US2869056A

US2869056A - Semi-conductor device and method of making

Info

Publication number: US2869056A
Application number: US428509A
Authority: US
Inventors: Roovers Wilhelmus Antonius; Heijligers Joris Daniel
Original assignee: US Philips Corp
Current assignee: US Philips Corp; North American Philips Co Inc
Priority date: 1953-05-13
Filing date: 1954-05-10
Publication date: 1959-01-13
Anticipated expiration: 1976-01-13
Also published as: FR1114841A; BE527478A

Description

Jan. 13, 1959 f Ill Filed.l May l0, 1954 W. A. ROOVERS ETAL v SEMI-CONDUCTOR DEVICE AND METHOD OF MAKING l 'Il' 5)/ Jar/5 Dan/e/ Jay/Ageing, fx ec ulf" AGENT United States Patent ,SEMI-CONDUCTOR DEVICE AND METHOD F MAKING Application May 10, 1954, Serial No. 428,509 Claims priority, application Netherlands May 13, 1953 7 Claims. (Cl. 317-236) Eindhoven, and Otto Louis This invention relates to an electrode system comprising a semi-conductive body secured to a support sealed in a glass envelope, and, more particularly, to semiconductor devices such as crystal diodesand transistors,

In such systems, the semi-conductive body is usually constituted by a crystal and will hereinafter be referred to as such. lIt is known to seal a` metal tube in the wall of an envelope and to secure the crystal support therein by means of soft solder. This construction is comparatively large and costly. However, it has the advantage that the soldering'joint may be established at .a'low temperature at which the crystal is not adversely affected. In this case, `the support for the crystal is comparatively thick, i. e., slightly larger than the cross-sectional `area of the crystal, so that it can thus be introduced into the j tube. A-modication of this construction involves seal- 'ing of the crystal support directly in the glass envelope; hence, the `temperatures employed are considerably higher. The crystal, however, in this case,\is secured to a materially thinner support, which is also comparatively -long in order to space the crystal as far from the seal ofthe support as possible.

One object of the present invention is to provide a comparatively short support for the crystal sealed directly in the glass envelope, the temperature of the crystal during the sealing operation remaining nevertheless low.

FA further object of the inventionis a short crystal support having low heat resistance, which may be advantageous with respect to the development of heat in the crystal in the case of high current strength.

According to the invention, a support sealed directly in a glass envelope has a portion inside the envelope having at least one section which is thicker than the portion thereof sealedin the envelope. Such` a` portion,

"hereinafter'referred to 'as-the -thickened portion, mayhave `a larger diameter-than the crystal. Such a thickened portion may be located-directly-adjacent the crystal,` but` it `may beadvantageous incertain applications to sarrange 1the thickened 4portion -between the joint of thekcrystal and the supportpandA the sealof-the support in the glass. It should be noted that although reference is made above toa glassen'velope, other insulating materials having a melting point exceeding that ofsoft solder, i. e. a melting point of more than 250 C., may be utilised.

According to a further aspect of the invention, which involves a method of manufacturing suchv an electrode system, during the sealing of the support in the envelope the thickened portions of the support are clamped in metal pincers.

The invention will now be described with reference to the accompanying drawing in which:

Figs. 1, 3, 5 to 7, and 9 and l0 are longitudinal crosssectional views illustrating crystal diodes in accordance with the invention;

Figs. 2, 4 and 8 show the support with the crystal and the envelope during the sealing operation.

ICC.

Fig. 1 shows a crystal diode having an envelope 1 constituted, for example, of glass. It comprises a semiconductive crystal 2, for example, germanium or silicon. This crystal is soldered to a support 3 constituted `by a thin wire portion sealed in the envelope at 4 and by a thickened portion 5, located between the seal 4 andthe crystal 2. On the base of the crystal remote from its support 3 fis located a point electrode 6, which is secured to a support 7. The latter is sealed at S in the envelope li.

The provision ofthe thickened portion 5 has `a number of advantages compared with the known. construction in which the crystal is secured to a support which is thin throughout its length. During the fastening of the crystal 2 tothe thickened portion 5 of the support 3, which is usually carried out before the sealing operation of the support to the envelope, the thickened portion may in this case be grasped with heated pincers, so that the heat transfer to the support is improved considerably over that of a thin wire. Further, the portion `5' has a large radiating surface, so that the crystal remains cooler during the sealing operation of the support to the envelope at 4. Finally, the thickened `portion ensures a satisfactory dissipation `of any heat `developed in the crystal, which may be comparatively great during the so-called power treatment, which -is a `transient electric treatment with high current strength carried out after the diode has been completed.

The temperature of the crystal may be controlled much more carefully during the sealing operation, if the thickened portion is grasped `in metal pincers ofthe kind shown in Fig. 2. The pincers or holding member shown in that gure are constituted by a copperrod 9` having a bore at `the upperend forming a tube lwhich may have saw cuts forming a few pincers 10. Ihese pincers grip a thickened portion 11, to which 'the 'crystal is secured. The rod 9 is slightly thinner at its `upper end than the inner diameter of the envelope 1, in order to avoid? local cooling of the glass during the sealing operation. The lower end lits in the envelopeand serves for centering the crystal. While the supportisgripped by the pincers 9, the wire portion 3 thereof is sealed to theenvelope at 4.

The weight of the support section inside the envelope ofthe diodes shown inFigs. 2 .and 3, wherein the thickcned portion is designated 11, `isflower than` that of the diodes shown Vin Fig. l, so that in general the former will have greater resistance to vibrations than the latter.

The support used in the diode shown in Fig. S has a thickened portion 12 provided with cooling -vanes `11i.

During the sealing operation carried out at` 4, cool air may be blown through one of the ducts 14 of .a double tube 15 into the envelope, this airbeing exhausted through the other duct. Instead of using air, use may, of course, be made of a gas which will protect thecrystal. In the embodiment `shown in Fig. `6, the thickened portion 16 has the `'shape of acircular `disc secured to the support near the seal 4. The crystal 2 is soldered `to the end of the `thin support 3. If` the `thickened portion 16 is `graspediin pincers during `thesealing operation, the temperature ofthe crystal may be still lower thanwinV fthe construction shown in Fig. 3. The construction shown in Fig. 6 has, moreover, a greater resistance to shocks, since the end vof the wire has a lower weight.

The construction shown in Fig. 7 corresponds largely to that shown in Fig. 6; however, the support has a second thickened portion below the crystal, so that a satisfactory dissipation of the heat developed in` the crystal is obtained. A

Due to the satisfactory cooling of the crystal during the sealing operation, a construction as shown in Figs. 8, 9 and l() may also be obtained. To the support 3 is welded a round nickel plate 19, to which the crystal 2 is soldered. In' the same manner as shown in Fig. 2, the support is gripped in pincers 9 and the glass of the envelope is heated and melted down on the support. As soon as the glass bears on the support, as is shown in Fig. 8, the interior of the envelope is evacuated through a lduct 20, bored in the pincers 9; thus, the glass is urged strongly on the support in a radial direction', it is, moref over, sucked into the envelope in an axialdirection; Hence, the envelope (Fig. 9) exhibits ya groove 21 in the outer surface around the seal of the crystal support, while the envelope may also have an axial, spherical recess 22 around the entrance of the support into the bulb. This recess may be adjacent the thickened portion of the support, as is shown in Fig. 10.

The exhaust operation during the sealing provides an improvement in the joint between the glass and the support, due to the pressure by which the glass is urged against the support. Thus, the sealing temperature may be lower. The external dimensions of the envelope are, moreover, decreased, since the glass is, so to speak, drawn in. To further improve the joint between the support and the envelope, the support may be previously provided with an enamel layer. This enamel is preferably provided in the form of paste, after the crystal has been secured to the support; the support, the enamel and the envelope are then sealed together simultaneously. The enamel could be applied by melting prior to the fasten ing of the crystal to the support, but in this case the enamel could be affected duringA the crystal etching. If the enamel is applied by melting to the support after the crystal has been secured thereto, the crystal would be exposed twice to high temperatures. However, if the envelope is sealed to the paste, the crystal need be heated only.once. During the sealing operation, this paste will melt at least partly together with the envelope and the support, but at the cooler portions of the support the paste may remain unmelted, which, however, is not objectionable. For the sake of simplicity, the drawing shows only diodes. However, all the constructions shown may be used for transistors, if instead of using one point electrode 6, use is made of two or more of these electrodes, arranged each on asupport 7 sealed in the envelope.

The thickened portion of the support may be provided in various ways. A thicker rod may be welded to the support, as is shown in Fig. l; as an alternative, a nail head may be clenched on the support (Figs. 2, 3 and 7). Further, provision may be made of cooling vanes (Figs. 4 and 5), and as afurther alternative, a plate may be secured by welding'(Figs. 8 to 10). Variants of this construction are, of course, possible.

2. An electrode system comprising an all-glass envelope, a first metal lead sealed in one end of said envelope, a second metal lead sealed in the other end of said envelope, said rst lead having a portion within the envelope of greater diameterthan the portion thereof sealed to the envelope, a semi-conductive member having a diameter -less than that of said portion of greater diameter and mounted `on said rst lead and within the envelope, an electrode secured to said second lead and coupled to said semi-conductive member, and cooling means associated with said first lead.

,3., A method of manufacturing an electrode system comprising a semi-conductive body mounted on a metal lead having a portion of greater diameter than the remainder of said lead, which comprises the stepsof in serting said lead within a cylindrical glass body so that the semi-conductive body and the portion of greater diameter are located between the ends of the glass body, grasping said portion of greater diameter with metal pincers inserted at one end of said glass body, thereafter heating the other end of said glass body to seal the same to the metal lead beyond the portion of greater diameter while the latter is held by the pincers, thereafter removingv the pincers, and thereafter sealing another conductive lead to said one end of said glass body.

. 4. A semi-conductor device comprising an insulating envelope, a semi-conductive body, a support member While we have described our invention in connection with specific embodiments and applications, other modications thereof will be readily apparent to those skilled in this art without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A method of manufacturing an electrode system comprising a semi-conductive crystal secured to a support sealed in a glass envelope and having a thicker portion within the envelope, comprising applying enamel paste to the support, and sealing the support to the envelope while the thicker portion is grasped with metal pincers.

sealed in said envelope and supporting said semi-con` ductive body therewithm, said support member having, located inside the envelope, at least one portion that is thicker than the portion of said member sealed in the envelope, and cooling vanes Aon said thicker portion.

5. A device as set forth in claim 4 wherein the thicker portion of the support member has a larger diameter than that of the semi-conductive body.

6. A method of manufacturing a semi-conductor de vice comprising a semi-conductive body secured to a support member having a thicker portion adjacent the body than that portion sealed in a glass envelope, said thicker portion having a diameter exceeding that of the semi-conductive body, which comprises the steps of grasping the thicker portion of said support with a heatconductive member, thereafter sealing the support member into the glass envelope, and thereafter removing the heat-conductive member.

7. A method as set forth in claim 6 wherein the interior of the envelope is exhausted during the sealing operation to provide a tighter seal to the support member.

References Cited in the le of this patent UNITED STATES PATENTS 765,676, Midgley Apr. 5, 1904 817,664 Plecher Apr. 10, 1906 2,682,022 Doran June 22, 1954 2,693,555 North et al. Nov. 2, 1954 2,697,805 Collins Dec. 2l, 1954 2,697,806 Gates Dec. 21, 1954 j FOREIGN PATENTS 696,896 Great Britain Sept. 9, 1953 696,904 Great Britain Sept. 9, 1953