High power double-slug diode package

Abstract

Abstract This invention is an improved, high power double-slug diode package, and a novel method for making the same. A preferred embodiment of the present invention is comprised of a pair of solid cylindrical molybdenum slugs having metallically coated end faces; a semiconductor die sandwiched between adjacent end faces of the pair of slugs, the surfaces of the die contacting the end faces of the slugs being metallically coated; a glass envelope entirely encapsulating the semiconductor die and the adjacent halves of the slugs; and a conductive lead brazed to the outer end face of each of the slugs. A novel feature of the present invention lies in the chemical bond achieved between the glass and the surface of the slugs. In the preferred embodiment described hereinbelow, each of the molybdenum slugs has a layer of molybdenum oxide disposed over that portion of its circumferential surface which is not metallically coated. The glass and molybdenum oxide form a chemical bond which provides a superior seal and greater strength than heretofore attainable. The seal renders the invented package substantially impervious to moisture, water, gas and other contaminants. The strength provided by the glass to molybdenum oxide chemical bond is sufficient to preclude having to braze the die to the slug faces in order to achieve satisfactory assembly strength as has been the practice of the prior art. A preferred method for making the invented package comprises the steps of metallically coating the cylindrical slugs of molybdenum; masking and etching the slugs so as to leave the metallic coating only on the end faces and adjacent circumferential edges thereof; oxidizing the uncoated molybdenum surfaces of the slugs; loosely assembling the semiconductor die, the slugs and a glass sleeve in a jig, the slugs and die being disposed within the glass sleeve, heating the assembly in an evacuated chamber to the point where the glass becomes molten; injecting nitrogen gas into the chamber causing the glass sleeve to collapse around the slugs and die; and brazing leads to the outer end faces of the slugs. A novel feature of the invented method is the above-described sealing step where, in a single step, the slugs and die are forced together, sealed and held in their contacting space relation by the chemical bond formed between the molten glass and the molybdenum oxide. An additional novel feature of the invented method lies in the fact that the sealing step can be carried out at relatively low temperatures; i.e., temperatures significantly below those required to braze the die to the slugs as disclosed by the prior art.

Inventors

• 👤 R Dibugnara

Bibliographic Details