CH205653A

CH205653A - Process for manufacturing voltage sensitive resistors.

Info

Publication number: CH205653A
Authority: CH
Inventors: Cie Aktiengesellschaft Boveri
Original assignee: Bbc Brown Boveri & Cie
Priority date: 1936-10-17
Filing date: 1937-09-18
Publication date: 1939-06-30

Description

  

  Verfahren zur Herstellung     spaunungsempfindlicher    Widerstände.         Die    vorliegende Erfindung bezieht sieh  auf     sogenannte        spannungsempfindlielleWider-          stände,    das heisst solche Leiter, deren     elek-          trieclier    Widerstand bei erhöhtem     elek-          trIschem        Spannungsabfall    mehr oder weniger  schnell herabgesetzt wird, weshalb die  Stromstärke mehr als proportional mit dem  Spannungsabfall wächst.

   Solche Widerstände       ssin-d    in letzter     Z & it    unter anderem als     Über-          spannungesicherungen        (Gewitterss,ellutz)    bei  elektrischen Anlagen weitgehend verwendet  worden, wobei eine Anzahl     spannungsemp-          findlieher        Widerstandsblöcke        aewöhnlich,

      mit  Funkenstrecke und     Schmelzsieherungen    oder  mechanischen     Aussehaltvorrichtungen    in  Reihe geschaltet     wer-den.    Auch bei ver  schiedenen andern Regulier- und     Schaltein-          riehtungen    sind solche spannungsempfind  liche Widerstände von Bedeutung.  



  Es ist schon bekannt,     Widerstandsblöcke     dieser Art aus körnigen     Halbleitern,    bei  spielsweise     Siliziumkarbid    oder Kohle (Gra  phit) anzufertigen, die durch ein Binde  mittel zusammengehalten werden.

      Beider     Anfertigung,der    Blöcke wird das  Körnermaterial in eine geeignete Form nach  Zusatz eines Bindemittels     gepresst,    wonach  man dasselbe eventuell durch Trocknen oder  Brennen erhärten     lässt.    Es hat sieh dabei  herausgestellt,     dass    es erhebliche Schwierig  keiten bietet, ein Bindemittel zu erzeugen,  das dem     Widerstandsblojck        zufriedenstellende     sowohl     merhanistlie        als    elektrische     Eigen-          echaften    gibt.

   Einerseits     muss        nämlieh    der  Widerstandskörper genügende     mechanieehe     Druckfestigkeit erhalten, anderseits darf     das     Bindemittel nach dem Trocknen oder Bren  nen die     Ilalbleiterkörner    nicht voneinander  isolieren.  



  Eingehende Versuche haben gezeigt,     dass     der     Widerstandder    Halbleiterkörner an sich  mit der Spannung nicht wechselt, sondern       dass    die Spannungsempfindlichkeit ihren  Ursprung in den Kontaktpunkten zwischen  angrenzenden. Halbleiterkörnern     bezw.    den  Mikroabständen zwischen denselben hat. Es  ist deshalb von grösster Wichtigkeit,     dass     die Bindung     zwisehen,den    Halbleiterkörnern    
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            selndem    Gehalt an kolloidalem     Zirkonoxyd,          EisenoxyJ        uGw.)    verwendet werden.  



  Es     leueUtet    ein,     dass    auch Mischungen  der betreffenden Stoffe verwendet werden  können. Hauptsache ist,     dass    solche Kombi  nationen vorliegen,     dass    ein Metallsalz einer       Sauerstoffslure    eines Elementes der fünften  Gruppe     des    periodischen Systems, beispiels  weise     Pho#spliat    oder     Arsenat    der genannten  Metalle, bei der Erhitzung gebildet wird.

   Die  sauren     Erdalkaliphosphate    und     Ammonium-          phosphate        bezw.    die analogen Arsenverbin  dungen werden bei der Reaktion unter<B>Ab-</B>  gabe von Wasser     bezw.    Ammoniak zerlegt,  wobei Phosphorsäure     bezw.    Arsensäure ent  bunden wird, die mit den übrigen Bestand  teilen reagiert.  



  Es hat sieh herausgestellt,     dass    im all  gemeinen<B>0,5</B> bis<B>5</B>     GewieUtsteile,der    sauren  Verbindung und 2 bis 20 Teile der Metall  oxyde     bezw.        Oxydhydrate    genügen, um<B>100</B>  Teile körnigen Halbleitermaterials zu binden.  



  Gute Resultate wurden zum Beispiel  durch Zugabe von<B>5</B> bis<B>10</B> Gewichtsteilen       Aluminiumoxyd'hydrat    (wie Bauxit oder       Laterit)        bezw.    Chromoxyd (Chromgrün) oder  gefälltem     Zirkonoxyd    nebst<B>5</B> bis<B>10</B>     Ge-          wielltsteilen    einer aus<B>1</B> Raumteil     konz.          Phosplior,säure        (spez.        Gew.#1,70)

      und 2 Raum  teilen Wasser bereiteten Lösung zu<B>100</B>     Ge-          wielitsteilen        körnigen        Siliziumkarbids,    sowie  Pressen, Trocknen und Erhitzen der Mischung  auf<B>500</B> bis<B>1100'C</B> erzielt.  



  Bei Verwendung von     Laterit    (das heisst  einem     "Bauxit"    mit hohem Gehalt     an    gebun  denem Wasser, etwa<B>25</B>     biss   <B>35 %)</B> in Verbin  dung mit Phosphorsäure wird der Vorzug  erzielt,     dass    die Bildung von     Aluminiumplios-          phat    schon bei etwa<B>100'</B> eintritt, und     dass     die     gepressten    Körper aus diesem Grunde  gute Druckfestigkeit; schon bei der genannten  Temperatur erhalten. Durch Erhitzen auf  höhere Temperaturen können die elektrischen  Eigenschaften des     Mateilials    abgeändert wer  den.



  Process for manufacturing resistors sensitive to sparks. The present invention relates to so-called voltage-sensitive resistors, that is to say those conductors whose electrical resistance is reduced more or less quickly with an increased electrical voltage drop, which is why the current strength increases more than proportionally with the voltage drop.

   Such resistors ssin-d have recently been used extensively as overvoltage protection (thunderstorms, ellutz) in electrical systems, whereby a number of voltage-sensitive resistor blocks are common,

      connected in series with spark gaps and fusible links or mechanical shut-off devices. Such voltage-sensitive resistors are also important for various other regulating and switching devices.



  It is already known to make resistor blocks of this type from granular semiconductors, for example silicon carbide or carbon (Gra phite), which are held together by a binding agent.

      When making the blocks, the granular material is pressed into a suitable shape after adding a binding agent, after which it is allowed to harden by drying or firing. It has been found that there are considerable difficulties in producing a binder which gives the resistor block satisfactory merhanistic and electrical properties.

   On the one hand, the resistance body must have sufficient mechanical compressive strength; on the other hand, the binder must not isolate the semiconductor grains from one another after drying or firing.



  Extensive tests have shown that the resistance of the semiconductor grains per se does not change with the voltage, but that the voltage sensitivity has its origin in the contact points between adjacent ones. Semiconductor grains respectively. has the micro-gaps between them. It is therefore of the greatest importance that the bond between the semiconductor grains
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            because of the content of colloidal zirconium oxide, iron oxide, etc.).



  It implies that mixtures of the substances in question can also be used. The main thing is that there are combinations such that a metal salt of an oxyacid of an element of the fifth group of the periodic table, for example phosphate or arsenate of the metals mentioned, is formed on heating.

   The acidic alkaline earth phosphates and ammonium phosphates respectively. the analog arsenic compounds are resp. during the reaction with <B> release </B> release of water. Ammonia decomposed, with phosphoric acid BEZW. Arsenic acid is released, which reacts with the other components.



  It has been shown that in general <B> 0.5 </B> to <B> 5 </B> weight parts, the acidic compound and 2 to 20 parts of the metal oxides or. Oxide hydrates are sufficient to bind <B> 100 </B> parts of granular semiconductor material.



  Good results were achieved, for example, by adding <B> 5 </B> to <B> 10 </B> parts by weight of aluminum oxide hydrate (such as bauxite or laterite) or. Chromium oxide (chrome green) or precipitated zirconium oxide together with <B> 5 </B> to <B> 10 </B> corrugated parts one of <B> 1 </B> conc. Phosphorus acid (spec. Weight # 1.70)

      and 2 rooms share water prepared solution to <B> 100 </B> by weight of granular silicon carbide, as well as pressing, drying and heating the mixture to <B> 500 </B> to <B> 1100'C </B> achieved.



  When using laterite (that is, a "bauxite" with a high content of bound water, about <B> 25 </B> to <B> 35%) </B> in conjunction with phosphoric acid, the advantage is achieved that the formation of aluminum phosphate already occurs at about <B> 100 '</B>, and that the pressed bodies have good compressive strength for this reason; obtained at the temperature mentioned. The electrical properties of the material can be changed by heating to higher temperatures.

Claims

PATENT CLAIM I: Process for producing voltage-sensitive resistors from granular, carbon-containing semiconductors, characterized in that the granular material is mixed with an acidic compound of an element of the fifth group of the periodic system and at least one metal oxide , and that this mixture is then pressed into a mold and heated, whereby a metal salt of an oxygen acid, which connects the grain material, is formed as an element of the fifth group of the periodic table.

SUBClaims: 1. Method according to patent claim. I, characterized in that an acidic compound of phosphorus is used. 2. Method according to claim. I, as characterized in that an acidic compound of arsenic is used. 3. Method according to patent claim I, Yes, characterized in that aluminum oxide is used as the metal oxide. 4. The method according to claim I, characterized in that iron oxide is used as the metal oxide.

5. Method according to patent claim I, characterized in that chromium oxide is used as the metal oxide. 6. Method according to patent claim I, characterized in that the metal oxide is zirconium oxide. is used. 7. Process according to Patenfansprucli I, characterized in that aluminum oxide and iron oxide are used as metal oxides. 8. Method according to patent claims I, characterized in that the metal oxides are aluminum oxide and zirconium oxide. be used.

9. Method according to claim I, characterized in that aluminum oxide and chromium oxide are used as metal oxides. 10. Method according to patent claim I, since through. marked that iron oxide and chromium oxide are used as metal oxides. 11. Process according to Patentaliepi-ne, h 1, indicated that iron oxide and zirconium oxide are used as metal oxide.

1-2. Method according to patent claim 1, characterized in that chromium oxide and zirconium oxide are used as metal oxides. 13. Method according to claim 3, characterized by that bauxite is used as the aluminum oxide. 14. The method according to dependent claim 3. characterized in that laterite is used as aluminum oxide.

15. Method according to claim 1 as characterized in that the granular semiconductor material is silicon carbide. 16. Method according to patent claim I, characterized in that the granular semiconductor material is graphite.

17. Method according to claim 1, as characterized by that on 100 like-lit parts of the granular semiconductor material 0, 5 to 5 parts of the acidic compound and 2 to 20 parts come from Mütalloxyd.

18. Method according to Unfer claim 17 as characterized in that on 100 molded parts of the granular semiconductor material 5 Up to 10 parts of metal oxide and 5 to 10 parts of a solution "come from 1 part of the volume of phosphoric acid from the specific Wants 1.70 and 1 to 3 to share space) Vasser exists.

PATENT CLAIM II: After your method according to patent claim 1 inherited, voltage sensitive resistor, characterized in that it consists of a granular, carbon-containing semiconductor and the grains connect the metal salt Oxygen acid is an element of the fifth group of the periodic system.