DE102012108820B4 - Sensor, electrical component, method for determining a temperature or operating time of an electrical component and use of an intermetallic phase or a phase boundary as a sensor - Google Patents

Abstract

A sensor (1, 7) is provided for detecting the temperature (T) or the operating time (t) of an electrical component (3) comprising a first metallic material (4, 9) and a second metallic material (5, 10). wherein an intermetallic phase (6) or a phase boundary (12) is formed between the first and second metallic material (4, 5, 9, 10) and wherein the thickness (d) of the intermetallic phase (6) or the position (P ) of the phase boundary (12) for determining the temperature (T) or the operating time (t) is used. Furthermore, a method for determining a temperature (T) or an operating time (t) of an electrical component (3) as well as a use of an intermetallic phase (6) or a phase boundary (12) as a sensor (1, 7) is specified.

Description

It is an electrical component comprising a sensor for detecting the temperature or the operating time of the electrical component specified. The component is designed for example as a piezoelectric actuator. Preferably, a temperature load of the electrical component should subsequently be detected with the sensor. Furthermore, an electrical component comprising such a sensor and a method for determining a temperature or a service life of an electrical component will be indicated.

The publication JP H10-2808A describes a method for determining an elevated temperature by measuring a thickness of an intermetallic diffusion layer between two layers of an alloy. The publication JP S58-35428A describes a sensor element which is subjected to a temperature treatment together with a wafer. The publication DE 14 73 295 A describes a device in which a temperature recording by migration of hydroxyl ions in a porous matrix and thereby takes place a color change takes place. The publication DE 10 80 682 B describes an arrangement for measuring the service life of electrical equipment, in which the amount of a substance migrated in a solid represents a measure of the operating time.

It is a problem to be solved to provide an electrical component comprising a sensor for detecting the temperature or the operating time of the electrical component. Furthermore, it is an object to be solved to specify a method for determining the temperature or the operating time of an electrical component.

The objects are achieved by electrical components according to claims 1 and 9, by methods according to claims 10 and 16 and a use according to claim 15. Advantageous embodiments of the components, the method and the use are subject matters of dependent claims.

It is an electrical component comprising a sensor for detecting the temperature or the operating time of the electrical component specified. The device is designed for example as a piezoelectric actuator, varistor, capacitor, thermistor or PTC thermistor.

Preferably, a temperature or operating time is retrieved by reading the sensor, i. in particular after removal of the electrical component from the operation determined. For example, the component is put into operation for a known, predetermined operating time. By subsequent readout of the sensor, a temperature during the service life of the device can be determined. In the case of temperature fluctuations during the operating period, for example, an average temperature can be determined by reading the sensor. Alternatively, if a temperature, in particular a mean temperature, is known, an operating period can be concluded by reading the sensor.

For example, by reading the sensor in case of damage or failure of the device, a possible misuse can be detected. In particular, an excessively high operating temperature or too long operating time, and thus operation in an impermissible field of application, can be detected. For example, allowable complaints in the event of a component failure can be distinguished from inadmissible complaints in case of improper use.

Preferably, the sensor is a passive sensor. A passive sensor does not require electrical energy to detect and store temperature or operating time.

The sensor comprises a first metallic material and a second metallic material. The second metallic material is preferably arranged on the first metallic material and in particular adjoins the first metallic material. In particular, the second metallic material may be disposed on the first metallic material. For example, at least one of the materials is formed as a layer. Both materials can also be formed as layers.

Preferably, the first metallic material is disposed on a support. For example, the sensor is arranged directly on an electrical component. The support may in particular be a base body of the component, for example a ceramic base body. Alternatively, the carrier may also be formed as a metal carrier layer.

Preferably, the sensor is permanently connected to the electrical component. The sensor can be integrated in the electrical component. In particular, the sensor can be integrated in a part of the component which is difficult to access from the outside. Thus, the detection of the temperature with the sensor in a region of the component is possible in which the temperature can not or only with difficulty be detected with conventional temperature sensors.

For example, at least one of the metallic materials has another function in the Component. In particular, at least one of the metallic materials may have a function as electrical contact in the component, for example as electrical contacting of internal electrodes of the component. Thus, the metallic material can simultaneously serve as a sensor and for electrical contact. For example, one of the materials, in particular the first material, as a conductor, z. B. copper track, a circuit board may be formed. The second material may for example be formed as a solder material, in particular as a solder material which is arranged on a first metallic material serving as an electrical contact. By the solder material, for example, an electrical connection to the component can be electrically and mechanically connected.

In one embodiment, there is an intermetallic phase between the first and second metallic materials. The intermetallic phase is preferably formed by disposing the second metallic material on the first metallic material, in particular by interdiffusion of a metal of the first metallic material and a metal of the second metallic material. The metals of the first and the second metallic material in the intermetallic phase enter into a chemical compound.

The thickness of the intermetallic phase can be used to determine the temperature or the operating time of the sensor and in particular of the electrical component. This is due to the fact that the thickness of the intermetallic phase changes depending on the temperature and the operating time of the sensor. In particular, the thickness of the intermetallic phase increases with time t and at a temperature load T.

mit k_B der Boltzmannkonstanten und E_a der spezifischen Aktivierungsenergie, sowie den Konstanten C und t₀. Die Konstanten E_a, C und t₀ sind technologiespezifisch als Kalibrierkonstanten zu bestimmen. Insbesondere entspricht t₀ dem Herstellzeitpunkt des Sensors. Vorzugsweise ist zu diesem Zeitpunkt die Dicke d = 0.The following relationship applies: $$d=C\sqrt{t-t_0}\text{exp}\left(-\frac{e_a}{k_{B}T}\right)$$

with k _{B of} the Boltzmann constant and E _{a of} the specific activation energy, as well as the constants C and t ₀ . The constants E _a , C and t ₀ are technology specific to determine as calibration constants. In particular, t ₀ corresponds to the manufacturing time of the sensor. Preferably, the thickness d = 0 at this time.

Thus, after determining the calibration constants and after the experimental determination of the thickness of the intermetallic phase and knowing the operating time, a temperature of the sensor can be determined. With temperature fluctuations during the operating period, an average temperature can be determined.

The thickness of the intermetallic phase can be determined experimentally, for example, by a micrograph and microscopic analysis of the sensor. The calibration constants can be determined, for example, by storage experiments of sensors at predetermined temperatures.

Alternatively, if the temperature is known, it is possible to deduce the operating time of the sensor and in particular the service life of the component.

In a further embodiment of the sensor, there is a phase boundary between the first and the second metallic material. The materials may in particular be selected such that no formation of an intermetallic phase occurs.

The phase boundary preferably shifts as a function of the temperature and the operating time of the sensor. Such a shift is known in particular as Kirkendall effect.

The position of the phase boundary can be used to determine the temperature or the operating time of the sensor and in particular of the component. The result is the shift of the phase boundary, that is, the difference between the position of the phase boundary at a second time and the position of the phase boundary at a first time, after an operating time and a temperature load analogous to the thickness of the intermetallic phase according to the formula given above. Thus, after a determination of the calibration constants, an experimental determination of the position of the phase boundary, knowing the position of an initial phase boundary and knowing the operating time, the temperature can be determined. Alternatively, if the temperature is known, the operating time can be determined.

Instead of a mathematical determination of the temperature or the operating time by the above-mentioned relationship, comparative values can also be used to determine the temperature or the operating time. These comparison values can be determined, for example, experimentally by different temperature loads of sensors at given operating times.

The first and second metallic materials may include one or more metals or may consist of one or more metals.

For example, at least one of the metallic materials has copper. Preferably, the first metallic material comprises copper. For example, at least one of the metallic Materials tin on. In particular, at least one of the materials may comprise copper and at least the other material may comprise tin. Alternatively or additionally, the other metallic material may comprise brass. In a further embodiment, at least one of the metallic materials, in particular the first metallic material, comprises gold.

Preferably, at least the other metallic material comprises aluminum.

In a combination of materials copper / tin or gold / aluminum, it is preferable to form an intermetallic phase, so that here the thickness of the intermetallic phase can be used to determine the temperature and operating time. In a combination of materials copper / brass, it is preferable to form a phase boundary, which shifts under a temperature load, so that the shift of the phase boundary can be used to determine the temperature and operating time.

Furthermore, an electrical component comprising a sensor as described above is specified. The component can be designed in particular as a piezoelectric actuator, varistor, capacitor, thermistor or PTC thermistor. Preferably, the sensor is integrated into the component. For example, as described above, one of the metallic materials of the sensor can fulfill a further function in the component, for example a function as an electrical contact.

Furthermore, a method for determining a temperature or a service life of an electrical component is specified. In this case, an electrical component is provided which comprises a first metallic material and a second metallic material. The second metallic material is preferably arranged on the first metallic material and in particular adjoins the first metallic material. For example, the second metallic material is disposed on the first metallic material. The thickness of an intermetallic phase or the position of a phase boundary between the first and second metallic materials is determined. Subsequently, a temperature or an operating time of the electrical component is determined from the thickness of the intermetallic phase or the position of the phase boundary. The temperature or operating time can be determined from the thickness of the intermetallic phase or the position of the phase boundary according to the relationship given above.

The device used in this method as well as the first and second metallic materials may all have functional and structural features described with respect to the sensor and the device.

Preferably, when determining the temperature or operating time by the position of the phase boundary, a position of the phase boundary at a first time is known. Then, in the method, the position of the phase boundary is preferably determined at a later, second point in time. In particular, the first time may be before the startup of the device. The second time is then, for example, after the commissioning of the device, in particular after a temperature load.

Preferably, the position of the phase boundary at the first time in the component is marked. Such identification can be done geometrically, for example. In particular, the metallic materials can be arranged such that the phase boundary is at the level of a characteristic geometric feature of the device.

For example, for this purpose, a depression is introduced into an outer side of the component. The first metallic material may be placed in the recess so that it is flush with the outside. The second metallic material is then applied to the first metallic material. In this case, the phase boundary is at the level of the outside at a first time. At a temperature load, the phase boundary shifts, for example, in a direction that leads away from the device.

By determining the position of the phase boundary at a second point in time, the phase boundary shift can thus be determined when the position of the phase boundary is known at the first time. From this shift, as described above, the temperature load or the operating time of the device can be determined.

In a further embodiment, the position of the phase boundary at the first time is characterized by a third material disposed between the first and second material. For example, the third material may cover only a part of a contact area between the first and second materials, so that the contact between the first and second materials continues to exist. The third material preferably does not change its position during the service life of the device, and especially not with thermal stress. Thus, by the third material, the position of the phase boundary can be marked at a first time.

In another aspect of the present disclosure, an application of an intermetallic phase or a phase boundary between a first metallic material and a second metallic material as a sensor for detecting a temperature or an operating time of an electrical component is provided. The metallic materials may have the same functional and structural characteristics as described with respect to the sensor, device and method. In particular, the second metallic material may be disposed on the first metallic material. The determination of the temperature or the operating time can be carried out in particular by determining the thickness of the intermetallic phase or by determining the position of the phase boundary as described above.

The objects described here are explained in more detail below with reference to schematic and not to scale embodiments.

• 1 in einem schematischen Schnittbild einen Sensor aufweisend eine intermetallische Phase,
• 2 der Sensor aus 1 nach einer Temperaturbelastung,
• 3A, 3B, 3C in schematischen Schnittbildern Verfahrensschritte bei der Herstellung eines Sensors aufweisend eine Phasengrenze,
• 4 der Sensor aus 3C nach einer Temperaturbelastung.

Show it:

• 1 in a schematic sectional view of a sensor having an intermetallic phase,
• 2 the sensor off 1 after a temperature load,
• 3A . 3B . 3C in schematic sectional views, process steps in the manufacture of a sensor having a phase boundary,
• 4 the sensor off 3C after a temperature load.

Preferably, like reference numerals refer to functionally or structurally corresponding parts of the various embodiments in the following figures.

1 shows a schematic sectional view of a sensor 1 for recording and storing a temperature or operating time.

The sensor 1 is on a carrier 2 arranged. The carrier 2 may have a ceramic material. At the carrier 2 it is preferably an integral part of an electrical component 3 , For example, the carrier 2 is the main body of an electrical component 3 , The base body has, for example, a stack comprising dielectric layers and electrode layers arranged alternately one above the other. The dielectric layers may be ceramic layers. For example, it is the device 3 to act a piezoelectric actuator having piezoelectric layers or a ceramic sensor.

The support may alternatively be formed of a metallic material. For example, the carrier is designed as a copper plate, which can also act as the first metallic material of the sensor at the same time.

The sensor 1 has a first metallic material 4 and a second metallic material 5 on. The first metallic material 4 is directly on the carrier 2 arranged. Both the first and the second metallic material 4 . 5 are formed as layers.

For example, the first metallic material 4 using thick-film technology on the carrier 2 applied. The first metallic material 4 may in particular be burned. For example, the first metallic material 4 Copper on or consists of copper.

The second metallic material 5 is over the first metallic material 4 arranged. For example, the second metallic material 5 be applied as a solder material, in particular in the form of a solder ribbon, and with the first metallic material 4 be soldered. For example, the second metallic material 5 Tin on or made of tin.

When connecting the second metallic material 5 with the first metallic material 4 Interdiffusion creates a thin intermetallic phase 6 between the first and second metallic material 4 . 5 , The intermetallic phase 6 is a layer in which at least one metal of the first metallic material 4 with at least one other metal of the second metallic material 5 makes a chemical connection. For example, the intermetallic phase indicates 6 Compounds of copper and tin on.

The intermetallic phase 6 has a thickness d on, depending on the temperature T and the operating time t increases.

mit k_B der Boltzmannkonstanten und E_a der spezifischen Aktivierungsenergie, sowie den Konstanten C und t₀. Diese Beziehung konnte von den Erfindern auch experimentell bestätigt werden. Die Kalibrierkonstanten können beispielsweise durch Lagerungsversuche bei vorgegebenen Temperaturen bestimmt werden. Die Dicke d kann experimentell beispielsweise durch eine Schliff- und Mikroskopieanalyse des Sensors 1 bestimmt werden.As described above, the following relationship applies: $$d=C\sqrt{t-t_0}\text{exp}\left(-\frac{e_a}{k_{B}T}\right)$$

with k _{B of} the Boltzmann constant and E _{a of} the specific activation energy, as well as the constants C and t ₀ . This relationship could also be confirmed experimentally by the inventors. The calibration constants can be determined, for example, by storage experiments at predetermined temperatures. The fat d can be experimental For example, be determined by a cut and microscopy analysis of the sensor 1.

Thus, after determining the calibration constants and after the experimental determination of the thickness d the intermetallic phase 6 and with knowledge of the operating time t to a temperature T of the sensor 1 getting closed. The temperature T can in this case in particular an operating or ambient temperature of the sensor 1 be. In case of temperature fluctuations, it can be concluded that the mean temperature is medium.

As in 1 is shown, the intermetallic phase 6 directly after the production of the sensor 1 the fat d = d ₁ on.

In 2 is the sensor 1 out 1 to see after a known operating time t and after a temperature load. The intermetallic phase now has a greater thickness d = d ₂ on. From the thickness d can now, as described above, the average temperature T be determined.

For example, the sensor is suitable 1 for the determination of temperatures between 150 ° C and 200 ° C. The operating time can for example be between 10 hours and several 1000 hours.

Layers of metallic materials 4 . 5 For example, they are between a few microns to a few tens of microns thick. In the area, the layers can have a few micrometers up to a few millimeters edge length.

Based on the expected service life and temperature loads, the temperature sensitivity of the sensor 1 can be determined by a suitable material selection of the first and second material 4 . 5 be set. For example, as an alternative to the abovementioned combination of materials copper / tin and a material combination of gold / aluminum can be selected.

In a second embodiment, a sensor is constructed from a material combination in which the position of a phase boundary between a first material and a second material is used to determine the operating time or temperature. The sensor can be like the one in 1 be described sensor, but here is instead of the intermetallic phase 6 a phase boundary exists. The position of the phase boundary shifts under a temperature load or with a sufficiently long operating time.

Preferably, an initial position of the phase boundary is marked. Then, from the shift of the phase boundary with respect to the initial position, a temperature load or an operation time can be calculated.

The 3A to 3C show in schematic sectional views process steps in the manufacture of a sensor 7 (please refer 3C ) according to the second embodiment.

3A shows a carrier 2 for the sensor 7 , The carrier 2 can as in the embodiment according to 1 be educated. In the carrier 2 becomes a depression 8th brought in. The recess 8 is filled with a first metallic material 9 filled. For example, the first material 9 Copper on or consists of copper.

The first metallic material 9 will be like in 3B then shown flat ground, leaving it with an outside 11 of the carrier 2 flush.

Subsequently, as in 3C shown a second metallic material 10 on the first metallic material 9 applied. The metallic materials 9 and 10 are chosen such that a phase boundary 12 between the metallic materials 9 and 10 is trained. For example, the second metallic material 9 Brass on or made of brass. At a first time has the phase boundary 12 an initial position P = P ₁ , The position P the phase boundary 12 shifts under a temperature load or after a certain period of operation. Thus, a sensor 7 formed, at which from the position P the phase boundary 12 at a second time on the temperature or the operating time can be concluded.

This should be the initial position P = P ₁ the phase boundary 12 be known. Because the first material 9 is flush with the outside 11 of the carrier, the phase boundary 12 is located directly after the application of the second material 10 at the level of the outside 11 of the carrier. So here's an initial position P ₁ the phase boundary 12 through the outside 11 of the carrier 2 marked and thus marked geometrically. Alternatively, the initial position P = P ₁ the phase boundary 12 For example, be marked by a third material that remains stationary in the temperature range considered.

4 shows the sensor 7 at a second time, in particular after a known period of operation t , The phase boundary 12 has shifted upwards. The new position P = P ₂ the phase boundary 12 can, for example, by a polished and microscopic analysis of the sensor 7 be determined. Thus, the shift a the phase boundary, ie, the distance of the phase boundary from the position P = P ₂ at the second time to the position P = P ₁ at the first time. From the shift a the phase boundary 12 can now have a mean temperature T of the sensor 7 and thus the component 3 be calculated as in the above formula for the thickness d. Alternatively, from a known temperature T, the operating time t be calculated. Such a sensor is particularly suitable for use in the high temperature range.

LIST OF REFERENCE NUMBERS

1

sensor

2

carrier

3

module

4

first metallic material

5

second metallic material

6

intermetallic phase

7

sensor

8th

deepening

9

first metallic material

10

second metallic material

11

outside

12

phase boundary

d

Thickness of the intermetallic phase

d ₁

Thickness of the intermetallic phase at the first time

d ₂

Thickness of the intermetallic phase at the second time

P

Position of the phase boundary

P ₁

Position of the phase boundary at the first time

P ₂

Position of the phase boundary at the second time

a

Shift of the phase boundary

T

temperature

t

operating time

Claims (16)

Electric component comprising a sensor for detecting the temperature or the operating time of the electrical component, comprising a first metallic material (4, 9) and a second metallic material (5, 10), wherein between the first and second metallic material (4, 5, 9, 10) a phase boundary (12) is formed and wherein the position (P) of the phase boundary (12) for determining the temperature (T) or the operating time (t), wherein the first metallic material (4, 9) in a Recess (8) on an outer side (11) of the component (3) is arranged and flush with the outer side (11), wherein the second metallic material (4, 5, 9, 10) on the first metallic material (4, 9 ) so that the initial position (P1) of the phase boundary (12) is characterized by the outside (11) of the carrier (2). Electrical component after Claim 1 in which at least one of the metallic materials (4, 5, 9, 10) comprises copper and at least the other metallic material (4, 5, 9, 10) comprises tin. An electrical component according to any one of the preceding claims, wherein at least one of the metallic materials (4, 5, 9, 10) comprises copper and at least the other metallic material (4, 5, 9, 10) comprises brass. An electrical component according to any one of the preceding claims, wherein at least one of the metallic materials (4, 5, 9, 10) comprises gold and the other metallic material (4, 5, 9, 10) comprises aluminum. Electrical component according to one of the preceding claims, in which the first and the second material (4, 5, 9, 10) each have the form of a layer. Electrical component according to one of the preceding claims, which is passive. Electrical component according to one of the preceding claims, wherein the first and / or the second metallic material (4, 5, 9, 10) are formed as electrical contact of the component (3). Electrical component according to one of the preceding claims, which is designed as a piezoelectric actuator. An electrical component comprising a sensor for detecting the temperature or the operating time of the electrical component, comprising a first metallic material (4, 9) and a second metallic material (5, 10), wherein between the first and second metallic material (4, 9, 5, 10) a phase boundary (12) is formed and wherein the position (P) of the phase boundary (12) for determining the temperature (T) or the operating time (t) is used, wherein between the first metallic material (4, 9) and the second metallic material (5, 10) is arranged a third material, which covers only a part of a contact surface between the first and the second material, wherein by the third material, the initial position (P1) of the phase boundary (12) is characterized. A method for determining a temperature or operating time of an electrical component, comprising the steps of: A) providing an electrical component (3) comprising a first metallic material (4, 9) and a second metallic material (5, 10), wherein the first and or the second metallic material (4, 9, 5, 10) is in the form of a contact for electrical contacting of the component B) determination of the thickness (d) of an intermetallic phase (6) or determination of the position (P) of a phase boundary (12) between the first and the second metallic material (4, 5, 9, 10), C) determining a temperature (T) or an operating time (t) from the thickness (d) of the intermetallic phase (6) or from the position (P ) of the phase boundary (12). Method according to Claim 10 , wherein the position (P) of the phase boundary (12) is known at a first time and in step B) the position (P) of the phase boundary (12) is determined at a later, second time. Method according to one of Claims 10 or 11 , wherein the phase boundary (12) at a first time at the level of an outer side (11) of the component (3). Method according to one of Claims 10 to 12 wherein the position (P) of the phase boundary (12) at the first time is characterized by introducing a third material between the first and second material (4, 5, 9, 10). Method according to one of Claims 10 to 13 wherein the first material is formed as an electrical contact and the second material is a solder material disposed on the electrical contact. Use of an intermetallic phase or a phase boundary between a first metallic material (4, 9) and a second metallic material (5, 10), wherein the first and / or the second metallic material (4, 9, 5, 10) as contact to electrical contacting of a component is formed, as a sensor (1, 7) for detecting a temperature (T) or an operating time (t) of an electrical component (3). Method for determining a temperature or a service life of an electrical component, comprising the steps of: A) providing an electrical component (3) according to one of Claims 1 to 9 , B) determining the position (P) of a phase boundary (12) between the first and the second metallic material (4, 5, 9, 10), C) determining a temperature (T) or an operating time (t) from the distance of certain position (P) and the initial position (P1) of the phase boundary (12).

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