DE102015202664A1 - Method for producing a sensor and sensor - Google Patents

Abstract

The invention relates to a method for producing a sensor and a sensor produced therewith. The sensor has a deformation body and an evaluation component. The deformation element and the evaluation component are connected to one another by means of a reaction medium. This allows a faster and easier process management than with glass solders, which are known from the prior art.

Description

The invention relates to a method for producing a sensor, which has a deformation element and an evaluation component. The invention further relates to such a sensor.

Generic sensors are widely used for example in automobiles or other means of transport. The deformation body is typically designed such that it changes its shape by a physical quantity to be measured, such as pressure, force or torque. This results in stretching on its surface. The evaluation component is typically mechanically connected to the deformation body to absorb this strain and convert it into a measurement signal. By means of this measurement signal, a connected circuit, for example an application-specific integrated circuit (ASIC), can determine a physical variable acting on the deformation element.

In known sensors, the mechanical connection between the deformation body and the evaluation component is typically generated by glass solders. An intermediate layer consisting of glass solder has the task of transmitting the strains to be measured unadulterated from the deformation body to the evaluation component. For this purpose, the glass solder should typically have a high modulus of elasticity and an adapted thermal expansion coefficient. A disadvantage of the use of glass solders is in particular a high process temperature, the requirement of an exact temperature profile during production, a long process time and the need for complete heating and cooling of the deformation body and evaluation component.

It is therefore an object of the invention to provide a method for producing a sensor, which is different, for example easier to carry out. It is further an object of the invention to provide a correspondingly manufactured sensor.

This is inventively achieved by a method according to claim 1 and a sensor according to claim 15. Advantageous embodiments can be taken, for example, the respective subclaims. The content of the claims is made by express reference to the content of the description.

• – Bereitstellen eines Verformungskörpers,
• – Bereitstellen eines Auswertebauelements,
• – Aufbringen eines Reaktionsmittels auf den Verformungskörper und / oder auf das Auswertebauelement,
• – Zusammenbringen des Verformungskörpers und des Auswertebauelements derart, dass das Reaktionsmittel zwischen dem Verformungskörper und dem Auswertebauelement angeordnet ist, und
• – Aktivieren des Reaktionsmittels.

The invention relates to a method for producing a sensor, which has the following steps:

• Providing a deformation body,
• Providing an evaluation component,
• Applying a reaction agent to the deformation element and / or to the evaluation component,
• - bringing together the deformation body and the evaluation component such that the reaction means between the deformation body and the evaluation component is arranged, and
• - Activate the reagent.

By means of the method according to the invention, a reaction agent can be used instead of the glass solder known from the prior art. Such allows a much faster process management and it is sufficient only a local temperature entry, which eliminates the need to suspend the entire composite of deformation body and Auswertebauelement a high temperature. Setting an exact melting temperature is no longer necessary. In addition, otherwise customary cleaning steps can be dispensed with prior to further processing, for example by means of wire bonding, since in the case of a typical reagent no organic components such as, for example, flux or binder are present.

The deformation body is typically a device that responds to a particular physical quantity such as pressure, force or torque. For example, it can be used to measure forces on a pedal or pressures on a valve or torque in a steering system or on the drive system of an electric bicycle. The deformation element is preferably a metal deformation element. In particular, stainless steel can be used, for example stainless martensitic curable chromium-nickel-copper steel. In particular, steel of the type 17-4 PH or steel with the material number 1.4542 can be used. This has proven itself in practice and in particular in connection with the method according to the invention.

The evaluation component is preferably strain-sensitive, so that it can absorb a deformation of the deformation body. In typical embodiments, it may comprise piezoresistive resistors, which can convert the deformation transmitted by the deformation body into an electrical signal. For this purpose, for example, a defined voltage is applied and the current flow is measured by the piezoresistive resistors.

Preferably, the reactant is designed to be an exothermic reaction after activation perform. This allows advantageous local heating by means of an exothermic, that is, energy-releasing reaction. In this case, a temperature of about 1,500 ° C. is particularly preferably achieved. Such a temperature is more preferably achieved for a period of about 1 ms. Such values have been found to be advantageous for typical realistic process designs. However, for example, temperatures between 1,400 ° C and 1,600 ° C can be used, and these can be achieved, for example, for a period between 0.5 ms and 1.5 ms.

According to a preferred embodiment, the reactant is activated by applying a temperature gradient. The temperature gradient is preferably about 200 K over a spatial extent of the reagent. For example, the temperature gradient can also be in a range between 150 K and 250 K. Such temperature gradients enable advantageous and selective activation of reagents which have proven to be particularly advantageous for use in the process of the invention. Exemplary reactants which can be so activated will be described below.

Preferably, the reactant is activated by means of a spark. Such a spark is easy to generate and allows specific local heat input at one end of the reactant. In this way, for example, the temperature gradient described above may arise, for example, if the other end of the reagent is not heated simultaneously.

According to a preferred embodiment, the reactant is a nanofoil. These have proved to be advantageous for use in the method according to the invention. In particular, these may be reactive nanofoils. They are typically multi-layered and contain various reactive components which perform an activation exothermic reaction.

The reactant is preferably composed of a number of at least one hundred AlNi layers. With particular preference, it is composed of several hundred or even more preferably of several thousand layers.

The respective layers preferably have a thickness of 10 nm to 40 nm, more preferably 20 nm to 30 nm and even more preferably 25 nm.

The structure just described with a plurality of AlNi layers having the thickness described corresponds to a typical structure of nanofoils.

Preferably, the reactant is applied as a film or paste. This allows the use of simple application methods. In addition, the reactant can be conveniently stored and handled.

According to a preferred embodiment, the reactant is designed to break up after activation. This makes it possible for components of the deformation body and of the evaluation component to connect to one another in regions in which the reaction agent breaks up. For example, they can connect form-fitting. This allows an advantageously stable connection.

According to a preferred embodiment, the deformation body is coated with a metallization layer with which it adjoins the reagent after being brought into contact. According to another, preferably combinable preferred embodiment, the evaluation component is coated with a metallization layer with which it adjoins the reagent after being brought into contact. By means of the metallization layers just described, the deformation element and the evaluation component can be connected to each other even better.

Preferably, the metallization layers are melted after activation of the reactant by the resulting heat. Thus, they can connect with each other. In particular, they can connect through areas in which the reactant is broken up. However, you can also connect to the reagent, for example. This allows the advantageous formation of an immediate cohesive connection between the metallization layers, which leads to a particularly advantageous stability of the connection between the evaluation component and the deformation body.

According to a preferred embodiment, at least in the step of activating the reaction medium, the evaluation component and the deformation body are pressed against each other. This allows a closer and better connection of the evaluation component with the deformation body.

According to one embodiment, the deformation body and / or the evaluation component have a respective curved surface, with which they adjoin one another or to the reagent. This allows the production of special sensors, for example with a rod-shaped deformation body, which has a different characteristic of the conversion of physical quantities into electrical signals as deformation body with angular surfaces. According to a further embodiment, the deformation element and / or the evaluation component have a respective planar surface, with which they adjoin one another or to the reagent. For example, the deformation body can also be cuboid.

According to one embodiment, the evaluation component is a silicon component. For example, it may be a silicon chip. This allows a high variability of the design of the evaluation component by using established technologies for the production of such evaluation components.

For example, a full bridge circuit may be formed on the evaluation component, in particular on a silicon chip. Such a full bridge circuit has proved to be advantageous for typical applications of a sensor made by the method according to the invention.

According to a preferred embodiment, the method further comprises a step of applying an application specific integrated circuit (ASIC) to the reactant before the step of heating. This makes it possible not only to connect the evaluation component to the deformation element, but also to apply such an application-specific integrated circuit in the same operation. Such an application-specific integrated circuit may in particular have a logic for evaluation. For example, this logic can be designed to measure changes in resistances of the evaluation component and convert them into an easier-to-process, for example, digital signal. The application specific integrated circuit may be implemented in CMOS technology, for example. It may, for example, contain operational amplifiers or other components.

According to a further preferred embodiment, the application-specific integrated circuit is coated with a metallization layer, wherein the application-specific integrated circuit is applied to the reaction medium such that the metallization layer adjoins the reaction medium. Thus, in the same manner as described above with respect to the connection between the reactant and the deformation body or the evaluation device, the connection between the application-specific integrated circuit and the reaction medium or the deformation body can be improved. In particular, the metallization layer of the application-specific integrated circuit can advantageously also melt after activation of the reaction medium and enter into a cohesive connection with the reaction medium or with the deformation element or a metallization layer applied thereon.

The invention further relates to a sensor which is produced by means of a method according to the invention. Thus, the advantages of the method described above for a sensor can be utilized. With regard to the method, all embodiments and variants described above can be used. Illustrated benefits apply accordingly.

Further features and advantages will be apparent to those skilled in the embodiments described below with reference to the accompanying drawings. Showing:

1 a sensor according to a first embodiment,

2 a sensor according to a second embodiment,

3 FIG. 3 is a sectional view through components of a sensor during manufacture. FIG.

1 shows a sensor according to a first embodiment. The sensor has a cuboid, metallic deformation body 2 and an evaluation component applied thereto in the form of a silicon chip 1 on. As shown, the evaluation component 1 directly on the deformation body 2 applied so that deformations of the deformation body 2 from the silicon chip 1 can be detected. For this purpose contains the silicon chip 1 a non-illustrated full bridge circuit of piezoresistive resistors.

The in 1 shown sensor according to the first embodiment is particularly suitable as a force sensor or pressure sensor. Will be on a in 1 right end of the deformation body 2 a force, which is shown here by way of example by an arrow denoted by F, exercised, then deforms the deformation body 2 in the way that he bends down with his right end. Any strain that occurs as a result of the silicon chip 1 converted into a resistance change and can be evaluated.

2 shows a sensor according to a second embodiment. Again, an evaluation device in the form of a silicon chip 1 on a deformation body 2 applied. In contrast to the embodiment according to the first embodiment, the deformation body 2 according to the second embodiment is not cuboid, but round. He therefore has a curved surface. Also the silicon chip 1 is adapted and has a circular arc segment-shaped, ie curved surface, with which it on the deformation body 2 borders. Thus, the sensor according to the second embodiment is particularly suitable as a torque sensor. Acts on the sensor, a torque which in 2 is shown by an arrow marked M, this leads to a rotation of the deformation body 2 , and thus to corresponding strains on the surface of the deformation body 2 , Such strains are from the silicon chip 1 converted into a resistance change and can be evaluated.

3 shows a layer sequence of components and materials used in the 1 and 2 shown sensors in a state as it occurs during the manufacture of a respective sensor. The sequence of layers is shown along the line designated AA.

As in 3 can be seen is located on the deformation body 2 first a metallization layer 5 , Likewise located on the silicon chip 1 another metallization layer 3 , The metallization layers 3 . 5 are formed of a metallic material which melts at temperatures typically reached during processing.

Between the two metallization layers 3 . 5 there is a reagent 4 , The reagent 4 In the present case, it is formed from 1000 AlNi layers, each of which has a thickness of 25 nm.

Starting from the in 3 In a typical process procedure, the components are now brought together in the vertical direction, so that the reagent 4 directly to the two metallization layers 3 . 5 borders. Subsequently, the reagent 4 activated. This is done by means of an igniter, not shown. The igniter generates a spark at one end of the reactant 4 and thus causes a temperature gradient of about 200 K over the spatial extent of the reagent 4 , The reagent 4 is thereby activated and performs an exothermic reaction through which energy is released. The reagent 4 is heated by it. In addition, the two metallization layers heat up 3 . 5 ,

Heating causes the reactant to break 4 in some places. The metallization layers that melt as a result of the heating 3 . 5 connect to each other, at least in areas where the reactant 4 broke up. In this case, a cohesive connection is formed. Thus are also the silicon chip 1 and the deformation body 2 cohesively connected to each other.

The method described above allows a firm and reliable connection between the silicon chip 1 and the deformation body 2 in a much shorter time than methods known in the art. In addition, the heating can be locally limited, which reduces the thermal load on the components.

Below is a further description of features that may be relevant to the invention. It should be understood that individual features in this description may or may not be assigned features of the previous description by virtue of their functionality or other criteria. All features described below can be combined with all features described above in any combinations and sub-combinations. In particular, the disclosure of this application also includes any selection, combination or sub-combination of features described above, wherein one or more of the features described below are explicitly excluded from protection. The following statements may, for example, be understood as an independent description of an invention or as a specification of the invention already described above.

In the prior art, it is known, especially in the automotive sector, to use silicon chip based sensors as a measurement variable converter. In this case, silicon chips are usually attached to metallic deformation bodies. The deformation body is changed in shape by the physical quantity to be measured (e.g., pressure, force, torque), thereby causing i.a. on its surface strains or voltages or compressions result. The Si chip converts these strains or voltages or compressions into a measuring signal via the implemented piezoresistive resistors.

• – Hohe Prozesstemperatur
• – Genaues Temperaturprofil
• – Sehr lange Prozesszeit (unter Temperatur)
• – Komplettes Aufheizen und Abkühlen der Fügepartner (Verformungskörper, Si-Chip) notwendig

The mechanical connection between the silicon chip and the metal deformation body is produced according to the prior art by glass solders. This intermediate layer (glass solder) has the task of transmitting the strains or stresses or compressions to be measured as unadulterated as possible from the metallic deformation body to the Si chip. In order to transmit these strains as unadulterated as possible, a high Elastic modulus and an adapted coefficient of thermal expansion of the intermediate layer needed. However, a disadvantage of the glass solder connection technique used hitherto is the following aspects:

• - High process temperature
• - Precise temperature profile
• - Very long process time (under temperature)
• - Complete heating and cooling of the joining partners (deformation body, Si chip) necessary

According to the invention, it is preferably provided to provide an improved connection technique based on an exothermic reaction. Due to an exothermic reaction, a high but very local temperature is very quickly generated between the joining partners. The reaction is preferably carried out via a temperature gradient in the reaction medium ( 4 ) started. Such a reaction agent is preferably designed as a film or paste. Due to the high temperature thus generated, the metallization layers deposited in advance merge ( 3 . 5 ) of the joining partners ( 1 . 2 ) and generate under application of a certain pressure (compression) an intermetallic connection between the joining partners.

• – Hohe Temperatur entsteht nur an den zu fügenden Stellen
• – Keine genaue Schmelztemperatur erforderlich
• – Extrem kurze Prozesszeit
• – Komplettes Aufheizen und Abkühlen der Fügepartner (Verformungskörper, Si-Chip) nicht notwendig
• – Keine Reinigungsschritte für Weiterverarbeitung (bspw. Drahtbonden) notwendig, da keine organischen Anteile wie bspw. Flussmittel oder Binder vorhanden

The main advantages of this invention are:

• - High temperature only occurs at the points to be joined
• - No exact melting temperature required
• - Extremely short process time
• - Complete heating and cooling of the joining partners (deformation body, Si chip) not necessary
• - No purification steps for further processing (eg wire bonding) necessary, since no organic components such as. Flux or binder present

Further preferred embodiments will become apparent from the subclaims and the following description of an embodiment with reference to figures. Reference is made to the same figures, which have already been explained above.

Show it

1 a metallic deformation body with a Si chip for detecting a force,

2 a metallic deformation body having a Si chip for detecting a torque, and

3 a layer structure according to the invention for joining a metallic deformation body and a Si chip.

1 shows metallic deformation body 2 with Si chip 1 , wherein metallic deformation body 2 with Si chip 1 for detecting a force F (represented by an arrow) is formed.

When force F acts on the deformation body 2 this bends in 1 down, eliminating the top of deformation body 2 on which Si chip 1 is stretched. This strain is due to the mechanical connection between the deformation body 2 and Si chip 1 on Si chip 1 passed, whereby a piezoresistive resistance in Si chip changes its electrical resistance. This change in the electrical resistance depends on the strength of the strain and thus of force F. Determining the change of electrical resistance thus enables determination of force F.

2 shows round metallic deformation body 2 with Si chip 1 , wherein metallic deformation body 2 with Si chip 1 for detecting a torque M (represented by an arrow) is formed. Upon the application of torque M to the deformation body 2 learns this particular on its surface, where Si chip 1 is an elongation against the direction of rotation of the arrow shown. This strain is due to the mechanical connection between the deformation body 2 and Si chip 1 on Si chip 1 passed, whereby a piezoresistive resistance in Si chip changes its electrical resistance. This change in the electrical resistance depends on the strength of the elongation and thus of the torque M. Determining the change in electrical resistance thus allows determination of torque M.

3 shows an example of a layer structure according to the invention for joining metallic deformation body 2 with Si chip 1 , The layer structure further comprises reactants 4 , which causes a strong exothermic reaction with appropriate energy. reactant 4 is designed as a foil. In addition, the layer structure exemplified comprises metallization layers 3 and 5 which by reactants 4 are melted and a mechanically strong connection between the deformation body 2 and Si chip 1 produce.

• 1. Herstellungsverfahren für einen Sensor, wobei der Sensor einen metallischen Verformungskörper und einen dehnungssensiblen Silizium-Chip umfasst, dadurch gekennzeichnet, dass eine mechanische Verbindung zwischen dem Verformungskörper und dem Silizium-Chip durch eine exotherme Reaktion eines Reaktionsmittels hergestellt wird.
• 2. Verfahren nach Aspekt 1, dadurch gekennzeichnet, dass die exotherme Reaktion derart ausgebildet ist, dass sie mindestens Metallisierungsschicht schmilzt.
• 3. Verfahren nach mindestens einem der Aspekte 1 und 2, dadurch gekennzeichnet, dass die mindestens eine Metallisierungsschicht beim Erstarren den Verformungskörper und den Silizium-Chip miteinander verbinden.
• 4. Verfahren nach mindestens einem der Aspekte 1 bis 3, dadurch gekennzeichnet, dass der Verformungskörper und den Silizium-Chip gekrümmte Oberflächen aufweisen.
• 5. Verfahren nach mindestens einem der Aspekte 1 bis 4, dadurch gekennzeichnet, dass der Sensor ein Kraft-, Druck- und/oder Drehmomentsensor ist.
• 6. System nach mindestens einem der Aspekte 1 bis 5, dadurch gekennzeichnet, dass weiterhin mindestens eine Signalverarbeitungseinheit (ASIC) mittels einer exothermen Reaktion am Verformungskörper und/oder am Silizium-Chip befestigt wird.
• 7. Verfahren nach mindestens einem der Aspekte 1 bis 6, dadurch gekennzeichnet, dass das der Verformungskörper, der Silizium-Chip, das Reaktionsmittel sowie mindestens ein Metallisierungsstreifen zum Zusammenfügen des Verformungskörper und des Silizium-Chips übereinander geschichtet werden.

Below is a systematic list of some aspects. These are not the claims of this application, it is understood, however, that the following list can be used as claims.

• A manufacturing method for a sensor, wherein the sensor comprises a metallic deformation body and a strain-sensitive silicon chip, characterized in that a mechanical connection between the deformation body and the silicon chip is produced by an exothermic reaction of a reactant.
• 2. The method according to aspect 1, characterized in that the exothermic reaction is formed such that it melts at least metallization.
• 3. The method according to at least one of aspects 1 and 2, characterized in that the at least one metallization during solidification connect the deformation body and the silicon chip together.
• 4. The method according to at least one of aspects 1 to 3, characterized in that the deformation body and the silicon chip have curved surfaces.
• 5. The method according to at least one of aspects 1 to 4, characterized in that the sensor is a force, pressure and / or torque sensor.
• 6. System according to at least one of aspects 1 to 5, characterized in that further at least one signal processing unit (ASIC) is fixed by means of an exothermic reaction on the deformation body and / or on the silicon chip.
• 7. The method according to at least one of aspects 1 to 6, characterized in that the deformation of the body, the silicon chip, the reagent and at least one Metallisierungsstreifen for joining the deformation of the body and the silicon chip are stacked.

The claims belonging to the application do not constitute a waiver of the achievement of further protection.

If, in the course of the procedure, it turns out that a feature or a group of features is not absolutely necessary, it is already desired on the applicant side to formulate at least one independent claim which no longer has the feature or the group of features. This may, for example, be a subcombination of a claim present at the filing date or a subcombination of a claim limited by further features of a claim present at the filing date. Such newly formulated claims or feature combinations are to be understood as covered by the disclosure of this application.

It should also be noted that embodiments, features and variants of the invention, which are described in the various embodiments or embodiments and / or shown in the figures, can be combined with each other as desired. Single or multiple features are arbitrarily interchangeable. Resulting combinations of features are to be understood as covered by the disclosure of this application.

Recoveries in dependent claims are not to be understood as a waiver of obtaining independent, objective protection for the features of the dependent claims. These features can also be combined as desired with other features.

Features that are disclosed only in the specification or features that are disclosed in the specification or in a claim only in conjunction with other features may, in principle, be of independent significance to the invention. They can therefore also be included individually in claims to distinguish them from the prior art.

Claims (15)

Method for producing a sensor, comprising the following steps: - providing a deformation body ( 2 ), - providing an evaluation component ( 1 ), - applying a reagent ( 4 ) on the deformation body ( 2 ) and / or on the evaluation component ( 1 ), - bringing together the deformation body ( 2 ) and the evaluation component ( 1 ) such that the reactant ( 4 ) between the deformation body ( 2 ) and the evaluation component ( 1 ), and - activating the reagent ( 4 ). The method of claim 1, wherein the reactant ( 4 ) is designed to perform an activation after activation an exothermic reaction. Method according to one of the preceding claims, wherein the reagent ( 4 ) is activated by applying a temperature gradient. Method according to one of the preceding claims, wherein the reagent ( 4 ) is activated by means of a spark. Method according to one of the preceding claims, wherein the reagent ( 4 ) is a nanofoil. Method according to one of the preceding claims, wherein the reagent ( 4 ) is made up of a number of at least 100 AlNi layers. A method according to claim 6, wherein each layer has a thickness of 10 nm to 40 nm, preferably 20 nm to 30 nm, particularly preferably 25 nm. Method according to one of the preceding claims, wherein the reagent ( 4 ) is applied as a foil or paste. Method according to one of the preceding claims, wherein the reagent ( 4 ) is designed to break after activation. Method according to one of the preceding claims, wherein the deformation body ( 2 ) with a metallization layer ( 5 ) is coated, with which it after contacting with the reagent ( 4 ) adjoins; and / or wherein the evaluation component ( 1 ) with a metallization layer ( 3 ) coated with it after contacting with the reagent ( 4 ) adjoins. Method according to one of the preceding claims, wherein at least in the step of activating the reagent ( 4 ) the evaluation component ( 1 ) and the deformation body ( 2 ) are pressed against each other. Method according to one of the preceding claims, wherein the deformation body ( 2 ) and / or the evaluation component ( 1 ) have a curved surface, with which they to the reagent ( 4 ). A method according to any one of the preceding claims, further comprising a step of applying an application specific integrated circuit, ASIC, to the reactant ( 4 ) before the step of activating. The method of claim 13, wherein the application specific integrated circuit is coated with a metallization layer, and wherein the application specific integrated circuit is applied to the reactant (10). 4 ) is applied, that the metallization layer to the reagent ( 4 ) adjoins. A sensor made by a method according to any one of the preceding claims.

Images