Modelling evaluation of Garofalo-Arrhenius creep relation for lead-free solder joints in surface mount electronic component assemblies

Abstract

The use of different sets of values of creep parameter in Garofalo-Arrhenius constitutive creep relation has generated distinct magnitude of creep strain (ɛacc) and strain energy density (ωacc) for the same set of solder joints in electronic assemblies. This study evaluates the effect of the use of four set of values on predicted magnitude of damage (ɛacc, ωacc) and number of cycle to failure ( and ) of two different solder joint geometries. The four set of values, proposed by Lau (2003), Pang et al. (2004), Schubert et al. (2003) and Zhang et al. (2003), are used to generate four hyperbolic sine creep relations. The relations are inputted in Ansys FEM software used to simulate the damage on Sn[3.0–4.0%]Ag[0.5–1.0%]Cu solder joints in flip chip model FC48 D6.3C457DC and resistor model R102. The components are assembled on printed circuit boards; and the relations are characterised by comparing the magnitude of each model simulation output with a reference least value. The assemblies are subjected to accelerated high-temperature cycles utilising IEC standard 60749–25 in parts. It was found that each model produces distinctive magnitude and history of stress, strain, hysteresis loop, ɛacc, ωacc, and with the values of stress and hysteresis loop histories generated using Pang et al. and Schubert et al. models being very close. Characterisation results show that the use of ωacc as input parameter in fatigue life model proposed by Syed 2004 demonstrates higher probability of predicting accurately the damage in resistor solder joints while the use of ɛacc demonstrates higher probability for BGA flip chip solder joints. Based on these results, the authors propose a paradigm for selecting suitable constitutive model(s) for accurate ɛacc, ωacc and Nf prediction whilst suggesting the development of new solder constitutive relations.