Issue 46

N. Hiyoshi et alii, Frattura ed Integrità Strutturale, 46 (2018) 25-33; DOI: 10.3221/IGF-ESIS.46.03 32 for SnAgCu+Bi, 3 0.73 1.75 10 da J dN      (5) for SnAgCu+BiNiGe, 3 0.72 3.29 10 da J dN      (6) Slope of the approximation line equations are almost same although there are data grouping due to Bi containing. This result indicates that J-integral range parameter evaluates the crack propagation rate of low-Ag solders independent of a small quantity of additive elements. Solid line colored in orange in Fig. 9 is lined based on all the low-Ag solders experimental data. Approximation line correlates almost all the experimental data within a factor of 2 scatter band. Crack propagation rate of the steady crack propagation stage is evaluated in the narrow band with J-integral range parameter and is expressed as following equation, 3 0.82 1.09 10 da J dN      (7) 10 -2 10 -1 10 0 10 1 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1  J, N/mm da/dN , mm/cycle SAC107 Solders, 313K SnAgCu SnAgCu+NiGe SnAgCu+Bi SnAgCu+BiNiGe  =0.3%  =0.4% 0.82 Figure 9 : Relationship between crack propagation rate and  J. C ONCLUSIONS ffect of additive elements on the crack initiation and propagation behaviour of Sn-low-Ag-Cu solders were discussed in this study. (1) Crack initiation cycle of solders containing Bi were earlier than that of Bi-free solders. Bi element hastened the crack initiation from a stress concentration part. (2) Crack propagation rate of solders containing Bi were faster than that of Bi-free solders. Bi element also hastened the crack propagation rate during cycle fatigue process. (3) Fatigue life ratio parameter correlates with the crack length within a factor of 2 scatter independent of the additive elements. (4) J-integral range parameter evaluates the crack propagation rate with grouping the solders containing Bi and Bi-free solders. Slope of the approximation line equation in the J-integral range evaluation are almost same independent of the additive elements. E