US2197632A - Electrical rectifier - Google Patents

Electrical rectifier Download PDF

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Publication number
US2197632A
US2197632A US213876A US21387638A US2197632A US 2197632 A US2197632 A US 2197632A US 213876 A US213876 A US 213876A US 21387638 A US21387638 A US 21387638A US 2197632 A US2197632 A US 2197632A
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US
United States
Prior art keywords
oxide
copper
elements
nickel
rectifier
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US213876A
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English (en)
Inventor
Philip H Dowling
John D Mccluer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Rail STS USA Inc
Original Assignee
Union Switch and Signal Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Union Switch and Signal Inc filed Critical Union Switch and Signal Inc
Priority to US213876A priority Critical patent/US2197632A/en
Priority to GB34788/38A priority patent/GB521827A/en
Priority to FR848927D priority patent/FR848927A/fr
Priority to GB1519/39A priority patent/GB523858A/en
Priority to FR51009D priority patent/FR51009E/fr
Priority to FR51016D priority patent/FR51016E/fr
Application granted granted Critical
Publication of US2197632A publication Critical patent/US2197632A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
    • H10D48/00—Individual devices not covered by groups H10D1/00 - H10D44/00
    • H10D48/01—Manufacture or treatment
    • H10D48/07—Manufacture or treatment of devices having bodies comprising cuprous oxide [Cu2O] or cuprous iodide [CuI]
    • H10D48/071—Preparation of the foundation plate, preliminary treatment oxidation of the foundation plate or reduction treatment
    • H10D48/075—Reduction of the copper oxide or treatment of the oxide layer

Definitions

  • Ourinvention relates to electrical rectifiers
  • One object of our invention is to provide a copper oxide rectifier in which good electrical contact is obtained between the oxide surface and an adherent metal such for example as nickel.
  • Another object of our invention is to provide a process for depositing a metal such as nickel onto the oxide surface of a copper oxide rectifier in a manner which will not impair its rectifying properties and which will insure good electrical and mechanical contact between the metal and the copper oxide surface.
  • Fig. 1 is a view showing in elevation one form of blank ready to be prepared as a rectifier element in accordance with one process of manufacture embodying our invention.
  • Fig. 2 is a view showing a number of blanks assembled on a support as they appear during one step in the process of manufacture.
  • Fig. 3 is a vertical sectional view showing, in an exaggerated form, a rectifier element as it appears in another step in the process of manufacture embodying our invention.
  • Fig. 4 is a view showing in elevation one form of blank ready to be prepared as a rectifier element in accordance with one process of manufacture embodying our invention.
  • Fig. 2 is a view showing a number of blanks assembled on a support as they appear during one step in the process of manufacture.
  • Fig. 3 is a vertical sectional view showing, in an exaggerated form, a rectifier element as it appears in another step in the process of manufacture embodying our invention.
  • Fig. 4 is a vertical sectional view showing, in an exagger
  • Fig. 5 is a longitudinal sectional view of an electrolytic bath utilized in the process of manufacture embodying our invention.
  • Fig. 6 is a side view of a masking device utilized in connection with the bath shown in Fig. 5 for a purpose which will be made clear in the following specification.
  • Fig. '7 is a vertical sectional view showing a rectifier element as it appears in a further step in the process of manufacture embodying our invention.
  • Fig. 8 is a vertical sectional view similar to Figs. 3, 4 and 7 showing a completed rectifier element constructed in accordance with our invention.
  • the reference character A designates a blank of suitable material such as copper. As here shown, this blank is of circular configuration, and is provided with a central aperture 8, although this particular form is not essential to our invention.
  • a number of these blanks are assembled on a suitable support B in pairs in the manner shown in Fig. 2, so that the blanks of each pair have their adjacent faces Al in contact, and the blanks are 5 then subjected to an oxidizing process, such for example, as the application of heat in an oxidizing atmosphere to form an oxide coating on the blanks.
  • the elements are cooled in any suitable manner as by quenching them in water, and the elements are then treated to remove the cupric oxide layer from the entire surface of the blank, and to remove the cuprous oxide coating from only one face Al of the blank.
  • This treatment may take a variety of forms, butwill preferably consist in subjecting the blanks to a solution consisting of 2 per cent -by volume of sulphuric, acid and .1 per cent by volume of hydrochloric acid in water.
  • the temperature at which the solution is used is not critical, but the desired action of the solution is materially speeded up if the solution is hot, preferably at a temperature of 80 to 100 centigrade.
  • the elements are preferably immersed in the solution for a time interval which is approximately twice as long as is required to remove the cupric oxide. After the elements are immersed in the solution for the desired period of time, the elements are then removed from the solution, washed in water, and thoroughly dried.
  • the elements are next preferably immersed for a short period ofti'me' (of the order of one 5 to three-seconds) in concentrated nitric acid, and are then thoroughly rinsed in water to remove all traces of the acid.
  • the final rinse water should be distilled water unless the available water is known to be free from injurious impurities.
  • the immersion in the nitric acid removes any loose or finely divided copper left on the blanks by the treatment of the sulphuric and hydrochloric acid solution and insures that the copper oxide surface will be sufiiciently clean for the next step which should preferably be performed before the elements havehad any chance to accumulate any foreign substances either from the atmosphere or otherwise.
  • the elements following this step willappear as illustrated in Fig. 4 in which D designates the coating of cuprous oxide remaining on the inner and outer edges of the blank and on one face A2 of the blank.
  • the elements are next treated to reduce the outer surface of the cuprous oxide coating of the blanks to metallic copper. This may be done in a variety of ways, but it is essential that the means employed for reducing the copper should not impair the rectifying properties of the elements, and it is also essential that the resultant copper coating should adhere firmly to the oxide coat.-
  • thedesired reduction can be accomplished electrolytically by immersing the elements as the cathode in a suitable electrolyte throughwhich a current is passed from an insoluble anode such as platinum or carbon, and in Figs. 5 and 6 we have shown a pair of elements A immersed as the cathode in'an electrolytic bath i2 contained in a tank 2, the elements being mounted in-a device C which serves both as a means for making electrical contact with the mother copper of the elements, and also as a means formasking the outside and inside edges of the elements to prevent the copper oxide from being reduced adjacent the edges where it joins the mother metal.
  • The'device C may assume a variety of forms and, as here shown, comprises a metal washer 3, such for example asbrass cemented, as by a latex compound, between two rubber washers l, and connected to a terminal wire 5.
  • the rubber washers have substantially the same thicknesses as the elements A following the previously described acid treatment, and substantially the same inside diameters as the outside diameters of the elements, and the elements are disposed within the openings in these washers with their faces, from which the oxide has been removed, in contact with the metal washer 3.
  • the outside edges of the elements are masked by means of a pair of rubber washers 6 having inside diameters that are slightly smaller than the outside diameters of the elements, and which washers are clamped against the outer edges of the oxidized faces of the elements in concentric relation thereto by means of insulating clamping washers l and bolts 8, whereby portions of the washers B overlap the oxidized faces of the elements adjacent their outer edges and serve to substantially seal the oxide surfaces against the action of the electrolyte for
  • the inside edges of the elements are masked by means of a pair of rubber washers 9 having outside ,diameters which are slightly largerthan the diameters of the holes in the elements, and which washers are clamped action of the electrolyte for a small annular area 10 adjacent the innercopper-cuprous oxide junction.
  • the anode as shown in Fig. 5 consists of a graphite electrode it, to which external connections are made by a conductor I l.
  • the electro- 15 lyte l2 may comprise dilute sulphuric acid, distilled water saturated with carbon dioxide, some tap waters, or any other electrolyte in which electrolytic reduction can be accomplished, and which does not have any injurious chemical effect on the rectifying characteristics of the elements.
  • sulphuric acid in distilled water made up to a concentration of about .35 gram per liter. The concentration should not exceed 17 grams of sulphuric acid per liter and concentrations below .35 gram materially slow up the process.
  • the reduced copperunder these conditions being bright, fine grained, extremely adherent, and disposed as a continuous film over the entire exposed oxide faces of the elements.
  • the amount of reduction which can be used before the rectifying properties of the elements become impaired depends on the original thickness of the oxide, and if the reduction is continued for too long a time, there is a tendency for the reduced copper to penetrate the oxide a sufficient amount to reach the mother copper, which condition may result'in short circuiting the rectifier elements. As the amount of reduction increases, the forward resistance of the elements decreases.
  • the elements Upon removing the elements from the electrolytic reduction bath, the elements are thoroughly rinsed in several rinse waters, the last rinse water preferably being distilled water, and the elements are then subjected to a vigorous blast of com-, pressed air.
  • the air blast appears to have the effect of blowing out some of the gas and liquid 7 which collects in the pores of the reduced copper, and seems to be helpful in preparing the elements for the next step which we shall now describe.
  • This step consists in depositing electrolytically on the reduced copper layer a layer of nickel.
  • the elements while still mounted in the support 0 are made the cathode in a nickel plating solution in the same manner that they are made the cathode in the acid bath during the preceding step.
  • a standard nickel plating solution may be used, which may for example, have the following composition.
  • nickel plating is a very helpful step following the reduction of the outer surface of the cuprous oxide to copper. With reduction alone a rectifier is obtained which initially has very good rectifying characteristics, but the rectifier appears to age in the forward direction much more rapidly than when the elements are subsequently plated with nickel in the manner just described. Moreover, nickel plating of the reduced copper surface appears to reduce the tendency of moisture to increase the resistance of the elements in the forward direction.
  • the oxidized blanks are thoroughly clean it is possible to plate the nickel directly onto the cuprous oxide surface without first reducing this surface to copper in the manner previously described. If the cupric oxide has been removed by successively treating the elements with the hydrochloric andsulphuric acid solution and by concentrated nitric acid in the manner previously described, and the elements are immediately transferred to the nickel plating solution, they will be sufllciently clean; but if the excess oxide has been removed by mechanical means for example, then the elements should first be cleaned as by giving them a quickdip (one or two seconds) in concentrated nitric acid followed by a thorough rinse in water which will not leave objectionable impurities on the elements.
  • the nickel plating solution may be the same as that previously described,and if theacidity of the solution is high and the current density is kept relatively low, the solution .and the electrolytically reduced will discharge both hydrogen and nickel at the hydrogen will reduce the cuprous oxide to metallic copper, and by properly controlling the acidity of the plating solution and the current density, an underlying layer of copper will be produced next to the cuprous oxide which layer will be covered by an outer layer of nickel.
  • the nickel when the nickel is being plated directly onto the cuprous oxide, it is being plated onto a reducible cathode, and the effect of this appears to be to limit the plating range, particularly in plating solutions the pH value of which is in the neighborhood of 5.8 to 6.0.
  • the nickel plating solution would deposit a good coat on certain metals, such for example, as copper, a deposit of nickel salt will be formed on cuprous oxide instead of metallic nickel. For this reason it appears to be desirable to maintain a rather high acidity in the nickel plating solution, particularly if relatively high current densities of the order of 18 amperes are to be used.
  • cupric oxide can be reduced electrolytically in the same manner that the cuprous oxide is reduced electrolytically.
  • rectifiers having a low resistance in the conducting direction the reduction must be carried clear through the cupric oxide so as to contact the underlying cuprous oxide.. Otherwise, the highly resistant layer of cupric oxide will be interposed between the low resistant cuprous oxide contact material.
  • the process of making contact with the cuprous oxide surface of a copper oxide rectifier element which process consists in first making the element the cathode in a bath containing about .35 gram per liter of sulphuric acid in water and passing current through said bath to said element to reduce the oxide surface to metallic-copper, and then plating said reduced surface with nickel.

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  • Electroplating Methods And Accessories (AREA)
US213876A 1938-06-15 1938-06-15 Electrical rectifier Expired - Lifetime US2197632A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
US213876A US2197632A (en) 1938-06-15 1938-06-15 Electrical rectifier
GB34788/38A GB521827A (en) 1938-06-15 1938-11-29 Improvements relating to electrical rectifiers
FR848927D FR848927A (fr) 1938-06-15 1939-01-16 Perfectionnements à la fabrication de dispositifs à conductibilité asymétrique
GB1519/39A GB523858A (en) 1938-06-15 1939-01-16 Improvements relating to electric dry-contact rectifiers
FR51009D FR51009E (fr) 1938-06-15 1939-05-13 Perfectionnements à la fabrication de dispositifs à conductibilité asymétrique
FR51016D FR51016E (fr) 1938-06-15 1939-12-05 Perfectionnements à la fabrication de dispositifs à conductibilité asymétrique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US213876A US2197632A (en) 1938-06-15 1938-06-15 Electrical rectifier

Publications (1)

Publication Number Publication Date
US2197632A true US2197632A (en) 1940-04-16

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Family Applications (1)

Application Number Title Priority Date Filing Date
US213876A Expired - Lifetime US2197632A (en) 1938-06-15 1938-06-15 Electrical rectifier

Country Status (3)

Country Link
US (1) US2197632A (fr)
FR (3) FR848927A (fr)
GB (2) GB521827A (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3432423A (en) * 1966-10-07 1969-03-11 Gen Dynamics Corp Electroplating apparatus

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4445942A (en) * 1979-11-26 1984-05-01 General Electric Company Method for forming nuclear fuel containers of a composite construction and the product thereof

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3432423A (en) * 1966-10-07 1969-03-11 Gen Dynamics Corp Electroplating apparatus

Also Published As

Publication number Publication date
FR51009E (fr) 1941-05-28
GB523858A (en) 1940-07-24
GB521827A (en) 1940-05-31
FR848927A (fr) 1939-11-09
FR51016E (fr) 1941-05-28

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