This SBIR Phase I project will develop the manufacturing capability for the production of ultra-low-background copper for use in electronic interconnects and support architecture- Copper is an attractive electronic and support material because of its favorable conductivity and mechanical properties- Fortuitously, the material can also be electroplated with high radiopurity, particularly if the electroforming is performed in shielded, buried facilities within which the cosmogenic background is minimized- The machining of the electroformed copper into wires, feedthroughs, and support hardware can potentially introduce impurities through the shop environment or through the dies used in wire-drawing and part formation- During Phase I, we will compare the purity of electroformed and drawn copper wires with colloidally-assembled copper nanoparticles, which can also be used to form conductive structures through a low-cost solution-based synthesis route- In nanoparticle form, copper forms in a crystalline lattice with very low impurity content, but its self-assembly is facilitated by organic capping ligands that can serveas impurity sources- Upon the formation of a colloidal solid, the copper particles can be fused and the organic components evaporated through vacuum annealing, the resulting radiopurity of which will be compared with the more traditional process-
