Electronic solders used in automotive under-the-hood applications experience severe thermal excursions. Under such conditions thermomechanical fatigue (TMF) is a major concern. Aging, creep/stress relaxation, and imposed temperature-time profile have been found to be major contributors for such failures. However, in the currently popular Sn-based solders, the anisotropic behavior of Sn and reversed shear also play significant roles. Our studies evaluate the role of all these parameters, and consider the role of alloying elements and reinforcements on the TMF behavior of Sn-based solders. This paper provides an overview of this effort.