US3260578A - Coated induction heating coil for zone refining apparatus - Google Patents

Coated induction heating coil for zone refining apparatus Download PDF

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Publication number
US3260578A
US3260578A US238203A US23820362A US3260578A US 3260578 A US3260578 A US 3260578A US 238203 A US238203 A US 238203A US 23820362 A US23820362 A US 23820362A US 3260578 A US3260578 A US 3260578A
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Prior art keywords
deposit
coil
grained
coarse
silver
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Expired - Lifetime
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US238203A
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English (en)
Inventor
Harry M Stevens
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Monsanto Co
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Monsanto Co
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Filing date
Publication date
Priority to BE639957D priority Critical patent/BE639957A/xx
Priority to NL300502D priority patent/NL300502A/xx
Priority to US238203A priority patent/US3260578A/en
Application filed by Monsanto Co filed Critical Monsanto Co
Priority to FR953840A priority patent/FR1374791A/fr
Priority to DEM58927A priority patent/DE1191921B/de
Priority to GB45238/63A priority patent/GB1055622A/en
Priority to LU44832D priority patent/LU44832A1/xx
Priority to US529612A priority patent/US3458408A/en
Application granted granted Critical
Publication of US3260578A publication Critical patent/US3260578A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/10—Induction heating apparatus, other than furnaces, for specific applications
    • H05B6/101—Induction heating apparatus, other than furnaces, for specific applications for local heating of metal pieces
    • H05B6/103—Induction heating apparatus, other than furnaces, for specific applications for local heating of metal pieces multiple metal pieces successively being moved close to the inductor
    • H05B6/104—Induction heating apparatus, other than furnaces, for specific applications for local heating of metal pieces multiple metal pieces successively being moved close to the inductor metal pieces being elongated like wires or bands
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/10—Electroplating with more than one layer of the same or of different metals
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/48—After-treatment of electroplated surfaces
    • C25D5/50—After-treatment of electroplated surfaces by heat-treatment
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/60—Electroplating characterised by the structure or texture of the layers
    • C25D5/615—Microstructure of the layers, e.g. mixed structure
    • C25D5/617—Crystalline layers
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B13/00—Single-crystal growth by zone-melting; Refining by zone-melting
    • C30B13/16—Heating of the molten zone
    • C30B13/20—Heating of the molten zone by induction, e.g. hot wire technique
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/22—Furnaces without an endless core
    • H05B6/30—Arrangements for remelting or zone melting
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12014—All metal or with adjacent metals having metal particles
    • Y10T428/12028—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, etc.]
    • Y10T428/12063—Nonparticulate metal component
    • Y10T428/1209—Plural particulate metal components
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12639—Adjacent, identical composition, components
    • Y10T428/12646—Group VIII or IB metal-base
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12771—Transition metal-base component
    • Y10T428/12861—Group VIII or IB metal-base component
    • Y10T428/12882—Cu-base component alternative to Ag-, Au-, or Ni-base component
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12771—Transition metal-base component
    • Y10T428/12861—Group VIII or IB metal-base component
    • Y10T428/12896—Ag-base component

Definitions

  • This invention relates to apparatus for processing semiconductor materials and more particularly relates to an improved inductive heating element for zone refining apparatus.
  • Zone refining apparatus is employed in the semiconductor industry to purify or convert to a single crystal a rod or the like of semiconductor material such as silicon.
  • the apparatus normally embodies an inductive heating element comprising a coil which is designed to surround a body of semiconductor material and to heat a small segment of the material by induced currents resulting from a flow of radio frequency (RF) current through the coil.
  • RF radio frequency
  • the condensed semiconductor material tends to flake from the heating element and to be retained largely in the vicinity of the melted segment of the body of the semiconductor material by the magnetic force field created by the RF coil.
  • the flakes originating from the heating element re-enter the body of semiconductor material being zone refined near the liquid-solid interface and provide nuclei for crystallization.
  • the crystallization nuclei provided by the flakes of material re-entering the body of semiconductor material from the heating element prevent the obtaining of the desired result and the body of semiconductor material remains a polycrystalline mass.
  • a coil with a reduced tendency to release particles or flakes of semiconductor material is provided by forming a coil of an electrically conductive base material, and thereafter disposing upon an area of the coil upon which condensation of semiconductor material normally occurs a firmly adherent coarse-grained deposit of an electrically conductive material.
  • adherence of the coarse-grained deposit to the base material is strengthened by superimposing upon the coarse-grained deposit a finegrained deposit of an electrically conductive material so that the area of contact of the grains of the first deposit with the base material is effectively increased without destroying the coarse-grained nature of the surface of the heating element.
  • a heating element in accordance with this invention can be employed with any conventional type of zone refining apparatus, but the new design of heating element is most advantageously employed in vacuum float zone refining apparatus. This is because it is in this type of apparatus that deposits of semiconductor material upon the heating element cause the greatest difiiculty. Difliculty is particularly prevalent with this type of apparatus when it is employed for zone refining silicon of the n conductivity type since with this material it is necessary, in order to minimize evaporation of the dopant, that single crystal material be produced in a minimum number of zone passes.
  • reference numeral 10 indicates a rotating, threaded support rod upon which is mounted, in threaded engagement therewith, a coil holder block 12.
  • the block 12 is prevented by any suitable means, not illustrated, from rotat ing with the support rod 10 so that upon rotation of the rod 19 the holder 12 moves upwardly or downwardly depending upon the direction of rotation of the support rod.
  • a rod of semiconductor material 14 Spaced from support rod 10 and extending generally parallel thereto is a rod of semiconductor material 14 which is to be zone refined.
  • the rod is held at one or both ends by conventional support means, not illustrated, with provision normally being made for rotation of at least one of the end support means so that at least a portion of the rod of semiconductor material 14 is rotated about its longitudinal axis during zone refining.
  • a heating element comprising a coil 16.
  • the coil 16 which is electrically insulated from the support 12, is connected to a suitable source of RF current through leads 18 and 20 and is designed to melt a thin section of the rod 14 intermediate the two ends of the rod.
  • the surfaces of the coil 16 are at least partially covered with granular metallic material so that flakes of condensed semiconductor material are only infrequently released from the surfaces of the coil.
  • a polycrystalline rod of semiconductor material is mounted in the apparatus and coil 16 is positioned near the lower extremity of the rod of semiconductor material.
  • the coil 16 is then activated by the passage of RF current therethrough and support rod 10 is slowly rotated so that a molten zone first generated at or near the lower end of the semiconductor material gradually transverses substantially its length.
  • it is customary to fuse the rod of semiconductor material at the lower extrernity to a seed crystal so that the upward movement of the zone results in the rod of polycrystalline semiconductor material being transformed into a single crystal.
  • the rod of single crystal semiconductor material is then sliced and employed in the fabrication of electronic devices.
  • a coil base used in the manufacture of a heating element for a zone refiner in accordance with this invention can correspond in configuration and construction to a conventional coil for any particular type of zone refining apparatus with which it is to be employed.
  • the base coil can suitably comprise a tubular element containing from one to ten turns in the form of a spiral or helix designed to closely surround a rod of semiconductor material.
  • At least the outer surface of the coil should be formed of a material capable of readily conducting an RF current with silver being the preferred material.
  • the base coil will be chemically uniform in cross section but if desired the base coil can have an exterior surface of a metal such as silver supported upon a different metal or material since in the conduction of RF currents the chemical nature of the surface layers of the conductor largely determines the conductivity characteristic of the conductor.
  • a metal such as silver supported upon a different metal or material since in the conduction of RF currents the chemical nature of the surface layers of the conductor largely determines the conductivity characteristic of the conductor.
  • a metal such as silver supported upon a different metal or material since in the conduction of RF currents the chemical nature of the surface layers of the conductor largely determines the conductivity characteristic of the conductor.
  • a metal such as silver supported upon a different metal or material since in the conduction of RF currents the chemical nature of the surface layers of the conductor largely determines the conductivity characteristic of the conductor.
  • silver In place of silver one can employ any material which is a satisfactory RF conductor and which does not result in un desirable contamination of the
  • the coarse-grained deposit which is placed upon the base coil in accordance with this invention can be of the same or different material as that of the base, but preferably comprises a metal which is capable of readily conducting RF currents since accepted theory is that RF currents are conducted largely in the surface layers of a conductor. Further, the deposit is preferably one that will not result in the vaporization of impurities which objectionably contaminate the semiconductor material being zone refined. Because of these considerations, the preferred material for forming the coarse-grained deposit in most instances is elemental silver, with examples of other suitable metals being gold and copper.
  • the coarsegrained deposit can be made by any suitable technique with the two preferred techniques comprising electroplating and flame spraying. For small scale production, electroplating is usually most convenient.
  • the mean grain size of the coarse-grained deposit can vary within wide limits, but is preferably such that the deposit has an obvious grainy nature when viewed through even a low power magnifying device.
  • the coarse-grained deposit preferably has a mean grain size of from about 10 to 50 microns and should in almost all instances have a mean grain size ranging from about to 200 microns.
  • the range of grain sizes in the coarse-grained deposit is of little importance and, in fact, can in some instances be advantageously quite large since the smaller grains aid in anchoring the larger grains to the metallic substrate upon which the deposit is made. Satisfactory results can be obtained when the range of grain sizes extends from 200 microns to submicroscopic as long as the deposit has a mean grain size within the range specified above.
  • the coarse-grained deposit placed upon the metallic coil substrate in accordance with this invention can be of any desired thickness, but for most applications has a maximum thickness not appreciably greater than the maximum grain size of the deposit so that base metal is visible through the deposit. This makes it possible to more readily anchor the deposit to the substrate. This, however, is merely a matter of convenience and satisfactory results can be obtained with an extremely thick deposit if sufiicient care is exercised in anchoring it to the substrate, and if the deposit is not so thick that it necessitates undesirably wide spacing between turns of the coil to prevent shorting. In most applications, however, it is seldom advantageous for the coarse-grained deposit to have a maximum thickness greater than about 200 microns.
  • the second deposit can be generally similar in nature to the first and, similarly, can be formed of any suitable material which is readily capable of conducting an RF current. Silver is preferred with examples of other suitable materials including gold and copper.
  • the fine-grained deposit can be appied by a vaporization technique or any other suitable means, but is preferably applied by electroplating. Procedures for electroplating fine-grained dedposits upon metal substrates are well known in the art and any such well known procedure is suitable. When the fine-grained deposit is to be formed of silver, a preferred procedure for electroplating comprises the use of an aqueous solution of silver cyanide.
  • the fine-grained deposit can suitably be of almost any desired thickness provided, however, that it should not be so thick that it obscures the coarse-grained nature of the deposit upon which it is superimposed, and provided it is of suflicient thickness to accomplish the desired result of firmly anchoring the coarse-grained deposit to the underlying substrate.
  • the fine-grained deposit is preferably from about 2 to microns in thickness and has a mean grain size not in excess of about 5 to 10 microns and preferably not in excess of about 3 microns.
  • Example I In a suitable container there is placed 10 parts by weight of silver nitrate which is then dissolved in about 400 parts by volume of doubly distilled Water. A clean, sand blasted, zone refiner coil formed from a tube of pure silver is then positioned in the bath and is connected to the negative terminal of a source of direct current. An anode, preferably formed from pure silver rod stock, is then inserted into the solution and is preferably disposed such that it extends axially through the center of the coil. The silver anode is then connected through an ammeter to the positive terminal of the source of DC. Current is then passed through the solution at the rate of to 140 milliamperes for a total of 3 to 4 minutes. The coil is then rinsed in doubly distilled water with care being exercised not to dislodge the coarse-grained deposit resulting from electroplating in the silver nitrate solution.
  • a zone refiner coil having a preliminary coarse-grained silver deposit applied as above is immersed in a container containing 10 parts by weight of silver cyanide, 10 parts by weight of sodium cyanide and 10 parts by weight of potassium perchlorate and water to make to 400 parts by volume and is connected to the positive terminal of a source of DC current as above.
  • a silver anode is introduced axially of the coil and current is passed through the solution for about 3 minutes at the level of 20 to milliamperes.
  • the coil is then thoroughly rinsed in doubly distilled water and dried with acetone.
  • This second plating operation results in the coarse-grained deposit having superimposed thereupon a very fine-grained deposit so that the coarse-grained deposit becomes firmly anchored to the silver coil to the extent that it cannot readily be removed by l or 2 strokes of a soft brush.
  • the coil containing the superimposed fine-grained deposit of elemental silver as prepared above is placed in the coil holder of a Siemens vacuum zone refiner and is employed in an otherwise conventional manner for zone refining silicon. It is found that the number of rods of semiconductor material transformed into single crystal silicon by less than 4 zone passes is normally increased by over 300% as compared to the use of a silver coil having a conventional mirror smooth surface finish.
  • Example 2 A coarse-grained deposit of elemental silver is applied to a base silver zone refiner coil from silver nitrate solution as in Example 1. The coil is then washed in doubly distilled water, dried with acetone and the dried coil is then heated to a dull red heat for 2 to 10 minutes to effect anchoring of the coarse-grains of silver to the base metal. Subsequent to this sintering operation, it is found that the coarse-grained crystals are so firmly adherent that they cannot be readily removed by 1 or 2 strokes of a soft brush.
  • the sintered coil is mounted in a zone refiner apparatus as in Example 1 and is found to produce similarly desirable results.
  • the procedure for metals other than silver can be generally similar to either of the procedures specifically illustrated above except that an appropriate change is made in the chemical nature of the anode and in the salt or salts used in formulating the electroplating solution or solutions.
  • An inductive heating element for zone refining apparatus comprising a rigid coil for encircling a rod of semiconductor mate-rial in a zone refining operation, said coil being formed of a base material having disposed upon at least a portion of its external surface a firmly adherent, coarse-grained deposit of a metal which is a conductor for RF current, said coarse grained deposit having a mean grain size of from 5 to 200 microns.
  • An inductive heating element for zone refining apparatus comprising a rigid coil for encircling a rod of semiconductor material in a zone refining operation, said coil being formed of an electrically conductive metallic base material having deposited over at least a portion of its area a coarse-grained deposit of a metal which is a conductor for RF current, said coarse grained deposit having a mean grain size of from about 5 to 200 microns, and a superimposed fine-grained deposit of a metal which is a conductor for RF current, said fine grained deposit having a mean grain size of less than 5 microns.
  • a heating element according to claim 4 wherein said coarse-grained deposit comprises crystals of metallic silver.
  • An inductive heating coil for zone refining apparatus comprising a rigid coil for encircling a rod of semiconductor material in a zone refining operation, said coil being formed of a tube of metallic silver upon which is deposited a coarse-grained deposit of silver crystals and a superimposed fine-grained silver deposit, said coarse grained deposit having a mean grain size of from 5 to 200 microns and said fine grained silver deposit having a mean grain size not in excess of about 3 microns.
  • An inductive heating element for Zone refining apparatus comprising a rigid coil for encircling a rod of semiconductor material in a zone refining operation, said coil being formed of an electrically conductive metallic base material having deposited thereon a coarse grained firmly adhering deposit of a metal which is a conductor for RF current, said coarse grained deposit having a mean grain size of from 5 to 200 microns and said deposit having a maximum thickness not greater than about 200 microns.
  • a heating element as in claim 9 wherein said coarse grained deposit is of a metallic silver and has a mean grain size of from 10 to microns.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Electrochemistry (AREA)
  • Electromagnetism (AREA)
  • Physics & Mathematics (AREA)
  • Power Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • General Induction Heating (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Liquid Deposition Of Substances Of Which Semiconductor Devices Are Composed (AREA)
US238203A 1962-11-16 1962-11-16 Coated induction heating coil for zone refining apparatus Expired - Lifetime US3260578A (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
BE639957D BE639957A (enrdf_load_stackoverflow) 1962-11-16
NL300502D NL300502A (enrdf_load_stackoverflow) 1962-11-16
US238203A US3260578A (en) 1962-11-16 1962-11-16 Coated induction heating coil for zone refining apparatus
DEM58927A DE1191921B (de) 1962-11-16 1963-11-15 Induktionsheizelement fuer Zonenschmelz- bzw. -reinigungsvorrichtung sowie Verfahrenzur Herstellung desselben
FR953840A FR1374791A (fr) 1962-11-16 1963-11-15 élément de chauffage par induction pour appareil de purification par fusion par zone et procédé pour sa fabrication
GB45238/63A GB1055622A (en) 1962-11-16 1963-11-15 Zone-refining apparatus
LU44832D LU44832A1 (enrdf_load_stackoverflow) 1962-11-16 1963-11-16
US529612A US3458408A (en) 1962-11-16 1965-10-15 Method for making an inductive heating element for zone refining apparatus

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US238203A US3260578A (en) 1962-11-16 1962-11-16 Coated induction heating coil for zone refining apparatus
US52961265A 1965-10-15 1965-10-15

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US3260578A true US3260578A (en) 1966-07-12

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US238203A Expired - Lifetime US3260578A (en) 1962-11-16 1962-11-16 Coated induction heating coil for zone refining apparatus
US529612A Expired - Lifetime US3458408A (en) 1962-11-16 1965-10-15 Method for making an inductive heating element for zone refining apparatus

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Application Number Title Priority Date Filing Date
US529612A Expired - Lifetime US3458408A (en) 1962-11-16 1965-10-15 Method for making an inductive heating element for zone refining apparatus

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US (2) US3260578A (enrdf_load_stackoverflow)
BE (1) BE639957A (enrdf_load_stackoverflow)
DE (1) DE1191921B (enrdf_load_stackoverflow)
FR (1) FR1374791A (enrdf_load_stackoverflow)
GB (1) GB1055622A (enrdf_load_stackoverflow)
LU (1) LU44832A1 (enrdf_load_stackoverflow)
NL (1) NL300502A (enrdf_load_stackoverflow)

Cited By (2)

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US3783212A (en) * 1971-07-28 1974-01-01 Ite Imperial Corp Contacts for use in vacuum switch arrangements
CN110938857A (zh) * 2018-09-21 2020-03-31 深圳市鑫六福珠宝有限公司 一种模块化电镀机

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4200452A4 (en) 2020-08-18 2024-10-09 Enviro Metals, LLC METAL REFINING

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Also Published As

Publication number Publication date
GB1055622A (en) 1967-01-18
US3458408A (en) 1969-07-29
NL300502A (enrdf_load_stackoverflow)
FR1374791A (fr) 1964-10-09
LU44832A1 (enrdf_load_stackoverflow) 1964-05-16
DE1191921B (de) 1965-04-29
BE639957A (enrdf_load_stackoverflow)

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