EP0489825A1 - Procede pour la fabrication d'un capteur d'humidite - Google Patents

Procede pour la fabrication d'un capteur d'humidite

Info

Publication number
EP0489825A1
EP0489825A1 EP19900913397 EP90913397A EP0489825A1 EP 0489825 A1 EP0489825 A1 EP 0489825A1 EP 19900913397 EP19900913397 EP 19900913397 EP 90913397 A EP90913397 A EP 90913397A EP 0489825 A1 EP0489825 A1 EP 0489825A1
Authority
EP
European Patent Office
Prior art keywords
polyimide
electrode
moisture
layer
connection
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.)
Withdrawn
Application number
EP19900913397
Other languages
German (de)
English (en)
Inventor
Helmut Mitter
Walter Scharizer
Herbert SÖLLRADL
Norbert Rossak
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.)
Lenzing AG
E&E Elektronik GmbH
Original Assignee
Lenzing AG
E&E Elektronik GmbH
Chemiefaser Lenzing AG
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
Application filed by Lenzing AG, E&E Elektronik GmbH, Chemiefaser Lenzing AG filed Critical Lenzing AG
Publication of EP0489825A1 publication Critical patent/EP0489825A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
    • G01N27/121—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid for determining moisture content, e.g. humidity, of the fluid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M3/00—Investigating fluid-tightness of structures
    • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
    • G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
    • G01M3/042—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point by using materials which expand, contract, disintegrate, or decompose in contact with a fluid
    • G01M3/045—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point by using materials which expand, contract, disintegrate, or decompose in contact with a fluid with electrical detection means

Definitions

  • the invention relates to a method for producing a moisture sensor, in particular a capacitive moisture sensor with a polyimide as the moisture-sensitive layer.
  • Humidity sensors with metal and semiconductor oxides and various polymers are known in various designs and are used in industry.
  • the oxidic materials are mainly used in the form of thin-film moisture sensors and mostly work resistively, i.e. they change their electrical resistance depending on the humidity.
  • polymer foils are mostly used, which generally have high sensitivity, but only low long-term stability.
  • Capacitive moisture sensors that have a polyimide as a moisture-sensitive layer can already be found in DE-OS 3,339,276, DE-OS 2,848,034, US Pat. No. 4,345,301 and US Pat. No. 4,761,710.
  • the polyimide is either applied as a polyimide precursor (precursor) and subsequently imidized, or in the present case already glued to a carrier material or coated with electrode material.
  • a prefabricated polyimide film is used, films of completely the same thickness having to be used in particular for the production of capacitive sensors and care being taken to ensure that the film is not scratched during processing, is kinked or broken.
  • DE-OS 3 339 276 has previously proposed to anodize a tantalum base electrode in order to prevent ohmic conduction of the sensor.
  • a series capacitance is formed with tantalum oxide as the dielectric, which limits the sensitivity of the sensor.
  • DE-OS 22 39 359 shows a circuit arrangement which has a stray field capacitor with three electrodes arranged next to one another, of which the middle one acts as a shielding electrode, another is connected to a signal transmitter and the third is connected to a receiver in an electrically conductive manner.
  • the structure in circuitry has a stray field capacitor with three electrodes arranged next to one another, of which the middle one acts as a shielding electrode, another is connected to a signal transmitter and the third is connected to a receiver in an electrically conductive manner.
  • the dielectric only having to lie between the electrodes and that
  • Dielectric not from a moisture-impermeable layer for example a moisture-impermeable layer
  • Electrode that may be shielded.
  • resistive Moisture sensors based on polyimide must be introduced with a suitable additive which increases the conductivity in view of the insulating properties of the polyimide.
  • resistive moisture sensors there is naturally only a much smaller risk of a short circuit between the electrodes, and the lowest possible homogeneous and uniform layer thickness is of primary interest here in view of the increased sensitivity.
  • the invention now aims to provide a method for producing a moisture sensor of the type mentioned at the outset, in particular a capacitive moisture sensor, with which a homogeneous, dense, particularly thin moisture-sensitive layer can be achieved in a particularly simple manner, so that a improved response and a higher sensitivity can be achieved and no damage occurs even after condensation of the sensor.
  • the method according to the invention essentially consists in applying the polyimide, in a completely imidized state, dissolved in a polar solvent to an insulating carrier material having at least one connection or base electrode, after which the solvent is removed. Glass, ceramics, oxidized silicon wafers or the like can be used as the insulating carrier material.
  • any layer thicknesses can be achieved with complete homogeneity, since during the subsequent removal, in particular evaporation, of the solvent, no chemical reaction takes place in the coating and thereby the risk of hole formation is avoided.
  • a high degree of homogeneity and density with consistently thin layers can be ensured from polyimide.
  • the base electrode can subsequently be finished together with a cover electrode together with the polyimide as a dielectric to form a capacitor, it being possible for a connection electrode to already be structured on the carrier material, which is subsequently contacted with the cover electrode .
  • a connection electrode in principle two connection electrodes on the carrier material are sufficient which, together with the polyimide connecting the connection electrodes as a thin coating, result in a resistance which varies as a function of the moisture, if the polyimide has previously been added with an additive which increases the conductivity was equipped.
  • the base electrode can usually be applied by vapor deposition or sputtering and structured photolithographically, and the connection electrode for the cover electrode required in the case of a capacitive moisture sensor can be produced in the same operation.
  • a moisture-permeable cover electrode is advantageously applied for the production of capacitive humidity sensors, the contacting of the cover electrode with a connection electrode which may have been previously made on the carrier material can be carried out in a particularly simple manner such that the polyimide layer over the connection surface of the base electrode and the Connection electrode is removed mechanically or by plasma etching or by laser, whereupon the cover electrode is electrically connected to the connection electrode and forms a capacitor with the base electrode with the polymer as a dielectric.
  • the moisture-permeable cover electrode can be applied in a technically particularly simple manner by vapor deposition or sputtering over the polymer and the connecting electrode, wherein the moisture-permeable cover electrode can consist of chrome or gold and if, for example, it can be structured photolithographically.
  • a structurally particularly simple structuring consists, for example, in the formation of a comb or lattice structure, the electrode material naturally being able to be applied in such a way that it is already very porous or cracked during manufacture, in particular in an island structure, and in this way a corresponding one Moisture exchange between the ambient air and the polyimide guaranteed.
  • a prerequisite for carrying out the method according to the invention is a polyimide which can be completely dissolved in a polar solvent in order to be able to produce a completely homogeneous, pinhole-free, very thin polyimide layer.
  • Such thin polyimide layers which are produced by applying the polyimide from the solution, do not have any kinks, cracks or holes even after drying.
  • Dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone or sulfolane can advantageously be used as the polar solvent in the context of the present invention, it being possible to ensure complete dissolution in such a polar solvent if a copolymer of 3,3 ', 4,4'-benzophenonetetracarboxylic acid dianhydride and '60 to 100 mol% toluenediamine (2,4- and / or 2,6-isomer) or toluenediisocyanate (2,4- and / or 2,6-isomer) and 0 to 40% mol.% 4,4-methylenebis (phenylamine) or 4,4'-methylenebis (phenyl isocyanate) and in particular a linear polyimide with a weight average of 30,000 to 300,000 units and a number average of 10,000 to 60,000 is used.
  • Such a linear polyimide can be applied from the solution by dipping, spraying or spinning and in this way it is ensured that the applied layer is uniformly thick and pinhole-free over the entire surface, the layers being significant compared to conventional polyimide films lesser thickness can be applied what is particularly important with regard to the response speed.
  • organofunctional silanes are easy to process and show a great affinity for commonly used carrier materials such as glass, ceramics, metal or the like, as well as for the linear soluble polyimides used for the production of the moisture-sensitive layer. Due to the good solubility of such organofunctional silanes, both in aqueous and non-aqueous solvents, extremely thin layers of the adhesion promoter can be applied to the carrier material, in particular by dipping, spraying or spinning, so that the overall thickness of the sensor is only uneven by the adhesion promoter is significantly enlarged.
  • Complete removal of the polar solvents is achieved in a simple manner by drying the polyimide at temperatures from 80 to 330 ° C., preferably drying in three stages, the temperature in each of the three stages being higher than that previously prevailing temperature is increased by 80 ° C to 100 ° C.
  • a thin, homogeneous polyimide layer is ensured on the carrier or the carrier pretreated with an adhesive, the preferred drying in stages ensuring that the polyimide is dried uniformly over the entire surface and depth of the component.
  • any traces of water and gas that may still be present are removed from the polymer solution, so that, in the subsequent temperature increases, the homogeneity of the polymer layer is not destroyed by vapor or gas bubbles enclosed in the curing material becomes.
  • the solvent is finally removed. In this way, the end product is a uniformly hard polyimide layer of particularly low layer thickness, which has no tendency to become brittle.
  • FIG. 1 shows a top view of a moisture sensor according to the invention and FIG. 2 shows a section along the line II-II of FIG.
  • 1 denotes an insulating carrier which can be used, for example, made of glass, ceramic or as an oxidized silicon wafer.
  • a base electrode 2 is applied to this carrier 1, for example by vapor deposition or sputtering, and structured photolithographically. Simultaneously with the base electrode 2, a connection electrode 3 for the cover electrode 5 is produced.
  • the solution of a polyimide or copolyimide that is still soluble in polar solvents in the fully identified state is applied to the cleaned and dried surface of the substrate provided with electrodes, optionally treated with an adhesion promoter, and then dried.
  • the thin polymer layer 4 is then removed over the connection surfaces of the electrode and the connection electrode either mechanically or by plasma etching or by means of a laser and a moisture-permeable cover electrode 5 is applied over the polymer and the connection electrode by vapor deposition or sputtering.
  • polyimide layer 4 a linear copolymer of 3,3 ', 4,4'-benzophenonetetracarboxylic acid dianhydride and 60 to 100 mol% toluenediamine (2,4- and / or 2,6-isomer) or tolylene diisocyanate (2,4- and / or 2,6-isomer) and 0 to 40% mol.% 4,4'-methylene bis (phenylamine) or 4,4'-methylene bis (phenyl isocyanate) in a strongly polar solvent such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide , N-methylpyrrolidone or sulfolane.
  • a strongly polar solvent such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide , N-methylpyrrolidone or sulfolane.
  • the polyimide was dried at temperatures from 80 to 330 ° C. with increasing drying, drying in three stages and in each of the three stages the temperature was increased by 80 to 100 ° C. in each case compared to the prevailing temperature.
  • the linear polyimide was applied from the solution by dipping, spraying or spinning. In principle, the processing of the linear statistical copolyimide for the production of the polyimide layer 4 is possible directly from the solution obtained in the polycondensation. Likewise, the polyimide be precipitated, dried and stored beforehand and a suitable solution can only be prepared if required.
  • the use of the copolymer mentioned has resulted in particularly good sensitivity and improved response behavior compared to conventional capacitive moisture sensors produced with polyimide films.

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  • General Physics & Mathematics (AREA)
  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

Dans le procédé de fabrication d'un capteur d'humidité, en particulier d'un capteur d'humidité capacitif avec un polyimide comme couche sensible à l'humidité (4), le polyimide (4), dissous dans un solvant polaire en étant complètement imidisé, est épandu sur un substrat isolant, présentant au moins une électrode de connexion ou de base (2, 3), à la suite de quoi le solvant est éliminé. De préférence on utilise pour des capteurs d'humidité capacitifs une électrode de recouvrement (5) laissant passer l'humidité.
EP19900913397 1989-08-29 1990-08-29 Procede pour la fabrication d'un capteur d'humidite Withdrawn EP0489825A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT2033/89 1989-08-29
AT203389 1989-08-29

Publications (1)

Publication Number Publication Date
EP0489825A1 true EP0489825A1 (fr) 1992-06-17

Family

ID=3526360

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900913397 Withdrawn EP0489825A1 (fr) 1989-08-29 1990-08-29 Procede pour la fabrication d'un capteur d'humidite

Country Status (4)

Country Link
EP (1) EP0489825A1 (fr)
JP (1) JPH05505234A (fr)
FI (1) FI920916A0 (fr)
WO (1) WO1991003735A1 (fr)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5408381A (en) * 1994-04-28 1995-04-18 Johnson Service Company Capacitance humidity sensor
US5751071A (en) * 1996-03-29 1998-05-12 Netzer; Yishay Window capacitive moisture sensor
AT3238U1 (de) * 1998-02-11 1999-11-25 E & E Elektronik Gmbh Bauelement zur gaskonzentrationsmessung
EP1138804A3 (fr) * 2000-03-27 2003-06-25 Infineon Technologies AG Composant avec au moins deux couches protectrices contigues et son procédé de fabrication
JP2002243689A (ja) * 2001-02-15 2002-08-28 Denso Corp 容量式湿度センサおよびその製造方法
SE0102426D0 (sv) 2001-07-06 2001-07-06 Bioett Ab Fuktsensor
DE102006053689A1 (de) * 2006-11-13 2008-05-15 Vishay Bccomponents Beyschlag Gmbh Sensoranordnung

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2848034A1 (de) * 1978-11-06 1980-05-14 Siemens Ag Kapazitiver feuchtefuehler
DE3339276A1 (de) * 1983-10-28 1985-05-09 Endress U. Hauser Gmbh U. Co, 7867 Maulburg Kapazitiver feuchtefuehler und verfahren zu seiner herstellung
JPS60168044A (ja) * 1984-02-10 1985-08-31 Sharp Corp 感湿素子
US4603372A (en) * 1984-11-05 1986-07-29 Direction De La Meteorologie Du Ministere Des Transports Method of fabricating a temperature or humidity sensor of the thin film type, and sensors obtained thereby
US4761710A (en) * 1987-06-23 1988-08-02 Industrial Technology Research Institute Polyimide capacitive humidity sensing element

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9103735A1 *

Also Published As

Publication number Publication date
WO1991003735A1 (fr) 1991-03-21
JPH05505234A (ja) 1993-08-05
FI920916A0 (fi) 1992-02-28

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