Mechanical properties of SnPb and lead-free solders at high rates of strain

Abstract

The mechanical properties of 63% Sn–37% Pb and lead-free solders have been measured at high strain rates (500–3000 s−1) using a split Hopkinson pressure bar. The solders were produced by quenching in water from the melt, to give the phase structure associated with rapid cooling. Measurements were made at −40 °C, room temperature and +60 °C. The Sn–Pb solder was strongly strain rate and temperature dependent, whereas the lead-free solders showed only a weak dependence on these parameters. All of the materials behaved elasto-plastically until a plateau stress of circa 200 MPa. An unexpected, and possibly important, feature of the lead-free solders was the division of the specimens into two groups with different strengths at low temperatures.

Dynamic Mechanical Properties and Microstructural Studies of Lead‐Free Solders in Electronic Packaging

“…Figure 16 shows typical loading curves of 0.76-mm virgin solder balls at two different compression rates-a slow rate of 3.6 × 10 −5 m/sec and a high rate of 12.5 m/sec for each solder composition. Similar data on lead-free solder balls were reported by Siviour et al at 8 m/sec [35]. Since they are spheres and not cylindrical specimens with uniform crosssectional area), force-displacement curves are shown instead of stress-strain curves.…”

“…An extensive list of references pertaining to the study of the SHPB can also be found in a review by Field et al [58]. Wang et al [25] and Siviour et al [35] obtained strain rates reaching up to a maximum of 3000 sec −1 from SHPB experiments on solder material. However, numerical simulation by Ong [59] shows that certain parts of the solder balls will experience higher strain rates (close to 10,000 sec −1 ) when the solder balls are compressed at a deformation rate of approximately 5 m/sec.…”

“…The report also agrees that traditional quasi-static bending experiments are not sufficient to quantify solder joint failure under shock loading. A better understanding of the dynamic response of solder materials is crucial, but to date high-strain-rate studies using Hopkinson bars are relatively sparse [25][26][27][28][29][30][31][32][33][34][35][36][37], and only Siviour et al [30] and Williamson et al [37] have researched lead-free solders.…”

Thermomigration in lead-free solder joints

“…For isothermal samples, the grain size is uniform across the solder joint according to this relation, and accordingly there is no gradient of hardness. Lead-free solder alloy, including SAC, has been shown to follow Hall-Petch relation (Siviour et al, 2005). For SnPb solder, nanoindetation results from Ye et al (2004) show that the mechanical properties are in agreement with the Hall-Petch relation.…”

A computational damage mechanics model for thermomigration

“…Young's Modulus E = (57.7-0.056T) GPa (Hong, 1998), Poisson ratio m = 0. 33 Hong, 1998, Yield stress r y = (140.67-0.2133T) MPa (Siviour et al, 2005), Equilibrium Vacancy concentration at a stress free state is 1.107 Â 10 6 lm À3 (Ye, 2004;Balzer and Sigvaldason, 1979), vacancy relaxation time is 0.0018 s (Sarychev et al, 1999), average vacancy relaxation ratio is 0.2 (Sellers et al, 2007;Bassman, 1999). The thermal properties are listed in Table 1.…”