Surface elastic wave device encapsulation system

Abstract

The invention relates to a compact and robust encapsulation system 1 for surface wave device protection. The encapsulation system 10 comprises a SAW device 3 and a sealing cord 9 that seals a second substrate 11 to the base substrate 1 of the SAW device 3 so as to form a cavity 13, as well as a connection means 11 arranged externally to the cavity 13 on the encapsulation system 1. Figure for the abstract: Fig. 1

Description

Title of the invention: Surface elastic wave device encapsulation system Scope of the invention

[0001] The invention of this application relates to surface acoustic wave devices, also called surface acoustic wave devices or SAW devices. It relates in particular to a protection system for said SAW devices, as well as a corresponding method for manufacturing such a device. Technological background of the invention

[0002] SAW devices are sensitive to variations in the resonant frequency of elastic waves on the surface of piezoelectric materials in response to external stimuli. These external stimuli can be electrical, physical, chemical, or biological in nature. The high versatility, reliability, sensitivity, and cost-effectiveness of these devices make their application highly desirable in a wide range of fields. Thus, SAW devices are used in various applications, including as sensors for temperature, pressure, force, etc.

[0003] The applicability of SAW devices presents two main limitations: firstly, the risks to proper functioning incurred by exposing sensitive parts of the devices to the external environment, and secondly, the bulkiness due to the communication connectors at the control station. Thus, a first encapsulation system enabling the protection of a sensor comprising three SAW devices for determining pressure and temperature is disclosed in S. Ballandras et al., "PII-5 Micro-Machined, All Quartz Package, Passive Wireless SAW Pressure and Temperature Sensor," 2006 IEEE Ultrasonics Symposium, 2006, pp. 1441-1444, doi: 10.1109 / ULTSYM.2006.363, and more specifically p. 1443. Object of the invention

[0004] In view of the above, the present invention aims to provide an improved SAW device protection solution, and in particular a solution which combines robustness with compactness and more economical production. Brief description of the invention

[0005] In this respect, the invention relates to a SAW device encapsulation system, comprising said SAW device comprising at least one base substrate and an interdigital transducer, also called an interdigital comb transducer or interdigital transducer, formed on said base substrate, the encapsulation system further comprising a sealing cord that seals a second substrate with said base substrate is arranged to form a cavity enclosing said interdigital transducer, as well as a connection means for connecting an antenna, linked to at least one interdigital transducer. The encapsulation system is characterized in that said antenna connection means, in particular a miniature coaxial radio frequency connector, is arranged externally to the cavity on the base substrate or on the second substrate.

[0006] By integrating the antenna connector directly into the encapsulation system, a more robust, compact, and economical SAW device protection can be achieved than previously available. Direct antenna integration eliminates the previously required communication channels and the additional constraints they present. This offers several advantages:

[0007] Initially, the total space occupied by the system can be reduced, increasing its compactness and versatility of placement, particularly in existing structures, as well as in restricted spaces.

[0008] Next, the number of components and production steps of the system can be reduced, reducing the production costs of such an encapsulation system.

[0009] Finally, by reducing the lengths of the conductive communication channels between the SAW device and a remote antenna connection means, the exposure of the communication channels to risks presented by the external environment can be advantageously dissipated by this encapsulation system. This can thus increase the reliability and robustness of the implementation of the protected surface elastic wave device.

[0010] In one embodiment of the invention, the link between said interdigital transducer and the antenna connection means may include wire cabling.

[0011] Establishing a link using wire cabling, for example by wirebonding, can ensure communication between the interdigital transducer(s) with inexpensive means. Commercially available wires, whose conductive elements are made of materials such as aluminum, copper, silver, platinum, or gold, can thus be used. Since the physical, electrical, and electromagnetic properties of these wires are studied and predetermined, the communication between the interdigital transducers and the connecting means can be dimensioned and operated with high precision.

[0012] In one embodiment of the invention, the link between said interdigital transducer and the antenna connection means may include at least one via passing through the second substrate.

[0013] The formation of one or more vias forming electrically conductive metallic bridges in the second substrate can establish a communication link between the interdigital transducer(s) inside the cavity of the system The system consists of an encapsulation layer and an antenna connection means arranged on the second substrate. Thus, the communication link resides primarily within the system cavity, advantageously protecting it from risks posed by the external environment, such as high temperatures, chemical pollution, or mechanical shocks. For example, the via can be assembled in the second substrate with electrical routing, such as an electrically conductive trace or layer, arranged on the second substrate to establish an electrical connection with an antenna connection means. Inside the cavity, the electrical connection of the vias to the SAW device can be made, for example, using one or more solder beads or solder bumps, also called solder bumps, placed in the cavity between the SAW device and the second substrate, establishing an electrical link with the vias in the second substrate.

[0014] In one embodiment of the invention, the link between said interdigital transducer and the antenna connection means may include at least one metallic pad formed on or in the base substrate and passing through the sealing cord.

[0015] The formation of such a metallic pad traversing the sealing cord can allow the re-establishment of connection and communication with one or more interdigital transducers hermetically sealed within the cavity of the encapsulation system following the sealing of the two substrates, without degrading or modifying the substrates themselves. Furthermore, thanks to such a conductive connection pad traversing the sealing cord, the connection with an antenna connection means arranged externally to the cavity on a primary or secondary substrate can be made and adjusted after the hermetically sealed cavity has been closed, without constraints related to the limited space of the cavity or the sequencing of the encapsulation system production steps.The metallic pad here can correspond to a metallic track in the same material as the interdigital transducer(s), for example in aluminium, gold, platinum, or copper or even a mixture of these materials, in particular in AlCu.

[0016] In one embodiment of the invention, the face of the base substrate opposite the second substrate may include a metallic layer.

[0017] Such metallization of the rear surface of the base substrate of the encapsulated SAW device aims to obtain better thermal conductivity, in particular allowing to optimize the proper functioning of a SAW device arranged as a temperature sensor.

[0018] In one embodiment of the invention, the base substrate may be equipped with at least one metallic via, in particular a via arranged so as to be electrically isolated from the interdigital transducer and preferably made of the same material as a metallic layer on the face of the base substrate opposite the second substrate. In a In another mode, at least one metallic via passes completely through the base substrate from its lower to its upper surface, and / or passes only partially through the base substrate, starting from the lower surface but not reaching the upper surface, particularly in the part of the base substrate facing the electrodes. Thus, without disturbing the waves propagating near the upper surface of the base substrate, a thermal bridge can be created.

[0019] In this alternative embodiment, one or more metallic vias added to the base substrate can serve as thermal bridges for the SAW device and similarly optimize the proper functioning of a SAW device arranged as a temperature sensor. The metallic vias can preferably be made of the same material as a thermally conductive metallic layer arranged on the base substrate. This further increases heat conduction to the SAW device. Moreover, the vias added to the base substrate can be arranged so as to be electrically isolated from the interdigital transducer(s). This reduces the risk of short-circuiting the electrodes of the SAW device's transducer(s).

[0020] In one embodiment of the invention, the sealing bead can be formed by anodic welding or glass frit.

[0021] By forming the sealing bead by anodic welding, a very durable and airtight seal between the two substrates can be achieved. Welding is particularly advantageous because it does not require the use of additional sealing materials, which could be costly and interfere with the proper functioning of the SAW device.

[0022] The use of glass frit for sealing the substrates and forming the airtight cavity can provide a durable and airtight seal, which is also compatible with the introduction of metallic conduction pads transversely to the sealing bead, without damaging either the sealing bead or the pad(s) themselves. Thus, re-establishing connection with the SAW device enclosed within the system cavity can be made possible.

[0023] In this embodiment, the glass frit can also be chosen so as to have a coefficient of expansion corresponding to that of the material of the base substrate and / or the second substrate.

[0024] By choosing a glass frit material whose coefficient of thermal expansion matches that of the base substrate material or the second substrate material, preferably both, the thermoelastic stresses induced by temperature variations can be limited, and even significantly reduced. Such a material choice can therefore increase the mechanical durability of the encapsulation system as well as the operational reliability of a SAW device.

[0025] In one embodiment of the invention, the basic substrate may comprise a piezoelectric material, in particular a material selected from quartz (SiO2), lithium tantalate (LiTaO3), lithium niobate (LiNbO3), aluminium nitride (AIN), zinc oxide (ZnO), gallium orthophosphate (GaPO4), barium titanate (BaTiO3), langasite (La3Ga5SiO14), langanite (La3Ga5.5NbO.5O14), gallium nitride (GaN), lead zirconate titanate (PZT) or langatate (La3Ga5.5TaO.5O14).

[0026] These materials exhibit resonance frequencies that are particularly sensitive to external stimuli and can therefore be advantageously used in SAW devices.

[0027] In one embodiment of the present invention, the second substrate may comprise the same material as the base substrate.

[0028] By assimilating the material of the second substrate to that of the base substrate, the differential of thermal expansion between the two substrates can be reduced, thus advantageously increasing the durability and robustness of the seal, and therefore the hermeticity of the encapsulation system.

[0029] The invention also relates to a method for manufacturing an encapsulation system for a SAW device, in particular an encapsulation system as described above. The method is notable in that it comprises the following steps:

[0030] The provision of a basic substrate comprising at least one interdigital transducer,

[0031] The sealing of a second substrate onto the first substrate so as to form a cavity enclosing said interdigital transducer(s), and

[0032] The external arrangement to the cavity of an antenna connection means, in particular a miniature coaxial radio frequency connector, on the base substrate or the second substrate.

[0033] As indicated above, this method can lead to a SAW device encapsulation system providing more robust, compact and economical protection than previously known for sensitive parts of such a device.

[0034] According to an advantageous feature, the second substrate of step ii) can be provided with at least one via, and the method can further comprise a step of electrically connecting at least one transducer to the antenna connection means using at least one via. Such a via through the second substrate can establish the electrical link between the interdigital transducer of step i, enclosed in the cavity, and the antenna connection means arranged according to step iii on the second substrate. Thus, an electrical link can be obtained running mainly, or at least partly, through the interior of the cavity formed by the seal, which can advantageously protect this link from risks presented by the environment. external. For example, the via can be assembled in the second substrate with an electrical routing arranged on the second substrate and solder beads arranged in the cavity interfacing with the interdigital transducer.

[0035] According to another advantageous feature, the base substrate provided in step i may include a metallic layer on its face opposite the second substrate and / or at least one metallic via. This or these features may allow for improved thermal conductivity to the encapsulated SAW device and thereby enhanced use of said SAW device, for example as a temperature sensor. In particular, the vias included in the base substrate may be arranged so as to be electrically isolated from the interdigital transducer(s). This may advantageously reduce the risk of short-circuiting the electrodes of the interdigital transducer(s).

[0036] According to another advantageous feature of the process, step ii may include the formation of at least one metallic pad passing through the seal. The formation of such a metallic pad is advantageous because it can establish a communication link with one or more interdigital transducers hermetically sealed within the cavity of the encapsulation system without altering or degrading either of the two substrates, after the two substrates have been sealed.

[0037] According to a final advantageous feature of the process, step iii may include a wired connection. Wired cabling can provide an inexpensive and reliable communication link. Brief description of the drawings

[0038] The objects, features and advantages of the invention as set forth above will be more fully understood and appreciated by studying the following more detailed description of preferred embodiments of the invention, together with the accompanying drawings.

[0039] Fig. 1 schematically represents a cross-section through an encapsulation system according to a first embodiment of the invention in which the antenna connection means is arranged on the base substrate.

[0040] Fig. 2 schematically represents a cross-section through an encapsulation system according to a second embodiment of the invention in which the antenna connection means is arranged on the second substrate.

[0041] Fig. 3 schematically represents a cross-section through an encapsulation system according to a third embodiment of the invention in which the antenna connection means is also arranged on the second substrate.

[0042] Figure 4 schematically represents a cross-section through an encapsulation system according to a fourth embodiment of the invention.

[0043] Figure 5 schematically illustrates an example of a method according to the invention. Detailed description of the invention

[0044] In the following, the same reference numerals on the figures are used for elements of the same type. The figures are schematic representations which, for the sake of readability, are not to scale. In particular, the thicknesses in the Z direction of the individual elements in Figures 1 to 4 are not to scale either relative to each other or relative to the dimensions of the elements in the Y direction.

[0045] Figure 1 schematically represents the cross-section of the first embodiment of the encapsulation system of the invention. It shows an encapsulation system 1 of a SAW device 3 comprising a base substrate 5 and at least one interdigital transducer 7, or 'IdT', having two metal electrodes with interdigital combs. The SAW device 3 may include other elements, such as at least one mirror, at least one resonance cavity, electrical connections, electronic components, etc. Figure 1 further shows a sealing bead 9 sealing a second substrate 11 onto the base substrate 5 so as to form a cavity 13.

[0046] The basic substrate 5 and the second substrate 11 are arranged substantially in the xy plane in the Cartesian coordinate system illustrated in [Fig. 1]. Thus, the basic substrate 5 has, relative to the z-axis, a top face 5a and a bottom face 5b. Similarly, the second substrate 11 has a top face 1a and a bottom face 11b. Also shown schematically is a radio frequency connector 15, in particular a miniature coaxial radio frequency connector, arranged externally to the cavity 13 on the base substrate 5. The SAW device 3 is electrically connected to the radio frequency connector 15 using an electrical connection 17, for example a conductive metal connection pad 19 disposed on the upper face 5a of the base substrate 5. The electrical connection 17 extends from the inside of the cavity 13 through the sealing cord 9 to the radio frequency connector 15.

[0047] The basic substrate 5 is a piezoelectric substrate, for example a bulk type substrate or piezoelectric on insulator (POI). For example, the basic substrate 1 is a single-crystal quartz substrate SiO2, in particular with a crystal orientation ST section.

[0048] Other piezoelectric materials are conceivable for the basic substrate 5, such as lithium tantalate (LiTaO3), lithium niobate (LiNbO3), aluminium nitride (AIN), zinc oxide (ZnO), gallium orthophosphate (GaPO4), barium titanate (BaTiO3), langasite (La3Ga5SiO14), langanite (La3Ga5.5NbO.5O14), gallium nitride (GaN), lead zirconate titanate (PZT) or langatate (La3Ga5.5TaO.5O14).

[0049] The second substrate 11 is preferably of the same material as the base substrate 5. By choosing the same material for the second substrate 11, the difference in thermal expansion between the two substrates is reduced. Thus, the device can be used over a wide temperature range, for example from 75 K to 700 K, without being subjected to mechanical stresses induced by temperature changes. This improves the durability of the encapsulation system 1.

[0050] The second substrate 11 is sealed onto the first substrate 5 using the sealing bead 9. In the case of a base substrate 5 and a second substrate 11 made of quartz, a glass frit seal is preferably used to form the sealing bead 9 surrounding the transducer 7 arranged on the upper face 5b of the base substrate 5.

[0051] Due to the material correspondence, glass frit sealing is particularly recommended in the present case of the choice of quartz as the material of the base substrate as well as the second substrate, since the coefficient of expansion remains essentially the same.

[0052] Depending on the choice of substrate material, another method of sealing the substrates can be used, for example anodic welding, bonding or eutectic bonding.

[0053] Preferably, the sealing cord 9 is arranged so as to leave a space dl around the transducer 7 and any other element of the SAW device 3, so as not to interfere with its operation. Typically, the space dl is at least 450 pm, preferably at least 500 pm.

[0054] Another space d2, typically of at least 5 pm, in particular between 6 pm and 9 pm, is granted between the lower face 11b of the second substrate 11 and the upper edge in the Z direction of the transducer 7 or any other element of the SAW device 3.

[0055] The contour defined by the sealing cord 9 on the upper face 5a of the base substrate 5 can be substantially circular, rectangular, or customized according to the arrangement of the SAW device 3 and its components, or according to the surface of the base substrate 3 requiring protection by encapsulation.

[0056] The assembly of the base substrate 5, with the sealing cord 9 and the second substrate 11 creates the cavity 13 inside the assembly in which the sensitive parts of the SAW device 3 are located. Thus, encapsulation of said sensitive parts, and in particular of the transducer 7, is established. In some embodiments, the cavity in which the transducer 7 is located can be placed under vacuum or under a controlled atmosphere, such as a nitrogen atmosphere.

[0057] In this embodiment, the chosen antenna connection means is the radio frequency connector 15. Preferably, the radio frequency connector 15 is a Hirose U.FL type male connector, chosen as the antenna connection means for remote interrogation of the SAW 3 device.

[0058] This connector is particularly advantageous because of its small size, with a diameter of approximately 1.25mm and a coupling height of less than 2mm, and its conduction properties, with a bandwidth of up to 18GHz.

[0059] This connector also exhibits a robustness of at least 10,000 coupling cycles.

[0060] Other miniature or micro-miniature coaxial connectors than the Hirose type U.FL are nevertheless conceivable, and in particular connectors according to IEC 61169-1 such as MCX, MMCX, SSMA, SSMB connectors, and in particular radio frequency connectors according to IEC 61169-65 or according to IEC 61169-64.

[0061] The electrical connection 17, made by the metal pad 19, establishes a communication link with the interdigital transducer 7 and allows the transmission of radio frequency signals in the context of an interrogation of the SAW device 3.

[0062] By the embodiment described above and illustrated in [Fig.1] an encapsulation system 1 of SAW device 3 is obtained comprising at least one interdigital transducer 7 formed on a basic substrate 1, protecting the sensitive parts of the SAW device against risks presented by the environment, in particular chemical pollution, mechanical shocks, and / or excessively high temperatures or pressures.

[0063] Thanks to the integration of a radio frequency connector 15 for interrogating the SAW 3 device directly into the encapsulation system of said SAW device, a versatile, economical and reliable SAW 3 device protection solution is obtained.

[0064] This embodiment is particularly advantageous because it avoids modifying or degrading the second substrate 11 to establish the link between the antenna connection means and the interdigital transducer 7. In an additional advantage, this embodiment allows for obtaining a thin encapsulated device in the Z direction.

[0065] According to a second embodiment of the invention illustrated in [Fig.2], the radio frequency connector 15 is arranged on the second substrate 11. This embodiment differs from the embodiment described above relating to [Fig.1] in particular by this different arrangement of the radio frequency connector 15, as well as by the separate implementation of the electrical link 17 between the radio frequency connector 15 and the interdigital transducer 7.

[0066] The encapsulation system 21 according to the second embodiment represented by [Fig.2] comprises, like the first embodiment represented by [Fig.1], the SAW device 3 with the base substrate 5 and the interdigital transducer 7 as well as the sealing cord 9 sealing the second substrate 11 onto the base substrate 5 so as to form the cavity 13. [Fig.2] also schematically illustrates the radio frequency connector 15 arranged externally to the cavity 13 on the upper face of the second substrate 11 and interfaced by the electrical link 17 with the interdigital transducer 7.

[0067] In this embodiment illustrated in [Fig. 2], at least one via 23, here two vias, passes through the second substrate 11 to allow an electrical connection between the radio frequency connector 15 and the SAW device 3, in particular the transducer 7. In this embodiment the electrical connection is made via an electrical routing 25 disposed on or in the upper surface lia of the second substrate 11, but according to a variant the radio frequency connector may be in direct contact with the vias 23. Inside the cavity 13, the electrical connection of the vias 23 with the SAW device 3 is made by using one or more solder beads or solder bumps 27, also called bumps, placed in the cavity 13 between the SAW device 3, in particular its transducer 7, and the lower face 11b of the second substrate 11 establishing an electrical link with vias 23 in the second substrate 7.

[0068] Implementing this second embodiment also provides a versatile, economical, and reliable SAW device protection solution. In particular, this embodiment is advantageous because it avoids interrupting and degrading the sealing bead 9 and allows for a thinner device in the Y direction. This embodiment offers an additional advantage due to its particularly rapid manufacturing process, requiring only a single sealing step. No assembly of parts or connections is necessary after sealing the base substrate 5 with the second substrate 11.

[0069] According to a third embodiment of the invention illustrated in [Fig.3], a radio frequency connector 15 is arranged on the second substrate 11 and interfaced with an interdigital transducer 7 by an electrical link 17 comprising a wired cabling 33.

[0070] The third embodiment represented by [Fig.3] includes another encapsulation system 31. In the third embodiment, the radio frequency connector 15 is positioned on the upper face 1 of the second substrate 11, but the electrical connection with the SAW device 3 is no longer made using vias 23 as illustrated in the second embodiment of the invention.

[0071] In this third embodiment, the electrical link 17 comprises the conductive metal pad 19 passing through the sealing cord 9 as in the first embodiment and, in addition, a wire 33. The wire 33 establishes the electrical connection between the conductive metal pad 19, which interfaces with the interdigital transducer 7 of the SAW device 3, and the antenna connection means. This connection can be direct or via a conductive layer 35 arranged on the upper surface 1 of the second substrate 11, on which the antenna connection means, in particular a radio frequency connector 15, is arranged.

[0072] Thus this third embodiment also presents a versatile, economical and reliable SAW device protection solution.

[0073] The fourth embodiment shown in [Fig. 4] is based on the first embodiment and comprises an encapsulation system 41 with a metallic layer 43 on the lower face 5b of the base substrate 5. In addition, at least one, here Two metallic vias, 45a and 45b, are formed in the base substrate 5. One metallic via 45a traverses the base substrate completely from the lower face 5b to the upper face 5a. Another via 45b traverses the base substrate 5 only partially, starting from the lower face 5b but not reaching the upper face 5a. The via 45b therefore does not modify the composition of the upper face 5a of the base substrate 5.

[0074] The metallic layer 43 and the vias 45a, 45b improve the thermal conductivity between the ambient environment of the encapsulated SAW 3 device and the interior of the cavity 13 in which the interdigital transducer 7 is disposed. The vias 45a, 45b form thermal bridges in the base substrate 5. They thus represent points of increased thermal conductivity in the base substrate 5 of the SAW 3 device which can direct thermal energy from the encapsulated cavity 13 to the ambient environment.This improves the use of the encapsulation system that is the subject of the invention, particularly when the SAW 3 device is arranged as a temperature sensor.

[0075] The vias 45a, 45b are arranged so that they are electrically isolated from the interdigital transducer(s) 7. This ensures the proper functioning of the SAW 3 device. In particular, it reduces the risk of short-circuiting the electrodes of an interdigital transducer.

[0076] For example, as illustrated in [Fig. 4], one or more non-through metallic vias 45b may be arranged opposite the interdigital transducer 7. Alternatively or additionally, in areas of the SAW device 3 that do not interfere with the operation of the interdigital transducer 7, through-through vias 45a may be arranged in the base substrate 5. Thus, thermal conductivity is increased without interfering with the proper functioning of the SAW device 3 and, in particular, of the interdigital transducer 7, which is sensitive to variations in the frequency of elastic surface waves on face 5a. In other embodiments, the use of through-through metallic vias 45a or non-through-through metallic vias 45b may be omitted or combined depending on the structure and dimensions of the encapsulation system 1, 2, 3, 4.

[0077] Furthermore, in order to optimize the homogenization of the temperature of the SAW device, several vias 45a, 45b can be arranged in matrix form for better thermal distribution, and this in a suitable way so as not to hinder the creation and propagation of the elastic wave.

[0078] The metallic vias 45a, 45b and the metallic layer 43 disposed on the lower face 5b of the base substrate 5 are preferably made of the same metallic material. This allows them to be manufactured together in a single production step and facilitates the migration of heat fluxes.

[0079] Thus, this fourth embodiment also presents a solution for protecting A versatile, economical, and reliable SAW device that is also optimized for a SAW device configured as a temperature sensor. Depending on the variant, this fourth mode can also be implemented based on the second or third embodiment.

[0080] A method for manufacturing a SAW device encapsulation system is described with reference to [Fig. 5], according to a fifth embodiment of the invention. This method can be implemented, for example, to obtain an encapsulation system as illustrated in Figures 1 to 4. [Fig. 5] shows a number of steps to be performed sequentially.

[0081] The process begins with step El of supplying a basic substrate 5 comprising at least the interdigital transducer 7. For example, a basic substrate 5 is supplied in ST-cut quartz.

[0082] During step E3, a second substrate 11 is sealed onto the base substrate 5 so as to form a cavity 13 surrounding the transducer(s) 7. The second substrate 11 can be sealed with the base substrate 5 using glass frit and forming a sealing bead 9 to obtain the cavity 13.

[0083] In step E5A, an antenna connection means, such as a radio frequency connector 15, is arranged externally to cavity 13 on the base substrate 5. Alternatively, in step E5B, the antenna connection means is arranged on the second substrate E5B or on the electrical routing 25, 35 outside of cavity 13. The radio frequency connector 15 is, for example, arranged by soldering onto the electrical routing 25, 35 or the metal pad 19.

[0084] For example, a miniature coaxial radio frequency connector such as a Hirose type U.FL connector can be arranged on a basic substrate 5 or a second substrate 11.

[0085] Step E5A or E5B can be performed after step E3 as described, but alternatively the connection means can also be arranged before the sealing step E3. The method according to the invention further includes an electrical connection step of the interdigital transducer with the antenna connection means, as illustrated, for example, by the electrical link 17 in embodiments one to four described above.

[0086] In an embodiment of the method according to the invention, the base substrate 5 provided in step 11 may comprise a metallic layer 43 on its lower face 5b and at least one metallic via 45a, 45b. An encapsulation system according to the fourth embodiment illustrated in [Fig. 4] can thus be obtained. In this embodiment, the via(s) 45a, 45b may be through-hole or non-through-hole, so as to be electrically isolated from the interdigital transducer 7. Furthermore, in this embodiment, the metallic layer 43 and the metallic via 45a, 45b in the supplied base substrate 5 may be made of the same material. This, on the one hand, increases the compatibility of thermal conduction between layer 43 and vias 45a, 45b, and on the other hand to achieve a combined one-step production of the vias 45a, 45b and the metal layer. 43

[0087] In another embodiment of the method according to the invention, the second base substrate 11 sealed onto the base substrate 5 in step E3 may include at least one via 23. Solder beads or bumps 27 are placed so as to obtain an electrical connection of at least one transducer 7 with the antenna connection means using at least one via 23. Thus, an encapsulation system according to the second embodiment illustrated in [Fig. 2] can be obtained.The process according to this variant has the advantage of particularly rapid manufacturing: thus, by preparing the second substrate 11 with the electrical routing 25, the radio frequency connector 15 and the via(s) 23, and by placing the corresponding solder beads or bumps 27 on the SAW device 3, the encapsulation system 21 can be completed in a single sealing step. It is preferable to place the beads or bumps during this sealing step ii to avoid melting or degradation of the solder beads or bumps during a subsequent sealing step. No assembly of parts or connections is required after sealing the base substrate 5 with the second substrate 11.

[0088] As described in the preceding sections, a more robust, compact and economical encapsulation system than previously known is thus obtained.

[0089] Of course, the invention is not limited to the modes of implementation and examples described, and alternative embodiments can be made without departing from the scope of the invention.

Claims

Demands

1. Surface elastic wave device (SAW device) encapsulation system, comprising said SAW device (3) comprising at least one base substrate (5) and an interdigital transducer (7) formed on said base substrate (5); a sealing cord (9) that seals a second substrate (11) with said base substrate (5) so as to form a cavity (13) enveloping said interdigital transducer (7); and a connection means for connecting an antenna (15) linked to at least one interdigital transducer (7);characterized in that said antenna connection means (15), in particular a miniature coaxial radio frequency connector, is arranged externally to the cavity (13) on the base substrate (5) or on the second substrate (11), wherein the link (17) between said interdigital transducer (7) and the antenna connection means (15) comprises at least one via passing through the second substrate (11), and using one or more solder beads (27) placed in the cavity (13) between the SAW device (3), in particular its transducer (7), and the second substrate (11) establishing an electrical link with the vias (23) in the second substrate (7).

2. Encapsulation system according to claim 1, wherein the link (17) between said interdigital transducer (7) and the antenna connection means (15) comprises a wire cabling (33).

3. Encapsulation system according to claim 1 or 2, wherein the link (17) between said interdigital transducer (7) and the antenna connection means (15) comprises at least one metallic pad (19) formed on the base substrate (5) and passing through the sealing cord (9).

4. Encapsulation system according to any one of the preceding claims, comprising a metallic layer (43) on the face (5b) of the base substrate (5) opposite the second substrate (11).

5. An encapsulation system according to any one of the preceding claims, wherein the base substrate (5) comprises at least one metallic via (45a, 45b), in particular a via (45a, 45b) made of the same material as a metallic layer (43) on the face (5b) of the base substrate (5) opposite the second substrate (11) and arranged so as to be electrically isolated from the interdigital transducer (7).

6. Encapsulation system according to any one of the preceding claims, wherein the sealing cord (9) is formed by anodic welding or by glass frit.

7. Encapsulation system according to the preceding claim, wherein the sealing cord (9) is formed by glass frit, and the material of said glass frit of the sealing cord (9) is chosen so as to have a coefficient of expansion corresponding to that of the material of the base substrate (5) and / or the second substrate (11).

8. Encapsulation system according to any one of the preceding claims, wherein the second substrate (11) comprises the same material as the base substrate (5).

9. A method for manufacturing a SAW device encapsulation system, the method comprising the following steps: i. Providing a base substrate comprising at least one interdigital transducer; ii. Sealing a second substrate onto the first substrate so as to form a cavity enclosing said interdigital transducer(s); iii.External arrangement to the cavity of an antenna connection means, in particular a miniature coaxial radio frequency connector, on the base substrate or the second substrate, wherein the second substrate of step ii) is provided with at least one via and further comprising an electrical connection step of at least one transducer with the antenna connection means using the at least one via, using one or more solder beads placed in the cavity between the SAW device, in particular its transducer, and the second substrate establishing an electrical link with the vias in the second substrate.

10. Method according to claim 9 for manufacturing an encapsulation system according to any one of claims 1 to 8.

11. A manufacturing method according to claim 9 or 10, wherein the base substrate supplied in step i) comprises a metallic layer on the opposite face to the second substrate and / or at least one metallic via.

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