US2726357A - Semiconductor device - Google Patents

Description

United StatesA SEMICONDUCTOR DEVICE Rudolph Sachs, Marblehead, Mass., assignor to Colunbia Broadcasting System, Inc'., Danvers, Mass., a corporation of New York, doing business' as HytronRdo & Electronics Co. f

Application October 22, 1,9502', Serial No. $116,258L "lY claims. (on 311-234) which often depend upon point contacts for their opera-V tion. For purposes of simplicity, thefollowing discussion will be limited to diodes, but the concepts have equal pertinence to other semi-conducting devices having point contacts. K

In the case of the diodes; proper operation is obtained only by careful adherence to proper orientation -of a' fine pointed wire relative to semiconducting inat'ei-ial.-y The semiconducting material is usually rn'o'nted on the end of one electrode and th pointed wire' on the, end of a second electrode. These electrodes are then brought 'together Within a Cartridge With the pointed end of the wire pressed against the semieonine'tingl inateial with a predetermined pressure. Spring loading of various kinds has been used, the n'iost common. arrangement being to form the wire into a rough s with the' 'point extending longitudinally outward from the si. This having been' done, some locking arrangement must be sed to insure that rotation of the electrodes does not alter the relationship of the Whisker and sen'iicor'iductgniatei'l." Such rotation would seriously affect the operating characteristies of the device. various structures have Been suggested to overc'oine thepr'oble'ii f to'q'' resistance. These have included electodfs of s'qiia cross-section for insertion in similar openings in Ythe catridg's, or locking screws placed radially iii the cartridges to Bc'r upon the electrodes amongst o'A The fatal defects in most of the expe'dients menti 7d Has been th'ii cost, thei failure to ineet torque requirements, and; most important their inutility in high speed mass production since the units often require a particularrelative orientation to be assembled. Press of intrference'iits pfconventional design are also of little value because of the extreme hardness of the cartridges used. When it is attempted to press a metallic pin' into a hard ceramic or plastic car'tidge", the cartridge usually splits because of its inhrent brittle'ness.

Another problem which has existed in vthe manufacture of semiconductor devices is that of impregnation. Since most semiconductor devices are not operated in vacuum, as are electron tubes, it is necessary that some protection be given the elements against humidity, shock and other hazards. The almost universally adopted technique is to impregnato the interior of the cartridge with wax or similar material. Since the impregnation can be feasibly carried out only after completion of the device, it has been the practice to provide a radial opening in the cartridge wall for introducing the impregnating substance. After the impregnating substance is thus introduced, the opening is often closed with a cement which dries to leave a hard external surface. Besides the apparent difliculties Patent r., Ice ila'te'nted'Dec.' 6; 1955 2 of manual and time-consuming operations following the steps of the foregoing procedure', the cartridge itself is more expensive and physically weakened because of the radial aperture.

The two outlined problems of torque resistance of tlie electrodes and impregnation have occupied those engaged in development of the semiconductor art for some time. The approach to the problems has been conventional in the sense that the problems have been separately attacked although neither problem has vyet been satisfactorily solved. A structure so designed that both of these problems are simultaneously solved would till a definite ed.

Hence, it is a primary object of the present invention to provide a semiconductor device wherein the electrodes are' highly resistant to applied torque.

It is another object to provide a semiconductor structur'e which permits impregnation of internal elements without physically weakening the device.

It is still another object of the invention to simplify the fabrication of semiconductor devices of the point contact type. i

In general,- the present invention consists in a semiconductor devicewhich includes an insulating cartridge into which there are axially inserted conducting electrodes. In the case of the diode these end electrodes are the only electrodes, but the invention has equal applicability in any similar structures which use axial electrodes. On the end of one electrode, there is aixed a wafer of semiconducting material and a point contact is affixed to the end of a second electrode. On a portion of each electrode adjacent the mounting' en'd longitudinal grooves are formed; The insulating cartridge also has grooves formed in' its internal surface. As will b'e explained in greater de` tail lereinbelow, the electrode and cartridge formations cooperate in the finished device to provide a high degree of resistance by the electrodes against rotation relative tothe' cartridge. Further, the configuration of abutting surfaces of cartridge and electrodes is such that impreg-'I n'ating material is easily introduced intov the interior of a' finished device. For a better understanding of the invention, together with' other and vfurther objects, features, and advantages, reference should be made to the following description which is to be read in connection with `theA accompanying drawings in which: Fig'. l is a front elevation View diode in its completed state; and

Fig. 2 is a transverse section of Fig. l taken along the line zz.

Referringnow to Fig. l, there is shown a cartridge V12 which may be made of a hard phenolic plastic, for'example. electrode 13 is inserted in the axial opening of cartridge 12 from one end and has a Whisker 14 soldered thereto. second electrode l5 is inserted in the' axial opening from the other end of cartridge 12 and has a wafer 16 of semiconducting material soldered thereto. The two electrodes are forced into cartridge 12 a suicient distance to cause Whisker 14to bear 'upon wafer 16 with predetermined pressure. Soldering pigtaiis 17 and 1S are welded to the ends of electrodes 13 and 1S respectively to permit the diode to be soldered into a circuit. Alternatively, electrodes 13 and 15 may be clipped into a circuit if that is desired. Finally, a chemically and electrically inert wax is used to impregnato the entire unit in a manner described in greater detail hereinbelow.

Referring now to Fig. 2, cartridge 12 is shown in section near one end along the line 2 2 of Fig. l. Rectangular grooves yare formed on the internal lwall surface of cartridge 12, groove 21 being typical. A straight knurl s formed along each of the electrodes fora portion of its length, and the knurled portion is inserted into the cartridge as maybe seen in Fig. l.

partly cut away of the In a representative structure, the major inside vdiam-v eter of 1A" cartridge 12, for example, from the bottom of groove 21 to the bottom of groove 22 is .082" to .085. The minor inside diameter, for example, from the top of nnb 23 to the top of nub 24 is .072l to .075". Each of the electrodes used in conjunction with cartridge 12 has a major outside diameter, as from the top of knurl 25 to the top of knurl 26, of .083 to .085L The minor diameter, as from the bottom of knurl 27 to the bottom of knurl 28, is .079" to .081. The grooving of cartridge 12 is full length and the knurling, which may be applied by a No. 50 knurling tool, extends for approximately .125 along the .335" electrode, as may be more plainly seen by reference to Fig. l. A slight chamfer is provided at the entries to cartridge 12 and at the leading edges of electrodes 13 and 15.

Dimensions such as those cited result in a fit between cartridge and electrodes which necessitates some broaching of the cartridge and also some shearing of the electrodes as the unit is assembled. However, because the material in the preferred embodiment of the invention is a phenolic plastic in the cartridge and a nickel alloy in the electrodes, no difficulty is encountered in assembling the parts no matter the relative orientation thereof. An extremely high torque resistance is developed, exceeding 3 in. lbs. in the device described.

As is apparent from Fig. 2, 6 grooves are found about the periphery of the opening in cartridge 12 while l0 grooves exist in the knurled portion of electrodes 13 and 14. As a result, no matter what the orientation of a given cartridge and electrode, openings for the entry of the impregnating substance are available, while portions of some of the nubs are cut by the knurl.

While what has been disclosed constitutes a preferred embodiment of the present invention, the invention should not be limited only to the details shown. The concept of high torque resistance and novel entry points for impregnation as embodied in applicants grooved structure should be evaluated in terms of the breadth of the appended claims.

What is claimed is:

l. A semiconductor device comprising, an insulating cartridge having a central axial opening formed therein and at least one electrode inserted in said axial opening,

lirst plurality of grooves formed in the wall thereof, and said electrodes having a second plurality of grooves formed on at least the portions of their lengths which are inserted in said axial opening, the maximum diameters of said electrodes being substantially similar and greater than the minimum diameter of said axial opening, said first plurality being a different number than said second plurality.

4. A semi-conductor device comprising, an insulating cartridge having an axial opening formed therein and at least one electrode inserted in said opening at one end thereof, said electrode and said cartridge having discontinuous abutting surfaces leaving apertures therebetween to permit the introduction of impregnating material.

5."A semi-conductor device comprising, an insulating cartridge having an axial opening formed therein and at least an electrode inserted in said opening at one end thereof, said opening having longitudinal grooves formed in the wall thereof and said electrode having longitudinal said axial opening having longitudinal grooves formed in the wall thereof, and said electrode having a straight knurl formed on at least the portion of its length which is inserted in said axial opening, said longitudinal grooves and said straight knurl being of different configurations, whereby at least an aperture is formed between said electrode and the wall of said axial opening.

2. A semiconductor device comprising, a plastic insulating cartridge having a central axial opening formed therein, and irst and second electrodes inserted in said axial opening, said axial opening having a rst plurality of longitudinal grooves formed in the wall thereof, and said electrodes having a second plurality of grooves formed on at least the portions of their lengths which are inserted in said axial opening, said rst plurality and said second plurality being ditferent numbers.

3. A semiconductor device comprising, a plastic insulating cartridge having a central axial opening therethrough, and first and second electrodes inserted in said axial opening at either end, said axial opening having a grooves formed along that portion of its length which is inserted in said axial opening, said grooves in said opening and in said electrodes being in close contact to inhibit relative rotation and mismatched to provide axial openings for the introduction of impregnating material.

6. A semiconductor device comprising, a phenolic plastic cartridge having a central axial opening therethrough, a pair of nickel alloy electrodes iitted into said axial opening, one of said electrodes penetrating each end of said axial opening, said axial opening having six longitudinal grooves cut in the wall thereof, said grooves being symmetrically arrayed about said opening and each of said wall grooves being substantially wider than each of the portions of the wall separating said grooves, each of said electrodes having the portion of its length inserted in said axial opening knurled to form ten symmetrically disposed similar'longitudinal grooves therein, the minimum diameter of said axial opening in said cartridge being less than the minimum diameter of said electrodes by an amount of the order of magnitude of thousandths of inches, the maximum diameter of said electrodes exceeding the minimum diameter of said axial opening by an amount of the order of magnitude of tens of thousandths of inches, whereby said electrodes are inhibited against rotation in said opening and a plurality of axial channels for the introduction of impregnating solution between said electrodes and the wall of said openings are provided.

7. A semiconductor device comprising, an insulating cartridge having an axial opening formedtherein, longitudinal grooves being formed in the wall of said opening, and at least an electrode inserted in said opening, said electrode also having grooves formed along that portion of its length which is inserted in said opening, the grooves formed in said opening having a contiguration which differs from that of the grooves formed on said electrode.

References Cited in the le of this patent UNITED STATES PATENTS 2,602,763 Scaif et al. July 8, 1952 2,603,692 vScali et al. July l5, 1952 2,615,857 Clarke Oct. 28, 1952. 2,693,556 Gahagan Nov. 2, 1954

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