasticstrain in bump. However, bending fatigue experiment revealed discrepant results from that ofCoffin-Manson criteria. Higher bending frequency, which was predicted to give rise to smaller [removed info]εp atsolder, showed dramatic bond deterioration of solder bump on UBM (under bump metallurgy). Thiswas confirmed experimentally through SEM (scanning electron microscopy) observation as crackswere found at the solder bump and UBM interfacial IMC, Ni3Sn4, in case of the higher bendingfrequency
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/18/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.580-582.177.pdf
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