US3717837A - Potentiometer - Google Patents

Potentiometer Download PDF

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Publication number
US3717837A
US3717837A US00096622A US3717837DA US3717837A US 3717837 A US3717837 A US 3717837A US 00096622 A US00096622 A US 00096622A US 3717837D A US3717837D A US 3717837DA US 3717837 A US3717837 A US 3717837A
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noble metal
cermet layer
layer
cermet
chromium
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US00096622A
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English (en)
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D Maclachlan
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Micro Electric AG
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Micro Electric AG
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C10/00—Adjustable resistors
    • H01C10/30—Adjustable resistors the contact sliding along resistive element
    • H01C10/308—Adjustable resistors the contact sliding along resistive element consisting of a thin film
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C10/00—Adjustable resistors

Definitions

  • PATENTfin'zmsra 837 sum ear 2 SLIDER 2O RESISTANCE FILM E3 CONCENTRATION OF NOBLE METAL, CARRIER v IN FILM FILM THICKNESS POTENTIOMETER Cross References to a Related Application This application is a continuation-in-part of U.S.
  • the present invention relates to potentiometers having cermet resistance elements, and more particularly to new and improved methods and compositions for improving potentiometer characteristics, i.e., increasing resolution and decreasing noise.
  • Potentiometers having electrical resistance elements fabricated from cermets are described, for instance, in U.S. Pat. No. 3,343,985, issued to Ronald C. Vickery, on Sept. 26, 1967.
  • vaporized cermet layers have been found to be particularly suitable for the manufacture of miniaturized potentiometers having relatively high resistance.
  • the resistance element is so small that high resistance cannot be realized by the employment of metallic resistance alloys, even when applied in the form of thin layers.
  • the cermet resistance element or layer of many prior art potentiometers is irregular and inconsistent in resistance, thereby providing poor electrical resolution and high noise. More particularly, it may happen that the contact area of the sliding wiper, when in a certain position, comes in contact with a region of the surface of the resistance element which is of relatively lowe conductivity, while the contact area of the slider, in some other position, may contact a region of the resistance element havingrelatively high conductivity. As a consequence, considerably varying contact resistance occurs at the interface between the resistance element and the wiper, thus producing the above-noted undersired irregular deviations from the characteristic resistance curve of the potentiometer, i.e., poor resolution.
  • a principal object of the present invention is to avoid the above-described deficiency of potentiometers having cermet resistance elements, and in particular to remedy these deficiencies in miniature potentiometers having cermet resistance elements, wherein these deficiencies are most aggravated.
  • FIG. 1 is a cross-sectional diagrammatic view, greatly enlarged and not to scale of a potentiometer cermet of the present invention
  • FIG. 2 is a plan view of a conventional potentiometer having cermet resistance elements
  • FIG. 3 is a sectional diagrammatic view greatly enlarged and not to scale, along the lines III-III of FIG. 2, showing the cermet resistance elements of FIG. 1 in assembly with the wiper of the potentiometer, and
  • FIG. 4 is an enlarged true microphotopicture of the cermet resistance element corresponding to the diagrammatic view of FIG. 1.
  • the cermet resistance element or layer 10 of a potentiometer 12 is infused at least in its surface region 14, with a noble metal, or a noble metal alloy 16, and thus the aforementioned problems of the prior art are obviated.
  • the effect of the infused or doped noble metal molecules or atoms may be explained by postulating that, collectively, they provide a rather large number of additional conductive bridges 18' across the interface between the contact surface of the slider 20 and the resistance element or layer. This is shown in the microphoto view of FIG. 4 exhibiting the noble metal islands 16 as white areas and the grayish to dark areas 10 as the cermet layer. These additional conductive bridges increase the statistical probability that the contact resistance between the slider and the resistance element will be low, and substantially equal, at every position of the slider.
  • the infused or doped atoms of noble metal, or noble metal alloy decrease the lateral resistance of the resistance element, but, at the same time, do not appreciably alter its longitudinal resistance.
  • the contact resistance across the interface between the slider and the resistance element is maintained substantially constant, in an efficient and economically realizable manner, and is considerably decreased when compared to untreated cermet resistance layers, which also is very desirable.
  • the total resistance of the resistance element or layer i.e., the resistance of the resistance element or layer, measured from one fixed end contact to the other, is reduced only slightly.
  • potentiometers 12 constructed in accordance with the instant invention are further characterized by extraordinarily low noise, i.e.,
  • the noble metal is introduced into the cermet resistance layer, or at least into the surface region thereof, by diffusion.
  • the cermet resistance layer is first applied to a nonconductive support and thereafter a noble metal is applied to the surface of the cermet layer, preferably in a vacuum chamber, this noble metal layer being thin as compared to the cermet layer, whereafter the noble metal coated cermet is subjected to heat treatment, causing at least substantial portions of the noble metal to diffuse to at least substantial portions of the noble metal to diffuse to at least in island areas of the surface region of the cermet layer.
  • suitable cermets are those whose base metallic component is chromium and whose ceramic-type component is at least one compound chosen from the group consisting of the siliconoxides.
  • a material chosen from the group'consisting of the chromiumsilicon compounds and alloys can advantageously be employed.
  • the metallic component of the cermet layer might also be silicon, and the ceramictype component thereof might be chromium oxide. in these representative embodiments of the present invention the surface of the cermet layer is subjected to the additional treatment of doping with atoms of a noble metal.
  • the selected noble metal is one which is nobler than silver.
  • Gold is particularly well-suited 'for this purpose, because its high corrosion resistance, and its excellent electrical conductivity, for gold is substanserving as the resistance element is present in the form of a thin layer, i.e., a layer having a thickness, at most,
  • the cermet layer is applied as shown in FIG. 1 to a glass substrate, or a ceramic substrate, preferably in the form of beryllium oxide or an aluminum oxide sinter mass.
  • a glass substrate or a ceramic substrate, preferably in the form of beryllium oxide or an aluminum oxide sinter mass.
  • These substrates are electrically insulating, and, furthermore, the beryllium oxide sinter mass has'the advantage that its heat conductivity is greater than that of aluminum.
  • the substrate is suitably maintained at an elevated temperature while the resistance layer is applied.
  • This elevated temperature may, for in stance, be up to 400C.
  • the thickness of the applied noble metal layer, as well as the temperature and duration of this heat treatment, are so selected as to eliminate the abovesaid short-circuiting effect.
  • This heat treatment is preferably carried out in vacuo, and, in the case of gold, is conducted at approximately 400 to 600 C.
  • the noble metal is distributed in a cermet layer in what is termed a diffusion gradient.
  • the most suitable amount of noble metal to be incor porated by diffusion can easily be determined by comparative tests.
  • the limit values can be defined, roughly, by considering that the amount of noble metal diffused into the layer must be sufficient to maintain the contact resistance between the path and the slider constant within at least plus or minus 10 percent, and should not exceed an amount which causes the total resistance of the resistance element to be lowered by more than percent.
  • a chromium-silicon oxide film subjected to a preliminary aging process, approximately 2000 Angstrom units thick, was provided with a gold layer approximately 100 Angstrom units thick by means of a vacuum vaporization process. The structure was then maintained under vacuum for 1 hour at The good electrical characteristics of the resistance element thus obtained are compared in the table below with the corresponding electrical characteristics of a resistance element which is identical to the resistance to theinvent ion, except that it was-not diffused .with gold.
  • a cermet layer containing noble metal not only in its surface region, but also in its interior.
  • the noble metal content in such a cermet layer suitably amounts to at least 0.1 percent byweight and at most 10 percent by weight, but
  • cermet layer containing the noble metal preferably should be 1 to 5 percent by weight.
  • Theapplication of the cermet layer containing the noble metal can be made by vaporization in vacuum from a single source to which there is fed a finely powdered mixture of all of the necessary components. Alternatively, two
  • sources are provided, one of which, for example, supplies the metallic component of the cermet composition such as chromium, having an addition of noble metal, and the other supplies the ceramic or ceramictype component, such as silicon monoxide.
  • the noble metal can be applied simultaneously with the cerrnet layer in such a manner as to provide the layer with a surface region doped with atoms of the noble metal.
  • the noble metal can be admixed with the starting material of the cerrnet layer, or with one of its components, and applied together therewith to the substrate or carrier.
  • Particularly suitable examples as starting materialsfor the application of the'cermet layer are the following compositions whose components, suitably mixed together in finely particulate form, are fed to the device for applying the layer:
  • the cerrnet layer obtained in this manner comprises conductive phases of chromium, silicon, chromium silicide, and chromium oxide (the latter having relatively high specific resistance) in combination with insulating deposits or intermediate layers containing, inter alia, silicon monoxide, silicon dioxide, and,
  • an artificial aging process can be conducted by subjecting thecermet layer to a heat treatment in order to oxidize conductive surface portions. If the process of the present invention is conducted in such a manner that the noble metal or noble metal alloy is applied to the cerrnet layer and is incorporated by diffusion at least into the surface region of the cermetlayer, it is recommended that the abovesaid aging process be carried out before the noble metal or the noble metal alloy is applied. In this manner, the resistance values become substantially stable over the entire life-time of the potentiometer.
  • the problem was a small glass plate coated with a layer of cerrnet of chrome silica oxide film. This cermet layer is by vaporization under vacuum condition coated with a layer of gold in an amount specified hereinafter. An investigation was carried out to ascertain whether or not in this process any gold diffuses into the cermet layer, and if so what extent.
  • the Method The presence of gold in a test specimen was detected by the neutron activation analysis, whereby the natural isotope of gold (Au l97) is transformed under irradiation with thermic neutrons into a radioactive nuclide of gold (Au 198) whose gamma radiation at 0.41 MeV can be used in the determination of the gold contents.
  • test specimen were placed into a single, suitable container and arranged in such a way that no transfer of gold from one test specimen to any other could occur.
  • test specimen were separated from one another inside the container by glass plates of identical diameter. into the container were further placed two samples of gold of l microgram and i0 microgram to determine the measurement standard, care being again taken that any contamination is precluded.
  • Irradiation of the container was performed in the reactor of the Federal institute for Reactor Research (Eidgenoessisches Institute fuer Reaktoraba) in Wuerenlingen, using an integrated neutron flux of approximately 5X10 neutrons.
  • This treatment created a number of radioactive gold nuclides Au 198, in proportion to the amount of natural stable gold isotope Au 197, the radioactive gold nuclides having a half-time value of 2.7 days and their gamma spectrum having its most intensive line at an energy level of 0.41 MeV.
  • test specimen After 6 days of waiting, the interfering radioactivity of the glass, which was created by the irradiation, had sufficiently faded. All the test specimen and standard specimen were then measured over a period of 4 hours Designation of test Specimen Glass plate, uncoated Glass plate, coated Weight of Gold Measurement Error (microgram) (microgram) less than 0.l less than 0.l
  • the detection limit of gold for the analysis described lay at approximately 0.1 microgram.
  • a comparison of the gamma spectra of the various test specimen showed that the evaluation of the gamma line selected for the gold analysis at 0.41 MeV was not interfered with by the gamma rays of other nuclides present in the glass or in the cermet layer, and that it was therefore usable for the calculation of the amount of gold.
  • the measurement error indicated refers exclusively to the measurement of the gamma ray intensity and is computed for a probability of 95 percent. in addition to this measurement error, the following other errors are possible:
  • the thickness of the layer, the type and mutual relationship of the cermet components, the conditions under which the layer is applied, such as the temperature of the support, and the conditions of the heat treatment, influence the magnitude of the total resistance of the resistance element, which is thus controllable.
  • Evaporation was carried on for a period of time which had been previously empirically determined to produce tracks of the desired resistance value.
  • One specimen designated as Specimen A
  • the second specimen designated Specimen B
  • the third specimen designated Specimen C
  • the fourth specimen designated Speciman D
  • the fifth specimen designated Specimen E
  • a potentiometer with a resistance element comprising:
  • cermet layer with a surface for contact with said slider
  • said cermet layer comprising a metallic component and a ceramic-type component
  • said cermet layer comprising in the region of said surface a noble metal distributed in a diffusion gradient in a concentration which is substantially higher than the concentration of noble metal in said metallic component in the remainder of said cermet layer.
  • a potentiometer according to claim 1 said cermet layer containing said noble metal in its surface region and said metallic component in its interior, in a uniform distribution.
  • a potentiometer according to claim 1 the content of said noble metal in said surface region in the cermet layer amounting to at least 0.1 percent by weight of said cerment layer to at most 10 percent by weight.
  • said cermet layer containing as the metallic component a component selected from the group consisting of chromium and chromium-silicon alloys, and as the ceramic-type component at least one compound selected from the group consisting of the silicon oxides.
  • a potentiometer according to claim 1 said cermet layer containing as the metallic component, a component selected from the group consisting of silicon and chromium-silicon compounds and, as the ceramictype component, chromium oxide.
  • a potentiometer according to claim 1 said cermet layer having the shape of a thin film.
  • a potentiometer according to claim 1 said carrier being a beryllium oxide sintered mass.
  • Apotentiometer according to claim 1 the carrier being an aluminum oxide sintered mass.
  • a potentiometer according to claim 1 the content of said noble metal in said surface region amounting to at least 1 percent by weight and at most 5 percent by weight of the total weight of said cermet layer.
  • a potentiometer with a resistive element comprising:
  • cermet layer adhering to said carrier, said cermet layer having a metallic component and a ceramictype component, said metallic component being selected from the groulp consisting of chromium and chromium silicon a oys and said ceramictype component being at least one compound selected from the group of silicon oxides,
  • said cermet layer further comprising in its contact surface region a noble metal in diffusion in an amount of 0.1% to 10% by weight, which concentration of noble metal is substantially higher than the concentration of noble metal in the remainder of said cermet layer.
  • a potentiometer with a resistive element comprising:
  • cermet layer adhering to said carrier, said cermet layer a metallic component and a ceramic-type component, said metallic component being selected from a group consisting of silicon and chromium silicon compounds and said ceramictype component being chromium oxide,
  • said cermet layer further comprising in its contact surface region a noble metal in diffusion in an amount of 0.1 to 10 percent by weight which concentration of noble metal is substantially higher than the concentration of noble metal in the remainder of said cermet layer.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Adjustable Resistors (AREA)
  • Physical Vapour Deposition (AREA)
  • Apparatuses And Processes For Manufacturing Resistors (AREA)
  • Resistance Heating (AREA)
US00096622A 1965-06-04 1970-12-09 Potentiometer Expired - Lifetime US3717837A (en)

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DEM0065490 1965-06-04
DEM0069378 1966-05-03

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US (1) US3717837A (enrdf_load_stackoverflow)
AT (1) AT276569B (enrdf_load_stackoverflow)
BE (1) BE681906A (enrdf_load_stackoverflow)
CH (1) CH466405A (enrdf_load_stackoverflow)
DE (1) DE1540167C3 (enrdf_load_stackoverflow)
DK (1) DK124642B (enrdf_load_stackoverflow)
FR (1) FR1481595A (enrdf_load_stackoverflow)
GB (1) GB1152683A (enrdf_load_stackoverflow)
NL (1) NL151201B (enrdf_load_stackoverflow)
SE (1) SE323443B (enrdf_load_stackoverflow)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4732802A (en) * 1986-09-26 1988-03-22 Bourns, Inc. Cermet resistive element for variable resistor
EP0391267A1 (de) * 1989-04-06 1990-10-10 Horst Siedle Kg Potentiometer
WO1991020088A1 (en) * 1990-06-15 1991-12-26 Bourns, Inc. Electrically conductive polymer thick film of improved wear characteristics and extended life
US5148143A (en) * 1991-04-12 1992-09-15 Beltone Electronics Corporation Precision thick film elements
US5243318A (en) * 1991-04-11 1993-09-07 Beltone Electronics Corporation Low noise precision resistor
US20020009860A1 (en) * 1996-04-18 2002-01-24 Joseph Fjelstad Methods for manufacturing resistors using a sacrificial layer
US20050064435A1 (en) * 2003-09-24 2005-03-24 Xing Su Programmable molecular barcodes
US7079005B2 (en) * 2003-12-01 2006-07-18 Cochran Gary D Mechanically buffered contact wiper

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4278725A (en) * 1980-01-21 1981-07-14 Spectrol Electronics Corp. Cermet resistor and method of making same
SE8204648D0 (sv) * 1982-08-11 1982-08-11 Andrzej Tomasz Iwanicki Rorkoppling
US5006421A (en) * 1988-09-30 1991-04-09 Siemens-Bendix Automotive Electronics, L.P. Metalization systems for heater/sensor elements

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Publication number Priority date Publication date Assignee Title
US2950995A (en) * 1957-03-18 1960-08-30 Beckman Instruments Inc Electrical resistance element
US3149002A (en) * 1957-03-18 1964-09-15 Beckman Instruments Inc Method of making electrical resistance element
US3193408A (en) * 1961-08-22 1965-07-06 David P Triller Method for producing integrated circuitry components
US3200010A (en) * 1961-12-11 1965-08-10 Beckman Instruments Inc Electrical resistance element
US3207706A (en) * 1962-09-20 1965-09-21 Du Pont Resistor compositions
US3252831A (en) * 1964-05-06 1966-05-24 Electra Mfg Company Electrical resistor and method of producing the same
US3308528A (en) * 1963-11-06 1967-03-14 Ibm Fabrication of cermet film resistors to close tolerances
US3326720A (en) * 1963-02-12 1967-06-20 Beckman Instruments Inc Cermet resistance composition and resistor
US3343985A (en) * 1963-02-12 1967-09-26 Beckman Instruments Inc Cermet electrical resistance material and method of using the same
US3353134A (en) * 1964-08-17 1967-11-14 Amphenol Corp Resistive element and variable resistor
US3479216A (en) * 1964-11-04 1969-11-18 Beckman Instruments Inc Cermet resistance element
US3573229A (en) * 1968-01-30 1971-03-30 Alloys Unlimited Inc Cermet resistor composition and method of making same

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2950995A (en) * 1957-03-18 1960-08-30 Beckman Instruments Inc Electrical resistance element
US3149002A (en) * 1957-03-18 1964-09-15 Beckman Instruments Inc Method of making electrical resistance element
US3193408A (en) * 1961-08-22 1965-07-06 David P Triller Method for producing integrated circuitry components
US3200010A (en) * 1961-12-11 1965-08-10 Beckman Instruments Inc Electrical resistance element
US3207706A (en) * 1962-09-20 1965-09-21 Du Pont Resistor compositions
US3326720A (en) * 1963-02-12 1967-06-20 Beckman Instruments Inc Cermet resistance composition and resistor
US3343985A (en) * 1963-02-12 1967-09-26 Beckman Instruments Inc Cermet electrical resistance material and method of using the same
US3308528A (en) * 1963-11-06 1967-03-14 Ibm Fabrication of cermet film resistors to close tolerances
US3252831A (en) * 1964-05-06 1966-05-24 Electra Mfg Company Electrical resistor and method of producing the same
US3353134A (en) * 1964-08-17 1967-11-14 Amphenol Corp Resistive element and variable resistor
US3479216A (en) * 1964-11-04 1969-11-18 Beckman Instruments Inc Cermet resistance element
US3573229A (en) * 1968-01-30 1971-03-30 Alloys Unlimited Inc Cermet resistor composition and method of making same

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4732802A (en) * 1986-09-26 1988-03-22 Bourns, Inc. Cermet resistive element for variable resistor
WO1988002309A1 (en) * 1986-09-26 1988-04-07 Bourns, Inc. Improved cermet resistive element for variable resistor
GB2206244A (en) * 1986-09-26 1988-12-29 Bourns Inc Improved cermet resistive element for variable resistor
GB2206244B (en) * 1986-09-26 1990-08-01 Bourns Inc Improved cermet resistive element for variable resistor
EP0391267A1 (de) * 1989-04-06 1990-10-10 Horst Siedle Kg Potentiometer
WO1991020088A1 (en) * 1990-06-15 1991-12-26 Bourns, Inc. Electrically conductive polymer thick film of improved wear characteristics and extended life
US5111178A (en) * 1990-06-15 1992-05-05 Bourns, Inc. Electrically conductive polymer thick film of improved wear characteristics and extended life
US5243318A (en) * 1991-04-11 1993-09-07 Beltone Electronics Corporation Low noise precision resistor
US5148143A (en) * 1991-04-12 1992-09-15 Beltone Electronics Corporation Precision thick film elements
US20020009860A1 (en) * 1996-04-18 2002-01-24 Joseph Fjelstad Methods for manufacturing resistors using a sacrificial layer
US20040194294A1 (en) * 1996-04-18 2004-10-07 Tessera, Inc. Methods for manufacturing resistors using a sacrificial layer
US6821821B2 (en) 1996-04-18 2004-11-23 Tessera, Inc. Methods for manufacturing resistors using a sacrificial layer
US20040233035A1 (en) * 1996-04-18 2004-11-25 Tessera, Inc. Methods for manufacturing resistors using a sacrificial layer
US6856235B2 (en) * 1996-04-18 2005-02-15 Tessera, Inc. Methods for manufacturing resistors using a sacrificial layer
US7091820B2 (en) 1996-04-18 2006-08-15 Tessera, Inc. Methods for manufacturing resistors using a sacrificial layer
US7165316B2 (en) 1996-04-18 2007-01-23 Tessera, Inc. Methods for manufacturing resistors using a sacrificial layer
US20050064435A1 (en) * 2003-09-24 2005-03-24 Xing Su Programmable molecular barcodes
US7079005B2 (en) * 2003-12-01 2006-07-18 Cochran Gary D Mechanically buffered contact wiper

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Publication number Publication date
DK124642B (da) 1972-11-06
DE1540167C3 (de) 1974-10-03
DE1540167B2 (de) 1974-03-07
BE681906A (enrdf_load_stackoverflow) 1966-11-14
AT276569B (de) 1969-11-25
NL6607657A (enrdf_load_stackoverflow) 1966-12-05
DE1665040B2 (de) 1976-02-19
SE323443B (enrdf_load_stackoverflow) 1970-05-04
DE1540167A1 (de) 1970-01-02
NL151201B (nl) 1976-10-15
GB1152683A (en) 1969-05-21
FR1481595A (fr) 1967-05-19
CH466405A (de) 1968-12-15
DE1665040A1 (de) 1970-12-17

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