EP4292395A1

EP4292395A1 - Ptc heating element, electric heater, and use of a ptc heating element

Info

Publication number: EP4292395A1
Application number: EP22709642.7A
Authority: EP
Inventors: Markus Koini; Michael Krenn; Markus Puff; Stephan Bigl
Original assignee: TDK Electronics AG
Current assignee: TDK Electronics AG
Priority date: 2021-02-15
Filing date: 2022-02-14
Publication date: 2023-12-20
Also published as: CN116868686A; US20240230156A9; WO2022171857A1; DE102021103480A1; US20240133587A1; JP2024506916A

Abstract

The invention relates to a PTC heating element (1) for an electric heater, having - at least one PTC element (2), at least one electrode (3) being formed on a surface (2a, 2b, 2c) of the PTC element (2) for electrically contacting the PTC element (2), - at least one additional contact (4) for electrically connecting the electrode (3) of the PTC element (2), - at least one carrier layer (5), the carrier layer (5) being electrically insulating, wherein the thickness (d) of the PTC element (2) is ≤ 500 µm, and the installation height (H) of the PTC heating element (1) is between 500 µm and 2500 µm. The invention also relates to an electric heater and to the use of the PTC heating element (1) in a motor vehicle.

Description

description

PTC heating element, electric heating device and use of a PTC heating element

The present invention relates to a heating element, in particular a PTC heating element. The present invention further relates to an electrical heating device having the PTC heating element. The present invention also relates to the use of the PTC heating element in a motor vehicle, for example in an electric vehicle.

Heating coils that are equipped with PTC ("Positive Temperature Coefficient" - thermistor) heating elements have the advantage that their property as a temperature-dependent resistance automatically limits the power consumption when a certain temperature is reached. This property not only serves as a safety Feature to avoid overloading the heating coil, but also to carry out the control by the self-regulation effect very easily.

The use in electric vehicles suggests operating the register directly with the high-voltage battery (200-400 V, sometimes also 800 V). The insulation strength must therefore be designed accordingly. Usually, PTC elements are electrically contacted on two opposite sides by means of a conductor track. The conductor track is carried by a substrate, which decouples the heat generated on the other side.

The heat output that can be extracted depends heavily on the thermal path through the layer structure described above. warmth must get from the point of origin (the PTC) via the contact and through the substrate to the decoupling surface. Here, thermal and electrical considerations for optimizing the heating element are often subject to opposing arguments, ie state-of-the-art designs are compromise solutions between power density, thermal agility and insulation capacity or robustness and reliability.

For example, the fact that the manufacturer of the PTC elements and that of the heating elements is not the same means that the PTC element must meet certain requirements in terms of geometric tolerances, transportability and handling in the assembly process. This means that a certain minimum thickness of the PTC elements cannot be undershot within the scope of reasonable effort.

It would also be thermally optimal to connect the PTC element directly to the (metallic) heat sink. However, since electrical insulation must be provided in a high-voltage system (230 V - 800 V), an electrically non-conductive barrier is required that sufficiently decouples the system voltage from the radiator. In addition, clearance and creepage distances (usually 4 mm for high-voltage heaters in electric vehicles) between different polarities must be maintained, which can only be achieved by using insulating materials.

The PTC element itself acts as a heat source when Joule heat is generated by energization. However, this is not generated homogeneously in the material, but depending on the geometry and possible material inhomogeneities, the electric field distribution in the component can cause a temperature gradient. The heat must emanate from hotspots only reach the surface of the elements before they can be transported further. Due to the relatively poor thermal conductivity of the PTC ceramics (usually ~ 5 W/mK), this can be very slow and sluggish.

The document EP 3101 999 A1 describes a PTC heating element for an electric heating device for a motor vehicle, which is electrically insulated in an improved manner on the outside, with the need for adequate heat transfer from the PTC element to the heat-emitting surface through the electric Insulating layer should be taken into account. An electrical insulating layer is provided for this purpose, which rests on the outside of at least one of the conductor tracks via which the PTC element is energized and has a film and an electrically insulating compound with good thermal conductivity applied thereto.

The document US 2017/0223776 A1 describes an electrical heating device with at least one electrical PTC heating element and radiation ribs, which are located on the outer surface of the electrical PTC heating element. The surface on the radiating fins that is not in contact with the PTC electric heating element is not charged. An insulating layer is provided between conductor tracks and the radiation ribs.

The document DE 112017 006 124 T5 also describes an electrical heating device with an insulating layer between conductor tracks and the cooling fins. The electric heater has a plurality of PTC elements and heat radiation fins for radiating heat transmitted from the PTC elements, and a resin sheet for insulating the electrode plates and a Compression spring which presses a laminated body in a lamination direction from both sides.

The document EP 1182 908 B1 describes a PTC heating device with at least one PTC element and two contact plates which contact the PTC element. A metal foil coated on both sides with adhesive is provided to connect the surface of the PTC element to the contact plates. The contact plates are not insulated.

The link https://air-lab.de/Index.html describes heating elements with direct contact to aluminum cooling fins for optimal heat extraction. In this case, no electrical insulation is provided.

The object of the present invention is to describe a PTC heating element and an electrical heating device which solve the above problems.

This object is achieved by a PTC heating element, an electrical heating device and the use of the PTC heating element according to the independent claims.

According to one aspect, a PTC heating element is described. The PTC heating element is designed to be integrated into an electrical heating device, for example into a heating register. The PTC heating element is designed for use in a motor vehicle, for example in an electric vehicle (xEV - x Electrical Vehicle).

The PTC heating element has at least one PTC element. The PTC heating element preferably has a multiplicity of PTC Elements, for example five, ten or 20 PTC elements. A cavity between two consecutive PTC elements can be filled with a temperature-resistant filling material. The filling material acts as a mechanical protection or barrier against the ingress of moisture and as an additional heat conductor (instead of air).

The PTC element is used to generate heat. The PTC element has at least one electrode, in particular two electrodes, for electrical contacting. The electrodes are formed on a surface of the PTC element.

The PTC heating element also has at least one additional point of contact. The additional contact is used for the electrical connection of the electrode of the PTC element. The additional contact can have copper, aluminum and/or tungsten, for example.

The PTC heating element also has at least one carrier layer. The carrier layer surrounds the PTC elements at least partially, preferably completely. The carrier layer is designed to be electrically insulating. The carrier layer has a high thermal conductivity. The carrier layer is used for mechanical stabilization and electrical insulation of the PTC heating element.

The PTC heating element is very compact. The PTC heating element is large and thin. The PTC heating element has an extremely small volume. A thickness of the PTC element is preferably <500 gm, preferably <250 gm, for example 10 gm to 150 gm or even <2 gm 2500mpi. A lateral dimension of the PTC heating element is preferably between 10 mm and 250 mm in both directions (length and width).

The PTC heating element is preferably designed to be plane-parallel. In particular, the carrier layer is preferably designed to be plane-parallel. The PTC element is preferably also designed to be plane-parallel.

The better defined the surface of the substrate / carrier layer is, the thinner and more efficient the thermal transition (e.g. to an aluminum heat sink) can be. Specifically, this means for the PTC element (~27 x 13 mm) < 100 pm, ideally: < 30 pm; (A1N or AlO _x ) carrier layer: (165 x

35 mm): 500 pm, ideal: < 100 pm.

The flatness and plane-parallelism of the PTC elements and the carrier layer is important for the performance of the PTC heating element. If the surfaces of the at least one PTC element/the carrier layer are not sufficiently well defined, the gap must be filled with leveling compound or casting compound, which increases the thermal resistance. The more precisely the components are manufactured, the thinner the gap.

The at least one PTC element is preferably designed to be very thin and in particular has a thickness <250 μm, with a plane-parallelism being <100 μm. The plane-parallelism of the PTC element is particularly preferably <30 μm. The carrier layer preferably has a plane parallelism of <500 μm, particularly preferably <100 μm. The composition of the PTC heating element described above allows an extremely compact design, which in turn enables a high degree of integration into an electrical heating device. This ensures a faster and more efficient heating effect (eg in the interior of a vehicle) compared to prior art heating devices. Weight savings, which come about through lower use of materials, enable an increase in the range of xEVs, while the low material consumption contributes to the conservation of resources and a reduction in the ecological footprint.

Through a suitable combination of materials and/or connection techniques - together with the optimization of the geometry at the heating element level - the volume of the PTC heating element and the heat extraction are optimized in such a way that the power density, the thermal response behavior as well as the robustness and reliability compared to the prior art are significantly improved.

According to one embodiment, the electrodes are arranged flat on the surface of the at least one PTC element. The electrodes are formed directly on the surface of the PTC element. The electrodes can be sputtered, electroplated, printed or squeegeed onto the surface of the PTC element.

The electrodes are designed with as large an area as possible in order to achieve favorable heat extraction. The electrodes can be designed, for example, in the form of strips, rectangular, comb-like or as an interdigital structure. The electrodes must have a sufficient distance from each other to keep creepage distances free and thus a to avoid electrical flashover. A particularly reliable PTC heating element is thus made available.

For example, at least one electrode is arranged on an upper side or an underside of the PTC element. Two electrodes can also be formed on the upper side or the lower side. One electrode each can also be formed on the upper side and on the lower side.

As an alternative to this, the electrodes can be formed on side surfaces, in particular opposite side surfaces, of the PTC element. This separates the thermal and electrical path and enables new designs and assemblies that may be advantageous for certain manufacturers. In addition, production-related material inhomogeneities in the PTC element can be better managed or avoided.

According to one exemplary embodiment, the further point of contact is designed to be self-supporting. In other words, the carrier layer only stabilizes the other components of the PTC heating element. In contrast, the carrier layer is not (absolutely) required to stabilize the further contacting.

As an alternative to this, the further point of contact can also be applied to the carrier layer for mechanical stabilization. For example, the additional contact can be sputtered, printed or squeegeed onto the carrier layer. According to one exemplary embodiment, the additional contact is integrated into the carrier layer. In other words, the additional point of contact is formed in an inner region of the carrier layer. In this case, the further point of contact is arranged <50 gm below a surface of the carrier layer.

According to one exemplary embodiment, a geometry of the additional contacting is adapted to a geometry of the electrode of the PTC element. For example, the additional contact is designed to be as large and thin as possible. For example, a thickness of

Further contacting < 10 gm. This increases the heat extraction of the PTC heating element and thus increases efficiency.

According to one exemplary embodiment, the further point of contact is electrically conductively connected to the at least one electrode by means of clamping, sintering, gluing or high-temperature soldering. By using standard connection techniques, the production costs can be reduced and a particularly cost-effective PTC heating element can thus be made available.

According to one embodiment, the carrier layer has a thickness of between 150 μm and 1000 μm. The carrier layer is therefore very compact and thin in order to optimize the power density of the PTC heating element, but thick enough to ensure the robustness and stability of the PTC heating element.

According to one embodiment, the carrier layer has a ceramic material with high thermal conductivity and good insulation properties. For example, the carrier layer has AlN, Si3N4, Al2O3, or SiC. These materials are ideal for the

To optimize heat decoupling and thus to increase the power density and the thermal response behavior of the PTC heating element.

As an alternative to this, the carrier layer can have a temperature-resistant plastic. For example, the carrier layer has polyimide or epoxy resin. Due to the low thermal conductivity (<10 W/mK) of plastic, the carrier layer must be sufficiently thin to keep the thermal resistance low and thus achieve a high power density of the PTC heating element.

As an alternative to this, the carrier layer can have a hybrid solution based on a ceramic material and plastic. For example, the carrier layer can have a plastic layer and a ceramic layer. In order to achieve optimal heat extraction, the plastic layer must be made significantly thinner than the ceramic layer.

According to one embodiment, the PTC heating element also has at least one metallic layer on a surface of the carrier layer. The metallic layer is used for further contacting of the PTC heating element, for example for connection to a radiator. The metallic layer can have Cu, Al or W, for example. The metallic layer is very thin. The metallic layer preferably has a thickness of between 1 gm and 100 gm. Because of the small thickness of the metallic layer, the thermal decoupling of the PTC heating element is not negatively influenced.

According to one exemplary embodiment, the at least one PTC element has a ceramic material, a metal-ceramic material or an organic-ceramic material. For example, the PTC element has PZT (lead zirconate titanate). A particularly cost-effective PTC heating element can be achieved by using standard materials.

Alternatively, the PTC element can be based on bismuth.

This has the advantage that the PTC element is lead-free. As an alternative to this, the PTC element can also have a bismuth and lead-free material.

According to one embodiment, a material of the at least one PTC element has a low specific resistance. For example, the specific resistance is <5000 W cm, for example 1000 W cm. As a result, the PTC effect can be significantly reduced below the operating point and the energy consumption/inrush current can be significantly reduced compared to more conventional HV PTCs with each switch-on process. This not only leads to a lower load (lower inrush current) of the other electronic components, but also leads to a further increase in the range of electric cars.

According to one embodiment, the PTC element is a low-temperature PTC element. This has the particular advantage that corresponding PTC elements can be made completely from bismuth and lead-free materials. According to one embodiment, the PTC heating element has a multiplicity of PTC elements. The PTC elements are arranged adjacent to one another or one after the other on the carrier layer. In particular, PTC elements are arranged one after the other in a direction along a main longitudinal axis X of the heating element. Furthermore, PTC elements are arranged one after the other in a direction perpendicular to the main longitudinal axis X (ie along a transverse axis Y).

Due to the design, a cavity occurs between consecutive PTC elements. A cavity between two consecutive PTC elements can be filled with an electrode for electrical contacting of the respective PTC element. In particular, the cavities running along the main longitudinal axis X can be filled with electrode material.

This means that the electrodes contact opposite side surfaces of the respective PTC element. In other words, the PTC elements are contacted here from an end face of the PTC elements. In this case, the top and bottom of the PTC element are free of electrodes. This separates the thermal and electrical path and enables new designs and assemblies that may be advantageous for certain manufacturers. In addition, production-related material inhomogeneities in the PTC element can be better managed or avoided.

The remaining cavities between the PTC elements that are not filled with electrode material (cavities perpendicular to the main longitudinal direction) can be used, for example, with the above be filled with the filling material described to improve the thermal contact between the PTC elements.

According to one exemplary embodiment, the PTC heating element has a multiplicity of further contacts. The additional contacts are formed directly on the carrier layer. In other words, no further component of the PTC heating element is arranged between additional contacting and carrier layer.

The respective further point of contact is, for example, in the form of a strip. The additional contacts are preferably in the form of metallization strips of the carrier layer. An additional point of contact preferably extends completely along the main longitudinal direction of the PTC heating element.

The additional contacts can be formed alternately above and below the PTC elements (in particular the electrodes). This ensures reliable contacting of the electrodes of the PTC elements.

According to one exemplary embodiment, the PTC heating element also has at least one connection element for the electrical connection between the at least one PTC element and the at least one additional contact. The PTC heating element preferably has a large number of connecting elements.

The at least one connecting element can be designed in the form of a strip. The respective connecting element preferably extends at least partially along the main longitudinal direction of the PTC heating element. The respective Connection element is formed at least between the respective additional contact and the respective electrode. The respective connecting element is in direct contact with an electrode of at least one PTC element.

The connecting element is also in direct contact with at least one, preferably with precisely one, additional contact. The at least one connecting element preferably has a conductive adhesive.

With the connecting element, an electrically conductive and mechanically strong connection between the electrodes and the additional contact can be ensured in a simple manner. According to a further aspect, an electrical heating device, for example a heating register, is described. The electrical heating device has a component with heat-emitting surfaces, such as cooling fins.

The electrical heating device also has at least one PTC heating element, preferably the PTC heating element described above. All properties that are disclosed in relation to the PTC heating element are consequently also disclosed in relation to the respective other aspect and vice versa, even if the respective property is not explicitly mentioned in the context of the respective aspect

The optimized design of the PTC heating element ensures a high level of integration in the heating device. This enables a quick and efficient heating effect (e.g. in the interior of a vehicle).

According to a further aspect, the use of the PTC heating element described above in a motor vehicle, for example in an electric vehicle, is described. The PTC heating element is designed extremely compact and is therefore suitable for every installation situation. Furthermore, the PTC heating element can ensure optimal heat extraction and thus high power density and reliability.

The drawings described below are not to be taken as true to scale. Rather, individual dimensions can be enlarged, reduced or also distorted for better representation.

Elements that are the same or that perform the same function are denoted by the same reference symbols.

Show it:

Figure 1 shows a PTC heating element according to the prior art

Technology

Figure 2 shows another PTC heating element after

State of the art

FIG. 3 shows another heating element according to the prior art

Figure 4 shows another PTC heating element after

State of the art

FIG. 5 shows the resistance-temperature behavior of an HV PTC ceramic with two different specific resistances

FIG. 6 shows a sectional illustration of a PTC heating element according to a first exemplary embodiment, Figure 7 is a sectional view of a PTC

Heating element according to another embodiment,

Figure 8 is a sectional view of a PTC

Heating element according to another embodiment,

Figures 9a to 9d perspective views of PTC

elements for a PTC heating element,

FIG. 10 shows a sectional view of a PTC heating element according to a further exemplary embodiment,

FIG. 11a is a perspective view of a portion of the PTC heating element according to FIG. 6,

Figure 11b is a perspective view of a portion of the PTC heating element according to Figure 10.

FIG. 1 shows a sectional illustration of a PTC heating element 100 according to the prior art. The PTC heating element 100 has a plurality (four in this embodiment) of PTC elements 101 for generating heat. The PTC elements 101 are arranged one after the other in the longitudinal direction of the PTC heating element 100 and are separated from one another by an air gap. Electrical contacts 102 (made of copper, for example) for the electrical connection of the PTC elements 101 are arranged on an upper side and underside of the PTC elements 101 .

The PTC heating element 100 also has insulating layers 103 which are arranged on the electrical contacts 102 and electrically insulate the PTC heating element 100 from the outside and in particular from heat spreaders or radiators 104 which are formed on an outer surface of the electrical PTC heating element 100 .

FIG. 2 shows a sectional illustration of a further PTC heating element 110 according to the prior art. In this case, the PTC elements 111 are in turn arranged between electrical contacts 112 . An insulating layer 113 made of plastic (for example polyimide) is formed on the electrical contacts 112 to electrically insulate the heating element 110 .

FIG. 3 shows a sectional illustration of a further PTC heating element 120 according to the prior art. The PTC elements 121 are connected by means of electrical contacts 122 and insulated from the outside by a plastic molding 123 (for example epoxy resin). The PTC elements 121 are completely surrounded by the molding 123.

FIG. 4 shows a sectional illustration of a further PTC heating element 130 according to the prior art. Here, the PTC elements 131 are in direct contact with the radiator 132 in order to achieve optimum heat extraction. There is no electrical isolation.

FIG. 6 shows a sectional illustration of a PTC heating element 1 according to a first exemplary embodiment. That PTC heating element 1 is designed for use in a motor vehicle, for example in an electric vehicle. The PTC heating element 1 is designed to be integrated into an electrical device (for example an electrical heating device) with a radiator or a heat sink (not explicitly shown).

The PTC heating element 1 has a plurality of PTC elements 2 (see also FIGS. 9a to 9d). The PTC heating element 1 also has electrodes/electrical contacts 3, further contacts/conductor tracks 4 and a carrier layer/substrate 5.

The PTC elements 2 serve as a heat source. In particular, 2 Joule heat is generated by energizing the PTC elements. In this exemplary embodiment, the heating element 1 has five PTC elements 2 . Of course, more than five PTC elements 2, for example eight or ten PTC elements 2, or fewer than five PTC elements 2, for example two PTC elements 2 or one PTC element 2 can also be provided. The number of PTC elements 2 depends, among other things, on the requirements of the PTC heating element 1, its material composition and the installation situation, for example in a motor vehicle.

The PTC elements 2 are arranged one after the other or consecutively along a main longitudinal axis X of the PTC heating element 1 . They have a ceramic material, a metal-ceramic material or an organic ceramic material. For example, the PTC elements have a PZT ceramic. An alternative composition based on bismuth is also conceivable. This has the advantage that the PTC elements 2 are lead-free can become. A completely lead and bismuth-free composition of the PTC elements 2 is also conceivable.

Due to the design, cavities can occur between the PTC elements 2 perpendicular to the main longitudinal axis X. In this exemplary embodiment, these cavities are filled with a temperature-resistant and thermally conductive filling material 7, for example silicone or epoxy. The optional filling material 7 acts as mechanical protection or as a barrier against the ingress of moisture and as an additional heat conductor (instead of air).

The respective PTC element 2 is very compact. In particular, a thickness d or extension perpendicular to the main longitudinal axis X (see also FIG. 9a) of the respective PTC element 2 is between 50 μm and 250 μm. The thickness d of the respective PTC element 2 is preferably <200 μm.

In order to achieve a corresponding thickness d, the respective PTC element 2 can be produced using a standard method (pressing method or multi-layer structure). With alternative production methods, however, even thinner PTC elements 2 (10 μm to 150 μm or even <2 μm) are also possible.

Thus, thinner PTC layers can be achieved by applying them to the carrier layer 5 by means of screen printing, as a result of which a thickness d of the respective PTC element 2 of between 10 μm and 150 μm can be achieved. These layer thicknesses can be reduced even further by application methods such as SolGel, inkjet printing or plasma jet methods in order to achieve a thickness d<2 μm. A lateral extension 1 (extension along and transverse to the main longitudinal axis X) of the respective PTC element 2 is preferably between 5 mm and 100 mm (FIGS. 9a and 9b).

For the electrical connection of the respective PTC element 2, the PTC element 2 has an electrical contact or electrodes 3, as can be seen from FIGS. 9a to 9d. The electrodes 3 are formed flat on a surface 2a, 2b, 2c of the respective PTC element 2. FIG. The electrodes 3 are designed with as large an area as possible in order to achieve favorable heat extraction. The electrodes 3 of opposite polarity must also have a sufficient distance from one another in order to prevent electrical flashovers.

In each case one electrode 3 can be formed on a bottom side 2b and on a top side 2a of the PTC element 2 (FIG. 9b). However, two electrodes 3 can also be formed on the upper side 2a and the underside of the PTC element 2 can be free of electrodes 3 (FIGS. 9a and 9d) or vice versa.

It is also possible for the electrodes 3 to make contact, for example, with opposite side faces 2c of the respective PTC element 2, as can be seen in FIG. 9c. In this case, the top 2a and the bottom 2b are free of electrodes 3. The thermal and electrical paths are thus separated from one another and new designs and assemblies that can be advantageous for certain manufacturers are made possible. In addition, production-related material inhomogeneities in the PTC element 2 can be better managed or avoided. An example for a PTC heating element 1 with correspondingly contacted PTC elements 2 can be found in FIGS. 10 and 11b.

The electrodes 3 are as large as possible while maintaining the creepage distances (usually 4 mm for high-voltage heaters). The electrodes 3 at least partially cover the upper side 2a or the lower side 2b of the PTC element. If the electrodes 3 are arranged on the side surfaces 2c, the side surfaces 2c can also be completely covered by the electrodes 3. For example, the electrodes are strip-shaped or rectangular (FIGS. 9a and 9c). A comb-like or an interdigital structure is also possible (FIGS. 9b and 9d). In the case of the interlocking electrode structures, particular care must be taken to ensure that the distance between the electrodes 3 is sufficiently dimensioned in order to avoid electrical flashovers.

The electrodes 3 have an electrically conductive material (for example a metal paste). The electrically conductive material is sputtered, printed or squeegeed onto the surface 2a, 2b, 2c of the respective PTC element 2. The electrodes 3 are preferably realized by means of a sputter layer or a metal firing paste.

By using the electrode configurations described (see FIGS. 9a to 9d), different specific resistances are required with regard to the PTC material compared to the prior art. This additional degree of freedom means that with lower specific resistances, the PTC effect is noticeably reduced below the operating point and thus the energy consumption or the inrush current is significantly reduced with each switch-on process more conventional HV (high voltage - high voltage) PTCs is reduced. This leads to a lower load (lower inrush current) .

In this context, FIG. 5 illustrates normalized characteristic curves (same measuring voltage) which show the resistance-temperature behavior of an HV PTC ceramic at two different specific resistances. Due to the lower resistivity, the drop in resistance is significantly reduced compared to the conventional higher resistivity.

In order to make electrical contact with the electrodes 3, the PTC heating element 1 also has the above-mentioned conductor tracks or further contacts 4. In this exemplary embodiment, the conductor tracks or further contacts 4 extend along the top side 2a and the bottom side 2b of the PTC elements 2 through the PTC heating element 1.

In other words, the further contacts 4 according to FIG. 6 are formed between the PTC elements 2 (or the electrodes 3) and the carrier layer 5. FIG. The additional contacts 4 are in particular in direct contact with the electrodes 3 of the PTC elements 2.

The additional contacts 4 extend along the main longitudinal axis X. The additional contacts 4 emerge from the PTC heating element 1 on a side surface la for the electrical connection of the PTC heating element 1.

An electrically conductive connection between the electrodes 3 and the additional contacts 4 can be implemented using a variety of technical solutions. Thus, a clamp contact is just as possible as a connection using Sintering techniques (pAg, pCu or TLPS (Transient Liquid Phase Sintering)) or high-temperature soldering.

The further contacts 4 can be self-supporting. This means that no further element (for example the carrier layer or the substrate 5) for the mechanical stabilization of the respective additional contact 4 is required. As an alternative to this, the further contacts 4 can be applied to the carrier layer 5 . In this case, the further contacts 4 are sputtered, electroplated, printed or squeegeed onto the carrier layer 5 . As mentioned above, the

Further contacts 4 in the two mentioned versions are in direct electrical and mechanical contact with the electrodes 3, as can be seen from FIG.

The further contacts 4 have, for example, copper, aluminum or tungsten. However, other electrically conductive metals, alloys or other electrically conductive materials are also conceivable for the further contacts 4 . A geometry of the respective

Additional contact 4 is adapted to that of the electrodes 3 of the PTC elements 2 in such a way that there are no excessive field increases or flashovers when the PTC element 2 is in operation.

The further point of contact 4 is preferably formed over a large area. The respective further point of contact 4 is designed to be as thin as possible in order to save installation space. A thickness of the further contacts 4 is preferred <10 gm. This is possible in particular if the further contacts 4 are applied to the carrier layer 5 by sputtering, printing or squeegeeing, as already mentioned above.

The PTC heating element 1 also has the carrier layer 5 that has already been introduced. The carrier layer 5 serves to electrically insulate the PTC heating element 1 from the outside and to mechanically stabilize the PTC heating element 1 . The PTC elements 2 are arranged entirely in an inner region of the carrier layer 5 . The further contacts 4 are also at least partially embedded in the carrier layer 5 .

The carrier layer 5 has a very small thickness (expansion perpendicular to the main longitudinal axis X). For example, the thickness of the carrier layer 5 is between 150 gm and 1000 gm. As a result, any heat caused by ohmic losses on the supply line, but also the heat transfer of the heating element, can be conducted to the outside as efficiently as possible.

The carrier layer 5 also has a material with high thermal conductivity and good electrical conductivity

insulation properties. In this exemplary embodiment, the carrier layer 5 has a ceramic material, for example AlN, S13N4, Al2O3 or SiC. By using carrier layers 5 with particularly good thermal conductivity (e.g. for AIN: up to 200 W/mK), the line cross-section for the electrical contacting can also be reduced, since heat can be dissipated immediately through the carrier layer 5 due to the ohmic losses.

In an alternative exemplary embodiment, the carrier layer 5 can also have a temperature-resistant plastic (eg polyimide or epoxy resin). In this case, due to the low thermal conductivity (< 10 W/mK) of the Plastic the thickness of the carrier layer 5 can be made so thin that the thermal resistance remains small enough.

In other words, a carrier layer 5 made of plastic must be made significantly thinner than a ceramic carrier layer. In particular, the plastic layer must be thin enough to guarantee thermal transport, but thick enough to guarantee electrical insulation and the mechanical stability of the PTC heating element 1 . For example, a carrier layer 5 made of plastic has a thickness of 50 gm. The electrical supply line (electrodes 3, additional contacts 4) can also function as a heat spreader here, in order to make the area that contributes to heat conduction in the carrier layer 5 as large as possible.

A carrier layer hybrid solution based on ceramics and plastic is also possible (see later the description of FIG. 8).

In this exemplary embodiment, a metallic layer 6 is also formed on the surface 5a of the carrier layer 5 . The metallic layer 6 completely covers an upper side and an underside of the carrier layer 5 . The metallic layer 6 facilitates the mechanical and thermal contacting of a (metallic) radiator or heat sink (not shown explicitly). The metallic layer 6 is very thin. For example, a thickness of the metallic layer 6 is between 1 μm and 100 μm. The metallic layer 6 has Cu, Al or W.

Overall, an overall height H of the PTC heating element 1 is between 500 gm and 2500 gm due to the construction described above. The lateral dimensions L of the PTC heating element 1 are between 10 mm and 250 mm in both directions (lateral dimensions L: length, ie extension along the main longitudinal axis X and width, ie extension transverse to the main longitudinal axis X).

The PTC heating element 1 is thus extremely compact, in particular large-area and thin. Through a suitable combination of the materials and connection techniques described above, together with the optimization of the geometry at the heating element level, the volume of the PTC heating element 1 and the heat extraction are optimized in such a way that the power density, the thermal response behavior as well as the robustness and reliability compared to the state of the art technology are significantly improved.

Due to the very efficient, thin and powerful design of the PTC heating element 1, there is also the possibility of using low-temperature PTCs. These can be made from completely bismuth and lead free materials.

FIG. 7 shows a sectional illustration of a PTC heating element 1 according to a further exemplary embodiment. In contrast to the exemplary embodiment shown in FIG. 6, the further contacts 4 are not formed between the carrier layer 5 and the PTC elements 2. Rather, the further contacts 4 are integrated into the carrier layer 5 . The additional contacts 4 emerge from the carrier layer 5 only on the side surface 1a of the PTC heating element 1 in order to ensure the electrical connection of the PTC heating element 1 . In this embodiment, the carrier layer 5 preferably has AlN. Each further point of contact 4 has a tungsten (W) layer. In other words, the additional contacts 4 embedded in the carrier layer 5 are preferably implemented by W contacts in an A1N carrier layer 5 . The W layer preferably has a thickness of 5 gm-20 gm. The W layer is preferably implemented in the carrier layer 5 over a large area.

As already explained in connection with FIG. 6, the carrier layer 5 has a typical thickness of 150 μm-1000 μm. The W layer may be formed symmetrically in a center portion of the base layer 5 or may be offset toward the center portion. In the embodiment according to FIG. 7, the respective further contacting 4 (W layer) is offset from the central area of the carrier layer 5 towards the PTC elements 2 . In any case, the W layer is arranged at least 50 μm below a surface of the carrier layer 5 .

In this exemplary embodiment, the PTC heating element 1 also has feedthroughs/vias 8 . The vias 8 preferably have tungsten. The vias 8 are preferably made of tungsten. However, the vias 8 can also have or consist of other electrically conductive materials.

The vias 8 completely penetrate the carrier layer 5 in a direction perpendicular to the main longitudinal axis X of the PTC heating element 1 . The vias 8 produce an electrically conductive connection between the W layers (additional contacts 4) and the electrodes 3 of the PTC elements 2. With regard to the properties and the other components/features of the PTC heating element 1, reference is made to the description in connection with FIG.

FIG. 8 shows a sectional illustration of a PTC heating element 1 according to a further exemplary embodiment.

In this embodiment, the carrier layer 5 has a hybrid solution based on ceramic and plastic materials. In particular, the PTC heating element 1 has a layer of temperature-resistant plastic 9 (e.g. polyimide or epoxy resin) on one side (here the upper side). On the opposite side (here underside), the PTC heating element 1 has a carrier layer 5 made of ceramic material—as already described in connection with FIG.

Of course, the plastic 9 can also be formed on the underside and the ceramic carrier material can be formed on the upper side.

The ceramic carrier layer 5 is used for mechanical stabilization and insulation of the PTC heating element 1 (in this case insulation of the underside). The plastic layer 9 serves to insulate the PTC heating element 1 (in this case insulation of the upper side). Both layers must be thick enough to ensure electrical insulation but thin enough to ensure thermal transport. In particular, due to the low thermal conductivity (<10 W/mK) of the plastic, the thickness of the plastic layer 9 must be made so thin that the thermal resistance remains small enough, as already described in connection with the exemplary embodiment according to FIG. The plastic layer 9 is in particular thinner than the ceramic layer 5. In this exemplary embodiment, for example, the thickness of the ceramic carrier layer 5 is ten to a hundred times greater than the thickness of the plastic layer 9. The plastic layer 9 has a thickness of between 2 μm and 50 μm. For example, the thickness of the plastic layer is 30 μm. The ceramic carrier layer 5 is between 0.5 mm and 1 mm thick in order to ensure the mechanical stability of the PTC heating element 1 .

With regard to the further properties or the further components/features of the PTC heating element 1, reference is made to the description in connection with FIG.

FIG. 11a shows a representation of a PTC heating element 1 according to the above statements. In particular, FIG. 11a shows a multiplicity of PTC elements 2, which are arranged one after the other along the main longitudinal axis X of the heating element 1. The PTC elements 2 are each contacted from the top 2a or the bottom 2b via electrodes 3 (see in particular Figures 6a, 9a, 9b and 9d).

The electrodes 3 are connected via strip-shaped additional contacts 4 from the upper side 2a or the lower side 2b of the PTC elements 2 . A connecting element 10 , for example a conductive adhesive, is formed between the electrodes 3 and the additional contacts 4 , which establishes an electrical and mechanical connection between the additional contacts 4 and the electrodes 3 . A filling material 7 can also be introduced into the cavity between two consecutive PTC elements 2 (not shown explicitly, see FIG. 6).

FIGS. 10 and 11b show a PTC heating element 1 according to a further exemplary embodiment. As already described above, the PTC heating element 1 is designed for use in a motor vehicle, for example in an electric vehicle. The PTC heating element 1 is designed to be integrated into an electrical device (for example an electrical heating device) with a radiator or a heat sink (not explicitly shown).

The PTC heating element 1 has electrodes/electrical contacts 3, further contacts 4 and a carrier layer/substrate 5. The carrier layer 5 preferably has a ceramic. The PTC heating element 1 also has connecting elements 10, as will be described in more detail below.

The PTC heating element 1 has a plurality of PTC elements 2 . Compared to the above statements (see also FIG. 11a in particular), the PTC elements 2 have a smaller extension perpendicular to the main longitudinal axis X of the PTC heating element 1. In other words, the PTC 2 elements according to FIGS. 10 and 11a have a shorter length than, for example, the PTC elements 2 according to FIG. 11a.

The PTC elements 2 are arranged adjacent to one another or one after the other on the carrier layer 5 . In particular, a plurality of PTC elements 2 are consecutive in the direction along the Main longitudinal axis X of the heating element 1 arranged. Furthermore, PTC elements 2 are arranged one after the other in a direction perpendicular to the main longitudinal axis X (ie along a transverse axis Y).

Design-related cavities occur between the PTC elements 2, as has already been described in connection with FIG. 6 (see also FIG. 11a). In this exemplary embodiment, the cavities run parallel and transverse to the main longitudinal axis X (see FIG. 11b).

As in the exemplary embodiments described above, the cavities transverse to the main longitudinal axis X can be filled with a temperature-resistant filling material 7 (not shown explicitly, see in particular FIG. 6). The thermal contact between the PTC elements 2 can thus be improved.

In the exemplary embodiment according to FIGS. 10 and 11b, the cavities parallel to the main longitudinal axis X are also filled with electrode material. In other words, in the respective cavity running along the main longitudinal axis X between two consecutive PTC elements 2 in the direction perpendicular to the main longitudinal axis X (i.e. along the transverse axis Y), an electrode 3 for electrical contacting of the two PTC elements 2 is formed.

The respective electrode 3 represents a metallization. The respective electrode 3 completely covers the side surface 2c (in particular a short side surface) of the respective PTC element 2 (see also the embodiment according to FIG. 9c). In other words, takes place in the Exemplary embodiment according to FIGS. 10 and 11b, the contacting of the PTC elements 2 from an end face of the PTC elements 2. In contrast to this, in the exemplary embodiments described above (see, for example, FIGS. 6 and 11a), contact is made with the PTC elements 2 from the top 2a and/or the bottom 2b of the PTC elements 2.

The respective electrode 3 or metallization fills the cavity between the PTC elements 2 completely. In this case, electrodes 3 with opposite polarity are arranged alternately. This means that a first cavity between two PTC elements 2 that follow one another in the direction along the transverse axis Y is filled with an electrode 3 of a first polarity. A second subsequent cavity in the direction along the transverse axis Y is filled with an electrode 3 of the opposite polarity. Two consecutive PTC elements 2 always share an electrode 3 or metallization, ie they are contacted by a common metallization.

In order to make electrical contact with the electrodes 3, the PTC heating element 1 also has the above-mentioned further contact 4, in particular a multiplicity of further contacts 4. The further contacts 4 are formed between the PTC elements 2 (in particular the electrodes 3) and the carrier layer 5.

This means that the additional contacts 4 are formed in particular at an interface between two PTC elements 2 that follow one another in the direction of the transverse axis Y. In other words, the additional contacts 4 cover at least those with electrode material filled cavities, which run along or parallel to the main longitudinal axis X.

The further contacts 4 are arranged alternately on the upper side 2a and the lower side 2b of the PTC elements 2 (see also FIG. 11a). The additional contacts 4 formed on the upper side 2a produce an electrical connection to the end-side electrodes 3 of a first polarity. The further contacts 4 formed on the underside 2b produce an electrical connection to the electrodes 3 of the opposite polarity on the face side.

The further contacts 4 are designed in the form of strips. The additional contacts 4 extend completely along the main longitudinal axis X. The individual additional contacts 4 are formed parallel to one another along the main longitudinal axis X.

The additional contacts 4 can emerge from the PTC heating element 1 on a side surface la (see FIG. 6) for electrical contacting of the heating element 1. The additional contacts 4 represent a metallization of the carrier layer 5. In particular, the additional contacts 4 in this exemplary embodiment correspond to metallization strips on a surface 5a of the carrier layer 5. The further contacts 4 are in direct contact with the carrier layer 5.

An electrically conductive connection between the electrodes 3 and the further contacts 4 is realized via the connection elements 10 . The respective connecting element 10 has a conductive adhesive, for example. The connecting elements 10 are formed between the PTC elements 2 (in particular the electrodes 3) and the further contacts 4. The connecting elements 10 are in particular in direct contact with the electrodes 3 (here on the face side) of the PTC elements 2 and the further contacts 4. The connecting elements 10 are designed in the form of strips. The respective connecting element 10 extends at least partially along the main longitudinal axis X.

In the exemplary embodiment according to FIGS. 10 and 11b, a connecting element 10 is formed at the interface between two PTC elements 2 that follow one another in the direction of the transverse axis Y. In other words, the respective connecting element 10 covers at least one cavity which is filled with electrode material and runs parallel to the main longitudinal axis X. Of course, the connecting elements 10 can also be made longer, so that they extend over several cavities and thus over more than two PTC elements 2 (not shown explicitly).

With regard to all other features with regard to the PTC elements 2, the carrier layer 5, the further contacts 4 and the electrodes 3, in particular also with regard to the composition and the dimensions of the components, reference is made to the above description.

The description of the objects given here is not limited to each specific embodiment. Rather, the features of the individual embodiments can be combined with one another as desired--insofar as this is technically reasonable. Reference List

1 PTC heating element la side surface of the PTC heating element

2 PTC element

2a Top of the PTC element

2b underside of the PTC element

2c side surface of the PTC element

3 electrode

4 Further contact

5 carrier layer

5a Surface of the carrier layer

6 Metallic layer

7 filling material

8 passage / Via

9 plastic

10 connection elements

1 Length of the PTC element d Thickness of the PTC element

H Overall height of the PTC heating element

L Lateral dimension of the PTC heating element

X Main longitudinal axis of the PTC heating element

Y transverse axis of the PTC heating element

100 PTC heating element

101 PTC element

102 Electrical contact

103 insulation layer

104 radiator

110 PTC heating element

111 PTC item 112 Electrical contact

113 insulation layer

120 PTC heating element 121 PTC element

122 Electrical contact

123 moulding

130 PTC heating element 131 PTC element

132 radiators

Claims

patent claims

Having a PTC heating element (1) for an electrical heating device

- at least one PTC element (2), wherein at least one electrode (3) is formed on a surface (2a, 2b, 2c) of the PTC element (2) for electrical contacting of the PTC element (2),

- at least one additional contact (4) for the electrical connection of the electrode (3) of the PTC element (2),

- at least one carrier layer (5), the carrier layer (5) being designed to be electrically insulating, the thickness (d) of the PTC element (2) being <500 gm and the overall height (H) of the PTC heating element (1) being between 500 gm and 2500 pm.

2. PTC heating element (1) according to claim 1, wherein a lateral dimension (L) of the PTC heating element (2) is between 10 mm and 250 mm in both directions.

3. PTC heating element (1) according to claim 1 or 2, wherein the at least one electrode (3) is formed flat on the surface (2a, 2b, 2c) of the at least one PTC element (2).

4. PTC heating element (1) according to one of the preceding claims, wherein in each case at least one electrode (3) is formed on an upper side (2a) and/or an underside (2b) of the PTC element (2) and/or wherein electrodes (3 ) are formed on side surfaces (2c) of the PTC element (2).

5. PTC heating element (1) according to one of the preceding claims, wherein the at least one electrode (3) is strip-shaped, rectangular, comb-like or designed as an interdigital structure and/or wherein the electrode (3) is on the surface (2a, 2b, 2c) of the PTC element (2) is sputtered, electroplated, printed or squeegeed.

6. PTC heating element (1) according to one of the preceding claims, wherein the further contact (4) is self-supporting or wherein the further contact (4) is sputtered, printed or doctored onto the carrier layer (5).

7. PTC heating element (1) according to one of claims 1 to 5, wherein the additional contact (4) is integrated into the carrier layer (5) and wherein the additional contact (4) <50 μm below a surface (5a) of the carrier layer (5) is arranged.

8. PTC heating element (1) according to one of the preceding claims, wherein a geometry of the further contact (4) is adapted to a geometry of the electrode (3) of the PTC element (2).

9. PTC heating element (1) according to one of the preceding claims, wherein a thickness of the further contact (4) is <10 μm.

10. PTC heating element (1) according to any one of the preceding claims, wherein the at least one additional point of contact (4) is electrically conductively connected to the at least one electrode (3) by means of clamping, gluing, sintering or high-temperature soldering.

11. PTC heating element (1) according to any one of the preceding claims, wherein the carrier layer (5) comprises a ceramic material with high thermal conductivity and / or a temperature-resistant plastic.

12. PTC heating element (1) according to one of the preceding claims, wherein the carrier layer (5) comprises AlN, S13N4, Al2O3, or SiC and/or wherein the carrier layer (5) comprises polyimide or epoxy resin.

13. PTC heating element (1) according to one of the preceding claims, wherein the carrier layer (5) has a thickness between 150 μm and 1000 μm.

14. PTC heating element (1) according to one of the preceding claims, further comprising at least one metallic layer (6) on a surface (5a) of the carrier layer (5) for further contacting of the PTC heating element (1).

15. PTC heating element (1) according to claim 14, wherein the metallic layer (6) has a thickness between 1 gm and 100 gm.

16. PTC heating element (1) according to any one of the preceding claims, wherein the at least one PTC element (2) comprises a ceramic material, a metal-ceramic material or an organic-ceramic material.

17. PTC heating element (1) according to any one of the preceding claims, wherein a material of the at least one PTC element (2) has a low specific resistance.

18. PTC heating element (1) according to any one of the preceding claims, wherein the at least one PTC element (2) comprises a bismuth and lead-free material.

19. PTC heating element (1) according to any one of the preceding claims, wherein the at least one PTC element (2) is a low-temperature PTC element.

20. PTC heating element (1) according to one of the preceding claims, wherein a thickness (d) of the PTC element (2) is <250 μm.

21. PTC heating element (1) according to any one of the preceding claims, wherein the at least one PTC element (2) and / or the at least one carrier layer (5) is formed plane-parallel.

22. PTC heating element (1) according to claim 21, wherein the at least one PTC element (2) has a plane parallelism of <100 mpi and/or wherein the at least one carrier layer (5) has a plane parallelism of <500 mpi.

23. PTC heating element (1) according to one of the preceding claims, wherein the at least one PTC element (2) is at least partially embedded in the carrier layer (5).

24. PTC heating element (1) according to any one of the preceding claims, comprising a plurality of PTC elements (2), wherein a cavity between two consecutive PTC elements (2) is filled with a temperature-resistant filling material (7).

25. PTC heating element (1) according to one of the preceding claims, having a plurality of PTC elements (2), wherein a cavity between two consecutive PTC elements (2) is filled with an electrode (3) for electrical contacting of the respective PTC element ( 2).

26. PTC heating element (1) according to claim 25, wherein contacting of the respective PTC element (2) takes place from an end face of the PTC element (2).

27. PTC heating element (1) according to any one of the preceding claims, having a plurality of additional contacts (4), wherein the respective additional contact (4) is designed in strip form.

28. PTC heating element (1) according to claim 27, wherein the additional contacts (4) are formed alternately on an upper side (2a) and an underside (2b) of the PTC elements (2).

29. PTC heating element (1) according to one of the preceding claims, further comprising at least one connecting element (10) for the electrical connection between the at least one PTC element (2) and the at least one additional contact (4).

30. PTC heating element (1) according to claim 29, wherein the at least one connecting element (10) is designed in strip form.

31. PTC heating element (1) according to claim 29 or 30, having a plurality of connecting elements (10), wherein the respective connecting element (10) at least between the respective additional contact (4) and the respective electrode (3) of the PTC element (2) is trained.

32. PTC heating element (1) according to any one of claims 29 to 31, wherein the at least one connecting element (10) has a conductive adhesive.

33. Having electrical heating device

- At least one PTC heating element (1) according to any one of the preceding claims,

- At least one component with heat-emitting surfaces.

34. Use of the PTC heating element (1) according to any one of claims 1 to 32 in a motor vehicle.