Temperature sensor with encapsulation and manufacturing process

Abstract

The present disclosure relates to an encapsulated temperature sensor and to a method for manufacturing a temperature sensor (1) comprising the following steps: providing the temperature sensor (1) comprising the thermistor element (2) and two electrical conductor elements (3, 6) connected to the thermistor element (2), arranging the sensor head in an injection mold, encapsulating the sensor head by injection molding.

Description

[0001] The present invention relates to a temperature sensor with encapsulation and a corresponding manufacturing or encapsulation method.

[0002] In existing methods for encapsulating NTC temperature sensors, the encapsulation process is carried out by immersing the sensor head in coating material.

[0003] In other words, the coating is produced by a dip coating process.

[0004] The dip coating process has the disadvantage that the encapsulation geometry is unstable, with the dimensions of the encapsulation potentially having a large tolerance range.

[0005] The production of precisely defined encapsulation shapes, surfaces, body structures, or surface structures is not possible.

[0006] Due to varying wall thicknesses of the encapsulation, the resistance of the encapsulation to environmental influences, mechanical impacts, moisture, stress breakdown, etc., can be unstable.

[0007] The invention according to the present disclosure at least partially eliminates the shortcomings of the prior art technical solutions.

[0008] The inventive method for manufacturing a temperature sensor and the inventive temperature sensor are defined in the claims.

[0009] A method according to the invention for manufacturing a temperature sensor comprises at least the following steps: The temperature sensor is provided in one step. The temperature sensor comprises the thermistor element and two electrical conductors connected to the thermistor element.

[0010] In a further step, the sensor head is arranged in an injection mold.

[0011] The sensor head is a head part of the sensor that includes at least the thermistor element. The sensor head may also include parts of the conductive elements adjacent to the thermistor element.

[0012] In some embodiments, the sensor head can also encompass all the conductive elements. Additional external conductive elements can be provided to electrically contact the conductive elements of the sensor head.

[0013] In a further step, the sensor head, which is placed in the mold, is encapsulated by forming an encapsulation through injection molding (= transfer molding) in a molding step.

[0014] In other words, the sensor head is encapsulated during a forming step by injection molding.

[0015] Injection molding is similar to compression molding. However, unlike simply pressing the molding compound between two molds, in injection molding the compound is preferably injected into the mold cavity via distributor channels using pistons, where it hardens under heat and pressure.

[0016] In this way, the molding compound, which is the encapsulation material, is advantageously exposed to increased temperature and pressure during manufacturing.

[0017] In contrast, conventional methods such as dip coating do not use elevated temperatures and pressures (compared to atmospheric conditions).

[0018] Therefore, in the inventive method, different encapsulation materials can be used than in conventional dip coating methods, which have advantageous properties with regard to dielectric strength and robustness.

[0019] Furthermore, conventional methods such as dip coating do not use molds. Therefore, flat, uniform, and consistent encapsulations cannot be produced.

[0020] In contrast, the injection molding process has the advantage that encapsulations with uniform surfaces and a homogeneous encapsulation thickness can be produced.

[0021] An encapsulation with homogeneous thickness is, in particular, an encapsulation in which the outer surface of the encapsulation is flat and has no bumps, protrusions, dents or irregularities.

[0022] This advantageously gives the manufactured sensor a controllable size and shape.

[0023] Since the thickness of the encapsulation is homogeneous, the electrical insulation performance, dielectric strength and moisture resistance of the encapsulation are also improved.

[0024] Furthermore, protection against other environmental influences such as mechanical shocks is also improved.

[0025] The use of molds can also minimize the effects of the environment on the encapsulation material.

[0026] The pressure exerted in the mold during injection molding also prevents the formation of unwanted air bubbles or cavities in the encapsulation.

[0027] By preventing air bubbles or cavities, the dielectric strength of the encapsulation can be increased and its resistance to moisture improved.

[0028] According to one embodiment of the method, the step of providing the sensor comprises the following individual steps.

[0029] The thermistor element is provided in one step.

[0030] In a further step, the two guide elements are provided.

[0031] In a further step, the thermistor element is positioned between the two conductive elements. In particular, the thermistor element can be designed as a flat chip that can be easily clamped between the conductive elements.

[0032] Preferably, the thermistor element is arranged only between two tips of the two guide elements, so that only the foremost end sections (tips) of the guide elements touch the thermistor element from only one side at a time.

[0033] By reducing the contact area between the thermistor element and the conductive element, thermomechanical effects on the thermistor during contacting and soldering processes between the conductive elements and the thermistor can be advantageously reduced.

[0034] In a further step, solder material is applied between the contact elements, preferably the tips of the contact elements, and the thermistor element by immersing the sensor head in solder material.

[0035] The soldering material is then hardened by drying the material.

[0036] Preferably, the solder material is applied very precisely only between the tips of the contact elements and the thermistor.

[0037] In one embodiment, the surface of the thermistor element is activated by plasma treatment before potting.

[0038] Activating the surface can improve surface roughness and surface area. Furthermore, it can enhance the chemical and / or physical adhesion properties of the surface.

[0039] Accordingly, early surface activation advantageously improves the adhesion of the encapsulation to the thermistor.

[0040] According to one embodiment, the guide elements are lead frames.

[0041] Ladder frames offer advantageously high stability. This allows the ladder frame to also serve as a support structure for holding the sensor during the forming step.

[0042] The inventive method allows multiple sensors to be manufactured in parallel.

[0043] According to one embodiment, the ladder frames of several sensors form a common support structure to hold the sensors during the forming step.

[0044] In other words, the ladder frames of several sensors are connected to the support structure.

[0045] In a further step, the sensors can be separated by separating the conductor frames from each other.

[0046] According to one embodiment, the guiding elements are wires.

[0047] A wire has the advantage of being more flexible compared to a ladder frame.

[0048] On the other hand, the ladder frame can serve directly as a support structure and not just as an electrical connecting element.

[0049] According to one embodiment, one or more wires can be held by a support structure during the forming step.

[0050] The conductor frame or wire may include a bronze material, a phosphor bronze material, another copper alloy material, or a copper material as an electrically conductive material.

[0051] The conductor frame or wire can be additionally tinned to improve corrosion resistance.

[0052] The thickness of the lead frame can be varied between 0.4 mm and 1 mm.

[0053] As already indicated above, the thermistor element can be clamped between the guide elements, at least in one embodiment. In this case, the guide elements can exert a clamping force on the thermistor element capable of holding it in place without further support. This can be advantageous because the position of the thermistor element relative to the guide elements can be clearly defined by precisely positioning the thermistor between them. This ensures that the position remains unchanged even during soldering or overmolding. This, in turn, can reduce the positional deviation of the thermistor element during overmolding, resulting in a more predictable or homogeneous cover thickness. This embodiment is particularly preferred for the conductor frame arrangement; that is, it is preferred that the conductor frames clamp the thermistor element.

[0054] According to one embodiment, at least one of the guide elements can have a projection in the area that contacts the guide element. Alternatively, both guide elements can have a projection. However, in some embodiments, it may be preferred that one guide element has a projection, while the other is flattened in the area that contacts the guide element. For example, the projection can be located at the tip of the guide element.

[0055] A projection can be understood as it is understood in practice and is not otherwise restricted. For example, the projection can be a part of the guide element that protrudes from it. In particular, the projection can be oriented towards the thermistor element. In this way, the projection can concentrate a clamping force on a smaller area than a guide element without a projection. For example, the projection can have a smaller area on the side facing the thermistor element than on the side where it is connected to the rest of the guide element. The projection can, for example, be pointed. Alternatively, the projection can be rounded, for example, hemispherical or semi-elliptical.

[0056] The protrusion has the advantage of supporting clamping. In particular, by focusing the clamping force on a reduced area, the clamping pressure can be increased. This has the advantage of increasing the friction generated by the clamping. Furthermore, compared to two flattened contact surfaces of the conductive elements, at least one with a protrusion and thus a reduced contact area can reduce wobbling of the clamped thermistor element.

[0057] The embodiment with the projection is also particularly preferred for the design of the ladder frame. That is, according to one embodiment, it may be preferred that at least one ladder frame has a projection. The aforementioned variants, embodiments, and features regarding the projection can, of course, also apply in this case.

[0058] According to one embodiment, the thermistor element is a negative temperature coefficient (NTC) thermistor element.

[0059] An NTC thermistor element has a comparatively small size compared to a positive temperature coefficient (PTC) thermistor element.

[0060] Preferably, the diameter of a sensor head containing an NTC thermistor element is not larger than 2.5 mm + / - 0.1 mm tolerance.

[0061] This minimizes material consumption.

[0062] In one embodiment, the sections of the guide elements and the thermistor element are overmolded in a single casting step.

[0063] In this way, a uniform encapsulation is formed around the sensor head. The encapsulation is preferably designed as a single piece, which exhibits advantageous properties with regard to dielectric strength and moisture resistance.

[0064] The thickness of the entire encapsulation can be constant, or the encapsulation can be thicker around the thermistor to ensure optimal protection.

[0065] In one embodiment, the injection molding process is carried out at an elevated temperature of 170 °C or higher, preferably at 180 °C or higher.

[0066] Such a high temperature can only be achieved with an injection molding process, where the molding compound (encapsulation material) is processed under high pressure. Such high temperatures are not possible with a dip coating process.

[0067] The advantage is that the high processing temperature during the injection molding step guarantees complete or almost complete evaporation of the moisture (water) in the encapsulation.

[0068] This prevents sensor defects caused by moisture in the encapsulation.

[0069] Furthermore, a lower moisture content in the encapsulation also improves the dielectric strength of the encapsulation.

[0070] According to one embodiment, the encapsulation comprises an epoxy resin material.

[0071] According to a more specific embodiment, the encapsulation comprises an epoxy resin material with a low electrical conductivity of no more or less than 100 µS / cm.

[0072] Selecting such a material is not possible using conventional dip coating processes, as the processing of such a material requires the high temperature and high pressure of the injection molding process.

[0073] According to one embodiment, the encapsulation is applied uniformly to the sensor head, preferably with a constant thickness as described above.

[0074] The dielectric strength of the encapsulation can be advantageously improved by ensuring a constant thickness, avoiding air bubbles, cavities, or moisture in the encapsulation, and using an epoxy resin material with a low electrical conductivity of no more or less than 100 µS / cm.

[0075] According to one embodiment, a mark or trace is printed onto a surface of the encapsulation during the forming step. In other words, a trace or mark is directly impressed into the surface of the encapsulation by the mold during the forming step.

[0076] The trace or marker can be a printed code or number, e.g. a QR code, to enable better traceability of the sensor.

[0077] One embodiment involves applying an internal coating prior to injection molding. Applying such an internal coating can improve the protection of the thermistor element. In particular, the thermistor element can be better protected against environmental influences during manufacturing, assembly, or measurement. For example, its resistance to moisture can be improved.

[0078] Furthermore, the inner coating can improve the adhesion of the injection-molded encapsulation.

[0079] According to one embodiment, the internal coating can be applied particularly after the soldering process.

[0080] There are no restrictions on the methods used to apply the internal coating. For example, the internal coating can be applied by dipping, spraying, or injection molding. Dip coating is the preferred method.

[0081] According to one embodiment, the inner coating comprises or consists of a curable resin. The curable resin can, for example, be in liquid form or in solution. The liquid form may be preferred.

[0082] After coating, a curing step can be carried out. This could be a heat treatment step or another curing step, such as irradiation. The internal coating can, for example, contain or consist of an epoxy resin. The epoxy resin could, for example, be a perfluoropolyether with diglycidyloxy end groups.

[0083] In one embodiment, the inner coating covers the thermistor element. In a preferred embodiment, the inner coating covers not only the thermistor element but also the parts of the conductive elements adjacent to the thermistor element.

[0084] The embodiments with an internal coating are particularly preferred for the embodiments with conductor frames. For example, the conductor frames with the thermistor element mounted between them are immersed in the liquid resin and then cured. Subsequently, injection molding is applied.

[0085] According to one embodiment, the process steps of applying an internal coating to multiple thermistor elements held by connected conductor frames can be carried out in parallel.

[0086] According to one embodiment, the inner coating is significantly thinner than the encapsulation. For example, the thickness of the inner coating can be less than 6 µm, for example between 1 µm and 6 µm.

[0087] Furthermore, the invention relates to a temperature sensor according to the claims.

[0088] All embodiments and features or properties of the manufacturing process for producing the temperature sensor can also apply to the temperature sensor (as a product) and vice versa.

[0089] The temperature sensor according to the invention comprises at least one thermistor element, two conductive elements arranged on opposite sides of the thermistor element and connected to the thermistor element by solder, and an encapsulation with a flat surface made of an epoxy resin material enclosing the thermistor element and adjacent sections of the conductive elements.

[0090] In other words, the encapsulation surrounds a sensor head that includes at least the thermistor element and adjacent parts of the conductive elements, or the entire conductive elements.

[0091] According to one embodiment, the encapsulation has a high dielectric strength due to its thickness, the material chosen, and the avoidance of air bubbles or cavities (the epoxy resin material of the encapsulation has a low electrical conductivity of less than 100 µS / cm).

[0092] In one embodiment, the encapsulation has a homogeneous density without air bubbles inside.

[0093] In one embodiment, the thickness of the covering is between 0.2 and 1 mm.

[0094] The epoxy resin material comprises at least one epoxy resin.

[0095] In embodiments, the proportion of epoxy resin in the encapsulation material can be between 5 and 10 wt.%, preferably between 8 and 10 wt.%.

[0096] Additionally, the epoxy resin material may contain other different resin materials.

[0097] According to one embodiment, the epoxy resin material comprises one or more of the following materials: epoxy resin, phenolic resin, silica, in particular glassy silica, silicon dioxide, carbon black.

[0098] Preferably, the glass transition temperature of the epoxy resin material can be 100 °C or higher.

[0099] According to one embodiment, the surface of the encapsulation is flat and even.

[0100] According to one embodiment, the encapsulation has a homogeneous thickness, meaning that the thickness of the encapsulation between the thermistor element and the environment is set to a constant value.

[0101] According to one embodiment, a trace or mark is printed onto a surface of the encapsulation.

[0102] In one embodiment, the trace is a QR code, which allows for better tracking of the sensor.

[0103] The track is clearly visible due to the advantageously flat and even surface of the encapsulation.

[0104] In one embodiment, only the tips of the conductive elements are connected to the thermistor element.

[0105] According to one embodiment, the thermistor element is clamped between the two conductive elements.

[0106] According to one embodiment, at least one guide element has a projection in the area that contacts the thermistor element. The above explanations and examples can apply to the projection.

[0107] According to one embodiment, the encapsulation has a defined, predetermined dimension and shape. The exact dimensions and shape depend on the customer's needs and specifications.

[0108] Depending on factors such as the installation conditions and location, the shape of the encapsulation can be varied as described below.

[0109] According to one embodiment, the encapsulation has a cuboid shape, e.g. a flat rectangular shape.

[0110] According to an alternative embodiment, the casing has a cylindrical shape. The base of the cylindrical shape can be a circle or an ellipse.

[0111] According to an alternative embodiment, the covering has the shape of a cylindrical segment.

[0112] According to one embodiment, an inner coating is arranged between the thermistor element and the encapsulation. Preferably, the inner coating is in direct contact with both the thermistor and the encapsulation. The features or properties described above may apply.

[0113] Exemplary embodiments of the invention are described in more detail below with reference to figures that illustrate the embodiments.

[0114] The invention is not limited or restricted to the exemplary embodiments.

[0115] The figures are depicted as follows: Fig. Figure 1 shows a schematic view of a first step in the manufacture of an embodiment of a sensor in which a thermistor chip is clamped between conductive elements. Fig. Figure 2 shows a schematic view of a second step in the manufacture of an embodiment of a sensor in which the thermistor chip and the conductive elements are connected by soldering. Fig. Figure 3 shows a schematic view of a third step in the production of a sensor variant, in which the sensor head is potted with a resin mold. Fig. Figure 4 shows a schematic view of an embodiment in which several sensors are connected by ladder frames that form a support structure. Fig. 5, Fig. 6, Fig. Figure 7 shows a schematic representation of an embodiment of the temperature sensor in which the encapsulation of the thermistor has a substantially cylindrical shape and the guide elements are conductor frames. Fig. 8, Fig. 9, Fig. Figure 10 shows schematic views of an embodiment of the temperature sensor in which the encapsulation of the thermistor has a substantially cuboid shape and the guide elements are conductor frames. Fig. 11, Fig. 12, Fig. Figure 13 shows schematic views of an embodiment of the temperature sensor in which the encapsulation of the thermistor has a substantially semi-circular shape and the guide elements are conductor frames. Fig. Figure 14 shows a schematic view of an embodiment of the temperature sensor in which the encapsulation of the thermistor has a substantially cylindrical shape and the conducting elements are wires. Fig. Figure 15 shows a perspective view of the embodiment of the temperature sensor. Fig. 8. Fig. Figure 16 shows an additional intermediate step in the manufacture of another embodiment of a temperature sensor. Fig. Figure 17 shows a schematic cross-section through another embodiment of a temperature sensor.

[0116] First, in the Fig. 1, Fig. 2 to Fig. 3 a method for manufacturing a temperature sensor 1 is shown.

[0117] In Fig. Figure 1 shows a first step. In the first step, a thermistor chip 2, which is a thermistor element in a flat circular or rectangular shape, and two conductor frames 3 are provided.

[0118] The thermistor chip 2 comprises a ceramic thermistor material. The thermistor ceramic material includes a ceramic with a negative or positive temperature coefficient (NTC ceramic, PTC ceramic).

[0119] Two essentially identical ladder frames 3 can be used.

[0120] The thermistor chip 2 is inserted between the foremost tips of the two symmetrically arranged conductor frames 3 and clamped in between.

[0121] To aid clamping, one of the conductor frames 3 (shown on the left in the figure) has a projection 7. The projection 7 extends from the tip of this conductor frame towards the thermistor chip 2. The projection has a predominantly semicircular cross-section. It can have a hemispherical or semi-elliptical three-dimensional shape.

[0122] The projection has the advantage of focusing the clamping force of the conductor frame 3 onto a smaller area. This can help to increase friction.

[0123] The other conductor frame, which does not have the protrusion, is flattened in the present exemplary embodiment. This has the advantage that the thermistor chip 2 is stabilized on one side by a flattened surface, while on the other side the small area of ​​the protrusion presses down on the chip. This reduces the wobbling of the thermistor chip 2.

[0124] This enables more precise positioning of the thermistor chip 2. Furthermore, additional means for holding the chip in place during later process steps may become unnecessary. In addition, precise positioning can contribute to achieving a defined, and especially homogeneous, coating.

[0125] In a second step, the entire assembly is dipped in solder material S to mechanically and electrically connect the chip 2 and the conductor frames 3.

[0126] The soldering material S can be any suitable material.

[0127] The solder material S can be applied precisely, or excess solder material S can be removed in an automated process, so that the solder material S is only applied between the thermistor chip 2 and the tips of the conductor frames 3.

[0128] The solder material S hardens and forms a solid solder joint, as in Fig. 2 shown.

[0129] During the soldering process and the subsequent encapsulation steps, the sensor, in particular the conductor frame, can be supported by a support structure, as also shown in Fig. 4 shown.

[0130] In one embodiment, the ladder frames of several sensors are connected to each other to form the support structure.

[0131] In the encapsulation steps, the sensor head with the thermistor chip 2 and the adjacent sections of the conductor frame 3 are arranged together with the molding compound in a mold for injection molding.

[0132] The molding compound is an epoxy resin material with electrically insulating properties, which is preferably a good heat conductor.

[0133] The mold for injection molding includes, in particular, two mold tools which are pressed together to form the mold and to shape the sensor encapsulation.

[0134] The encapsulation is precisely shaped using the injection molding process.

[0135] During the injection molding process, the resin to be formed is subjected to high pressures and temperatures. This allows for the use of a different resin material than in conventional dip coating processes.

[0136] A preferred forming temperature is between 170 °C and 180 °C.

[0137] The clamping force of the molds is preferably between 20 and 40 tons. The transfer pressure during injection molding is preferably between 50 and 70 kg / cm². 2 .

[0138] During the injection molding process, the shape and surface of the encapsulation 4 surrounding the sensor head are formed according to the predetermined shape of the tool.

[0139] A very even and smooth surface is achieved.

[0140] After forming, the encapsulation can be cured for 3 to 5 hours at an elevated temperature between 170 °C and 180 °C.

[0141] Because the surface is very even and smooth, it is even possible to create delicate structures on the surface directly during the forming process.

[0142] In the exemplary embodiment, a marking 5 is created on the surface of the encapsulation 4.

[0143] The marking or trace can be a brand logo, a product name or number, a tracking number, a code, a QR code, etc.

[0144] The formation of the track or code 5 on the surface makes the individual sensor 1 (better) traceable / identifiable.

[0145] The encapsulation 4 can cover part of the conductor frame in the sensor head or the entire conductor frame 3.

[0146] A modification of the preceding method and a further embodiment of a temperature sensor 1 is described based on the Fig. 16 and Fig. 17 explained.

[0147] In Fig. Step 16 shows an intermediate step, which is optional after the one in Fig. The process step described in point 2, i.e., after soldering and before the step of forming the encapsulation by injection molding, can be carried out.

[0148] In particular, the temperature sensor 1, manufactured up to that point, is provided with an internal coating 8 after soldering. The internal coating 8 is formed by immersing the temperature sensor 1 in the liquid form of an epoxy resin. In this case, the resin is a diglycidyloxy-terminated perfluoropolyether. The resin is then cured by heating.

[0149] The inner coating 8 is applied such that it at least covers the thermistor chip 2. Preferably, and as shown, the inner coating can extend onto the conductor frames 3 and cover parts of the conductor frames 3 next to the thermistor chip 2.

[0150] As shown in the figure, the inner coating can be comparatively thin. In particular, it can be thinner than the subsequently applied encapsulation 4. For example, the inner coating 8 can have a thickness of 1 to 6 µm.

[0151] In the present embodiment, the inner coating 8 is arranged such that it covers each conductor frame 3 individually, with the inner coating 8 having a gap in the area of ​​the conductor frames below the thermistor chip 2. This is not necessarily the case in every realized embodiment. The described space can also be closed by the inner coating 8.

[0152] After applying the inner coating 8, the encapsulation 4 can be carried out in the next step / in the next steps as described above.

[0153] In Fig. Figure 17 shows a schematic cross-sectional representation of an embodiment of a finished temperature sensor 1. The present embodiment also has the internal coating 8. Otherwise, it is identical to the one shown in Figure 17. Fig. 3 described temperature sensor 1.

[0154] The encapsulation 4 completely surrounds the inner coating 8.

[0155] The inventors have discovered that implementing an internal coating 8 can further improve the robustness against the penetration of moisture or wetness.

[0156] Fig. Figure 4 shows a support structure 10 for supporting and carrying the sensors during the manufacturing process.

[0157] Additionally or alternatively, several sensors can be connected to a support structure via their ladder frames.

[0158] After the encapsulation process, the sensors can be separated by removing the support structure or by disconnecting the connections between the individual conductor frames.

[0159] In the Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11, Fig. 12 to Fig. Figure 13 shows different views of the finished temperature sensor.

[0160] In the Fig. 5, Fig. 6 and Fig. 7 The encapsulation of the thermistor chip 2 has an essentially cylindrical shape.

[0161] Up in Fig. 5 is a top view, shown below in Fig. 6 a front view. Right in Fig. Figure 7 shows a side view.

[0162] The further shape of the encapsulation 4 is adapted to the shape of the conductor frames 3. In the exemplary embodiment, the conductor frames 3 are bent accordingly, so that the two conductor frames 3 become narrower in the area of ​​the thermistor chip 2 in order to clamp the chip 2.

[0163] The shape of the encapsulation 4 is preferably adapted to facilitate the mounting or fixing of the sensor 1 at the place of use.

[0164] Furthermore, the structure, shape and surface of the encapsulation can be adapted and modified during the molding process to facilitate assembly.

[0165] In the Fig. 8, Fig. 9 and Fig. 10 The encapsulation of the thermistor chip 2 has an essentially cuboid shape.

[0166] In particular, the shape is essentially cuboid with rectangular side faces.

[0167] The surfaces of the essentially cuboid body can be slightly inclined, with an edge in the middle of the surface, or they can be flat.

[0168] Up in Fig. 8 shows a top view, below in Fig. 9 a front view. Right in Fig. Figure 10 shows a side view.

[0169] All embodiments can be axially symmetrical when viewed from one of the six spatial directions.

[0170] In the Fig. 11, Fig. 12 and Fig. 13 The encapsulation of the thermistor chip 2 has an essentially semi-circular shape of a cylindrical section. The shape can also resemble or correspond to a prismatic shape with a semi-circular, semi-rectangular base.

[0171] In particular, the shape is essentially semi-square with rectangular side faces and semi-cylindrical.

[0172] The surfaces of the essentially cuboid body part may be slightly inclined, with an edge in the middle of the surface, or they may be flat.

[0173] Thus, the embodiment can be implemented in the Fig. 11, Fig. 12 and Fig. 13 a combination of the embodiments shown in the previous figures.

[0174] Up in Fig. 11 shows a top view, below in Fig. 12 a front view. Right in Fig. Figure 13 shows a side view.

[0175] The Fig. 14 and Fig. Figure 15 shows another embodiment of the temperature sensor 1, which has wires 6 as guide elements instead of conductor frames 3.

[0176] The wires can be more flexible compared to the conductor frames.

[0177] Part of the wires 6 can be encapsulated by the encapsulation 4.

[0178] The manufacturing and encapsulation process is otherwise similar to the process using ladder frames 3.

[0179] In this example, the encapsulation covering thermistor chip 2 has a cylindrical shape. However, as previously described, the encapsulation can have any suitable geometric shape, e.g., prismatic, cuboid, cylindrical, semi-cylindrical, spherical, etc.

[0180] Alternatively, the thermistor of the present invention can also be a PTC thermistor.

[0181] The thermistor can have a monolithic ceramic structure or a structure with multiple layers.

[0182] The thermistor may also include electrodes or electrode layers for electrical connection.

[0183] The electrode layers can comprise suitable metallic or electrically conductive polymer materials.

[0184] The encapsulation can also be referred to as wrapping, covering, housing, casing, enclosure, etc. Reference sign 1 sensor 2 Thermistor chips 3 ladder frames 4 Encapsulation 5 Mark 6 wire 7 lead 8 Interior coating 10 Support structure Soldering material

Claims

Method for manufacturing a temperature sensor (1), comprising the steps: - Providing the temperature sensor (1) with the thermistor element (2) and two electrical conductor elements (3, 6) connected to the thermistor element (2), - Arranging the sensor head with the thermistor element (2) and at least parts of the conductor elements (3, 6) next to the thermistor element (2) in an injection mold, - Encapsulating the sensor head by forming an encapsulation (4) by injection molding in one forming step. Method according to claim 1, wherein the provision of the sensor (1) comprises the following steps: - providing the thermistor element (2), - providing two conductive elements (3, 6), - arranging the thermistor element (2) only between two tips of the two conductive elements (3, 6), - applying solder material (S) between the tips and the thermistor element (2) by dip coating, - curing the solder material (S). Method according to one of claims 1 or 2, wherein the surface of the thermistor element (2) is activated by plasma treatment prior to encapsulation. Method according to one of claims 1 to 3, wherein the guiding elements are ladder frames (3). Method according to claim 4, wherein the ladder frames (3) of several sensors (1) form a support structure (10) to hold the sensors during the forming step, wherein the sensors (1) are separated by separating the ladder frames (3) in a subsequent step. Method according to any one of claims 1 to 3, wherein the guiding elements are wires (6). Method according to claim 6, wherein one or more wires (6) are held by a support structure during the forming step. Method according to any one of claims 1 to 7, wherein the thermistor element (2) is a thermistor element with a negative temperature coefficient. Method according to any one of claims 1 to 8, wherein the sections of the guide elements (3) and the thermistor element (2) are overmolded in a single forming step. Method according to any one of claims 1 to 9, wherein the injection molding is carried out at an elevated temperature of 170 °C or higher. Method according to any one of claims 1 to 10, wherein the encapsulation (4) comprises an epoxy resin material. The method of claim 11, wherein the epoxy resin material comprises between 5 and 10 percent by weight epoxy resin. Method according to claim 11 or 12, wherein the encapsulation (4) comprises an epoxy resin material having a low electrical conductivity of not more or less than 100 µS / cm. Method according to any one of claims 1 to 13, wherein the encapsulation (4) is applied uniformly to the sensor head. Method according to any one of claims 1 to 14, wherein during the forming step a conductor track (5) is printed into a surface of the encapsulation (4). Method according to one of the preceding claims, wherein at least one guide element (3, 6) has a projection (7) facing the thermistor element (2). Method according to one of the preceding claims, wherein an inner coating (8) is realized prior to forming the encapsulation (4) which covers at least the thermistor element (2). Method according to the preceding claim, wherein the inner coating (8) extends to the part of the conductive elements (3, 6) adjacent to the thermistor element (2). Method according to the preceding claim, wherein the inner coating (8) is formed by immersing the soldered thermistor element (2) in an epoxy resin in liquid or dissolved form and subsequently curing the resin. Temperature sensor (1) comprising a thermistor element (2), two conductive elements (3, 6) arranged on opposite sides of the thermistor element (2) and connected to the thermistor element by solder (S), an encapsulation (4) with a flat surface comprising an epoxy resin material and enclosing the thermistor element (2) and adjacent sections of the conductive elements (3, 6). The temperature sensor (1) according to the preceding claim, wherein the epoxy resin material has a low electrical conductivity of not more or less than 100 µS / cm. Temperature sensor (1) according to claim 20 or 21, wherein the encapsulation (4) has a homogeneous density without air bubbles inside. Temperature sensor (1) according to one of claims 20 to 22, wherein a marking (5) is printed into a surface of the encapsulation. The temperature sensor (1) according to claim 23, wherein the marking (5) is a QR code. Temperature sensor (1) according to one of claims 20 to 24, wherein only the tips of the conductive elements (3) are connected to the thermistor element (2). Temperature sensor (1) according to one of claims 20 to 25, wherein the encapsulation (4) has a cuboid shape. Temperature sensor (1) according to one of claims 20 to 26, wherein the encapsulation (4) has a cylindrical shape. Temperature sensor (1) according to one of claims 20 to 27, wherein the encapsulation (4) has a homogeneous thickness. Temperature sensor (1) according to one of claims 20 to 28, wherein the encapsulation (4) has the form of a cylindrical segment. Temperature sensor (1) according to one of claims 20 to 29, wherein at least one guide element (3, 6) has a projection (7) facing the thermistor element (2). Temperature sensor (1) according to one of claims 20 to 30, wherein an inner coating (8) is arranged between the thermistor element (2) and the encapsulation (4).

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