FLEXIBLE HEATING ELEMENT, METHOD FOR PRODUCING SUCH A HEATING ELEMENT, AND USE OF A FLEXIBLE HEATING ELEMENT

Abstract

The invention relates to a flexible heating element exhibiting a temperature resistance of at least 250° C., in particular of at least 300° C., comprising an electrically conductive substrate formed from a metal foil, an insulation layer formed on at least one side of the substrate, and a heating structure formed on the side of the insulation layer facing away from the substrate, wherein the heating element has a heating-element thickness of less than 1.0 mm, the substrate has a substrate thickness of 0.02 mm-0.5 mm, and the insulation layer has an insulation-layer thickness of 0.2 μm-30 μm.

Claims

1. A flexible heating element exhibiting a temperature resistance of at least 250° C., in particular of at least 300° C., comprising: an electrically conductive substrate formed from a metal foil, an insulation layer formed on at least one side of the substrate, and a heating structure formed on the side of the insulation layer facing away from the substrate, wherein the heating element has a heating element thickness of less than 1.0 mm, the substrate has a substrate thickness of 0.02 mm-0.5 mm, and the insulation layer has an insulation layer thickness of 0.2 μm-30 μm.

2. The flexible heating element according to claim 1, wherein the insulation layer is a metal oxide layer, in particular an intrinsically grown or an anodized metal oxide layer, or a metal nitride layer or a metal oxide nitride layer.

3. The flexible heating element according to claim 2, wherein the insulation layer comprises aluminum oxide and/or aluminum titanate and/or titanium dioxide and/or silicon dioxide and/or silicon oxide and/or magnesium oxide and/or magnesium titanate and/or a binary zirconium dioxide alloy and/or a ternary zirconium dioxide alloy and/or boron nitride and/or aluminum nitride and/or silicon nitride.

4. The flexible heating element according to claim 1, wherein the insulation layer is produced by means of the aerosol deposition method.

5. The flexible heating element according to claim 1, wherein the flexibility of the heating element is defined as a reversible deflection of a front side or a rear side of the heating element at a bending radius of at least 30 mm, in particular of at least 25 mm, in particular of at least 20 mm, in particular of at least 10 mm, in particular of at least 0.5 mm.

6. The flexible heating element according to claim 1, wherein the metal foil is formed from aluminum and/or steel and/or titanium and/or niobium and/or tantalum or alloys thereof.

7. The flexible heating element according to claim 6, wherein the steel is a FeCrAl alloy, in particular X8CRAl20-5 or FeCr25Al5.

8. The flexible heating element according to claim 1, wherein the at least one heating structure is applied directly to the insulation layer.

9. The flexible heating element according to claim 1, wherein the at least one heating structure is formed between two substrate portions, the two substrate portions being formed by folding the substrate.

10. The flexible heating element according to claim 1, wherein the at least one heating structure has at least two contact pads or is connected to at least two contact pads, the at least two contact pads being formed on the side of the insulation layer facing away from the substrate.

11. A method for producing a heating element according to claim 1, comprising the steps of: a) providing a substrate formed from a metal foil, b) forming at least one insulation layer on at least one side of the substrate, and c) applying a heating structure to the side of the insulation layer facing away from the substrate.

12. The method according to claim 11, wherein, in step b) in order to form the insulation layer, an anodized metal oxide layer is produced by means of an anodizing method or a hard anodizing method, or an oxidation method is carried out at an oxidation temperature of at least 800° C., or an aluminum layer is applied on at least one side of the substrate and then an aluminum oxide layer is produced by means of oxidation at temperatures of 800° C.-1,200° C., or an electrically insulating layer is applied to at least one side of the substrate by means of the ADM method or CVD method or CSD method or PVD method.

13. The method according to claim 11, wherein, in step c) in order to apply the heating structure, a structured metal element, in particular a structured metal foil element, is applied to the insulation layer, or the heating structure is formed on the insulation layer by means of thin-foil metal deposition, or the heating structure is formed on the insulation layer by printing a paste containing metal or an ink containing metal.

14. The method according to claim 11, wherein at least partially applying a passivation layer to the heating structure.

15. The use of a flexible heating element according to claim 1 in combination with a temperature sensor and/or in combination with a temperature sensor chip and/or in an electrical smoking device.

Description

[0138] In the drawings:

[0139] FIG. 1a is a plan view of a flexible heating element according to the invention;

[0140] FIG. 1b shows the flexible heating element in a side view; and

[0141] FIG. 2 shows a further embodiment with respect to a flexible heating element.

[0142] The flexible heating element 10 according to the invention substantially comprises five layers or elements.

[0143] The heating element 10 comprises a substrate 15, an insulation layer 20, a heating structure 30, contact pads 31 and 32, and a passivation layer 40.

[0144] The flexible heating element 10 has a temperature resistance of at least 250° C.

[0145] The electrically conductive substrate 15 is formed from a metal foil. The substrate comprises a first side 16, which faces upward, and a second side 17, which faces downward.

[0146] An insulation layer 20 is formed on the first side 16 of the substrate 15. The insulation layer 20 in turn has a first side 21 and a second side 22. The second side 22 rests on the substrate 15. The first side 21 of the insulation layer 20, by contrast, faces away from the substrate 15.

[0147] A heating structure 30 is formed on the side 21 of the insulation layer 20 facing away from the substrate 15. The heating structure 30 has a meandering shape. This heating structure 30 is preferably designed as a structured metal foil element. This metal foil element 30 can be applied to the first side 21 of the insulation layer 20.

[0148] A passivation layer 40 is additionally applied to the side 33 of the heating structure facing away from the substrate 15 or the insulation layer 20. Due to the meandering shape of the heating structure 30, the passivation layer 40 also reaches the portions of the side 21 of the insulation layer 20 that are not covered by a heating structure 30.

[0149] The heating structure 30 comprises contact pads 31 and 32 at both ends or is connected to these contact pads 31 and 32. The passivation layer 40 completely covers the heating structure. Furthermore, the contact pads 31 and 32 are partially covered by the passivation layer 40.

[0150] The heating element thickness DH shown is less than 1.0 mm. The substrate 15 has a substrate thickness DS of 0.02 mm to 0.5 mm. The insulation layer 20 has an insulation layer thickness DI of 0.2 μm to 30 μm.

[0151] The heating element 10 is flexibly designed, wherein the flexibility of the heating element 10 is defined as a relative deflection of the front side 11 or the rear side 12 of the heating element 10 at a bending radius of at least 30 mm, in particular of at least 25 mm, in particular of at least 20 mm, in particular of at least 10 mm, in particular of at least 0.5 mm.

[0152] The flexible heating element according to the invention is produced according to the following method steps: [0153] a) First the substrate 15 formed from a metal foil is provided. The metal foils used are preferably foils made of materials which form dense metal oxide layers with a high electrical insulation during an anionic oxidation. Particularly suitable metal foils are foils made of aluminum, steel, titanium, niobium or tantalum. Alloys containing chromium and aluminum are particularly suitable as steel foils. These are, for example, FeCrAl alloys. [0154] b) In this step, at least one insulation layer is formed on the first side 16 of the substrate 15. The insulation layer 20 is produced, for example, by anionic oxidation. Such an insulation layer 20 is an anodized metal oxide layer. [0155] c) In this step, the heating structure 30 is applied to the side 21 of the insulation layer 20 facing away from the substrate 20. The heating structure 30 can be provided in an upstream method by producing a structured metal foil element. This can subsequently be applied to the side 21 of the insulation layer 20.

[0156] The contact pads 31 and 32 may be formed as a portion of the heating structure 30. Alternatively, it is possible for the contact pads 31 and 32 to be provided as separate elements or components.

[0157] It is possible, for example, for the contact pads 31 and 32 to be formed from sinter paste material. Such a sinter paste material is applied to the side 21 of the insulation layer 20. If the contact pads 31 and 32 are separate components, the heating structure 30 must be connected to the contact pads 31 and 32.

[0158] Finally, a passivation layer 40 is applied to the upwardly facing side 33 of the heating structure 30. The contact pads 31 and 32 are also partially coated with the passivation layer 40.

[0159] FIG. 2 shows an alternative embodiment with respect to a heating element 10. It can be seen that a heating element 10 may also comprise a plurality of substrate portions, namely a first substrate portion 15a and a second substrate portion 15b. The illustrated substrate portions 15a and 15b are formed separately from one another. The substrate portions 15a and 15b may be formed from different materials.

[0160] An insulation layer portion 20a or 20b is in turn formed on a first side 16 of each substrate portion 15a and 15b. The first sides 16 of the substrate portion are the inwardly facing sides. The second sides 17 of the substrate portions 15a and 15b each face outwardly and thus form the outer surfaces of the heating element.

[0161] FIG. 2 shows that the flexible heating element 10 can be bent. In particular, the heating element 10 can be bent further in such a way that the heating element 10 forms the shape of a cylindrical hollow body. Depending on the extent to which the side edges 18 of the substrate portions 15a and 15b are spaced apart from one another or, for example, are designed to be overlapping, the hollow body, in particular the cylindrical hollow body, can also comprise a slot-shaped recess.

[0162] The heating structure 30 is formed between the two insulation layer portions 20a and 20b. Based on the embodiment shown in FIG. 2, a type of sandwich arrangement of a heating element 10 is formed. The heating structure 30 is arranged in such a way by the electrically conductive substrate portions 15a and 15b that they do not lie one on top of the other or are not directly in electrical contact with one another.

[0163] The heating structure 30 is embedded between the insulation layer portions 20a and 20b in such a way that the insulation layer portions 20a and 20b each point toward one another on the first sides 21 or abut one another at least in portions.

[0164] The individual layers of the heating element 10 can, for example, be connected to one another by the weld spots 50 that are shown. A flexible heating element 10 as shown in FIG. 2 is particularly suitable for use in an electrical smoking device.

LIST OF REFERENCE SIGNS

[0165] 10 heating element [0166] 11 front side of heating element [0167] 12 rear side of heating element [0168] 15 substrate [0169] 15a, 15b substrate portions [0170] 16 first side of substrate [0171] 17 second side of substrate [0172] 18 side edge [0173] 20 insulation layer [0174] 20a, 20b insulation layer portions [0175] 21 first side of insulation layer [0176] 22 second side of insulation layer [0177] 30 heating structure [0178] 31 first contact pad [0179] 32 second contact pad [0180] 33 side of heating structure [0181] 40 passivation layer [0182] 50 weld spot [0183] DH thickness of heating element [0184] DS thickness of substrate [0185] DI thickness of insulation layer