METHOD FOR PRODUCING A PRINTED MAGNETIC FUNCTIONAL ELEMENT, AND PRINTED MAGNETIC FUNCTIONAL ELEMENT

Abstract

A method for producing a printed magnetic functional element, in which a substrate is provided on one surface with at least one contact made of an electrically conductive material. Subsequently, a structure made of a material which has a magnetoresistive effect and is in the form of a paste, a gel, a dispersion or a suspension is printed on or onto the at least one contact and touches the contact directly, and the structure becomes electrically conductive and sensitive to magnetic fields by irradiation with electromagnetic radiation over a time period in the millisecond range.

Claims

1-10. (canceled)

11. A method for producing a printed magnetic functional element, comprising: a substrate is provided on a surface having at least one contact made of an electrically conductive material, a structure arranged below, above or next to the contact and made of a material having a magnetoresistive effect is printed as a paste, gel, dispersion or suspension on or onto the at least one contact and directly touching it, and subsequently the contact and/or the structure is functionalized by irradiation with electromagnetic radiation over a period of time in the millisecond range and becomes electrically conductive and sensitive to magnetic fields at least by forming a mechanical connection between individual particles of the electrically conductive material and/or the one magnetoresistive effect material, wherein the material exhibiting a magnetoresistive effect is selected from bismuth, indium, antimony, iron, nickel, cobalt or an alloy of the elements mentioned, or at least contains bismuth, indium, antimony, iron, nickel, cobalt or an alloy of the elements mentioned.

12. The method according to claim 11, wherein the period of time in the millisecond range is between 0.1 ms and 100 ms.

13. The method according to claim 11, wherein the irradiation with electromagnetic radiation is carried out with a laser radiation, comprising diode laser radiation, and/or an irradiation using a flash lamp.

14. The method according to claim 11, wherein the at least one contact made of an electrically conductive material is applied by at least one printing process, a gas phase deposition or a lamination of the contact.

15. The method according to claim 11, wherein when printing the structure, a gel, a paste, a dispersion or a suspension of a powder containing at least one metallic, semi-metallic or semiconducting material, a dispersant containing a polymer and/or a binder is produced, wherein an average particle size of the powder containing metallic, semi-metallic or semiconducting material is between 10 nm and 100 μm.

16. The method according to claim 15, wherein a binder-free suspension or a binder-free powder is used for printing the structure, which suspension or powder is applied to the substrate and is subsequently activated by the application of pressure and/or friction in combination with the irradiation with electromagnetic radiation over a period of time in the millisecond range in order to achieve a magnetoresistive effect.

17. A printed magnetic functional element, comprising: a substrate comprising at least one contact made of an electrically conductive material and applied to a surface of the substrate, a structure printed on the at least one contact and directly touching it below, above or next to the contact and made of a material exhibiting a magnetoresistive effect, the material exhibiting a magnetoresistive effect being selected from bismuth, indium, antimony, iron, nickel, cobalt or an alloy of said elements or at least containing bismuth, indium, antimony, iron, nickel, cobalt or an alloy of said elements.

18. The printed magnetic functional element according to claim 17, wherein a material from which the substrate is formed is a glass, a semiconductor, comprising silicon, a ceramic, paper, a textile, a rubber and/or a polymer comprising polyethylene terephthalate, polyethylene naphthalate, polyimide, polyetheretherketone or a composite material comprising FR4.

19. The printed magnetic functional element according to claim 18, wherein the at least one contact is formed from an electrically conductive material, comprising silver, gold, platinum, copper, aluminum or an alloy of the elements mentioned.

20. The printed magnetic functional element according to claim 19, wherein the substrate, the at least one contact and the printed structure are coated with an organic or non-organic protective layer based on polymer, glass or glass ceramic.

21. The method according to claim 11, wherein the period of time in the millisecond range is between 0.5 ms and 2 ms.

Description

[0023] Shown are:

[0024] FIG. 1 a schematic sequence of a production process for a printed magnetic functional element and

[0025] FIG. 2 a plan view and a measured value diagram of the printed magnetic functional element produced.

[0026] FIG. 1 shows a schematic view of a method for producing printed magnetic functional elements. In FIG. 1a), the upper illustration, a thermally stable substrate 1 is provided using a method known from the prior art by printing or physical or chemical vapor deposition (PVD, CVD) having a contact structure 2 made of a metal, extending over a surface of the substrate 1. A structure 3 made of a material having a magnetoresistive effect is then applied and everything is heat-treated for hours, for example, for three hours, at a temperature of around 250° C. in an inert gas atmosphere or in a vacuum.

[0027] A thermally less stable substrate 1 can also be used in the embodiment of a method according to the invention shown in FIG. 1b), the middle image. A contact structure 2 made of a metal, for example, silver, is also applied to the surface of this substrate 1. The contact structure 2 is irradiated by a diode laser array for 0.5 ms in an air atmosphere, whereby the material of the contact structure 2 is dried or sintered and becomes electrically conductive. The structure 3 made of bismuth is then printed on as a dispersion touching the contact structure 2, that is, in direct contact therewith. This structure 3 is also treated by the diode laser array for 2 ms in an air atmosphere, whereby the bismuth is functionalized and becomes electrically conductive.

[0028] In the embodiment shown in FIG. 1b), a bismuth-based structure (that is, bismuth or a bismuth alloy) having the ability to detect magnetic fields is thus produced using a wet chemical process by first producing a dispersion, paste, ink or aqueous mass using an electrically conductive or semiconducting powder. Individual materials are bismuth or bismuth alloys as described, but other metals, semiconductors, semi-metals or intermetallic alloys can also be used. The mean particle size here is between 10 nm and 100 μm, wherein a polymer-based dispersant and a binder are added to the dispersion or the like.

[0029] The thermally sensitive substrate is also used in the embodiment shown in FIG. 1c), the lower image. The contact structure 2 made of a metal, for example, silver, is applied to the surface of said substrate 1. As a next step, the structure 3 made of bismuth is then printed on as a dispersion touching the contact structure 2, that is, in direct contact therewith. The printed structures are then treated together by the diode laser array for 1 ms in an air atmosphere, whereby the two components are functionalized, that is, dried or sintered.

[0030] The bismuth is deposited or applied as a structure 3 by inkjet printing, screen printing, stencil printing or dispenser printing of said dispersion onto the rigid or flexible substrate 1, which can be formed from glass, a silicon wafer, a ceramic, a metal, a flexible polymer, paper, a textile or a rubber. Applied as a structure is intended here to mean in particular that the dispersion already structured, that is, having a defined outer contour, is applied to the substrate, so that no additional shaping layers are formed on the substrate or no subsequent shaping process steps take place. The contact structure 2 can also be printed on in the same way, but a different method can be used therefor in further exemplary embodiments.

[0031] For example, a conventional process of physical vapor deposition or chemical vapor deposition can be used to apply the contact structure 2 made of, for example, gold, platinum, silver, aluminum or copper or an alloy thereof. The contact structure 2 can be arranged below, above or next to the structure 3 and is typically designed in a two-point or four-point measurement configuration.

[0032] Bismuth is advantageous as a sensor material because it shows a large magnetoresistive effect in single crystals and in 1 μm to 20 μm thick single crystal films: At room temperature and magnetic fields up to 5 T up to 230 percent. In addition, bismuth powder is easy to obtain and produce. However, since bismuth layers do not show any electrical conductivity immediately after printing and drying without thermal post-processing, a heating process usually has to be carried out in an oven. According to the present invention, the electrical conductivity and the magnetoresistive effect can be realized faster and more reliably by irradiation with electromagnetic radiation, which also eliminates the need for a post-processing step following the thermal treatment, such as polishing, to remove organic decomposition products. Due to the irradiation in the millisecond range, a sensor produced in this way shows an isotropic sensitivity and a magnetoresistive effect in the range of approx. 4-6 percent at a magnetic field strength of 500 mT, which can probably be increased to more than 8 percent through optimization.

[0033] A functionalization of the structure 3, which enables the occurrence of electrical conductivity and magnetoresistive functionality, takes place by thermal treatment in air over a period in the millisecond range, during which drying also takes place. In further embodiments, this can also take place in a vacuum or in an inert gas atmosphere. A conventional laser, a diode laser, a micro-optically optimized diode laser array or a flash lamp can be used for thermal treatment over a period of time in the millisecond range. This means that a plurality of materials or combinations of materials can also be used.

[0034] Finally, the substrate 1 with the contact structure 2 and the structure 3 can be provided with an encapsulation in order to make the entire system less sensitive to harsh or aggressive media and moisture. In conclusion, the produced sensor can be processed as a magnetic functional element by static or alternating magnetic fields in order to remove offsets and hysteresis effects. The sensor shows good temperature stability in air up to approximately 125° C. after this encapsulation.

[0035] In FIG. 2a) (the left half of FIG. 2), an embodiment of a correspondingly produced functional element in four-point measurement geometry is shown in a plan view. In this figure, recurring features are provided with the same reference numerals as in FIG. 1. FIG. 2b) shows a diagram of the course of the electrical resistance in the configuration shown in FIG. 2a) with a change in the applied magnetic field. Measured values are shown for the magnetic field direction in the sample plane (in-plane), perpendicular to the sample plane (out-of-plane) and at an angle of 45°.

[0036] The printed magnetic functional element described can register various types of movement such as displacement, rotation or vibration. Position sensors or angle sensors can be implemented accordingly. Alternatively or additionally, magnetic switches can also be built with the printed magnetic functional element or magnetic field sensor.

[0037] Features of the various embodiments that are only disclosed in the exemplary embodiments can be combined with one another and claimed individually.