METHOD OF PACKAGING AN ELECTRICAL DEVICE

An electrical device having a pair of projecting leads, such as a capacitor, is packaged in an aluminum container by first chemically etching the inner and outer surfaces of the container and then chemically oxidizing the surfaces with an ammonium hydroxide solution to form a film layer of various aluminum compounds thereon. The container then is heat treated to break down and convert a substantial portion of the formed aluminum compounds to aluminum oxide (A12O3), and to further oxidize the surfaces of the container, with the ammonia being driven off in the form of a gas so as to leave no contaminating residue, thus producing a dielectric film layer comprised primarily of aluminum oxide (A12O3) and having a substantially increased d.c. voltage breakdown strength in comparison to the d.c. voltage breakdown strength of the initially formed layer. The electrical device then is placed in the container with its leads projecting therefrom, and a dielectric potting material is introduced into the container to form a substantially fluid-impervious bond with the inner aluminum oxide surfaces. In the alternative, the container may be subjected to additional oxidizing by an ammonium hydroxide solution and heat-dried, to further increase the d.c. voltage breakdown strength of the dielectric film layer, prior to encapsulating the electrical device in the container.