Magnetic-field sensor having a sensor board

Abstract

The invention relates to a magnetic-field sensor (1) having a microwave source (6) and a sensor board (2), the sensor board (2) comprising a sensor crystal (5) having at least one magneto-optical defect, an excitation-light source (3), a detector (7) and at least two permanent magnets (8). The sensor crystal (5) is arranged in such a way that microwave radiation generated by the microwave source (6) can be absorbed by the at least one magneto-optical defect of the sensor crystal (5). The excitation-light source (3) is designed to emit an excitation-light beam (4) and is designed and arranged in such a way that the excitation-light beam (4) emitted by the excitation-light source (3) can cause fluorescent radiation to be emitted in the at least one magneto-optical defect of the sensor crystal (5). The detector (7) is designed and arranged so as to detect the emitted fluorescent radiation. The at least two permanent magnets (8) are arranged and designed so as to generate a homogeneous static magnetic field in the sensor crystal (5).

Description

[0001] Description

[0002] title

[0003] Magnetic field sensor with a sensor board

[0004] The present invention relates to a magnetic field sensor based on a sensor board, as well as a method for producing such a magnetic field sensor.

[0005] Background of the invention

[0006] To detect a magnetic field, so-called NV magnetic field sensors are used. These comprise a diamond whose crystal lattice exhibits defects in the form of NV centers. In an NV center, a nitrogen atom occupies the lattice site of a carbon atom, with a defect located directly adjacent to the nitrogen atom - again on the lattice site of a carbon atom. If such a crystal lattice is irradiated with excitation radiation with a wavelength between 490 nm and 575 nm, an electronic transition from a ground state to a 3AJ into an excited state 3 E induced. From the excited state 3 E relaxes the NV center back to the ground state by emitting fluorescence radiation in a wavelength range between 650 nm and 750 nm 3 A2. The ground state 3 AJ has three magnetic substates with m s =0, m s =±1. The states with m s =0 and m s =±1 are distinguished by an energy difference of 2.87 GHz (zero field splitting). The excited state 3 E also has three magnetic substates with m s =0, m s =±1. If the NV center in the ground state 3 AJ exposed to microwave radiation with a frequency of 2.87 GHz, the NV center oscillates between the m s =0, 3 AJ - ground state and the m s =±1 , 3 Aj -ground state. Upon irradiation with the excitation radiation, the NV center is now partially removed from the ms =±1 , 3 Aj- ground state in the excited m s =±1 , 3 E state. From there, it relaxes back to the ground state, predominantly without radiation. If the amplitude of the fluorescence radiation is measured as a function of the frequency of the microwave radiation, a sudden drop in the amplitude of the fluorescence radiation (a so-called dip) occurs at a frequency of 2.87 GHz. The drop in the amplitude of the fluorescence radiation can be explained by the fact that - when microwave radiation with a frequency of 2.87 GHz is applied - fewer NV centers in the m s =0, 3 AJ ground state are available, which are optically excited and emit fluorescence radiation into the m s =±1 , 3 Aj -ground state can relax.

[0007] In an external magnetic field, the m s =±1 , 3 Aj -ground state into two states with spin quantum number m s=1 and m s =-1 (Zeemann effect). If the amplitude of the fluorescence radiation is now measured while changing the frequency of the microwave radiation, two dips are obtained. The frequencies at which these dips occur depend on the size of the splitting of the m s =±1 , 3 Aj ground state and thus on the field strength of the external magnetic field. In this way, the field strength of an external magnetic field can be determined.

[0008] Such a magnetic field sensor is known, for example, from DE 10 2020 204 732. Here, the excitation radiation is generated using a laser diode arranged in a cavity. The cavity is formed by a recess in a carrier wafer and a glass substrate that hermetically seals the cavity. The excitation radiation is guided through the glass substrate into a lower plane, where it is focused onto an NV diamond. The lower plane comprises a substrate on which the remaining system components, such as the diamond, a radio-frequency device, photodetectors, and other optical components, are arranged. The substrate is closed with a cap substrate containing an opening through which the excitation radiation can reach the diamond.

[0009] Disclosure of the invention

[0010] The present invention relates to a magnetic field sensor and a method for producing a magnetic field sensor having the features of the independent claims. Advantageous embodiments are the subject of the dependent claims and the following description.

[0011] In particular, a magnetic field sensor comprising a microwave source and a sensor board is proposed, wherein the sensor board has a sensor crystal with at least one magneto-optical defect, an excitation light source, a detector, and at least two permanent magnets. The sensor crystal and the microwave source are aligned with each other such that microwave radiation generated by the microwave source can be absorbed by the magneto-optical defect. The sensor crystal is preferably a diamond, and the magneto-optical defect is an NV center. The excitation light source is configured to emit an excitation light beam and is designed and arranged such that the excitation light beam emitted by the excitation light source can cause an emission of fluorescent radiation in the at least one magneto-optical defect of the sensor crystal.The excitation light source is preferably a diode laser with a wavelength between 490 nm and 575 nm. The detector is designed and arranged such that it can detect the emitted fluorescent radiation and is designed, for example, as a photodiode that can detect radiation in a wavelength range of the fluorescent radiation, in particular between 650 nm and 750 nm. The at least two permanent magnets are arranged and configured such that a homogeneous, static magnetic field is present in the sensor crystal. In particular, the excitation light source and the sensor crystal are arranged directly or indirectly on an upper side of the sensor board. The excitation light beam generated by the excitation light source can be focused via an optical element, in particular a lens, and directed onto the sensor crystal. The sensor crystal is preferably designed as a cube, plate, or rod.In addition to the detector, a reference detector, which is particularly designed as a photodiode, can be arranged on or in the sensor board. The excitation light beam can be directed through the sensor crystal onto a deflection element, which directs the excitation light beam onto the reference detector. The provision of a reference detector makes it possible to filter out fluctuations, for example in the intensity of the excitation light source, from the signal measured at the detector. The detector is arranged in particular between the sensor crystal and the sensor board. In addition, a filter element can be arranged between the sensor crystal and the detector, which filters out radiation outside the wavelength range of the fluorescence radiation. Such a filter element can also be arranged in front of the reference detector, viewed in the beam direction of the excitation light beam.Such a filter element enables an improved signal-to-noise ratio of the fluorescence radiation and / or the excitation light beam detected by the detector and / or reference detector. The microwave source can also be located on top of the sensor board or integrated into the sensor board.

[0012] Such an arrangement of the components of a magnetic field sensor on or in a sensor board enables a very compact and simple design, allowing such a magnetic field sensor to be used in a wide variety of applications. Furthermore, such an arrangement allows all components on or in the sensor board to be attached and contacted using soldering, bonding, and / or adhesive technologies, resulting in simple and cost-effective production of the magnetic field sensor.

[0013] In one embodiment of the invention, the sensor board of the magnetic field sensor has one or more inner layers and is thus designed as a multi-layer sensor board. This enables an even more compact design of the magnetic field sensor, since individual components can also be arranged on the inner layer(s) of the sensor board. In a further embodiment of the invention, the sensor board of the magnetic field sensor has one or more recesses, in which the detector and / or the reference detector are preferably arranged. In particular, the detector and / or the reference detector are arranged in the recess(es) and thus on the inner layer of the sensor board. If the reference detector is arranged in the recess, the excitation light beam can be directed onto the reference detector via an optical element, e.g. a mirror, a prism or a beam splitter. This enables further miniaturization of the magnetic field sensor.

[0014] In a further embodiment of the invention, the magnetic field sensor has one or more contact elements, each of which is electrically conductively connected to the detector and / or the reference detector and is arranged on the inner layer of the sensor board. The detector and / or the reference detector are advantageously designed as a photodiode, particularly preferably as a S(urface)M(ounted)D(evice), wherein a detection region of the photodiode is opposite a contact region of the photodiode. An interface for electrically contacting the photodiode is provided in the contact region. A sensitive surface suitable for detecting incident radiation is provided in the detection region. The photodiode is now arranged in particular on the inner layer of the sensor board, wherein the contact region points towards the inner layer of the sensor board or rests on the inner layer.By contacting the detector via a contact element arranged on the at least one inner layer, there is no need to arrange contact elements on the top side of the sensor board. In addition, this makes it possible to arrange the detector horizontally, i.e. with its contact area pointing towards the sensor board, and not - as in the prior art - upright, i.e. with one of its narrow surfaces adjacent to the detection and contact area resting on the sensor board, which results in an unstable and space-consuming arrangement. By contacting the detector via a contact element arranged in the at least one inner layer, a very compact design of the magnetic field sensor is thus enabled. In a further embodiment of the invention, the permanent magnets are arranged on the inner layer of the sensor board; in particular, this should be laminated in.This in turn enables a space-saving arrangement of the permanent magnets.

[0015] In a further embodiment of the invention, the permanent magnets are arranged on the top and / or bottom of the sensor board. The permanent magnets are arranged, in particular, in a single- or multi-layer Halbach array, so that a homogeneous permanent magnetic field is present in the sensor crystal. The individual permanent magnets can be arranged in a circle around the sensor crystal in the form of a cylindrical Halbach array. Such a cylindrical Halbach array is composed of individual permanent magnets or segments of permanent magnets whose magnetization directions are each tilted by 90° relative to each other in the direction of the circular line of the cylindrical array.

[0016] In principle, the magnetization directions of adjacent permanent magnets or segments can also enclose an angle of less than 90°, thereby achieving an even more homogeneous field inside the cylindrical arrangement.

[0017] The permanent magnets can also be arranged in a straight line next to one another in a Halbach arrangement, forming a rod-shaped arrangement of permanent magnets with a homogeneous static magnetic field on one side of the rod-shaped arrangement and a vanishing magnetic field on the opposite side. Such a Halbach arrangement consists of permanent magnets or segments of permanent magnets whose magnetization directions are tilted by 90° relative to one another in the direction of the longitudinal axis of the rod-shaped arrangement. In principle, the magnetization directions of adjacent permanent magnets or segments of permanent magnets can also enclose an angle of less than 90°, making the static magnetic field even more homogeneous. In this case, too, the sensor crystal is arranged in the homogeneous static magnetic field.In the case of a two-layer Halbach arrangement, a first layer of permanent magnets can be arranged on the top side and a second layer of permanent magnets on the underside of the sensor board. A first layer of permanent magnets can also be arranged on the top side, a second layer on the at least one inner layer, and optionally a third layer of permanent magnets on the underside of the sensor board. If the sensor board has multiple inner layers, layers of permanent magnets can be arranged on each of the inner layers or only on some of the inner layers. In the case of a cylindrical Halbach arrangement, the individual cylindrical layers can be arranged one above the other such that they have the same cylinder axis and, in particular, the same cylinder radius. This enables a very compact design of the magnetic field sensor, while at the same time generating a very homogeneous magnetic field in the region of the sensor crystal.

[0018] In one embodiment of the invention, a first heat sink is arranged on the top side and / or on the at least one inner layer of the sensor board, in particular in the region below the excitation light source. This first heat sink can be connected to the underside of the sensor board by one or more vias. The heat sink is designed in particular as a metal surface, e.g. as a metal surface made of copper or with copper components. The heat sink can have a coating, e.g. made of gold. The heat sink can be connected to the underside of the sensor board by one or more vias. The vias can contain a metal, be filled with a metal, or consist of a metal.

[0019] A second heat sink can be arranged on the underside of the sensor board, which is preferably connected to the vias. The second heat sink can be formed as a metal surface, for example, made of copper, aluminum, or with copper or aluminum components. In particular, to form the heat sink, a metal surface made of aluminum can be laminated onto another surface. The first and / or second heat sink can be between 33 pm and 300 pm thick and made of copper, for example. This enables efficient dissipation of the heat generated by the operation of the excitation light source.

[0020] The sensor board can further comprise one or more inner layers made of metal or with metal components in an area below the excitation light source. Alternatively, only parts of the inner layer(s) located in the area below the excitation light source—particularly those with the largest possible surface area—can be made of metal or contain metal components. This prevents moisture from penetrating the area of ​​the excitation light source.

[0021] In a further embodiment of the invention, the magnetic field sensor can have a protective cover arranged on the sensor board such that at least the excitation light source and the detector are completely enclosed. The protective cover can have a height of less than 5 mm, in particular less than 1 mm. The width of the protective cover can also be 5 mm, in particular less than 1 mm. This ensures that the volume beneath the protective cover is as small as possible.

[0022] The protective cover can be made of a non-magnetic metal, such as copper. The protective cover can also be made of a metallized plastic or another electrically conductive material. Metal surfaces can be provided below the protective cover on the top side or in the sensor board. The sensor board can also contain a small proportion of a plastic material, such as polychlorinated biphenyl or a thermoset, in this area.

[0023] In this way, a quasi-hermetic protection of the excitation light source and - during operation of the excitation light source - also of the excitation light beam propagating freely in the magnetic field sensor is ensured against interference.

[0024] In one embodiment of the invention, the magnetic field sensor is completely encased in a plastic material. Alternatively, the magnetic field sensor can be encased in the plastic material only on the top side, leaving the underside of the sensor board unencased. The plastic material can be a thermoplastic or thermosetting material. Encasement, particularly with a thermosetting material, makes the magnetic field sensor only slightly heavier and provides optimal protection from its environment.

[0025] In particular, in the case where the magnetic field sensor is completely encased, a contact element, e.g. a plug, can be part of this encasement.

[0026] The sheathing provides cost-effective packaging for the magnetic field sensor, protecting it from environmental influences and damage. It ensures reliable operation even outside the laboratory.

[0027] A complete sheathing is particularly advantageous in the case where some of the permanent magnets are arranged on the underside of the sensor board, since the complete sheathing also protects these permanent magnets from damage and environmental influences.

[0028] Electronic components, particularly circuits required for the operation of the magnetic field sensor, can be mounted on the sensor board as open semiconductors and / or surface-mounted devices (SMD). SMD components are components that can be mounted on a surface. The electronic components can also be integrated into unpackaged semiconductors and / or one or more ASIC semiconductors and electrically contacted, for example, via chip-on-board or flip-chip technology. This enables a very compact design of the magnetic field sensor.

[0029] The magnetic field sensor can be provided with solder contacts on its underside, allowing it to be soldered to another circuit board, for example. Likewise, the magnetic field sensor can have bump-like contacts, solder pads, and / or connectors for contacting the sensor board, the latter being soldered to the sensor board using SMD technology, for example. An RF-compatible substrate can be arranged on the sensor board of the magnetic field sensor. Alternatively, the sensor board can also consist at least partially of an RF-compatible substrate. The microwave source or a microwave coupling device is thus arranged on the top side of the sensor board or integrated into it, resulting in a particularly compact design of the magnetic field sensor.

[0030] The invention further comprises a method for producing a magnetic field sensor. First, a sensor board is produced as a multilayer sensor board with one or more inner layers or as a single-layer sensor board. The sensor board is produced, for example, using thin-film technology or as a PCB (printed circuit board). The sensor board is produced, in particular, with one or more receptacles for later accommodating one or more detectors and / or one or more heat sinks and / or metal layers and / or vias. If the sensor board is produced as a multilayer sensor board, an inner layer can be equipped with at least two permanent magnets such that a homogeneous, static magnetic field can be generated in the sensor crystal.To do this, a first or a first group of permanent magnets is first arranged and secured on the inner layer of the sensor board, and then a second or a second group of permanent magnets is arranged and secured on the inner layer of the sensor board. The inner layer equipped with the permanent magnets can then be mechanically connected to a top and bottom side of the sensor board, for example, by lamination. In this process, the inner layer of the sensor board is equipped with the permanent magnets, particularly during the production of the sensor board, and then laminated in.

[0031] After its manufacture, the sensor board is equipped with an excitation light source, at least one detector, and a sensor crystal such that an excitation light beam generated by the excitation light source causes the sensor crystal to emit fluorescent radiation, and the detector can detect the fluorescent radiation. The detector and / or the reference detector are preferably designed as a surface-mounted device (SMD) or can be attached to the top or an inner layer of the sensor board using SMD technology, particularly by soldering or conductive bonding.

[0032] After the sensor board has been equipped with the excitation light source, the detector(s), and the sensor crystal, the top and / or bottom of the sensor board can be equipped with the permanent magnets. To do this, a first or a first group of permanent magnets can be arranged and secured on the top and / or bottom of the sensor board, and then a second or a second group of permanent magnets can be arranged and secured on the top and / or bottom of the sensor board. This has the advantage that the permanent magnets can be attached in a defined position relative to the sensor crystal. This ensures that a homogeneous magnetic field is present in the sensor crystal. In particular, this prevents the permanent magnets from changing their position during the assembly process due to their mutual interaction.The excitation light source, the sensor crystal, the detector(s), and the permanent magnets are mounted on specific reference marks on the sensor board, allowing for any etching tolerances that may occur during the etching process. Furthermore, special tools, such as die collets, can be used to prevent the permanent magnets from slipping during placement. Furthermore, to prevent the permanent magnets from slipping during placement, fast-curing adhesives, which harden due to heat or radiation, can be used to fix the permanent magnets during placement.

[0033] Furthermore, a protective cover can be attached to the top of the sensor board, particularly by gluing, plugging, or soldering, so that at least the excitation light source and the detector are completely enclosed. Particularly good sealing of the magnetic field sensor from its environment is achieved by soldering the protective cover to the top of the sensor board, particularly using a high-melting solder, so that existing solder contacts do not melt again during subsequent processing.

[0034] The sensor board can be equipped with electronic components, especially circuits. These can be integrated into one or more ASIC semiconductors and bonded to the sensor board, for example, as open semiconductors.

[0035] For this purpose, a chip on board process (e.g. die attach and / or wire bonding) or a flip chip process can be used.

[0036] Furthermore, the sensor board equipped with the excitation light source, the at least one detector, and the sensor crystal can be encased in a plastic material, in particular a thermoplastic or thermosetting plastic material. The overmolding can be performed using a single or multiple mold.

[0037] The populated sensor boards can be individually back-injected using a molding process, e.g., an in-mold process. Alternatively, the populated sensor boards can also be back-injected in a printed circuit board panel, e.g., using a casting process – such as the process described in DE 10 2017 216 711 A1. These processes can be used to process materials that, due to their ionic purity and flowability, enable the use of packaged components, passive SMDs, open semiconductor devices, or so-called bare dies to accommodate the assemblies required for the function of the magnetic field sensor.

[0038] If a chip on board process (e.g. die attach and / or wire bonding) or a flip chip process is used, for example to attach an open semiconductor to the sensor board, a mold process or a L(ow)P(ressure)M(ould) process is suitable for applying the plastic in the case of chip on board technology; in the case of flip chip technology, the DIM process is also possible.

[0039] The individual sensor boards can then be separated using sawing processes, which enables very cost-effective mass production, especially for very small sensor boards. The sensor board can be completely encapsulated or only on the top side. In the latter case, solder contacts can be applied to the exposed underside of the sensor board. This can be done before or after the components are separated, during sensor board manufacturing, during assembly, or after the sensor board has been encapsulated.

[0040] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0041] The invention is illustrated schematically in the drawing using exemplary embodiments and is described below with reference to the drawing.

[0042] Short description of the drawings

[0043] Figure 1 shows a magnetic field sensor, wherein several permanent magnets are arranged on a top and a bottom side of a sensor board;

[0044] Figure 2 shows a magnetic field sensor in which several permanent magnets are arranged on an inner layer of a sensor board;

[0045] Figure 3 shows a magnetic field sensor, wherein several permanent magnets are arranged on an inner layer of a sensor board and a protective cover is attached to the top of the sensor board;

[0046] Figure 4 shows a fully enclosed magnetic field sensor;

[0047] Figure 5 shows a magnetic field sensor encased only on the top side of the sensor board.

[0048] Embodiments of the invention Figure 1 shows a magnetic field sensor 1 with a sensor board 2. An excitation light source 3, a sensor crystal 5, a detector 7 and permanent magnets 8 are arranged on an upper side 10 of the sensor board 2. A filter element 26 is arranged between the detector 7 and the sensor crystal 5. Permanent magnets 8 are also arranged on the underside 11 of the sensor board 2. The sensor crystal 5 is on the upper side of the detector 7 and is thus arranged such that the detection area of ​​the detector 7 faces one of the surfaces of the cuboid- or cube-shaped sensor crystal 5. The sensor crystal 5 is designed as a diamond and has at least one magneto-optical defect in the form of an NV center.The permanent magnets 8 are arranged in a circular or rod-shaped Halbach arrangement on both the underside 11 and the top side 10 of the sensor board 2, so that a homogeneous static magnetic field is present in the region of the sensor crystal 5. The excitation light source 3 is designed to generate an excitation light beam 4, which is guided via a lens 20 through the sensor crystal 5 onto a prism 25. The excitation light beam 4 is deflected at the prism 25 onto a reference detector 15. A further filter element 27 is arranged between the reference detector 15 and the prism. The reference detector 15 is arranged in a recess 9 and thus on an inner layer 13 of the sensor board 2. A microwave source 6 is arranged on the top side 10 of the sensor board 2 so that microwave radiation generated by the microwave source 6 can be absorbed by the magneto-optical defect of the sensor crystal 5.

[0049] The magnetic field sensor 1 shown in Figure 2 corresponds to the magnetic field sensor 1 shown in Figure 1 with the difference that the permanent magnets 8 are not arranged on the top or bottom side of the sensor board 2, but on an inner layer 13, 21 of the sensor board 2.

[0050] The magnetic field sensor 1 shown in Figure 3 corresponds to the magnetic field sensor 1 shown in Figure 2, with the difference that a protective cover 14 is attached to the top side 10 of the sensor board 2, with the excitation light source 3, the sensor crystal 5, the detector 7, and the reference detector 15 being arranged below the protective cover 14. Solder contacts 19 are attached to the underside 11 of the sensor board 2, with which the sensor board 2 can be attached to another board. The microwave source 6 is also arranged on the top side 10 of the sensor board 2. The excitation light source 3 is arranged on a base 22, in which the electronic components necessary for the operation of the excitation light source 3 are housed. A first heat sink 16 is arranged below the excitation light source 3 and is designed to absorb heat generated during operation of the excitation light source.The first heat sink 16 is designed as a metal surface and is connected by a through-plating 17 to a second heat sink 23 arranged on the underside 11 of the sensor board 2, which second heat sink is also designed as a metal surface.

[0051] The magnetic field sensor 1 shown in Figure 4 corresponds to the magnetic field sensor 1 shown in Figure 1, with the difference that the magnetic field sensor 1 is completely encased in a plastic material. A first heat sink 16 is arranged below the excitation light source 3 and is designed to absorb heat generated during operation of the excitation light source. The first heat sink 16 is formed as a metal surface and is connected by a via 17 to a second heat sink 23, which is also formed as a metal surface and is arranged on the underside 11 of the sensor board 2.

[0052] The magnetic field sensor 1 shown in Figure 5 corresponds to the magnetic field sensor 1 shown in Figure 3 with the difference that only the top side 10 of the sensor board 2 is covered with a plastic material.

Claims

Claims 1. A magnetic field sensor (1) comprising a microwave source (6) and a sensor board (2), wherein the sensor board (2) comprises: a sensor crystal (5) having at least one magneto-optical defect, wherein the sensor crystal (5) is arranged such that microwave radiation generated by the microwave source (6) can be absorbed by the at least one magneto-optical defect of the sensor crystal (5), an excitation light source (3) configured to emit an excitation light beam (4) and configured and arranged such that the excitation light beam (4) emitted by the excitation light source (3) can cause an emission of fluorescent radiation in the at least one magneto-optical defect of the sensor crystal (5), a detector (7) configured and arranged to detect the emitted fluorescent radiation, and at least two permanent magnets (8) arranged and configured to form a homogeneous,generate a static magnetic field in the sensor crystal (5)., 2. Magnetic field sensor (1) according to claim 1, wherein the sensor board (2) has at least one inner layer (13).

3. Magnetic field sensor (1) according to one of the preceding claims, wherein the sensor board (2) has a recess (9) in which the detector (7) and / or a reference detector (15) is preferably arranged.

4. Magnetic field sensor (1) according to one of the preceding claims, wherein the magnetic field sensor (1) has one or more contact elements (18) which are each electrically conductively connected to the detector (7) and / or the reference detector (15) and are arranged in the inner layer (13) of the sensor board (2).

5. Magnetic field sensor (1) according to one of the preceding claims, wherein the permanent magnets (8) are arranged on the inner layer (13) of the sensor board (2).

6. Magnetic field sensor (1) according to one of the preceding claims, wherein the sensor board (2) has a top side (10) and a bottom side (11) and the permanent magnets (8) are arranged on the top side (10) and / or the bottom side (11) of the sensor board (2).

7. Magnetic field sensor (1) according to one of the preceding claims, wherein on the upper side (10) and / or on the at least one inner layer (13) of the sensor board (2), preferably in the region of the excitation light source (3), a first heat sink (16), in particular a first metal surface, is arranged, which is connected to the underside (11) of the sensor board (2) by one or more vias (17).

8. Magnetic field sensor (1) according to claim 7, wherein a second heat sink (23) is arranged on the underside (11) of the sensor board (2) and is connected to the vias (17).

9. Magnetic field sensor (1) according to one of the preceding claims, wherein the magnetic field sensor (1) has a protective cover (14), in particular one which is designed to be electrically conductive, which is arranged on the sensor board (2) in such a way that at least the excitation light source (3), the detector (7) and the sensor crystal (5) are completely enclosed.

10. Magnetic field sensor (1) according to claim 9, wherein the magnetic field sensor (1) is in particular completely encased in a plastic material, in particular a thermoplastic or thermosetting material.

11. Magnetic field sensor (1) according to one of the preceding claims, wherein an RF-suitable substrate is arranged on the sensor board (2) or the sensor board (2) consists partly of an RF-suitable substrate.

12. A method for producing a magnetic field sensor (1), comprising the steps of: a. producing a sensor board (2); b. Equipping the sensor board (2) with an excitation light source (3), at least one detector (7, 15), and a sensor crystal (5) such that an excitation light beam (4) generated by the excitation light source (2) causes the sensor crystal (5) to emit fluorescent radiation, and the detector (7, 15) can detect the fluorescent radiation; c.Equipping an inner layer (13) and / or a bottom side (11) and / or a top side (10) of the sensor board (2) with at least two permanent magnets (8) such that a homogeneous, static magnetic field can be generated in the sensor crystal (5), wherein firstly a first or a first group of permanent magnets (8) is arranged and fastened on the inner layer (13) and / or a bottom side (11) and / or a top side (10) of the sensor board (2), next a second or a second group of permanent magnets (8) is arranged and fastened on the inner layer (13) and / or a bottom side (11) and / or a top side (10) of the sensor board (2) and - in the case that the inner layer (13) of the sensor board (2) has been equipped with permanent magnets (8) - connecting the inner layer (13) equipped with permanent magnets (8) to the top and bottom sides of the sensor board (2), in particular by lamination.

13. The method according to claim 12, wherein the equipping of the inner layer (13) with the at least two permanent magnets (8) and the connecting of the inner layer (13) equipped with permanent magnets (8) to the top and bottom of the sensor board (2) takes place during the manufacture of the sensor board (2).

14. Method according to one of claims 12 or 13, wherein a protective cover (14) is attached to the sensor board (2), in particular by gluing, plugging or soldering, so that the excitation light source (3) and the detector (7) are completely enclosed.

15. Method according to one of claims 12 to 14, wherein the sensor board (2) equipped with the excitation light source (3), the at least one detector (7, 15) and the sensor crystal (5) is made of a plastic material, in particular a thermoplastic or thermosetting plastic material.

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