Laurent Vivet

A design of a new miniature device for solder joints’ mechanical properties evaluation

This paper makes a focus on the design of a micro-testing machine used for evaluating the mechanical properties of solder alloys. The different parts of the testing device have been developed and assembled in a manner that will facilitate the study of miniature solder joints as used in electronic packaging. A specific procedure for fabricating miniature lap-shear joint specimens is proposed in this work. The tests carried out with the newly developed machine serve to determine the material behavior of solder joints under different controlled loading and temperature conditions. Two new solder alloys, namely SACBiNi and Innolot, are characterized in the study, showing the influence of strain rate and temperature parameters on their respective mechanical responses. In addition, the as-cast and fracture surfaces of the solder joints are observed with a scanning electron microscope to reveal the degradation mechanisms. The SACBiNi solder alloy, which contains less Ni and Sb elements, is found to have smaller shear strength than the Innolot alloy, while its elongation to rupture is significantly improved at the same strain rate level and testing temperature. The highest shear strength is 58.9 MPa and 61.1 MPa under the shear strain rate of 2.0 × 10−2 s−1 and room temperature for the SACBiNi and Innolot solder joints, respectively. In contrast, the lowest shear strength values, 26.6 MPa and 29.5 MPa for SACBiNi and Innolot, respectively, were recorded for the strain rate value of 2.0 × 10−4 s−1 and at temperature of 125℃.

Microstructural effects of isothermal aging on a doped SAC solder alloy

Abstract An Sn–Ag–Cu based solder alloy, including Ni, Bi and Sb additives, is investigated in this study under isothermal aging conditions. Shear creep tests are conducted on different aged solder joints with copper substrate, giving the creep resistance evolution with aging time. Microscopy analyses reveal the limited growth of the Cu-rich intermetallic layer due to the Ni content and allow for determination of the time-dependent growth of the Sn-rich intermetallic layer. The aged specimens also exhibit a partial dynamically recrystallized microstructure after creep deformation and a brittle-to-ductile fracture transition is found with occurrence of intergranular cracking in the joint.