Sensor device with surface wave resonator

Abstract

To provide a novel sensor device with a surface wave resonator.SOLUTION: The present invention relates to a sensor device 100 comprising a metallic support substrate 200 and a surface wave resonator 300 having a chip body 310. A resonator structure 320 is embedded in or deposited on an upper side 313 of the chip body 310. The surface wave resonator 300 is fixed to the support substrate 200 with the aid of a glass layer 400.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a sensor device including a passive surface acoustic wave resonator (referred to as “surface acoustic wave resonator” in English and abbreviated as SAW resonator hereinafter), which is configured to measure mechanical stress or strain in a deformable body.

[0002] Passive acoustic surface wave sensors (SAW resonators) are generally used to wirelessly monitor physical conditions, especially in harsh environments. However, the limitations in applications for strain measurement usually arise from the design of the functional intermediate layer that connects the SAW resonator to the surface of the deformable body.

[0003] In applications for mechanical strain measurement, such as torque measurement or force measurement, the SAW resonator is usually adhered to the surface of the deformable body using an intermediate layer or deposited directly on the deformable body. Hereinafter, the surface of the deformable body is referred to as a support substrate, while the optionally provided intermediate layer is referred to as a SAW resonator substrate, a SAW wafer substrate, or a chip body.

[0004] Integrating the SAW resonator directly onto the surface of a metallic deformable support places high demands on the deposition of the piezoelectric layer. Compared with conventional manufacturing on SAW wafer substrates, these devices have a significantly lower quality factor, poor signal characteristics, and a significantly higher manufacturing cost per sensor. Furthermore, the piezoelectric layer is prone to cracking when subjected to a large load.

[0005] When attaching a SAW resonator to a support substrate, just as in the case of attaching a strain sensor based on a polymer film, an adhesive connection with established protection is used. The use of a high-performance adhesive indicates that the connection technology here has the ability to achieve a high strain transfer ratio. Compared to an elastic strain sensor based on a polymer film, the rigidity of a piezoelectric SAW resonator is significantly higher. Therefore, despite the optimized design of the adhesive connection, time-dependent and temperature-dependent effects occur. In particular, in the region of the glass transition temperature of the adhesive, significant changes occur in the strain transfer characteristics, and irreversible malfunctions occur in the SAW resonator.

[0006] For a SAW sensor with a metal support substrate using a highly reactive nanofilm, the approach of melting the deposited back metallization causes strong thermal stress to be locally introduced based on the temperature gradient inside the SAW resonator. Furthermore, the high temperature required for melting the metal interface damages the crystal structure of the SAW resonator substrate.

[0007] Therefore, an alternative bonding method (hereinafter also referred to as the bonding method) is required to fix a SAW resonator with an extended operating temperature range and a high strain transfer rate onto a metal deformation body under harsh environmental conditions.

[0008] Problems of the Invention The problem of the present invention is to provide a novel sensor device provided with a surface wave resonator.

[0009] This problem is solved by a sensor device having the features described in claim 1.

[0010] Advantageous configurations of the present invention are the subject of each dependent claim.

[0011] Summary of the Invention According to the present invention, a sensor device includes a metal support substrate and a surface wave resonator.

[0012] Here, the metal support substrate is, for example, a part of a deformable body that is exposed to mechanical loads or mechanical forces and deformed by these mechanical loads and forces. The deformation of the deformable body can be detected by a surface wave resonator, which can also be referred to as a sensor element. In particular, the support substrate, i.e., the deformable body, is at least partially formed of special steel. Thereby, the deformable body can be used in many applications. For example, the deformable body can be configured as a press scale or as a load cell.

[0013] The surface wave resonator includes a chip body. Further, the resonator structure is embedded in or adhered to the upper surface of the chip body.

[0014] For example, the resonator structure can include a so-called single-mode resonator having a transmit-receive interdigital transducer between two electrode gratings with substantially perfect reflectivity that form a resonant space. The wave traveling between the interdigital transducer and the reflection grating and reflected interferes with the standing wave. The thus formed wave field becomes extremely narrowband as a result of multiple reflections.

[0015] The surface wave resonator is fixed on the support substrate by a glass layer. In this case, the glass layer can be a particularly lead-free glass layer. This is because, based on the increasing normative environmental awareness on the market side, lead-containing glass should be increasingly avoided. In the context of using glass as a connecting means, the glass can also be referred to as glass solder or solder glass. The glass layer can be produced, for example, by applying a glass frit or a glass paste on the support substrate and subsequently melting the glass frit or the glass paste.

[0016] Instead of using adhesives known from the prior art to couple a surface acoustic wave resonator to a support substrate, glass can be used, enabling the use of the sensor device under significantly more diverse and demanding environmental conditions. Here, glass solder is generally not vulnerable to moisture and has material properties that are nearly temperature-independent over a wide temperature range (as long as the ambient temperature is below the glass transition temperature). This applies in particular to the dynamic elastic modulus of the glass and its coefficient of thermal expansion (CTE in English). Furthermore, glass exhibits significantly weaker viscoelastic behavior compared to adhesives. Therefore, over another temperature range, it is possible to transmit mechanical stress from the support substrate to the surface acoustic wave resonator at a constant height, independent of the loading time, and thus improve the measurement accuracy.

[0017] In an exemplary configuration of the sensor device, the glass layer is arranged at least partially between the lower surface, opposite to the upper surface of the chip body, and the support substrate. In this case, the glass layer has an outer edge portion surrounding the edge portion formed between the upper surface and the lower surface of the chip body. In this case, the outer edge portion of the glass layer is in contact with the surface section of the support substrate that is covered and defined by the glass layer. In particular, the glass layer is adhered to the entire surface of the said surface section on the support substrate, and there is no gas enclosure or air enclosure. The edge region of the chip body is surrounded by the outer edge portion of the glass layer, which means that the chip body is fixed on the support substrate by glass solder along its entire bottom surface defined by the basic shape, and does not protrude beyond the outer edge portion of the glass layer at any position, that is, at any corner portion. Instead, the outer edge portion of the glass layer extends completely beyond the basic shape of the chip body, which means that when viewed in a plan view, there is a non-zero distance from the outer edge portion to the chip body at each location. In particular, there is no gas enclosure or air enclosure between the glass layer and the chip body. According to such an exemplary configuration, it is possible to achieve a particularly uniform transmission of mechanical stress from the support substrate to the surface wave resonator. Furthermore, in this configuration, the coupling of the surface wave resonator is particularly stabilized with respect to its adhesion strength on the support substrate. In this configuration, the fact that the glass layer is arranged "at least partially" between the lower surface of the chip body and the support substrate means that a section of the glass layer is exactly at that location. Note that other sections of the glass layer, especially the sections that protrude laterally from the chip body when viewed in a plan view, can also extend completely into the region above the lower surface. In this case, the glass layer can in particular partially or even completely cover the edge portion of the chip body formed between the upper surface and the lower surface of the chip body, whereby, as will be further described in more detail based on another exemplary configuration below, only the upper surface of the chip body protrudes completely from the glass layer or is at least not covered by the glass layer.

[0018] In an exemplary development form of this configuration, the chip body can have a basic shape, and the glass layer can have a base shape that is symmetric with respect to the basic shape of the chip body. However, since the base shape is scaled larger than the basic shape, the chip body can be reliably surrounded by the glass layer as described in the above exemplary configuration. The chip body is centered and symmetrically positioned within the glass layer. Thus, in particular, the center of gravity and the axis of symmetry of the base shape overlap vertically with the center of gravity and the axis of symmetry of the basic shape, and the base shape protrudes beyond the basic shape by at least substantially the same width on all sides. That is, the distance from the outer edge of the base shape to the outer edge of the basic shape is at least substantially constant.

[0019] In an exemplary configuration of the sensor device, the chip body, i.e., its basic shape, and the base shape of the glass layer are formed in a polygonal shape. In particular, in this case, the chip body has a predetermined height and a basic shape defined perpendicular to the height. The basic shape is defined, for example, by an even number of at least four corner portions and a corresponding number of linear side edge portions formed between each two adjacent corner portions. Further, the basic shape has, for example, at least two symmetry axes. Thus, the basic shape of the chip body can correspond to, for example, a rectangle or a square. Differently, the basic shape and the base shape may each have a different number of corner portions. Also, the basic shape and the base shape may be configured in a non-angular shape such as a circular or elliptical shape, or may be configured as a freeform shape. In an angular configuration, one side edge portion is formed between each two adjacent corner portions, and the number of corner portions of the base shape matches the number of corner portions of the basic shape. Due to the surface tension and viscosity of typical glass solder, especially in the case of low melting point glass solder (which may be particularly advantageous for the applications described below in the context of the exemplary configuration), any sharp corner portions or completely linear edge regions cannot be realized. Instead, the outer edge of the glass layer extends seamlessly and continuously without step changes or inflection points. Thus, within the scope of this configuration, without departing from the teachings of the exemplary configuration, the "corner portions" of the base shape correspond more or less to rounded portions having a small radius, and the side edge portions of the base shape can have rounded portions, raised portions, and recesses instead of being linear extensions. The aspect ratio of the base shape is equal to the aspect ratio of the basic shape on the same symmetry axis with a technically achievable accuracy, at least during the application of the glass frit or glass paste and during the melting of the glass frit or glass paste.

[0020] In an exemplary configuration of the sensor device, the outer edge portion of the glass layer has raised portions oriented outward at each corner portion of the basic shape. Thereby, advantageously, it is possible to achieve forming a plateau region in the center of the glass layer that does not drop overly strongly in the region of the corner portions of the basic shape. Especially when it is desired to dispose the chip body partially sunken in the glass layer, in the said plateau region, the chip body can be reliably bonded over its entire bottom surface and its side surfaces.

[0021] In an exemplary configuration of the sensor device, the outer edge portion of the glass layer may be spaced apart by a maximum of a first length from the closest side edge of the chip body, at least partially, at at least one position between at least two consecutive corner portions of the basic shape. At the same time, the outer edge portion may be spaced apart by at least a second length from the closest corner of the chip body, at least partially, in at least one of the raised portions, where the second length is at least 10% greater than the first length. In particular, the second length is at least 50% greater than the first length, especially at least 100% greater. The fact that the distances described above should exist "at at least one position between consecutive corner portions of the basic shape" or respectively "in at least one of the raised portions" means that (while maintaining the symmetry introduced above) it is not necessary to maintain the same distance at all positions between all possible pairs of two consecutive corner portions of the basic shape, or respectively at all raised portions.

[0022] However, in an exemplary configuration of the sensor device, the outer edge portion has a position that is at least partially separated from the closest side edge of the chip body by a maximum of a first length between each pair of adjacent raised portions. At the same time, in this configuration, the outer edge portion is at least partially separated from the closest corner portion of the chip body by at least a second length at each raised portion. "At least partially" means that in the context of this example and in all of the following parts having a similar context, each feature (i.e., the respective minimum or maximum distance) is satisfied at at least one point along the outer edge portion. However, in particular, each feature is maintained not only at one point but also along the combined segments of the outer edge portion. The maximum or minimum distance resulting from such a configuration enables the features and advantages of the above-described exemplary configuration to be realized particularly efficiently. By partially maintaining the maximum distance, which is at most the first length, in the region between the two raised portions in this way, the overall dimensions of the surface section covered by the glass layer are restricted, and thereby the total amount of glass frit or glass solder bumps required to manufacture this surface section is also restricted. At the same time, by at least partially maintaining the minimum distance of at least the second length at the raised portions, a plateau region is formed in the center of the glass layer, and the chip body can be stably and precisely arranged with high reliability inside this plateau region.

[0023] Furthermore, by way of example, the basic shape of the glass layer can protrude laterally or beyond the basic shape by 3 to 7 times, particularly 4 to 6 times, and particularly exactly 5 times the height of the chip body over the entire circumference. This means that the outer edge is always at least that distance away from the closest corner or side edge of the chip body. That is, the minimum distance from the outer edge to the chip body is defined by that distance shown as a multiple of the height of the chip body. In the parameter region here, the flow of force or the transmission of mechanical stress from the support substrate to the surface wave resonator can be realized particularly effectively and with optimized material consumption. In this case, in relation to the configuration described immediately above, the first length is configured to be exactly equal to or slightly larger than a multiple of the height of the chip body described in that example, that is, for example, 5% to 10% larger. Thereby, the advantages of the two exemplary configurations can be combined.

[0024] In another exemplary development of the above-described configuration, (regardless of the specific basic shape of the glass layer), the outer edge is at least partially separated from the chip body by a maximum of the first length in the region along at least one side edge of the chip body, and in the region of at least one corner of the chip body, it is at least partially separated from the corner by at least the second length, where the second length can be configured to be at least 10% larger, particularly at least 50% larger, and particularly at least 100% larger than the first length. In this case, it can be understood that the first length or the second length in this example corresponds to the first length or the second length introduced in the above example. The explanations regarding concepts such as "at least one" and "at least partially" in the above paragraph are equally applicable in this example. Similarly, the features of this example can achieve the same advantages as those described for the first length and the second length in the above paragraph. This example is not limited to the requirement that the glass layer must have a basic shape with recognizable protrusions, unlike the above example.

[0025] Also in this case, the chip body can have a basic shape formed by the side edges and an even number of at least four corner parts, where the basic shape has, for example, at least two symmetry axes. Note that also in this case, a more angular configuration different from the basic shape is possible.

[0026] Furthermore, in this developed form, the outer edge can be configured to be separated from the nearest side edge or corner part of the chip body by at least 3 to 7 times, particularly 4 to 6 times, and particularly 5 times the height of the chip body at each point. Therefore, according to this exemplary configuration, the minimum distance from the outer edge to the chip body is defined. In such a parameter range, the flow of force or the transmission of mechanical stress from the support substrate to the surface wave resonator can be realized particularly effectively with optimized material consumption. In this case, in relation to the above-described features of this developed form, the first length can be configured to be exactly equal to or slightly larger than a multiple of the height of the chip body cited in this example, that is, for example, 5% to 10% larger. Thereby, the advantages of the two exemplary developed forms can be combined.

[0027] In another exemplary configuration of the sensor device, the surface of the glass layer is connected to the upper surface of the chip body such that it is at least substantially coplanar with the upper surface of the chip body, at least along the edge section of the chip body. In this case, the edge section can include at least in part the edge surface of the chip body, in particular one or more side edges of the chip body and / or one or more corner sections of the chip body. In the context here, "substantially coplanar" means that the glass layer does not cover a portion of the upper surface of the chip body, i.e., does not extend beyond the side edges of the upper surface of the chip body. Similarly, this means that there are no abrupt steps remaining between the surface of the glass layer and the upper surface of the chip body. That is, the surface of the glass layer terminates precisely at the edge section defining the upper surface of the chip body. In particular, in this case, the surface of the glass layer transitions continuously to the upper surface of the chip body at the edge section. However, an abrupt change in the gradient, i.e., a bend in the extension transitioning from the glass layer to the upper surface, should likewise be understood to be substantially coplanar in the context of this configuration. Such a configuration can achieve a particularly effective force flow or can particularly effectively transmit mechanical stress between the support substrate and the surface wave resonator. In particular, the force or mechanical stress can be directly transmitted to the uppermost layer of the chip body, where surface waves are transmitted within the resonator structure. At the same time, by terminating substantially coplanarly, damage to the function of the surface wave resonator is effectively prevented. That is, it has been found that even a small amount of glass extending beyond the edge section on the upper surface of the chip body significantly interferes with the surface waves excited on the upper surface of the chip body. Furthermore, such a glass layer portion extending partially across the upper surface of the chip body can cause distortion on the upper surface when a temperature change occurs, and such distortion can likewise significantly interfere with the measurement characteristics of the wave field or the surface wave resonator.Furthermore, by connecting the glass layers to form a coplanar structure at the edge section, it is possible to repair microcracks, microscopic edge fractures or edge failures in the chip body that may occur depending on the process during the manufacturing process of the chip body by the wetting of the solder glass according to the geometric features of the configuration. This means that the glass can flow into these crack and failure areas during the bonding of the chip body to the support substrate and fill them. Thereby, the measurement characteristics of the surface acoustic wave resonator can be improved, the sensitivity to its environmental impact can be reduced, and the mechanical stability of the sensor device and the fail-safe performance of the sensor device under long-term load and replacement load can be improved. Correspondingly, in one example, advantageously, the surface of the glass layer is connected to the side edges and corner portions such that it is substantially coplanar along all the side edges and corner portions of the chip body, and thus, the surface of the glass layer can be configured not to be connected to be coplanar with the upper surface in the edge section of the chip body.

[0028] In another exemplary configuration of the sensor device, the corner portions of the basic shape of the chip body are formed to be rounded. Such a shape of the corner portions can be achieved, for example, by an etching process. With this configuration, the bonding of the chip body to the glass layer can be improved. In particular, in this configuration, as proposed in the above exemplary configuration, it becomes easy to connect the surface of the glass layer to be at least substantially coplanar with the upper surface of the chip body over the entire circumference.

[0029] In another exemplary configuration, the surface of the glass layer first rises to a highest point higher than the upper surface of the chip body in a direction away from the extension of the chip body toward the outer edge of the chip body, at least along the edge section of the chip body. Depending on the surface tension, viscosity, and the angle at which the surface of the glass layer connects to the edge section of the chip body, the surface can initially change its curvature from concave to convex, but it can also extend convexly from the edge section to the outer edge across the entire extension of the surface. After reaching the highest point, the surface continuously descends toward the outer edge without forming a macroscopic concave molding section in any case. Thus, the curvature remains convex over a further extension but can be reduced toward the edge. That is, for example, when viewed in a cross-section extending perpendicular to the surface and the edge section of the support substrate, the surface of the glass layer first has a maximum, an inflection point, and subsequently a vertex in a direction away from the edge section of the chip body toward the outer edge of the glass layer, but then does not have any further inflection points, further end points, or further vertices. The fact that the glass layer may form a convex end section at the outer edge directly on a microscopic plane depending on its surface tension, viscosity, and the possible microstructure of the surface of the support substrate does not contradict the above description. Subsequently, the edge section in which the surface of the glass layer has an extension defined according to this configuration may at least partially include one or more side edges of the chip body and / or one or more corner sections of the chip body. By this configuration, advantageously, the effective cross-sectional area of the portion of the glass layer surrounding the chip body can be increased, thereby reducing or deflecting the peak of the mechanical stress. Thereby, the stability of the sensor device can be improved, and strong deformation can be transmitted from the support substrate to the surface wave resonator without damaging the glass layer. This means that the maximum allowable expansion degree is increased. Furthermore, by forming an extension having a highest point higher than the upper surface of the chip body, the surface wave resonator can be partially protected against contact with other bodies, which will be explained in more detail particularly in the context of the following developments.

[0030] In an exemplary development form of this configuration, correspondingly based on the above-described advantages, the surface of the glass layer extends along the edge section in a direction away from the edge section to the outer edge as described above, and all side edges and corner portions of the chip body can be included in the edge section. That is, the glass layer forms an annular collar surrounding the entire circumference of the surface acoustic wave resonator. Thereby, the above-described advantages of the chip body can be utilized completely comprehensively and effectively.

[0031] The highest point of the surface transition of the glass layer described in this configuration can be, for example, 10% to 75%, particularly 25% to 50% of the height of the chip body, higher than the upper surface of the chip body. Thereby, the advantageous effects of this configuration can be realized particularly effectively with optimized material consumption. Further, by limiting the height of the highest point according to the boundaries described herein, the tensile rigidity of the sensor device is significantly increased, thereby preventing a decrease in sensitivity.

[0032] In another exemplary development of this kind, the sensor device can further include a cover panel and a holding frame. The holding frame surrounds the entire surface portion coated with the glass layer and connects the cover plate to the support substrate. The connection here is especially hermetically sealed. Protecting a surface wave resonator with a cover panel from damage (especially dust, liquids and other mechanical ambient influences) is known in the prior art. However, hitherto, if one of the above-described members abuts or collides with the upper surface of the chip body, damage to the surface wave resonator may occur during the attachment of the cover panel and the holding frame. Such an error can be avoided by means of a curved portion of the glass layer oriented upwards having a highest point above the upper surface of the chip body. Because in such a case the glass layer shields the glass panel or the glass frame before hitting the sensitive upper surface of the surface wave resonator or the chip body. Correspondingly, such a protective action can be particularly efficiently exerted if the glass layer forms a wall-like collar completely surrounding the chip body as shown in one of the above-described developments.

[0033] In an exemplary embodiment of the above-described development of the configuration, the holding frame is formed by means of an additional annular glass solder or by means of an additional frame consisting of glass solder. Here, the holding frame can be manufactured using the same or similar process steps and process parameters as the bonding between the chip body and the support substrate, whereby the manufacture of the sensor device can be carried out efficiently. In particular, for the holding frame, a glass solder having a melting temperature lower than that of the glass solder used for the formation of the glass layer is used. This makes it possible to manufacture the holding frame after the glass layer, without having to raise the process temperature to such an extent that the glass layer itself melts again.

[0034] The term "rim section" is used in the description of the above exemplary configuration to represent, on the one hand, a section in which the surface of the glass layer is connected to the upper surface such that it is at least substantially coplanar with the upper surface of the chip body. On the other hand, the same term is also used to represent a section in which the surface of the glass layer rises first to a point higher than the upper surface of the chip body towards the outer edge in its extension, and then continuously descends towards the outer edge without forming a macroscopic concave-shaped forming section. To avoid ambiguity, here it is explicitly stated that in the exemplary configuration of the sensor device, the section may be the same rim section (i.e., a combination of a connection part in the same plane and a corresponding extension to the highest point in the same rim section), or it may be a different rim section (i.e., a connection part that is only coplanar with a section in which the rise does not reach the highest point from the surface of the glass layer to the outer edge). Similarly, a rim section having one feature and a rim section having the other feature can only overlap partially. Similarly, the two features can also be applied simultaneously over the entire circumference, i.e., the two features can be provided continuously along all the side edges and all the corner parts of the chip body without interruption.

[0035] In another exemplary configuration of the sensor device, the chip body has a first coefficient of thermal expansion and a first expansion sensitivity in a first direction, and a second coefficient of thermal expansion and a second expansion sensitivity that are different from the first coefficient of thermal expansion or the first expansion sensitivity, respectively, in a second direction orthogonal to the first direction. In this case, the chip body is shaped and cut such that the first direction and the second direction are located in a plane parallel to the upper surface of the chip body. Here, the second coefficient of thermal expansion is lower than the first coefficient of thermal expansion. Further, the coefficient of thermal expansion of the support substrate is selected to be lower than the first coefficient of thermal expansion and at the same time higher than the second coefficient of thermal expansion. Thereby, a mismatch in the coefficient of thermal expansion with different signs can be caused along the first direction and the second direction between the chip body and the support substrate. Here, for example, when the temperature rises, the chip body is relatively compressed in the first direction (i.e., negative expansion occurs or the degree of expansion decreases), while it is relatively expanded in the second direction at the same time (i.e., positive expansion occurs or the degree of compression decreases). Since the surface acoustic wave resonator is fixed on the support substrate by glass solder, during the progress of the bonding process and during the cooling and solidification of the glass solder, it expands in the first direction, i.e., undergoes positive expansion, and is compressed in the second direction, i.e., undergoes negative expansion. That is, at the end of the bonding process, a bias is applied to the chip body based on the set mismatch in the coefficient of thermal expansion. Here, in this configuration, the material of the chip body is selected and aligned such that the first expansion sensitivity is negative and the second expansion sensitivity is positive. The negative expansion sensitivity means, in the context here, that the resonance frequency of the surface acoustic wave resonator decreases as the positive expansion, i.e., the increase in expansion, increases. Correspondingly, the positive expansion sensitivity means that the resonance frequency increases as the positive expansion, i.e., the increase in expansion, increases. In a surface acoustic wave resonator, the expansion sensitivity can be expressed as the rate of change of the resonance frequency, i.e., δΔf / δε, where Δf is the difference between the resonance frequency and the output frequency at that time, and ε is the degree of expansion. Therefore, the bidirectional bias of the chip body respectively results in a reduction in the resonance frequency.However, at the same time, it is desirable that the material of the chip body has a temperature dependence of the resonance frequency that causes an increase in the resonance frequency during temperature transition, i.e., the cooling process. Correspondingly, the bidirectional effects of the inconsistent thermal expansion coefficients act in directions that oppose the temperature transition of the chip body, respectively, and thus effectively reduce the lateral thermal sensitivity of the surface wave resonator. Correspondingly, when the resonator structure, and thus the direction of the wave field (also referred to as the propagation direction of the wave field), extends parallel to the first direction or the second direction, a higher measurement accuracy can be achieved over a wide temperature range by the sensor device of this configuration.

[0036] The effectiveness of such bias and reduction of lateral thermal sensitivity can be utilized based on the bonding according to the invention using glass solder instead of an adhesive over a wide temperature range. The adhesive usually has a thermal expansion coefficient with strong temperature dependence, while the glass solder has an essentially temperature-independent thermal expansion coefficient.

[0037] In another exemplary configuration of the sensor device, the surface wave resonator has an average resonance frequency of 434 MHz or 2.4 GHz, and the chip body has a side length of at least 1.5 mm to a maximum of 5 mm, particularly a side length of at least 2 mm to a maximum of 3 mm. By using the above-mentioned frequencies, the surface wave resonator can be read out non-contact without a license in many regions and can even be operated without approval. This is because these frequencies are within the standardized IMS band. Alternatively or additionally, the resonator structure has a length of at least 1 mm, particularly at least 1.5 mm. By combining these parameters, a sufficiently high quality of the resonator and at the same time small structural dimensions are achieved, thereby ensuring the use of the sensor device for performing the measurement task.

[0038] In another exemplary configuration of the sensor device, the chip body has a thickness of at least 20 μm to at most 100 μm, in particular at least 25 μm to at most 60 μm. At the same time, the glass layer has a thickness of at least 10 μm to at most 200 μm, in particular at least 12.5 μm to at most 120 μm, in the surface region directly below the chip body. These dimensions make it possible to achieve a stable bond between the chip body and the support substrate and a reliable transmission of force from the support substrate to the chip body while simultaneously optimizing the material requirements.

[0039] In another exemplary configuration of the sensor device, the chip body is formed of α-quartz, where the chip body has a Y-35°X cross-section, a Y-34°X cross-section or a Y-33°X cross-section. In this case, the resonator structure is oriented to extend along the x-direction. This material selection can be used in particular to realize the above-described configuration in which an intentionally defined thermal bias is formed in the chip body. Because all requirements for the chip body are thereby met and a glass solder that meets the necessary conditions in combination with the chip body material here is obtained. Here, the Y-35°X cross-section means a Y cross-section rotated 35° about the X-axis. The non-rotated Y cross-section is a cross-section extending perpendicular to the Y-axis. Thus, in the notation according to ANSI / IEEE Std 176-1987, the cross-section can be denoted as YXwlt0° / 35° / 0°.

[0040] In another exemplary configuration of the sensor device, the glass layer is formed from a low melting point glass solder, in particular a glass solder having a melting temperature below 500 °C. Thereby, since not too high a temperature is required for melting the glass solder, the sensor device can be manufactured at a relatively low cost and in a relatively short time. Furthermore, since the temperature difference during the manufacturing process is small, the thermal bias as a whole can be reduced, but this should not be regarded as contrary to the above exemplary configuration in which a certain thermal bias is intentionally adjusted for the purpose of reducing the lateral thermal sensitivity of the surface wave resonator. With the configuration here, despite the fact that there may sometimes be a large difference between the melting temperature required during manufacturing and the often significantly lower operating temperature, whether due to thermal mismatch and residual stress, whether intentionally or unintentionally, between the materials of the chip body, the glass layer and / or the support substrate, it is possible to achieve that no high mechanical stress that could cause damage to the surface wave resonator is induced in the surface wave resonator.

[0041] In another exemplary configuration of the sensor device, the resonator structure is oriented in or on the upper surface of the chip body such that the wave field direction of the resonator structure extends parallel to one of at least two symmetry axes of the basic shape of the chip body. In particular, at least two symmetry axes of the chip body are positioned perpendicular to each other, the resonator structure is centered around the intersection of these symmetry axes, and the wave field direction extends parallel to one of these two symmetry axes. With such an orientation, the forces and deformations of the chip body can act on the resonator structure substantially symmetrically, thereby improving the measurement accuracy and furthermore reducing the lateral sensitivity. Particularly advantageously, when the symmetry axes of the chip body and the crystal directions are mutually adjusted with respect to the corresponding material properties, the above configuration can be combined with the exemplary configuration described in the above paragraph, which intentionally uses a specific thermal bias to reduce the lateral thermal sensitivity. Thereby, the advantages of the two configurations can be combined with each other.

[0042] The following will describe in detail some of the embodiments of the present invention and their exemplary configurations, embodiments, and development forms with reference to the drawings. The following are shown in each figure.

Brief Description of the Drawings

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Figure 7

[0044] Members corresponding to each other are denoted by the same reference numerals in all the figures.

[0045] Detailed Description of the Drawings FIG. 1 shows an exemplary configuration of the sensor device 100 in a plan view. The surface acoustic wave resonator 300 is fixed on the support substrate 200 by the glass layer 400. Here, although the support substrate 200 is only partially illustrated, it can be formed, for example, by a surface section of a deformable body, such as by a strain gauge, a pressure measurement diaphragm, or a force sensor. The surface acoustic wave resonator 300 includes a chip body 310 having a square basic shape defined by four corner portions 311 and four side edge portions 314 in this example. A resonator structure 320 is disposed within or on the upper surface 313 of the chip body 310. However, the resonator structure 320 is depicted in a significantly simplified state merely schematically in this figure and the following figures. The glass layer 400 has a peripheral outer edge portion 410 surrounding the surface portion of the support substrate 200 that is completely covered by the glass layer 400. In this case, the glass layer 400 has a basic shape 413 shown in detail in FIGS. 4A to 4D. The basic shape 413 corresponds to the basic shape 316 of the chip body 310 also shown in detail in FIGS. 4A to 4D, but is scaled up more, so the basic shape 413 of the glass layer 400 overlaps or surrounds the basic shape 316 of the chip body 310 on all sides. Further, the outer edge portion 410 has a raised portion 416 in the region of each corner portion 311 of the chip body 310. The chip body 310 is concentrically and symmetrically disposed on or within the glass layer 400. Thereby, a state is obtained in which the outer edge portion 410 is at least partially separated from the nearest side edge portion 314 by a maximum first length L1 in the region along the side edge portion 314. At the same time, the outer edge portion 410 is at least partially separated from the nearest corner portion 311 of the chip body 310 by at least a second length L2 in the region of the raised portion 416. Here, the second length L2 is at least 10% greater than the first length L1.

[0046] FIG. 2 shows an exemplary configuration of a surface acoustic wave resonator 300 similar to the surface acoustic wave resonator 300 of FIG. 1. The chip body 310 has a square basic shape 316 and has a height H which can also be referred to as the thickness of the chip body 310.

[0047] FIGS. 3A, 3B, 3C, and 3D show various exemplary configurations of chip bodies 310 having different basic shapes 316. Also shown are the symmetry axes 312 of the respective different basic shapes 316. Although the illustration of the resonator structure 320 is omitted in these figures, the resonator structures 320 are each oriented such that the wave field direction of the resonator structure 320 is parallel to one of the symmetry axes 312 and the resonator structure 320 is centered with respect to the intersection of the symmetry axes 312.

[0048] The chip body 310 of FIG. 3A has a square basic shape 316 and is thus similar to the embodiments of FIGS. 1 and 2. In contrast, the chip body 310 of FIG. 3B has a rectangular basic shape 316, and thus the number of symmetry axes 312 is reduced. FIG. 3C shows a chip body 310 having a hexagonal basic shape 316, in which example all side edges 314 have equal lengths. The chip body 310 shown in FIG. 3D is similar to the chip body 310 of FIG. 3A in terms of its basic shape 316, but the corner portions 311 are rounded and formed. Each of the various basic shapes 316 is defined by an even number of at least four corner portions 311 and the same number of side edges 314 disposed between each adjacent pair of corner portions 311. In FIG. 3C, the reference signs of the side edges 314 are omitted for clarity.

[0049] In FIGS. 4A, 4B, 4C, and 4D, exemplary chip bodies 310 from the corresponding FIGS. 3A, 3B, 3C, and 3D are shown in plan view as part of an exemplary configuration of the sensor device 100. For this purpose, each chip body 310 is positioned within a glass layer 400. The glass layer 400 has one respective base shape 413 with each axis of symmetry 415, and each base shape 413 corresponds to the basic shape 316 of the chip body 310 associated therewith in terms of shape and orientation, but is larger, so that the outer edge portion 410 of the glass layer 400 surrounds all sides of the edge surface of the chip body 310 that extends between the upper surface 313 and the lower surface of the chip body 310. The chip bodies 310 are each concentrically and symmetrically arranged inside the glass layer 400, whereby the outer edge portion 410 of the glass layer 400 is circumferentially (within the range of technically possible manufacturing precision) point-symmetrically spaced from the chip bodies 310. In this case, the base shape 413 protrudes from the basic shape 316 by at least a minimum distance M on all sides. Additionally, the glass layer 400 has raised portions 416 in the regions of all corner portions 311 of each basic shape 316 (and thus in the regions of all corner portions 414 of the base shape). Along the side edge portion 314 of the chip body 310 (not labeled with reference numerals in FIGS. 4A, 4B, 4C, and 4D for clarity), the outer edge portion 410 is partially spaced from the chip body 310 by a maximum distance L1. In the region of the raised portion 416, the outer edge portion 410 is also partially spaced from the respective nearest corner portion 311 (not labeled with reference numerals in FIGS. 4A, 4B, 4C, and 4D for clarity) by at least a second length L2.

[0050] In FIG. 5A, another exemplary configuration of the sensor device 100 is shown in perspective view. The chip body 310 is arranged within the glass layer 400 in a partially sunken state. In this case, the surface 411 of the glass layer 400 is connected to the upper surface 313 of the chip body 310 so as to be coplanar therewith along the edge section 315.

[0051] In FIG. 5B, the edge section 315 of FIG. 5A is shown as a cross-sectional view by plane A as shown in FIG. 5A. The surface 411 of the glass layer 400 is connected to the upper surface 313 so as to be in the same plane as the upper surface 313, that is, the surface of the chip body 310 and the side edge portion 314 of the chip body 310 are connected so as to be in the same plane. In this case, "being in the same plane" means that the glass layer 400 does not extend beyond the side edge portion 314, and thus does not cover the portion of the upper surface 313, and at the same time, as exemplified in the corner portion 311 of FIG. 5A, no step is formed between the surface 411 and the upper surface 313. In particular, the surface 411 of the glass layer 400 is connected to be in the same plane as the upper surface 313 continuously over the entire circumference, that is, along all the corner portions 311 and all the side edge portions 314. In FIG. 5B, the transition portion from the surface 411 to the upper surface 313 extends continuously, but within the scope of this embodiment, as suggested by the dashed line in FIG. 5B, a slight bent portion in the gradient should be understood as the same-plane connection as well.

[0052] In FIG. 6A, another exemplary embodiment of the sensor device 100 is shown in a perspective view. Here, the surface 411 of the glass layer 400 rises first to the highest point 412 higher than the upper surface 313 of the chip body 310 in the direction away from the chip body 310 at its extending portion. Subsequently, the surface 411 of the glass layer 400 continuously descends toward the outer edge portion 410 without forming a macroscopic concave forming section. The fact that the glass layer 400 may form a convex end section at the direct outer edge portion 410 on a microscopic plane depending on its surface tension, viscosity, and possible fine structure of the surface of the support substrate 200 does not contradict the above description. Therefore, the glass layer 400 forms an annular collar surrounding the surface wave resonator 300 or the chip body 310 over the entire circumference.

[0053] FIG. 6B is a cross-sectional view taken along plane B of FIG. 6A, partially showing the edge section 315 of FIG. 6A. Here, an extension of the surface 411 can be seen in the direction from the side edge 314 of the chip body 310 to the outer edge 410. In this case, the highest point 412 is, for example, at a position 10% to 75% higher than the height H of the chip body 310 than the upper surface 313 of the chip body 310.

[0054] FIG. 7 shows another exemplary embodiment of the sensor device 100 in a cross-sectional view. In this example, the glass layer 400 forms a color extending around the chip body 310, and the highest point 412 here is higher than the upper surface 313 of the chip body 310 respectively. Further, the surface wave resonator 300 and the glass layer 400 are surrounded by a holding frame 510 that supports the cover plate 500. The holding frame 510 is formed of glass solder and hermetically seals the surface wave resonator 300 and the glass layer 400 together with the cover plate 500. Since the glass layer 400 forms a color having the highest point 412, the sensitive upper surface 313 of the chip body 310 will not be damaged by the cover panel 500 even if the cover panel 500 sinks or tilts and is placed on the holding frame 510 during the manufacturing process. In such a case, the cover panel 500 abuts against the stable color formed by the glass layer 400 instead of the upper surface 313 of the chip body 310.

[0055] The disclosure of this specification is not limited to the features of the above-described exemplary embodiments, configurations, and / or development forms, and any combination of these features is also included as long as these features are not logically exclusive of each other. Further, the present invention can be modified within the scope of the following claims. Similarly, the individual aspects according to each dependent claim can also be combined with each other.

Explanation of Reference Numerals

[0056] 100 Sensor device 200 Support substrate 300 Surface wave resonator 310 Chip body 311 Basic shape or corner part of the chip body 312 Axis of symmetry of the basic shape of the chip body 313 Upper surface of the chip body 314 Basic shape or side edge part of the chip body 315 Edge section 316 Basic shape of the chip body 320 Resonator structure 400 Glass layer 410 Outer edge part of the glass layer 411 Surface of the glass layer 412 Highest point 413 Basic shape of the glass layer 414 Corner part of the basic shape 415 Axis of symmetry of the basic shape 416 Protrusion 500 Cover panel 510 Holding frame A, B plane L1 First length L2 Second length H Height of the chip body M Minimum distance

Claims

1. A sensor device (100), a metallic carrier substrate (200), - a chip body (310), and A resonator structure (320) embedded in or attached to the top surface (313) of the chip body (310). A surface wave resonator (300) comprising: where The sensor device (100), wherein the surface wave resonator (300) is fixed on the carrier substrate (200) by a glass layer (400).

2. The sensor device (100) of claim 1, wherein the glass layer (400) is at least partially disposed between a lower surface of the chip body (310) opposite the upper surface (313) and the carrier substrate (200), and an outer edge (410) of the glass layer (400) surrounds an edge surface formed between the upper surface (313) and the lower surface of the chip body (310).

3. - said tip body (310) has a basic shape (316); - the glass layer (400) has a basic shape (413) that is symmetrical with respect to the basic shape (316) of the chip body (310); - the chip body (310) is centered and positioned symmetrically with respect to the base shape (413) of the glass layer (400); The sensor device (100) of claim 2.

4. The sensor device (100) of claim 3, wherein the outer edge (410) has one outwardly oriented ridge (416) at each corner (414) of the base shape (413).

5. The outer edge (410) is at least partially at one location between two consecutive corners (414) of said basic shape (413) spaced at most a first length (L1) from the nearest side edge (314) of said tip body (310); and at least one of the ridges (416) is at least partially spaced from a nearest corner (311) of the tip body (310) by at least a second length (L2), where The second length (L2) is at least 10% greater than the first length (L1), in particular at least 50% greater, in particular at least 100% greater; The sensor device (100) of claim 4.

6. The outer edge (410) is at least one location between each pair of two adjacent ridges (416) at least partially has a distance to the respective nearest side edge (314) of said tip body (310) that corresponds at most to said first length (L1); and - each respective ridge (416) has, at least in part, a distance to the respective nearest corner (311) of the tip body (310) that corresponds at least to the second length (L2); The sensor device (100) of claim 5.

7. The sensor device (100) according to any one of claims 3 to 6, wherein the basic shape (413) protrudes laterally from the basic shape (316) of the chip body (310) on all sides by a minimum distance (M), the minimum distance (M) being 3 to 7 times, in particular 4 to 6 times, in particular 5 times the height (H) of the chip body (310).

8. The basic shape (316) has an even number of at least four corners (311) and at least two axes of symmetry (312); The base shape (413) has a corresponding number of corners (414) and an axis of symmetry (415). The sensor arrangement (100) according to any one of claims 3 to 7.

9. The outer edge (410) is at least partially in a region along at least one side edge (314) of said tip body (310) and spaced apart from said tip body (310) by up to a first length (L1); and at least partially in the region of at least one corner (311) of said tip body (310) and spaced at least a second length (L2) from said corner (311), in which The second length (L2) is at least 10% greater than the first length (L1), in particular at least 50% greater, in particular at least 100% greater; The sensor device (100) of claim 2.

10. The outer edge (410) is at least partially spaced apart from the tip body (310) by at most the first length (L1) in each region along each side edge (314) of the tip body (310); and - each at least partially in the region of each corner (311) of the tip body (310) spaced apart from the corner (311) by at least the second length (L2); The sensor device (100) of claim 9.

11. The sensor device (100) according to claim 9 or 10, wherein the outer edge (410) is at each point laterally spaced a minimum distance (M) from the nearest side edge (314) or corner (311) of the chip body (310), respectively, the minimum distance (M) being 3 to 7 times, in particular 4 to 6 times, and particularly preferably 5 times, the height (H) of the chip body (310).

12. The tip body (310) has a basic shape (316) defined by the side edges (314) and an even number (311) of at least four corners; The basic shape (316) has at least two axes of symmetry (312). The sensor arrangement (100) according to any one of claims 9 to 11.

13. The sensor device (100) of any one of claims 1 to 12, wherein a surface (411) of the glass layer (400) is connected to the upper surface (313) so as to be at least substantially coplanar with the upper surface (313) at least along an edge section (315) of the chip body (310).

14. The surface (411) of the glass layer (400) extends at least along an edge section (315) of the chip body (310) away from the edge section (315) to an outer edge (410); - first, it rises to a highest point (412) that is higher than the upper surface (313) of the tip body (310); - then it descends continuously towards said outer edge (410) without forming a macroscopic concave molded section The sensor device (100) according to any one of claims 1 to 13, wherein the sensor device (100) extends as follows:

15. The sensor device (100) according to claim 14, wherein the highest point (412) is higher than the upper surface (313) of the chip body (310) by 10% to 75%, in particular by 25% to 50% of the height (H) of the chip body (310).

16. The sensor device (100) according to any one of claims 13 to 15, wherein the edge section (315) includes all edge surfaces of the chip body (310), in particular all side edges (314) and all corners (311) of the chip body (310).

17. The sensor device (100), - a cover panel (500) - a holding frame (510) where the holding frame (510) surrounds the outer edge (410) and connects the cover panel (500) to the carrier substrate (200); The sensor arrangement (100) according to any one of claims 2 to 16.

18. The holding frame (510) is made of glass solder, and the holding frame (510) is particularly - made from a glass solder different from said glass layer (400), - the different glass solder has a lower melting temperature than the glass solder forming the glass layer (400); The sensor device (100) of claim 17.

19. The tip body (310) is formed from an anisotropic material, the anisotropic material comprising: having a first coefficient of thermal expansion and a first expansion sensitivity in a first direction; a second coefficient of thermal expansion and a second expansion sensitivity in a second direction orthogonal to the first direction, wherein: the second coefficient of thermal expansion is lower than the first coefficient of thermal expansion; and the thermal expansion coefficient of the carrier substrate (200) and / or the thermal expansion coefficient of the glass layer (400) is smaller than the first thermal expansion coefficient and at the same time larger than the second thermal expansion coefficient; the first expansion sensitivity is negative and the second expansion sensitivity is positive; The tip body (310) the first direction and the second direction lie in a plane parallel to a top surface (313) of the tip body (310), and The resonator structure (320) extends parallel to the first direction or parallel to the second direction. The sensor device (100) according to any one of claims 1 to 18, wherein the sensor device (100) is formed.

20. The surface wave resonator (300) has an average resonant frequency of 434 MHz or 2.4 GHz; the tip body (310) has a side length of at least 1.5 mm and at most 5 mm, in particular at least 2 mm and at most 3 mm; and / or The resonator structure (320) has a length of at least 1 mm, in particular a length of at least 1.5 mm. The sensor arrangement (100) according to any one of the preceding claims.

21. The chip body (310) has a thickness of at least 20 μm to at most 100 μm, in particular at least 25 μm to at most 60 μm, in particular the glass layer (400) has a thickness of at least 10 μm to at most 200 μm, in particular at least 12.5 μm to at most 120 μm, in the surface area directly under the chip body (310); The sensor arrangement (100) according to any one of the preceding claims.

22. The chip body (310) is formed from α-quartz, the chip body has a Y-35°X cross section, a Y-34°X cross section, or a Y-33°X cross section, and the resonator structure (320) extends along the x direction. The sensor arrangement (100) according to any one of the preceding claims.

23. The sensor arrangement (100) according to any one of the preceding claims, wherein the glass layer (400) is formed from a low melting point glass solder, in particular a glass solder having a melting temperature below 500°C.

24. 24. The sensor device (100) according to claim 1, wherein corners (311) of the tip body (310) are rounded.

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