An implantable pulse generator configured for delivering one or more electrical pulses to a target region within a body of a patient using an implantable neurostimulation lead, the implantable pulse generator comprising a hermetically sealed housing comprising a ceramic portion defining an inner volume configured to receive a charging coil assembly comprising a charging coil wrapped around an optional ferrite core material; an intermediate metal ring; and a case, wherein the intermediate metal ring comprises a first side joined to the ceramic portion by either a braze material or a diffusion bond, wherein the braze material or the diffusion bond is substantially free of nickel, and wherein the intermediate metal ring comprises a second side joined to the case portion.

Disclosed is a metal particle that includes a basal phase that contains Sn, an SnCu alloy and Sb; and an intermetallic compound crystal that contains Sn, Cu, Ni, Ge, Si and Ti, included in the basal phase, the metal particle has a chemical composition given by 0.7 to 15% by mass of Cu, 0.1 to 5% by mass of Ni, 0.1 to 14% by mass of Sb, 0.001 to 0.1% by mass of Ge, 0.001 to 0.1% by mass of Si, 0.001 to 0.1% by mass of Ti, and the balance of Sn; the basal phase has a chemical composition given by 85 to 99.9% by mass of Sn, 5% by mass or less of Cu, and 0.1 to 14% by mass of Sb; and, at least parts of the basal phase and the intermetallic compound crystal form an endotaxial joint.