Surface-mountable temperature sensor

Abstract

The present invention relates to a surface-mountable temperature sensor (1) of flip-chip design for mounting on a printed circuit board (10), the temperature sensor comprising: a sensor element (2), the electrical properties of which vary depending on the temperature; and an outer metallisation (3) for contacting the printed circuit board (10), the outer metallisation (3) extending both over a surface (2A, 3A) which faces the printed circuit board (10) in the mounted state, and, in the form of a solder-wettable side flank (3B), over a side surface (2B) which is perpendicular to the surface (3A). The invention also relates to a sensor device comprising the sensor (1) and a printed circuit board (10) on which the sensor (1) is mounted by means of the flip-chip method.

Description

[0001] Description

[0002] Surface-mountable temperature sensor

[0003] The invention relates to a surface-mountable temperature sensor and a sensor device comprising a circuit board and a surface-mountable temperature sensor which is attached to the circuit board in a flip-chip design.

[0004] One problem with known surface-mountable temperature sensors is the targeted modification of heat transfer to the sensor, especially with increasing miniaturization of the components.

[0005] The object of the present invention is therefore to provide constructive possibilities for modifying the heat transfer to the sensor.

[0006] This task is solved by a sensor described in the claims and a corresponding sensor device comprising a circuit board and the sensor.

[0007] Further details can be found in the description.

[0008] The surface-mountable temperature sensor according to the invention in flip-chip design comprises a sensor element that changes its electrical properties depending on the temperature.

[0009] The temperature sensor is suitable for mounting on a circuit board using the flip-chip method, meaning that the sensor's conductive structures face the circuit board when the sensor is mounted. Furthermore, the temperature sensor includes an outer metallization for contacting the circuit board. This outer metallization is located on at least one surface that faces the circuit board when installed, or extends over a section of the surface, allowing the outer metallization to be directly soldered or otherwise connected to the circuit board's contacts (see flip-chip design of the temperature sensor).

[0010] In addition, the external metallization also extends in the form of a side flank that can be wetted with solder on a side surface perpendicular to the surface.

[0011] The external metallization comprises a closed metallization layer that extends over the edge between the surface and the side surface of the sensor element and is preferably homogeneously and monolithically structured.

[0012] This allows for improved contact with miniaturized sensors and more precise adjustment of heat transfer between the sensor and the circuit board or between the sensor and the environment.

[0013] According to one embodiment, the sensor element includes a thermistor which has a temperature-dependent electrical resistance.

[0014] Such a thermistor can, for example, comprise a ceramic, a semiconductor, or a metallic resistor. Further modifications are explained in the exemplary embodiments. According to one embodiment, the sensor element can further comprise a support, also called a substrate, on which the thermistor is applied or which supports the substrate, and which preferably provides mechanical stability to the sensor element. The thermistor can, in particular, be applied to the support as a functional layer. The support can, for example, comprise glass, sapphire, or a semiconductor material.

[0015] According to one embodiment, the side face of the outer metallization has a higher heat absorption from radiation from the environment than the sensor element, so that a larger side face can increase the heat absorption from the environment, especially e.g. of thermal radiation.

[0016] According to one embodiment, the side face of the outer metallization has a lower heat absorption from radiation from the environment than the sensor element, so that a larger side face can reduce heat absorption from the environment, especially e.g. from thermal radiation.

[0017] In particular, the heat transfer from the environment to the electrode and then to the sensor element can also be adjusted by using solder material with a correspondingly high or low heat absorption coefficient, with which the side flank is preferably wettable or is wetted.

[0018] According to one embodiment, the external metallization is monolithic and preferably exhibits homogeneous properties. The external metallization is therefore uniform regardless of its orientation.

[0019] According to one embodiment, the surface-mountable temperature sensor is enclosed by an insulating encapsulation, except at the exposed areas of the outer metallization, which inhibits heat transfer between the environment and the sensor element.

[0020] This allows the heat transfer to the sensor to be adjusted even more precisely by the shape, geometry and properties of the electrodes and the adjacent solder material.

[0021] According to one embodiment, the surface-mountable temperature sensor is enclosed by an insulating encapsulation, except at the exposed areas of the outer metallization, which enhances heat transfer between the environment and the sensor element.

[0022] This can increase the heat transfer from the environment to the sensor element.

[0023] This can advantageously ensure, for example, a high heat transfer from the circuit board via the solder material and from the environment both via the solder material and the encapsulation.

[0024] According to one embodiment, the surface-mountable temperature sensor is implemented as a die or chip, preferably as part of a wafer or isolated from a wafer. Manufacturing the structures at the wafer level (wafer-level manufacturing and packaging) allows for a particularly efficient production process. This method is especially suitable for sensor elements based on semiconductors such as silicon.

[0025] According to one implementation form, the thermistor is an NTC ceramic component, preferably built using thin-film technology or thick-film technology.

[0026] Thin-film technology enables further miniaturization.

[0027] According to one embodiment, the temperature sensor has two outer metallizations with side flanks, which are particularly preferably symmetrical and applied to opposite ends of the sensor, and preferably function as differently polarized electrodes.

[0028] There may also be more than two outer metallizations, which may or may not be in contact with contacts on the circuit board.

[0029] The invention further relates to a sensor device comprising a circuit board and the surface-mountable temperature sensor applied to the circuit board by means of the flip-chip method, as previously described.

[0030] Here, the contact point of the circuit board is electrically contacted and mechanically connected to the outer metallization of the surface-mountable temperature sensor by means of a solder flank, preferably made of solder material. According to one embodiment, the solder flank connects the contact point of the circuit board directly to the side flank of the outer metallization.

[0031] The thermal resistance during heat transfer from the circuit board to the sensor element can preferably be adjusted via the solder flank, its shape and material.

[0032] According to one implementation, the contact point of the circuit board is directly connected to both surfaces of the outer metallization. This ensures sufficient heat transfer from the circuit board to the sensor element.

[0033] According to one design, the side flank of the external contact is completely wetted by the solder flank. This results in high heat transfer from the solder flank to the external contact.

[0034] In particular, the solder edge can be designed in such a way that it absorbs heat radiation from the environment well, so that consequently a high heat input from the environment onto the sensor element takes place.

[0035] According to one design, the side flank of the external contacts is only partially wetted by the solder flank.

[0036] This is particularly advantageous for heat input from the environment when the side flank has a high heat absorption coefficient, preferably higher than the solder flank. At the same time, this reduces heat transfer from the circuit board. According to one embodiment, the unwetted surface area of ​​the side flank is larger than the wetted surface area.

[0037] According to one implementation form, the non-wetted surface of the side flank is smaller than the wetted surface.

[0038] Depending on the properties of the side flanks, the sensor element and the solder flanks, the heat transfer from the environment to the sensor element and from the circuit board to the sensor element can be specifically adapted.

[0039] The heat transfer from the circuit board to the sensor element can also be adjusted by modifying the solder pads or other contact points of the circuit board.

[0040] According to one implementation, the surface area of ​​the outer metallization facing the circuit board is larger than the surface area of ​​the side flank. This increases heat transfer between the sensor and the circuit board while reducing the intensity of heat transfer from the environment.

[0041] According to one design, the size of the surface of the outer metallization facing the circuit board is maximized, the size of the contact point of the circuit board is maximized, and the size of the side flank is minimized.

[0042] The solder flank fills the entire gap between the surface of the outer metallization facing the circuit board and the contact point of the circuit board, so that the ratio of heat transfer from the circuit board to the sensor element compared to the heat input into the sensor element from the environment is comparatively high, especially compared to the following two design forms.

[0043] The solder flank preferably has the largest possible cross-section on average (wide solder flank) in order to improve heat transfer.

[0044] If, on the other hand, the solder flank has a different design with a cross-section that is as small as possible on average (narrow solder flank), the heat transfer between the circuit board and the sensor element is reduced.

[0045] According to one implementation, the surface area of ​​the outer metallization facing the circuit board is smaller than the surface area of ​​the side flank. This reduces heat transfer between the sensor and the circuit board while increasing the intensity of heat transfer from the environment.

[0046] According to one embodiment, the size of the surface of the outer metallization facing the circuit board is minimized, the size of the contact point of the circuit board is minimized, and the size of the side flank is maximized, so that the ratio of heat transfer from the circuit board to the sensor element compared to the heat input into the sensor element from the environment is comparatively low, especially compared to previously mentioned embodiments.

[0047] The statement that "the ratio of heat transfer from the circuit board to the sensor element compared to the heat input into the sensor element from the environment is comparatively low or high" does not mean that "the heat transfer from the circuit board to the sensor element compared to the heat input into the sensor element from the environment" is high or low, but merely that the ratio of the two heat transfer flows is high or low compared to other implementation forms.

[0048] According to one embodiment, the side of the sensor element facing the circuit board has small dimensions, with the size of the surface of the outer metallization facing the circuit board being minimized, the size of the contact point of the circuit board being maximized, the size of the side flank being maximized, and the solder flank filling the entire space between the side flank and the contact point of the circuit board, so that the heat transfer from the circuit board to the sensor element is comparatively high despite the small dimensions of the side of the sensor element facing the circuit board.

[0049] This ensures sufficiently high heat transfer from the circuit board to the sensor element or vice versa, even with small sensor element dimensions.

[0050] In one embodiment, the outer metallization is coated in such a way that the solder material adheres particularly well or at least does not adhere to the electrode surface in certain sections.

[0051] For example, the thermal coupling between the outer metallization and the solder flank can be specifically increased or decreased by a corresponding surface coating of the outer metallization.

[0052] In one execution form, the material of

[0053] External metallization, the solder material of the solder flank, the soldering process and surface coatings of the electrodes are specifically modified and adapted.

[0054] Preferably, the sensor device has two of the outer metallizations with side flanks on the temperature sensor and the circuit board has two contact points and each of the contact points is connected to one of the side flanks by means of a solder flank.

[0055] The individual features of the design forms can be combined as appropriately as desired to reduce or increase the heat transfer between the circuit board and the sensor element and / or between the environment and the sensor element.

[0056] The heat transfer to the sensor can be specifically adjusted, depending on which temperature the sensor is supposed to detect.

[0057] An overview of individual features is given in the following table.

[0058] Table 1:

[0059] The invention will now be described in more detail with reference to exemplary embodiments and accompanying figures.

[0060] Figure 1 shows a first embodiment of the surface-mountable temperature sensor with sensor elements and electrodes, wherein, according to the invention, the electrodes also cover the side surfaces of the sensor element.

[0061] Figure 2 shows an exemplary cross-sectional structure of the sensor element, with a support carrying the thermistor.

[0062] Figure 3 shows an exemplary sensor device with a circuit board and temperature sensor chip, where high thermal coupling is set between the sensor chip and the circuit board. Figure 4 shows another exemplary sensor device with a circuit board and temperature sensor, where low thermal coupling is set between the sensor chip and the circuit board and the connecting solder material absorbs thermal radiation from the environment well.

[0063] Figure 5 shows another exemplary sensor device with circuit board and temperature sensor, wherein a low thermal coupling is set between the sensor chip and the circuit board and a side flank of the electrode absorbs thermal radiation from the environment better than the connecting solder material.

[0064] Figure 6 shows another exemplary sensor device with circuit board, wherein the temperature sensor is further shortened in length parallel to the circuit board, and has dimensions similar to or shorter than the spacing of the contacts of the circuit board.

[0065] Figure 7 shows another exemplary sensor device with circuit board and temperature sensor, wherein a high thermal coupling is set between the sensor chip and the circuit board as well as between the sensor chip and the environment.

[0066] Figure 8 shows a side view of a sensor chip with sensor element and a side flank of an electrode, the side flank having a rectangular shape.

[0067] Figure 9 shows a side view of a sensor chip with a sensor element and a side flank of an electrode, the side flank having a semicircular shape. Figure 10 shows a side view of a sensor chip with a sensor element and a side flank of an electrode, the sensor element being flattened for further miniaturization.

[0068] Figure 11 shows an exemplary design with encapsulation.

[0069] Similar or seemingly identical elements in the figures are marked with the same reference symbol. The figures and their proportions are not to scale. The optional features of the exemplary embodiments can be combined as desired.

[0070] Figure 1 shows a first embodiment of a surface-mountable temperature sensor 1 according to the invention, which is in particular implemented as a mouse-shaped sensor chip. The temperature sensor 1 comprises a sensor element 2 and two symmetrically applied outer metallizations 3, which function as electrodes 3 of the sensor.

[0071] The external metallizations 3 are suitable for being wetted with solder. However, the surfaces of the external metallizations 3 can also be treated in such a way that sections of the external metallizations 3 cannot be wetted with solder.

[0072] In the example shown, sensor element 2 is cuboid-shaped, but it can also have other geometric shapes, for example, a cubic or prismatic shape. Sensor element 2 comprises a temperature-sensitive

[0073] Material, preferably a thermistor that changes its electrical resistance depending on the temperature.

[0074] In this example, the sensor element can be a semiconductor, for example based on silicon, a platinum resistor (e.g., PtlOO), or a ceramic material. The thermistor 21 is preferably mounted on a substrate 22, e.g., made of glass, sapphire, or silicon, as shown in Figure 2. In particular, the sensor element can be a chip or a die that has been machined, separated, or isolated from a wafer, e.g., based on a silicon, glass, or sapphire substrate material.

[0075] If the sensor is isolated from a wafer as a chip, several methods are conceivable. The chip can be provided either as a separate die, but not yet completely isolated from the wafer, in the form of a wafer-level chip-scale package (see, for example, publication WO 2021 / 219254Al), or separately and isolated in the form of a lead frame package.

[0076] The materials can have either a negative temperature coefficient (NTC) or a positive temperature coefficient (PTC). This means that with increasing temperature, the electrical resistance either decreases (NTC) or increases (PTC).

[0077] The electrical resistance in a semiconductor is known to change through the pn junction. Examples of ceramic materials include AlOx, Al₂O₅, and ZnMnNiO ceramic compounds.

[0078] In the present example, this is, for example, an NTC ceramic sensor element.

[0079] The sensor element again comprises the carrier 22 and a functional thermistor layer 21 as a thermistor, which is applied to the carrier 22.

[0080] In a functional NTC ceramic layer, which acts as an active thermistor layer, one or more internal electrodes are preferably incorporated.

[0081] The layers can be applied as thick or thin films. The application of thin films is preferred.

[0082] The thin films can be applied, for example, by CVD (chemical vapor deposition), PECVD (plasma-enhanced CVD), sputtering, sol-gel technology, or screen printing. Applying thin films allows for further miniaturization of sensor element 2.

[0083] The sensor element 2 preferably has the smallest possible component size of a maximum of 0.6 x 0.3 x 0.5 mm (length x width x height) in accordance with standard EIA 0201 (according to CSP 01005) or smaller. The height is preferably a maximum of 0.3 mm, more preferably a maximum of 0.2 mm, and most preferably a maximum of 0.1 mm. The height is the dimension of the sensor 1 extending perpendicularly to a circuit board onto which the sensor is surface-mounted using the flip-chip method.

[0084] The electrodes 3 comprise a metal with good electrical conductivity or consist of such a metal, such as copper, silver, nickel or an alloy of the metals.

[0085] The electrodes 3 are applied as thin layers to each of two adjacent surfaces and the intermediate edge of the sensor element 2 (see Figure 1).

[0086] Each electrode 3 comprises a section 3A on a surface 2A of the sensor element 2, which faces a circuit board, and a related section 3B, the side flank 3B, on a side surface 2B perpendicular to the surface 2A. The electrodes 3 are applied directly to the sensor element 2 and cover sections of its surfaces 2A and 2B.

[0087] The circuit board 10 includes electrical connections and circuits for external electrical contact and for controlling the sensor 1.

[0088] The two electrodes 3 are arranged on different side faces. Namely, on opposite side faces 2B-1 and 2B-2.

[0089] The thickness and extent of the electrode sections 3A and 3B are preferably homogeneous, as is the material structure. Preferably, the electrodes 3 are monolithic. The electrodes 3 serve to contact the sensor element 2 with contacts on the circuit board. The extension of the electrodes 3 over the side surfaces 2B has the particular advantage that the sensor 1 can also be contacted from the circuit board via the side surfaces, thus further reducing the extent of the sensor element 2 between the side surfaces 2B, i.e., the length of the sensor element 2 defined above, and allowing the sensor to be manufactured in a smaller size, i.e., miniaturized.

[0090] In particular, for temperature sensor 1, it is crucial where and how the heat transfer to sensor 1 takes place.

[0091] In various applications of the temperature sensor 1, heat transfer is desired either from the circuit board 10 to the temperature sensor 1 or from the environment (especially thermal radiation) to the temperature sensor 1. The side faces 3B of the electrodes 3 serve to modify the type and amount of heat transfer.

[0092] In a first scenario, a high heat transfer from a circuit board 10 to the temperature sensor 1 is desired, since the temperature of the circuit board 10 or of a coupled electrical device is to be measured by the sensor 1. For this, close thermal contact and good heat transfer from the circuit board 10 to the temperature sensor 1 or to the temperature-sensitive sensor element 2 are required.

[0093] For this purpose, as shown in Figure 3, the side flanks 3A are made as short as possible and the sections 3B of the electrodes 3 on the surface 2A are made as long as possible. At the same time, the solder pads 11 on the circuit board 10, which act as contacts of the circuit board 10 opposite the sensor 1, are made as long as possible. The space between the solder pads 11 and the electrodes 3 is preferably completely filled with solder material 20 in the form of a solder flank, through which the electrical, mechanical, and thermal coupling takes place.

[0094] In other words, the amount of solder material 20, and thus the thermal resistance between the sensor 2 and the circuit board 10, can be adjusted via the shape, position, and size of the electrodes 3 and the solder pads 11. Larger electrodes 3 and solder pads 11 reduce the thermal resistance between the sensor 2 and the circuit board 10.

[0095] According to a second scenario in Figure 4, as little heat as possible should be transferred between the circuit board 10 and the sensor 1, which is then primarily used to detect the

[0096] Heat radiation from the surroundings serves .

[0097] In this second S scenario, the side flanks 3B of the electrodes 3 are preferably as high as possible and the section 3A of the electrodes 3 is preferably narrow.

[0098] The electrodes 3 preferably comprise material that absorbs heat radiation from the environment well.

[0099] Furthermore, the solder material 20 is preferably designed to absorb heat radiation from the environment effectively. Depending on whether the solder material 20 or the side faces 3B absorb heat better, particularly heat radiation, it is preferred that the solder material 20 wets the entire side faces 3B (Figure 4) or covers only a portion thereof (Figure 5). For this purpose, the surface of sections of the side faces 3B is modified accordingly. The solder pads 11 on the circuit board 10 are preferably smaller in the second scenario than in the first. The embodiments are shown in Figures 4 and 5.

[0100] In another embodiment (Figure 6), the sensor element 2 is so narrow in length and width that it is shorter, the same length, or only slightly longer than the distance between two contacts on the circuit board in the same direction. Sufficient heat transfer from the circuit board 10 to the sensor element 2 can then only be achieved by contacting the side flanks 3B. For this purpose, both the side flanks 3B and the solder pads 11 are designed to be as large as possible, and the entire space between the side flanks 3B and the solder pads 11 is preferably filled with solder material 20.

[0101] A corresponding implementation form is shown in Figure 6.

[0102] Furthermore, a scenario is possible in which both the heat of the circuit board 10 and the ambient temperature are to be detected by the temperature sensor 1. In this embodiment (Figure 7), both the side flanks 3B and the sections 3A of the electrodes 3 have a large surface area. A corresponding embodiment is shown in Figure 7.

[0103] In further implementation forms, the shape and geometry of the sensor element 2 and the electrodes 3, in particular the side flanks 3B, can be changed.

[0104] Figure 8 shows a sensor 1 with standard rectangular side flanks 3B of the electrodes 3 and Figure 9 shows a sensor 1 with semicircular side flanks 3B, each shown from the side view.

[0105] Figure 10 shows a sensor 1 with a particularly low component height.

[0106] Furthermore, in various embodiments, the material of the electrode 3, the material of the solder material 20, the soldering process and surface coatings of the electrodes 3 can be specifically modified and adapted.

[0107] For example, the electrode 3 can be coated in such a way that the solder material 20 adheres particularly well or at least does not adhere to the electrode surface in certain sections (see the exemplary illustration in Figure 5). For example, the thermal coupling between the electrode 3 and the solder material 20 can also be further increased or selectively reduced by a surface coating of the electrode 3.

[0108] Possible coatings for the electrodes 3 that improve solder adhesion include, for example, nickel-tin alloys or ENIG (Electroless Nickel Immersion Gold) or other suitable materials.

[0109] All the described, partly optional, design features have in common that, through their targeted combination (which is not limited to the specifically described combinations), the amount, location, and direction of the heat input can be adjusted very precisely, or the thermal resistance between sensor element 2 and circuit board 10 can be specifically set. Figure 11 shows one of the exemplary embodiments, which, by way of example, has an insulating encapsulation around the sensor element 2 of the sensor 1.

[0110] The encapsulation can also be a component of all other embodiments. The encapsulation serves in particular to protect, electrically insulate, and preferably also thermally insulate the temperature-sensitive sensor element 2.

[0111] The encapsulation 30 preferably consists of an insulating layer 30, which preferably comprises or consists of a resin such as an epoxy resin or a composite material or another suitable organic material.

[0112] The encapsulation 30 preferably covers the entire surface of the sensor element 2, except for the areas of the surface where the electrodes 3 are placed for external contact with the sensor element 2. Such an encapsulation 30 thus allows the temperature input into the sensor element 2 to be controlled in a targeted manner.

[0113] The temperature input is then preferably only, or at least only substantially, at points on the surface of the sensor element 2 where there is no encapsulation, i.e., via the electrodes 3. In this way, the heat input from the circuit board 10 or from the environment to the sensor element 2 can be adjusted even more precisely by means of the arrangement and geometry of the electrodes and the adjacent solder material 20.

[0114] In an alternative embodiment, the

[0115] Encapsulation 30 also includes straight material or consists of a

[0116] The material should be one that absorbs thermal radiation particularly well, thus ensuring a high heat input into the sensor element 2, preferably higher than at the points where the electrodes 3 are in contact. In such a case, the heat input from the environment could be further increased in a targeted manner. Furthermore, the encapsulation also serves for electrical insulation and protection against external physical, mechanical, or chemical influences.

[0117] Alternatively, encapsulations that selectively reflect thermal radiation are also conceivable. Possible materials that absorb or reflect thermal radiation include, for example, dielectric filter materials.

[0118] Reference character list

[0119] 1 temperature sensor

[0120] 2 Sensor element 2A, 2B Surface and side surfaces of the sensor element

[0121] 21 Thermistor

[0122] 22 carriers

[0123] 3 Electrode, external metallization

[0124] 3A, 3B sections of the electrodes 10 circuit board

[0125] 11 solder pad

[0126] 20 solder material

[0127] 30 Encapsulation

Claims

Patent claims 1. Surface-mountable temperature sensor (1) in flip-chip design for mounting on a circuit board (10), comprising a sensor element (2) which changes its electrical properties depending on the temperature, an outer metallization (3) for contacting a circuit board (10), wherein the outer metallization (3) extends on a surface (2A, 3A) which faces the circuit board (10) in the installed state, and in the form of a side flank (3B) wettable with solder (20) on a side surface (2B) perpendicular to the surface (3A).

2. Surface-mountable temperature sensor (1) according to claim 1, wherein the sensor element (2) comprises a thermistor (21) , which has a temperature-dependent electrical resistance, and optionally includes a support (22) for the thermistor (21).

3. Surface-mountable temperature sensor (1) according to one of claims 1 to 2, wherein the side flank (3B) of the outer metallization (3) has a higher heat absorption from radiation from the environment than the sensor element. (2) .

4. Surface-mountable temperature sensor (1) according to one of claims 1 to 2, wherein the side flank (3B) of the outer metallization (3) has a lower heat absorption from radiation from the environment than the sensor element. (2) .

5. Surface-mountable temperature sensor (1) according to one of claims 1 to 2, wherein the outer metallization (3) is monolithic and has homogeneous properties.

6. Surface-mountable temperature sensor (1) according to one of claims 1 to 5, which, except at the points of the outer metallizations (3) that are exposed, is enclosed by an insulating encapsulation (30) which inhibits the heat transfer between the environment and the sensor element (2).

7. Surface-mountable temperature sensor (1) according to one of claims 1 to 5, which, except at the points of the outer metallizations (3) that are exposed, is enclosed by an insulating encapsulation (30) which enhances the heat transfer between the environment and the sensor element (2).

8. Surface-mountable temperature sensor (1) according to one of claims 1 to 7, which is designed in the form of a die as part of a wafer.

9. Surface-mountable temperature sensor (1) according to one of claims 1 to 7, which is an NTC ceramic component.

10. Surface-mountable temperature sensor (1) according to claim 9, which is constructed using thin-film technology.

11. Surface-mountable temperature sensor (1) according to any one of claims 1 to 10, wherein the side flank (3B) has a rectangular shape.

12. Surface-mountable temperature sensor (1) according to any one of claims 1 to 10, wherein the side flank (3B) has a semicircular shape.

13. Surface-mountable temperature sensor (1) according to one of claims 1 to 12, comprising two of the external metallizations (3) with side flank (3B).

14. Sensor device comprising a circuit board (10) and the surface-mountable temperature sensor (1) applied to the circuit board (10) by means of a flip-chip method according to one of claims 1 to 13, wherein a contact point (11) of the circuit board (10) is electrically contacted and mechanically connected to the outer metallization (3) of the surface-mountable temperature sensor by means of a solder flank (20).

15. Sensor device according to claim 14, wherein the solder flank (20) connects the contact point (11) of the circuit board (10) directly to the side flank (3B) of the outer metallization (3).

16. Sensor device according to one of claims 14 to 15, wherein the solder flank (20) forms the contact point (11) of the circuit board (10) directly connects to both surfaces of the outer metallization (3).

17. Sensor device according to one of claims 14 to 16, wherein the side flank (3B) of the external contact is completely wetted by the solder flank (20).

18. Sensor device according to one of claims 14 to 17, wherein the side flank (3B) of the external contacts is only partially wetted by the solder flank (20).

19. Sensor device according to claim 18, wherein the non-wetted surface of the side flank (3B) is larger than the wetted surface.

20. Sensor device according to claim 19, wherein the non-wetted surface of the side flank (3B) is smaller than the wetted surface.

21. Sensor device according to one of claims 14 to 20, wherein the surface (3A) of the outer metallization (3) facing the circuit board (10) is larger than the surface of the side flank (3B) .

22. Sensor device according to claim 21, wherein the size of the surface (3A) of the outer metallization (3) facing the circuit board (10) is maximized, the size of the contact point (11) of the circuit board (10) is maximized, the size of the side flank (3B) is minimized, and the solder flank (20) fills the entire space between the surface (3A) of the outer metallization (3) facing the circuit board (10) and the contact point (11) of the circuit board (10), such that the ratio of heat transfer from the circuit board (10) to the sensor element (2) is comparatively high in comparison to the heat input into the sensor element (2) from the environment.

23. Sensor device according to one of claims 14 to 20, wherein the surface (3A) of the outer metallization (3) facing the circuit board (10) is smaller than the surface of the side flank (3B) .

24. Sensor device according to claim 23, wherein the size of the surface (3A) of the outer metallization (3) facing the circuit board (10) is minimized and the size of the The contact point (11) of the circuit board (10) is minimized and the size of the side flank (3B) is maximized, so that the ratio of heat transfer from the circuit board (10) to the sensor element (2) is comparatively low compared to the heat input into the sensor element (2) from the environment.

25. Sensor device according to claim 23, wherein the side (2A) of the sensor element (2) facing the circuit board (10) has small dimensions, wherein the size of the surface (3A) of the outer metallization (3) facing the circuit board (10) is minimized, the size of the contact point (11) of the circuit board (10) is maximized, the size of the side flank (3B) is maximized, and the solder flank (20) fills the entire space between the side flank (3B) and the contact point (11) of the circuit board (10), so that the heat transfer from the circuit board (10) to the sensor element (2) is comparatively high despite the small dimensions of the side of the sensor element (2) facing the circuit board (10).

26. Sensor device according to one of claims 14 to 25, wherein the surface-mountable temperature sensor (1) has two of the outer metallizations (3) with side flanks (3B) and the circuit board (10) has two contact points (11) and each of the contact points (11) is connected to one of the side flanks (3B) by means of a solder flank (20).

27. Sensor device according to claim 14, wherein the size of the surface (3A) of the outer metallization (3) facing the circuit board (10) is maximized, the size of the contact point (11) of the circuit board (10) is maximized, and the solder flank (20) is as wide as possible, so that the Heat transfer between the circuit board (10) and the sensor element (2) is as high as possible.

28. Sensor device according to claim 14, wherein the size of the surface (3A) of the outer metallization (3) facing the circuit board (10) is minimized and the size of the contact point (11) of the circuit board (10) is minimized and the solder flank (20) is as narrow as possible, so that the heat transfer between the circuit board (10) and the sensor element (2) is as low as possible.

29. Sensor device according to claim 14, wherein the size of the side flank (3B) is minimized and wherein the solder flank (20) has the lowest possible heat absorption coefficient and further comprising an insulating encapsulation (30) according to claim 6, such that the heat transfer between the environment and the sensor element (2) is as low as possible.

30. Sensor device according to claim 14, wherein the size of the side flank (3B) is maximized and wherein the solder flank (20) has the highest possible heat absorption coefficient and further comprising an insulating encapsulation (30) according to claim 7, such that the heat transfer between the environment and the sensor element (2) is as high as possible.

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