DE102017100820A1 - sensor - Google Patents

Abstract

The present invention relates to a sensor (1) comprising a ceramic support (3) to which a sensor element (2) is fixed and which has a metallization (5) electrically contacted with the sensor element (2) and a lead (8) fixed to the metallization (5) and configured to electrically contact the sensor element (2) via the metallization (5), the lead (8) being mechanically fixed to the ceramic support at a further position (3) is fixed.

Description

The present invention relates to a sensor, in particular a temperature sensor.

The ever-increasing demands on temperature sensors with regard to the long-term stability in aggressive media and high operating temperatures require in the future particularly reliable temperature sensors. At the same time such novel sensors should be produced by a cost-effective production.

Preferably, a temperature sensor should be specified with a cost-effective electrode systems paired with a stable electrical contacting of the supply line. The sensors should also be suitable for use at high application temperatures and in particularly aggressive media or gases. When installing the sensors in the system as well as in the application, a sufficiently mechanically stable connection of the supply line to the sensor element should be ensured.

For sufficient mechanical stability and protection against external influences and to avoid corrosion by aggressive media, a sensor element may be provided with a coating of a polymer or a glass.

The object of the present invention is to specify an improved sensor.

The object is achieved by the sensor according to claim 1.

A sensor is proposed which has a ceramic carrier, a sensor element and a feed line. The sensor element is attached to the ceramic carrier. The carrier has a metallization that is electrically contacted with the sensor element. The lead is attached to the metallization and configured to electrically contact the sensor element via the metallization, wherein the lead is mechanically fixed to the ceramic support at a further position.

The supply line can be attached to a connection surface with the metallization. A direction parallel to the surface normal of the joint surface may be referred to as a radial direction. A direction perpendicular to the surface normal of the joint surface may be referred to as an axial direction. In this case, the axial direction can extend along a longitudinal axis of the ceramic carrier. The axial direction may be parallel to the metallization of the carrier.

The lead may be attached to the metallization by, for example, a solder joint, a welded joint, an adhesive bond or a sintered bond. All these compounds are characterized by a high load capacity against forces acting in the axial direction. However, the connections may have a lower load capacity against forces acting in the radial direction. For example, the load capacity against forces in the radial direction may be smaller by a factor of 5 to 10 than the load capacity in the axial direction.

Due to the mechanical attachment of the supply line to the carrier at a further position, the connection of the supply line to the metallization can now be relieved. For example, acts a force in the radial direction of the supply line, the supply line can be held by the attachment to the other position in position relative to the carrier, without causing a significant mechanical stress on the attachment of the lead to the metallization. The embodiment of the sensor specified here can thus make it possible to relieve the connection of the supply line to the metallization against high radial loads and thus to protect the electrical contacting of the sensor element.

The sensor is preferably a temperature sensor, i. a sensor configured to measure a temperature. Sensors for measuring temperatures are used for monitoring and control in a wide variety of applications.

The sensor element may be, for example, an NTC thermistor (NTC = Negative Temperature Coefficient), a silicon temperature sensor having a positive temperature coefficient, a platinum resistance temperature detector (PRTD) or a thermocouple. Preferably, the sensor element is an NTC thermistor. These are characterized by low production costs. A further advantage of NTC thermistors over thermocouples and metallic resistive elements, e.g. Pt elements, consists in the pronounced negative resistance temperature characteristic.

The metallization may be, for example, silver metallization or gold metallization. For example, silver or gold pastes can be applied to the support via a screen printing process followed by firing. The silver metallization can be used predominantly for solder joints with connecting wires. The gold metallization can be used for metallic sintered paste bonding. The gold metallizations Can be used for sintering contact pastes with connecting wires. The operating temperature of solder joints is limited by the melting temperature of the solders. High-lead solders have a melting temperature of approx. 300 ° C and most lead-free solders melt even at temperatures below 230 ° C. Solder joints are not sufficiently reliable during frequent thermal cycling. For higher operating temperatures of 250 ° C to 300 ° C or higher, contacting with a sintering paste is possible. In addition, much higher temperatures are necessary in the manufacturing process, since a glass envelope instead of a polymer sheath is required due to the operating temperature. However, this type of sensor elements produced in this way is associated with high costs, since the electrode as well as the contacting paste consist of gold. In addition, process costs are very high due to the paste application and drying and the subsequent penetration of the paste.

The feed line can be any element which is suitable for making electrical contact with the ceramic carrier. For example, the feed line may be a wire, a ribbon, a stranded wire or a metal mesh.

The ceramic carrier may be free of metallization at the further position. The ceramic carrier may have a base body on which the metallization is applied. The supply line may be attached to the further position directly on the main body of the ceramic carrier. The fact that the supply line is attached to the further position on the support so that it is not located on the metallization at the further position, a mechanical stress on the connection of the supply line with the metallization can be reduced.

The lead may have a first end and a second end, the first end of the lead attached to the metallization, and a portion of the lead mechanically fixed to the support at the further position between the first end and the second end , Thus, a force acting on the second end of the lead can first be absorbed by the attachment of the portion to the support before the force acts on the first end attached to the metallization.

The mechanical fixation of the lead to the ceramic support may be such that the mechanical fixation is the attachment of the lead to the metallization against a force acting on the lead in a direction perpendicular to a surface of the metallization away from the ceramic support. relieved. Accordingly, the load capacity of the sensor against forces acting in the radial direction on the supply line can be increased.

The lead may be mechanically fixed by a ceramic cement bonded to the ceramic support and the lead at the one further position relative to the ceramic support. The lead may be mechanically fixed by an adhesive bonded to the ceramic support and the lead at the one further position relative to the ceramic support.

The ceramic cement or the adhesive may be non-positively connected to the ceramic carrier and the supply line. Due to the non-positive connection, an electrical connection point between the supply line and the metallization can also be protected against a torsion of the supply line or an axial pull on the supply line.

The ceramic cement or the adhesive can be frictionally connected to the ceramic support and surround the supply line in a form-fitting manner. By precedently surrounding the supply line, a movement of the supply line, the radial direction can be prevented relative to the carrier. The positive connection can allow movements of the supply line in the radial direction to a certain extent. For example, the lead could expand or contract in the radial direction. In this embodiment, a mechanical stress at the electrical connection point of the feed line with the metallization can be avoided by different thermal expansion coefficients of the ceramic carrier and the feed line.

The ceramic cement or the adhesive can be arranged selectively on the ceramic support and the supply line. In this case, the ceramic cement or the adhesive cover each of the carrier and the supply line. In this way, an attachment of the supply line to the further position can be made possible with a minimum use of material.

Alternatively, the ceramic cement or adhesive can form a track running around the ceramic carrier. Through the track, the surface on which adheres the ceramic cement or the adhesive can be increased. Further, the ceramic cement or the adhesive may have a high strength, so that the track can mechanically stabilize the sensor.

Alternatively or additionally, the supply line can be mechanically fixed at a further position relative to the ceramic carrier by a body which is slid onto the ceramic carrier and encloses the ceramic carrier and the supply line be. The body may be configured to prevent movement of the lead in the radial direction relative to the carrier. The body can enclose the supply line, for example, positively. Movements of the supply line in the axial direction could not be restricted by the body, so that it does not come to mechanical loads due to different thermal expansion coefficients.

The body may be made of a ceramic material. The body may be made of the same material as a body of the ceramic carrier. Accordingly, the body and the carrier may have the same thermal expansion coefficients. With temperature changes can thus be prevented that mechanical stresses are caused by the body.

The body may have a through opening through which the supply line passes. Also, the ceramic carrier may extend through the through opening of the body. Accordingly, the opening may have a diameter sufficient to receive the carrier and the lead.

Alternatively, the body may have a blind hole defining a stop against which the ceramic carrier abuts.

An unilaterally closed opening can be referred to as a blind hole.

The lead may have a deformation which cooperates with the mechanical fixing of the lead to the ceramic support and thereby prevents movement of the lead relative to the ceramic support in an axial direction which is perpendicular to the surface normal of the metallization.

The lead may be mechanically attached to the metallization by a solder joint, a welded joint, an adhesive joint or a sintered joint.

The sensor may be a temperature sensor, wherein the sensor element is an NTC thermistor.

• 1 zeigt einen Sensor.
• 2 zeigt ein erstes Ausführungsbeispiel eines Sensors, bei dem eine Zuleitung zusätzlich an einem keramischen Träger fixiert ist im Querschnitt.
• 3 zeigt die Oberseite des in 2 gezeigten Sensors.
• 4 zeigt eine Seitenansicht des in 2 gezeigten Sensors.
• 5 zeigt ein zweites Ausführungsbeispiel eines Sensors im Querschnitt.
• 6 zeigt einen Körper in einem Querschnitt.
• 7 zeigt den in 5 gezeigten Sensor in einer perspektivischen Ansicht von oben.
• 8 zeigt eine Seitenansicht des in 5 gezeigten Sensors.
• 9 zeigt eine alternative Variante des zweiten Ausführungsbeispiels.

The invention will be described below with reference to the figures.

• 1 shows a sensor.
• 2 shows a first embodiment of a sensor in which a supply line is additionally fixed to a ceramic support in cross section.
• 3 shows the top of the in 2 shown sensor.
• 4 shows a side view of the in 2 shown sensor.
• 5 shows a second embodiment of a sensor in cross section.
• 6 shows a body in a cross section.
• 7 shows the in 5 shown sensor in a perspective view from above.
• 8th shows a side view of the in 5 shown sensor.
• 9 shows an alternative variant of the second embodiment.

1 shows a sensor 1 , The sensor is a temperature sensor. The sensor 1 has a sensor element 2 and a ceramic carrier 3 on. The sensor element 2 is on the ceramic carrier 3 attached.

The sensor element 2 is an NTC thermistor. The sensor element 2 is suitable for use temperatures up to 650 ° C. The ceramic carrier 3 has a basic body 4 made of aluminum oxide ceramics. Two opposite outer surfaces of the body 4 each have a metallization 5 on. The sensor element 2 is with the carrier 3 over short wire bridges 6 connected, each by a welded joint with one of the metallizations 5 are contacted.

Furthermore, the sensor has 1 a glass serving 7 on. The glass serving 7 surrounds the sensor element 2 and the wire bridges 6 Completely. Accordingly, the sensor element 2 and the connection of the sensor element 2 to the carrier 3 through the glass cladding 7 protected. Furthermore encloses the glass envelope 7 the end of the ceramic carrier 3 at which the sensor element 2 is attached.

The end of the carrier 3 that of the sensor element 2 points away is also referred to as the back end. At the back end of the carrier 3 can be a supply line 8th be attached. In particular, a supply line 8th with the on top of the ceramic carrier 3 arranged metallization 5 and another supply line 8th with the arranged on the underside of the ceramic support metallization 5 get connected.

In the following, usually only the one on top of the ceramic support 3 arranged metallization 5 and the associated supply line 8th considered. The features disclosed in this connection also apply in the same way to those on the underside of the ceramic carrier 3 disposed metallization 5 and the associated additional supply line 8th to.

The supply lines 8th are designed to the sensor element 2 about the metallizations 5 to contact electrically. With the supply lines 8th For example, they may be ribbon, stranded wire, metal mesh or wire. For example, it can be a silver wire.

The supply lines 8th are each at one of the metallizations 5 mechanically fastened. The supply lines 8th For example, by means of thermode welding on the metallizations 5 be attached. Alternatively, the supply lines 8th by another weld joint, a solder joint, an adhesive bond or a sintered bond to the metallizations 5 be attached.

The fastening of the supply line 8th at the metallization 5 is characterized by a high tensile strength against loads in the axial direction A out. The axial direction A runs along a longitudinal axis of the ceramic carrier 3 , The axial direction A is perpendicular to the surface normal of the metallization 8th , On the other hand, has the attachment of the supply line 5 at the metallization 8th against a stress in a radial direction R by a factor of between 5 and 10 lower load capacity than against axial load. As stress in the radial direction R In this case, the stress is designated by a force which is at least one component in the direction of the surface normal of the metallization 5 having. The radial direction R is perpendicular to the surface of the ceramic carrier 3 ,

To the lower load capacity of the mechanical attachment of the supply line 8th at the metallization 5 to compensate for radial forces compared to the load capacity against axial forces, is the supply line 8th further at a position of the ceramic carrier 3 that are free from the metallization 5 is mechanically attached to the ceramic carrier 3 fixed.

2 shows a first embodiment of a sensor 1 in which the supply line 8th additionally fixed to the ceramic carrier 3. 2 shows the sensor 1 according to the embodiment in cross section. 3 shows the top of the sensor 1 according to the first embodiment. 4 shows a side view of the sensor 1 according to the first embodiment.

The supply line 8th is at a connection surface 13 at the metallization 5 attached. At the interface 13 are the supply line 8th and the metallization 5 both mechanically fastened together and electrically contacted each other. The interface 13 is flat. The surface normal of the connection surface 13 shows it in the radial direction R , The axial direction A is perpendicular to the interface 13 ,

The sensor 1 has a ceramic cement 9 on that with the carrier 3 and the supply line 8th connected is. The ceramic cement 9 glued a section of the supply line 8th that is between a first end of the supply line 8th that at the metallization 5 is attached, and a second end of the supply line 8th that of the sensor element 2 points away, is arranged with the main body 4 of the carrier 3 , This will cause a movement of the supply line 8th in the radial direction R relative to the main body 4 difficult. Accordingly, the ceramic cement provides 9 for making the connection between the supply line 8th and the metallization 5 better against stress from one in the radial direction R acting force is protected.

The ceramic cement 9 is non-positive with the carrier 3 connected. The ceramic cement 9 can with the supply line 8th either also make a positive connection or with the supply line 8th be positively connected. In a positive connection of the ceramic cement 9, the supply line 8th just enclose.

In both cases, the ceramic cement could 9 for a relief of the mechanical connection between the supply line 8 and the metallization 5 provide against radial forces. Is the ceramic cement 9 also with the supply line 8th positively connected, so can the ceramic cement 9 the electrical connection point of the supply line 8th with the metallization 5 even before a twist or an axial pull on the supply line 8th protect. Are the ceramic cement 9 and the supply line 8th only positively connected with each other, so there is the advantage that mechanical stresses at the electrical connection point by different thermal expansion coefficients of the carrier 3 and the supply line 8th can be avoided.

In the embodiment shown here, the ceramic cement is arranged in each case at points on the ceramic support and the supply line. In this case, a first sticking point is on an upper side of the carrier 3 arranged and a second glue dot on a bottom of the carrier 3 arranged, which the further supply line 8th with the on the bottom of the carrier 3 arranged metallization 5 combines.

In an alternative embodiment, the ceramic cement 9 one around the ceramic carrier 3 to form an encircling track. In particular, the track encloses the longitudinal axis of the ceramic carrier 3 , Here are also the supply lines 8th from the trail of the ceramic cement 9 covered. The embodiment of the ceramic cement 9 as a revolving track offers several advantages. First, the surface on which the ceramic cement 9 is applied adhesively, compared to a punctual application significantly increased. This will increase the adhesion of the ceramic cement 9 improved overall. The strength of the ceramic cement 9 is higher than its adhesion to the surface of the carrier 3 , Therefore, the circumferential track of the ceramic cement contributes 9 to an improved mechanical stability of the sensor 1 at. The revolving trace of the ceramic cement 9 can be done by rotating the sensor 1 be produced, the ceramic cement 9 is sprayed on.

The ceramic cement 9 covers the supply lines 8th and wets the ceramic carrier 3 sufficient to allow good adhesion. The ceramic cement 9 can be cured at a temperature of about 200 ° C. After that, the supply line 8th also in the radial direction R in the same way as in the axial direction A be charged.

Instead of the ceramic cement 9 Alternatively, an adhesive may be used. For example, a ceramic adhesive may be used. The adhesive can be applied selectively or as a circulating track.

5 shows a second embodiment of the sensor 1 in a cross section. Here is the supply line 8th to the carrier 3 with the help of a body 10 attached. The body 10 may comprise a ceramic material or consist of the ceramic material. The body 10 also allows a discharge of the connection of the supply line 8th with the metallization 5 against radial loads.

The body 10 is on the carrier 3 and the supply line 8th postponed. The body 10 has an opening 11 on that by the body 10 goes through it.

6 shows the body 10 in a cross section. Both the supply line 8th as well as the carrier 3 extend through the opening 11 of the body 10 therethrough. The cross-sectional profile of the opening 11 is attached to the ceramic carrier 3 and the supply line 8th customized. The opening 11 in the body 10 is shaped so that the body 10 a movement of the supply line 8th in the radial direction R relative to the carrier 3 prevented. The body 10 allows axial movements of the supply line 8th relative to the carrier 3 to. Accordingly, it comes by different thermal expansion coefficients of the carrier 3 and the supply line 8th not to a mechanical load on the mechanical connection between the lead 8 and the metallization 5 ,

7 shows the in 5 shown sensor 1 in a perspective view from above. 8th shows a side view of the sensor 1 ,

9 shows an alternative variant of the second embodiment. Here, the body points 10 a first opening 11 up, moving through the body 10 extends through. The diameter of the first opening 11 is chosen so that the supply line 8th through the first opening 11 of the body 10 can pass through it. Further, the body points 10 a blind hole 12 on, which forms a non-continuous opening. The body 10 is on the carrier 3 deferred, with one end of the main body 4 in the blind hole 12 is arranged. The blind hole 12 forms a stop on which the wearer 3 strikes, reducing its position relative to the body 10 is predetermined.

The fixation of the supply line 8th on the carrier 3 through a body 10 who is on the supply line 8th and the carrier 3 can be postponed, with a fixation by the ceramic cement 9 or a glue combined. By a combination of these embodiments, an even better resilience against radially acting forces can be achieved.

Furthermore, the supply line 8th Have deformations that the supply line 8th axially on the body 10 or on the ceramic cement 9 fixed. For example, the supply line 8th be formed by a wire. This wire may have a substantially linear course. The deformations may form kinks or curves in the wire which are arranged to contact bodies 10 or on the ceramic cement 9 abut and so axial movements of the supply line relative to the body 10 or to the ceramic cement 9 prevent.

LIST OF REFERENCE NUMBERS

1

sensor

2

sensor element

3

ceramic carrier

4

body

5

metallization

6

jumper

7

glass envelope

8th

supply

9

ceramic cement

10

body

11

opening

12

blind

13

interface

A

axial direction

R

radial direction

Claims (15)

Sensor (1), comprising a ceramic carrier (3) to which a sensor element (2) is fixed and which has a metallization (5) which is electrically contacted with the sensor element (2), and a lead (8) attached to the metallization (5) and configured to electrically contact the sensor element (2) via the metallization (5), wherein the supply line (8) is mechanically fixed to the ceramic support (3) at a further position. Sensor (1) according to the preceding claim, wherein the ceramic support (3) is free of the metallization (5) at the further position. Sensor (1) according to one of the preceding claims, wherein the supply line (8) has a first end and a second end, the first end of the feed line (8) being fastened to the metallization (5), wherein a portion of the lead (8) mechanically fixed to the ceramic support (3) at the further position lies between the first end and the second end. Sensor (1) according to one of the preceding claims, wherein the mechanical fixation of the supply line (8) on the ceramic support (3) is designed such that the mechanical fixing the attachment of the supply line (8) to the metallization (5) against a Force acting on the lead (8) in a direction (R) perpendicular to a surface of the metallization (5) away from the ceramic support (3) relieves. Sensor (1) according to one of the preceding claims, wherein the feed line (8) by a ceramic cement (9) or an adhesive, which is connected to the ceramic support (3) and the supply line (8), at the at least one further position is mechanically fixed relative to the ceramic support (3). Sensor (1) according to the preceding claim, wherein the ceramic cement (9) or the adhesive is non-positively connected to the ceramic carrier (3) and surrounds the feed line (8) in a form-fitting manner. Sensor (1) according to one of Claims 5 or 6 , wherein the ceramic cement (9) or the adhesive is arranged selectively on the ceramic support (3) and the supply line (8). Sensor (1) according to one of Claims 5 or 6 , wherein the ceramic cement (9) or the adhesive forms a track surrounding the ceramic carrier (3). Sensor (1) according to one of the preceding claims, wherein the feed line (8) by a on the ceramic support (3) pushed body (10) which encloses the ceramic support (3) and the supply line (8), at the one further Position is mechanically fixed relative to the ceramic support (3). Sensor (1) according to the preceding claim, wherein the body (10) has a through opening (11) through which the supply line (8) extends. A sensor (1) according to the preceding claim, wherein the ceramic carrier (3) extends through the through opening of the body (10). Sensor (1) according to the Claim 10 wherein the body (10) has a blind hole (12) defining a stop against which the ceramic support (3) abuts. Sensor (1) according to one of the preceding claims, wherein the feed line (8) has a deformation which cooperates with the mechanical fixing of the feed line (8) to the ceramic carrier (3) and thereby movement of the feed line (8) relative to the ceramic support (3) in an axial direction (A), which is perpendicular to the surface normal of the metallization (5) prevented. Sensor (1) according to one of the preceding claims, wherein the feed line (8) is mechanically fastened to the metallization (5) by means of a solder connection, a welded connection, an adhesive connection or a sintered connection. Sensor (1) according to one of the preceding claims, wherein the sensor (1) is a temperature sensor and wherein the sensor element (2) is an NTC thermistor.

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