US3705993A - Piezoresistive transducers and devices with semiconducting films and their manufacturing process - Google Patents

Piezoresistive transducers and devices with semiconducting films and their manufacturing process Download PDF

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Publication number
US3705993A
US3705993A US162525A US3705993DA US3705993A US 3705993 A US3705993 A US 3705993A US 162525 A US162525 A US 162525A US 3705993D A US3705993D A US 3705993DA US 3705993 A US3705993 A US 3705993A
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US
United States
Prior art keywords
substrate
strips
devices
coated
mica
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Expired - Lifetime
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US162525A
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English (en)
Inventor
Radu G Grigorovici
Andrei Gavrila Devenyi
Valer Florea
Gheorghe Korony
Carol Costachescu
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INST DE FIZICA
INST FIZICA
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INST FIZICA
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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R21/00—Variable-resistance transducers
    • H04R21/02—Microphones
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/18—Measuring force or stress, in general using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
    • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
    • G01L1/2287—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges constructional details of the strain gauges
    • G01L1/2293—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges constructional details of the strain gauges of the semi-conductor type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C10/00—Adjustable resistors
    • H01C10/10—Adjustable resistors adjustable by mechanical pressure or force
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R21/00—Variable-resistance transducers
    • 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
    • Y10T29/00—Metal working
    • Y10T29/42—Piezoelectric device making
    • 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
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/49005—Acoustic transducer

Definitions

  • a method of making a piezoresistive device in which a mica, synthetic resin or metallic substrate (the latter coated with a layer of insulating enamel) is coated with strips of colloidal-silver paste, is fired to fuse the resulting conductive strips to the substrate, is provided with a layer of vapor depositing germanium bridging the strips, is formed with wire terminals and is thereafter coated with a lacquer.
  • transducers with semiconductor films with unoriented crystallites or with preferential surface orientation whose gauge factor G is /3 or /2 of the corresponding value for single crystal devices, but whose temperature coefficient of the gauge factor and of the electric resistance is by one order of magnitude lower than that of the single crystal devices.
  • Such transducers are deposited on glass or mica, having on the latter a less satisfactory adhesion.
  • Other disadvantages reside in the cumbersome process of making the electrodes and in the insufficient stability of the terminals due to the fact that the latter are fastened on the electrodes only by means of colloidalsilver paste.
  • the process according to this invention has as its object a method of making piezoresistive transducers and devices using same by means of vacuum deposition of polycrystalline germanium films, between metallic electrodes, on different insulating or conducting substrates, as for instance mica, kaptons, steel diaphragms, etc. whereby the disadvantages mentioned above are reduced.
  • the substrate metallic electrodes either of a colloidal-silver conductive paste, or of layers of Ag, Pt, Au, Al, Ni etc.
  • the deposition of germanium is done under vacuum, preferably at a pressure p 5 10 torr, the substrate temperature being between 300 and 700 C., the deposition rate of the germanium film being less than 2000 A./ minute.
  • the terminals are fastened upon the substrate either by spot welding or by means of a colloidal-silver conductive paste, the mechanical stability being improved by gluing the terminals on the substrate with a polymer adhesive, for instance an epoxy-polymer, the operational stability being ensured by means of a heat-resistant protecting lacquer.
  • the substrate may be of any adequate insulating material, as for instance mica or kapton (the commercial name of a Teflon and Mylar based plastic which is utilized as a substrate in microelectronics) or of a conducting material, for instance plain carbon steel, or stainless steel, on which an insulating heat resistant enamel layer is applied by known technology.
  • a conducting material for instance plain carbon steel, or stainless steel, on which an insulating heat resistant enamel layer is applied by known technology.
  • FIG. 1 is a top view of a device with transducer deposited on an insulating substrate
  • FIG. 2 is a vertical section taken along line PP of the device in FIG. 1;
  • FIG. 3 is a vertical section of a device with a transducer applied on a metallic substrate with an insulating film thereon.
  • Example 1 On a transparent mica substrate 1 a thickness between 10 and 1,000 microns, previously cleaned with detergents, absolute alcohol, water and distilled water, are applied by painting two conducting electrodes 2 of colloidal-silver paste following the outline of a pattern placed under the substrate.
  • the surface of the electrodes and the distance between them are chosen in accordance with the desired electric resistance of the device, which may be between 1X 10 and 1X10 ohms.
  • the thickness of the polycrystalline germanium film must lie between 0.05 and 2 microns.
  • the thus prepared substrate is heated with the side without electrodes of colloidal-silver conductive paste resting on the surface of a copper furnace to bond the assembly.
  • the same furnace may be glued a large number of substrates.
  • Masks of aluminum foil strips of 20 microns in thickness are then applied over the inactive surface of each element, as well as over the outer halves of the electrodes.
  • a plaited filament of 0.2-0.5 mm. diameter tungsten wire is made by pressing small pieces of polycrystalline germanium into the mesh.
  • the substrates are degased at 500-600 C. for 10 to 40 minutes, in vacuum at a pressure p 5 10 (FIGS. 1 and 2) of torr. Thereafter the previously degased germanium is deposited by evaporation from the tungsten wire onto the mica substrate maintained at a temperature between 470 and 500 C., with a deposition rate less than 2,000 A./ minute to form the polycrystalline film 3.
  • silver wire terminals are fastened by gummed transparent tape 4 onto the substrate in the inactive region in such a way, that an electric contact between the electrodes and the terminals may be made by soldering with collodial-silver paste 6.
  • collodial-silver paste 6 The whole surface of mica substrate is covered on that side on which the piezoresistive element is deposited, with a protecting lacquer 7.
  • a metallic substrate 8 (FIG. 3) of carbon steel of at least 0.1 mm. thickness, degreased and etched by a detergent and sulphuric acid or hydrochloric acid, thereafter neutralized with sodium carbonate, borax and sodium nitrate and dried, a heat-resistant enamel film 9 of max. 0.4 mm. thickness is applied by pouring, simple spraying, by spraying in an electrostatic field, or by electrophoresis. After air-drying at up to 120 C., the substrate is placed in a furnace previously heated at 800- 830 C., for 3-4 minutes, in the burning in zone.
  • the surface On the side of the substrate opposite that on which the transducer is to be deposited and which may come into contact with a corroding medium, the surface may be protected either by means of a stainless steel film 10, or a heatresistant acidand alkali-proof enamel layer.
  • the thus prepared substrate is placed with its side opposite to that on which the transducer is to be deposited on a copper furnace surface to bond colloidal-silver paste strips thereto as described.
  • the electrodes 11 After the paste is dried the electrodes 11 are painted by means of a pattern with colloidal-silver paste or a paste of gold solution. Thereafter the inactive surfaces are masked with 20-microns-thick aluminum foil strips, the outer halves of the electrodes being similarly masked. On each electrode there are deposited according to requirements several transducers 12.
  • a filament is made from 0.2-0.5 mm. diameter plaited wires, in to the meshes of which are fastened by pressing small pieces of polycrystalline germanium.
  • the substrate is degased at 470-550 C. over a period of 30-60 minutes, in vacuum, at a pressure p 5 10- torr. After that, the previously degased germanium is deposited by evaporation in vacuum on the enamel-covered metallic substrate, the temperature of the substrate during the deposition being between 470 and 530 C., the deposition rate being less than 2,000 A./minute.
  • the terminals 13 out of 0.1 mm. diameter silver wire are fastened on the uncovered side of the electrodes by means of silver paste, after which the whole transducer element is covered by a heat-resistant lacquer 14.
  • Example 3 According to Example 2, a maximum 0.1 mm. thick enamel film is applied on the surfaces of steel parallelopipeds of different sizes, as for instance x 10 x 15 mm. On the enamel, employing a convenient pattern, are deposited an electrode of a gold solution by painting and thermal treatment at 700 C., during 5 minutes. The specimen thus obtained is correspondingly masked for instance by means of aluminum foil and is introduced into a small tantalum boat of adequate dimensions, with which the specimen is heated in vacuum to 350-400 C. at a pressure p 5 10- torr. On the thus-prepared support is deposited the polycrystalline Ge film, as in Example 2. Thereafter the contacts are laid and the device is covered with heat-resistant lacquer, as in Example 2.
  • the thus-obtained device can be utilized for measuring stresses, signalling limit stresses, and for other tensometrical measurements.
  • This invention offers the advantages of a gauge factor 3:1, a linear variation of dR/R with 8, as well as a' temperature coefficient of the gauge factor and of the electric resistance of say --lX10 to --5 X l0- /degree C. in each case.
  • the device also has a good time constancy, as well for R as for G; the stability of R is better than i0.2% in 24 hours at 20 C. and that of G better than :0.05% in 24 hours at 20 C.
  • better adherence is ensured between the polycrystalline film and the substrate, allowing measurements at large mechanical deformations, the maximum admissible deformation being 1 l0- the deviation from linearity at a maximum deformation 5 between 6X10- and 10 10- being beneath 0.2%.
  • the device utilizes as raw material polycrystalline germanium, which is much cheaper than the single crystals, allows the formation of well fastened terminals, which ensure a perfect electric contact and ruggedness, is protected against external agents, and ensures a more secure fastening of the transducer on the article whose deformation is to be measured in such Way, that it forms practically a single body therewith.
  • a method of making a piezoresistive mechanicalelectrical transducer comprising the steps of:
  • said substrate is selected from the group which consists of mica, kapton or enamel-coated metal, said strips are applied to said substrate at room temperature and said wires are bonded to said substrate by epoxy resin.
  • strips consist of silver, gold or platinum paste fired to bond the strips to the substrate or are constituted of silver, platinum, aluminum, gold, nickel or molybdenum film.
  • strips are formed by applying colloidal-silver conductive paste to said substrate and heating said substrate with the colloidal-silver conductive paste thereon to form the strips and simultaneously bond the same to said substrate.
  • a piezoresistive mechanical-electrical transducer comprising:
  • a substrate selected from the group which consists of mica, capton or iron coated with enamel and' baked at substantially 800 C. to 900 C. for a period of 3 to 4 minutes;
  • two spaced-apart conductive strips selected from the group which consist of silver, gold, platinum, aluminum, nickel or molybdenum on said substrate;

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Measuring Fluid Pressure (AREA)
  • Measurement Of Force In General (AREA)
US162525A 1970-07-16 1971-07-14 Piezoresistive transducers and devices with semiconducting films and their manufacturing process Expired - Lifetime US3705993A (en)

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Application Number Priority Date Filing Date Title
RO6394670 1970-07-16

Publications (1)

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US (1) US3705993A (enExample)
DE (1) DE2135455A1 (enExample)
FR (1) FR2098451B1 (enExample)
NL (1) NL7109824A (enExample)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4236832A (en) * 1977-06-29 1980-12-02 Tokyo Shibaura Denki Kabushiki Kaisha Strain insensitive integrated circuit resistor pair
US4506250A (en) * 1981-05-16 1985-03-19 Crystalate Electronics Limited Strain gauge
US5482678A (en) * 1993-05-25 1996-01-09 Rosemount Inc. Organic chemical sensor
WO2003008922A1 (de) * 2001-07-19 2003-01-30 Robert Bosch Gmbh Herstellungsverfahren für ein dünnschichtbauelement und dünnschichtbauelement
US20070023738A1 (en) * 2005-07-18 2007-02-01 Olding Timothy R Low temperature fired, lead-free thick film heating element
US20100126273A1 (en) * 2008-11-25 2010-05-27 New Jersey Institute Of Technology Flexible impact sensors and methods of making same
US11209931B2 (en) 2011-11-18 2021-12-28 Sentons Inc. Localized haptic feedback
US11262253B2 (en) * 2017-08-14 2022-03-01 Sentons Inc. Touch input detection using a piezoresistive sensor
US11327599B2 (en) 2011-04-26 2022-05-10 Sentons Inc. Identifying a contact type
US11580829B2 (en) 2017-08-14 2023-02-14 Sentons Inc. Dynamic feedback for haptics
US11829555B2 (en) 2011-11-18 2023-11-28 Sentons Inc. Controlling audio volume using touch input force

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4327350A (en) * 1979-07-17 1982-04-27 Data Instruments, Inc. Pressure transducer

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4236832A (en) * 1977-06-29 1980-12-02 Tokyo Shibaura Denki Kabushiki Kaisha Strain insensitive integrated circuit resistor pair
US4506250A (en) * 1981-05-16 1985-03-19 Crystalate Electronics Limited Strain gauge
US5482678A (en) * 1993-05-25 1996-01-09 Rosemount Inc. Organic chemical sensor
WO2003008922A1 (de) * 2001-07-19 2003-01-30 Robert Bosch Gmbh Herstellungsverfahren für ein dünnschichtbauelement und dünnschichtbauelement
US20040013894A1 (en) * 2001-07-19 2004-01-22 Volker Wingsch Thin-film component and method for producing said thin-film component
US20070023738A1 (en) * 2005-07-18 2007-02-01 Olding Timothy R Low temperature fired, lead-free thick film heating element
US7459104B2 (en) * 2005-07-18 2008-12-02 Datec Coating Corporation Low temperature fired, lead-free thick film heating element
US20100126273A1 (en) * 2008-11-25 2010-05-27 New Jersey Institute Of Technology Flexible impact sensors and methods of making same
US11907464B2 (en) 2011-04-26 2024-02-20 Sentons Inc. Identifying a contact type
US12299226B2 (en) 2011-04-26 2025-05-13 Sentons Inc. Identifying signal disturbance
US11327599B2 (en) 2011-04-26 2022-05-10 Sentons Inc. Identifying a contact type
US11209931B2 (en) 2011-11-18 2021-12-28 Sentons Inc. Localized haptic feedback
US11829555B2 (en) 2011-11-18 2023-11-28 Sentons Inc. Controlling audio volume using touch input force
US11435242B2 (en) 2017-08-14 2022-09-06 Sentons Inc. Increasing sensitivity of a sensor using an encoded signal
US11580829B2 (en) 2017-08-14 2023-02-14 Sentons Inc. Dynamic feedback for haptics
US11340124B2 (en) 2017-08-14 2022-05-24 Sentons Inc. Piezoresistive sensor for detecting a physical disturbance
US11262253B2 (en) * 2017-08-14 2022-03-01 Sentons Inc. Touch input detection using a piezoresistive sensor

Also Published As

Publication number Publication date
NL7109824A (enExample) 1972-01-18
DE2135455A1 (de) 1972-01-20
FR2098451A1 (enExample) 1972-03-10
FR2098451B1 (enExample) 1973-06-29

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