CN112217491A

CN112217491A - BAW filter

Info

Publication number: CN112217491A
Application number: CN201910627844.1A
Authority: CN
Inventors: 于洋; 张会会
Original assignee: Beijing Dream Ink Technology Co Ltd
Current assignee: Beijing Dream Ink Technology Co Ltd
Priority date: 2019-07-12
Filing date: 2019-07-12
Publication date: 2021-01-12

Abstract

The invention provides a BAW filter, and relates to the technical field of electricity. The BAW filter provided by the invention comprises; a substrate; a first electrode on a first side of the substrate; the piezoelectric layer is positioned on one surface of the first electrode, which is far away from the substrate; a second electrode on a side of the piezoelectric layer remote from the first electrode; the material of the first electrode and the second electrode is low-melting-point metal, and the low-melting-point metal is a simple metal with a melting point below 300 ℃, an alloy, a mixture of the simple metal and the alloy, or a curable conductive fluid with the simple metal and/or the alloy as a main component. The technical scheme of the invention can simplify the manufacturing method of the BAW filter and reduce the manufacturing cost of the BAW filter.

Description

BAW filter

Technical Field

The invention relates to the technical field of electricity, in particular to a BAW filter.

Background

Miniaturization, integration and high performance are requirements of the wireless terminal on frequency devices. The traditional solutions for rf/microwave frequency band frequency devices are dielectric filters and Surface Acoustic Wave (SAW) filters. The former has better performance but too large volume, while the latter has the disadvantages of low working frequency, large insertion loss and low power capacity although the volume is small. Bulk Acoustic Wave (BAW) filter technology is the only radio frequency filter technology which is expected to be integrated at present, integrates the advantages of superior performance of a dielectric filter and small size of an SAW filter, overcomes the defects of the two, and has the advantages of high working frequency, large power capacity, low loss, small size, good temperature stability, integration with an RFIC or an MMIC and the like.

In the prior art, a BAW filter is manufactured on a high-resistance silicon substrate and comprises a sandwich structure consisting of a lower electrode, a piezoelectric motor and an upper electrode, the manufacturing of the BAW filter follows the planar manufacturing technology of a large-scale integrated circuit, the process procedures of the BAW filter comprise cleaning, film coating, masking, photoetching, etching, stripping and the like, and the manufacturing method is complex and the manufacturing cost is high.

Disclosure of Invention

The invention provides a BAW filter, which can simplify the manufacturing method of the BAW filter and reduce the manufacturing cost of the BAW filter.

The invention provides a BAW filter, which adopts the following technical scheme:

the BAW filter comprises;

a substrate;

a first electrode on a first side of the substrate;

the piezoelectric layer is positioned on one surface of the first electrode, which is far away from the substrate;

a second electrode on a side of the piezoelectric layer remote from the first electrode;

the material of the first electrode and the second electrode is low-melting-point metal, and the low-melting-point metal is a simple metal with a melting point below 300 ℃, an alloy, a mixture of the simple metal and the alloy, or a curable conductive fluid with the simple metal and/or the alloy as a main component.

Optionally, the first electrode and/or the second electrode are made of the low melting point metal by one or more of screen printing, steel screen printing, pad printing, gravure printing, letterpress printing, and flexography printing.

Optionally, the metal simple substance with the melting point below 300 ℃ is one of a gallium simple substance, an indium simple substance, a tin simple substance, a sodium simple substance, a potassium simple substance, a rubidium simple substance, a cesium simple substance, a zinc simple substance and a bismuth simple substance;

the alloy with the melting point below 300 ℃ is one or more of gallium indium alloy, gallium indium tin alloy, gallium zinc alloy, gallium indium zinc alloy, gallium tin zinc alloy, gallium indium tin zinc alloy, bismuth indium alloy, bismuth tin alloy, bismuth indium zinc alloy, bismuth tin zinc alloy and bismuth indium tin zinc alloy.

Optionally, at least one side of the piezoelectric layer is non-planar.

Optionally, a surface of the first electrode away from the substrate is a plane, and the piezoelectric layer has at least two portions with different thicknesses.

Optionally, a surface of the first electrode away from the substrate is non-planar, and the piezoelectric layer has at least two portions with different thicknesses.

Optionally, a surface of the first electrode, which is away from the substrate, is a non-planar surface, a shape of a surface of the piezoelectric layer, which is away from the substrate, is the same as a shape of a surface of the first electrode, which is away from the substrate, and the thickness of the piezoelectric layer is consistent.

Further, the substrate is obtained by deforming a flexible substrate with a uniform thickness, and the first electrode, the piezoelectric layer and the second electrode are all located in a deformed area of the substrate.

Optionally, one surface of the piezoelectric layer, which is away from the substrate, includes one or more of a folding surface, a cylindrical surface, a conical surface, an elliptic cylindrical surface, an elliptic conical surface, a hyperbolic paraboloid, a conical surface, a cylindrical surface, a spherical surface, or an annular surface.

Optionally, the piezoelectric layer is made of ZnO, AlN, CdS, or PZT.

Optionally, the BAW filter further includes an insulating support and a second electrode connecting line located on the substrate, the insulating support is located at least on one side of the first electrode and the piezoelectric layer, the second electrode is lapped on the insulating support, a through hole is provided on the insulating support, and the second electrode is connected to the second electrode connecting line through an electrical connection located in the through hole.

The invention provides a BAW filter with the structure, because the first electrode and the second electrode of the BAW filter are made of low-melting-point metal, the low-melting-point metal is a simple metal with a melting point below 300 ℃, an alloy, a mixture of the simple metal and the alloy, or a curable conductive fluid taking the simple metal and/or the alloy as main components, after the low-melting-point metal is melted, the electrodes (the first electrode and the second electrode are collectively called) can be manufactured on a substrate or a piezoelectric layer through processes of printing, spraying, transfer printing, screen printing, steel mesh printing, pad printing, intaglio printing, relief printing, flexographic printing and the like, the manufacturing process is not influenced by the surface shapes of the substrate and the piezoelectric layer, the manufacturing method of the BAW filter can be simplified, and the manufacturing cost of the BAW filter can be reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a first schematic structural diagram of a BAW filter according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a BAW filter according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram three of a BAW filter according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a BAW filter according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of a BAW filter according to an embodiment of the present invention;

fig. 6 is a sixth schematic structural diagram of a BAW filter according to an embodiment of the present invention;

fig. 7 is a seventh schematic structural diagram of a BAW filter according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the technical features in the embodiments of the present invention may be combined with each other without conflict.

An embodiment of the present invention provides a BAW filter, and specifically, as shown in fig. 1 to 6, fig. 1 to 7 are respectively a first structural schematic diagram to a seventh structural schematic diagram of the BAW filter provided by the embodiment of the present invention, where the BAW filter includes;

a substrate 1;

a first electrode 2, the first electrode 2 being located on a first side of the substrate 1;

the piezoelectric layer 3 is positioned on one surface of the first electrode 2 far away from the substrate 1;

a second electrode 4, wherein the second electrode 4 is positioned on one surface of the piezoelectric layer 3 far away from the first electrode 2;

the first electrode 2 and the second electrode 4 are made of low-melting-point metals, and the low-melting-point metals are simple metals with a melting point below 300 ℃, alloys, mixtures of the simple metals and the alloys, or curable conductive fluids with the simple metals and/or the alloys as main components.

Because the first electrode 2 and the second electrode 4 of the BAW filter are both made of low-melting-point metal, the electrodes (the first electrode 2 and the second electrode 4 are collectively called) can be manufactured on the substrate 1 or the piezoelectric layer 3 by only melting the low-melting-point metal (if the melting point of the low-melting-point metal is lower than room temperature, the step can be omitted), and then the manufacturing process is not influenced by the surface shapes of the substrate 1 and the piezoelectric layer 3, so that the manufacturing method of the BAW filter can be simplified, and the manufacturing cost of the BAW filter can be reduced.

The substrate 1 in the embodiment of the present invention is any substrate to which a low melting point metal can be adhered, such as one of a polyvinyl chloride substrate, a polyethylene terephthalate substrate, a polybutylene terephthalate substrate, a polypropylene substrate, a polybutylene adipate-terephthalate substrate, a natural rubber substrate, an isoprene rubber substrate, a styrene butadiene rubber substrate, a chloroprene rubber substrate, an ethylene propylene rubber substrate, a nitrile butadiene rubber substrate, a silicone rubber substrate, a polysulfide rubber substrate, a glass substrate, a polyurethane substrate, an acryl substrate, a stainless steel substrate, a silicon substrate, and nylon cloth.

Alternatively, the low melting point metal in embodiments of the present invention may include one or more of gallium, indium, tin, zinc, bismuth, lead, cadmium, mercury, silver, copper, sodium, potassium, magnesium, aluminum, iron, nickel, cobalt, manganese, titanium, vanadium, boron, carbon, silicon, ruthenium, rhodium, palladium, osmium, iridium, platinum, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, scandium, and the like.

Optionally, the metal simple substance with the melting point below 300 ℃ in the embodiment of the invention is one of a gallium simple substance, an indium simple substance, a tin simple substance, a sodium simple substance, a potassium simple substance, a rubidium simple substance, a cesium simple substance, a zinc simple substance, and a bismuth simple substance.

Optionally, the alloy with the melting point below 300 ℃ is one or more of gallium-indium alloy, gallium-indium-tin alloy, gallium-zinc alloy, gallium-indium-zinc alloy, gallium-tin-zinc alloy, gallium-indium-tin-zinc alloy, bismuth-indium alloy, bismuth-tin alloy, bismuth-indium-zinc alloy, bismuth-tin-zinc alloy and bismuth-indium-tin-zinc alloy.

Alternatively, the curable conductive fluid containing the above simple metal substance and/or alloy as a main component may include one or more of a non-metal filler, a resin, a solvent, an auxiliary agent, and the like, in addition to the above simple metal substance and/or alloy.

Alternatively, in the embodiment of the present invention, the first electrode 2 and/or the second electrode 4 are made of low melting point metal by one or more of screen printing, steel screen printing, pad printing, gravure printing, letterpress printing, and flexography printing.

Optionally, the piezoelectric layer 3 in the embodiment of the invention is made of zinc oxide (ZnO), aluminum nitride (AlN), cadmium sulfide (CdS) or lead zirconate titanate (PZT).

The piezoelectric layer 3 of the BAW filter can drive a standing acoustic wave with a wavelength twice the total thickness of the piezoelectric layer 3, the first electrode 2 and the second electrode 4. The standing acoustic wave propagates in the vertical direction (i.e., the thickness direction of the BAW filter).

The parameters that affect the filtering performance of the BAW filter mainly include the following:

piezoelectric coupling coefficient, which determines the degree of energy exchange between the electrical domain and the mechanical domain. The piezoelectric coupling coefficient is determined by the material selected for the piezoelectric layer 3, and if the piezoelectric coupling coefficient is too low, the piezoelectric layer 3 cannot be used to manufacture a BAW filter meeting the bandwidth requirement of mobile phone applications.

The dielectric constant, the impedance level of the BAW filter is determined by the size of the BAW filter, the thickness of the piezoelectric layer 3, the dielectric constant. The piezoelectric layer 3 has a higher dielectric constant, and the size of the BAW filter can be reduced.

The acoustic velocity (longitudinal direction) is lower, and a thinner piezoelectric layer 3 can be used, thereby being beneficial to realizing the lightness and thinness of the BAW filter.

In addition, the performance of the BAW filter is indirectly affected by several other parameters of the piezoelectric layer 3. This will help to improve the ability of the BAW filter to handle high power signals if the piezoelectric layer 3 has a high thermal conductivity.

As can be seen from the above, the shape and thickness of the piezoelectric layer 3 of the BAW filter have an influence on the filtering performance.

Optionally, in the embodiment of the present invention, as shown in fig. 1 to 7, at least one surface of the piezoelectric layer 3 is a non-planar surface, so that the shape design of the piezoelectric layer 3 is more varied, and the relative position between the first electrode 2 and the second electrode 4 is also more varied, so that the BAW filter can meet different application requirements (for example, requirements for a filtering effect, or for a shape, or for a mounting position, etc.), and the application range is wider.

The above-mentioned "at least one surface of the piezoelectric layer 3 is non-planar" includes various cases, for example, a surface of the piezoelectric layer 3 which is away from the first electrode 2 is non-planar, or a surface of the piezoelectric layer 3 which is in contact with the first electrode 2 is non-planar, or both a surface of the piezoelectric layer 3 which is in contact with the first electrode 2 and a surface away from the first electrode 2 are non-planar.

Based on the previous definition of "at least one side of the piezoelectric layer 3 is non-planar", several specific design ways of the piezoelectric layer 3 are provided in the embodiments of the present invention to meet the performance requirements of BAW filters in different situations.

In one example, as shown in fig. 1 to 3, the surface of the first electrode 2 away from the substrate 1 is a flat surface, and in this case, the surface of the piezoelectric layer 3 formed thereon contacting the first electrode 2 is also a flat surface.

Since the side of the piezoelectric layer 3 remote from the first electrode 2 is non-planar, the piezoelectric layer 3 may have at least two portions of different thicknesses, in the example shown in fig. 1, the thickness of the piezoelectric layer 3 increases and then decreases in the left-to-right direction, in the example shown in fig. 2, the piezoelectric layer 3 includes three portions of different thicknesses, and in the example shown in fig. 3, the thickness of the piezoelectric layer 3 gradually increases in the left-to-right direction. This can be set by a person skilled in the art according to the target shape and performance of the BAW filter and is not limited here.

The shape (i.e. whether or not it is a plane) of the surface of the first electrode 2 away from the substrate 1 is determined by the surface of the substrate 1 and the process for manufacturing the first electrode 2, and those skilled in the art can reasonably select the above two to make the surface of the first electrode 2 away from the substrate 1 be a plane.

In another example, as shown in fig. 4 and 5, the surface of the first electrode 2 away from the substrate 1 is non-planar, and in this case, the surface of the piezoelectric layer 3 formed thereon contacting the first electrode 2 is also necessarily non-planar.

When the face of the piezoelectric layer 3 remote from the first electrode 2 is non-planar and has a different shape from the surface of the first electrode 2 as shown in fig. 4, the piezoelectric layer 3 has at least two portions of different thicknesses. When the shape of the face of the piezoelectric layer 3 remote from the first electrode 2 is the same as the shape of the first face of the first electrode 2 as shown in fig. 5 and 6, the thickness of the piezoelectric layer 3 is uniform. This can be set by a person skilled in the art according to the target shape and performance of the BAW filter and is not limited here.

The shape (i.e. whether or not it is a plane) of the surface of the first electrode 2 away from the substrate 1 is determined by the surface of the substrate 1 and the process for manufacturing the first electrode 2, and those skilled in the art can reasonably select the above two to make the surface of the first electrode 2 away from the substrate 1 be a non-plane surface.

Alternatively, as shown in fig. 6, the substrate 1 is formed by deforming a flexible substrate with a uniform thickness, and the first electrode 2, the piezoelectric layer 3, and the second electrode 4 are all located in the deformed region of the substrate 1. The substrate 1 may be any flexible substrate that can adhere to low melting point metal and has a certain supporting force, such as PET, PVC, PI, etc.

The deformation may occur before the first electrode 2 is fabricated, before the piezoelectric layer 3 is fabricated, or before any step of fabricating the second electrode, or after the first electrode 2, the piezoelectric layer 3, and the second electrode 4 are fabricated on the substrate 1, the substrate 1 may be deformed according to actual needs (such as a mounting position). In addition, when the melting point of the selected low melting point metal is equal to or lower than room temperature, the low melting point metal has good flexibility, and even if the substrate 1 is deformed after the first electrode 2 and the second electrode 4 are manufactured, the first electrode 2 and the second electrode 4 are not damaged.

In each of the above examples, when the thicknesses of the piezoelectric layers 2 are uniform, the filter bandwidth of the BAW filter is narrow; when the piezoelectric layer 2 has at least two parts with different thicknesses, the filtering bandwidth of the BAW filter is wider, or the BAW filter can enable signals of a plurality of interval frequency bands to pass or disable the signals of the plurality of interval frequency bands, at this time, one BAW filter can play the role of a plurality of BAW filters by designing the appearance of the surface of the piezoelectric layer 2 far away from the first electrode 2, which is beneficial to reducing the occupied area of the BAW filter in an integrated circuit and improving the integration level of the integrated circuit.

Optionally, in the embodiment of the present invention, a surface of the piezoelectric layer 3 away from the first electrode 2 includes one or more of a folding surface, a cylindrical surface, a conical surface, an elliptic cylindrical surface, an elliptic conical surface, a hyperbolic paraboloid, a conical surface, a cylindrical surface, a spherical surface, or a toroidal surface. Of course, the side of the piezoelectric layer 3 facing away from the first electrode 2 can also comprise one or more flat surfaces on this basis. This can be set by a person skilled in the art according to the target shape and performance of the BAW filter and is not limited here.

Optionally, as shown in fig. 7, the BAW filter in the embodiment of the present invention further includes an insulating support 5 and a second electrode connecting line 7 located on the substrate 1, the insulating support 5 is located at least on one side of the first electrode 2 and the piezoelectric layer 3, the second electrode 4 is overlapped on the insulating support 5, a through hole is provided on the insulating support 5, and the second electrode 4 is connected to the second electrode connecting line 7 through an electrical connecting element 6 located in the through hole.

Alternatively, the electrical connection 6 may be a hollow copper tube, conductive paste, filled low melting point metal or other curable conductive fluid, or formed by electroplating, electroless plating, or the like.

Optionally, the second electrode connecting line 7 and the first electrode 2 are in the same film layer and made of the same material, so that the above structures can be formed in the same manufacturing process, for example, by printing with a low melting point metal through a printing process, which can help to simplify the manufacturing process of the BAW filter.

Optionally, the BAW filter in the embodiment of the present invention further includes a first electrode connection line connected to the first electrode 2. The first electrode connection line and the first electrode 2 may be in the same film layer and made of the same material, so that the above structures may be formed in the same manufacturing process, for example, by printing with a low melting point metal through a printing process, which may help to simplify the manufacturing process of the BAW filter.

When the BAW filter comprises both the first electrode connection line and the second electrode connection line 7, both may be located on the same side of the BAW filter to simplify the connection between the BAW filter and other devices.

The BAW filter provided by the embodiment of the invention can be applied to communication devices such as mobile phones.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A BAW filter, comprising;

a substrate;

a first electrode on a first side of the substrate;

2. The BAW filter of claim 1, wherein the low melting point metal is used to form the first electrode and/or the second electrode by one or more of screen printing, pad printing, gravure printing, letterpress printing, and flexography printing.

3. The BAW filter of claim 1, wherein the elemental metal with a melting point below 300 ℃ is one of elemental gallium, elemental indium, elemental tin, elemental sodium, elemental potassium, elemental rubidium, elemental cesium, elemental zinc, and elemental bismuth;

4. A BAW filter as claimed in any one of claims 1 to 3, wherein at least one face of the piezoelectric layer is non-planar.

5. The BAW filter of claim 4, wherein a face of the first electrode distal from the substrate is planar, the piezoelectric layer having at least two portions of different thickness.

6. The BAW filter of claim 4, wherein a face of the first electrode distal from the substrate is non-planar, the piezoelectric layer having at least two portions of different thickness.

7. The BAW filter of claim 4, wherein a face of the first electrode remote from the substrate is non-planar, and a shape of a face of the piezoelectric layer remote from the substrate is the same as a shape of a face of the first electrode remote from the substrate, the piezoelectric layer having a uniform thickness.

8. The BAW filter of claim 7, wherein the substrate is deformed from a flexible substrate of uniform thickness, and wherein the first electrode, the piezoelectric layer, and the second electrode are all located in an area of the substrate where the deformation occurs.

9. The BAW filter of claim 4, wherein a side of the piezoelectric layer distal from the first electrode comprises one or more of a folded surface, a cylindrical surface, a conical surface, an elliptic cylindrical surface, an elliptic conical surface, a hyperbolic paraboloid, a conical surface, a cylindrical surface, a spherical surface, or an annular surface.

10. A BAW filter according to any one of claims 1 to 3, further comprising an insulating support member and a second electrode connecting line on the substrate, the insulating support member being located at least on one side of the first electrode and the piezoelectric layer, the second electrode being bonded to the insulating support member, the insulating support member being provided with a through hole, the second electrode being connected to the second electrode connecting line by an electrical connection located in the through hole.