Creep in microelectronic solder joints: finite element simulations versus semi-analytical methods

Abstract

The presence and change of thermal stresses in solders, which are used for mounting microelectronic packages on PC-boards, will eventually lead to material fatigue. The number of cycles to failure can be predicted from empirical relations of the Coffin-Manson type provided the increments of creep strains and/or energy densities are known, for example, from (rather extensive) FE-simulations. A special problem arises for newly developed solders for which the Coffin-Manson equations are not known yet and need to be established first from a combination of FE and costly reliability experiments. In any case the goal of the industry and research institutions is to replace experiments as much as possible by reliable predictive simulations. However, FE calculations, which are widely used to perform this task, can-as indicated-be rather time-consuming, due to the huge effort involved for component meshing, and due to the various non-linear constitutive equations required for the description of creep in solders and other package materials. In a previous paper (Müller and Hauck in Mech Adv Mater Struct, 15(6):485-489, (2008)) a simple analytical 1D-model was presented that allows computing characteristic damage quantities, such as creep strain and creep energy density, for different solder materials and different temperature profiles in a very efficient manner, provided a creep law is known. In this paper the proposed procedure is validated by comparison with results from detailed FE-simulations.

Potential interconnect technologies for high power LEDs assemblies

“…In this study, the anand model is used for SAC [4] while the hyperbolic sine functions are used for SAC+ and AuSn as shown in (1). The values for A, B, n and ΔH/R are 8000,0.05, 4 and 7600 for SAC+ and 4.62e+15, 2e-5, 2.07 and 12267 for AuSn respectively [5,6] cr eq ε -Equivalent Creep rate σ eq -Equivalent Stress For all simulations the modules are assumed to be stress free at the melting point of the solder, which is 217 °C for SAC/SAC+ and 271? °C for eutectic AuSn.…”

Thermo-mechanical challenges of reflowed lead-free solder joints in surface mount components: a review

“…Lead-based eutectic and lead-free solder joints are used in the SMCs to ensure electrical and mechanical functionalities between the packages and the PCB (Hannach et al , 2009; Qian and Liu, 1999). The high tin contents of lead-free alloys (of around 95-99.3 wt.%) have proved to be problematic in terms of void formation, large undercooling during solidification, overly rapid IMC formation and spalling of interfacial IMCs during high temperature storage (Kotadia et al , 2014).…”

“…The plastic strain of solder materials included time-dependent creep and time-independent plastic was proven as a dominant parameter that affected low-cycle fatigue. The modelling of irreversible strains of solder materials can be done by hyperbolic sine creep law (Lee et al , 2006; Hannach et al , 2009; Towashiraporn et al , 2002) or Garofalo-Arrhenius creep constitutive equation (Wang and Lai, 2005; Lau and Pan, 2001). Darveaux et al (1995) published the properties of four different alloys, including SnPb and lead-free solder.…”

“…Darveaux et al (1995) published the properties of four different alloys, including SnPb and lead-free solder. Lee et al (2000) reviewed various fatigue laws; the simplest fatigue laws were the Coffin–Manson law (Hannach et al , 2009; Peng et al , 2004), strain energy-based law (Akay et al , 2003) and the Darveaux (2000) fatigue law. From the simulation model, either the accumulated effective plastic strain per cycle or the accumulated strain energy density per cycle of each element (ΔW) was extracted to be used in a fatigue law (Darveaux, 2000).…”