Abstract: Covers for semiconductor packages are made by diffusion pressure bonding a coated substrate to a preform at a temperature below the melting point of the preform alloy. An alloy preform is coated on one side with a thin layer of the preform alloy component that has a lower melting point than the preform alloy, preferably the lowest melting point. Coated substrate and coated preform are assembled and the assembly is compressed and heated below the melting point of the preform alloy but above the melting point of the preform coating to form a diffusion pressure bond between substrate and preform.