Acceleration models, constitutive equations, and reliability of lead-free solders and joints

Abstract

408)55.3-2358, jolu?_lau@~agilent.coiii -Agilcnt Technologies. Inc.. 4.380 Zicglcr Road Forl Collins, CO (970)288-4657. \valter_daukslicragilent.com 'Sandia National Laboratories Albuquerque. NM (505)844-3429, ph%ncc@!sandia.gov ~ Abst ractA set of accclcration niodels for lead-frec solder joints is proposed and discussed in this shidy. Useful equations for the acceleration models, life distribution. and failure m e are also provided. Furthennorc, methods for selecting the acceleration factor are discussed. In addition. non-lincar 3D creep analyscs of the 256-pin plastic ball grid array PCB (printed circuit board) assembly are presented. The solder joints are made of 95.5wt%Sn-j.9wt%Ag-O.~~~tY~u lead-free soldcr. The leadfree results will be coinparcd to those with Sn-Pb solder joints.

The compression stress-strain behavior of Sn-Ag-Cu solder

“…Experimental studies have utilized compression-testing methodologies to determine time independent (stress-strain) mechanical properties, including yield strength and static elastic modulus as well as time-dependent (creep) properties of the alloy. [3][4][5] Both time-independent and time-dependent strength data have also been compiled on several tin-based, lead-free solders, in particular, the eutectic 96.5Sn-3.5Ag alloy, using tensile test studies. 6,7 There are two scenarios by which Sn-Ag-Cu solders of different copper contents can be present in an interconnection.…”

A Novel Submodeling Scheme on Thermal Cycle Test for CMOS Image Sensor

“…where Ay = Ac is total shear train range, Ac is the effective strain range, Er 0.65/2 is the fatigue ductility coefficient, C is fatigue ductility exponent which is define as C = -0.442 -6xl 0-4Tm+ 1.74x1l 0221n(1 +) (3) where Tm (°C) is the mean cyclic solder alloy temperature and f is the cyclic frequency per day. For SnAgCu alloy, the thermal fatigue life can be expressed as accumulated equivalent strain range form Nf = 4.5£cr295 also as dissipated creep strain energy density form Nt = 345wcr102 (4) (5) where 8cr is the creep equivalent strain range and wcr is the equivalent strain energy density.…”

“…From mechanics observations, the finite element simulation is applied to predict the thermal/hygroinduced stresses in the electronic package when the structure, materials and loadings are complex [1][2][3]. The analysis type of Thermal Cycle Test (TCT) is transient because the temperature loading is function of time.…”

Shear deformation of lead free solder joints

“…Several good studies have been published on the deformation behavior and constitutive relations for various lead free solders [5,6,[9][10][11][12][13][14][15][16][17]19,20]. A particularly good comparison of steady state creep data from several different sources is given by Clech [17].…”

“…There has been some excellent work done in developing predictive fatigue models for lead free solder joints as well (see for example refs [5][6][7][8]). …”