DE102018130145B4 - Electroacoustic resonator device and method for its production - Google Patents

Abstract

An electroacoustic resonator device comprises a resonator section (110) and a substrate (210). A layer of anisotropic conductive resin (330) is placed between the resonator section and the substrate to create electrical contact between a conductive contact region (227) of the substrate and a conductive layer (153) of the resonator section.

Description

Technical field

The present disclosure relates to an electroacoustic resonator device. The present disclosure particularly relates to an electroacoustic resonator device comprising a resonator section and a substrate section to which the resonator section is attached. The resonator section comprises an acoustically active area and a cover arranged above it.

background

Electroacoustic resonator devices are widely used in electronic systems. A resonator comprises a pair of electrodes in connection with a piezoelectric layer. A resonating acoustic wave is generated by applying an electrical RF signal in the piezoelectric material. Electroacoustic resonators can be used in electronic RF filters or other RF components that take advantage of the frequency-selective function of the resonators. Electroacoustic resonators can be designed as surface acoustic wave (SAW) resonators if the electrodes are arranged on one side of the piezoelectric material, or as acoustic bulk wave (BAW) resonators if the piezoelectric material is sandwiched between the pair of electrodes be.

The acoustically active area of SAW and BAW resonators must be protected from environmental influences. A possibility of protection comprises a cover which is arranged on the acoustically active area, as a result of which a cavity is formed above the acoustically active area, so that the resonance space is protected from the surroundings, the cover not influencing the acoustic operation. Such a dome-shaped cover is available under the trade name Thier Film Acoustic Package (TFAP). Furthermore, the device can be accommodated in an injection-molded housing in order to increase the mechanical stability and to provide further protection and functionality in the form of a coil inductance and a soldering interface for the customer.

Although a TFAP provides adequate protection for resonators operated under controlled conditions, for example in communication devices and other electronic systems, the use of resonators under harsh environmental conditions, such as can occur in the automotive field or industrial applications in the manner of process control or others, requires additional protective measures . These applications are characterized by a relatively wide temperature range and humid environmental conditions.

document US 2014/0333177 A1 discloses an electroacoustic resonator device that can operate reliably under harsh operating conditions.

An object of the present disclosure is to provide an electroacoustic resonator device that can operate reliably under harsh operating conditions.

Another object of the present disclosure is to provide an electroacoustic resonator device that can be used in automotive and industrial applications.

Another object of the present disclosure is to provide a method of manufacturing an electroacoustic resonator device that can be operated under harsh environmental conditions such as in automotive and industrial applications.

short version

One or more of the above-mentioned objects are achieved by an electroacoustic resonator device which comprises the features of the present claim 1.

According to one embodiment, an electroacoustic resonator device comprises a resonator section and a substrate to which the resonator section is attached. The resonator section has an acoustically active area and a cover arranged above the acoustically active area. A conductor track is coupled to the acoustically active area. The conductor track can be connected to an electrode of the resonator section. A conductive layer is connected to the conductor track and extends onto the cover. A layer of anisotropic conductive resin is disposed between the substrate and the resonator section. The substrate has a conductive contact area so that the anisotropic conductive resin creates an electrically conductive path between the contact area of the substrate and the conductive layer. As a result of the anisotropic mode of operation of the resin, conductivity is achieved within the overlap of the contact area with the conductive layer, while no conductivity is generated outside this overlap area. The anisotropic conductive resin covers the surface of the resonator and hermetically seals the surface of the resonator. Accordingly, the anisotropic conductive resin has a dual function of providing electrical conductivity between the Resonator section and the substrate and the hermetic sealing of the resonator section. One or more resonator sections can be provided in the resonator. The principles of the present disclosure are applicable to one resonator section and also to several or many resonator sections. Several resonator sections can be accommodated in some chips arranged on a carrier substrate.

The conductive region of the substrate can comprise a metallization region. Another metallization area can be arranged on the conductive layer of the resonator section. Both metallization areas are opposite to each other, so that the conduction path is generated between the metallization area of the substrate and the other metallization area arranged on the conductive layer of the resonator section, where both areas have an overlap when they are superimposed. The anisotropy of the resin provides electrical insulation in the lateral or horizontal direction outside the direct path between the two metallization areas.

The anisotropic conductive resin may include a cured epoxy and conductive particles. The conductive particles create the electrically conductive path between the metallization region of the substrate and the other metallization region of the resonator. The epoxy resin provides the hermetic seal and good protection against the ingress or migration of moisture in the manner of water, water vapor, acids and other aggressive substances.

The metallization regions of the substrate and the resonator section are formed from metal. The metal can be one of copper, nickel, chrome and gold. The metallization regions can be formed from a single one of the metals or a composition in the manner of an alloy of the metals. The metallization areas can also be a layer stack of the metals or compositions / alloys of the metals.

According to embodiments, the electroacoustic resonator device can comprise a surface acoustic wave (SAW) resonator, which comprises at least one electrode arranged on a piezoelectric layer. The electrodes may comprise an array of several hundred interdigitated fingers. The conductor track is connected to one of the electrodes. The piezoelectric layer can be a bulk layer or a thin film layer which is arranged on a substrate. The piezoelectric material can be lithium tantalate, lithium niobate, aluminum nitride or aluminum scandium nitride or another piezoelectric material.

In accordance with embodiments, the resonator may be an acoustic bulk wave (BAW) resonator comprising a piezoelectric layer sandwiched between upper and lower electrodes, the interconnect being connected to one of the upper and lower electrodes. Although the cavity above the acoustically active area is provided by the cover, another cavity or a reflective element such as a fixed Bragg mirror is arranged below the acoustically active area in order to prevent scattering of acoustic energy.

The cover, which surrounds the cavity, has a dome shape, which is arranged above the acoustically active area. The cover can comprise a layer stack of a lowermost cover layer which faces the cavity and is arranged directly opposite the acoustically active area. The cover layer can consist of an oxide in the manner of silicon dioxide. A sealing layer made of a smooth polymer material in the manner of benzocyclobutene (BCB) can be arranged thereon. A reinforcing layer made of a relatively rigid, rigid material can be arranged thereon, which can consist of a nitride in the manner of silicon nitride. When using a cured anisotropic conductive resin, the pressure exerted on the top layer stack during its manufacture is only moderate and much less than in a conventional process in which molding pressure is used to fill the gap between the resonator and the substrate. The layers of the layer stack can be dimensioned with a lower mechanical stability, so that the thicknesses of layers can be reduced. On the other hand, the hermetic seal achieved with the anisotropic conductive resin increases the mechanical stability of the arrangement, so that one or more layers of the top layer stack can be produced with a smaller thickness.

According to one embodiment, the conductor track of the resonator section, which is connected to one of the electrodes, extends from an area below the cavity, crossing the cover layer stack, to an area outside the cavity and outside of the cover layer stack. The conductor track forms a contact area with which the conductive layer is connected. The contact area is located outside the cavity and outside the cover. The conductive layer is disposed on the cover and folded back from the contact area to an area on the cover and the cavity. A conductive contact area is opposite to the conductive layer arranged conductive contact area of the substrate, so that an electrically conductive path between the conductive contact areas of the substrate and the conductive layer is generated by the anisotropic conductive resin.

The substrate may comprise a laminate of several layers of the polymer resin type, one or more metal lines and vias being arranged within the laminate and between the layers. The leads may extend from one side of a layer to the other side of the layer through a via in the vertical direction and along one side of the layer in the lateral or horizontal direction in order to redistribute the contacts connected to the resonator to another arrangement of contacts on the to reach opposite side of the laminate.

One or more of the above-mentioned objects are also achieved by a method according to the features of the present claim 12.

According to the method, a resonator section and a substrate section are provided. The resonator section has an acoustically active region, a cover arranged thereon, a conductor track connected to an electrode of the acoustically active region and a conductive layer connected to the conductor track. The conductive layer extends onto the cover. An anisotropic conductive paste is then applied either to the resonator or to the substrate. Then the resonator and the substrate are brought closer to one another or connected to one another. The anisotropic conductive paste can cure to produce a cured anisotropic conductive resin that effects the conduction path between the resonator and the substrate. The approach between the resonator and the substrate can be done by applying mechanical pressure to the substrate and the resonator. The approximation can also be done at an elevated temperature if a thermosetting resin is used. The temperature can range from more than 100 ° C to 170 ° C.

The anisotropic conductive paste can be applied to the resonator section or the substrate by a printing process in the manner of a screen printing. A coating process such as spin coating can also be used. The anisotropic conductive paste can be applied on the wafer level or after the wafer has been divided into individual chips.

It is to be understood that both the foregoing general description and the following detailed description are intended to be exemplary only and are intended to provide an overview or framework for understanding the nature and nature of the claims. The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments and, together with the description, serve to explain the principles and operation of the various embodiments. The same elements in different figures of the drawings are designated by the same reference numbers.

Figure list

• 1 einen Querschnitt eines Resonatorabschnitts in einem anfänglichen Schritt,
• 2 den Eingriff des Resonatorabschnitts mit einem Laminatsubstrat und einer dazwischen angeordneten anisotropen Leitpaste in einem nachfolgenden Herstellungsschritt,
• 3 die fertige Resonatorvorrichtung, die ein gehärtetes anisotropes leitendes Harz und eine geformte Baugruppe aufweist, und
• 4 einen Teil des Querschnitts aus 3 in weiteren Einzelheiten.

Show it:

• 1 3 shows a cross section of a resonator section in an initial step,
• 2nd the engagement of the resonator section with a laminate substrate and an anisotropic conductive paste arranged between them in a subsequent manufacturing step,
• 3rd the finished resonator device having a hardened anisotropic conductive resin and a molded assembly, and
• 4th part of the cross section 3rd in more detail.

Detailed description of embodiments

The present disclosure will now be described more fully with reference to the accompanying drawings, in which embodiments of the disclosure are shown. However, the disclosure can be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided to fully convey the scope of the disclosure to those skilled in the art. The drawings are not necessarily to scale, but are intended to clearly illustrate the disclosure.

1 shows a cross section of a surface acoustic wave resonator. The resonator was manufactured as a semi-finished product. The resonator 100 comprises a piezoelectric substrate 110 made of lithium tantalate or lithium niobate. The substrate 110 can be a bulk substrate or a thin film substrate, which is further arranged on a carrier substrate. There are two resonators 120 , 130 shown. Each resonator comprises a metal electrode made of interdigitated fingers 121 , 131 that are on the surface of the piezoelectric substrate 110 are arranged. A cover 140 is over the electrodes 121 , 131 arranged, the cover having a dome-shaped portion above each of the electrodes, creating a corresponding cavity 122 , 132 is included. Conductor tracks 151 , 152 are with the respective electrodes 121 , 131 connected and carry the electrical signal at the electrodes 121 , 131 out of the cavity and into the outer area of the cover 140 . A corresponding conductive layer 153 , 154 is with the respective conductor tracks 151 , 152 connected and leads the electrical signal to a location on the cover 140 .

By applying an electrical signal to the electrodes 131 , 121 through the conductive layers 153 , 154 will be below the electrodes inside the piezoelectric substrate 110 generates a resonating wave. The electrodes and the adjacent section of the substrate form an active area in which the electroacoustic operation takes place. The cavities 122 , 132 allow free acoustic functionality within the active area in that they avoid mechanical contact with the acoustically active area. The cover 140 protects the acoustically active area from environmental or mechanical influences. Although the figures show the principles of the present disclosure in connection with a SAW resonator, they are also applicable to the concept of a BAW resonator. In this case, the acoustically active region comprises upper and lower electrodes, a piezoelectric layer being sandwiched between the upper and lower electrodes.

Regarding 2nd A subsequent process step is shown during the manufacture of a resonator device. 2nd shows a laminate substrate 210 that is multiple layers 210a , 210b , 210c based on polymer resin. Metallization areas in the form of metal contact points 221 , 223 , 225 , 227 are on both sides of the main surfaces of the laminate 210 arranged. Electrical lines routed through the laminate provide an electrical connection between the contact points 223 , 227 on one side of the laminate to the contact points 221 , 225 ready on the other side of the laminate. The contact points 225 , 227 are through a vertical line or a vertical via 226 which passes through the three layers of the laminate. The administration 222 connects the contact points 223 and 221 in that it consists of vertical and horizontal line / via sections 222b , 222a exists through the laminate layer 210b and through the area between the laminate layers 210b and 210c such as 210a and 210b are led. The laminate 210 allows redistribution of the on the side facing the resonator 100 faces, received signals on contact points on the outside of the device.

An anisotropic conductive adhesive 250 in the form of an anisotropic conductive paste (ACP) or an anisotropic conductive film (ACF) is between the resonator section 100 and the laminate 210 arranged. According to one embodiment, the ACP 250 by a screen printing process or a spin coating process on the substrate 210 upset. According to another embodiment, the ACP 250 by screen printing or spin coating on the resonator section 100 be applied. The resonator section 100 may at this point be part of a larger wafer, of which the 1 and 2nd only that the resonators 120 , 130 showing section. Alternatively, the resonator section 100 already be separated from the wafer, so that it is a separate piece. In this example, the resonator section 100 turned so that the top of the cover 140 the laminate 210 faces.

The anisotropic conductive paste 250 is made of a resin 251 composed of a multitude of small conductive particles 252 having. The particles 252 are about the resin 251 distributed. Several types of resin are possible. In one embodiment, the resin is 251 an epoxy type resin. The epoxy resin may comprise at least two components, which in the in 2nd process step shown are fed separately and mixed together.

As with arrows 260 is indicated, a mechanical pressure on the back of the turned resonator section 100 and the laminate 260 exercised so that the top surface of the cover 140 the adjacent surface of the laminate 210 is approaching. If a thermosetting resin composition 251 is used, this process can be carried out at an elevated temperature in the range, for example, between 100 ° C and 170 ° C. Although the room temperature can also be sufficient to cure the epoxy resin, the curing process is accelerated by an elevated temperature. During the application of mechanical pressure 260 and / or, if applicable, heat cures the resin 251 . The conductive particles 252 can be in the area between the contact points 223 , 227 and the oppositely arranged conductor tracks 154 , 153 concentrate so that an electrically conductive path is created in between. The curing of the epoxy resin ensures that the electrical contact and the mechanical relationship of the elements with respect to one another are maintained. The conductive particles 252 are set up along the route between the contact points 223 , 227 and the oppositely arranged conductive layers 154 , 153 , which is the in 2nd vertical orientation shown is to produce electrical conductivity, wherein essentially no electrical conductivity is generated in the lateral or horizontal direction. This is due to the anisotropic functioning of the anisotropic conductive paste 250 attributed.

The resulting arrangement is in 3rd shown, the resonator section 100 and the laminate 210 were brought closer together. It is a polymer form 310 trained, which provides mechanical protection. That comes from the anisotropic conductive paste 250 resulting hardened anisotropic conductive epoxy 330 is between the laminate substrate 210 , the resonator section 100 and the shape 310 locked in. In particular, the area between the cover 140 and the substrate 110 that at 321 is circled, and the connection between the form 310 and the laminate 210 that at 322 is circled, hermetically sealed. The use of an epoxy resin makes the seal particularly watertight and prevents the migration of moisture in the manner of water vapor from the external environment into the cavities and into the acoustically active areas, which could be corroded by the ingress of water. Such a hermetic seal achieved through the use of the anisotropic conductive paste enables the production of an electroacoustic resonator device which can be operated in harsh environmental conditions, for example in the automotive field or in industrial applications.

Regarding 4th is the section 350 out 3rd presented in more detail. The in 4th The cross section shown shows the electrodes 121 made up of interlocking fingers of the resonator 120 consist. A dome-shaped top layer stack 140 confines a cavity above the active area. The top layer stack 140 comprises a lowermost silicon dioxide layer 441 , a BCB polymer layer arranged thereon 442 and a cover layer 443 made of silicon nitride. A conductor track 151 is with the electrode 121 connected and extends from the electrode through the cover layer 140 to a contact area 451 outside the top layer stack 140 . A stack of layers 153 forms a conductive layer on the cover 140 that differ from the contact area 451 to the top of the cover 140 extends. The conductive layer 153 is a composite layer consisting of a lower seed layer made of titanium, a layer made of copper and an upper layer made of nickel. A metallization area 453 is on the cover 140 in contact with the top nickel layer of the conductive layer 153 . The metallization area 453 is opposite to the contact point 227 of the laminate 210 arranged.

The entire space between the resonator section 110 and the laminate 210 is with a hardened anisotropic conductive resin 332 filled that from the previously applied anisotropic conductive paste 250 ( 2nd ) was obtained. By applying pressure and, if applicable, heat during the bonding of the laminate 210 with the resonator section 110 becomes an electrically conductive path 331 between the metallization areas 453 and 227 generated. Due to the anisotropic effect within the anisotropic conductive resin 330 will be in the horizontal direction 332 no electrical conductivity generated. In particular, the anisotropy of the anisotropic conductive resin creates 330 instead of a horizontal route, a vertical route, as in 4th is shown. The only electrically conductive route from the conductive layer 153 to the laminate 210 is at the contact area 227 receive. The neighboring electrical contact 223 on the laminate 210 ( 2nd ) is from the conductive layer 153 far away. Because of the anisotropic conductivity of the layer 330 is between the layer 153 and the contact 223 no electrically conductive path is created. According to the ACP principle, any conductive particles remain within the anisotropic conductive resin 330 in the way of particles 417 , with the exception of the conductive particles between the overlapping, opposite metallization areas 453 and 227 , no short circuit. In particular, the probability of a short circuit and an electrically conductive path between the area 331 of the resonator 120 and the corresponding area of the adjacent resonator 130 essentially zero because of the anisotropic function of the epoxy 330 prevents horizontal conductivity.

The neighboring resonator 130 from which in 4th one section is shown, one on the cover 140 arranged conductive layer 154 on. Between the conductive layer 154 of the resonator 130 and the conductive layer 153 of the resonator 120 there is a gap 461 so that the connections to the active areas of the resonators 130 and 120 due to the horizontal insulation function of the anisotropic conductive resin 330 are isolated from each other.

The resonator section 110 and the laminate 210 are through the hardened adhesive resin 330 glued together over their entire surfaces, whereby the hardened anisotropic conductive resin 330 the surface of the resonator section is completely covered and the entire space within the resonator section 110 and the laminate 210 fills, so that the mechanical stability of the overall device is increased. As a result, the individual layers within the layer stack 140 have a smaller thickness, so that the overall size of the device can be reduced and production can be less expensive.

Another aspect is the joining of the laminate 210 with the resonator section 110 one over the entire surface of the laminate 210 distributed pressure, which prevents selective pressure points, so that the mechanical action on the cover 140 is reduced compared to a conventional mold filling. The metallization areas 453 , 227 can comprise one or more metals. The metals can be selected from the group consisting of copper, nickel, chromium and gold. The metallization areas 453 , 227 can be formed from a layer or a layer stack with one of these metals or a combination or an alloy of these metals.

The metallization areas 453 , 227 can be vertical to the in 4th shown cross section, so that a larger contact area between the resonator section 110 and the laminate 210 can be achieved.

Claims (15)

An electroacoustic resonator device comprising: - a resonator section (100) comprising: - an acoustically active area (121), a cover (140) which is arranged above the acoustically active area, - A conductor track (151), which is coupled to the acoustically active area, and a conductive layer (153) which is connected to the conductor track and extends onto the cover, - a substrate (210) comprising a conductive contact region (227), and - a layer of anisotropic conductive resin (330) disposed between the substrate and the resonator section. Electroacoustic resonator device according to Claim 1 , wherein the conductive contact region (227) of the substrate comprises a metallization region and the resonator section comprises another metallization region (453) which is arranged on the conductive layer (153) in an area opposite to the metallization region (227) of the substrate. Electroacoustic resonator device according to Claim 2 wherein the layer of anisotropic conductive resin (330) comprises a cured epoxy resin (251) and conductive particles (252), the conductive particles forming an electrically conductive path (331) between the metallization region of the substrate (227) and the other metallization region (453 ) of the resonator. Electroacoustic resonator device according to Claim 3 wherein the layer of anisotropic conductive resin (330) provides a hermetic seal of the resonator section. Electroacoustic resonator device according to one of the Claims 2 to 4th wherein the metallization region (227) of the substrate and the metallization region (453) of the resonator section comprise one or more of copper, nickel, chromium and gold. Electroacoustic resonator device according to one of the Claims 1 to 5 , wherein the resonator section (100) comprises a surface acoustic wave resonator which comprises at least one electrode (121) arranged on a piezoelectric layer (110), the conductor track (151) being connected to the at least one electrode. Electroacoustic resonator device according to one of the Claims 1 to 5 , wherein the resonator section (100) comprises a bulk acoustic wave resonator which comprises a piezoelectric layer arranged between at least two electrodes, the conductor track being connected to one of the electrodes. Electroacoustic resonator device according to one of the Claims 1 to 7 , wherein the cover (140) of the resonator section has a dome shape arranged above the acoustically active area (121), thereby enclosing a cavity (122) arranged opposite the acoustically active area. Electroacoustic resonator device according to Claim 8 , wherein the cover (140) comprises a layer stack comprising: - a cover layer (441), which is arranged opposite to the acoustically active region, whereby the cavity (122) is enclosed, wherein the cover layer is formed from an oxide, - a sealing layer (442), which is arranged on the cover layer, wherein the sealing layer is formed from a polymer material, and - a reinforcing layer (443), which is arranged on the sealing layer, wherein the reinforcing layer is formed from a nitride. Electroacoustic resonator device according to Claim 8 or 9 wherein the conductive line (151) of the resonator section extends from an area below the cavity (122) to an area outside the cover, the conductive layer (153) at a contact area (451) located outside the cover with the Conductor is connected, wherein the conductive layer (153) extends from the contact region (451) to an opposite region to the cavity (122) on the cover (140), a conductive Contact region (453) is arranged on the conductive layer (153) in an area opposite to the conductive contact region (227) of the substrate. Electroacoustic resonator device according to one of the Claims 1 to 10th wherein the substrate (210) comprises a laminate of a polymer resin having one or more layers of metal lines (222a, 222b, 226), at least one of the lines being connected to the conductive contact region (223, 227) of the substrate. Method for producing an electroacoustic resonator device, comprising the following steps: - Providing a resonator section (110) comprising: - an acoustically active area (121), a cover (140) which is arranged above the acoustically active area, - A conductor track (151) which is connected to the acoustically active area, and a conductive layer (153) which is connected to the conductor track and extends onto the cover, Providing a substrate (210) which comprises a conductive contact region (227), - Applying a layer of an anisotropic conductive paste (250) on the resonator (100) or on the substrate (210) and - Approaching the resonator and the substrate. Procedure according to Claim 12 wherein the step of approximating the resonator (100) and the substrate (210) is carried out by applying mechanical pressure to the substrate and the resonator. Procedure according to Claim 12 or 13 , wherein the anisotropic conductive paste (250) is hardened and an electrically conductive connection (331) is generated between the conductive layer (153) and the conductive contact region (227) of the substrate. Procedure according to one of the Claims 12 to 14 wherein the step of applying a layer of anisotropic conductive paste (250) comprises printing or screen printing or spin coating the anisotropic conductive paste (250) onto one of the resonator (100) and the substrate (210).

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