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
  • H10D48/04—Manufacture or treatment of devices having bodies comprising selenium or tellurium in uncombined form
  • H10D48/043—Preliminary treatment of the selenium or tellurium, its application to foundation plates or the subsequent treatment of the combination
• • 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
  • H10D48/04—Manufacture or treatment of devices having bodies comprising selenium or tellurium in uncombined form
  • H10D48/043—Preliminary treatment of the selenium or tellurium, its application to foundation plates or the subsequent treatment of the combination
  • H10D48/044—Conversion of the selenium or tellurium to the conductive state
• • 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
  • H10D48/04—Manufacture or treatment of devices having bodies comprising selenium or tellurium in uncombined form
  • H10D48/043—Preliminary treatment of the selenium or tellurium, its application to foundation plates or the subsequent treatment of the combination
  • H10D48/045—Treatment of the surface of the selenium or tellurium layer after having been made conductive

Definitions

• This invention relates to a method of manufacturing blocking-layer electrode systems of the kind comprising a selenium electrode and also to the blocking-layer electrode system produced thereby.
• the invention has primarily for its object to improve the blocking layer of such an electrode system.
• the quality of this layer is of very high importance as regards satisfactory operation of blocking-layer electrode systems, for example in industrial rectifiers.
• an increased blocking efiect ensures that the leakage current is reduced so that the losses are reduced,
• this leakage current primarily governs the evolution of heat in the rectifier and it is this evolution of heat which generally causes the electrode system to deteriorate.
• An increase of the blocking effect leads to a decrease of th evolution of heat and thus to an increase of the life, and the loading capacity.
• the inven-' tion is characterized in that the selenium layer has a blocking layer formed on it after its transformation, at least at the surface, into the crystalline modification (Sen) exhibiting poor conductivity but before it is converted completely into the modification (Sec) of good conductivity.
• SEA selenium after being applied to a carrierand smoothed, generally shows the so-called amorphous structure, which is non-conductive and is referred to hereinafter as SEA.
• this selenium is subjected, if desired under a press, to heat-treatment, for example at about the amorphous selenium passes into the crystalline modification which, however, is of poor conductivity and which is referred to herein as See.
• the transformation into the conducting modification, which is finally desired, takes place at a substantially higher temperature, generally at about 200 C.
• the selenium thus formed is referred to herein as See.
• the blocking layer is not applied until crystalline selenium (Sea) has been formed at least superficially. Furthermore, the complete transformation of the crystalline selenium Sen into the conducting form see does not take place until the blocking layer has been applied.
• the blocking layer is applied between two treatments the former of which has already led to the formation of See on the surface, whereas the latter completes the process rendering the selenium conductive. It has been found that this is particularly advantageous as regards the density, the uniformity and the firm adhesion of the blockin layer.
• This method is particularly important in connection with that kind of blocking-layer formation in which surface treatment of the selenium is conducted to render the substance on the surface (selenium and/or an admixture therewith) non-conducting.
• Such a method is described in French specification 826,933, it being highly advantageous to carry out several successive forming treatments, each succeeding treatment being preferably performed at a higher temperature than the previous one.
• treatment at high temperature results in a continuous transformation of the selenium because the time of applying the blocking layer is chosen in such manner that the complete transformation into Sea has not yet taken place.
• a good basis for the blocking layer is provided because the crystalline selenium Sea has already been formed, at least superficially.
• the selenium is found to be highly sensitive to the action of the substances that serve for the formation of the blocking layer during the progess of transformation. If a second treatment is carried out at a higher temperature than the first this progress in the transformation of the selenium is sure to ensue.
• a quantity of molten selenium has added to it an admixture for increasing the conductivity.
• a large number of such admixtures are serviceable.
• zirconium chloride may be added.
• a quantity of this mixture is applied in the'liquid state on a rotaryaluminium carrier which may be previously roughened for better adhesion and also provided with layers of zinc and carbon (see U. S. Patent No. 2,244,664, issued June 10, 1941). Due to the centrifugal force the selenium is distributed evenly over the surface (see patent application Serial No. 254,508, filed February 3, 19 39).
• the selenium layer formed may have, for example, a
• a small roughened mica plate is laid on the carrier comprising the selenium layer, said plate being previously coated on the side adjacent the seleniuin with a liquid which, due to its action on the selenium layer, forms a blocking layer.
• a liquid which, due to its action on the selenium layer, forms a blocking layer.
• Such liquids must have a comparatively high boiling point because the action ensues at a temperature of about 160 and the liquid must be prevented from being vaporised too rapidly.
• use may be made with advantage of a substance in which the selenium is slightly dissolved. Due to the selenium particles on the surface being brought into solution a much more intense action-on the selenium and the admixture may result so that it is more easily possible to render the material on the surface non-conductive.
• the selenium layer and the mica plate, jointly with the interposed quinoline, are then compressed in a press having a temperature of about 160. This treatment takes about 5 minutes. Due tothe compression the selenium layer is caused, to an even greater extent than that obtained by centrifuging, to assume a uniform thickness and made compact. Due to the action of the quinoline a firstblocking-layer fonnation also ensues. As may be seen from French Patent 826,933 no other treatment than thisblockinglayer formation used to be performed and subsequent treatment was only carried out for converting the S813 formed under the press into the conducting modification Sec.
• a further forming treatment is; carried out with the selenium which is converted into the crystalline modification (See) but has not yet obtained the final form Sec, since after the aggregate has been withdrawn from the press and the mica plate is removed quinolin is again applied to the surface of the electrode.
• the quinoline is preferably applied by spraying, so that a fine distribution over the surface is obtained. The intimate contact between the quinoline and the selenium surface which was obtained under the press by the pressure of the press is now produced due to the fact that the quinoline is sprayed in fine drops on to the entire surface.
• the blocking layer is to be further intensified this is not effected by applying more quinoline, which involves a longer action, but is preferably effected -by using a further independent forming treatment.
• the second treatment described is carried out at a temperature between and the melting point of the selenium.
• the seleniumelectrode may, for example, be introduced into a furnace having a temperature of 200 C. After the temperature of the plate has reached about the plate, while staying in the furnace, is subjected for 2 minutes to spraying with quinoline. The selenium electrode is then left in the furnace for another three minutes.
• the blocking layer then has applied to it by spraying a complementary electrode consisting, for example, of a low-melting alloy of tin, bismuth and cadmium.
• this forming stage is independent of the application and smoothing of the selenium layer of the operation of rendering the selenium compact under the press and finally of the final complete conversion into the conducting modification See itcan be controlled entirely and can be affected in a manner capable of ready reproduc-
• the preceding blocking-layer formation under the press has the effect that a single following stage suflices in this case. Instead of carrying out the blocking-layer formation under the press it is, however, possible to add a blocking-layer forming treatment after compression.
• the treatment may be repeated as many times as desired.
• Each successive treatment procures an intensification and greater homogeneity of the blocking layer obtained in the previous treatment. Feeble spots which lead to a high leakage current are in effect nullified.
• the forward current of an electrode system of well-known form and also of a system in which blocking-layer formation has been effected under the press by the action of an alkaline liquid is, at 2 volts, about 0.25 amp./cm..
• the admissible blocking voltage for such a system is from about 16 to 18 volts. In this case a leakage'current of about 8 maJcm. occurs: a hibglher leakage current is regarded as inadmis- S er Q
• the admissible blocking voltage is, however, from 30 to 45 volts.
• the output current can be increased to 0.1 ampJcmF.
• the operating temperature of the rectifiers is comprised between and C.
• trode system the steps of applying a selenium electrode to a substratum, forming on the selenium electrode a blocking layer in a plurality of consecutive intensifying treatments after the selenium at the surface thereof has been converted into its poor-conducting crystalline modification (Sen), and converting the selenium at the surface of the electrode into its good-conducting modification (Sec).
• a blocking-layer electrode system the steps of applying a selenium electrode to a substratum, forming on the selenium electrode a blocking layer in a plurality of consecutive treatments after the selenium at the surface of the selenium electrode has been converted into its poor-conducting modification (Sen), and converting the selenium at the surface of the electrode into its good-conducting modification (Sec) the first treatment being effected at a lower temperature than the subsequent treatments.
• a blocking-layer electrode system the steps of applying a selenium electrode to a substratum, forming a-blockinglayer on the selenium electrode by applying thereto a dosed quantity of a substance which renders the surface of the selenium electrode non-conductive, the formation of the blocking layer being eflectedafte'r at least the selenium at the surface has been convertedinto its poorconducting crystalline modifications (S613), and
• a blocking-layer electrode system the steps of applying a selenium electrode to a substratum, forming a; blockinglayer on the selenium electrode by applying to the surface of the selenium electrode a dosed quantity of a substance which has an alkaline reaction and dissolves selenium, the blocking layer formation being effected after at least the selenium at the surface has been converted into its poor-conducting crystalline modification (Sen), and converting the selenium at the surface of the electrode into its good-conducting modifications (Sec).
• a. blocking-layer electrode system the steps of applying a selenium electrode to a substratum, forming a blocking layer in a plurality of treatments, the first treatment being efi'ected at a temperature of about C. after the selenium at the surface has been converted into its poor-conducting crystalline modification (Sen), and converting the selenium at the surface of the electrode into its good-conducting modification (Sec), one of the latter of said blocking-layer formation treatments being effected at a temperature of about 200 C.
• a blocking-layer selenium electrode system the steps of forming a selenium electrode on a carrier plate, placing a pressing plate upon the surface of the selenium electrode with the interposition of a uniformlydistributed layer of a liquid adapted to act upon the selenium to form a blocking layer, pressing the assembly while heating the same to a temperature of about 160 C., removing the pressin; plate, applying to the so-formed surface a 'substance in a finely-divided state and adapted to act on the selenium to form a'blockinx layer, and heating the assembly at a temperature of about 200 C.
• a blocking-layer electrode system comprising a. selenium electrode, the selenium at the surface of the electrode consisting of the goodconducting modification (Bee), and a blocking-

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Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

Country Status (6)

Cited By (2)

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• 1939
  • 1939-03-15 DE DEN43061D patent/DE742762C/de not_active Expired
• 1940
  • 1940-02-27 US US321134A patent/US2303522A/en not_active Expired - Lifetime
  • 1940-03-11 GB GB4564/40A patent/GB539491A/en not_active Expired
  • 1940-03-12 BE BE438295D patent/BE438295A/xx unknown
  • 1940-03-12 CH CH220586D patent/CH220586A/de unknown
  • 1940-03-12 FR FR864056D patent/FR864056A/fr not_active Expired

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