US2810873A - Transistors - Google Patents

Description

Oct; 22,1957 4 R. D. KNOTT 2,810,873

TRANSISTORS Filed Aug. 10, 1956 '0 I 7 lNvEN-roR m? .DFIVID T agumgdl aa gw United States Patent TRANSISTORS Ralph David Knott, North Greenford, England, assignor to The General Electric Company Limited, London, 7

This invention relates to transistors.

It is desirable that the heat generated in a transistor during operation should be efiiciently dissipated, since the characteristics of a transistor deteriorate at elevated temperatures and this factor normally imposes a limit on the power handling capacity of the transistor.

It is an object of the present invention to provide a tran sistor designed in accordance with this requirement, without involving undue structural complexity.

According to the invention, there is provided a transistor comprising a semiconductor body having in contact therewith emitter, collector and base electrodes, said body being housed in an envelope of which at least the major part is metal, and the base electrode being constituted by a relatively massive metallic member to which the semiconductor body is intimately connected over an appreciable area and part of which bears resiliently over an appreciable area against the internal surface of a metallic part of the envelope.

One arrangement in accordance with the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure l is a sectional view of a germanium junction transistor, the section being along the line II in Figure 2; and

Figure 2 is a section on the line ll-il in Figure 1.

Referring to the drawings, the transistor includes a square plate 1 of N-type germanium which is provided with emitter and collector electrodes 2 and 3 respectively, the electrodes 2 and 3 being centrally disposed on opposite main faces of the plate 1. The electrodes 2 and 3 are formed in known manner by fusing small quantities of indium to the appropriate faces of the plate 1 and are respectively provided with leads in the form of line wires 4 and 5 whose ends are respectively embedded in the indium beads thus produced. The main face of the germanium plate 1 on which the emitter electrode 2 is disposed is soldered to a base electrode 6 formed from sheet metal, the base electrode 6 being in the general form of a channel member of U-shaped cross-section having pressed into its base a square well 7 extending into the interior of the U. This well 7 serves to locate the germanium plate 1, which is soldered to the base electrode 6 at the bottom of the well 7, a centrally disposed circular hole 8 having a diameter somewhat less than the length of a side of the germanium plate 1 being provided in the base electrode 6 to accommodate the emitter electrode 2.

The unit described above is mounted on a support con- Patented 2.2, 1957 sisting of a copper skirt 9 in which is sealed a glass bead 10 through which are sealed three wires 11, 12 and 13. The wires 11, 12 and 13 are respectively welded to the emitter and collector lead wires 4 and 5 and a tag 14 formed on the base electrode 6. The main part of the envelope of the transistor is constituted by a circular cylindrical copper cap 15 into which the mounted unit is inserted with the skirt 9 disposed in the open end of the cap 15 and with the longitudinal axis of the base electrode 6 extending parallel to the axis of the cap 15. The base electrode 6 is initially made of such a size that when it is inserted into the cap 15 the arms of the base electrodes 6 are pushed inwards, so that they bear resiliently on the internal surface of the cap 15; the corners of the base electrode 6 at the end which is inserted first are suitably rounded to facilitate insertion.

The envelope is hermetically sealed by cold pressure welding together flanges 16 and 17 respectively formed on the outer ends of the skirt 9 and the cap 15, the welding being carried out in an atmosphere of dry nitrogen so as to provide a permanent inert gas filling for the envelope. Finally, the space within the skirt 9 is filled with an electrically insulating synthetic resin 18.

It will be appreciated that in the arrangement described above the form of the base electrode 6 is such that there is a good thermal connection between the germanium plate 1 and the copper cap 15, this materially assisting in the eificient dissipation of heat generated during operation of the transistor; it will further be appreciated that this result is achieved without requiring any extra joints to be made between parts of the transistor over and above the case where no such thermal connection is provided.

In an alternative arrangement to that described above the base electrode may be provided with one or more tongues projecting transversely to its longitudinal axis and arranged to bear resiliently on the closed end of the cap when the base electrode is inserted into the cap.

I claim:

1. A transistor comprising a semiconductor body having in contact therewith emitter, collector and base electrodes, said body being housed in an envelope of which at least the major part is metal, and the base electrode being constituted by a relatively massive metallic member to which the semiconductor body is intimately connected over an appreciable area and part of which bears resiliently over an appreciable area against the internal surface of a metallic part of the envelope.

2. A transistor according to claim 1, in which the main part of the envelope is constituted by a metal cap in the open end of which is sealed a support on which the base electrode is mounted, the base electrode being in the general form of a channel member of U-shaped cross-section of such a size that when the base electrode is inserted into the cap the arms of the base electrode are pushed inwards so that they bear resiliently on the internal surface of the cap.

References Cited in the file of this patent UNITED STATES PATENTS 2,615,965 Amico Oct. 28, 1952 2,661,448 Rodgers Dec. 1, 1953 2,673,311 Amico Mar. 23, 1954

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