US2197632A - Electrical rectifier - Google Patents
Electrical rectifier Download PDFInfo
- 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
- Authority
- 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
Links
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 57
- 229910052802 copper Inorganic materials 0.000 description 35
- 239000010949 copper Substances 0.000 description 35
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 33
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 32
- 238000000034 method Methods 0.000 description 31
- 229910052759 nickel Inorganic materials 0.000 description 28
- 229960004643 cupric oxide Drugs 0.000 description 25
- 238000007747 plating Methods 0.000 description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 21
- BERDEBHAJNAUOM-UHFFFAOYSA-N copper(I) oxide Inorganic materials [Cu]O[Cu] BERDEBHAJNAUOM-UHFFFAOYSA-N 0.000 description 19
- 229940112669 cuprous oxide Drugs 0.000 description 19
- 239000005751 Copper oxide Substances 0.000 description 18
- 229910000431 copper oxide Inorganic materials 0.000 description 18
- KRFJLUBVMFXRPN-UHFFFAOYSA-N cuprous oxide Chemical compound [O-2].[Cu+].[Cu+] KRFJLUBVMFXRPN-UHFFFAOYSA-N 0.000 description 16
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 11
- 239000001117 sulphuric acid Substances 0.000 description 11
- 235000011149 sulphuric acid Nutrition 0.000 description 11
- 238000004519 manufacturing process Methods 0.000 description 10
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 6
- 238000000576 coating method Methods 0.000 description 6
- 230000007423 decrease Effects 0.000 description 6
- 230000000873 masking effect Effects 0.000 description 6
- 239000002253 acid Substances 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 239000012153 distilled water Substances 0.000 description 4
- 229920001971 elastomer Polymers 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- 229910017604 nitric acid Inorganic materials 0.000 description 4
- 230000001464 adherent effect Effects 0.000 description 3
- 235000019270 ammonium chloride Nutrition 0.000 description 3
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 3
- 239000004327 boric acid Substances 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 238000000151 deposition Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 230000000266 injurious effect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 150000002815 nickel Chemical class 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 235000019568 aromas Nutrition 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 230000002925 chemical effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 239000004816 latex Substances 0.000 description 1
- 229920000126 latex Polymers 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
- 239000003643 water by type Substances 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/16—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising cuprous oxide or cuprous iodide
- H01L21/161—Preparation of the foundation plate, preliminary treatment oxidation of the foundation plate, reduction treatment
- H01L21/165—Reduction of the copper oxide, 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.
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Electroplating Methods And Accessories (AREA)
Description
April 16, 1940. P. H. DOWLING El" AL ELECTRICAL RECTIFIER Filed June 15, 1938 pm D Z 0, M p mm W c Dv A uufi Q L 5 mm C .9 @w l W 1... WP u A m Eleozmlyzzballg pedat'ed- Copper.
Caprz'oOxzde yleducea' iNVENTORS Copper Make! Y C'cgzz aar Oxide Philip [ID 1 1/ [60g and THEIR ATTORNEY Patented Apr. 16, 1940 NITED STATES PATENT OFFICE ELECTRICAL RECTIFIER Application June 15, 1938, Serial No. 213,876
9 Claims.
Ourinvention relates to electrical rectifiers,
and particularly to electrical rectifiers of the well-known copper oxide variety.
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.
Other objects and characteristic features of our invention will appear as the description proceeds.
We shall describe several forms of rectifiers embodying our invention and several processes for manufacturing said rectifiers, and shall then point out the novel features thereof in claims.
In the accompanying drawing, 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 a rectifier element as it appears in still another step in the process of manufacture embodying our invention. 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.
Similar reference characters refer to similar parts in each of the several views.
Referring to the drawing, 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.
an inspection of Fig. 3 that the flat face of the blank which is exposed during the oxidizing process, that is to say, the lower face has a much heavier oxide coating than the upper face.
After the oxidation is completed, 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. To insure that no impurities are left on the elements from the water, 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 portion of the process of manufacture of the rectifier elements thus far described is well-known, and for a further description of this portion of the process reference may be had to Letters Patent of the United States No. 2,094,642, granted October 5, 1937, to Philip H. Dowling, for the Manufacture of electrical rectifiers.
In accordance with our present invention, 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.-
- ing and should make good electrical connection with it. It is further essential that the surface of the .oxide at the copper-cuprous oxide junctions should not be reduced because if it were reduced the elements would become short circuited and would therefore be rendered useless for their intended purpose.
We have found that 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 a small annular area inside of the adjacent copper-cuprous oxide junction. 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. We prefer, however, to use 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. If the concentration becomes too great, the reduced copper does not have'good adhering qualities, and the elements tend to have a high resistance in the forward direction. To accomplish the reduction, current is, of course, passed from the anode to the elements, and we have found that excellent results are obtained ata current density of the order of 12 amperes per square foot maintained for about three minutes, 35
preferably with mechanical agitation of the bath, 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 exact reasons for this decrease are very dimcult to determine, but this decrease, would appear to be due to one or more of the following: (1) A decrease in the resistance offered by the oxide resulting from the decreased thickness of the oxide. (2) A decrease in the resistance between the oxide and the copper layer formed by the reduction resulting from the fact that as the amount of the reduction is increased the reduced copper penetrates more deeply into the interstices between crystals, thereby providing a contact area between the oxide and the copper layer which may have many times the plane surface area of the oxide layer. (3) A decrease in the resistance per unit area of the contact between the oxide and the copper formed by the reduction.
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. To accomplish this step 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.
Ounces per gallon Nickel sulphate .s..... 8 Ammonium chloride 1 Boric acid 1 Sodium chloride The current density during this step depends upon the plating solution used and the pH value of that solution, and with the solution mentioned above mechanically agitated and maintained at a pH value of about 5.8, excellent results are obtained with a current density of about 18 amperes per square foot continued for about two minutes at roomtemperature. If the washers are plated for too long a period of time, a short circuit may be formed between the nickel and the mother copper which would destroy the rectifying properties of the elements. The maximum permissible current density that can be employed is that at which nickel salts start to become deposited on the elements. The pH value of the nickel plating solution appears to be relatively critical and should preferably be kept below 5.8- The nickel when deposited under the above outlined conditions is bright and very adherent.
We have found that 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.
We have also found that metals other than nickel can be plated onto the reduced copper surface, but that the best results appear to be obtained when nickel is used.
We have further found that if 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.
We have discovered, however, that good coats of nickel, with no visible evidence of copper under them, can be deposited directly onto the cuprous oxide with the hereinbefore described nickel plating solution at current densities of the order of 5 or 6 amperes per square foot in a time of between five and ten minutes when the pH value of the solution is about 5.8.
It should be noted that 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. At relatively high current densities where 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.
It should be pointed out that while for most applications of rectiflers it appears to be desirable to remove the cupric oxide before subjecting the elements to the electrolytic treatment, it is not necessary to do this, and we have found that the cupric oxide can be reduced electrolytically in the same manner that the cuprous oxide is reduced electrolytically. In cases where rectifiers having a low resistance in the conducting direction are desired, 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.
Although we have herein shown and described only a few forms of rectifiers embodying our invention and a few processes for manufacturing said rectiflers, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of our invention.
Having thus described our invention,.what we claim is: p
1. The process of electrolytically reducing the copper oxide surface of a copper oxide rectifier element to metallic copper tofacilitate making contact with said surface which process consists in making the element the cathode in an electrolytic bath comprising approximately .35 gram of sulphuric acid per liter in water and passing a current through said bath to said element.
2. The process of electrolytically reducing the copper oxide surfacefof a copper oxide rectifier element to metallic copper tofacilitate making electrical contact with said surface which process consists in masking the edges of said surface and then immersing said element as the cathode in an' electrolytic bath comprising .35 gram of sulphuric acid per liter in water and passing a current through said bath to said element.
I 3. The process of electrolytically reducing the copper oxide surface of a copper oxide rectifier element to metallic copper to facilitate making electrical contact with said surface which process consists in making the element the cathode in an electrolytic bath comprising approximately .35 gram of sulphuric acid per liter in water and passing a current of the order of 12 amperes per square foot through said bath to said element for about three minutes.
4. The-process of electrolytically reducing the copper oxide surface of a copper oxide rectifier element to metallic copper to facilitate making electrical contact with said surface which process consists in masking the edges of the oxide surface and making the element the cathode in an electrolytic bath comprising approximately .35 gram of sulphuric acid per liter in water and passing a current of the order of 12 amperes per square foot through said bath to said element for about three minutes.
5. 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. 3
6. The process .of making contact with the cuprous oxide surface of a copper oxide rectifier element which process consists in first masking the edges of the oxide surface, then making the element the cathode in a bath containing about .35 gram per liter of sulphuric acid in water and passing a. current .of about 12 amperes per square foot through said bath to said electrode for about three minutes to reduce the oxide surface to metallic copper, and finally plating said reduced surface with nickel.
7. The process of making contact with the aromas cuprous oxidesurface of a copper omde rectifier element which process consists in first masking the edges of the oxide surface, then making the element the cathode in a bath containing about .35 gram per liter of sulphuric acid in. water and passing a current of about 12 amperes per square foot through said bath to said electrode for about three minutes to reduce the oxide surface to metallic copper, and finally making the element the cathode in a nickel plating solution and passing a current of about 18 amperes per square foot through said plating solution to said element for about two minutes.
8. The process of making contact with the cuprous oxide surface of a copper oxide rectifier element which process consists in first masking the edges of the oxide surface, then making the element the cathode in a bath containing about .35 gram per liter of sulphuric. acid in water and passing a current of about 12 amperes per square foot through said bath to said electrode for about three minutes to reduce the oxidesurface to metallic copper, and finally making the element the cathode in a nickel plating solution consisting of 8 oz. nickel sulphate per gal., 1 oz. of ammonium chloride per gal., 1 oz. of boric acid per gal. and /2 oz. sodium chloride per gal. and passing a current of about 18 amperes per square foot through said plating solution to said element for about two minutes.
9. The process of making contact with the oxide surface of a copper oxide rectifier which consists in making the element the cathode in a nickel plating solution consisting of 8 oz. nickel sulphate per gal., 1 oz; of ammonium chloride per gal., 1 oz. of boric acid per gal. and oz. of sodium'chloride per gal and passing a current of the order of 5 or 6 amperes per square foot. ,through said solution for from five to ten minutes, said'solution having a pH value of about 5.8.
PHILIP H. DOWLING. JOHN D. McCLUER.
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 |
GB1519/39A GB523858A (en) | 1938-06-15 | 1939-01-16 | Improvements relating to electric dry-contact rectifiers |
FR848927D FR848927A (en) | 1938-06-15 | 1939-01-16 | Improvements in the fabrication of asymmetric conductivity devices |
FR51009D FR51009E (en) | 1938-06-15 | 1939-05-13 | Improvements in the fabrication of asymmetric conductivity devices |
FR51016D FR51016E (en) | 1938-06-15 | 1939-12-05 | Improvements in the fabrication of asymmetric conductivity devices |
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 |
Family
ID=22796848
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 (en) |
FR (3) | FR848927A (en) |
GB (2) | GB521827A (en) |
Cited By (1)
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)
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 |
-
1938
- 1938-06-15 US US213876A patent/US2197632A/en not_active Expired - Lifetime
- 1938-11-29 GB GB34788/38A patent/GB521827A/en not_active Expired
-
1939
- 1939-01-16 FR FR848927D patent/FR848927A/en not_active Expired
- 1939-01-16 GB GB1519/39A patent/GB523858A/en not_active Expired
- 1939-05-13 FR FR51009D patent/FR51009E/en not_active Expired
- 1939-12-05 FR FR51016D patent/FR51016E/en not_active Expired
Cited By (1)
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 |
---|---|
GB523858A (en) | 1940-07-24 |
FR848927A (en) | 1939-11-09 |
FR51009E (en) | 1941-05-28 |
GB521827A (en) | 1940-05-31 |
FR51016E (en) | 1941-05-28 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US3654099A (en) | Cathodic activation of stainless steel | |
US2814589A (en) | Method of plating silicon | |
US4097342A (en) | Electroplating aluminum stock | |
US3147547A (en) | Coating refractory metals | |
US1745912A (en) | Chromium-coated wire and method of manufacture | |
US4126522A (en) | Method of preparing aluminum wire for electrical conductors | |
US3984290A (en) | Method of forming intralayer junctions in a multilayer structure | |
US2161636A (en) | Method of protectively coating aluminum or aluminum alloys | |
US3393091A (en) | Method of producing semiconductor assemblies | |
US2197632A (en) | Electrical rectifier | |
US3006821A (en) | Manufacture of silver chloride electrodes | |
US4549941A (en) | Electrochemical surface preparation for improving the adhesive properties of metallic surfaces | |
US3867265A (en) | Process for electroplating an aluminum wire | |
US2649409A (en) | Electrodeposition of selenium | |
US2075623A (en) | Zinc plating | |
CN111636077A (en) | Process for preventing ceramic chip from being plated with nickel or gold by creeping plating | |
US2291592A (en) | Electrical rectifier | |
US3489603A (en) | Surface pretreatment process | |
US2969295A (en) | Chemical gold plating | |
US4552627A (en) | Preparation for improving the adhesion properties of metal foils | |
US2368749A (en) | Electrolytic method of preparing electrical rectifiers | |
US2689399A (en) | Plated article and method of making it | |
US2328626A (en) | Manufacture of electrical rectifiers | |
US2667453A (en) | Method of electroplating copper on metal articles | |
US2215890A (en) | Electrical rectifier |