NTC sensor and method of manufacturing the same

Abstract

The present invention relates to an NTC sensor (100) comprising a chip (1), two parallel wires (2) each with a contact (5, 6, 7), and a contact between the chip (1) and the contacts (5, 6, 7) of each of the wires (2), wherein the maximum lateral dimension of the NTC sensor in each direction perpendicular to the extension direction of the wires (2) is equal to or smaller than the sum of the lateral dimensions of the chip (1) and the wires (2). The present invention further relates to a method for manufacturing the NTC sensor (100).

Description

[Technical field]

[0001] The present invention relates to an NTC sensor and a method for manufacturing an NTC sensor. [Background technology]

[0002] Conventionally available NTC thermistor temperature sensors having a plastic coating are manufactured by conventional assembly and coating techniques.

[0003] The electrical resistance of an NTC thermistor ceramic changes with temperature. In particular, the resistance of an NTC thermistor decreases with increasing temperature. In this case, NTC stands for negative temperature coefficient. NTC thermistors are also called hot wires.

[0004] The NTC thermistor ceramic is integrated into the circuit via a connecting wire. That way, the temperature of the NTC thermistor can be measured indirectly through the change in resistance in the circuit. That way, the ambient temperature can also be measured, since the temperature of the NTC thermistor usually depends on the ambient temperature. The plastic housing can protect the thermistor from environmental influences, but should have good thermal conductivity to allow the measurement of the ambient temperature.

[0005] An example of an NTC thermistor element is known from US Pat. No. 5,399,633. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] DE 102005017816 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to improve the known NTC sensor and the method for manufacturing the NTC sensor. [Means for solving the problem]

[0008] The defined problem can be solved, at least in part, by the NTC sensor according to the invention.

[0009] An NTC sensor includes a tip, two parallel wires, each with a contact, and contacts between the tip and each of the contacts on the wires.

[0010] In this case, the maximum lateral dimension of the NTC sensor in each direction perpendicular to the extension direction of the wire is equal to or less than the sum of the lateral dimensions of the tip and the wire.

[0011] What is referred to as extension direction is the direction in which the wires extend. The wires are arranged parallel to one another and preferably in a straight line.

[0012] The wire may be provided with an insulating sheath. The wires may be directly adjacent to each other or spaced apart. It may be two single wires or a double wire in which the insulating sheaths of the two wires are directly joined.

[0013] The wire has a junction where the conductive wire is free of the insulating sheath, which can be, for example, the wire end or a portion to the side of the wire where the insulating sheath has been targeted removed.

[0014] The tip is disposed at the contact point of the wire. The tip may be disposed such that its largest dimension is oriented perpendicular to the extension of the wire. This arrangement is achieved by forming two contact points adjacent to each other on two parallel wires.

[0015] Both a mechanical bond and an electrical contact are formed between the chip and the wire.

[0016] Preferably, the chip comprises an external electrode for electrical contact, connected to the wire, the bond or contact between the chip and the wire being established by soldering or by application of a conductive adhesive.

[0017] As stated above, the maximum lateral dimension of the NTC sensor in each direction is equal to or less than the sum of the lateral dimensions of the tip and wire.

[0018] The lateral dimension is the dimension of the NTC sensor perpendicular to the extension of the two parallel wires.

[0019] Due to the targeted contact with a small amount of contact material, such as solder or adhesive, and the advantageous placement of the chip on the wire, the overall dimensions of the NTC chip can be reduced as described above, which has the advantage, among other things, that the NTC sensor can be easily inserted into an assembly having small dimensions through an insertion channel having small dimensions.

[0020] In this case, what is called the insertion channel is in particular the exposed path between the outside of the assembly and the site in the assembly where the sensor is to be installed. The exposed cross-sectional dimensions of the insertion channel can therefore be selected to be very small. The entire assembly can be embodied as small as possible, which saves space and costs.

[0021] According to one embodiment, the maximum lateral dimension of the NTC sensor is not larger or only slightly larger than the lateral dimension of the chip in the same direction.

[0022] This can be achieved by advantageous placement of the chip on the wire, and further by advantageous contact with a small amount of contact material such as solder or adhesive.

[0023] The chip is, in this embodiment, the limiting component when the NTC sensor is inserted into its installation situation in the assembly through the insertion channel. If the chip is embodied with the smallest possible dimensions, the size of the NTC sensor can also be minimized.

[0024] In one embodiment, the lateral dimension of the chip in each direction perpendicular to the extension direction of the wires is no greater than the dimension of the two wires in the same direction.

[0025] For example, in the direction in which the two wires are adjacent to each other, the dimension of the tip is no greater than the sum of the diameters of the wires. Preferably, the wires are directly adjacent to each other such that the dimension of the NTC sensor in the lateral direction is no greater than the dimension of the tip.

[0026] Perpendicular to this, in a direction in which the wires are not adjacent to one another, the lateral dimension of the chip is no greater than the diameter of one of the wires.

[0027] The wires preferably both have the same diameter in all embodiments.

[0028] In one embodiment, the lateral dimension of the chip in each direction perpendicular to the extension direction of the wires is smaller than the dimension of the two wires in the same direction.

[0029] The diameter of each wire is measured including any insulating sheath that may be present.

[0030] The maximum dimension of the tip is not greater than the sum of the diameters of the two wires. Thus, the sensor head, including the tip to which the wire is applied, preferably has dimensions that do not differ significantly from the dimensions of the remaining part of the wire. The sensor head is usually the part of the sensor that has the widest dimension. Thus, the above-mentioned sensor with a very small sensor head can be easily integrated into very small assemblies, such as batteries, in which the wires can be inserted through a channel.

[0031] In one embodiment, the tip has a maximum spread of 0.6 mm.

[0032] A typical dimension of a wire with a surrounding sheath is 0.3 mm. Two wires or double wires directly adjacent to each other therefore have a width of 0.6 mm. A tip with a maximum extension of 0.6 mm is attached to the head end of the wire, which ensures that the tip does not protrude beyond the wire in the lateral direction if the tip is properly oriented. The sensor head therefore has dimensions that are not much larger or only slightly larger than the wire.

[0033] For wires having smaller or larger diameters, the tip may have correspondingly smaller or larger dimensions, but the dimensional ratio between the tip and the wire should be maintained.

[0034] The tip is preferably embodied in a rectangular parallelepiped shape. The tip has a maximum extension of 0.6 mm. The tip has a maximum extension of 0.3 mm in a lateral direction perpendicular to the maximum extension. If the tip is attached in a suitable orientation to the head ends of two adjacent wires, each having a diameter of 0.3 mm, the tip thereby does not protrude beyond the wires in the lateral direction.

[0035] The extension of the tip along a third direction perpendicular to the contact surface between the tip and the wire, ie along the extension direction of the wire, can be variable but preferably has a maximum extension of 0.33 mm.

[0036] In one embodiment, the chip is a ceramic multi-layer component with internal electrodes.

[0037] Multilayer components consist of several NTC thermistor ceramic layers with metallic internal electrodes between them. The electrical resistance of such multilayer components can be very precisely defined. For example, a resistance tolerance of less than 1% can be achieved.

[0038] The resistance of NTC materials is temperature dependent. At higher temperatures, the resistance decreases (hot wire). The temperature dependent behavior of the resistance is described by the resistance-temperature characteristic. The resistance tolerance can be set not to exceed a value of 1% relative to the nominal temperature.

[0039] In the described embodiment, the internal electrodes can be electrically contacted by external electrodes on the surface of the chip. The external electrodes are preferably attached to two opposite sides of the chip. The external electrodes can be configured in a cap shape and cover different sides of the chip. Preferably, the internal electrodes stacked in the multi-layer component are alternately connected to two oppositely arranged external electrodes, respectively.

[0040] The external electrodes include a metallization layer, for example made of silver, which is applied, for example, via a dipping process with subsequent baking. In addition, a Ni-Sn (nickel-tin) layer can be electrically applied. The Ni-Sn layer is preferably applied on the outside of the metallization layer made of silver.

[0041] According to a further embodiment, the chip comprises a monolithic NTC thermistor ceramic. The ceramic in the chip can therefore be shaped as a through monolith. Inside the ceramic there are no further components such as internal electrodes. Such a chip can be provided very easily. For contacting the chip there are external electrodes on two opposite surfaces.

[0042] In one embodiment, the two wires are arranged in parallel, preferably extending straight and adjacent to each other.

[0043] In the case of coated wires, the insulating sheaths of the wires may be directly adjacent to one another.

[0044] Wires that are adjacent to each other require less space than wires that are spaced apart when assembled into an electronic assembly. A chip having the dimensions mentioned above can be easily contacted via two wires that are adjacent to each other.

[0045] In a preferred embodiment, it is not two single wires, but a double wire in which the sheaths of two wires are firmly joined together, which is easier to handle in the production process than a single wire.

[0046] In one embodiment, the end faces of the wires serve as contacts to which the chips are attached.

[0047] The end face of the wire may be embodied as a blunt end of the wire, which occurs, for example, when the wire is chopped transversely to its longitudinal direction, at which the metallic conductive wire is exposed from the insulating sheath.

[0048] If desired, the sheath may be further removed around the end faces of the wire ends, for example by mechanical cutting or by laser ablation.

[0049] If the tip, whose dimensions do not exceed or only slightly exceed the dimensions of the wires, which are preferably arranged parallel to one another, is applied directly to the end faces of the wires, the tip does not or only slightly protrudes laterally beyond the wires. In that case, the tip is like an extension of the wires, with dimensions similar to the wires. The dimensions of the sensor head, i.e. of the tip with the wires attached thereto, correspond approximately to the dimensions of the tip. In that way, the sensor head can be easily inserted into the assembly together with the wires.

[0050] In one embodiment, the contacts are formed in an L-shape and the chip is mounted on the L-shaped contacts.

[0051] Preferably, the end faces of the wires serve as contacts formed in an L-shape, for which purpose the aforementioned blunt ends of the wires can be partially flattened so that said ends have a shovel shape.

[0052] The dimension of each wire in the flattened direction is negligible compared to the diameter of the wire. The flattened sides of the wire are shaped similarly to the blade of a shovel.

[0053] The shovel-shaped surface provides a large contact surface onto which the chip can be attached, thus establishing a stable and reliable connection and electrical contact with low connection resistance between the chip and the wire.

[0054] In particular, the L-shaped faces (shaped like shovel blades) of the two wires can be provided on two opposing outer faces of the chip, so that the chip can be placed between the wires, which further improves the stability of the sensor.

[0055] Due to the flattening of the wire, the dimensions of the sensor head also in this embodiment correspond approximately to those of the tip. If the tip dimensions are appropriately selected, the sensor head does not or barely protrudes laterally beyond the wire and thus forms, as it were, an extension of the wire with similar dimensions. In that way, the sensor head can be easily inserted into the assembly together with the wire.

[0056] In one embodiment, the contacts are formed by exposing the portions of the wires intended for them from the insulating sheath.

[0057] In one embodiment, the connection between the chip and the wires is established by soldering.

[0058] In one embodiment, the contacts are formed with as little solder as possible.

[0059] In one embodiment, the heat required for soldering is provided by the self-heating of an NTC thermistor ceramic upon application of a voltage.

[0060] Solder paste is applied to the wire ends of the wires to which the chips will be soldered. The solder paste may be composed of various metals such as lead, tin, zinc, silver, copper, gold, antimony and bismuth. Preferably, the solder paste may be lead-free. Additionally, the solder paste may be impregnated with a flux.

[0061] The chip can then be placed in a horde between the wire ends wetted with solder paste. A voltage is applied through the wires. The application of the voltage heats up the NTC thermistor ceramic in the chip.

[0062] Self-heating of the chip causes the solder paste to melt and then solidify upon cooling, thus producing the soldered joints.

[0063] The small but locally limited heat supply during self-heating of the chip allows the production of solder connections using a minimal amount of solder paste, and the dimensions of the sensor head, including the chip and the wire ends soldered to it, can thus be minimized.

[0064] The amount of solder paste per solder connection is preferably so small that the solder connection has no or little effect on the lateral dimensions of the sensor. The amount of solder paste depends on the chip and wire dimensions and is preferably between 0.1 mg and 10 mg.

[0065] The solder joints produced as described above have a very high strength, particularly when produced by self-heating, compared to conventional solder joints produced by externally supplied heat.

[0066] The strength of the solder connections can furthermore be adjusted very precisely. Preferably, the solder connections withstand a tensile force of up to 6 N (Newtons). More preferably, the solder connections withstand a tensile force of up to 8 N or up to 10 N or even more.

[0067] In one embodiment, the contact between the chip and the wire contacts is made with a conductive adhesive, which may include, for example, a polymeric material having conductive particles dispersed therein, such as metallic particles of, for example, silver.

[0068] In one embodiment, the contact is formed with as little adhesive as possible.

[0069] The amount of adhesive is preferably so small that it has no or little effect on the lateral dimensions of the sensor. The amount of adhesive per contact depends on the chip and wire dimensions and is preferably between 0.1 mg and 10 mg.

[0070] In one embodiment, the conductive adhesive is cured by self-heating of the NTC thermistor ceramic upon application of a voltage.

[0071] Similar to that described above with respect to soldering, a voltage can be applied to the chip through a bridge formed from wire and conductive adhesive. Application of the voltage results in heating of the NTC thermistor material.

[0072] With a small but locally limited heat supply, a strong connection between the chip and the wire can be established with a minimal amount of adhesive.

[0073] According to one embodiment, the sensor head of the NTC sensor is coated with a polymer material. The sensor head includes a tip and a contact portion.

[0074] The coating with polymer material protects the sensor head, i.e. the chip to which the wires are connected, from external mechanical, chemical or physical influences. The coating is preferably electrically insulating and impermeable to moisture.

[0075] The sensor head may include a tip, wire contacts applied thereto, contacts between the tip and wires formed, for example, by solder or conductive adhesive, and a coating of a polymeric material.

[0076] The coating can be applied using a variety of techniques, such as by dipping in a liquid polymer material, by covering heat shrink tubing, or by melting a polymer powder applied to the sensor head in a fluidized bed.

[0077] Alternatively, the coating can also be obtained by dipping the sensor head in a polymer powder and subsequent self-heating of the chip, similar to the case of soldering or curing of an adhesive. The last-mentioned method allows the formation of a particularly thin coating, which is formed with minimal material consumption but which tightly surrounds the sensor head.

[0078] Alternatively, the coating may be cured after application by self-heating of the chip and subsequent heat treatment in an oven.

[0079] In one embodiment, the lateral dimension of the sensor head, including the coated polymer material, in each direction perpendicular to the extension direction of the wires is not greater than twice the combined dimension of the two wires in the same direction.

[0080] In one embodiment, the lateral dimension of the sensor head, including the coated polymer material, in each direction perpendicular to the extension direction of the wires is not greater than the combined dimension of the two wires in the same direction.

[0081] Preferably, the diameter of the wire is less than or equal to 0.3 mm, so that the sum of the two diameters is less than or equal to 0.6 mm.

[0082] Preferably, the wires extend linearly adjacent to each other. The two wires may be embodied as a double wire that is firmly joined. Thus, the width of the two adjacent wires or the double wire consisting of two adjacent and connected wires in the extension direction is 0.6 mm or less.

[0083] The width of the sensor head in the same direction perpendicular to the extension direction of the wire is preferably 1.3 mm or less, regardless of the diameter of the wire.

[0084] For a dual wire width of 0.6 mm, the width of the sensor head is preferably 1.2 mm or less, more preferably 1 mm or less, even more preferably 0.8 mm or less.

[0085] In an advantageous embodiment, the sensor head is no wider than a double wire or two parallel wires.

[0086] In a particularly advantageous embodiment, the width of the sensor head is approximately 0.6 mm or exactly 0.6 mm or less than 0.6 mm.

[0087] The dimension of the sensor head perpendicular to the extension direction of the wire and perpendicular to the width is less than or equal to 1.3 mm, preferably less than or equal to 0.6 mm. Particularly preferably, said dimension of the sensor head is less than or equal to the wire diameter of 0.3 mm.

[0088] The increasing miniaturization and automation of electrical and electronic components increases the demand for sensors with very small dimensions that can be integrated into miniaturized components. The limiting factor here is usually the sensor head, which naturally has a larger extension than the connecting wires.

[0089] By minimising the dimensions of the sensor head, which preferably no longer exceed the dimensions of the remaining wires, the entire sensor can be easily used by inserting the wires together with the sensor head into the electronic component.

[0090] Possible areas of use are, for example, batteries and accumulators in the automotive or industrial sector.

[0091] The invention further relates to a method for manufacturing an NTC sensor. An NTC sensor manufactured according to this method may have all or some of the characteristics described above in relation to the NTC sensor. Furthermore, the above-mentioned sensor may have all the characteristics described below and may be manufactured by the described method.

[0092] The method for manufacturing an NTC sensor involves several steps.

[0093] In one step, two wires with contacts and a chip containing an NTC thermistor ceramic are prepared.

[0094] The tip is disposed at the contact point of the wire so that the maximum lateral dimension of the NTC sensor in each direction perpendicular to the extension direction of the wire is less than the sum of the lateral dimensions of the tip and the wire.

[0095] The largest dimension of the NTC sensor in one embodiment is no larger than the dimension of the tip, which in a preferred embodiment is no larger than the dimension of two wires in the same direction.

[0096] The mechanical bond and electrical contact between the chip and the wires is formed by soldering or applying a conductive adhesive.

[0097] In one embodiment of the method, the connection between the chip and the wire is established by soldering.

[0098] In one embodiment, the heat required for soldering is provided by the self-heating of an NTC thermistor ceramic upon application of a voltage.

[0099] For this purpose, a wire, the contacts of which are coated with solder paste, is brought into contact with the chip, preferably with an external electrode of the chip.

[0100] The solder paste may be composed of various metals such as lead, tin, zinc, silver, copper, gold, antimony, and bismuth. Preferably, the solder paste may be lead-free. Additionally, the solder paste may be infiltrated with a flux.

[0101] A voltage is then applied to the chip via the wires, which heats up the NTC thermistor ceramic.

[0102] Self-heating of the chip causes the solder paste to melt and then solidify upon cooling.

[0103] Solder paste may be applied to the contacts of the wires, preferably by dipping the wires into a reservoir having the solder paste. Alternatively, a metered amount of solder paste may be applied to the contacts through a dispenser device. The latter is particularly suitable when the contacts are to be placed on the sides of the wires rather than at the ends of the wires.

[0104] The small but locally limited heat supply during self-heating of the chip allows the production of solder connections using a minimal amount of solder paste, and the dimensions of the sensor head, including the chip and the wire ends soldered to it, can thus be minimized.

[0105] The solder joints produced as described above have a very high strength, and in particular the strength of the solder joints produced by self-heating is higher than that of conventional solder joints produced by externally supplying heat.

[0106] The strength of the solder connections can furthermore be adjusted very precisely. Preferably, the solder connections withstand a tensile force of up to 6 N (Newtons). More preferably, the solder connections withstand a tensile force of up to 8 N or up to 10 N or even more.

[0107] In one embodiment of the method, the bond and electrical contact between the chip and the wire contacts is established by a conductive adhesive, which comprises a polymeric material having conductive particles dispersed therein, such as metallic particles of silver.

[0108] In one embodiment of the method, the conductive adhesive is cured by self-heating of the NTC thermistor ceramic upon application of a voltage.

[0109] Application of a voltage results in heating of the NTC thermistor material. With a small but locally limited heat supply, a strong connection between the chip and the wire can be established with a minimal amount of adhesive.

[0110] Preferably, the wire end is briefly dipped into the adhesive in a first step, so that some adhesive adheres to the wire contact. The wire contact is then placed on the external electrode or external metallization of the chip, and the chip is heated. For this purpose, a voltage can be applied to the chip via the material bridge consisting of the wire and the conductive adhesive. By heating, the thermosetting adhesive hardens, and a strong mechanical and conductive connection is established between the wire and the chip.

[0111] In one embodiment of the method, the conductive adhesive is cured by irradiation with ultraviolet light. For this purpose, an ultraviolet-curable adhesive is used instead of a thermally curable adhesive. The rest can be carried out as in the previous embodiment. An external ultraviolet radiation source is then required to cure the adhesive.

[0112] In one embodiment of the method, the wires are arranged in parallel, with multiple contacts formed along the wires by exposing each wire from an insulating sheath.

[0113] One chip each is placed on the contacts and then the wire is chopped between the individual chips, resulting in multiple NTC sensors.

[0114] By the methods described above, the chip can also be applied and contacted on the side of the wire, which is particularly suitable for the continuous production of NTC sensors directly from wire coils.

[0115] The wire coil is unwound in respective predetermined portions for this purpose. The contacts are then cut from the insulating sheath and a tip is applied onto the contacts.

[0116] The wire between the chips is then subdivided to obtain the individual sensors: two adjacent contacts must be exposed on each of the two wires so that the chips can make contact with both wires, respectively.

[0117] Preferably, the sheath is removed so that the entire tip is embedded in the remaining sheath and can be placed directly on the two contacts. In that case, the entire tip can be placed directly on the metal wire. The sensor head in this embodiment has dimensions that do not exceed or barely exceed the dimensions of the tip.

[0118] In one embodiment, for this purpose, multiple chips are placed along a parallel arranged wire on multiple contacts formed along the wire, and the wire is subsequently chopped between the individual chips, resulting in multiple NTC sensors.

[0119] The wires are for this purpose preferably arranged adjacent to one another in a straight line. A respective pair of contacts, one for each of the two wires, is arranged adjacent to one another along the wires. On each pair of contacts a chip can be arranged. Correspondingly embodied wires allow for serial production of NTC sensors.

[0120] The wire may be two single wires adjacent to each other, a double wire, or a partially unwound coil of wire.

[0121] In the following, the invention will be explained in detail on the basis of examples and the accompanying drawings, in which similar or obviously identical elements are provided with the same reference signs. The drawings and the size ratios therein are not to scale. The invention is not limited to the examples shown in the drawings. [Brief description of the drawings]

[0122] [Figure 1] 1 shows a first embodiment of an NTC sensor. [Diagram 2] 1 shows a first embodiment of an NTC thermistor chip. [Diagram 3] 2 shows a second embodiment of an NTC sensor. [Figure 4] 3 shows a third embodiment of an NTC sensor. [Diagram 5] 4 shows a fourth embodiment of the NTC sensor. [Figure 6] 1 illustrates an exemplary embodiment of an NTC sensor having a coating. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0123] A first embodiment of an NTC sensor 100 is shown in FIG.

[0124] A chip 1 and two wires 2 are prepared. The chip 1 contains an NTC thermistor material. NTC here stands for Negative Temperature Coefficient, i.e. the thermistor material has a smaller electrical resistance at higher temperatures (hot wire).

[0125] The chip 1 is shown in Figure 2 and has a rectangular parallelepiped structure. The chip has a length L of up to 0.6 mm, a width W of 0.3 mm and a height H of 0.33 mm. At both longitudinal ends the chip is electrically contacted via external electrodes 3. The external electrodes 3 are preferably mounted in the form of caps on both longitudinal ends.

[0126] The external electrodes 3 comprise a metallization layer, for example made of silver, which is applied, for example, via a dipping process with subsequent baking. In addition, a Ni-Sn layer can be electrically applied.

[0127] The chip 1 is in this example embodied as a ceramic multilayer component with internal electrodes. Between each two ceramic layers, a metallic internal electrode is arranged. The internal electrodes are preferably electrically contacted by two alternating external electrodes 3.

[0128] The electrical resistance of such a multi-layer component can be set very accurately: the resistance tolerance, i.e. the possible deviation of the resistance from a predetermined desired electrical resistance at nominal temperature, is less than 1%.

[0129] Alternatively, the chip 1 may, in an embodiment not shown here, comprise a monolithic NTC ceramic block. The NTC ceramic block does not comprise an internal electrode and can be easily manufactured. On two opposite sides, external electrodes 3 are applied onto the NTC ceramic block. The external electrodes preferably cover the entire side surfaces of the ceramic block and via which the NTC ceramic block can be electrically contacted.

[0130] The wire 2 is, for example, a silver plated nickel wire, a copper wire, a copper strand, a Ni-Fe or a Cr-Ni wire with a Cu, Ag or Pt sheath.

[0131] The wire 2 is preferably covered by an electrically insulating sheath 4. The sheath 4 consists of a non-conductive polymeric material, such as perfluoroalkoxyalkane (PFA), Teflon, polyurethane (PU), polyamide (PA), polyimide (PI), silicone, polyester, polyacrylate, epoxy polymer, resin or epoxy resin.

[0132] The two wires 2 have blunt ends 5 at their end faces, where the conductive wire is exposed. The blunt ends 5 are therefore the contacts to which the chip 1 is attached.

[0133] There are several possible ways to achieve this.

[0134] According to a first exemplary method, the blunt end 5 of the wire 2 is dipped into the solder paste, whereby a small amount of solder paste is applied onto the blunt end 5 of the wire 2. The blunt end 5 of the wire 2 with the solder paste applied thereto is then placed on two opposing external electrodes 3 of the chip 1.

[0135] A voltage is then applied to the chip 1 via the wire. The application of voltage heats the chip 1 and melts the solder paste. The flux in the solder paste evaporates and the subsequent cooling causes the solder to harden. Thus, the solder connection between the external electrodes 3 and the contacts of the wires 2 is obtained solely by the self-heating of the chip 1 upon application of voltage.

[0136] The method described above allows the application of at least the minimum amount of solder paste necessary to obtain a reliable connection between the chip 1 and the wires 2. In this way, the dimensions of the sensor head, including the chip 1 and the connecting wires 2, can be minimized.

[0137] In an alternative method, the chip 1 is glued onto the contact of the wire 2. For this, the blunt end 5 of the wire 2 is dipped into a thermosetting adhesive. The blunt end 5 of the wire is then applied onto the external electrode 3 of the chip 1. By applying a voltage to the wire, the chip 1 is heated and the thermosetting adhesive is hardened.

[0138] In an alternative method, the chip 1 is likewise glued onto the contacts of the wires 2. For this, the blunt ends 5 of the wires 2 are immersed in a UV-curable adhesive. The blunt ends 5 of the wires 2 are then applied onto the external electrodes 3 of the chip 1. The adhesive is then hardened by irradiation with UV light.

[0139] The adhesive is electrically conductive. An example of such an adhesive is a polymer-based adhesive containing conductive metal particles, for example silver particles. The method described above allows the application of a minimal amount of adhesive to establish the connection between the chip 1 and the wire 3, so that the dimensions of the sensor head can be minimized.

[0140] Furthermore, the geometry of the sensor head is optimized by suitable dimensions of the tip 1 and by advantageous placement of the tip 1 on the wire 2 .

[0141] For example, in this method a tip 1 is used that is not longer than the sum of two diameters of two adjacent wires 2 and not wider than the diameter of the wires 2 .

[0142] The length L is understood here and below to be the dimension of the tip 1 between the two external electrodes 3. This direction of extension corresponds to the direction in which the two wires 2 adjoin one another.

[0143] Here and below, what is referred to as the width W of the tip 1 is the direction of extension perpendicular to the contact surface between the tip 1 and the wire 2. Here and below, what is referred to as the height H is the direction perpendicular to the contact surface.

[0144] The tip 1 is here placed on the blunt ends 5 of two adjacent wires 2. The dimensions of the tip 1 mean that it does not protrude beyond the wires 2, either in length or width. The sensor head is therefore neither longer nor wider than the remaining double wire 2.

[0145] 3 and 4 show second and third embodiments of the NTC sensor 100. Features of the second and third embodiments that are consistent with the first embodiment will not be explicitly described.

[0146] Unlike the first embodiment, the wire 2 in the second and third embodiments has an L-shaped end 6, i.e. the end face of the wire is not embodied in a blunt manner but is shaped like a shovel.

[0147] By L-shaped here it is meant that the wire 2 is flattened at its end. The flat part of the wire 2 therefore has a geometric shape similar to the blade of a shovel. The L-shaped end 6 of the wire 2 can be attached laterally onto the external electrode 3 of the chip 1. The L-shaped end 6 has the advantage, compared to the blunt end 5 of the wire 2, that the contact surface between the wire 2 and the chip 1 is made larger.

[0148] The L-shaped ends 6 of the wires 2 can either rest on the cap-like external electrodes 3 at two opposite ends, as shown in FIG. 3, or contact them from the same side, as shown in FIG. 4.

[0149] If the two external electrodes 3 are contacted from the same side, there must be two external electrodes 3 on one side of the chip 1 .

[0150] The exact placement depends, among other things, on practicality during production. The L-shaped end 6 of the wire 2 has very small dimensions that are negligible compared to the diameter of the remaining non-flat part of the wire 2. Thus, even in the above-described configurations of the second and third embodiments, the sensor head has dimensions that are barely large compared to the dimensions along the remaining double wire 2.

[0151] The contact area between the wire and the chip can be embodied in this embodiment to be large enough that a reliable contact with low connection resistance is achieved.

[0152] The large contact surface further increases the mechanical stability of the sensor, which can be further improved if the tip is placed between the wires, as shown in FIG.

[0153] 5 shows a fourth embodiment of the NTC sensor 100. Features of the fourth embodiment that are consistent with the first embodiment will not be explicitly described.

[0154] Unlike the first embodiment, the wire 2 in the fourth embodiment has not yet been cut to its final size but exists as a complete wire coil 200. Prior to the production process, portions having predetermined lengths are each unwound from the wire coil 200.

[0155] Subsequently, the insulating sheath 4 of the contacts 7 up to the conductive wire 2 is removed, thereby exposing the contacts 7 laterally of the wire 2. Always two adjacent contacts 7 are exposed for two wires 2. In this embodiment, the sheath 4 is preferably removed so that the entire tip 1 can be mounted directly on the wire 2 and so that the sensor head including the wire 2 and tip 1 does not have unnecessarily large dimensions.

[0156] As in the previous embodiment, the chips 1 can be fixed to the wires 2 both by gluing and by soldering. For this, a small amount of solder paste or adhesive is applied to the exposed contacts 7, preferably by means of a dispenser device. The chips 1 can then be mounted on the contacts 7. By applying a voltage, the connections to all chips 1 mounted on the wires 2 can be soldered simultaneously or the adhesive can be cured simultaneously.

[0157] After the chips 1 are fully attached, the double wires 2 with the chips 1 are cut between the chips 1 to obtain the desired individual sensors 100, respectively.

[0158] The method described above allows to save steps and simplifies mass production of chips 1.

[0159] Regardless of the embodiment described above, the sensor head is covered with a polymer material for protection from external mechanical influences, for protection from contamination, for protection from moisture, and for electrical insulation.

[0160] Fig. 6 shows an exemplary NTC sensor having a coating 8. The dimensions HL and CL of the sensor shown in Fig. 6 in the extension direction of the wire, as well as the dimensions perpendicular thereto, should be understood to be merely exemplary and do not necessarily correspond to the dimensions of an NTC sensor according to the invention.

[0161] Here, dimension HL is the dimension of the sensor head from the wire end in the direction of wire extension, dimension CL is the dimension of the entire coating 8 around the sensor head and wire in the direction of wire extension, and dimension HD is the diameter of the rotationally symmetric coating in the direction perpendicular to the direction of wire extension.

[0162] The coating is carried out after the chip 1 is connected to the wire 2. The polymer material can be applied by various methods.

[0163] For example, the sensor head may be immersed in a reservoir of polymer powder and subsequently self-heated by application of a voltage, which melts the polymer powder and forms a thin polymer coating around the sensor head. In this way, a very thin coating 8 may be formed, which further minimizes the dimensions of the sensor head.

[0164] Preferably, the lateral dimension HD of the sensor head including the coating polymer material 8 is, in any direction perpendicular to the extension direction of the wires, less than or equal to twice the sum of the dimensions of the two wires in the same direction, and more preferably less than or equal to the sum of the dimensions of the two wires in the same direction.

[0165] In addition, a thermal post-treatment may be performed in an oven to increase the degree of hardening.

[0166] In an alternative method, the sensor head is immersed in an already liquefied polymer material to form the coating 8. After immersion, the coating 8 must be cured.

[0167] According to a third possible method, a heat shrink tube is placed over the sensor head and shrunk by applying heat in an oven. By selecting the shrink parameters, the shrinkage can be adjusted to produce a complete and dense coating of the sensor head.

[0168] In another method, a polymer powder is electrostatically charged and fluidized by supplying a gas flow in a fluidized bed. The electrostatically charged powder particles remain attached to a sensor head immersed in the fluidized bed and can then be heated in an oven, melted, and subsequently cured.

[0169] All four methods described above allow the application of an advantageous thin polymer coating 8 to protect the sensor head.

[0170] In a mass production process, a polymer coating may be applied around the sensor head before the individual NTC sensors 100 are singulated by separating the wire 2 from the wire coil 200. [Explanation of symbols]

[0171] 1 chip 2 Wire 3 External electrode 4 Sheath 5 Blunt Ends 6 L-shaped end 7 Lateral Contacts 8. Coating 100 NTC Sensors 200 wire coil

Claims

1. An NTC sensor (100) comprising a chip (1), two parallel wires (2) each having a contact (5, 6, 7), and contacts between the chip (1) and the contacts (5, 6, 7) of each of the wires (2), The maximum lateral dimension of the NTC sensor in any direction perpendicular to the extension direction of the wire (2) is equal to or smaller than the sum of the lateral dimensions of the tip (1) and the wire (2); The contact (6) of the wire (2) is formed as an L-shaped surface, The L-shaped contacts (6) are provided on two opposing outer surfaces of the chip (1); The L-shaped surface provides an enlarged contact surface onto which the chip (1) is attached, NTC sensor (100).

2. 2. The NTC sensor (100) of claim 1, wherein the maximum lateral dimension of the NTC sensor (100) is not greater than a lateral dimension of the tip (1) in the same direction.

3. 3. An NTC sensor (100) as described in claim 1 or 2, wherein the lateral dimension of the chip (1) in any direction perpendicular to the extension direction of the wires (2) is not greater than the combined dimension of the two wires (2) in the same direction.

4. 2. The NTC sensor (100) of claim 1, wherein the chip (1) has a maximum lateral extent of 0.6 mm.

5. 2. The NTC sensor (100) of claim 1, wherein the chip (1) is a ceramic multi-layer component having internal electrodes.

6. The NTC sensor (100) of claim 1, wherein the chip (1) comprises a monolithic NTC thermistor ceramic.

7. The NTC sensor (100) of claim 1, wherein the two wires (2) are directly adjacent to each other.

8. 2. The NTC sensor (100) of claim 1, wherein end faces of the wire (2) serve as contacts (5, 6) on which the chip (1) is attached.

9. 2. The NTC sensor (100) of claim 1, wherein the contact (7) is formed by exposure of the wire (2) from an insulating sheath (4).

10. The NTC sensor (100) of claim 1, wherein the contact portion is formed by solder.

11. The NTC sensor (100) of claim 1, wherein the contact portion is formed from a conductive adhesive.

12. 2. The NTC sensor (100) of claim 1, wherein a sensor head of the NTC sensor (100) including the tip (1) and the contacts is covered by a polymer material (8).

13. The NTC sensor (100) of claim 12, wherein the lateral dimension of the sensor head including the covering polymer material (8) in any direction perpendicular to the extension direction of the wire (2) is not greater than twice the total dimension of the two wires (2) in the same direction.

14. A method for manufacturing an NTC sensor (100), comprising the steps of: Providing two wires (2) having contacts (5, 6, 7); Providing a chip (1) containing an NTC thermistor ceramic; positioning the chip (1) on the contacts (5, 6, 7) of the wire (2) such that the maximum lateral dimension of the NTC sensor (100) in any direction perpendicular to the extension direction of the wire (2) is smaller than the sum of the lateral dimensions of the chip (1) and the wire (2); forming a mechanical bond and electrical contact between the chip (1) and the wires (2) by soldering or applying a conductive adhesive; Including, The contact (6) of the wire (2) is formed as an L-shaped surface, The L-shaped contacts (6) are provided on two opposing outer surfaces of the chip (1); The L-shaped surface provides an enlarged contact surface onto which the chip (1) is attached.

15. 15. The method of claim 14, wherein the heat required for the soldering is provided by self-heating of the NTC thermistor ceramic upon application of a voltage.

16. The method of claim 14 , wherein the conductive adhesive is cured by self-heating of the NTC thermistor ceramic upon application of a voltage.

17. The method of claim 14 , wherein the conductive adhesive is cured by exposure to ultraviolet light.

18. The method according to any one of claims 14 to 17, wherein the wires (2) are arranged in parallel, and a plurality of contacts (7) are formed along the wires (2) by exposing the wires (2) from an insulating sheath, and a chip (1) is attached to each of the contacts (7), and the wires (2) are subsequently chopped between the individual chips (1) to obtain a plurality of NTC sensors (100).

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