In situ observations on creep fatigue fracture behavior of Sn–4Ag/Cu solder joints

The creep fatigue behavior of Sn–Ag/Cu solder joints was investigated in this study. Low-cycle creep fatigue tests were conducted on an in situ tensile stage, the deformation morphologies were observed by scanning electron microscopy and the microstructure of the solder was characterized using an electron back-scattered diffraction system. The results show that the creep fatigue process can be divided into three stages: a strain hardening stage, a steady deformation stage and an accelerating fracture stage. During the initial few cycles the strain increases rapidly because the solder is soft. After strain hardening of the solder becomes saturated, the strain increases approximately linearly with increasing cycles, strain concentration occurs in the solder close to the solder/Cu6Sn5 interface and initial microcracks are generated. When the microcracks evolve into long cracks, the failure accelerates and the specimens fracture at the interface shortly thereafter. The creep fatigue strain is contributed by plastic deformation and creep of the solder. Grain subdivision occurs in the solder when the plastic strain reaches a threshold, and then grain rotation takes place in the newly formed grains to accommodate further straining. Dislocation climb is the major creep mechanism, and grain boundary sliding can also be promoted after subdivision.

[1]  H. D. Solomon,et al.  Low Cycle Fatigue of Sn96 Solder With Reference to Eutectic Solder and a High Pb Solder , 1991 .

[2]  N. Hansen,et al.  Microstructural evolution and hardening parameters , 2001 .

[3]  Abhijit Dasgupta,et al.  Micro-Mechanics of Creep-Fatigue Damage in PB-SN Solder Due to Thermal Cycling—Part II: Mechanistic Insights and Cyclic Durability Predictions From Monotonic Data , 2002 .

[4]  M. Shine,et al.  Fatigue of solder joints in surface mount devices , 1988 .

[5]  Xiaolei Wu,et al.  Microstructure and evolution of mechanically-induced ultrafine grain in surface layer of AL-alloy subjected to USSP , 2002 .

[6]  R. Mccabe,et al.  Creep of tin, Sb-solution-strengthened tin, and SbSn-precipitate-strengthened tin , 2002 .

[7]  Subra Suresh,et al.  Computational modeling of the forward and reverse problems in instrumented sharp indentation , 2001 .

[8]  Q. Zhang,et al.  Tensile and Fatigue Behaviors of Aged Cu/Sn-4Ag Solder Joints , 2009 .

[9]  Masanari Takahashi,et al.  Tensile test for estimation of thermal fatigue properties of solder alloys , 1997 .

[10]  Nikhilesh Chawla,et al.  Deformation behavior of (Cu, Ag)–Sn intermetallics by nanoindentation , 2004 .

[11]  King-Ning Tu,et al.  Rate of consumption of Cu in soldering accompanied by ripening , 1995 .

[12]  N. Chawla,et al.  Creep deformation behavior of Sn–3.5Ag solder/Cu couple at small length scales , 2004 .

[13]  Ikuo Shohji,et al.  Tensile properties of Sn–Ag based lead-free solders and strain rate sensitivity , 2004 .

[14]  Fu Guo,et al.  Evaluation of creep behavior of near-eutectic Sn–Ag solders containing small amount of alloy additions , 2003 .

[15]  Abhijit Dasgupta,et al.  Micro-Mechanics of Creep-Fatigue Damage in PB-SN Solder Due to Thermal Cycling—Part I: Formulation , 2002 .

[16]  B. Moran,et al.  Creep, stress relaxation, and plastic deformation in Sn-Ag and Sn-Zn eutectic solders , 1997 .

[17]  Y. Miyashita,et al.  Influence of frequency on low cycle fatigue behavior of Pb-free solder 96.5Sn–3.5Ag , 2003 .

[18]  Mingliang L. Huang,et al.  Creep behavior of eutectic Sn-Cu lead-free solder alloy , 2002 .

[19]  Jin-wook Jang,et al.  Correlation between mechanical tensile properties and microstructure of eutectic Sn-3.5Ag solder , 2002 .

[20]  M. Abtew,et al.  Lead-free Solders in Microelectronics , 2000 .

[21]  Yi Li,et al.  Recent advances of conductive adhesives as a lead-free alternative in electronic packaging: Materials, processing, reliability and applications , 2006 .

[22]  M. D. Mathew,et al.  Creep deformation characteristics of tin and tin-based electronic solder alloys , 2005 .

[23]  G. S. Murty,et al.  Experimental constitutive relations for the high temperature deformation of a PbSn eutectic alloy , 1981 .

[24]  Seungbae Park,et al.  Measurement of deformations in SnAgCu solder interconnects under in situ thermal loading , 2007 .

[25]  K. Ohguchi,et al.  A quantitative evaluation of time-independent and time-dependent deformations of lead-free and lead-containing solder alloys , 2006 .

[26]  Qingke Zhang,et al.  Fracture mechanism and strength-influencing factors of Cu/Sn-4Ag solder joints aged for different times , 2009 .

[27]  Cong-qian Cheng,et al.  Kinetics of intermetallic compound layers and shear strength in Bi-bearing SnAgCu/Cu soldering couples , 2009 .

[28]  Hwa-Teng Lee,et al.  Shear strength and interfacial microstructure of Sn–Ag–xNi/Cu single shear lap solder joints , 2007 .

[29]  R. S. Sidhu,et al.  Influence of reflow and thermal aging on the shear strength and fracture behavior of Sn-3.5Ag solder/Cu joints , 2005 .

[30]  Q. Liu,et al.  Effect of grain orientation on deformation structure in cold-rolled polycrystalline aluminium , 1998 .

[31]  Toshio Narita,et al.  The effect of strain rate and temperature on the tensile properties of Sn–3.5Ag solder , 2005 .

[32]  Yong Sun,et al.  In Situ Observation of Small-Scale Deformation in a Lead-Free Solder Alloy , 2009 .