US2358211A - Method of forming resistors and the like - Google Patents

Method of forming resistors and the like Download PDF

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Publication number
US2358211A
US2358211A US462944A US46294442A US2358211A US 2358211 A US2358211 A US 2358211A US 462944 A US462944 A US 462944A US 46294442 A US46294442 A US 46294442A US 2358211 A US2358211 A US 2358211A
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US
United States
Prior art keywords
methacrylate
granules
resistors
mixture
solvent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US462944A
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English (en)
Inventor
Carl J Christensen
Christensen Howard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
Original Assignee
Bell Telephone Laboratories Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to NL91385D priority Critical patent/NL91385C/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US462944A priority patent/US2358211A/en
Application granted granted Critical
Publication of US2358211A publication Critical patent/US2358211A/en
Priority to CH267201D priority patent/CH267201A/fr
Priority to GB19262/47A priority patent/GB640465A/en
Priority to FR979047D priority patent/FR979047A/fr
Priority to BE475547D priority patent/BE475547A/xx
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B33/00—Clay-wares
    • C04B33/02—Preparing or treating the raw materials individually or as batches
    • C04B33/13—Compounding ingredients
    • C04B33/1315—Non-ceramic binders
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B33/00—Clay-wares
    • C04B33/02—Preparing or treating the raw materials individually or as batches
    • C04B33/13—Compounding ingredients
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
    • H01B1/08—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances oxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
    • H01B3/447—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from acrylic compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
    • H01C17/06—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base
    • H01C17/065—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base by thick film techniques, e.g. serigraphy
    • H01C17/06506—Precursor compositions therefor, e.g. pastes, inks, glass frits
    • H01C17/06573—Precursor compositions therefor, e.g. pastes, inks, glass frits characterised by the permanent binder
    • H01C17/06586—Precursor compositions therefor, e.g. pastes, inks, glass frits characterised by the permanent binder composed of organic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
    • H01C17/30—Apparatus or processes specially adapted for manufacturing resistors adapted for baking
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/001—Mass resistors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/04—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having negative temperature coefficient
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/04—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having negative temperature coefficient
    • H01C7/042—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having negative temperature coefficient mainly consisting of inorganic non-metallic substances
    • H01C7/043—Oxides or oxidic compounds

Definitions

  • This invention relates to methods of making formed bodies such as resistors, insulators, and the like from finely divided materials. More particularly, the invention involves the use of a temporary binder for holding the fine particles of material together during the preliminary stages
  • the temporary binders of this invention and the method of using them are particularly applicable to materials comprising those metal-oxygen compounds which are useful in the making of resistors with negative temperature coefiicients of resistivity.
  • a temporary binder for use in making resistors and particularly resistors, the resistance characteristics of which are relatively critical, should have certain characteristics which will be herein set forth.
  • the temporary binder when mixed with a material to be formed into a body, should impart to the mixture sufiicient cohesion to assure reasonable handleability of the formed bodies prior to heat treatment.
  • the temporary binder should not cause the mixture to adhere to forming apparatus.
  • the temporary binder should render the mixture sufilciently plastic so that it will flow readily into all corners, to completely fill dies or molds; or to allow it to be rolled or extruded properly.
  • the basic material plus the temporary binder should be of such consistency that it may be machine fed in uniform quantities to dies and the like.
  • the temporary binder should be of such nature that only a relatively small amount is needed to impart the desired characteristics to the mixture, e. g., less than about 10 per cent.
  • the temporary binder should leave the formed body during drying or firing without deforming the body or causing it to adhere to adjacent bodies.
  • the temporary binder should leave no residue in the body. This characteristic is particularly necessary for resistor bodies of themetalthe die, mold, roll, or other content of the conducting oxides when the latter are sintered at an elevated temperature.
  • a feature of this invention is a. temporary binder comprising a polymeric ester of methacrylic acid.
  • Another feature of this invention resides in the controlled heating of the formed bodies to remove the temporary binder prior to sintering, without damage to the bodies.
  • Figs. 1 to 5, inclusive show several forms of resistor devices, the resistance elements of which may be made by means of the process of this invention.
  • Fig. 1 is a disc resistor
  • Fig. 2 a pellet or short cylinder
  • Fig. 3 a rod or stick resistor.
  • Figs. 4 and 5 represent resistors in which the resistance element is a thin sheet of resistance material, the thickness having been exaggerated in the interest of clarity of illustration.
  • Devices such as those shown in Figs. 1 and 2 may be made by pressing the resistance material in dies. Where the required dimensions of the Fig. 2 type of device are so small that difiiculty is encountered in die pressing, they may be made by punching" out pellets from larger sheets or discs of suitable thickness or by extruding long strips of proper diameter and then cutting them up into cylinders of appropricate length.
  • the rod or stick. device of 3 may be made by extruding or mold ng. or by other suitable methods.
  • the thin ts. used in the devices of Figs. 4 and 5 may made by die pressing or by rolling.
  • thermistors i. e., resistors in which the resistance changes greatly with changes in temperature.
  • suitable thermistor materials to which the method of this invention may be applied are one or more of the metal oxides, e. g., those of manganese, nickel, cobalt and copper.
  • the particular method of making the disc resistor illustrated in Fig. 1 will serve to point out the details of the method of this invention.
  • the resistance material should be finely divided, that is, in the form of a powder. If, for ex-' ample, several of the above-mentioned oxides are to be used they should be intimately mixed before further processing.
  • the prepared resistance material is mixed into a thin paste or slurry with a polymeric ester of methacrylic acid, a plasticizer and a volatile solvent.
  • suitable methacrylic acid esters are isobutyl methacrylate, normal butyl methacrylate and methyl methacrylate.
  • the phthalates have been found to be suitable as plasticizers. One of these which has been successfully used is dimethyl phthalate.
  • suitable plasticizers are butyl phthalyl butyl glycollate, dibutyl sebacate, dibutyl adipate, triethylene glycol di-Z-ethyl butyrate, and any of a large number of waxes and softening agents. Any of a considerable number of solvents may be used.
  • a solvent which will not burn or cause an explosive mixture is preferable. Also, the solvent which is most volatile and least toxic is in general the most desirable. The danger from toxic solvents may be substantially eliminated by use of suitable ventilating means.
  • Some solvents presenting a fire hazaard but which may be used with suitable precautions are acetone, ethyl acetate, benzene, xylene and a hydrocarbon product known as Solvesso #2.
  • Two solvents presenting no fire hazard are acetylene tetrachloride and a mixtureof ethylene dichloride about '75 per cent and carbon tetrachloride about per cent.
  • the resistance material, methacrylate, plasticizer and solvent are thoroughly mixed and gently heated, if necessary, to drive off the solvent. After sumcient mixing the material takes the form of small doughy lumps or globules. Materials in this form may be spread out to allow any remaining solvent to evaporate. Then the material is reduced to granules by suitable methods, such aspressing through a screen of proper mesh. The granule size may range between 40 and 300 mesh.
  • the granular material is fed to a die and pressed at about 13,000 pounds per square inch. This may be done in automatic machinery, such as a tablet machine, since the granules will flow freely from'a hopper and may be accurately leveled with a shoe or like means. After pressing, the disc will come cleanly from the die because discs are tough enough so that they may be hanto the monomer which immediately volatilizes and passes oil. Hence the binder passes through no intermediate stage where the binder is all liquid, and thus the danger of the units sticking together is removed.
  • volatilized organic material should be continuously removed from the vicinity of the discs so that no chemical reduction of the oxides is induced to take place because or the reducing character of the orga ic p Since inany of these vapors are toxic, a suitable nieans for protecting the operator should be prov ded.
  • the discs may be stacked on a plate of suitable material, e. g., zirconium silicate, with a suitable powder between discs to prevent-their sticking together during firing.
  • suitable material e. g., zirconium silicate
  • a powder which has been found satisfactory is 120-mesh aluminum oxide.
  • the loaded plate is placed in a furnace, the temperature of which is initially below 600 C. The temperature is then raised to a proper sintering temperature for the material being processed, e. g., within the range 600 to 1450 C. for thermistors made from one or more of the oxides of manganese, nickel, cobalt and copper.
  • the following treatment may bev given:
  • the furnace temperature is raised from below 600 to 1200:25 C. in four hours, maintained at this point for twelve hours and then allowed to cool down to about 600 C. in four hours.
  • the discs are then removed from the furnace and allowed to cool to room temperature.
  • Resistors in other than disc form may be made by suitable modifications of the foregoing technique.
  • the short cylinders or pellets of Fig. 2 may be made by extrud- 40 ing long pieces and cutting them up or by makdled as much as necessary for completing the processing without danger of breakage, if reasonable care is used.
  • the binder is removed by gentle heating of the discs. This may be done by spreading them out on a suitable plate, e. g., one of aluminum oxide, and applying radiant heat from heat lamps or like devices thereto. For example, with heating, the methacrylate polymer breaks down 76 ing relatively large sheets and punching out the pellets.
  • the rods or sticks of Fig. 3 may be made by extruding or molding. Either pressing or rolling is suitable for making thin sheets of resistance material, such as are used in the resistance of Figs. 4 and 5.
  • the constituents of the temporary binder and the amount of binder used in the mixture may be varied to suit the particular method of forming to be employed.
  • terminal or contact means may be provided. Some forms which these may take are described in connection with trated shapes.
  • the disc i0, short cylinder or pellet 20, or sheet 40 of Figs. 1, 2 and 4, respectively, may-be provided on opposite faces with adherent metallic coatings H, 2
  • the stick resistor 30 of Fig. 3 may be furnished with metal caps 3
  • the resistance element of Fig. 5 comprising the sheet 50 of resistance material may be provided with rod-like or wire terminals 5
  • the method of making a resistor that comprises mixing finely divided resistance material with a polymeric ester of methacrylic acid, a plasticizer and a volatile solvent, drying the mixture to remove the solvent, reducing the mixture to granules, forming the granules into a body and heat treating the body at gradually increasing temperature up to but not higher than the lowest sintering temperature for the resistance material employed, to depolymerize the methacrylate and completely vaporize and drive off the depolymerized methacrylate and the plastlcizer, and then further heat treating the body to sinter it.
  • the method of making a resistor that comprises mixing finely divided metal oxide material with a polymeric ester of methacrylic acid, a plasticizer and a volatile solvent, drying the mixture to remove the solvent, mechanically reducing the mixture to granules, forming the granules into a, body and heat treating the body at gradually increasing temperature up to but not higher than about 600 C. to depolymerize the methacrylate and completely vaporize and drive off the depolymerized methacrylate and the plasticizer, and then further heat treating the body between 600 and 1450 C. to sinter it.
  • the method of making a resistor that comprises mixing finely divided oxides of one or more of the metals, manganese, nickel, cobalt, and copper with isobutyl methacrylate, a plasticizer and a volatile solvent, drying the mixture to remove the solvent, mechanically reducing the mixture to granules, forming the granules into a the resistance material.
  • the method of making a resistor that comprises mixing finely divided metal oxides with normal butyl methacrylate, a plasticizer and a volatile solvent, allowing the solvent to evaporate, mechanically reducing the mixture to granules, forming the granules into a body and heating the body at gradually increasing temperature up to but not higher than the lowest sintering tempera ture of the metal oxides to depolyrnerize the methacrylate and completely vaporize and drive off the depolymerized methacrylate and pies" tic'izer and then further heat treating the body to sinter it,
  • the method of making a resistor prises mixing finely divided metal oxide resistance material with methyl methacrylate, a plasticizer and a volatile solvent, allowing the solvent to evaporate, mechanically reducing the mixture to granules, forming the granules into a body and heating the body at gradually increasing temperature up to but not higher than the lowest sintering temperature tor the oxides employed to depolymerize the methacrylate a completely vaporize and drive on the depolymerized methacrylate and the plasticizer, and then heat treating the body to sinter it.
  • the method of making a resistor that comprises mixing finely divided metal oxide resistance material with a polymeric ester of methacrylie acid, a plasticizer and a volatile solvent, continuing the mixing until most of the solvent is evaporated, and the mixture is in the form of small, doughy globules, spreading the mixture in a relatively thin layer to allow the remaining solvent to evaporate, reducing the mixture to granules by pressing it through a screen, charging a die with the granules, pressing them into a disc, gradually heating the disc until it assumes a dull red color to depolymerize the methacrylate and vaporize and drive off the depolymerized methacrylate and the plasticizer and then heating at a higher temperature to sinter 8.
  • the method of making a conductive body that comprises mixing finely divided semiconductive material with a polymeric ester of methacrylic acid, a. plasticizer and a volatile solvent, allowing the solvent to evaporate, forming the mixed material into granules, forming the granules into a body, gradually heating the body to a temperature below the sintering temperature of the semiconductive material to depolymerize the methacrylate and completely vaporize and drive or! the depolymerlzed methacrylate and the plastieizer, and then heat treating the body at a temperature suilicient to sinter it.
  • the method of making a conductive body that comprises mixing finely divided, semiconductive, metal oxides with a polymeric ester of methacrylic acid, a plasticizer and a volatile solvent, allowing the solvent to evaporate, reducing the mixture to granules, forming the granules into a body, gradually heating the body to a dull red color to depolymerize the methacrylate and completely vaporize and drive of! the depolymerized methacrylate and the plasticizer, and then further heating the body to sinter it.
  • a method 01. forming finely divided metal oxide semiconductive material into a relatively self-supporting body by holding the material together with a temporary binder prior to sintering in which the binder comprises a polymeric ester of methacrylic acid, a plasticizer and a volatile solvent, the step of removing the binder without damage to the body that comprises first exposing the body to mild radiant heat and then to the heat of an oven until it assumes a dull red color, to depolymerize the methacrylate and drive oi! the depolymerized methacrylate and the plasticizer.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Ceramic Engineering (AREA)
  • Electromagnetism (AREA)
  • Organic Chemistry (AREA)
  • Structural Engineering (AREA)
  • Materials Engineering (AREA)
  • Dispersion Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Thermistors And Varistors (AREA)
  • Apparatuses And Processes For Manufacturing Resistors (AREA)
US462944A 1942-10-22 1942-10-22 Method of forming resistors and the like Expired - Lifetime US2358211A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
NL91385D NL91385C (en)) 1942-10-22
US462944A US2358211A (en) 1942-10-22 1942-10-22 Method of forming resistors and the like
CH267201D CH267201A (fr) 1942-10-22 1947-07-09 Procédé de fabrication de résistances électriques et résistance obtenue par ce procédé.
GB19262/47A GB640465A (en) 1942-10-22 1947-07-18 Methods of making electrically resistive bodies from finely divided material
FR979047D FR979047A (fr) 1942-10-22 1947-07-22 Procédé de fabrication de résistances, etc.
BE475547D BE475547A (en)) 1942-10-22 1947-08-21

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US462944A US2358211A (en) 1942-10-22 1942-10-22 Method of forming resistors and the like

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US2358211A true US2358211A (en) 1944-09-12

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US (1) US2358211A (en))
BE (1) BE475547A (en))
CH (1) CH267201A (en))
FR (1) FR979047A (en))
GB (1) GB640465A (en))
NL (1) NL91385C (en))

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2552640A (en) * 1947-07-05 1951-05-15 Bell Telephone Labor Inc Oxide resistors and method of making them
US2674583A (en) * 1949-12-23 1954-04-06 Bell Telephone Labor Inc High temperature coefficient resistors and methods of making them
US2683836A (en) * 1947-03-10 1954-07-13 Gen Electric Electric discharge device construction
US2847314A (en) * 1955-06-02 1958-08-12 Bell Telephone Labor Inc Method for making ceramic articles
US2937354A (en) * 1957-08-02 1960-05-17 Bendix Aviat Corp Thermally-sensitive resistor
US2966719A (en) * 1954-06-15 1961-01-03 American Lava Corp Manufacture of ceramics
US2988456A (en) * 1958-02-14 1961-06-13 Thompson Ramo Wooldridge Inc Slip-cast ceramic base optical mirrors
US3015633A (en) * 1957-01-23 1962-01-02 Csf Manufacture of thermistors
US3061501A (en) * 1957-01-11 1962-10-30 Servel Inc Production of electrical resistor elements
US3074104A (en) * 1957-05-24 1963-01-22 Ici Ltd Spinning apparatus
US3078550A (en) * 1959-06-25 1963-02-26 Specialties Dev Corp Method of adjusting the resistance of thermistor elements
US3345596A (en) * 1965-11-08 1967-10-03 Ibm Hygrometer and method of fabrication
FR2084703A5 (en) * 1970-03-17 1971-12-17 Lucas Industries Ltd Silicon nitride articles
US3808678A (en) * 1972-08-16 1974-05-07 Matsushita Electric Ind Co Ltd Method of making pressure-sensitive resistor element
US3967229A (en) * 1973-11-14 1976-06-29 Danfoss A/S High-duty PTC-resistor and method for its manufacture
US3981075A (en) * 1973-11-14 1976-09-21 Danfoss A/S Method of making high-duty PTC-resistor
US4086467A (en) * 1976-07-19 1978-04-25 Texas Instruments Incorporated Electronic heater for high voltage applications
US5800611A (en) * 1997-09-08 1998-09-01 Christensen; Howard Method for making large area single crystal silicon sheets

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4257904A (en) * 1974-12-30 1981-03-24 International Business Machines Corp. Dielectric glass coating composition containing polymethylmethacrylate fugative binder
US5660878A (en) * 1991-02-06 1997-08-26 Commissariat A L'energie Atomique Process for the reduction of breakdown risks of the insulant of high voltage cable and lines during their aging

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2683836A (en) * 1947-03-10 1954-07-13 Gen Electric Electric discharge device construction
US2552640A (en) * 1947-07-05 1951-05-15 Bell Telephone Labor Inc Oxide resistors and method of making them
US2674583A (en) * 1949-12-23 1954-04-06 Bell Telephone Labor Inc High temperature coefficient resistors and methods of making them
US2966719A (en) * 1954-06-15 1961-01-03 American Lava Corp Manufacture of ceramics
US2847314A (en) * 1955-06-02 1958-08-12 Bell Telephone Labor Inc Method for making ceramic articles
US3061501A (en) * 1957-01-11 1962-10-30 Servel Inc Production of electrical resistor elements
US3015633A (en) * 1957-01-23 1962-01-02 Csf Manufacture of thermistors
US3074104A (en) * 1957-05-24 1963-01-22 Ici Ltd Spinning apparatus
US2937354A (en) * 1957-08-02 1960-05-17 Bendix Aviat Corp Thermally-sensitive resistor
US2988456A (en) * 1958-02-14 1961-06-13 Thompson Ramo Wooldridge Inc Slip-cast ceramic base optical mirrors
US3078550A (en) * 1959-06-25 1963-02-26 Specialties Dev Corp Method of adjusting the resistance of thermistor elements
US3345596A (en) * 1965-11-08 1967-10-03 Ibm Hygrometer and method of fabrication
FR2084703A5 (en) * 1970-03-17 1971-12-17 Lucas Industries Ltd Silicon nitride articles
US3808678A (en) * 1972-08-16 1974-05-07 Matsushita Electric Ind Co Ltd Method of making pressure-sensitive resistor element
US3967229A (en) * 1973-11-14 1976-06-29 Danfoss A/S High-duty PTC-resistor and method for its manufacture
US3981075A (en) * 1973-11-14 1976-09-21 Danfoss A/S Method of making high-duty PTC-resistor
US4086467A (en) * 1976-07-19 1978-04-25 Texas Instruments Incorporated Electronic heater for high voltage applications
US5800611A (en) * 1997-09-08 1998-09-01 Christensen; Howard Method for making large area single crystal silicon sheets
WO1999013136A1 (en) * 1997-09-08 1999-03-18 Single Crystal Semiconductor Corporation Method for making large area single crystal silicon sheets

Also Published As

Publication number Publication date
GB640465A (en) 1950-07-19
BE475547A (en)) 1947-09-30
CH267201A (fr) 1950-03-15
NL91385C (en))
FR979047A (fr) 1951-04-20

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