1. An electronic assembly, comprising: a carrier wafer of a first material, having a top wafer surface and a bottom wafer surface; said carrier wafer comprising a through-wafer cavity having walls that join said top wafer surface to said bottom wafer surface; and an insulator of a second material, different from the first material, having insulator top and bottom surfaces, joined by insulator side surfaces, and having a conducting via that passes through said insulator between said insulator top surface and said insulator bottom surface; wherein the insulator is held in said through-wafer cavity by direct contact of the insulator side surfaces with an attachment metal that fills said through-wafer cavity; the electronic assembly further comprising a component chip having a top surface and a bottom surface joined by chip side surfaces, said component chip being held in said through-wafer cavity by direct contact of said chip side surface with said attachment metal.