JP5277883B2 - Elastic wave filter device - Google Patents

Description

  The present invention relates to an acoustic wave filter device, and more particularly to an acoustic wave filter device characterized by a package structure.

A surface acoustic wave device that includes a surface acoustic wave element inside and has improved the airtightness of an exterior member is disclosed in Patent Document 1. FIG. 1 is a cross-sectional view of the surface acoustic wave device disclosed in Patent Document 1. As shown in FIG.
In FIG. 1, a surface acoustic wave device 1 includes a surface acoustic wave element 2, a base substrate 3, a solder bump member 4, a solder bonding member 5, and an exterior member 6. In the surface acoustic wave element 2, an inter digital transducer electrode (IDT electrode) (not shown) is formed on one main surface of the piezoelectric substrate 20, and a connection electrode 8 connected to the IDT electrode is formed. Further, an annular outer peripheral sealing electrode 9 is formed on the outer periphery of the piezoelectric substrate 20 so as to surround the IDT electrode and the connection electrode 8 over the entire periphery.

  The base substrate 3 is composed of a multilayer substrate such as a glass-ceramic material, and has an annular surface facing the element connection electrode 10 facing the connection electrode 8 of the surface acoustic wave element 2 and the outer peripheral sealing electrode 9 on the surface. The outer peripheral sealing conductor film 11 is formed. An external terminal electrode 12 is formed on the bottom surface of the base substrate 3, and the element connection electrode 10 and the external terminal electrode 12 are connected by an internal wiring pattern including a via-hole conductor 13.

  In the surface acoustic wave element 2, a predetermined gap is formed between one main surface of the surface acoustic wave element 2 and the surface of the base substrate 3 by connecting the connection electrode 8 and the element connection electrode 10 of the base substrate 3 with a solder bump member 4. Electrical connection is made at the same time as forming. Further, by bonding the outer peripheral sealing electrode 9 and the outer peripheral conductor film 11 with the solder bonding member 5, the gap between one main surface of the surface acoustic wave element 2 and the surface of the base substrate 3 is sealed, and the gap Keep the inside airtight.

On the other hand, Patent Document 2 discloses a duplexer including a surface acoustic wave filter and an impedance matching circuit. The duplexer of Patent Document 2 includes a transmission side filter, a reception side filter, and respective impedance matching circuits, and is provided in an alumina ceramic package in order to reduce the size of the impedance matching circuit.
JP 2004-207665 A JP-A-6-310979

  However, in the conventional acoustic wave filter devices as shown in Patent Documents 1 and 2, when realizing a low profile, ensuring airtightness, and providing a matching circuit in the package, the following is performed. Problems arise.

  The antenna phase matching circuit needs to be designed to be approximately 50Ω. When a ceramic package is used to ensure hermeticity, the package has a relatively large dielectric constant. Therefore, in order to obtain a characteristic impedance of 50Ω, it is necessary to increase the thickness of the package. It will be difficult to realize.

In order to reduce the height, the line width of the elements constituting the matching circuit may be narrowed. However, it is difficult to create a line with a width of several tens of μm due to the problem of accuracy. Impedance cannot be obtained.
Further, when a resin substrate is used for the package in order to reduce the line width of the element, airtightness becomes a problem.

  For this reason, with the conventional structure, it has been difficult to reduce the height, ensure airtightness, and provide a matching circuit in the package. In addition, the electrodes in the ceramic package are likely to vary in thickness and width, and it is difficult to obtain a desired impedance. In particular, when forming a 50Ω impedance line, it is necessary to arrange the ground of the line, and in order to reduce the leakage and stabilize the impedance, it is necessary to arrange a ground plane on the upper and lower surfaces of the line. preferable. At this time, how to form a line with a small loss and a small loss becomes a problem.

  An object of the present invention is to provide an acoustic wave filter device having a matching circuit in a package and having a low profile and high airtightness.

In order to solve the above problems, an elastic wave filter device of the present invention is configured as follows.
(1) A base substrate having a ceramic substrate on the upper side and a resin substrate on the lower side, and an acoustic wave element provided with an excitation part on one main surface, and mounting the acoustic wave element on the ceramic substrate, An additional circuit for the acoustic wave element is built in the resin substrate.

  In this way, the portion that keeps hermeticity is composed of the ceramic substrate, and the portion that forms the matching circuit is composed of the resin substrate. That is, the upper part of the base substrate on which the surface acoustic wave element is flip-chip mounted is constituted by a ceramic substrate and the lower part is constituted by a resin substrate. By using a resin substrate that has a small dielectric constant and can be finely processed, a predetermined impedance line can be configured in a thin package, and the surface of the surface acoustic wave element mounted on a ceramic substrate can be used as a matching circuit. The acoustic wave filter device having a low profile and high airtightness can be configured.

(2) A cavity is provided on the surface of the ceramic substrate, and the acoustic wave element is mounted in the cavity.
Thereby, the elastic wave filter device can be reduced in height without being affected by the thickness of the elastic wave element.

(3) The additional circuit includes a line, an inductor element, or a capacitive element constituting a matching circuit connected to the acoustic wave element.
Thereby, an elastic wave filter device incorporating an impedance matching circuit can be configured.

  The “acoustic wave filter device” according to the present invention includes a surface acoustic wave filter element and a boundary acoustic wave filter element.

  According to the present invention, a predetermined impedance line can be formed with a low profile by using a resin substrate having a small dielectric constant and capable of fine processing, and the mounting surface of the surface acoustic wave element is a ceramic substrate. Thus, a matching circuit is provided in the package, and a low-profile and highly airtight acoustic wave filter device can be configured.

<< First Embodiment >>
The elastic wave filter device 101 according to the first embodiment will be described with reference to FIGS.
FIG. 2A is a cross-sectional view of acoustic wave filter device 101 on a plane passing through a one-dot chain line in FIG. The acoustic wave filter device 101 includes an acoustic wave element 60, a base substrate 50, bumps 72 and 73, hermetic sealing frames 44 and 71, and an exterior resin 80. The acoustic wave filter device 101 includes a plurality of surface acoustic wave filters. An IDT electrode (inter-digital transducer electrode) 61 is formed on one main surface of a piezoelectric substrate such as lithium niobate, lithium tantalate, or quartz. A wiring electrode connected to the IDT electrode 61 is provided to constitute a surface acoustic wave element. The IDT electrode 61 corresponds to the “excitation unit” of the present invention. Further, an airtight sealing frame 71 is provided on the outer periphery of the formation surface of the IDT electrode 61 so as to surround the lDT electrode and the wiring electrode over the entire periphery.

  The IDT electrode 61 and the wiring electrode are made of, for example, Al or Cu, and are formed by a normal photolithography technique. In addition to the surface acoustic wave element, a boundary acoustic wave element may be configured.

  The base substrate 50 is composed of a ceramic substrate 40 whose upper part is made of, for example, a glass-ceramic material and a lower part that is made of a resin substrate 30 made of, for example, an epoxy resin material. Further, element connection electrodes (electrode pads) 41 and 42 and a rectangular annular hermetic sealing frame 44 are formed on the surface of the ceramic substrate 40 that forms the upper portion of the base substrate 50, and forms the lower portion of the base substrate 50. Inside the resin substrate 30, a conductor pattern 33 constituting a matching circuit is formed on the bottom surface. Mounting terminals 34 and 35 are formed, respectively.

An additional circuit for impedance matching is formed inside the resin substrate 30.
The conductor pattern 33 inside the resin substrate 30, the element connection electrodes 41 and 42 on the surface of the ceramic substrate 40, and the mounting terminals 34 and 35 on the bottom surface of the resin substrate 30 are inside the via electrodes 36, 37, and 43, respectively. Connected by wiring.

  FIG. 2B is a plan view of three layers of the resin substrate 30. 2A and 2B, the conductor pattern 33 is disposed so as to be sandwiched between the ground electrodes 31 and 32, and the conductor pattern 33 and the ground electrodes 31 and 32 are The strip line is constituted by the above.

  In addition, although the conductor pattern is formed in addition to the conductor pattern 33, it does not appear in FIGS. 2 (A) and 2 (B).

  FIG. 3 is a diagram illustrating an example of a specific circuit configuration of the acoustic wave filter device 101 according to the first embodiment. In the example of FIG. 3A, an acoustic wave filter device 101A is configured by including a transmission filter TX, a reception filter RX, and an impedance matching line 91 that is an additional circuit. In the example of FIG. 3B, an acoustic wave filter device 101B is configured by including a transmission filter TX, a reception filter RX, and an impedance matching inductor 92 that is an additional circuit.

  The transmission filter TX and the reception filter RX are constituted by the acoustic wave element 60 shown in FIG. The impedance matching line 91 or the impedance matching inductor 92 is formed on the resin substrate 30 shown in FIG.

The impedance matching line 91 is formed of, for example, a 50Ω λ / 4 phase circuit.
For example, consider the case of forming a λ / 4 phase circuit of 50Ω in the 800 MHz band. Assuming that the relative dielectric constant of the ceramic substrate is 8 to 9 and the line width processing limit is about 75 μm, in order to form a λ / 4 strip line of 50Ω, between the ground electrodes 31 and 32 above and below the electrodes. The interval is 0.36 mm and the length is 31 mm.

  On the other hand, when a phase circuit of λ / 4 with 50Ω is formed on a resin substrate, the effect of improving the limit of the line width processing to about 50 μm is added to the effect that the dielectric constant is almost half as 4.5, and the ground electrode The distance between them is 0.11 mm, and the length is 44 mm. The line length is about 1.5 times longer, but the thickness is about 1/3, and it can be seen that it is very effective for reducing the height.

  In the example shown in FIG. 3, a line or an inductor is used as the impedance matching element, but a capacitive element may be provided in addition.

FIG. 4 is a diagram showing a method for manufacturing the acoustic wave filter device 101 shown in FIG.
First, as shown in FIG. 4A, an airtight sealing frame 44 is formed around the upper surface of the ceramic substrate 40. The ceramic substrate 40 is alumina having a relative dielectric constant εr = 8-9, and the hermetic sealing frame 71 is patterned by printing a metal material such as solder.
On the other hand, the additional circuit is configured on the resin substrate 30.

Next, as illustrated in FIG. 4B, the resin substrate 30 is bonded to the ceramic substrate 40.
Thereafter, as shown in FIG. 4C, the acoustic wave element 60 is mounted on the ceramic substrate 40. That is, the bumps 72 and 73 formed on the acoustic wave element 60 are connected to the element connection electrodes 41 and 42 of the ceramic substrate 40. Further, the hermetic sealing frame 71 on the acoustic wave element 60 side is joined to the hermetic sealing frame 44 on the ceramic substrate 40 side by soldering or the like.

  In this way, a predetermined gap is formed between the one main surface of the acoustic wave element 60 and the surface of the ceramic substrate 40, and at the same time, electrical connection is performed. Further, the gap between the lower surface of the acoustic wave element 60 and the upper surface of the ceramic substrate 40 is sealed by the hermetic sealing frames 44, 71, etc., the inside of the gap is kept airtight, and the IDT electrode is deteriorated due to intrusion of moisture or the like. To prevent.

Thereafter, an exterior resin 80 is deposited on the upper surface of the ceramic substrate 40.
Although FIG. 4 shows a single acoustic wave filter device, actually, the resin substrate 30 and the ceramic substrate 40 are bonded together in the state of a mother substrate, and the exterior resin 80 shown in FIG. Divide individually after deposition.

<< Second Embodiment >>
An elastic wave filter device 102 according to a second embodiment will be described with reference to FIGS.
FIG. 5 is a cross-sectional view of the acoustic wave filter device 102. The acoustic wave filter device 102 includes an acoustic wave element 60, a base substrate 50, bumps 72 and 73, a frame body 81, and a lid body 82. The frame 81, the lid 82, and the ceramic substrate 40 constitute a cavity. The acoustic wave filter device 102 includes a plurality of surface acoustic wave filters. An inter-digital transducer electrode (IDT electrode) is formed on one main surface of a piezoelectric substrate such as lithium niobate, lithium tantalate, or quartz. A wiring electrode connected to the IDT electrode is provided.

The base substrate 50 is composed of a ceramic substrate 40 having an upper portion made of, for example, a glass-ceramic material, and a lower portion being made of a resin substrate 30 having, for example, an epoxy resin material. Further, element connection electrodes (electrode pads) 41 and 42 are formed on the surface of the ceramic substrate 40 that forms the upper portion of the base substrate 50, and a matching circuit is provided inside the resin substrate 30 that forms the lower portion of the base substrate 50. The conductor pattern 33 to be formed is formed on the bottom surface. Mounting terminals 34 and 35 are formed, respectively.
As in the case of the first embodiment, an additional circuit for impedance matching is formed inside the resin substrate 30.

FIG. 6 is a diagram showing a method for manufacturing the acoustic wave filter device 102 shown in FIG.
First, as shown in FIG. 6A, a frame body 81 is formed on the upper surface of the ceramic substrate 40.
On the other hand, the additional circuit is configured on the resin substrate 30.

Next, as illustrated in FIG. 6B, the resin substrate 30 is bonded to the ceramic substrate 40.
Thereafter, as shown in FIG. 6C, the acoustic wave element 60 is flip-chip bonded onto the ceramic substrate 40. That is, the bump formed on the acoustic wave element 60 is connected to the element connection electrode of the ceramic substrate 40.
Thereafter, the lid body 82 is deposited on the upper surface of the frame body 81.

  In this manner, the periphery of the acoustic wave element 60 is kept airtight by the ceramic substrate 40, the frame body 81, and the lid body 82, and the deterioration of the IDT electrode due to intrusion of moisture and the like is prevented.

  Although FIG. 6 shows a single acoustic wave filter device, the resin substrate 30 and the ceramic substrate 40 are joined in the state of a mother substrate, and the lid 82 shown in FIG. You may make it divide | segment separately.

According to the first and second embodiments described above, the following effects can be obtained.
By mounting the acoustic wave element on the base substrate obtained by bonding the ceramic substrate and the resin substrate, a predetermined impedance can be ensured even if the ceramic substrate for ensuring airtightness is thinned.

-The required strength of the base substrate can be maintained, so that the product height can be lowered.
-Since a device with a matching circuit can be created, it can be inspected as a product with an additional circuit.
-Since it can be created without using bumps or the like for bonding the ceramic substrate and the resin substrate, the height can be reduced.
・ Ceramic board and resin board can be cut at the same time, so there is no margin for deviation during mounting and miniaturization is possible.
Since the conductor pattern of the additional circuit is formed on the resin substrate, a fine pattern having a rectangular cross-sectional shape and a good conductivity can be formed, so that the loss can be reduced while being small.
-Since the outermost layer is a resin substrate, cracks and chips are less likely to occur than when only a ceramic substrate is used.

  In the embodiment described above, the ceramic substrate is one layer, but two or more ceramic substrates may be provided.

1 is a cross-sectional view of a surface acoustic wave device disclosed in Patent Document 1. FIG. FIG. 2A is a cross-sectional view of the acoustic wave filter device 101. FIG. 2B is a plan view of three layers of the resin substrate 30. It is a figure which shows the example of the concrete circuit structure of the elastic wave filter apparatus 101 which concerns on 1st Embodiment. It is a figure shown about the manufacturing method of the elastic wave filter apparatus 101 shown in FIG. It is sectional drawing of the elastic wave filter apparatus 102 which concerns on 2nd Embodiment. It is a figure shown about the manufacturing method of the elastic wave filter apparatus 102 shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Elastic wave filter apparatus 101A ... Elastic wave filter apparatus 101B ... Elastic wave filter apparatus 102 ... Elastic wave filter apparatus 30 ... Resin board 31, 32 ... Ground electrode 33 ... Conductor pattern 34, 35 ... Mounting terminal 36, 37, 43 ... Via electrode 40 ... Ceramic substrate 41, 42 ... Element connection electrode 44 ... Airtight sealing frame 50 ... Base substrate 60 ... Elastic wave element 61 ... IDT electrode 71 ... Airtight sealing frame 72, 73 ... Bump 80 ... Exterior resin 81 ... Frame body 82 ... Lid body 91 ... Impedance matching line 92 ... Impedance matching inductor RX ... Reception filter TX ... Transmission filter

Claims (3)

  A base substrate composed of a ceramic substrate on the upper side and a resin substrate on the lower side; and an acoustic wave element provided with an excitation portion on one main surface, wherein the acoustic wave element is mounted on the ceramic substrate, and the resin substrate And an additional circuit for the elastic wave element.   The acoustic wave filter device according to claim 1, wherein a cavity is provided on a surface of the ceramic substrate, and the acoustic wave element is mounted in the cavity.   The elastic wave filter device according to claim 1, wherein the additional circuit includes a line, an inductor element, or a capacitive element that forms a matching circuit connected to the elastic wave element.

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