Abstract 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.
The method of packaging an electrical device as recited in claim 1, which further comprises: exposing the outer surfaces of the aluminum container to an etchant solution to clean and roughen the surfaces and remove existing parasitic contaminants therefrom; and exposing the outer surfaces of the aluminum container to an ammonium hydroxide solution to neutralize the etchant solution and to form an initial film layer of aluminum compounds on the outer surfaces, with a substantial portion of the aluminum compounds in the initial film layer being converted to aluminum oxide and additional aluminum oxide being formed on the outer surfaces upon the subsequent heating of the container.
Claim 2
Dependent Claim
30 words
The method of packaging an electrical device as recited in claim 1, in which: the aluminum container is heated to a temperature in a range on the order of 500*-800*F.
Claim 3
Dependent Claim
27 words
The method of packaging an electrical device as recited in claim 1, in which: the aluminum container is heated to a temperature on the order of 700*F.
Claim 4
Dependent Claim
77 words
The method of packaging an electrical device as recited in claim 1, in which: at least the inner surfaces of the aluminum container are exposed to an ammonium hydroxide solution which contains water in a range on the order of two to four times that of the ammonium hydroxide, at a temperature in a range on the order of 160*-200*F., and for a time period in a range on the order of 15 minutes to 2 hours.
Claim 5
Dependent Claim
61 words
The method of packaging an electrical device as recited in claim 1, in which: at least the inner surfaces of the aluminum container are again exposed to an ammonium hydroxide solution and then heat-dried prior to encapsulating the electrical device therein, to further oxidize the inner surfaces and increase the dielectric breakdown strength of the oxide film layer on the surfaces.
Claim 6
Dependent Claim
68 words
The method of packaging an electrical device as recited in claim 6, in which: at least the inner surfaces of the aluminum container are again exposed to an ammonium hydroxide solution which contains water in a range on the order of two to three times that of the ammonium hydroxide, at a temperature on the order of 180*F., for a time period not substantially less than 45 minutes.