WO1991010240A1 - Process for making a wear-resistant layer - Google Patents

Process for making a wear-resistant layer Download PDF

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Publication number
WO1991010240A1
WO1991010240A1 PCT/DE1990/000873 DE9000873W WO9110240A1 WO 1991010240 A1 WO1991010240 A1 WO 1991010240A1 DE 9000873 W DE9000873 W DE 9000873W WO 9110240 A1 WO9110240 A1 WO 9110240A1
Authority
WO
WIPO (PCT)
Prior art keywords
paste
added
wear
layer
glassy carbon
Prior art date
Application number
PCT/DE1990/000873
Other languages
German (de)
French (fr)
Inventor
Siegfried Woerner
Werner Gruenwald
Kurt Schmid
Ralf Haug
Original Assignee
Robert Bosch Gmbh
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 Robert Bosch Gmbh filed Critical Robert Bosch Gmbh
Publication of WO1991010240A1 publication Critical patent/WO1991010240A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C10/00—Adjustable resistors
    • H01C10/30—Adjustable resistors the contact sliding along resistive element
    • H01C10/305—Adjustable resistors the contact sliding along resistive element consisting of a thick film
    • H01C10/306—Polymer thick film, i.e. PTF
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/24—Electrically-conducting paints
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C10/00—Adjustable resistors
    • H01C10/30—Adjustable resistors the contact sliding along resistive element
    • H01C10/305—Adjustable resistors the contact sliding along resistive element consisting of a thick film

Definitions

  • the invention relates to a method for producing an abrasion-resistant layer, in particular resistance tracks in a potentiometer, this layer being applied to a non-conductive carrier as a paste.
  • a potentiometer is a continuously adjustable electrical resistor with a sliding contact for tapping partial resistors.
  • the resistance path consists of a resistance wire wound on a ceramic body, for example, or of a resistance layer that is as abrasion-resistant as possible.
  • a paste is used according to the invention to which a mixture of graphite powder and preferably rounded glassy carbon grains is added as the conductive pigment, such wear on the grinder is substantially reduced since the grinder rolls on the rounded glassy carbon particles. Furthermore, it has been found that a very hard, low-wear layer is produced by this paste according to the invention, the web wear being reduced by a factor of about 15 in comparable continuous runs compared to commercially available pastes. At the same time, wiper wear is reduced by approximately a factor of 2.
  • the electrically conductive glass carbon grains should have a hardness of 7 to 8 so that they are not destroyed by the grinder and then in turn act as emery particles. With this hardness, the glassy carbon grains also ensure a corresponding hardness of the screen-printed plastic layer, while the comparatively soft graphite also acts as a lubricant for the slider of the potentiometer sliding over the layer surface.
  • the effect is similar to that of bearing bushes made of porous, hard sintered metal, which with a "soft" lubricating component, such as. B. plastic (Teflon) is infiltrated.
  • the pigment is dispersed in the paste, a paste as a binder and / or an organic carrier for adjusting the flow behavior (pressure properties) being added to the paste in the customary manner.
  • a phenolic resin for example, comes in as resin
  • the organic carrier can consist, for example, of a mixture of benzyl alcohol and ethyl cellulose. It is also possible to add carbon black to the paste to adjust the resistance.

Abstract

In a process for making a wear-resistant layer, especially of resistance tracks in a potentiometer, this layer is applied in paste form to a non-conductive substrate. A mixture of powdered graphite and preferably rounded glass-carbon grains is added to the paste as a conductive pigment.

Description

Verfahren zum Herstellen einer abriebfesten SchichtProcess for making an abrasion resistant layer
Stand der TechnikState of the art
Die Erfindung betrifft ein Verfahren zum Herstellen einer abriebfesten Schicht, insbesondere von Wider¬ standsbahnen in einem Potentiometer, wobei diese Schicht auf einen nichtleitenden Träger als Paste aufgebracht wird.The invention relates to a method for producing an abrasion-resistant layer, in particular resistance tracks in a potentiometer, this layer being applied to a non-conductive carrier as a paste.
Bei einem Potentiometer handelt es sich um einen stetig regelbaren elektrischen Widerstand mit einem Schleif ontakt zum Abgreifen von Teilwiderständen. Die Widεrstandsbahn besteht aus einem auf einen bei- spielsweise Keramikkörper aufgewickelten Widerstands¬ draht oder aus einer möglichst abriebfesten Wider¬ standsschicht.A potentiometer is a continuously adjustable electrical resistor with a sliding contact for tapping partial resistors. The resistance path consists of a resistance wire wound on a ceramic body, for example, or of a resistance layer that is as abrasion-resistant as possible.
Zur Herstellung dieser Widεrstandsbahn sind verschie- dεne Verfahren und Werkstoffe bekannt. In der Regel wird Graphit und Ruß verwendet. Als FeststoffSchmier¬ mittel kann ein Zusatz von isolierendem oS~ (Molyb- dänit) zu dem Graphit verwendet werden. Ferner besteht auch die Möglichkeit des Zusatzes von feinst disper- giertem Aerosil (SiO„) als Thyxotropier-Zusatz . Andererseits finden käufliche Pasten Anwendung, in welchen harte, nicht leitfähige Pigmente aus TiO_ und A1„0-, eingemischt sind.Various methods and materials are known for producing this resistance web. As a rule, graphite and carbon black are used. An addition of insulating oS ~ (molybdenite) to the graphite can be used as the solid lubricant. There is also the possibility of adding finely dispersed Aerosil (SiO „) as a thyxotropic additive. On the other hand, commercially available pastes are used, in which hard, non-conductive pigments of TiO_ and A1 “0-, are mixed.
Allen aus diesen Stoffen gebildeten Widerstandsbahnen ist jedoch gemeinsam, daß sie einem erheblichen Ver¬ schleiß unterliegen oder aber, wie bei den letzt¬ genannten keramischen Zusätzen zu einem hohen Ver¬ schleiß am Schleifer führen. Dies ist vor allem darauf zurückzuführen, daß einzelne aus der Schicht losge¬ rissene Keramikteilchen mit ihrer zerklüfteten, un¬ regelmäßigen Oberfläche wie Schmirgelteilchen wirken und den Verschleiß verstärken.However, all the resistance tracks formed from these substances have in common that they are subject to considerable wear or, as with the latter ceramic additives, lead to high wear on the grinder. This is mainly due to the fact that individual ceramic particles torn loose from the layer, with their jagged, irregular surface, act like emery particles and increase wear.
Vorteile der ErfindungAdvantages of the invention
Wird dagegen erfindungsgemäß eine Paste verwendet, der als leitfähiges Pigment eine Mischung aus Graphit¬ pulver und vorzugsweise abgerundeten Glaskohlekörnern zugesetzt ist, so ist ein derartiger Verschleiß der Schleifer wesentlich vermindert, da der Schleifer auf den abgerundeten Glaskohleteilchen abrollt. Des weiteren hat sich herausgestellt, daß durch diese erfindungsgerαäße Paste eine sehr harte, verschleißarme Schicht hergestellt wird, wobei sich der Bahnverschleiß in vergleichbaren Dauerläufen gegenüber handelsüblichen Pasten um etwa den Faktor 15 verringert. Der Schleifer¬ verschleiß reduziert sich gleichzeitig um etwa den Faktor 2.If, on the other hand, a paste is used according to the invention to which a mixture of graphite powder and preferably rounded glassy carbon grains is added as the conductive pigment, such wear on the grinder is substantially reduced since the grinder rolls on the rounded glassy carbon particles. Furthermore, it has been found that a very hard, low-wear layer is produced by this paste according to the invention, the web wear being reduced by a factor of about 15 in comparable continuous runs compared to commercially available pastes. At the same time, wiper wear is reduced by approximately a factor of 2.
Praktische Versuche haben erwiesen, daß Glaskohlekörner mit einer Korngröße von 1 bis 15 um am wirkungsvollsten sind. Ferner sollten die elektrisch leitenden Glas- kohlekδrner eine Härte von 7 bis 8 aufweisen, damit sie durch den Schleifer nicht zerstört werden und dann wiederum als Schmirgelteilchen wirken. Bei dieser Härte sorgen die Glaskohlekörner auch für eine entsprechende Härte der siebgedruckten Kunst¬ stoff-Schicht, während der vergleichsweise weiche Graphit daneben als Schmiermittel für den über die Schichtoberfläche hinweggleitenden Schleifer des Potentiometers wirkt. Die Wirkung ähnelt derjenigen von Lagerbuchsen aus porösem, hartem Sintermetall, welches mit einer "weichen" Schmierkomponente, wie z. B. Kunststoff (Teflon), infiltriert ist.Practical tests have shown that glassy carbon grains with a grain size of 1 to 15 µm are most effective. Furthermore, the electrically conductive glass carbon grains should have a hardness of 7 to 8 so that they are not destroyed by the grinder and then in turn act as emery particles. With this hardness, the glassy carbon grains also ensure a corresponding hardness of the screen-printed plastic layer, while the comparatively soft graphite also acts as a lubricant for the slider of the potentiometer sliding over the layer surface. The effect is similar to that of bearing bushes made of porous, hard sintered metal, which with a "soft" lubricating component, such as. B. plastic (Teflon) is infiltrated.
Das Pigment wird in der Paste dispergiert, wobei der Paste noch in üblicher Weise ein Harz als Binder und/oder ein organischer Träger zur Einstellung des Fließverhaltens (Druckeigenschaften) zugeseczt wird. Als Harz kommt beispielsweise ein Phenolharz inThe pigment is dispersed in the paste, a paste as a binder and / or an organic carrier for adjusting the flow behavior (pressure properties) being added to the paste in the customary manner. A phenolic resin, for example, comes in as resin
Betracht, der organische Träger kann beispielsweise aus einer Mischung von Benzylalkohol und Äthylcellulose bestehen. Ferner ist es möglich, der Paste noch zur Einstellung des Widerstandes Ruß hinzuzufügen. Consider, the organic carrier can consist, for example, of a mixture of benzyl alcohol and ethyl cellulose. It is also possible to add carbon black to the paste to adjust the resistance.

Claims

- k -Patentansprüche - k patent claims
1. Verfahren zum Herstellen einer abriebfesten Schicht, insbesondere von Widerstandsbahnen in einem Poten¬ tiometer, wobei diese Schicht auf einen nicht leitenden Träger als Paste aufgebracht wird,1. Process for producing an abrasion-resistant layer, in particular resistance tracks in a potentiometer, this layer being applied as a paste to a non-conductive carrier,
dadurch gekennzeichnet,characterized,
daß der Paste als leitfähiges Pigment eine Mischung aus Graphitpulvεr und vorzugsweise abgerundeten Glaskohlekörnern zugesetzt wird.that a paste of graphite powder and preferably rounded glassy carbon grains is added to the paste as a conductive pigment.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Glaskohlekörner mit einer Korngröße von 1 bis 40 μ zugesetzt werden.2. The method according to claim 1, characterized in that the glassy carbon grains are added with a grain size of 1 to 40 μ.
-3. Verfahren nach Anspruch 1 oder 2, dadurch gekenn¬ zeichnet, daß die elektrisch leitenden Glaskohle- körnεr eine Härte von 7 bis 8 aufweisen.-3. A method according to claim 1 or 2, characterized gekenn¬ characterized in that the electrically conductive glassy carbon grains have a hardness of 7 to 8.
4. Verfahren nach wenigstens einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß das Pigment in der Paste dispergiεrt wird.4. The method according to at least one of claims 1 to 3, characterized in that the pigment is dispersed in the paste.
5. Verfahren nach wenigstens einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß der Paste noch ein Harz als Binder zuσesetzt wird. 5. The method according to at least one of claims 1 to 4, characterized in that the paste is added a resin as a binder.
6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, daß das Harz ein Phenolharz ist.6. The method according to claim 5, characterized in that the resin is a phenolic resin.
7. Verfahren nach wenigstens einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß der Paste ein organischer Träger zur Einstellung des Fließver¬ haltens zugesetzt wird.7. The method according to at least one of claims 1 to 6, characterized in that the paste is added an organic carrier for adjusting the Fliessver¬ behavior.
8. Verfahren nach Anspruch 7, dadurch gekennzeichnet, daß der organische Träger aus einer Mischung von8. The method according to claim 7, characterized in that the organic carrier from a mixture of
Benzylalkohol und Äthylcellulosε besteht.Benzyl alcohol and ethyl cellulose exist.
9. Verfahren nach wenigstεns εinem dεr Ansprüche9. The method according to at least one of the claims
1 bis 8, dadurch gekennzeichnet, daß zur Einstellung des Widerstandes Ruß hinzugefügt wird. 1 to 8, characterized in that soot is added to adjust the resistance.
PCT/DE1990/000873 1989-12-23 1990-11-14 Process for making a wear-resistant layer WO1991010240A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3942799A DE3942799A1 (en) 1989-12-23 1989-12-23 METHOD FOR PRODUCING AN ABRASION-RESISTANT LAYER
DEP3942799.4 1989-12-23

Publications (1)

Publication Number Publication Date
WO1991010240A1 true WO1991010240A1 (en) 1991-07-11

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DE1990/000873 WO1991010240A1 (en) 1989-12-23 1990-11-14 Process for making a wear-resistant layer

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DE (1) DE3942799A1 (en)
WO (1) WO1991010240A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5111178A (en) * 1990-06-15 1992-05-05 Bourns, Inc. Electrically conductive polymer thick film of improved wear characteristics and extended life
JP3699864B2 (en) * 1999-08-02 2005-09-28 アルプス電気株式会社 Conductive resin composition and encoder switch using the same

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2405449A (en) * 1943-12-31 1946-08-06 Sprague Electric Co Electrical resistance element
US3686139A (en) * 1970-03-10 1972-08-22 Globe Union Inc Resistive coating compositions and resistor elements produced therefrom
EP0223355A1 (en) * 1985-11-11 1987-05-27 Nitta Industries Corporation Method of manufacturing a pressure-sensitive conductive elastomer compound
EP0399295A2 (en) * 1989-05-24 1990-11-28 Preh-Werke GmbH & Co. KG Resistive paste able to make electrical resistive layer and resistive layer fabricated with it

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2405449A (en) * 1943-12-31 1946-08-06 Sprague Electric Co Electrical resistance element
US3686139A (en) * 1970-03-10 1972-08-22 Globe Union Inc Resistive coating compositions and resistor elements produced therefrom
EP0223355A1 (en) * 1985-11-11 1987-05-27 Nitta Industries Corporation Method of manufacturing a pressure-sensitive conductive elastomer compound
EP0399295A2 (en) * 1989-05-24 1990-11-28 Preh-Werke GmbH & Co. KG Resistive paste able to make electrical resistive layer and resistive layer fabricated with it

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Publication number Publication date
DE3942799A1 (en) 1991-06-27

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