Thermal cycling reliability of Cu/SnAg double-bump flip chip assemblies for 100 mu m pitch applications

Cited 6 time in webofscience Cited 12 time in scopus
  • Hit : 326
  • Download : 1055
A thick Cu column based double-bump flip chip structure is one of the promising alternatives for fine pitch flip chip applications. In this study, the thermal cycling (T/C) reliability of Cu/SnAg double-bump flip chip assemblies was investigated, and the failure mechanism was analyzed through the correlation of T/C test and the finite element analysis (FEA) results. After 1000 thermal cycles, T/C failures occurred at some Cu/SnAg bumps located at the edge and corner of chips. Scanning acoustic microscope analysis and scanning electron microscope observations indicated that the failure site was the Cu column/Si chip interface. It was identified by a FEA where the maximum stress concentration was located during T/C. During T/C, the Al pad between the Si chip and a Cu column bump was displaced due to thermomechanical stress. Based on the low cycle fatigue model, the accumulation of equivalent plastic strain resulted in thermal fatigue deformation of the Cu column bumps and ultimately reduced the thermal cycling lifetime. The maximum equivalent plastic strains of some bumps at the chip edge increased with an increased number of thermal cycles. However, equivalent plastic strains of the inner bumps did not increase regardless of the number of thermal cycles. In addition, the z-directional normal plastic strain epsilon(22) was determined to be compressive and was a dominant component causing the plastic deformation of Cu/SnAg double bumps. As the number of thermal cycles increased, normal plastic strains in the perpendicular direction to the Si chip and shear strains were accumulated on the Cu column bumps at the chip edge at low temperature region. Thus it was found that the Al pad at the Si chip/Cu column interface underwent thermal fatigue deformation by compressive normal strain and the contact loss by displacement failure of the Al pad, the main T/C failure mode of the Cu/SnAg flip chip assembly, then occurred at the Si chip/Cu column interface shear strain deformation during T/C. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3042236]
Publisher
AMER INST PHYSICS
Issue Date
2009-01
Language
English
Article Type
Article
Keywords

SOLDER JOINTS; MECHANISM; PACKAGE

Citation

JOURNAL OF APPLIED PHYSICS, v.105, no.1

ISSN
0021-8979
DOI
10.1063/1.3042236
URI
http://hdl.handle.net/10203/23080
Appears in Collection
ME-Journal Papers(저널논문)MS-Journal Papers(저널논문)
Files in This Item
000262534100055.pdf(1.11 MB)Download
This item is cited by other documents in WoS
⊙ Detail Information in WoSⓡ Click to see webofscience_button
⊙ Cited 6 items in WoS Click to see citing articles in records_button

qr_code

  • mendeley

    citeulike


rss_1.0 rss_2.0 atom_1.0